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van Puijenbroek, Marinka E. B., Corjan Nolet, Alma V. de Groot, Juha M. Suomalainen, Michel J. P. M. Riksen, Frank Berendse e Juul Limpens. "Exploring the contributions of vegetation and dune size to early dune development using unmanned aerial vehicle (UAV) imaging". Biogeosciences 14, n.º 23 (7 de dezembro de 2017): 5533–49. http://dx.doi.org/10.5194/bg-14-5533-2017.
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Abstract. Dune development along highly dynamic land–sea boundaries is the result of interaction between vegetation and dune size with sedimentation and erosion processes. Disentangling the contribution of vegetation characteristics from that of dune size would improve predictions of nebkha dune development under a changing climate, but has proven difficult due to the scarcity of spatially continuous monitoring data. This study explored the contributions of vegetation and dune size to dune development for locations differing in shelter from the sea. We monitored a natural nebkha dune field of 8 ha, along the coast of the island Texel, the Netherlands, for 1 year using an unmanned aerial vehicle (UAV) with camera. After constructing a digital surface model and orthomosaic we derived for each dune (1) vegetation characteristics (species composition, vegetation density, and maximum vegetation height), (2) dune size (dune volume, area, and maximum height), (3) degree of shelter (proximity to other nebkha dunes and the sheltering by the foredune). Changes in dune volume over summer and winter were related to vegetation, dune size and degree of shelter. We found that a positive change in dune volume (dune growth) was linearly related to initial dune volume over summer but not over winter. Big dunes accumulated more sand than small dunes due to their larger surface area. Exposed dunes increased more in volume (0.81 % per dune per week) than sheltered dunes (0.2 % per dune per week) over summer, while the opposite occurred over winter. Vegetation characteristics did not significantly affect dune growth in summer, but did significantly affect dune growth in winter. Over winter, dunes dominated by Ammophila arenaria, a grass species with high vegetation density throughout the year, increased more in volume than dunes dominated by Elytrigia juncea, a grass species with lower vegetation density (0.43 vs. 0.42 (m3 m−3) week−1). The effect of species was irrespective of dune size or distance to the sea. Our results show that dune growth in summer is mainly determined by dune size, whereas in winter dune growth was determined by vegetation type. In our study area the growth of exposed dunes was likely restricted by storm erosion, whereas growth of sheltered dunes was restricted by sand supply. Our results can be used to improve models predicting coastal dune development.
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Itzkin, Michael, Laura J. Moore, Peter Ruggiero, Sally D. Hacker e Reuben G. Biel. "The relative influence of dune aspect ratio and beach width on dune erosion as a function of storm duration and surge level". Earth Surface Dynamics 9, n.º 5 (13 de setembro de 2021): 1223–37. http://dx.doi.org/10.5194/esurf-9-1223-2021.
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Abstract. Dune height is an important predictor of impact during a storm event given that taller dunes have a lower likelihood of being overtopped than shorter dunes. However, the temporal dominance of the wave collision regime, wherein volume loss (erosion) from the dune occurs through dune retreat without overtopping, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change, to analyze storm-induced dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer and more intense storms when the beach width is controlled for. In managed dune scenarios, where sand fences are used to construct a “fenced” dune seaward of the existing “natural” dune, we find that fenced dunes effectively prevent the natural dune behind them from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We then control for dune morphology to assess volume loss as a function of beach width and confirm that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances while the width of the dune determines how long the dune will last under persistent scarping. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, a trade-off may exist in maintaining wide beaches and dunes in that the protection offered in the short-term must be considered in concert with potentially long-term detrimental effects of limiting overwash, a process which is critical to maintaining island elevation as sea level rises.
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LEE, JAE HWAN, A. O. SOUSA, E. J. R. PARTELI e H. J. HERRMANN. "MODELLING FORMATION AND EVOLUTION OF TRANSVERSE DUNE FIELDS". International Journal of Modern Physics C 16, n.º 12 (dezembro de 2005): 1879–92. http://dx.doi.org/10.1142/s0129183105008400.
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We model formation and evolution of transverse dune fields. In the model, only the cross section of the dune is simulated. The only physical variable of relevance is the dune height, from which the dune width and velocity are determined, as well as phenomenological rules for interaction between two dunes of different heights. We find that dune fields with no sand on the ground between dunes are unstable, i.e., small dunes leave the higher ones behind. We then introduce a saturation length to simulate transverse dunes on a sand bed and show that this leads to stable dune fields with regular spacing and dune heights. Finally, we show that our model can be used to simulate coastal dune fields if a constant sand influx is considered, where the dune height increases with the distance from the beach, reaching a constant value.
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Hovenga, Paige, Peter Ruggiero, Nick Cohn, Sally Hacker, Katya Jay, Laura Moore e Michael Itzkin. "POST-STORM DUNE RECOVERY IN CAPE LOOKOUT NATIONAL SEASHORE, NC". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 40. http://dx.doi.org/10.9753/icce.v36.sediment.40.
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Coastal dunes are often the first and primary form of defense against destructive surge and waves that accompany extreme storm events. Beach grasses are known to affect dune height, width, and stability, contributing to the dune’s ability to protect the hinterland from wave and flooding hazards (Hacker et al. 2012). However, the interaction and feedbacks between dune development and properties of beach grasses (e.g., species, density) is not fully understood. In particular, our knowledge of the ecomorphodynamic processes controlling the recovery of coastal dunes following storms and the long-term ability of dunes to adapt to changes in climate remains inadequate. The objective of this interdisciplinary research is to characterize the temporal and spatial variability of coastal foredune recovery following major storm events and the subsequent impact of this recovery on future vulnerability. The study region consists of three low-lying barrier islands within the Cape Lookout National Seashore (CALO) along the central coast of North Carolina. The 90 km stretch of coast exhibits spatial variability in dominant dune grass species, grass cover density, coast orientation, beach slope, and wave energy. Using physical and ecological field datasets and process-based numerical modeling, post-storm dune recovery is assessed following Hurricane Matthew (2016).
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Almutlaq, Fahad, e Kevin Mulligan. "Using Texture Statistics to Identify and Map Different Dune Types within the Rub’ al Khali". Remote Sensing 15, n.º 19 (22 de setembro de 2023): 4653. http://dx.doi.org/10.3390/rs15194653.
