Defining Culverts for HEC-RAS Bridge Modeling

In GeoHECRAS, the Culverts data panel of the Bridge & Culvert Data dialog box allows the user to define the culverts at a roadway crossing. This article describes how to use the Culverts data panel.

Follow the steps below to use the Culverts data panel:

Select the Culverts option from the Roadway Crossing Specifications dropdown combo box of the Bridge & Culvert Data dialog box.
The Culverts data panel will be displayed.

The following sections describe how to interact with the Culverts data panel of the Bridge & Culvert Data dialog box.

Culvert Definition

Culvert set ID: This editable dropdown combo box allows the user to select the current culvert set from the Culvert Set table. Alternatively, the user can select a row in the Culvert Set table and the dropdown combo box will update with the current Culvert set ID.
Shape: This read-only dropdown combo box allows the user to select the desired culvert shape from the dropdown list.
Chart number: This read-only dropdown combo box lists all of the associated chart numbers for the selected culvert shape.
Scale number: This read-only dropdown combo box lists all of the associated scale numbers for the selected culvert shape and chart numbers.
Solution criteria: This read-only dropdown combo box lists the solution criteria that the HEC-RAS software will use in determining the controlling flow type for the culvert set. The following options are provided in the dropdown list:
1. Computed Flow Control
2. Inlet control
3. Outlet control

The user can also use the buttons provided in this section to add a culvert set, copy a culvert set, pick a culvert, and delete the desired culvert sets, respectively.

Clicking the [Add] button allows the user to add the culvert set.

Clicking the [Copy] button allows the user to copy culverts from the original culvert set.

Clicking the [Pick] button allows the user to select the culvert from the Map View.

Clicking the [Delete] button allows the user to delete the culvert set.

Clicking the [Delete All] button allows the user to delete all of the culvert sets.

Culvert Barrel Centerline Stationing

This section of the panel defines the centerline stationing for each of the culvert barrels that make up a culvert set. The user can manually enter the culvert barrel centerline station. Alternatively, the user can click on the […] pick button under the Upstream Station and Downstream Station column to select the centerline station from the Map View or from the roadway crossing cross section plot for both the upstream and downstream faces. Clicking the […] pick button under the Barrel Alignment column allows the user to select the culvert barrel alignment polyline from the Map View and draw the culvert barrel centerline alignment on the Map View, respectively. Note that a maximum of 25 culvert barrels can be defined in the table.
Culvert Barrel Centerline Stationing

Auto-Assign Culvert Parameters

The Auto-Assign Culvert Parameters is an optional section that is used to auto-assign the culvert parameters. The following options are provided in this section:

Assign inverts using terrain surface: This option allows the user to choose the desired terrain surface type from the dropdown combo box.
Assign using shapefile layer: This option allows the user to choose the desired shapefile layer type from the dropdown combo box. Note that the following dropdown combo box entries are enabled only when the user selects the Assign using shapefile layer option.
1. Upstream invert elevation attribute
  This dropdown combo box allows the user to select the elevation attribute of the culvert invert at the upstream end.
2. Downstream invert elevation attribute
  This dropdown combo box allows the user to select the elevation attribute of the culvert invert at the downstream end.
3. Culvert shape attribute
  This dropdown combo box allows the user to select the attributes of the culvert’s shape.
4. Diameter or height attribute
  This dropdown combo box allows the user to select the diameter or height attributes of the culvert.
5. Width or span attribute
  This dropdown combo box allows the user to select the width or span attributes of the culvert.

Culvert Dimensions

This section of the panel defines the dimensions of the culvert set being defined. The following entries are provided in this section:

Diameter or height: This entry field defines the maximum diameter or height inside of the culvert. The user can click the [Pick] button to measure the height from the roadway crossing cross section plot.
Width or span: This entry field defines the maximum width inside of the culvert. The user can click the [Pick] button to measure the span from the roadway crossing cross section plot. Note that for circular culvert shapes, this entry field is disabled.
Distance to upstream cross section: This entry field is used to locate the culvert in space, relative to the two cross sections that bound the culvert crossing. The user can click the [Pick] button to measure the distance from the upstream side of the culvert to the next upstream cross section from the Map View.
Culvert length: This entry field defines the length of the culvert along the centerline of the barrel. The user can click the [Pick] button to measure the culvert length from the Map View.
Upstream invert elevation: This entry field defines the elevation of the culvert invert at the upstream end. The user can click the [Pick] button to select the invert elevation from the roadway crossing cross section plot.
Downstream invert elevation: This entry field defines the elevation of the culvert invert at the downstream end. The user can click the [Pick] button to select the invert elevation from the roadway crossing cross section plot.
Culvert slope: This entry field defines the slope of the culvert. The software computes the value of the Culvert slope entry field based on the upstream and downstream invert elevations. Note that if the upstream and downstream invert elevation entry fields are blank, then the Culvert slope field will be displayed as NA (not applicable).

Culvert Coefficients

This section of the panel defines the coefficients for the culvert set being defined. The following entries are provided in this section:

Entrance loss coefficient: The coefficient entered in this entry field is computed as a coefficient multiplied by the absolute velocity head of the flow inside the culvert at the upstream end. This value represents the amount of energy loss that occurs as flow transitions from the upstream cross section to inside the culvert barrel. Clicking the […] lookup button next to the Entrance loss coefficient entry field displays the Culvert Entrance Loss Coefficients lookup dialog box. To learn more about the Entrance loss coefficient, refer to this article in our knowledge base.
Exit loss coefficient: The coefficient entered in this entry field is computed as a coefficient multiplied by the change in velocity head from inside the culvert at the downstream end to outside the culvert at the downstream end. This value represents the energy loss that occurs as water exits the culvert. Clicking the […] lookup button next to the Exit loss coefficient entry field displays the Culvert Exit Loss Coefficients lookup dialog box. To learn more about Exit loss coefficient, refer to this article in our knowledge base.
Manning’s n for top: This entry field is used to enter the Manning’s n values of the culvert barrel and allows the user to enter a separate n value for the top (which includes the top and sides) of the culvert, as well as for the bottom. If the culvert has the same roughness at the top and bottom, the user can enter the value for the top. Clicking the […] lookup button next to Manning’s n for top entry field displays the Manning’s Roughness lookup dialog box.
Manning’s n for bottom: This entry field is used to enter a Manning’s n value for the bottom of the culvert. This n value will be used up to a user specified depth inside the culvert. When the water surface exceeds that depth, a composite Manning’s n value is computed based on the bottom and top n values and their corresponding wetted perimeters. Clicking the […] lookup button next to the Manning’s n for bottom entry field displays the Manning’s Roughness lookup dialog box.
Depth to use bottom Manning’s n: This entry field is used to specify the depth at which the Bottom n value is applied inside the culvert. The surface of the culvert below this depth is given the n value for the bottom of the culvert, while the surface of the culvert above this depth is given the n value for the top of the culvert. The user can click the [Pick] button to measure the depth from the roadway crossing cross section plot.
Depth blocked: This entry field is used to block off a portion of the bottom of the culvert. When a value is entered into this field, the culvert is completely blocked up to the depth specified. This blocked out area persists the entire way through the culvert. The user can click the [Pick] button to measure the depth from the roadway crossing cross section plot.