河川生態的效益評估是當今河川環境營造重要的課題，因此進行河川規劃傳統上除了做水理計算外，也應該進行生態棲地的量化模擬與評估。以往國內通常使用一維水理棲地模式來模擬河川棲地，應用斷面資料、水力粗糙度等資料演算，提供每一斷面的平均水面高程與流速，僅能應用於大尺度的河川狀況之研究，而針對複雜的地形或小尺度之河川區段則較不易探討。在二維或是三維模式當中，利用連續的網格來進行模擬地形，適合演算區域性河流的水力行為，並配合適合度曲線來求得棲地可使用面積。本文的研究目的為探討利用二維棲地模式River2D模擬南崁溪各種流量情況下之棲地可使用面積與相同狀況下一維水理棲地模式PHABSIM的比較，並討論河道中攔河堰等構造物對於棲地的影響。結果中若以二維模式運算所得之WUA結果值為基準，若使用一維模式之斷面間地形變化過大，則容易高估或是低估其WUA值，高流量或低流量下之一維模式WUA值運算結果，皆有可能產生WUA高估或低估的現象；若斷面資料愈密集，一維模式所求的之WUA值可更準確的模擬出研究河段之棲地環境而趨近於二維模式運算所得之WUA結果。 The river ecology benefit appraisal becomes an important topic and should be taken into consideration when the river environment is built. Traditionally, one-dimensional hydrodynamic models are generally used for determining flood stage at various reach locations, and can only be applied if the changes in cross-sectional area and the hydraulic roughness are gradual. In fact, one-dimensional models provide the average water level and velocity at each cross-section and are only effective for large scale flow calculations. These models do not, in general, offer the resolution required for the detailed, localized resolutions that are necessary to assess structure performance and undertake habitat assessments. Two-dimensional or three-dimensional hydrodynamic models are more appropriate for characterizing local river hydraulic behavior. Instead of viewing the stream as a set of cross-sections (as with a 1D approach), 2D models view the stream as a continuum of individual points in a 2D mesh. This study demonstrates the value of detail weight usable area (WUA) can be estimated with a 2D model (River2D). The comparisons of the estimated WUA values from a 1D model and that from a 2D model for a specific river in Northern Taiwan are provided.
