Inline Structure Data Command

In hydraulic modeling, inline structures refer to hydraulic structures that are placed within a river or channel reach. These structures are designed to modify the flow characteristics of the watercourse, such as its depth, velocity, and conveyance capacity. Inline structures are incorporated into the hydraulic model to accurately represent their influence on river flow. By defining the geometry, characteristics, and operational rules of these structures, engineers can simulate and analyze the hydraulic behavior of rivers and channels under various conditions, such as floods or dam releases.

This article describes how the Inline Structure Data command of GeoHECRAS can be used to view or modify the data associated with inline structures.

Follow the steps below to view or modify inline structure data in GeoHECRAS:

1. From the Input ribbon menu, select the Inline Structure Data command.
   Alternatively, from the Input ribbon menu, expand the Inline Structures dropdown menu and select the Inline Structure Data command.
   
2. The Inline Structure Data dialog box will be displayed.
   

The following sections describe how to define the inline structure data and interact with the above dialog box.

Selecting Inline Structure

The Select Inline Structure section allows the user to switch between inline structures.

This section contains the following options:

• River
  This read-only dropdown combo box displays the river(s) defined in the project. When the user changes a river, the Reach dropdown combo box automatically updates to display a valid corresponding river reach.
• Reach
  This read-only dropdown combo box displays all the reach(s) defined in the project that corresponds to the selected river.
• River Station
  This editable dropdown combo box displays all the inline structures defined in the project that correspond to the selected reach. The up and down arrow buttons adjacent to this dropdown combo box allow the user to switch between the next downstream and upstream inline structure. If there are no other inline structures defined for the selected river reach, then these buttons are disabled (grayed out). Alternatively, the user can click the […] pick button adjacent to this dropdown to select the inline structure from the Map View.
• Node name
  This entry field allows the user to assign an optional text label to the current inline structure.
• Description
  This optional text box entry field allows the user to include information on the current inline structure.
• Less/More
  The [< Less] and [More >] buttons at the Select Inline Structure section header allow the user to hide and display the right side of the dialog box containing the inline structure plot. This allows the dialog box to be smaller when the user does not want to see the inline structure plot view.
• New
  The [New] button allows the user to draw a new inline structure on the Map View.
• Copy
  The [Copy] button allows the user to create a copy of the current inline structure on the Map View.
• Delete
  The [Delete] button allows the user to delete the current inline structure.

Once the inline structure is selected, the user can switch between the following panels from the Inline Structure Specifications dropdown panel selector to view or modify the associated inline structure data.

Inline Structure Specifications

This dropdown panel selector contains the following data panel entries, which allow the user to define inline structure data:

• Structure Specifications
• Culverts
• Gates
• Rating Curve
• Outlet Time Series
• Ineffective Flow Areas
• Dam Breach
• Geometry Adjustment
• Geometry Point Reduction
• Profile Results

Structure Specifications

This data panel is used to define the specifications of the inline structure.

This data panel contains the following sections:

Inline Structure Crest Geometry

This section provides a data table for entering and editing inline structure top of structure geometry (weir geometry). This data table is used to describe the embankment blocking the stream as well as any uncontrolled overflow weirs. The geometry of the inline structure is entered from the left to right station looking in a downstream direction. The user enters stations and elevations for the top of the embankment and weir. The stationing does not have to match the ground stations of the bounding upstream cross section, but it must be based on the same origin. Everything below the defined crest geometry elevations will be filled-in down to the ground. The […] button at the Horizontal Station column header allows the user to select the horizontal station of the inline structure from the Map View. The [Draw] button is used to draw weir crest geometry on the Inline Structure Plot. The [Reset] button resets the inline structure crest geometry on the Map View.

Inline Structure Dimensional Specifications

This section provides the following options to define the dimensions of the inline structure:

• Distance between bounding cross sections
  This entry field specifies the distance between the bounding cross sections where the inline structure is defined.
• Structure width (parallel to flow)
  This entry field specifies the width of the inline structure (measured along the flow direction). By default, the software uses a value of 46 feet. The user can enter a different value or click the [Pick] button to interactively measure this width from the Map View.
• Distance from US face to US XS
  This entry field specifies the distance from the upstream side of the inline structure to the cross section immediately upstream of the inline structure. By default, the software uses a value of 10 feet. The user can enter a different value or click the [Pick] button to interactively measure this distance from the Map View.
• Upstream embankment side slope (V:H)
  This entry field specifies the embankment side slope of the inline structure (measured in the direction of flow) on the upstream face of the structure. The slope is represented by the number of horizontal units per vertical unit. For vertical side slope embankments, enter a value of 0. By default, the software uses a value of 3.0 (i.e., 1:3).
  Note that this variable is generally not used in the computations but is used for display purposes in the profile plot. However, if the user has selected the FHWA WSPRO Method for low flow, this field will be used in the computation of the bridge discharge coefficient. Refer to this article in our knowledge base to learn more about the FHWA WSPRO Method.
• Downstream embankment side slope (V:H)
  This entry field specifies the embankment side slope of the inline structure (measured in the direction of flow) on the downstream face of the structure. The slope is represented by the number of horizontal units per vertical unit. For vertical side slope embankments, enter a value of 0. By default, the software uses a value of 3.0 (i.e., 1:3).
  Note that this variable is generally not used in the computations but is used for display purposes in the profile plot. However, if the user has selected the FHWA WSPRO Method for low flow, this field will be used in the computation of the bridge discharge coefficient.

