I have a sluice gate controlling flow in and out of a basin that is tidally influenced. I have the tide elevations as the downstream boundary condition with only a small place holder flow at the upstream end to simulate dry weather conditions (tidal flushing) in the basin. When I model just the culvert, the flow goes in and out of the basin with the downstream head forcing positive and negative flow values. When I put the sluice gate on the culvert, flood flows are not allowed to pass in the “Upstream” direction. Is there any way to simulate a sluice gate that allows bi-directional flow? I’m thinking the weir equation doesn’t work when the tail water is higher than the head water elevation. I was thinking of making the invert artificially low = to the bay side invert of the culvert. Thanks for any advice I can get.