Our county also proposed to run a big scale floodplain inundation mapping model. It will be 1D cross section model on top of Lidar Surface; Approx. 300 cross sections on top 50 river miles lidar (surface).
Will Hec Ras able to handle such scale model? (such big lidar surface)?
For processing the Lidar, do you processing it in Autocad or Arcgis and export the surface to HecRas, or use some other programs?
I have done models that are over hundreds of miles in 1D/2D. so it should be able to handle it.
I use ArcGIS for initial LiDAR processing and once you have the terrain, HEC-RAS will copy the terrain to a tif format. Other software might be Global Mapper.
Depends on inflow hydrograph, timestep, number of 2D cells, how well the mesh is made, number of structures, solver you are using, how well the 1D/2D model iterates between the two, and probably other things.