Mesotidal Beach Research Articles

Assessing Satellite-Derived Shoreline Detection on a Mesotidal Dissipative Beach

The accuracy and robustness of the shoreline definition from satellite imagery on different coastal types are crucial to adequately characterising beach morphology and dynamics. However, the generic and widespread application of satellite-derived shoreline algorithms is limited by the lack of robust methods and parameter assessments. This work constitutes a quantitative and comprehensive assessment of the satellite-derived waterlines from Sentinel-2 by using the novel SAET tool (Shoreline Analysis and Extraction Tool) on the exposed and mesotidal beach of La Victoria (Cádiz, SW Spain). The diverse parameters available in SAET, such as water indexes, thresholding methods, morphological filters, and kernel sizes, were combined to define water/land interface positions that were compared against coincident video-derived waterlines. Satellite-derived waterline errors are found to be affected by extraction parameters, as well as by the oceanographic and morphological conditions at the time of the image acquisition. The application of a morphological erosion filter on the water mask, which tends to shift the extracted waterline seawards and reduce bias, is the best solution at the dissipative site of La Victoria Beach. Moreover, using a 3 × 3 kernel size consistently shows higher accuracies than a larger kernel. Although there was no parameter combination showing the best skill for all dates, the employment of the Automated Water Extraction Index for images with no shadows (AWEInsh) with a threshold = 0, erosion morphological filter, and 3 × 3 kernel was, overall, the best combination of extraction parameters for this beach (average waterline RMSE of 5.96 m). The combination of the Modified Normalised Difference Water Index (MDNWI) with the Otsu thresholding also led to similar positions of the resulting waterlines and offered good accuracies. In line with other recent research efforts, our work stresses the lack of generic shoreline extraction solutions that can be applied automatically at a global level and the necessity to adapt and validate the extraction methodologies to the different types of coastlines.

Morphodynamic Response of Open and Embayed Beaches to Winter Conditions: Two Case Studies from the North Atlantic Iberian Coast

The morphological responses of two mesotidal beaches located in different coastal settings (embayed and open sandy beaches) on the northwestern Iberian coast were monitored during the winter of 2018/19. The offshore wave time series analysis is related to high-resolution topo-bathymetric measurements to explore spatial-temporal morphological variability at monthly to seasonal scales. Both locations are subjected to the North Atlantic wave climate which exhibits a pronounced seasonality. Throughout the last decade (2010–2020), significant wave heights reached values of up to Hs~9 m during winters and up to Hs~6 m during summers. On average, approximately 12 storms occurred annually in this region. The results clearly reveal divergent morphological responses and sediment transport behaviors at the upper beach and the intertidal zone during the winter for each location. In the embayed beach (Patos), sediment transport in the nearshore is governed by cross-shore processes between the beach berm and a submerged sandbar. In contrast, the open beach (Mira) showed dynamic sediment exchanges and three-dimensional morphologies alternating between accumulation and erosion zones. Overall, both beaches exhibited an erosional trend after the winter, particularly concerning berm erosion and the subaerial beach volume/shoreline retreat. This study highlights the contrasting morphodynamic response on open and embayed beaches to winter conditions, integrating both the subaerial and submerged zones. Local geological and environmental factors, as well as the coastal management strategies applied, will influence how the beach responds to winter wave events. Monitoring and understanding these responses are essential for effective coastal management and adaptation to changing climate.

Shoreline Identification Bias: Theoretical and Measured Value for Meso-Tidal Beaches in Kuala Nerus, Terengganu (Malaysia)

Shoreline Identification Bias: Theoretical and Measured Value for Meso-Tidal Beaches in Kuala Nerus, Terengganu (Malaysia)

Video-Based Nearshore Bathymetric Inversion on a Geologically Constrained Mesotidal Beach during Storm Events

