Modeling a Dam in WMS for Use in HEC-HMS

Do you have a project that requires modeling a dam, or similar structure, in HEC-HMS? WMS can make this process smoother with tools designed to help define the structure quickly and efficiently.

This blog presents a workflow for modeling a dam in WMS to later analyze in HEC-HMS. The workflow is as follows:

1. Begin with a delineated watershed with attributes defined.
2. Determine where you would like to place your reservoir and place an outlet point there.
3. Delineate your watershed and compute basin attributes using your new outlet point.
4. Create a simulation in HEC-HMS and compare the runoff from the upper basin to the lower basin in order to size your reservoir.
5. Convert the outlet node to a reservoir.
1. Switch to Hydrologic Modeling Module.
2. Using Select outlet tool, select the outlet at the location where you want to model a reservoir.
3. Right-click and select Add | Reservoir.
6. Select Calculators | Detention Basins.
7. Click Define to bring up Storage Capacity Input.
1. For a dam: Use DEM and enter the height of the desired dam.
2. Click OK to exit Storage Capacity Input dialog. The Detention Basin Analysis dialog will appear.
3. Define the storage curve for your reservoir.
4. Click Map to Hydrologic Model to open Map to Model. Name the series as desired.
8. Double-click on the reservoir point to open the HMS Properties dialog.
1. Here, you can choose the storage curve defined earlier, and define all other curves.
2. To add an orifice to your dam, select Orifice Outlet from the Outlet Type drop-down.
1. Define the orifice Center Elevation, Cross-sectional Area, and Discharge Coefficient.
3. To add a spillway, select Broadcrested Spillway or Ogee Spillway from the Spillway Type drop-down.
1. Define the required characteristics for the selected spillway.
4. You can also choose to model an overflow type and dam break type if desired.

With the dam, spillway and orifice defined, you can now run your model through HEC-HMS again to see how your reservoir will perform under the selected storm.

Try out modeling dam structures and other applications in WMS today!