基于不同评价单元的三峡库区滑坡易发性对比——以重庆市云阳县为例

Comparison of Landslide Susceptibility in Three Gorges Reservoir Area Based on Different Evaluation Units--Take Yunyang County in Chongqing as an Example

为探究不同评价单元对区域滑坡易发性评估的影响,基于网格单元与斜坡单元对三峡库区典型县域重庆市云阳县开展了滑坡易发性研究。首先选取高程、坡度、曲率等22个评价因子,根据研究区988个历史滑坡数据,通过30 m×30 m的栅格数据提取斜坡单元,并基于网格单元及斜坡单元分别建立22个滑坡影响因子地理空间数据库;然后利用随机森林与贝叶斯优化算法来构建滑坡易发性模型,对研究区滑坡进行易发性评估;最后结合ROC(受试者工作特征)曲线与混淆矩阵结果检验评价单元的易发性模型预测精度。结果表明:易发性评估的结果可划分为低、较低、中、较高、高5个等级;基于网格单元的滑坡易发性模型中,高程、与道路距离、坡度这3个因子对滑坡发生的贡献率大,基于斜坡单元的模型中,I_(NDV)(归一化植被指数)、剖面曲率、平面曲率这3个因子对滑坡发生的贡献率大,并且2个模型的滑坡密度均随着滑坡易发性等级的升高而变大;与网格单元相比,斜坡单元能更好地解释地形间的联系,以斜坡单元(AUC=0.744)为最小评价单元的滑坡易发性模型比网格单元(AUC=0.714)精度更高。

In order to explore the influence of different evaluation units on the assessment of regional landslide susceptibility,the landslide susceptibility of Yunyang County in Chongqing,a typical county in the Three Gorges reservoir area,was studied based on grid units and slope units.Twenty-two evaluation factors such as elevation,slope and curvature were selected.Combined with 988 historical landslide data in the study area,slope units were extracted from 30 m×30 m raster data,and geospatial databases of landslide impact factors were established based on slope units and grid units.The landslide susceptibility model was constructed by random forest and Bayesian optimization algorithm to evaluate the landslide susceptibility in the study area.The results indicate that the susceptibility assessment can be divided into five levels:low,moderately low,medium,moderately high,and high.In the landslide susceptibility model based on the grid units,the three factors of elevation,distance from the road and slope contribute greatly to the landslide occurrence.In the model based on slope units,the three factors of I_(NDV)(normalized difference vegetation index),profile curvature and plane curvature contribute greatly to the landslide occurrence.The landslide density of both models increases with the increase of susceptibility level.Compared with grid units,slope units can better explain the relationship between terrain,and the landslide susceptibility model with slope units(AUC=0.744)as the minimum evaluation unit is more accurate than grid units(AUC=0.714).