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Multiple intertidal barred systems (MITB) are complex coastal features observed under specific conditions including low to moderate energy waves and macrotidal forcing. Although primarily tide-dominated, MITBs can undergo significant morphological changes under storms and extreme events. In December 2021, storm Barra crossed the U.K. and was the 2nd most energetic event in the past 25 years, to occur on Northern Ireland’s east coast. At the MITB site in Dundrum Bay, offshore waves reached a maximum significant wave height of 5.5 m on December 7th, 2021 and were associated with a peak period and wave direction of 10s and 179°N-oriented respectively. Pre- and post-Barra intertidal DGPS surveys were conducted at Dundrum Bay on the 6th and 9th of December to identify beach morphological changes on MITBs. Despite direct onshore waves reaching the bay, a strong alongshore variability was recorded in the response to Murlough and Ballykinler beaches to Storm Barra. Indeed, according to preliminary results, the western end of the bay shows an elevation of the beach profile, the central area presents onshore migrations of the bars to no significant changes, while the eastern side of the bay (Ballykinler) displays bar crests flattening and linear post-storm profiles.Although storm Barra was the most energetic event recorded during the winter 2021/2022, smaller storm events had modified the morphology of Murlough and Ballykinler beaches throughout the preceding season, leading to some already low pre-Barra beach profiles. Secondly, at the peak of Barra’s energy, the waves were southeast oriented. But the direction of the waves rapidly shifted from onshore to offshore, possibly modifying the impact of Barra on the system. Finally, the shape of the bay, the location of the different profiles and the complex nearshore bathymetry and local geology must have also played a key role dictating the alongshore pattern shown. Previous studies of Dundrum Bay have shown that physical processes driven by waves/tide and geomorphology interactions can undergo significant local modification, leading to a strong alongshore variability in the profiles’ response to seasonal events. Nearshore SWAN simulations will help highlight the role of nearshore hydrodynamics including wave dissipation and re-orientation, wave-driven sediment transport and the impact of storm surge on MITB during an extreme event.

Shoreline change analysis of the entire coast of Northern Ireland was conducted for the period from 1830 to 2021. Even with its 790Km length (including the main offshore islands) the Northern Ireland coastline is remarkably diverse, comprising several notable coastal typologies (cliffs, rocky coasts, sandy beaches, sand dunes, etc.) as well as a number of commercial and industrial activities. Human pressure co-exists with the natural coast and each impacts the other in many ways.Shorelines were digitised using multiple temporal and spatial datasets (historical maps, aerial photos and orthophotos). The average temporal interval of shorelines ranges from 7.8 to 37 years, depending on location and data availability. The seaward vegetation line was selected as the primary shoreline proxy, whereas cliff edge, rock-water line or anthropogenic structures were chosen subordinately or if deemed more appropriate. Shoreline uncertainty was assessed using various errors inherent from each dataset from which the shoreline was digitised. The ArcMap® tool DSAS 5.0 was used to calculate shoreline rates and distances along 25 m spaced transects covering the entire coastline.Over the last two centuries the maximum retreat value was highlighted in Lough Foyle between the Roe River mouth and Magilligan Point where the shoreline progressively retreated up to -250 m. The largest shoreline advancement (+3.500 m) was recorded in Belfast following its port expansion.Sandy coastlines were shown to have the larger natural changes. Magilligan point, after an advancement phase toward its northern extremity between 1830 and 1919, underwent a constant retreat phase that has now extended to its eastern side up. Benone Beach, Castlerock and Portstewart Strand are the only vegetated coastal dune sites along Northern Ireland’s north coast that are advancing in the last 190 years(190-270m) Significant shoreline retreat was recorded at White Rocks (-85 m), Ballycastle (-65 m), Runkerry (-25 m) and White Park Bay (-65 m). In Dundrum Bay, Co. Down, the largest retreat values (-75 m) occurred at Murlough and maximum advancements greater than 200 m at Ballykinler.The largest shoreline advancements were all attributed to human activities such as land reclamation in the loughs (mainly during the 19th century), seaward expansions of ports (e.g., Belfast, Bangor, Carrickfergus, Portavogie and Warren Point) or construction of power stations and wastewater treatment areas. Shoreline advancements recorded for the salt marshes of Larne and Foyle Loughs and White Water River mouth also followed human interventions. High rocky coasts, apart from limited rockfalls, were less subject to shoreline changes. The work will contribute to better define coastal cells along the Northern Ireland coastline and inform coastal managers for future development plans of the coast.

Geological evidence of past storminess is fundamental for contextualizing long-term climate variability and investigating future climate. Unlike the Atlantic and Pacific basins, robust storminess reconstructions do not exist for most of the Indian Ocean, despite the hazard that tropical cyclones pose to the SE African margin. Here we combine seismic stratigraphy with analysis of marine sediment cores to look for regionally representative storm-related sediment deposits (tempestites) intercalated in shoreface sediments from the SW Indian Ocean off South Africa. Tempestites, represented by hummocky seismic units, whose sediments have clear marine geochemical signatures, are found to have been deposited between 7.0 and 4.8 cal kyr BP, when sea level was between 0 and +3 m above present. Deposition and preservation of the tempestites reflect unprecedented tropical cyclone impacts, associated with periods of strongly positive Indian Ocean Dipole anomalies and linked to warmer sea surface temperatures. Future climate projections suggest stronger positive IOD anomalies and further intensification and poleward migration of tropical cyclones, like their mid-Holocene predecessors. Given the rarity of tropical cyclone landfalls in South Africa, this urges a revaluation of hazards in areas along the SE African coast likely to become more vulnerable to landfalling tropical cyclones in the future.

