Abstract
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.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/2iBrnXs4b3M
Highlights
Coastal area modelling suites such as Delft3D, MIKE21 and Telemac are powerful process-based modelling suites that couple hydrodynamic modules with sediment transport and morphodynamic modules to simulate complex coastal environments
Several models related the C0 to the sand pickup rate or Shields Parameter
Such models were adept in reproducing SSC in the shoaling zone where there was no external TKE, but performed poorly in the breaking zone, around the plunging point, where breaking-induced TKE is highest
Summary
Coastal area modelling suites such as Delft3D, MIKE21 and Telemac are powerful process-based modelling suites that couple hydrodynamic modules with sediment transport and morphodynamic modules to simulate complex coastal environments. Such modelling suites (as well as other process-based models) are often considered to be inefficient and unsuitable for simulating medium- to long-term morphodynamics. A common view held in existing literature is that extending small-scale process-based morphology models for simulation of longterm morphodynamics is unsuitable, due to the various theoretical (e.g. robustness of sediment transport models) and practical (e.g. computational costs) limitations. As SSC is highest in the breaking zone, under breaking conditions, large discrepancies between measured and predicted SSC in the breaking zone (which were observed to be up to an order of 101 kg/m3; see Fig.1) would result in unrealistic transport rates and resulting morphodynamic predictions
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