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We present a comprehensive and critical review of work on the numerical modelling of swash zone processes between 2005 and 2015. A wide range of numerical models has been employed for the study of this region and, hence, only phase-resolving approaches (i.e., depth-averaged and depth-resolving models) are analyzed. The current advances in the modelling of swash zone processes are illustrated by comparing different numerical models against laboratory experiments of a dam-break-driven swash event. Depth-averaged and depth-resolving models describe well the swash flow for both coarse sand and gravel impermeable beach cases. Depth-averaged models provides a practical tool for engineering use, whereas depth-resolving models improve the flow description, especially for the backwash phase, with a significantly higher computational cost. The evolution and magnitude of bed shear stresses predicted by all models is reasonable when compared with laboratory estimates based on the log-law. However, differences between modelling approaches cannot be rigorously evaluated owing to the uncertainty in shear stress estimates while employing such approximation. Furthermore, small-scale processes, such as turbulence evolution, are investigated with depth-resolving models, finding differences between the two-dimensional and three-dimensional approaches. Numerical models allow us to investigate other processes such as beach morphology changes, the evolution of the turbulence coherent structures, and the infiltration/exfiltration effects on the swash flow. A discussion on the advantages and limitations of each model is presented. The future of swash zone modelling depends on the increase of the computational power and, more importantly, on the improvement of the current capability to obtain intra-wave measurements for model validation, calibration, and greater resolution of physical processes. [ABSTRACT FROM AUTHOR]

In this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatures of swash from contrasting beach types. The field data set includes the full range of micro-tidal beach types (reflective, intermediate and dissipative), with beach gradients ranging from approximately 1:6 to 1:60 exposed to offshore significant wave heights of 0.5-3.0 m. The ratio of swash energy in the short-wave (f > 0.05 Hz) to long-wave (f < 0.05 Hz) frequency bands is found to be significantly different between the three beach types. Swash energy at short-wave frequencies is dominant on reflective and intermediate beaches and swash at long-wave frequencies is dominant on dissipative beaches; consistent with previously reported spectral signatures for the surf zone on these beach types. The available swash spectra were classified using an automated algorithm (CLARA) into five different classes. The ordered classes represent an evolution in the spectrum shape, described by a frequency downshifting of the energy peak from the short-wave into the long-wave frequency band and an increase in the long-wave swash energy level compared to a relatively minor variation in the short-wave swash energy level. A universally common feature of spectra from all beach-states was an f- 4energy roll-off in the short-wave frequency band. In contrast to the broadly uniform appearance of the short-wave frequency band, the appearance of the long wave frequency band was highly variable across the beach-states. We incorporate the results presented here and previously published observations into the morphodynamic beach-state model, and propose an ordered sequence of swash spectra under increasing and decreasing incident wave energy level. This extension of the beach-state model to include the swash zone leads to the following propositions for morphodynamic controls on the nature of the swash spectrum. (1) The short-wave part of the swash spectrum is relatively constant in form across all beach-states (f- 4 energy roll-off) and the energy density per unit frequency is controlled by the beach face gradient alone. (2) The spectral bandwidth of the energy roll-off varies directly with offshore wave energy level and inversely with beach face gradient (or beach-state), in a manner consistent with the non-linear wave breaking criterion. (3) The infragravity part of the swash spectrum is highly variable in form across all beach-states and the energy level is related to the offshore wave energy level and surf zone morphology. [ABSTRACT FROM AUTHOR]

Abstract: Novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone. An experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse. The advection scales and settling of this sediment were measured during the uprush along a rigid sediment-free beach face by a sediment trap located at varying cross-shore positions. Measurements were made using a number of repeated solitary broken waves or bores. Approximately 25% of the pre-suspended sediment picked up by the bores reaches the mid-swash zone (50% of the horizontal run-up distance), indicating the importance of the sediment advection in the lower swash zone. The pre-suspended sediment is sourced from a region seaward of the shoreline (still water line) which has a width of about 20% of the run-up distance. An Eulerian–Lagrangian numerical model is used to model the advection scales of the suspended sediment. The model resolves the hydrodynamics by solving the non-linear shallow water equations in an Eulerian framework and then solves the advection–diffusion equation for turbulence and suspended sediment in a Lagrangian framework. The model provides good estimates of the measured mass and distribution of sediment advected up the beach face. The results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre-suspended sediment to the net sediment transport in the swash zone. [Copyright &y& Elsevier]

Abstract: The present work analyzes the hydro-morphodynamics characterizing the swash region during the uprush stage. A comparison is illustrated between the sediment transport measured in a series of dam-break experiments and that predicted by the numerical hydro-morphodynamic model of Postacchini et al. (2012). The primary aim is to investigate the differences arising between the weakly coupled or uncoupled model and the measurements, in terms of hydrodynamics, tip celerity and sediment transport. The hydrodynamics are well described by the model and results have been used to calibrate both friction factor and subgrid turbulent viscosity. Comparison of numerically-computed tip celerity with experimental data reveals a fairly good agreement, i.e. a mean error of about 10%, while modeled sediment transport differs by about 40% from the available data. No evident differences are found between results obtained from the coupled and uncoupled model runs (2% for the celerity and 11% for the sediment transport rate at the tip), suggesting that for the specific flow under investigation, at the leading edge of the swash front, hydro-morphological coupling is not an issue of fundamental importance. However, for the special case here of a swash forced by a dam-break, scour occurs at the dam location, and in this case the erosion of the bed is significantly larger in the uncoupled model. [Copyright &y& Elsevier]