Inline Structure Weir Specifications

This section provides the following parameters to define spillway flow through the inline structure:

• Spillway weir crest shape
  This dropdown combo box defines the spillway shape at the inline structure. The following options are provided:
  1. Broad Crested (default) – This option should be used with typical spillways.
  2. Ogee – This option should be used with ogee spillways.
     
     If the user selects the Ogee shaped weir, two additional parameters–Spillway approach height and Design energy head are displayed in the Inline Structure Weir Specifications section.
     
• Spillway approach height
  This entry field is used to specify the height that is equal to the elevation of the spillway crest minus the mean elevation of the ground just upstream of the spillway.
• Design energy head
  This entry field is used to specify the height that is equal to the energy grade line elevation (i.e., at the design discharge) minus the elevation of the spillway crest.
• Weir coefficient (Cd)
  This entry field specifies the coefficient of discharge for use in the weir flow equation for spillway flow. By default, the software uses a value of 2.60. Clicking the […] button displays the Weir Coefficients lookup dialog box.
  
  For an ogee shaped spillway, defining Spillway Approach Height and Design Energy Head, and clicking on the [Compute] button causes the software to calculate the weir coefficient at the design discharge corresponding to the design head.

Other Specifications

This section contains an optional Pilot (low base) flow field, which is used only for unsteady flow computations. This entry defines the minimum flow that will be released from the structure. The HEC-RAS unsteady flow computations require no cross sections to go dry during the simulation. Therefore, if water is not flowing over the spillway at an inline structure, the user can use this field to ensure that there is always some minor flow going through the structure.

Culvert Flow Direction

In addition to the weir geometry, inline structures can include culverts. These culverts typically have flap gates to prevent flow reversal so that the flood in the main river channel does not flow out into the overbank areas.

The following flap gate options are available to describe culvert flow:

• No Flap Gates – Flow is allowed to flow in either direction through the culvert
• No Negative Flow – Allows water to flow from the river into the overflow area
• No Positive Flow – Allows water to flow into the river from the overflow area

Culverts

In HEC-RAS, culverts in inline structures can be modeled using the appropriate culvert geometry, including the shape, size, and slope of the culvert, as well as other relevant parameters such as roughness coefficients and inlet control conditions. These parameters can further be used for the simulation of water flow through the culvert and the analysis of hydraulic performance, such as water surface profiles, flow rates, velocities, and energy losses. Refer to this article in our Knowledge base to learn how to define culverts using the Culverts panel.

Gates

Inline structures are hydraulic structures that are placed along a river channel or a conduit to control the flow of water. Gates are used within these structures to regulate the water flow by opening or closing them. Some common types of gates used in inline structures are Sluice Gates, Radial Gates, etc. Refer to this article in our Knowledge base to learn how to define gates using the Gates panel.

Rating Curve

In HEC-RAS, the rating curve is a fundamental concept used to relate water surface elevations (stage) to corresponding discharge (flow rate) in inline structures. It provides a functional relationship between the water level and the flow capacity of a particular structure. The rating curve is typically derived through a combination of field data collection, hydraulic modeling, and analysis. It represents the hydraulic performance of the inline structure and is specific to its geometry, dimensions, and operational characteristics.

This data panel contains the following sections:

Rating Curve Outlet Flow Computation

This section provides the following options that are used to define rating curve computations:

• Rating Curve ID
  This entry field is used to assign an ID to the rating curve.
• Outlet flow horizontal station
  This entry field is used to select the horizontal station for the outlet discharge location on the weir geometry. The user can also click the [Pick] button to interactively select an outlet flow horizontal station from the Map View.
• Outlet width (perpendicular to flow)
  This entry field is used to enter the outlet width from the connection weir. The user can also click the [Pick] button to interactively measure the outlet width from the Map View.
• Inlet location
  The user can click the [Pick] button to select the inlet location upstream of the weir from the Map View. The [Clear] button clears the selected inlet location.
• Outlet location
  The user can click the [Pick] button to select the outlet location downstream of the weir from the Map View. The [Clear] button clears the selected outlet location.
• Outlet flow based upon upstream
  This dropdown combo box allows the user to select the computation type for the rating curve, either in the form of Water Surface Elevation or Flow.

Outlet Flow Rating Curve Data and Plot

The rating curve can be expressed in the form of a table under the Outlet Flow Rating Curve Data section and its corresponding plot under the Outlet Flow Rating Curve Plot section. The graph or a table shows the relationship between water surface elevation (stage) and the corresponding discharge (flow rate) passing through the structure.

