Beetham, E.; Kench, P.S., and Popinet, S., 2018. Model skill and sensitivity for simulating wave processes on coral reefs using a shock-capturing Green-Naghdi solver.

Wave-flume data from published benchmark experiments were used to extensively evaluate numerical model skill and sensitivity for applying a shock-capturing Green-Naghdi (GN) model to simulate nonlinear wave-transformation processes on complex coral reefs. Boussinesq-type models that utilise nonlinear shallow-water equations (NSWEs) to represent wave breaking and dissipation hold significant potential for understanding coastal hazards associated with global environmental change and sea-level rise. These fully nonlinear phase-resolving models typically require a threshold condition to switch from dispersive equations to shock-capturing NSWEs in areas of active wave breaking. However, limited information exists regarding how this splitting approach influences the behaviour of different surf-zone processes that contribute to wave runup and inundation on reef environments. This paper presents a comprehensive analysis of model sensitivity to explore how input parameters that control wave breaking and dissipation influence the behaviour of sea-swell waves, infragravity waves, wave setup, runup, and solitary waves on coral reefs. Results show that each wave process exhibits unique sensitivity to the free-surface slope threshold (B) that is used to represent areas of active wave breaking by locally switching from the weakly dispersive GN equations to the shock-capturing NSWEs. Accurate representation of all wave processes, however, can be achieved if the wave-face steepens to at least 35° (B ≥ 0.7) before breaking is initiated. Results from this research support and encourage the use of nonlinear phase-resolving wave models as tools for academic research, coastal management, coastal engineering, and hazard forecasting on atoll and fringing reef environments.