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Understanding the movement, direction, and shape of sand dunes can contribute to reducing their impact on infrastructure and the environment. The Rub’ al Khali desert has a distribution of dune types. This study aims to identify and map the different types of dunes within the Rub’ al Khali using a texture analysis method based on a digital elevation model (DEM). Statistical texture analysis methods (variance, skewness, and kurtosis) show three different textures of sand dune shapes, according to the geography of the dunes, using data contained in global DEMs. The analysis presented in this study focused on the use of DEMs to investigate the varied dune morphology within the Rub’ al Khali. The GMTED2010 and EarthEnv_DEM90 digital elevation models were compared. Spatial variability in dune height, spatial variability in dune texture, and profile graphs were created to examine dune surfaces in cross-section. The results provided six different dune types within the sand sea: giant compound linear dunes, simple linear dunes, simple transverse dunes, compound crescentic dunes (megabarchans), huge star dunes, and many transitional forms that defy classification. The results showed that the compound linear dune and simple linear dune were the dominant dune types, covering 41.61% and 31.7% of the total study area, respectively. The maps of variance, using either 10 × 10 and 30 × 30 focal blocks, produced a fairly sharp distinction in dune texture. It is hoped that future research in aeolian geomorphology will greatly benefit from these results, which could easily be expanded with the use of more sophisticated pattern recognition software, which clearly shows the value of using such an approach.
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Durán, O., V. Schwämmle, P. G. Lind e H. J. Herrmann. "Size distribution and structure of Barchan dune fields". Nonlinear Processes in Geophysics 18, n.º 4 (13 de julho de 2011): 455–67. http://dx.doi.org/10.5194/npg-18-455-2011.
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Abstract. Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.
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Husemann, Paul, Frederico Romão, Márcia Lima, Susana Costas e Carlos Coelho. "Review of the Quantification of Aeolian Sediment Transport in Coastal Areas". Journal of Marine Science and Engineering 12, n.º 5 (30 de abril de 2024): 755. http://dx.doi.org/10.3390/jmse12050755.
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Coastal dunes, formed and shaped by aeolian sediment transport, play a crucial role in ecosystem services and act as natural flood and coastal erosion defenses. This paper delves into theoretical equations and numerical models predicting sediment transport. Numerical models like cellular automata, XBeach-DUNA, the coastal dune model, and others are analyzed for their ability to simulate dune morphology, erosion processes, and vegetation impacts accurately. Evaluated are field observation and measurement techniques, such as sand traps, impact sensors, and optical sensors, for their precision in quantifying aeolian dynamics. Further examined is the effectiveness of vegetation and fencing in dune stabilization, noting species-specific responses and the influence of fence design on sediment accumulation. These tools offer insights into optimizing aeolian sediment management for coastal protection. By conducting a systematic review and connecting theoretical, empirical, and modeling findings, this study highlights the complex challenge of measuring and managing aeolian sediment transport and proposes integrated strategies for enhancing coastal dune resilience against the backdrop of climate change and erosion. This study’s objectives to bridge gaps in current understanding are met, highlighting the need for a multidisciplinary approach to coastal dune management and conservation, especially combining wind- and wave-driven processes.
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He, Nan, Yuanwei Lin, Yang Zhang e Bin Yang. "Approximate uniformity of the size distribution in the crescent-shaped dune swarm: A downsized experimental reinvestigation". AIP Advances 12, n.º 3 (1 de março de 2022): 035102. http://dx.doi.org/10.1063/5.0083088.
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Crescent-shaped dunes, or barchans, usually move in swarms in nature, where their sizes become closer to each other while migrating downstream collectively. A major cause of such a phenomenon is the collision among the dunes. Therefore, it is of importance to elucidate the pattern of the local dune interaction process, i.e., the double-dune collision. In this study, based on a downsized water tunnel experiment that adopts two colors of sand samples, the double-dune collision pattern is parameterized, which is investigated as a function of the initial mass ratio of the two dunes. The results depict from a distinctive perspective that the double-dune collision is essential in realizing the uniformity of the size distribution in a dune swarm. The proposed concepts could aid in the development of a comprehensive parameterization for the double-dune collision system.
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Bird, Tania Leah Fairfax, Amos Bouskila, Elli Groner e Pua Bar Kutiel. "Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?" Applied Sciences 10, n.º 7 (28 de março de 2020): 2310. http://dx.doi.org/10.3390/app10072310.
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Coastal dune habitats have been declining globally over the last several decades due to rapid urbanization. Within remaining dune systems, dune fixation has resulted in further losses of mobile dunes with negative impacts on their associated species. Some studies suggest vegetation removal can initially promote habitat heterogeneity, and increase availability of suitable habitats for psammophile, xeric and endemic mobile dune species, but longer-term responses are generally unknown. We investigated the temporal trends of four taxonomic groups to determine the effect of vegetation removal on dune assemblages over a 12-year period at an LTER site. Three different forms of removal are investigated here—removal in a grid form on fixed dunes, removal of the wind-facing slope vegetation on semi-fixed dunes and opportunistic off-road driving on disturbed dunes. Results were varied across taxa, highlighting the need for multi-taxa monitoring in conservation and restoration management. Overall, fixed dune treatment had very little effect, while a stronger response was found in semi-fixed treatments in particular for mobile dune indicator species, which showed evidence of recolonization within a few years following treatment. Disturbed dunes were most similar to mobile dunes for animal taxa indicating that pulse removal may not be as effective as continuous press disturbance. Nevertheless, a less destructive form of disturbance such as re-introduction of grazing might be preferable and requires further investigation.
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Gralher, Christine, Nobuhisa Kobayashi e Kideok Do. "WAVE OVERWASH OF VEGETATED DUNES". Coastal Engineering Proceedings 1, n.º 33 (15 de dezembro de 2012): 34. http://dx.doi.org/10.9753/icce.v33.sediment.34.
