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Foredunes constitute a fundamental part of the coastal environment, acting as a buffer against storm erosion and natural coastal defence. Foredune size and volume play a pivotal role in determining coastal vulnerability to marine hazards, and the governing processes driving variations in foredune morphology, particularly over regional, or larger spatial scales, are still relatively poorly understood. This paper presents a regional‐scale investigation into foredune morphology along the New South Wales (NSW) coast (SE Australia), comprising not only a state‐wide inventory of foredune morphology for use in management/hazard assessment, but also testing long‐standing hypotheses and conceptual models of the physical processes that are driving, or influencing, foredune size. We applied a remote sensing protocol to 47 foredune environments, covering the length of the NSW coastline, comparing morphology (including dune height, width, shape, and volume) of established and incipient foredunes both along, and between, sandy embayments. Results, at regional spatial scales, show that the largest foredunes (volumes up to 850 m3 m−1) occur along the central coast as large, steep landforms; intermediate‐sized dunes (550–650 m3 m−1) were found on both the Mid‐north and Far North coast, and the smallest foredunes (334–380 m3 m−1) occur on the south coast as wider dunes with steep stoss slopes. Surfzone–beach state was found to be the most significant factor influencing foredune size and volume. The more energetic and more dissipative/high‐energy intermediate surfzone–beach states were correlated with larger foredunes (i.e. greater dune volume, width and crest elevation), whereas the lower‐energy surfzone–beach states generally had smaller dunes. Changes in vegetation cover, shoreline orientation and associated onshore (and alongshore) wind systems were also demonstrated to be important factors in determining foredune morphology. The largest foredunes in NSW generally occur to the north of embayments, with dune size decreasing southward with decreasing exposure to wind/wave energy. [ABSTRACT FROM AUTHOR]

Barchan dunes do not often coexist with grasslands. However, in Gonghe Basin, north‐eastern part in Qinghai‐Tibetan Plateau (QTP), China, many barchan dunes are distributed on the grassland at high altitude. Identifying celerity and morphodynamics of barchan dunes and exploring the interaction between barchans and grassland landscape can help us better understand aeolian system sand mitigate damages. In this work, we tracked dune celerity and observed three‐dimensional changes of symmetrical and asymmetrical barchan dunes in Ertala based on high‐resolution UAV‐SfM reconstruction in short‐term monitoring and discussed the factors influencing dune celerity and deformation at high altitude. The results revealed that the barchan dunes are highly mobile with an average celerity of 0.85 m/M for the whole study area. Based on observations of dune morphology and dynamics, we found the following: (1) The dune deformation degree in a short time is not large but is widespread, especially in the elongated arm of asymmetric dune. The deformation of symmetric dune is symmetrical, whereas that of dune with extended horn is asymmetrical; (2) the sand supply, vegetation and airflow at low air density all influence the celerity and deformation degree in the development of barchan dunes; (3) the asymmetric airflow and sediment supply are important cause of dune asymmetry. The above results help us understand the deformation of barchan dune from the three‐dimensional, especially the difference reflected by the symmetry of barchan dune at high altitude. [ABSTRACT FROM AUTHOR]

The impact of waves, storm surge, and aeolian transport associated with Post-tropical Storm Fiona (offshore significant wave height ∽ 8 m, storm surge up to 2 m) on the sandy beaches and foredunes of the north shore of Prince Edward Island National Park (PEINP), Canada, are assessed. Management policies and practices, as they apply to sandy beach systems within PEINP, are reviewed in the context of the shoreline changes attributed to Fiona. The effectiveness of these policies and practices are evaluated to inform the potential performance of beach-foredune systems as natural protection measures that mitigate the impacts of large-magnitude storms and relative sea-level rise (RSLR) on shoreline change. The analyses utilise survey data, ground photography, and unoccupied aerial vehicle (UAV) imagery collected before (October 2021 to July 2022) and after (October 2022 and May 2023) Fiona. In general, the largest dunes were characterised by erosion of the stoss slope, with landward retreat of the dune toe by < 6 m and minimal impact on crest height and position. Small foredunes (< 5 m in height) generally showed significantly greater erosion in terms of dune profiles, with dune breaching occurring at some locations. Foredunes perched on bedrock and till, which were typically smallest in size, were subject to complete erosion, thereby exposing the hard underlying surface. Overall, the impact of Fiona on sandy beach systems in PEINP was relatively modest in many locations, reflecting the success of existing management policies and practices that protect and maintain the integrity of foredunes by minimizing human impacts and avoiding ‘coastal squeeze’. [ABSTRACT FROM AUTHOR]

This study develops an integrative and thorough assessment of storm-related coastal risk in Mexico. Through Bayesian networks (BN), we explore an approach that blends an ecological understanding of coastal dynamics and concepts of coastal risk based on hazards, exposure, and vulnerability. We used two approaches. First, we calculate a coastal risk index based on coastal hazards (storms, flooding potential and shoreline change rate), exposure (occurrence and size of human settlements), and vulnerability (extension of natural ecosystems which provide storm protection: mangroves and coastal dunes). Then, we used a Bayesian network approach to perform a causal-driven and spatially explicit probabilistic assessment of storm-induced risks. This study shows that the population living on the coast has grown drastically over the last decades, resulting in more significant exposure of people and assets to risk. We showed the importance of natural ecosystems in reducing coastal risk and that the highest coastal risk was associated with (i) the reduced cover (or absence) of mangroves and coastal dunes, (ii) the conservation status of vegetation, and (iii) higher population density. Overall, the study shows that utilizing a Bayesian network is an effective tool for exploring coastal risk scenarios. [ABSTRACT FROM AUTHOR]

