汶川地震次生灾害毁坏耕地的遥感快速评估方法——以北川县唐家山地区为例
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摘要
以四川省北川县唐家山地区为研究区,利用2006-11-10的SPOT卫星影像数据,依据NDVI和地形信息进行耕地识别,辅以少量的人工修正,快速获取灾前耕地分布信息。应用2008-05-14的FORMOSAT-II卫星影像数据和2008-06-04的ALOS卫星影像数据,采用人机交互解译快速获取地震诱发的崩塌滑坡、堰塞湖等次生灾害信息。灾前耕地分布信息叠加地震次生灾害数据及影像,进行变化检测,实现耕地损毁的快速评估。结果表明,研究区内崩塌滑坡、堰塞湖等次生灾害严重,崩塌滑坡533处,面积1408.20hm2,堰塞湖水面面积已达604.69 hm2。共毁坏耕地86.88 hm2,耕地毁坏率8.84%。崩塌滑坡、被毁耕地分布与断裂带分布一致,断裂破碎带内耕地毁坏率达18.74%,占研究区被毁耕地面积的74.53%。
The main suffering area of the Wenchuan Earthquake locates in the mountainous area of western Sichuan,an area which is very prone to mountain hazards such as landslides and debris flows because of the mountains and deep valleys,complex geological structure as well as well developed fault zones there.The Wenchuan Earthquake had directly induced massive secondary disasters such as collapse and landslides which destructed large area of farmlands.At the same time,the Wenchuan Earthquake also induced more than 30 barrier lakes making some farmlands be inundated and destructed.In order to make a scientific evaluation of the disaster situation and provide scientific basis for reconstruction and rational settlement of people in the suffering area,it is necessary to acquire the information of the destructed farmlands.In this paper,satellite remote sensing data as well as appropriate information extraction methods were used to acquire the distribution information of farmlands before the Wenchuan Earthquake and information of collapse,landslides,barrier lakes after Wenchuan Earthquake based on information such as landform features in mountainous area,landuse information and imagery characteristics of seasonal aspect.Spatial analysis was applied to evaluate the farmland loss to provide reference for the reconstruction planning.In this paper,Tangjiashan area of Beichuan county was taken as a case study area for evaluating the farmland loss caused by secondary disasters.NDVI was derived from the SPOT image data of November 10th,2007.Based on NDVI and landform information,the farmlands were identified and the distribution information of farmlands was obtained.Manual corrections were then used to eliminate possible errors in the previous farmland identification.The FORMOSAT-II image of May 14th,2008 and the ALOS image of June 4th,2008 were used to acquire the information of these secondary disasters such as collapse,landslides as well as barrier lakes induced by the Wenchuan Earthquake based on man-computer interactive interpretation.Based on GIS technology,the rapid evaluation of farmland destruction was carried out according to the comprehensive analyses of farmland distribution before the Wenchuan Earthquake and the distribution information of these secondary disasters induced by the Wenchuan Earthquake.Then the temporal and spatial characteristics of farmland loss were analyzed.The results show that the secondary disasters such as collapse,landslides as well as barrier lakes were very serious in the study area.There were 533 sites of collapse and landslides which had a total area of 1408.20 hm2,as well as barrier lakes with an area of 604.69 hm2 in the study area.The area of the farmlands destructed by secondary disasters were 86.88 hm2 accounting for 8.84% of the total farmland area.The distribution of collapse,landslides and destructed farmlands was consistent with the distribution of fault zone.And the destruction rate of the farmland on the fault zone was 18.74%,accounting for 74.53% of the farmlands destructed in the study area.The secondary disaster induced by the main shock had seriously destructed the farmlands while the aftershocks furthered the destruction.With the advent of rain season,the secondary disaster will still be of great threats to the farmlands so it is necessary to strengthen the dynamic monitoring of the farmland in the study area.As there is good forest coverage in this area,suitable seasonal aspects with vegetation index were used to extract the distribution information of farmlands before the Wenchuan Earthquake with the assist of landform information.In the FORMOSAT-II and ALOS imagery the distribution information of collapse and landslides induced by the earthquake was quickly extracted by visual interpretation according to the hue,shape information in the imagery,landform features and reference to the satellite imagery before the earthquake as well,then the farmland loss information was acquired using GIS.However,the rapid acquirement of the collapse and landslides information by automated classification needs further study.
