Need for Rehabilitation of Dam Considering the Cascading Impact of Flood

Risk from cascading reservoir is enormous as compared with single reservoir. To ensure the safety of river basin, risk assessment from cascading impact of flood is of utmost importance. Rehabilitation of a dam in today’s climate change is not only the act of restoring the distressed dam to its original state but also to meet added requirements caused by changes in the safety criteria and risk assessment from time to time. Climate change can lead to increase in the frequency and severity of hazards like glacial lake outburst floods (GLOFs), torrential floods, debris flows, landslides, glacier movement, snow melt and extreme precipitation. The cascading impact of flood can pose danger to series of dams in River and downstream residents in terms of hydraulic discharge, debris flow etc. Most dams in existence today were built during the 1970s. The risks from aging dams are of particular concern in the face of climate change. Dams at the time of construction are designed to withstand worst case conditions. However, extreme weather events have begun occurring with increasing regularity, putting dams at great risk of either failure or a significant weakening of their integrity.

The recent collapse of series of dams in Libya was due to sudden accumulation of water beyond dam capacity. The dam could not hold 30 MCM of accumulated water due to rainstorm and failed. The recent incident of a Glacial Lake Outburst Flood in North Sikkim has raised alarm about the safety of hydropower potential in Himalayas. The tragic dam failure due to cascading impact of flood in Libya and Sikkim is a warning signal from the dangers of climate change and also old infrastructure. This paper presents the case studies on failure of dams from cascading impact of flood and suggests need for comprehensive rehabilitation considering the impact of series of dams in a River. It emphasis on the need to have integrated early warning system that can alert the people towards the impending disaster.