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High quality laboratory measurements of nearshore waves and morphology change at, or near prototype-scale are essential to support new understanding of coastal processes and enable the development and validation of predictive models. The DynaRev experiment was completed at the GWK large wave flume over 8 weeks during 2017 to investigate the response of a sandy beach to water level rise and varying wave conditions with and without a dynamic cobble berm revetment, as well as the resilience of the revetment itself. A large array of instrumentation was used throughout the experiment to capture: (1) wave transformation from intermediate water depths to the runup limit at high spatio-temporal resolution, (2) beach profile change including wave-by-wave changes in the swash zone, (3) detailed hydro and morphodynamic measurements around a developing and a translating sandbar. Measurement(s) surf zone waves • swash hydrodynamics • surf zone flow velocity • morphology • sediment Technology Type(s) Gauge or Meter Device • Lidar • velocimetry • mechanical profiler • optical backscatter sensor • Pressure transducers Factor Type(s) Wave height • Wave period • beach morphology Sample Characteristic - Environment beach • shingle beach Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.13194872 [ABSTRACT FROM AUTHOR]

Parameterization of wave runup is of paramount importance for an assessment of coastal hazards. Parametric models employ wave (e.g., Hs and Lp) and beach (i.e., β) parameters to estimate extreme runup (e.g., R2%). Thus, recent studies have been devoted to improving such parameterizations by including additional information regarding wave forcing or beach morphology features. However, the effects of intra-wave dynamics, related to the random nature of the wave transformation process, on runup statistics have not been incorporated. This work employs a phase- and depth- resolving model, based on the Reynolds-averaged Navier-Stokes equations, to investigate different sources of variability associated with runup on planar beaches. The numerical model is validated with laboratory runup data. Subsequently, the role of both aleatory uncertainty and other known sources of runup variability (i.e., frequency spreading and bed roughness) is investigated. Model results show that aleatory uncertainty can be more important than the contributions from other sources of variability such as the bed roughness and frequency spreading. Ensemble results are employed to develop a new parametric model which uses the Hunt (J Waterw Port Coastal Ocean Eng 85:123–152, 1959) scaling parameter β H s L p 1 / 2 . [ABSTRACT FROM AUTHOR]

An extensive previously published (Hughes et al. Mar Geol 355, 88-97, 2014) field data set representing the full range of micro-tidal beach states (reflective, intermediate and dissipative) is used to investigate swash saturation. Two models that predict the behavior of saturated swash are tested: one driven by standing waves and the other driven by bores. Despite being based on entirely different premises, they predict similar trends in the limiting (saturated) swash height with respect to dependency on frequency and beach gradient. For a given frequency and beach gradient, however, the bore-driven model predicts a larger saturated swash height by a factor 2.5. Both models broadly predict the general behavior of swash saturation evident in the data, but neither model is accurate in detail. While swash saturation in the short-wave frequency band is common on some beach types, it does not always occur across all beach types. Further work is required on wave reflection/breaking and the role of wave-wave and wave-swash interactions to determine limiting swash heights on natural beaches. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1038/s41597-021-00874-2. [ABSTRACT FROM AUTHOR]

The response of nourished beaches to sea level rise is investigated experimentally with random waves in a laboratory wave flume (20 m × 1 m × 1 m), following on from a previous investigation of the response of non-nourished beaches (Atkinson et al., 2018). The nourishments are placed on beach profiles previously exposed to sufficient durations of waves to have approached a near-equilibrium state, i.e., with stable shoreline, bars and berms. Nourishment was placed in three different locations: on the berm, within the bar trough, and as a shoreline placement. In the latter case, and following Bruun rule concepts (Bruun, 1962), the volume of sediment placed was estimated a priori to lead to zero recession under the chosen water level rise. The nourished beaches were then exposed again to sufficient durations of waves to reach a near-equilibrium state at the raised water level. The shoreline recession and the mean recession of the profile following a rise in water level are compared for both the nourished and non-nourished beaches, and to theoretical estimates based on Bruun rule concepts and a previously developed Profile Translation Model (PTM). Quantitative agreement is found with the variants of the Bruun Rule that account for nourishment and with the PTM, and the predicted recession is within an order of ±30% of the observed recession. Overall, the PTM provides the best estimate of the recession. The mean recession of the profile is found to be in better agreement with the model predictions than the recession measured at the shoreline, because the latter is affected by changes in profile shape around the still water line. The efficacy of the nourishment was investigated from the reduction in the observed recession. The efficacy depends on how the recession is measured. For the mean recession, highest efficacy was observed when all the nourishment is added into the active profile. Conversely, for the shoreline recession, highest efficacy was observed with the nourishment placed on the upper beach because it prevents additional recession through wave overtopping. • Direct comparison of nourishment and non-nourishment experiments. • Nourishment reduces recession associated with sea level rise. • Nourishment placed further landward reduces chance of loss of sediment offshore. • The effective nourishment volume is important to consider when predicting recession. [ABSTRACT FROM AUTHOR]

