聂拉木县冲堆普流域冰湖变化及溃决危险性分析

Change of Ice Lake and Collapse Hazards Evaluation of Chongdui Gully Basin in Nyalam County

聂拉木县冲堆普流域曾于2002年爆发过两次大规模泥石流灾害,主要原因是冰湖溃决引发,通过对2017年、2001年遥感影像并与1987年的数据对比,发现近30年来流域内的主要冰湖面积均发生了巨大的变化,初步分析得出部分冰湖存在可能溃决的危险。结果表明:近30年来,嘎龙错面积增加了225%,嘉龙错面积增加了101%;处于高度危险和较高危险状态的冰湖各有1个;通过嘎龙错终碛堤1/3和1/2溃决模式进行计算,得到溃决流量分别为3954m3·s-1、9340m3·s-1。当嘎龙错按1/3模式溃决时,洪水洪峰到达聂拉木县灾后重建普洛规划新区后,将有45m宽的场区范围被淹没,一旦形成泥石流,峰值流量达6899m3·s-1,泥石流泥深达13m,淹没场区深度增加2倍,淹没范围扩大30%,同时将对沟口中尼公路大桥造成严重破坏。建议沟口规划区采用相应的防治措施以减轻冰湖溃决泥石流的危害。

Two large-scale debris flow hazards broke out in the Chongduipu Basin of Nyalam County in 2002,which were mainly caused by the ice lake break.Through the comparison of the remote sensing images in 2017and 2001and data in 1987,it is observed that the area of main ice lakes in the basin has changed greatly in the past 30years.It is preliminarily analyzed that some ice lakes might break.The results show that the area of Galongcuo has increased by 225%and that of Jialongcuo by 101%in the past 30years;There is one ice lake in a highest-risk state and one in a high-risk state.According to 36.3 the analysis of the 1/3and 1/2breakout modes of Galongcuo Zhongqi Dike,the breakout discharge is 3954m3/s and 9340m3/s,respectively.When the Galongcuo collapses according to the 1/3mode,after the flood peak reaches the post disaster reconstruction Puluo planned new area of Nyalam County,a 45mwide site area will be submerged.Once a debris flow is formed,the peak flow will reach 6899m3/s,the mud depth of the debris flow will reach 13m,the depth of the submerged site will be doubled,and the submerged area will be expanded by 30%.At the same time,it will cause serious damage to the Zhongni highway bridge at the gully mouth.It is suggested that corresponding prevention and control measures should be taken in the planning area of the gully mouth to reduce the harm of ice lake break debris flow.