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Sand dunes play a significant role during coastal storms by absorbing the impacts of storm surge and high waves. Therefore, rapid profile changes and destruction of sand dunes, which may be caused by wave-induced overwash, lead to an increased flood risk landward of dunes. The effects of vegetation on dune erosion and overwash during storm events, however, have never been studied. This study is based on a laboratory experiment investigating the effects of woody plants on dune erosion and overwash of high and low dunes. During the five tests conducted foredune scarping was observed for the three high dune tests but did not occur for the two low dune tests. A narrow vegetation placed on the steep backdune of the high dune did not reduce wave overtopping and sand overwash. However, the wide vegetation figuration, which covered the backdune and foredune, reduced foredune scarping, prevented wave overtopping initially and reduced sand overwash after the initiation of wave overtopping for the high
dune. It also slowed down the erosion process of the low dune significantly by retarding wave uprush and reducing wave overtopping and overwash.
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Molina, Rosa, Giorgio Manno, Carlo Lo Re e Giorgio Anfuso. "Dune Systems’ Characterization and Evolution in the Andalusia Mediterranean Coast (Spain)". Water 12, n.º 8 (23 de julho de 2020): 2094. http://dx.doi.org/10.3390/w12082094.
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This paper deals with the characterization and evolution of dune systems along the Mediterranean coast of Andalusia, in the South of Spain, a first step to assess their relevant value in coastal flood protection and in the determination of sound management strategies to protect such valuable ecological systems. Different dune types were mapped as well as dune toe position and fragmentation, which favors dune sensitivity to storms’ impacts, and human occupation and evolution from 1977 to 2001 and from 2001 to 2016. Within a GIS (Geographic Information System) project, 53 dune systems were mapped that summed a total length of ca. 106 km in 1977, differentiating three dune environments: (i) Embryo and mobile dunes (Type I), (ii) grass-fixed dunes (Type II) and (iii) stabilized dunes (Type III). A general decrease in dunes’ surfaces was recorded in the 1977–2001 period (−7.5 × 106 m2), especially in Málaga and Almería provinces, and linked to dunes’ fragmentation and the increase of anthropic occupation (+2.3 × 106 m2). During the 2001–2016 period, smaller changes in the level of fragmentation and in dunes’ surfaces were observed. An increase of dunes’ surfaces was only observed on stable or accreting beaches, both in natural and anthropic areas (usually updrift of ports).
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Zhi, Dejuan, Wenbin Nan, Xiaoxia Ding, Qinjian Xie e Hongyu Li. "Soil nematode community succession in stabilised sand dunes in the Tengger Desert, China". Soil Research 47, n.º 5 (2009): 508. http://dx.doi.org/10.1071/sr08196.
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In order to examine how nematodes respond to sand dune succession after stabilisation and reclamation techniques, nematode communities were investigated in sand dunes stabilised for 0, 16, 26, 43, and 51 years in the Tengger Desert, China. Our results revealed that the abundance of nematodes; the proportion of fungivores, omnivores, and predators; maturity index (MI); Shannon index; evenness; and structure index (SI) were affected significantly by the age of stabilised sand dunes, and were correlated with soil physical and chemical properties to different degrees. There were differences in nematode abundance, the proportion of fungivores, Shannon index, and evenness between the shifting dunes and the stabilised dunes, but not within the different succession stages of the stabilised dunes. MI showed a tendency to increase with dune age and SI increased significantly with dune age. MI, and especially SI, could act as robust indicators of stabilised sand dune succession. Redundancy analysis using data on nematode community composition showed that shifting sand dunes were clearly separated from stabilised sand dunes, and younger sand dunes stabilised for 16 and 26 years were also separated from older dunes stabilised for 43 and 51 years to a lesser degree. The results indicated that changes in nematode communities could predict initial sand dune stabilisation due to the planting of artificial vegetation, and clearly differentiate sand dune succession accompanied by vegetation succession and variation of soil properties.
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Bar Kutiel, Pua, e Michael Dorman. "The Importance of Annual Plants and Multi-Scalar Analysis for Understanding Coastal Dune Stabilization Process in the Mediterranean". Applied Sciences 11, n.º 6 (22 de março de 2021): 2821. http://dx.doi.org/10.3390/app11062821.
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Since ecological phenomena and patterns vary with scale, scalar analysis is a developing practice in ecology. Scalar analysis is most valuable in heterogeneous environments, since habitat heterogeneity is a key factor in determining biodiversity. One such case can be seen in the changes in annual vegetation in coastal sand dune systems. Most studies in these environments are carried out at the dune scale, comparing dunes at different stabilization states. However, a broader understanding of dune stabilization processes requires analyses at the finer scales of dune slope aspects (directions of exposure to wind) and patches (under and between woody perennial species). Here, we present the results of a study that combines the three scales (dune, slope, and patch) in the Mediterranean coastal dune systems in Israel. Through this multi-scalar analysis, we are able to describe processes at the finer patch and aspect scale and explain how they shape patterns at the dune scale. The results indicate that the dune scale exposes the differences in annual plant characteristics between mobile and fixed dunes, their slopes and patches and the reorganization and spatial distribution of annual plants within mobile and fixed dunes during the stabilization process.
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Zomer, Judith Y., Bart Vermeulen e Antonius J. F. Hoitink. "Coexistence of two dune scales in a lowland river". Earth Surface Dynamics 11, n.º 6 (13 de dezembro de 2023): 1283–98. http://dx.doi.org/10.5194/esurf-11-1283-2023.
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Abstract. A secondary scale of bedforms, superimposed on larger, primary dunes, has been observed in fluvial systems worldwide. This notwithstanding, very little is known about the morphological behavior and characteristics of this secondary scale. This study aims to better characterize and understand how two dune scales coexist in fluvial systems and how both scales adapt over time and space, considering their interdependence. The study is based on analysis of a large biweekly multibeam echo sounding dataset from the river Waal, a lowland sand-bedded river. Results reveal that the secondary dune scale is ubiquitous across space and time and not limited to specific flow or transport conditions. Whereas primary dunes lengthen during low flows, secondary dune height, lee slope angle, and length correlate with discharge. Secondary dune size and migration strongly depend on the primary dune lee slope angle and height. Secondary dunes can migrate over the lee slope of low-angled primary dunes, and their height is inversely correlated to the upstream primary dune height and lee slope angle. In the Waal river, a lateral variation in bed grain size, attributed to shipping, largely affects dune morphology. Primary dunes are lower and less often present in the southern lane, where grain sizes are smaller. Here, secondary bedforms are more developed. At peak discharge, secondary bedforms even become the dominant scale, whereas primary dunes entirely disappear but are re-established during lower flows.