Topographic steering has been observed around Gran Canaria, a high-profile circular island located in the Canary Island Archipelago, Spain, culminating in a complex lee-side wind regime at the Maspalomas dunefield. Maspalomas has experienced rapid environmental changes since the 1960s, coincident with a boom in the tourism industry in the region and requires further examination on the linkages between meso-scale airflow patterns and aeolian processes modifying the landscape. The aim of this work is to simulate mean and turbulent airflow conditions at Maspalomas due to incremental changes in the regional wind direction and to compare these results to the predicted and observed aeolian dynamics taken from meteorological records, a global wind retro-analysis model, and remote sensing data. A Smagorinsky Large Eddy Simulation (S-LES) model was used to identify meso-scale airflow perturbations and turbulence at different locations around the island. Variability in meteorological data was also identified, with sites recording accelerated or retarded velocities and directional distributions ranging between unimodal to bimodal. Using a global retro-analysis model, relatively consistent up-wind conditions were predicted over a period coinciding with three aerial LiDAR surveys (i.e., 2006, 2008, and 2011) at the Maspalomas dunefield. Despite the consistent predicted airflow conditions, dune migration rates dropped from 7.26 m y−1 to 2.80 m y−1 and 28% of dunes experienced crest reversal towards the east, or opposite of the primary westerly migration direction during the second time period. Our results indicate that meso-scale airflow steering alters local wind conditions that can modify sediment transport gradients at Maspalomas. Given the rapidity of environmental changes and anthropogenic impacts at Maspalomas, these findings improve our understanding on the aeolian dynamics at Maspalomas and can be used to inform future management strategies. Lastly, the approach used in this study could be applied to other high-profile island settings or similarly complex aeolian environments.

Evidence for sea-level change during and around Marine Isotopic Stage 5e (ca. 125 ka) in southern Africa derives from a wide variety of geomorphic and sedimentological sea-level indicators, supported in the past 2 decades by absolute chronological control. In addition to these proxies, data provided by both terrestrial (dune sediments and archaeological remains) and marine (lagoonal and nearshore littoral sediments) limiting points provide broad constraints on sea level. Here, we review publications describing these data points. Using the framework of the World Atlas of Last Interglacial Shorelines, we insert in a standardized database all the elements needed to assess former paleo relative sea level, and the chronological constraints associated with them (including uncertainties). Overall, we reviewed 69 studies, from which we extracted 35 sea-level indicators and 25 limiting points. As far as age attribution is concerned, early dating of molluscs and whole-rock beachrock samples using U-Series allowed ating of several sea-level indicators during the 1980s but the more widespread application of Optically Stimulated Luminescence dating since 2004 has yielded many more (and more accurate) dates from several sites. This has helped resolve the nature and timing of MIS5e shorelines and has the potential to further elucidate the apparent presence of two or more sea-level peaks at several South African sites during this interval. The standardized sea-level database presented in this paper is the first of its kind for this region. Future research should be directed to improve the stratigraphic description of LIG shorelines and to obtain better dating, high-accuracy elevation measurements with better palaeo-RSL interpretation.

Conventional aeolian sand transport models relate mass transport rate to wind speed or shear velocity, usually expressed and empirically tested on a 1-s time scale. Projections of total sand delivery over long time scales based on these models are highly sensitive to any small bias arising from statistical fitting on empirical data. We analysed time series of wind speed and sand transport rate collected at 14 independent measurement stations on a beach during a prior field experiment. The results show that relating total sand drift to cumulative above-threshold wind run yields models which are more statistically robust when fitted on empirical data, generating smaller prediction errors when projected to longer time scales. Testing of different power exponents indicates that a linear relationship between sand drift and above-threshold wind run yields the best results. These findings inspire a speculative novel phenomenological model relating the mass flow of air in the boundary layer to the mass transport of sand over the surface.

Wind flows on Mars are the dominant contemporary force driving sediment transport and associated morphological change on the planet’s dune fields. To fully understand the atmospheric – surface interactions occurring on the dunes, investigations need to be conducted at appropriate length scales (at or below that of any landform features being examined).The spatial resolution of Martian Global Circulation Models (GCMs) is too low to adequately understand atmospheric-surface processes. Nevertheless, they can be utilised to establish initial state and boundary conditions for finer-scale simulations. Mesoscale atmospheric models have been used before to understand forcing and modification of entire dune fields. However, their resolution is still too coarse to fully understand interactions between the boundary layer and the surface. This study aims to examine and improve our understanding of local-scale processes using microscale (e.g., 1.5m cell spacing) airflow modelling to better investigate localised topographic effects on wind velocity and associated aeolian geomorphology.Toward these aims, this study will simulate microscale wind flow using computational fluid dynamics software (OpenFOAM) at a series of sites containing a variety of topographies and wind regimes. A Mars GCM will provide input for baseline mesoscale modelling runs, the output of which will then be used as input for microscale airflow modelling. The sites used for the study will have excellent orbital, or preferentially, in situ data coverage. Detailed HiRISE imagery will provide high-resolution Digital Terrain Models (DTMs) which will be used by the OpenFOAM simulations. Results from model simulations will be evaluated/validated using both in situ data and geomorphic analysis of imagery.

Beachrocks are coastal sediments that are lithified through the precipitation of carbonate cements. It is widely acknowledged that lithofacies in beachrocks are variable and their interpretation is useful when using beachrock as a sea level indicator or when studying shoreline evolution over the centurial to millennial scales. Surprisingly however, the facies variability of beachrocks remains understudied as they are almost exclusively described as seaward dipping, slab-shaped outcrop forming in low energy dissipative beach environments. The Mission Rocks coastline of north-eastern South Africa is in stark contrast. Here the coast comprises an up to 3 m thick raised shore platform of beachrock, where a variety of sedimentological facies are observed. These comprise seaward-dipping planar bedded sandstones and conglomeratic units, often interbedded with bimodally-orientated trough cross bedded sandstones. In our study we aim to use sedimentological facies analysis, petrography and cathodoluminescence to unravel the deposition- and cementation processes of this beachrock facies.In particular, an unusual beachrock breccia interposed amongst the breakdown remnants of the platform forms the basis of this paper. The breccia documents a cycle of simultaneous erosional breakdown and depositional buildup of the beachrock platform, a yet undescribed process for the development of beachrock. Since it forms as a thin veneer (< 0.10 m), with a slightly thicker infill (≤ 0.5 m) amidst erosional hollows and gullies of the + 2 m high rocky platform, it raises into question the necessity of a thick sedimentary overburden, that is typically considered the requirement for beachrock cementation in the mixing zone. Timing of beachrock formation is constrained by recent anthropogenic activities, as the underlaying platform was mined for building purposes during WWII and it is in these quarry slots and crack that the beachrock is found. While it is generally suspected that beachrocks may form at the centennial scale, evidence for this remains weak. Not only can the interpretation of this facies contribute to our understanding of the long term processes that form and break down beachrocks on high energetic coastlines, it provides insight into rapid beachrock formation and as such its utility as a sea level index point.

