Effect of Coral Reefs on Wave Height

Coral reefs, among other benefits, provide natural protection from waves for coastal communities. In the context of climate change and its role in the degradation of coral reefs and the intensification of extreme weather events, there has been a growing interest in understanding the sheltering properties of coral reefs. Despite this interest, there remains a lack of comprehensive studies that systematically assess wave behaviour on coral reefs using remote sensing techniques.This study utilized along-track altimetry observations from the European Space Agency's Sea State Climate Change Initiative (CCI) v3 L3 dataset, complemented by ERA5 data, to examine the influence of coral reefs on wave height. Changes in significant wave height (SWH) on coral reefs, derived from the multi-mission altimetry dataset, are compared with those computed from ERA5 reanalysis in its gridded format and interpolated on satellite tracks. The assessment is conducted on a global and regional scale, considering different offshore sea states. Additionally, the study explores the influence of the structural complexity of coral reefs on their capacity to attenuate waves. This is achieved through a regional analysis of altimetry measurements in years with a high percentage of hard coral cover and years after destructive storms.The results demonstrate a high degree of agreement between SWH attenuation computed from the satellite altimetry dataset and ERA5 interpolated on the satellite tracks, yielding a correlation coefficient of 0.724. Additionally, this study contributes to the expanding body of knowledge regarding the influence of coral reefs on wave height. Despite the pronounced variability contingent upon the state of coral reefs and the local wave climate, about 80% of observations show a reduction in wave height as waves traverse coral reefs. Statistical evaluation reveals an increase in the reduction of wave height with an increase in offshore wave conditions, as evident in the analysis of all three datasets. Furthermore, case studies on extreme events show a regional decrease in wave attenuation on coral reefs with reduced hard coral cover. The study highlights the potential of satellite altimetry in the observation of wave height changes across coral reefs, as well as the ability of coral reefs to attenuate waves and mitigate the destructive potential of storms, thereby contributing to coastal protection and resilience.