本研究使用地理資訊系統(GIS)從數值地形模型中萃取蘭陽溪及陳有蘭溪流域內土石流潛勢溪流之地貌參數，計算集水區內沿程各溪流點的集水區險峻值(Melton Ratio, MR)，並將子集水區中集水區險峻值(MR)的變化趨勢分為趨勢向上、趨勢持平、趨勢向下三類。不同土砂類型的集水區，其子集水區中的MR變化趨勢不盡相同，高含砂水流集水區大多為趨勢向上，土石流集水區則為趨勢持平或向下。影響MR變化的因子除了高程與面積外，集水區的形狀係數亦是影響參數，本研究另外使用形狀係數來探討其對Melton Ratio的影響，結果為趨勢向下之集水區其形狀係數較小，表示集水區形狀大多呈現細長型。;In this study, Geographic Information System (GIS) was used to extract the geomorphological parameters of the potential debris flow torrents in the digital elevation model of Lanyang River and Chenyoulan River basin. The Melton Ratio of each stream in the watershed, and classify the trends of Melton Ratio in the sub-watersheds were classified into three categories: upward trend, flat trend, and downward trend. The watershed with different soil hazard types, their sub-watersheds also have different trend of Melton Ratio. Most of the debris flood watersheds are show the upward trend, while the debris flow watersheds are usually with flat or downward trend. In addition to the elevation and area, the other factor affecting the trend of Melton Ratio is the Form Factor. The influence of Form factor on the Melton Ratio was explored in this study. When the watersheds have downward trend, the value of Form Factor will be smaller which means the watershed is a elongate shape.
