Numerical Simulation and Risk Assessment of Cascade Reservoir Dam-Break

Liangming Hu,Xu Yang,Shuyu Li,Qian Li

doi:10.3390/w12061730

Abstract

Despite the fact that cascade reservoirs are built in a large number of river basins nowadays, there is still an absence of studies on sequential embankment dam-break in cascade reservoirs. Therefore, numerical simulations and risk analyses of cascade reservoir dam-break are of practical engineering significance. In this study, by means of contacting the hydraulic features of upstream and downstream reservoirs with flood routing simulation (FRS) and flood-regulating calculation (FRC), a numerical model for the whole process of cascade reservoir breaching simulation (CRBS) is established based on a single-embankment dam-break model (Dam Breach Analysis—China Institute of Water Resources and Hydropower Research (DB-IWHR)). In a case study of a fundamental cascade reservoir system, in the upstream Tangjiashan barrier lake and the downstream reservoir II, the whole process of cascade reservoir dam-break is simulated and predicted under working schemes of different discharge capacities, and the risk of cascading breaching was also evaluated through CRBS. The results show that, in the dam-break of Tangjiashan barrier lake, the calculated values of the peak outflow rate are about 10% more than the recorded data, which are in an acceptable range. In the simulation of flood routing, the dam-break flood arrived at the downstream reservoir after 3 h. According to the predicted results of flood-regulating calculations and the dam-break simulation in the downstream reservoir, the risk of sequential dam-break can be effectively reduced by setting early warnings to decrease reservoir storage in advance and adding a second discharge tunnel to increase the discharge capacity. Alongside the simulation of flood routing and flood regulation, the whole process of cascade dam-break was completely simulated and the results of CRBS tend to be more reasonable; CRBS shows the great value of engineering application in the risk assessment and flood control of cascade reservoirs as an universal numerical prediction model.

Highlights

Reservoir dams have played a momentous role in flood control, irrigation, electricity generation, shipping, water supply, aquaculture and the improvement of the ecological environment, and create considerable economic value and social benefits [1]
The Dam-Break Flood Forecasting model (DAMBRK), a numerical model proposed by Fread in 1988 [5] which can be used for simplified calculations of cascade reservoir failure, needs to input parameters about the final shape of the breach and the starting time of dam-break
This study aims to establish a numerical model that could simulate the whole process of sequential embankment dam-break occurring from upstream to downstream

Summary

Introduction

Reservoir dams have played a momentous role in flood control, irrigation, electricity generation, shipping, water supply, aquaculture and the improvement of the ecological environment, and create considerable economic value and social benefits [1]. The Dam-Break Flood Forecasting model (DAMBRK), a numerical model proposed by Fread in 1988 [5] which can be used for simplified calculations of cascade reservoir failure, needs to input parameters about the final shape of the breach and the starting time of dam-break. These parameters are very difficult to preset when lacking measured data. Xue et al [7] conducted an experiment on rectangular glass flume to simulate the sequential embankment dam-break This experiment indicated that the hydraulic features of dam-break water flow will be influenced by the initial water level and the distance between upstream and downstream dams. As the most direct and effective research tool, it is of great scientific significance and applied engineering importance to establish a reasonable numerical prediction model to simulate the sequential embankment dam-break for a cascade reservoir

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Conclusion