洪水漫過主深槽而淹沒佈滿植生之洪水平原時，植生覆蓋會增加糙度而遲緩流速，能減少土壤沖刷達保護底床及固土護岸之功能，也具維護生態及景觀遊憩之價值，但也因而將增加主流深槽流量，影響深槽之沖淤現象，因而需要分析主流深槽流量。
本文旨在研究如同深槽與洪水平原植生情況不同之部分植渠道之水理現象，以分析無植生之主流區流量。本研究基於一維定量緩變速流理論推導浸沒之部分植生矩形斷渠流之基本方程式並設計水工試驗。本研究對於植生主要考慮莖幹之影響，並以硬性圓柱群模擬植生莖幹分佈。
由實驗結果可看出:
1. 當水流進入植生段時，各橫斷面之植生區與主流區(無植生)之水位可視為相等，故可假設橫斷面水面為水平，以推導動量方程式及能量方程式。
2. 植生段之主流區(無植生)及植生區之下層(植生內部)及上層(植生頂部以上)之流速明顯不同。應用實驗資料可得出動能修正係數公式及動量修正係數公式。
( 4-12 )
( 4-13 )
3. 植生段上游流速分佈接近均勻，進入植生段入口段之主流區及植生區下層之流量為沿渠增之變積流現象，植生段下層則為沿渠減少之變積流現象，而後漸趨穩定，接近出口時，主流區流量為漸減之變積流現象。由實驗數據之分析可得主流區與全斷面流量關係可以 ( 4-3 )表示。 ( 4-3 )

4. 基於一維定量緩變速渠流之能量坡度與摩擦坡度相等之假設，本研究推導出曼寧糙率係數可由植生莖幹曳引力係數、渠床及岸壁摩擦係數計算之公式，並由實驗資料之分析，顯示頗為符合，誤差在 以內:

( 2-37 )
( 2-40 )
5. 植生密度足夠大時，部分植生段對水流會造成過度束縮，以至主流區形成超臨界流，並因尾水為亞臨界流而出現水躍現象。依據實驗資料比較，發生水躍之判別式為 ( 4-1 )式:
( 4-1 )
研究依據所推導之全斷面能量方程式、曼寧糙率係數公式及動能修正係數公式、主流區流量比公式等，發展以一維緩變速流標準步驟法為基礎之主流區流量演算法，可用於計算主流區流量。

When the flood occurs and water flows above the vegetation in the floodplain, the vegetation can increase roughness and retard the flow velocity so that this can prevent bed erosion and enhance bank stability. In addition, it also maintains ecological condition and increases the value of landscaping entertainment. However, the existence of plants will increase the capacity of the main zone and affect on the sediment transport. Hence, the analysis of the discharge in the mainstream is imperative.
The main objective of the present study is to investigate the hydraulic phenomenon of the partly-vegetated channels and the flow capacity of the main zone (non-vegetated zone). In the steady gradually-varied flow, we could derive governing equations of the partly-vegetated open channels under a submerged situation and then design the laboratory experiment. To examine the influence of stems on the experiment, stiff cylinders were used to simulate the stems of the vegetation.
Based on our research, some crucial results can be drawn:
1. When the flow moves into vegetated channels, it is found that the stages of each cross section in the vegetated and non-vegetated (main channel) zones are almost the same. By assuming the water level to be the horizontal, the momentum and energy equations were obtained mathematically.
2. The velocity distributions were obviously different between the main channel and vegetated channels (i.e. upper and inner the vegetation). After anallyzing the experimental data, we obtained correction factors ( and ) for the formulas of momentum and energy.
( 4-12 )
( 4-13 )
3. In the upstream of the vegetated channels, the velocity distribution is closed to be uniform. It was the spatially-varied flow when the water flows into the vegetated channels and the discharge was increased from the upstream to the downstream, including the non-vegetated zone and inside the vegetation; it was decreased along the channels within the vegetation. Around the exit of the vegetated channels, the discharge of the main zone is decreased with the spatially varied condition. Based on the analysis of the experimental date, we could get the relation between the discharge of the main zone and all cross sections, which can be expressed by (4-3).
( 4-3 )
4. Based on the assumption that the energy slope was equal to the friction slope in the one- dimension steady gradually-varied flow, we derived the expression of the Manning roughness coefficient from the vegetation steam drag coefficient and friction coefficients of bed and wall. The application of the Manning roughness coefficient was verified to be very well from experiment data, which is within the 10% error.

( 2-37 )
( 2-40 )
5. It was over contraction in the partly-vegetated channels if the density of the vegetation is great enough, and then the supercritical flow can be observed in the main zone. The hydraulic jump occurs at the end of the channel, because the flow condition changes from the supercritical flow to the subcritical flow. The discriminant of hydraulic jump could be compared with experimental data, which is express by (4-1):
( 4-1 )
Based on the formulas of the energy equation, Manning rough coefficient, the energy correction factor, as well as the ratio of the discharge within the main zone and all cross sections, the discharge of the main zone can be determined in order to get the capacity of the main zone following the standard step method under the one-dimensional steady gradually varied flow.

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