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Accurately mapping the evolving bathymetry under energetic wave breaking is challenging, yet critical for improving our understanding of sandy beach morphodynamics. Though remote sensing is one of the most promising opportunities for reaching this goal, existing depth‐inversion algorithms using linear approaches face major theoretical and/or technical issues in the surf zone, limiting their accuracy over this region. Here, we present a new depth‐inversion approach relying on Boussinesq theory for quantifying nonlinear dispersion effects in nearshore waves. Using high‐resolution datasets collected in the laboratory under diverse wave conditions and beach morphologies, we demonstrate that this approach results in enhanced levels of accuracy in the surf zone (errors typically within 10%) and presents a major improvement over linear methods. The new nonlinear depth‐inversion approach provides significant prospects for future practical applications in the field using existing remote sensing technologies, including continuous lidar scanners and stereo‐imaging systems. Plain Language Summary The coastal science community currently lacks insights into the morphological evolution of sandy beaches, including rapid changes that occur during storms. This is, to a large extent, explained by the difficulty to monitor the seabed elevation under such conditions in a region of the nearshore where high‐energy waves break. If a relationship can be established between observed wave dynamics at the surface and the water depth below, remote‐sensing technology presents a promising opportunity to reach this goal since it requires no physical interaction with the water environment. However, the existing algorithms to retrieve the water depth rely on the linear wave dispersion relation, which fails at describing the nonlinear dynamics of shoaling and breaking waves. Here, we develop a new depth‐inversion approach based on a Boussinesq theory, which better describes such dynamics. Using a range of wave conditions and beach morphologies, we demonstrate that our approach results in significant improvement compared to the classic approaches, achieving typical accuracy within 10% in regions of the nearshore where waves break. The new nonlinear depth‐inversion approach provides very promising prospects for future practical applications in the field using, for instance, high‐resolution datasets collected with lidar scanners or stereo imaging systems. Key Points A new depth‐inversion approach for the nearshore is proposed, based on a Boussinesq theory for quantifying nonlinear dispersion effects Unprecedented levels of accuracy (typically within 10%) are obtained in the surf zone over both planar and barred beaches Improvement over the linear wave theory method, which overestimates depths by 40% or more in surf zones (up to 80% at the shoreline)

Resolving surf-zone bathymetry from high-resolution imagery typically involves measuring wave speeds and performing a physics-based inversion process using linear wave theory, or data assimilation techniques which combine multiple remotely sensed parameters with numerical models. In this work, we explored what types of coastal imagery can be best utilized in a 2-dimensional fully convolutional neural network to directly estimate nearshore bathymetry from optical expressions of wave kinematics. Specifically, we explored utilizing time-averaged images (timex) of the surf-zone, which can be used as a proxy for wave dissipation, as well as including a single-frame image input, which has visible patterns of wave refraction and instantaneous expressions of wave breaking. Our results show both types of imagery can be used to estimate nearshore bathymetry. However, the single-frame imagery provides more complete information across the domain, decreasing the error over the test set by approximately 10% relative to using timex imagery alone. A network incorporating both inputs had the best performance, with an overall root-mean-squared-error of 0.39 m. Activation maps demonstrate the additional information provided by the single-frame imagery in non-breaking wave areas which aid in prediction. Uncertainty in model predictions is explored through three techniques (Monte Carlo (MC) dropout, infer-transformation, and infer-noise) to provide additional actionable information about the spatial reliability of each bathymetric prediction.

Human impacts on ecosystems often transcend ecosystem boundaries and environmental realms, complicating ecosystem assessment, conservation, and management. Whether and how different impacts affect ecosystems in distinct but adjacent domains remains untested in many settings, and is rarely tested concurrently at the same spatial scales. In this study, we quantified the effects of coastal urbanisation on the structure of terrestrial coastal vertebrate assemblages (including birds, reptiles and mammals using baited trail cameras) and marine surf zone fish assemblages (using baited underwater videography) at 100 sites along 50 km of beach in eastern Australia. Sites occurred along a gradient of intensities of urban land conversion in the hind dunes. While the effects of urbanisation on the species sampled were pervasive across both ecosystems, the area of urbanised land mattered more for the coastal vertebrates observed, while proximity to urbanised land was more important for the surf zone fish observed. Here, fewer individuals and species of coastal vertebrates were found at sites with a greater extent of urbanised land within 5 km. Conversely, fish assemblages were more diverse in the surf zones abutting urban areas and more abundant at sites approximately 150 m from urbanised land. The spatial properties of these landscapes, including proximity to headlands for coastal vertebrates and reefs for fish, modified the effects of urbanisation. Our findings suggest that urbanisation can have ecologically nuanced effects that are detectable across the land-sea boundary, and stress the importance of landscape context when assessing and conserving animal assemblages in and around coastal cities.

