I am trying to determine the best way to represent "leaf" gates in SWMM5. The gate consists of two panels that overlap each other. The top gate serves as an overflow weir and drops as the upstream water level rises. If the top gate is fully lowered and the upstream water level is still rising, then both gates would be lifted up to create an underflow outlet. This would then eliminate the overflow aspect.
My thought is to model two separate gates. The overflow gate would need some kind of timeseries to control (lower) the crest elevation of the overflow gates until the upstream water surface elevation exceeds level X. At that time, the overflow gate would close and flow goes to zero.
A separate underflow gate would open to full capacity if the upstream water surface elevation exceeds level X.
I welcome your suggestions on how best to tackle this issue. Thanks.