Flood Frequency Estimating Techniques for Small Watersheds

This report describes a literature search undertaken to identify hydrologic methods suitable for defining the flood frequency characteristics of streams of less than 20 sq mile drainage area. Results of comparative testing on 11 small watersheds using digital computer simulation, regional flood frequency analysis, Potter's statistical procedure, and an arbitrarily standardized version of the rational method are reported. For the streams tested, digital simulation using the Hydrocomp Simulation Program was most successful in reproducing the flood frequency curves determined from the historic streamflow. The study reaffirmed the basic problems involved in frequency analysis of short flow records on small streams. Further research to resolve some of these problems is recommended. A program of research and development to adapt digital simulation to the derivation of design flows for highway culverts is also proposed.