摘要
　　防砂壩是台灣河川中最常見的水利設施之一，其主要的功能在於攔蓄河道泥沙、調節泥沙輸送、防止侵蝕及抑止土石流等，但卻也對河川生態造成了極大的影響。若能建立防砂壩對河川生態影響之評估方法，則對於防砂壩在設計、規劃與改善上將有極大的幫助。
RVA法是利用IHA的32個水文參數來評估河川流量的改變程度，以瞭解該位址之河川流量受到水利設施之影響程度，以及是否仍保有水利設施興建前之自然流量變化。防砂壩的建立將使得河道坡度減緩，造成淤砂範圍內河道輸砂量的減少，因此本研究希望以RVA法評估河川輸砂量的改變程度，以評估防砂壩對河川棲地環境之影響。

　　本研究以HEC-HMS模式模擬大埔壩上游位置各時期之流量，再將所得之流量資料代入HEC-RAS模式中，估算大埔壩影響範圍內各設定斷面之流速、水深與輸砂量。最後以RVA法求出各設定斷面之流量、流速、水深、水面寬與輸砂量在事件前後之IHA以及所對應之改變度。

　　由結果發現，輸砂量改變度在河道之上游處(即離壩較遠之位置)較小，應該是由於離壩較遠的位置受壩之影響較小，因此變動也相對較小。輸砂量改變度沿河道之變動趨勢與流速改變度之趨勢較相近，而與水深改變度之變動趨勢卻完全相反。以RVA法來評估輸砂量受防砂壩影響之改變程度時，以低值區之改變度進行評估似乎較為可行。

Abstract
　Check dam is one of the most common hydraulic equipments among Taiwan Rivers. Its main functions are to stop and store the river course sand, regulate sand transportation, prevent erosions and restrain the debris flow. However, it also causes a great influence to the river ecosystem. If we are able to build an evaluation method on the influence of the river ecosystem of the check dams, then it will be extremely helpful on the design, plan and improvement of the check dams.

　RVA method uses 32 hydrologic parameters of IHA to estimate the changing level of the river flow, to understand the effect of the river flow by the hydraulic equipments, as well as whether it maintains the natural flow variation before the hydraulic equipments were built. The construction of the check dams will enable the river course a gentle slope and reduce the sediment transport amount of the river course in the silt area. Therefore, this research wishes to estimate the changing level of the river sediment transport amount by using RVA method, and also to evaluate the influence of check dam on river habitat.

　This research uses HEC-HMS model to simulate the flow of each period at the upper flow of DA-BA Dam. And then by calculating the acquired flow data through HEC-RAS model, we can estimate the flow speed, water depth, and sediment transport amount of each set section in the influential area of DA-BA Dam. Finally, using RVA method to figure out IHA of the flow amount, flow speed, water depth, water width, and sediment transport amount of each set section before and after the event and its corresponding changing level.

　According to the result, we can find out that the changing degree of the sediment transport amount in smaller at the upper flow of river course (the distant place from the dam). The reason may be that the location which is distant from the dam has lower impact from the dam, and therefore, the changing is relatively smaller. The variation tendency of sediment transport amount changing degree along the river course is closer to the tendency of flow speed changing degree, and it’s completely opposite from the variation tendency of water depth changing degree. While utilizing RVA method to evaluate the changing degree of the sediment transport amount that influenced by the check dam, estimate the changing degree by using lower value area sees to be more effective.

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