七家灣拆壩後之河道演變模式

This study focused on channel responses one and a half years after dam removal in the Chijiawan Creek and proposed a channel evolution model based on analyses of hydrology, morphology, and images. Channel adjustment is highly influenced by the distance between the dam and the headcut erosion. We defined nine and six stages of the channel evolution model for the upstream and downstream reach, respectively, according to the cross sections 48 m upstream and 30 m downstream from the dam. It took a couple of minutes to reach stage B (main channel migration) and one year or so to reach stage E3 (widening and continued incision). As Chijiawan Creek has not reached the quasi-equilibrium state, stage F’, we suggest that the establishment of a long-term channel evolution model is critical for in-situ monitoring.為探究七家灣溪一號壩拆壩後達到準平衡階段之河道演變模式，本研究蒐集水文、地形與影像資料，分析拆壩後一年半之河道演變情形，做為建立長期河道演變模式之基礎。七家灣溪之河道調整程度和距壩遠近與溯源侵蝕有關。本研究根據壩上游48 m 處與下游30 m 處斷面，分別定義上下游九個與六個河道演變階段。在時間尺度上，上游河道進入階段B(主河道調整) 僅需數分鐘、進入階段E3(河道拓寬並持續下切) 需1~2 年、而準平衡階段F’尚未達到，因此以此研究所建立之河道演變模式為基礎，持續監測未來七家灣溪達到準平衡階段之過程有其必要

Heat transfer of a three-dimensional flow due to an unsteady bidirectional stretching surface

[[abstract]]本研究主要探討導電性黏性流體受非穩態雙向拉伸表面驅動下的熱傳遞特徵，邊界溫度與熱通量條件以距離原點作冪次分佈改變，對時間也作冪次變化，利用相似變換法將非線性之偏微分方程式簡化成一組非線性常微分方程式，透過數值方法來解此問題。表面溫度梯度與表面溫度之相關參數以一些標準值給定後，數值結果顯示在給定表面溫度的條件下，當非穩態參數A<0時，無因次溫度分佈隨著時間項冪次m的增加而增加，隨著空間項冪次r與s的增加而減少；在給定表面熱通量的條件下，當非穩態參數A<0時，無因次溫度分佈亦隨著時間項冪次m的增加而增加，隨著空間項冪次r與s的增加而減少。[[abstract]]The heat transfer characteristics of a three-dimensional electrically-conducting viscous fluid due to an unsteady bidirectional stretching surface are investigated. The temperature and heat flux at the surface are assumed to vary in a power-law distribution with distance from the origin, and also with time. Similarity transformation is used to transform the governing nonlinear partial differential equations into a set of nonlinear ordinary differential equations and this problem is solved using numerical method. Some criteria of the values of the surface temperature gradient and surface temperature for relevant parameters are given. Numerical results showed that the temperature profiles increase with the increase of the time parameter m, but decrease with the increase of the distance parameter r and s when unsteady parameter A<0 for prescribed surface temperature (PST) case; whereas when unsteady parameter A<0 for prescribed heat flux (PHF) case, the temperature profiles increase with the increase of the distance parameter m, but decrease with the increase of the distance parameter r and s.[[note]]碩

台灣壩體拆除決策流程建立與應用

In order to review the effectiveness of dam removal and to develop a river management model, it is necessary to establish a suitable decision-making process for dam removal in Taiwan. This study develops a 7-step process for reducing the ecological impact and hazard risk of dam removal. Four dams located in the Wuling region were used for this research: Yousheng Creek Dam #1, Chijiawan Dam #1, Dam #3 and Dam #4. Along with river and dam surveys, Shei-Pa National Park collected ecological monitoring data over a period of decades. Such analyses allow for the ecological, economic and safety assessment of dam removal. The results of the proposed 7-step process show that Chijiawan Dam #1 is a priority spot for improvement. This finding is in agreement with prior research. This consistency over the years shows the process has a certain level of predictability. The application of the 7-step process would help decision-makers to master the whole dam removal process.為評估台灣現存壩體之改善效益並降低改善後可能導致安全及生態等層面衝擊，本研究建立適用台 灣壩體改善決策之七步驟流程，選取台灣中部武陵地區之有勝溪一號壩、七家灣溪一號壩、七家灣溪三號壩 及七家灣溪四號壩為對象，蒐集生態環境監測與壩體現況調查資料，以安全、生態及經濟面向評估其壩體改 善效益。評估結果為七家灣溪一號壩為優先改善，與前人研究一致，顯示流程具有一定可預期性，並有助決 策者對於整體壩體改善作業流程之掌握