This happens to frequently in the jurisdiction where I work, that detention of the 1 year storm is not required. Often, jurisdictions will leave it up to the engineer's interpretation of what would be acceptable. In my experience, 0.4 cfs is negligible. Often times, that amount of flow can...
I read in the Civil 3D stormwater discussion group that Hydraflow recently updated it's modeling of pipe flow. I would check that forum, because people were getting different flows even between version of Hydraflow.
Michael
www.revisionblock.com
Import Hydraflow Into Excel
