The Extract Cross Section Geometry command allows the user to extract the cross section geometry from an underlying elevation grid where valid elevation data are present. The software will automatically recognize the limits of the elevation data and extract the cross section geometry for that data. It will not try to extract cross section geometry data where valid elevation data are not present.

For example, the underlying elevation grid might be of the river channel only. Previously, extracting the cross section geometry for this area required that the user define the channel bank stations at the limits of the elevation data and then extract the cross section geometry only for the cross section channel. If the user tried to extract the cross section geometry for the overbank areas, the overbank geometry would be flat.

Follow the steps below to use the Extract Cross Section Geometry command:

1. From the Input ribbon menu, click the Cross Sections dropdown menu and select the Extract Cross Section Geometry command.
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2. The Extract Cross Section Geometry dialog box will be displayed.
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The following sections describe how to use the Extract Cross Section Geometry command and interact with the above dialog box.

Selecting Cross Sections

The Select Cross Sections section is used to manually select single or multiple cross section(s) to extract geometry. This section includes a table listing all cross section(s) in the current scenario of the project, as shown below.

The user can select the cross section(s) using any of the following methods for extracting geometry:

• Check the checkboxes corresponding to each cross section in the Select Cross Sections section.
• Click the [Pick] button, the Extract Cross Section Geometry dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the cross section(s) from the Map View. Either select cross sections one by one or click on the reach and all associated cross sections will be selected from the Map View. After selecting the cross section(s), press the [Enter] key or right-click and choose Done from the displayed context menu. The Extract Cross Section Geometry dialog box will be redisplayed.
• Alternatively, press and hold down the [Ctrl] key while selecting the cross section(s) directly from the Map View. When finished, open the Extract Cross Section Geometry dialog box, and the selected cross section(s) will be shown as selected/checked within the Select Cross Sections section.

After selecting the cross section(s), the total number of selected cross section(s) will be displayed in the Total selected read-only field, as shown below.

Other Specifications

The Other Specifications section is used to define additional specifications for extracting cross section geometry, including elevation data sources, extraction limits, roughness values, and bank station assignments. The following panels are available in this section:

• Extraction Data
• Other Data
• Roughness

Extraction Data

The Extraction Data panel is used to define the data extraction specifications for the selected cross sections.

Extracting Elevation Data

The Extract Elevation Data subsection is used to define the elevation data source(s) to be used for extracting the cross section geometry. Depending on the terrain elevation source selected, the content of this subsection changes to specify additional elevation data information. Refer to this article in our knowledge base for information on the types of terrain elevation data that can be used for extracting cross sections.

The following options are available in the Terrain elevation source dropdown combo box:

• CAD Drawing
• Elevation Grid
• GIS Contours
• LandXML Data
• Terrain Surface
• TIN Surface

CAD Drawing

If the user selects CAD Drawing as the terrain elevation source, the content of the Extract Elevation Data subsection changes, as shown below.

The following options are displayed when CAD Drawing is selected as the terrain elevation source:

• CAD drawing layer: This dropdown combo box allows the user to select the CAD drawing layer available in the project.
• Drawing layers: Clicking the [Define] button adjacent to the Drawing layers entry displays the CAD Drawing Layers dialog box, allowing the user to define the properties of the drawing layers, as shown below.
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Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the content of the Extract Elevation Data subsection changes, as shown below.

The following option is displayed when the Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer: This dropdown combo box allows the user to select the elevation grid layer available in the project.

GIS Contours

If the user selects GIS Contours as the terrain elevation source, the contents of the Extract Elevation Data subsection changes, as shown below.

The following options are displayed when GIS Contours is selected as the terrain elevation source:

• GIS polyline layer: This dropdown combo box allows the user to select the GIS polyline layer type.
• Elevation attribute: This dropdown combo box allows the user to select the elevation attribute type.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the content of the Extract Elevation Data subsection changes, as shown below.

The following options are displayed when the LandXML Data is selected as the terrain elevation source:

• TIN surface layer: This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface: This dropdown combo box allows the user to select the TIN surface type.

Terrain Surface

If the user selects Terrain Surface as the terrain elevation source, the contents of the Extract Elevation Data subsection changes, as shown below.

The following option is displayed when the Terrain Surface is selected as the terrain elevation source:

• Terrain surface layer: This dropdown combo box allows the user to select the terrain surface layer type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the contents of the Extract Elevation Data subsection changes, as shown below.

The following options are displayed when the TIN Surface is selected as the terrain elevation source:

• TIN surface layer: This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface: This dropdown combo box allows the user to select the TIN surface type.

Cross Section Geometry Extraction Control

The Cross Section Geometry Extraction Control subsection is used to control the amount of cross section geometry data to be extracted from the terrain model for the selected cross section polylines. These controls provide additional intelligence on whether to extend or limit the cross section cutting, based upon whether specific criteria have been met. This ensures that adequately deep cross sections are created on both sides of the river reach. The software will try to compute the cross section geometry data up to the specified depth and within the maximum cross section width defined in this subsection. Note that the checkbox at the Cross Section Geometry Extraction Control subsection should be checked to enable the content of this subsection. Otherwise, the content of this subsection is disabled (i.e., grayed out).

If the selected polylines do not extend outward far enough to get the cross section depth specified, the software will automatically extend the cross sections further outward. Similarly, if the selected polylines extend too far outward for the cross section depth specified, the software will automatically trim the cross sections.

Cross Section Extraction Options

The Cross Section Extraction Options subsection is used to control which portions of the cross section(s) are to be extracted.

For example, the user may have survey data for the cross section channel and a LIDAR digital terrain surface for the overbank areas. In this example, the user would only want to extract the cross section geometry for the overbank areas since the surveyed channel geometry is already accurate.

The Extract cross section geometry for dropdown combo box entry contains the following options:

• Both Overbanks
• Channel Only
• Entire Cross Section (default)
• Left Overbank Only
• Right Overbank Only
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The Retain existing cross section geometry checkbox option is used to retain the geometry of the cross sections that were extracted previously using the CAD file. By default, this checkbox is unchecked.

Other Data

The Other Data panel allows the user to assign bank stations for the cross sections using channel width, channel depth, or bank polylines/polygons. The checkbox at the Assign Bank Stations subsection should be checked to enable the content of this panel. Otherwise, the content of this panel is disabled (i.e., grayed out).

Assign Bank Stations

The Assign Bank Stations subsection is used to extract channel bank locations based on the selected option.

The following options are available in this subsection:

• Define by channel width
  This radio button option is used to assign the bank stations using a defined channel width. The software first identifies the thalweg location on the cross section, then extends outward from the thalweg symmetrically until the required channel width is achieved. Clicking the […] button allows the user to measure the channel width from the Map View.
• Define by channel depth
  This radio button option is used to assign the bank stations using an assumed normal flow depth and a maximum channel width search distance. The software first identifies the thalweg location on the cross section, then extends outward from the thalweg until the required channel depth is reached while staying within the specified maximum channel width. Clicking the […] button allows the user to measure the maximum channel width from the Map View.
• Define by bank polylines/polygons
  This radio button option is used to assign the bank stations using selected polylines or polygons. Using the corresponding [Pick] buttons, the user can interactively select individual polylines or polygons on the Map View to be associated as bank stations. The user can click the [Clear] button to cancel the previous selection and redo the entire process. The software first identifies the thalweg location on the cross section, then extends outward from the thalweg until it reaches a previously selected bank polyline or polygon edge.

Assigning Manning’s Roughness and Flow Lengths

During the extraction of the cross section geometry, the software will automatically assign a default Manning’s roughness for the left overbank, channel, and right overbank areas. However, the user can adjust these Manning’s roughness values in the Roughness panel, as shown below.

Note that, while defining the Manning’s n values, the user can click the […] lookup buttons adjacent to these Manning’s roughness entry fields to display the Manning’s Roughness dialog box. This dialog box provides a reference to Manning’s roughness coefficients for some commonly used surface materials.

Extracting Cross Section Geometry

When all the options have been defined in the Extract Cross Section Geometry dialog box, click the [OK] button. The software will then extract the cross section geometry from the elevation terrain.

Low Impact Development (LID) is a modern stormwater management approach that supports natural hydrologic processes rather than disrupting them. Instead of routing runoff quickly into pipes and channels, LID structures slow, spread, infiltrate, and reuse stormwater close to where it falls. This allows developed sites to more closely resemble pre-development conditions, helping reduce downstream flood peaks, improve water quality, and recharge groundwater.

The Subbasin LID Structures command allows the user to create Low Impact Design (LID) structures within the defined subbasins.

Follow the steps below to use the Subbasin LID Structures command:

1. From the Input ribbon menu, click the Drainage Subbasins dropdown menu and select the Subbasin LID Structures command.
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2. The Subbasin LID Structures dialog box will be displayed, as shown below.
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The following sections describe how to use the Subbasin LID Structures command and interact with the above dialog box.

Selecting LID Structure

The Select LID Structure section allows the user to select the LID structure for which LID structure data will be defined. In this section, the user can create, delete, copy existing LID structure data to a new LID structure, and select the type of LID structure. In addition, the user can navigate between LID structures and view a description for each LID structure type.
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The following entries are available in this section:

• LID structure ID
  This dropdown combo box lists all the LID structures defined in the current scenario. Click on the edit option (i.e., pencil icon) to edit the LID structure name. The user can navigate between the previous and next LID structure using the Up and Down arrow buttons. Note that the Up and Down arrow buttons will be disabled (i.e., grayed out) if the current scenario contains a single LID structure.
• LID structure type
  This dropdown combo box allows the user to select the type of LID structure to be defined. The following LID structure types are available:
• • Bioretention Cell
  • Bioswale
  • Green Roof
  • Infiltration Trench
  • Permeable Pavement
  • Rain Barrel
  • Rain Garden
  • Rooftop Capture
• Description
  This field shows additional information that describes the selected LID structure type.
• New
  The [New] button allows the user to create a new LID structure on the Map View. The ID of every newly created LID structure must be unique.
• Copy
  The [Copy] button allows the user to copy an existing LID structure along with its associated data to a new LID structure. The software automatically provides a unique ID to the copied LID structure.
• Delete
  The [Delete] button allows the user to delete the selected LID structure from the current scenario.
• LID element picture
  The image available to view in this section displays the preview of the selected LID element. Clicking the LID element image displays a dialog box with a detailed view of the selected LID element type.
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LID Structure Specifications

The dropdown combo box at the LID Structure Specifications section header contains the following data panel entries, which allow the user to define LID structure data:

• Layer Specifications
• Discharge Specifications

These data panel entries will be enabled or disabled depending on the selected type of LID structure. The following table shows which data panel entries are enabled or disabled for each LID structure type:

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LID Drain System

The drain system in an LID unit is performance-based rather than design-based. Rather than specifying physical pipe dimensions, the user controls how the drain behaves by specifying its height above the bottom of the storage layer and how the drain flow rate (per unit area) changes based on the height of saturated media above it.

When defining the parameters of an LID drain system, consider the following guidelines:

• If the storage layer has an impermeable bottom, place the drain at the bottom with zero offset. If the goal is to allow the storage volume to fill completely before drainage begins, place the drain at the top of the storage layer.
• If the storage layer does not contain a drain, set the drain coefficient to 0.
• If the drain can handle all inflow into the storage layer up to a specific maximum limit, set the drain coefficient equal to that flow limit and set the drain exponent to 0.
• If the drain consists of slotted pipes (where slots function like orifices), set the drain exponent to 0.5. The drain coefficient can then be estimated as:
  Drain Coefficient = 60,000 × (Total Slot Area ÷ LID Area).
  For example, drain pipes with five 1/4 inch diameter holes per foot spaced 50 feet apart produce an area ratio of 0.000035, which results in a drain coefficient of approximately 2.
• If the goal is to drain a fully saturated unit within a specified time, set the drain exponent to 0.5 (for orifice flow) and calculate the drain coefficient.
  Drain Coefficient = 2D^1/2
  where:
• • D = Distance from the drain to the surface plus any berm height (in inches or mm)
  • o   T = Required drain time (hours)

For example, to drain a depth of 36 inches of water in 12 hours, the drain coefficient would be 1. If this drain uses the slotted pipes described in the previous example (with a coefficient = 2), then a flow regulator (such as a capped orifice) must be placed at the discharge outlet to achieve the reduced flow rate.

The following sections describe each type of LID structure and how to define its associated data.

Bioretention Cell

A bioretention cell is an LID structure that consists of a depression filled with vegetation and engineered soil above a gravel drainage bed, designed to store, infiltrate, and evaporate rainwater and runoff. Bioretention cells are among the most versatile LID controls available, performing well in a wide range of climates and site conditions.
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Layer Specifications

This panel allows the user to define the layer specifications of the Bioretention Cell LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Berm height
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Berm Height lookup dialog box, showing depression storage values based upon land surface type.
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• Vegetative volume fraction
  This spin control entry field represents the fraction of the volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 20% for very dense vegetative growth. By default, the software uses a value of 5. However, the user can enter a different value ranging from 0 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for bioretention cell overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Surface slope (H:V)
  This entry field defines the slope of the surface layer of the bioretention cell.

Soil Layer Definition

This section allows the user to define the soil properties of the LID structure. The following entries are provided in this section:

• Soil layer thickness
  This entry field defines the thickness of the soil layer.
• Soil porosity
  This entry field represents the volume of pore space relative to the total soil volume. Clicking the […] button displays the Soil Porosity lookup dialog box, showing soil porosity values for typical soils.
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• Field capacity
  This entry field represents the volume of pore water relative to the total soil volume after the soil has been allowed to fully drain. Below this level, vertical drainage of water through the soil layer does not occur. Clicking the […] button displays the Field Capacity lookup dialog box, showing field capacity values for typical soils.
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• Wilting point
  This entry field represents the volume of pore water relative to the total volume of well-dried soil, where only bound water remains. The soil moisture content cannot fall below this limit. Clicking the […] button displays the Wilting Point lookup dialog box, showing wilting point values for typical soils.
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• Hydraulic conductivity
  This entry field represents the hydraulic conductivity for fully saturated soil. Clicking the […] button displays the Hydraulic Conductivity lookup dialog box, showing hydraulic conductivity values for typical soils.
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• Conductivity slope
  This entry field represents the average slope of the curve of log (hydraulic conductivity) versus soil moisture deficit (i.e., porosity minus moisture content).
• Suction head
  This entry field represents the average soil capillary suction along the wetting front. Clicking the […] button displays the Suction Head lookup dialog box, showing suction head values for typical soils.
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Storage Layer Definition

This section allows the user to define the storage properties of the crushed stone or gravel layer used in bioretention cells. The following entries are provided in this section:

• Storage layer thickness
  This entry field defines the thickness of the bottom gravel layer. Crushed stone and gravel layers are typically 6 to 18 inches (15 to 45 cm) thick.
• Void ratio
  This spin control entry field represents the volume of void space relative to the volume of solids in the layer. By default, the software uses a value of 40. However, the user can enter a different value ranging from 1 to 100.
• Seepage rate
  This entry field represents the rate at which water seeps into the native soil below the layer. Clicking the […] button displays the Soil Saturated Hydraulic Conductivity lookup dialog box, showing saturated hydraulic conductivity values for typical soils.
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• Clogging factor
  This checkbox entry field represents the total volume of runoff processed by the LID structure to completely clog the storage layer, divided by the void volume of the layer. The user can use a value of 0 to ignore clogging. Clogging progressively reduces the infiltration rate in direct proportion to the cumulative volume of runoff processed by the LID structure and may only be of concern for infiltration trenches with permeable bottoms and no underdrains. By default, this checkbox is unchecked, and the entry field is disabled (i.e., grayed out).

Discharge Specifications

This optional panel allows the user to define discharge specifications of the Bioretention Cell LID structure.
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Storage Layer Discharge Specifications

This section is used in a situation where the bioretention cell does not directly discharge any of the stored rainwater. By default, the checkbox at the section header is unchecked, and the contents are disabled (i.e., grayed out). Check the checkbox to enable the contents of this section.

The following entries are available in this section:

• Discharge flow coefficient
  This entry field defines the discharge flow coefficient “C.” This coefficient value is applied to the following equation that computes the flow rate (per LID unit area) through an outlet as a function of the height of stored water above the discharge outlet’s offset. The user can use a discharge flow coefficient of 0 if the layer has no drain.
  Q = C x h^e
  Where:
  Q = Outflow per unit area
  C = Coefficient, dependent upon unit system and assigned exponent
  h = Height of saturated media above the discharge outlet
  e = Exponent, typically 0.5 to act as an orifice
• Discharge flow exponent
  This entry field defines the discharge flow exponent “e.” This exponent value is applied to the previous entry’s equation that computes the flow rate (per LID unit area).
• Discharge outlet height
  This entry field represents the height of the outlet above the bottom of the bioretention cell.
• Open discharge outlet at height
  This checkbox entry field defines the height of stormwater contained in the bioretention cell’s storage layer at which the discharge outlet automatically opens when the water level rises above it. By default, this checkbox is unchecked, and the entry field is disabled (i.e., grayed out).
• Close Discharge outlet at height
  This entry field defines the height of the stormwater in the bioretention cell’s storage layer at which the discharge outlet automatically closes when the water level falls below it. Note that this entry field is only enabled when the Open discharge outlet at height checkbox is checked.

Storage Layer Discharge Adjustment

This section allows the user to define the control curve that adjusts the computed outflow based on the water head above the discharge outlet. By default, the checkbox at the section header is unchecked, and the contents are disabled (i.e., grayed out). Check the checkbox to enable the contents of this section.

This section contains a table with Water Head Above Outlet and Adjustment Factor columns. The Water Head Above Outlet column specifies the water head above the discharge outlet. The Adjustment Factor column specifies the adjustment factor applied to the computed outflow. Once the control curve data is entered, the corresponding graphical plot is displayed next to this table.

Bioswale

A bioswale is an LID structure consisting of a shallow channel or depression with sloped, vegetated sides. It is designed to slow runoff and promote infiltration into the native soil. Bioswales are commonly used along roadways and parking lots to intercept sheet flow before it reaches storm drains.
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Layer Specifications

This panel allows the user to define the layer specifications of the Bioswale LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Bioswale cross section depth
  This entry field defines the maximum depth to which water will start to overflow the bioswale cross section.
• Vegetative volume fraction
  This spin control entry field represents the fraction of the volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 10 to 20% for very dense vegetative growth. By default, the software uses a value of 5. However, the user can enter a different value ranging from 0 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for bioswale overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Bioswale longitudinal slope (H:V)
  This entry field defines the longitudinal slope (in the implied flow direction) of the bioswale.
• Bioswale cross section side slope (H:V)
  This entry field defines the slope of the bioswale cross section side walls.

Green Roof

A green roof is an LID structure that is a variation of bioretention cells, featuring a soil layer on a drainage mat to manage excess rainfall from rooftops. Green roofs reduce the volume and peak rate of rooftop runoff, improve building insulation, and reduce the urban heat island effect.
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Layer Specifications

This panel allows the user to define the layer specifications of the Green Roof LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Berm height
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Berm Height lookup dialog box, showing depression storage values based upon land surface type.
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• Vegetative volume fraction
  This spin control entry field represents the fraction of the volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 20% for very dense vegetative growth. By default, the software uses a value of 5. However, the user can enter a different value ranging from 0 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for green roof overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Surface slope (H:V)
  This entry field defines the slope of the surface layer of the green roof.

Soil Layer Definition

This section is similar to the Soil Layer Definition section explained above for the Bioretention Cell LID structure type.

Drainage Mat Layer Definition

This section allows the user to define the drainage mat layer properties of the LID structure. The following entries are available in this section:

• Drainage mat layer thickness
  This entry field defines the thickness of the bottom drainage mat. Drainage mat layers are typically 1 to 2 inches (2.5 to 5 cm) thick.
• Void fraction
  This spin control entry field represents the volume of void space relative to the volume of solids in the mat layer. By default, the software uses a value of 50. However, the user can enter a different value ranging from 1 to 100.
• Drainage mat Manning’s roughness
  This entry field defines Manning's roughness coefficient used to compute the horizontal flow rate of drained water through the mat. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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Infiltration Trench

An infiltration trench is an LID structure consisting of a narrow gravel-filled ditch that captures runoff from impermeable surfaces, allowing it to be stored and infiltrated into the native soil. Infiltration trenches are particularly effective in areas with well-draining soils and where horizontal space for LID controls is limited.
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Layer Specifications

This panel allows the user to define the layer specifications of the Infiltration Trench LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Berm height
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Berm Height lookup dialog box, showing depression storage values based upon land surface type.
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• Vegetative volume fraction
  This spin control entry field represents the proportion of volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 10 to 20% for very dense vegetative growth. By default, the software uses a value of 0. However, the user can enter a different value ranging from 0 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for infiltration trench overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Surface slope (H:V)
  This entry field represents the slope of the infiltration trench.

Storage Layer Definition

This section is similar to the Storage Layer Definition section explained above for the Bioretention Cell LID structure type.

Discharge Specifications

This panel is similar to the Discharge Specifications panel explained above for the Bioretention Cell LID structure type.
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Permeable Pavement

Permeable pavement is an LID structure that consists of an excavated area filled with gravel and topped with porous concrete or asphalt to facilitate water drainage. Permeable pavement allows stormwater to pass through the surface into the underlying layers where it is stored and gradually infiltrated into the native soil, reducing surface runoff volumes and peak flows.
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Layer Specifications

This panel allows the user to define the layer specifications of the Permeable Pavement LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Berm height
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Berm Height lookup dialog box, showing depression storage values based upon land surface type.
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• Vegetative volume fraction
  This spin control entry field represents the proportion of volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 10 to 20% for very dense vegetative growth. By default, the software uses a value of 0. However, the user can enter a different value ranging from 0 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for permeable pavement overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Surface slope (H:V)
  This entry field defines the slope of the surface layer of the permeable pavement.

Pavement Layer Definition

This section allows the user to define the pavement properties of the LID structure. The following entries are available in this section:

• Pavement layer thickness
  This entry field defines the thickness of the pavement layer.
• Void ratio
  This spin control entry field represents the volume of void space relative to the volume of solids in the pavement in the case of continuous systems or the fill material in the context of modular systems. By default, the software uses a value of 15. However, the user can enter a different value ranging from 1 to 100.
• Impervious surface fraction
  This spin control entry field represents the ratio of impervious paver material to the total area for modular systems. A zero value should be defined for continuous porous pavement systems. By default, the software uses a value of 0. However, the user can enter a different value ranging from 0 to 100.
• Permeability
  This entry field represents the permeability of the concrete or asphalt used in continuous systems or the hydraulic conductivity of the fill material (i.e., gravel or sand) used in modular systems. For fill material, the nominal conductivity should be multiplied by the fraction of the total area it covers. The permeability of new porous concrete or asphalt is extremely high (i.e., 700 to 5,700 inches/hr, 1,800 to 14,400 cm/hr) but can drop off over time due to clogging by fine particulates in the runoff.
  This entry field defines the number of pavement layer void volumes of runoff treated that it takes to completely clog the pavement. A value of 0 can be used to ignore clogging. Clogging progressively reduces the pavement's permeability in direct proportion to the cumulative volume of runoff treated.
• Regeneration interval
  This entry field defines the number of days that the pavement layer is allowed to clog before its permeability is restored, typically by vacuuming its surface. By default, the software uses a value of 0 that indicates no permeability regeneration occurs.
• Regeneration fraction
  This spin control entry field defines the fractional degree to which the pavement's permeability is restored when a regeneration interval is reached. A value of 0 indicates no restoration, while a value of 100 indicates complete restoration to the original permeability value. Once regeneration occurs, the pavement begins to clog once again at a rate determined by the clogging factor. By default, the software uses a value of 80. However, the user can enter a different value ranging from 0 to 100.

Pavement Bedding Layer Definition

This section allows the user to define the permeable pavement bedding properties for the LID structure. If the pavement bedding layer does not need to be defined, then uncheck the header checkbox. By default, the checkbox at the section header is checked. If unchecked, the contents of this section are disabled (i.e., grayed out).

Note that this section is similar to the Soil Layer Definition section explained above for the Bioretention Cell LID structure type, except for the additional Pavement bedding layer thickness entry field. The Pavement bedding layer thickness entry field defines the thickness of the pavement bedding layer.

Storage Layer Definition

This section is similar to the Storage Layer Definition section explained above for the Bioretention Cell LID structure type.

Discharge Specifications

This panel is similar to the Discharge Specifications panel explained above for the Bioretention Cell LID structure type.

Rain Barrel

A rain barrel is an LID structure that consists of a container used to collect roof runoff during storms, allowing for the storage and reuse of rainwater during dry periods. Rain barrels provide a simple, cost-effective way to reduce stormwater runoff volumes and conserve water for irrigation.
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Layer Specifications

This panel allows the user to define the layer specifications of the Rain Barrel LID structure.

Rain Barrel Definition

The following entries are available in this section:

• Rain barrel height
  This entry field defines the maximum depth of the rain barrel structure before overflow occurs.
• Covered rain barrel
  This checkbox option allows the user to define whether the rain barrel is covered or not. A covered rain barrel receives no direct rainfall. By default, this checkbox is unchecked.

Discharge Specifications

This panel is similar to the Discharge Specifications panel explained above for the Bioretention Cell LID structure type, except for the additional Rain barrel discharge delay checkbox entry field. The Rain barrel discharge delay checkbox entry field defines the number of dry-weather hours that must lapse before the discharge outlet in a rain barrel is opened. By default, this checkbox is unchecked, meaning the discharge outlet remains open and drains continuously. When checked, the outlet is assumed to close once rainfall begins and will reopen only after the specified delay period has passed.
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Rain Garden

A rain garden is an LID structure that is a type of bioretention cell with an engineered soil layer but without a gravel bed, designed to manage stormwater through infiltration and evapotranspiration. Rain gardens are shallow, planted depressions that collect and absorb runoff from impervious surfaces such as roofs, driveways, and walkways.
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Layer Specifications

This panel allows the user to define the layer specifications of the Rain Garden LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Berm height
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Berm Height lookup dialog box, showing depression storage values based upon land surface type.
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• Vegetative volume fraction
  This spin control entry field represents the proportion of volume within the storage depth that is filled with vegetation. This is the volume occupied by stems and leaves, not their surface area coverage. Normally, this volume can be ignored, but it may be as high as 20% for very dense vegetative growth. By default, the software uses a value of 5. However, the user can enter a different value ranging from 1 to 100.
• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for rain garden overland flow. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
• Surface slope (H:V)
  This entry field defines the slope of the surface layer of the rain garden.

Soil Layer Definition

This section is similar to the Soil Layer Definition section explained above for the Bioretention Cell LID structure type.

Storage Layer Definition

This section allows the user to define the storage properties of the crushed stone or gravel layer used in rain gardens. The following parameter is provided in this section:

• Seepage rate
  This entry field represents the rate at which water seeps into the native soil below the layer. Clicking the […] lookup button displays a Soil Saturated Hydraulic Conductivity dialog box, showing saturated hydraulic conductivity values for typical soils.
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Rooftop Capture

A rooftop capture is an LID structure that directs downspouts to permeable areas and lawns rather than storm drains. It can also simulate roofs that overflow onto these surfaces. Rooftop capture controls are particularly useful for modeling disconnected impervious areas and green infrastructure strategies that leverage existing rooftop drainage systems.
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Layer Specifications

This panel allows the user to define the layer specifications of the Rooftop Capture LID structure.

Surface Layer Definition

This section allows the user to define the surface properties of the LID structure. The following entries are available in this section:

• Rooftop depression storage depth
  This entry field defines the maximum depth to which water can pond above the surface of the LID structure before overflow occurs. Clicking the [...] button displays the Rooftop Depression Storage Depth lookup dialog box, showing depression storage values based upon land surface type.
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• Manning’s overland flow roughness
  This entry field defines Manning’s roughness coefficient for rooftop runoff. Clicking the […] button displays the Overland Flow Roughness lookup dialog box, showing Manning’s roughness values for overland flow.
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• Rooftop surface slope (H:V)
  This entry field defines the slope of the surface layer of the rooftop capture.

Discharge Specifications

This panel allows the user to define the discharge specifications of the LID structure.
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Rooftop Capture Discharge Specifications

This section allows the user to define the rooftop capture discharge specifications of the LID structure. The following parameter is provided in this section.

• Rain gutter maximum flow rate
  This checkbox entry field defines the maximum flow rate that the roof’s drainage system (i.e., gutters, downspouts, etc.) can manage before overflowing. By default, this checkbox entry field is checked. If unchecked, no maximum flow rate is applied, meaning the LID structure can manage any flow rate.

Computing subbasin slopes is a critical aspect of hydrologic modeling and watershed analysis. Some of the runoff methods being used in the stormwater project utilize the computed subbasin slope.

This article describes the computational method used to compute the subbasin slope and how the Compute Slopes command works in the CivilGEO software.

Subbasin Slope Computational Method

When calculating the slope for subbasins, the software uses an elevation grid, or Digital Elevation Model (DEM), and applies an algorithm that divides the subbasin area into smaller grid cells. The slope of each grid cell is then calculated based on the rate of change in both the horizontal and vertical directions from the center of the neighboring grid cells.

The illustration below demonstrates how the algorithm computes the slope of a subbasin on a cell-by-cell basis, analyzing the cells from left to right and top to bottom.

• The algorithm of the software does not store the slope for every grid cell. Instead, a slope accumulator keeps track of the total slope, and a cell count accumulator counts how many cells have had their slope calculated.
• The slope is only calculated in four directions (shown as blue lines in the illustration). The other four directions (grey lines) do not need to be calculated again because they were already processed in the previous row of cells.
• Only the cells within the subbasin boundary are considered. Cells outside the boundary are skipped.
• For each cell, the slope is calculated in all four directions, and the absolute value of each slope is determined. The slope can represent either an upward or downward gradient, but by taking the absolute value, the algorithm is only concerned with the steepness or rate of change, not the direction (up or down). For example, a slope of -5 (downward) and a slope of +5 (upward) both have an absolute value of 5, focusing purely on the steepness.
• The direction with the steepest slope is assigned to the cell whose slope is being computed. This maximum slope value is added to the slope accumulator, and the cell count accumulator is increased by one.
• The above algorithm is repeated for every cell in the subbasin.

