Optimising Artificial Reef Design through Large-Scale Experiments

Abstract

Low-lying coral islands are highly vulnerable to sea-level rise and climate change, with coral reefs, essential for coastal protection, facing significant decline due to climate change and anthropogenic stressors. Artificial reefs present a potential solution by restoring ecology and mitigating coastal flooding, but their effectiveness and impact on wave dynamics remain unclear. This study investigates the effects of an artificial reef on spectral wave transformation over fringing reefs, combining numerical modelling with SWASH and large-scale experiments conducted in the Deltares Delta Flume. The experiments involved a scaled reconstruction of a fringing reef island with a geometric scaling factor of 3. Numerical modelling was used to optimise the laboratory experiments by adjusting reef placement and element density for maximum wave height reduction.

The results of this thesis show a limited impact of an optimised artificial reef on the reef flat, with effectiveness expected to decrease further as sea levels rise. However, the smaller scale of the reef elements prioritises ecological benefits, and when combined with larger structures, these reefs can still offer valuable benefits for biodiversity and wave mitigation. The experiments provide a valuable new dataset on the hydrodynamics of complex canopies, and can be used to calibrate several numerical models and methods of schematising artificial reefs.