At an early stage, the Soil and Water Conservation Bureau (SWCB) conducted a field survey to delimit marginal agroforestry land. In 1976, the “Slopeland Conservation and Utilization Act” was promulgated as well as the classification of slopeland utilization limitations becoming standardized. In the last decade, due to extreme
rainfall events, numerous landslides frequently occurred in mountainous areas. According to the act, the land damaged by the disaster must be categorized as conservation land where rehabilitation is required. Nevertheless,large-scale disasters on slope land are under the constraint of field investigation by SWCB officers. A rapid post-disaster procedure for slopeland suitability evaluation should be initiated. Chen-You-Lan Watershed was selected as a case study. The slopeland classification criteria parameters, i.e., average slope, effective soil depth and degree of soil erosion for a given cadaster unit were derived and/or calculated from the Digital Elevation Model (DEM),Topographic Wetness Index (TWI) and Universal Soil Loss Equation (USLE), respectively, using Geographic Information Systems (GIS). The parent rock criterion was assumed to be soft rock. The result showed the concordance of slopeland suitability classification between the SWCB field survey and GIS-based rapid assessment give an overall
consistency of 78%. However, the classification method in this study is correct according to the field survey. In addition,the post-disaster areas of Typhoon Morakot in 2009 were interpreted using SPOT-5 satellite imageries. It was found satellite based real time disaster mapping technology can be used to specify the intensive conservation areas.
Key Words : Assessment for classification on slopeland utilizable limitation, topographic wetness Index, geographic information system.