For the above illustration, the following equations are used to compute the cell slopes:

Where, abs = Absolute slope value

Note: The subbasin slope is equal to the slope accumulator divided by the cell count accumulator.

Compute Slopes Command

Follow these steps to use the Compute Slopes command:

1. From the Watershed ribbon menu, select the Compute Slopes command.
   
2. The Compute Slopes dialog box will be displayed.
   

The following sections describe how to use the Compute Slopes command and interact with the above dialog box.

Selecting Subbasins

The Select Subbasins section includes a table that lists all the subbasins contained within the current scenario.

This section is used to manually select subbasins from the Map View. If a subbasin is already selected on the Map View prior to running this command, the same subbasin will be shown selected within the table.

Alternatively, click the [Pick] button to interactively select subbasins from the Map View. Clicking on the [Pick] button will cause the dialog box to temporarily disappear, allowing the user to select subbasins from the Map View. Upon returning to the Compute Slopes dialog box, the total number of selected subbasins will be displayed in the Total selected entry.

Selecting Terrain Surface

The Terrain surface dropdown combo box lists all the elevation grids (i.e., DEMs) loaded in the project. Select the elevation grid to be used in computing the subbasin slope.

Computing Subbasin Slopes

Once the data have been defined in the Compute Slopes dialog box, click the [Compute] button. The software will then look at each subbasin selected and compute the average overland flow slope for each subbasin.

After the slopes are computed, the values will be shown in the Computed Slope (ft/ft) editable column, as shown below. The software also allows the user to modify these computed values.

Once the slope is computed, all stormwater runoff methods that require a subbasin slope will have the data populated into the appropriate fields.

Hydrology methods are used to estimate runoff volumes, peak flow rates, and the manner by which rainfall interacts with land surfaces. These methods help engineers design effective drainage and flood control systems, and stormwater infrastructure.

GeoSTORM includes several methods for modeling physical runoff processes. The user can select the most suitable hydrology method based on data availability (e.g., Rainfall data, soil properties, land use/land cover data, etc.) and project requirements. Selecting the right hydrology method ensures accurate modeling, reduces flood risks, and supports sustainable stormwater management.

The following hydrology methods are supported:

• DeKalb Rational
• EPA SWMM
• Modified Rational
• Rational Method
• SCS TR-20/TR-55

Follow the steps below to select a hydrology method in GeoSTORM:

1. From the Input ribbon menu, click the Scenario Manager dropdown menu, and select the Scenario Manager command.
2. The Scenario Manager dialog box will be displayed, as shown below.
3. From the Hydrology analysis engine dropdown combo box, select the hydrology method to use. Refer to this article in our knowledge base to learn more about the Scenario Manager command.

The following sections describe each hydrology method available in GeoSTORM.

DeKalb Rational Method

The DeKalb Rational method was developed by DeKalb County Public Works Department located in Decatur, Georgia. This method computes runoff ordinates by scaling the peak discharge by a scale factor. One of the deficiencies of the Rational method is that it produces only a peak rate of runoff and not a complete flood hydrograph. The DeKalb County Dimensionless Hydrograph method was developed to generate a flood hydrograph based on the Rational Formula and the unit hydrograph theory. This hydrology method can be used with either the hydrodynamic or kinematic wave hydraulic routing methods for computing flows through a stormwater network.

The application of this method includes designing detention ponds and outlet drainage structures. This method assumes that the land uses in the subbasin are homogeneously distributed. If a large portion of a residential subbasin contains commercial, woodland, or other non-residential land use, the subbasin should be further subdivided into separate smaller homogeneous subbasins when using the hydrology method. This hydrology method can be used for calculating runoff hydrographs for subbasins of less than 10 acres.

Limitations

• Limited to small subbasin areas (less than 10 acres).
• Assumes uniform land use within the subbasin.
• Not suitable for large or complex watersheds.

EPA SWMM Method

The EPA SWMM hydrology method is used to simulate how rainfall turns into surface and subsurface runoff for both single storm and long-term (continuous) events. It is primarily applied in urban and suburban areas and operates on a collection of subcatchments within a subbasin. These subcatchments receive precipitation and generate runoff after simulation of evaporation and infiltration losses from the subcatchments.

In EPA SWMM, each subcatchment is conceptualized as a nonlinear reservoir to simulate the rainfall-runoff process. Unlike traditional hydrology methods that rely on simplified empirical equations, EPA SWMM dynamically models runoff by continuously solving a water balance equation.

In the nonlinear reservoir model, inflow components include precipitation and any designated upstream subcatchments. Outflow components include infiltration, evaporation, and surface runoff. The reservoir capacity is defined by maximum depression storage, which represents the surface storage due to ponding, interception, and surface wetting. Surface runoff occurs when the water level in the reservoir exceeds the maximum depression storage, with the outflow calculated using Manning's equation. The depth of water over the subcatchment is continuously updated with time by solving numerically a water balance equation.

The image below illustrates how rainfall runoff is modeled using a nonlinear reservoir model.

The EPA SWMM method calculates the rainfall runoff value using the following equation:

Where:

𝑄 = Flow rate (cfs or m³/s)

𝑛 = Manning’s roughness coefficient

𝐴 = Flow area (ft² or m²)

𝑅 = Hydraulic radius (ft or m)

𝑆 = Slope of the subcatchment

Since the flow area and hydraulic radius depend on the evolving depth of water in the subcatchment, EPA SWMM solves this equation iteratively over time to update runoff conditions dynamically

Limitations

• Requires accurate parameter estimation (e.g., roughness, depression storage).
• Not optimized for real-time monitoring or operational control.

Rational Method

The Rational method is a simplified approach used to estimate peak flow rates for stormwater design when hydrograph information is not required. It is widely used in urban drainage design, particularly for sizing storm sewers. For example, this method is commonly used when designing catch basin inlets because it provides a peak flow value that helps determine captured flow, bypass flow, and gutter spread.

The Rational method estimates the peak flow rate using the following equation:

Q = CIA

Where:

Q = Peak flow rate (acre-inch/hr)

C = Dimensionless runoff coefficient used to adjust for the rainfall abstraction, where C has been adjusted with the storm frequency factor

I = Rainfall intensity for a duration equal to the time of concentration of the individual basin (inch/hr)

A = Basin area (acres or hectares)

Limitations

• Limited to small drainage areas (not recommended for areas larger than 100 - 200 acres).
• Not recommended for storage volume design, like detention pond sizing.
• Less accurate for complex basins with varied land uses or topography changes.

Modified Rational Method

The Modified Rational method extends the Rational method by generating a runoff hydrograph, which provides flow variation over time instead of just a peak flow. It is commonly used for detention pond sizing.

This method first applies the following equation to estimate the peak flow rate:

Q = CIA

Then, the hydrograph is computed based on the following assumptions:

• Time of Concentration (Tc) = Time to Peak (Tp) = Time to Recede (Tr)
• The length of the Critical Duration Storm (De) is from 0 minutes until the time of selected duration.
• The flow rate is 0 at time 0 minutes, which increases linearly with time until the peak flow rate is reached at time Tp.
• The peak flow rate is maintained from time Tp until the duration of the Critical Duration Storm (De). The flow rate then decreases to 0 at time De plus Tr.
• The peak flow rate is based on the average rainfall intensity (I) for the given storm duration.

Limitations

• Same limitations as the Rational method, so it is not good for large or complex areas.
• Assumes uniform rainfall intensity, which may not match real storm patterns.
• Better suited for urban areas with well-defined drainage systems.

SCS TR-20/TR-55 Method

The Soil Conservation Service (SCS) TR-20 and TR-55 methods are widely used hydrologic models developed by the USDA Natural Resources Conservation Service (NRCS, formerly SCS). These methods estimate stormwater runoff based on rainfall, land use, and watershed characteristics, making them essential for designing drainage systems, flood control structures, and stormwater management plans.

SCS TR-20

SCS TR-20 is a complex hydrologic model designed for the simulation of rainfall runoff occurring from a single storm event in watersheds of any size. It provides a detailed flood hydrograph from rainfall runoff and routes the flow through stream channels and reservoirs. Hydrographs, peak discharges, and peak elevations can be obtained at any cross section along the stream at the outlet of a structure. The application of this method includes designing detention ponds and reservoirs, floodplain analysis, FEMA flood mapping, etc.

SCS TR-55

SCS TR-55 is a simplified hydrologic model designed for estimating peak discharge and runoff volume in small watersheds (typically less than 25 square miles). The application of this method includes designing small urban and rural watersheds (≤10 mi² or 6,400 acres).

Limitations

• Less accurate for small storm events.
• Assumes uniform soil and land use, which may not reflect groundwater variations.
• Uses predefined design storms that may not match actual rainfall events.
• Not suitable for detailed urban drainage systems or engineered infrastructure.

Hydrology Method Comparisons

In GeoSTORM software, the Import Stormwater Shapefile Geometry command is used to import GIS geometry data shapefiles to create a new stormwater project.

Follow the steps below to use the Import Stormwater Shapefile Geometry command:

1. From the Input ribbon menu, click on the Import Data dropdown menu and select the Import Stormwater Shapefile Geometry command.
   
2. The Import Stormwater Shapefile Geometry dialog box will be displayed.
   

The following sections describe how to use the Import Stormwater Shapefile Geometry command and interact with the above dialog box.

Subbasins

The Subbasins panel allows the user to import the subbasin geometry using the polygon shapefile, which can be used to define the subbasin elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Subbasins panel to enable the content of this panel.

Note that the subbasin shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Subbasin Shapefile Data

The following options are available in this section:

• Polygon Shapefile: This dropdown combo box allows the user to select the subbasin shapefile to be imported into the stormwater project. This dropdown combo box lists only polygon shapefiles.
• Subbasin ID field: This naming option allows the user to define the subbasin ID using the subbasin attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name subbasin ID: This radio button option allows the user to automatically specify the ID for each subbasin. The user can assign these IDs using a predefined format or by manually defining the format of the ID.

The different subbasin naming formats present in the Auto-name subbasin ID option are as follows:

• 1. Subbasin ID prefix: This checkbox entry allows a prefix to be added to the subbasin ID.
  2. Subbasin ID digits: This entry field allows the user to set the number of digits to be used for subbasin ID. For example, using 3 digits causes the subbasin ID to be of the format 001, 002, and 003.
  3. Next available subbasin ID: This entry field defines the next subbasin ID number to be used.
  4. Subbasin ID increment: This entry field defines the increment to use when numbering subbasins. The default value is 1.
  5. Subbasin ID suffix: This checkbox entry allows a suffix to be added to the subbasin ID.
  6. Subbasin ID preview: This read-only field provides a preview of the subbasin ID defined in this section.
• Drainage area field: This dropdown combo box allows the user to define the subbasin area using the subbasin attributes defined in the shapefile data. The user can select the attribute field from the dropdown combo box provided next to this option. This dropdown combo box lists only those attributes that contain numeric values.
• Compute drainage area from subbasin polygons (for missing data): This checkbox option causes the software to automatically compute the drainage area from the digitized polygon. This option allows the user to compute drainage area when data are missing or present an unreadable value. Note that this option is checked by default.

Other Subbasin Shapefile Data

This section allows the user to define various subbasin properties using the subbasin attributes defined in the imported shapefile data as:

• Curve number
• Impervious data
• Lag time
• Time of concentration, and
• Overland flow slope

Subbasin Network Connectivity Options

The following options are available in this section:

• Downstream connection element field: This dropdown combo box allows the user to select downstream connection element attributes within the set snap distance that the selected subbasin drains to.
• Auto-snap to downstream connection element (for missing data): While importing GIS data, if downstream connection data are missing or do not match other elements, the software will automatically search the nearest node for the digitized polygon. In this subsection, the Element connection snap distance entry field allows the user to define the search distance to snap the subbasin to an element.Alternatively, the user can click the […] button to measure the snap distance from the Map View. The auto-snap option can be utilized for the following project elements:
  1. Manhole and junctions
  2. Pipes and reaches
  3. Ponds and storage areas

Manholes

The Manholes panel allows the user to import the manhole geometry using the node shapefile, which can be used to define manhole elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Manholes panel to enable the content of this panel.

Note that the manhole shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Manhole Shapefile Data

This section contains the following options:

• Node shapefile: This dropdown combo box allows the user to select the manhole shapefile to be imported into the stormwater project. This dropdown combo box lists only node shapefiles.
• Manhole ID field: This naming option allows the user to define the manhole ID using the manhole attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name manhole ID: This radio button option allows the user to automatically specify the ID for each manhole. The user can assign these IDs using a predefined format or manually define the format of the ID. Note that this auto-name option is similar to the Auto-name subbasin ID option explained above for the Subbasins panel.

Assign Rim Elevation

This section contains the following options:

• Rim elevation field: This dropdown combo box allows the user to assign the manhole rim elevation using the manhole attributes defined in the imported shapefile data. This dropdown combo box lists only those attributes that contain numeric values.
• Compute rim elevation from terrain surface (for missing data): If the imported manhole rim elevation data contain missing or unreadable values, this section causes the software to automatically compute the rim elevation from the defined terrain surface. To assign rim elevation, the Terrain elevation source dropdown combo box supports the following surface types:
  1. CAD Drawing
  2. Elevation Grid
  3. GIS Contours
  4. LandXML Data
  5. Terrain Surface
  6. TIN Surface

  Based on the selected terrain elevation source, the content of the Assign Rim Elevation section will change accordingly.

Assign Invert Elevation

This section contains the following options:

• Invert elevation field: This dropdown combo box allows the user to assign the manhole invert elevation using the manhole attributes defined in the imported shapefile data. The dropdown combo box lists only those attributes that contain numeric values.
• Compute invert elevation from terrain surface (for missing data): If the imported invert elevation data for the manhole contain missing or unreadable values, this section causes the software to automatically compute the invert elevation from the defined terrain surface. To assign invert elevation, the Terrain elevation source dropdown combo box supports the following surface types:
  1. CAD Drawing
  2. Elevation Grid
  3. GIS Contours
  4. LandXML Data
  5. Terrain Surface
  6. TIN Surface

  Based on the selected terrain elevation source, the content of the Assign Invert Elevation section will change accordingly.

• Manhole depth field: This dropdown combo box allows the user to define an invert depth by raising or lowering the invert of the manhole by the specified amount.
• Default depth (for missing data): If during computation of the invert elevation data, the terrain surface data are missing or contain unreadable values for manhole depth, this entry causes the software to assume a manhole depth to compute the invert elevation from the defined terrain surface.
• Manhole sump depth field: This dropdown combo box entry allows the user to define sump depth for the defined manholes.
• Default sump depth (for missing data): If during computation of the invert elevation data, the terrain surface data are missing or contain unreadable values for manhole sump depth, this entry causes the software to automatically compute the invert elevation from the defined terrain surface.

Junctions

The Junctions panel allows the user to import the junction geometry using the node shapefile, which can be used to define junction elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Junctions panel to enable the content of this panel.

Note that the junction shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Routing Junction Shapefile Data

This section contains the following options:

• Node shapefile: This dropdown combo box allows the user to select the junction shapefile to be imported into the stormwater project. This dropdown combo box lists only node shapefiles.
• Routing junction ID field: This naming option allows the user to define the routing junction ID using the junction attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name routing junction ID: This radio button option allows the user to automatically specify the ID for each routing junction. The user can assign these IDs using a predefined format or manually define the format of the ID. Note that this auto-name option is similar to the Auto-name subbasin ID option explained above for the Subbasins panel.

Assign Routing Junction Elevation

This section contains the following options:

• Routing junction elevation field: This dropdown combo box allows the user to select the junction elevation using the junction attributes defined in the imported shapefile data. This dropdown combo box lists only those attributes that contain numeric values.
• Compute routing junction elevation from terrain surface (for missing data): If the imported junction elevation data contain missing or unreadable values, this section causes the software to automatically compute the routing junction elevation from the defined terrain surface. To assign routing junction elevation, the Terrain elevation source dropdown combo box supports the following surface types:
  1. CAD Drawing
  2. Elevation Grid
  3. GIS Contours
  4. LandXML Data
  5. Terrain Surface
  6. TIN Surface

  Based on the selected terrain elevation source, the content of the Assign Routing Junction Elevation section will change accordingly.

Storage Areas

The Storage Areas panel allows the user to import the storage area geometry using the polygon shapefile, which can be used to define the storage area elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Storage Areas panel to enable the content of this panel.

Note that the storage area shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Storage Area Shapefile Data

This section contains the following options:

• Polygon shapefile: This dropdown combo box allows the user to select the storage area shapefile to be imported into the stormwater project. This dropdown combo box lists only polygon shapefiles.
• Storage Area ID field: This naming option allows the user to define the storage area ID using the storage area attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name storage area ID: This radio button option allows the user to automatically specify the ID for each storage area. The user can assign these IDs using a predefined format or manually define the format of the ID. Note that this auto-name option is similar to the Auto-name subbasin ID option explained above for the Subbasins panel.

Assign Invert Elevation

This section is similar to the Assign Invert Elevation section of the Manholes panel. Refer to this section of this article as explained above.

Storage Area Network Connectivity Options

This section is similar to the Subbasin Network Connectivity Options section of the Subbasins panel. Refer to this section of this article as explained above.

Pipes

The Pipes panel allows the user to import the pipe geometry using the polyline shapefile, which can be used to define the pipe elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Pipes panel to enable the content of this panel.

Note that the pipe shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Pipe Shapefile Data

This section contains the following options:

• Polyline shapefile: This dropdown combo box allows the user to select the pipe shapefile to be imported into the stormwater project. This dropdown combo box lists only polyline shapefiles.
• Pipe ID field: This naming option allows the user to define the pipe ID using the pipe attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name pipe ID: This radio button option allows the user to automatically specify the ID for each pipe. The user can assign these IDs using a predefined format or manually define the format of the ID. Note that this auto-name option is similar to the Auto-name subbasin ID option explained above for the Subbasins panel.

Other Pipe Shapefile Data

This section contains the following sections:

• Pipe diameter field: This dropdown combo box allows the user to define the pipe diameter using the pipe attributes defined in the imported shapefile data.
• Default diameter (for missing data): If during the importing of the pipe diameter data, the data are missing or contain unreadable values, this entry causes the software to assign a default diameter to the pipe.
• Pipe Manning’s roughness field: This dropdown combo box allows the user to define Manning’s roughness for the pipe using the pipe attributes defined in the imported shapefile data.
• Default roughness (for missing data): If during the importing of the pipe roughness data, the data are missing or contain unreadable values, this entry causes the software to assign a default roughness for the pipe. Clicking the […] lookup button allows the user to view the reference Manning’s roughness values.
• Upstream invert elevation field: This dropdown combo box allows the user to define upstream invert elevation using the pipe attributes defined in the imported shapefile data.
• Downstream invert elevation field: This dropdown combo box allows the user to define downstream invert elevation using the pipe attributes defined in the imported shapefile data.
• Default sump depth (for missing data): If during the importing of the pipe invert data, the data are missing or contain an unreadable value, this entry causes the software to automatically compute the pipe inverts using the defined sump depth and the connecting manhole invert elevations.
• Pipe length field: This dropdown combo box allows the user to define pipe length using the pipe attributes defined in the imported shapefile data.
• Compute lengths for missing pipe length data: If there is missing or unreadable data while importing pipe length data, enabling this checkbox option will cause the software to automatically calculate the pipe length based on the digitized pipe polyline.

Pipe Network Connectivity Options

This section contains the following options:

• Upstream connecting node ID field: This dropdown combo box allows the user to define the upstream connection node ID using the pipe attributes defined in the imported shapefile data.
• Downstream connecting node ID field: This dropdown combo box allows the user to define the downstream connection node ID using the pipe attributes defined in the imported shapefile data.
• Compute nearest node connection for missing pipe connectivity data: If during the importing of the connection element data, data are missing or do not correspond to any other element in the imported GIS data, this checkbox option causes the software to automatically determine the closest node for the digitized pipe end. This checkbox is checked by default.
• Create manholes (if missing) at pipe ends: This checkbox option will create a manhole at the pipe end if there is no node already defined within the connection snap distance. The manhole rim elevation is set equal to the terrain surface elevation. The manhole invert elevation is set equal to the pipe invert elevation. This entry is checked by default.
• Connection snap distance: This entry field defines the search distance to snap the pipe end to a node (i.e., manhole or junction) element or a storage area element. Alternatively, the user can click the […] button to measure the snap distance from the Map View.
• Correct pipe direction (flip end for end) to maintain downstream pipe slope: If after importing it is determined that the GIS definition of upstream and downstream pipe ends is backward (as the pipe should always slope downstream), this checkbox option causes the pipe ends to be flipped.
  Note that whenever this issue occurs, it is reported in the Shapefile Import Validation Report.

Reaches

The Reaches panel allows the user to import the routing reach geometry using the polyline shapefile, which can be used to define the routing reach elements. By default, the content of this panel is disabled (i.e., grayed out). Select the checkbox option at the Reaches panel to enable the content of this panel.

Note that the routing reach shapefile should be loaded before using this panel. Otherwise, no geometry will be imported.

General Routing Reach Shapefile Data

This section contains the following options:

• Polyline shapefile: This dropdown combo box allows the user to select the routing reach shapefile to be imported into the stormwater project. This dropdown combo box lists only polyline shapefiles..
• Routing Reach ID field: This naming option allows the user to define the routing reach ID using the routing reach attributes defined in the imported shapefile data. The adjacent dropdown combo box lists only those attributes that contain text.
• Auto-name routing reach ID: This radio button option allows the user to automatically specify the ID for each routing reach. The user can assign these IDs using a predefined format or manually define the format of the ID. Note that this auto-name option is similar to the Auto-name subbasin ID option explained above for the Subbasins panel.

Other Routing Reach Shapefile Data

This section contains the following options:

• Channel bottom width field: This dropdown combo box allows the user to define the channel bottom width of reach using the reach attributes defined in the imported shapefile data.
• Default bottom width (for missing data): If during the importing of the channel bottom width data, data are missing or contain an unreadable value, this entry causes the software to automatically assign the channel bottom width using the defined value.
• Channel height field: This dropdown combo box allows the user to define the channel height of reach using the reach attributes defined in the imported shapefile data.
• Default channel height (for missing data): If during the importing of the channel height data, data are missing or contain an unreadable value, this entry causes the software to automatically assign the channel height using the defined value.
• Channel side slope field (V:H): This dropdown combo box allows the user to define the channel side slope using the reach attributes defined in the imported shapefile data.
• Default side slope (for missing data, V:H): If during the importing of the channel side slope data, data are missing or contain an unreadable value, this entry causes the software to automatically assign the channel side slope using the defined value.
• Channel Manning’s roughness field: This dropdown combo box allows the user to define Manning’s roughness for the reach using the reach attributes defined in the imported shapefile data.
• Default roughness (for missing data): If during the importing of the reach roughness data, the data are missing or contain an unreadable value, this entry causes the software to assign a default roughness to the reach. Clicking the […] lookup button allows the user to view the reference Manning’s roughness values.
• Reach length field: This dropdown combo box allows the user to define reach length using the reach attributes defined in the imported shapefile data.
• Compute lengths for missing reach length data: If there are missing or unreadable data while importing reach length data, enabling this checkbox option will cause the software to automatically calculate the length based on the digitized pipe polyline.

Assign Invert Elevation

This section contains the following options:

• Upstream invert elevation field: This dropdown combo box allows the user to define the upstream invert elevation using the reach attributes defined in the imported shapefile data.
• Downstream invert elevation field: This dropdown combo box allows the user to define the downstream invert elevation using the reach attributes defined in the imported shapefile data.
• Compute invert elevation from terrain surface (for missing data): If the imported invert elevation data for the routing reach contain missing or unreadable values, this section causes the software to automatically compute the invert elevation from the defined terrain surface. To assign invert elevation, the Terrain elevation source dropdown combo box supports the following surface types:
  1. CAD Drawing
  2. Elevation Grid
  3. GIS Contours
  4. LandXML Data
  5. Terrain Surface
  6. TIN Surface

  Based on the selected terrain elevation source, the content of the Assign Invert Elevation section will change accordingly.

Routing Reach Network Connectivity Options

This section is similar to the Pipe Network Connectivity Options section of the Pipes panel. Refer to this section of this article as explained above.

Importing GIS Geometry Data Shapefiles

When all the options have been properly defined, click the [Import] button to import GIS geometry data shapefiles for the stormwater project.

After importing the stormwater shapefile geometry, the extent of the project will be displayed on the Map View.

In GeoSTORM software, the Export Project to LandXML command allows the user to export subbasins (catchments), pipes, manholes, and other related data to a LandXML file. This exported data can then be used with other applications effortlessly.

Follow the steps below to use the Export Project to LandXML command:

1. From the Input ribbon menu, click the Export Data dropdown menu and select the Export Project to LandXML command.
   
2. The Export Project to LandXML dialog box will be displayed.
   

The following sections describe how to use the Export Project to LandXML command and interact with the above dialog box.

Selecting Data to Export

The Select Data to Export section allows the user to select the subbasins and the pipe network data to be exported. This section consists of two panels:

• Subbasins
• Pipe Network

Subbasins

In the Subbasins panel, the Select Subbasins to Export section contains a radio button group, which allows the user to select the subbasins to be exported.

The following radio button options are available:

• No subbasins
  This radio button option allows the user to export the project without including any subbasins. By default, this radio button option is selected.
• All subbasins
  This radio button option allows the user to export all subbasins contained within the current scenario of the project.
• Select subbasins
  This radio button option allows the user to export specific subbasins. It includes a data grid that lists all subbasins contained within the current scenario of the project.
  
  The user can select subbasins using any of the following methods:
  
  
  1. By pressing and holding down the [Ctrl] key while selecting the subbasins directly from the Map View. After selecting subbasins, open the Export Project to LandXML dialog box, and the selected subbasins will be shown as selected/checked in the data grid under the Select subbasins option.
  2. By checking the checkboxes corresponding to each subbasin in the data grid under the Select subbasins option.
  3. By clicking the [Pick] button, the Export Project to LandXML dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the subbasins from the Map View. After selecting subbasins, pressing the [Enter] key or right-clicking and choosing Done from the displayed context menu redisplays the Export Project to LandXML dialog box.

  After selecting subbasins, the total number of selected subbasins will be displayed in the Total selected read-only field. Click the [Clear] button to cancel the previous selection and redo the entire process.
  

  

Pipe Network

In the Pipe Network panel, the Select Pipes & Connected Manholes to Export section contains a radio button group, which allows the user to select the pipes to be exported. The manholes associated with the pipes also get exported.

The following radio button options are available:

• No pipes & manholes
  This radio button option allows the user to export the project without including pipes and associated manholes. By default, this radio button option is selected.
• All pipes & connected manholes
  This radio button option allows the user to export all pipes along with their associated manholes contained within the current scenario of the project.
• Select pipes & connected manholes
  This radio button option allows the user to export specific pipes along with their associated manholes. It includes a data grid that lists all pipes contained within the current scenario of the project.
  
  The user can select pipes using any of the following methods:
  
  
  1. By pressing and holding down the [Ctrl] key while selecting the pipes directly from the Map View. After selecting pipes, open the Export Project to LandXML dialog box, and the selected pipes will be shown as selected/checked in the data grid under the Select pipes & connected manholes option.
  2. By checking the checkboxes corresponding to each pipe in the data grid under the Select pipes & connected manholes option. Note: To select all pipes at once, check the checkbox at the Pipe ID column header.
  3. By clicking the [Pick] button, the Export Project to LandXML dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the pipes from the Map View. After selecting pipes, pressing the [Enter] key or right-clicking and choosing Done from the displayed context menu redisplays the Export Project to LandXML dialog box.

  After selecting pipes, the total number of selected pipes will be displayed in the Total selected read-only field. Click the [Clear] button to cancel the previous selection and redo the entire process.
  

  

Specify LandXML Export File

In the Specify LandXML Export File section, the user can specify the file path and name for the exported LandXML file by clicking the […] browse button next to the LandXML file field.

Exporting the Project

After all the options have been defined, click the [Export] button and the software will export the project to a LandXML file at the specified location.

In GeoSTORM software, users can export their stormwater project to EPA SWMM input data files using the Export Project to EPA SWMM command. This allows the exported stormwater project to be used with EPA SWMM software.

Follow the steps below to export a stormwater project to EPA SWMM input data files:

1. From the Input ribbon menu, select the Export Project to EPA SWMM command from the Export Data dropdown combo box.
   
2. The Export EPA SWMM Project dialog box will be displayed as shown below.
   
3. From the Select EPA SWMM File Type to Export section, select one of the following radio button options:
   • EPA SWMM input data folder: Select this radio button option to export all input data files of the stormwater project into a specific folder. Click the [...] browse button to define the directory location and folder name. Note that this radio button option is selected by default.
   • EPA SWMM archive (ZIP) file: Select this radio button option to archive all input data files of the stormwater project into a single ZIP file. After selecting this radio button option, click the [...] browse button to define the directory location and ZIP file name.
4. If the user selected the EPA SWMM archive (ZIP) file radio button option, the Include output results checkbox option will be enabled. Select this checkbox option to move all analysis output files into the previously defined ZIP file.
5. From the Select Scenarios (Plans) to Export section, select one of the following radio button options:
   • All scenarios: Select this option to export all scenarios contained within the stormwater project. This radio button option is selected by default.
   • Select scenarios: Select this option to export specific scenarios. Click the dropdown combo box adjacent to this option and select the scenarios to be exported.
     
6. When all options have been properly defined, click the [Export] button to export the stormwater project to EPA SWMM input data files.

