I am currently looking to prepare a 1D static flow model of a channel bounded by flat sloped weirs on both ends and had a question related to ineffective flows. The channel is approximately 900 feet long by about 100 feet wide with two small diameter culverts through the downstream weir that aren’t currently modeled. I am using permanent ineffective areas on both sides of both weirs, but non-permanent ineffective flows in between the permanents to account for movement of water in larger storm events that overtop the downstream weir. Is this an accurate assumption to make for ineffective flow areas? I have reviewed some flume videos that show a similar flow uplift at a weir and trying to determine if this is a valid approach for modeling with HEC-RAS. Below is a video of what I am anticipating at the downstream weir:
https://www.youtube.com/watch?v=cRnIsqSTX7Q