I have a 2D model coupled with 1D components. At the downstream end of my model I have a box culvert discharging into an open channel. Additionally, there's about 1500 cfs spilling into the open channel from overland flow that bypasses the box culvert. I'm trying to transition the 2D overland flow into 1D so that I can set a head discharge curve at the outlet which represents the the hydraulics of the downstream channel. The head discharge curve should only affect the box culvert outlet and not the overland flow. I've tried adding in an Inline Bank to transition the 2D flow into 1D; however, the peak flows being computed over the Inline Bank are incorrect. If I cut a 2D results line just upstream of the inline bank it reports approximately 1500 cfs. The results for the Inline Bank is reporting 2500 cfs going over the inline bank and into my 1D outlet. When viewing the hydrograph it appears to be very unstable. Any ideas on how to stabilize the inline bank or another way to transition the 2D flow into 1D?


Hydrograph of Inline Bank
Inlne Bank Hydrograph.JPG

Hydrograph of 2D results line upstream of Inline Bank
2D Results Line.JPG