Magnitude and frequency of floods in California

The magnitude and frequency of floods from gaged and ungaged drainage areas in California, for any recurrence interval from 2 to 100 years, can be estimated by use of the method presented. Equations relating flood magnitudes of selected frequency to basin characteristics such as drainage area, precipitation, and altitude were developed for six regions in the State. Nomographs are included for solution of the equations. Annual peak discharges for more than 700 streamflow stations, including more than 340 stations on streams with basins smaller than 10 square miles, were included in the analysis. Maximum known peak discharges are shown and their relation to drainage areas defined. Data on basin characteristics used in the regression analyses are tabulated. Some adjustments for urbanization effects based on flood-peak ratios for developed and undeveloped areas are suggested. (Woodard-USGS)