汶川地震触发潜在性泥石流研究——以岷江上游关山沟为例
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摘要
汶川地震后,由于地震作用,大量的潜在泥石流沟被激活成活动性泥石流沟,这些泥石流沟将在今后较长一段时间内处于活跃期,泥石流暴发规模和频率显著增加,威胁灾区人民生命财产安全,影响灾区重建工作的顺利开展。以岷江上游关山沟为例,初步探讨地震触发潜在性泥石流的成因、起动方式、危害等问题。通过对关山沟震前遥感影像、震后航空影像的解译,结合野外考察、访问,该沟可定性为地震触发的典型潜在性泥石流沟。关山沟由潜在性泥石流而转变成活动性、高频泥石流沟,其成因主要是地震引起了流域内大量的崩塌、滑坡,为泥石流提供了丰富的物源条件。通过估算,关山沟由于地震震动导致流域内发育2处滑坡、21处崩塌,松散固体物质储量为122×104m3。关山沟泥石流的起动方式为在一定的降水条件下,流域上游的滑坡转变成泥石流,沿途接纳两侧山坡表层径流冲刷下来的物质,同时强烈冲刷沟床中松散固体物质以增大泥石流规模,从而形成危害性泥石流。关山沟在P=1%、2%的暴雨频率下,泥石流造成堵河的可能性较大。泥石流一旦堵塞主河,其堵塞回水和溃决洪水将严重威胁到沟口上下游人民生命财产的安全,同时也威胁到"213国道"的安全通行。
After the Wenchuan earthquake,a lot of potential debris flow gullies are activated as active debris flow gullies because of the earthquake.These debris flow gullies will be in the active period for a long time in the future.The debris flow outbreak scale and frequency increase obviously,which threatens life and property safety of the people in the disaster area and influences the reconstruction of the disaster area.This paper takes Guanshan gully in the upper minjiang river as an example to discuss about the cause,starting mode and damage of the potential debris flow triggered by the earthquake preliminarily.The Guanshan gully can be defined as a typical potential debris flow gully through the interpretation of remote sensing image before the earthquake and aerial image after the earthquake.The Guanshan gully changes from a potential debris flow gully into an active and high-frequency debris flow gully.The cause is that the earthquake results in many collapses and landslides in the basin,which provides rich material sources for the debris flow.Through estimation,there are 2 landslides,21 collapses and 7.8 million m3 loose solid materials in the Guanshan gully.The starting mode of the debris flow in the Guanshan gully is that under the condition of precipitation,the landslides in the upper basin turn into debris flows,then with the acceptance of the materials runoff scoured from the two-side slope surface,the debris flows scour the loose materials in the gully bed strongly to increase debris flow scale at the same time,therefore harmful debris flows are formed.If the rainstorm frequency of P equals to 1% or 2%,the blockage caused by debris flows has more possibility.Once debris flows block the main river,the blockage backwater and outburst flood will threaten the safety of people's life and property in the upper and lower river.at the same time,debris flow will threaten the safety of "213 provincial road".
After the Wenchuan earthquake,a lot of potential debris flow gullies are activated as active debris flow gullies because of the earthquake.These debris flow gullies will be in the active period for a long time in the future.The debris flow outbreak scale and frequency increase obviously,which threatens life and property safety of the people in the disaster area and influences the reconstruction of the disaster area.This paper takes Guanshan gully in the upper minjiang river as an example to discuss about the cause,starting mode and damage of the potential debris flow triggered by the earthquake preliminarily.The Guanshan gully can be defined as a typical potential debris flow gully through the interpretation of remote sensing image before the earthquake and aerial image after the earthquake.The Guanshan gully changes from a potential debris flow gully into an active and high-frequency debris flow gully.The cause is that the earthquake results in many collapses and landslides in the basin,which provides rich material sources for the debris flow.Through estimation,there are 2 landslides,21 collapses and 7.8 million m3 loose solid materials in the Guanshan gully.The starting mode of the debris flow in the Guanshan gully is that under the condition of precipitation,the landslides in the upper basin turn into debris flows,then with the acceptance of the materials runoff scoured from the two-side slope surface,the debris flows scour the loose materials in the gully bed strongly to increase debris flow scale at the same time,therefore harmful debris flows are formed.If the rainstorm frequency of P equals to 1% or 2%,the blockage caused by debris flows has more possibility.Once debris flows block the main river,the blockage backwater and outburst flood will threaten the safety of people's life and property in the upper and lower river.at the same time,debris flow will threaten the safety of "213 provincial road".
引文
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[2]Cui Peng,Wei Fangqiang,Chen Xiaoqing,et al.Geo-haz-ards in Wenchuan Earthquake area and countermeasures fordisaster reduction[J].Bulletin of Chinese Academy of Sci-ences,2008,23(4):317-323.[崔鹏,韦方强,陈晓清,等.汶川地震次生山地灾害及其减灾对策.中国科学院院刊,2008,23(4):317-323.]
[3]Yin Yueping.Researches on the geo-hazards triggered byWenchuan Earthquake,Sichuan[J].Journal of Engineer-ing Geology,2008,16(4):1-12.[殷跃平.汶川八级地震地质灾害研究[J].工程地质学报,2008,16(4):1-12.]
[4]Chang Xiaojun,Ding Jun,Wei Lunwu,et al.Distributionof the geological hazards in the upper reaches of the Min-jiang River,Sichuan[J].Sedimentary Geology and Tethy-an Geology,2007,27(1):103-108.[常晓军,丁俊,魏伦武,等.岷江上游地质灾害发育分布规律初探[J].沉积与特提斯地质,2007,27(1):103-108.]
[5]Zhong Dunleng.The role of earthquake influence on debrisflowoccurrence.Articles collection of debris flow(1)[C]//Chongqing:Chongqing Branch of Publishing House for Sci-entific Reference.1981:30-35.[钟敦伦.论地震在泥石流活动中的作用.泥石流论文集(1)[C]//重庆:科技文献出版社重庆分社.1981:30-35.]
[6]Tang Chuan,Liang Jingtao.Characteristics of debris flows inbeichuan epicenter of the Wenchuan Earthquake triggered byrainstorm on September24,2008[J].Journal of Engineer-ing 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.
[7]周必凡,李德基,罗德富,等.泥石流防治指南[M].北京:科学出版社,1991:80-92.
[8]吴积善,田连权,康志成,等.泥石流及其综合治理[M].北京:科学出版社,1993:152-153;164-180.
[9]Xie Hong,Zhong Dunlun,Li Yong,et al.Features of debrisflow s in the upper reaches of the Changjiang River[J].Resources and Environment in the Yangtza Basin,2004,13(1):94-99.[谢洪,钟敦伦,李泳,等.长江上游泥石流灾害的特征[J].长江流域资源与环境,2004,13(1):94-99.]
[10]Zhang Jinshan,Shen Xingju,Xie Hong.Study on factorsaffecting the river-blocking due to debris-flow in the upperreaches of Minjiang River[J].Journal of Catastrophology,2007,22(2):82-86.[张金山,沈兴菊,谢洪.泥石流堵河影响因素研究———以岷江上游为例[J].灾害学,2007,22(2):82-86.]
[11]Zhang Jinshan,Xie Hong.Calculation of the possibility ofriver-blocking due to debris flow in the upper reaches ofMinjiang River[J].Resources and Environment in the Yan-gtze Basin,2008,17(4):651-655.[张金山,谢洪.岷江上游泥石流堵河可能性的经验公式判别[J].长江流域资源与环境,2008,17(4):651-655.]
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