In GeoSTORM software, the Import EPA SWMM Project command allows the user to import EPA SWMM input data files to create a new stormwater project.

Follow the steps below to import an EPA SWMM input file:

1. From the Input ribbon menu, select the Import EPA SWMM Project command from the Import Data dropdown combo box.
   
2. The Import EPA SWMM Project dialog box will be displayed, as shown below.
   
3. From the Select EPA SWMM Project section, click the […] browse button to select the EPA SWMM input data file.
4. The Import EPA SWMM Project File dialog box will be displayed, as shown below.
   
5. Select the required EPA SWMM input data file and click the [Open] button.
   
6. The Import EPA SWMM Project dialog box will be redisplayed. The directory location of the selected input data file will be displayed in the EPA SWMM project file entry field.
   
7. Click the [Import] button to import the selected EPA SWMM input data file into the GeoSTORM software.

For stormwater projects, GeoSTORM software allows the user to create, edit, analyze, and review an unlimited number of variations to the project’s scenarios (or plans). Each project scenario associates a specific geometry model, storm data, and a set of analysis specifications with a specific condition or circumstance, such as pre-developed and post-developed phases of a project. This allows the user to work with multiple scenarios in a single project and analyze computational results as different parameters are applied to the project.

Elements of a Project

The following data are used to construct a complete stormwater project within a scenario:

• Geometry data – Defines the geometric representation of a model.
• Storm data – Defines precipitation data.
• Analysis specifications – Defines the configuration for start time, end time, and time interval.
• Model calibration data – References the above files when performing an analysis.

Selecting Active (Current) Scenarios

In GeoSTORM software, the Input ribbon menu displays the Scenario ID of the currently selected scenario. The read-only field below the Scenario ID dropdown combo box displays the description of the current scenario.

The Scenario ID dropdown combo box allows the user to quickly switch between scenarios. Moving from one scenario to another will cause the contents of the Map View to change to represent the geometry of the selected scenario.

From the Input ribbon menu, expand the Scenario Manager dropdown combo box and the following commands will be displayed:

• Scenario Manager
• Duplicate Current Scenario
• Delete Scenarios
• Scenario Summary

Scenario Manager

Selecting the Scenario Manager command will display the below dialog box. The Scenario Manager dialog box displays the details of the currently selected scenario in the project.

This dialog box is used to manage geometry data, storm data, analysis specifications and model calibration data associated with the current scenario. In addition, a new scenario, geometry model, storm model, and analysis specifications can be created, as well as copied from an existing scenario.

The following sections describe how to use the Scenario Manager command and interact with the above dialog box.

Scenario (Simulation Run)

This section allows the user to create new scenarios as well as manage existing scenarios. The Scenario (simulation run) dropdown combo box lists all the scenarios in the project. The user can select the preferred scenario to view or modify its corresponding data. The other sections of the dialog box will be updated based on the user’s selection.

To create a new scenario, the user can select the Add New Scenario option from the Scenario (simulation run) dropdown combo box or alternatively, click the [New] button in the section. This will apply the default settings to the other sections of the Scenario Manager dialog box. The user can then specify the details for geometry, storm, analysis, and calibration in their respective sections.

To copy the current scenario for use in another scenario, the user can click the [Copy] button. To delete the currently selected scenario, the user can click the [Delete] button.

Geometry

The Geometry panel outlines the geometry data (i.e., subbasins, pipes, routing reaches, manholes, junctions, 2D mesh, etc.) that defines a model.

The Geometry data dropdown combo box lists all existing geometry models in the current project. In addition, the adjacent Edit icon allows the user to edit the selected geometry model ID.

The Terrain surface dropdown combo box lists the existing terrain surfaces in the project. Note that the user can select the blank option from the Terrain surface dropdown combo box to disassociate a terrain surface from the selected geometry model.

The user can define a new geometry model, copy the details of an existing geometry model to use in another geometry model, and delete the selected geometry model using the [New], [Copy], and [Delete] buttons, respectively.

Storm

The Storm panel outlines the storm specifications (i.e., rainfall, distribution, etc.) that define the boundary conditions applied to the model.

The Rainfall data dropdown combo box lists all the existing storm models in the current project. Any descriptive information about the storm model can be included in the Description text box.

The user can define a new storm model, copy the details of an existing storm model to use in another storm model, and delete the selected storm model using the [New], [Copy], and [Delete] buttons, respectively.

Analysis

The Analysis panel defines the analysis specifications that are used in running the stormwater analysis for the defined model.

The Analysis data dropdown combo box lists all the existing analysis specifications in the current project. Any descriptive information about the analysis specification can be included in the Description text box.

The user can define a new analysis specification, copy the details of an existing analysis specification to use in another analysis specification, and delete the selected analysis specification using the [New], [Copy], and [Delete] buttons, respectively.

Note that the Analysis panel is disabled (i.e., grayed out) when the Rational Method option is selected in the Hydrology analysis engine dropdown combo box of the Analysis Options section.

Calibration

The Calibration panel is used to define the model calibration data.

The following entries are available in this panel:

• Calibration type
• Calibration multiplier (ratio)

Calibration type

The Calibration type dropdown combo box allows the user to select the type of calibration to aid the simulation run.

Note that the Calibration panel is enabled only when the SCS TR-20/TR-55 option is selected from the Hydrology analysis engine dropdown combo box of the Analysis Options section.

The following options are available in this dropdown combo box:

• None (default)
• Flow
• Precipitation

Calibration multiplier (ratio)

The Calibration multiplier (ratio) spin control defines the multiplication ratio to be applied to the data. By default, this entry is listed as 1.000. The spin control will go up and down in increments of 0.010.

Analysis Options

The Analysis Options section is used to define analysis options within a project.

The following entries are used to define the analysis options:

• Hydrology analysis engine
• EPA SWMM infiltration method
• Flow routing method
• Precipitation type

Hydrology analysis engine

This dropdown combo box defines the hydrology method to be used in the project. Note that the default selection is determined by the option defined in the Analysis Options section of the Options backstage page.

The following options are available:

• EPA SWMM
• Modified Rational
• Rational Method
• SCS TR-20/TR-55

EPA SWMM infiltration method

This dropdown combo box defines the EPA SWMM infiltration method to be used in the project. Note that the default selection is determined by the option defined in the Analysis Options section of the Options backstage page.

The following options are available:

• Green Ampt
• Horton
• Modified Green Ampt
• Modified Horton
• SCS Curve Number

Note that the EPA SWMM infiltration method dropdown combo box is enabled only when the EPA SWMM option is selected from the Hydrology analysis engine dropdown combo box.

Flow routing method

This dropdown combo box entry defines the routing method to be used in the project. The following options are available in this dropdown combo box:

• Hydrodynamic
• Kinematic Wave
• Steady State Peak Flow

Note that the default selection is determined by the option defined in the Analysis Options section of the Options backstage page.

Precipitation type

This dropdown combo box entry defines the precipitation type to be used in the project. Note that the default selection is determined by the option defined in the Analysis Options section in the Options backstage page.

Note that the options displayed in the Precipitation type dropdown combo box will change based on the option selected in the Hydrology analysis engine dropdown combo box.

If the user selects the EPA SWMM option in the Hydrology analysis engine dropdown combo box, the following options will be displayed in the Precipitation type dropdown combo box.

• Rain Gage
• Rainfall Distribution

If the user selects the SCS TR-20/TR-55 option in the Hydrology analysis engine dropdown combo box, the following options will be displayed in the Precipitation type dropdown combo box.

• HMR52 Storm
• Rainfall Distribution
• SCS Storm

Note that the Precipitation type dropdown combo box is disabled (i.e., grayed out) when either the Rational Method or Modified Rational option is selected in the Hydrology analysis engine dropdown combo box.

Duplicate Current Scenarios

The Duplicate Current Scenario command allows the user to make an identical copy of the current scenario (simulation run). Once the copy has been made, it is independent of the original and they do not interact.

To learn more about the Duplicate Current Scenario command, refer to this article in our knowledge base.

Delete Scenarios

The Delete Scenarios command allows the user to delete data that no longer apply to the project and should not be submitted as part of the project. The following types of data can be removed: Scenario (simulation run), Geometry, Storm, and Analysis Specification.

To learn more about the Delete Scenarios command, refer to this article in our knowledge base.

Scenario Summary

In the Scenario Manager dialog box, clicking on the [Summary] button will display an informational dialog box that provides information for all scenarios contained in a project. It includes a complete summary of all the scenarios, geometry models, storm models, analysis specifications, and other details of the current scenario.

Alternatively, the user can view the scenario summary by selecting the Scenario Summary command from the Scenario Manager dropdown combo box.

To learn more about the Scenario Summary command, refer to this article in our knowledge base.

Multiple Plan Analysis

Computations on the multiple scenarios can be performed sequentially (one immediately after the other) using the Multiple Scenarios command.

To learn more about the Multiple Scenarios command, refer to this article in our knowledge base.

Displaying Multiple Scenario Results

After the computations have been performed, the software can display results from multiple scenarios for all elements (i.e., subbasins, pipes, manholes, routing junctions, etc.).

To view the output results, select the Plot Hydrographs command from the Results ribbon menu.

The Plot Hydrographs dialog box will be displayed.

The above dialog box has separate panels (i.e., Subbasins, Pipes, Routing Reaches, Roadway Crossings etc.) to show output results for each element type present in the project. Within each element type panel, the user can select the preferred scenario from the Scenarios dropdown combo box of the Select Items panel.

The Variables dropdown combo box allows the user to select the desired output variables associated with an element type whose results are to be displayed.

Note that the Variables dropdown combo box is not available in the Result Summary panel. The Result Summary panel displays the summary of the current stormwater analysis results for each element in tabular form.

All elements (corresponding to the element type) present in the stormwater model of the selected scenario will be displayed under the Elements section. The user can check the checkbox corresponding to the preferred element(s) from the Elements section to see output results associated with them. Alternatively, the user can click the [Pick Elements] button to select the element(s) from the Map View. The user can click the [Clear Elements] button to clear the selected element(s). The output results related to the selected element(s) will be displayed under the Plots, Data Tables and Data Summary panels.

The Delete Scenarios command in GeoSTORM allows the user to select and delete scenario data, geometry data, storm data, and analysis specification data from a project. This command helps to reduce project file size by deleting data that are no longer relevant to a project or otherwise necessary.

Follow the steps below to use the Delete Scenarios command:

1. From the Input ribbon menu, select the Delete Scenarios command from the Scenario Manager dropdown combo box.
   
2. The Delete Scenarios dialog box will be displayed. This dialog box displays scenario (simulation run), geometry, storm, and analysis specification data associated with the project.
   
3. Select the checkboxes corresponding to scenario, geometry, storm, and analysis specification data that needs to be removed from the project.
4. Click the [Delete] button.
   
5. The software will successfully delete the selected scenario, geometry, storm, and analysis specification data.

Note that after the scenario data have been deleted from the project, they cannot be recovered with the Undo command. However, if the project is not saved, then the user can reload the project and the scenario data will still be present. Alternatively, if the project has been saved, then the project backup file can be used to recover the previous state of scenario data.

The Duplicate Current Scenario command in GeoSTORM allows the user to make an identical copy of the current scenario. This copy is independent of and does not interact with the original after it has been created. If required, the user can also create copies of the current geometry model, storm model, or analysis specification data.

Follow the steps given below to use the Duplicate Current Scenario command:

1. From the Input ribbon menu, select the Duplicate Current Scenario command from the Scenario Manager dropdown combo box.
   
2. The Duplicate Current Scenario dialog box will be displayed, as shown below.
   
3. Enter the scenario name in the Scenario (simulation run) entry field to create an identical copy of the current scenario. By default, the Scenario (simulation run) checkbox is checked. If unchecked, then the Scenario (simulation run) and Description entries are disabled.
4. Enter the description in the Description entry to describe the scenario.
5. By default, the software utilizes the current scenario’s geometry model, storm data, and analysis specifications for the duplicated scenario.
6. Additionally, the user can check the Geometry model, Storm data, and Analysis specification checkboxes to create identical copies of the current scenario’s geometry, storm, and analysis specification data. Note that this is useful when creating alternative designs for comparison.
7. Click the [Apply] button.
   
8. A copy of the current scenario will be successfully created.

In GeoSTORM, the Scenario Summary command provides an overview of all scenarios, geometry models, storm models, analysis specifications and other details (such as element details, modeling specifications, and storm data) associated with a project.

Follow the steps given below to use the Scenario Summary command:

1. From the Input ribbon menu, select the Scenario Summary command from the Scenario Manager dropdown combo box.
   
2. The Scenario Summary dialog box will be displayed, as shown below.
   
   Note that the Scenario Summary dialog box can also be displayed by clicking the [Summary] button of the Scenario Manager dialog box.
   

The below sections describe the information displayed in the Scenario Summary dialog box.

General Information

This section displays the project name, the project run file name, and the directory path for the project. It also displays a read-only field containing the project description added by the user.

Scenario (Geometry Models)

This section lists the names of all scenarios and their corresponding geometry models, storm models and analysis specifications in a tabular format. The current scenario of the project is selected by default. The user can select a scenario and its corresponding storm model and analysis specification will also be selected in the Storm Models and Analysis Specifications sections.

Storm Models

This section lists all storm models associated with the project.

Analysis Specifications

This section lists all analysis specifications associated with the project.

Current Simulation Run Detailed Information

This section provides detailed information relating to the scenario selected in the Scenario (Geometry Models) section.

Element Details

The Element Details panel lists all the elements contained within the selected scenario (e.g., subbasins, junctions, manholes, pipes, etc.).

Modeling Specifications

The Modeling Specifications panel lists the selected hydrology engine and other modeling specifications defined for the selected scenario.

Storm Data

The Storm Data panel lists the precipitation type and other related storm data defined for the selected scenario.

Note that by clicking the [Copy to Clipboard] button, the contents of the Scenario Summary dialog box is copied to the Windows clipboard.

The GeoSTORM software includes functionality that permits the user to perform analysis on multiple scenarios (plans) at the same time. The Multiple Scenarios command can be used to perform computations on multiple plans sequentially (one immediately after the other). The user can specify which scenarios to compute, and the order in which they should be computed.

This article describes how to use the Multiple Scenarios command in the GeoSTORM software.

Follow the steps below to use the Multiple Scenarios command:

1. From the Analysis ribbon menu, click the Compute Analysis dropdown menu and select the Multiple Scenarios command.
   
2. The Compute Analysis – Multiple Scenarios dialog box will be displayed.
   
3. From the Available Scenarios section, check the checkboxes corresponding to the scenarios that needs to be computed. The user can also navigate between the scenarios using the up and down arrow buttons.
   
   Note: To select/deselect all scenarios at once, check/uncheck the Compute Scenario checkbox option.
4. Check the Show only selected scenarios checkbox option to hide unselected scenarios in the data grid as shown below. By default, this checkbox option is unchecked.
   
5. Click the [Compute] button to start the analysis.
6. Once the analysis is performed, the name of the scenario selected for analysis is displayed in the Scenario being analyzed read-only field of the Analysis Summary section. In addition, the elapsed analysis time is displayed in the Elapsed analysis time read-only field.
   
7. Once the analysis is complete, the status will be displayed in the Analysis Progress read-only section as shown below.
   
   Note: If the Exit status is equal to 0, the analysis was successful. If the Exit status is equal to -1, the analysis failed, and the corresponding error(s)/warning(s) will be displayed under the Analysis Progress read-only section.
   
8. The user can click the [Copy to Clipboard] button to copy the computed analysis progress into the clipboard.

Once the analysis has been computed successfully, the user can evaluate the results of the simulation to ensure that they are reasonable and consistent. The user can click the [Close] button to close the dialog box.

In GeoSTORM, the appearance of stormwater model elements in the Map View can be customized using the Stormwater Properties dialog box. This dialog box allows the user to adjust colors, line thicknesses, symbol sizes, label visibility and placement, border styles, fill colors, transparency, and other display settings for each type of stormwater element shown on the Map View.

Customizing these display properties is especially useful when working with dense models in which multiple element types overlap, preparing Map Views for reports or project deliverables, or maintaining a consistent visual standard across a project team.

The user can change the display properties of the following stormwater elements shown on the Map View:

• Cross Sections
• Junctions
• LID Structures
• Manholes
• Pipes
• Rain Gages
• Reaches
• Roadway Crossings
• Roadway Gutters
• Storage Areas
• Subbasin TOC/Lag Time Flow Paths
• Subbasins
• Terminal Outfalls
• and more…

Follow the steps below to view or edit the display properties of stormwater elements:

1. In the Map Data Layers panel, click the […] button next to the Stormwater layer.
   unknown node
2. The Stormwater Properties dialog box will be displayed.
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The Stormwater Properties dialog box contains the following panels:

• General Options
• Spatial Reference
• Transformation
• Label Options

General Options

The General Options panel is used to adjust the display properties for all stormwater element types shown on the Map View. The following sections are available in this panel:

Subbasin Display Properties

This section is used to configure the display properties of subbasins on the Map View.

The following options are available in this section:

• Subbasin
  This checkbox option is used to enable or disable the display of subbasins and their associated properties on Map View.
• Subbasin symbol
  This checkbox option allows the user to change the size of the subbasin symbol. Unchecking this option hides all subbasin symbols from the Map View. The size of subbasin symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.
• Subbasin connection line
  This checkbox option allows the user to change the thickness, color, and style of the subbasin connection lines. Unchecking this option hides all subbasin connection lines from the Map View. The user can set the thickness of the subbasin connection lines on a scale of 1 to 11 using the adjacent spin control entry field.
• Subbasin border
  This checkbox option allows the user to change the thickness, color, and style of the subbasin borders. Unchecking this option disables all the subbasin display properties within this section and also hides subbasins from the Map View. The user can set the thickness of subbasin borders on a scale of 1 to 11 using the adjacent spin control entry field.
• Filled-in subbasins
  This checkbox option allows the user to change the color and transparency of subbasins. Unchecking this option will only display subbasin borders on the Map View.

LID Structures Display Properties

This section is used to configure the display properties of the LID (Low Impact Design) structures on the Map View.

The following options are available in this section:

• LID structures
  This checkbox option is used to enable or disable the display of LID structures and their associated properties on Map View.
• LID structure border
  This checkbox option allows the user to change the thickness, color, and style of the LID structure borders. Unchecking this option disables all the LID structure display properties within this section and also hides LID structures from the Map View. The user can set the thickness of the LID structure borders on a scale of 1 to 11 using the adjacent spin control entry field.
• Bioretention cell
  This checkbox option allows the user to change the color of bioretention cell LID structures using the adjacent dropdown color palette. Unchecking this option hides all bioretention cell LID structures from the Map View.
• Bioswale
  This checkbox option allows the user to change the color of bioswale LID structures using the adjacent dropdown color palette. Unchecking this option hides all bioswale LID structures from the Map View.
• Green roof
  This checkbox option allows the user to change the color of green roof LID structures using the adjacent dropdown color palette. Unchecking this option hides all green roof LID structures from the Map View.
• Infiltration trench
  This checkbox option enables the user to change the color of infiltration trench LID structures using the adjacent dropdown color palette. Unchecking this option hides all infiltration trench LID structures from the Map View.
• Permeable pavement
  This checkbox option allows the user to change the color of permeable pavement LID structures using the adjacent dropdown color palette. Unchecking this option hides all permeable pavement LID structures from the Map View.
• Rain barrel
  This checkbox option allows the user to change the color of rain barrel LID structures using the adjacent dropdown color palette. Unchecking this option hides all rain barrel LID structures from the Map View.
• Rain garden
  This checkbox option allows the user to change the color of rain garden LID structures using the adjacent dropdown color palette. Unchecking this option hides all rain garden LID structures from the Map View.
• Rooftop capture
  This checkbox option allows the user to change the color of rooftop capture LID structures using the adjacent dropdown color palette. Unchecking this option hides all rooftop capture LID structures from the Map View.

Subbasin TOC/Lag Time Flow Path Display Properties

This section is used to configure the display properties of the subbasin TOC (time of concentration) and lag time flow paths.

The following options are available in this section:

• Flow path
  This checkbox option is used to enable or disable the display of flow paths and their associated properties on the Map View.
• Flow path direction arrows
  This checkbox option allows the user to change the color of the flow path direction arrows. Unchecking this option hides all flow path direction arrows from the Map View.
• Sheet flow segment color
  This dropdown color palette allows the user to change the color of the sheet flow segment.
• Shallow concentrated flow segment color
  This dropdown color palette allows the user to change the color of the shallow concentrated flow segment.
• Channel flow segment color
  This dropdown color palette allows the user to change the color of the channel flow segment.

Manhole Display Properties

This section is used to configure the display properties of manholes on the Map View.

The following option is available in this section:

• Manhole
  This checkbox option is used to enable or disable the display of manholes and their associated properties on the Map View. The size of manhole symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.

Junction Display Properties

This section is used to configure the display properties of junctions on the Map View.

The following option is available in this section:

• Junction
  This checkbox option is used to enable or disable the display of junctions and their associated properties on Map View. Enabling this checkbox option allows the user to change the color, size, style, border, and border color of the junctions. The size of junction symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.

Terminal Outfall Display Properties

This section is used to configure the display properties of terminal outfalls on the Map View.

The following option is available in this section:

• Terminal outfall
  This checkbox option is used to enable or disable the display of terminal outfalls and their associated properties on the Map View. The size of terminal outfall symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.

Rain Gage Display Properties

This section is used to configure the display properties of rain gages on the Map View.

The following option is available in this section:

• Rain gage
  This checkbox option is used to enable or disable the display of rain gages and their associated properties on Map View. Enabling this checkbox option allows the user to change the color, size, style, border, and border color of the rain gages. The size of rain gage symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.

Pipe Display Properties

This section is used to configure the display properties of pipes on the Map View.

The following options are available in this section:

• Pipe
  This checkbox option is used to enable or disable the display of pipes and their associated properties on Map View. Enabling this checkbox option allows the user to change the size and border color of the pipes. The size of pipe symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.
• Pipe direction arrow
  This checkbox option is used to change the color of pipe direction arrows using the adjacent dropdown color palette. Unchecking this option hides all pipe direction arrows from the Map View.

Reach Display Properties

This section is used to configure the display properties of routing reaches on the Map View.

The following options are available in this section:

• Reach
  This checkbox option is used to enable or disable the display of routing reaches and their associated properties on the Map View. Enabling this checkbox option allows the user to change the color, thickness, and style of the routing reaches. The user can set the thickness of routing reaches on a scale of 1 to 11 using the adjacent spin control entry field.
• Reach direction arrow
  This checkbox option allows the user to change the color of routing reach direction arrows using the adjacent dropdown color palette. Unchecking this option hides all routing reach direction arrows from the Map View.

Roadway Gutter Display Properties

This section is used to configure the display properties of roadway gutters, ditches, or inlets on the Map View.

The following options are available in this section:

• Roadway
  This checkbox option is used to enable or disable the display of roadway segments and their associated properties on the Map View. Enabling this checkbox option allows the user to change the color, thickness, and style of the roadway segments. The user can set the thickness of roadway segments on a scale of 1 to 11 using the adjacent spin control entry field.
• Roadway direction arrow
  This checkbox option allows the user to change the color of roadway segment direction arrows using the adjacent dropdown color palette. Unchecking this option hides all roadway segment direction arrows from the Map View.

Roadway Crossings Display Properties

This section is used to configure the display properties of roadway crossings on the Map View.

The following options are available in this section:

• Roadway
  This checkbox option is used to enable or disable the display of roadway crossings and their associated properties on the Map View. Enabling this checkbox option allows the user to change the color, thickness, and style of the roadway crossings. The user can set the thickness of roadway crossings on a scale of 1 to 11 using the spin control entry field.
• Roadway direction arrow
  This checkbox option allows the user to change the color of roadway crossing direction arrows using the adjacent dropdown color palette. Unchecking this option hides all roadway crossing direction arrows from the Map View.

Cross Section Display Properties

This section is used to configure the display properties of cross sections on the Map View.

The following options are available in this section:

• Cross section
  This checkbox option is used to enable or disable the display of cross sections and their associated properties on the Map View. Enabling this checkbox option allows the user to change the color, thickness, and style of the cross sections. The user can set the thickness of cross sections on a scale of 1 to 11 using the adjacent spin control entry field.
• Cross section direction arrows
  This checkbox option allows the user to change the color of cross section direction arrows using the adjacent dropdown color palette. Unchecking this option hides all the cross section direction arrows from the Map View. By default, this option is disabled (i.e., grayed out).
• Roughness segments
  This checkbox option allows the user to change the thickness of roughness segments of given cross sections. Unchecking this option hides all the roughness segments from the Map View. The user can set the thickness of roughness segments on a scale of 1 to 20 using the adjacent spin control entry field.
• Bank stations
  This checkbox option allows the user to change the color, size, style, border, and border color of the bank stations. Unchecking this option hides all bank stations from the Map View. The size of bank station symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.

Storage Area Display Properties

This section is used to configure the display properties of storage areas on the Map View.

The following options are available in this section:

• Storage area
  This checkbox option is used to enable or disable the display of storage areas and their associated properties on the Map View.
• Storage area symbol
  This checkbox option allows the user to change the size of the storage area symbol. Unchecking this option hides all storage area symbols from the Map View. The size of storage area symbols can be adjusted to small, medium, and large using the adjacent dropdown combo box.
• Storage area connection line
  This checkbox option allows the user to change the thickness, color, and style of the storage area connection lines. Unchecking this option hides all storage area connection lines from the Map View. The user can set the thickness of storage area connection lines between 1 and 11 using the spin control.
• Storage area border
  This checkbox option allows the user to change the thickness, color, and style of the storage area borders. Unchecking this option disables all the storage area properties within this section and hides storage areas from the Map View. The user can set the thickness of the storage area borders on a scale of 1 to 11 using the adjacent spin control entry field.
• Filled-in storage areas
  This checkbox option allows the user to change the color and transparency of storage areas. Unchecking this option will only display storage area borders on the Map View.

Other Display Properties

This section is used to configure additional display properties that apply across all stormwater element types.

The following options are available in this section:

• Stamp geometry polylines
  This checkbox option allows the user to hide or unhide stamp geometry polylines.
• Disable adaptive element display
  This checkbox option, when checked, disables adaptive elements from being displayed in the Map View when the user zooms out. By default, this checkbox option is unchecked.

Spatial Reference

The Spatial Reference panel allows the user to manually assign the project’s coordinate reference system (CRS) to the stormwater layer. This panel is useful when the layer’s data coordinates fall within the extent of the project’s CRS, but the layer does not contain embedded CRS information. Refer to this article in our knowledge base to learn more about spatial reference.

Transformation

The Transformation panel allows the user to automatically apply a transformation scale factor to the stormwater layer so that it accurately maps to the project's coordinate reference system. Refer to this article in our knowledge base to learn more about layer transformation.

Label Options

The Label Options panel allows the user to define how each stormwater element is labeled on the Map View. The user can select the attributes included in each label, define the field order and separator, and configure the font, color, border, and other visual label settings. Refer to this article in our knowledge base to learn more about label options.

After configuring the display properties of stormwater elements, click the [OK] button to apply them on the Map View.

Modifying Stormwater Element Properties From the Ribbon Menu

Stormwater element properties can also be modified directly from the ribbon menu. When a stormwater layer is selected in the Map Data Layers panel, a dedicated Display Options ribbon menu becomes available. This ribbon menu provides quick access to the most commonly used display customization options for the element type. To learn more about project layer display properties, refer to this article in our knowledge base.

The Rational Method and Modified Rational Method require that the user define the Runoff Coefficient (RC) for each subbasin in order to compute runoff amount given storm intensity. In GeoSTORM software, the Compute RC command can be used to utilize the land use layer, soil map layer, and subbasin average slope to determine a composite runoff coefficient for each subbasin.

Follow the steps below to use the Compute RC command:

1. From the Watershed ribbon menu, select the Compute RC command.
   
2. The Compute RC dialog box will be displayed, as shown below.
   

The following sections describe how to use the Compute RC command and interact with the above dialog box.

Selecting Subbasins

The Select Subbasins section allows the user to select the subbasins for which the runoff coefficient value is to be computed. If a subbasin is already selected on the Map View prior to running this command, the same subbasin will be shown selected within the given data grid table.

Alternatively, the user can click the [Pick] button to manually select the subbasins from the Map View. The Compute RC command will temporarily disappear, allowing the user to select the desired subbasins. Once finished, press the [Enter] key or right-click and choose Done from the displayed context menu.

The dialog box will be redisplayed and the total number of selected subbasins will be displayed in the Total selected read-only field, as shown below.

Note that the user can select multiple subbasins from the Map View prior to running the Compute RC command by holding the [Ctrl] key while selecting the desired subbasins.

Defining Computational Data

The Define Computational Data section allows the user to define the land cover data and hydrologic soil group data used for computing the runoff coefficient for the selected subbasins. This section contains three panels:

• Land Use Data
• Hydrologic Soil Type Data
• Intermediate Results

Land Use Data

The Land Use Data panel contains three subpanels, which are described below:

NLCD Layer

The NLCD Layer subpanel is used to determine land type with data from the National Land Cover Database (NLCD), which is represented by 75 ft cells throughout the USA. The NLCD map service is used to determine the runoff coefficient based upon the hydrologic soil group (i.e., A, B, C, D) as shown below.

Notes:

• This subpanel will only be displayed for a project having an assigned Coordinate Reference System (CRS).
• For countries other than the USA, the software provides similar land cover databases. The content of this data panel will change to represent the one that is available for the project area. Currently, our software supports Africa, Australia, Canada, Europe, India, New Zealand, and the USA land cover database.

The Land cover data source dropdown combo box allows the user to select which land use data source to use for the newly created land cover layer. By default, the software selects the most recent land use data.

