Shore Break Research Articles

Do red and yellow flags indicate a danger zone?: Exploring Japanese university students’ beach safety behaviour and their perceptions of Australian beach safety signage

BackgroundCoastal drowning is a tragic regular occurrence in Australia, and in the decade 2012–2022, 455 overseas-born beachgoers drowned. Being one of the top five countries of international visitors who drown, Japanese tourists are an at-risk group. This study investigates Japanese university students’ knowledge of beach safety and their perceptions of Australian beach safety signage. MethodsThe present study conducted an online survey with 152 university students in Japan, comprising both closed and open questions. Although the survey was in Japanese, the signage terms used in the survey were in English as used in Australia. Descriptive analysis was conducted on the statistical data via SPSS and deductive thematic analysis was conducted on the open responses using Nvivo. Results90 % of them planned to visit beaches and 64 % would enter the water when or if visiting Australia. However, 60 % interpreted the safer supervised zone denoted by red and yellow flags as signifying a danger zone. Regardless of their English proficiency, almost none fully understood terms commonly used on safety and warning signs such as submerged objects, shore dump, shore break and rip currents, and 60 % of them didn’t know the Japanese term of rip currents, riganryuu. Visual icons were understood much better than these English terms. So what?This study explored a specific (i.e. Japanese) cultural perception and understanding of Australian beach signs beyond the scope of CALD communities. Future studies should continue exploring those of other cultures so Australian beach signs can be revised and improved based on scientific evidence.

What is a shore dump?: Exploring Australian university students’ beach safety knowledge and their perceptions of Australian beach safety signage

BackgroundOn average 122 coastal drownings deaths are recorded in Australia every year. Typically, young adult beachgoers (15–34 years old), many of whom were born overseas, account for 25 % of these fatalities. This study identifies university students as appropriate subjects for investigating typical interpretations of beach safety messages and signage among this high-risk demographic. MethodsThis study involved an online survey of Australian university students (domestic: n = 136 international: n = 84). The survey comprised both closed and open-ended questions about beach safety terms and signage. Participants were recruited through university newsletters, course announcements, social media, and at beach safety workshops. Data were analysed with SPSS for descriptive analyses and Pearson Chi-Square to test for statistical differences between domestic and international students. ResultsOver 55% of domestic and over 75% of international students did not understand the common safety terms shore dump and shore break and approximately half of both groups misunderstood the sign, always swim between the flags, believing that surfers should also stay between the flags. Concerningly, 21% of international students perceived this meant that beachgoers who don’t or can’t swim need to stay outside the flags. So what?Existing beach safety signage is not as effective as authorities assume due to linguistic and translation challenges. Some terms are improperly translated into Japanese and Chinese in the current search on Google Translate. Such linguistic issues must be addressed so as to improve the delivery of coastal safety messages.

The Junction Between the Peristaltic and Non-peristaltic Bowel (Shore Break) is Found in the Transition Zone in Hirschsprung's Disease

BackgroundThe junction between the peristaltic and non-peristaltic bowel, which is named the “shore break” (SB), observed on endoscopy is thought to be the boundary between normal and abnormal motility in Hirschsprung's disease (HD). The transition zone (TZ), which is the histopathological border, does not have normal motility and should be resected. This study aimed to evaluate the histopathological findings of the SB and determine the association between the SB and TZ. MethodsA retrospective review of surgical specimens of patients with HD who underwent preoperative SB marking was conducted. The TZ was defined if nerve hypertrophy, myenteric hypoganglionosis, or partial circumferential aganglionosis was detected. ResultsTen patients (9 boys and 1 girl) were studied. The median age at surgery was 30 days. The median distance from the anal verge to the marked SB site was 14 cm. No patients manifested any obstructive symptoms resulting from a residual TZ bowel. In eight patients, nerve hypertrophy was identified at the proximal margin and at the SB. Myenteric hypoganglionosis was identified in three patients at the proximal margin and SB. Partial circumferential aganglionosis was identified at the SB in two patients. As a result, in all patients, the pull-through site and SB site had histopathological features indicating TZ. ConclusionsThe SB is located in the TZ. Our results suggest that the proximal part of the TZ has normal motility and that functional border points may be present in the TZ. Level of EvidenceIV.

