Assessment of dam appurtenant structures under multiple flow discharge scenarios

Abstract

This study investigates the capacities of chute spillway and stilling basin under multiple flow discharge scenarios. Thirteen cases, categorised as low, medium, and high flow discharges were experimentally conducted, with a 100% increase of Probable Maximum Flood (PMF) as the modified maximum flow. An analysis is extended to flood and scour potential at the Type II and III stilling basin. Low and medium discharge scenarios have no significant impact on the spillway but posed insufficient capacity to confine efficiently the hydraulic jump within the stilling basin. Types II and III basins reduced the length of hydraulic jump up to 50% and 73%, respectively at PMF. Similarly, potential of severe scour particularly at the spillway exit increases to 5 times more than the cases for low discharge. Similarly, potential of severe scour at PMF, particularly at the spillway exit increases to 5 times more than the cases for low discharge. High discharge not only compromises the spillway integrity due to overflow but also increases flood and scour potential at the stilling basin. An up-to-date evaluation of the existing dam appurtenances capacities to withstand the future flow pattern is crucial to ensure smooth dam operations and avoiding catastrophic events such as dam breach, jeopardising the river environmental flow and water resources.