Editing Manning’s Data

In GeoHECRAS, the Edit Manning’s Data command is used to manually edit Manning’s roughness so that the computed water surface elevations correspond to observed values.

In GeoHECHMS, the Edit Manning’s Data command is used to edit Manning’s roughness for:

Reaches that contain irregular cross sections.
Multiple reaches that reference the irregular cross section geometry.
Left overbank, channel, and right overbank.

Editing Manning’s Data (HEC-RAS)

Follow the steps below to use the Edit Manning’s Data command in GeoHECRAS:

From the Input ribbon menu, click the Manning’s Roughness dropdown menu and select the Edit Manning’s Data command.
The Edit Manning’s Data dialog box will be displayed.

The following sections describe Edit Manning’s Data command in GeoHECRAS and how to interact with the above dialog box.

Manning’s Roughness Data

This section is used to select the river and the corresponding reach for editing Manning’s data for the associated cross sections. The user can select the river and the reach from the River and Reach dropdown combo boxes, respectively. Alternatively, the user can click the [Pick] button to select the river reach from the Map View.

The table under this section displays Manning’s roughness (n) of cross sections associated with each River Station.

The structures such as culverts, lateral structures, and roadway crossings falling within the reach are identified and displayed in the Type column. For identified structures, the corresponding rows for Manning’s values will be disabled.

The dropdown combo box present on the Manning’s Roughness Data section header allows the user to filter Manning’s roughness displayed in the table for different regions. The following dropdown entries are available:
Manning’s roughness for different regions

All Subareas
Left Overbank
Channel
Right Overbank
Both Overbanks

Note that while drawing a cross section using the Draw Cross Sections command, the table will only display Manning’s n value for left overbank, channel, and right overbank. Refer to this article in our knowledge base to learn more about Draw Cross Sections command.

The table will also display Manning’s roughness for additional subareas if different land covers fall over the entire cross section length. The Assign Manning’s Data command gives the option to assign Manning’s roughness based on the NLCD land cover data. Refer to this article in our knowledge base to learn more about Assign Manning’s Data command.

Color Legend

The color codes for different Manning regions displayed in the Manning’s Roughness Data table are listed in this section.
Color Legend section

Selected Cells Group Editing

This section provides different options for the user to edit Manning’s data. The user can manually edit a single Manning’s cell value, drag and select multiple cells from a table column, and use the following editing options:
Selected Cells Group Editing section

No change
This is the default option. No changes will be made in Manning’s values when this radio button option is selected.
Add constant
Select this radio button option to add a constant value to a group of Manning’s values. The value entered in the adjacent entry field will be added to all the cells that are selected.
Multiply by factor
Select this radio button option to multiply a group of Manning’s values by a factor. The value entered in the adjacent entry field will be multiplied by each of the selected cells’ values.
Apply value
Select this radio button option to set a group of Manning’s values to the same number. The value entered in the adjacent entry field will replace all of the selected values.

The user can click the […] lookup button to display the Manning’s Roughness lookup dialog box, which can be used for reference.

After selecting the desired option and entering the required value, click the [Apply Change] button to accept the changes in the data table.

Once all the editing is done, click the [OK] button to save the changes.

Editing Manning’s Data (HEC-HMS)

Follow the steps below to use the Edit Manning’s Data command in GeoHECHMS:

From the Input ribbon menu, click the Cross Sections dropdown menu and select the Edit Manning’s Data command.
The Edit Manning’s Data dialog box will be displayed.

The following sections describe Edit Manning’s Data command in GeoHECHMS and how to interact with the above dialog box.

Manning’s Roughness Data

The data table in this section displays Manning’s roughness of Left Overbank, Channel, and Right Overbank for every cross section associated with a Reach. In addition, the data table also displays the Element Shape of every cross section.