Development and Validation of Surf Prediction System for Macro-tidal Beach

Abstract

Development of a surf prediction system aims to support societal activities at a beach such as swimming, diving, surfing, etc., and military planning and operations as well. In this study, the developed surf prediction system is tested with a macro-tidal beach, i.e. the Malipo sand beach, in the west coast of Korea. The Malipo beach is characterized by a wide inter-tidal flat (O (1 km)) with a tide range of about 7m. The surf prediction system requires the incident boundary conditions for shallow water wave transformation model and local tide model. The boundary condition for shallow water wave transformation is provided by one of the third generation wave models, WAM, using daily-based meteorological forcing produced by the NCEP-WRF model. The boundary condition for local tide model is provided by a regional tide model covering the North East Asia Regional Seas. One-dimensional surf prediction model established for each transect, perpendicular to the beach, is tested. In addition, 2-D surf model is applied for all the beach area. Outputs include surf zone width, wave induced currents, wave breaker type such as spilling, plunging, or surging. Since wave dynamics in the macro-tidal beach are significantly influenced by tidal motions such as strong tidal currents larger than 1 m/s, the developed surf prediction system is investigated with an emphasis on the effect of the tidal currents on the surf zone formations. The Malipo beach was spatially monitored and recorded using the remote imaging methods during the period of a field experiment campaign in December, 2008. The surf prediction results are compared to the field observation results by optical (video) and radar (X-band) imaging techniques. The spatial surf characteristics were extracted from the remotely sampled image sequences using a linear feature detection method. More carefully designed field experiments will be also carried out for a much longer period of time in November and December in 2009 to obtain mor