NRCS (SCS) methods to predict runoff volume and peak discharge from rainfall have been in use for 70 years. Despite their universal application for highway drainage infrastructure, there is no clearly identified limitation on drainage area size for single, homogeneous watersheds. We compare flow frequency from more than 100 small watershed stream gages in Nebraska to estimates using TR-20 and TR-55. We also compare results from regression equations to the gage estimates. Work continues to determine if there is a statistically significant watershed area size that favors use of NRCS methods over regression equations.
