Observations of Wave Setup on a Coral Atoll

Abstract Atoll island nations (such as the Maldives, Marshall Islands, and Tuvalu) are amongst the most critically vulnerable to climate change due to rising sea levels and subsequent flooding and overwash events. To investigate the wave and water level dynamics on a coral atoll, a six-month dataset consisting of three pressure gauges was collected at three distinct sites on the island of Dhigelaabadhoo in the Republic of the Maldives along with a tide gauge located in a nearby harbor. The observed setup varied across the sites and was found to correlate with the offshore significant wave height and period, as well as tidal water level. The sites with wider reef platforms and steeper forereef slopes were observed to have higher wave setup at the shore and a slightly stronger linear correlation between setup and offshore conditions. Furthermore, the results indicate the potential influence of incident wave direction on alongshore setup gradients.