XBeach-G model simulation of 2.5-m sea-level rise on sand and gravel coral reef island (Masselink et al., JGR(ES), 2021)

XBeach-G model simulation of 2.5-m sea-level rise on sand and gravel coral reef island (G. Masselink, R. McCall, E. Beetham, P. Kench and C. Storlazzi, 2021, Role of Future Reef Growth on Morphological Response of Coral Reef Islands to Sea-Level Rise, Journal of Geophysical Research (Earth Surface).Coral reef islands are particularly exposed to the impacts of sea-level rise. They are usually fronted by ‘living’coral reef platforms that protect the island shoreline from energetic wave action. Healthy reef platforms grow vertically and can keep up with rising sea level, maintaining a constant water depth in front of the island. It is therefore suggested that future reef growth may be a critical factor in reducing the vulnerability of coral reef islands to sea-level rise. We use a computer model to simulate the response of coral reef islands to sea-level rise with and without future reef growth. We find that as sea level rises, the islands evolve by retreating, while at the same time building up vertically. Island build up is accomplished by waves overwashing the island and depositing sediment on the top of the island. According to our model results, vulnerability of the reef islands to sea-level rise is not dependent on whether the reef platform grows or not. In both cases, islands are regularly overwashed, but this is necessary for islands to grow vertically. Island accretion by overwash offers hope for uninhabited and sparely populated islands, but will negatively impact infrastructure and assets on urbanized islands