臺灣西南沿海的七股潟湖為典型的潟湖沙洲系統，兼具生態保育、防洪保護與漁業資源等多重功能，受到波浪、潮汐與季風流場等自然動力影響，近年來該區域沙洲持續出現侵蝕現象，潟湖內也有逐漸淤積陸化的趨勢，威脅其自然功能與周邊聚落安全。為了探討該區域之水動力特性與沉積物輸移行為，進而了解沙洲與潟湖歷年來的變化原因，並評估設置離岸堤是否可以有效緩解沙洲侵蝕與潟湖淤積的問題，本研究應用 Delft3D 數值模式，模擬 2023 年七股沿海與潟湖區域的水動力與地形變遷過程，並結合實測與文獻資料進行驗證，建立具有準確性與應用性的數值模型，透過模擬結果分析不同季節下的海流、波浪與漂砂特性，探討沙洲侵蝕與潟湖淤積的動態機制，並且評估離岸堤設置對地貌變化與潟湖水文環境的影響，以提供後續海岸防護策略之參考依據。
根據研究結果顯示，七股沿海水動力受季風主導，夏季西南季風盛行時，海流向北流動，波浪自西南方向近垂直入射造成沙洲外側強烈侵蝕；冬季東北季風盛行，海流改為南下，波浪自西北斜向入射，同樣集中波能於沙洲外緣，延續侵蝕趨勢。漂砂模擬顯示沉積物流向與流場一致，兩季之間方向相反，並在外海區域呈現西南側侵蝕、東北側堆積的特徵，說明風、流、波三者的耦合作用驅動沉積物流動與地形變遷。潟湖的三個主要潮口（青山港與網仔寮沙洲間，以及網仔寮與頂頭額沙洲間兩處）為海水進出的主要通道，受潮汐驅動下形成水位差與潮流收縮效應，導致潮口流速明顯增加並產生侵蝕，並將沖刷所夾帶的沉積物堆積於潟湖內沙洲內測，長期可能導致嚴重淤積與水體容量下降，進一步影響生態與排水功能。網仔寮沙洲呈現向南與向東（內陸）遷移的趨勢，反映出波浪與潮流作用下沉積物由海向潟湖推進的演變機制。
在離岸堤防護效益評估上，模擬七座與沙洲平行之200公尺離岸堤，研究顯示，離岸堤雖然可以降低堤後波能並產生局部堆積效果，但無法有效改變海流傳遞方向與漂砂路徑，導致沙洲整體侵蝕仍持續發生。顯示目前的防護結構設計，在整體沙洲的保護效益上有限，須進一步調整堤體排列或搭配其他工法與結構物，來提升沙洲與潟湖的保護效果。

This study uses the Delft3D numerical modeling system to simulate the hydrodynamic and sediment transport characteristics of the coastal and lagoonal region of Chiku, Tainan, during the year 2023. The research further investigates the influence of offshore breakwater installation on barrier island stability and the lagoon’s hydrodynamic environment. As a critical wetland and ecological habitat in southwestern Taiwan, the Chiku Lagoon and its associated barrier island system have long been subjected to morphological changes and erosion driven by wave action, tidal currents, and monsoonal forces. A two-dimensional hydrodynamic model was developed to simulate seasonal variations in wave and current fields, which was then validated against field observations including water level, significant wave height, current velocity, and direction. The results demonstrate strong agreement with measured data, indicating the model’s high accuracy and reliability in reproducing the local hydrodynamic conditions.
The study also simulates sediment transport and morphological evolution, revealing a pronounced pattern of seasonal alternation between erosion and deposition along the coastal barrier islands, corresponding to the prevailing southwest and northeast monsoons. Wave action was identified as the primary erosive force, while currents influenced the direction and extent of sediment redistribution, with both processes jointly driving morphological changes. Analysis of the three main tidal inlets indicated that the channel between Qingshan Port and Wangzailiao Sandbar serves as the dominant water exchange pathway, exhibiting a net inflow that may contribute to sediment accumulation within the lagoon. Simulations of offshore breakwater configurations suggest that while the structures can locally reduce wave energy and promote deposition, their effectiveness is limited due to excessive offshore placement and large spacing between units. These factors hinder their capacity to prevent large-scale erosion along the outer sandbar. Future coastal protection strategies should therefore consider reconfiguring the orientation and spacing of breakwaters, potentially in combination with other engineering approaches.

