Georgia Water Science Center
This report is available online in pdf format (1 MB): USGS WRIR 95-4017 ()
Ernest J. Inman
U.S. Geological Survey Water-Resources Investigations Report 95-4017, 27 pages (Published 1995)
A statewide study of flood magnitude and frequency in urban areas of Georgia was made to develop methods of estimating flood characteristics at ungaged urban sites. A knowledge of the magnitude and frequency of floods is needed for the design of highway drainage structures, establishing flood-insurance rates, and other uses by urban planners and engineers.
A U.S. Geological Survey rainfall-runoff model was calibrated for 65 urban drainage basins ranging in size from 0.04 to 19.1 square miles in 10 urban areas of Georgia. Rainfall-runoff data were collected for a period of 5 to 7 years at each station beginning in 1973 in Metropolitan Atlanta and ending in 1993 in Thomasville, Ga. Calibrated models were used to synthesize long-term annual flood peak discharges for these basins from existing long-term rainfall records. The 2- to 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.
Multiple-regression analyses were used to define relations between the station flood-frequency data and several physical basin characteristics, of which drainage area and total impervious area were the most statistically significant. Using these regression equations and basin characteristics, the magnitude and frequency of floods at ungaged urban basins can be estimated throughout Georgia.
Abstract
Introduction
Purpose and scope
Previous studies
Acknowledgments
Site selection
Data collection and processing
Current data
Long-term rainfall and daily pan-evaporation data
Flood-frequency relations
Description of rainfall-runoff model
Calibration
Verification
Flood-frequency analysis
Regional regression analysis
Regional flood-frequency estimating equations
Testing of regression equations
Bias
Sensitivity
Standard error of prediction
Use of flood-frequency relations
Summary
Selected references
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