Transmittal of Report "Simulation of Flood Hydrographs for Georgia Streams" In Reply Refer To: July 7, 1986 WGS-Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 86.07 Subject: PUBLICATIONS--Transmittal of Report "Simulation of Flood Hydrographs for Georgia Streams" by E. J. Inman The attached report should be of interest to personnel in your office involved in flood hydrology studies. This report describes a simplified method of estimating flood hydrographs for ungaged rural or urban streams. This method- ology can be used to estimate flood hydrographs for a variety of purposes including risk analysis for bridge and culvert design. The Federal Highway Administration advocates the use of risk analysis for the cost-effective design of bridges, culverts, and embankments for our Nation's highways. In the study documented in the attached report, observed flood hydrographs and rainfall were used to estimate basin lag time and to develop a statewide dimensionless hydrograph. This dimensionless hydrograh relates a given dis- charge divided by the peak discharge of the hydrograph to time since beginning of runoff divided by basin lag time. Given the ordinates of the dimensionless hydrograph, a flood hydrograph for a T-year peak discharge was developed by multiplying the ordinates of the dimensionless hydrograph by the T-year peak discharge and the basin lag time. The T-year peak discharge and basin lag time were estimated by multiple-regression analysis using basin characteris- tics as independent variables. The computer procedures for developing and verifying the dimensionless hydro- graph are being documented in a separate report by the Georgia District. As long as the supply lasts, additional copies of the attached report can be obtained by contacting the Georgia District. Verne R. Schneider Chief, Office of Surface Water Attachment Distribution: A, FO-L