Existing empirical and theoretical models for swash overtopping are considered and reconciled by using the positive volume flux of the incident waves and the deficit in freeboard as scaling parameters. This scaling holds for solitary waves, monochromatic waves and random waves. The empirical model of Battjes (1974), the EurOtop model (EurOtop, 2016) and the theoretical model of Peregrine and Williams (2001) can all be written in terms of the positive volume flux with consistent coefficients. This scaling can be rationalised physically by equating the positive volume flux to the volume of fluid displaced by a wavemaker. The empirical exponential vertical scaling in EurOtop is very similar to the empirical vertical scaling identified by Battjes (1974). Here, it is shown that the latter can be rationalised theoretically from a simple ballistic swash model. New experiments on swash overtopping a truncated plane beach are presented for monochromatic and random waves and shown to scale well with these two parameters. Data for equivalent smooth planar beaches from the CLASH database are compared to the new scaling, with good agreement. The influence of beach slope on overtopping has some uncertainty between the theoretical and empirical models, and in the present data, particularly for high deficit in freeboard as the truncation point approaches the still water line. This is likely to be a result of different processes occurring in the surf and swash zones, or over the subaqueous beach face and sub-aerial beach face. • Different empirical and theoretical scaling laws for swash overtopping can be reconciled. • The volume flux provides a consistent scale for solitary waves, monochromatic waves and random waves. • The deficit in freeboard provides the vertical scale of the new scaling. • New experiments are compared with existing and the new scaling. • The influence of beach slope is not fully resolved, and different to that indicated by the theory. [ABSTRACT FROM AUTHOR]

Bayle, P.M.; Beuzen, T.; Blenkinsopp, C.E.; Baldock, T.E., and Turner, I.L., 2020. Beach profile changes under sea level rise in laboratory flume experiments at different scales. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 192–196. Coconut Creek (Florida), ISSN 0749-0208. Laboratory wave flume experiments have been used to provide improved understanding of beach profile evolution under different wave and water level conditions. However, the understanding of the processes involved in the evolution of beach profile under Sea Level Rise (SLR) toward equilibrium is unclear. Two similar, but distorted experiments were performed at large and medium scale in order to study the qualitative morphological changes involved in beach profile evolution under SLR. Both experiments showed similar beach profile evolution. The profile change predicted by the Profile Translation Model (PTM) and the Bruun Rule underestimated the observed reatreat in both experiments. The length of the active beach profile increased under SLR. For the large scale experiment, the reflection coefficient of the beach decreased while the vertical runup increased significantly. The beachface changed faster than the outer surf zone, making the beach more dissipative. [ABSTRACT FROM AUTHOR]

Laboratory investigations of beach morphology change under wave action are undertaken to gain insight into coastal processes, design coastal structures and validate the predictions of numerical models. For the results of such experiments to be reliable, it is necessary that they are repeatable. The equilibrium beach concept, that beach morphology will evolve to a quasi-static equilibrium shape for a given forcing suggests that experiments should be repeatable to some degree. However, sediment transport in turbulent breaking and broken waves is complex and highly variable and the level of repeatability at different temporal and spatial scales is challenging to measure, as such, previous work has restricted comparisons to small numbers of waves. Here we use the results of two identical, 20-h large-scale wave flume experiments to investigate the repeatability of sediment transport and beach morphology change under waves at timescales down to individual swash events. It is shown that while flow characteristics from identical swash events are very repeatable, the sediment transported can be very different in both magnitude and direction due to differences in turbulence, sediment advection and morphological feedback. Over longer periods containing multiple matching swash events however, the beach responds in a very similar manner, with the level of morphological repeatability increasing with time. The results also demonstrate that gross swash zone sediment transport remains high even as a beach profile approaches quasi-equilibrium, but the proportion of individual swash events that cause large sediment fluxes (>±7.5 kg/event/m) reduces with time. The results of this laboratory study indicate that beach morphology change has a level of determinism over timescales of several minutes and longer, giving confidence in the results from physical modelling studies. However, the large differences in sediment transport from apparently identical swash events questions the value in pursuing numerical predictions of sediment transport at the wave-by-wave timescale unless the reversals in sediment transport between apparently near identical swash events can also be predicted. • Large-scale flume experiments are used to assess morphological repeatability. • The results of laboratory investigations of morphology change are repeatable. • Sediment fluxes from almost identical waves vary in magnitude and direction. • Over longer timescales, sediment fluxes from identical wave groups converge. • Gross sediment transport remains high even as beaches approach quasi-equilibrium. [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: Measured probability distributions of shoreline elevation, swash height (shoreline excursion length) and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions. The theoretical distributions are based on assumptions that the time series are weakly steady-state, ergodic and a linear sum of random variables. Despite the swash process being inherently non-linear, results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution. The RMS-errors for a range of exceedence level statistics (50, 10, 5, 2, and 1%) were restricted to <10cm (and often <5cm) for all of the swash variables that were investigated. The results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic-type morphodynamic modeling of beach response to waves. Further work is required, however, to relate the parameters of swash probability distributions to wave conditions further offshore. [Copyright &y& Elsevier]

