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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: 10.6084/m9.figshare.13194872

Wave-by-wave and cumulative overtopping data from fixed planar impermeable smooth beaches will be presented from random wave experiments and compared with predictions from two nonlinear sh...

The creation and protection of surfing breaks along populated coastlines have become a consideration for many councils and governments as surfing breaks are a major driver of tourism. To assess the surf amenity of surfing breaks, a quantitative and objective assessment method is required. A new wave peel tracking (WPT) method has been developed using a shore-based camera to assess surf amenity by measuring and quantifying potential surfing ride rate, length, duration, speed and direction on a wave-by-wave basis. The wave peel (or “curl” below the wave peak) is the optimal surfing region on a wave, and each wave peel track represents a surfable ride. Wave peel regions are identified, classified and tracked using traditional and machine learning-based computer vision techniques. The methodology is validated by comparing the rectified wave peel tracks with GPS-measured tracks from surfers in the wave peel regions. The WPT methodology is evaluated with data from a reef and adjacent natural beach at the Gold Coast, Australia. The reef produced longer ride lengths than the nearshore region and showed a consistent breaking location along the reef crest. Spatial maps of the wave peel tracks show the influence of tides on the wave breaking patterns and intensity. The WPT algorithm provides a robust, automated method for quantifying surf amenity to provide baseline data for surf break conservation. The methodology has potential uses to verify numerical modelling of surf breaks and to assess the impact of coastal development on surf breaks.

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 $\beta \left (H_{s}L_{p}\right )^{1/2}$.

Reef-protected beaches are vulnerable to the effects of sea level rise and degradation of their associated fringing reefs. The SWAN hydrodynamic wave model is combined with classical theory describing the planform of beaches in equilibrium with the wave forcing to estimate the reef top hydrodynamics and the shoreline configuration in the lee of the reefs. Open access Bayesian Belief Networks with high accuracy and simple user interfaces have been built to communicate the results. The BBN enable end users to access all the model results and to compare different scenario to determine how changes in the wave climate or reef elevation change the shoreline configuration. The results show that recession of the shoreline in the lee of fringing reefs due to sea level rise may be much greater than that expected on open coast beaches. Loss of reef flat elevation can also lead to severe shoreline erosion.

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.

Wave measurements from a new, low-cost, real-time wave buoy (Spotter) are investigated in a comparative study as part of a site characterization study at a wave energy candidate site at King Island, Tasmania, Australia. Measurements from the Sofar Ocean Spotter buoy are compared with concurrent measurements from a Teledyne RD Instrument (RDI) 1200 kHz Work Horse ADCP and two RBRsolo3 D wave16 pressure loggers. The comparison period between 8th August – 12th October 2019 provides both the shallowest and longest continuous published comparison undertaken with the Spotter buoy.Strong agreement was evident between the Spotter buoy and RDI ADCP of key wave parameters including the significant wave height, peak wave period, and mean wave direction, with the mean values of those parameters across the full deployment period agreeing within 3%. Surface wave spectra and directional spectra are also analyzed with good agreement observed over the majority of the frequency domain, although the Spotter buoy records approximately 17% less energy within a narrow frequency band near the peak frequency when compared to the RDI ADCP. Measurements derived from the pressure loggers routinely underestimated the significant wave height and overestimated the mean wave period over the deployment period. The comparison highlights the suitability of the Spotter buoy for low-cost wave resource studies, with accurate measurements of key parameters and spectra observed.

Field observations of tsunami show that tsunami waves travel faster and further along coastal rivers than inland due to reduced obstructions and converging boundaries, causing inundation and damage to hydraulic structures. Hence, the objective of the present study is to investigate tsunami wave heights and overtopping volumes along river walls in a converging channel. Experiments were conducted in a wave flume (using non-breaking solitary waves and solitary breaking bores) with a 9.14m long, 0.2m high PVC sheet in the flume representing converging river wall. Later, simulation of the test cases was performed using two numerical models ANUGA and BASEMENT. The results from the numerical modelling were then compared to that of experiments to evaluate the performance of the models and their applicability for tsunami warnings in these scenarios. Different propagation and overtopping behaviour was observed for non-breaking solitary waves and solitary breaking bores.

