物源条件对震后泥石流发展影响的初步分析
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摘要
强震过后一定时期内,泥石流的活跃性增强,即数量增多、规模增大、频率增加。而随着松散物质储量的减少,泥石流的活跃性会随之衰减。为了具体考察物源条件对震后泥石流活动的影响,使用震后泥石流逐年平均输沙量作为刻画泥石流活跃性的指标,在云南蒋家沟和西藏古乡沟泥石流数据的基础上,定量地分析了震后泥石流活跃性的变化过程。分析表明存在降雨控制型和物源控制型两种泥石流流域。前者的泥石流在震后很长一段时间内都不衰减,其发生主要取决于降雨条件。后者最大规模的泥石流发生于地震过后的短时间内,尔后泥石流活动随时间显著减弱。泥石流规模和频率的关系与暴雨不一致。当物源控制型流域的无量纲化活跃性指标值降为0.12左右时,可以认为泥石流进入了稳定或者衰弱期,不会再有大规模的泥石流事件发生。数据拟合结果表明,整个泥石流活跃性的衰减过程可以用幂函数来描述。其衰减指数与剩余物质储量和总物质储量之比存在密切的关系。这为定量预测震后泥石流发展趋势提供了一个初步的模型。
The influence of debris supply on the activity of post-quake debris flows was quantitatively examined by two cases: Jiangjia basin in Yunnan province and Guxiang basin in Tibet,southwestern China.Mean annual sediment discharge was served as the index of activity.According to the temporal behavior of the mean discharges,the two basin systems were identified.One is the rainfall-dominated basin of which debris-flow activity has not decayed even forty years after earthquake.The occurrence of debris flow in the first basin is determined by rainstorm,and then its return period is equal to that of rainstorm.The other is the supply-dominated basin in which the activity of debris flow decreases significantly along with the decreasing volume of loose materials.The latter should be in inactive or decline phase when the value of the dimensionless activity index reduces to 0.12 in the case of Guxiang.After that,there is no more large scale debris-flow accident.The decay process of debris-flow activity was described well by a power function,and the function’s exponent showed a close relationship with the ratio of the volume of the remaining loose material to the original materials,which provides a start point for developing a quantitative model to predict the trend of post-quake debris flow activity.
The influence of debris supply on the activity of post-quake debris flows was quantitatively examined by two cases: Jiangjia basin in Yunnan province and Guxiang basin in Tibet,southwestern China.Mean annual sediment discharge was served as the index of activity.According to the temporal behavior of the mean discharges,the two basin systems were identified.One is the rainfall-dominated basin of which debris-flow activity has not decayed even forty years after earthquake.The occurrence of debris flow in the first basin is determined by rainstorm,and then its return period is equal to that of rainstorm.The other is the supply-dominated basin in which the activity of debris flow decreases significantly along with the decreasing volume of loose materials.The latter should be in inactive or decline phase when the value of the dimensionless activity index reduces to 0.12 in the case of Guxiang.After that,there is no more large scale debris-flow accident.The decay process of debris-flow activity was described well by a power function,and the function’s exponent showed a close relationship with the ratio of the volume of the remaining loose material to the original materials,which provides a start point for developing a quantitative model to predict the trend of post-quake debris flow activity.
引文
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[2]日本:中村浩之,土屋智,井上公夫,等.地震砂防[C].社團法人砂防學會、地震砂防研究會，古今書院，2000:190-220.Nakamura,H.,Tsuchiya,S.,Inoue,K.,et al.Saboagainst Earthquakes[C].Kokon Shoin,Tokyo,Japan.2000:190-220.
[3]Lin,C.W.,C.L.Shieh,et al.Impact of Chi-Chiearthquake on the occurrence of landslides and debrisflows:example from the Chenyulan River watershed,Nantou,Taiwan.[J].Engineering Geology,2004,71(1-2):49-61.
[4]Lin,C.W.,Liu,S.H.,Lee,S.Y.,et al.Impacts on theChi-Chi earthquake on subsequent rainfall-inducedlandslides in central Taiwan[J].Engineering Geology,2006,86(2-3):87-101.
