Rocky Mountain Project—Probable Maximum Floods

by Norman L. Schickedanz, Harza Engineering Co, Chicago, United States,
James E. Lindell, Harza Engineering Co, Chicago, United States,
Ben C. Trammell, Jr., Harza Engineering Co, Chicago, United States,
John M. Boknecht, Harza Engineering Co, Chicago, United States,

Document Type: Proceeding Paper

Part of: Waterpower '91: A New View of Hydro Resources


Probable maximum floods (PMF's) were estimated for use in designing spillways for the lower reservoir main dam and two auxiliary pool dams at the Rocky Mountain pumped-storage project in northwest Georgia. The hydrologic analyses were made using standard site-specific methods. They included deducting from rainfall an infiltration rate based on hydrologic soil groups and computing unitgraphs using the dimensionless graph-lag curve technique with data from the project area. The resulting design floods are compared with flood hydrographs using the Soil Conservation Service runoff curve number method for infiltration and for unitgraphs with Kirpich's time of concentration formula. The site-specific methods produced hydrograph peaks about 60 percent lower. Sensitivity of the flood peaks to the methods and parameters and impact on spillway size is discussed.

Subject Headings: Mountains | Floods | Earthfill dams | Infiltration | Hydro power | Power plants | Spillways | Hydraulic design | Rocky Mountains | Georgia | United States

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