Evolution of the Surf Zone on a Macro-tidal Beach Observed using X-band Radar

Abstract

Yoo, J., Kim, S.-I., Lee, D.-Y., Park, K.-S., Shim, J.-S. and Jun, K.-C., 2011. Evolution of the surf zone on a macro-tidal beach observed using X-band radar. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 1676 - 1680. Szczecin, Poland, ISSN 0749-0208 This paper proposes a remote sensing technique to monitor surf zone processes. Specifically, we assessed tidal cycle-induced surf zone evolution on the Mallipo (Korea) sand beach by associating X-band radar images and transmitted wave-buoy data, in all weather conditions. Much of the west coast of Korea is bounded by dynamic macro-tidal sand beaches considerably influenced by wave breaking processes in the surf zone. Since wave dynamics on a macro-tidal beach can be significantly influenced by rapid and large changes of water depth, X-band radar image data were used to estimate wave attenuation coefficients, monitoring of which in the surf zone throughout the tidal cycle is essential in describing beach processes. To do this, an image pixel array defined along the cross-shore transect was collected from sequential radar images to generate a cross-shore image timestack. Thereafter, the surf-zone area evolving in time was identified from the image timestack using a line detection method. The computed widths of the surf zone in the cross-shore direction were compared to incident wave heights from the transmitted wave-buoy data, thereby estimating the dissipation rate of breaking waves across the surf zone. The attenuation coefficient on the Mallipo sand beach was found by this method to be 0.58 overall, which is not considerably different from earlier observations on micro-tidal beaches.