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:
- From the Input ribbon menu, click the Manhole Structures dropdown menu and select the Manhole Data command.
- 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 options 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: 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 parameters 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:
- Bolted Cover Manhole
- Force Main Connection
- Junction Box
- Standard Manhole (default)
- 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 parameters 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 parameters 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 defined in the current scenario. If this dropdown list is left blank, then no direct inflow will be applied 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 plates and vortex flow control devices to the downstream pipe.
Outflow Control Specifications
The following parameters 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.
- None (default)
- Orifice
- Vortex
- 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 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:
- None (default)
- Head Differential
- Water Surface Depth
- 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 is selected as the outflow control type. Otherwise, this dropdown combo box is disabled (i.e., grayed out). The following orifice shapes are available:
- Circular (default)
- 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 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 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 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 is selected as the outflow control type. Otherwise, this subpanel is disabled (i.e., grayed out).
The following column entries are provided in the data grid:
- Water Surface Depth
This entry 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 entry 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 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.