Transmittal of Report "Simulation of Flood Hydrographs for Georgia Streams"

In Reply Refer To:                                             July 7, 1986
WGS-Mail Stop 415


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


Distribution:  A, FO-L