TECHNIQUES FOR ESTIMATING FLOOD HYDROGRAPHS FOR UNGAGED URBAN WATERSHEDS by V.A. Stricker and V.B. Sauer Prepared by the U.S. Geological Survey in cooperation with the U.S. Department of Transportation, Federal Highway Administration April 1982 Open-File Report 82-365 TABLE OF CONTENTS Abstract Introduction Data base Hydrograph estimating procedure     Dimensionless hydrograph     Estimating basin lagtime     Estimating peak discharge     Estimating design flood hydrographs     Comparison of estimated and observed hydrographs Hydrograph-width relation Hydrograph-volume relation     Estimating flood volume     Comparison of estimated and actual volumes Application of technique     Stepwise procedure     Example problem     Effects of in-channel storage Selected references FIGURES 1. Graph showing dimensionless hydrograph 2-16. Graphs showing comparison of actual hydrographs and estimated hydrographs using measured and estimated lagtime for:     2. White Rock Creek above Greenville Ave., at Dallas, Tx (08057200), for storm of September 21, 1964     3. Cobbs Creek at U.S. Hwy. 1, at Philadelphia, Pa (01475530), for storm of July 13, 1975     4. Conley Creek near Forest Park, Ga (02203884) for storm of July 2, 1974     5. Conley Creek near Forest Park, Ga (02203884) for storm of January 10, 1975     6. North Fork Peachtree Creek tributary near Atlanta, Ga (02336102), for storm of June 20, 1973     7. Cobbs Creek near Atlanta, Ga (02203870), for storm of June 19, 1975     8. Shotwell Creek at Hwy. 304, near Ellisville, Mo (06935800), for storm of July 23, 1973     9. Fanno Creek at Portland, Or (14206900), for storm of December 13, 1977     10. Paddock Creek at Lindbergh Blvd., at St. Louis, Mo (06936380), for storm of July 23, 1973     11. Turtle Creek at Dallas, Tx (08056500), for storm of May 6-7, 1969     12. Watkins Creek at Coal Bank Rd., near St. Louis, Mo (07002000), for storm of April 21, 1972     13. Deep Fork at Portland Ave., at Oklahoma City, Ok (07242200), for storm of November 2, 1974     14. Joes Creek at Dallas, Tx (08055600), for storm of April 28, 1966     15. Bachman Branch at Dallas, Tx (08055700), for storm of April 28, 1966     16. Coldwater Creek at Old Halls Ferry Rd., near St. Louis, Mo (06936460), for storm of September 7, 1972 17. Graph showing hydrograph-width relation for dimensionless hydrograph TABLES 1. Time and discharge ratios of the dimensionless hydrograph 2. Drainage basin characteristics 3. Relation of discharge ratios to hydrograph-width ratios 4. Hydrograph-width comparisons 5. Runoff volume comparisons ABSTRACT The Clark Method, modified slightly, was used to develop a synthetic, dimensionless hydrograph that can be used to estimate flood hydrographs for ungaged urban watersheds. Application of the technique results in a typical (average) flood hydrograph for a given peak discharge. Input necessary to apply the technique is an estimate of basin lagtime and the recurrence interval peak discharge. Equations for this purpose were obtained from a recent nationwide study on flood frequency in urban watersheds. A regression equation was developed which relates flood volumes to drainage area size, basin lagtime, and peak discharge. This equation is useful where storage of floodwater may be a part of design or flood prevention. LizardTech's Djvu plug-in is needed to view these reports. CLICK HERE TO VIEW THE ENTIRE REPORT For questions or comments, contact K. Van Wilson.