The following options are available in the Land cover data source dropdown combo box:

• NLCD Land Cover 2021
• NLCD Land Cover 2019
• NLCD Land Cover 2016
• NLCD Land Cover 2013
• NLCD Land Cover 2011
• NLCD Land Cover 2008
• NLCD Land Cover 2006
• NLCD Land Cover 2004
• NLCD Land Cover 2001
  

If the “Overwrite existing data” checkbox option is checked, then the new land cover data selected in the Land cover data source dropdown combo box will overwrite the existing land cover data (if one exists).

Additionally, the user can click the [Edit] button to display the NLCD Land Cover dialog box that provides an editable data grid, allowing the user to change the RC values of different hydrologic soil groups.

After editing the required cell values, the user can click the following buttons:

• [Default] – This button will restore the default RC values and close the dialog box.
• [Save] – This button will save the user changes and close the dialog box.
• [Cancel] – This button will discard any user changes and close the dialog box.

Note that the NLCD Layer subpanel will be replaced by other subpanels based on the modeling region, as described below:

GIS Polygon Layer

The GIS Polygon Layer subpanel is used for user-defined land use polygon data. The land use data can either directly assign the RC value for each polygon or provide a standard land use type for the software to cross reference.

When the user selects the Standardized land use type attribute field radio button option, then the Soil Group RC attribute field dropdown combo box entries become enabled. The Soil Group RC attribute field dropdown combo box entries show text, float, and integer fields contained within the selected GIS land use layer. Then, the software determines which RC value should be applied based upon the corresponding soil type and RC attribute field value.

Default Values

The Default Values subpanel allows the user to either define the default RC value or leverage Use standardized land use RC values option for the software to cross-reference. The user can enter integer or float values into these default value fields.

Hydrologic Soil Type Data

The Hydrologic Soil Type Data panel contains three subpanels, which are described below:

NRCS Layer

The NRCS Layer subpanel allows the user to utilize data from the NRCS Soil Survey Database for determining the hydrologic soil group data for the watershed region.

Note that for countries other than the USA, the software provides similar soil survey databases. The content of this data panel will change to represent the one that is available for the project area. Currently, our software supports Africa, Australia, Canada, Europe, India, New Zealand, and the USA land cover database.

The NRCS Layer subpanel will be replaced by other subpanels based on the modeling region, as described below:

GIS Polygon Layer

The GIS Polygon Layer subpanel is used for the user-defined soil map polygon data. The soil map data provides hydrologic soil group data for each defined polygon.

Default Value

The Default Value subpanel is used to define a default hydrologic soil type for the software to cross-reference, as shown below.

Intermediate Results

The Intermediate Results panel allows the user to compute the intermediate results of the selected subbasin(s) in a shapefile, save the results at the user-specified location and load the results in a project.

By default, the content of this panel is disabled (i.e., grayed out). Select the Compute Intermediate Results checkbox to enable the content of this panel.

Clicking the […] browse button adjacent to the Intermediate results shapefile path entry field allows the user to define the location where the intermediate computed results are to be saved.

Note that the Load intermediate results checkbox option must be checked to load the computed intermediate results in the specified project.

Computing Runoff Coefficient

After defining the data in the Compute RC dialog box, click the [Compute] button to compute the runoff coefficient for the selected subbasin(s).

Once the runoff coefficients are computed, the values will be shown in the Computed RC column, which can be further edited by the user, as shown below.

In addition, all stormwater methods that require runoff coefficients will have the data populated into their respective fields within the software.

In the Map Data Layers panel, the software provides a data legend for computed intermediate results of each subbasin that lists the land covers included within that layer. The user can expand the layer to view the data legend.

Click the […] button adjacent to the intermediate results computed for the subbasin(s) to display the GIS polygon properties dialog box. This allows the user to adjust the color and style of the polygon(s) according to the land and soil type. To learn more about the GIS polygon properties dialog box, refer to this article in our knowledge base.

Subbasins define the drainage area polygons that produce runoff to the other elements in the stormwater model. In the GeoSTORM software, the Subbasin Data command allows users to add new subbasins, edit subbasin data, and display the associated output results of a project.

The user can create or assign new subbasins using the Draw Subbasins or Assign Subbasins commands. Refer to this article in our knowledge base to learn more about these commands.

This article describes how to use the Subbasin Data command in the GeoSTORM software.

Follow the steps below to view or modify the subbasin data:

1. From the Input ribbon menu, click the Drainage Subbasins dropdown menu and select the Subbasin Data command.
   
2. The Subbasin Data dialog box will be displayed.
   

The following sections describe how to interact with the Subbasin Data dialog box.

Defining Subbasin Data

The Subbasin Data dialog box contains the following options to select and define subbasin data:

• Select Subbasin Section
• Subbasin Specifications Data Panel Selector:
  • General Specifications Data Panel
  • LID Specifications Data Panel

Selecting Subbasin

The Select Subbasin section allows the user to select the subbasin for defining the subbasin data. The user can create a new subbasin, copy existing subbasin data to a new subbasin, and delete a subbasin. In addition, the user can navigate between subbasins and enter a description detailing the defined subbasins.

The following entries are provided in this section:

• Subbasin ID
  This dropdown combo box lists all the subbasins defined in the current scenario of the project. Click on the edit option (i.e., the pencil icon) to edit the subbasin ID. The user can navigate between the previous and next subbasin using the Up and Down arrow buttons. Alternatively, the user can click the […] button to select the subbasin from the Map View. Note that the Up and Down arrow buttons will be disabled (i.e., grayed out) if the current scenario contains a single subbasin.

• Description
  This optional field allows the user to enter additional information that describes the selected subbasin.

• New
  The [New] button allows the user to create a new subbasin on the Map View. The ID of every newly created subbasin must be unique.

• Copy
  The [Copy] button allows the user to copy an existing subbasin along with its associated data to a new subbasin. The software automatically provides a unique ID to the copied subbasin.

• Delete
  The [Delete] button allows the user to delete the selected subbasin from the current scenario.

• Less/More
  The [<Less] and [More>] buttons at the Select Subbasin section header allow the user to collapse or expand the Computed Results section.

Defining Subbasin Specifications

The Subbasin Specifications dropdown selector contains General Specifications and LID Specifications entries. Selecting these entries displays corresponding data panels to define general and low-impact design (LID) specifications for the subbasins defined in the current scenario of the project.

Defining General Specifications Based on Hydrology Method

In the Subbasin Data dialog box, the contents of the General Specifications data panel change based on the hydrology and infiltration methods selected in the Scenario Manager dialog box, as shown below.

In addition, selecting different hydrology methods enables and disables the infiltration methods. The table below shows the infiltration methods available depending on the hydrology method selected.

EPA SWMM Hydrology Method

The combination of different infiltration methods with the selected EPA SWMM hydrology method changes the contents of the General Specifications data panel.

Refer to this article in our knowledge base to learn how the EPA SWMM hydrology method, along with different infiltration methods, changes the contents of the General Specifications data panel.

Modified Rational Hydrology Method

The following General Specifications data panel is displayed when the Modified Rational is selected as the hydrology method.

General Specifications

This section allows the user to define the general parameters of the defined subbasin.

The following parameters are available in this section.

• Drainage area
  This entry field defines the area of the selected subbasin. The user can click the […] button to measure the subbasin area from the Map View. Clicking the [Recalc] button will cause the software to recalculate the area of the digitized subbasin. Similarly, the [Recalc All] button will cause the software to recalculate the area of all the digitized subbasins.

• Downstream connection
  This read-only entry field defines the downstream element that the selected subbasin drains to. The user can click the [...] button to select the subbasin downstream connection from the Map View.

The following elements can be selected:

• • Manhole
  • Routing Junction
  • Storage Area
  • Subbasin (only when using EPA SWMM hydrology method)
  • Terminal Outfall

The user can click the [Clear] button to remove the downstream element connection.

Modified Rational Method Specifications

The parameters in this section are important for running the analysis using the modified rational method.

Note that the header of this section changes based on the selected hydrology method. For example, if the user selects Rational Method as the hydrology method, the header of this section changes to Rational Method Specifications. Similarly, for the DeKalb Rational hydrology method, the header of this section changes to DeKalb Rational Method Specifications.

The following parameters are available in this section:

• Runoff coefficient
  This entry field defines the runoff coefficient for the defined subbasin. Clicking the […] button displays a Runoff Coefficients lookup table dialog box, as shown below.
  
• Time of concentration
  This entry field defines the time of concentration for the defined subbasin.

Computational Results

After successfully computing the analysis, this section provides a summary of the computational results for the defined subbasin.

The following results are provided in this section:

• Peak runoff rate
  This read-only field displays the peak runoff rate that occurred from the subbasin during the storm event.

• Rainfall intensity
  This read-only field displays the rainfall intensity applied to the subbasin during the storm event.

• Total runoff
  This read-only field displays the total runoff volume from the subbasin during the storm event.

DeKalb Rational Hydrology Method

The following General Specifications data panel is displayed when DeKalb Rational is selected as the hydrology method.

The contents of the dialog box for the DeKalb Rational hydrology method are similar to those for the Modified Rational hydrology method. Refer to the Modified Rational Hydrology Method section of this article for more information.

Rational Method Hydrology Method

The following General Specifications data panel is displayed when the Rational Method is selected as the hydrology method.

The contents of this dialog box for the Rational Method hydrology method are similar to those for the Modified Rational hydrology method. Refer to the Modified Rational section of this article for more information.

SCS TR-20/TR-55 Hydrology Method

The following General Specifications data panel is displayed when the SCS TR-20/TR-55 is selected as the hydrology method.

General Specifications

This section allows the user to define the general parameters of the defined subbasin.

The following parameters are available in this section:

• Drainage area
  This entry field is similar to the Drainage area entry field available in the General Specifications section for the Modified Rational hydrology method.

• Downstream connection
  This entry field is similar to the Downstream connection entry field available in the General Specifications section for the Modified Rational hydrology method.

• Runoff (flow) adjustment ratio
  This entry field defines an adjustment ratio for calibrating the runoff from the selected subbasin. The default value for this entry is 1.000, meaning that there is no adjustment.

SCS Hydrology Method Specifications

This section allows the user to define the SCS hydrology method parameters for the defined subbasin.

The following parameters are available in this section:

• Curve number
  This entry field defines the curve number for the defined subbasin. Clicking the […] button will display a SCS Curve Number lookup table dialog box as shown below.
  unknown node
• Impervious surface area
  This entry field defines the percent impervious surface area for the selected subbasin.
• Time of concentration
  This entry field is similar to the Time of concentration entry field available in the Modified Rational Method Specifications section for the Modified Rational hydrology method.

Computational Results

After successfully computing the analysis, this section allows the user to see a summary of the computational results for the defined subbasin.

Note that the Detailed Results section provides additional analysis results computed for the defined subbasin.

Defining LID Specifications

The LID Specifications data panel of the Subbasin Data dialog box allows the user to define general specifications for Low Impact Design (LID) elements within the selected subbasin. Note that this data panel is only enabled when EPA SWMM is selected as the hydrology method.

Refer to this article in our knowledge base to learn more about the LID Specifications data panel of the Subbasin Data dialog box.

In GeoSTORM, the Subbasin Table Edit command allows the user to view and edit all the parameters of the subbasins in a single editable table. The user can also view the corresponding output results from this table.

Follow the steps below to use the Subbasin Table Edit command:

1. From the Input ribbon menu, click the Drainage Subbasins dropdown menu and select the Subbasin Table Edit command.
   
2. The Subbasin Table Edit dialog box will be displayed.
   

The following sections describe how to use the Subbasin Table Edit command and interact with the above dialog box.

Selecting Hydrology Analysis Engine & Infiltration Method

The content of the Subbasin Table Edit dialog box changes based on the hydrology analysis engine and infiltration method selected from the Scenario Manager dialog box, as shown below.

Note: The infiltration method is only available when EPA SWMM is selected as the hydrology analysis engine.

Upon selecting the hydrology analysis engine and infiltration method, the parameters displayed in both the Subbasin Data and Result Data panels of the Subbasin Table Edit dialog box change. Refer to this article in our knowledge base to learn more about the Scenario Manager command.

Selecting Storm Results

In the Select Storm Results section, the Storm result to display dropdown combo box allows the user to select the storm frequency whose result is to be displayed.

Note: The Select Storm Results section is only available if the Dekalb Rational Method or Modified Rational or Rational Method is selected as the hydrology analysis engine in the Scenario Manager dialog box. Otherwise, this section is unavailable.

Subbasin Parameters

In the Subbasin Parameters section, the following panels are available:

• Subbasin Data
• Result Data

Subbasin Data

In the Subbasin Parameters section, the Subbasin Data panel contains a table with editable columns listing the subbasin parameters available in the current scenario.

Result Data

In the Subbasin Parameters section, the Result Data panel contains a table with read-only columns listing the corresponding output results for subbasins available in the current scenario.

Sorting the Subbasin Parameters Table

The data in the Subbasin Parameters table can be sorted by multiple columns. The user can sort the data by holding down the [Shift] key while clicking the Up and Down arrows in the column headers. This allows for multi-column sorting without losing the previous sort. The sorting order is determined by the sequence in which the column headers are selected.

Follow the steps below to sort the data using multiple columns:

1. Select the header of the first column and click the Up or Down arrow to sort the data in ascending or descending order.
2. Hold down the [Shift] key, then select the header of the second column and click the Up or Down arrow to sort the second column.
3. Repeat step 2 to sort the data of any additional column.

For example, first, select the Subbasin ID column and click the Up arrow to sort the data in ascending order. Then, while holding the [Shift] key, select the Drainage Area column and click the Down arrow to apply a secondary sort.

Copying and Exporting the Table

The data in the Subbasin Parameters table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using right-click context menu commands such as Copy, Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF.

After editing the required subbasin parameters, click the [Close] button to close the Subbasin Table Edit dialog box.

The LID Specifications data panel of the Subbasin Data dialog box allows the user to define general specifications for Low Impact Design (LID) elements within the selected subbasin. Note that this data panel is only enabled when EPA SWMM is selected as the hydrology analysis engine in the Scenario Manager dialog box. Otherwise, this data panel is disabled (i.e., grayed out). Refer to this article in our knowledge base to learn more about the hydrology analysis engine.

This article explains how to interact with the LID Specifications data panel of the Subbasin Data dialog box.

Follow the steps below to define the specifications for the LID elements:

1. In the Subbasin Data dialog box, select the LID Specifications data panel from the Subbasin Specifications dropdown combo box.
   
2. The corresponding data panel with options for defining LID specifications will be displayed.
   

The following sections describe how to define specifications for LID elements and interact with the above data panel.

Defined LID Elements

The table under this section lists all the LID elements defined for the current subbasin.

The following read-only columns are available in this table:

• LID Element ID
  This read-only column lists the IDs of the defined LID elements.

• LID Element Type
  This read-only column lists the LID element types for the added LID elements.

• Subbasin Area Collected
  This read-only column lists the total subbasin area being processed by the defined LID element.

• Collected from Impervious Area
  This read-only column lists the percentage of the impervious portion of the subbasin non-LID area whose runoff is processed by the LID element.

• Collected from Pervious Area
  This read-only column lists the percentage of the pervious portion of the subbasin non-LID area whose runoff is processed by the LID element.

LID Element Parameters

This section allows the user to define the LID element parameters for the selected LID element.

Note that these parameters change based upon the selected LID element listed in the table under the Defined LID Elements section. The following LID element parameters are available in this section:

• Entire subbasin area processed by LID
  This checkbox option denotes that the entire subbasin drainage area is processed by the LID element.

• Subbasin area processed by each LID unit
  This entry field defines the area processed by each LID unit. Click the [Pick] button to select a polygon from the Map View that represents the subbasin’s LID unit. Click the […] button to measure the area processed by subbasin’s LID unit from the Map View.

• Number of LID units
  This spin control entry field defines how many LID units are defined for the subbasin.

• Total subbasin area processed by LID
  This read-only entry field defines the total subbasin area being processed by the defined LID units.
  This value is computed using the following equation:

(Subbasin Area Processed by Each LID Unit) x (Number of LID Units)

• Surface width processed by each LID unit
  This entry field defines the subbasin surface width processed by the defined LID unit. Click the [Pick] button to measure the subbasin surface width processed by each LID unit from the Map View. Note that this entry field and the [Pick] button are only enabled for the following LID element types:

• 1. Bioswale
  2. Green Roof
  3. Infiltration Trench
  4. Permeable Pavement
  5. Rooftop Capture

• LID unit initial saturation
  For most of the LID element types, this spin control entry field defines the degree to which their storage zone is initially filled with water.

However, for Bioretention Cell, Green Roof, and Rain Garden LID element types, this spin control entry field defines the degree to which the LID unit’s soil is initially filled with water. A value of 0% saturation corresponds to the wilting point moisture content, whereas a value of 100% saturation corresponds to a moisture content equal to the soil porosity. The storage zone beneath the soil zone of the LID unit is assumed to be completely dry.

• Impervious area processed by LID
  This spin control entry field defines the percentage of the impervious portion of the subbasin non-LID area whose runoff is processed by the LID unit. Note that this entry will be displayed as disabled (i.e., grayed out) when the Entire subbasin area processed by LID checkbox is checked.

• Pervious area processed by LID
  This spin control entry field defines the percentage of the pervious portion of the subbasin non-LID area whose runoff is processed by the LID unit. Note that this entry will be displayed as disabled (i.e., grayed out) when the Entire subbasin area processed by LID checkbox is checked.

• LID unit drain flow connection
  This checkbox entry allows the LID outflow to be routed to a different location than the outlet of the current subbasin. By default, the element ID displayed in the Downstream connection entry in the General Specifications data panel of the Subbasin Data dialog box will be shown in this entry.

The user can click the […] button to select the LID unit drain flow connection from the Map View.

The user can click the [Clear] button to remove the LID unit drain flow connection.

• Route LID outflow to pervious area
  This checkbox option causes all the outflow from the LID unit to be routed onto the pervious area of the current subbasin. Note that if the drain outflow was specified to be routed to a different location than the subbasin outlet, then only surface outflow will be routed to the pervious area of the current subbasin.

LID Results

After successfully computing the analysis, the table under this section will provide a summary of the LID results for the defined LID elements in the selected subbasin.

Urban subbasins with storm sewer interconnects are drainage areas that are hydraulically connected through an underground network of inlets, catch basins, manholes, pipes, and outfalls. Together, these components collect surface runoff, convey it through the storm sewer network, and discharge it safely at designated outfall locations.

For stormwater engineers, accurately modeling this connectivity is essential. An undersized or poorly connected storm sewer system can lead to surcharging, localized flooding, infrastructure damage, and regulatory non-compliance.

When designing storm sewer systems, engineers must consider factors such as subbasin imperviousness, topography, soil conditions, and drainage area characteristics. These factors directly influence runoff coefficients, peak flow calculations, and the overall hydraulic performance of the storm sewer network.

GeoSTORM provides a complete environment for building storm sewer models of interconnected storm sewer systems. Users can delineate subbasins, assign them to manholes or junctions, build hydraulic connectivity across the pipe network, analyze runoff using integrated hydrologic methods, and review system performance through profile plots — all within a single, map-based workflow.

Why Model Subbasins with Storm Sewer Interconnects

Inaccurately designed storm sewer systems lead to real consequences, including flooded roads, eroded channels, damaged utilities, and costly emergency repairs. A well-designed and accurately modeled storm sewer system provides several important benefits:

• Reduced flood risk: Efficient conveyance of runoff minimizes surface water accumulation on roads, parking lots, and other urban surfaces.
• Protected infrastructure and property: Properly sized pipes and well-placed outfalls reduce the risk of damage to roads, utilities, and buildings.
• Sustainable urban development: Reliable stormwater infrastructure supports long-term land use planning and community resilience.
• Public health and safety: Effective drainage reduces exposure to waterborne hazards and prevents the localized flooding that endangers pedestrians and vehicles.

Key Considerations for Effective Hydrological Management

Before building a storm sewer model, engineers should gather sufficient information about the watershed and the existing or proposed infrastructure. The accuracy of the model depends heavily on how well the drainage area and storm sewer network are represented. The following factors are essential for effective hydrological management in the design of storm sewer systems:

1. Assess catchment characteristics.
   Review rainfall patterns, soil types, land use, and impervious cover for each subbasin. These inputs directly affect runoff volume and peak discharge calculations.
2. Conduct hydrological analysis and modeling.
   Estimate stormwater runoff rates and volumes using an appropriate method for the drainage area size and available data. See the Design Principles section below for method guidance.
3. Design for anticipated flows.
   Size pipes and other components to handle both peak discharge rates and total runoff volumes, while also accounting for future land use changes where applicable.

Design Principles and Best Practices

Hydrological Analysis

Hydrologic analysis is the foundation of storm sewer system design. It estimates the runoff volume and peak discharge generated from each subbasin during a storm event. Selecting the right method is important because using a method outside the intended range can produce unreliable flow estimates and lead to under-designed or over-designed infrastructure.

Common hydrological analysis methods used for urban storm sewer design include:

• Rational Method: Best suited for small urban catchments, typically under 80 hectares (200 acres). Estimates peak discharge using rainfall intensity, the runoff coefficient, and the time of concentration. Simple, widely accepted, and appropriate for inlet and pipe sizing in urban settings.
• SCS Curve Number Method: Considers soil type, land use, and antecedent moisture conditions to estimate runoff volume and peak discharge. More appropriate for larger or more complex drainage areas where storage and routing effects are significant.

Pipe Sizing

Proper pipe sizing is essential to ensure that storm sewer systems can convey peak flows without surcharge, overflow, or excessive backwater effects. Undersized pipes are one of the most common causes of localized urban flooding.

Key considerations for pipe sizing include:

• Expected peak flow from upstream subbasins.
• Pipe characteristics, such as material, roughness, and slope.
• Available cover, utility conflicts, and right-of-way constraints.
• Existing infrastructure limitations, such as fixed pipe alignments, inverts, or downstream capacity.

Pipe Slope

The longitudinal slope of a storm sewer pipe directly affects flow velocity, sediment transport, and hydraulic capacity. Pipes that are too flat allow sediment to accumulate and reduce capacity over time. Pipes that are too steep may cause erosion at outfall locations or generate excessive scour velocities inside the pipe barrel.

As a general design guideline, the pipe slope should be sufficient to maintain a minimum flow velocity of 0.75 m/s (2.5 ft/s) under peak flow conditions. This threshold helps prevent sediment deposition within the pipe. Always verify minimum velocity requirements against local design standards, which may differ from this general guideline.

Components of Storm Sewer Systems

A storm sewer system consists of several interconnected components that collect, convey, and discharge stormwater runoff. Each component plays a specific role in moving runoff from the drainage area to the downstream outfall. Understanding these elements is important for building an accurate and reliable storm sewer model.

The table below provides a quick summary of each component and its role in the overall drainage network.

unknown node

Subbasins

Subbasins represent individual drainage areas that produce surface runoff during storm events. Subbasins are delineated based on surface topography, land use, and the direction of overland flow. Each subbasin is defined by parameters such as area, imperviousness, soil type, and slope, all of which influence how much runoff is generated and how quickly it reaches the downstream inlet, manhole, or junction. In GeoSTORM, subbasins can be drawn and assigned directly to manholes or junctions within the storm sewer network. Refer to this article in our knowledge base to learn how to draw subbasins.

Inlets and Catch Basins

Inlets are the points where stormwater enters the underground drainage system. They are commonly placed at low points along roads, parking lots, and other paved areas to capture runoff from impervious surfaces.

Catch basins are underground chambers positioned beneath inlets. Catch basins temporarily store stormwater runoff and trap sediment and debris to prevent clogging in downstream pipes. Regular maintenance of catch basins is essential to ensure effective pollutant removal and uninterrupted flow.

Pipes

Stormwater pipes convey collected runoff from inlets and catch basins through the underground network toward the terminal outfall. Pipes are typically made of materials such as concrete, cast iron, and PVC. Material selection affects roughness coefficients, structural capacity, and long-term durability. Refer to this article in our knowledge base to learn how to draw pipes.

Manholes

Manholes are covered openings in the ground that provide access to storm sewer pipes for inspection, maintenance, and cleaning. Manholes are typically located at pipe junctions, changes in pipe direction or size, and at regular intervals along the pipe run. Manholes are usually covered with heavy lids to prevent unauthorized access and to ensure safety. Refer to this article in our knowledge base to learn how to draw manholes.

Terminal Outfalls

Terminal outfalls are the downstream discharge points where the storm sewer system releases collected stormwater into a receiving water body, such as a river, lake, or ocean. Outfall design must account for outlet velocity and the potential for erosion of the receiving channel or streambank. Energy dissipaters, riprap aprons, or flared end sections are commonly used to reduce outlet velocity and protect receiving waters. Refer to this article in our knowledge base to learn how to draw terminal outfalls.

How Subbasins Connect to Storm Sewer Network

In a storm sewer model, each subbasin should be connected to the underground drainage network through an appropriate outlet point, such as a manhole, junction, or inlet. This connection defines where surface runoff enters the pipe network and how it is routed downstream.

Subbasins can be connected to the storm sewer network in the following ways:

Subbasin-to-Manhole/Junction Connection

Subbasins are typically connected to the storm sewer network by assigning each subbasin to a nearby manhole or junction. The outlet should represent the actual point where runoff from the drainage area enters the underground network.

When defining this connection,

• Delineate subbasins based on the surface topography, land use, and the direction of overland flow.
• Assign each subbasin an outlet point, typically a nearby manhole or junction within the underground pipe network.
• Verify that runoff from the subbasin is routed into the intended portion of the underground pipe network.

Routing through the Storm Sewer Network

• After runoff enters the storm sewer network, it is routed through the connected pipes, manholes, catch basins, and other hydraulic structures until it reaches the terminal outfall.
• Where necessary, additional components such as detention storage, control structures, weirs, orifices, valves, or overflow connections can be included to regulate flow, manage surcharge conditions, or represent more complex stormwater infrastructure.

Observing Pipe Profiles

After defining the storm sewer model and running a simulation, it is important to review pipe profiles to visualize and validate overall storm sewer system performance. In GeoSTORM, the Profile Plot command allows the user to display stormwater pipe and ditch profile (long section) plots. A profile plot helps you to:

• Visualize the underground layout: See pipe inverts, manhole rim elevations, pipe grades, and the relative positions of all network components along the selected alignment.
• Review hydraulic performance: Display the Hydraulic Grade Line (HGL) and Energy Grade Line (EGL) overlaid on the pipe profile to quickly identify surcharging, pressure flow conditions, or inadequate hydraulic capacity.
• Adjust the design: Modify pipe diameters, slopes, and invert elevations directly within the profile view and immediately see the impact on computed hydraulic grades.
• Export for documentation: Export profile drawings to AutoCAD or MicroStation for inclusion in construction plan sets and design documentation packages.

Refer to this article in our knowledge base to learn more about the Profile Plot command.

The following image shows how subbasins are connected within a storm sewer model in GeoSTORM.

Advantages of Modeling Storm Sewer Systems

The key benefits of modeling storm sewer systems include:

• Public Safety
  Prevents water accumulation on streets and sidewalks during storm events, reducing traffic hazards and risks of injury.

• Property Protection
  Minimizes the risk of water intrusion, erosion, and flood damage to buildings, roads, and underground utilities.

• Environmental Compliance
  Controls discharge and captures sediment to reduce pollutant transport to natural water bodies, supporting regulatory compliance and environmental health.

• Infrastructure Planning
  Provides insights into system capacity and performance, helping engineers plan upgrades, optimize pipe sizing, and reduce costly future retrofits.

Conclusion

Urban subbasins with storm sewer interconnects should be modeled as part of a connected drainage system, not as isolated runoff areas. When subbasins, inlets, pipes, manholes, and outfalls are connected correctly in a storm sewer model, engineers can better evaluate system performance, identify capacity shortfalls, and design infrastructure that protects communities and the environment. GeoSTORM streamlines this process by combining subbasin delineation, hydrologic analysis, pipe network routing, and profile visualization in a single, map-based environment. As a final check, engineers should review the pipe profile, HGL, EGL, and outfall discharge to confirm that the storm sewer model reflects real-world system behavior.

In stormwater drainage systems, flow-control manholes (FCMs) are critical elements used to regulate flow between different segments of a network, especially storage units and downstream conduits (pipes or culverts). These flow control manholes are crucial for managing the volume and velocity of stormwater in a drainage system, ensuring its efficiency and stability. Improper handling of flow direction or backflows can lead to downstream flooding during periods of heavy rainfall.

Flow Control Manhole

A flow control manhole is a junction structure included in a stormwater drainage system that is designed to restrict, delay, or control the movement of water through a conduit or open channel. These controls may be achieved through use of the following elements in a drainage system:

• Orifices
• Weirs
• Flap gates
• Internal restrictions caused by specific pipe geometry

Flow control manholes are often placed between a storage unit and an outlet pipe to prevent overflow or backflow during peak storm events.

Understanding Backflow Conditions

Backflow in a drainage system occurs when water flows in a direction opposite of its intended flow. This happens due to:

• High tailwater elevations in the downstream system
• Flat or zero-sloped conduits
• Surcharged manholes or pipes
• Improper configuration of pipe flow directions

Design Considerations and Best Practices for Modeling Flow Control Manholes

• Check and verify pipe orientation to ensure expected flow behavior.
• Utilize invert elevations and storage depth limits to manage surcharge and reverse flow in a drainage system.
• Model orifices and flap gates correctly in the software to simulate the internal hydraulic behavior of flow control manholes.

Handling Outflows and Backflows in GeoSTORM

GeoSTORM simulates flow behavior using the dynamic wave routing method, including the reversal of flow when downstream hydraulic grades exceed upstream inverts. GeoSTORM uses the St. Venant equations, accounting for flow reversal based on head differentials between nodes.

Stormwater pipes are modeled with designated start and end nodes, and the flow direction is computed dynamically. If the downstream head (Hydraulic grade line) exceeds the upstream invert elevation, GeoSTORM allows flow reversal, and results may show negative flow rate values.

