2013年西藏嘉黎县“7.5”冰湖溃决洪水成因及潜在危害

The cause and potential hazard of glacial lake outburst flood occurred on July 5,2013 in Jiali County,Tibet

冰湖溃决洪水(泥石流)是西藏自治区主要自然灾害之一.2013年7月5日,西藏自治区嘉黎县忠玉乡发生"7.5"冰湖溃决洪水灾害事件,导致人员失踪,房屋被毁,桥梁、道路等基础设施遭到严重破坏,直接经济损失高达2.7亿元.基于不同时间段地形图和遥感影像资料,利用地理信息技术,发现导致"7.5"洪灾的溃决冰湖为然则日阿错.该冰湖溃决的直接诱因可能是雪崩和冰崩的共同作用,溃决前的强降水过程及气温的快速上升是其间接原因,而冰湖长期稳定的扩张导致水量聚集是其溃决并造成巨大灾害的基础.然则日阿错溃决后形成2个冰湖,面积分别为0.25 km2和0.01 km2,再次发生溃决的概率极小.这次溃决洪水和泥石流灾害事件阻塞了尼都藏布的罗琼沟及衣布沟,并形成2处面积分别为0.33 km2和0.13 km2堰塞湖,且存在溃决风险,在今后一段时间内应加强监测工作与排险工程实施.

Glacial lake outburst flood （GLOF）, together with debris flow, is one of main natural hazards in Ti- bet Autonomous Region （TAR）. On July 5, 2013, a glacial lake outburst flood happened in Zhongyu Town of Jiali County, TAR. As a result, some persons were missing, numerous buildings were destroyed, and some in- frastructures such as bridge and road were damaged. The economic loss was estimated as 270 million RMB Yuan. Based on topographic maps and remote sensing images in different periods, Ranzeria Co Lake was be- lieved to be responsible for this GLOF event by using RS and GIS technology. According to the detailed meteor- ological data including precipitation and 1Lemperature in day, month and annual scale, avalanche and glacier cal- ving possibly induced the outburst of Ranzeria Co Lake, and the indirectly cause was the continued heavy precip- itation and quick temperature increase before the GLOF. Meanwhile, the steady expansion of Ranzeria Co Lake during 1970-2013 provided abundant mass of the GLOF. Because all villages are located in the low banks of the narrow Niduzangbu valley, and the high altitude gap is between Ranzeria Co Lake and Zhongyu Town, the GLOF caused severe damage to this area. After the break, Ranzeria Co Lake was abruptly diminished and was separated into two parts with area of 0.2：5 km2 and 0.01 km2, respectively. The re-occurrence probability of the GLOF from Ranzeria Co Lake is infinite,simal. However, after this GLOF, two dammed lakes form in the Luo- qiong valley and Yibu valley of the Niduzangbu River. So far, the area of these two dammed lakes is 0.33 km2 and 0. 13 km2, respectively. Due to the large area of the watershed or the dammed lake being completed blocked, these two dammed lakes are considered to be in a high risk. So monitoring work and engineering meas- ures on these dammed lakes should be strengthened in the future.