Modeling inline lake with Hec Ras Cross Sections

[slange]

All,
How do you model a lake in HEC RAS that is just upstream from a FIS, has a low flow channel, and overtops and floods an adjacent road during the 100 year event. I have a model set up but don't think that I am modeling the lake right. I believe I need to go the path of setting up a weir at the elevation of the overtopping of the pond but not sure what to do.

any help would be appreciated.

thank you

 

[cvg]

typically this would be modeled using an inflow design flood hydrograph, storage route through the reservoir and then outflow hydrograph for overflow of the spillway / road and/or outflow through the low level pipe. outflow would vary with time based on the reservoir stage. so you would need a stage - storage - outflow relationship. while this can be done in HEC-RAS, we typically use HEC-1 or HMS for something like this. you need to consider your starting condition, lake full or not full at the beginning of the storm?