I have a steady state 1D model with 1 crossing that shows the headwater difference between an existing and proposed condition. An interested party wants the model to be extended downstream to the next crossing to see if the proposed bridge has any impacts down there. However, I’m fairly confident, given the equations that HECRAS uses to calculate steady-state 1D modeling, that this additional model change will not show any impact to the downstream bridge. I’ve attempted to explain this, but I’m looking for some kind of official documentation to support me. Any thoughts that you may have would be beneficial.