“8.13”四川清平群发性泥石流灾害成因及其影响
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摘要
汶川地震触发的大量崩塌滑坡改变了泥石流流域的物源条件,地震灾区震后泥石流活动呈现出愈加明显的高频率、群发性、大规模的特征。地处四川省绵竹市西北部的绵远河上游震后已多次暴发了泥石流。2010-08-13和08-18,在局地暴雨诱发作用下,绵远河上游的清平乡和天池乡境内的24条沟谷同时暴发了泥石流,冲出的固体物质高达1.08×107m3,其中仅清平乡附近,泥石流堆积扇规模就达到7.62×106m3,泥石流淤满河道形成了1.5 km2的堰塞体,致使14人死亡和失踪,清平乡境内大量震后重建的民房遭淤埋,泥石流多次中断九环线的重要支线——绵(竹)茂(县)公路汉旺-清平段,直接经济损失高达4.3亿元。此次群发性泥石流灾害剧烈的改变着震后局部的河流微地貌形态,对灾后恢复重建和发展规划也将产生深远影响。本研究从汶川地震对绵远河上游泥石流流域物源条件的影响分析入手,着眼于泥石流形成的基本条件,分析了2010-08-13(简称"8.13")特大群发性泥石流的成因:汶川地震后绵远河上游两侧支沟内积聚的巨量固体松散物源是此次泥石流形成的前提条件;1 h雨强达37 mm、累计达203.5 mm的高强度暴雨是泥石流最直接的激发因素。泥石流物源区和堆积区的堆积物颗粒分析结果表明,泥石流以粘性泥石流活动为主。作为汶川地震后典型的次生山地灾害链过程,泥石流活动是自然地貌演化的必然结果,但此类远远超越常规规模和频率的泥石流灾害的影响将是一个长期的过程。因此,建议对危害居民点的重点沟谷提高泥石流治理标准,调整汛期的防洪方案。
Debris flow in the affected area has become more and more frequent and of bigger magnitude after the Wenchuan earthquake.The upper Mianyuan River is one of the typical areas,where a number of debris flow occurred in the last three years.In August,2010,debris flows occurred in more than 20 gullies in the upstream of Mianyuan river,Mianzhu,Sichuan,at stimulus of regional rainstorms.The events delivered deposit of 1.08×107 m3 in volume,just near Qingping town,the deposits are 7.62×107 m3 in volume and 1.5 km2 in area,caused 14 deaths and missing,blocked the river and inundated new houses,and disrupted the Mianzhu-Maoxian highway repeatedly.In addition,they have sharply changed river morphology and will have a long influence on reconstruction and developing programs.This study explores the cause of the events based on investigation of the material supplies caused by the earthquake.Analysis shows that the rainstorm had an intensity of 37 mm/h and the cumulative rainfall reached 203.5 mm,and this was the triggering factor of the debris flows.Soil samples indicate that the flow is viscous given material supplies in the area,such extreme events are expected to be encountered frequently in the near future.
Debris flow in the affected area has become more and more frequent and of bigger magnitude after the Wenchuan earthquake.The upper Mianyuan River is one of the typical areas,where a number of debris flow occurred in the last three years.In August,2010,debris flows occurred in more than 20 gullies in the upstream of Mianyuan river,Mianzhu,Sichuan,at stimulus of regional rainstorms.The events delivered deposit of 1.08×107 m3 in volume,just near Qingping town,the deposits are 7.62×107 m3 in volume and 1.5 km2 in area,caused 14 deaths and missing,blocked the river and inundated new houses,and disrupted the Mianzhu-Maoxian highway repeatedly.In addition,they have sharply changed river morphology and will have a long influence on reconstruction and developing programs.This study explores the cause of the events based on investigation of the material supplies caused by the earthquake.Analysis shows that the rainstorm had an intensity of 37 mm/h and the cumulative rainfall reached 203.5 mm,and this was the triggering factor of the debris flows.Soil samples indicate that the flow is viscous given material supplies in the area,such extreme events are expected to be encountered frequently in the near future.
