近年來，由於社會需求的轉變、政府機關與民間團體對於生態保育的重視，永續發展的概念逐漸被廣泛提倡，且政府機關亦與各界合作投人力物力進行生態保育之相關研究。台灣以七家灣溪流域-櫻花鉤吻鮭棲地復育之相關案例最為著名。其中，最具突破性的即是高山溪四座防砂壩移除之相關研究。壩體移除後，後續為物理棲地所帶來的變動乃交縱複雜，並非只考量環境是否改善，仍涉及各領域許多未知的潛勢因素。過去在高山溪的壩體移除研究僅進行物理模型試驗，並無依靠動床輸砂模式予以佐證，為了因應七家灣溪主流第一號防砂壩亦即刻移除且更掌握未來於壩體移除後河道變化的趨勢，必須了解底床變化之重要變因。有鑑於此，本研究即利用NETSTARS 擬似二維輸砂模式模擬高山溪壩體移除後之河床地形，針對模式模擬結果與實測資料作比較，以探討NETSTARS 擬似二維輸砂模式在陡坡河床之限制與應用，並藉由比較結果了解陡坡河床於輸砂模式之主控因素。
本研究針對四個主控參數(輸砂公式、流管數、可沖刷厚度、模擬時距)設定不同數值以建立15 組模擬案例相互比較。結果發現Meyer-Peter and Muller輸砂公式較適合作高山溪輸砂演算，流管數多寡對模擬結果影響不大，模擬時距縮短反使河床變動更為劇烈，可沖刷厚度調整為0.1 其模擬結果最符合現場底床變動趨勢。率定最佳的模擬結果平均誤差為1.97m，驗證的模擬結果平均誤差為3.95m。應用方面乃採用2004 年4 月之高山溪斷面資料作為起始條件，模擬至2009 年底之情況，由模擬結果發現高山溪河床已處於穩定平衡之狀態。由於七家灣溪一號壩已有計畫拆除，故本研究所作之參數率定將來可供七家灣溪作相關動床模擬的參考依據。

In planning and assessing dam removal options, the ability to predict sediment dynamics following dam removal can inform management decisions. Thus, it is important to consider the strengths and limitations of models that are commonly used for such predictions. The most famous dam removal case in Taiwan was motivated by habitat restoration of the Formosan Landlocked Salmon in the Chichiawen Creek. Four check dams on one of its tributaries, Kaoshan Creek, were removed during 1999-2001.
While the knowledge was still limited during the time the dams were removed, only studies on physical experiments were done. In order to understand the channel responses better for future dam removal cases this study used the quasi two-dimensional sediment transport model, NETSTARS, to simulate the riverbed form after dam removal on Kaoshan Creek, and investigated the limitations and applications of such model on steep mountainous creeks.
This study focused on the sensitivity analysis of four main control parameters, i.e. sediment transport formula, number of stream tube, erodible thickness and simulation interval, by 15 numerical simulation cases with different values of these parameters. The results showed the Meyer-Peter and Muller formula was the most suitable to on the study area, Kaoshan Creek. Tests on different numbers of stream tubes didn’t vary significantly, while shorter simulation interval generated much more significant bed form changes. When the erodible thickness was adjusted to 0.1, the simulated results matched well with the actual situation. The best average error among the 15 cases was 1.97m, and the average error for verification was 3.95m.
By using the four tuned parameters, the study further simulated the bed form condition of the December 2009. The results showed a stable river bed on Kaoshan Creek since April 2004. As the #1 dam on Chichiawan Creek is scheduled to be removed next year, the results found in this study can be a good reference for future application.

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