In recent decades, there have been significant problems worldwide related to global warming and the intensification of extreme temperature and rainfall events. This research evaluated daily temperature and rainfall indices trends to identify whether warming signals have occurred in South Australia over the past fifty years. Extreme cold, hot, and rainfall events were calculated using climatic data from 37 weather stations. A Mann–Kendall test was used for trend analysis with Sen's estimator. As a result, we determined that for the 1970–2021 period, the maximum and minimum temperatures increased by 1.1 and 0.7 °C, respectively, while precipitation had a negative trend (−52.2 mm per period). Since statistical significance was found in analysing extreme cold and hot events, we find that warming signals have several impacts on South Australia. In the case of rainfall events, we identified a heterogeneous pattern characterised by a reduction in the annual amount and an increase in extreme rainfall events. The findings enable us to conclude that the area shows signs of global warming that could affect the intensity and magnitude of droughts. This information is essential for continuing with current management strategies to adapt and mitigate the effects of global warming in South Australia. [ABSTRACT FROM AUTHOR]

This study presents an analysis of wind flow and sediment transport from the beach up a 50 m high, long (130 m), steep (mean slope 26°) climbing dune and across a 1.5 m high max, 85 m long and 17.5 m wide clifftop dune 30 km south of Dakhla in Morocco, NW Africa, during highly oblique incident wind conditions. Multiple 2D sonic and cup/vane anemometers and sand traps were utilized for measurements. Flow steering was significant on the upper climbing dune. Flow deceleration occurred near the dune toe, and topographic forcing of flow was considerable on the upper slopes of the climbing dune. Near‐surface flow steadiness (CVU1, CVU0.25) on the climbing dune straight slope segment was low and constant. The distance upslope over which the airflow reached a speed comparable to that on the beach increases as the incident wind speed increases. The greatest flow acceleration and speed‐up was observed at the cliff edge reaching 250% at 1 m height and 220% at 0.25 m height for the lowest incident wind speed class (4–5 m/s). The sand transport rate declined from the beach to the climbing dune toe and lower slope, but at the uppermost section of the climbing dune was 4 times higher than in the beach for the 7–8 m/s incident wind speed. Sand in aeolian transport was generally finer than surface sand, with the mean grain size increasing up the slope. A comparison of the sand transport data collected with sand transport models, and the effects of slope on Aeolian transport are also examined. Plain Language Summary: The wind flow and sediment transport across a beach, up a 50 m high, long, and steep climbing dune and across a 1.5 m high clifftop dune was measured at a site 30 km south of Dakhla in Morocco, NW Africa. Multiple 2D sonic and cup/vane anemometers and sand traps were utilized for measurements. Flow steering and speed‐up was significant on the upper climbing dune, and the greatest flow acceleration and speed‐up was observed at the cliff edge reaching 250% at 1 m height at the lowest incident wind speed measured on the beach. Sand transport rates declined from the beach to the climbing dune toe and lower slope, but rapidly increased up the climbing dune and transport at the uppermost section of the climbing dune was 4 times higher than in the beach. Wind flow near the cliff edge was characterized by a reversing vortice, and then gradually increased downwind to the highest point on the clifftop dune. A comparison of the sand transport data collected with sand transport models and the effects of slope on Aeolian transport are also examined. Key Points: Wind flow and sand transport measured across a beach‐climbing dune‐clifftop dune system 30 km south of Dakhla in Morocco, NW AfricaFlow steering and topographic acceleration were significant on the climbing dune, and the speedup reached 250% at the cliff top edgeSand transport was 4 times higher at the uppermost section of the climbing dune compared to the rate in the beach [ABSTRACT FROM AUTHOR]

Fire has been suggested to be an initiation mechanism of landscape instability and coastal dune transgression, but modern evidence showing a shift to a transgressive dune phase is lacking. Following the largest wildfire in historical records on Kangaroo Island, South Australia, bimonthly uncrewed aerial vehicle (UAV) surveys were conducted on three coastal dune sites to study their post‐fire responses. The three sites studied here represent the landscape diversity of the temperate dunes of Kangaroo Island with both active coastal and inland relict stabilised dune fields studied. UAV surveys were used to reconstruct landscapes with structure from motion (SfM) photogrammetry and compared over time to illustrate significant changes in the landscape. The geomorphic and vegetation changes are compared in net and intra‐survey comparisons to illustrate the post‐fire dunefield response and trends towards stabilisation. Because of a lack of reliable baseline pre‐fire data, satellite geomedians are used to compute spectral indices to show the trajectory of ground cover in the study sites in the years preceding and following the fire. Satellite indices are used to separate 3D changes according to ground cover types and show their differing post‐fire responses. Local and regional wind, temperature and rainfall records are presented to provide weather patterns of the years preceding and following the fire, illustrating the wet and mild post‐fire weather. The overall results indicate no significant landscape instability across the studied sites and that the ground cover of vegetation is nearing pre‐fire baselines, showing that a severe fire has not caused a transgressive dunefield to develop. [ABSTRACT FROM AUTHOR]