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Prodanov, Bogdan, Lyubomir Dimitrov, Iliyan Kotsev, Radoslava Bekova e Todor Lambev. "Spatial distribution of sand dunes along the Bulgarian Black Sea Coast: inventory, UAS mapping and new discoveries". Nature Conservation 54 (5 de dezembro de 2023): 81–120. http://dx.doi.org/10.3897/natureconservation.54.105507.
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Coastal sand dunes are amongst the world’s most sensitive and dynamic landforms. Unfortunately, during the last thirty years, heavy anthropogenic alterations have been observed, encompassing the greater part of the Bulgarian Black Sea coast (BBSC), which has changed the land-sea interactions significantly. As a consequence, the depositional coast has shrunk to 131 km or 25% of the aggregate Bulgarian Black Sea shoreline length. Although our research reveals that 86% of BBSC dunes are included in the Natura 2000 network of protected sites established under the Habitats Directive (Council Directive 92/43/EEC 1992), they are often heavily modified, subjected to environmental vandalism and destroyed due to mismanagement or lack of accurate information and prevention. These facts were the main reason for carrying out an inventory of the Bulgarian Black Sea coastal dune systems in 2021-2022. Our research aimed to identify all dune systems/sand dunes, update their spatial distribution and classify the observed coastal sand dunes landforms along the BBSC. The article demonstrates a successful methodology for combining unmanned aerial systems (UAS), Structure-from-Motion (SfM) photogrammetry, in situ sediment sampling, video imaging and verification and GNSS-RTK ground control points for coastal mapping. As of June 2022, over 97% of the Bulgarian shoreline has been surveyed with this technique, excluding military areas and national security sites. Based on the acquired data, as of 2021, the shoreline length was estimated to be 518.7 km at a scale 1:5000. The integrated UAS approach includes using Digital surface models (DSM), raster orthophotomosaics (OM) and 3D models, based on SfM photogrammetry to analyse the coastal topography, detect dune forms and update their spatial distribution. Throughout the inventory, 46 beach-dune systems were identified along the BBSC, which were divided into 62 dune sectors. The area of coastal dune systems was estimated at 988.21 ha (0.0089% of Bulgaria) and a total length of 73 km (14% of the shoreline). A comprehensive geomorphological analysis of the relationships between landforms morphology, aeolian and morphodynamic processes, vegetation density and type was the basis for the coastal dune landforms (CDLs) or dune systems to be classified into primary (312 ha; 32%) and secondary (676 ha; 68%). Additionally, the CDLs were classified according to Natura 2000 habitats: fixed (grey) dunes (546.27 ha; 55.28%), wooded dunes (222.61 ha; 22.53%), shifting (white) dunes (150.30 ha; 15.21%), embryonic dunes (68.3 ha; 6.91%) and humid dune slacks (0.94 ha; 0.09%). The highest positioned CDLs on the Balkan Peninsula were registered at perched Sozopol Sand Dunes (61 m a.s.l.) and cliff-top dunes at Arkutino (50.2 m a.s.l.). The multi-temporal analysis of photogrammetric DSMs and raster OMs showed the permanent loss of five dune systems in the Pomorie-Burgas-Rosenets coastal sector. The accrued UAS data approach allowed us to identify and map eight dune systems for the first time: Zlatni Pyasatsi (Panorama), Asparuhovo (Varna), Byala, Atanasovska Kosa, Central Beach (Burgas), Chernomorets, Kavatsite (partly) and Rezovo-Kastrich. A high anthropogenic footprint was registered on 50.7 ha (5.1%) of the entire dune surface. In the final stage of the study, human interventions that caused degradation and permanent loss of dunes (12 ha) over the last 15 years along the BBSC were shown. The main causes for dune degradation along BBSC have been documented, such as massive tourism development after the socialist period, road construction, recreational pressure exerted on the dunes, human trampling, lack of designated footpaths in areas with fixed and mobile dunes, off-road vehicles and parking lots (especially at camping sites), dumping of garbage and anthropogenic marine litter on the sand dunes etc.
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Els, A., S. Merlo e J. Knight. "Comparison of two Satellite Imaging Platforms for Evaluating Sand Dune Migration in the Ubari Sand Sea (Libyan Fazzan)". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-7/W3 (30 de abril de 2015): 1375–80. http://dx.doi.org/10.5194/isprsarchives-xl-7-w3-1375-2015.
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Sand dunes can change location, form or dimensions depending on wind direction and strength. Sand dune movements can be effectively monitored through the comparison of multi-temporal satellite images. However, not all remote sensing platforms are suitable to study sand dunes. This study compares coarse (Landsat) and fine (Worldview) resolution platforms, specifically focussing on sand dunes within the Ubari Sand Sea (Libya). Sand dune features (crest line, dune ridge basal outlines) were extracted from Landsat and Worldview 2 imagery in order to construct geomorphic maps. These geomorphic maps were then compared using image overlay and differencing, and the Root Mean Squared Error (RMSE) was used to determine if the mapped dune patterns were significantly different. It was found that Landsat is a sufficient data source when studying dune patterns within a regional sand sea, but smaller dunes identified from Worldview data were not capable of being extracted in the data sourced from Landsat. This means that for studies concerned with the dune patterns and movements within sand seas, Landsat is sufficient. But in studies where the specific dynamics of specific dunes are required, a finer resolution is required; platforms such as Worldview are needed in order to gain more detailed insight and to link the past and present day climate and environmental change.
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Mahmoud, Ahmed Mutasim Abdalla, Ekbal Hussain, Alessandro Novellino, Panos Psimoulis e Stuart Marsh. "Monitoring the Dynamics of Formby Sand Dunes Using Airborne LiDAR DTMs". Remote Sensing 13, n.º 22 (19 de novembro de 2021): 4665. http://dx.doi.org/10.3390/rs13224665.