Outlet Time Series

In HEC-RAS, the outlet time series for inline structures refers to the hydraulic data recorded at the downstream end of a structure or a reach in a river or channel model. Inline structures are typically defined as structures that are located within a river reach, such as bridge piers, culverts, weirs, or gates. The outlet time series for an inline structure provides information about the flow rate, water level, velocity, or other hydraulic parameters at the downstream end of the structure over a specified time period. It is generated as part of the HEC-RAS simulation and represents the hydraulic response of the inline structure to the input hydrologic and hydraulic conditions.

This data panel contains the following section:

Time Series Specifications

This section contains the following options:

• Time series ID
  This entry field is used to assign an ID to the outlet time series.
• Horizontal station for outlet flow
  This entry field is used to select the horizontal station for an outlet discharge location on weir geometry. The user can also click the [Pick] button to interactively select an outlet discharge location from the Map View.
• Outlet width (perpendicular to flow)
  This entry field is used to enter the outlet width from the connection weir. The user can also click the [Pick] button to interactively measure the outlet width from the Map View.
• Outlet location
  The user can click the [Pick] button to select the outlet location downstream of the weir geometry from the Map View.

The [Delete All] button can be used to clear all the data specified within this section.

Ineffective Flow Areas

Ineffective flow areas allow the user to define areas of the cross section that will contain water that is not actively being conveyed. Ineffective flow areas are often used to describe portions of a cross section in which water will pond and the velocity of that water, in the downstream direction, is close to zero. This water is included in the storage calculations and other wetted cross section parameters but is not included as part of the active flow area. When using ineffective flow areas, no additional wetted perimeter is added to the active flow area. Refer to this article in our knowledge base to learn how to define ineffective flow areas using the Ineffective Flow Areas panel.

Dam Breach

In order to plan for the possibility of a dam break, dam breach information is entered to simulate the dam break. The dam breach data is only used for unsteady flow models and is ignored in steady flow models. Refer to this article in our knowledge base to learn how to define dam break data using the Dam Breach panel.

Geometry Adjustment

Using this data panel, the user can adjust the geometry of the inline structure at any time during the modeling. Typically, this panel is used to revise the inline structure geometry where there is insufficient terrain data available to adequately define the inline structure geometry.

This data panel contains the following sections:

Adjust Inline Structure Geometry

This section allows the user to define the type of adjustment to be applied to the inline structure geometry.

This section contains the following options:

• No change
  This option is selected by default and results in no changes to the inline structure geometry.
• Adjust elevations
  This option allows the user to adjust the inline structure geometry elevations by the defined amount.
  
• Adjust stations
  This option allows the user to adjust the inline structure geometry stations by the defined amount.
• Shift stationing
  This option allows the user to shift the inline structure geometry stationing using an existing reference point. The user selects the corresponding reference point from the dropdown combo box and then assigns the station to be assigned to the reference point. The following reference points are provided in the dropdown combo box entry:
  1. Leftmost Station
  2. Left Bank
  3. Thalweg (lowest elevation between channel banks)
  4. Centered Between Banks
  5. River Reach Intersection
  6. Right Bank
  7. Rightmost Station

Adjustment Extents

This section is used to select which inline structure and river reaches are to be changed by the specified adjustment. If bridge structures or inline structures are defined for selected reach(s), then their corresponding cross section geometry is also adjusted. Clicking the [Apply] button applies the defined inline structure adjustment method.

Geometry Point Reduction

This data panel allows the user to automatically filter out unnecessary station elevation. HEC-RAS limits the number of geometry points for cross sections, lateral structures, high chord and low chord geometry of cross section, and inline structures to a maximum of 500 geometry points. These point limitations may appear sufficiently large, but when these HEC-RAS entities are computer generated from Light Detection and Ranging (LiDAR) or Digital Elevation Models (DEMs) or data is acquired with equipment such as an echo sounder, the number of data points can be fairly high. Refer to this article in our knowledge base to learn how to implement geometry point reduction using the Geometry Point Reduction panel.

Profile Results

This data panel allows the user to select the analysis results on the inline structure plot. The table displayed under the Profile Results section lists all of the analyzed water surface profiles for the steady state and maximum water surface for the unsteady state. This allows the user to specify for which profiles the results should be displayed.

This data panel contains the following sections:

Profile Results

This section contains the following options:

• Profile
  This read-only table column lists the profile name.
• Water Surface
  This table column lists a checkbox option that controls the display of computed water surface on the inline structure geometry.
• Energy Grade
  This table column lists a checkbox option that controls the display of the computed energy grade line on the inline structure geometry.
• Critical Depth
  This table column lists a checkbox option that controls the display of computed critical depth on the inline structure geometry.
• Filled-in water surface
  This checkbox option causes the selected water surface to be filled in on the inline structure geometry. If more than one profile has been selected and both have the water surface checkbox option selected, then the lowest water surface elevation value is used.

Clicking the [Remove All] button removes all profile results from the inline structure plot.

Other Options

This section allows the user to enable additional curves for the plot terrain surface, fixed sediment, and pilot channel in the inline structure plot.