An investigation of wind flow and sand transport over a low to high density Ammophila dominated foredune on the Łeba barrier, Poland, utilizing multiple anemometers and sand traps is presented. The study provides the first high resolution data on modified saltation and suspended sand transport over a foredune under conditions of both canopy and skimming flow. Topographic acceleration of flow and topographic steering over the foredune were observed during oblique incident above threshold flow conditions. The concentration of sand in aeolian transport decreases with height to a minimum that is reached at different elevations above the ground, depending on Ammophila grass density. Of the three Ammophila (marram) grass densities investigated, nearly half (46%) of the total sand‐transport rate occurred above the lower density Ammophila grass, whereas up to 70% of the total transport occurred above the higher density marram grass. This likely results from both elastic collisions of sand grains with grass leaves over the Ammophila canopy and the different positions of the canopy rebounding surface, which is sensitive to even slight changes in wind speed. In addition, as plant density increases, there is less flow penetration into the canopy, vegetative forcing (similar to topographic forcing) of vertical flow is greater, and sand in both modified saltation and suspension is forced higher above the canopy in skimming flow. The maximum sand transport above the vegetation canopy increased in elevation from 32 to 48 to 53 cm as the vegetation density increased from low to moderate to high, respectively. The study also demonstrates that in skimming flow, relatively more sand is transported at higher elevations above a canopy surface than above a bare sand surface. Plain Language Summary: This study examines wind flow and aeolian sediment transport across a low to moderate to well‐vegetated foredune in Poland during strong oblique onshore wind conditions. The study provides the first high resolution data on modified saltation (sand grains bouncing off plant leaves) and suspended sand transport over a foredune under conditions of both canopy and skimming flow. High resolution sand traps were utilized to trap sand. The concentration of sand in aeolian transport decreases with height to a minimum that is reached at different elevations above the ground, depending on Ammophila grass density. A significantly higher percentage of sand is transported in skimming flow above the higher density plants (70%) compared to the lower density plants (46%). As plant density increases, there is less flow penetration into the plants, flow is increasingly forced above the plant canopy, and sand is therefore transported across the canopy in greater amounts and at higher elevations. The study also demonstrates that in skimming flow, relatively more sand is transported at higher elevations above a canopy surface than above a bare sand surface. Key Points: Oblique onshore gale wind may induce both canopy and skimming flow within Ammophila grass covering a foredune crest preventing sand depositionSand transported in both modified saltation and suspension is forced higher above the canopy in skimming flowBetween 46% and 70% of the total sand transport occurred above the lower and higher density Ammophila grass, respectively [ABSTRACT FROM AUTHOR]

The vast majority of coastal dunes in Europe have been stabilized by increasing vegetation cover since the mid‐20th century. However, some systems may experience a remobilization phase, generally occurring locally and further propagating alongshore, the drivers of which remain poorly documented. This study investigates the evolutionary paths (stabilization/destabilization/remobilization) from 1945 to 2020 of a 2 km‐long modern coastal transgressive dunefield located in southwest France with a holistic approach (GPR profiles, aerial photographs and LiDAR topographic data). Results show a landward migration of the transgressive dune by approximately 233 ± 7.5 m, through two distinct stages of rapid landward migration from 10 to 23 m/yr (Stage I: 1949–1959 and Stage III: 2000–2021) separated by an approximately 40‐year stage of slow to no migration, but with substantial windward slope deflation (Stage II). The onset of Stage II is due to the fixation of vegetation by human action between 1950 and 1959. The onset of Stage III is hypothesized to be driven by long and sustained upper backshore/dune toe erosion beginning in 1968 due to a massive shoal welding that locally disturbed the longshore drift. It induced a destabilization of the dune and erosion of the vegetation cover over some decades. A non‐synchronization is therefore observed between the start of the perturbation (1968), then the migration (2000), in line with the hysteresis concept of Tsoar (2005). This study shows that almost all of the sedimentary volume of the 1945 dune has been remobilized by translation to shape the dune system in its current form. The 2.2 km dunefield has grown by approximately 673 000 ± 190 000 m3 during the 2005–2020 period. Among this volume, there is a new foredune that was built from 2005 between the upper beach and the transgressive dune (volume in 2020 of about 394 000 ± 68 000 m3). [ABSTRACT FROM AUTHOR]

The Itapeva dunefield is an active aeolian transgressive dunefield system and an important conservation area (PEVA State Park) in Torres-RS, Brazil. It is cataloged as a geosite and contains geoforms of scientific value for studying the sedimentary environments and paleoclimates of southern Brazil. It stands out for its esthetic, cultural, and recreational value for the development of tourism. However, the use and occupation of its surroundings developed rapidly, and the environmental problems associated with these changes make it desirable to apply the principles of coastal management with geoconservation to the region. This study characterizes the geoforms and analyzes how they have changed over time, in addition to describing some of the challenges for the geoconservation of the area. A geomorphological analysis was performed in this study, focusing on the identification and characterization of aeolian landforms and landform units present in the Itapeva dunefield. Recent satellite imagery, field observations, and photographs were used to conduct this research. The results show that the main aeolian depositional units present in the Itapeva dunefield are reversing transverse dunes, U-shaped sub-parabolic dunes, precipitation ridges, nebkhas, deflation plains, vegetated transgressive sand sheets, and foredunes. Erosional features such as blowouts occur mainly in the foredune area and/or are associated with nebkhas/remnant knobs. Understanding the importance of geoconservation within coastal management can be an important step toward the preservation of the few sectors comprising dunefields in Brazil. To benefit the Park’s sustainable development, it is prudent to promote geodiversity, geoconservation, and geotourism, incorporating these principles into coastal management. [ABSTRACT FROM AUTHOR]

Wind flow and sediment transport across a northern California beach‐foredune system with two adjacent vegetation types are examined for the same incident wind conditions. The invasive Ammophila arenaria was taller (c. 1 m) with denser coverage than the neighbouring Elymus mollis alliance canopy (c. 0.65 m), which consisted of a variety of interspersed native plants. Wind flow was measured with rotating cup and sonic anemometry, while sediment transport was measured using laser particle counters. Wind speed profiles over the two canopies were significantly different because of differing vegetation height, coverage density, and stem stiffness. In both cases, there was a lower zone of semi‐stagnant air (below about 0.3 m) that transitioned upward to a shear zone comprising the upper part of the canopy and immediately above. The shear zone above the Elymus canopy was relatively thin (confined to 0.3–0.5 m above‐ground) whereas the shear zone in the Ammophila canopy was thicker extending from a height of about 0.5h (h is average plant height) to about 1.5h. Vertical profiles of Reynolds shear stress (RSS) and turbulence kinetic energy (TKE) are consistent with the shear layer structure over these two contrasting vegetation canopies. The degree of topographically‐forced and vegetation‐enhanced flow steering was significant, with Ammophila strongly shifting the highly oblique (55°) incident wind to essentially shore‐perpendicular trajectories. In comparison, the shore‐perpendicular steering effect was not as pronounced for the Elymus canopy. Sediment transport intensity on the beach was continuous, but decreased progressively to the dune toe, and then dropped to essentially zero once the vegetation canopy was encountered (on the stoss slope). Overall, the study illustrates the significant differences in wind flow and turbulence conditions that may occur in contrasting plant canopies on foredunes, suggesting that greater attention needs to be placed on vegetation roughness characteristics in models of foredune morphodynamics and sediment transport potential. [ABSTRACT FROM AUTHOR]