Abstract This paper assesses the accuracy of seven empirical models and an explicit Gene-Expression Programming (GEP) model to predict wave runup against a large dataset of runup observations. Observations consist of field and laboratory measurements and include a wide array of beach types with varying sediment sizes (from fine sand to cobbles) and bed roughness (from smooth steel to asphalt). We show that the best performing models in the literature are prone to significant errors (minimum RMSE of 1.05 m and NMSE of 0.23) when used with unseen data, i.e., uncalibrated models; however, overall error values and correlations are significantly reduced when models are optimised for the dataset. The best performing empirical models use a Hunt type scaling with an additional parameter for wave induced setup. The predictive ability of the explicit GEP model, which better captures the complex nonlinear effects of the key factors on the wave runup length, resulted in a statistically significant improvement in predictive capacity in comparison to all other empirical models assessed here, even on unseen data. Wave height, wavelength, and beach slope are shown to be the three primary factors influencing wave runup, with grain size/bed roughness having a smaller, but still significant influence on the runup. The r2 of the best optimised existing models (which takes the form of Holman (1986) and Atkinson et al. (2017) their M2 model) was 0.77, with a RMSE of 0.85 m. These were improved to an r2 of 0.82 (6% increase) and RMSE of 0.75 m (12% decrease) in the GEP-based model. The sensitivity of the proposed GEP-based model to each input variable is assessed via a partial derivative sensitivity analysis. The results demonstrate a higher sensitivity in the model to small values of each input and that wave steepness and beach slope are the primary factors influencing wave runup. [ABSTRACT FROM AUTHOR]

This paper assesses the accuracy of 11 existing runup models against field data collected under moderate wave conditions from 11 non-truncated beaches in New South Wales and Queensland, Australia. Beach types spanned the full range of intermediate beach types from low tide terrace to longshore bar and trough. Model predictions for both the 2% runup exceedance ( R 2% ) and maximum runup ( R max ) were highly variable between models, with predictions shown to vary by a factor of 1.5 for the same incident wave conditions. No single model provided the best predictions on all beaches in the dataset. Overall, model root mean square errors are of the order of 25% of the R 2% value. Models for R 2 % derived from field data were shown to be more accurate for predicting runup in the field than those developed from laboratory data, which overestimate the field data significantly. The most accurate existing models for predicting R 2% were those developed by Holman [12] and Vousdoukas et al. [40], with mean RMSE errors of 0.30 m or 25%. A new model-of-models for R 2% was developed from a best fit to the predictions from six existing field and one large scale laboratory R 2% data-derived models. It uses the Hunt [17] scaling parameter tan β H o L o and incorporates a setup parameterisation. This model is shown to be as accurate as the Holman and Vousdoukas et al. models across all tidal stages. It also yielded the smallest maximum error across the dataset. The most accurate predictions for R max were given by Hunt [17] but this tended to under predict the observed maximum runup obtained for 15-min records. Mase's [22] model has larger errors but yielded more conservative estimates. Greater observed values of R max are expected with increased record length, leading to greater differences in predicted values. Given the large variation in predictions across all models, however, it is clear that predictions by uncalibrated runup models on a given beach may be prone to significant error and this should be considered when using such models for coastal management purposes. It should be noted that in extreme events, which are lacking in the dataset, runup may be truncated by beach scarps, cliffs, and dunes, or may overtop, and as a result, the probability density functions will have different tail shapes. The uncertainty already present in current models is likely to increase in such conditions. [ABSTRACT FROM AUTHOR]

