Japan Geoscience Union Meeting 2025

Presentation information

[J] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS21] Coastal ocean circulation and material cycle

Mon. May 26, 2025 5:15 PM - 7:15 PM Poster Hall (Exhibition Hall 7&8, Makuhari Messe)

convener:Taira Nagai(Japan Fisheries Research and Education Agency), Toshimi Nakajima(Atmosphere and Ocean Research Institute, The University of Tokyo), Mitsuko Hidaka(Kagoshima University), Yusuke Ushijima(Ehime University)

5:15 PM - 7:15 PM

[AOS21-P02] Field observations and numerical modeling of rip currents in a fringing coral reef channel

*Heng Wu1, Yusuke Uchiyama2, Satoshi Mitarai1 (1.Okinawa Institute of Science and Technology , 2.Graduate School of Engineering, Kobe University )

Keywords:rip currents , coral reefs

Rip currents in rocky coral reefs have been seldom studied, despite their dynamics potentially differ from the well-studied sandy shore rip currents due to the complex bathymetry.

To investigate the formation and duration of bathymetric rip currents occurring in a channel within a fringing coral reef, we combined flow observations with idealized numerical modeling.

Field observations were conducted using an Acoustic Doppler Current Profiler (ADCP) to measure flows in the rip channel and an ADCP or a moored surface buoy to measure the incoming wave condition offshore. The data revealed a strong correlation between rip current occurrence and significant wave height, a moderate correlation with onshore wind, and a much weaker negative correlation with tidal elevations.

To further explore the formation and structure of these rip currents, we developed an idealized numerical model using the Coastal and Regional Ocean COmmunity model (CROCO). The model incorporated satellite-derived bathymetry and was forced with monochromatic waves on the offshore side of the domain. Multiple tests were performed under varying wave conditions and the results were compared with field observations.

This study provides new insights into the dynamics of rip currents in coral reef environments, contributing to improve safety measures for water activities in Okinawa and similar coral reef areas.