In 2015, an active dune field on Mars was visited up close by the Curiosity rover in Gale Crater providing the first high resolution ground images of fine scale windblown features not previously resolved from orbital-based imagery. For the first time, these images allow for direct comparison with terrestrial aeolian dynamics and provide critical ground truth data to bridge the gap between model predictions and satellite observations. The image data from the slipface on the Namib dune within the Bagnold dune field shows grainflow morphologies that are similar to dunes on Earth. Quantitative estimates of flow thickness, based on shadow length are presented for the grainflows on the Namib dune slipface and compared to grainflow characteristics measured by terrestrial laser scans from the Maspalomas dune field located in Gran Canaria, Spain. Using observations from Maspalomas to support interpretations of martian slipface dynamics, we discuss implications for the local wind regime, style of grainflow, seasonal activity, and dune migration. The presence of multiple large-magnitude grainflows on the Namib slipface suggests an active aeolian environment, capable of delivering enough sediment to the slipface to initiate these flows and transport sediment to the bottom of the lee slope. However, the thinness of grainflows on the Namib dune, the formation of smaller grainflows directly below the dune brink and limited grainfall suggest a lower wind energy environment, at least for the most recent slipface activity. Large, actively migrating stoss ripples obliquely oriented to the dune crest regularly deposit sediment on to the upper slipface and may be a mechanism in which larger grainflow occur during seemingly low energy wind events. This mechanism of sediment delivery may also explain the existence of a variety of slipface morphologies, both young and old, which are otherwise quickly erased on Earth due to sediment redistribution and grainfall.

On the SE African shelf, a submerged shoreline at a depth of 60 m is examined and its attributes compared between two shelf sectors with different morphologies, yet similar energy regimes. The aim is to assess the controls of antecedent conditioning on shoreline development and later preservation from transgressive ravinement. Using a combination of multibeam bathymetry and single-channel seismic profiles, the stratigraphy and morphology of the shoreline is investigated. Low-gradient bedrock examples reveal several distinctive seismic facies, including onlapping chaotic reflector packages which are interpreted as calcarenite rubble fields. These palaeo-shorelines possess planform equilibrium morphologies, including parabolic dunes and blowout forms along with relict shore platforms. They are strongly associated with incised valleys of last glacial maximum age which underlie the shoreline locations; these provide wide, back-barrier accommodation space during transgression. In contrast, palaeo-shorelines on the steeper-gradient shelf have a simpler stratigraphic arrangement. They are not as well preserved, are generally covered by thick drapes of sediment, and lack the elaborate planform morphologies of their lower-shelf gradient equivalents. Isolated incised valleys and the steep bedrock gradient limit accommodation space. The comparison indicates that antecedent bedrock slope and available accommodation are amongst the dominant controls on overstepping, and thus potential preservation, of palaeo-shorelines on the shelf. Lower-gradient shelves not only promote rapid shoreline translation but, together with wide, sandy back-barrier accommodation, also foster larger barrier volumes. In suitable climates such as in the Mediterranean and other sub-tropical areas, the ensuing shoreline stability promotes rapid and effective cementation of the barrier. In comparison, steep bedrock profiles with limited back-barrier accommodation have much lower preservation potential. Transgressive ravinement is more focussed on steep slopes, effectively removing more material during the ravinement process. The more dynamic environment may also reduce the effectiveness of diagenesis. The potential of beachrock and aeolianite palaeo-shorelines as submerged sea-level indicators may be optimal in low-gradient settings in Mediterranean to subtropical environments.

This study examines a Holocene-aged submerged shoreline, Limestone Reef, located in the shallow subtidal zone of South Africa’s east coast. It comprises an elongate, coast-oblique, slab-like outcrop of beachrock situated above the contemporary fair-weather wave base. It is currently undergoing mechanical disintegration. Its unique and rare preservation in a high-energy setting affords an opportunity to examine the mechanical processes occurring during wave ravinement associated with rising sea level. The submerged shoreline and the adjacent shoreface were examined using high-resolution seismic reflection, side-scan sonar and shallow-water multibeam echosounding techniques. Limestone Reef rests on top of unconsolidated Holocene deposits. The structure’s surface is characterised by reef-perpendicular gullies with rubble derived from the slab fringing its seaward edge. Limestone Reef slopes gently seawards and has a steep landward-facing edge where gullies are most prominently developed. Teardrop-shaped rippled scour depressions, marked by high backscatter, are located seawards of the submerged shoreline. These elongate in a seaward direction and are filled with bioclastic gravels and residual rubble from Limestone Reef. The gullies in the upstanding structure are indicative of wave plucking and abrasion of the shoreline. The material exposed by the rippled scour depressions is identical to that comprising the postglacial ravinement surface identified in the offshore stratigraphy. These deposits are considered to represent the contemporary, actively forming wave ravinement surface. The results suggest that wave ravinement of submerged shorelines is a discontinuous process dominated by the seaward entrainment of material from its landward edge controlled by high-energy drawback during storm surges. The ravinement process appears to operate at the seasonal scale and averages out over the long-term millennial scale for the continuous surface.