The study is based on lifeguard data from 44 Goa beaches over a period of 2008–2020; a total of 4837 surf zone injury (SZI) cases were analyzed. Calangute reported the highest SZIs with 24.63% followed by Baga and Candolim in the North Goa. In South Goa, Colva recorded the highest percentage of beach victims with 18.25%. Since Goa beaches are world famous, many tourists from foreign countries have become victims with a total percentage of 22.2%, thereby showing its importance to the global community. Out of all Indian states, Karnataka recorded nearly 21.93% cases as compared to Goa with 13.53%. Since there is a stringent lifeguard system available at Goa beaches, the drowning percentage is just 2.86%. Rips are found to be the primary cause responsible for most cases accounting for 59.32% with nearly 3030 victims. The secondary cause is due to shore breaking. The most common injury type is a fracture of the legs which accounts for 8.02%. Apart from rip current related cases, there are other cases reported due to tourism activities. Out of all recreational activities, wading resulted in more number of SZIs with 19.61% followed by surfing and body boarding. The SZI-related cases have also been examined based on age and gender. The predominant age group involved in the injuries was between 19 and 25 years (36.33%) with the majority of victims being males (78.59%). Few rip currents outbreak events with large number of victims rescued at Baga and Calangute beaches have been studied using multi-temporal high-resolution satellite imageries and able to identify dangerous hot spots. These details give an idea of which regions along the beaches management have to focus on and restrict the zones from any kind of recreational activities. This analysis is the first of its kind in India, where a detailed study is carried on based on lifeguard reports, suggesting the importance of rescue or drowning data.

Sandy beaches offer numerous health and well-being benefits, but engaging in water-based recreational activities also exposes beachgoers to risks from natural hazards, such as rip currents and waves that break at the shoreline (shore break waves), which can result in fatal drownings and surf zone injuries. A contributing factor to these incidents is that individuals often misunderstand the risks they are exposed to. This study used a unique multidisciplinary database combining beachgoer surveys, marine and weather data and lifeguard hazards assessments to examine beachgoer’s risk perception at a beach located in southwest France. We identified a number of factors that can have potentially contradictory influences on beachgoers’ perceptions. Beachgoers’ perceived risk of rip current and shore break hazards increases with increasing wave height and increasing wave period. Tide level has a significant statistical influence on individuals’ perceived risk of the shore break wave hazard only. Beachgoers familiar with La Lette Blanche beach had higher rip current and shore break risk perceptions although regular recreational beach users (in general) tend to underestimate risks. Similarly, males and younger people express lower perceived risks compared to others. For a large number of environmental conditions, beachgoers perceive rip currents to be a greater risk than shore breaks wave risks although they tend to overestimate beach hazards compared to lifeguards. These results create new avenues for preventive communication, in particular by emphasizing the danger of shore breaks, and the specific nature of the risks on the beaches of south-west France. Some of these safety messages should communicated well before the beachgoers arrive at the beach.

Surf zone injuries (SZIs) are common worldwide, yet limited data are available for many geographical regions, including Europe. This study provides the first preliminary overview of SZIs along approximately 230 km of hazardous surf beaches in SW France during the summer season. A total of 2523 SZIs over 186 sample days during the summers of 2007, 2009 and 2015 were analysed. Documented injury data included date and time; beach location; flag colour; outside/inside of the bathing zone; age, gender, country and home postal code of the victim; activity; cause of injury; injury type and severity. Injuries sustained ranged from mild contusion to fatal drowning, including severe spinal injuries, wounds and luxation. While the most severe injuries (drowning) were related to rip currents, a large number of SZIs occurred as a result of shore-break waves (44.6%; n = 1125) and surfing activity (31.0%; n = 783) primarily inside and outside of lifeguard-patrolled bathing zones, respectively. Victims were primarily French living more than 40 km from the beach (75.9% of the reported addresses; n = 1729), although a substantial number of victims originated from Europe (14.7% of the addresses reported; n = 335), including the Netherlands (44.2%; n = 148), Germany (26.3%; n = 88) and Belgium (12.5%; n = 49). The predominant age group involved in the incidents was between 10 and 25 years (54.5%; n = 1376) followed by between 35 and 50 years (22.6%; n = 570), with the majority of SZIs involving males (69.6%, n = 1617). Despite the large predominance (74.1%; n = 33) of males involved in the most severe drowning incidents, all of which occurred outside the bathing zone, a surprisingly large proportion of females (48.0%; n = 133) experienced milder drowning incidents involving only minor to moderate respiratory impairment, peaking at 58.2% (n = 85) within the age group 10–25. The spine/cervical injury population is very young, with 58.5% (n = 313) within the age group 10–20. Specific injuries tended to occur in clusters (e.g. rip-current drowning or shore-break injury) with particular days prone to rip-current drowning or hazardous shore-break waves, suggesting the potential to predict the level of risk to beachgoers based on basic weather and marine conditions. This study calls for increased social-based beach safety research in France and the development of more effective public awareness campaigns to highlight the surf zone hazards, even within a supervised bathing zone. These campaigns should be targeted towards young males and females, in order to reduce the number of injuries and drownings occurring on beaches in SW France.