Although geologically constrained sandy beaches are ubiquitous along wave-exposed coasts, there is still a limited understanding of their morphological response, particularly under storm conditions, which is mainly due to a critical lack of nearshore bathymetry observations. This paper examines the potential to derive bathymetries from video imagery under challenging wave conditions in order to investigate headland control on morphological beach response. For this purpose, a video-based linear depth inversion algorithm is applied to three consecutive weeks of frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France). Video-derived bathymetries are compared against in situ topo-bathymetric surveys carried out at the beginning and end of the field experiment in order to assess the performance of the bathymetric estimates. The results show that the rates of accretion/erosion within the surf zone are strongly influenced by the headland, whereas the beach morphological response can be classified into three main regimes depending on the angle of wave incidence θp: (1) under deflection configuration (θp>0°), the alongshore sediment transport was trapped at the updrift side of the headland, promoting sand accretion. (2) Under shadowed configuration (θp<0°), the interruption of the longshore current drove a deficit of sand supply at the downdrift side of the headland, leading to an overall erosion in the surf zone. (3) Under shore-normal configuration (θp=0°), rip channels developed, and up-state beach transition was observed. A comparison between video-derived bathymetries and surveys shows an overall root mean square error (RMSE) around 0.49 to 0.57 m with a bias ranging between −0.36 and −0.29 m. The results show that video-derived bathymetries can provide new insight into the morphological change driven by storm events. The combination of such inferred bathymetry with video-derived surface current data is discussed, showing great potential to address the coupled morphodynamics system under time-varying wave conditions.

Littoral drift analysis based on long-term observation of mesotidal beach profile in Kuta Beach, Bali for coastal retreat assessment

The beach profile survey in the intertidal zone is crucial for a temporal variability study of shoreline and beach profile change for coastal management. The combination of numerical modelling and field data has proven to be successful in identifying the primary hydrodynamic and sediment transport processes such as littoral and cross-shore drift. Those parameters are relevant to the sandbar migration process and shoreline changes. The purpose of the present study is to analyse the littoral drift that caused temporal variability shoreline change in mesotidal beach for coastal retreat mitigation. Beach profile data of Kuta Beach was analyzed by 7 years of long-term field observation data both east monsoon and west monsoon situation. The shoreline definition used mean sea level (MSL)1.3 m and high water level (HWL) 2.6 m as reference. By using the MeEPASoL program as a graphical user interface program, shoreline changes converging to an equilibrium state can be simulated by taking into account the existing breakwater. Temporal shoreline position resulting from littoral drift and beach width change from its initial position is estimated for coastal erosion analysis. The result showed that dominantly, the littoral drift pattern moved from south to north. Furthermore, this study can be used in the process of identifying the primary hydrodynamic analysis in erosion disaster management as assessment of the beach erosion.

The Three Domains of Life Within the Discharge Area of a Shallow Subterranean Estuary at a High Energy Beach

Subterranean estuaries (STEs) play an important role in linking nutrient cycling between marine and terrestrial systems. As being the primary drivers of nutrient cycling, the composition of microbial communities and their adaptation toward both, terrestrial and marine conditions are of special interest. While bacterial communities of STEs have received increasing scientific attention, archaeal and meiofaunal diversity was mostly neglected. Previous studies at the investigated sampling site, the STE of a mesotidal beach at the German North Sea island of Spiekeroog, focused on spatial and seasonal patterns of geochemical and bacterial diversity. By additionally investigating the archaeal and meiofaunal diversity and distribution, we now aimed to fill this gap of knowledge to understand the microbial response to submarine groundwater discharge (SGD). The topography of Spiekeroog beach and associated geochemical gradients in porewater displayed a distinct cross-shore zonation, with seawater infiltration on the upper beach at the high water line (HWL), and saline and brackish porewater exfiltration (SGD) at the ridge-runnel structure and the low water line (LWL) on the lower beach. This led to a higher evenness of prokaryotic communities in lower beach areas impacted by SGD compared to unimpacted areas. Archaea contributed 1–4% to the 16S rRNA gene sequence dataset. Those were dominated by Nitrosopumilaceae, corresponding well to higher concentrations of NH4+ in the discharge area of the STE. The unimpacted sites had elevated abundances of Wosearchaeia, which were also detected previously in impacted areas of an STE at Mobile Bay (Gulf of Mexico). While a large proportion of prokaryotes were present in the entire intertidal area, meiofaunal community compositions were site specific and dominated by nematodes. Nematode communities of the high-water line differed distinctively from the other sites. Overall, our data indicates that the three domains of life display distinctly different adaptations when facing the same conditions within the STE. Therefore, distribution patterns of any domain can only be understood if all of them, together with basic environmental information are investigated in an integrated context.