Airflow dynamics and potential sediment transport were measured and modelled across various barchan dune topographies and incident wind conditions. Modification of near surface flow was recorded simultaneously in three dimensions (3D) using dense arrays of high-resolution 3D ultrasonic anemometers. In situ measurements provided rigorous validation and calibration for computational fluid dynamics (CFD) modelling. Measured and modelled results show good agreement between flow velocity, directionality, and turbulence intensity. Modelling of characteristic airflow conditions and surface shear stress beyond the instrument locations, elucidated airflow dynamics across the entire landform surface at an unprecedented level of detail. Emergent turbulent airflow patterns were identified in the form of two counter-rotating vortices that converge at the dune centreline downwind of the dune crest. Integrating a sediment transport function with CFD surface airflow allows for the spatial mapping of flux patterns across the entirety of the dune and interdune surface. On the stoss slope and laterally along the outer barchan arms, there is strong potential sediment flux in response to increased streamwise stress. In lee-side locations, sediment transport remains at ‘above threshold’ conditions and is redirected in response to complex turbulent vortices identified in the overlying wake zone. The precision of the models allows for the identification of complex flow perturbations and associated surface stresses that prove difficult to measure in the field. CFD in combination with a sediment transport function is demonstrated to be a useful tool in investigating morphodynamics of mobile dune systems.

The distribution and geomorphology of aeolianite outcrop on the coast of KwaZulu-Natal, South Africa are described in the context of its preservation potential in the geological record. Aeolianite on the contemporary coast comprises discontinuous, widely spaced, outcrops less than 100 m in longshore extent and typically 50–60 m wide that reflects the combined action of subaerial weathering and physical abrasion in the coastal zone since the mid-Holocene (approximately 7000 yrs). The dominant morphological component is an intertidal erosional platform that slopes gently landward. It is fronted by a notch in the mid intertidal zone (0 m MSL) and contains active erosional potholes on its seaward margin. The platform surface is encrusted by a variety of marine organisms. Landward of and contiguous with the intertidal surface are small elevated outcrops of aeolianite in the supratidal zone. These comprise a 3 m-high seaward scarp with a basal notch in the high intertidal zone + 1 m MSL. Gullies in the scarp trap coarse clasts of eroded aeolianite as well as bedrock. The upper surface of the supratidal aeolianite is planar with large potholes within which accumulations of coarse clasts and oyster shells have been cemented. The upper surface is interpreted as a remnant of an intertidal platform formed at a higher mid-Holocene sea level. The supratidal outcrop is subject to weathering and disintegration. Major joints divide the outcrop into cuboid blocks with axes of 3–4 m. Eroded blocks on the seaward face that exceed 1 m diameter, remain in-situ and become locked in place by repeated shaking. Smaller blocks that collapse from the seaward face accumulate in small gullies or are dispersed. The facet most likely to be preserved in the geological record is the planar intertidal platform. The morphology of aeolianite on the contemporary coast is markedly different from submerged aeolianite ridges on the adjacent shelf which are of higher relief, wider and more laterally extensive. Preservation potential of aeolianite under subaerial conditions is low and the widespread high-relief aeolianite on the shelf is attributed to rapid inundation or burial during transgression.

This work is part of a Vice Chancellor's Research Scholarship funding for PhD studies at the Centre for Coastal and Marine Research, School of Environmental Sciences, University of Ulster.

The coast of southeast Africa is dominated by sandy beaches that tend to be confined within log-spiral or headland-bound embayments. Investigations using serendipitous air imagery data set have been previously undertaken and conclusions drawn about the stability of the coast. We show that conclusions drawn from this data, with respect to the high water mark (HWM) position are fraught with errors, which include tidal state, pressure regime, beach slope, high-swell erosion, seasonal and multi-annual changes. We highlight and discuss these sources of error, together with their magnitudes. The most significant of these are the high-swell, seasonal and multi-annual variations. From case studies we show that the seasonal beach rotation and long-term beach width variation are responsible for tens of metres of unaccounted HWM variation, 30 to 50 m is common, with maximums reaching 60 to 100 m. Overall the southeast African coastline appears to be in a state of long-term dynamic equilibrium. There is no evidence of any sea-level rise-forced transgression in the coastal sediment budget, despite sea-level rise (SLR). If such a signal is, in fact present, it is lost within the beach width variation. Some southeast African coastal reaches are suffering chronic erosion, but these are related to anthropogenic impacts. The extreme difficulty of placing a HWM, with any temporal validity on this coast precludes the routine use of the Bruun Rule. Although no transgressive signature is found, there is evidence of a decreasing coastal sand budget as a result of anthropogenic or natural climate change, or both. This decrease in the coastal sand volume is likely to result in increased future erosion. Copyright © 2016 John Wiley & Sons, Ltd.

Nearshore bars play a pivotal role in coastal behaviour, helping to protect and restore beach systems particularly in post-storm conditions. Examination of bar behaviour under various forcing conditions is important to help understand the short- to medium-term evolution of sandy beach systems. This study carried out over a nine-week period examines, the behaviour of three intertidal bars along a high energy sandy beach system in northwest Ireland using high-frequency topographic surveys and detailed nearshore hydrodynamic modelling. Results show that, in general, there was onshore migration for all the bars during the study period, despite the variability observed between bars, which was driven mostly by wave dominated processes. Under the prevailing conditions migration rates of up to 1.83 m day−1 and as low as 0.07 m day−1 were observed. During higher wave energy events the migration rates of the bars decelerated in their onshore route, however, under lower wave energy conditions, they quickly accelerated maintaining their shoreward migration direction. Tidal influence appears to be subordinate in these conditions, being restricted to moderating the localized wave energy at low tides and in maintaining runnel configurations providing accommodation space for advancing slip faces. The study highlights the intricate behavioural patterns of intertidal bar behaviour along a high energy sandy coastline and provides new insights into the relative importance of wave and tidal forcing on bar behaviour over a relatively short time period. Copyright © 2016 John Wiley & Sons, Ltd.

Ireland experienced a spatially complex pattern of relative sea-level (RSL) changes and shoreline development caused by the interplay of isostatic and eustatic (ice equivalent sea level) processes since the Last Glacial Maximum (LGM). Using a combination of high-resolution marine geophysical data, vibrocores, foraminiferal analysis and 10 AMS radiocarbon dates, we reconstruct the Late Quaternary evolution and RSL history of Bantry Bay, a large (40 km long, 5–10 km wide) embayment in SW Ireland. The data indicate two infill phases: one before and one after the LGM, separated by glacial and lowstand sediments. The pre-LGM history is not dated and the depositional history is inferred. A large sediment lobe formed at the outer edge of Bantry Bay as a lowstand ice-proximal glacimarine outwash system as the ice retreated after the LGM, at a sea level ca. 80 m lower than present. Iceberg scour immediately west of this location likely relate to the break-up of the local Kerry–Cork Ice Cap. Long curvilinear ridges, seen both offshore and on top of the sediment lobe, probably formed as shoreface ridges under stronger-than-present tidal currents during a period of RSL stability (pre-14.6 ka cal BP). A subsequent infill phase is characterised by a basin-wide erosional (ravinement) surface and the deposition of inter- and sub-tidal estuarine sediments. Although our data support the general trends, our stratigraphic and radiocarbon data suggest a higher sea level between 11 and 13.5 ka cal BP than predicted by existing glacial isostatic adjustment models.

