How can I create a synthetic rainfall curve for a duration other than 24 hours?

Product(s): PondPack, SewerGEMS, CivilStorm
Version(s): 10.XX.XX.XX, 08.11.XX.XX
Area: Modeling

Problem

How can I create a synthetic rainfall curve for a duration other than 24 hours (for example, a 6 hour storm)? Can I use a duration multiplier with the included SCS type curves? (such as Type II 24hr)?

Solution

The 24 hr. SCS type curves are only meant for use with a 24 hr duration. It’s not a valid approach to try adjusting them using a duration multiplier.

You can try using Bul70-71 curves since they are dimensionless in both time and rainfall depth. With these, you can scale it how you want.

For example use a 6.0 duration multiplier to create a 6 hour storm. Other similar curves are available, though these and the Bul70-71 curves are only intended for regions in the Midwest United States.

If your area is not in the Midwest United States, you will need to figure out an approach for the region. You may need to develop a balanced storm distribution outside of the program using IDF data and then add that to the Engineering Library.

See Also

Forum Thread - SewerGEMS V8i Hydrology

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