LABORATORY EXPERIMENTS OF WAVE OVERTOPPING OF REVETMENT STRUCTURES IN REEF ENVIRONMENTS
AbstractReefs offer natural protection to many coastal island nations through the physical processes of wave breaking on the reef rim and thus, reducing the wave energy that reaches the shoreline. However, both mean and infragravity water levels build up over the reef due to wave breaking on the reef top that can lead to coastal inundation and serious damage (Gourlay 1996a; Gourlay 1996b; Blacka et al. 2015). To protect the community around the coastal region, the construction of defensive structures, such as revetments or sea dikes may be required. The present study is focused on wave overtopping discharge on smooth revetments within the reef environment, which is not fully understood. Classical formulas that estimate overtopping of revetments (see Van der Meer et al. 2016 and references therein) are based on waves breaking in deep to shallow water either in front of the structure or directly on the structure. Recently, Altomare (2016) updated Van Gent's (1999) formula of overtopping discharge of smooth sea dikes on shallow foreshores to include very shallow foreshores. The updated equation estimates dimensionless over-topping as a function of the full spectrum wave properties at the toe of the structure and an equivalent slope term. As the reef environment can often be described as a very flat and shallow lagoon seaward of the shoreline, the Altomare formula can potentially be adopted to predict the overtopping discharge on smooth revetments in reef environments, but this has yet to be tested.
Altomare, C. et al., (2016) Wave overtopping of sea dikes with very shallow foreshores. Coastal Engineering, 116, pp.236-257.
Blacka, M.J. et al., (2015) Estimating wave heights and water levels inside fringing reefs during extreme conditions. In Australasian Coasts & Ports Conference 2015. Auckland, NZ, pp. 83-89.
Van Gent, M., (1999) Physical model investigations on coastal structures with shallow foreshores: 2D model tests with single and double-peaked wave energy spectra, Delft, Netherlands.
Gourlay, M.R., (1996a) Wave set-up on coral reefs. 1. Set-up and wave-generated flow on an idealized two dimensional horizontal reef. Coastal Engineering, 27, pp.161-193.
Gourlay, M.R., (1996b) Wave set-up on coral reefs. 2. Set-up on reefs with various profiles. Coastal Engineering, 28, pp.17-55.
Van der Meer, J.W. et al., (2016) EurOtop 2016. Manual on wave overtopping of sea defences and related structures. An overtopping manual largely based on European research, but for worldwide application, Available at: www.overtopping-manual.com.