可靠的設計海況是颱風頻繁地區進行海岸與離岸工程規劃的重要基礎。傳統做法多以單變量極值分析推估特定重現期的顯著波高，再藉由經驗公式估計對應的週期；然而這種方式無法反映波高與週期之間的聯合機率關係，也容易產生不符合波浪物理特性的設計組合。為改善上述問題，本研究以長期浮標觀測為基礎，建立一套結合物理限制與工程反應評估的颱風設計海況分析架構。
本研究蒐集臺灣周邊十座長期波浪浮標資料，涵蓋東北部、東部、南部、西南部及臺灣海峽沿岸，並分別以年最大值與颱風事件兩種方式建立極值樣本。分析上先建立波高與週期的邊際極值分布，再以聯合機率模型描述兩者的相依關係，據以建構不同重現期的環境等值線。為避免統計外推產生不合理的波浪組合，接著納入波浪尖銳度與水深限制碎波條件，篩除不具物理可行性的設計海況。在各測站完成物理篩選後的五十年重現期颱風環境等值線上，選取最大波高、最大週期與最大波浪能量指標三個代表性設計點，並以非線性淺化與碎波公式將其由離岸傳遞至近岸；再於相同的堤趾水深與結構條件下，分別評估各設計點對波浪越波與海堤護面穩定性的影響。
結果顯示，臺灣周邊的颱風設計海況呈現明顯的區域差異。主要設計波向隨海岸位置與地理環境系統性改變，波高與週期的聯合極值特性也在面向太平洋的開放海岸、南部過渡區域與臺灣海峽測站之間呈現不同型態。其中蘇澳與鵝鑾鼻受長週期颱風波影響較為顯著，新竹與澎湖的週期分布則較集中，環境等值線主要由波高主導。工程應用方面則發現，沒有任何單一設計點能同時支配波浪越波與海堤穩定性：在本研究設定的淺水堤趾條件下，水深限制碎波使各設計點傳遞至近岸後波高趨於一致，週期因而成為造成工程反應差異的主要因素。整體而言，最大週期設計點多半產生較大的越波量，最大波高設計點則對海堤護面塊石尺寸的需求較高。此差異反映不同工程公式對週期的敏感度並不一致，因此何者為控制設計海況會隨所評估的工程反應而改變。
綜上所述，設計海況不宜僅以單一波高搭配經驗週期表示，而應自符合物理條件的聯合環境等值線中選取，並依實際工程反應加以判斷。由於本研究在各測站採用一致的結構條件進行比較，所得的控制設計點主要反映統一假設下的初步篩選結果，而非可直接套用於所有工程的通則。整體而言，本研究提出的方法可作為兼顧區域差異、物理合理性與工程應用意義的臺灣颱風設計海況分析基礎。

Reliable design sea states are essential for coastal and offshore engineering in typhoon-prone regions. Conventional practice estimates a univariate return-level Hs (spectral significant wave height) and assigns an associated Tm (spectral mean zero-crossing wave period) using empirical Hs–Tm relationships, but this cannot represent the joint probability structure of Hs and Tm and may produce design combinations that are not physically admissible. This dissertation develops a buoy-based, physically screened, response-oriented framework for characterizing typhoon-driven design sea states around Taiwan.
Long-term wave buoy records from ten locations around Taiwan, spanning the northeastern, eastern, southern, southwestern, and Taiwan Strait coasts, are analyzed using both annual-maximum (AM) and typhoon-event (TY) sampling. Marginal extreme-value distributions and copula-based dependence models are fitted to construct inverse first-order reliability method (IFORM) environmental contours, which are then screened for physical feasibility using wave-steepness and depth-limited breaking constraints.
From each physically admissible 50-year TY environmental contour, three representative design points—MaxHs, MaxTm, and MaxHs²Tm—are selected and transformed shoreward using the Goda nonlinear shoaling and breaking formulation. Their engineering implications are then evaluated through wave overtopping and dike-stability calculations at a common design toe depth.
The results show that typhoon-driven design sea states around Taiwan are strongly site dependent: dominant design wave directions rotate systematically with coastal setting, and the joint Hs–Tm tail structure differs between exposed Pacific-facing coasts, southern transition areas, and Taiwan Strait sites, with long-period typhoon influence most pronounced at Suao and Eluanbi and height-dominated, compact contours at Hsinchu and Penghu. No single contour-based design point governs both the overtopping and dike-stability responses: at the shallow design toe depth used for this screening comparison, depth-limited breaking compresses the transformed Hs of the three candidates to a nearly common value at every site, leaving wave period as the deciding factor. As a result, MaxTm typically governs wave overtopping, whereas MaxHs typically governs dike armor stability, reflecting the opposite sensitivity of the two response formulas to wave period once the waves reach the surging regime.
These findings indicate that design sea states should be selected from physically admissible joint environmental contours and interpreted according to the engineering response of interest, rather than a single empirical Hs–Tm pair; because the reported governing design points reflect one fixed structural configuration applied uniformly across all sites, they represent a screening-level, assumption-dependent comparison rather than a universally applicable design rule. The proposed framework nonetheless provides a regionally differentiated and physically consistent basis for typhoon-driven coastal design sea states around Taiwan.

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