Foredune initiation and early development through biophysical interactions.

Coastal dunes result from complex interactions between sand transport, topography and vegetation. However, uncertainty still persists due to limited quantitative analyses, integrating plant distribution and morphologic changes. This study aims to assess the initiation and maintenance of feedback processes by analysing the early development stages of incipient foredunes, combining data on the evolution of the plant cover and communities and dune morphology. Over three years, the monitoring of a newly formed dune (1 ha plot) reveals the progressive plant colonisation and the episodic accumulation of sand around vegetated areas controlled by sediment availability. Distinct colonisation rates were observed, influenced by inherited marine conditions, namely topography and presence of beach wrack. Berm-ridges provided elevations above the critical threshold for plant colonisation and surface roughness, aiding sediment accumulation. Beach wrack above this threshold led to rapid expansion and higher plant concentration. In the initial stages, vegetation cover significantly influenced sediment accumulation patterns, with higher accumulation around areas with high plant cover and low slopes or around areas with sparse vegetation but milder slopes. As the dune system matured and complexity grew, the link between vegetation cover and accumulation became nonlinear. Mid to low coverages (5-30 %) retained most of the observed accumulation, especially when coupled with steep slopes, resulting from positive feedbacks between vegetation, topography and sand transport. As foredune developed, vegetation cover and diversity increased while inherited morphologies grew vertically, explaining the emergence of dune ridge morphological types. Flat surfaces lacking wrack materials experienced a three-year delay in colonisation and sand accumulation, leading to the formation of terrace-type incipient foredunes. These observations underline feedback processes during the early stages of dune formation, with physical feedbacks primarily driving initiation and biophysical feedbacks prevailing in subsequent colonisation stages.

Environmental variables affecting an arid coastal nebkha.

Foredunes in arid coastal dune systems comprise nebkhas, which originate by interactions between vegetation and aeolian sedimentation. While continuous foredunes in temperate climates have been widely studied, knowledge of interactions between biotic and abiotic drivers in foredunes formed by nebkha is still scarce. With the aim of exploring variables affecting arid foredunes, a range of morphological, sedimentological, and vegetation characteristics were measured on a single nebkha formed by a Traganum moquinii plant located in the foredune of Caleta de Famara beach (Lanzarote, Canary Islands). Variables were sampled at 120 plots in a 0.5 × 0.5 m square grid. A two-step process using multiple linear regression (MLR) analyses was developed to characterize 1) the influence that morphological variables and distance from the sea have on plant and sediment patterns on nebkha, and 2) the influence of plants on depositional sediment characteristics. Results indicate close relationships between distance from the sea, plant coverage, and sediment patterns. Empirical results were used to develop a conceptual model that explains the spatial distribution of bio- and geo-morphological characteristics of an arid nebkha foredune.

TEMPORARY REMOVAL: Sand, Sun, Sea and Sex with Strangers, the "five S's". Characterizing "cruising" activity and its environmental impacts on a protected coastal dunefield.

The publisher regrets that this article has been temporarily removed. A replacement will appear as soon as possible in which the reason for the removal of the article will be specified, or the article will be reinstated. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Sea level rise outpaced by vertical dune toe translation on prograding coasts.

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.

Nebkha development and sediment supply.

This study examines the role of sediment supply in controlling the formation and the spatial patterns of nebkha, numbers and sizes, present in foredunes fronting coastal dunefields of the arid northwest African and the Canary Islands coasts. Sediment supply is estimated qualitatively and quantitatively by various measures, and the number and size of nebkhas are obtained on a range of beach-dune systems. In the case of the Canary Islands, LiDAR data and orthophotos with high spatial resolution (0.25 m) are used to measure sediment supply/activity, nebkha numbers and sizes, and vegetation variables, whereas data availability is less on the African coast. Results show that sediment supply exerts a major control on nebkha development such that as sediment supply increases, the number of coastal nebkha decreases, and the size of individual plants/nebkha increases. Once sediment supply is large, nebkha can only form on the immediate backshore if space is available, and a point is reached when the sediment supply is so large that nebkha do not, or cannot form. The data presented here provide two indicators which could be applicable to other dune systems. Firstly, by estimating the number of nebkha and the vegetation cover, the degree of aeolian sedimentary activity or sediment supply might be estimated. Secondly, the type of aeolian landform present provides a qualitative indication of sediment supply and aeolian activity.

Rapid shoreline erosion and dunefield Change, Salmon Hole, South Australia.

