| Product(s): | PondPack, CivilStorm, SewerGEMS |
| Version(s): | 08.11.XX.XX, 10.00.00.XX |
| Area: | Modeling |
Problem
How can the Snyder Unit Hydrograph Method be used for catchments in PondPack, CivilStorm or SewerGEMS?
Solution
Since the Synder method is a synthetic unit hydrograph, consider modeling it as a custom SCS dimensionless unit hydrograph.
However, this assumes that the method can still utilize the underlying SCS Unit Hydrograph methodology. If the Snyder Method has differences beyond the unit hydrograph used, there are two other options to consider:
1) Externally calculate a unit hydrograph for every catchment, and use the Generic Unit Hydrograph method. This is found in the "Unit Hydrograph Method" dropdown field. A reference on this can be found here: http://ponce.sdsu.edu/textbookhydrologychapters.html
2) Compute the overall runoff hydrographs externally and insert them as User Defined hydrographs (User Defined Hydrograph as the Runoff Method).
Note that Synder and S-curve are directly supported in HEC-HMS.
Here is a screenshot of the relevant input for the custom dimensionless unit hydrograph, using the included Delmarva unit hydrograph as an example:
Here is a screenshot of the Generic Unit Hydrograph data entry:
See Also
Catchment's total runoff and peak flow are different than HEC-HMS