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Coastal dunes play an important role in coastal erosion risk management, where they act as a dynamic natural sea defence line. Formby coast is part of the Sefton coast in the Northwest of England and is one of the largest and most rapidly evolving sand dune systems in the UK. Such dune systems require continuous comprehensive monitoring activity to understand their dynamics. In this research, we investigate the use of airborne LiDAR digital terrain model DTMs for monitoring the dynamics of the sand dunes at Formby between 1999 and 2020. We found that the rate of elevation change for the beach and the dune areas ranges from −0.78 to 0.02 m/year and −0.92 to 0.73 m/year, respectively. The beach and the frontal dunes have had significant sand erosion, while the inner dunes gained sand during the measurement period. Vegetated areas remained unchanged due to the impact of vegetation in stabilizing the movement of the dunes. Formby beach had a volume loss of about 907,000 m3 in the last 21 years, while the dunes had a volume increase of about 1,049,000 m3 over the same period. The total volume of the entire dune system, consisting of both the beach and dune areas, remained unchanged, which indicates that the growth of the inland dunes is fed by sand from the beach. All the volumetric changes occurred due to sand redistribution within the system, with erosion along the beach, and deposition and erosion in the dune areas.
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Abdikerem, Xamxinur, Akbar Eziz, Abudoukelimu Abudoureheman e Mamtimin Gheni. "Numerical Simulation of Sand Dune Formation with Periodical Uniform Stream Field". Advanced Materials Research 33-37 (março de 2008): 1069–74. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.1069.
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In this study, to conduct numerical simulation of sand dune forming processes, the mathematical model for sand dune dynamics are studied. Due to sand dune dynamics and the stream field, which includes wind flow over a dune field, analyses process is complex the uniform sand field and stream fields are consider for the numerical simulation process. Then the dune forming process simulated by considering the dunes induced factor and interactions phenomenon.
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Ellis, Jean T., e Mayra A. Román-Rivera. "Assessing Natural and Mechanical Dune Performance in a Post-Hurricane Environment". Journal of Marine Science and Engineering 7, n.º 5 (2 de maio de 2019): 126. http://dx.doi.org/10.3390/jmse7050126.
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The purpose of this study is to document the geomorphic evolution of a mechanical dune over approximately one year following its installation and compare it to the recovery of a natural dune following the impact of Hurricane Matthew (2016). During the study period, the dunes’ integrity was tested by wave and wind events, including king tides, and a second hurricane (Irma, 2017), at the end of the study period. Prior to the impact of the second hurricane, the volumetric increase of the mechanical and natural dune was 32% and 75%, respectively, suggesting that scraping alone is not the optimal protection method. If scraping is employed, we advocate that the dune should be augmented by planting. Ideally, the storm-impacted dune should naturally recover. Post-storm vegetation regrowth was lower around the mechanical dune, which encouraged aeolian transport and dune deflation. Hurricane Irma, an extreme forcing event, substantially impacted the dunes. The natural dune was scarped and the mechanical dune was overtopped; the system was essentially left homogeneous following the hurricane. The results from this study question the current practice of sand scraping along the South Carolina coast, which occurs post-storm, emplacement along the former primary dune line, and does not include the planting of vegetation.
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Villard, P. V., e M. Church. "Dunes and associated sand transport in a tidally influenced sand-bed channel: Fraser River, British Columbia". Canadian Journal of Earth Sciences 40, n.º 1 (1 de janeiro de 2003): 115–30. http://dx.doi.org/10.1139/e02-102.
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Dunes form annually on the sand bed of the tidally influenced South Arm of Fraser River, British Columbia. Bathymetric surveys along the center of the main channel throughout a snow-melt freshet provided measurements of dune geometry and migration. Dune length, height, and steepness all increase with river discharge. However, lag between the highest flow conditions and development of the largest, steepest dunes reflects the influence of antecedent flow conditions on dune geometry. Population averages of dune height and steepness ratio change more rapidly than dune length, whilst coefficients of variation of dune height, length, and steepness ratio indicate high variability in dune geometry within the estuarine reach during periods of dune growth and decay. Unlike dune geometry, dune migration rates display little lag with flow conditions. The largest coefficients of variation for dune migration occur during periods of rapid change in discharge and tidal fall, corresponding to the onset of rapid change in dune geometry on both rising and falling limbs. Migration rate estimates and geometry measurements are used to estimate associated sand transport. In the absence of hydraulic measurements in the estuary, Mission and Hope discharges are adopted to drive simple statistical models of sand transport as a function of discharge and tidal fall. The models cover 6570% of the transport, and tidal fall is only marginally significant. Comparison with historical direct measurements indicates that the dune-associated transport coincides with bed-load transport in the estuary, and arguments are made that it constitutes the preponderance of all bed-material transport.
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Larson. "Topographic Effects on Titan’s Dune-forming Winds". Atmosphere 10, n.º 10 (3 de outubro de 2019): 600. http://dx.doi.org/10.3390/atmos10100600.
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The Cassini mission made an unexpected discovery when it found evidence of linear dune fields on Titan’s surface. The orientation of the dunes and their interaction with topography allow scientists to estimate the dominant wind direction on the surface of Titan. There is some consensus in the community that the dune-forming winds must be net westerly, however, there is an active debate about the dune-forming wind regime. This debate has been guided by several studies of Earth dune fields considered analogous to the Titan dunes including those in Namibia, the Sahara, the Serengeti, and China. Complicating this active debate about the surface wind regime is the fact that global circulation models (GCMs) have historically not been able to reproduce westerly surface winds in the tropics. Here we use the Titan Community Atmosphere Model (CAM) to quantify the impact of topography and an added torque on Titan’s dune-forming winds. Dunes tend to form at higher elevations on Titan, and adding topography to the model alters the near-surface wind directions, making them more westerly and consistent with the dune orientations. The addition of topography and added torque create a wind regime that is consistent with linear dunes in areas of stabilized sediment.
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Gao, Jinjuan, David M. Kennedy e Teresa M. Konlechner. "Coastal dune mobility over the past century: A global review". Progress in Physical Geography: Earth and Environment 44, n.º 6 (22 de maio de 2020): 814–36. http://dx.doi.org/10.1177/0309133320919612.