The multiple hypotheses which exist to explain the initiation of transgressive aeolian sand sheets and dunefields, are reviewed and discussed. Direct evidence supporting many of these hypotheses is largely lacking. In South Australia, the Younghusband Peninsula coastal barrier extends ~180 km and predominantly comprises transgressive and parabolic dunefields. The 42 Mile Crossing area on the barrier is undergoing significant erosion at variable rates of 0.5 to 5.0 m/yr, and a new transgressive aeolian sand sheet has rapidly developed in ~1 year and is extending landwards at an average rate of 13 m/yr. This research provides unequivocal evidence that large‐scale shoreline and dunefield erosion does lead to the development of a new transgressive aeolian sand sheet (and eventual dunefield) phase thereby demonstrating an initiation mechanism that is likely linked to future sea level rise and climate change. We also show that the initiation process, and, in particular, the subsequent rate of sand sheet transgression occurs at an incredibly rapid rate (+100 m in 8 years). Plain Language Summary: Coastal sand dunes border many of the world's coastlines and are highly adapted to local climate and conditions. How coastal dunes transition from predominantly vegetated and stable systems to wind‐blown sand sheets and dunefields transgressing prior terrain is a research area of pressing relevance due to forecasts of sea level rise and climate change. The factors or triggers that are considered to initiate transgressive aeolian sand sheets and dunefields are reviewed. The formation and evolution of a new transgressive aeolian sand sheet phase triggered by large‐scale shoreline erosion in South Australia is presented. According to the results from historical and satellite images, local shoreline erosion began in the late 1970s and has continued at highly variable rates. We show that once the foredune was removed, the high scarp created by wave erosion of the relict, vegetated transgressive dunefield destabilized and was then eroded by wind processes leading to the rapid development of a transgressive aeolian sand sheet. The initiation and evolution of the sand sheet provides an excellent example of how dunefields might respond to future sea level rise and climate change. [ABSTRACT FROM AUTHOR]

Warner, A.L.; Hesp, P.A.; Keane, R., and Gontz, A.M., 2022. Ground penetrating radar of paleoblowouts and transgressive dunes, Younghusband Peninsula, South Australia. Journal of Coastal Research, 38(5), 885–895. Coconut Creek (Florida), ISSN 0749-0208. Ground penetrating radar (GPR) can be used to elucidate the spatial and temporal relationships of paleoshorelines and dunefield evolution and aid in understanding past landscapes in order to help predict future evolutionary pathways of barrier development. GPR was used on the Younghusband Peninsula coast of Southern Australia at a location known as 42 Mile Crossing. The barrier is on the longest beach in Australia and hosts a Holocene transgressive dunefield system. The site also contains many active, modern, and stabilized blowouts. This study aimed to image buried (paleo) blowouts, analyze the subsurface strata of the area, and attempt to relate these findings to the past transgressive dunefield processes, phases, and architecture. The study was able to characterize the buried blowout's shape, size, and dominant wind direction, and the site's stratigraphic evolution. [ABSTRACT FROM AUTHOR]

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Sea level is rising due to climate change and is expected to influence the development and dynamics of coastal dunes. However, the anticipated changes to coastal dunes have not yet been demonstrated using field data. Here, we provide evidence of dune translation that is characterized by a linear increase of the dune toe elevation on the order of 13–15 mm/year during recent decades along the Dutch coast. This rate of increase is a remarkable 7–8 times greater than the measured sea level rise. The observed vertical dune toe translation coincides with seaward movement of the dune toe (i.e., progradation), which shows similarities to prograding coasts in the Holocene both along the Dutch coast and elsewhere. Thus, we suspect that other locations besides the Dutch coast might also show such large ratios between sea level rise and dune toe elevation increase. This phenomenon might significantly influence the expected impact of sea level rise and climate change adaptation measures. [ABSTRACT FROM AUTHOR]

DaSilva, M.; Miot da Silva, G.; Hesp, P.A.; Bruce, D.; Keane, R., and Moore, C., 2021. Assessing shoreline change using historical aerial and RapidEye satellite imagery (Cape Jaffa, South Australia). Journal of Coastal Research, 37(3), 468–483. Coconut Creek (Florida), ISSN 0749-0208. The coastal zone is a dynamic area which can experience substantial natural change in short time periods, but changes are also associated with human modifications to the coastline. This case study is focused around assessing shoreline change associated with the Cape Jaffa Marina and canal estate in South Australia. The research comprises a GIS based analysis of shoreline change utilising aerial imagery from 1975 to 2005, which provides information of the morphological coastal trends prior to construction in 2008 of the marina/canal estate. In addition, imagery collected by the RapidEye satellite constellation was used to assess shoreline changes in the decade since construction, 2009 to 2019. The shoreline change statistics over the past few decades were calculated using the Digital Shoreline Analysis System extension of ESRI's ArcGIS. The image analysis workflow is based on the objective extraction of shoreline proxies from individual image statistics in a semi-automated process and is used to identify the waterline and edge of vegetation shoreline proxies in a time series analysis. The results provide a case study of a historically progradational sandy coastline experiencing substantial amounts of alongshore sediment transport, the corresponding obstruction from coastal infrastructure, and the resulting morphological changes to the Cape Jaffa shoreline. Shoreline change trends were altered from a predominantly accretional shoreline before the construction of the marina to one oscillating between extremes of erosion and accretion. The results showed significant accretion occurring updrift (Net Shore Movement (NSM) of 106 m) and significant erosion downdrift (NSM of –80 m) of the marina's training walls and entrance. The information derived from Earth observation satellites, such as RapidEye, can provide valuable insights into trend analysis due to their relatively high spatial (5 metre) and temporal resolution (5.5-day revisit). [ABSTRACT FROM AUTHOR]

