Erosion-based analysis of breaching of Baige landslide dams on the Jinsha River, China, in 2018
Erosion-based analysis of breaching of Baige landslide dams on the Jinsha River, China, in 2018
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DOI：
10.1007/s10346-019-01247-y
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发表时间：
2019-10
期刊：
影响因子：
6.7
通讯作者：
Limin Zhang;T. Xiao;Jian He;Chen Chen-Chen
中科院分区：
文献类型：
--
作者：
Limin Zhang;T. Xiao;Jian He;Chen Chen-Chen
长江流域面积大，沿江人口众多，河上大型水坝、水库众多，是中国最重要的河流之一。长江上游金沙江近期在西藏白格两次筑坝，一次于2018年10月10日，另一次于2018年11月3日（UTC + 8）。因此，每隔 3 周就形成了两座大型滑坡坝，坝顶最低高度分别为 61 m 和 96 m。由于筑坝时来水量大，堰塞湖水位迅速上升，给下游居民和财产带来巨大风险。在滑坡坝风险管理中，重要任务之一是提前预测溃坝洪水。本文主要研究两座滑坡坝溃坝过程线和溃口几何参数的快速预测。在两座滑坡坝溃决之前，利用基于侵蚀的经验方程和数值模拟及时做出了预测，并在溃决后根据现场详细的现场调查进行了完善。进行了全面的现场调查，以确定滑坡坝的地质结构，表征坝材料的侵蚀性，并测量最终的海滩尺寸。模拟的溃坝过程、流出过程线、湖水位变化和最终溃口尺寸通过现场观察进行了验证。与第二座滑坡坝没有导流渠道的假设情景相比，15 m 深的导流渠道成功地将洪峰流量降低了约三分之一，有助于显着缓解洪水风险。分析结果作为下游居民预警、疏散以及制定相应工程风险缓解方案的依据。
The Yangtze River is one of the most important rivers in China due to its large basin size, the large population along the river, and the numerous large dams and reservoirs on the river. The Jinsha River, the upper reach of the Yangtze River, was dammed twice recently at Baige, Tibet, one on 10 October 2018 and the other on 3 November 2018 (UTC + 8). Accordingly, two large landslide dams, 61 m and 96 m in height to the lowest dam crest, were formed in a 3-week interval. Due to the large inflow rates at the time of damming, the barrier lake level rose rapidly, posing huge risks to the downstream residents and properties. In managing the landslide dam risk, one of the important tasks is to predict the dam breaching flood beforehand. This paper focuses on rapid prediction of the dam breaching hydrograph and breach geometric parameters of the two landslide dams. The predictions were made timely before the breaching of the two landslide dams using both erosion-based empirical equations and numerical simulation and were refined based on detailed field investigation at the site after breaching. Comprehensive field investigations were conducted to determine the geological structures of the landslide dams, characterize the erodibility of dam materials, and measure the final beach dimensions. The simulated dam breaching processes, outflow hydrographs, lake water level changes, and final breach dimensions were validated by field observations. Compared with the hypothetical scenario without a diversion channel on the second landslide dam, a diversion channel 15 m in depth successfully lowered the peak flood discharge by about one third and helped to mitigate the flood risk significantly. The analysis outcome serves as basis for warning and evacuation of the downstream residents and making appropriate engineering risk mitigation plans.