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The mobility of coastal dunes is characterised by bio-geomorphological responses related to change in boundary conditions, particularly sediment supply, wind and vegetation cover, as well as human activities. There remains uncertainty regarding the relative importance of these drivers on dune mobility at a global scale. In this study, trends and dominant drivers of coastal dune mobility are synthesised through the literature review focusing on shifts in dune mobility over the last century (1870–2018). In total, 176 individual dunes, with 55 dunes from the Europe-Mediterranean area, 23 from Africa, 30 from North America, 23 from South America, 20 from Oceania and 23 from Asia, are reviewed in this work. The results show that there is a worldwide trend of dune stabilisation, with 93% (164 out of 176) of the reviewed sites showing a loss of bare sand area due to an increase in vegetation cover and urbanisation expansion. Multiple factors have contributed to the stabilisation process, including (a) land-use change such as the change of traditional farming practises, coastal urbanisation and tourism development; (b) dune stabilisation projects; (c) sediment decline caused by the riverine and coastal constructions; and (d) change in climate (i.e. the decrease in windiness, and the increase in temperature and rainfall) and storms. Our results suggest human intervention played a dominant role in altering dune mobility for most dunes during the past century, while climate and storms are also important drivers, especially for dune sites with limited human activities.
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Delgado Blasco, José Manuel, Marco Chini, Gert Verstraeten e Ramon F. Hanssen. "Sand Dune Dynamics Exploiting a Fully Automatic Method Using Satellite SAR Data". Remote Sensing 12, n.º 23 (6 de dezembro de 2020): 3993. http://dx.doi.org/10.3390/rs12233993.
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This work presents an automatic procedure to quantify dune dynamics on isolated barchan dunes exploiting Synthetic Aperture RADAR satellite data. We use C-band datasets, allowing the multi-temporal analysis of dune dynamics in two study areas, one located between the Western Sahara and Mauritania and the second one located in the South Rayan dune field in Egypt. Our method uses an adaptive parametric thresholding algorithm and common geospatial operations. A quantitative dune dynamics analysis is also performed. We have measured dune migration rates of 2–6 m/year in the NNW-SSE direction and 11–20 m/year NNE-SSW for the South Rayan and West-Sahara dune fields, respectively. To validate our results, we have manually tracked several dunes per study area using Google Earth imagery. Results from both automatic and manual approaches are consistent. Finally, we discuss the advantages and limitations of the approach presented.
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Munyikwa, Kennedy. "The role of dune morphogenetic history in the interpretation of linear dune luminescence chronologies: a review of linear dune dynamics". Progress in Physical Geography: Earth and Environment 29, n.º 3 (setembro de 2005): 317–36. http://dx.doi.org/10.1191/0309133305pp451ra.
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Contemporary knowledge on aeolian dune dynamics is reviewed to enable an appraisal of evolutionary mechanisms involved in linear dune stratigraphic sequence development. The degrees of depositional record retention in the dune structures are evaluated and the corollary applied to methods used in the interpretation of luminescence dating chronologies acquired from such sedimentary accumulations. It is demonstrated that morphogenetic aspects of dune development are an imperative element to invoke when carrying out palaeoenvironmental reconstruction using luminescence dating ages acquired from linear dune sequences. To help depict the role of dune morphogenesis, hypothetical scenarios that simulate the preservation of stratigraphical records in linear dune sequences are presented using two different theories that have been advanced to explain origin and development of linear dunes: bidirectional wind regime and helical roll vortices. It is illustrated that linear dune systems that evolve under bidirectional wind influence are intrinsically inefficient at preserving complete records of their depositional history and this places major constraints for palaeoenvironmental reconstruction using luminescence chronologies. When linear dunes develop under the influence of helical roll vortices, on the other hand, it is shown that the degree of sequence preservation would be higher. The possibility of lateral migration of linear dune structures is indicated to be an additional limitation that may encumber the interpretation of luminescence ages.
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Lubke, Roy A. "Current State of Ammophila arenaria (Marram Grass) Distribution in the Eastern Cape, South Africa, and the Possible Effect of the Grass on the Dune System Dynamics". Plants 11, n.º 17 (30 de agosto de 2022): 2260. http://dx.doi.org/10.3390/plants11172260.
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The principal aim of this paper is to show that marram grass is not an invasive alien in South Africa although it affects the dune dynamics as a useful pioneer species in the dune successional process. The historical perspective of marram introduction as a dune stabiliser and the studies and conclusions reached from our European Union funded project, INVASS, in the 1990s and early 2000s is presented. Although these studies showed that marram was non-invasive, this was not clearly carried through to the authorities, and the use of the grass as a dune stabiliser was limited without a special permit. This prompted a survey of the current situation of marram on dune sites in the Eastern Cape. Along with earlier (1980s) data on the dunes, 69 relevés with 66 species abundance from sites along the Eastern Cape shoreline were assembled. These data were analysed with Detrended Correspondence Analysis to show the relationships of the samples (relevés) and species in a 2-dimensional scatter diagram. The survey showed that there are four dune sites where marram grass is no longer present, due to either marram being out of its climatic range, erosion of sand under storm conditions which made the habitat unsuitable, or in one case where marram simply disappeared. Marram often remains in other sites where three to five dune pioneer species were recorded. On some dunes, although marram is the most abundant dune pioneer, it is never dominant in the dune environment but has a presence of as much as 75% at any site. The eight pioneer species are widely dispersed on the DCA scatter diagram, while the shrub species characterising the Coastal Scrub are tightly clustered, showing that all the pioneer dune communities behave similarly in the dune successional series. The conclusion from these studies is that marram grass does not always persist in the dune systems. If marram does persist, it does not compete and behaves identically to the indigenous species as a dune pioneer. These studies show that marram grass is a non-invasive species that can be successfully used in dune stabilisation on Cape dunes.
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Zhao, Feifei, Benjamin T. Cardenas e Wonsuck Kim. "Controls of aeolian dune height on cross-strata architecture: White Sands Dune Field, New Mexico, U.S.A." Journal of Sedimentary Research 91, n.º 5 (14 de maio de 2021): 495–506. http://dx.doi.org/10.2110/jsr.2020.138.