徐如娟、黃清和、陳建志、曾森煌、林秀美、林東廷、蔡立宏（2006），生態型海岸保護工法研究(1/4)，交通部運輸研究所運輸技術研究中心。
內政部營建署（2017），整體海岸管理計畫。
經濟部水利署（2016），海岸防護設施規劃設計手冊。
經濟部水利署（2020），臺南市一級海岸防護計畫。
吳盈志、劉景毅、黃煌煇 (2013) ，七股潟湖沙洲地形變遷之研究，海洋工程學刊，13:4 2013.12[民102.12] ， 367-391。
林俊全、鄭宏祺、黃光瀛（2013），七股潟湖沙洲地形變遷及保育策略之研究，國家公園學報論文選集-濕地保育篇，23(1):24-35。
吳銘志、鄭由聖、黃淑媚、楊孟學（2010），影響海岸型濕地生態環境健康度變化因子之研究，行政院國家科學委員會專題研究計畫成果報告。
薛煜達（2021），應用Delft3D模式探討石門水庫排淤對淡水河口地貌變遷之影響，國立臺灣大學碩士論文。
Almar, R., Castelle, B., Ruessink, B., Sénéchal, N., Bonneton, P., & Marieu, V. (2010). Two- and three-dimensional double-sandbar system behaviour under intense wave forcing and a meso–macro tidal range. Continental Shelf Research, 30(7), 781–792. https://doi.org/10.1016/j.csr.2010.02.001
Brakenhoff, L., Schrijvershof, R., Van Der Werf, J., Grasmeijer, B., Ruessink, G., & Van Der Vegt, M. (2020). From Ripples to Large-Scale Sand Transport: The Effects of Bedform-Related Roughness on hydrodynamics and sediment transport patterns in Delft3D. Journal of Marine Science and Engineering, 8(11), 892. https://doi.org/10.3390/jmse8110892
Chang, Y., Chu, K., & Chuang, L. Z. (2018). Sustainable coastal zone planning based on historical coastline changes: A model from case study in Tainan, Taiwan. Landscape and Urban Planning, 174, 24–32. https://doi.org/10.1016/j.landurbplan.2018.02.012
Chasten, M. A. (1993). Engineering design guidance for detached breakwaters as shoreline stabilization structures / by Monica A. Chasten . . . [et al.] ; prepared for U.S. Army Corps of Engineers. https://doi.org/10.5962/bhl.title.48264
Dean, R. G., & Dalrymple, R. A. (2001). Coastal Processes with Engineering Applications. https://doi.org/10.1017/cbo9780511754500
Dean, R. G., & Dalrymple, R. A. (2004). Coastal Processes with Engineering Applications. Cambridge University Press.
Deltares (2023). Simulation of Multi-dimensional Hydrodynamic Flows and Transport Phenomena, Including Sediments. User Manual Delft3D-FLOW. Delft, The Netherlands.
Deltares (2023). D-Morphology, 1D/2D/3D. User Manual Delft3D FM SUITE 2D3D. Delft, The Netherlands.
Deltares (2023). Computational Cores and User Interface. User Manual D-Flow Flexible Mesh. Delft, The Netherlands.
Deltares (2023). Simulation of short-crested waves with SWAN. User Manual D-Waves. Delft, The Netherlands.
