Wave Transformation Over Reefs: Evaluation of One-Dimensional Numerical Models

Abstract : Three one-dimensional (1D) numerical wave models are evaluated for wave transformation over reefs and estimates of wave setup, runup, and ponding levels in an island setting where the beach is fronted by fringing reef and lagoons. The numerical models are based on different governing equations. BOUSS-1D and RBREAK2 are phase-resolving models that respectively solve the time-dependent Boussinesq and shallow water equations. WAV1D solves the 1D wave-averaged energy conservation equation. Laboratory data obtained from four physical modeling studies conducted by Seelig (1983), Gourlay (1994), Thompson (2005), and Demirbilek and Nwogu (2007) are used in the evaluation of numerical models. The numerical models produced reasonable correlation with the data. Overall BOUSS-1D representation of wave breaking and wave dissipation were realistic and compared well to data. The model's estimates are sensitive to values of input bottom friction and turbulence length scale coefficients. RBREAK2 is robust because it does not attempt to explicitly represent the wave breaking processes. However, the model is highly dissipative when applied to wide fringing reefs and is only applicable when the runup beach is reasonably close to the predominant wave breaking location. The model predictions were also found to be less sensitive to values of friction factor. The correlation with one of the data sets was good, but not as good for two other data sets. WAV1D is the simplest model evaluated in this study. This model is appropriate for preliminary and feasibility level estimates.