基于栅格GIS滑坡风险评价方法中格网大小选取分析

以地理信息系统（GIS）作为工具和研究手段的滑坡风险评价方法已得到了普遍的认可和使用，较为成熟的方法是基于栅格GIS的滑坡风险评价方法，即将滑坡风险评价中考虑的各种因子归一化处理后转换成相同空间分辩率的定量数据，然后根据特定模型进行数据运算，最后得到风险评价结果图。但在风险评价过程中存在这样的问题：对于已经量化的各影响因子，采用什么样的空间分辩率来栅格化这些因子数据才比较合适。该文以基于地形的香港大屿山滑坡风险评价为例，分析了影响空间分辩率选择的因子，并给出了影响因子空间分辩率确定的经验公式。

Appropriate Grid Size for Terrain Based Landslide Risk Assessment in Lantau Island,Hong Kong

Aided by raster-based Geographical Information System (GIS) function, one method for terrain based landslide risk assessment for Lantau Island of Hong Kong was given in the paper. In this method, slope, aspect, vegetation covered, geology, elevation and distance to drainage line were considered as landslide related elements, and each element as given different weight in landslide risk assessment matrix. In raster based landslide risk assessment methodology, the grid size (pixel) selection for dataset concerned is a key task and must be solved. To find the most appropriate grid size for each elements, 5m, 10m, 20m, 40m and 80m five kinds of grid size were tested in this study. Following the state that landslide risk assessment result is the key to evaluate the appropriate grid size, landslide risk assessment parameters characteristic, risk assessment results were analyzed and compared thoroughly, 20m grid size was found the appropriate grid size for the pilot area according to most features described in the paper such as area frequency for each kind of grid size, landslide frequency under each grid size, area frequency for each class landslide susceptibility under different grid size. Generally, the appropriate grid size selection for certain cases are connected to area of pilot region, user requirement, gromorphology and topography characteristics of pilot region, and other case sensitive elements. Based on the results obtained in the pilot area, one experimental formula was given for grid size selection of landslide risk assessment.