Note that a flap gate or control element (such as an orifice plate or vortex flow control device) must be correctly modeled for the software to prevent flow reversal.

In GeoSTORM, the user can navigate to the Outflow Control panel in the Manhole Data dialog box to specify how the manhole discharges flow from control devices to the downstream pipe.

Refer to this article in our knowledge base to learn more about the Outflow Control panel of the Manhole Data command.

Common Issues Affecting Flow Control and Backflows

A manhole is a covered opening in the ground that provides access to underground public utilities such as sewers, storm drains, electricity, etc. for the purpose of inspection, cleaning, unblocking, or repair. In a stormwater drainage system, a manhole represents a physical junction that acts as a connection point between elements such as pipes.

In GeoSTORM software, manholes can be drawn or assigned using Draw Manholes and Assign Manholes commands. Refer to this article in our knowledge base to learn how to incorporate manholes into your stormwater project.

After adding manholes to the stormwater project, the Manhole Data command can be used to define additional data and view the corresponding output results associated with the manholes.

Follow the steps below to use the Manhole Data command:

1. From the Input ribbon menu, click the Manhole Structures dropdown menu and select the Manhole Data command.
   
2. The Manhole Data dialog box will be displayed as shown below.
   

The following sections of this article describe how to use the Manhole Data command and interact with the above dialog box.

Selecting Manhole

The Select Manhole section allows the user to select the manhole for which manhole data will be defined. In this section, the user can create, delete, and copy existing manhole data to a new manhole. In addition, the user can navigate between manholes and enter a description for each manhole.

The following entries are provided in this section:

• Manhole ID
  This dropdown combo box lists all manholes defined in the current scenario. Click on the edit option (i.e., the pencil icon) to edit the manhole ID. The Up and Down arrow buttons allow the user to switch between the next adjacent downstream and upstream manholes. Alternatively, the user can click the […] button to select the manhole from the Map View. Note that the Up and Down arrow buttons will be disabled (i.e., grayed out) if the current scenario contains only one manhole.

• Description
  This optional text field allows the user to enter additional information that describes the selected manhole.

• New
  The [New] button allows the user to draw a new manhole on the Map View. The ID of every newly created manhole must be unique.

• Copy
  The [Copy] button allows the user to create a copy of the selected manhole on the Map View along with its associated data. The software automatically provides a unique ID to the copied manhole.

• Delete
  The [Delete] button allows the user to delete the selected manhole from the current scenario.

• Less/More
  The [< Less] and [More >] buttons at the Select Manhole section header allow the user to expand or collapse the Computed Results section. Note that The Computed Results section will be unavailable when Rational Method is selected as the hydrology analysis engine in the Scenario Manager dialog box. Refer to this article in our knowledge base to learn more about the hydrology analysis engine.

Manhole Specifications

This section allows the user to define general parameters for the selected manhole and the following data panel entries are available in this dropdown combo box:

• General Specification
• Additional Inflows
• Outflow Control

General Specification

The General Specification panel allows the user to define general parameters for the selected manhole.

Manhole Definition

The following entries are provided in this section:

• Manhole structure type
  This dropdown combo box allows the user to select the type of manhole structure to be defined. The following manhole structure types are available:

• 1. Bolted Cover Manhole
  2. Force Main Connection
  3. Junction Box
  4. Standard Manhole
  

• Rim elevation
  This entry field allows the user to define the manhole rim elevation. The user can click the […] button to select the manhole rim elevation from the Map View. Note that this entry field is disabled (i.e., grayed out) when Force Main Connection is selected as the manhole structure type.

• Invert elevation
  This entry field allows the user to define the manhole invert elevation.

• Bolted cover blowout elevation
  This entry field allows the user to define the maximum additional pressure head above the ground elevation that the manhole can sustain before overflowing. This value should be specified high enough above the rim elevation. Note that this entry field is only enabled when Bolted Cover Manhole is selected as the manhole structure type. Otherwise, this entry field is disabled (i.e., grayed out).

• Sump depth
  This entry field allows the user to define the sump depth required at the manhole. The sump depth of a manhole represents the vertical offset from the manhole bottom invert elevation to the lowest invert of the connected pipes. Note that this entry field is typically used when laying out a pipe run.

• Interior footprint area
  This entry field allows the user to define the manhole’s interior storage area. Alternatively, the user can click the […] button to measure interior storage area from the Map View by drawing a temporary polygon. Note that this entry field is only enabled when Junction Box is selected as the manhole structure type. Otherwise, this entry field is disabled (i.e., grayed out).

• Maximum pipe cover
  If a terrain surface has been defined in the model, the software automatically computes what the maximum pipe cover is for the selected manhole by examining all pipes connected to the manhole and determining the distance from the rim to the pipe crown.
  

• Minimum pipe cover
  If a terrain surface has been defined in the model, the software automatically computes what the minimum pipe cover is for the selected manhole by examining all pipes connected to the manhole and determining the distance from the rim to the pipe crown.

• Initial water surface elevation
  This entry field allows the user to define the water surface elevation in the manhole at the start of the simulation.

• Ponded area
  This entry field allows the user to define the storage area occupied by ponded water at the top of the manhole once the water depth exceeds the rim elevation of the manhole.

Additional Inflows

The Additional Inflows panel allows the user to specify any external inflows at the manhole. These inflows can consist of both a constant and a time-varying component. The additional inflows are applied directly to the manhole and can be used for flow routing in the absence of any runoff computations (e.g., in a study area where no subbasins are defined). In river or stream modeling, user-defined inflows can be used to define the baseflow.

Baseline Inflows

The following entries are provided in this section:

• Baseline inflow
  This entry field allows the user to define a constant baseline inflow. If this field is left blank, then no baseline inflow is assumed.

• Baseline pattern (optional)
  This dropdown combo box allows the user to select an optional time pattern defined in the current scenario whose factors adjust the baseline inflow. If this dropdown list is left blank, then the baseline inflow will not be adjusted.
  
  Clicking on the [Define] button displays the Time Patterns Data dialog box, which allows the user to define a specific pattern to be applied to the defined Baseline Inflow. Refer to this article in our knowledge base to learn more about the Time Patterns Data dialog box.

Time Series Inflows

The following entries are provided in this section:

• Time series scale factor
  This entry field allows the user to define a multiplier to adjust the values of the inflow time series.

• Time series inflow
  This dropdown combo box allows the user to select the time series inflow defined in the current scenario. If None is selected, no time series inflow will be assigned to the manhole.
  
  Clicking on the [Define] button displays the Time Series Data dialog box, which allows the user to define a specific time series inflow data set to be used. Refer to this article in our knowledge base to learn more about the Time Series Data dialog box.

Outflow Control

The Outflow Control panel allows the user to specify how the manhole discharges flow from orifice and vortex control devices to the downstream pipe.

Outflow Control Specifications

The following entries are provided in this section:

• Outflow control type
  This dropdown combo box allows the user to select the outflow control type to be used. The following outflow control types are available:

• 1. None
  2. Orifice Control
  3. Vortex Control
  
• Backflow flap gate
  This checkbox option specifies whether a flap gate will be enabled to prevent backflow (or flow reversal). By default, this checkbox option is unchecked.

• Routing reference method
  This dropdown combo box allows the user to select the routing reference method to be used. Note that this dropdown combo box is only enabled when Vortex Control is selected as the outflow control type. Otherwise, this dropdown combo box is disabled (i.e., grayed out). The following routing reference methods are available:

• 1. None
  2. Head Differential
  3. Water Surface Depth
  4. Water Surface Elevation
  

• Orifice shape
  This dropdown combo box allows the user to select the horizontal orifices that the software supports. Note that this dropdown combo box is only enabled when Orifice Control is selected as the outflow control type. Otherwise, this dropdown combo box is disabled (i.e., grayed out). The following orifice shapes are available:

• 1. Circular
  2. Rectangular
  

• Control structure invert elevation
  This entry field allows the user to define the invert elevation of the control structure defined.

• Orifice diameter or width
  This entry field allows the user to define the width of a rectangular orifice or the diameter of a circular orifice. Note that this entry field is only enabled when Orifice Control is selected as the outflow control type. Otherwise, this entry field is disabled (i.e., grayed out).

• Orifice height
  This entry field allows the user to define the height of a rectangular orifice. Note that this entry field is only enabled when Orifice Control is selected as the outflow control type. Otherwise, this entry field is disabled (i.e., grayed out).

• Orifice coefficient
  This entry field allows the user to define the orifice discharge coefficient for the horizontal orifice embedded into the vertical riser structure. Clicking on the […] lookup button displays the Orifice Discharge Coefficients dialog box that allows the user to select the orifice discharge coefficient to be assigned. Note that this entry field is only enabled when Orifice Control is selected as the outflow control type. Otherwise, this entry field is disabled (i.e., grayed out).
  

Rating Curve Data

This subpanel displays a data grid that defines the rating curve parameters corresponding to the method selected in the Routing reference method dropdown combo box. Note that this subpanel is only enabled when Vortex Control is selected as the outflow control type. Otherwise, this subpanel is disabled (i.e., grayed out).

The following columns are provided in the data grid:

• Water Surface Depth
  This column defines the water surface depth that is used to construct the rating curve. Note that this column header name changes based upon the selected routing reference method, as shown in the below table.
  

  Routing Reference Method	Column 1	Column 2
  Head Differential	Head Differential	Flow Rate
  Water Surface Depth	Water Surface Depth	Flow Rate
  Water Surface Elevation	Water Surface Elevation	Flow Rate

• Flow Rate
  This column references the flow rate that is used to construct the rating curve.

Rating Curve Plot

This subpanel displays a graphical plot corresponding to the data defined in the Rating Curve Data subpanel. Note that this subpanel is only enabled when Vortex Control is selected as the outflow control type. Otherwise, this subpanel is disabled (i.e., grayed out).

Computational Results

After successfully computing the analysis, this section provides a summary of the stormwater computational results for the selected manhole.

The following results are provided in this section:

• Peak inflow
  This read-only field displays the peak inflow at the manhole during the storm event.

• Maximum WSEL
  This read-only field displays the maximum water surface elevation at the manhole during the storm event.

• Maximum water depth
  This read-only field displays the maximum water depth at the manhole during the storm event.

• Minimum freeboard
  Freeboard height of the manhole is the distance between the rim elevation of the manhole and the water surface level. This read-only field displays the minimum freeboard at the manhole during the storm event.

• Stored water volume
  This read-only field displays the total stored water volume at the manhole during the storm event.

In GeoSTORM software, the Assign Manhole Elevations command allows the user to assign rim and invert elevations to the selected manhole(s). This command uses the elevation terrain surface to compute the rim and invert elevation of an individual manhole(s) with respect to the terrain surface available in the project.

Follow the steps below to use the Assign Manhole Elevations command:

1. From the Input ribbon menu, click the Manhole Structures dropdown menu and select the Assign Manhole Elevations command.
   
2. The Assign Manhole Elevations dialog box will be displayed, as shown below.
   

The following sections describe how to use the Assign Manhole Elevations command and interact with the above dialog box.

Selecting Manholes

The Select Manholes section allows the user to select one or more manholes to assign rim and invert elevations. This section includes a table that lists all the manhole(s) contained within the current scenario of the project, as shown below.

The user can select manhole(s) using any of the following methods to assign rim and invert elevations:

• Check the checkboxes corresponding to each manhole in the Select Manholes section.
  
  
• Click the [Pick] button, the Assign Manhole Elevations dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the manhole(s) from the Map View. After selecting the manhole(s), press the [Enter] key or right-click and choose Done from the displayed context menu. The Assign Manhole Elevations dialog box will be redisplayed.
  
  
• Alternatively, press and hold down the [Ctrl] key while selecting the manhole(s) directly from the Map View. When finished, open the Assign Manhole Elevations dialog box, and the selected manhole(s) will be shown as selected/checked within the Select Manholes section.

After selecting the manhole(s), the total number of selected manhole(s) will be displayed in the Total selected read-only field, as shown below.

Assign Rim and Invert Elevations

This section allows the user to:

• Assign the rim and invert elevations to the manhole(s) using a terrain model.
  
  
• Define the invert depth using the Manhole depth entry field to raise or lower the invert of the manhole by the specified amount. A negative invert depth value lowers the manhole by the specified amount.
  
  
• Define the sump depth required at a manhole using the Sump depth entry field. The sump depth of the manhole represents the vertical offset from the manhole bottom invert elevation to the lowest invert of the connected pipes.

Terrain Elevation Source

Depending upon the terrain elevation source type selected, the contents of the Assign Rim & Invert Elevations section changes to specify additional elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• Elevation Grid
• LandXML Data
• TIN surface

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the contents of the Assign Rim & Invert Elevations section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the contents of the Assign Rim & Invert Elevations section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the contents of the Assign Rim & Invert Elevations section changes, as shown below.

The following options are displayed when TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Assigning Manhole Elevations

Once the data have been defined in the Assign Manhole Elevations dialog box, click the [Assign] button and the software will assign the rim and invert elevations to the selected manhole(s).

In GeoSTORM, the Manhole Table Edit command allows the user to view and edit all the parameters of the manholes in a single editable data grid. The user can also view the corresponding output results from this data grid.

Follow the steps below to use the Manhole Table Edit command:

1. From the Input ribbon menu, click the Manhole Structures dropdown menu and select the Manhole Table Edit command.
   
2. The Manhole Table Edit dialog box will be displayed, as shown below.
   

The following sections describe how to use the Manhole Table Edit command and interact with the above dialog box.

Selecting Storm Results

In the Select Storm Results section, the Storm result to display dropdown combo box allows the user to select the storm frequency whose result is to be displayed.

Note: The Select Storm Results section is only available when either the DeKalb Rational Method, Modified Rational, or Rational Method is selected as the hydrology analysis engine in the Scenario Manager dialog box. Otherwise, this section is unavailable. Refer to this article in our knowledge base to learn more about the hydrology analysis engine.

Manhole Parameters

In the Manhole Parameters section, the following panels are available:

• Manhole Data
• Results Data

Manhole Data

This panel displays editable data grid columns listing all the manhole parameters contained in the current scenario.

The following manhole parameters are provided in the data grid columns:

• Manhole ID
  This editable column lists all manhole IDs contained in the current scenario.

• Rim Elevation
  This editable column lists the manhole rim elevation. The user can manually edit the manhole rim elevation directly from the entry or by clicking the corresponding [...] button and measuring the manhole rim elevation from the Map View.

• Invert Elevation
  This editable column lists the manhole invert elevation.

• Sump Depth
  This editable column lists the sump depth at the manhole. The sump depth of the manhole represents the vertical offset from the manhole bottom invert elevation to the lowest invert of the connected pipes.

• Structure Type
  This column contains a dropdown combo box that allows the user to select a type of manhole structure. The following manhole structure types are available:

• 1. Bolted Cover Manhole
  2. Force Main Connection
  3. Junction Box
  4. Standard Manhole
  

• Footprint Area
  This editable column lists the manhole’s interior storage area. Note that this column is enabled only when Junction Box is selected as the structure type. Otherwise, this column is disabled (i.e., grayed out).

• Initial WSEL
  This editable column lists the water surface elevation (WSEL) of the manhole at the start of the simulation.

• Overflow Ponding Area
  This editable column lists the overflow ponded area. The overflow ponded area is the storage area occupied by the ponded water on the top of the manhole after flooding occurs.

• Baseline Inflow
  This editable column lists the constant baseline inflow.

• Time Series Inflow
  This column contains a dropdown combo box that allows the user to select the time series inflow. Clicking the […] button displays the Time Series Data dialog box, which allows the user to define time series inflow data for manholes. Refer to this article in our knowledge base to learn more about the Time Series Data dialog box.

Results Data

This panel displays data grid columns listing the corresponding output results for manholes contained in the current scenario after the analysis is successfully computed.

The following manhole parameters are provided in the data grid columns:

• Manhole ID
  This editable column lists all manhole IDs contained in the current scenario.

• Peak Inflow
  This read-only column lists the computed peak inflow at the manhole during the storm event.

• Maximum WSEL
  This read-only column lists the computed maximum water surface elevation (WSEL) at the manhole during the storm event.

• Maximum Depth
  This read-only column lists the computed maximum water depth at the manhole during the storm event.

• Minimum Freeboard
  This read-only column lists the computed minimum freeboard height at the manhole during the storm event. Freeboard height of the manhole is the distance between the rim elevation of the manhole and the water surface level.

• Max Stored Water Volume
  This read-only column lists the computed maximum stored water volume at the manhole during the storm event. Note that this column shows values only for the junction box structure type. Otherwise, this column will show N/A.

• Maximum Pipe Cover
  This read-only column lists the computed maximum ground cover measured from the top of the pipe (crown) along the pipe length.

• Minimum Pipe Cover
  This read-only column lists the computed minimum ground cover measured from the top of the pipe (crown) along the pipe length.

Sorting the Manhole Table

The data in the Manhole Parameters table can be sorted by multiple columns. Users can sort the data by holding down the [Shift] key while clicking the Up or Down arrows in the column headers. This allows for multi-column sorting without losing the previous sort. The sorting order is determined by the sequence in which the column headers are selected.

Follow the steps below to sort the data by using multiple columns:

• Select the header of the first column and click the Up or Down arrow to sort the data in ascending or descending order.
• Hold down the [Shift] key, then select the header of the second column and click the Up or Down arrow to sort the second column.
• Repeat step 2 to sort the data for any additional column.

For example, first, select the Manhole ID column and click the Up arrow to sort the data in ascending order. Then, while holding down the [Shift] key, select the Invert Elevation column and click the Down arrow to apply a secondary sort.

Copying and Exporting Manhole Table

The data in the Manhole Parameters table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using right-click context menu commands such as Copy, Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF.

After editing the required manhole parameters, click the [Close] button to close the Manhole Table Edit dialog box.

In GeoSTORM software, the Renumber Interconnected Manholes command allows the user to automatically renumber manholes and connected pipes along a defined pipe path.

Follow the steps below to use the Renumber Interconnected Manholes command:

1. From the Input ribbon menu, click on Manhole Structures dropdown menu and select the Renumber Interconnected Manholes command.
   
2. The Renumber Interconnected Manholes dialog box will be displayed, as shown below.
   

The following sections describe how to use the Renumber Interconnected Manholes command and interact with the above dialog box.

Selecting Pipes

The Select Pipes panel allows the user to select pipes that define the pipe path.

Select Multiple (Interconnected) Pipes

The Select Multiple (Interconnected) Pipes section is used to sequentially number pipes and manholes along the selected pipe path that has pipes interconnected end-to-end with each other.Click the [Pick] button to manually select the pipes from the Map View. The Renumber Interconnected Manholes dialog box will temporarily disappear, allowing the user to select the downstream most and upstream most pipes from the Map View that make up the pipe path. Once finished, press the [Enter] key or right-click and choose Done from the displayed context menu. The dialog box will be redisplayed, and the total number of selected pipes will be displayed in the Total selected read-only field.

Alternatively, if pipes are pre-selected on the Map View, opening the Renumber Interconnected Manholes dialog box will show those pipes selected in the corresponding table section. The selected pipes can be further unselected by unchecking the checkboxes corresponding to them.

Note that the user can pre-select multiple pipes from the Map View by pressing and holding down the [Ctrl] key while selecting the pipes.

Manual Editing

This section contains a table that displays the selected pipes, manholes, pipe distances, and total pipe distances. The values in the New Pipe ID and New Manhole ID columns provide a preview of the renumbered pipes and manholes defined in the Pipe Renumbering and Manhole Renumbering panels.

The data contained in a table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using the Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF commands of the right-click context menu.

Pipe Renumbering

The Pipe Renumbering panel allows the user to renumber pipes based on pipe length or sequentially. By default, the checkbox on this panel is checked. If unchecked, then the content of this panel will be disabled (i.e., grayed out) and pipe renumbering cannot be performed.

The following options are provided in this panel:

• Pipe ID prefix: This optional checkbox entry allows a prefix to be added to the pipe ID.
• Pipe ID suffix: This optional checkbox entry allows a suffix to be added to the pipe ID.
• Pipe ID preview: This read-only field provides a preview of the pipe ID defined in this panel.
• Numbering direction: This dropdown combo box allows the user to select the flow direction in which the pipe IDs can be renumbered. The following options are available:
  • Downstream
  • Upstream

Use Auto Increment

The Use auto increment subsection allows the user to renumber pipes using a fixed increment. Select the Use auto increment radio button option to enable this subsection.

The following options are provided in this subsection:

• Pipe ID digits: This entry field allows the user to set the number of digits to be used for the pipe ID. For example, using 3 digits causes the pipe ID to be of the format 001, 002, etc.
• Next available pipe ID: This entry field defines the next pipe ID number to be used.
• Pipe ID increment: This spin control entry defines the increment to use when numbering pipes. The default value is 1.

Use Pipe Length

The Use pipe length subsection allows the user to renumber pipes based on their length along the defined pipe path. By default, the Use pipe length radio button option is selected when the Pipe Renumbering panel is checked.

The following options are provided in this subsection:

• Downstream pipe ID: This entry provides a pipe ID that will be used as the downstream most pipe number. Note that if the Downstream option is selected in the Numbering direction dropdown combo box, then the Downstream pipe ID entry will be changed into the Upstream pipe ID, as shown below.
  
• Distance units: This dropdown combo box defines the unit of pipe length. The available options are:
  • Feet
  • Miles
• Decimal precision: This checkbox entry defines the decimal precision to be used in renumbering pipes. By default, this checkbox is unchecked. If checked, then the user can enter a value ranging from 0 to 15.

After defining all the required data in this panel, click the [Preview] button to preview the IDs of the renumbered pipes in the New Pipe ID column of the Manual Editing table, as shown below.

Manhole Renumbering

The Manhole Renumbering panel allows the user to renumber manholes based on pipe length or sequentially. By default, the checkbox on this panel is checked. If unchecked, then the content of this panel will be disabled (i.e., grayed out) and the manhole renumbering cannot be performed.

The following options are provided in this panel:

• Manhole ID prefix: This optional checkbox entry allows a prefix to be added to the manhole ID.
• Manhole ID suffix: This optional checkbox entry allows a suffix to be added to the manhole ID.
• Manhole ID preview: This read-only field provides a preview of the manhole ID defined in this panel.
• Numbering direction: This dropdown combo box allows the user to select the flow direction in which the manhole IDs can be renumbered. The following options are available:
  • Downstream
  • Upstream

Use Auto Increment

The Use auto increment subsection allows the user to renumber manholes using a fixed increment. Select the Use auto increment radio button option to enable this subsection.

The following options are provided in this subsection:

• Manhole ID digits: This entry allows the user to set the number of digits to be used for manhole ID. For example, using 3 digits causes the manhole ID to be of the format 001, 002, etc.
• Next available manhole ID: This entry field defines the next manhole ID number to be used.
• Manhole ID increment: This spin control entry defines the increment to use when numbering manholes. The default value is 1.

Use Pipe Length

The Use pipe length subsection allows the user to renumber manholes based on pipe length defined along the pipe path. By default, the Use pipe length radio button option is selected when the Manhole Renumbering panel is checked.

The following options are provided in this subsection:

• Downstream manhole ID: This entry provides a manhole ID that will be used as the downstream most manhole number. Note that if the Downstream option is selected in the Numbering direction dropdown combo box, then the Downstream manhole ID entry will be changed into the Upstream manhole ID, as shown below.
  
• Distance units: This dropdown combo box defines the unit of pipe length. The available options are:
  • Feet
  • Miles
• Decimal precision: This checkbox entry defines the decimal precision to be used in renumbering manholes. By default, this checkbox is unchecked. If checked, then the user can enter a value ranging from 0 to 15.

After defining all the required data in this panel, click the [Preview] button to preview the IDs of the renumbered manholes in the New Manhole ID column of the Manual Editing table, as shown below.

When all the required data have been defined in the Renumber Interconnected Manholes dialog box, click the [Apply] button. The software will then assign the user-defined changes to the pipes and the connected manholes along a defined pipe path. Click the [Close] button to close the dialog box.

Note that when the user clicks the [Preview] button and clicks the [Close] button without applying the changes, the following confirmational dialog box will be displayed.

A manhole is a covered opening in the ground that provides access to underground public utilities such as sewers, storm drains, electricity, etc. for the purpose of inspection, cleaning, unblocking, or repair. In a stormwater drainage system, a manhole represents a physical junction that acts as a connection point between elements such as pipes. In GeoSTORM software, manholes can be defined by either drawing or assigning nodes on the Map View using the following commands:

• Draw Manholes
• Assign Manholes

After drawing/assigning manholes, the user can use the Manhole Data command to define additional manhole data. Refer to this article in our knowledge base to learn more about the Manhole Data command.

Drawing/Assigning Manholes

The Draw/Assign Manholes command allows the user to manually draw/assign single or multiple manhole nodes on the Map View. Follow the steps below to use the Draw/Assign Manholes command:

1. From the Input ribbon menu, click the Manhole Structures dropdown menu and select the Draw/Assign Manholes command.
2. The following dialog box(s) will be displayed.
   • Draw Manholes:
   • Assign Manholes:

The following sections describe how to use the Draw/Assign Manholes command and interact with the above dialog boxes.

Drawing Manhole Nodes

The Draw Manhole Nodes section allows the user to draw single or multiple manhole nodes on the Map View. To draw a manhole node, follow the steps below:

1. Click the [Draw] button, and the dialog box will temporarily disappear.
2. The status bar (shown under the Map View) will prompt the user to draw a manhole node on the Map View. Click on the Map View to draw the manhole node.Note: From the Manhole Specifications section, if:
   • Manhole ID option is selected, then the user can draw only one manhole node on the Map View.
   • Auto-name manhole ID option is selected, then the user can draw multiple manhole nodes on the Map View one after another until completed.
3. When finished, press the [Enter] key or right-click and select Done from the displayed context menu.
4. The Draw Manholes dialog box will be redisplayed, and the status of the Manhole nodes read-only field will be changed from Not Drawn to Drawn.

Notes:

• To place the node more accurately, use the mouse roller wheel to zoom into a specific location.
• The Snap Mode option can be enabled to cause the drawn manhole to snap to the nearest stormwater element.

Assigning Manhole Nodes

The Select Manhole Nodes section can be used to manually assign single or multiple nodes on the Map View as manholes. To assign a manhole node, follow the steps below:

1. Click the [Pick] button and the dialog box will temporarily disappear.
2. The status bar (shown under the Map View) will prompt the user to select a manhole node from the Map View. Click on the previously drawn manhole node on the Map View to select it.Note: From the Manhole Specifications section, if:
   • Manhole ID option is selected, then the user can select only one manhole node on the Map View.
   • Auto-name manhole ID option is selected, then the user can select multiple manhole nodes on the Map View one after another until completed.
3. When finished, press the [Enter] key or right-click and select Done from the displayed context menu.
4. The Assign Manholes dialog box will be redisplayed, and the status of the Manhole nodes read-only field will be changed from Not Selected to Selected.
5. Click the [Clear] button to cancel the previous selection and redo the entire process.

Manhole Specifications

This section is common to both the Draw Manholes and Assign Manholes dialog boxes and allows the user to specify the manhole ID for each drawn/assigned manhole. The user can assign these IDs either manually or automatically using some predefined formats. Follow the steps below to assign manhole IDs to the manholes:

1. If a manhole was drawn/assigned while the Manhole ID radio button option was selected, the user can manually enter the manhole ID in the corresponding field, as shown below.
2. Alternatively, the user can enable the Auto-name manhole ID radio button option in order to automatically name every newly drawn/assigned manhole as per the user’s predefined naming formats as shown below.

The different manhole naming formats present in the Auto-name manhole ID radio button option are as follows:

• Manhole ID prefix: This option allows a prefix to be added to the manhole ID.
• Manhole ID digits: This option permits the specification of a set number of digits to use for the manhole ID. For example, using 3 digits causes the manhole ID to be of the format 001, 002, 003, and so on as new elements are created.
• Next available manhole ID: This option defines the next manhole ID number to be used.
• Manhole ID increment: This option defines the increment to use when numbering manholes. The default value is 1.
• Manhole ID suffix: This option allows a suffix to be added to the manhole ID.
• Manhole ID preview: This read-only field provides a preview of the manhole naming specifications defined above.

Assign Rim and Invert Elevations

This section allows the user to:

• Assign the rim and invert elevation to the manhole using a terrain model.
• Define the invert depth using the Manhole depth entry field to raise or lower the invert of the manhole by the specified amount. A negative invert depth value lowers the manhole by the specified amount.
• Define the sump depth required at a manhole using the Sump depth entry field. The sump depth of the manhole represents the vertical offset from the manhole bottom invert elevation to the lowest invert of the connected pipes.

Note: Define this section before drawing/assigning manholes so that the rim and invert elevation can be assigned.

Terrain Elevation Source

Depending upon the terrain elevation source type selected, the content of the Assign Rim & Invert Elevations section changes to specify additional elevation data information. The Terrain elevation source dropdown combo box supports the following surface types:

• Elevation Grid
• LandXML Data
• TIN surface

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the content of the Assign Rim & Invert Elevations section changes as shown below.

The following option is displayed when the Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer This dropdown combo box allows the user to select the elevation grid layer available in the project.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the content of the Assign Rim & Invert Elevations section changes as shown below.

The following options are displayed when the LandXML Data is selected as the terrain elevation source:

• TIN surface layer This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface This dropdown combo box allows the user to select the TIN surface type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the content of the Assign Rim & Invert Elevations section changes as shown below.

The following options are displayed when the TIN Surface is selected as the terrain elevation source:

• TIN surface layer This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface This dropdown combo box allows the user to select the TIN surface type.

After defining all the required data, click the [Apply] button to complete drawing/assigning manholes. Note that if manholes are drawn/assigned using the Auto-name manhole ID option, then the [Apply] button will be displayed as disabled since the just drawn/assigned manhole have already been named and created.

