基于土壤水力侵蚀分级标准,考虑地震造成的特殊土壤侵蚀类型,构建了地震重灾区土壤侵蚀强度分级知识库;综合利用RS和GIS技术,结合专家知识判断,快速提取了四川省北川县土地利用、地面坡度、植被盖度、特殊侵蚀类型等土壤侵蚀因子空间信息;基于EcoHAT系统中的知识库和空间信息耦合型土壤侵蚀模型,快速完成了北川县震后土壤侵蚀强度的判定与分析.结果表明,地震使北川县土壤侵蚀加剧,相比2000年全国土壤侵蚀遥感调查成果,震后土壤侵蚀面积增加了275.13km2,增长量为23.83%;特殊侵蚀类型面积占北川县面积的2.48%;林地土壤侵蚀面积最大,占总侵蚀面积的一半以上;耕地土壤侵蚀比例为98.95%;坡度是北川县土壤侵蚀的主要贡献因子,植被则是主要控制因子,坡耕地治理是今后北川县土壤侵蚀控制的重点.

The powerful earthquake occurred in Wenchuan county in northwestSichuan province on May 12th,2008 has brought a series of ecological environmental problems, especially the soilerosion deterioration. Themountains become less crowded and cracked, geologicaldisasters such as coast, dilapidation, mud-rock flow, and chipping flow, happen contin-ually and lots ofbuildings have been destroyed in differentextent, which are all special types of soil erosion. Finding out the status of the soil erosion in disaster region is very mi portant to the rehabilitation of ecological environment after disaster. Based on the classification criterion ofwatersoilerosion and considering the specialerosion type, we constructthe soil erosion classification repository and analyze the soil erosion intensity inWenchuan earthquake disaster region. The basic source data collected include: 1) the land usemapwith 1∶100000 scale in 2005 provided by Institute ofRemote Sensing Applications,ChineseAcademy ofScience,2)themulti-spectrum remote sensing mi ageswith 32meters spatial resolution ofBeijing-1 before and after the earthquake,3) the digital elevationmodel(DEM) with 1∶50000 scale provided byState Bureau ofSurveyingMapping,4)some othermaterials about the status of the earthquake disaster. Utilizing remote sens-ing (RS) and geographic information system (GIS) asmain techniques and integrating expertknowledge, we obtain the soil erosion factor s spatial information after earthquake which is involved in the soil erosion classification criterion:1)land use type, obtained from themodification of the land usemap in 2005 through human-computer interaction interpreta-tion which isbased on the contrastofRS mi agesbefore and after the earthquake; 2) vegetation fraction, based on the nor-malized difference vegetation index (NDVI)and computedwith the sub-pixelmode;l 3)ground slope, computed from the DEM based on the terrain analysis function ofGIS;4) specialerosion type, obtained from human-computer interaction in- terpretation of remote sensing mi ages after earthquake. Then we assess the soil erosion intensity based on the coupling model of repository and spatial informationwhich is developed by InteractiveDataLanguage and coupled in Ecohy drological AssessmentTools (EcoHAT) as a sub-module. The procedure takes mi age pixel as basic calculative unit, identifies the soil erosion factor s spatial informationwith forward reasoningmachinewhile reading the pixels one by one, and com-pletes the estmi ation ofsoil erosion intensitywith supportofsoil erosion classification repository. When the user enters the soil erosion spatial information and classification repository, the system estmi ates the soil erosion intensity automatically.The application shows that the couplingmodelof repository and spatial in formation model can be used to analysis soil erosion fleetly. This paper alsomakes a deep analysis of the characteristics of the soil erosion factors and themain cause of soil erosion inBeichuan county. The resultshows:1)the earthquake hasdeteriorated the soilerosion inBeichuan county,both area and intensity. Comparedwith the publicized result of remote sensing investigation ofsoilerosion in 2000, the area ofsoilerosion after the earthquake has increased about275.13 km2, which is about23.83% ofthe totalsoilerosion area in 2000, and the acute degree soil erosion has increased nearly12 tmi es.2) The special erosion type distributes in the region where aftershock occurred frequently covering 71.19 km2.3) The forestryhas the largestsoilerosion area, which is 724. 46 km2, halfof the total area of soil erosion.4) Slope is themain contributing factorof soil erosion.About 97% soil erosion takes place on the landwhose slope isgreater than 15°.5) Vegetation fraction is themain control factor of soilero-sion. The erosion proportion is only 16.31% in the land whose vegetation fraction is greater than 75%. 6)The erosion proportion of plantation is considerable high which reaches 98.95%.We can see that sloping plantation fathering is the main direction of soil erosion controlling in Beichuan county.