Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/33436
標題: Flume Experiment of Mountain Step-Pools Streams
山區河流階梯-深潭之渠槽實驗研究
作者: Tsou, Ching-Ying
鄒青穎
關鍵字: step-pool;階梯-深潭;mountain streams;channel stability;山區河流;河床穩定
出版社: 水土保持學系
摘要: 
Step-pools are fundamental components of channel morphology in mountain streams. Knowing the formation of step-pools will contribute to increasing the understanding of mountain streams morphology. Because of attention to river restoration more bio-engineering structures such as step-pools are adopted. But the mechanisms of river flow are complicated, in-stream structures can never be built directly. Bio-engineering structures should based on the river morphology. It is important to understand the formation process of step-pools.
The formation process of step-pools under the conditions of sediment mixtures, different discharges, channel bed slopes(2-7) are studied experimentally in laboratory. On this basis, the mechanisms of step-pools are further investigated. We find some results as follows, many varied step-pools forms are observed which develop in conditions where the largest floods are just capable of transporting the largest debris. Those will tend to form steps acting as keystones retaining smaller debris. Eight types of steps are classified according to arrangement of sediments in this research. Dimensional analysis and the index namely Wsp coefficient is proposed to evaluate the relation between the formation of step-pools and the variation of sediment discharge. The expression is established according to the experimental data which can illustrate the step-pools as adjust their profile vertically, increase the channel-bed roughness and decrease the channel slope to minimize the time rate of expenditure of potential energy. These have effect on decreasing the sediment discharge of stream flow and stabilization of the channel-bed.

階梯-深潭為山區河流常見之地貌,透過階梯-深潭的瞭解,將有助於增加對山區河床演變的認識;隨著人們對河流生態棲地復育之重視,採用生態工法進行河道治理的案例日益增多,亦常見運用砌石工法排列近似階梯-深潭之固床工進行整治,由於河流作用機制複雜,任何工法仍須順應河流自然調整機制,才能達到河流棲地復育之目的,故對瞭解階梯-深潭此一河床演變過程實為一不可或缺之課題。本研究採用混合泥砂粒徑,以渠槽實驗配合不同流量及渠槽坡度(2°-7°)方式進行清水流沖刷之動床實驗,藉此觀察床形演變之現象,並著重於階梯-深潭形成現象之定性描述。研究結果顯示,渠床呈現多樣化之階梯-深潭形式,與常見之肋骨狀橫向連續排列的階梯-深潭結構不同,且發現階梯的形成與關鍵性顆粒存在與否有關,本研究亦由顆粒排列方式將階梯分為八種形式,並藉由因次分析與階梯-深潭發育權重Wsp之定義,分析階梯-深潭的發育與輸砂率變化之關係,進而建立一關係式,從中說明當河流趨於動態平衡時,透過幾何形態的調節將使能耗率趨小,而階梯-深潭的發育則為水流縱向調整之結果;實驗顯示床面粗化將使渠床糙率增大,此外,階梯-深潭的發育增加了水流流路而減緩渠床坡降,兩者作用下皆使水流能耗率減小,進而降低水流輸砂的能力,達到穩定河床之作用。
URI: http://hdl.handle.net/11455/33436
Appears in Collections:水土保持學系

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