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ABSTRACT The stratal types composing aeolian dunes preserve a record of the transport and sorting of grains and are categorized into: 1) grainflow strata, 2) grainfall laminae, and 3) wind-ripple laminae. The arrangement of these deposits in the cross beds of a formative dune is largely unexplored. Here, field results from White Sands Dune Field, New Mexico, USA, are used to test the hypothesis that dune height controls the arrangement, abundance, and geometry of cross-stratification types. Grainflow thicknesses and deposit widths were measured on wind-scoured stoss-side exposures of seven crescentic dunes with heights ranging from 1.7 m to 11.2 m. Dozens of grainflow thickness measurements were taken along transverse-oriented strata normal to the crest on each dune. The results show that grainflow thickness averages from 1 cm to 4 cm. These data show a positive trend between mean grainflow thickness and dune height but only for the grainflow thicknesses measured at the bases of dunes. The tallest dune (11.2 m) produced many thick grainflow packages of 10 cm to 30 cm in which individual grainflow strata were indistinguishable from each other. This amalgamation was also found to be characteristic of larger dunes—the product of a lack of grainfall deposits separating individual grainflows. These differences in grainflow strata at the bases of dune lee slopes are linked to the temporary storage of sediment along the upper parts of lee slopes. In taller dunes with longer lee slopes, amalgamated grainflows which require multiple avalanche events and take longer time to reach the base transport temporarily stored sediment at upper parts of the slope. This allows time for wind ripples to rework accumulations near the base, where grainfall deposition is also limited. Shorter dunes lack this temporary storage mechanism, as individual grainflows can move across the entire lee slope in a single event, and grainfall accumulates across the entire lee slope. These stratigraphic measurements and process-based understanding will be useful in estimating original dune height in ancient cross-strata and will lead to a better interpretation of aeolian stratigraphy.
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Darke, Ian B., Ian J. Walker e Patrick A. Hesp. "Beach-dune sediment budgets and dune morphodynamics following coastal dune restoration, Wickaninnish Dunes, Canada". Earth Surface Processes and Landforms 41, n.º 10 (8 de março de 2016): 1370–85. http://dx.doi.org/10.1002/esp.3910.
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Halsey, L. A., N. R. Catto e N. W. Rutter. "Sedimentology and development of parabolic dunes, Grande Prairie dune field, Alberta". Canadian Journal of Earth Sciences 27, n.º 12 (1 de dezembro de 1990): 1762–72. http://dx.doi.org/10.1139/e90-182.
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The Grande Prairie dune field in northwest central Alberta is composed of parabolic and dome dunes, presently inactive but which had developed under westerly winds. Two parabolic dune types are recognized on the basis of arm length, nose width, and dune height. Variations in parabolic dune morphology are attributed to spatial and (or) temporal differences in sediment budget as elucidated from sedimentary sequences preserved in the dunes.Seven facies and four subfacies are distinguished from sedimentary sequences examined in nine dune sections. Lee-side deposits of parabolic dunes are typically composed of concave-downward cross-strata that develop from grainfall on a cohesive slipface and are interbedded with avalanche cross-strata. Lee-side deposits interfinger downwind with low-angle to horizontal ripple and grainfall laminations of bottomset deposits and are overlain by shallow-dipping topset deposits. Topset deposits of type 2 parabolic dunes contain sedimentary structures that are indicative of moisture (e.g., adhesion laminae and wet grainfall deposits) and vegetation (e.g., scour surfaces associated with calcareous root tubules) during deposition. These indicators suggest that type 2 parabolic dunes retained sediment effectively, whereas their absence in type 1 parabolic dunes suggests that these dunes did not retain sediment effectively. Type 2 parabolic dunes contain abundant grainfall deposits in topset beds, indicating a high sediment supply, whereas type 1 parabolic do not, suggesting they had a lower sediment supply.
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Zheng, Shuwei, Xinmeng Yuan, Suxian Yang, Heqin Cheng, Xingjie Guo, Yurong Cui, Enfeng Liu e Zijun Li. "Seasonal Variation of Catenary-Bead Dunes in the Yangtze River Estuary: Causes and Implications". Journal of Marine Science and Engineering 10, n.º 7 (27 de junho de 2022): 886. http://dx.doi.org/10.3390/jmse10070886.
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Low-angle lee-side slopes of dunes are commonly developed on the world’s riverbeds, and dune migration associated with sediment transport exert a major influence on riverine processes. However, the catenary-bead dune has been identified in the Yangtze River (YR) Estuary, featuring a higher lee-side angle. To date, the morphological variation and formation reasons of catenary-bead dunes in the YR Estuary remain uncharacterized. In this study, we used a multibeam echo system (MBES) to investigate the bedforms of the YR estuary during 2014–2015, as well as to discuss the seasonal variation of catenary-bead dunes. The results indicate that the catenary-bead dunes of the YR Estuary are characterized by growth during the flood season and extinction during the dry season. The lee-side angle is typically ~16.7°, which is larger than that of other dune types (3.7–8°) in the estuary; moreover, the catenary-bead dunes are higher than other dune types of the same length in the YR Estuary. The relationship between the dune height (H) and length (L) was found to be H = 0.1667L0.603 (R2 = 0.38), while the other dune types yielded the relationship of H = 0.0845L0.758 (R2 = 0.52). Strong runoff superimposing the ebb tide led to the development of catenary-bead dunes. Furthermore, the higher coarse sediment content (69.9–72%) and lower clay content (6.3–6.7%) of the riverbed sediment are favorable for their formation, while the higher curved crest-lines are favorable for the formation of the associated elliptical pits.
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Macdonald, S. Ellen, C. C. Chinnappa, David M. Reid e Brett G. Purdy. "Population differentiation of the Stellaria longipes complex within Saskatchewan's Athabasca sand dunes". Canadian Journal of Botany 65, n.º 8 (1 de agosto de 1987): 1726–32. http://dx.doi.org/10.1139/b87-235.
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Stellaria arenicola, a recent derivative within the S. longipes complex, is an endemic of the Athabasca sand dunes. Analysis of 11 morphological characters on 40 genets showed that both the endemic and parental (S. longipes) species are present within the Thomson Bay dune field and that the two forms are distinct. Individuals of S. arenicola were distinguished by only a few characters, typically, large yellow capsules with reflexed teeth and yellowish leaf and stem pigmentation. The endemic also exhibited a higher sexual reproductive output. Many characteristics of vegetative morphology showed plasticity in both species, but the two remained distinct when grown in a common garden. On the sand dunes S. longipes is restricted to beach dunes bordering Lake Athabasca while S. arenicola is predominant on the active dune field inland. The two dune systems represented environmentally distinct microhabitats. The active inner dunes were characterized by an unstable, fine sand substrate and intense insolation. Field reciprocal transplants showed S. longipes was selected against in the inner dune habitat, while S. arenicola performed relatively well on the beach. Stellaria arenicola possibly arose in the active sand dune habitat as a result of selection pressure and genetic isolation.
