Experimental and numerical assessment of marine flood reduction by coral reefs

Coral reefs are crucial components of oceanic ecosystems. Reefs play a vital role in providing habitats for marine life and serve as a natural wave barrier against high-energy marine floods generated by long-period waves such as tsunamis and storms. Here, we performed experimental studies and numerical analyses and compared the results to investigate coral reef-induced marine flood reduction. In this study, 3D-printed corals were used as they closely resembled actual coral reefs, and marine floods were generated using a rotatory crank system. The results showed that healthy corals decreased flow velocity and depth at the end of the coral zone by 22.2% and 13.5%, respectively. Different boundary wave characteristics and coral roughness were assessed using idealized bathymetry with a 1% gradient. Additionally, numerical simulations revealed that wave height reduction was as high as 51% for corals with a Manning roughness of 0.25. Both the experimental and numerical assessments indicate significant wave energy reduction, which was compared with non-dimensional parameters such as the Froude Number that showed similarity between the results and the ratio between water depth and coral extent, which differed owing to limitations.