The Georeference Manholes command allows the user to manually georeference each of the manholes to the background base map displayed in the Map View.

The process of georeferencing a manhole to the Map View can be a trial and error process—especially when the exact location of the original manhole is not known. With the use of the Georeference Manholes command, the georeferencing process can be accelerated.

Note that a CRS should be assigned before running this command. Otherwise, the software will display the below informational dialog box.

Refer to this article in our knowledge base to learn how to assign a coordinate reference system to a project.

Follow the steps below to georeference an existing manhole:

1. From the Input ribbon menu, click on the Manhole Structures dropdown menu and select the Georeference Manholes command.
   
2. The Georeference Manholes dialog box will be displayed.
   

The following sections describe how to georeference an existing manhole and interact with the above dialog box.

Selecting Manhole to Georeference

The Select Manhole to Georeference section allows the user to select the manhole that is to be georeferenced.

Follow the steps below to select the manhole to be georeferenced:

1. Select the manhole from the Manhole ID dropdown combo box listing all the manholes contained within the current scenario.
   
2. Alternatively, the user can click the [Pick] button to select the manhole from the Map View. After clicking the [Pick] button, the Georeference Manholes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next.
3. Upon selecting the manhole, the user is immediately returned to the dialog box, and the selected manhole will be highlighted on the Map View.
4. The user can click the [Clear] button to cancel the previous selection and redo the entire process.

Once the manhole has been selected, the user can choose between the following options to georeference the manhole:

• Snap to Alignment Point
• Slide Along Alignment Polyline
• Draw on Map View

Snapping Manhole to an Alignment Point

If an existing alignment point for the manhole exists on the Map View, the Snap to Alignment Point option can be used to snap the manhole to the alignment point.

Follow the steps below to use the Snap to Alignment Point option:

1. Select the Snap to Alignment Point radio button option.
2. Click the [Pick] button.
   
3. The Georeference Manholes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the alignment point.
4. Select the alignment point on the Map View. Note that the user can select only one alignment point at a time to use for georeferencing.
5. The Georeference Manholes dialog box will be redisplayed and the status of the Select alignment point read-only field will be changed from Not Selected to Selected. The user can click the [Clear] button to cancel the previous selection and redo the entire process.
   
6. Click the [Snap] button to snap the selected manhole to the alignment point.
   
   Once the user clicks the [Snap] button, the following informational dialog box will be displayed.
   
   Click the [Yes] button to split the entity or abort the split process by clicking the [No] button.

Sliding Manhole Along Alignment Polyline

If a manhole has been snapped to an alignment point on the Map View but is not precisely located where it should be, the Slide Along Alignment Polyline option can be used to slide the manhole along the alignment polyline.

Follow the steps below to use the Slide Along Alignment Polyline option:

1. Select the Slide Along Alignment Polyline radio button option.
2. Click the [Pick] button.
   
3. The Georeference Manholes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the alignment polyline from the Map View.
4. After selecting the alignment polyline, the following informational dialog box will be displayed. Click the [Yes] button to select the polyline or abort the selection by clicking the [No] button.
   
5. Once the alignment polyline is selected, the Georeference Manholes dialog box will be redisplayed and the status of the Select alignment polyline element read-only field will be changed from Not Selected to Selected. Then click the [Slide] button.
   
6. The Georeference Manholes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the manhole and drag it along the underlying alignment polyline.
7. Click and drag the manhole on the Map View to revise its alignment.
8. When finished, press the [Enter] key or right-click and select Done from the displayed context menu. The Georeference Manholes dialog box will be redisplayed, and the manhole will be georeferenced at the new location.

Note that for more precision, the user can use the Snap to Alignment Point option first and then use the Slide Along Alignment Polyline option.

Drawing Manhole on Map View

The Draw on Map View option allows the user to draw a manhole node on the Map View and automatically snap the selected manhole to the drawn node.

Follow the steps below to use the Draw on Map View option:

1. Select the Draw on Map View radio button option and click the [Draw] button.
   
2. The Georeference Manholes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to draw the manhole node on the Map View.
3. Draw the manhole node on the Map View. When finished, press the [Enter] key or right-click and select Done from the displayed context menu.
4. The Georeference Manholes dialog box will be redisplayed, and the manhole will automatically snap to the drawn node.

Assigning Rim & Invert Elevations

The user can check the Assign Rim & Invert Elevations checkbox option to assign rim and invert elevations to the manhole using a terrain model.

Define this section before georeferencing manholes so that the rim and invert elevations can be assigned.

To assign rim and invert elevations, the Terrain elevation source dropdown combo box supports the following surface types:

• Elevation grids
• LandXML data
• TIN surfaces

Depending upon the elevation data source type that is selected, different options are provided to specify additional elevation data information.

The user can define an invert depth using the Manhole depth entry field to raise or lower the invert of the manhole by the specified amount. A negative invert depth value lowers the manhole by the specified amount.

The user can use the Sump depth entry field to define the sump depth required at the manhole. The sump depth of a manhole represents the vertical offset from the manhole bottom invert elevation to the lowest invert of the connected pipes.

Pipes are conduits in stormwater drainage systems, designed to transport captured runoff from one node to another. Pipes play a vital role in urban drainage by efficiently managing stormwater runoff and preventing flooding. Pipes connect various drainage system elements, such as manholes, catch basins, and outlets. Pipes can be constructed from materials like concrete, cast iron, and PVC.

In GeoSTORM software, pipes can be drawn or assigned using Draw Pipes and Assign Pipes commands. Refer to this article in our knowledge base to learn how to incorporate pipes into a stormwater project.

After adding pipes to a stormwater project, the Pipe Data command can be used to define additional data and view the corresponding output results associated with the pipes.

Follow the steps below to use the Pipe Data command:

1. From the Input ribbon menu, click the Stormwater Pipes dropdown menu and select the Pipe Data command.
   
2. The Pipe Data dialog box will be displayed, as shown below.
   

The following sections describe how to use the Pipe Data command and interact with the above dialog box.

Selecting Pipe

The Select Pipe section allows the user to select the pipe for which pipe data will be defined. In this section, the user can create, delete, and copy existing pipe data to a new pipe. In addition , the user can navigate between pipes and enter a description for each pipe.

The following entries are provided in this section:

• Pipe ID
  This dropdown combo box lists all the pipes defined in the current scenario. Click on the edit option (i.e., the pencil icon) to edit the pipe ID. The user can navigate between the previous and next pipe using the Up and Down arrow buttons. Alternatively, the user can click the [...] button to select the pipe from the Map View. Note that the Up and Down arrow buttons will be disabled (i.e., grayed out) if the current scenario contains a single pipe.
• Description
  This optional field allows the user to enter additional information that describes the selected pipe.
• New
  The [New] button allows the user to create a new pipe on the Map View. The ID of every newly created pipe must be unique.
• Copy
  The [Copy] button allows the user to copy an existing pipe along with its associated data to a new pipe. The software automatically provides a unique ID to the copied pipe.
• Delete
  The [Delete] button allows the user to delete the selected pipe from the current scenario.
• Less/More
  The [< Less] and [More >] buttons at the Select Pipe section header allows the user to expand or collapse the Computed Results section.

Pipe Specifications

Pipe Definition

This section allows the user to define general parameters for the selected pipe.

The following options are provided in this section:

• Shape
  This dropdown combo box lists all the pipe shapes that the software supports. By default, a Circular pipe shape is selected.
  
  Clicking on the [...] button displays the Select Pipe Shape dialog box, which allows the user to select any non-circular pipe shape that the software supports.
  
• Backflow flap gate
  This checkbox option specifies whether a flap gate will be enabled to prevent backflow (or flow reversal) for the pipe. By default, this checkbox option is unchecked.
  
• Number parallel pipes
  This spin control entry field specifies the number of identical parallel pipes to be defined. By default, the software uses a value of 1. However, the user can enter a different value ranging from 1 to 100.
  
• Diameter
  This dropdown combo box defines the internal diameter for the selected pipe. The user can click on the edit option (i.e., the pencil icon) to edit the pipe diameter. Clicking on the […] button displays the Define Standard Pipe Dimensions dialog box that allows the user to define additional pipe diameters. These additional pipe diameters will then be listed in the Pipe diameter dropdown combo box. Note that this dropdown combo box is available only for the Circular pipe shape.
  
  
• Width
  This entry field defines the width of the pipe. The following table shows when this field is enabled or disabled based on the shape of the pipe:
  

  Pipe Shape	Width
  Arch	Enabled
  Basket Handle	Disabled
  Basket Handel, Modified	Enabled
  Catenary	Disabled
  Circular	Disabled
  Egg	Disabled
  Ellipse, Horizontal	Enabled
  Ellipse, Semi	Disabled
  Ellipse, Vertical	Enabled
  Gothic	Disabled
  Horseshoe	Disabled
  Rectangular	Enabled
  Rectangular & Circular	Enabled
  Rectangular & Triangular	Enabled
  Semi-Circular	Disabled

  
  
• Size code
  This read-only entry field displays the specific code for each pipe dimension selected in the dropdown combo box next to this field. Note that the dropdown combo box is available only for the Arch, Ellipse Horizontal, or Ellipse Vertical pipe shape.
  
• Length
  This entry field defines the length of the pipe being modeled. The user can click the [Pick] button to measure the pipe length from the Map View. Clicking on the [Recalc] button allows the software to recalculate the digitized length of the current pipe. Similarly, clicking on the [Recalc All] button allows the software to recalculate the digitized length of all pipes in the network.
  
• Inlet invert elevation
  This entry field defines the pipe invert elevations on the upstream end. Clicking on the [Up] arrow button causes the pipe invert elevation to be set so that the crown (top) of the pipe matches the crown of the largest diameter pipe that already connects to the same node. Clicking on the [Down] arrow button causes the pipe invert elevation to be set equal to the connecting node invert elevation.
  
• Outlet invert elevation
  This entry field defines the pipe invert elevation on the downstream end. Clicking on the [Up] arrow button causes the pipe invert elevation to be set so that the crown (top) of the pipe matches the crown of the largest diameter pipe that already connects to the same node. Clicking on the [Down] arrow button causes the pipe invert elevation to be set equal to the connecting node invert elevation.
  
• From (Inlet node)
  This read-only field defines the node ID on the inlet end of the pipe. The user can click the […] button to select the inlet node from the Map View. Clicking on the [Swap] button allows the user to switch the inlet and outlet nodes, effectively reversing the direction of the pipe.
  
• To (Outlet node)
  This read-only field defines the node ID on the outlet end of the pipe. The user can click the […] button to select the outlet node from the Map View.
  
• Pipe slope (H:V)
  This entry field displays the slope of the pipe. In addition, this field can be used to set the slope of the pipe. The user can click on the edit option (i.e., the pencil icon) adjacent to the Pipe slope (H:V) field to change the read-only field into an editable field. The user can then enter the pipe slope and click on the [Accept changes] button. The software will then adjust the unlocked pipe end invert elevation to meet the updated slope value.
  
  Note: To set the slope of the pipe, the user should first select the end of the pipe invert elevation that is to be locked. The following options are provided in the dropdown combo box adjacent to the Pipe slope (H:V) entry field:
  1. Lock Downstream Invert
  2. Lock Upstream Invert

Note that based upon the selected shape of the pipe, the following additional options will be available in the Pipe Definition section:

• Height
  This entry field defines the height of the pipe. Note that this entry field is available only for the non-circular pipe shape.
  
• Triangle depth
  This entry field defines the depth of the triangular pipe, which is the vertical distance from the base to the topmost point (apex). Note that this entry field is available only for the Rectangular & Triangular pipe shape.
  
• Top radius
  This entry field defines the radius of the pipe, which is the distance from the center of the top curve to the outer edge of the pipe. Note that this entry field is available only for the Basket Handle, Modified pipe shape.
  
• Bottom radius
  This entry field defines the radius of the pipe, which is the distance from the center of the bottom curve to the outer edge of the pipe. Note that this entry field is available only for the Rectangular & Circular pipe shape.
  

Pipe Coefficients

This section allows the user to define Manning’s roughness, entrance loss, exit loss, and other head losses coefficients for the selected pipe.

The following options are provided in this section:

• Manning’s roughness
  This entry field defines the roughness of the pipe. Clicking on the [...] button displays the Channel and Pipe Manning’s Roughness lookup dialog box, which allows the user to choose Manning’s roughness coefficient to be assigned to a pipe.
  
• Entrance loss coefficient
  This entry field defines the head loss coefficient associated with energy losses at the inlet of the pipe as the flow enters the pipe from a node (i.e., manhole, junction box, routing junction, catch basin, or storage area). Clicking on the [...] button displays the Entrance Loss Coefficients For Pipes lookup dialog box, which allows the user to choose the entrance loss coefficient to be assigned to a pipe.
  
• Exit/bend loss coefficient
  This entry field is used to define the head loss coefficient associated with energy losses at the outlet of the pipe as the flow leaves the pipe and enters a node (i.e., manhole, junction box, routing junction, catch basin, or storage area). Clicking on the [...] button displays the Exit Loss Coefficients For Pipes lookup dialog box, which allows the user to choose the exit loss coefficient to be assigned to a pipe.
  
• Other head losses coeff
  This entry field defines the head loss coefficient associated with energy losses along the length of the pipe.

Computational Results

After successfully computing the analysis, this section provides a summary of the stormwater computational results for the selected pipe.

The following results are provided in this section:

• Peak flow rate
  This read-only field displays the peak flow rate in the pipe during the storm event.
• Maximum flow velocity
  This read-only field displays the maximum flow velocity in the pipe during the storm event.
• Design flow capacity
  This read-only field displays the flow rate capacity of the pipe for gravity flow conditions (i.e., non-pressurized).
• Additional flow capacity
  This read-only field displays the difference between the Peak flow rate and the Design flow capacity values.
• Max/design flow ratio
  This read-only field displays the ratio of the Peak flow rate to the Design flow capacity values.
• Max/total depth ratio
  This read-only field displays the ratio of pipe flow depth to pipe diameter.
• Total time surcharged
  This read-only field displays the duration (in minutes) during hydrodynamic routing when the pipe's Max/Total Depth Ratio was ≥ 100%.
• Maximum pipe cover
  This read-only field displays the computed maximum ground cover measured from the top of the pipe (crown) along the pipe length.
• Minimum pipe cover
  This read-only field displays the computed minimum ground cover measured from the top of the pipe (crown) along the pipe length.

In stormwater modeling and drainage system design, understanding the behavior of water as it flows through a closed conduit, such as a pipe or culvert, is essential. One crucial aspect to determine this is the water surface profile, which represents the longitudinal variation in flow depth along the pipe.

Accurately determining the water surface profile helps the user anticipate flow conditions, locate hydraulic jumps, and verify that systems perform within acceptable limits.

Factors Impacting the Water Surface Profile

The following factors impact the water surface profile in a pipe:

• Flow Rate
  Flow rates can change the flow pattern and affect how full the pipe is.

• Pipe Slope
  The slope of the pipe impacts flow velocity and energy grade, which in turn affects depth variations.

• Pipe Geometry
  The diameter, shape, and cross-section of the pipe determine the hydraulic radius and flow area, which further impacts the water surface profile.

• Pipe Roughness
  The Manning’s roughness value (represented by “n”) impacts the flow velocity and depth.

• Boundary Conditions
  Tailwater level, flow pattern, and inlet/outlet control also impact how the water surface profile develops.

Applications of Water Surface Profiling

The following represent widespread applications associated with determining water surface profiles within a pipe:

• Stormwater Management
  Determining the water surface profile helps to design pipes that avoid surcharging or flooding during storm events.

• Hydraulic Engineering
  Civil engineers can use the water surface profile to analyze the gradually varied flow and identify transitions such as supercritical to subcritical flow (hydraulic jump) within a pipe.

• Water Distribution Systems and Drainage Network
  Determining the water surface profile also ensures optimal system performance and flow capacity under varied demand conditions.

Key Hydraulic Equations for Analysis

Continuity Equation

This equation expresses the conservation of mass in a flowing system. The discharge (Q) is the product of flow velocity (v) and cross-sectional flow area (A).

Where:

Q = Discharge (flow rate)

v = Flow velocity

A = Cross-sectional flow area

Manning’s Equation

This equation estimates flow in an open channel or under partially full pipe conditions. It accounts for pipe shape and cross-sectional area (A), surface roughness (or Manning’s roughness) coefficient (n), hydraulic radius (R), and channel slope (S).

Where:

Q = Discharge (flow rate)

n = Manning's roughness coefficient

A = Cross-sectional flow area

R = Hydraulic radius

s = Channel slope

Energy Equation

This equation compares energy at two points in the system. It considers velocity head (v²/2g) and elevation head (Y), allowing engineers to evaluate changes in flow energy along the pipe.

Where:

v²/2g = Velocity head

Y = Elevation head

Determining Water Surface Profile within a Pipe

The water surface profile within a pipe is determined by comparing energy levels at two sections along the pipe. Starting from a known depth at one end, the energy is calculated for the next section to estimate the flow depth there. This process is repeated along the length of the pipe until the profile is established from start to end.

To determine the water surface profile within a pipe, the user can:

Define the Pipe System

Define the pipe geometry, that is, length, diameter, and slope of the pipe.

Determine the Flow Pattern

Determine the pattern of the flow through the flow type. The full flow represents the pressurized flow conditions, and the partially full flow represents open channel flow conditions.

Apply the Key Hydraulic Equations

Use the appropriate equations (Continuity, Manning’s, and Energy) to compute the flow depth at each section.

Identify Potential Hydraulic Jumps

In some cases, a hydraulic jump may occur when supercritical flow transitions to subcritical flow, often causing a sudden rise in the water surface. This occurs due to a change in slope, downstream controls, or other energy-loss conditions. Identifying where a hydraulic jump might occur is important for assessing energy dissipation and flow behavior within the pipe. Refer to this article in our knowledge base to learn more about the hydraulic jump.

Water Surface Profiles in GeoSTORM

In GeoSTORM, users can compute and visualize the water surface profile within a pipe using the Profile Plot command. The following illustration displays a typical water surface profile within a pipe in GeoSTORM:

Refer to this article in our knowledge base to learn more about the Profile Plot command.

In GeoSTORM, pipes can be defined by either drawing or assigning polylines on the Map View using the following commands:

• Draw Pipes
• Assign Pipes

After adding pipes to a stormwater project, the user can use the Pipe Data command to define additional pipe data. Refer to this article in our knowledge base to learn more about the Pipe Data command.

Draw Pipes Command

Follow the steps below to use the Draw Pipes command:

1. From the Input ribbon menu, click the Stormwater Pipes dropdown menu and select the Draw Pipes command.
   
2. The Draw Pipes dialog box will be displayed.
   

Drawing Pipe Elements

The Draw Pipe Elements section allows the user to draw single or multiple polylines on the Map View as pipes.

Follow the steps below to draw pipes:

1. Click the [Draw] button and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt the user to draw a pipe polyline on the Map View in the upstream to downstream direction.Note: From the Pipe Specifications section of the Pipe Naming panel, if:
   • Pipe ID option is selected, then the user can draw only one pipe polyline on the Map View.
   • Auto-name pipe ID option is selected, then the user can draw multiple pipe polylines on the Map View one after another until completed.
3. After drawing pipe polyline(s), the Draw Pipes dialog box will be redisplayed, and the pipe polyline(s) will be drawn on the Map View.

Notes:

• If the “Insert intermediate manholes at pipe bends” checkbox option is checked, then the software places intermediate manholes at the pipe where it bends. If this checkbox option is unchecked, manholes can only be inserted at the ends of the pipe.
• If the “Discard accidentally digitized pipe less than” checkbox option is checked, then the software discards accidentally digitized pipes that are shorter than the defined length. The user can define the length of the pipe in the entry field next to this checkbox option.
• The [Reverse Direction] button reverses the flow direction of the pipe polyline drawn.

Naming Specifications

This section allows the user to define the naming specifications for each drawn pipe along with the associated manholes.

Pipe Naming

Pipe Specifications

In the Pipe Naming panel, the Pipe Specifications subsection allows the user to specify the pipe ID for each drawn pipe. The user can assign these IDs either manually or automatically using some predefined formats.

Follow the steps below to define naming specifications for pipes:

1. If a pipe was drawn while the Pipe ID radio button option was selected, the user can manually enter the pipe ID in the corresponding field, as shown below.
   
2. Alternatively, the user can enable the Auto-name pipe ID radio button option in order to automatically name every newly drawn pipe as per the user’s predefined naming formats, as shown below.
   The different pipe naming formats present in the Auto-name pipe ID radio button option are as follows:
   • Pipe ID prefix: This option allows a prefix to be added to the pipe ID.
   • Pipe ID digits: This option permits the specification of a set number of digits to use for the pipe ID. For example, using 3 digits causes the pipe ID to be of the format 001, 002, 003, and so on as new pipes are created.
   • Next available pipe ID: This option defines the next pipe ID number to be used.
   • Pipe ID increment: This option defines the increment to use when numbering pipes. The default value is 1.
   • Pipe ID suffix: This option allows a suffix to be added to the pipe ID.
   • Pipe ID preview: This read-only field provides a preview of the pipe naming specifications defined above.

Manhole Naming

Auto-Name Manhole ID

In the Manhole Naming panel, the Auto-Name Manhole ID subsection allows the user to specify the IDs for each manhole that are created automatically while drawing pipes. The user can assign these IDs automatically using some predefined formats.

The different manhole naming formats present in the Auto-name manhole ID radio button option are as follows:

1. Manhole ID prefix: This option allows a prefix to be added to the manhole ID.
2. Manhole ID digits: This option permits the specification of a set number of digits to use for the manhole ID. For example, using 3 digits causes the manhole ID to be of the format 001, 002, 003, and so on as new manholes are created.
3. Next available manhole ID: This option defines the next manhole ID number to be used.
4. Manhole ID increment: This entry defines the increment to use when numbering manholes. The default value is 1.
5. Manhole ID suffix: This option allows a suffix to be added to the manhole ID.
6. Manhole ID preview: This read-only field provides a preview of the manhole naming specifications defined above.

Assigning Invert Elevations

This section allows the user to:

• Assign an invert elevation to the pipe using a terrain model.
• Define the invert depth using the Pipe invert depth entry field to raise or lower the invert of the pipe by the specified amount.
• Define the sump depth required at a manhole using the Manhole sump depth entry field.

Note: Define this section before drawing pipes so that the invert elevation and manhole sump depth can be assigned.

Terrain Elevation Source

Depending upon the type of terrain elevation source selected, the content of the Assign Invert Elevations section changes to specify additional elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• Elevation Grid
• LandXML Data
• TIN Surface

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the contents of the Assign Invert Elevations section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the contents of the Assign Invert Elevations section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the contents of the Assign Invert Elevations section changes, as shown below.

The following options are displayed when TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Other Specifications

This section allows the user to define the physical properties for the drawn pipes.

The following options are provided in this section:

• Pipe diameter
  This dropdown combo box allows the user to define the internal diameter for the drawn pipe. The user can click on the edit option (i.e., the pencil icon) to edit the pipe diameter. Clicking on the […] browse button displays the Define Standard Pipe Dimensions dialog box that allows the user to define additional pipe diameters. These additional pipe diameters will then be listed in the Pipe diameter dropdown combo box.
  

• Manning’s roughness
  This entry field allows the user to define Manning’s roughness for the drawn pipe. Clicking on the […] browse button displays the Channel and Pipe Manning’s Roughness lookup dialog box, which allows the user to select a Manning’s roughness coefficient to be assigned to a pipe.
  

After defining all the required data, click the [Apply] button to complete drawing pipes.

Note that if pipes are drawn using the Auto-name pipe ID option, then the [Apply] button will be displayed disabled since the just drawn pipes have already been named and created.

Assign Pipes Command

Follow the steps below to use the Assign Pipes command:

1. From the Input ribbon menu, click the Stormwater Pipes dropdown menu and select the Assign Pipes command.
   
2. The Assign Pipes dialog box will be displayed.
   

Selecting Pipe Polylines

The Select Pipe Polylines section allows the user to manually assign single or multiple polylines on the Map View as pipes.

Follow the steps below to assign polylines as pipes:

1. Click the [Pick] button and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt the user to click near the downstream end of the already drawn pipe polyline on the Map View to select it.Note: From the Pipe Specifications section, if:
   • Pipe ID option is selected, then the user can select only one pipe polyline on the Map View.
   • Auto-name pipe ID option is selected, then the user can select multiple pipe polylines on the Map View one after another until completed.
3. After selecting polyline(s), the Assign Pipes dialog box will be redisplayed, and the pipe polyline(s) will be selected on the Map View.
4. Click the [Clear] button to cancel the previous selection and redo the entire process.

Notes:

• If the “Discard accidentally digitized pipe less than” checkbox option is checked, then the software discards accidentally digitized pipes that are shorter than the defined length. The user can define the length of the pipe in the entry field next to this checkbox option.
• The [Reverse Direction] button reverses the flow direction of the pipe polyline assigned.

Pipe Specifications

This section is similar to the Pipe Specifications subsection explained above for the Draw Pipes dialog box.

Assigning Invert Elevations

This section is similar to the Assigning Invert Elevations section explained above for the Draw Pipes dialog box.

Other Specifications

This section is similar to the Other Specifications section explained above for the Draw Pipes dialog box. It contains an additional checkbox option “Create manholes (if missing) at pipe ends.” This checkbox option allows the software to create a manhole at the pipe ends if there is no node already defined within the connection snap distance. The manhole invert elevation is set equal to the pipe invert elevation.

Note that the Create manholes (if missing) at pipe ends entry is checked by default.

After defining all the required data, click the [Apply] button to complete assigning pipes.

Note that if pipes are assigned using the Auto-name pipe ID option, then the [Apply] button will be displayed disabled since the just assigned pipes have already been named and created.

In GeoSTORM software, the Assign Pipe Invert Elevations command allows the user to assign pipe invert elevations based on the defined invert computation methods. In addition, this command allows the user to view the corresponding pipe profile plot of the selected pipe profile path.

Follow the steps below to use the Assign Pipe Invert Elevations command:

1. From the Input ribbon menu, click on the Stormwater Pipes dropdown menu and
   select the Assign Pipe Invert Elevations command.
   
2. The Assign Pipe Invert Elevations dialog box will be displayed.
   

The following sections describe how to use the Assign Pipe Invert Elevations command and interact
with the above dialog box.

Define Pipe Profile

Selecting Profile Path

In the Define Pipe Profile panel, the table under the Define Profile Path section displays the pipes or routing reaches that make up the profile path. The user can select from a pipe/routing reach/manhole/junction at both ends of the path. The software will then automatically determine the connected pipes/routing reaches between them that make up the profile path.

Follow the steps below to manually select the pipes/routing reaches to be assigned for pipe invert elevation:

1. Click the [Pick] button to select the pipe/routing reach/manhole/junction from the Map View that makes up the profile path.
   
2. The Assign Pipe Invert Elevations dialog box will temporarily disappear, allowing the user to select the most downstream and upstream pipe/routing reach/manhole/junction from the Map View.
3. Once finished, press the [Enter] key or right-click and select Done from the displayed context menu.
4. The dialog box will be redisplayed, and the total number of selected pipes/routing reaches will be shown in the Total Selected read-only field.
   
5. The selected profile path will also get added under the Select profile path dropdown combo box.

Profile Path Table

After selecting pipe/routing reach/manhole/junction at both ends of the profile path, the table under the Define Profile Path section displays the list of all the user-selected pipes/routing reaches and their associated properties. The user can also select from the already saved profile paths from the Select profile path dropdown combo box.

The following options and properties are provided in the table viewable under the Define Profile Path section:

• Lock/Unlock
  This table column contains a padlock icon that defines whether a row is locked or unlocked. Unlocking a row allows the software to compute new invert elevations for the pipe, as well as allow the user to manually edit the invert elevation entries. By default, the rows are unlocked.

• Pipe/Reach ID
  This read-only table column lists the pipe or reach IDs for the selected pipe profile.

• Upstream Invert Elevation
  This editable table column defines the pipe upstream invert elevation. If the row is locked, then this entry is displayed as a read-only field.

• Downstream Invert Elevation
  This editable table column defines the downstream pipe invert elevation. If the row is locked, then this entry is displayed as a read-only field.

• Maximum Ground Cover
  This read-only table column defines the computed maximum ground cover measured from the top of the pipe (crown) along the pipe length.

• Minimum Ground Cover
  This read-only table column defines the computed minimum ground cover measured from the top of the pipe (crown) along the pipe length.

• Element Length
  This read-only table column defines the pipe element length.

• Element Slope
  This read-only table column defines the computed pipe element slope.

Notes:

• Clicking the [Clear] button will clear the current pipe profile path from the Define Profile Path section. Additionally, the populated data in the table will be emptied.
• Clicking the [Delete] button displays a confirmation dialog box. This dialog box allows the users to delete the selected pipe profile path.
  

Saving Profile Path

The user can save the currently selected profile path for the user-selected profile path elements. Clicking the [Save Profile Path] button displays the Save Pipe Profile Path dialog box that allows the user to name and save the current pipe profile path.

Note that within the current scenario, the name of the pipe profile paths that are to be saved must be unique. Therefore, if the user applies the same pipe profile path name as an existing path, the software will
confirm whether to overwrite the existing pipe profile path.

Extract Elevation Data

This section is used to define the elevation data source to be used for assigning the pipe invert elevations. Depending on the selected elevation data source type, the contents of this section changes to specify additional elevation data information.

The following options are available in the Terrain elevation source dropdown combo box:

• Elevation Grid
• LandXML Data
• TIN Surface

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the contents of the Extract Elevation Data section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer: This dropdown combo box allows the user to select the elevation grid layer available in the project.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the contents of the Extract Elevation Data section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer: This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface: This dropdown combo box allows the user to select the TIN surface type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the contents of the Extract Elevation Data section changes, as shown below.

