Physical investigation of hydrodynamic properties of tsunami-like wave over an uneven coral reef with a seawall

Abstract Coral reefs in their natural state exhibit complex topographic and morphological characteristics. Moreover, recent anthropogenic engineering activities on coral reefs have accelerated changes in their topographic and geomorphic features, including artificial island construction and the creation of artificial excavation pits, which all contribute to an uneven reef flat. Previous research of coral reef wave hydrodynamics frequently simplified coral reef terrain as a step-like structure, overlooking the effects of uneven reef flats and neglecting the influence of human-engineered structures. As a necessary supplement, this study analyzed wave hydrodynamic properties of tsunami-like waves over an uneven coral reef with a seawall. Hydrodynamic influences of wave height and submergence water depth were analyzed in detail based on physical experiments. Besides, a numerical analysis was conducted on the hydrodynamic impacts of reef-step dimensions on wave hydrodynamics of tsunami-like waves. Research findings of present study indicate that tsunami-like waves will undergo complex transforming and breaking at the uneven reef flat. The tsunami-like waves will experience a surging breaker at the outer-reef flat and a plunging breaker at the inner-reef flat. Moreover, backwash water can be generated at the vertical seawall, resulting in additional wave reflection in addition to that occurring at the forereef slope.