Assessment of wave overtopping models for fringing reef fronted beaches.
Alejandro Astorga-Moar, Tom E. Baldock
Abstract
This study presents new experiments and analysis to evaluate the performance of overtopping models for fringing reef fronted beaches. Physical experiments were conducted to measure the overtopping landward of an ideal fringing reef profile of different widths. Water depths over the reef flat were varied, together with the freeboard elevation of the beach crest or coastal maximum. The analysis evaluated the performance of conventional and new models in predicting overtopping flows, leading to the development of two new expressions based on a recently proposed general expression. The analysis compares model performance using both offshore wave conditions and wave and water level conditions at the beach toe at the landward end of the reef flat, with the latter providing more robust predictions. The current empirical overtopping models perform poorly using offshore wave conditions. Using wave conditions at the beach toe, the squared normalized deficit of freeboard emerged as a robust predictor, exhibiting a strong linear correlation with overtopping flow rate and overtopping volume. Two new empirical constants for the conventional overtopping models were derived from the data, which reflect the influence on the overtopping of wave transformation and momentum transfer during wave breaking and propagation across the reef.