Tourism in the COVID-19 context in mesotidal beaches: Carrying capacity for the 2020/2021 summer season in Pehuén Co, Argentina

As a result of the COVID-19 pandemic, there is an evident decrease in economic activity, especially in the tourism sector. On the southwest coast of the Buenos Aires Province (Argentina), coastal cities base their economy on 3S tourism. In this context, the analysis of social views is crucial for participatory coastal management. As well as the forecast of beach use areas in semi-diurnal mesotidal and low-slope beach conditions, wherein few hours the available beach can double or disappear. Therefore, our objective was to determine the beach's optimal use according to its tides, socio-environmental characteristics, and the perception of the interested parties about the 2020/2021 summer season in the pandemic context in Pehuén Co Beach. We employed camera images (January 2019 and 2020) to obtain the behaviour of normal, spring and neap tides, beach geomorphology, and daily and hourly beach use curves. Online surveys were also conducted with residents, second homeowners, and Pehuén Co visitors about their perception for the 2020/2021 summer season. With this analysis, we were able to divide the beach into four areas according to its potential carrying capacity. During low tide, users' maximum capacity on the beach, respecting sanitary distances, may be 6400 people. Meanwhile, at low tide, this number may rise to 34,000. This information is essential for coastal management after the COVID-19 irruption to ensure maximum efficiency in using the beach maintaining a safe social distance.

Seasonality of pluviosity and saline intrusion drive meiofauna and nematodes on an Amazon freshwater-oligohaline beach

Salinity in estuarine environments is one of the most important influencing factors for meiofauna. The effects of seasonal variation in rainfall and saline intrusion on meiofauna/nematodes diversity and abundance on a mesotidal beach located in the mixing zone of an Amazon estuary were analyzed. Samplings occurred bimonthly over one year at four stations in the intertidal zone. Density variation in meiofauna community had a direct relationship with increased rainfall and decreased salinity. Oligochaeta had the highest density during the months with the highest rainfall and lowest salinity. The highest total Nematoda richness value, as well as richness of brackish water genera value, was registered in September and gradually decreased until March, a month with the highest rainfall. Enoplolaimus, a typical predator, had the highest densities in the months with the highest rainfall, probably due to the food availability (Oligochaeta). The highest Nematoda density at the station closest to the high-tide mark occurred due to detritus accumulation. On the other hand, the lower densities at the middle stations are due to the higher desiccation that occurs in these regions compared to the station closer to the low-tide mark. Meiofauna was strongly affected by seasonal changes in rain and salinity, both at the level of large groups and at the level of Nematoda genera. In addition, seasonal changes in salinity clearly affected organisms indirectly through their prey-predator interactions.

FIELD MEASUREMENTS AND MODELLING OF NEARSHORE CURRENTS AT A HIGH-ENERGY GEOLOGICALLY-CONSTRAINED BEACH

We present field measurements of nearshore currents at a high-energy mesotidal beach with the presence of a 500-m headland and a submerged reef. Small changes in wave forcing and tide elevation were found to largely impact circulation patterns. In particular, under 4-m oblique wave conditions, our measurements indicate the presence of an intense low-frequency fluctuating deflection rip flowing against the headland and extending well beyond the surf zone. An XBeach model is further set up to hindcast such flow patterns.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/EiqnjBIkWJE

FOREDUNE EVOLUTION AT A PROGRADING LOW-ENERGY SEA-BREEZE DOMINATED MICRO-TIDAL BEACH

Foredunes provide habitat and natural protection in coastal areas. The dune formation and development are controlled by aeolian, marine, and ecological processes (Hesp, 2002; Houser, 2009). The dune height is a key parameter for determining storm impact on barrier islands (Sallenger, 2000) and for calculating the Coastal Resilience Index (Dong et al., 2018). Therefore, the understanding of the relative role of both aeolian and marine processes on controlling dune evolution are fundamental for coastal hazards assessment on the context of climate change. A previous study (Cohn et al., 2018) conducted on a meso-tidal beach suggested that extreme water level can contribute to dune growth. The purpose of the present study is to investigate the role of aeolian and marine processes on the dune growth at a low-energy sea-breeze dominated micro-tidal beach located in northern Yucatan peninsula by means of high-resolution beach surveys.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/6f7pM01_jho

High‐Energy Surf Zone Currents and Headland Rips at a Geologically Constrained Mesotidal Beach

