Bumping Lake Emergency Spillway
by Jim Higgs
to support a Safety of Dams study by Dan Mares and John Ellingson
Objective: To investigate discharge conditions using CFD.Bumping Lake Dam is an earthfill structure constructed by hydraulic fill methods. At dam crest elevation 3,435.0 (ft) the embankment has a structural height of 61 feet, a hydraulic height of 38 feet, a crest width of 20 feet, and a crest length of 2,925 feet. The reservoir impounded by the dam inundated a natural lake on the Bumping River. The dam and reservoir provide storage for irrigation water, although the reservoir is operated to provide flood control storage insofar as irrigation water supplies are not jeopardized. At elevation 3426.2 the reservoir extends 4.3 miles up the Bumping River and has a average width of 0.47 miles.
The spillway, an uncontrolled concrete weir with a concrete and wooden chute, is located at the left abutment. It has a crest length of 235 feet and a crest elevation of 3426.2.
A safety of Dams study, in part by Dan Mares and John Ellingson of Concrete Dams, Spillways, Outlets Group investigated the discharge capacity of the spillway using a 1-dimensional analysis. The results indicated that for some discharges, the front water approach indicated supercritical flow in the converging chute, while back water analysis indicated subcritical flow in the converging chute. To study the inconstancies CFD was used.As displayed in the figure below, both were true, with supercritical (high velocity) flow on the right side of the spillway (closest to the bottom of the page) while subcritical (low velocity) flow on the left side of the spillway.
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Last reviewed: 11/2/2008