Knowledge of wind flow over dune scarps and, as scarps fill, their subsequent various slopes, is important for understanding sediment transport pathways from beach to dunes. In this study, flow over scarps (also termed forward-facing steps) is reviewed, and the flow over a vertical scarp (90°) and three slopes of 45°, 24°, and 14°, all 2 m in height, is examined via CFD modelling. The flow over three 90° scarps, with heights of 1 m, 2 m and 4 m, and over a 2-m high vertical (90°) scarp for three oblique incident winds is studied. The extent of wind flow deceleration and separation becomes smaller with decreased slope, with maximum flow separation and reverse vortex development occurring on the vertical scarp. The extent of crest wind flow separation is greatest for the scarp and considerably less for the 45° slope. As scarp height increases, so too does the spatial extent of turbulent wind flow, wind speed, and extent of the flow separation region. As incident wind direction became more oblique over a vertical scarp, less deceleration occurs, and helicoidal vortices replace roller vortices. Our results demonstrate how scarp morphology and wind direction are likely to influence transport pathways. [ABSTRACT FROM AUTHOR]

The controls that affect the degree of spatio-temporal change to foredunes following scarping are reviewed herein. As sea-levels rises and climate changes, dune scarping will become more common. Thus, it is critical to understand what factors contribute to the magnitude of scarping, and what effect this has on dune systems to better manage coastal erosion into the future. Scarping occurs when foredunes are partially eroded by waves, generally during periods of high water level. The controls on the degree and magnitude of scarping examined include water level, foredune vegetation cover and species present, plant root mass, height and volume of the foredune, the original foredune morphology, surfzone–beach type, and compaction of sediment. Water-level height and duration of high water is the most significant control as it determines the elevation at which wave action can erode the dune and, therefore, the extent of scarping and dune volumetric loss. Higher plant density, greater rooting depth, high root mass, and greater compaction aid in reducing the degree of scaping. The presence of large woody debris and wrack may also influence the degree of scarping. The effects scarping has on the morphology of a foredune after the initial erosion event can range from small changes (e.g. minor, small scarps and slight slumping), to moderate changes such as the foredune translating landwards, to large change such as the transition of an entire dune system into a new transgressive dunefield phase. A new model summarising the key controls and their relationship/significance to the magnitude and extent of scarping is presented. [ABSTRACT FROM AUTHOR]

Salt spray mainly originates from the bursting of bubbles in breaking waves and is often considered as one of the dominant factors contributing to vegetation zonation in coastal dunes. In this paper, the literature on salt spray distribution and impact on dune plants are reviewed. Salt spray distribution is greatly affected by wave energy, wind conditions, distance from the coast, topography, vegetation, precipitation, and sand/soil properties. The amount of salt accumulation and trapping efficiency of the vegetative canopy are largely dependent on the plant characteristics such as architecture and leaf morphology. Salt concentrations in sand mainly vary with soil texture. Salt spray has negative impacts on plant growth and can cause water stress, promote tissue necrosis and leaf loss, reduce stomatal conductance, water use efficiency, photosynthesis, affect assimilates, or hormone supply to the growing organs. Damage to plants is increased by sand and wind abrasion and insect damage on leaves. High humidity, dew formation, light drizzle, and fog increase the rates of salt uptake by plant leaves. Plant seedlings and reproductive organs are more significantly affected by salt spray compared with mature plants and plant leaves respectively. Salt spray can also provide nutrition to plants particularly in coastal dunes with lower soil nutrition and salt accumulation rates. Species near the sea often show phenological, morphological, and physiological adaptations to salt spray including dormant times/seasons, low heights, compacted and asymmetrical canopies, unique leaf morphologies and/or orientations, dense hairs, rigid cuticles, and closed stomata. Surfactants produced from human activities can aggravate the damage on plants at average salt spray levels. Methods to trap salt vary considerably in the literature, and results from different studies may not be comparable due to trap type, placement, and landscape position. Greenhouse versus field experiments and sampling may not always be compatible. The relations between salt spray distribution and vegetation zonation will be further complicated under climate change and human activities. [ABSTRACT FROM AUTHOR]

UAVs‐SfM (unmanned aerial vehicles‐structure‐from‐motion) systems can generate high‐resolution three‐dimensional (3D) topographic models of aeolian landforms. To explore the optimization of UAVs‐SfM for use in aeolian landform morphodynamics, this study tested flight parameters for two contrasting aeolian landform areas (free dune and blowout) to assess the 3D reconstruction accuracy of the UAV survey compared with field point measurements using differential RTK‐GPS (real‐time kinematic‐global positioning system). The results reveal the optimum UAVs‐SfM flight set‐up at the free‐dune site was: flying height = 74 m, camera tilt angle = −90°, photograph overlap ratio = 85%/70% (heading/sideways). The horizontal/vertical location error was around 0.028–0.055 m and 0.053–0.069 m, respectively, and a point cloud density of 463/m3 was found to generate a clear texture using these flying parameters. For the < 20 m deep blowout the optimum set‐up with highest accuracy and the lowest cliff texture distortion was: flying height = 74 m combined camera tilt angle = −90° and −60°, photograph overlap ratio = 85%/70% (heading/sideways), and an evenly distributed GCPs (ground control points) density of 42/km2 using these flying parameters. When the depth of the blowouts exceeded 40 m, the optimum flight/survey parameters changed slightly to account for more challenging cliff texture generation: flying height = 80 m (with −90° and −60°combined camera tilt angle), GCPs density = 63/km2 to generate horizontal and vertical location error of 0.024 m and 0.050 m, respectively, and point cloud density of 2597.11/m3. The main external factors that affect the successful 3D reconstruction of aeolian landforms using UAVs‐SfM are the weather conditions, manipulation errors, and instrument system errors. The UAVs‐SfM topographic monitoring results demonstrate that UAVs provide a viable and robust means for aeolian landform morphodynamics monitoring. Importantly, the rapid and high precision 3D reconstruction processes were significantly advanced using the optimal flight parameters reported here. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Coastal dunes are experiencing increases in vegetation cover and reduced mobility levels in many sites around the world. Ecology-led approaches to coastal dune management perceive this change as 'undesirable' because the increase in plant cover leads to a reduction in partially vegetated to bare sand habitats and the species depending on them. This has generated a shift in the management paradigm where the objective is to revert this trend by intervening in the landscape, with actions ranging from re-introducing grazing and mowing, to mechanical removal of dune form and vegetation (dune 'rejuvenation'). In some cases, such as many coastal dunes in Britain, this has also led to low controls on visitor pressure and allowing/promoting human trampling as a 'natural' way to free up areas of bare sand. This commentary critically analyses the main principles (and terminology) underlying this relatively recent shift in management paradigm, and questions assumptions such as 'bare sand is good' and/or 'mobility is natural' in the context of dune evolutionary cycles and responses to abiotic and biotic drivers. We review the limitations and dangers of this approach and argue that it is not sustainable given the current climatic and environmental conditions, and that it can increase the risk of coastal erosion and force dune systems to deviate from adapting and changing to direct/indirect drivers. Finally, we present the benefits of a management approach that focuses on minimizing human impacts so that natural processes continue to occur. [ABSTRACT FROM AUTHOR]

