@gbam
The help tutorial says that it can handle the submerged weir flow but that it has to flip over to the Villemonte Equation but it doesn't go into much detail.
So far the best I can come up with is reducing the width of the weir, seems to help the instability a bit but there are still some...
I created an SSA model for my site. The site is next to a creek that is undersized and floods. I have been given a tailwater condition of this creek that puts the upper right corner of my site underwater. We are proposing a detention basin in this corner to provide extra storage capacity and...