Dora, G. U., Rasheed, K., & Kankara, R. (2018). Impact of seasonal monsoon on coastal weather condition: a case study at Vengurla, west coast of India. Indian Journal of Geo-Marine Sciences. http://nopr.niscair.res.in/bitstream/123456789/45445/1/IJMS%2047%2812%29%202382-2389.pdf
Fredsøe, J. (1984). Turbulent boundary layer in wave‐current motion. Journal of Hydraulic Engineering, 110(8), 1103–1120. https://doi.org/10.1061/(asce)0733-9429(1984)110:8(1103
Galappatti, G., & Vreugdenhil, C. B. (1985). A depth-integrated model for suspended sediment transport. Journal of Hydraulic Research, 23(4), 359–377. https://doi.org/10.1080/00221688509499345
Grunnet, N. M., Walstra, D. R., & Ruessink, B. (2004). Process-based modelling of a shoreface nourishment. Coastal Engineering, 51(7), 581–607. https://doi.org/10.1016/j.coastaleng.2004.07.016
Hasselmann, K., Barnett, T., Bouws, E., Carlson, H., Cartwright, D., Enke, K., Ewing, J., Gienapp, H., Hasselmann, D., Kruseman, P., Meerburg, A., Müller, P., Olbers, D., Richter, K., Sell, W., & Walden, H. (1973). Measurements of wind-wave growth and swell decay during the Joint North Sea Wave Project (JONSWAP). Ergänzungsheft Zur Deutschen Hydrographischen Zeitschrift, 12, 1–95. http://repository.tudelft.nl/assets/uuid:f204e188-13b9-49d8-a6dc-4fb7c20562fc/Jonswap-Hasselmann1973.pdf
Jan, S., Wang, J., Chern, C., & Chao, S. (2002). Seasonal variation of the circulation in the Taiwan Strait. Journal of Marine Systems, 35(3–4), 249–268. https://doi.org/10.1016/s0924-7963(02)00130-6
Jenkins, R. L., Smith, C. G., Passeri, D. L., & Ellis, A. M. (2024). Model Sensitivity Analysis for Coastal Morphodynamics: Investigating sediment parameters and bed composition in Delft3D. Journal of Marine Science and Engineering, 12(11), 2108. https://doi.org/10.3390/jmse12112108
Kuang, C., Han, X., Zhang, J., Zou, Q., & Dong, B. (2021). Morphodynamic Evolution of a Nourished Beach with Artificial Sandbars: Field Observations and Numerical Modeling. Journal of Marine Science and Engineering, 9(3), 245. https://doi.org/10.3390/jmse9030245
Lesser, G., Roelvink, J., Van Kester, J., & Stelling, G. (2004). Development and validation of a three-dimensional morphological model. Coastal Engineering, 51(8–9), 883–915. https://doi.org/10.1016/j.coastaleng.2004.07.014
Lesser, G. (2009). An approach to medium-term coastal morphological modelling. http://repository.tudelft.nl/assets/uuid:27a1ffa0-580e-4eae-907b-ce6f901e652e/PHD_THESIS_LESSER1.pdf
Longuet-Higgins, M. S., & Stewart, R. W. (1964). Radiation stresses in water waves; a physical discussion, with applications. Deep Sea Research and Oceanographic Abstracts, 11(4), 529-562.
Masselink, G., Austin, M., Scott, T., Poate, T., & Russell, P. (2014). Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach. Geomorphology, 226, 76–93. https://doi.org/10.1016/j.geomorph.2014.07.025
Mendes, J., Ruela, R., Picado, A., Pinheiro, J. P., Ribeiro, A. S., Pereira, H., & Dias, J. M. (2021). Modeling dynamic processes of Mondego Estuary and Óbidos Lagoon using Delft3D. Journal of Marine Science and Engineering, 9(1), 91. https://doi.org/10.3390/jmse9010091
Pan, S., & Fairbairn, G. (2016). Impacts of submerged breakwaters on nearshore sediment transport. Journal of Coastal Research, 75(sp1), 1212–1216. https://doi.org/10.2112/si75-243.1
Phuah, T. L., & Chang, Y. (2023). Socioeconomic adaptation to geomorphological change: An empirical study in Cigu Lagoon, southwestern coast of Taiwan. Frontiers in Environmental Science, 10. https://doi.org/10.3389/fenvs.2022.1091640
Pradhan, S., Mohanty, P. K., Samal, R. N., Mahanty, M. M., Pradhan, U., Panda, U. S., & Mishra, P. (2024). Nearshore hydrodynamics and sediment transport modeling along the shorefront of a tropical lagoon. Regional Studies in Marine Science, 103993. https://doi.org/10.1016/j.rsma.2024.103993
Reyns, J., McCall, R., Ranasinghe, R., Van Dongeren, A., & Roelvink, D. (2023). Modelling wave group-scale hydrodynamics on orthogonal unstructured meshes. Environmental Modelling & Software, 162, 105655. https://doi.org/10.1016/j.envsoft.2023.105655
Roelvink, D., & Reniers, A. (2011). A guide to Modeling Coastal morphology. https://doi.org/10.1142/7712
Shmakova, M. (2022a). GEOECOLOGICAL ASPECTS OF SEDIMENT TRANSPORT IN WATER OBJECTS: NEW APPROACHES AND FORMULAS. Izvestiya of Samara Scientific Center of the Russian Academy of Sciences, 24(5), 117–123. https://doi.org/10.37313/1990-5378-2022-24-5-117-123
Shmakova, M. (2022b). Sediment transport in river flows: New approaches and formulas. In IntechOpen eBooks. https://doi.org/10.5772/intechopen.103942
Song, L. (2008). Unstable sandbar movement under wave action. Ocean Engineering. http://en.cnki.com.cn/Article_en/CJFDTOTAL-HYGC200801005.htm
Soulsby, R. (1997). Dynamics of marine sands. Thomas Telford.