A number of studies have measured and numerically modelled near surface wind velocity over a range of aeolian landforms and made suppositions about topographic change and landform evolution. However, the precise measurement and correlation of flow dynamics and resulting topographic change have not yet been fully realized. Here, using repeated high‐resolution terrestrial laser scanning and numerical flow modelling within a bowl blowout, we statistically analyse the relationship between wind speed, vertical wind velocity, turbulent kinetic energy and topographic change over a 33‐day period. Topographic results showed that erosion and deposition occurred in distinct regions within the blowout. Deposition occurred in the upwind third of the deflation basin, where wind flow became separated and velocity and turbulent kinetic energy decreased, and erosion occurred in the downwind third of the deflation basin, where wind flow reattached and aligned with incident wind direction. Statistical analysis of wind flow and topographic change indicated that wind speed had a strong correlation with overall topographic change and that vertical wind velocity (including both positive and negative) displayed a strong correlation with negative topographic change (erosion). Only weak or very weak correlations exist for wind flow parameters and positive topographic change (accretion). This study demonstrates that wind flow modelling using average incident wind conditions can be utilized successfully to identify regions of overall change and erosion for a complex aeolian landform, but not to identify and predict regions where solely accretion will occur. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The nature of wind flow over a small, 0.6 m high foredune scarp is investigated on the Sir Richard Peninsula, South Australia during a variety of incident wind directions and speeds. The study provides additional supporting evidence that the presence of the scarp and the dune exerts a strong influence on a landwards trending reduction in wind velocity and an increase in turbulence, with the greatest area of turbulence occurring near and at the foredune scarp base. For an incident oblique wind, an alongshore helicoidal flow is formed within a separation region along the scarp basal region. In this region, the coefficient of variation (CV) of wind speed is high and displays significant fluctuations. The flow at the scarp crest is compressed, streamlined and accelerated, turbulence is suppressed, and local jets may occur depending on the incident wind approach angle. Jets are more likely where the incident flow is perpendicular or nearly so. A flow separation region does not develop downwind of the scarp crest where the morphology of the foredune stoss slope downwind of the scarp is more convex (as in this case) rather than relatively flat, and possibly due to the presence of vegetation at the scarp crest. A tentative model of the flow regions developed across a backshore–scarp–foredune region during oblique incident flow is provided. © 2018 John Wiley & Sons, Ltd. The dynamics of wind flow over a small, 0.6 m high foredune scarp is investigated. For an incident oblique wind, an alongshore helicoidal flow is formed within a separation region along the scarp basal region. The flow at the scarp crest is compressed, streamlined and accelerated, turbulence is suppressed, and local jets may occur. [ABSTRACT FROM AUTHOR]

Studies have shown that the impact of climate change, human and animal actions on coastal vegetation can turn stabilized dunes into active mobile dunes and vice versa. Yet, the driving factors that trigger vegetation changes in coastal dunes are still not fully understood. In the transgressive dunefields of the Younghusband Peninsula (south‐east coast of South Australia) historical aerial photographs show an increase in vegetation cover over the last ~70 years. This study attempts to identify the causes of the changes in vegetation cover (1949 to 2017) observed in a typical section of the coastal dune systems of the Peninsula. Vegetation cover was first estimated for various years using the available historical aerial photography (long‐term changes – 1949 to 2017) and recent satellite imagery (short‐term annual changes – 2010 to 2017) for the area, and then results were discussed against the observed changes in climatic variables and rabbit density, factors that could have played a role in this transformation. Results of long‐term changes show that the vegetation cover has increased significantly from 1949 to 2017, from less than 7% vegetation cover to almost 40%, increasing dune stabilization and forming parabolic dune systems. Periods with the largest growth in vegetation cover (1952‐1956 and 2009‐2013) coincide with a significant decline in rabbit numbers. Rabbit density was found to be the primary factor linked to the rapid vegetation growth and stabilization of the dunefield, for both decadal long‐term (last 68 years) and annual short‐term changes (last 8 years). Other factors such as changes in rainfall, aeolian sediment transport, land use practices, and the introduction of invasive plants have apparently played a limited to negligible role in this stabilization process. © 2018 John Wiley & Sons, Ltd. Historical aerial images show that vegetation cover has increased significantly in one of Australia's largest dune systems, the Younghusband Peninsula dunefield (SA). In the last seven decades, vegetation cover has changed from less than 7% to almost 40% (1949‐2017), increasing dune stabilization and forming parabolic dunes. The reduction of grazing by exotic rabbits was found to be the primary factor linked to the rapid modification of the vegetation cover and indirectly the geomorphology of the dunefield. [ABSTRACT FROM AUTHOR]

