近年來大規模海嘯（Tsunami）事件頻傳，使世人開始關注海嘯所帶來之破壞力以及其科學與工程上之議題。在海嘯減災上，海岸植生消能法（Dissipation by the Vegetation）是重要且環保之手段之一。台灣地處於太平洋火環上，有遭受海嘯攻擊之危機，因此海岸植生對台灣海嘯災害之影響將是本文探討之重點。本文第一階段將以與海嘯湧潮（Tsunami Bore）有相似行為之潰壩湧潮（Dam-Break Bore）為研究主軸，以三維LES-VOF紊流數值模式進行模擬，並以實驗數據進行驗證與分析，以探討湧潮與複雜柱狀陣列結構物之交互作用。結果發現本三維數值模式能準確預測湧潮與結構物撞擊後所產生之飛濺碎波以及消能行為。然而三維數值模擬相當耗時，因此本研究第二階段接續發展孔隙介質模式，希望將複雜但又均勻之植生結構物以孔隙介質取代。本文分析不同孔隙介質阻力模式於不同孔隙率之適用性，並設計實驗以供數值模式驗證，以發展適合之孔隙介質模式。結果發現海岸植生之孔隙阻力模式中，重要參數為孔隙率、流速與阻力係數，本研究據此發展適合大孔隙介質之阻力模式。模擬結果與實驗數據比對有相當優良之一致性。本研究於最後階段進行台灣墾丁地區之海岸植生調查，並結合真實地形進行數值模擬，探討墾丁地區海岸植生對於馬尼拉海溝潛在大規模海嘯之消散作用。結果發現植生孔隙介質於海嘯上溯（Run - Up）高度、湧潮深入陸地之距離與湧潮退回海面之回溯（Run - Down）皆有影響。由計算出之流速分布圖可知，模式所設置之孔隙樹林介質確有阻滯水體而削弱海嘯能量之效果。比較無孔隙介質、孔隙率0.95之真實樹林介質與孔隙率0.75之自然樹林介質結果，將不同案例之結果進行比對並以無樹林案例為基準，當樹林較稀疏時（孔隙率=0.95），將會造成5.36 %上溯高度減少之消散效果，而當樹林自然生長時（孔隙率=0.75），將可減少23.21 %之上溯高度，由於距野外調查當地樹林密度所估計之孔隙率約為0.95，由模擬之結果可推斷目前之樹林情形相較於無樹林之情形，約可於海嘯事件中產生5.36 %之上溯高度消散效果。Due to the frequent large-scale Tsunami events recently, attention has been drawn to the destruction brought by these events and the relevant scientific and engineering issues. Dissipation induced by coastal vegetation is an important and environment-friendly method for reducing the hazard caused by tsunamis. Due to locating on the Pacific ring of fire, Taiwan is under the threat of tsunami events. The present study focuses energy reduction caused by the coastal vegetation to the tsunami events in Taiwan. At first, the present study focuses on describing the bore behavior of dam-break cases. The experimental data are used to validate the numerical model, LES-VOF model. The interaction between a bore and a complex pillar array is presented. We found that the LES-VOF model is capable of precisely predicting breaking waves and energy dissipation that occur after the impact of the bore to the structure.However, as considering the time-consuming issue on the 3D simulation, we develop a porous media model that aims at replacing the complex yet uniform vegetation structure with a porous structure. The applicability of different porous drag models with different porosities is analyzed, and validated with the experimental data. It is found that the simulation results and the experimental data are highly consistent. At the last part of this study is to investigate the effect of energy caused by vegetation in Kenting area. A real-bathymetry numerical simulation is conducted, and a tsunami scenario which oriented from Manila trench is considered. The result shows that the dense vegetation will have significant effect on the maximum run-up height, inundation distance, flow velocity and maximum run-down. In this case, two porosities of the filed vegetation are considered. The result shows that run-up height of porosity 0.95 is increased by 5.36%, and porosity 0.75 is increased by 23.21%.