Since the 1940's, rapid shoreline and dunefield changes have been ongoing at Salmon Hole, an embayment situated near Beachport in the SE of South Australia. Storm induced erosion has nearly removed the entire dunefield and created a lagoon confined by a calcarenite reef. This study examines the progress, dynamics and causes of the erosion to determine why it has been so severe, using historical aerial imagery, wave reanalyses data, Digital Surface Models (DSM's) from drone surveys and through the volumetric analysis of topographic profiles. The results gained through analysing shoreline change at Salmon Hole are then discussed based on Phillips (2009) change assessment system. This study found that a combination of the formation of the 'lagoon' between the mainland/dune system and the offshore reef and the resultant breakthrough of the tombolo that have led to the acceleration of the erosion processes seen at Salmon Hole. The formation of the lagoon initiated a divergent evolution that continues in the form of a significant geologically controlled longshore current and terminal rip that enhances removal of sediment during and following erosion of the dunes. It appears that each time the lagoon widened post storm erosion it resulted in an increase in the efficiency of the current, resulting in a positively reinforcing feedback loop furthering the erosion level during each successive storm. The profiles taken from the drone survey DEM's reveal the processes involved in scarping and demonstrate how dune systems with zero sediment supply will respond to future climate and wave conditions. Coastal systems experiencing a deficit in sediment supply will not be able to translate landwards/upwards resulting in their removal. If the current rate of erosion at Salmon Hole is maintained into the future, the entire system is likely to be fully eroded within the next 30 years.

Decadal monitoring of Traganum moquinii's role on foredune morphology of an human impacted arid dunefield.

Foredunes in arid zones have been little studied, being significantly different than tropical and temperate foredunes. In the case of the foredune of the arid Canary Islands' dune systems, Traganum moquinii is the predominant plant species, forms nebkhas and nebkhas fields, and acts as a structuring element in the dune field. In this work, the eco-anthropogenic evolution of the foredune surface, and the morphology and distribution of Traganum moquinii species in the Maspalomas dunefield (Gran Canaria, Canary Islands) are analysed, to understand the role that this plant species plays on the foredune's geomorphology and on the biogeomorphological processes altered by human actions. Eight variables were measured in 10 plots at five different times, from the 1960's to the present, through historical aerial photographs and orthophotos, integrated in a GIS. Significant decadal changes in the number and distribution/morphology of Traganum moquinii plants and also in the morphology of the foredune are observed, although not in a spatially homogeneous manner, as three different foredune behaviors are observed. The number of nebkhas/number of T. moquinii plants, has decreased between 1961 and 2012. The largest changes occurred in the north and south of the study area, and the lowest numbers of nebkhas occur where tourist activities and services are intense. In addition, the distance between Traganum moquinii individuals and variables measured in the foredune front (e.g. the diameter of the individuals) have significant relationships. Also, the greater the distance between plant individuals in the foredune front, the greater is the distance of T. moquinii individual plants in the rest of the plot. The alongshore variations in foredune development are due to natural processes (e.g. natural decline or growth of plants), and human impacts (e.g. carpark and kiosk construction, heavy tourist use). This research could be useful for the management of foredunes in arid regions.

Climate as a control on foredune mode in Southern Australia.

Foredunes are formed by aeolian sand deposition in vegetation on the backshore of beaches. In this paper, the foredune mode (nebkha, discontinuous foredune, and continuous foredune), and transgressive dunefield development is studied along the Great Australian Bight (GAB), 2668 km of coastline. Orthophotos are used to classify the foredune mode, coastal landforms and the vegetation, through geographic information systems (GIS), with fieldwork support. The results show that the foredune mode is strongly controlled by rainfall and temperature with respect to latitude, and to drift potential with respect to longitude across the GAB. Between 200 and 300 mm annual rainfall, nebkha predominate. When the annual rainfall is between 300 and 400, at latitude 32°, a clear pattern is not observed in foredune mode and this is identified as a transition zone. Discontinuous foredunes and continuous foredunes are strongly represented in regions experiencing above 400 mm annual rainfall. The main contribution of this study is the identification of foredune modes which are not only related to a climatic gradient and latitude, but also related to variations in longitude, vegetation cover and diversity, and dune mobility indices. Finally, there are other environmental relationships between the wind and longitude, where the geomorphology of the bay could be playing an important role.

Biogeomorphological processes in an arid transgressive dunefield as indicators of human impact by urbanization.

Urban and tourist developments can have long-lasting impacts on coastal environments and fundamentally alter the evolution of coastal dune systems. This is the case of the Maspalomas dunefield (Gran Canaria, Canary Islands), hosting one of the largest tourist resorts in Spain. The resort was built on top of a sedimentary terrace at 25 m above sea level (El Inglés) in the 1960s, and has subsequently affected local winds and therefore aeolian sediment transport patterns. Buildings on the terrace deflect the winds to the south of the dunefield, where the rate of sediment transport accelerated. A shadow zone appeared to the lee side of the resort with a consequent decrease in wind speed and aeolian sediment transport and an increase in vegetation cover. In this paper, first we characterize the environmental changes around El Inglés terrace in recent decades, and describe the changes in the shadow zone through an analysis of the evolution of sedimentary volumes and vegetation characteristics (density, spatial patterns, and plants communities). A series of historical aerial photographs, recent orthophotos and digital elevation models obtained by digital photogrammetry and LiDAR, as well as fieldwork were used to characterize plant communities and spatial-temporal changes in erosive landforms. Results show changes in the pattern and migration rates of dunes located at the southern edge of the urbanization, as well as the formation of blowouts and large deflation areas, where the vegetation increases in density and number of plant communities. We discuss eco-anthropogenic factors that have produced these environmental changes.