Generalized Flood Skew: Map versus Watershed Skew
Publication: Journal of Hydrologic Engineering
Volume 6, Issue 4
Abstract
The skew coefficient is an important statistic in flood estimation at gaged sites, but sample values are subject to considerable sampling variation, and the map skew lacks both a conceptual basis and acceptable accuracy. While weighting the sample skew with the Bulletin 17B map skew can temper the variation inherent to sample skew coefficients, the inaccuracy of the map suggests that the weighted value of skew may still not have either the desired accuracy or the accuracy that would be possible if a more realistic generalized skew were used in place of the map skew. A new generalized skew coefficient is proposed herein, namely watershed skew. It has a conceptual basis in its relationship to the skew of the rainfall that generates the floods and the watershed and channel storage that transform rainfall skew to the skew of the runoff. Weighting the sample skew with the watershed skew will provide an estimate of the skew coefficient that incorporates the effects of the physical processes inherent to measured flood data both with rainfall frequency effects and with watershed characteristics that reflect watershed and channel storage. The resulting weighted skew should be more accurate than the current approach. The proposed procedure is applied to four moderately sized watersheds.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Amorocho, J. ( 1963). “Measures of the linearity of hydrologic systems.” J. Geophys. Res., 68(8), 2237–2249.
2.
Dunne, T., and Leopold, L. B. ( 1978). Water in environmental planning, Freeman, San Francisco.
3.
Guillot, P., and Duband, D. ( 1967). “La methode du gradex pour le calcul de la probabilite des crues a partir des pluies.” Proc., Leningrad Symp., IASH Publ. 84, Oxfordshire, U.K., 560–569.
4.
Hardison, C. H. ( 1974). “Generalized skew coefficients of annual floods in the United States and their application.” Water Resour. Res., 10(4), 745–752.
5.
Hicks, D. M., and Mason, P. D. ( 1991). “Roughness characteristics in New Zealand rivers.” Water Resour. Survey, Wellington, New Zealand.
6.
Hosking, J. R. M., and Wallis, J. R. ( 1997). Regional frequency analysis, Cambridge University Press, New York.
7.
Interagency Advisory Committee on Water Data (IACWD). ( 1982). “Guidelines for determining flood flow frequency.” Bulletin 17B, Hydrology Subcommittee, U.S. Geological Survey, Reston, Va.
8.
Kirby, W. ( 1974). “Algebraic boundedness of sample statistics.” Water Resour. Res., 10(2), 220–222.
9.
Klemes, V. ( 1976). “Comment on `regional skew in search of a parent' by Matalas et al.” Water Resour. Res., 12(6), 1325–1326.
10.
Landwehr, J. M., Matalas, N. C., and Wallis, J. R. ( 1978). “Some comparisons of flood statistics in real and log space.” Water Resour. Res., 14(5), 902–920.
11.
Laurenson, E. M. ( 1964). “A catchment storage model for runoff routing.” J. Hydrol., Amsterdam, 2, 141–163.
12.
Levy, B. and McCuen, R. H. (1999). “Assessment of storm duration for hydrologic design.”J. Hydrologic Engrg., ASCE, 4(3), 209–213.
13.
McCuen, R. H. (1979). “Map skew.”J. Water Resour. Plng. and Mgmt. Div., ASCE, 105(2), 269–277.
14.
McCuen, R. H. ( 1999). “Determination of the distribution of unit hydrograph peak rate factors.” Tech. Rep., Dept. of Civ. and Envir. Engrg., University of Maryland, College Park, Md.
15.
McCuen, R. H., and Hromadka, T. V. (1988). “Flood skew in hydrologic design on ungaged watersheds.”J. Irrig. and Drain. Engrg., ASCE, 114(2), 301–310.
16.
Neghettini, M., Potter, K. W., and Illangasekare, T. ( 1996). “Estimating the upper tail of flood-peak frequency distributions using hydrometeorological information.” Water Resour. Res., 32(6), 1729–1740.
17.
Rantz, S. E. ( 1971). “Suggested criteria for hydrologic design of storm-drainage facilities in the San Francisco Bay region, CA.” U.S. Geological Survey (USGS) Open File Rep., Menlo Park, Calif.
18.
Sauer, V. B., Thomas, W. O., Jr. Stricker, V. A., and Wilson, K. V. ( 1983). “Flood characteristics of urban watersheds in the United States.” U.S. Geological Survey Water-Supply Paper 2207, Alexandria, Va.
19.
Soil Conservation Service (SCS). ( 1972). National engineering handbook, Chap. 16, Section 4, Washington, D.C.
20.
Soil Conservation Service (SCS). ( 1984). “Computer program for project formulation.” Tech. Release No. 20, Washington, D.C.
21.
Spencer, C. S., and McCuen, R. H. (1996). “Detection of outliers in Pearson type III data.”J. Hydrologic Engrg., ASCE, 1(1), 2–10.
22.
Tasker, G. D. ( 1978). “Flood frequency analysis with a generalized skew coefficient.” Water Resour. Res., 14(2), 373–376.
23.
Tasker, G. D., and Stedinger, J. R. (1986). “Regional skew with weighted LS regression.”J. Water Resour. Plng. and Mgmt., ASCE, 112(2), 225–237.
24.
van de Leur, D. A. K. ( 1966). “Chapter 2: Runoff models with linear elements.” Recent trends in hydrograph synthesis, Comm. for Hydrologic Research, Proc. No. 13, Hague, The Netherlands.
25.
Wallis, J. R., Matalas, N. C., and Slack, J. R. ( 1974). “Just a moment!” Water Resour. Res., 27(12), 211–221.
26.
Yevjevich, V., and Obeysekera, J. T. B. ( 1984). “Estimation of skewness of hydrologic variables.” Water Resour. Res., 20(7), 935–943.
Information & Authors
Information
Published In
History
Received: Oct 6, 1999
Published online: Aug 1, 2001
Published in print: Aug 2001
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.