Landslide monitoring and assessment in taiwan using SPOT series satellites

Abstract

Taiwan Island poses very rough and steep terrain along the Central Range to east coast with only about 30% of plain area along the west coast. It suffers from strikes from typhoon and flush storms almost every year. For example, the Mindulle typhoon in July 2004 carried heavy rainfalls and raged viciously to the several counties in Middle Taiwan. The aim of this paper was to understand and document the caused landslides by means of a model using satellite images in order to assess the potential risk, to build up the attribution properties, and to compare with the past analysis result. It is hoped that we may improve our understanding about the status and trend of the catchments, drainage network, and watersheds.From the analysis results, it was found that the model to extract landslide is workable, and when the accumulation rainfall is over 1600mm, the new developed landslide was obviously added. The tatal landslide is 23,748.37 hectares, only 11 %( 2607.23 hectares) belong to mountainside range, the others were part of forest area. In terms of the scale by numbers of landslide, mostly were fallen between 0.1 to 0.5 hectares, or about 33.4% in total; if terms of area, areas between 2 to 10 hectares had 33% of the total; gradient at most number is 53% between 30 with 45 degree. It was also found that most landslides were in between 45 to 60 degrees and 25% of them were between 1,500 to 2,000 meters in altitude. It was worth mentioning that Nantou County, the 921 great earthquake site, wrap up a total of 13,270 hectares, increasing 1,792 hectares from previous report.