Glacier lake outburst flood disasters in China

Abstract

Floods caused by outbursts from lakes dammed either by end moraines or by glaciers are the most important disasters related to glaciers in China. The former occur mainly in Tibet, and the latter in Xinjiang Province. Exceptionally large outbursts from lakes dammed by end moraines have been reported 19 times since 1935 amd 30 outbursts from glacier-dammed lakes have been recorded since 1956. Outbursts from lakes dammed by end moraines are closely associated with ice avalanches, and 79% of all dam failures occur during July to August when ice avalanches are frequent. Outbursts from glacier-dammed lakes often occur in years of very high air temperature, and 63.3% of all failures are between August and September when the storage capacities of glacier lakes reach their limit. Whether or not the end moraine-dammed lakes are of potential danger depends on the flow of the glacier that feeds the lake and the vertical distance between the terminus of the glacier and the level of the lake. The frequency of periods of outbursts from glacier-dammed lakes corresponds to the periods of glacier advance. During the last 160 years, three periods of frequent outbursts from glacier-dammed lakes have occurred. Their duration has been 20 to 30 years and the interval between them about 40 years. The frequency of glacier lake outbursts could increase early in the next century if glaciers advance and dam up new marginal lakes in response to a cold period since 1940.