Uncertainty and Risk Analyses for FEMA Alluvial-Fan Method
Publication: Journal of Hydraulic Engineering
Volume 122, Issue 6
Abstract
Alluvial fans along mountain bases pose quite interesting problems for the design of hydraulic structures and highway crossings and for flood insurance studies. The Federal Emergency Management Agency (FEMA) alluvial-fan method is subject to uncertainties because it is an approximate method. In this paper, Rosenblueth's point-estimate is applied to the FEMA alluvial fan method to compute the mean and standard deviation for the 100-yr discharge at any point on the fan and the mean and standard deviation for the fan arc width. The mean and standard deviation for the 100-yr discharge are used to obtain the risk that the 100-yr discharge will exceed the discharge capacity of hydraulic structures on the fan. The mean and standard deviation for the fan arc width are used to estimate the risk that a given location on the fan is within the hazard flood zone. The HEC-1 rainfall-runoff computer model is used to compute inputs to the FEMA method. The proposed uncertainty and risk analyses are applied to an alluvial fan in north Scottsdale, Ariz.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Abramowitz, M., and Stegun, I. A. (1972). Handbook of mathematical functions with formulas, graphs and mathematical tables, 9th Ed., Dover Publications, Inc., New York, N.Y.
2.
Burknam, D. E. (1988). “Methods for delineating flood-prone areas in the Great Basin of Nevada and adjacent sites.”Water Supply Paper 2316, U.S. Geological Survey, Phoenix, Ariz.
3.
Cella Barr Associates. (1988). “Hydrologic analysis of Scottdale alluvial fans 1-6 Marcopa County.”Rep. Prepared for Federal Emergency Mgmt. Agency, Phoenix, Ariz.
4.
Chang, C.-H., Tung, Y.-K., and Yang, J.-C.(1995). “Evaluation of probability point estimate methods.”Appl. Math. Modelling, 19, 95–105.
5.
Dawdy, D. R.(1979). “Flood frequency estimates on alluvial fans.”J. Hydr. Div., ASCE, 107(3), 1407–1413.
6.
DMA. (1985). “Alluvial fan flooding methodology—an analysis.”Rep. Prepared for Federal Emergency Mgmt. Agency, Contract EMW-84-c-1488.
7.
Federal Emergency Management Agency (FEMA). (1985). “Flood insurance study—guidelines and specifications for study contractors.” Washington, D.C.
8.
Federal Emergency Management Agency (FEMA). (1992). “Flood insurance study—guidelines and specifications for study contractors.” Washington, D.C.
9.
“Guidelines for determining flood flow frequency.” (1982). Bull. 17B., U.S. Water Resources Council, Washington, D.C.
10.
Harr, M. E.(1989). “Probabilistic estimates for multivariate analysis.”Appl. Math. Modelling, 13(5), 313–318.
11.
Kemna, S. P. (1990). “Some geomorphic models of flood hazards on distributary flow areas in Southern Arizona,” MS thesis, Dept. of Hydro. and Water Resour., Univ. of Arizona, Tucson, Ariz.
12.
Li, K. S.(1992). “Point-estimate method for calculating statistical moments.”J. of Engrg. Mech., ASCE, 118(7), 1506–1511.
13.
MathWorks, Inc. (1989). MATLAB user's guide . South Natick, Mass.
14.
Mays, L. W., and Tung, Y. K. (1992). Hydrosystems engineering and management, McGraw-Hill Book Co., Inc., New York, N.Y.
15.
National Oceanic and Atmospheric Administration. (1973). “Precipitation-frequency atlas of the Western United States.”NOAA Atlas 2, Silver Spring, Md.
16.
Rosenblueth, E.(1975). “Point estimates for probability moments.”Proc., Nat. Acad. of Sci., 72(10), 3812–3814.
17.
Rosenblueth, E.(1981). “Two-point estimates in probabilities.”Appl. Math. Modelling, 5(5), 329–335.
18.
Soil Conservation Service. (1978). “Soil survey for Aquila-Carefuree area, parts of Maricopa and Pinal Counties, Arizona.” Tucson, Ariz.
19.
Soil Conservation Service. (1986). “Urban hydrology for small watershed, technical release 55.” Washington, D.C.
20.
Tung, Y. K., and Mays, L. W.(1980). “Risk analysis for hydraulic design.”J. Hydr. Engrg., ASCE, 106(5), 893–913.
21.
Tung, Y. K., and Yen, B. C. (1993). “Some recent progress in uncertainty analysis for hydraulic design.”Reliability and uncertainty analyses in hydraulic design, B. C. Yen and Y. K. Tung, eds., ASCE, New York, N.Y.
22.
Zoppou, C., and Li, K. S.(1993). “New point estimate method for water resources modeling.”J. Hydr. Engrg., ASCE, 119(11), 1300–1307.
Information & Authors
Information
Published In
Copyright
Copyright © 1996 American Society of Civil Engineers.
History
Published online: Jun 1, 1996
Published in print: Jun 1996
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.