汶川地震驱动的灾害链对岷江上游输沙量的影响

Influences of disaster chain driven by Wenchuan earthquake on sediment discharge in upper reaches of Minjiang river,Sichuan,China

2008年5月12日龙门山汶川8.0级特大地震对地表产生强烈震动和破坏,引发了大量崩塌滑坡灾害。震后伴随强降雨天气,山洪泥石流灾害频发,显示了地震及震后洪水的灾害链:地震-崩塌、滑坡、泥石流-堰塞湖-溃决洪水。作者采用岷江上游紫坪铺水文站1980～2007年的输沙量数据以及岷江上游21个雨量站的降雨资料,探讨了岷江上游降水量-输沙量的相关关系,分析了输沙量的变化趋势;在此基础上,分析了汶川地震后4年时间该流域频发的特大暴雨对河流输沙量增加的作用,探讨了汶川地震驱动的灾害链对输沙量的控制因素。结果表明,强降水是震后输沙量增多的诱发因素;坡度对输沙量的变化具有控制作用;汶川地震的同震作用和地震断裂带的控制作用是导致河流输沙量增加的重要因素;汶川地震后植被覆盖率降低、水土流失加剧是河流输沙量增加的重要条件。

Ms.8.0 earthquake hit Wenchuan of Longmen Mountain zone in China on May 12,2008.It caused strong vibration and destruction for the ground surface.With the action of the post-seismic heavy rain,flash floods and debris flows happened frequently.This shows the post-seismic disaster chain.：earthquake-collapse,landslide,debris flows-dammed lake-outburst flood.Based on the sediment discharge data of the Zipingpu hydrological station from 1980 to 2007 and the rainfall data of 21 rain-gauge stations in the upper reaches of the Minjiang river,this paper explores the relationship between the rainfall and the sediment discharge in the zone and analyses the change trend.Furthermore,it researches the effect of the frequent heavy rain on the sediment discharge in the 4 years after the Wenchuan Earthquake and analyses the controlling factors.The results show that the heavy rainfall is the inducing factor which leads to increase of the sediment discharge after the earthquake,the slope controls the change of the sediment discharge,the coseismic effect and the controlling effect of the earthquake fault zone are the important factors to induce the increment of sediment discharge,and the decreasing vegetation coverage and aggravating soil erosion after the earthquake are the important prerequisites to lead to the increment of the sediment discharge.