Sherwood, C. R., Van Dongeren, A., Doyle, J., Hegermiller, C. A., Hsu, T., Kalra, T. S., Olabarrieta, M., Penko, A. M., Rafati, Y., Roelvink, D., Van Der Lugt, M., Veeramony, J., & Warner, J. C. (2021). Modeling the morphodynamics of coastal responses to extreme events: What shape are we in? Annual Review of Marine Science, 14(1), 457–492. https://doi.org/10.1146/annurev-marine-032221-090215
Stokes, G. (1847). On the theory of oscillatory waves. Trans. Reports of the British Association, 8, 441–473. http://ci.nii.ac.jp/naid/10016936381
Soulsby, R., Hamm, L., Klopman, G., Myrhaug, D., Simons, R., & Thomas, G. (1993). Wave-current interaction within and outside the bottom boundary layer. Coastal Engineering, 21(1–3), 41–69. https://doi.org/10.1016/0378-3839(93)90045-a
Toso, C., Madricardo, F., Molinaroli, E., Fogarin, S., Kruss, A., Petrizzo, A., Pizzeghello, N. M., Sinapi, L., & Trincardi, F. (2019). Tidal inlet seafloor changes induced by recently built hard structures. PLoS ONE, 14(10), e0223240. https://doi.org/10.1371/journal.pone.0223240
Van Rijn, L. C. (1993). Principles of sediment transport in rivers, estuaries and coastal seas. http://ci.nii.ac.jp/ncid/BA28467043
Wang, J., You, Z., Liang, B., Wang, Z., & Yang, B. (2023). The physical processes of sandy beach evolution under storm and non-storm wave conditions simulated in wave flume. Marine Geology, 462, 107065. https://doi.org/10.1016/j.margeo.2023.107065
Wang, P., Cheng, J., Horwitz, M. H., & Legault, K. R. (2015). COMPARING TWO NUMERICAL MODELS IN SIMULATING HYDRODYNAMICS AND SEDIMENT TRANSPORT AT a DUAL INLET SYSTEM, WEST-CENTRAL FLORIDA. The Proceedings of the Coastal Sediments 2011. https://doi.org/10.1142/9789814689977_0135
Warner, J. C., Sherwood, C. R., Signell, R. P., Harris, C. K., & Arango, H. G. (2008). Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model. Computers & Geosciences, 34(10), 1284–1306. https://doi.org/10.1016/j.cageo.2008.02.012
Wright, L., & Short, A. (1984). Morphodynamic variability of surf zones and beaches: A synthesis. Marine Geology, 56(1–4), 93–118. https://doi.org/10.1016/0025-3227(84)90008-2
Yang, R. J., Liu, J. T., Su, C., Chang, Y., Xu, J. J., & Lui, H. (2021). Land-Ocean interaction affected by the monsoon regime change in western Taiwan strait. Frontiers in Marine Science, 8. https://doi.org/10.3389/fmars.2021.735242
Youn, S., & Jang, C. (2022). The relative merits of sediment transport formulas applied to the Nakdong Estuary, Korea using a coupled numerical modeling system. Journal of Measurements in Engineering, 10(2), 54–67. https://doi.org/10.21595/jme.2022.21919