報告書番号

U01018

タイトル（和文）

露岩域を有する砂浜海岸に港湾を建設する場合の海浜変形予測モデルの適用

タイトル（英文）

Application of beach deformation numerical model to a field site of sandy beach including exposed rock area around a harbor

概要 （図表や脚注は「報告書全文」に掲載しております）

海岸構造物の建設に伴う現地海域の海浜変形予測を行うために，1～3年程度の期間を予測でき，露岩域を含む砂浜海岸に適用できる３次元海浜変形予測モデルをを開発した．ついで，岩礁模型を用いた３次元移動床実験により漂砂量モデルを検証した上で，露岩域を含む自然砂浜海浜に港湾が徐々に建設される過程を対象とした東北電力東通発電所地点への現地適用性を検証した．また，現地観測データを用いて，港湾建設前に広領域で実施した1ラインモデルによる海岸線変化を再計算し予測結果を検証した．その結果，本３次元海浜変形モデルは，岩礁上を通過する漂砂量，波，流れ，浮遊砂濃度，露岩域を含む海底地形変化をよく再現でき，1～3年程度の現地海浜変形に適用できることがわかった．また，１ラインモデルによる広領域の海岸線変化は，港湾完成後の現地観測結果をよく再現できることがわかった．

概要 （英文）

A 3-D beach deformation numerical model for ordinary sandy beach has been recently developed and applied to hydraulic model tests or field sites. However, there are several field sites including exposed rocks in the actual sandy seabed areas necessary to predicting and measure beach deformation, such as the Tohoku Electric Power Company Higashidori Power Plant site. So, it is actually necessary to modify 3-D beach deformation numerical model capable of correctly evaluating the suspended and bed sediment transport passing over such exposed rocks in the case of thinner sand layer thickness. It is also necessary to efficiently improve 3-D beach deformation numerical model capable of predict the effects of construction of a coastal structure at least in the term of 1～3 years. In this report, first, a practical numerical model for 3-D beach deformation due to multi-directional random waves is developed by modeling the suspended and bed sediment transports passing over exposed rocks in the case of thinner sand layer thickness. Next, these sediment transport models are verified by beach model tests around exposed rocks using multi-directional random waves. Next, this numerical model is applied to the above field site of sandy beach including exposed rock area around a harbor. Using 1-line numerical model, with which prediction of shore line change has been performed before construction of a harbor at the Higashidori Power Plant site, shore line change is re-computed and also verified through comparison with field observation. As a result, this 3-D beach deformation numerical model can well reproduce sediment transport passing over exposed rocks, wave deformation, currents, suspended concentration, and seabed topography changes including the rock area in the term of 1～3 years. This 1-line numerical model can well reproduce long-term shore line change after construction of the harbor, obtained by field observation.

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