Date of Publication :31st July 2021

Abstract: Idukki reservoir is a part of the Idukki Hydroelectric Project and comprises of Idukki Arch Dam, Kulamavu Dam and Cheruthoni dam. The two reservoirs- Mullaperiyar Dam and Idukki reservoir together form 24 per cent of Periyar’s catchment. This study is aimed to evaluate the wave which forms when water from the Mullaperiyar hits the water column of the Idukki reservoir that could overtop the Cheruthoni Dam and how it affects the Kulamavu dam which is 22km apart from Cheruthoni dam, Kerala, India. These dams are operational since 1976 and 1977 respectively. It is important to examine the effect of water that rushes into it at the time of emergency and the magnitude of kinetic energy at the time of breaching. The present study includes the dam-break flood analysis of the Mullaperiyar dam up to the Idukki reservoir. This project is an extension of it. Dam break failures are often caused by overtopping of the dam due to inadequate spillway capacity during large inflows into the reservoir from heavy rainfall-generated runoff. Dam failure may also be caused by seepage or piping through the dam or along internal conduits, earthquake and landslide generated waves in the reservoir. For a cascade of dams, the breaking of one dam may cause subsequent damage to other dams located downstream due to their overtopping. Partial or catastrophic failure of a dam leading to uncontrolled release of water causes severe damages to lives and properties of people situated downstream. The effect of such a flood disaster can be mitigated to a great extent, if the resultant magnitude of flood peak and its time of arrival at different locations downstream of the dam can be estimated, facilitate the planning of emergency action measures. The most suitable instruments for the analysis and prediction of a dam break flood are mathematical hydrodynamic simulation models. These models can be used for the prediction of dam breach flood hydrograph and its routing through the downstream valley to obtain the time series of discharge and water level at different locations of the valley. The present study includes the dam-break flood analysis of the Mullaperiyar dam up to the Idukki reservoir.

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