WILDWINGS27
Civil/Environmental
- Mar 5, 2006
- 30
I have always been a bit confused as to how to develop a proposed Time of Concetration in which to model detention. Most of the work my firm does are small (~5 acres commercial sites). Most time of concetration models assume all water is channeled directly to the pond. For instance, TR-55 assumes sheet flow, shallow concentrated, and channelized. This is easy to figue in an undeveloped state.
However, in a proposed commercial site, water will sheet flow to the storm sewer. The inlets and pipe are generally designed for the 10 year event. In the 100 year event, water will pond above the inlets and flow to the detention basin through overland flow routing. So to get a time of concetraion for the 100 year event is almost impossible. Does it make sence to use the final time of the 10 year storm sewer to model the detention?
I guess, I usually see engineers state that they used the TR-55, LAG, or some other equation to get a Time of Concetration to model their detention. But in a developed state, I do not see how that is possible.
However, in a proposed commercial site, water will sheet flow to the storm sewer. The inlets and pipe are generally designed for the 10 year event. In the 100 year event, water will pond above the inlets and flow to the detention basin through overland flow routing. So to get a time of concetraion for the 100 year event is almost impossible. Does it make sence to use the final time of the 10 year storm sewer to model the detention?
I guess, I usually see engineers state that they used the TR-55, LAG, or some other equation to get a Time of Concetration to model their detention. But in a developed state, I do not see how that is possible.