Cliff-top dunes are a locally important geomorphic features of sedimentary coasts. They are traditionally interpreted as being sourced by (or with) sand derived from the beach below the cliff. This paper presents the results of a stratigraphic and geochronological study of Carlo Sand Blow, a coastal blowout that has developed on top of a high sandy cliff in the Cooloola Sand Mass, south-east Queensland. We use a combination of sedimentological, pedological and geophysical techniques along with optically stimulated luminescence dating to determine the depositional history and evolution of the blowout. We demonstrate that the blowout is dominantly nourished by sand eroded from its floor rather than the adjacent beach. The original dune surface dates to the first half of the last glacial period (c. 40–70 ka) and this dune was deflated in the late-Holocene. Dune activity is directly associated with cliff undercutting because of coastal retreat in the late-Holocene, but coastal erosion on its own is not capable of maintaining aeolian activity. Blowout activity occurred between 2.6 and 2.3 ka and again at 0.3 ka with aeolian sand burying palaeosols. Both soil surfaces contained charcoal and tree stumps in growth position and our study suggests that fire is the immediate trigger for blowout reactivation. It is likely that these fires were anthropogenic in origin, because the site is somewhat protected from natural fire and the ages coincide with intensification of human use of coastal sites in the area. [ABSTRACT FROM AUTHOR]

Abstract: Geomorphological changes in recent decades in an arid transgressive coastal dune system (Maspalomas, Gran Canaria, Canary Islands) are analyzed. The methodology used is based on the generation of two geomorphological maps (1961 and 2003) by interpretation of digital orthophotos. The overlay of both maps in a geographic information system (GIS) enabled the spatial and surface changes of the landforms to be determined, and the processes that generated these changes. Twelve cultural and geomorphological processes were identified from highest to lowest importance, namely: anthropization by urban occupation (114 ha changed), stabilization (92.5 ha), barchanization (37 ha), salinization/halophytication (15 ha), anthropization (12.4 ha), deflation (11.8 ha), dune loss/beach gain (11.3 ha), dune formation (9.6 ha), progradation (8 ha), retrogradation (7.7 ha), destabilization (2.7 ha) and flooding (0.7 ha). Geomorphological changes are associated with a combination of five main factors, three of anthropogenic origin and two natural ones. The natural factors are: (1) the arid climate, which favors changes occurring at high speed; (2) the existence of a progressive sedimentary deficit. Anthropogenic factors are: (3) construction of tourist urbanizations, infrastructures and facilities; (4) installation of equipment or infrastructure on the beaches; (5) the activities carried out by users. These human factors have altered the aeolian dynamics and reduced the area occupied by vegetation in some areas, causing changes in aeolian sedimentary processes. The geomorphological processes identified can be used as indicators of environmental change, allowing us to synthesize the changes in landforms detected, and group all combinations derived from the analysis by GIS and analyze them spatially. Thus, the environmental changes in the transgressive coastal dune systems could be interpreted more effectively. Copyright © 2018 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The form, height and volume of coastal foredunes reflects the long‐term interaction of a suite of nearshore and aeolian processes that control the amount of sand delivered to the foredune from the beach versus the amount removed or carried inland. In this paper, the morphological evolution of more than six decades is used to inform the development of a simple computer model that simulates foredune growth. The suggestion by others that increased steepness of the seaward slope will retard sediment supply from the beach to the foredune due to development of a flow stagnation zone in front of the foredune, hence limiting foredune growth, was examined. Our long‐term data demonstrate that sediment can be transferred from the beach to the foredune, even with a steep foredune stoss slope, primarily because much of the sediment transfer takes place under oblique rather than onshore winds. During such conditions, the apparent aspect ratio of the dune to the oncoming flow is less steep and conditions are not as favourable for the formation of a stagnation zone. The model shows that the rate of growth in foredune height varies as a function of sediment input from the beach and erosion due to storm events, as expected, but it also demonstrates that the rate of growth in foredune height per unit volume increase will decrease over time, which gives the perception of an equilibrium height having been reached asymptotically. As the foredune grows in size, an increasing volume of sediment is needed to yield a unit increase in height, therefore the apparent growth rate appears to slow. Copyright © 2018 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Jet flows, which are localized flows exhibiting a high speed maxima, are relatively common in nature, and in many devices. They have only been occasionally observed on dunes, and their dynamics are poorly known. This paper examines computational fluid dynamic (CFD) two-dimensional (2D) modelling of jet flow over a foredune topography. Flow was simulated in 10° increments from onshore (0°) to highly oblique alongshore (70°) incident wind approach angles. CFD modelling reveals that the formation of a jet is not dependent on a critical wind speed, and an increase in incident wind velocity does not affect the magnitude of jet flow. A jet is first formed at ~1.0 m seawards of the foredune crest on the Prince Edward Island foredune morphology example examined here. A jet is not developed when the incident wind is from an oblique approach angle greater than ~50° because there is significantly less flow acceleration across a much lower slope at this incident angle. The presence of a scarp does influence the structure of the crest jet, in that the jet is more pronounced where a scarp is present. Surface roughness affects the magnitude of jet expansion and jets are better developed on bare surfaces compared to vegetated ones. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The results from three years of surveying and monitoring a dynamic foredune and dunefield restoration effort on Vancouver Island, Canada is presented. Complete removal of foredune vegetation occurred in three phases spaced a year apart in an effort to control invasive Ammophila spp. The collection of airborne LiDAR, orthophotographs, and bi-monthly topographic surveys provided a means to quantify and examine sediment budgets and geomorphic responses. Three survey swaths, corresponding with each phase of vegetation removal, were established to provide detailed topographic coverage over the impacted beach, foredune, and dunefield landscape units. The swath corresponding with the first phase of removal recorded a positive sediment budget of 1·3 m3 m−2 after three years. A control swath, with data collected for a year prior and two years following removal, exhibited a distinct pulse of sediment delivery into the dunefield unit with a maximum gain of 0·03 m3 m−2 pre-removal compared to 0·11 m3 m−2 post-removal. Vegetation analysis zones, associated with each of the three swaths, demonstrate a range of vegetation responses due to variation in the vegetation removal and subsequent re-invasion or removal methods employed. The first site to be cleared of vegetation, received ongoing invasive re-growth control, and three years following removal vegetation cover dropped from 57% in 2009 to 13% in 2012 (−44%). An adjacent site was cleared of vegetation two years later (only one year of recovery) but experienced rapid Ammophila re-invasion and percent cover changed from 61% in 2009 to 26% in 2012 (−35%). The data presented provides insights for improving the application of sediment budget monitoring in dynamic restorations and discusses the potential for detailed spatial-temporal survey data to improve our understanding of meso-scale landscape morphodynamics following foredune disturbance. Overall, the vegetation removal treatments reduced the extent of invasive grass and increased dunefield mobility and dynamic activity. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hesp, Patrick A. and Smyth, T.A.G., 2016. Surfzone-Beach-Dune interactions: Review; and flow and sediment transport across the intertidal beach and backshore. 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.8-12. Coconut Creek (Florida), ISSN 0749-0208. The original wave-beach-dune model (Hesp, 1982) stated that in the medium to long term, modal dissipative beaches display maximum onshore wave driven sediment transport, maximum aeolian transport off beaches, the largest foredune heights and volumes, and the largest Holocene dunefields. Modal reflective beaches display the opposite, while modal intermediate beaches display a trend in these from relatively high to relatively low sediment transport, foredune volumes, and Holocene barrier volumes with a trend from dissipative to reflective. New Computational Fluid Dynamic (CFD) modelling of flow and calculation of sediment transport over three modal beach types presented here shows that the original conceptual ideas and field data regarding aeolian sediment transport are correct. Dissipative beaches show the greatest long term potential for sediment delivery to the backshore whilst reflective beaches display the least, with a trend from relatively high to low in the intermediate beach state range. [ABSTRACT FROM AUTHOR]

