Sands Escaping Haeundae Beach

Abstract

Haeundae Beach has been hypothesized to lose sands from the nearshore of the western extremity of its pocket-beach system with a tidal range of 0.5 - 1.2 m. To test the hypothesis, a measurement station was located in this area to observe a suspended transport of sands near the seabed. The hydrodynamic measurements included water level, wave, currents and suspended sediment concentration with a benthic tripod for longer than one month of the 2013-2014 winter. In addition, a Telemac-2D tide model was run to simulate tidal currents for the same period of time as the measurements. A total of 6 events of two tidal cycles each were selected and analyzed to represent a variety of combinations of tidal phase, wave energy and wave direction. The results show that the suspended sand transport occurred continuously and was controlled predominantly by ebb-dominant tidal currents. Thus it was always directed offshore. Waves higher than 1 m sporadically took place during the measurements. However, high waves could just reorient the offshore suspended sand transport from obliquely to normal to the shoreline. This is because they created residual currents flowing roughly parallel to the shoreline. Neither offshore wave direction nor tidal phase evidently influenced the characteristics of residual currents. Therefore, the escape of the Haeundae sand from the area of interest has been proven to occur year round intrinsically by tidal currents. Waves intermittently contribute much to enhancing the suspended sand flux offshore by vigorous resuspension processes.