Data for: "Alongshore Setup Gradients Drive Reef Flat Currents on a Coral Atoll Island"

This study presents extensive in situ observations from a coral atoll island in the Maldives to investigate the alongshore variability of wave setup and reef flat currents driven by heterogeneity in morphology and wave forcing. The island’s diverse reef morphology provided an ideal natural laboratory for assessing its impact on spatial hydrodynamic variability. Results indicate that shoreline wave setup increased with incident wave height and low reef flat water levels, regardless of reef geometry. Despite the significant variations in topography, bathymetry, and wave exposure, theoretical predictions of wave setup using existing parameterizations demonstrated strong agreement with observations across three distinct areas of the island, with the best performance at the most wave-exposed locations. Additionally, normally-incident waves produced higher local wave setup, thus inducing alongshore gradients in wave setup. These alongshore setup gradients were found to be the dominant driver of reef flat currents, although wave direction had minimal impact on the current speeds and directions. These findings highlight the importance of resolving alongshore hydrodynamic variability, which is often overlooked in reef hydrodynamic studies due to their great morphologic complexity and resource limitations. Improved understanding of these processes is essential for forecasting sediment dynamics and atoll island evolution. Future work should integrate spatially extensive field observations with high-resolution, process-based modeling to better model reef hydrodynamics and morphodynamics to assess coral island resilience under changing storms and sea levels.