Design of Cascade Stilling Basins for High Dam Spillways

Abstract

Conventional methods of energy dissipation by single‐fall hydraulic jump‐type stilling basin, roller bucket, or ski‐jump bucket may not be suitable for high dam spillways because of very high velocities at the end of the spillway, inadequate tailwater depths, and/or site conditions. A suitable spillway alternative can be a cascade of falls with a stilling basin below each fall. This spillway can be constructed on the side of the valley downstream of the dam. Relationships for cascading stilling basins have been developed and demonstrated by the numerical example of the 714.76‐ft (218.00‐m) high Tehri dam spillway on the Bhagirathi River in the Ganga Valley of the Central Himalayas.