Comprehensive Assessment of the Effects of Environmental Factors on Low-Energy Rip Currents

Rip currents are fast offshore currents and a critical component of nearshore circulation, significantly influencing public safety and material transport. This study employs the Generalized Additive Model, an effective approach for uncovering complex nonlinear relationships, to provide a comprehensive quantitative understanding of rip current drivers. By integrating field observations from a headland beach in southern China with Delft3D numerical modeling, which incorporates wave-current coupling, the contributions and interactions of environmental factors to low-energy rip current generation were quantified. Results indicate that rip currents form only within specific parameter combinations, with an annual occurrence rate of 5.9% in the study area. Significant nonlinear relationships were found between rip current generation and key environmental factors, including wave period (Period), significant wave height (SWH), wave direction (Direction), wind direction (WindDir), and water level. Variations in Direction and SWH were particularly influential. The formation of rip currents depends on the interaction of environmental factors, and the response to a single factor diminishes if other factors have not reached their thresholds. Certain environmental factor ranges, while not strongly influencing rip current velocity, can significantly increase rip current frequency. This distinction between rip current velocity (hazard intensity) and frequency provides novel insights into rip current generation mechanisms and supports the development of early warning systems.