The main suffering area of the Wenchuan Earthquake locates in the mountainous area of western Sichuan,an area which is very prone to mountain hazards such as landslides and debris flows because of the mountains and deep valleys,complex geological structure as well as well developed fault zones there.The Wenchuan Earthquake had directly induced massive secondary disasters such as collapse and landslides which destructed large area of farmlands.At the same time,the Wenchuan Earthquake also induced more than 30 barrier lakes making some farmlands be inundated and destructed.In order to make a scientific evaluation of the disaster situation and provide scientific basis for reconstruction and rational settlement of people in the suffering area,it is necessary to acquire the information of the destructed farmlands.In this paper,satellite remote sensing data as well as appropriate information extraction methods were used to acquire the distribution information of farmlands before the Wenchuan Earthquake and information of collapse,landslides,barrier lakes after Wenchuan Earthquake based on information such as landform features in mountainous area,landuse information and imagery characteristics of seasonal aspect.Spatial analysis was applied to evaluate the farmland loss to provide reference for the reconstruction planning.In this paper,Tangjiashan area of Beichuan county was taken as a case study area for evaluating the farmland loss caused by secondary disasters.NDVI was derived from the SPOT image data of November 10th,2007.Based on NDVI and landform information,the farmlands were identified and the distribution information of farmlands was obtained.Manual corrections were then used to eliminate possible errors in the previous farmland identification.The FORMOSAT-II image of May 14th,2008 and the ALOS image of June 4th,2008 were used to acquire the information of these secondary disasters such as collapse,landslides as well as barrier lakes induced by the Wenchuan Earthquake based on man-computer interactive interpretation.Based on GIS technology,the rapid evaluation of farmland destruction was carried out according to the comprehensive analyses of farmland distribution before the Wenchuan Earthquake and the distribution information of these secondary disasters induced by the Wenchuan Earthquake.Then the temporal and spatial characteristics of farmland loss were analyzed.The results show that the secondary disasters such as collapse,landslides as well as barrier lakes were very serious in the study area.There were 533 sites of collapse and landslides which had a total area of 1408.20 hm2,as well as barrier lakes with an area of 604.69 hm2 in the study area.The area of the farmlands destructed by secondary disasters were 86.88 hm2 accounting for 8.84% of the total farmland area.The distribution of collapse,landslides and destructed farmlands was consistent with the distribution of fault zone.And the destruction rate of the farmland on the fault zone was 18.74%,accounting for 74.53% of the farmlands destructed in the study area.The secondary disaster induced by the main shock had seriously destructed the farmlands while the aftershocks furthered the destruction.With the advent of rain season,the secondary disaster will still be of great threats to the farmlands so it is necessary to strengthen the dynamic monitoring of the farmland in the study area.As there is good forest coverage in this area,suitable seasonal aspects with vegetation index were used to extract the distribution information of farmlands before the Wenchuan Earthquake with the assist of landform information.In the FORMOSAT-II and ALOS imagery the distribution information of collapse and landslides induced by the earthquake was quickly extracted by visual interpretation according to the hue,shape information in the imagery,landform features and reference to the satellite imagery before the earthquake as well,then the farmland loss information was acquired using GIS.However,the rapid acquirement of the collapse and landslides information by automated classification needs further study.
引文
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[2]Zhao Y S.Principle and Methods of Remote Sensing ApplicationAnalysis[M].Beijing:Science Press,2003.[赵英时.遥感应用分析原理与方法[M].北京:科学出版社,2003.]
[3]Jia HF,Liu X H.The Principle of Environment Remote Sensingand its Applications[M].Beijing:Tsinghua University Press,2006.[贾海峰,刘雪华.环境遥感原理与应用[M].北京:清华大学出版社,2006.]
[4]Fan J R,Tian B W,Cheng G W,et al.Investigation on DammingObject Induced by the Earthquake of Wenchuan on May 12Based on Multi-platform Remote Sensing[J].Journal ofMoun-tain Science,2008,26(3):257—262.[范建容,田兵伟,程根伟,等.基于多源遥感数据的5.12汶川地震诱发堰塞体信息提取[J].山地学报,2008,26(3):257—262.]
[5]Cui P,Wei F Q,He S M,et al.Mountain Disasters Induced by theEarthquake of May 12 in Wenchuan and the Disasters Mitigation[J].Journal ofMountain Science,2008,26(3):280—282.[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.]
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