Francis, H. and Traykovski, P., 2021. Development of a highly portable unmanned surface vehicle for surf zone bathymetric surveying. Journal of Coastal Research, 37(5), 933–945. Coconut Creek (Florida), ISSN 0749-0208. This study reviews the design and subsequent effectiveness of a prototype autonomous survey vehicle built to collect data specifically in the surf zone. The breaking wave transitional zone between ocean and land is an important location to survey due to its impact on human infrastructure and vulnerability to the effects of climate change. However, this environment is notoriously difficult to survey due to its shallow depth and the turbulence of waves and currents. Three distinctive design choices were made at the beginning of the project with the goal of operating in the surf zone: First, the surface vehicle is light (15 kg) and fast (up to 7 m/s), both characteristics intended to enable one person to deploy it quickly and easily into the surf zone. Second, an electric motor that is connected to a jet drive eliminates a combustion engine's air intake, which can be contaminated with seawater and sand. The jet drive also removes any danger of spinning propellers and allows the vessel to run in very shallow water. Finally, the vessel has a foam bulb hatch cover that is watertight and allows the vessel to right itself if capsized by a wave. The outcome of this development effort is an unmanned vessel that has the maneuverability and power sufficient for surf zone operations and is self-righting. It runs off the waypoint based Ardupilot Mavlink program, which allows rapid transitions from autonomous modes to remote controlled modes and has a runtime of approximately 1.5 hours. The vessel has initially been used with a single beam echosounder and precision GPS to create highly detailed shallow water bathymetric maps. This study demonstrates this technique as a highly efficient method of creating bathymetric maps in coastal environments.

The retention of floating matter within the surf zone on a rip‐channeled beach is examined with a combination of detailed field observations obtained during the Rip Current Experiment and a three‐dimensional (3‐D) wave and flow model. The acoustic Doppler current profiler–observed hourly vertical cross‐shore velocity structure variability over a period of 3 days with normally incident swell is well reproduced by the computations, although the strong vertical attenuation of the subsurface rip current velocities at the most offshore location outside the surf zone in 4 m water depth is not well predicted. Corresponding mean alongshore velocities are less well predicted with errors on the order of 10 cm/s for the most offshore sensors. Model calculations of very low frequency motions (VLFs) with O(10) min timescales typically explain over 60% of the observed variability, both inside and outside of the surf zone. The model calculations also match the mean rip‐current surface flow field inferred from GPS‐equipped drifter trajectories. Seeding the surf zone with a large number of equally spaced virtual drifters, the computed instantaneous surface velocity fields are used to calculate the hourly drifter trajectories. Collecting the hourly drifter exits, good agreement with the observed surf zone retention is obtained provided that both Stokes drift and VLF motions are accounted for in the modeling of the computed drifter trajectories. Without Stokes drift, the estimated number of virtual drifter exits is O(80)%, almost an order of magnitude larger than the O(20)% of observed exits during the drifter deployments. Conversely, when excluding the VLF motions instead, the number of calculated drifter exits is less than 5%, thus significantly underestimating the number of observed exits.

A model that accurately simulates surf zone waves, mean currents, and low‐frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion. In this paper, a wave‐resolving time‐dependent Boussinesq model is compared with waves and currents observed during five surf zone dye release experiments. In a companion paper, Clark et al. (2011) compare a coupled tracer model to the dye plume observations. The Boussinesq model uses observed bathymetry and incident random, directionally spread waves. For all five releases, the model generally reproduces the observed cross‐shore evolution of significant wave height, mean wave angle, bulk directional spread, mean alongshore current, and the frequency‐dependent sea surface elevation spectra and directional moments. The largest errors are near the shoreline where the bathymetry is most uncertain. The model also reproduces the observed cross‐shore structure of rotational velocities in the infragravity (0.004 < f < 0.03 Hz) and very low frequency (VLF) (0.001 < f < 0.004 Hz) bands, although the modeled VLF energy is 2–3 times too large. Similar to the observations, the dominant contributions to the modeled eddy‐induced momentum flux are in the VLF band. These eddies are elliptical near the shoreline and circular in the mid surf zone. The model‐data agreement for sea swell waves, low‐frequency eddies, and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion. Key Points Boussinesq model reproduces surf zone waves and currents Reproduces the IG band bulk rotational velocities In the VLF band, the model is too (2–3×) energetic

