Influence of Uncertainties in the Estimation Procedure of Floodwater Level
Publication: Journal of Hydraulic Engineering
Volume 132, Issue 10
Abstract
Despite the recent development of risk-based assessments in flood defense, in practice, flood levels in channels are generally estimated for a design return period by using the discharges of the same return period. The flood levels are also influenced by other factors such as bed roughness, flow area, wetted perimeter, and friction slope which are random in nature. The surveyed cross sections and calibrated values of roughness coefficients are generally used without any allowance for their variability to assess the water levels based on discharge of a selected return period. This simplifies a multivariate random process to a single-variate random process. When the uncertainties of selected influencing parameters were considered in sample studies using Monte Carlo simulation, it was found that the traditional procedures result in an underestimation of water level at high return periods and over estimation of water levels at low return periods. The overall effect is the diffusion of the density function from the center toward the tails of the distribution. Sample studies using the variation in channel roughness and friction slope indicated that the return period of the water level, based on a 100 year return period discharge, varied from 32 to 82 years, depending on the statistical properties of the influencing random parameters. The frequency analysis of water levels was undertaken by analyzing 25–800 million generated data sets.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The writers would like to thank Mr. Charlie Rickard, ex-Divisional Director, and Mr. Keith Howells, Managing Director of Mott MacDonald Group for their suggestions and contributions to this paper.
References
Chow, V. T., Maidment, D. R., and Mays, L. W. (1988). Applied hydrology, McGraw-Hill, New York.
Environment Agency. (2000). “Fluvial freeboard guidance note.” R&D Technical Rep. No. W187, WRc, Swindon, U.K.
Guganesharajah, R. K. (2001). “Development of computational hydraulic and water quality models for rivers, estuaries, reservoirs and aquifers with particular reference to waste stabilization ponds.” Ph.D. thesis, School of Engineering, Univ. of Surrey, U.K.
Hosking, J. R. M., and Wallis, J. R. (1997). Regional frequency analysis: An approach based on L-moments, Cambridge University Press, Cambridge, Mass.
Institute of Hydrology. (1999). Flood estimation handbook, 4, Wallingford, U.K., 1–288.
Lee, H., and Mays, L. M. (1986). “Hydraulic uncertainties in flood levee capacity.” J. Hydraul. Eng., 112(10), 928–934.
Mott MacDonald Ltd. (2002). “Uncertainty analysis of flood levels.” User manual for program HYDRO-UA, Cambridge, U.K.
Shaw, E. M. (1994). Hydrology in practice, Chapman and Hall, London.
U.S. Army Corps of Engineers. (1996). “Risk-based analysis for flood damage reduction studies.” Rep. No. ER 1110-2-1619, Washington, D.C.
Information & Authors
Information
Published In
Copyright
© 2006 ASCE.
History
Received: Aug 13, 2002
Accepted: Nov 30, 2005
Published online: Oct 1, 2006
Published in print: Oct 2006
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.