本研究以桃園市二級海岸防護計畫中之侵蝕熱點「新屋事業性海堤改善工程」為對象，探討傳統剛性海岸防護工程轉型為近自然柔性護岸之設計實務與環境效益。經實證分析，新屋海岸受突堤效應阻斷漂沙，加之新屋溪輸沙不足，在波浪長期淘刷下，海岸線以每年 5.24 公尺之速率劇烈退縮，導致舊有剛性海堤掏空傾倒。 為落實《海岸管理法》之「自然海岸零損失」精神並回應自然解方（NbS）趨勢，本工程採「後撤海堤、降低高程 1.6 公尺、放緩外坡至 1:6」之近自然拋石護岸設計，第一線臨海側採用粒徑達 100 公分之重型塊石消能。完工後歷經三次強烈颱風與工作船正面撞擊考驗，主體結構均無損，驗證柔性防禦之高韌性。拋石結構保留 20% 至 30% 孔隙率以建構潮池微棲地，並配置生態廊道，使自然海岸比例增加 1.84 % 並達成陸蟹零路殺效益。 此外，本研究導入生命週期評估（LCA）。本工程跨界媒合去化桃園在地公共工程 B5 類賸餘土石方 44，117.7 公噸及廢玻璃砂 346.86 公噸，完全替代傳統高碳排混凝土；並落實「在地取才」將運輸距離大幅縮短至 20 公里以內 。經科學公式計算，實質創造 4，233.2 公噸之總減碳效益，整體減碳率高達 36 %，具體落實聯合國永續發展目標 SDGs 12 與 SDGs 14 之核心精神。本案榮獲第九屆桃園市政府公共工程金品獎肯定。;This study focuses on the "Xin-Wu Commercial Seawall Improvement Project，" a designated coastal erosion hotspot under Tao-Yuan City’s Second-Stage Coastal Protection Plan， to investigate the engineering practices and environmental benefits of transforming traditional rigid coastal structures into near-natural flexible revetments. Empirical analysis reveals that the legacy rigid seawalls were undermined and destroyed due to severe coastal retreat， which occurred at an annual rate of 5.24 meters. This erosion was primarily triggered by the groin effect of northern artificial structures that blocked longshore sediment transport， compounded by insufficient sediment supply from the Xin-Wu River. To fulfill the mandate of "ensuring zero net loss of natural coastlines" under the Coastal Zone Management Act and to adopt Nature-based Solutions (NbS)， a flexible near-natural riprap revetment was engineered. This design featured a setback layout， a 1.6-meter crest elevation reduction， a flattened seaward slope of 1:6， and heavy armor stones exceeding 100 cm in diameter for wave energy dissipation. The structure maintained high resilience and structural stability through three severe typhoons and a direct collision by a platform barge. Furthermore， the riprap matrix was designed with a 20% to 30% porosity to create tidal pool micro-habitats， expanding the local natural coastline by 1.84% and achieving zero land-crab roadkill. Additionally， this study applies Life Cycle Assessment (LCA) to evaluate carbon reduction. The project integrated and diverted 44，117.7 metric tons of localized B5-category surplus excavation soil and 346.86 metric tons of waste glass sand to entirely replace high-emission concrete， while reducing material transport distance to under 20 km. Precise carbon accounting demonstrates a net greenhouse gas mitigation of 4，233.2 metric tons of $\text{tCO}_2\text{e}$， representing an overall carbon reduction rate of 36% and fulfilling UN SDGs 12 and 14. This project received the 9th Tao-Yuan City Public Engineering Quality Award， serving as a standardized low-carbon demonstration for green engineering transitions in Taiwan.