Seascape connectivity (landscape connectivity in the sea) can modify reserve performance in lowenergy marine ecosystems (e.g., coral reefs, mangroves, and seagrass), but it is not clear whether similar spatial linkages also shape reserve effectiveness on high-energy, exposed coastlines. We used the surf zones of ocean beaches in eastern Australia as a model system to test how seascape connectivity and reserve attributes combine to shape conservation outcomes. Spatial patterns in fish assemblages were measured using baited remote underwater video stations in 12 marine reserves and 15 fished beaches across 2000 km of exposed coastline. Reserve performance was shaped by both the characteristics of reserves and the spatial properties of the coastal seascapes in which reserves were embedded. Number of fish species and abundance of harvested fishes were highest in surf-zone reserves that encompassed > 1.5 km of the surf zone; were located < 100 m to rocky headlands; and included pocket beaches in a heterogeneous seascape. Conservation outcomes for exposed coastlines may, therefore, be enhanced by prioritizing sufficiently large areas of seascapes that are strongly linked to abutting complementary habitats. Our findings have broader implications for coastal conservation planning. Empirical data to describe how the ecological features of high-energy shorelines influence conservation outcomes are lacking, and we suggest that seascape connectivity may have similar ecological effects on reserve performance on both sheltered and exposed coastlines. La conectividad entre paisajes marinos puede modificar el desempeño de las reservas en los ecosistemas marinos de baja energía (p. ej.: arrecifes de coral, manglares, pastos marinos), pero no está claro si las conexiones espaciales similares también moldean la efectividad de las reservas en costas expuestas con alta energía. Usamos las zonas de rompimiento de las playas oceánicas en el este de Australia como sistema modelo para probar cómo la conectividad entre paisajes marinos y los atributos de la reserva se combinan para moldear los resultados de la conservación. Los patrones espaciales en los ensamblados de peces se midieron con estaciones remotas de video subacuático con carnada en doce reservas marinas y 15 playas a lo largo de 2000 km de costas expuestas. El desempeño de las reservas estuvo moldeado por las características de las reservas y las propiedades espaciales de los paisajes costeros en los cuales estaban insertadas las reservas. El número de especies de peces y la abundancia de peces recolectados fue mucho mayor en las reservas en las zonas de rompimiento que abarcaban > 1.5 km de la zona de rompimiento; estaban localizadas a < 100 m de cabos rocosos; e incluían playas pequeñas entre los cabos en un paisaje marino heterogéneo. Los resultados de conservación para las costas expuestas pueden, por lo tanto, mejorarse con la priorización suficiente de grandes áreas de paisajes marinos que están conectados fuertemente con hábitats complementarios colindantes. Nuestros hallazgos tienen consecuencias más generales para la planeación de la conservación costera. Los datos empíricos para describir cómo las características ecológicas de las costas con alta energía influyen sobre los resultados de conservación son muy pocos, y sugerimos que la conectividad entre paisajes marinos puede tener efectos ecológicos similares sobre el desempeño de las reservas en costas expuestas y resguardadas. 海洋景观连接度会影响低能量的海洋生态系统珊瑚礁、红树林、海草生态系统) 保护区的保护成效， 但目前尚不清楚高能量、裸露海岸线的保护区成效是否也受到类似空间关联的影响。我们以澳大利亚东部海滩 的碎波区为模型，分析了海洋景观连接度和保护区特性如何共同决定保护成效。我们利用2000公里裸露海岸 线沿线的 12 十海洋保护区和バ 15 十钓鱼海滩的诱饵式远程水下视频监控位点，测定了鱼类群落的空间格局。保 护区的特性及其所在海岸线景观的空间特性共同影响着保护区成效。在含有超过1.5公里碎波带、距离多岩石 的海角不足 100 米，或是在异质性景观中含有小海滩的碎波带保护区中，鱼类物种数和渔获量最高。因此，优先 保护那些与蛾邻的互补生境紧密相连，且面积足够大的海洋景现可以提高裸露海岸线的保护成效。我们的研究 结果对海岸带的保护规划有广泛的意义。目前，描述高能量海岸线的生态学特性如何影响保护成效的数据仍十 分缺乏，我们提出，海洋景观连接度对受保护和未受保护海岸线可能有相似的生态学影响并决定保护区的保护成 效。