The seismic stratigraphy, architecture and evolution of a large subtropical embayment, Maputo Bay, Southern Mozambique is described. Nine seismic units are documented; and show repeated phases of incised valley formation and transgressive infilling. Trangressive infilling alternates between the classic wave-dominated transgressive succession of fluvial and central estuarine bay deposits and the filling by intertidal flat and tidal bedforms developed during stages of inlet restriction and shallowing associated with barrier growth at stillstand intervals. Imprinted on the succession are several key facets of subtropical stratigraphy, hurricane-generated erosional surfaces and beachrock horizons. The upper stratigraphy comprises the highstand bayhead delta, a prograding feature constructed by several flood events. In comparison with literature from other similar systems such as lagoons, coastal lakes and estuaries, a generic three stage stratigraphic model of large marine embayments is proposed that includes incision during glaciations; transgressive infilling during deglaciations; and shallowing during the stillstand episodes of the recent deglaciation.

Pilkey, O.H. and Cooper, J.A.G. 2014. Are natural beaches facing extinction? In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa) Journal of Coastal Research, Special Issue, No. 70 pp. 431–436. ISSN 0749-0208. On a generational scale, on developed shorelines, the world's recreational beaches are doomed. This is largely because of the widespread assumption that preservation of buildings is a higher priority than preservation of beaches in response to sea level rise. Continuing beach degradation will be inevitable through active or passive processes. Active degradation means the actual removal of the beach, mostly as a result of shoreline engineering or mining. By far, the most important cause of beach loss in this category will be hard structures, especially seawalls. The incorrectly but widely perceived panacea of each replenishment will become economically impossible because of raised sea levels. Replenishment leads to intensified bea...

Loureiro, C., Ferreira, O., Cooper, J.A.G., 2014. Non-uniformity of storm impacts on three high-energy embayed beaches. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 326–331, ISSN 0749-0208. Coastal storms are highly significant and destructive events and important natural hazards that have major impacts upon the physical and human-cultural coastline environments. Exceptional coastal storms in the last decades have emphasized the urgent need to reinforce scientific knowledge regarding the frequency, impact and role of these extreme events. This is particularly relevant for embayed beaches, where geomorphological control promotes characteristic morphodynamic responses that are distinct from the better studied long-linear beaches. This paper analyses storm response from datasets of morphological change obtained from three embayments located in three distinct wave environments...

In spite of the worldwide abundance of beachrocks and their acknowledged utility as an indicator of former sea level position, some studies have expressed doubt as to their position of cementation on paleo shorelines. These criticisms are not, however, coupled with nuanced sedimentological studies of beachrocks. Instead, few beachrock studies acknowledge any facies and therefore disregard important signatures of the depositional environment and, consequently, utility as paleo sea level indicators. This study presents detailed sedimentological descriptions and interpretations from two beachrock localities along the subtropical, microtidal, wave-dominated eastern coastline near Durban, South Africa. The outcrops record the migration of a paleo inlet and deposition in sub, inter, and supra tidal environments. Understanding the inferred depositional environment, and observed stratigraphic relationships between various beachrock facies is critical to teasing out the local evolution of shoreline and relative sea level. The outcrops studied here record multiple episodes of Holocene sea level rise and fall.

The distribution of decisional power and ability of local communities to participate in natural hazard risk governance (NHRG) are critical success factors for sustainable development. This article assesses the evolution of power distribution and participation at the local level in NHRG using bibliometric and international discourse analysis. The results show that participation-related concepts are underrepresented in NHRG, compared to environmental resource management and community & livelihood development fields of research. This implies the existence of societal/community barriers that impede the development of a sustainable paradigm in NHRG. In addition, when present, participation is mostly passive (non-decisional), a finding also observed in the representation of these concepts in the international discourse of United Nations International Strategy for Disaster Reduction (UNISDR). For sustainable NHRG, it is necessary to have explicit targets of authentic and long-term support for active community in...

Late Pleistocene–Holocene shoreline sequences and associated shelf stratigraphy are described from a high gradient, high wave-energy shelf. Although shoreline preservation by overstepping is considered unlikely in such an environment as a result of intense ravinement during shoreline translation, the development and preservation of two distinct shorelines at − 100 m and − 60 m are evident and attributed to century to millennial scale periods of stillstand. During these periods shoreline equilibrium forms developed, characterised by early diagenesis of beachrock and aeolianite. Between these features the shelf is dominated by erosional surfaces reflecting ravinement during periods of slowly rising sea-level. Where shorelines are not preserved, areas of scarping in the ravinement surface, at similar depths to the adjoining shorelines, represent rocky headlands separating the sandy coastal compartments where the depositional shorelines formed. Shoreline preservation by overstepping was facilitated by rapid relative sea-level rise associated with meltwater pulses 1A and 1B, although the features preserved are likely to represent only the cemented cores of the coastal dunes and linear beachrock outcrops formed. The steep antecedent shelf gradient fostered the erosion of significant portions of the shorelines by ravinement, with loose sediment re-organised into a thick post-ravinement drape. The removal of shorelines during ravinement was countered by the rapid rate of sea-level rise and early sub-tropical diagenesis. It is clear that due to the combined effects of subtropical diagenesis, long periods of stillstand and drowning by meltwater pulses, the governing controls on shoreline preservation can be over-ridden by combinations of local (climatic) and global (eustatic) factors.

