I am trying to import an SDF file that was created by HEC-RAS 4.0. I have tried Map > Tools > Import, and I have tried File menu > Create DWG From > Autodesk SDF 2 (MapGuide 6.x). Both ways I get an error telling me that I don't have an SDF file or that it is improperly formatted.

Can anyone tell me how to import an SDF file that has been exported from HEC-RAS?

Any help would be greatly appreciated.