Hello all swmmers out there,

I was wondering if any of you had experienced the same difference when using SWMM5. I did a simple runoff example in SWMM 4.4(h) and built the same one in SWMM5, and found a problem I could not solve: I am aware of the current bugs in the conversion of mm/h in feet or inches, so I adapted that (dividing the rainfall amounts by 12) which worked. Apparently the slope is read as an absolute slope (as in SWMM4) instead of a % so I adapted that too.

But my results are still 5 times lower than the SWMM4 results. I think the problem may come from the infiltration method (I am using Green-Ampt), so I have been trying to adapt the hydraulic conductivity to match the runoff amount. I had to change my conductivity from 3mm/hr to 0.39mm/hr to get similar results. But the hydrographs look pretty different, so I still don't think this is the problem.

I don't know if I am doing something wrong, or if there is a bug I can't seem to locate.

Any help would be greatly appreciated!

My files are included here (the SWMM4 file is a PCSWMM file).

Alex Wilson.
CBCL Limited
alexanderw@CBCL.CA