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Long-term beach observation data for several decades are essential to validate beach morphodynamic models that are used to predict coastal responses to sea-level rise and wave climate changes. At the Hasaki coast, Japan, the beach profile has been measured for 34 years at a daily to weekly time interval. This beach morphological dataset is one of the longest and most high-frequency measurements of the beach morphological change worldwide. The profile data, with more than 6800 records, reflect short- to long-term beach morphological change, showing coastal dune development, foreshore morphological change and longshore bar movement. We investigated the temporal beach variability from the decadal and monthly variations in elevation. Extremely high waves and tidal anomalies from an extratropical cyclone caused a significant change in the long-term bar behavior and foreshore slope. The berm and bar variability were also affected by seasonal wave and water level variations. The variabilities identified here from the long-term observations contribute to our understanding of various coastal phenomena.

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2 正会員 神戸大学教授 大学院工学研究科市民工学専攻(〒657-8501 兵庫県神戸市灘区六甲台町1-1)

Connectivity evaluates stochastic processes of larval dispersal due to chaotic coastal circulations (e.g., Mitarai et al., 2009). In the present study, we quantify Lagrangian PDFs and connectivity using many Lagrangian particles released from 140 source sites in the modeled SIS circulation field in a double-nested, high-resolution ROMS configuration (Uchiyama et al., 2012). In winter, the fraction of particles transported to another region is about less than 40% except for both the channels, suggesting that particles largely remain in the release region. The regional connectivity is correlated with the seasonal variation of the mass fluxes at the straights between two neighboring regions. Particles released from Harima-Nada, representing larvae of marbled sole, are mainly transported towards the northern shore of Shodo Island, while particles arriving there originate mostly from the western shore of Harima-Nada.

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