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Numerical Simulation and Analysis of the River Estuary Sediment
|Contributors: ||NTOU:Department of Harbor and River Engineering|
Coastal sediment transportation;Estuarine sediment transportation;Coastal morphology;Climate change
|Issue Date: ||2013-10-07T02:25:48Z
|Abstract: ||摘要:本計畫擬針對河口海岸範圍的地形變遷機制進行研究，建立現場調查及數值模擬的 研究流程，分析河川流量、波浪、近岸流及潮汐等各項營力對海岸地形變遷影響的權重， 最後模擬氣候變遷的情境下，河口海岸的變遷趨勢以及溢淹範圍，以提出對此敏感區位 的管理對策及治理措施。 本計畫擬針對河口海岸範圍的地形變遷機制進行研究。藉著現場調查及數值模擬分 析河川流量、波浪、近岸流及潮汐等各項營力對海岸地形變遷影響的權重。最後在氣候 變遷的情境下，模擬河口海岸的變遷趨勢以及溢淹範圍，以提出對此敏感區位的管理對 策及治理措施。 由於這個範圍動力機制異常複雜，過去相關研究不論以現場調查或是數值模擬進行 分析時，常將河川及海岸輸沙分為兩個領域處理，或是以忽略部份營力(如波浪)的方式 簡化分析方法。然而，台灣河川常於颱洪時期的洪流夾帶著豐沛輸沙，在流進海域後， 伴隨著強大的波浪能量及近岸流，常於一次性的事件，即改變了河口海岸範圍整體的型 態。因此，在研究這個範圍的海岸地形變遷，需結合前述兩領域同時將各營力納入考量， 才可得到較全面的評估結果。本計畫在數值模擬部份擬先將「海岸輸沙模式」及「河口 輸沙模式」分開處理，再以線性疊加的方式進行綜合評估，並與實測之地形侵淤結果比 較，以確認整個研究流程的正確及可行性。 現場調查部份，擬於颱洪時期，建立可行之調查方法，監測河川流量、水位及懸浮 質濃度以做為數值模擬河川輸沙的源流(source)的動力邊界。整體計畫結合現場調查與數 值模擬，相互彌補其不足，以較完整之方法，分析河口輸沙對海岸地形變遷之影響機制。|
abstract:The proposed study is aimed at integrating results of numerical simulation and field measurement to analyze the mechanism of the sediment transport around estuary to facilitate future management decisions. The effect of the waves, wave-induced currents, tidal currents, and river discharges are all taken into consideration. The morphology of an estuary is the result of both marine and fluvial processes. The hydrodynamics of this region are complicated by flows inland and coastal flows which vary both in time and space. Due to complexity of the hydrodynamics in this regime, researchers have often treated sediment transports in the river and in coastal areas independently, and some important driving forces were also neglected to simplify the numerical scheme. However, Taiwan often suffers typhoon invasions in the summer and autumn. With typhoons approaching, flows in estuary are dominated by strong wave activities, combined with large amount of discharge from the river. It is believed that these two factors can play pivotal roles in estuarine sediment transport and morphodynamics, and should be addressed together. In this project, sediment transportations in coastal and river are modelled separately at first. Assuming a linear dependency, the two results are combined through addition. In the second, the two results are combined through addition under the simplifying assumption of linear dependency. Finally, numerical results are compared with field measurements for the assessments of the model. Field measurements of flow discharge and the suspended load during typhoon are also included in this project. It is intended to derive a relationship between discharge and suspended load that can be used as boundary conditions for further simulation. Once a methodology to model coastal evolution had been set up, it will be very helpful for integrated coastal management under the climate change scenario.
|Appears in Collections:||[河海工程學系] 研究計畫|
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