Nantou County with the total area of 4106 km2 lies in central Taiwan. Due to the fragile geological structure and steep topographic condition, sediment disasters caused by landslide and debris flow were often resulted from heavy rainfall during storm season. The environment of hill slope at Nantou is so sensitive that slope failures were apt to happen due to improper operations of human activity, earthquake and heavy rainfall. Seriously landslide frequently threatens the rural and city development of Nantou area, and get more severely after Chi-Chi earthquake and typhoons in the following years. In this study, slope failure sites are investigated from Nantou area on hill slope. The GIS was used to analyze the characteristics of selected communities around Nantou area. The GPS/GIS technology integration is used to investigate geological calamities of six major factors were selected and analyzed on building up a risk assessment model by means of Analytic Network Process (ANP) method. The GPS/GIS/ANP integrated technology would also be critical to establish an assessment model with functions of auto-mapping the regions of potential slope failures on Nantou hillslope. All results and map layers established by this study can help Nantou County set up his own disaster prevention system to keep well development of the rural in the future.
Large scale landslide and soil mass movement have attracted the attention of human in the same way as other uncontrollable natural disaster, such as earthquake, volcanism, floods and debris flow, which threaten human lifes and their properties. Slope failures is usually related to human activity such as deforestation, hillslope development and surface mining operation. In general, when slope stability is disturbed, a great variety of sliding movements take place. Because of the great damage caused by landslides to forest stands, farmland, buildings, transportation facilities and other engineering structures, they also can be recognized as a serious economic problem such as the sediment disasters occurred at Nantou County in central Taiwan.
