中文摘要：

汶川大地震对龙门山区造成了严重破坏。地震引发的次生山地灾害以及剧烈的土壤侵蚀仍将长期持续地影响着当地居民的生产与生活。对地震前后小流域的土壤侵蚀严重性进行评价并分析其变化,将对灾后小流域水土保持综合治理及生态恢复与重建工作具有重要的指导意义。基于GIS技术,以四川省彭州市龙门山区为研究区,以小流域作为基本单元,针对研究区地震灾区小流域土壤侵蚀,构建侵蚀严重性指数评价及分级方法,对地震前后土壤侵蚀严重性及变化特征并进行评价与分析。结果表明,地震后绝大部分小流域的土壤侵蚀趋重。震后土壤侵蚀程度不严重、较严重的小流域数量别由震前8个及21个降至5个及8个,新增严重、极严重小流域分别为12个及4个,相应面积分别为183.76 km2,52.70 km2。空间上流域土壤侵蚀严重性由西北向东南递减。地震前后小流域平均海拔、平均坡度与侵蚀严重程度正相关,且平均坡度对侵蚀严重程度加重贡献更大。

英文摘要：

The 8.0Ms Wenchuan Earthquake has caused severe damage to the Longmen mountain areas.Serious secondary disasters and soil erosion induced by the earthquake would constant influence on the life and production of the local people.It is of great significance to evaluate soil erosion in a small watershed for post-earthquake reconstruction and Soil and Water Conservation.Taking the Longmen mountain areas as an example,the study area was divided into 29 small watersheds by GIS technology.The evaluation model and grading method of Index of soil erosion severity（ISES） was determined by the overlay tools of GIS.We conducted the evaluation of the severity of soil erosion and analysis of the variation characteristics of soil erosion in every small watershed before and after the earthquake.The results indicated that soil erosion in all the small watersheds had worsened.The number of small watersheds moderately eroded decreased from 8 to 5,and severely eroded decreased from 21 to 8.12 newly moderately eroded and 4 newly severely eroded small watersheds were increased,with the covered area were 183.76 km2 and 52.70 km2 respectively.The distribution of soil erosion severity decreases from west-north to south-east.The average altitude and average gradient showed positive correlation to ISES in small watersheds before and after the earthquake,furthermore,the average gradient contributed to the change of ISES more.