Laboratory wave flume experiments in coastal engineering and physical oceanography are widely used to provide an improved understanding of morphodynamic processes. Wave flume facilities around the world vary greatly in their physical dimensions and differences in the resulting distortion of the modelled processes are reconciled using scaling laws. However, it is known that perfect model-prototype scaling of all hydro and morphodynamic processes is rarely possible and there is a lack of understanding to what extent distorted models can be used for direct morphological comparison. To address this issue, distorted scale laboratory flume experiments were undertaken in three different facilities, with the aim to measure and compare beach profile evolution under erosive waves and increasing water levels. A novel approach was developed to transform and scale the different experimental geometries into dimensionless coordinates, which enabled a direct quantitative comparison of the beach profile evolution and sediment transport rates between the differing distorted experimental scales. Comparing results from the three experiments revealed that the dimensionless scaled morphological behaviour was similar after the same number of waves – despite very different degrees of model distortion. The distorted profiles appeared to be suitable for comparison as long as a modified version of the Dean number is maintained between them. The new method was then validated with two further published datasets, and showed good agreement for both dimensionless profile shape, dimensionless sediment transport and morphodynamics parameters. The new approach scales the sediment transport by the square of the runup, proportional to HL, rather than H 2, and yields good agreement between the datasets. It is further shown that the new scaling method is also applicable for comparing distorted profile evolution under water level increase, as long as the water level is raised in a similar way between the experiments and by the same total increment relative to the significant wave height (Δh/H s). • Three distorted laboratory wave flume experiments of different scales are compared. • Development of a new scaling methodology for comparing beach profiles of distorted experiments. • Analysis and validation of the method for a fixed and increasing water level. • Qualitative and quantitative comparison of distorted profiles possible by scaling with HL. • Two examples of application of the method, for a fixed and increasing water level. [ABSTRACT FROM AUTHOR]

New large-scale experiments on the influence of storm sequencing on beach profile evolution are presented. The experiments comprised three sequences that commenced from the same initial beach profile. Each sequence consisted of two storms of different energy, with each storm followed by a recovery phase. A specific focus of the experiments was the influence of storm chronology as well as the influence of the recovery wave energy and duration on beach evolution. The breaker bar and the shoreline are studied as indicators for the beach response. Both evolve towards an equilibrium location for each wave condition where the breaker bar reaches its equilibrium much faster than the shoreline. Overall, no enhanced beach erosion due to storm sequencing is observed. Despite a similar cumulative wave power of the three sequences, the final beach configuration of each sequence seems to be determined by the last wave condition instead of previous storms. However, storm sequencing is important when the beach profile has not yet fully recovered before being disrupted by the subsequent storm. In this case, the second storm does not necessarily cause further erosion but can result in onshore sediment transport and hence, form part of the recovery. The bulk onshore sediment transport as well as the shoreline recovery rate vary depending on the wave condition and the profile disequilibrium and show a maximum value for a recovery condition with an intermediate wave energy. The very low energy condition that was performed for a long duration (24 hours) generated a near-stationary beach profile with typical features of a reflective beach. • New large-scale experiments on storm sequencing and beach response. • The beach evolves towards an equilibrium state under the performed storm sequences. • The rate of beach change varies depending on the antecedent beach morphology. • Largest bulk onshore sediment transport occurs for intermediate low energy conditions. • A very low energy condition of long duration (24 h) results in a reflective beach profile. [ABSTRACT FROM AUTHOR]

Large-scale experiments on beach profile evolution, performed within the HYDRALAB+ experiments 'RESIST', will be presented providing new insights into the influence of storm sequencing on beach response. Three storm sequences with the same cumulative wave power were generated; each sequence consisted of two high energy (storm) wave conditions each of which was followed by a recovery stage. Beach profile measurements, observations of the wave breaking location and sediment bed samples are used to study the influence of storm sequences on beach profile evolution, including the effect of storm chronology and beach recovery of different energy and duration.The beach profile is found to evolve towards an equilibrium state that is specific for each wave condition indicating no cumulative effect of storm sequencing on beach erosion in the present experiments. This means that, despite the same cumulative power of each sequence, the final beach configuration of each sequence is different and it depends on the wave condition that was performed at the end of the sequence. Storm sequencing is, however, important for the rate of beach change: As the beach evolves towards equilibrium for each wave condition, the rate of beach change varies for the same wave conditions but different initial beach profiles (different sequencing). This means that the same wave condition can result in either beach erosion or recovery depending on if the beach is in recovered or eroded condition compared to the equilibrium beach configuration for these wave conditions.This contribution will present one of the first large-scale data sets comprising more than one high energy and subsequent recovery stage in one sequence. We will discuss the influence of the storm chronology, beach equilibrium configuration and recovery conditions on the beach profile evolution. [ABSTRACT FROM AUTHOR]