FLOOD04444

• County: Statewide
• Basin: Statewide
• Title: Flood Flow Frequency for Ungaged Waterways: a Literature Evaluation
• Date: 11/1/1977
• Prepared By: USDA
• Floodplain - Doc Type: Educational/Technical/Reference Information

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TECHNICAL REPORT STANDARD TITLE PAGE

1. Report No. i:. Government Acc.sslon No. 3. Recipient', Catalog No.
FHWA-RD-77-159
4. Title and Subtltl. 5. Report Oat.
Runoff Estimates for Small Rural Watersheds and , Octobllr 1977
Development of a Sound Design Method 6. Performing Organization Cod.
~e~~~~ n ii~~~~QlJIIllend~~;lgns" fo~ P~ep~r~ng D~sign
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7. Autho.(.) 8. Performln, Organization R4I!port No.
Joel E.Fletcher, A. Leon Huber,
Frank W. Haws, and Calvin G. Clyde
9. P.rfotming Organization Name and "Address 10. Worle Unit No.
Utah Water Research Laboratory FCP 3'5H'l-012
Utah State University 11. Contract or Gron' Ho.
Logan, Utah 84322 DOT-FH-1l-780Q
13. Type of Repor:t and Period Coyered
12. Sponsoring Ageney Nome and Addre...
Federal Highway Administration Final Renort
U.S. Department of Transportation 14. Sponsoring Agency Cod.
Washington. D.C. 20590 ,
IS. .Supplementary Notes c-
FHWA Contract Manager: Frank K. Stovicek
16. Abstract
Frequency analyses of more than 1,000 small, watersheds in the United States
and Puerto Rico were used to develop the estimation method for design of peak flow ,
for ungaged watersheds. This method, called the Federal Highway Administration
(FHWA) method, is conceptually similar to the Bureau of PubliC' Roads (BRP)
method developed by W. D. Potter. The FHWA method relates the runoff peak to
easily determined hydrophysiographic parameters and is intended for use on
watersheds smaller than 50 square miles. The' concept of risk is incorporated
into the design procedure. The risk is the probability that one or more events
will exceed a specified peak flow within the usable lifetime of the drainage
structure. The return period of the design flood peak can then be modified
,
according to the. risk the designer is willing to take. Another concept',dealing
with the probable maximum runoff peak derived as a function of watershed area
is included. The flow obtained from this relationship is considered to be the
upper limit of the design flow that may realistically be expected to ever occur.
As such it may be appropriate to use in situations where the consequences of
failure are extremely great.
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The other volumes of this report are:
FHWARD- Subtitle
17-158 Vol t, Research Report
77-160 '1of :rn, Appendix A "Frequency Curves and Data Base"
17. K.v Wo,d. Hydrology, small watersheds, 18. Distribution Statement. This document is
hydrophysiographic zones, peak runoff, available to the public through the
flood frequency" regression analysis, National Technical Information Service,
graphical correlation, estimating Springfield, Virginia 22161.
discharge, design, nomographs.
19. Security Clonl'. (of this r.port) 20, Security Classlf. (of this pagel 21. No. of Page. 22. Price
I Unclassified Unclassified 368

. Form DOT F 1700;7 '8.09)