Verification of the Region 3 urban flood-frequency equations for Tifton, Georgia

A U.S. Geological Survey rainfall-runoff model was calibrated for four urban drainage basins ranging in size from 0.16 to 0.71 square mile in Tifton, Ga. Rainfall-runoff data were collected over a period of about five years at each station, beginning in April 1991 and ending in July 1996. Calibrated models were used to synthesize long-term annual flood-peak discharges from existing long-term rainfall records for these basins. The 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year flood-frequency estimates were developed for each basin by fitting a Pearson Type III frequency distribution curve to the logarithms of these annual peak discharges.

The 2- through 500-year flood-frequency estimates from the four Tifton stations were compared to the 2- through 500-year flood-frequency estimates computed from the equations presented in a statewide urban flood-frequency report in 1995. All floods, except the 2-year flood at one site, were within the average standard error of prediction; thereby, verifying the urban flood-frequency equations for use in the Tifton area.