| Summary: | 碩士 === 國立中興大學 === 水土保持學系 === 89 === Large-scale landslides, caused by the catastrophic 921 earthquake, occurred at the Ninety-nine Peaks of Wu-Chi basin. Areas of denudation are estimated to 908.96ha and are urgent to be restored for the secondary disaster prevention in the rainy season. Satellite images and digital terrain models were used to process the vegetation index analysis for identifying landslide sites and to extract topographic information of the areas. A system coupled with GIS developed in this research could be used to monitor and/or assess the recovery rate of vegetation for the landslides.
The distribution of landslides is obviously affected by the direction of quake’s shaking, the most distribution of landslides are located at the range of aspect from northeast to west counterclockwise and in the steep slopes (greater than 55%). Results show that after a year of 921 earthquake, the average rate of vegetation recovery for the landslides in the Ninety-nine peak areas is over 40% under the circumstance of natural succession. It’s worth to observe and discuss if we need to throw massive human and material resources into the vegetation recovery of the landslides.
Large amounts of sediment yield usually derived from the lack of vegetative coverage of the slopelands in a watershed, hence sediment yield can be the index of priority for the watershed management. Watershed #4, #6, #8, and #12 with the considerable amount of erosion depth should be list at the high rank of treatment priority. The sites of summit are susceptible to landslide due to the quake. From the viewpoint of sediment delivery ratio, the riparian zones are the suitable places for landslide revegetation to decrease the sediment yield and control disaster economically.
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