Use of parametric classification of beach morphodynamic state has been steadily increasing in coastal research, despite identification of several shortcomings of their representativeness as elementary beach descriptors. In this paper, we analyse the parametric classification of beach morphodynamic state in a set of six embayed beaches in southwestern Portugal, exposed to diverse settings, from high-energy (dissipative to intermediate) to low-energy (intermediate to reflective) conditions. Applicability of parametric approaches considered within the dimensionless space defined by Ω (dimensionless fall velocity) and RTR (relative tidal range) according to averaged wave, tide and sediment characteristics of beaches, was assessed in association with a probabilistic analysis, implemented through a Bayesian network model, that considered the full range of wave, tide and sediment conditions at each site. Both parametric approaches were compared to field-based beach state classification implemented using a novel hierarchical framework for beach state analysis. The classification obtained within a probabilistic framework provided an innovative approach for analysis of beach state and mobility, extending the insights on beach morphodynamic behaviour obtained from averaged environmental parameters. Reflective to lower-intermediate beach conditions showed better agreement with parametric approaches, while poor beach state differentiation was achieved for intermediate beach types. Limitations in the application of beach classification models result from (i) an inadequacy of existing beach state types in differentiating beaches, particularly within the intermediate domain and for geologically controlled embayed beaches, and (ii) shortcomings involved in the parametric approaches. The beach state models disregard the major role of geological control in embayed beach morphodynamic behaviour (in modulating beach shape and segmentation, influencing sediment size and availability, causing alongshore variations in the wave field and creating topographically induced nearshore circulations). Existing beach state models are unable to adequately represent the widely variable conditions observed in embayed beaches.

This paper presents an analysis of decadal (mesoscale) geomorphic change on sandy barrier islands in thefetch-limited environment of Chesapeake Bay. Low energy barrier islands exist in two settings: on the fringe of marshes and in open water and this analysis shows the various types of barrier island to be genetically related.Barrier islands that face the dominant wind and wave direction (E or W) retreat via barrier translation, preserving the barrier island volume. Those that exist in re-entrants are dominated by longshore transport processes, are strongly affected by sediment supply and are subject to disintegration.Marsh fringe barrier islands are perched on or draped over the surface of the underlying marsh. They migrate landwards via barrier translation during periodic high water events accompanied by large waves (hurricanes and northeasters). The underlying marsh surface erodes under all water levels and the rate of retreat of the barrier island and underlying marsh may take place at different rates, leading to various configurations from perched barrier islands several metres landward of themarsh edge, to barrier islands that have a sandy shoreface extending into the subtidal zone. The coastal configuration during landward retreat of marsh fringe barrier islands is subject to strong local control exerted by the underyling marsh topography. As erosion ofmarsh promontories occurs and marsh creeks are intersected and bypassed, the configuration is subject to rapid change. Periodic sediment influxes cause spits to develop at re-entrants in themarsh. The spits are initiated as extensions of adjacentmarsh fringe barrier islands, but as the sediment volumeis finite, the initial drift-aligned spits become sediment-starved and begin to develop a series of swash-aligned cells as they strive formorphodynamic equilibrium.The individual cells are stretched until breaches form in the barrier islands, creating inlets with tidal deltas. At this stage the low energy barrier islands closely resemble open ocean barrier islands. Continued reworking leads towidening of the inletswith consequent loss of constriction of tidal flow. The tidal deltas are, thus, no longermaintained and ultimately the island systemdisintegrates through inlet widening and is transformed to subtidal shoals. Barrier islands at various stages in this evolutionary cycle can be observed around the bay. Mid-bay barrier islands are affected by wave processes from both sides. This helps maintain the barrier island form and enables barrier islands to persist as sediment is exchanged between both sides of the island.Rates of barrier island translation are extremely high (up to 30 m/year over a 12 year period). This is attributed to the lowvolume of sand, which facilitates complete rollover in short periods. Accelerated sea level rise is likely to hasten the translation rates ofmarsh fringe barrier islands. The rapid disintegration ofmost spits compared to the persistence of marsh fringe barrier islands points to a reliance on the marsh as a stabilising point. If the marshes are overstepped by rising sea level as appears to be happening, the complete disintegration of the barrier islands is highly likely.

Green, A.; Cooper, J.A.G., and LeVieux, A., 2013. Unusual barrier/inlet behaviour associated with active coastal progradation and river-dominated estuaries. The mesoscale behaviour of unusual barrier inlets on the east coast of South Africa is described. The inlets are associated with river-dominated estuaries and are consequently subject to periodic closure during low river flow. They are also located on a prograding barrier coast. Deflection of the estuary channel of a small river in the direction of longshore transport by 1230 m resulted in its capture by the estuarine channel of a larger river. The larger catchment river was not deflected by coastal progradation but maintained its position by periodic breaching of a channel through the barrier during floods. Flood breaches reseal by landward reworking of ephemeral deltas and may undergo limited migration. A tidal inlet at the northern end of the barrier is maintained by a small tidal prism and has a flood-tidal delta. It exhibits limited late...

The duration of shoreline occupation at a given sea-level, coastal response to sea-level change and the controls on preservation of various shoreline elements can be recognized by detailed examination of submerged shorelines on the continental shelf. Using bathymetric and seismic observations, this article documents the evolution and preservation of an incised valley and lithified barrier complex between −65 m and −50 m mean sea-level on a wave-dominated continental shelf. The barrier complex is preserved as a series of aeolianite or beachrock ridges backed by laterally extensive back-barrier sediments. The ridges include prograded cuspate lagoonal shoreline features similar to those found in contemporary lagoons. The incised valley trends shore-parallel behind the barrier complex and records an early phase of valley filling, followed by a phase of extensive lagoonal sedimentation beyond the margins of the incised bedrock valley. Sea-level stability at the outer barrier position (ca −65 m) enabled accumulation of a substantial coastal barrier that remained intact during a phase of subsequent slow sea-level rise to −58 m when the lagoon formed. These lagoonal sediments are stripped seawards by bay ravinement processes which caused the formation of several prograded marginal cuspate features. An abrupt rise in sea-level to −40 m, correlated with melt-water pulse 1B, enabled the preservation of thick lagoonal sediments at the top of the incised valley fill and preservation on the sea bed of the cemented core of the barriers. This situation is unique to subtropical coastlines where early diagenesis is possible. The overlying sandy sediment from the uncemented upper portion of the barriers is dispersed by ravinement, partly burying the ridges and protecting the underlying sediments. The high degree of barrier or shoreline preservation is attributed to rapid overstepping of the shoreline, early cementation in favourable climatic conditions and the protection of the barrier cores by sand sheet draping.

