New Austrian Dam Side-Channel Spillway

Stevens, Michael A.; Todaro, Sal A.; ,

New Austrian Dam Side-Channel Spillway

by Michael A. Stevens,
Sal A. Todaro,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

The Loma Prieta earthquake of 17 October 1989 damaged the chute spillway at the Austrian Dam near San Jose, California. The replacement spillway, with a higher design discharge of 11,500 ft³/s (326 m³/s), is located in the opposite abutment where the side slope is steep and high. Cuts into this slope are expensive. To minimize costs, a 65-ft (19.8 cm) long side-channel spillway with an open-channel chute was chosen. The preliminary design was based on US Bureau of Reclamation's Design of Small Dams and their Paonia project spillway which has a similar discharge. The changes to the initial design were based on tests of a 1-to-36 scale hydraulic model. The main objective was to raise the floor of the trough at the base of the spillway crest and to narrow the trough as much as possible and still have satisfactory hydraulic performance. As a result of the model tests, the final configuration of the side-channel was much simpler and less expensive than the initial design. The trough is shallow and its floor is horizontal. There are no wingwalls nor rise from the trough floor to the chute floor. The backwall of the trough is straight and aligned with the chute wall. This design results in large standing waves in the chute downstream from the crest but these waves are reduced to insignificant heights as they pass over the 17.5 degree vertical curve in the chute 100 ft (30 m) downstream from the crest.

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