对甘肃舟曲特大泥石流灾害的初步认识

Preliminary Analysis of Extra-large-scale Debris Flow Disaster in Zhouqu County of Gansu Province

2010-08-07T23:00左右,甘肃省甘南藏族自治州舟曲县县城北面的罗家峪、三眼峪流域突降强暴雨,引发了特大泥石流灾害。泥石流将沿途村庄和城区夷为平地,摧毁了沿途的楼房民居,毁坏了大量的农田。泥石流还冲进白龙江形成堰塞湖,将半个舟曲县城淹在水中。此次泥石流流速快、流量大、规模超大,发生于半夜,且表现为山洪-泥石流-堰塞湖灾害链形式,因而造成重大人员伤亡和财产损失。截止08-15,共造成4496户、20227人受灾,水毁农田约95hm2、房屋5508间,1248人遇难,496人失踪,是建国以来我国损失最严重的泥石流灾害。现场调查与遥感图像分析表明,舟曲泥石流是局部强降雨作用下发生的百年一遇的水力型特大泥石流灾害。三眼峪、罗家峪泥石流总方量约220×104m3。沟内储存的大量的崩塌、滑坡体及坡积物、残积物为泥石流提供了丰富的固体物质。形成区陡峭的地形以及沟道内堆石坝、拦沙坝形成的陡坎级联堵溃效应,加大了泥石流的流速、流量与破坏力。在分析本次泥石流的背景条件、灾害成因、特征以及发展趋势的基础上,提出了相应的减灾对策。

A debris-flow catastrophe hit the city of Zhouqu of Gansu Province at midnight on August 7th,2010.Following a local intensive rainfall of 97 mm/（40min）,the debris flows happened in Sanyanyu and Luojiayu ravines which are located in the north of the urban area.A great mass of debris material formed a 1.2km long dam in Bailong River which the two ravines flow into.As of August 15th,1 248 people were killed,496 missed,and 4 496 families suffered from the disaster.The event also destroyed 233.4 acre farmland,and damaged 5 508 rooms,which has been the most severe debris-flow disaster since 1949.Field investigation and remote sensing image interpretation indicate that the debris flows were formed by upstream flood.Massive debris from avalanches,landslides,colluvium and weathered rock is the main source for debris-flow occurrence.Big slope and narrow downstream channel provides a high mobility of debris flows.A cascade of natural rock-fill dams and silt trapping dams was outburst to greatly increase the discharge up to 1 485 m3/s and the magnitude to 2.2 million m3.Finally,several countermeasures against future hazards are presented on the basis of causes,characteristics and trend of the disaster.