Height above nearest drainage : assessment and recommendations for improved rating curve generation

Real-time flood forecasting for the Conterminous United States is currently underway. Powered by improvements to the Height Above Nearest Drainage methodology, coupled with the recent publication of streamflow predictions through the National Water Model, few uncertainties remain before implementation can be realized. Of these uncertainties, rating curve generalizations for all NHDPlusV2 stream reaches in the nation has persistently proven problematic, particularly regarding approximations of Manning’s roughness and stream reach slope values. This research attempts to address these concerns through detailed analyses of various rating curves along Onion Creek in Austin, Texas. From this research, alternatives are proposed to the currently used roughness and slope values, and the overall performance of these alternatives is assessed to provide recommendations for future rating curve approximations.