Tsunami propagating into a coastal river can severely damage hydraulic structures including bridge piers as reported during past tsunami events. Hence, in the present study, laboratory experiments are performed initially by generating tsunami bores on to a wet bed in a 24m long, 0.8m wide wave flume and later in a 12mx0.5mx0.465m recirculating channel to maintain a time scale of 1:6 required as per Froude scaling to observe reliable scour depth at the pier model. Three-dimensional flow velocities (using rigid bed) and scour patterns, depths (using mobile bed) around a circular bridge pier model were obtained to understand the scour process. Finally, the scour depth due to tsunami bore is compared to empirical steady flow scour estimations. Therefore, the present study proposes new scour design standards for bridge piers or vertical evacuation towers which are already inundated by the first wave of tsunami.

Offshore aquaculture systems require protection from extreme seas and swell waves. However, floating wave breakwaters are known to be ineffective in long waves unless their size is comparable to the wavelength, which is impractical and not cost effective. This study develops a novel floating breakwater, using HDPE pipes common in the aquaculture industry, which automatically adopts the shape of a parabolic beach. A comprehensive series of laboratory experiments was performed to investigate the performance of a scaled model breakwater with a fixed edge anchored to the bottom of the wave flume. Results demonstrate that the effectiveness of floating breakwaters can be greatly improved using a beach-shaped semi-flexible floating structure to dissipate energy by breaking, instead of systems that reflect wave energy or dissipate energy in pores.

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.

Surf amenity can be significantly affected by coastal infrastructure and is a growing consideration for local governments. Quantitative assessment of the surf amenity of artificial reefs is also growing in interest. Surf amenity has been quantified using metrics derived from the surfable region near the breaking edge of a wave, defined as the ‘wave pocket’. Wave pocket tracking software has been developed to track potential surfing rides using computer vision. This software enabled a surf amenity assessment of the Rainbow Bay (QLD) ‘superbank’ during Cyclone Eusi and the Palm Beach artificial reef. The produced data revealed new insights into the surf amenity of natural and artificial surf locations.

This chapter describes the morphological features and key processes related to the swash zone, situated at the landward edge of the inundated part of the beach system. It is where incoming surf zone waves force oscillatory motion of the shoreline at a variety of frequencies. Morphological features addressed include the beach face slope, beach berms, beach steps and beach scarps. Sediment sorting across the beach face profile and the formation of heavy mineral deposits are also discussed. In the recent literature, swash flow kinematics/dynamics and sediment transport mechanics have received more attention than the morphology. This research is discussed in the context of its relevance to an improved understanding of swash zone morphodynamics. Rather than presenting a detailed review of the available literature, the authors present their perspective on current research directions and outstanding issues still to be resolved.

The use of physics-based wave propagation predictions requires a considerable time commitment, a high level of expertise and extensive climate and reef data that are not always available when undertaking planning for management of coasts and coral reef ecosystems. Bayesian belief networks (BBNs) have at least three attributes that make them an excellent choice to communicate physics-based wave model predictions. First, BBNs subsume thousands of predictions to provide probabilistic outcomes. Second, by using prior probabilities, a practitioner can still obtain predictions of wave outcomes even when their knowledge of input parameters is incomplete. Third, BBNs can propagate evidence from outputs to inputs, which can be used to identify input conditions that are most likely to deliver a chosen outcome. These three attributes are tested and found to hold for a BBN developed for this purpose.

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.

Rising sea levels are expected to cause widespread coastal recession over the course of the next century. In this work, new insight into the response of sandy beaches to sea level rise is obtained through a series of comprehensive experiments using monochromatic and random waves in medium scale laboratory wave flumes. Beach profile development from initially planar profiles, and a 2/3 power law profile, exposed to wave conditions that formed barred or bermed profiles and subsequent profile evolution following rises in water level and the same wave conditions are presented. Experiments assess profile response to a step-change in water level as well as the influence of sediment deposition above the still water level (e.g. overwash). A continuity based profile translation model (PTM) is applied to both idealised and measured shoreface profiles, and is used to predict overwash and deposition volumes above the shoreline. Quantitative agreement with the Bruun Rule (and variants of it) is found for measured shoreline recession for both barred and bermed beach profiles. There is some variability between the profiles at equilibrium at the two different water levels. Under these idealised conditions, deviations between the original Bruun Rule, the modification by Rosati et al. (2013) and the PTM model predictions are of the order of 15% and all these model predictions are within ±30% of the observed shoreline recession. Measurements of the recession of individual contour responses, such as the shoreline, may be subject to local profile variability; therefore, a measure of the mean recession of the profile is also obtained by averaging the recession of discrete contours throughout the active profile. The mean recession only requires conservation of volume, not conservation of profile shape, to be consistent with the Bruun Rule concept, and is found to be in better agreement with all three model predictions than the recession measured at the shoreline.

