臺灣地區早在數十年前，即開始於各河川出海口陸續設置導流堤，以改善河口淤積的情況，惟早期並無適當之近岸水動力模式，無法針對導流堤設置後，河口附近水動力機制之變化進行分析評估。許等人 (2000) 已成功研發了適用於臺灣本土海域之波潮流模式，而Klein等人 (2003) 則以Hsu及Evans (1989) 所提出的岬灣經驗公式為基礎，發展了MEPBAY (Model of Equilibrium Planform of BAYed beaches) 海岸線變遷應用軟體，因此吾人擬採用上述模式，評估導流堤對河口附近海域之水動力與海岸線變遷機制的影響。

　　本文選定高雄市後勁溪河口導流堤為研究對象，首先蒐集後勁溪河川水文資料、河口近岸海象與氣象資料，作為模式輸入之資料庫，再應用波潮流模式模擬導流堤興建前後，不同波浪條件作用下，河口附近海域之近岸波流場變化。此外，吾人更進一步以MEPBAY軟體，預測後勁溪出海口導流堤兩側之靜態平衡岸線，藉以了解未來海岸線變遷之趨勢。

　　研究結果顯示後勁溪導流堤之範束已達到預期效果，淤積地點已由河口往外延伸，以往河口淤積現象因導流堤的興建而獲得改善。此外，突堤效應造成後勁溪河口導流堤「北淤南侵」現象，而堤口處地形則有呈現喇叭狀的趨勢。另由後勁溪導流堤兩側之靜態平衡岸線，可預測未來海岸線變遷趨勢將形成侵淤共存現象。

　　In the past decades, many kinds of groin have been constructed at the estuary for the improvement of the estuary sediments. For the lack of near shore hydraulic dynamic model, it was very difficult to analyze the dynamic change near estuary after the construction of groin. Hsu et al. (2000) has successfully developed the wave and current model for Taiwan seashore region and Klern et al.(2003) has also developed the MEPBAY(Model of Equilibrium Planform of BAYed beaches) shoreline change model based on the headland control experience model suggested by Hsu and Evan(1989). Therefore, this study is to analyze the effects of hydrodynamic and shoreline changes after the construction of groin at river estuary by means of above models.

　　The groin at the estuary of Hojing Creek in Kaohsiung has been chosen for this study. Data collection, including the hydrological data of Hojing creek, the oceanographic and meteorological observation data at the estuary, was first conducted and used as data base for the input of the applied models. Then, the shoreline changes before and after the construction of groin will be analyzed and simulated under different wave conditions by the application of wave and current models. Finally, this study predicts the static shoreline at the both sides of the groin for the evaluation of future shoreline changes by the application of MEPBAY model.

　　The results reveal that the confinement of groin has been achieved, the sediments was shifted from the estuary to the outlet sea. Hence the condition of sediments at river estuary was improved. Also, the groin effect on groins results in the erosion at south side and the sediment at north side of groin. The topographic changes at the bead of groin tends to accumulate into trumpet shape. Furthermore, it is possible to predict that both the sediments and erosion would exist simultaneously during shoreline changes according to the static balancing shoreline at both sides of the groin.

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