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Title: Chute spillway for Cowanesque Dam, Cowanesque River, Pennsylvania
Authors: United States. Army. Corps of Engineers. Baltimore District
Fletcher, Bobby P.
Keywords: Chute spillways
Cowanesque Dam
Hydraulic models
Cowanesque River
Hydraulic structures
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; H-76-12.
Description: Technical Report
Abstract: Tests to investigate the hydraulic performance of the chute spillway for Cowanesque Lake were conducted using a 1:60-scale model. Particular emphasis was placed on the development of a structure that would convey flow through the chute with a minimum of turbulence and waves. Flow approaching the structure from the left created a severe flow contraction at the left spillway abutment which became progressively more severe as the discharge increased. The flow contraction generated a standing wave that overtopped the chute sidewall. Flow distribution at the downstream end of the chute was unsymmetrical. Lateral flow from the left side of the exit area tended to concentrate the jet emerging from the chute along the right side of the exit channel, and velocities as high as 55 fps were measured. The flow contraction at the left abutment, unsymmetrical flow distribution in the chute, and the standing waves in the chute were attenuated by installing an elliptical wall, deepening the approach along the inside of the wall at the left abutment, and reducing the rate of convergence of the chute sidewalls. The minimum stone size (d𝟧𝟢 = 18 in.) required for protection of the elliptical wall was determined from the model. The elliptical wall also increased the capacity of the structure, permitting passage of 224,000 cfs at a pool elevation of 1146.1. Economically, it was desirable to move the intake tower closer to the dam. Model tests indicated that the intake tower could be moved 150 ft closer to the dam embankment without adversely affecting flow conditions. Due to structural and foundation conditions, the spillway structure was rotated 0°-55'-37" in a southeasterly direction about a point near the downstream end of the chute, and 90 ft of the downstream end of the left chute sidewall was removed. No significant change in the hydraulic performance of the structure was observed. Severe currents, waves, and turbulence were observed along the right side of the exit channel for spillway discharges above 50,000 cfs. Velocities and wave heights along the left side of the exit area (dam embankment) were within acceptable limits for the range of anticipated discharges. Model tests indicated that a stilling basin located at the downstream end of the chute would improve the performance of flow from the chute and in the exit channel. However, due to economic and structural considerations, a stilling basin was not considered feasible, and only preliminary stilling basin tests were conducted.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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