Author(s): Zhang Lijuan; Chen Zhaohe; Li Qijun
Linked Author(s):
Keywords: Overtopping risk; Reservoirs in series; Total probability; Safety reliability; Earth dam
Abstract: In this paper, the overtopping risk theory for cascade reservoirs was developed based on the overtopping risk theory for single reservoir developed by previous researchers[1 -- 5]. The overtopping risk model and computation method for two reservoirs in series are studied in detail, considering all uncertainties of inflow flood, wind wave, reservoir storage, discharge capacity and interaction of reservoirs each other. A case study for two existing reservoirs in series was analysed by applying the method and computation procedure presented herein. In the application the overtopping risk for Xiaonanhai and Zhangwu reservoirs in series and the possibility of increasing the limiting level before flood (LLBF) were analysed. The results show that if the order of magnitude of10-6 was taken as overtopping risk criterion, or the corresponding safety reliability against overtopping was taken as 99.999%, the overtopping risks of both Zhangwu and Xiaonanhai reservoir as well as the two reservoirs system against simultaneous actions of flood series and wind wave during flood period under the respective original regulation scheme are over the criterion. Whereas the LLBF should be lowered, instead of increasing. An analysis for the highest water level in both reservoirs was carried out, and the results show that both discharge capacities in the beginning period are not enough. In order to improve flood control and ensure safety, we suggest that either increase the dam height or increase the discharge capacity, which should be decided by technical and economical analyses and comparison. The authors have also developed the overtopping risk model and computation method for multiple reservoirs in series, which will not be discussed here due to the limited space.
Year: 2001