Modeling wave processes in a reef-lagoon-channel system based on a Boussinesq model

Abstract

The reef-lagoon-channel system is very typical on the low-lying reef-lined coasts in tropical and subtropical areas. Comparing to the well-studied one-dimensional horizontal (1DH) fringing reefs, little is known about the alongshore wave runup variation and its implication for coastal flooding in such a two-dimensional horizontal (2DH) reef configuration. To better understand the wave processes in an idealized reef-lagoon-channel system, a numerical model is presented in this study, which is based on a set of fully nonlinear Boussinesq equations. Wave breaking is addressed by a shock-capturing scheme and bottom friction is formulated by the Manning frictional law. The adopted model is first validated by a published laboratory dataset in view of wave spectrum, wave height, wave setup, mean current as well as wave runup on the back-reef beach. Subsequently, the effects of hydrodynamic (incident wave height, incident wave period, reef-flat wave level) and reef morphological (fore-reef slope, cross-shore reef-flat width, channel width and frictional coefficient) parameters that are not fully considered by the laboratory experiments are investigated through the numerical simulations. Finally, the model is used to analyze the infragravity (IG) wave resonant modes in the system, and the effects of channel on such modes are also demonstrated.