New Suspended Sand Concentration Model for Breaking Waves

Process-based morphodynamic modelling suites (as well as other process-based models) are often considered to be inefficient and unsuitable for simulating medium- to long-term morphodynamics due to the various theoretical (e.g. robustness of sediment transport models) and practical (e.g. computational costs) limitations. In particular, a lack of knowledge of sediment transport processes and how they relate to hydrodynamics makes the application of short-term models to long-term coastal evolution challenging. Even the state-of-the-art coastal area modelling suites (such as Delft3D and MIKE21) consist of relatively simple physics, relying instead on numerous semi-empirical parameterizations, which are often poorly supported by measured data and/or physical process understanding. In particular, suspended sediment transport in the highly turbulent surf zone is poorly modelled under breaking wave conditions. Six existing suspended sand concentration (SSC) models were critically evaluated against four high-resolution datasets with field-scale breaking waves and co-located velocity and concentration measurements over multiple cross-shore zones (shoaling, breaking and inner-surf zones). A new improved concentration model was proposed based on a novel empirical relationship observed between local water depth and reference concentration, as well as latest process understanding and insights.