[5]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[J].中国科学院院刊,2008,23(4):317-323.CUI Peng,WEI Fangqiang,Chen Xiaoqing,et al.Geo-hazards in Wenchuan Earthquake Area andCountermeasures for Disaster Reduction[J].Bulletin ofthe Chinese Academy of Sciences,2008,23(4):317-323.
[6]黄润秋,李为乐.“5.12”汶川大地震触发地质灾害的发育分布规律研究[J].岩石力学与工程学报,2008,27(12):2585-2592.HUANG Runqiu,LI Weile.Research on development anddistribution rules of geohazards induced by Wenchuanearthquake on 12th May,2008[J].Chinese Journal ofRock Mechanics and Engineering,2008,27(12):2585-2592.
[7]Tang C,Zhu J,Li W L.Rainfall triggered debris flowsafter Wenchuan earthquake[J].Bull.Eng.Geol.Environ.,2009,68:187-194.
[8]崔鹏,韦方强,何思明,等.5.12汶川地震诱发的山地灾害及减灾措施[J].山地学报,2008,26(3):280-282.CUI Peng,WEI Fangqiang,HE Siming,et al.Mountaindisasters induced by the earthquake of May 12 inWenchuan and the disasters mitigation[J].Journal ofMountain Science,2008,26(3):280-282.
[9]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.XIE Hong,ZHONG Dunlun,JIAO Zhen,et al.Debris flowin Wenchuan quake-hit area in 2008[J].Journal ofMountain Science,2009,27(4):501-509.
[10]杜榕桓,李鸿琏,王立伦,等.西藏古乡沟冰川泥石流的形成与发展[A].中国科学院兰州冰川冻土研究所集刊第4号(中国泥石流研究专辑)[C].北京:科学出版社,1985:1-18.DU Ronghuan,LI Honglian,WANG Lilun,et al.Formation and development of glacial debris flow in theGuxiang Gully,Xizang[A].Memoirs of Lanzhou Instituteof Glaciology and Cryopedology of Chinese Academy ofSciences(No.4)[C].Beijing:Science Press,1985:1-18.
[11]王文濬,章书成,王家义,等.西藏古乡沟冰川泥石流特征[A].中国科学院兰州冰川冻土研究所集刊第4号(中国泥石流研究专辑)[C].北京:科学出版社,1985:19-35.WANG Wenjun,ZHANG Shucheng,WANG Jiayi,et al.Properties of glacial debris flow in the Guxiang gully,Xizang[A].Memoirs of Lanzhou Institute of Glaciologyand Cryopedology of Chinese Academy of Sciences(No.4)[C].Beijing:Science Press,1985:19-35.
[12]杜榕桓,章书成.西藏古乡沟1953年特大冰川泥石流剖析[A].中国科学院兰州冰川冻土研究所集刊第4号(中国泥石流研究专辑)[C].北京:科学出版社,1985:36-47.DU Ronghuan,ZHANG Shucheng.A large-scale glacialdebris flow in the Guxiang gully of Xizang in 1953[A].Memoirs of Lanzhou Institute of Glaciology andCryopedology of Chinese Academy of Sciences(No.4)[C].Beijing:Science Press,1985:36-47.
[13]罗德富,毛济周,等.川藏公路南线(西藏境内)山地灾害及防治对策[M].北京:科学出版社,1995:179-187.LUO Defu,MAO Jizhou,et al.Mountain hazards and theircountermeasures along the South section of Chuan-Zanghighway[M].Beijing:Science Press,1995:179-187.
[14]朱平一,何子文,等.川藏公路典型山地灾害研究[M].成都:成都科技大学出版社,1999:54-102.ZHU Pingyi,HE Ziwen,et al.A study of typical mountainhazards along Sichuan-Tibet highway[M].Chengdu:Chengdu Science and Technology University PublishingHouse,1999:54-102.
[15]王裕宜,李昌志,洪勇.暴雨泥石流输沙年际变率的旋回性研究[J].自然灾害学报,2000,9(4):99-104.WANG Yuyi,LI Changzhi,HONG Yong.Study on thecyclic property of the annual sediment discharge variationof debris flows at Jiangjia Ravine,Yunnan[J].ChinaJournal of Natural Disasters,2000,9(4):99-104.
[16]Bovis,M.J.,Jakob M.The role of debris supplyconditions in predicting debris flow activity[J]Earth Surf.Process.Landforms,1999,24:1039-1054.
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