摘要
在2008-05-12汶川地震后的极震区暴发了多处群发性泥石流灾害,龙溪河流域的龙池"8.13"群发泥石流灾害就是其中之一。龙溪河流域在2010-08-13遭遇强降雨过程,流域内共有45处暴发泥石流,其中34处沟谷泥石流,11处坡面泥石流,泥石流冲出总量共334×104 m3,造成大量泥沙淤积在龙溪河下游河道内,该段河床平均淤高5 m。诱发"8.13"群发泥石流的最大1 h降雨量达75 mm,相当于20 a一遇的1 h降雨量。"8.13"群发泥石流中88.9%的泥石流活动集中在汶川地震发震断裂带附近3 km范围内,仅有11.1%的泥石流分布在距汶川地震发震断裂带3～5 km范围。除受汶川地震发震断裂带影响外,泥石流分布还受地层岩性和地形的影响。龙池群发泥石流以粘性泥石流为主,占总数的88.9%,而稀性泥石流很少,仅占总数的11.1%。小规模泥石流占多数,达到总数的60.0%;大规模泥石流很少,仅占总数的11.1%,其他为中等规模泥石流。泥石流流域主要为小流域,<1 km2的泥石流流域占多数,达到总数的68.9%;而>3 km2的泥石流流域很少,仅占总数的6.7%。龙溪河河道内的泥沙淤积受泥石流活动、主河道坡度和宽度的控制,河道上半段没有泥沙淤积,而下半段有大量泥沙淤积。龙溪河河道内淤积的泥沙颗粒粒径受沿岸泥石流流域岩性的影响,粒径从龙溪河上游到下游呈明显的从大到小的变化规律。龙溪河流域在遭遇较强降雨时还会暴发泥石流灾害;在汶川地震发震断裂带附近的山区,在暴雨激发下还有可能暴发群发性泥石流灾害。在雨季到来时需要提高警惕,预防地震次生泥石流灾害,特别要提防不易被发现的小流域泥石流灾害,做好防灾预案和预警报工作,最大程度地减轻泥石流灾害。
Many group debris flow hazards were triggered by subsequent rainstorm in the Wenchuan Earthquake area after the main shock.Group debris flow hazards in Longchi,Dujiangyan,Sichuan Province is one of these disasters.There were 45 debris flows triggered by heavy rainfall in the catchment of Longxi River on August 13,2010.In the all 45 debris flows,there were 34 channelized debris flows and 11 debris flows on the slope.The total volume of debris flow was 3.34×106 m3 and plenty of sediment was deposited in the downstream of Longxi River.The rainfall which triggered the debris flows in Longxi River catchment on August 13,2010 was 75 mm in one hour.It was the same as one hour rainfall of twenty years return period.Most debris flows were distributing in 3 km from the triggering belt of Wenchuan Earthquake,only 11.1% of total debris flows were located in 3-5 km from the triggering belt.The distribution of debris flows were also controlled by the rock characteristics and geomorphology.Most of debris flows are viscous debris flows,only 11.1% of total debris flows were less viscous debris flows.There were 60.0% small scale debris flows and 11.1% large scale debris flows in total debris flows.Most catchments of debris flow were small catchment,68.9% of total catchments was less than 1 km2,only 6.7% of total catchments was larger than 3 km2.The sediment deposited in Longxi River was controlled by the activity of debris flows,the width of channel,and the slope of channel： there was no sediment deposited in the upper stream of Longxi River,but there was plenty of sediment deposited in the downstream.The size of sediment deposited in Longxi River was partly decided by the rock characteristics of debris flow catchments,as the results the particle sizes were decreasing from upper stream to downstream of Longxi River.The debris flow hazards will be triggered again when it is heavy rainfall in Longxi River catchment.To reduce the hazards of debris flows in the Wenchuan Earthquake area,forecast and prevention work must be done in the next raining season.
出处
《山地学报》
CSCD
北大核心
2011年第6期738-746,共9页
Mountain Research
基金
国家自然科学基金(40871054)
973项目(2008CB425801)
地质灾害防治地国家重点实验室自主研究基金(SKLGP2009Z004)~~
关键词
龙池
龙溪河
群发
泥石流
地震
Longchi
Longxi River
group
debris flow
Wenchuan Earthquake
