數值高程模型 (Digital Elevation Model, DEM) 在水文學的領域中扮演了一個相當重要的角色。針對DEM進行地形的計測分析，可以用來自動化產生水文模式所需要的參數。集流面積 (contributing area) 在集水區水文學的研究中，是一個相當有用的參數，它可以幫助研究者決定河道的位置，判斷土壤沖蝕的潛勢。而集流面積的計算通常受到DEM解析度與流向演算法的影響。本文以陳有蘭溪內的一個次集水區進行DEM解析度與流向演算法之比較分析。藉由三種模式的模擬 (單流向、多流向、整合式)，分別計算不同解析度之下，集流面積的空間分佈情形。研究結果指出，在相同解析度之下，整合式模式的空間產出，可以同時保留單流向與多流向模式之優點，產生最合理的集流面積分佈。然而經過「再採樣」之後產生的粗解析度DEM，其模擬結果卻會出現空間上的偏差。整合式模式唯一參數「流向臨界值」的變動，會強烈影響模擬結果。根據研究結果顯示，DEM解析度越高所需要用以收斂水流的流向臨界值越小，因此依照DEM解析度「等比例」調整流向臨界值，將可有效提升整合式模式收斂水流之能力，進而凸顯「河道單元」與「邊坡單元」之差異。

Digital Elevation Model (DEM) plays a very important role in hydrological simulation. Hydrological parameters such as contributing area can be calculated from DEM automatically. Contributing area is a common parameter for delineating channel cells and for evaluating the potential of soil erosion. But calculation of contributing area is usually affected by DEM resolution and flow direction algorithms. This paper presents a case study that evaluates these effects in a sub-watershed of the Chenyulan Hsi. Three flow algorithms were used to calculate the contributing area at different DEM resolutions. The result shows that within the same DEM resolution, the hybrid model retains the advantage of both single-flow and multi-flow models and yields the most reasonable output. However, some spatial errors occur when coarser resampled DEMs were used. The only parameter in the hybrid model, the flow direction threshold, strongly affects the simulated result. The higher the DEM resolution is, the smaller the flow direction threshold should be. Adjustment of the flow direction threshold according to DEM resolution with a geometric ratio facilitates conversion in the calculation of the hybrid model and enables the distinction between “river unit” and “slope unit”