Modeling lateral overflow weir connected to two ponds in series

[max0000]

I've got a question about handling tailwater in HEC-HMS.

Situation: I'm modeling a proposed lateral overflow weir on an existing engineered channel. Overflow from the weir, along with watershed runoff, will be collected in a detention pond (Pond #1), Pond #1 will be connected downstream to a secpmd pond (Pond #2) by two 6-foot concrete box culverts (two ponds because of a utility easement running through the property). Pond #2 will outfall into the channel downstream of the lateral weir.

My current modeling approach is to use a diversion element in HEC-HMS with the lateral weir option connecting to two reservoir elements in series, which then connect to the downstream end of the reach. I can create a tailwater rating curve for the outfall from Pond #2 based on a HEC-RAS model of the channel. My question is, how do I model the tailwater effect on the outfall from Pond #1 into Pond #2 and also from the overflow weir into Pond #1? Is this something HEC-HMS can do, or do I need to try tackling it in SWMM?

 

[gbam]

It has been some time since I used HMS, but, I do recall that it does not account for tailwater. You can develop a rating table that accounts for submergence on a weir based on tailwater. That is an external analysis, however, and will require coding the rating table into HMS. ICPR is a program that will allow flow to be routed upstream and downstream based depending on water surface elevations. I am not sure SWMMM will do that. Hope that helps.