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磨子沟位于四川省汶川县银杏乡,属岷江上游右岸支流,5·12汶川地震对其造成了严重影响。地震引发了大量的崩塌、滑坡,其中8处大型崩塌和滑坡对沟道造成了严重堵塞,并为泥石流活动提供了良好的条件。地震后磨子沟泥石流十分活跃,仅2008年7-9月就暴发了75阵阵流,3次堵断岷江并形成堰塞湖,淹没了岷江左岸村庄;2009-2011年又多次暴发泥石流并堵塞岷江。持续的降雨监测数据表明,震后初期磨子沟发生泥石流的日雨量条件急剧降低,目前有逐步回升的趋势。通过对比磨子沟流域震前(2005年6月)、震后(2008年6月)及泥石流事件后(2010年12月)等不同时段的遥感影像,结合实地调查和震后高分辨率航空影像的解译,分析了地震对磨子沟的影响,估算出地震形成的崩塌和滑坡方量超过3 000×104m3;根据不同暴雨频率下的泥石流流量计算,得出2008年7月14日最大一场堵江泥石流的规模为2.57×105m3,其峰值流量为541 m3/s,为50年一遇的规模;已发生的泥石流仅从沟道内带走约2.5×106m3的固体松散物质,沟内剩余的巨量固体松散物质将使磨子沟的泥石流活动持续相当长的时间,并具有再次堵断岷江的风险。
Mozi ditch is located in Ginkgo Township, Wenchuan County, Sichuan Province, which belongs to the right bank tributary of the upper reaches of Minjiang River. The 5.12 Wenchuan earthquake severely affected it. The earthquake triggered a large number of landslides and landslides. Eight of the major collapses and landslides caused serious blockage of the channel and provided favorable conditions for debris flow activities. After the earthquake, the Mozi ditch debris flow was very active. Only 75 burst bursts broke out from July to September in 2008, blocked the Minjiang River three times and formed a dammed lake, submerging the left bank of the Minjiang River. In 2009-2011, many outbreaks of mudslides And blocked the Minjiang River. Ongoing rainfall monitoring data show that the conditions of daily rainfall at the Mozi ditch at the initial post-earthquake period have drastically decreased, and there is a gradual upward trend now. By comparing remote sensing images in different periods such as before the earthquake (June 2005), after the earthquake (June 2008) and after the debris flow event (December 2010) in the Mozhaigou Valley, combining the field survey and post-earthquake high-resolution aviation According to the interpretation of the images, the impact of earthquakes on the Moogou is analyzed, and the collapse and landslide of the earthquakes are estimated to exceed 3 000 × 104m3. According to the calculation of the debris flow at different storm frequency, the maximum of July 14, 2008 A blockade of debris flow of 2.57 × 105m3, the peak flow of 541 m3 / s, a scale of once in 50 years; debris flow has occurred only from the channel to take away about 2.5 × 106m3 of solid loose material within the trench The remaining huge amount of solid loose material will make the debris flow in the Mozi ditch continue for a long time and have the risk of blocking the Minjiang again.