| Summary: | 碩士 === 國立屏東科技大學 === 水土保持系所 === 106 === This study discusses the potential evaluation method of potential debris flow torrents in central and south Taiwan based on the prone ability of hillslope type debris flow (HDF). HDFs recognition model was developed by Fisher’s discriminant analysis considering 35 HDFs and 35 landslides occurred during Typhoon Morakot in 2009. 16 HDFs and 16 landslides event were selected to be verification for the recognition model. The research shows the classification rate of samples and verification reached 91.4% and 88% of the HDFs recognition model composed by 7 factors of Watershed area, Form factor of the initiation region, Depression ratio of the initiation segment, Length of the transport segment, Ratio of landslide susceptibility area , Form factor ratio, and Gradient ratio of the initiation region. 7 factor are not only independent, but also presented a physical meaning of HDF.
Furthmore, the study develops a new potential evaluation model of debris flow torrents based on the content of HDF prone units in the catchment. The HDF units were discriminated by the HDF recognition model which has developed in previously. 32 sample of potential debris flow torrents and 10 verification torrents were studied. Each catchment is divided into dozens of analysis units, and each unit is interpreted by HDF recognition analysis one by one. Results show that 3 indexs, the accumulation area of HDF units, the accumulation of initial area of HDF units, and average elevation difference of pass ratio of HDF units, are effective to be the potential evaluation index of debris flow torrents.
The potential of debris flow torrent is divided into low, medium, and high potential grades. For the index of accumulation area of HDF units in the catchment, the accumulation area below 84 hectares is classified into low potential debris flow torrent , the area large than 263 hectares classified as high potential torrent, the area between both is the median potential torrent; Next for the index of accumulation of initial area of HDF units in the catchment, the accumulation area below 79 hectares is classified into low potential debris flow torrent, the area large than 189 hectares classified as high potential torrent, the area between both is the median potential torrent; Last, For the index of average elevation difference of pass ratio of HDF units in the catchment, the rate large 0.71 hectares is classified into low potential debris flow torrent, the rate low than 0.62 classified as high potential torrent, the rate between both is the median potential torrent.
Summying results shows that 3 indexs, the accumulation area of HDF units, the accumulation of initial area of HDF units, and average elevation difference of pass ratio of HDF units, poss good representablity of potential evaluation on debris flow torrents comparing to actual occurrent of debris-flow events.
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