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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/42958

Title: 河川輸砂對臺東卑南溪口海岸地形變遷之影響
The Effect of Estuarine Sediment on the Coastal Morphology of the Beinan River in Taitung, Eastern Taiwan
Authors: Hsuan-Ying Huang
黃暄穎
Contributors: NTOU:Department of Harbor and River Engineering
國立臺灣海洋大學:河海工程學系
Keywords: MIKE21數值模擬;海岸地形變遷;臺東卑南溪;河川輸砂
Numerical Model;Coastal Topography Change;Beinan River;Sediment Transport
Date: 2015
Issue Date: 2017-05-24T08:40:06Z
Abstract: 臺灣是位於環太平洋西側之海島型國家。西鄰臺灣海峽水深大約-200公尺,東邊太平洋大洋區水深達-5000公尺以上。因臺灣位於颱風好發地區,且東部海岸在大陸棚較窄及坡度較陡的情況下,使外海波浪能量未經大量消減即侵襲至近岸,使部分岸段在颱風過後常呈現侵蝕的趨勢。然於河口附近,颱洪期間所帶來的大量土砂,又使得部分岸段得以獲得砂源補助,呈現動態平衡。 本研究主要以臺東卑南溪河口與鄰近海岸為例,分析其地形變遷之機制。由歷史調查資料顯示,研究區域除受到颱風波浪營力影響外,復受到卑南溪河川輸砂影響,於河口附近提供砂源補助。然現場調查結果僅顯示海岸地形變化,無法釐清波、流及河川輸砂等動力條件交互作用等海洋營力對海岸地形變遷影響之權重,因此本研究透過數值模式的輔助,藉以研判研究區域受颱風影響的近岸水動力機制,以及卑南溪河川輸砂造成的海岸地形變遷,以做為後續海岸侵蝕防制及管理參考依據。考量研究區域動力機制,數值模式需能整合波浪、潮流、波生流(wave-induced currents)和輸砂等現象,故本研究選擇丹麥DHI的MIKE21模擬軟體進行案例模擬,以瞭解極值事件下各項營力對海岸地形變遷影響之權重。 本研究利用MIKE21數值軟體,模擬颱風事件研究範圍內的水動力及輸砂機制。首先以颱風資料建立螺旋風場,模擬颱風場作用下而形成之波浪場,再將波浪場之波浪輻射應力、潮汐及河道流量套入潮流模式中,模擬研究範圍的水動力情況,最後模擬受波潮流影響下的砂體傳輸運動,建立一套足以呈現卑南溪河口鄰近海岸複雜的漂砂運動模型。 本研究選擇的案例包括:2005年之海棠、泰利及龍王颱風。三場颱風皆屬強烈颱風,但所帶來的雨量則極不相同。海棠颱風屬長時間降雨,累積雨量為三場最大;泰利颱風屬集中降雨形態;龍王颱風則幾乎無降雨。經由模擬成果發現,影響河口地形侵淤主要為河川輸砂供給砂源大小,流出河口後再受到海洋營力作用而影響分布。而鄰近岸段則主要受海洋營力影響地形變遷。比較實際地形調查與模擬成果發現,海棠與泰利颱風影響期間,地形受到河川輸砂影響,河口區域侵淤為北淤南侵,可得知近岸流呈向南流的情形;龍王颱風期間,因河川幾乎無輸砂使河口地形呈現侵蝕的狀態。另外,因臺東地形陡峭的關係,當流速太大時,河道中的懸浮載會直接被帶到深海區,無法供給鄰近海岸作為砂源補助。
Taiwan is hit by typhoon almost every summer. There is narrow conshelf and steep slope eastern Taiwan. Deep water wave energy without dissipating that is up to coastal and cause shoreline erosion. In addition, the sediment transport resulted from the river flow so that it can supply sediment to coastal. Both of the results, coastal zone’s accretion and erosion of sediment become balance. The study area is focus on Beinan River and near sea area. This project combined with topographic survey data and numerical model to figure out the effect of Beinan River. According to the survey results are found out that Beinan River is the main source of coastal sediment during typhoon attacks, its mechanisms of influence that the change of estuarine coastal morphology in typhoon is important. In order to clear understand the ocean and river force's influence of changes in coastal topography. This study explored the forces uses DHI MIKE21 as research tools. All the simulation process consist of five modules: Spectral Waves Module (SW), Parabolic Mild-Slope Wave Module (PMS), Hydrodynamic Module (HD), Sand Transport Module (ST), and Particle Analysis Module(PA). There are three cases in this study: Haitang typhoon, Talim typhoon and Longwang typhoon in summer 2005. There are different characteristics. Haitang typhoon is the mainly event that topography changed depositing in north estuary. Talim typhoon is short-term rainfall causing accretion in north estuary. Longwang typhoon is almost no rainfall and no sediment transport causing erosion in estuary. Overall, topographic change is deposit in north estuary and erosion in south estuary in summer 2005. That is persuasive to prove the main affect of the short-term coastal topography change is by Beinan River sediment transport in rainfall typhoon season. The result found that the general direction of the net longshore sediment transport by wave and current is from north to south. In the estuary zone main sediment supplied is from river transport, after into the sea is attacked by wave and current interaction then cause topographic change.
URI: http://ethesys.lib.ntou.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=G0010252045.id
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/42958
Appears in Collections:[河海工程學系] 博碩士論文

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