Abstract
Hydrological dam safety assessment methods traditionally assume that the reservoir is full while it receives the design flood. In practice, reservoir management strategy determines the probability distribution of reservoir levels at the beginning of flood episodes. In this study, we present a method to economically assess the influence of reservoir management strategy on hydrological dam safety and downstream flood risk. The method was applied to a gated spillway dam located in the Tagus River basin. A set of 100,000 inflow hydrographs was generated through a Monte Carlo procedure, reproducing the observed statistics of main hydrograph characteristics: peak flow, volume, and duration. The set of 100,000 hydrographs was routed through the reservoir applying the volumetric evaluation method as a flood control strategy. Three different scenarios were studied: Initial reservoir level equal to maximum normal level, equal to a maximum conservation level, and following the probability distribution of initial reservoir levels. In order to evaluate economically the influence of initial variable reservoir level and compare the three scenarios, a global risk index was applied. The index combines the hydrological risk for the dam, linked to the maximum water level experienced in the reservoir while the flood is routed, and the flood risk in the downstream river reach, linked to the discharge releases from the dam. The results highlighted the importance of considering the fluctuation of initial reservoir level for assessing the risk related to hydrological dam safety.
Highlights
The failure of large dams is a concern in many countries due to the high economic and social consequences associated with it
We proposed a methodology to analyze economically the influence of initial reservoir level in hydrological dam and downstream safety by the application of economic riskindexes [6,7]
Depending on the scenario studied, an initial reservoir level was assigned to each inflow hydrograph
Summary
The failure of large dams is a concern in many countries due to the high economic and social consequences associated with it. Engineers usually use techniques to assure that the risk associated to dam failure is low, being the standards applied different depending on the country in which the dam is located [1]. The dam risk assessment field has evolved worldwide, with the appearance of different guides and procedures in several countries [3,4,5] to support dam stakeholders in the decision-making process related to dam safety. We proposed a methodology to analyze economically the influence of initial reservoir level in hydrological dam and downstream safety by the application of economic riskindexes [6,7]. Afterwards, we apply this methodology to a dam configuration based on a real case study. We analyze and discuss the results obtained, highlighting the main conclusions of this study
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