A Study of the Characteristics of Landslides in the Catchments of Tahen River

• Main Authors: Chi-yue Liao, 廖啟岳
• Other Authors: Ching-Weei Lin
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/00943598486109188207

碩士 === 國立成功大學 === 地球科學系碩博士班 === 96 === This proposed study, the catchment of Tahen river are chosen as the study area .I collect the earlier and later SPOT2 images of typhoon Herb before the Chi-Chi earthquake and the earlier and later subsequent rainfalls SPOT 5 and FORMOSAT-II images after the Chi-Chi earthquake to recognize the landslide and analyze the variations in the landslides . I used the GIS to construct the landslide layer, discussing the characteristics of the landslides in the basin including the location, area and analysis of the connection with PGA, lithology , rainfall and slope, expecting to comprehend the affection of the earthquake to the tendency of landslides occurrence and the aftermath. In the process of analysis, we viewed the former landslide as continuing existed, and viewed the overlapping landslides of the earlier and later analyzed satellite images as the expanding landslides along the former landslides. The rest regions are the new landslides. The assumption of these two types are so called the total landslides. The study results indicate : (1) The characteristics and the tendencies of landslides in the Tahen river basin are obviously affected by the Chi-Chi earthquake but as time goes, the bankacy came to an equilibrium. (2) The Chi-Chi earthquake elevated the occurrence slope of landslides and the landslide continued at the top of bank. (3) The landslides gathered in the sedimentary rock and slate. In the slate had the biggest landslide ratio, in other hand, the metasandstone had the smallest landslide ratio. (4) The landslides located in the PGA 50~249 gal regions and the landslide ratio rise along with the PGA. The landslide ratio of high PGA regions descended along with the time from earthquake which shows the subsequent earthquake effect have diminished. (5) Around the structure in 2 km, the characteristic that nearer the structure easier to slide before the earthquake is opposite to that after the earthquake. The landslide returned to the tendency before the earthquake until the typhoon Talim came. (6) PGA controls the locations of the landslides. Though the affection of the earthquake was diminished, it still need sufficient rainfall intensity and accumulation to reveal the affection of rainfall. (7) When I used the instability index method to analyze the landslide susceptibility of typhoon Aere, the factor of lithology had the largest weight whether considering the triggering factors. Furthermore, the regions where had the higher instability index intend to have more landslides that indicated this method is feasible. The regions where the index value are higher than 4 have about 90% of the landslides. The command of the occurrence of landslides in high index value regions is more excellent when adding the triggering factors .