湍流模擬實驗之水面與底床觀測

Boulder and water surface topography in steep torrent experiment

于芃(Peng Yu)

指導教授 ： 卡艾瑋

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01223

摘要

本研究目的是以南投之溪頭森林教育園區神木溪為目標，探討梯狀潭之形成與穩定性。分析方法是利用閃光同步攝影技術及三維成像軟體紀錄實驗之水面與底床地形。實驗分為兩個部分:定床實驗是以現地調查資料製作神木溪1/25縮尺模型，並將水文分析得到的溪頭洪水流量以福祿數轉換後作為洪水事件提供給模型，進而觀察洪水溢淹範圍並與現地比較。另外，本研究利用水尺量測數據與實驗分析結果相互比較，證明閃光同步攝影確實可以應用於水面觀測；動床實驗目標則是用實驗模擬小尺度之梯狀潭河床並探討其形成過程與穩定性。本團隊從現地帶回兩種不同大小之卵石，並設計4種比例放入渠道作為底床，再提供3種不同流量之洪水事件以觀察梯狀潭的形成。實驗結果顯示當河床與特定流量逐漸達成平衡時，只有供給更大的洪水事件才會讓河川形貌繼續發展，但發展到最後仍會趨於穩定。在本實驗之案例中，當小卵石總體積為大卵石總體積之7倍時，梯狀潭的形貌會最顯著。

關鍵字

梯狀潭 ； 攝影測量 ； 神木溪 ； 水面觀測 ； 同步攝影

並列摘要

Step pool is a kind of channel morphology of steep mountain streams which is similar to stairs in the bed of the stream. In this thesis we use field survey data and laboratory experiment to investigate the step pool morphology of Shen-Mu Torrent, Central Taiwan, including its formation and current degree of stability. Digital photogrammetry using flash-synchronized multiple views is used to experimental water surfaces in addition to be topography. We conduct experiment in both rigid bed and mobile bed conditions. In rigid bed model experiment, we built a 1/25 scale model of Shen-Mu river and supplied a 50-year flood to determine the flood surface and check photogrammetry measurements against pin gage data. The results of this experiment demonstrate that photogrammetry can be used for water surface observations. The objective of mobile bed experiment is to investigate the formation and stability of step pool topography. We design three discharges and five cases with different particle mixing ratio. The results show that channel bed will evolve when subject to a record discharge, but gradually become stable to floods of this and lower magnitudes. Among the five mixing cases, the clearest step pool morphology is obtained when the volume of small particles is 7 times the volume of large particles.

並列關鍵字

step pool ； photogrammetry ； Shen-Mu Torrent ； water surface observation ； flash-synchronized multiple views

參考文獻

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Comiti, F., D. Cadol, and E. Wohl (2009), “Flow regimes, bed morphology, and flow resistance in self-formed step-pool channels.” Water Resour. Res., 45, W04424.

Duckson, D.W., and L.J. Duckson (1995), “Morphology of Bedrock Step Poo Systems.” Water Resources Bulletin, AWRA, 31(1), 43-51.

Fonstad, M.A., J.T. Dietrich, B.C. Courville, J.L. Jensen, and P.E. Carbonneau. (2013), “Topographic structure from motion: a new development in photogrammetric measurement.” Earth Surf. Process. Landforms ,38, 421-430.