Fixed Sediment Elevations Command

In GeoHECRAS, the Fixed Sediment Elevations command allows the user to define filled-in sediment elevations for a river channel. This command is used to fill in portions of cross sections with sediment. The sediment is assumed to be at a constant elevation in any particular cross section.

Follow the steps below to use the Fixed Sediment Elevations command:

1. From the Input ribbon menu, select the Cross Sections dropdown menu and select the Fixed Sediment Elevations command.
   
2. The Fixed Sediment Elevations dialog box will be displayed.
   

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

Selecting River Reach

The Select River Reach section allows the user to select the river and reach to be assigned for sediment elevation.

Follow the steps below to manually select the river and reach to be assigned for sediment elevation:

1. Click on the River dropdown combo box and select the river to be assigned for sediment elevation.
   
2. Then, click the Reach dropdown combo box and select the reach to be assigned for sediment elevation.
   

Alternatively, click the [Pick] button to select the river and reach from the Map View as shown below. The Fixed Sediment Elevations dialog box will temporarily disappear, allowing the user to select the river reach from the Map View. After selecting the river reach, press the [Enter] key or right-click and select Done from the displayed context menu. The dialog box will be redisplayed with the river and reach shown as selected in the respective dropdown combo boxes.

In addition, a graphical plot showing a longitudinal view of the river reach and the sediment elevation along the river reach will be displayed in this section.

Notes:

• If a river reach is preselected from the Map View prior to running this command, then the selected river reach will be displayed in the River and Reach dropdown combo boxes.
• If the model contains a single river and reach, they will be automatically selected in the River and Reach dropdown combo boxes.

Sediment Elevation Editing

This section allows the user to set or edit the sediment values over a range of cross sections that define filled-in sediment elevation for the selected river channel.

The following options are provided to have a sediment fill over a range of cross sections:

• Draw
• Project Slope
• Interpolate Elevation

Draw

This panel allows the user to manually draw the sediment elevation along the selected river channel.

Follow the steps below to define sediment elevation:

1. Click the [Draw] button.
   
2. Place the cursor over the graphical plot available under the Select River Reach section. The cursor will change into a crosshair. Now, draw the sediment elevation on the graphical plot available under the Select River Reach section.
3. After drawing the sediment elevation, press the [Enter] key or right-click and select Done from the displayed context menu.
4. The software will then automatically draw and compute the sediment elevation along the selected river channel.
   

Note that the drawn sediment elevation should be sloped downwards for best computational results.

Project Slope

This panel allows the user to define the sediment elevation at the upstream and the downstream cross sections and then project the sediment fill on a slope over the range of selected cross sections.

The following subsections are available in this panel:

Select Cross Section Range

This subsection allows the user to select the downstream-most and upstream-most river stations. The following entries are available in this subsection:

• Downstream cross section
  Click on this dropdown combo box to select the cross section that will be used as the downstream-most river station. Alternatively, click the [Pick] button adjacent to the Downstream cross section dropdown combo box to select the downstream cross section from the Map View.
  
  Note that by default, the software selects the cross section at the downstream end of the river reach.
• Upstream cross section
  Click on this dropdown combo box to select the cross section that will be used as the upstream-most river station. Alternatively, click the [Pick] button to select the upstream cross section from the Map View.
  
  Note that by default, the software selects the cross section at the upstream end of the river reach.

Define Sediment Elevation

This subsection allows the user to define the sediment elevation for the cross sections along the river channel.

The sediment elevation can be defined by manually entering the value in the Sediment Elevation entry field.

The Options subsection allows the user to select a specific option in order to define the sediment elevation for each of the cross sections within the selected range. The following options are available:

• The Same fill for all cross sections radio button option allows the user to define the same sediment elevation for each cross section in the selected range.
• The Project from upstream XS at a slope (V:H) radio button option allows the user to project the sediment fill at a slope from the selected upstream cross section.
• The Project from downstream XS at a slope (V:H) radio button option allows the user to project the sediment fill at a slope from the selected downstream cross section.

After defining the sediment elevation, click the [Apply] button to define the filled-in sediment elevation for the selected river channel.

Interpolate Elevation

This panel allows the user to define the sediment elevation for the downstream-most and the upstream -most cross sections and then automatically interpolate sediment elevations for all the cross sections in between the selected range.

The following subsections are available in this panel:

Select Cross Section Range

This subsection allows the user to select the downstream-most and upstream-most river stations. The following entries are available:

• Downstream cross section
  Click on Downstream cross section dropdown combo box to select the cross section that will be used as the downstream-most river station. Alternatively, click the [Pick] button to select the downstream cross section from the Map View.
  
  Note that by default, the software selects the cross section at the downstream end of the river reach.
• Upstream cross section
  Click on Upstream cross section dropdown combo box to select the cross section that will be used as the upstream-most river station. Alternatively, click the [Pick] button to select the upstream cross section from the Map View.
  
  Note that by default, the software selects the cross section at the upstream end of the river reach.

Define Sediment Elevation Parameters

This subsection allows the user to define the sediment elevation for the upstream and downstream cross sections to be used for linear interpolation.

The user can define the downstream and upstream sediment elevation by manually entering the values in the Downstream sediment elevation and Upstream sediment elevation entry fields, respectively.

After defining the sediment elevation, click the [Apply] button to define the filled-in sediment elevation for the selected river channel.

Sediment Elevation Data

This section provides a table that displays the final sediment elevation values for each cross section. The user can further modify these sediment elevation values for the cross sections populated in the table.

Selected Cells Group Editing

This section allows the user to enter/edit the sediment elevation data in the Sediment Elevation Data summary table (described above).

Follow the steps below to update the sediment elevation data:

1. Select the cell in the Sediment Elevation Data table whose data is to be updated. Hold down the [Ctrl] key to select multiple cells.
2. Click the Define change dropdown combo box and select one of the options to update the cell’s value.
   

   The following options are available:

   • No Change: This option will not make any changes to the selected cell’s value.
   • Add Constant: This option adds a constant value to the selected cell’s value.
   • Multiply By Factor: This option multiplies the selected cell’s value by a user-defined number.
   • Apply Value: This option replaces the selected cell’s value with the user-specified value.
3. Enter the change coefficient in the adjacent entry field.
4. Click the [Apply Change] button to apply the defined sediment elevation adjustment. Note that the [Apply Change] button is disabled when No Change option is selected.

When all the sediment elevation information is defined in the Fixed Sediment Elevations dialog box, click the [OK] button to define the filled-in sediment elevation for the selected river channel.