Spillway and Stilling Basin John Day Dam, Columbia River, Oregon and Washington. Hydraulic Model Investigation

Two sectional models were used to check performance of the proposed spillway for John Day Dam and to develop improvements if necessary. A three-bay section of the 20-bay spillway was studied in a 1:41.14-scale model. A two-bay section of the 17 low bays to be used during second-step construction was...

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Bibliographic Details
Main Author: Perkins,Louis Z
Format: Report
Language:English
Subjects:
BAFFLES
CHANNEL FLOW
CHANNELS(WATERWAYS)
Civil Engineering
Columbia River
DAMS
FACILITIES
HYDRAULIC MODELS
John Day Dam
OREGON
PIERS
RIVERS
Spillways
Stilling basins
WASHINGTON(STATE)
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Summary:Two sectional models were used to check performance of the proposed spillway for John Day Dam and to develop improvements if necessary. A three-bay section of the 20-bay spillway was studied in a 1:41.14-scale model. A two-bay section of the 17 low bays to be used during second-step construction was reproduced in a 1:24-scale model. Modifications of the crest piers to reduce the danger of cavitation during unusually large spillway flows were recommended. Discharge ratings in the three-bay model indicated that capacity of the spillway was slightly greater than computed for the design flow of 2,250,000 cfs. A 185-ft-long stilling basin at elev 114 performed as well as a 210-ft-long basin at elev 118. Three 10-ft-high baffle piers produced desired flow conditions in bay 2 of the stilling basin.