The Influence of Coral Reef Spur and Groove Morphology on Wave Energy Dissipation in Contrasting Reef Environments

Coral reefs protect coastlines from inundation and flooding and serve over 200 million people globally. Wave transformation has previously been studied on coral reef flats with limited focus on forereef zones where wave transformation is greatest during high-energy conditions. This study investigates the role of forereef spur and groove (SaG) morphology in wave energy dissipation and transmission at the reef crest. Using XBeach on LiDAR-derived bathymetry from One Tree Island in the southern Great Barrier Reef, we reproduced dissipation rates comparable to SaG field studies. We examined how wave energy dissipation differs between realistic bathymetry and those with SaG features removed, demonstrating an up to 40% decrease in dissipation when SaG features are absent. We then investigated changes to wave energy dissipation and wave transmission at the reef crest based on IPCC AR5 emission scenarios (RCP2.6 and RCP8.5) and a total disaster scenario (TD) for the year 2100. For RCP2.6, an increase in wave heights of 0.8 m and an increase in water level of 0.3 m resulted in a two-fold increase in dissipation rates. For RCP8.5 and TD, with no increase in incident wave height, dissipation rates were 29% and 395% lower than RCP2.6. This resulted in increased wave transmission at the reef crest by 1.8 and 2.7 m for the RCP8.5- and TD based models, respectively, when compared to the RCP2.6-based model. The results from our novel modeling approach of using long-shore varying accurate bathymetry on forereefs show increased wave energy dissipation rates with implications for reducing coastal flooding and island inundation on reef-lined coasts.