Does HydroCAD have any lower limtis on the watershed size? For urban watersheds less than 5 acres, I have been told the SCS TR-20 Method may not be reliable and a rational method should be used. I do not see any hints or errors when running small watersheds.
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Small Urban Watersheds 1
- Thread starter TCE2009
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HydroCAD does not impose any lower limits on the watershed size or Tc, so this is really a matter of using the most appropriate methodology.
Some localities specify the Rational method for small waterersheds, while others specify the SCS/NRCS method regardless of size.
I generally recommend SCS over Rational whenever it is accepted by local regulations, partly because it provides a complete runoff hydrograph that is required for volume-sensitive calculations, such as detention ponds.
For details please see
Peter Smart
HydroCAD Software
Some localities specify the Rational method for small waterersheds, while others specify the SCS/NRCS method regardless of size.
I generally recommend SCS over Rational whenever it is accepted by local regulations, partly because it provides a complete runoff hydrograph that is required for volume-sensitive calculations, such as detention ponds.
For details please see
Peter Smart
HydroCAD Software
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