Wind flow within blowouts is extremely complex as streamline compression, expansion and reversal may occur over and around a single landform. As a result high resolution temporal and spatial measurements are required during a range of incident wind conditions to resolve near surface airflow patterns and turbulent structures. This study examined three-dimensional airflow within a coastal dune trough–bowl blowout using 15 ultrasonic anemometers (UAs) and a high resolution computational fluid dynamics model. Measured total wind speed and vertical wind speed behaved consistently through 5 Beaufort wind scales ranging from ‘fresh breeze’ to ‘strong gale’, increasing relative to incident wind speed, whilst wind direction at each UA did not alter. Due to the agreement of modelled and measured data, ‘hurricane’ (37 m s −1 ) incident winds were also simulated and were consistent with modelled and measured wind direction at lower wind speeds. Modelled wind turbulence data was not compared with measured as only average conditions were simulated. However, the standard deviation of measured wind direction remained constant at each anemometer throughout the range of incident wind speeds, whilst the standard deviation of wind speed and turbulent kinetic energy increased relative to incident wind speed. This paper demonstrates that wind flow behaviour within blowouts throughout this range of wind speeds is governed by topography and is relative to, but does not change structurally with incident wind speed. As a result the extent of streamline compression, expansion, steering and reversal remain constant.

The South African coast contains abundant estuaries and lagoons, most of which originated as river valleys incised during Quaternary sea-level fall and subsequently drowned and/or infilled during rising interglacial sea levels. This chapter discusses these changes and highlights the geomorphological and sedimentological evolution of several southern African estuaries during the Pleistocene to present. The development, infilling and positioning of incised valley systems is mainly controlled by sea-level variation as well as fluvial and marine sediment supply. Most contemporary estuaries in southern Africa show dramatic responses to shorter term sea-level fluctuations and sediment supply during the Holocene. Barring anthropogenic interference, the dynamic behaviour of estuaries, dictated by their transient position and geomorphic character within an incised valley, is considered to fluctuate on centennial to millennial timescales.

Blowouts are common landforms found within coastal dunes. Their dynamics are primarily driven by aeolian transport caused by surface wind stress, though patterns of deflation and deposition within blowouts are poorly understood as near surface wind flow is complex. Three‐dimensional wind flows around blowouts have yet to be properly quantified, especially within zones of separation, re-attachment and acceleration. This has been largely due to inadequate measurement of airflow and a lack of suitable airflow models. With this in mind, we present results from a study that has quantified alongshore and oblique onshore wind flow dynamics over a bowl blowout on the Belmullet Peninsula, Ireland. Using ultrasonic three-dimensional anemometry (measuring at 50 Hz) and three-dimensional computational fluid dynamic (CFD) modelling, we measure and model for the first time in 3D a detailed picture of the heterogeneity of wind flow over this type of terrain. During alongshore wind conditions, wind speeds within the deflation basin were retarded by 50% compared to the foredune zone and flow separation restricted to a small zone in lee of the windward rim. Wind was directed into the deflation basin through a gap in a western erosional wall, termed the blowout throat. In oblique onshore wind, airflow orientated with the blowout throat remained unchanged in direction and slowed by only 30% compared to wind speed on the foredune. In lee of the erosional wall adjacent to the blowout throat, small zones of flow separation occurred close to the erosional wall. In both cases, the highest variation in wind speed and direction occurred in zones of separation and attachment whilst flow increased in steadiness with height over the erosional walls. The results illustrate that wind is manipulated according to localised topography within the bowl blowout itself. Resulting zones of potential sediment transport (erosion and deposition) are spatially complex and alter with wind direction. The presence of a blowout throat has a significant influence on airflow patterns within a deflation basin. Modelled (CFD) and measured anemometer data demonstrated excellent comparisons for wind direction and speed, allowing much greater spatial measurement resolution than physical instrumentation. Simulated turbulence did not correlate well with measured data, highlighting the requirement for high frequency, three-dimensional anemometry in areas of complex flow.

Headlands, rock outcrops and engineering structures impact beach and nearshore dynamics of coastal embayments, inducing boundary effects that constrain the lateral and vertical beach variability. This study analyses morphological change in six embayed beaches with diverse levels of exposure to wave action and various degrees of geological control in the mesotidal coast of southwestern Portugal. The aim is to identify whether geological boundaries constrain the morphological behaviour of embayed beaches and assess whether their effects can be decoupled from datasets of morphological change. Topographic data, obtained over a two-year period on each of the six embayments, were analysed using empirical orthogonal functions (EOF) to decompose temporal and spatial variability in the datasets. First and second mode eigenfunctions were explored using time-variable linear correlation analysis with several nearshore parameters that include hydrodynamic variables, sedimentary and geometric characteristics of each embayment in order to derive forcing–response relationships. Our results demonstrate that natural geological boundaries constrain the morphological behaviour of embayed beaches, producing conspicuous alongshore variability in all embayments. Localised responses induced by lateral and vertical boundary interference with beach and nearshore dynamics include beach rotation, topographically-controlled rip circulation and restrained profile fluctuation. Spatial decoupling in cross- and longshore responses is accompanied by a temporal decoupling in response times, both of which are slower in more constrained embayments (from 1 day in exposed embayments to 1 week or more in the most sheltered ones). Normalised wave power was correlated at the 99% confidence level with the primary mode of morphological variability at most embayments, which represent 67% to 94% of the variance in the datasets. This correlation stresses the importance of combined parameterization of wave and tide forcing in process–response relations between hydrodynamics and morphological change for mesotidal coastal environments. Lateral and vertical geological boundaries exert their effects fundamentally by restraining longshore sediment transport, inducing cellular surf zone circulation and by impacting cross-shore sediment transport. It is postulated that decreasing sediment abundance and substrate depth intensify vertical boundary effects, while higher indentation and wave obliquity enhance the effects of lateral boundaries.