引文
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[2]Yin Y,Wang F,Sun P.Landslide hazards triggered by the 2008Wenchuan earthquake,Sichuan,China[J].Landslides,2009(6):139-151
[3]Tian Lianquan.Debris flow after Luhuo earthquake,Sichuan prov-ince[G]//Debris flow(3).Chongqing:Chongqing branch,Sci-ence and Technology Literature Publishing House,1986:58-66[田连权.四川炉霍地震泥石流[G]//泥石流(3).重庆:科学技术文献出版社重庆分社,1986:58-66
[4]Zhu Pingyi,Luodefu,Kou Yuzhen.Debris flow development trendof Guxiang Ravine,Xizang[J].Mountain Research,1997,15(4):296-299[朱平一,罗德富,寇玉贞.西藏古乡沟泥石流发展趋势[J].山地研究(现山地学报),1997,15(4):296-299]
[5]Chen H,Hawkins A.B.Relationship between earthquake disturb-ance,tropical rainstorms and debris movement:an overview fromTaiwan[J].Bulletin of Engineering Geology and the Environment,2009,68:68:161-186
[6]Ching Weei Lin,Chjeng Lun Shieh,Bee-Deh Yuan.et al.Impactof Chi-Chi earthquake on the occurrence of landslides and debrisflows:example from the Chenyu lan Riverwatershed,Nantou,Tai-wan.Engineering[J].Geology,2003,71:49-61
[7]Tang Chuan,Liang Jingtao.Characteristics of Debris flow in Bei-chuan Epicenter of the Wenchuan earthquake triggered by rainstormon September 24,2008[J].Journal of Engineer Geology,2008,16(6):751-758[唐川,梁京涛.汶川震区北川9.24暴雨泥石流特征研究[J].工程地质学报,2008,16(6):751-758]
[8]Tang Chuan.Activity Tendency prediction of rainfall induced land-slides and debris flows in the Wenchuan earthquake areas[J].Journal of mountain science,2010,28(3):341-349[唐川.汶川地震区暴雨滑坡泥石流活动趋势预测[J].山地学报,2010,28(3):341-349]
[9]Xie Hong,Zhong Dunlun,Jiao Zheng,et al.Debris flow in Wen-chuan quake-hit area in 2008[J].Journal of Mountain Science.Journal of Mountain Science,2009,27(4):501-509[谢洪,钟敦伦,矫震,等.2008年汶川地震重灾区的泥石流[J].山地学报,2009,27(4):501-509]
[10]Xinhua News Agency.75 times Geo-hazards were occurred within8days in Sichuan province,16 people lose their life.www.sc.xin-huanet.com[EB/OL][新华网四川频道.四川省8天发生较大规模地质灾害75处,因灾死亡16人[EB/OL].http://www.sc.xinhuanet.com/content/2010-08/21/content_20684202.htm]
[11]Committee of Chorography of Mianzhu County,Chorography of Mi-anzhu county[M].Chengdu:Sichuan Science and TechniquePublishing House,1992[四川省绵竹县志编纂委员会.绵竹县志[M],成都:四川科学技术出版社,1992]
[12]Huang Heqing,Zhao Qihua.Basic characteristics and preliminarymechanism analysis of large Scale rockslide-sturzstrom at wenjiagoutriggered by Wenchuan earthquake[J].Journal of Engineer Geol-ogy,2010,18(2):168-177[黄河清,赵其华.汶川地震诱发文家沟巨型滑坡-碎屑流基本特征及成因机制初步分析[J].工程地质学报,2010,18(2):168-177]
[13]Wang Rudiao.Huaxian,Shaanxi strong earthquake infrequent sec-ondary disaster Chain caused by the earthquake in the World-Talkfrom engineering ground condition[J].Earthquake Research inShanxi,2006(2):4-6[王汝雕.陕西华县大地震引发世界罕见的地震次生灾害链[J].山西地震,2006(2):4-6]
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