Investigation of Environmental Characteristics on Landslide Site for Ji-Guang Bridge Watershed of Lan-Yang River

• Main Authors: Chun-He Li, 李春和
• Other Authors: 陳文福
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/45260818774518376966

碩士 === 中興大學 === 水土保持學系所 === 95 === Being located on the plate compressing zone site, the geology is fragile and the morphology is steep in Taiwan. On the other hands,the yearly accumulative rainfall is high up to 2,500mm because she also locates on the Pacific Monsoon area and on the route of typhoon. Further more, owing to the fast economic development and population expansion in resent 50 years, the land have been over used on slope-land and those always cause flood and debris flow disaster when storm rainfall comes. Above all, after 921 Earthquake occurred on September the 21-th in 1999, the debris-flow disasters, caused by landslide, had become more and more severe and big and those did threaten people’s property and lives. Yi-lan Country attached to The Central Mountains and faced Pacific Ocean so as has been attacked by Typhoon very ofen. The roads and bridges were broken by heavy rainfall from typhoons and traffic problems from landslides. The purpose of this study is to research and analyze the site characters of landslides and finally to propose their factors and propose strategies for preventing. This study selected the Watershed at Jiguang Bridge near to Lanyang River as the researching area. Through the discussion of environmental characters about the collapse of landslides, the study proposes some preventing strategies. The information comes from three ways. First, the statistic data from Soil and Water Conservation Bureau referred to the newborn landslides caused by typhoon Toraji and typhoon Mindulle. Second, using the set of GIS tests the basic special database in the researching area. Final is comparing these with Ground Truth. According to the data, there are three findings of environmental characters in the researching region. 1. Characters of height： According to 250M as the interval of height, result from typhoon Toraji and typhoon Mindulle showed the height from 1251M to 1500M and from 2501M to 2750M and those were decided by the position of Storm rainfall center. 2. Characters of geology and morphology：The landslides easily occurred with the geologic conditions for Lushan formation, northeast-trending slope, and sixth-leveled steep region. So, forms and elements of rocks are the critical factors for landslides. 3. The major reasons cause most areas of landslides to reach the distance to water within 50M are continuously assembling the runoff and eroding the banks.