AbstractWe analyze Eulerian and Lagrangian measurements of wave‐induced circulation collected during a 3‐week field experiment at a high‐energy mesotidal barred beach with the presence of a 500‐m headland and a submerged reef. Small changes in wave and tide conditions were found to largely impact circulation patterns. Three main regimes were identified depending on offshore wave obliquity: (1) Under shore‐normal configuration, the flow was dominated by cross‐shore motions, except for moderate waves at low tide, with the presence of a quasi‐steady circulation cell on the reef. (2) Under shadowed configuration, an onshore‐directed current flowing away from the headland and a weak oscillating eddy were present outside and inside the shadow region, respectively. (3) Under deflection configuration, a deflection rip flowing against the headland and extending well beyond the surf zone was present, with activity maximized around low tide for moderate waves. Under 4‐m oblique waves, the deflection rip was active regardless of the tide with mean depth‐averaged velocities up to 0.7 m/s 800‐m offshore in 12‐m depth, with energetic low‐frequency fluctuations. Our results emphasize the ability of deflection rips to transport materials far offshore, suggesting that such rips can transport sediment beyond the depth of closure. This study indicates that a wide variety of wave‐driven circulation patterns can occur and sometimes coexist on beaches with prominent geological settings. Changes in the dominant driving mechanism can occur as a result of small changes in wave and tide conditions, resulting in more spatially and temporally variable circulation than along open sandy beaches.

Shoreline "Proxies" Evaluation for Mid-term Erosion Rates Calculation in Mesotidal and Microtidal Beaches (Andalusia, Spain)

Shoreline "Proxies" Evaluation for Mid-term Erosion Rates Calculation in Mesotidal and Microtidal Beaches (Andalusia, Spain)

Satellite Derived Shorelines at an Exposed Meso-tidal Beach

Cabezas-Rabadan, C.; Pardo-Pascual, J.E.; Palomar-Vazquez, J.; Ferreira, O., and Costas, S., 2020. Satellite Derived Shorelines at an exposed meso-tidal beach. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1027–1031. Coconut Creek (Florida), ISSN 0749-0208.Shoreline position data offer extremely valuable information for understanding coastal dynamism and beach changes. This research applies SHOREX system for defining the shoreline position from free mid-resolution Landsat-8 (L8) and Sentinel-2 (S2) satellite imagery. This system allows an automatic definition of Satellite Derived Shorelines (SDS) over large regions and periods. Accuracy and utility of the resulting SDS have been previously assessed with positive results at low energy, microtidal, Mediterranean beaches. This work assesses SDS extracted using SHOREX at a mesotidal and moderate to highly (during storms) energetic environment, namely at Faro Beach, a barrier beach located in Ria Formosa (Algarve, South Portugal). Accuracy was defined for 14 SDS derived from S2 and 10 from L8 by measuring the differences in position with respect to the shoreline inferred from profiles obtained on close dates (or simultaneously) to imagery acquisition. For non-simultaneous datasets, the water level was estimated for the time of the satellite images acquisition using oceanographic data and run-up formulations. The measured and estimated shoreline positions were then compared with the extracted SDS. The overall accuracy is good, with errors about 5 m RMSE, supporting the application of the used methodology to define shoreline dynamics and evolution at challenging environments, as mesotidal exposed and dynamic beaches.

Spatial and Temporal Patterns of Pore Water Chemistry in the Inter-Tidal Zone of a High Energy Beach

Submarine groundwater discharge (SGD) is a ubiquitous source of meteoric fresh groundwater and recirculating seawater to the coastal ocean. Due to the hidden distribution of SGD, as well as the hydraulic- and stratigraphy-driven spatial and temporal heterogeneities, one of the biggest challenges to date is the correct assessment of SGD-driven constituent fluxes. Here, we present results from a 3-dimensional seasonal sampling campaign of a shallow subterranean estuary in a high-energy, meso-tidal beach, Spiekeroog Island, Northern Germany. We determined beach topography and analyzed physico-chemical and biogeochemical parameters such as salinity, temperature, dissolved oxygen, Fe(II) and dissolved organic matter fluorescence (FDOM). Overall, the highest gradients in pore water chemistry were found in the cross-shore direction. In particular, a strong physico-chemical differentiation between the tidal high water and low water line was found and reflected relatively stable in- and exfiltrating conditions in these areas. Contrastingly, in between, the pore water compositions in the existing foreshore ridge and runnel system were very heterogeneous on a spatial and temporal scale. The reasons for this observation may be the strong morphological changes that occur throughout the entire year, which affect the exact locations and heights of the ridge and runnel structures and associated flow paths. Further, seasonal changes in temperature and inland hydraulic head, and the associated effect on microbial mediated redox reactions likely overprint these patterns. In the long-shore direction the pore water chemistry varied less than the along the cross-shore direction. Variation in long-shore direction was probably occurring due to topography changes of the ridge-runnel structure and a physical heterogeneity of the sediment, which produced non-uniform groundwater flow conditions. We conclude that on meso-tidal high energy beaches, the rapidly changing beach morphology produces zones with different approximations to steady-state conditions. Therefore, we suggest that zone-specific endmember sampling is the optimal strategy to reduce uncertainties of SGD-driven constituent fluxes.

