本研究以北勢溪支流金瓜寮溪之粗窟1 號防砂壩上、下游300m 河段作為研究河段，應用河川棲地二維模式(River2D)模擬防砂壩不同改善方案之河川棲地重可用面積(WUA)，並探討現有魚道之功能及改善建議。研究結果顯示：常流量及10 年重現期距流量下，將原有防砂壩改為連續低壩型式時河川棲地之WUA 值最高；2 年重現期距流量下，將原有防砂壩改為複式斷面型式時之WUA 值最高；25 年重現期距流量下，將原有防砂壩移除時河川棲地之WUA 值最高；常流量及10 年重現期距流量下，將原有防砂壩改為連續低壩型式時河川棲地之歧異度指數(H’)最高；隨著模擬流量增加各防砂壩改善方案模擬之WUA 值及流況歧異度指數(H’)均漸遞減。將現有防砂壩改為複式排水斷面、滯洪壩及連續低壩之型式，皆可提供河川生態廊道，取代現有之魚道。另為考量降低對現有河川棲地之擾動及節省工程經費等因素，建議將現有魚道阻流板缺口改為對開型式，並將魚道坡度降為1/12，以改善現有魚道之功能。

In the past, the river engineering planning designs are mostly based on human concerns focusing on food control, development and utilization. Neglecting river biological living area may result in natural habitat
quality deterioration and disappearance. Moreover, it may further impact the river biological diversity. Recently, the river ecological conservation concept becomes important, the living right and diversity maintenance are main topics on river engineering and water resources development. In this study, the river of Beishi Stream (with the total length of 300 meters) was selected for investigating different types of improvements on the Chuku #1 check dam .Atwo-dimensional river habitat model (River2D) was employed to simulate river weighted usable area (WUA) in different enhancement scenarios. The fishway functions of check dam facility are also discussed and enhancement suggestions are proposed. Study results indicated that under modifying check dam into serial low dams drainage pattern, the WUA may reach the maximum values for instream and 10-year return period flood discharge. Under modifying check dam into a combined section pattern, the WUA may reach the maximum value for 2-year return period flood discharge. Under check dam removal simulation, the WUA may reach the maximum value for 25-year return period flood discharge. Under modifying check dam into serial low dams drainage pattern, the flow pattern diversity index (H’) may reach the maximum values for instream and 10-year return period flood discharge. The
calculated WUA and flow pattern diversity (H’) are decreased by increasing
flow discharge under each simulated scenario. Check dam modification
method such as combined section, detention dam, and serial low dams can
provide river ecological corridor and substitute some fishway functions.
However, under reducing river habitat disturbance and saving engineering
budget considerations, current fishway slots for baffles are suggested to
modify as opposite sides and fishway slope are suggested to reduce as 1/12 to improve current fishway functions.