臺灣博碩士論文加值系統

海底辮狀河道常出現在海底沖積扇及深海平原，主要成因是濁流通過海底峽谷後，夾帶泥砂堆積形成複數砂洲及海底河道。過去對於辮狀河道的機制多來自陸上之辮狀河川，僅有極少數仔細探究海底辮狀河道之文獻，並提出流量及坡度組合會強烈影響其形貌。因此本研究欲透過小尺度之物理模型實驗，探討河寬及水流功率對影海底辮狀河道之影響。本研究之實驗使用飽和鹽水作為異重流，混合樹脂砂後模擬濁流，使海底辮狀河道自行產生不受限制之河道寬度。透過每五秒一次的高解析度間隔攝影，詳實紀錄海底地形隨時間之演化過程，並使用雷射切頁掃描技術重建各階段之數值高程模型。
以異重流流量、供砂量及底床坡度為操縱變因，成功沖出海下辮狀河到的形貌。實驗中定性觀察的部分，可看到異重流夾帶泥砂於河道內運移，產生加積作用並出現許多河中砂洲，砂洲前後分別有分流及匯流的情況，也可看到異重流自由發展河寬的過程，這些形貌都與陸上辮狀河道之流動特色相仿；定量分析顯示，辮狀指數於不同河寬下，仍能適當的反應水下河道之辮狀程度。流量較大及坡度較陡的實驗，會造成河道內擁有更均勻的堆積。研究中各項辮狀指數與無因次水流功率，相較於前人水上或水下的實驗呈低相關性，推測是因為並未考慮起始河寬及供砂量之影響，未來應可加入考慮此兩項因素。

Submarine braided channels produced by turbidity currents have multiple bars and channels, similarly to the morphology of subaerial braided rivers. How-ever, we still have limited understanding for the mechanism of submarine braided channels. In this study, we used physical experiment to study the effects of limited channel width and stream power on the submarine braided channels. For the ex-periments, plastic sand was used to simulate deep-sea sediment, and saturated brine was used as the dense underflow. Our results show that total braiding inten-sity (BIT) and active braiding intensity (BIA) in all runs approach to a stable value and reflect the degree of braiding. Furthermore, the ratio of braiding intensity (BIR) produced in this study are higher than that of Lai et al., [2017]. Finally, we find that the braiding intensities in our study have low correlation with dimen-sionless power. The possible reason may due to the absence of considering the effects of sediment discharge and initial channel width.

目錄
致謝 I
摘要 II
目錄 XIV
表目錄 XVI
圖目錄 XVII
第一章 緒論 1
第二章 實驗配置及影像處理 7
2-1實驗配置 7
2-1-1材料選擇 15
2-1-2實驗組數參數 16
2-1-3實驗流程 18
2-2數位影像處理 20
2-2-1校正 20
2-2-2影像處理 22
2-2-3數值高程模型 25
2-3問題與解決 28
第三章 結果與討論 30
3-1現象觀察與描述 31
3-2實驗照片之影像分析 49
3-2-1正射影像圖(orthophoto) 49
3-3數值高程模型之地形分析 61
3-3-1 光源陰影圖 (hillshaded DEM) 61
3-3-2 高程差異變化 67
3-3-3 橫斷面變化 72
3-3-4 縱剖面分析 75
3-4辮狀指數 77
3-4-1基本定義 77
3-4-2各項辮狀指數 80
3-4-3動態河道自動化分析 83
3-5穩定性理論預測水下辮狀河道 88
3-6 水流功率與辮狀指數之關係 92
第四章 結論與建議 95
參考文獻 98

參考文獻
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