| Summary: | 碩士 === 國立中興大學 === 水土保持學系 === 90 === Large-scale landslide, caused by the catastrophic 921 earthquake, occurred nearby the foot of Kan-Dou mountain at Guoshing township in Nantou. Two landslide-dammed lakes were formed at the Chiutsaihu and Satsikeng creek respectively. Areas of denudation are urgent to be restored for secondary disaster prevention in the following rainy seasons. Satellite images and digital terrain model(DTM) were used to process the vegetation index analysis for identifying landslide sites and to extract topographic information of the areas. This research applies information of DTM and satellite images to monitor and/or assess vegetative restoration ratio for the landslide. The functions of site analysis, dynamic watershed query, revegetation monitoring, sediment yield and life span evaluation of the landslide-dammed lakes in Chiufenershan watershed are all integrated in this study
Vegetation analysis show that there exists a good trend of vegetation recovery (C factor changing from 0.79 to 0.47 and VRR=59.9%) at the landslide sites. The better restorative sites are located at the filling areas with elevation of 500-700m, gentle slope (< 30%), no obvious aspect. The worse sites are at areas of dip slope with elevation of 700-900m, east and/or southeast aspect.
The estimated life spans of Satsikeng and Chiutsaihu landslide-dammed lake are 12-18 years and 10-16 years. The corresponding annual watershed erosion depth is 0.92cm and 1.38cm, which are derived from USLE and sediment delivery ratio at watershed scale.
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