Numerical modeling and analysis of laboratory and field data are combined to show new evidence of breakpoint forced long waves. The laboratory data and numerical modeling show that the breakpoint can oscillate at frequencies not directly linked to the wave group envelope for specific bichromatic wave groups. The breakpoint therefore oscillates at frequencies where incident bound long waves are not present, enabling direct identification of breakpoint forced waves. Spectral analysis and cross-shore wave propagation patterns indicate that the breakpoint forced waves occur at subharmonic wave groups frequencies, the repeat frequency of the short waves within the group, and at frequencies associated with triad interactions. The results indicate that in this case the long waves are generated by breakpoint forcing rather than by energy transfer during shoaling of the incident waves. The slowly varying shape of the short waves in the groups and wave merging at the breakpoint controls the modulation of the breakpoint in these cases. The spectral analysis is applied to two field data sets where the breakpoint oscillation, incident waves and shoreline oscillation were measured, and infragravity wave generation is again identified at discrete frequencies that are not present in the incident wave group envelope, with merging of waves at the breakpoint again evident. The magnitudes of the generated infragravity waves outside the surf zone are also dependent on the normalized surf zone width. Both sets of observations provide further evidence for the generation of infragravity waves by the breakpoint forcing mechanism in the field.

Disequilibrium-type models for two beach profile parameters, P, the shoreline position and net bulk sediment transport, are developed for laboratory experiments that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The model principle follows the classical disequilibrium approach but with non-monotonic relationships between the forcing and the chosen beach profile parameter at equilibrium, Peq, previously verified and presented in part 1 of this work (Baldock et al., 2017). Two such relationships are required to model beach profile evolution that exhibits morphological hysteresis. The model coefficients are derived for monochromatic and random wave experiments and subsequently used to model data obtained from cyclic erosive and accretive wave conditions of shorter durations, alternating through multiple cycles. In these conditions equilibrium conditions were not reached and hysteresis does not occur. The model is used to investigate the morphological feedback between the outer and inner bars and the resulting behaviour of the bulk transport, and the relative depth over the bar crest is shown to be an attractor in this case. The model coefficients and morphological time-scales derived from the cyclic experiments are very similar to those derived from the equilibrium experiments for the bulk transport. Normalised mean square model errors range from 1% to 20% when applied to independent data. The data from the cyclic wave conditions can be inverted to derive the conditions expected at equilibrium, which match those observed, indicating a robust model relationship between the forcing and Peq. The relationship between the forcing and Peq can also be determined directly from the cyclic experiments. This approach may be more robust than determining the relationship from periods where P is stationary since, in a time-series of P versus the forcing, stationary points can occur due to changes in wave conditions, in addition to the instances when P=Peq.

We use our previous numerical and measuring experience and the evidence from a rather unique episode at sea to summarise our doubts on the present physical approach in wave modelling. The evidence strongly suggests that generation by wind and dissipation by white-capping have a different physics than presently considered. Most of all they should be viewed as part of a single physical process.

A new methodology is proposed to estimate storm demand and dune recession by clustered and non-clustered events, to determine if the morphological response to storm clusters results in greater beach erosion than that from individual storms that have the same average recurrence interval (ARI) or return period. The method is tested using a numerical morphodynamic model that combines both cross-shore and longshore beach profile evolution processes, forced by a 2D wave transformation model, and is applied as an example within a 20 km long coastal cell at an erosion hotspot at Old Bar, NSW mid-north coast, Australia. Wave and water level data hindcast in previous modelling (Davies et al., 2017) were used to provide two thousand different synthetic wave and tide records of 100 years duration for input to a nested nearshore 2D SWAN model that provides wave conditions at the 12 m depth contour. An open-source shoreline evolution model was used with these wave conditions to model cross-shore and longshore beach profile evolution, and was calibrated and verified against long-term dune recession observations. After a 50 year model spin up, 50 years of storm demand (change in sub-aerial beach volume) and dune toe position were simulated and ranked to form natural estimators for the 50, 25, 16, 12.5 and 10 year return period of individual events, together with confidence limits. The storm demand analysis was then repeated to find the return period of clustered and non-clustered morphological events. Morphological clusters are defined here by considering the response of the beach, rather than the forcing, with a sensitivity analysis of the influence of different recovery thresholds between storms also investigated. The new analysis approach provides storm demand versus return period curves for the combined population of clustered and non-clustered events, as well as a curve for the total population of individual events. In this approach, non-clustered events can be interpreted as the response to isolated storms. For clustered and non-clustered morphological events the expected storm demand for a 50-year return period is approximately 25% greater than that for individual events. Alternatively, for clustered and non-clustered events the magnitude of the storm demand that occurs at a return period of 17 years is the same as that which occurs at a return period of 50 years for individual events. However, further analysis shows that for a 50-year return period, the expected storm demand for the population of non-clustered events is similar to that of the clustered events, although the size of the population of the latter is much greater. Hence, isolated storms can generate the same storm demand as storm clusters, but there is a much higher probability that a given storm demand is generated by a morphologically clustered event.

Novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The experiments were conducted in a wave flume at medium scale using both monochromatic and random waves, representing 2D conditions. Beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler, from which shoreline location, bar position and sediment transport rates were derived. Experiments were conducted for sequences of wave climates, where a sequence comprised of 6–13 sequential tests, each commencing with the beach profile from the preceding test. Each test was run until equilibrium conditions were obtained and had a constant wave height, increased or decreased relative to the preceding test. Cyclical conditions were also included, with erosive and accretive wave conditions of short durations alternating through multiple cycles, so that equilibrium conditions were not reached during a test. With a sequence of increasing wave heights, the relationship between the shoreline position and the bulk cross-shore sediment transport, at equilibrium, was non-monotonic, indicating a maximum in the landward sediment transport rate. For test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights, morphological hysteresis was observed in the equilibrium shoreline position and bulk cross-shore sediment transport, such that shoreline recession, or offshore transport, continued in some instances after reductions in wave height. This is inconsistent with classical equilibrium type shoreline evolution models. However, when equilibrium conditions were not reached, in the cyclic sequences, no such morphological hysteresis was observed and a dynamic equilibrium is reached. The morphological hysteresis occurs because of the decay, stranding, or increased relative depth, of the breaker bar following a reduction in wave height, often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone. Similar sequences of morphological response are evident in field data and larger scale tests in the literature. Finally, it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of Wright et al. (1985) by introducing the concept of a subsequent alternate active beach state, which may occur following a change in wave conditions.

A framework is presented for the probabilistic modelling of non-stationary coastal storm event sequences. Such modelling is required to integrate seasonal, climatic and long-term non-stationarities into coastal erosion hazard assessments. The framework is applied to a study site on the East Australian Coast where storm waves are found to exhibit non-stationarities related to El Nino-Southern Oscillation (ENSO) and seasonality. The impact of ENSO is most prominent for storm wave direction, long term mean sea level (MSL) and the rate of storms, while seasonal non-stationarity is more ubiquitous, affecting the latter variables as well as storm wave height, duration, period and surge. The probabilistic framework herein separates the modelling of ENSO and seasonal non-stationarity in the storm wave properties from the modelling of their marginal distributions, using copulas. The advantage of this separation is that non-stationarities can be straightforwardly modelled in all storm wave variables, irrespective of whether parametric or non-parametric techniques are used to model their marginal distributions. Storm wave direction and steepness are modelled with non-parametric distributions whereas storm wave height, duration and surge are modelled parametrically using extreme value mixture distributions. The advantage of the extreme value mixture distributions, compared with the standard extreme value distribution for peaks-over-threshold data (Generalized Pareto), is that the statistical threshold becomes a model parameter instead of being fixed, and so uncertainties in the threshold can be straightforwardly integrated into the analysis. Robust quantification of uncertainties in the model predictions is crucial to support hazard applications, and herein uncertainties are quantified using a novel mixture of parametric percentile bootstrap and Bayesian techniques. Percentile bootstrap confidence intervals are shown to non-conservatively underestimate uncertainties in the extremes (e.g. 1% annual exceedance probability wave heights), both in an idealized setting and in our application. The Bayesian approach is applied to the extreme value models to remedy this shortcoming. The modelling framework is applicable to any site where multivariate storm wave properties and timings are affected by seasonal, climatic and long-term non-stationarities, and can be used to account for such non-stationarities in coastal hazard assessments.