The following options are displayed when TIN Surface is selected as the terrain elevation source:

• TIN surface layer: This dropdown combo box allows the user to select the TIN surface layer type.
• TIN surface: This dropdown combo box allows the user to select the TIN surface type.

Pipe Invert Elevation Computation Options

This section allows the user to specify the general options used for assigning the pipe invert elevations.

The following options are available in this section:

• Allow manhole invert to lower to meet pipe invert requirements
  This checkbox option allows the user to lower the manhole invert elevations to meet computed pipe invert requirements.
• Apply defined elevation changes to adjacent upstream pipes
  This checkbox option allows the user to adjust all upstream pipe elevations entering a manhole along the defined pipe profile path.
  Note that when this checkbox option is left unchecked, only the elevations of the upstream pipes along the defined pipe profile path are modified.
• Manhole sump depth
  This checkbox entry field allows the user to define the sump depth required at a manhole.

Multiple Upstream Pipes - Invert Computation Method (Flowing into Manhole)

This section allows the user to specify the computational method used to assign the pipe invert elevations for the inflowing pipes that meet at a manhole.

The following options are available in this section:

• Do not change pipe invert elevations
  This radio button option is used to prevent changes to the pipe invert elevations.
• Match pipe invert elevations
  This radio button option causes the pipe invert elevations to match each other.
• Match pipe crown elevations
  This radio button option causes the pipe crown elevations to match each other.
• Invert elevation drop across manhole from inlet pipe to outlet pipe
  This radio button entry field defines the drop in invert elevation from the inlet pipes to the outlet pipe.

Pipe Profile Checks

This section allows the user to define what checks should be used for the defined pipe profile path.

For those pipes that violate the defined checks, the corresponding table cells under the Define Profile Path section will be displayed in red, as shown below.

The following options are available in the Pipe Profile Checks section:

• Maximum allowable ground cover above pipe
  This checkbox entry field defines the maximum allowable ground cover along the length of the pipe. If the computed maximum ground cover is larger than the defined maximum allowable ground cover, then the Maximum Ground Cover table column will be displayed in red. By default, the maximum allowable ground cover above the pipe is 12 ft.
• Minimum allowable ground cover above pipe
  This checkbox entry field defines the minimum allowable ground cover along the length of the pipe. If the computed minimum ground cover is less than the defined minimum allowable ground cover, then the Minimum Ground Cover table column will be displayed in red. By default, the minimum allowable ground cover above the pipe is 3 ft.
• Maximum and minimum allowable pipe slopes
  This checkbox option defines the maximum and minimum allowable pipe slopes from a design perspective. Clicking the [Define] button will display the Allowable Pipe Slopes dialog box.
  
  This dialog box allows the user to define the recommended maximum and minimum pipe slope based on pipe diameters and the defined maximum and minimum flow velocities during the storm peak. If the computed pipe slope is outside the defined allowable pipe slopes, then the Element Slope data column is displayed in red.

Downstream Pipe - Invert Computation Method (Flowing out of Manhole)

This section allows the user to compute pipe invert elevations for the downstream pipe flowing out of the current manhole.

The following options are available in this section:

• Do not change pipe invert elevation
  This radio button option prevents the change of downstream pipe invert elevation.
• Invert depth from elevation surface
  This radio button option causes the software to set the pipe invert elevations to a specific depth below the terrain elevation surface.
• Invert depth above manhole invert (in addition to manhole sump depth)
  This radio button option causes the software to set the pipe invert elevations to a specific height above the bottom of the manhole inverts, or above the manhole sump depth (if defined).
• Pipe slope from most upstream manhole, starting pipe invert depth at upstream end
  This radio button option causes the software to compute the pipe invert elevations starting from the most upstream manhole and then moving downstream.
• Pipe slope from most downstream manhole, starting pipe invert depth at downstream end
  This radio button option causes the software to compute the pipe invert elevations starting from the most downstream manhole and then moving upstream.

View Pipe Profile

The View Pipe Profile panel allows the user to view the pipes, manholes, and ground surfaces along the defined pipe profile path.

Computing and Assigning Invert Elevations

After defining all the required data, click the [Compute] button to compute new pipe invert elevations for unlocked pipes.

Once the computation is done, click the [Assign] button to assign the defined pipe invert elevations for the unlocked pipe.

In GeoSTORM software, the user can assign invert elevations to project elements, such as routing reach and roadway segments based on the selected terrain surface. Following are the types of commands that can be used to assign invert elevations to the project elements:

• Assign Routing Reach Invert Elevations
• Assign Roadway Segment Invert Elevations

In this article, we will use the Assign Roadway Segment Invert Elevations command to describe how to assign roadway segment invert elevations in GeoSTORM software.

Follow the steps below to use the Assign Roadway Segment Invert Elevations command:

1. From the Input ribbon menu, click the Roadway Gutter/Ditch/Inlets dropdown menu and select the Assign Roadway Segment Invert Elevations command.
   
2. The Assign Roadway Invert Elevations dialog box will be displayed, as shown below.
   

The following sections describe how to use the Assign Roadway Invert Elevations command and interact with the above dialog box.

Selecting Roadway Segments

The Select Roadway Segments section allows the user to select single or multiple roadway segment(s) for which elevations are to be assigned. This section includes a data grid table that lists all the roadway segment(s) contained within the current scenario of the project, as shown below.

The user can select the roadway segment(s) using any of the following methods to assign elevations:

• Check the checkboxes corresponding to each roadway segment in the Select Roadway Segments
• Click the [Pick] button, the Assign Roadway Invert Elevations dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the roadway segment(s) from the Map View. After selecting the roadway segment(s), press the [Enter] key or right-click and choose Done from the displayed context menu. The Assign Roadway Invert Elevations dialog box will be redisplayed.
• Alternatively, press and hold down the [Ctrl] key while selecting the roadway segment(s) directly from the Map View. After the selection is done, open the Assign Roadway Invert Elevations dialog box, and the selected roadway segment(s) will be shown as selected/checked within the Select Roadway Segments

After selecting the roadway segment(s), the total number of selected roadway segment(s) will be displayed in the Total selected read-only field, as shown below.

In addition, the data contained in a data grid table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using the right-click context menu commands, such as Copy, Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF.

Assigning Invert Elevation

This section allows the user to assign an invert elevation to the roadway segment(s) using a terrain model. In addition, the user can define the elevation offset to raise or lower the roadway segment by the specified amount using the Apply elevation offset checkbox option. On selecting this checkbox option, the entry field next to it becomes available to enter an elevation offset value. A negative offset value will lower the roadway segment by the specified amount.

Note: Define this section before assigning roadway segments so that the invert elevation can be assigned.

Terrain Elevation Source

Depending upon the terrain elevation source type selected, different options are provided to specify additional elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• CAD Drawing
• Elevation Grid
• GIS Contours
• LandXML Data
• Terrain Surface
• TIN Surface

CAD Drawing

If the user selects CAD Drawing as the terrain elevation source, the contents of the Assign Invert Elevation section changes as shown below.

The following options are displayed when CAD Drawing is selected as the terrain elevation source:

• CAD drawing layer
  This dropdown combo box allows the user to select the CAD drawing layer available in the project.

• Drawing layers
  Clicking the [Define] button adjacent to the Drawing layers entry displays the CAD Drawing Layers dialog box, which allows the user to define the properties of the drawing layers.
  

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the contents of the Assign Invert Elevation section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

GIS Contour

If the user selects GIS Contours as the terrain elevation source, the contents of the Assign Invert Elevation section changes, as shown below.

The following options are displayed when GIS Contours is selected as the terrain elevation source:

• GIS polyline layer
  This dropdown combo box allows the user to select the GIS polyline layer type.

• Elevation attribute
  This dropdown combo box allows the user to select the elevation attribute type.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the contents of the Assign Invert Elevation section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Terrain Surface

If the user selects Terrain Surface as the terrain elevation source, the contents of the Assign Invert Elevation section changes, as shown below.

The following option is displayed when Terrain Surface is selected as the terrain elevation source:

• Terrain surface layer
  This dropdown combo box allows the user to select the terrain surface layer type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the contents of the Assign Invert Elevation section changes, as shown below.

The following options are displayed when TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  

  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Assigning Roadway Segment Invert Elevations

After defining all the required options, click the [Assign] button and the software will compute and display the invert elevation for the selected roadway segment(s).

In GeoSTORM software, the Renumber Interconnected Pipes command allows the user to automatically renumber pipes and connected manholes along a defined pipe path.

Follow the steps below to use the Renumber Interconnected Pipes command:

1. From the Input ribbon menu, select the Renumber Interconnected Pipes command from the Stormwater Pipes dropdown menu.
   
2. The Renumber Interconnected Pipes dialog box will be displayed, as shown below.
   

The following sections describe how to use the Renumber Interconnected Pipes command and interact with the above dialog box.

Selecting Pipes

The Select Pipes panel allows the user to select pipes that define the pipe path.

Selecting Multiple (Interconnected) Pipes

The Select Multiple (Interconnected) Pipes section is used to sequentially number pipes and manholes along the selected pipe path that has pipes connected end-to-end with each other. Click the [Pick] button to manually select pipes from the Map View. The Renumber Interconnected Pipes dialog box will temporarily disappear, allowing the user to select the downstream most and upstream most pipes from the Map View. Once finished, press the [Enter] key or right-click and choose Done from the displayed context menu. The dialog box will be redisplayed, and the total number of selected pipes will be shown in the Total selected read-only field, as shown below.

Alternatively, if pipes are pre-selected on the Map View, opening the Renumber Interconnected Pipes dialog box will show those pipes selected in the corresponding table section. The selected pipes can be further unselected by unchecking the checkboxes corresponding to them.

Note that the user can pre-select multiple pipes from the Map View by pressing and holding down the [Ctrl] key while selecting the pipes.

Manual Editing

This section contains a table that displays the selected pipes, manholes, and their associated data. The values in the New Pipe ID and New Manhole ID columns provide a preview of the renumbered pipes and manholes defined in the Pipe Renumbering and Manhole Renumbering panels.

The data contained in the table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using the Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF commands of the right-click context menu.

Pipe Renumbering

The Pipe Renumbering panel allows the user to renumber pipes based on pipe length or sequentially. By default, the checkbox on this panel is checked. If unchecked, then the contents of this panel will be disabled (i.e., grayed out) and the renumbering of pipes cannot be performed.

The following options are provided in this panel:

• Pipe ID prefix: This optional checkbox entry allows a prefix to be added to the pipe ID.
• Pipe ID suffix: This optional checkbox entry allows a suffix to be added to the pipe ID.
• Pipe ID preview: This read-only field provides a preview of the pipe ID defined in the panel.
• Numbering direction: This dropdown combo box allows the user to select the flow direction in which the pipe IDs can be renumbered. The following options are available:
  • Downstream
  • Upstream

Use Auto Increment

The Use auto increment subsection allows the user to renumber pipes using a fixed increment. Select the Use auto increment radio button option to enable this subsection.

The following options are provided in this subsection:

• Pipe ID digits: This entry field allows the user to set the number of digits to be used for pipe ID. For example, using 3 digits causes the pipe ID to be of the format 001, 002, and 003.
• Next available pipe ID: This entry field defines the next pipe ID number to be used.
• Pipe ID increment: This entry field defines the increment to use when numbering pipes. The default value is 1.

Use Pipe Length

The Use pipe length subsection is used to renumber pipes based on their length along the defined pipe path. By default, the Use pipe length radio button option is selected when the Pipe Renumbering panel is checked.

The following options are provided in this subsection:

• Downstream pipe ID: This entry provides a pipe ID that will be used as the downstream most pipe number. Note that if the Downstream option is selected in the Numbering direction dropdown combo box, then the Downstream pipe ID entry will change into the Upstream pipe ID, as shown below.
  
• Distance units: This dropdown combo box defines the unit of pipe length. The available options are:
  1. Feet
  2. Miles
• Decimal precision: This optional checkbox entry defines the decimal precision that will be used in renumbering pipes. By default, this checkbox is unchecked. If checked, then the user can enter a value ranging from 0 to 15.

After defining all the required data in this panel, click the [Preview] button to preview the IDs of the renumbered pipes in the New Pipe ID column of the Manual Editing table, as shown below.

Manhole Renumbering

The Pipe Renumbering panel allows the user to renumber manholes based on pipe length or sequentially. By default, the checkbox on this panel is checked. If unchecked, then the contents of this panel will be disabled (i.e. grayed out) and the renumbering of manholes cannot be performed.

The following options are provided in this data panel:

• Manhole ID prefix: This optional checkbox entry allows a prefix to be added to the manhole ID.
• Manhole ID suffix: This optional checkbox entry allows a suffix to be added to the manhole ID.
• Manhole ID preview: This read-only field provides a preview of the manhole ID defined in this panel.
• Numbering direction: This dropdown combo box allows the user to select the flow direction in which the manhole IDs can be renumbered. The following options are available:
  • Upstream
  • Downstream

Use Auto Increment

The Use auto increment subsection allows the user to renumber manholes using a fixed increment. Select the Use auto increment radio button option to enable this subsection.

The following options are provided in this subsection:

• Manhole ID digits: This entry allows the user to set the number of digits to be used for manhole ID. For example, using 3 digits causes the manhole ID to be of the format 001, 002, and 003.
• Next available manhole ID: This entry field defines the next manhole ID number to be used.
• Manhole ID increment: This entry field defines the increment to use when numbering manholes. The default value is 1.

Use Pipe Length

The Use pipe length subsection is used to renumber manholes based on their length along the defined pipe path. By default, the Use pipe length radio button option is selected when the Manhole Renumbering panel is checked.

The following options are provided in this subsection:

• Downstream manhole ID: This entry provides a manhole ID that will be used as the downstream most manhole number. Note that if the Downstream option is selected in the Numbering direction dropdown combo box, then the Downstream manhole ID entry will change into the Upstream manhole ID, as shown below.
  
• Distance units: This dropdown combo box defines the unit of pipe length. The available options are:
  1. Feet
  2. Miles
• Decimal precision: This optional checkbox entry defines the decimal precision that will be used in renumbering manholes. By default, this checkbox is unchecked. If checked, then the user can enter a value ranging from 0 to 15.

After defining all the required data in this panel, click the [Preview] button to preview the IDs of the renumbered manholes in the New Manhole ID column of the Manual Editing table, as shown below.

When all the required data have been defined in the Renumber Interconnected Pipes dialog box, click the [Apply] button. The software will then assign the user-defined changes to the pipes and connected manholes along a defined pipe path. Click the [Close] button to close the dialog box.

Note that when the user clicks the [Preview] button and clicks the [Close] button without applying the changes, the following confirmational dialog box will be displayed.

The process of georeferencing a pipe to the Map View can be a trial and error process—especially when the exact location of the original pipe is not known. The Georeference Pipes command of GeoSTORM software allows the user to manually georeference each of the pipes to the background base map displayed on the Map View.

Note that a CRS should be assigned before running this command. Otherwise, the software will display the below informational dialog box.

Refer to this article in our knowledge base to learn how to assign a coordinate reference system to a project.

Follow the steps below to use the Georeference Pipes command:

1. From the Input ribbon menu, click on Stormwater Pipes dropdown menu and select the Georeference Pipes command.
   
2. The Georeference Pipes dialog box will be displayed.
   

The following sections describe how to georeference an existing pipe and interact with the above dialog box.

Selecting Pipe to Georeference

The Select Pipe to Georeference section allows the user to interactively select the pipe to georeference.

Follow the steps below to select the pipe to be georeferenced:

1. Select the pipe from the Pipe ID dropdown combo box that lists all the pipes contained within the project.
   
2. Alternatively, the user can click the [Pick] button to select the pipe from the Map View. On clicking the [Pick] button, the Georeference Pipes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the pipe from the Map View.
3. Upon selecting the pipe, the Georeference Pipes dialog box will be redisplayed, and the selected pipe will be highlighted on the Map View.
   Notes:
   • The user can select only one pipe at a time.
   • The user can click the [Clear] button to cancel all the previous selections and redo the entire process.
   • If the model contains a single pipe, then it will be automatically displayed as selected in the Pipe ID dropdown combo box.

Once the pipe has been selected, the user can select among the following georeferencing options:

• Snap to Alignment Polyline
• Slide Along Alignment Polyline
• Draw on Map View

Snapping Pipe to an Alignment Polyline

If an existing alignment polyline for the pipe exists on the Map View, the Snap to Alignment Polyline georeferencing option can be used to snap the pipe to the alignment polyline.

Follow the steps below to use the Snap to Alignment Polyline georeferencing option:

1. Select the Snap to Alignment Polyline radio button option to enable this section.
2. Click the [Pick] button next to the Select alignment polyline read-only field.
   
3. The Georeference Pipes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the alignment polyline from the Map View.
4. After selecting the alignment polyline, the dialog box will be redisplayed and the status of the Select alignment polyline read-only field will be changed from Not Selected to Selected. The user can click the [Clear] button to cancel all the previous selections and redo the entire process.
5. After selecting the alignment polyline, click the [Snap] button. The software will then snap the selected pipe to the alignment polyline.
   

Sliding Pipe Along Alignment Polyline

If a pipe has been snapped to an alignment polyline on the Map View but is not precisely located where it should be, the Slide Along Alignment Polyline georeferencing option can be used to slide the pipe along the alignment polyline.

Follow the steps below to use the Slide Along Alignment Polyline georeferencing option:

1. Select the Slide Along Alignment Polyline radio button option to enable this section.
   
2. Click the [Pick] button next to the Select alignment polyline element read-only field.
   
3. The Georeference Pipes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select an alignment polyline from the Map View.
4. After selecting the alignment polyline, the following Snap Entity dialog box will be displayed. Click the [Yes] button to snap the entity on the selected polyline or click the [No] button to abort the selection.
   
5. Once the alignment polyline is selected, click the [Slide] button from the redisplayed Georeference Pipes dialog box.
   
6. The Georeference Pipes dialog box temporarily disappears, and a prompt will be displayed on the status bar instructing the user to select the pipe and drag it along the underlying alignment polyline.
7. Click and drag the pipe on the Map View to revise its alignment.
8. When finished, press the [Enter] key or right-click and select Done from the displayed context menu. The Georeference Pipes dialog box will be redisplayed, and the pipe will be placed at the new location.
9. The user can also check the Recompute adjacent node element elevations checkbox option to recompute the elevation of the adjacent node type elements while georeferencing the pipe. By default, this checkbox is checked.
   
   Note that if the endpoints of the pipe do not overlay the same continuous alignment polyline, then the following informational dialog box will be displayed.
   

Drawing Pipe on Map View

The Draw on Map View georeferencing option allows the user to draw an alignment polyline on the Map View and automatically snap the selected pipe to the drawn polyline.

Follow the steps below to use the Draw on Map View georeferencing option:

1. Select the Draw on Map View radio button option and click the [Draw] button.
   
2. The Georeference Pipes dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to draw an alignment polyline on the Map View.
3. Once the alignment polyline is drawn on the Map View, press the [Enter] key or right-click and choose Done from the displayed context menu.
4. The Georeference Pipes dialog box will be redisplayed, and the pipe will then automatically snap to the drawn alignment polyline.
   Notes:
   • The user can turn on the Create curvilinear polyline checkbox option to draw the polyline using a curvilinear segment. Refer to this article in our knowledge base to learn more about element digitizing on the Map View.
   • The user can turn on the Scale to fit checkbox option to scale the pipe to fit within the alignment polyline.

Assigning Pipe Invert Elevation

The user can check the Assign Pipe Invert Elevation checkbox option to assign an invert elevation to the georeferenced pipe using a terrain model. The options under this section must be defined before georeferencing pipes so that the invert elevation can be assigned.

For assigning invert elevation, the Terrain elevation source dropdown combo box supports the following surface types:

• CAD Drawing
• Elevation Grid
• GIS Contours
• LandXML Data
• Terrain Surface
• TIN Surface

Depending upon the elevation data source type selected, different options are provided to specify additional elevation data information. The user can define an invert depth using the Pipe invert depth entry field to raise or lower the invert of the pipe by the specified amount. A negative invert depth value lowers the pipe by the specified amount.

In GeoSTORM, the Recompute Pipe Properties command allows the user to recompute pipe properties, such as pipe lengths, pipe slopes, and maximum and minimum pipe cover based upon connected manholes.

Follow the steps below to use the Recompute Pipe Properties command:

1. From the Input ribbon menu, select the Recompute Pipe Properties command from the Stormwater Pipes dropdown menu.
   
2. The Recompute Pipe Properties dialog box will be displayed as shown below.
   

The following sections describe how to use the Recompute Pipe Properties command and interact with the above dialog box.

Selecting Pipes

The Select Pipes section includes a data grid table that lists all the pipes contained within the current scenario along with their pipe lengths, slopes, and maximum and minimum pipe covers. This section allows the user to select single or multiple pipes defined in the project for computing pipe parameters.

The user can select or deselect any pipe by checking and unchecking the checkbox corresponding to each pipe. If a pipe is already selected on the Map View before running this command, the same pipe will be shown selected within the table. The user can also use the checkbox contained within the column header to select or deselect all the pipes.

Alternatively, the user can click the [Pick] button to select pipes from the Map View. On clicking the [Pick] button, the Recompute Pipe Properties dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the pipes on the Map View. After selecting the pipes, press the [Enter] key or right-click and choose Done from the displayed context menu. The dialog box will be redisplayed, and the total number of selected pipes will be displayed in the Total selected read-only field.

Note that the user can select multiple pipes from the Map View before running the Recompute Pipe Properties command by pressing the [Ctrl] key.

Pipe Properties

This section is used to define the elevation data source and other parameters to be used for recomputing pipe properties.

Terrain Elevation Source

Depending upon the terrain elevation source type selected, different options are provided to specify additional detail and elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• CAD Drawing
• Elevation Grid
• GIS Contours
• LandXML Data
• Terrain Surface
• TIN surface

CAD Drawing

If the user selects CAD Drawing as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following options are displayed when CAD Drawing is selected as the terrain elevation source:

• CAD drawing layer
  This dropdown combo box allows the user to select the CAD drawing layer available in the project.

• Drawing layers
  Clicking the [Define] button adjacent to the Drawing layers entry displays the CAD Drawing Layers dialog box allowing the user to define the properties of the drawing layers.
  

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following option is displayed when the Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

GIS Contours

If the user selects GIS Contours as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following options are displayed when GIS Contours is selected as the terrain elevation source:

• GIS polyline layer
  This dropdown combo box allows the user to select the GIS polyline layer type.

• Elevation attribute
  This dropdown combo box allows the user to select the elevation attribute type.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following options are displayed when the LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Terrain Surface

If the user selects Terrain Surface as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following option is displayed when the Terrain Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the content of the Pipe Properties section changes as shown below.

The following options are displayed when the TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

After selecting the terrain elevation source, the user can check the checkbox of the following properties to be recomputed for the selected pipes.

• Pipe length
  This checkbox option is used to compute pipe length.

• Pipe slope
  This checkbox option is used to compute pipe slope based upon the pipe invert elevations.

• Maximum pipe cover
  This checkbox option is used to compute the maximum ground cover measured from the top of the pipe (crown) along the pipe length.

• Minimum pipe cover
  This checkbox option is used to compute the minimum ground cover measured from the top of the pipe (crown) along the pipe length.

Computing Pipe Properties

Once the data have been defined in the Recompute Pipe Properties dialog box, click the [Compute] button. The software will then recompute the pipe properties for the selected pipes.

In GeoSTORM software, the Pipe Table Edit command allows the user to view and edit all the parameters of the pipes in a single editable data grid. The user can also view the corresponding output results from this data grid.

Follow the steps below to use the Pipe Table Edit command:

1. From the Input ribbon menu, click the Stormwater Pipes dropdown menu and select the Pipe Table Edit command.
   
2. The Pipe Table Edit dialog box will be displayed, as shown below.
   

Selecting Storm Results

In the Select Storm Results section, the Storm result to display dropdown combo box allows the user to select the storm frequency whose result is to be displayed.

Note: The Select Storm Results section is only available when either the Dekalb Rational Method, Modified Rational or Rational Method is selected as the hydrology analysis engine in the Scenario Manager dialog box. Otherwise, this section is unavailable. Refer to this article in our knowledge base to learn more about the hydrology analysis engine.

Pipe Parameters Table

In the Pipe Parameters section, the following panels are available:

• Pipe Data
• Results Data

Pipe Data

This panel displays editable data grid columns listing all the pipe parameters defined in the current scenario.

The following pipe parameters are provided in the data grid column entries:

• Pipe ID
  This editable entry lists all pipe IDs defined in the current scenario.

• Pipe Diameter
  This dropdown combo box lists the internal diameter of the pipe. The user can change the internal diameter for any pipe from the corresponding dropdown combo box.

• Pipe Length
  This editable entry lists the length of the pipe. The user can manually edit the pipe length directly from the entry or by clicking the corresponding […] button and measuring the pipe length from the Map View.

• Inlet Invert Elevation
  This editable entry lists the pipe invert elevation on the upstream end.

• Outlet Invert Elevation
  This editable entry lists the pipe invert elevation on the downstream end.

• Manning’s Roughness
  This editable entry lists the Manning’s roughness of the pipe. Clicking the […] button displays the Channel and Pipe Manning’s Roughness dialog box, which allows the user to select the Manning’s roughness coefficient to be assigned to a pipe.
  

• Entrance Loss Coefficient
  This editable entry lists the head loss coefficient at the inlet of the pipe associated with energy losses as the flow enters the pipe from a node (i.e., manhole, junction box, routing junction, catch basin, or storage area). Clicking the […] button displays the Entrance Loss Coefficients for Pipes dialog box, which allows the user to select the entrance loss coefficient to be assigned to a pipe.
  

• Exit/Bend Loss Coefficient
  This editable entry lists the head loss coefficient at the outlet of the pipe associated with energy losses as the flow leaves the pipe and enters a node (i.e., manhole, junction box, routing junction, catch basin, or storage area). Clicking the […] button displays the Exit Loss Coefficients for Pipes dialog box, which allows the user to select the exit loss coefficient to be assigned to a pipe.
  

• Average Loss Coefficient
  This editable entry lists the head loss coefficient associated with energy losses along the length of the pipe.

• Pipe Slope (H:V)
  This read-only entry lists the slope of the pipe.

Results Data

The data grid columns in this panel list corresponding output results for pipes contained in the current scenario after the analysis is successfully computed.

The following pipe parameters are provided in the data grid column entries:

• Pipe ID
  This editable entry lists all pipe IDs defined in the current scenario.

• Peak Flow Rate
  This read-only entry lists the peak flow rate in the pipe during the storm event.

• Design Flow Capacity
  This read-only entry lists the flow rate capacity of the pipe for gravity flow conditions (i.e., non-pressurized).

• Maximum Velocity
  This read-only entry lists the maximum flow velocity in the pipe during the storm event.

• Max/Design Flow Ratio
  This read-only entry lists the ratio of the Peak flow rate to the Design flow capacity values.

• Max/Total Depth Ratio
  This read-only entry lists the ratio of pipe flow depth to the pipe diameter.

• Maximum Pipe Cover
  This read-only entry lists the computed maximum ground cover measured from the top of the pipe (crown) along the pipe length.

• Minimum Pipe Cover
  This read-only entry lists the computed minimum ground cover measured from the top of the pipe (crown) along the pipe length.

Sorting the Pipe Table

The data in the Pipe Parameters table can be sorted by multiple columns. Users can sort the data by holding down the [Shift] key while clicking the Up or Down arrows in the column headers. This allows for multi-column sorting without losing the previous sort. The sorting order is determined by the sequence in which the column headers are selected.

Follow the steps below to sort the data by using multiple columns:

1. Select the header of the first column and click the Up or Down arrow to sort the data in ascending or descending order.
2. Hold down the [Shift] key, then select the header of the second column and click the Up or Down arrow to sort the second column.
3. Repeat step 2 to sort the data for any additional column.

For example, first, select the Pipe ID column and click the Up arrow to sort the data in ascending order. Then, while holding down the [Shift] key, select the Pipe Length column and click the Down arrow to apply a secondary sort.

Copying and Exporting Pipe Table

The data in the Pipe Parameters table can be copied to the clipboard or exported as a Microsoft Excel or PDF document by using the right-click context menu commands such as Copy, Copy Table to Clipboard, Export Table to Excel, or Export Table to PDF.

After editing the required pipe parameters, click the [Close] button to close the Pipe Table Edit dialog box.

This article describes how the Merge Pipes command of GeoSTORM software allows the user to merge two or more connected pipes into a single pipe. Notes:

• When merging pipes, the attributes of the selected pipe with the largest diameter will be applied to all the merged pipes.
• When merging pipes, all interior nodes (i.e., manholes, junction boxes, catch basins, and routing junctions) connecting adjacent link elements will be deleted.

Follow the steps below to merge two or more connected pipes:

1. From the Input ribbon menu, click the Stormwater Pipes dropdown menu and select the Merge Pipes command.
2. The Merge Pipes dialog box will be displayed.
3. From the Select Pipes section, check the corresponding checkboxes of the pipes that need to be merged. Alternatively, click the [Pick] button to manually select pipes from the Map View. Note: To select/deselect all pipes at once, check/uncheck the Pipe checkbox.
4. The number of selected pipes will be displayed in the Total selected read-only field.
5. After selecting the pipes, click the [Apply] button and the software will merge all the selected pipes.
6. If the user has selected pipes that are not connected along a single alignment, the following informational dialog box will be displayed on clicking the [Apply] button.

In EPA SWMM, a cyclic loop network refers to a connected series of channels or pipes within the drainage system where the flow can travel in a continuous loop, i.e., starting and ending at the same point. Since the flow does not typically circulate in a continuous loop without a driving force, such as a pump, it can cause computational instability in the model, further leading to conflicts in flow calculations.

A cyclic network loop error typically arises in a complex drainage system or network having interconnected nodes and conduits. Theoretically, in such a network, water could flow endlessly in a circular pattern without reaching an outlet. Consequently, determining the flow direction and solving the equations governing the flow becomes difficult for the software, impacting the accuracy of the SWMM simulation.

