Study on estimation for the destruction of the moraine dam for the risk assessment on the disaster that causes glacier lake outburst flood

针对冰川湖突发性洪水(GLOF)破坏的现实，得到了以下结论：1)GLOF开始是一种泥石流，大量的泥石流沿冰漠坝向下沉积几公里；2)随后，水流侵蚀谷底并向下长达数十公里，并间歇性地导致两岸坍塌。3)GLOF造成的崩塌边坡，其植被在20年或更长时间内无法恢复。正因为如此，这些斜坡长期受到间歇性侵蚀。因此，不仅要考虑大尺度冰雹的产生情况，而且要考虑植被产生后恢复的一系列措施。关于冰雹坝的稳定性，得到了以下结果：1)在冰雹坝前，通过地震勘探测得了厚达60m的冰凌沉积物。结果表明，由于泥沙作用于…，该坝处于稳定状态。更多的是作为冰体滑入冰漠坝的平衡重量。2)由计算结果可知，冰漠坝剩余冰体的融化对评价冰漠坝的稳定性具有重要意义。此外，还要通过航拍观察冰川湖(不仅仅是坝址)的周围环境、坡度和悬挂的冰川。这些都是评估坍塌风险的重要因素。而且，进入冰雹大坝的温度全年从未低于0℃。在湖水上，冬季湖水各深度的这些也多为0℃。因此，由于冰体条件一直在加速融化，因此需要对冰体融化过程进行模拟，并提出了相应的对策：1)有人说，冰凌坝爆破是降低冰川融化风险最有效的方法。然而，作者并不同意这种观点。起初，由于冰体的规模，爆破难度很大。冰雹大坝也是因为它的构图松散。此外，如果产生GLOF，则会造成长期的坡面侵蚀。2)冰体下沉进展太慢。因此，如果我们能够控制它，它将成为应对GLOF的有效对策。较少

About the realities of the glacial lake outburst flood (GLOF) damage, the following results were obtained ;1)Starting of GLOF is a debris flow, and a large amount of debris is sedimented a few km down the moraine dam.2)Afterwards, the flow erode the bed of valley and down a long distance over several tens km while inducing the collapse of both sides intermittently.3)At the collapse slopes caused by GLOF, its vegetation is not recovered in 20 years or more. Due to so, these slopes have been eroded intermittently for a long term. Therefore, it is necessary to consider not only the case of generation of large-scale GLOF, but also a long series of measures of the recovery of this vegetation after it is generated.About the stability of the moraine dam, the following results were obtained ;1)At the front of moraine dam, the thick moraine sediment, 60m more thick, was measured by the seismic explorations. The results clearly show that the moraine dam was been steady because its sediment acts … More as the counter weight for slide of the ice body remaining into the moraine dam.2)It was found from the result that the melting of the ice body remaining the moraine dam is important for the estimating of the stability of the moraine dam. In addition, it is necessary to observe the surroundings, slopes and hanging glacier of the glacial lake (not only dam site) by the aero photograph. These are important points for evaluating the collapse risk.And, the temperatures into the moraine dam had never be 0℃ or less through the year. On the lake water, these of every depth of the lake also be 0℃ more in winter season. Therefore, the authors pointed that the simulation of melting of the ice body is needed for the risk evaluation of GLOF, because the condition of ice body has been progressing the melt now.Finally, the authors indicate the countermeasures ;1)Somebody says that the blasting of the moraine dam is most effective for reduce the GLOF. However, the authors do not concur with such kind of opinion. At first, the blasting of the ice body is difficult due to its scale. The moraine dam is also due to its composed loose. In addition, if GLOF is generated, the erosion of the slopes is caused for a long term.2)The subsidence of ice body has been progress too slowly. So, if we can control it, it will become the effective countermeasure for GLOF. Less