All- I created a model in which I am breaching a dam. I am using a combo of 2d with two (2) flow areas being connected through a large culvert. The breach model runs. When I go to RAS Mapper, the model is showing flow in the DOWNSTREAM Channel at time stamp zero (before I push the play button in RAS MAPPER). Why is this happening and is this an issue?
Check to see if you have a water surface elevation set as an initial condition for the downstream 2D flow area. If that is the case, the initial condition shouldn’t matter if it is not significant compared to the flood wave.
I actually set an initial condition hydrograph. Completely forgot about the logic of the floodwave that there WILL be water in the downstream channel due to the initial hydrograph. Man, this was giving me heartburn until I took a step back and thought things through. Thanks for the reply! Hope all is well.