Tidal and wave modulation of rip current dynamics. (1st July 2022)

• Record Type: Journal Article
• Authors: Zhang, Yao; Hong, Xiao; Qiu, Ting; Liu, Xunan; Sun, Yuxi; Xu, Guodong
• Is Part Of: Continental shelf research. Volume 243(2022)
• Publication Date: 2022-07-01
• Subjects: Rip current -- Tidal modulation -- Oblique wave -- Pocket beach -- Sandbar; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2022.104764
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: Rip currents have become the primary coastal hazard globally with direct implications for surf-zone recreational safety. Among 101 China's recreational beaches, headland bay with large tidal range and wave-dominated sandbar shorelines are identified with high occurrence risk of rip currents by the morphodynamic assessment. The variability of rip current under tidal and wave modulation is explored by the case simulations. At macro-tidal pocket beach, the strongest rip currents occur in ebb, 20%–50% faster than that during flood, while offshore flows are barely developed at low tide. This asymmetry depends on the quasilinear superimposition of wave-driven and tidal currents. Nearshore circulations are found not sensitive to the wave direction in a macro-tidal environment. For sandbar morphology with weak tidal variations, rip currents are best developed towards low tide with maximum topographic effect on wave dissipation and show high sensitivity to the incident wave angle. The magnitude of vortex increases with wave angle but is not explicitly related to wave height. Rip currents are mostly suppressed by oblique incident waves while the offshore flow may get strengthened as incoming waves slightly deviate from normal incidence when the wave height is small. The decay of rip currents with wave angle did not show clear dependence on channel width which was found in other literatures. The incident wave angle should be incorporated into existing statistical methods or probabilistic models to improve the accuracy of rip current prediction.