四川5·12地震灾区滑坡堰塞坝溃决灾害风险评估

Breaking risk evaluation of earthquake-induced lakes in Sichuan,China

四川5·12地震造成大量山体崩塌和滑坡,在灾区河流上形成了上百个雍塞体和堰塞湖,其中比较大的有34个,这些不同规模的地震堰塞湖的稳定性和溃决风险成为最严重的地震次生灾害,对于这些堰塞坝的处理需要进行科学地评估.对四川地震堰塞湖的比较研究发现,流域面积很大(大于5000平方公里)的河流,堰塞体很难形成完全堵江的堰塞湖,不用担心堵溃风险;流域面积很小(小于300平方公里)的河流,径流量很小,相对库容较大,暂时不存在溃决风险,甚至可以保留下来加以利用;而对那些中等流域的河流,堰塞湖的相对库容较小,在连续暴雨情况下容易发生漫溢溃决,才是应该关注的重点.

More than 100 barrier lakes induced by earthquakes have been formed by wedged debris on the river channels after the massive earthquake happening on May 12 in Sichuan, China. Among them the Tangjianshan barrier lake is the largest one. It faces very urgent risk of dam breaking when water level reaches the top and begins overflow in case of storm rainfalls and/or continually aflershocks, threatening already devastated cities and villages with about 1.5 million people downstream. The outburst of a similar barrier lake occurred in the Minjiang River in 1933, causing a catastrophic flood. Risk analysis indicates that not all barrier lakes ,are highly dangerous. Only those lakes with high dams and strong flow discharge to be filled up in short period are of high risk and need to be dealt with immediately. Some of barrier lakes with solid dam and mild flow are stable, which can be reinfbrced and kept for making use of.