Subject: How to Subdivide Subcatchments in SWMM 5
If you want to subdivide a larger Subcatchment in SWMM 5 and get around the same peak flow then a good suggestion would be to make sure that (Figure 1):
1. The sum of the new areas equals the original Subcatchment Area and
2. The sum of the total Width values equals the original Subcatchment Width on the one Subcatchment
3. The infiltration, percent imperviousness, roughness and depression storage should be the same.
Figure 1. Subdividing a Subcatchment