Hesp, Patrick A.; Smyth, Thomas A.G.; Walker, Ian J.; Gares, Paul A., and Wasklewisz, Thad, 2016. Flow within a trough blowout at Cape Cod. 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. 288-292. Coconut Creek (Florida), ISSN 0749-0208. The Province Lands dunefield at Cape Cod is characterised by large parabolic dunes on which have developed very significant numbers of active saucer and bowl blowouts. Blowouts occur across the entire dune landscape but many are initiated on the high lee margins of large erosional ridges and bowl blowouts within the larger parabolic dune landscape. Evolution of these blowouts is characterised by multiple stages. The first few evolutionary stages are described. In addition, the aerodynamics and flow structure within a trough blowout and former saucer blowout developed within a high ridge crest is elucidated from 2D sonic anemometer data, smoke bombs and videography. The flow is characterised by decreasing then increasing flow up the blowout centreline, and marked, highly turbulent opposed flow separation immediately inside and around the marginal entrance walls of the blowout. [ABSTRACT FROM AUTHOR]

Smyth, T.A.G. and Hesp, Patrick A., 2016. Numerical Modelling of Turbulent Flow Structures in a Blowout. 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. 328-332. Coconut Creek (Florida), ISSN 0749-0208. Blowouts are erosional landforms often formed on coastal sand dunes by the deflation of sediment by wind flow. Quantitative observations of wind flow within blowouts aided by the deployment of smoke-bombs, have noted that temporal and spatial variations in sediment transport occur with the presence of turbulent flow structures. However because of the discrete nature of anemometry data, the presence of flow structures has been difficult to quantify and our understanding remains largely conceptual. This study presents a detailed investigation of turbulent flow structures within a trough blowout using high resolution, three-dimensional computational fluid dynamic modelling. We show that when incident wind flow was parallel to the blowout axis, only limited flow steering took place but a well-defined near surface jet developed along the deflation basin. Conversely when incident wind flow was oblique to the axis of the blowout wind flow became steered along the axis of the blowout but no near surface jet was produced. During neither incident wind direction were corkscrew or helicoidal vortices produced. Our study concludes that the incident wind flow direction is critical to the effectiveness of a trough blowout as a corridor for wind-blown sediment. While wind from a range of oblique angles may be steered along the axis of blowout, its relative effectiveness of eroding and transporting sediment beyond the deflation basin and erosional walls is much reduced compared to axis parallel wind flows of the same incident wind speed. [ABSTRACT FROM AUTHOR]

Dillenburg, S.; Hesp, P.; Cecílio, R., and Miot da Silva, G., 2016. Wave Energy as a Control on Dune Development on two Regressive Barriers in Southern Brazil. 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. 273-277. Coconut Creek (Florida), ISSN 0749-0208. Two regressive barriers (Cassino and Curumim) were developed during the middle and late Holocene along gentle re-entrants of the Rio Grande do Sul coast, and they have prograded up to 17 km and 5 km, respectively. While Cassino is marked by a surface morphology characterised predominantly by foredune ridges, Curumim displays a surface completely covered by widely spaced ridges, corresponding to phases of transgressive dunefield formation. As wave period and shoreline orientation are very similar for both barriers, and considering that they are subjected to the same deepwater wave climate, the substantial surface morphological differences between the barriers is, at least in part, a direct consequence of variations in wave height at the two sites. In addition, there is a significant difference in potential sand transport and wind power between the two sites. As transgressive dunefields and parabolic dunes can develop as a consequence of foredune destabilization, followed by wind action, it is very possible that at Cassino, during barrier development storm waves were not strong enough to destabilised the foredune system and, in addition, if storm scarping occurred, winds were not competent to destabilise the foredunes, thus providing conditions for the formation predominantly of a foredune ridge plain. Only occasionally, presumably during very strong storms (or multiples thereof), foredune destabilization has resulted in dune transgression. At Curumim, either storm waves and higher wind strengths were more effective in dune destabilization, or foredunes rarely developed allowing the formation of multiple phases of transgressive dunefields during barrier progradation. [ABSTRACT FROM AUTHOR]