| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 96 === Most Taiwan’s safety evaluation of rivers in the mountain regions are often the researches on the dynamic mechanism of landslide occurring and their causes. Those researches use the statistics and calculate the experience formulae of occurring mechanism and then apply the results to the systems of dangerous rivers evaluation and landslide alarming. This research no longer uses the concept of overall region evaluation, but adopts the viewpoint of topography to take the chosen rivers in the research region as the research unit to conduct case study and hopes to evaluate the relative dangerous divisions in the rivers.
This study uses Arc Hydro Tools module of GIS and 3D analysis module. Furthermore, through DTM, we build the data of small divisions of water gathering and water system in the research region and collect the data of altitude and length of rivers. We also build the data of river longitudinal section based on Yang’s(1971) theory of river longitudinal sectional formula. Then, via the comparison of river gradient index between the longitudinal sections of two rivers, we make the drawing of abnormal river gradient divisions and through analyzing the model of abnormal river gradient division, we try to evaluate the relative dangerous divisions in rivers.
According to the best method of fit function from Chen Rou-Fei（1999）, Chen Yen-Jie（2004）, the R2 value of 80.6% rivers is over 0.96 and the R2 value of 16.1% rivers is between 0.90 and 0.95 in the research region.
In the research region, there are 66 abnormal river divisions. Among them, the abnormal river divisions with relatively bigger scale, that is, the divisions which the river gradient difference value are over 1000 or have longer abnormal divisions mostly are located in the Jia-Tzou-Liau river basin and Shih-Gu-Pan river basin; if referring to the distribution of geology, we find that the abnormal river divisions with bigger scale mostly are located in Nan-Juang layer, Guei-Chu-Li layer, Cho-Lan layer and the regions with geological structure with fault line, syncline and anticline.
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