A novel remote sensing methodology to determine the dominant infragravity mechanism in the inner surf and swash zone in the field is presented. Video observations of the breakpoint motion are correlated with the shoreline motion and inner surf zone water levels to determine the relationship between the time-varying breakpoint oscillations and the shoreline motion. The results of 13 field data sets collected from three different beaches indicate that, inside the surf zone, the dominance of bound wave or breakpoint forcing is strongly dependent on the surf zone width and the type of short wave breaking. Infragravity generation by bound wave release was stronger for conditions with relatively narrow surf zones and plunging waves; breakpoint forcing was dominant for wider surf zones and spilling breaker conditions.

Coastal engineers design harbors, coastal structures, and beach protection measures to guard infrastructure and communities located in coastal zones. The accurate forecasting of coastal erosion and inundation is crucial for planning the protection of existing and new coastal zone infrastructure.

In this study, we explain contradictory previous observations of the contribution of coherent wave organised motion to the downward transfer of momentum through wave Reynolds stresses (ρu˜w˜¯) below wind waves. The generation of non-zero u˜w˜¯ is potentially significant because 1) the turbulent mixing is not then the only momentum transport mechanism under wind waves as was previously assumed, 2) this provides a wave-current energy exchange pathway that could explain inconsistencies in measured air- and water-side wind-wave energy transfer and 3) it can be a critical term in the wave-current coupling formulation under wind waves. However, such a mechanism for momentum transfer has generally been ignored, since contradictory observations were reported. Here, two new sets of wind-wave laboratory experiments are reported. For the first set, contradictory u˜w˜¯ were observed, as in previous literature. Investigating the sources of such inconsistency, we examined spatial inhomogeneity due to wave reflection through a second set of experiments, by varying instrument location and additionally considering random waves. The results resolve the inconsistencies observed in the first set of experiments and previous measurements. In addition, we emphasise the contribution of secondary circulation cells in momentum transfer under wind waves.

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 (R2%) and maximum runup (Rmax) 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 R2% value. Models for R2% 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 R2% 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 R2% was developed from a best fit to the predictions from six existing field and one large scale laboratory R2% 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 Rmax 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 Rmax 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.

A new parametric model is developed to describe the wind field asymmetry commonly observed in tropical cyclones or hurricanes in a reference frame fixed at its center. Observations from 21 hurricanes from the North Atlantic basin and TC Roger (1993) in the Coral Sea are analyzed to determine the azimuthal and radial asymmetry typical in these mesoscale systems after removing the forward speed. On the basis of the observations, a new asymmetric directional wind model is proposed which adjusts the widely used Holland (1980) axisymmetric wind model to account for the action of blocking high-pressure systems, boundary layer friction, and forward speed. The model is tested against the observations and demonstrated to capture the physical features of asymmetric cyclones and provides a better fit to observed winds than the Holland model. Optimum values and distributions of the model parameters are derived for use in statistical modeling. Finally, the model is used to investigate the asymmetric character of TC systems, including the azimuth of the maximum wind speed, the degree of asymmetry, and the relationship between asymmetry and forward speed.

Robust measurements of bed shear stress under wave runup flows are necessary to inform beachface sediment transport modelling. In this study, direct measurements of swash zone bed shear stress were obtained in medium and prototype-scale laboratory experiments on steep slopes. Peak shear stresses coincided with the arrival of uprush swash fronts and high-resolution measurement of swash surface profiles indicated a consistently seaward sloping swash surface with minimal evidence of a landward sloping swash front. The quadratic stress law was applied to back-calculate time-varying friction factors, which were observed to decrease with increasing Reynolds number on smooth slopes, consistent with theory for steady flows. Additionally, friction factors remained relatively constant throughout the swash cycle (except around flow reversal), with a variation of approximately &plusmn, 20% from the mean value and with only small differences between uprush and backwash. Measured friction factors were observed to be larger than expected when plotted on the Moody or wave friction diagram for a given Reynolds number and relative roughness, consistent with previous field and laboratory studies at various scales.

The influence of grain size on sediment transport during the initial stages of dam break-type flows over horizontal mobile sediment beds was investigated through dimensional analysis and experiments. A new dimensional analysis reconciles the unbalanced dimensions in Bagnold's formulations describing the grain size influence on steady-flow sediment transport and indicates that the sediment transport is inversely proportional to the square root of the grain size, consistent with Bagnold's empirical correlation. Total transport rates were measured for quartz grains ranging from 0.22 to 2.65 mm in diameter. Regression between the dimensionless variables indicated that the mobility number collapses the sediment transport data better than the Shields number and indicated that the total sediment transport is approximately inversely proportional to the square root of the grain size and the velocity to the fourth power. The Meyer-Peter Muller transport model based on the Shields number requires transport coefficients for the finest sand that are significantly larger than the conventional values suggested in the literature, between 30 for k = 2.5D and 40 for k = D . The values for other sediment sizes are closer to conventional values, within the usual range of 10-12 for k = 2.5D , but somewhat higher at 16-22 for k = D . The occurrence of sheet flow in a suspension regime appears possible, which may explain the significantly larger transport coefficients required for the finest grain size.