Observations and modelling of shoreline and multiple sandbar behaviour on a high-energy meso-tidal beach

This contribution describes 10 years of observed sandbar and shoreline cross-shore position variability at a meso-tidal, high energy, multiple sandbar beach. To examine relationships between the temporal variability in shoreline/sandbar position with offshore wave forcing, a simple equilibrium model is applied to these data. The analysis presented in this paper shows that the equilibrium model is skilled at predicting the alongshore-averaged, time-varying position of the shoreline (R = 0.82) and the outer sandbar position (R = 0.75), suggesting that these end members of the nearshore sediment system are most strongly influenced by offshore wave forcing in a predictable, equilibrium-forced manner. The middle and inner bars are hypothesized to act as sediment transport pathways between the shoreline and the outer bar. Prediction of these more transient features by an equilibrium model was less skilful.Model coefficients reveal that these two end members (outer bar and shoreline) in the sediment system act in opposite directions to changes in the annual offshore wave forcing. During high wave events, sediment is removed from the shoreline and deposited in the nearshore sediment system with simultaneous landward retreat of the shoreline and offshore migration of the outer sandbar. While both end member features have cycles at annual and inter-annual scales, their respective equilibrium response factor differs by almost a factor of 10, with the shoreline responding around an inter-annual mean (ϕ = 1000 days) and the outer bar responding around a seasonal mean (ϕ = 170 days). The model accurately predicts shoreline response to both mild (e.g. 2004/05, 2008/09) and extreme (e.g. 2005/06, 2009/10) winter storms, as well as their summer recovery. The more mobile and dynamic outer sandbar is well-modelled during typical winters. Summer onshore sandbar migration of the outer bar in 2005 and 2006 is under-predicted as the system transitioned between a triple (winter) and double (summer) sandbar system. The changing of the number of bars present in the system is something that this simple model cannot predict. Analysis of the data suggests that this multi-bar system adjusts its cross-shore seasonal movement when there is a significant change in the sediment supply to the system (e.g., nourishment projects, severe storms).

Seasonal morphodynamics of the subaerial and subtidal sections of an intermediate and mesotidal beach

This study provides a detailed insight into the seasonal morphological evolution of the subaerial and subtidal sections of an intermediate and mesotidal beach in relation to the nearshore wave conditions. For this purpose, fortnightly−to−monthly topographic and bathymetric measurements were collected on Ensenada Beach (Baja California, Mexico) from November 2012 to February 2016. Wave data were concurrently measured at 20m water depth, enabling the correlation of the observed morphological changes to the hydrodynamic forcing. The seasonal morphological variability of the beach comprised ±200,000m3 (±70m3m−1) and resulted primarily from the cross-shore exchange of sediment. The volumetric fluctuations alongshore were up to ±100,000m3 and event-driven, and played an inportant role in the overall sediment balance. In association with the incoming wave conditions, the subaerial and subtidal beach sections experienced a strong seasonal variability. The subaerial beach reached the maximum volumes in the end of summer (September−October) and minimum in winter (January−February) while the opposite response was obtained for the subtidal beach, with the largest and smallest volumes occurring during the same months in winter and summer, respectively. The morphological fluctuations of the upper and lower beach sections were associated with the preceding monthly averaged wave conditions. The subtidal volume variations were highly and positively correlated to the wave height and period, while the subaerial section was highly but negatively correlated to the same variables. The morphological beach response to energetic waves was more rapid than to low-energy conditions. The largest subaerial erosion and subtidal accretion happened in three months (October−January) while the subaerial accretion and subtidal erosion occurred smoothly over nine months (January−October). The total beach volume (subaerial and subtidal) lacked of seasonal variability, and an annual loss of 50,000m3 (17m3m−1) occurred from August 2014 to August 2015, indicating that the beach remained fairly stable over that period of time. The largest volumetric variations of 300,000m3 (105m3m−1) occurred during the beginning of the 2015–2016 El Niño winter.

