A base level engineering study with 2d rain on grid for the entire County is the best available data for a proposed floodplain modification project. This is a bit new for me and our FEMA CTP. My first approach of reusing the mesh from the BLE for the pre/post development models may not pan out as the refinement regions used to define the streams aren’t within the 5.0.7 model or part of the supplemental data as a shapefile. Does 5.0.7 store refinement regions in a separate file? The layer is empty when viewed in 5.0.7 RAS Mapper.
I’d rather not recreate the regions for the entire basin to keep the mesh as close as possible to the effective model when we update it for our topo and looking at another approach. Use a profile line in the effective model to extract a hydrograph at the downstream end of our project and use it as an upstream boundary condition for a 2d model limited to our portion of the reach. It is only about 5000 feet of stream and there are not any major flow changes within this stretch. Have others dealt with BLEs and would this be a reasonable approach for a CLOMR? Would the downstream boundary condition be normal depth or stage hydrograph to match the effective model?