Pebble and cobble transport on a steep, mega-tidal, mixed sand and gravel beach

Natural tracer pebbles and cobbles were deployed on a steep (slope: 0.1) mixed sand and gravel mega-tidal beach located at the head of the Bay of Fundy. Two experiments were carried out to investigate the response of natural pebble- and cobble-sized material, both to energetic wave conditions during individual storm events, and to tidal-only forcing conditions between storms. Net displacement of different tracer sizes was the focus of the first experiment, while the effect of different shapes was tested in the second. The pebbles and cobbles were painted in fluorescent colors, labeled, and their positions measured at low tide over periods of 10–12days. The tracers were emplaced at mid-tide level on the beach face at low water, and later recovered and re-deployed on successive low tides. Net travel distance and direction were measured upon recovery. Hydrodynamic forcing conditions and local morphology at mid-tide level on the beach face were monitored continuously during the experiments. In the first experiment, recovery rates were 100% during calm and moderate wave conditions (Hs≤ 0.5m), but decreased significantly in more energetic wave forcing (Hs up to 1m). Recovery rates were lower for smaller tracers. During a three day wind-wave event, net displacements of up to 48m were measured. Comparable net displacements were observed for all tracers. Maximum displacements were 39m onshore, 42m offshore, and 46m alongshore. In calm conditions, maximum displacements were less than 1m, indicating that the bottom stresses due to tidal currents alone are too low to cause significant tracer displacement on time scales of weeks, despite the high tidal range. In the second experiment, recovery rates were lower, due to more energetic wave forcing: significant wave heights reached Hs >0.5m on 80% of the particle tracking days and Hs >1m on 30% of the days. Flat pebbles and cobbles reached the longest transport distances, with a maximum net displacement of 98m. The flat tracers were observed to be flipped by the shore break and to “ride” the swash bore, and were in this manner transported long distances, shoreward up to 66m. In both experiments, the directions of alongshore displacements were consistent with deviations of the angle of wave incidence from the shorenormal. Tracer burial and re-exposure was observed – via rotary imaging sonar – with the evolution and migration of m-wavelength ripples. The study allowed a direct correlation of pebble and cobble tracer displacements to hydrodynamic forcing during individual storm events, with consideration of tracer particle size, and shape.

Bathymetric control on the spatial distribution of wave breaking in the surf zone of a natural beach

A non-hydrostatic wave model (SWASH) that phase-resolves the free surface and fluid motions in the water column is applied to investigate wave transformation and the spatial distribution of wave breaking over different morphological features. The model is forced using observed directional energy spectra and results are compared to wave observations collected outside the surf zone using acoustic wave sensors, and over a 100m nearshore transect using high-frequency measurements of the sea surface from a LIDAR sensor mounted on the beach dune at the Field Research Facility in Duck, NC. The model is applied to four cases with different wave conditions and bathymetry, tested for sensitivity of model parameters to these different natural conditions, and used to predict the spatial variability in wave breaking and correlation between energy dissipation and morphologic features. Model results compare very well with observations of spectral evolution outside the surf zone, and generally well with the remotely sensed observations of wave transformation inside the surf zone with R = 0.85-0.93 for Hs along the cross-shore transect. In particular the model is able to spatially resolve wave shoaling and dissipation at the shore break at the same location as observed in the LIDAR data. The results indicate that nearshore morphology has a significant effect on the spatial distribution of wave energy dissipation. Alongshore variability in bathymetry due to bars, rip channels, and larger morphological features such as the scour depression under the pier, causes large alongshore changes in cross-shore wave energy flux that influence the location and intensity of wave breaking.

A Conceptual Model for Spatial Grain Size Variability on the Surface of and within Beaches

Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1–1.5 m long) collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm) and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~−1.4 to −1.6 m NAVD88), which are constantly being reworked by the energetic shore break, there is a thick layer (60–80 cm) of very coarse sediment (~2 mm). Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level) are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.

Sediment dynamics on a steep, megatidal, mixed sand–gravel–cobble beach

Abstract. Results are presented from a pilot study of shore-face sediment dynamics on a steep, poorly sorted, coarse-grained, megatidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wideband, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-à-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the unexpected observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation – in wave-dominated conditions – of metre-scale wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shore break on the subsequent ebb.

Observations and modeling of steep‐beach grain‐size variability

Novel observations of surface grain‐size distributions are used in combination with intra‐wave modeling to examine the processes responsible for the sorting of sediment grains on a relatively steep beach (slope = 1:7.5). The field observations of the mean grain size collected with a digital camera system at consecutive low and high tides for a 2 week period show significant temporal and spatial variation. This variation is reproduced by the modeling approach when the surf zone flow‐circulation is relatively weak, showing coarse grain sizes at the location of the shore break and finer sediment onshore and offshore of the shore break. The model results suggest that grain size sorting is dominated by the wave‐breaking‐related suspended sediment transport which removes finer sediment from the shore break and transports it both on‐shore and offshore. The transport capacity of wave‐breaking‐related suspended sediment is controlled by the sediment response time scale in the advection‐diffusion equation, where small (large) values promote onshore (offshore) transport. Comparisons with the observed beach profile evolution suggest a relatively short time scale for the suspended sediment response which could be explained by the vigorous breaking of the waves at the shore break.