Impact of downstream boundary condition on 1D/2D model

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Impact of downstream boundary condition on 1D/2D model

M. L. Harris
I have a combined 1D/2D model where there is an upstream 2D flow area connected to a downstream 2D flow area with a 1D reach (due to presence of a bridge), and another 1D reach downstream of that (with more bridges).

I am using a constant stage boundary at the downstream-most XS and am running a sensitivity analysis on the starting WSE at this XS. I noticed that when I INCREASED the fixed WSE at this XS, it caused the WSE results in my upstream 2D flow area to become LOWER.

Can anyone speculate what may be causing this phenomenon?
M. L. Harris, P.E. | Water Resources Engineer
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Re: Impact of downstream boundary condition on 1D/2D model

Luis Partida
how does the interface of your 1D and 2D region look and intereact? What is the initial flow you have used for the 1D most US cross section?