Flood frequency of Mississippi streams

Techniques have been developed for estimating future flood magnitudes having recurrence intervals as great as 100 years. Estimates for gaged sites were obtained by application of the log-Pearson Type III frequency distribution. Estimates for ungaged sites are defined by mathematical relations which may be solved using data from topographic maps. Nomographs were designed for making rapid estimates for floodfrequency values. Snythetic records generated by a digital computer Model of the rainfall-runoff process for drainage areas ranging from 0.04 to 4.35 square miles (0.1 to 11.3 square kilometres) were combined with long-term observed records to define the relation of basic characteristics to flood frequency on drainage areas as great as 6,630 square miles (17,200 square kilometres). Multiple-regression techniques indicated that drainage area, slope, and length were the most significant variables affecting flood frequency.