Dealing with EPA SWMMs subcatchment model

[Ken MacKenzie]

How to derive the catchment parameters for KW application is one of the
classic, fundamental questions in use of SWMM. The width of the KW plane has
been suggested to be 1.6 to 2.2 times the length of the central channel
through the watershed. The predicted runoff flow is absolutely sensitive to
the width of the plane. Using the principles of mass and energy
conservation, the latest development is presented in the article as
attached:

Guo, C.Y. James, and Urbonas, Ben (2009) "Conversion of Natural Watershed to
Kinematic Wave Cascading Plane", ASCE J. of Hydrologic Engineering, Vol 14,
No 8, August.

Good luck.

Dr. James C.Y. Guo, Prof and P.E.
Civil Engineering, U. of Colorado Denver Denver, Colorado 80217
(303-556-2849)
Guo's Webpage - Ctrl key+Click to read
http://www.cudenver.edu

-----Original Message-----
From: UDFCD-...@googlegroups.com [mailto:UDFCD-...@googlegroups.com]
On Behalf Of GKCOTTON
Sent: Tuesday, July 14, 2009 10:17 AM
To: UDFCD Computational Tools and USDCM Support
Subject: [UDFCD-support] Dealing with EPA SWMMs subcatchment model


I wanted to get some feed back and opinions on the SWMM subcatchment model
from others that have used this basic component.

The conceptual framework is very different compared to unit hydrograph based
approaches (CUHP, SCS, Sneider, etc). Computation of a lag time for a unit
hydrographic typically breaks the flow path down into an overland flow
segment and a swale or gutter flow segment. For SWMM all runoff from a
subcatchment is sheet flow. There are pervious and impervious subareas and
these can cascade to each other or go directly to the outlet. The subareas
can also have their own n-values.
However, there is only one slope and one width for the entire subcatchment.

I have recently reviewed a model that used the subcatchment model in UDSWM.
Porting it to EPA SWMM 5.0 resulted in the same subcatchment hydrographs.
So, this routine seems to be very stable but maybe a bit of a dinosaur.

If anyone has come across guidance or research on how to estimate SWMM
subcatchment parameters, I would be interested in knowing about them.