台灣早期河川整治常以防洪與穩定河道為主要做法，未考慮環境保護與生態保育，近年來已有許多單位於河川治理時將生態保育觀念納入規劃中，本研究以筏子溪為例，利用加拿大亞伯他大學土木與環境學系所發展的河川棲地二維模式（River 2D）為演算核心，結合水理模式(HEC-RAS），模擬原始河道和束縮10%、38%及53%的河道權重棲地可使用面積（WUA）之差異，針對台灣石(魚賓)、明潭吻鰕虎、中華花鳅、粗首鱲四種魚種探討。 四種魚之結果顯示，無論是何種寬度，以台灣石(魚賓)在研究河段的適合度最高、其次為粗首鱲，之後是明潭吻鰕虎，最差為中華花鳅。 四種河寬研究結果顯示，同一種魚在低流量時期各種河型的WUA值很接近，從原始河道曲線看出在流量125cms前WUA值是上升的，流量125cms之後WUA值開始下降，束縮比例愈大的河型，其WUA值下降得愈快，並且流量愈大，束縮對棲地的影響愈大，因此本研究認為河流應保留其高灘地，河寬應保留其適當寬度，不應過度與河爭地。 This research focuses on the habitat conditions of the Fazih River under different channel contraction by Weighted Usable Area (WUA) method. The River 2D model and the HEC-RAS model were used to simulate four channel conditions, namely the original width of river and 10%, 38% and 53% of the original river width contraction. Four species of fish, the Acrossocheilus paradoxus, Rhinogobius candidianus, Cobitis sinensis and Zacco pachycephalus, were chosen as target species. The result indicates that the four river widths provide similar WUA under low flow condition. However, in the normal flow case, channel with the original river width shows better WUA than that of other channel cases with contractions of river width, among those the 58% channel contraction results the worst case. When WUA decreases and flow increases, the suitable habitat for a certain fish species decreases. In this study, the simulation results show that the Acrossocheilus paradoxus presented the best survival ability because of the highest WUA in all channel width conditions, while the Cobitis sinensis suffered from the lowest WUA. In conclusion, adequate river channels are necessary for habitat preservation, as well as to maintain the flood plain ecologically sound.
