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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 8 August and 12 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. [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]

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 depth. Data were subsequently fitted to a Weibull distribution with a varying exponent to allow for a change in the shape of the distribution with changing depth. The data show distributions with a wide range of exponents, but a mean of 2.4 indicating that, on average, data are more narrowly distributed than a Rayleigh distribution (exponent of 2). The value of the exponent was observed to increase in shallower water, with a strong inverse correlation between depth and the exponent. [ABSTRACT FROM AUTHOR]

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. [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]

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]

• Scour patterns measured experimentally around a scaled Oscillating Water Column. • Scour shown to undermine the structure, comparable with the tunnel erosion effect. • Undermining scour leads to settlement of the gravity-based structure. • Increasing the corner curvature shown to reduce scour depths by 23%. • Comparison with field observations reveals similar scour patterns. Experimental measurements of wave scour are reported for a 1:20 scaled model of an operating 200 kW Oscillating Water Column (OWC) Wave Energy Converter (WEC) in King Island, Tasmania, Australia. Test cases include different wave conditions (Keulegan-Carpenter (KC) number range of 0.45-1.02) and multiple geometric changes to the device, which are compared to scour measurements taken in the field around the King Island OWC WEC device. The measurements therefore provide the first ever comparison of field data with a scaled laboratory model of scour around an OWC WEC. Results highlight that scour forms at the back corners of the device before undermining the structure with depths up to 64 mm (scour depth to structure width ratio, S / B , of 0.094), although the magnitude of this scour is shown to be reduced by 23% by curving the back corners. Scour at the front of the device is highly sensitive to the configuration of the front chamber door, with very different scour scenarios depending on whether the chamber door is open, closed, or removed entirely. Comparison with field data shows that undermining scour at the back of the device is reproduced in both settings, and this leads to settlement of the structure in both the laboratory and field. This suggests that the physical modelling forms an accurate representation of a real-world site, and therefore demonstrates scour processes with applicability to OWC WECs and other gravity-based bluff body structures such as caissons or gravity-based foundations. [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]