Create Geometry Files from Sediment Results

It is very common for users to convert the results from a sediment simulation into a new HEC-RAS geometry file. The most common motivation for this is re-evaluating risk assessment (e.g. run HEC-FDA, the 1% flood or a 2% riparian flow) for future conditions, after a period of record sediment simulation. However, this feature can also useful for "robustness" tests or model warm-up.

To create a geometry file from the updated cross sections from a sediment transport simulation press the Create Geometry Files from Sediment Results button on the Sediment Output Options menu.

A dialogue will appear (below) with all the result profiles from the sediment simulation. Select one or more of these to convert the cross-section station-elevation points from that (those) time(s) in the simulation into geometry files. For example, to create a geometry file from the final simulation result, scroll to the bottom profile and select it.
A naming dialogue will appear for each of the profiles selected. Name the geometry file(s)

The new geometry file will inherit all of the parameters, variables, settings and features of the geometry file used for the sediment simulation (e.g. n-values, ineffective flow areas, structures, etc…) and will only update the station-elevation points (and, in cases where BSTEM is not used, only the elevations of those points).

HEC-RAS will add the new geometry file to the project, and it becomes available for new steady, unsteady or sediment simulations.

Modeling Note – XS Htab Starting Elevation Error:

When using a geometry file created from a sediment simulation in a new hydraulic or sediment simulation, the new simulation will often throw an Htab error (below). The HTab (Hydraulic Table) editor sets the increments for the pre-processed hydraulic computations and is supposed to start at or near the thalweg. The new geometry file inherits these from the geometry file used during the sediment simulation, but the thalwegs of many of the cross sections have probably changed.

This issue has a simple fix. Open the geometry file and press the HTab button on the left, vertical, button bar (you may need to expand the geometry editor vertically to see it). This will open the Cross Section Table Properties editor (below). Select the header of the Starting El column to select all of the initial elevations. Then press the Copy Invert button. This will reset the base elevation of all the HTab tables and will clear up the error message.