Spillway redesign for increased flow capacity

Abstract

Many developments in science, legislation, modelling techniques and global weather patterns have occurred over the past 30 years. These have resulted in the overflow capacity of a number of existing reservoirs being called into question. During the 2005 statutory inspection the overflow capacity of one such category A reservoir in the UK was considered with reference to the ICE publication ‘Floods and reservoir safety’. This requires the overflow to pass the probable maximum flood without overtopping of the dam. Following a physical model study MWH was tasked with the outline and detailed design of the new spillway structure at this reservoir in order to accommodate this flow rate. This paper aims to explore some of the reasons for increasing reservoir overflow capacities. The reasons and issues involved with increased reservoir overflow capacity are discussed in the context of the spillway redesign at the aforementioned reservoir and a background to this project is included to provide a frame of reference.