Factors Causing the Formation of Cyclic Loop Network

A cyclic loop network in a complex drainage system can form due to several factors, such as:

• Incorrect Node Connections
  If interconnected nodes, such as routing junctions or terminal outfalls, are not connected as designed, paths that link back to an earlier point in the network may result, forming a loop.

• Design Errors
  Misplacing or duplicating pipes and routing junctions in the model design can result in unintended loops.

• Improper Flow Direction
  If pipes are oriented incorrectly and lead back to a previous node, a cyclic loop can be created. Hence, accurate flow direction must be maintained throughout the drainage system.

• Lack of Outlets
  In a drainage network without proper outfalls or discharge points, water may circulate through the system indefinitely, resulting in a cyclic loop network.

Steps to Fix Cyclic Loop Network Errors in EPA SWMM

The following steps can be taken to fix a cyclic loop network error in EPA SWMM:

1. Identifying Loop
   Review the error message or computed results generated by the software to identify the part of the drainage network demonstrating cyclic loops.

2. Checking Node Connections
   Ensure that the interconnected nodes are correctly connected to pipes or channels, contributing to the flow in a clear direction towards a downstream node.

3. Eliminating Unnecessary Connections
   Simplify the drainage network by removing redundant or unnecessary connections that form cyclic loops.

4. Converting to Series Flow
   Convert branch connections into series flow paths rather than parallel paths if they are displaying a cyclic loop error.

5. Using Outlet Nodes
   Use overflow conditions or outlet nodes to guide the flow in one direction and prevent cyclic scenarios.

6. Rerunning the Model
   After making the necessary adjustments, run the model again to check if the cyclic loop error has been resolved.

How to Fix a Cyclic Loop Network Error

In GeoSTORM, cyclic loop network errors can be resolved by selecting a suitable flow routing method. The following flow routing methods are supported by the software:

• Hydrodynamic
• Steady State Peak Flow
• Kinematic Wave

Refer to this article in our knowledge base to learn more about the flow routing methods supported by GeoSTORM.

Steady State Peak Flow and Kinematic Wave routing methods only support dendritic (or tree-like) routing networks. Consequently, the software displays an error when performing stormwater analysis in a cyclic loop network.

In such situations, the Hydrodynamic routing method must be specified. This routing method offers a more comprehensive and accurate simulation of flow conditions in a complex drainage network.

Follow the steps below to select the Hydrodynamic routing method in GeoSTORM:

1. From the Input ribbon menu, select the Scenario Manager command.
   
2. The Scenario Manager dialog box will be displayed.
   
3. From the Flow routing method dropdown combo box, select the Hydrodynamic routing method.
   
4. Now, from the Analysis ribbon menu, select the Compute Analysis command to perform stormwater analysis.
5. The software will successfully run the analysis.
   

Note that the Flow routing method dropdown combo box will be displayed as disabled when the Rational Method is selected as the hydrology analysis engine.

Therefore, in the case of the Rational Method, the user needs to simplify the network by removing or modifying the node connections forming a cyclic loop. Alternatively, the user can eliminate the cyclic loop network by reversing the direction of one of its links (i.e., switching the inlet and outlet nodes of the link).

The Underground Pipe Gallery panel of the Storage Area Data dialog box allows the user to define the underground pipe gallery specifications for the storage area. This article describes how to interact with the Underground Pipe Gallery panel. Refer to this article in our knowledge base to learn more about the Storage Area Data dialog box.

Follow the steps below to define the specifications for the underground pipe gallery:

1. In the Storage Area Data dialog box, select Underground Pipe Gallery from the Storage Area Specifications dropdown combo box.
   
   Note: The Underground Pipe Gallery data panel entry is enabled only when the user selects the Underground Pipe Gallery option in the Storage area volume dropdown combo box of the General Specifications panel. Otherwise, this data panel entry is disabled (i.e., grayed out).
   

2. The corresponding panel with options for defining the underground pipe gallery will be displayed.
   

The following subpanels are available in the Underground Pipe Gallery data panel:

• Pipe Details
• Pipe Gallery Design
• Summary

Pipe Details

In the Pipe Details subpanel, the Underground Pipe Details section allows the user to define the underground pipe parameters for the selected storage area.

The following entries are available:

• Select perforated pipe type
  This dropdown combo box allows the user to select the type of perforated pipe. The following types of perforated pipes are available:

• 1. Arched Flat Bottom
  2. Arched Round Bottom
  3. Circular
  

• Pipe barrel length
  This entry field defines the length of individual pipe barrels.

• Pipe diameter
  This entry field defines the diameter of the pipe to be used in the pipe runs. Note that this field is enabled only for the Circular pipe type.

• Select arched pipe size
  This dropdown combo box allows the user to select the size of the arched pipe. Note that this dropdown combo box is enabled only for the Arched Round Bottom pipe type.
  

• Arched pipe height
  This entry field defines the height of the arched pipe to be used in the pipe runs. Note that this field is enabled only for the Arched Flat Bottom pipe type. Otherwise, this field is disabled (i.e., grayed out) for the Circular pipe type and becomes read-only for the Arched Round Bottom pipe type.
  

• Arched pipe width
  This entry field defines the width of the arched pipe to be used in the pipe runs. Note that this field is enabled only for the Arched Flat Bottom pipe type. Otherwise, this field is disabled (i.e., grayed out) for the Circular pipe type and becomes read-only for the Arched Round Bottom pipe type.

Pipe Gallery Design

In the Pipe Gallery Design subpanel, the Pipe Gallery Specifications and Layout section allows the user to define the specifications and layout of the pipe gallery system.

The following tab panels are available in the Pipe Gallery Design subpanel:

• Pipe Gallery Design
• Pipe Gallery Layout

Pipe Gallery Design

In the Pipe Gallery Design tab panel, the Define Pipe Gallery Layout Specifications section allows the user to define the parameters for the pipe gallery layout.

The following entries are available:

• Terrain surface
  This dropdown combo box allows the user to select the terrain elevation surface available in the project.

• Include header pipe
  This dropdown combo box allows the user to specify how the header pipe is connected to the parallel pipe runs. The following options are available:

• 1. None
  2. On One End
  3. On Both Ends
  

• Space between pipe runs
  This entry field defines the gap between pipe runs so that stone fill can be inserted.

• Storage area excavation wall to pipe runs
  This entry field defines the buffer distance provided from the storage area boundary to the pipe runs. Note that pipes can only be placed inside this buffer region.

• Outside edge space to pipe runs
  This entry field defines the extra space that is placed on the pipe run outside the edge perimeter for stone fill.

• Outside end space to pipe runs
  This entry field defines the extra space that is placed on the pipe run outside the end perimeter for stone fill.

• Stone cover
  This entry field defines the stone cover to be placed over the pipe runs.

• Stone base
  This entry field defines the stone base to be placed under the pipe runs.

• Stone base invert elevation
  This entry field defines the invert elevation of the stone base.

• Stone void space
  This spin control entry field defines the stone void space, represented as a percentage. By default, the software uses a value of 40. However, the user can enter a different value ranging from 10 to 90.

Once all required data have been defined, click the [Generate] button. The software generates the pipe gallery layout and immediately takes the user to the Pipe Gallery Layout tab panel.

Note: The [Generate] button is enabled only when all required data have been defined in the Pipe Gallery Design tab panel. Otherwise, this button will be disabled (i.e., grayed out).

Pipe Gallery Layout

The Pipe Gallery Layout tab panel displays a preview of the pipe gallery created on the Map View. Initially, the preview shows the current Map View extents, but the user can zoom and pan this view using the mouse cursor.

The following entries are available:

• Project base map provider
  This dropdown combo box allows the user to select the project base map from several high-quality base maps.

• Use grayscale base map
  This checkbox option allows the user to change the base map to grayscale instead of color.

Editing Pipe Gallery Layout

Clicking the [Edit Layout] button temporarily disappears the Storage Area Data dialog box and displays the Edit Layout dialog box. This dialog box allows the user to adjust the pipe gallery layout more precisely. In this dialog box, the user can define the pipe gallery boundary and manually add or remove pipes. After making the necessary changes, click the [OK] button to save the layout. The Storage Area Data dialog box will be redisplayed, and the Pipe Gallery Layout preview tab will be updated with the changes made. To abort the process, click the [Cancel] button.

The Edit Layout dialog box provides the following toolbar commands for editing the pipe gallery layout:

In addition, the user can zoom and pan the pipe gallery layout grid in the Map View. Refer to this article in our knowledge base to learn more about the other tools available in this dialog box.

Summary

The Summary subpanel provides a volume summary for the pipe gallery system, including the depth-area-volume plot and corresponding data in a tabular format.

The following tab panels are available in the Summary subpanel:

• Volume Summary
• Depth-Area Volume Plot
• Data Table

Volume Summary

In the Volume Summary tab panel, the Pipe Gallery Volume Summary section displays the volume summary for the pipe gallery system. Note that this section is populated only when the user has generated the pipe gallery layout in the Pipe Gallery Design subpanel.

The following entries are available:

• Total number of pipe barrels
  This read-only field displays the total pipe barrels placed in the pipe gallery system.

• System footprint area (including buffer)
  This read-only field displays the footprint area of the pipe gallery system, which is equal to the area of the buffer polygon.

• Total excavation volume (including buffer & cover)
  This read-only field displays the volume of the earthwork to be excavated for the pipe gallery system, including exterior buffer and ground cover.

• Total ground cover volume
  This read-only field displays the volume of excavation required for providing the ground cover to the pipe gallery system.

• Total pipe gallery volume (without stone fill)
  This read-only field displays the total storage volume of the pipe gallery.

• Total stone fill required (includes void space)
  This read-only field displays the storage volume of the stone fill (including void space).

• Stone void volume
  This read-only field displays the storage volume provided by the voids of the stone fill.

• Total gallery storage volume (pipe & stone void space)
  This read-only field displays the total storage volume defined by the pipe gallery system. This volume includes the storage volume of the pipe gallery and the stone fill voids.

Clicking the [Calc] button computes the volume summary for the pipe gallery system. Note that the [Calc] button is enabled only when changes are made in the pipe gallery layout using the Edit Layout dialog box. Otherwise, this button is disabled (i.e., grayed out).

Clicking the [Pipe Gallery Report] button displays the Pipe Gallery Report dialog box, which allows the user to generate a report of the pipe gallery system in Microsoft Word or PDF format. Refer to this article in our knowledge base to learn more about the Pipe Gallery Report dialog box.

Depth-Area-Volume Plot

In the Depth-Area-Volume Plot tab panel, the Pipe Gallery Depth-Area-Volume Plot section displays the depth-area-volume plot of the pipe gallery system based on the computed volume summary from the Volume Summary tab panel.

Data Table

In the Data Table tab panel, the Pipe Gallery Depth-Area-Volume Data Table section displays the depth vs. area and volume data in a tabular format, based on the computed volume summary from the Volume Summary tab panel.

The following read-only columns are available in the Pipe Gallery Depth-Area-Volume Data Table section:

• Depth
  This read-only column lists the cumulative depth value of the pipe gallery system.

• Void Space Area
  This read-only column lists the cumulative value of the void space area of the pipe gallery system at the corresponding depth.

• Void Space Volume
  This read-only column lists the cumulative value of the void space volume of the pipe gallery system at the corresponding depth.

In GeoSTORM software, roadway segments (i.e., roadway gutter, ditch, or storm drain inlet) can be defined by either drawing or assigning polylines on the Map View using the following commands:

• Draw Roadway Segments
• Assign Roadway Segments

Draw Roadway Segments Command

Follow the steps below to use the Draw Roadway Segments command:

1. From the Input ribbon menu, click the Roadway Gutter/Ditch/Inlets dropdown menu and select the Draw Roadway Segments command.
2. The Draw Roadway Segments dialog box will be displayed.
   
   

Drawing Roadway Segment Polylines

The Draw Roadway Segment Polylines section allows the user to draw single or multiple polylines on the Map View as roadway segments.

Follow the steps below to draw roadway segments:

1. Click the [Draw] button and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt the user to draw a roadway segment on the Map View in the upstream to the downstream direction.
   Note: From the Roadway Segment Specifications subsection of the Roadway Naming panel, if:
   • Roadway segment ID naming option is selected, then the user can draw only one roadway segment polyline on the Map View.
   • Auto-name roadway segment ID naming option is selected, then the user can continuously draw roadway segment polylines one after the other on the Map View.
3. After drawing roadway segment polyline(s), the Draw Roadway Segments dialog box will be redisplayed, and the roadway segment polyline(s) will be drawn on the Map View.

Notes:

• If the “Draw curvilinear polylines” checkbox option is checked, then it allows the user to draw curvilinear polyline segments for the roadway segments.
• If the “Discard accidentally digitized roadway less than” checkbox is checked, then the software discards accidentally digitized roadway segments that are shorter than the defined length. The user can define the length of the roadway segment in the entry field adjacent to this checkbox option.
• The [Reverse Direction] button reverses the flow direction of the roadway segment polyline drawn.

Naming Specifications

This section allows the user to define the naming specifications for each drawn roadway segment along with the associated junctions and manholes.

Roadway Naming

Roadway Segment Specifications

The Roadway Segment Specifications subsection under the Roadway Naming panel allows the user to specify the roadway segment ID for each drawn roadway segment. The user can assign these IDs either manually or automatically using some predefined formats.

Follow the steps below to define naming specifications for roadway segments:

1. If a roadway segment is drawn while keeping the Roadway segment ID radio button option selected, the user can manually enter the roadway segment ID in the corresponding field, as shown below.
   
2. If a roadway segment is drawn while keeping the Auto-name roadway segment ID radio button option selected, then it automatically names every newly drawn roadway segment as per the user’s predefined naming formats, as shown below.
   

The following naming formats are available in the Auto-name roadway segment ID radio button option:

• Roadway segment ID prefix: This option allows a prefix to be added to the roadway segment ID.
• Roadway segment ID digits: This option permits the specification of a set number of digits to use for the roadway segment ID. For example, using 3 digits causes the roadway segment ID to be of the format 001, 002, 003, and so on as new roadway segments are created.
• Next available roadway segment ID: This option defines the next roadway segment ID number to be used.
• Roadway segment ID increment: This option defines the increment to use when numbering roadway segments. The default value is 1.
• Roadway segment ID suffix: This option allows a suffix to be added to the roadway segment ID.
• Roadway segment ID preview: This read-only field provides a preview of the roadway segment naming specifications defined above.

Junction Naming

Auto-Name Junction ID

The Auto-Name Junction ID subsection under the Junction Naming panel allows the user to specify the IDs for each routing junction that are created automatically while drawing roadway segments. The user can assign these IDs automatically using some predefined formats, as shown below.

The following naming formats are available in the Auto-Name Junction ID subsection:

• Routing junction ID prefix: This option allows a prefix to be added to the routing junction ID.
• Routing junction ID digits: This option permits the specification of a set number of digits to use for the routing junction ID. For example, using 3 digits causes the routing junction ID to be of the format 001, 002, 003, and so on as new routing junctions are created.
• Next available routing junction ID: This option defines the next routing junction ID number to be used.
• Routing junction ID increment: This option defines the increment to use when numbering routing junctions. The default value is 1.
• Routing junction ID suffix: This option allows a suffix to be added to the routing junction ID.
• Routing junction ID preview: This read-only field provides a preview of the routing junction naming specifications defined above.

Manhole Naming

Auto-Name Manhole ID

The Auto-Name Manhole ID subsection under the Manhole Naming panel allows the user to specify the IDs for manholes associated with roadway segments. The user can assign these IDs automatically using some predefined formats, as shown below.

The following naming formats are available in the Auto-Name Manhole ID subsection:

• Manhole ID prefix: This option allows a prefix to be added to the manhole ID.
• Manhole ID digits: This option permits the specification of a set number of digits to use for the manhole ID. For example, using 3 digits causes the manhole ID to be of the format 001, 002, 003, and so on as new manholes are created.
• Next available manhole ID: This option defines the next manhole ID number to be used.
• Manhole ID increment: This option defines the increment to use when numbering manholes. The default value is 1.
• Manhole ID suffix: This option allows a suffix to be added to the manhole ID.
• Manhole ID preview: This read-only field provides a preview of the manhole naming specifications defined above.

Assigning Invert Elevations

This section allows the user to assign an invert elevation to the roadway segments using a terrain model.

Note that this subsection is common to both the Draw Roadway Segments and Assign Roadway Segments dialog boxes.

Terrain Elevation Source

Depending upon the type of terrain elevation source selected, the content of the Assign Invert Elevations section changes to specify additional elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• Elevation Grid
• LandXML Data
• TIN Surface

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the content of the Assign Invert Elevations section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the content of the Assign Invert Elevations section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the content of the Assign Invert Elevations section changes, as shown below.

The following options are displayed when the TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Other Specifications

This section allows the user to define the following physical properties for the drawn roadway segments:

• Roadway width
  This entry field defines the distance from the curb to the high point of the roadway segment (i.e. crown) including gutter width.
• Curb height
  This entry field defines the height of the curb with respect to the roadway cross slope.
• Roadway cross slope (V:H)
  This entry field defines the roadway cross slope.
• Roadway & gutter roughness
  This entry field allows the user to define Manning’s roughness for the drawn/assigned roadway segments. Clicking the […] lookup button displays the Manning’s Roughness lookup dialog box, which allows the user to select a Manning’s roughness coefficient to be assigned to a roadway segment.
  

• Roadway gutter routing
  This dropdown combo box specifies if one or both sides of the roadway gutter should be considered in the reach routing. The following options are provided:
  • One Side: Select this option if the street section extends only to the street crown.
  • Both Sides: Select this option if the same street section shape exists on the opposite side of the street crown.

After defining all the required data, click the [Apply] button to complete drawing roadway segments. Note that if roadway segments are drawn using the Auto-name roadway segment ID option, then the [Apply] button will be displayed disabled since the just drawn roadway segments have already been named and created.

Assign Roadway Segments Command

Follow the steps below to use the Assign Roadway Segments command:

1. From the Input ribbon menu, click the Roadway Gutter/Ditch/Inlets dropdown menu and select the Assign Roadway Segments command.
   
2. The Assign Roadway Segments dialog box will be displayed.
   

Selecting Roadway Segment Polylines

The Select Roadway Segment Polylines section allows the user to manually assign single or multiple polylines on the Map View as roadway segments.

Follow the steps below to assign polylines as roadway segments:

1. Click the [Pick] button and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt the user to click near the downstream end of the already drawn roadway segment polyline on the Map View to select it.
   Note: From the Roadway Segment Specifications section, if:
   • Roadway segment ID naming option is selected, then the user can select only one roadway segment polyline on the Map View.
   • Auto-name roadway segment ID naming option is selected, then the user can select roadway segment polylines one after the other from the Map View.
3. After selecting polyline(s), the Assign Roadway Segments dialog box will be redisplayed and the roadway segment polyline(s) will be selected on the Map View.
4. Click the [Clear] button to cancel the previous selection and redo the entire process.

Notes:

• If the “Discard accidentally digitized roadway less than” checkbox is checked, then the software discards accidentally digitized roadway segments that are shorter than the defined length. The user can define the length of the roadway segment in the entry field adjacent to this checkbox option.
• The [Reverse Direction] button reverses the flow direction of the roadway segment polyline assigned.

Roadway Segment Specifications

This section is similar to the Roadway Segment Specifications section explained for the Draw Roadway Segments dialog box.

Assigning Invert Elevations

This section is similar to the Assign Invert Elevations section explained for the Draw Roadway Segments dialog box.

Other Specifications

This section is similar to the Other Specifications section explained for the Draw Roadway Segments command.

This section contains an additional “Create routing junctions (if missing) at routing roadway ends” checkbox option. This checkbox option allows the software to create a routing junction at the routing roadway ends if there is no node already defined within the connection snap distance. The routing junction invert elevation is set equal to the roadway segment invert elevation.

After defining all the required data, click the [Apply] button to complete the process of assigning roadway segments. Note that if roadway segments are assigned using the Auto-name roadway segment ID option, then the [Apply] button will be displayed disabled since the just assigned roadway segments have already been named and created.

In GeoSTORM software, the Automated Draw Roadway Segments command allows the user to automatically compute roadway segment alignment between two points using an elevation terrain surface.

Follow the steps below to use the Automated Draw Roadway Segments command:

1. From the Input ribbon menu, click on the Roadway Gutter/Ditch/Inlets dropdown menu and select the Automated Draw Roadway Segments command.
   
2. The Automated Draw Roadway Segments dialog box will be displayed.
   

The following sections describe how to use the Automated Draw Roadway Segments command and interact with the above dialog box.

Selecting Roadway Segment Starting Point

The Select Roadway Segment Starting Point section is used to select a starting point on the Map View for drawing the roadway segment.

To select a starting point, follow the steps below:

1. Click on the [Pick] button, and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt the user to select a point on the Map View. Select the starting point to draw a roadway segment.
3. After selecting the starting point, the user is immediately returned to the Automated Draw Roadway Segments dialog box. The Start point read-only field will be changed from Not Drawn to Selected.
   

Roadway Segment Draw Direction

This section is used to define the direction of the roadway segment to be drawn based on the selected starting point.

The following options are provided in this section:

• Downstream flow direction
  This radio button option is used to define the flow direction of the roadway segment downstream from the starting point.

• Upstream flow direction
  This radio button option is used to define the flow direction of the roadway segment upstream from the starting point.

Roadway Segment Specifications

This section is used to specify a roadway segment ID for each roadway segment drawn. The user can assign these IDs either manually or automatically using some predefined formats.

Follow the steps below to assign roadway segment IDs:

1. If the starting point for a roadway segment is selected while keeping the Roadway segment ID radio button option enabled, the user can manually enter the roadway segment ID in the corresponding field, as shown below.
   
2. Alternatively, the user can enable the Auto-name roadway segment ID radio button option to automatically name newly drawn roadway segments as per predefined naming formats.
   
   The different naming formats present in the Auto-name roadway segment ID option are as follows:
   • Roadway segment ID prefix: This optional checkbox entry allows a prefix to be added to the roadway segment ID.
   • Roadway segment ID digits: This entry field allows the user to set the number of digits to be used for the roadway segment ID. For example, using 3 digits causes the roadway segment ID to be of the format 001, 002, and 003.
   • Next available roadway segment ID: This entry field defines the next roadway segment ID number to be used.
   • Roadway segment ID increment: This entry field defines the increment to use when numbering roadway segments. The default value is 1.
   • Roadway segment ID suffix: This optional checkbox entry allows a suffix to be added to the roadway segment ID.
   • Roadway segment ID preview: This read-only field provides a preview of the roadway segment ID defined in this section.

General Options

This section is used to define the general options for drawing roadway segments.

The following options are provided in this section:

• Terrain surface
  The dropdown combo box lists the terrain surfaces associated with the project which are used to define the roadway segment. By default, the current scenario’s terrain surface is selected. If there is no terrain surface defined for the selected scenario, then this entry is blank.

• Roadway segment maximum length
  This optional checkbox option is used to define the maximum length for the roadway segment polyline that is to be drawn. Click the [Pick] button to draw a polyline representing the maximum reach length. The Automated Draw Roadway Segments dialog box will temporarily disappear, allowing the user to draw an approximate roadway segment on the Map View. Once finished, press the [Enter] key or right-click and select Done from the displayed context menu. The drawn polyline will be removed, and the Automated Draw Roadway Segments dialog box will be redisplayed with the measured distance, as shown below.
  
  Notes:
  1. If this checkbox option is left blank, the polyline will extend to the limits of the underlying flow direction grid that the software computes using the selected elevation grid.
  2. The [Pick] button will be disabled (i.e., grayed out) until the user selects a starting point for the roadway segment.

Computing Flow Direction

When all the required data have been defined in the Automated Draw Roadway Segments dialog box, click the [Compute] button to compute the flow direction grid corresponding to the selected terrain surface. During the computation process, the [Compute] button will change into the [Cancel] button, which allows the user to abort the command if needed. After computing the flow direction grid, the software will internally assign the created polyline as a roadway segment on the Map View.

In GeoSTORM software, the Recompute Roadway Segment Properties command allows the user to recompute roadway segment properties based on the connected routing junctions and catch basin inlets.

Follow the steps below to use the Recompute Roadway Segment Properties command:

1. From the Input ribbon menu, click on the Roadway Gutter/Ditch/Inlets dropdown menu and select the Recompute Roadway Segment Properties command.
   
2. The Recompute Roadway Segment Properties dialog box will be displayed.
   

The following sections describe how to use the Recompute Roadway Segment Properties command and interact with the above dialog box.

Selecting Roadway Segments

The Select Roadway Segments section allows the user to select single or multiple roadway segments for which properties are to be recomputed. This section includes a table that lists all the roadway segments contained within the current scenario of the project, as shown below.

The user can select roadway segments using any of the following methods for recomputing properties:

1. By pressing and holding down the [Ctrl] key while selecting the roadway segments directly from the Map View. Immediately after selecting the roadway segments, open the Recompute Roadway Segment Properties dialog box, and the selected roadway segments will be shown as selected/checked within the Select Roadway Segments section.
2. By checking the checkboxes corresponding to each roadway segment in the Select Roadway Segments section.
3. By clicking the [Pick] button, the Recompute Roadway Segment Properties dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user to select the roadway segments from the Map View. After selecting roadway segments, pressing the [Enter] key or right-clicking and choosing Done from the displayed context menu redisplays the Recompute Roadway Segment Properties dialog box.

After selecting roadway segments, the total number of selected roadway segments will be displayed in the Total Selected read-only field, as shown below.

Sorting the Roadway Segments Table

The data in the Select Roadway Segments table can be sorted by multiple columns. The user can sort the data by holding down the [Shift] key while clicking the Up or Down arrows in the column headers. This allows for multi-column sorting without losing the previous sort. The sorting order is determined by the sequence in which the column headers are selected.

Follow the steps below to sort the data by using multiple columns:

1. Select the header of the first column and click the Up or Down arrow to sort the data in ascending or descending order.
2. Hold down the [Shift] key, then select the header of the second column and click the Up or Down arrow to sort the second column.
3. Repeat step 2 to sort the data of any additional column.

For example, first, select the Length column and click the Down arrow to sort the data in descending order. Then, while holding the [Shift] key, select the Downstream Invert Elevation column and click the Up arrow to apply a secondary sort.

Roadway Segment Properties

This section is used to define the elevation data source and other parameters to be used to recompute the properties for the selected roadway segments.

Terrain Elevation Source

Depending upon the terrain elevation source type selected, the content of the Roadway Segment Properties section changes to specify additional elevation data information.

The Terrain elevation source dropdown combo box supports the following surface types:

• CAD Drawing
• Elevation Grid
• GIS Contours
• LandXML Data
• Terrain Surface
• TIN Surface

CAD Drawing

If the user selects CAD Drawing as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following options are displayed when CAD Drawing is selected as the terrain elevation source:

• CAD drawing layer
  This dropdown combo box allows the user to select the CAD drawing layer available in the project.

• Drawing layers
  Click the [Define] button adjacent to the Drawing layers entry to display the CAD Drawing Layers dialog box, allowing the user to define the properties of the drawing layers, as shown below.
  

Elevation Grid

If the user selects Elevation Grid as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following option is displayed when Elevation Grid is selected as the terrain elevation source:

• Elevation grid layer
  This dropdown combo box allows the user to select the elevation grid layer available in the project.

GIS Contours

If the user selects GIS Contours as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following options are displayed when GIS Contours is selected as the terrain elevation source:

• GIS polyline layer
  This dropdown combo box allows the user to select the GIS polyline layer type.

• Elevation attribute
  This dropdown combo box allows the user to select the elevation attribute type.

LandXML Data

If the user selects LandXML Data as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following options are displayed when LandXML Data is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

Terrain Surface

If the user selects Terrain Surface as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following option is displayed when the Terrain Surface is selected as the terrain elevation source:

• Terrain surface layer
  This dropdown combo box allows the user to select the terrain surface layer type.

TIN Surface

If the user selects TIN Surface as the terrain elevation source, the content of the Roadway Segment Properties section changes, as shown below.

The following options are displayed when TIN Surface is selected as the terrain elevation source:

• TIN surface layer
  This dropdown combo box allows the user to select the TIN surface layer type.

• TIN surface
  This dropdown combo box allows the user to select the TIN surface type.

After selecting the terrain elevation resource, the user can proceed with the following roadway segment properties to be recomputed for the selected roadway segments.

• Roadway segment length
  This checkbox option is used to recompute the roadway segment length.

• Upstream and downstream invert elevation
  This checkbox option is used to recompute the invert elevations of roadway segments on the upstream (inlet) and downstream (outlet) ends.

• Entrance loss coefficient
  This checkbox entry field allows the user to define the head loss coefficient associated with energy losses at the roadway segment inlet as flow enters the roadway segment from a node (i.e., routing junction). Alternatively, clicking the […] lookup button displays the Entrance Loss Coefficients For Pipes lookup dialog box, which allows the user to choose an entrance loss coefficient to be assigned to the selected roadway segments.
  
  Note that in an open channel cross section where the discharge is already channelized, an entrance loss coefficient of 0.0 should be used (i.e., no head loss). For complete head loss, such as a storage area flow entering a roadway segment, a coefficient of 1 should be entered.

• Exit loss coefficient
  This checkbox entry field allows the user to define the head loss coefficient associated with energy losses at the roadway segment outlet as the flow leaves the roadway segment and enters a node (i.e., routing junction). Alternatively, clicking the […] lookup button displays the Exit Loss Coefficient For Pipes lookup dialog box, which allows the user to choose an exit loss coefficient to be assigned to the selected roadway segments.
  
  Note that for no head loss, such as roadway segment flow entering another roadway segment, a coefficient of 0 should be entered. For complete head loss, such as roadway segment flow entering a storage area, a coefficient of 1 should be used.