COMPREHENSIVE RISK ASSESSMENT OF MAITHON DAM – HYDROLOGIC RISK

Abstract

With around 5700 large dams, India ranks third in the number of large dams. Along with thousands of medium and small dams spread across the length and breadth of the country, they provide a range of economic and social benefits, including irrigation, municipal and industrial water supply, hydropower, flood control, etc. While dams are vital for any country, especially in a water-stressed country like India, failure of such structures would lead to a substantial loss in terms of lives, economy and environment. Dam Safety Act - 2021 mandates comprehensive risk assessment for each large dam within five years of its implementation, i.e., by December 2026. Risk assessment of dam promotes risk-informed dam safety management and rehabilitation. The evaluation involves analysis of risks, their categorisation and necessary intervention to reduce the overall risk associated with the dam, such as required dam rehabilitation measures or taking up new studies or instrumentation in a dam. The thesis presents the general discussion on comprehensive risk assessment of the Maithon dam of Damodar Valley Corporation (DVC) with a detailed assessment of risk owing to hydrologic load. Risk analysis involves estimating the probability of loads causing failure, i.e. the initiating events, which in this case is the hydrologic load, the failure probability of the dam subject to the given load and consequence assessment owing to the dam's failure. Event trees are used as a mathematical tool for quantitative risk estimate, representing a logical model that includes all the possible chains of events resulting from an initiating event. An influence diagram provides a compact conceptual representation of the logic of a system for the risk model event tree. For the hydrologic risk estimation of Maithon dam, the variables, such as floods, reservoir pool level, gate reliability, failure conditions and consequences, were logically connected using an Influence diagram and event trees.