Storm swash terraces are a distinctive and previously unreported component of the cliff-shore platform sedimentary system. They consist of laminated marine sands and gravels with occasional large, rounded clasts and fine muddy laminae. The planar deposits dip gently seaward, are up to 1 m thick at the seaward margin, and thin landwards, forming a wedge. They are laterally continuous over tens of meters in a coast-parallel dimension. They occur in coastal re-entrants at the rear of boulder beaches and shore platforms at elevations between 1 and 9 m above contemporary high-tide level. The terrace sediments represent deposition at the limit of wave run-up during extreme storms; during such events wave energy is largely dissipated by a shore platform and/or boulder beach but sufficient energy remains to carry water and fine sediment to higher levels, where it then accumulates. The deposition and preservation of storm swash terraces depend on a coastal topography that combines partial wave-energy dissipation on a shore platform or boulder beach with available depositional space to landwards. These deposits contain a sedimentary record of past storminess on high-energy coasts that has yet to be exploited.

The literature on incised river valley sedimentology is dominated by studies of sediment-rich systems in which the valley has been filled during and/or shortly after drowning. In contrast, the Holocene evolution of the Kosi Lagoon, South Africa (an incised coastal plain river valley) took place under very low sedimentation rates which have produced a distinctive stratigraphy and contemporary sedimentary environments. The findings are based on a synthesis of the results of studies of seismic stratigraphy, sediment distribution, morphodynamics and geomorphology. Barrier migration was prevented by a high pre-Holocene dune barrier against which Holocene coastal deposits accumulated in an aggradational sequence. Holocene evolution of the back barrier involved: (i) drowning of the incised valley; (ii) wave-induced modification of the back-barrier shoreline leading to segmentation during the highstand; and (iii) marine sedimentation adjacent to the tidal inlet. Segmentation has divided the estuary into a series of geochemically and sedimentologically distinctive basins connected by channels in the estuarine barriers. The seismic stratigraphy of the back barrier essentially lacks a transgressive systems tract, shoreline modification and deposition having been accomplished during the highstand. The lack of historical geomorphological change suggests that the system has achieved morphological equilibrium with ambient energy conditions and low sediment supply. This study presents a classification for estuarine incised valley fills based on the balance between sea-level rise and sedimentation in which Kosi represents a ‘give-up’ estuary where much of the relict incised channel form is drowned and preserved. It exhibits a fundamentally different set of evolutionary processes and stratigraphic sequences to those of the better known incised valley systems in which sedimentation either keeps pace with sea-level (‘keep-up’ estuaries) or occurs after initial drowning (‘catch-up’ estuaries).

Surveys of beach visitor motivation in Ireland, Wales, Turkey and the USA indicate that beach awards play an insignificant role in motivation to visit beaches. However, a number of criteria closely identified with awards, notably cleanliness and water quality, are revealed to be very important. Aesthetic and emotional factors such as scenic setting and general ambience, and practical concerns such as proximity and range of activities available are much more important than beach awards in attracting visitors to beaches. The merits of beach awards are critically reviewed and it is concluded that any benefits that might accrue are in areas other than attracting visitors.

Shoreline and ebb channel evolution between 1834 and 2008 was recorded at three embayed beaches in northwest Ireland with historically stable relative sea level. The beaches are geologically constrained within bedrock valleys and have minimal contemporary sediment input. Their behavior is strongly influenced by tidal-inlet dynamics of adjacent estuaries; major observed changes in shoreline position are linked to fluctuations in inlet ebb-channel orientation. Comparison of the available historical record of geomorphological change with instrumental and proxy climate records suggests that inlet changes may be driven by fluctuations in average storminess: periods of high storminess perturb the inlet system, causing major changes in ebb-channel configuration, after which sediment redistribution returns the system to its former state over a prolonged period (years to decades).

Coastal hazard management involves the assessment of vulnerability in natural and human environments. Indices incorporating a diversity of indicators have therefore been used extensively to provide spatial analyses of the degree of vulnerability. Such indices are typically applied at global and national scales, and they involve varying degrees of simplification and aggregation of information. The degree of simplification that is desirable depends on the management scale, and higher resolution is required at the local compared to the global scale. To investigate the implications of spatial scale in depicting coastal hazard risk, coastal vulnerability indices were developed at national (Northern Ireland), local authority and site levels. Variables were separated into three sub-indices: a coastal characteristics sub-index concerned with the resilience and susceptibility of the coast to erosion, a coastal forcing sub-index to characterize the forcing variables contributing to wave-induced erosion and a socio-...

During 2006–2007, the KwaZulu-Natal coast of South Africa was exposed to several large swell events (Ho > 3 m), near the peak of the lunar nodal cycle, causing shoreline recession. The largest swell (Hs = 8.5 m) struck the coast on the March equinox (18th–20th) and generated a strong storm-return flow. Observations made before, during and after record dramatic coastal erosion (shoreline recession of up to 40 m and substantial property damage). This swell event removed the semi-continuous nearshore bar system and ‘conditioned’ the coast such that lesser subsequent swell events accomplished much greater amounts of coastal erosion than expected (up to 100 m at certain erosion hotspots) because waves reached the coast without significant energy dissipation. Subsequent bar generation rebuilt the inshore bars within six months. The styles of erosion during the March ’07 event and other 2007 swells were markedly different. Lesser swells are focused by headlands and result in megarip development and activation of erosion hotspots. The March ’07 event still-water level was raised (equinoctial spring high tide and a storm surge of 0.33–0.45 m) to a level that rendered most headlands (and erosion hotspots) ineffective and resulted in laterally extensive erosion of soft shorelines. Results record cumulative effects of successive swell events on coastal behaviour that proved to be critical in enabling erosion to proceed at rapid rates after the coast had been initially destabilized. Unlike hurricanes and tsunamis, surges associated with swell events are relatively minor and therefore extensive erosion is linked with high lunar tides. There is circumstantial evidence that swell-induced erosion follows the broad 18.6 yr lunar nodal tidal cycle when the chances of large swells coinciding with high water levels are increased.