Diatom accumulations on a tropical meso-tidal beach: Environmental drivers on phytoplankton biomass

Diatom accumulations are important phenomena that occur on many sandy beaches worldwide, but little is known about their seasonal occurrence and environmental drivers at lower latitudes. The results revealed that the diatom Anaulus cf. australis and Asterionellopsis tropicalis were accumulated on a tropical beach near the Equator (3°41′S; northeastern Brazil). The highest frequency of diatom accumulation (81%) occurred during the rainy season, when wind intensity was weak and waves had lower heights. The main environmental driver that control occurrence of the patches on this oligotrophic sandy beach is a rainfall that is associated with the availability of nutrients. Tides are a physical driver that affect the phytoplankton biomass at the surf zone, large tidal ranges were related to dispersal and biomass reduction of the diatom accumulations. In addition, there was an association between swell and patches, this kind of wave appear be an important physical driver, however this mechanism is not fully understood. These findings provide novel insights into the environmental drivers and general knowledge of diatom accumulations worldwide.

Contribution of storms to shoreline changes in mesotidal dissipative beaches: case study in the Gulf of Cádiz (SW Spain)

Abstract. In this study an analysis of storminess and rates of shoreline change is performed and discussed jointly in four geomorphological units of the Gulf of Cádiz (SW Spain) for the period of 1956–2010. For this purpose, storm events are identified based on the following characteristics: wave height above 2.5 m, a minimum duration of 12 h and events with calm periods of less than 24 h were considered as a single event. Subsequently, energy parameters are determined in order to characterize storm-induced impacts. Conversely, geographic information system (GIS) tools are used to measure shoreline changes in aerial photographs and orthophotographs of each site, selecting the high water line as shoreline proxy. Each geomorphological unit is divided into different behavioural patterns according to recorded coastal changes, so that each one shows a particular behaviour.In general the variability of shoreline changes that is explained by storms and the relation between storm parameters and coastal changes present better results in exposed areas (Cádiz and Vistahermosa) than in sheltered areas (Valdelagrana spit barrier) because the former are more sensitive to storm impacts. On the contrary, in areas where there is no relation between coastal changes and storm parameters (Valdelagrana and Sancti Petri sand spit), it is suggested that anthropogenic factors are the main forcing agents determining shoreline behaviour. However, in these areas the storminess also modulates coastline recession by increasing erosion when the number of storms is high.

Multi-decadal shoreline change and beach connectivity in a high-energy sand system

ABSTRACTUnderstanding how and why the world’s coastlines are changing is a pressing international concern in a context of rising sea levels, increased climatic variability and intensifying coastal development. Medium to long-term records of coastal change are rare worldwide and often limited to individual beach compartments. This study presents a 70-year (1940–2010) aerial imagery record to compare decadal changes in shoreline position across four high-energy west coast beaches near Auckland, New Zealand/Aotearoa: Whatipu, Karekare, Piha and Te Henga (Bethells). The common exposure of these adjacent mesotidal beaches to changing wind and wave conditions might, if they present the dominant controls on shoreline position, be expected to produce synchronous change. Whatipu (935 m), Piha (32 m) and Te Henga (52 m) showed net overall progradation for the study period, while Karekare retreated slightly (−4.1 m). All except Whatipu underwent periods of beachwide erosion. Shoreline change was not coherent between beaches, despite similar exposure to variations in wind, wave and sea level. Variable sediment supply from northward littoral drift is implicated as the primary control on decadal-scale shoreline change for these beaches, highlighting the importance of local context in influencing shoreline response to changing environmental conditions.

Cusp Development on a Gravel Beach

ABSTRACT Wang, J., and Sherman, D.J., 2016. Cusp development on a gravel beach. 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. 937–941. Coconut Creek (Florida), ISSN 0749-0208. Field experiments were conducted on a gravel foreshore at Portmore Beach, Ireland, to test edge wave, self-organization, and process-based hypotheses. The study site is on a 350 m long, meso-tidal beach, open to waves from the northeast. The gravel foreshore comprises 20–250 mm particles, and cusps are ubiquitous thereon. The foreshore is fronted by a sandy nearshore. Water levels, waves, and currents were measured with an instrument array that comprised seven Marsh-McBirney model 511, bi-directional current meters, and eleven KPSI pressure transducers. Prior to the experiment the study area was graded to remove existing cusps and a video camera installed to monitor morpho...