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 H2, 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/Hs).

The morphological response of reef-fronted beaches to sea level rise and reef degradation is investigated by physical modelling. Coral barrier and fringing reefs limit the wave energy reaching sandy beaches, providing protection to many communities worldwide (Ferrario et al., 2014). Sea level rise and loss of reef flat elevation through coral mortality are expected to alter water levels over such reefs in the future. Assessing the morphological response to these processes in the field is very difficult due to the timescale involved, and lack of data for current conditions. Numerical modelling of beach profile response is also poor, even for open coast sandy beaches, and there is limited work modelling of reef fronted beaches, although hydrodynamics can be modelled reasonably well (Buckley et al., 2014). Here, new experiments on beach response to rising water levels and reducing reef flat elevation without tides are presented and compared to a conceptual model that links total sediment transport to the wave height landward of the reef (Baldock et al., 2015). A summary of recent numerical modelling of 2D planform changes for the same scenario will also be presented.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/0ya0UH1Vpsk

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.

In the swash zone, an assessment of swash flow properties requires an understanding of swash depth and swash velocity, which can affect sediment movement, as well as the design of coastal structures. The method of characteristics provides a useful tool to model unsteady shallow water flows, such as dam-break flow, swash flow and tsunami run-up. In this paper, bottom resistance was incorporated into the nonlinear shallow water equations to extend the application of the method of characteristics to account for frictional effects in the swash zone. The new characteristic equations are solved by the specified time interval scheme. The bottom resistance has little influence on the seaward swash hydrodynamics (initial swash stage), e.g., water depth and flow velocity, while its influence becomes significant in the small water depth region near the swash front, which reduces the maximum run-up height. At a specified time and location, and comparing with a frictionless swash solution, the uprush flow velocity reduces due to the bottom resistance, while the flow velocity increases during the initial phase of the backwash owing to the earlier reversal time with the bottom resistance. However, the differences with the inviscid solution are small within the swash lens. Conversely, the maximum backwash velocity is reduced significantly as a result of the shorter duration of the backwash. Consistent with previous field observations, friction does not significantly alter the gradient of the water surface elevation and a seaward-dipping water surface elevation is observed during the majority of the swash process. The dominant effect of bottom resistance is to reduce the range of inundation, particularly with larger resistance coefficients. The incorporation of the bottom resistance extends the application of method of characteristics in the swash zone to more practical problems, particularly where run-up elevation is critically important, e.g. overtopping flows.

A one-dimensional lattice Boltzmann model is developed to solve the shallow water equations for steady and unsteady flows within both the subcritical and supercritical regimes. Previous work is extended through a generalized Galilean transformation applied to the standard scheme. The transformation yields a general asymmetric lattice Boltzmann model scheme which can successfully model a wide range of both subcritical and supercritical flow regimes, and enables implementation of the asymmetric model for practical purposes. In current work, a new set of equilibrium functions, boundary conditions and the external force weights are derived for the generalized transformed scheme. A new stability region is also defined, allowing selection of a lattice speed that maintains numerical stability for a wider range of sub- and supercritical flows and combinations of those flow conditions, compared to the previous scheme with fixed asymmetry. The model is validated against a range of benchmark cases in open-ch...

Power, H.E.; Nielsen, P.; Hughes, M.G.; Aagaard, T., and Baldock, T.E., 2016. Wave height distributions in the surf zone on natural beaches. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 917–921. Coconut Creek (Florida), ISSN 0749-0208. Wave height distributions in the surf zone are examined using a large existing field dataset. Observed distributions are compared to the Rayleigh distribution, the Weibull distribution, and the normal distribution. In more than half the 15-minute data runs (57%), wave height distributions were statistically significantly different to a Rayleigh distribution, of which the majority were more narrowly distributed, with fewer extrema. In contrast, only 6% of distributions were statistically significantly different to a normal distribution. The distributions were observed to become narrower with decreasing de...