| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 91 === In this study, a total number of 180 debris flow locations were investigated and differentiated between different types of failure according to the collected information of debris flows in the central area of Taiwan after 921 earthquake and typhoon Toraji . Based on field investigations, the mapped slope-type debris flow are reclassified into five different failure modes: slope-type debris flow, stream-type debris flow, debris fall, shallow slide and erosion gully. The slope-type debris flow are characterized as small-scaled with steeper slopes and often occurred rapidly along mainstream banks. Accordingly, a database for debris flow in the central area of Taiwan was built based on the result of investigations.
Seven influence factors were selected, which included stream length, watershed area, basin form factor, average degree of watershed slope, average degree of streambed, hypsometric integral and geology, and used discriminant analysis to identify the differences between different failure modes. Without considering the different geologic area, no significant difference between debris fall and slope-type debris flow was found, the accuracy of classification was 64.9%. However, significant difference betweem slope-type debris flow and stream-type debris flow was found and the accuracy of classification reached 89.0%. Furthermore, potential slope-type debris flow could be identified by using discriminant analysis. For the value of discriminate function higher than 0.7956, the potential for slope-type debris flow is high. When it is lower than 0.3411, it is in low potential. Cases with values between those are in moderate potential.
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