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Łabuz, Tomasz Arkadiusz, Ralf Grunewald, Valentina Bobykina, Boris Chubarenko, Algimantas Česnulevičius, Artūras Bautrėnas, Regina Morkūnaitė e Hannes Tõnisson. "Coastal Dunes of the Baltic Sea Shores: A Review". Quaestiones Geographicae 37, n.º 1 (30 de março de 2018): 47–71. http://dx.doi.org/10.2478/quageo-2018-0005.
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Abstract The article summarises results of studies conducted along the Baltic Sea sandy coasts by scientists involved in coastal dune research, and presents an attempt to describe the types and distribution of dune coasts. The Baltic Sea coasts feature lower and higher foredunes. The lowland behind the coastal dune belt is covered by wandering or stabilised inland dunes – transgressive forms, mainly parabolic or barchans. The source of sediment for dune development includes fluvioglacial sands from eroded coasts, river-discharged sand, and older eroded dunes. Due to the ongoing erosion and coastal retreat, many dunes have been eroded, and some are withdrawing onto the adjacent land. There are visible differences between the south-eastern, western, and northern parts of the Baltic Sea coast with respect to dune development. The entire southern and eastern coast abounds in sand, so the coastal dunes are large, formerly or currently wandering formations. The only shifting dunes are found at the Polish and the Russian–Lithuanian coasts on the Łebsko Lake Sandbar as well as on the Vistula and Curonian Spits. The very diverse shoreline of the south-western coast experiences a scarcity of larger sandy formations. Substantial parts of the Baltic Sea sandy coasts have been eroded or transformed by humans. The northern part of the Baltic Sea coast features mainly narrow and low sandy coasts (e.g. in Estonia). Further north, sandy dunes are virtually absent.
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Rodrigues, Guilherme Da Silva, Ulisses Rocha de Oliveira e Karine Bastos Leal. "Variação das dunas no Balneário Barra do Chuí, extremo sul do Brasil, entre 2005-2018". Revista Brasileira de Geografia Física 14, n.º 2 (14 de abril de 2021): 522. http://dx.doi.org/10.26848/rbgf.v14.2.p522-536.
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As dunas costeiras são feições naturais formadas a partir das praias arenosas, devido a interação do vento, areia e vegetação. No entanto, a ação humana torna-se uma variável cada vez mais relevante em sua dinâmica, ocasionando problemas ambientais. O presente trabalho tem como objetivo quantificar e caracterizar, a partir de uma série temporal de imagens orbitais no intervalo entre 2005 e 2018, a mobilidade das dunas no Balneário Barra do Chuí – RS, especificamente a variação na base das dunas frontais. O intuito é verificar processos de erosão e sedimentação na orla do balneário, bem como a variação do limite do reverso do campo de dunas, onde se encontra a área urbana edificada do balneário. A metodologia foi empregada a partir de imagens orbitais adquiridas no software Google Earth Pro® e técnicas realizadas nos softwares ArcGIS 10.3.1® e ERDAS Imagine 2013®. A variação das linhas de costa analisadas foi obtida a partir do Método do Polígono de Mudança, por meio de uma linha de controle aplicada aos limites praia-duna frontal e reverso da duna. O Balneário Barra do Chuí, no período estudado, apresentou predomínio de taxas de erosão das dunas frontais, onde depósitos pleistocênicos estão sendo diretamente trabalhados pela ação marinha. O reverso das dunas apresentou tendência de avanço em relação à retroterra. Constatou-se que em alguns locais o transporte eólico de sedimentos está soterrando algumas residências. Palavras-chave: Limite praia-duna. Reverso das Dunas. Geotecnologias. Método do Polígono de Mudança. Foredune variation in the Barra do Chui coastal settlement, southern Brazil, between 2005-2018ABSTRACT Foredunes are natural features formed from sandy beaches, due to the interaction of wind, sand, and vegetation. However, human action becomes an increasingly relevant variable in its dynamics, causing environmental problems. The present work aims to quantify and characterize, from a time series of orbital images in the interval between 2005 and 2018, the dune mobility in the Barra do Chui coastal settlement, specifically the variation in the base of the frontal dunes, in order to check erosion and sedimentation at the edge of the resort, as well as the variation of the limit of the reverse of the dune field, where the built-up area of the resort is located. The methodology was used based on orbital images acquired in the Google Earth Pro® software and techniques performed in the ArcGIS 10.3.1® and ERDAS Imagine 2013® software. The variation of the coastlines analyzed was obtained from the Change Polygon Method, through a control line applied to the frontal and reverse dune beach-dune limits. The Barra do Chui coastal settlement, in the studied period, presented a predominance of erosion rates of the frontal dunes, where Pleistocene deposits are being directly worked by the marine action. The reverse side of the dunes showed an upward trend in relation to the retrograde, in fact, in some places, wind sediment transport has already been burying some homes. Keywords: Dune-Beach Limit. Dunes Reverse. Geotechnologies. Change Polygon Method
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Alvarez, Carlos A., e Erick Franklin. "Experimental study on the formation of subaqueous barchan dunes in closed conduits". EPJ Web of Conferences 180 (2018): 02002. http://dx.doi.org/10.1051/epjconf/201818002002.
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The present paper reports the formation of subaqueous barchan dunes by analyzing the temporal evolution of their main geometrical characteristics (width W, length L and horn lengths Lh). After certain time, the dunes reach an equilibrium state and it is possible to study the relation between W versus L, and the dependence of the dune velocity on L. The barchan dunes were formed from spherical glass and zirconium beads. An initial conical heap of beads was placed on the bottom wall of a rectangular channel and it was entrained by a water turbulent flow. The evolution of the dunes was filmed with a CCD camera placed above the channel and mounted on a traveling system. Our results show that after a characteristic time the dune shape does not change and it travels with a roughly constant velocity. Once the equilibrium state is reach, W and L are measured, showing linear dependence. Furthermore, we show that the dune velocity Vd scales with the inverse of the dune length.
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Domínguez Acosta, Miguel, Richard P. Langford e Thomas E. Gill. "Morphometry of the Samalayuca dunes, northern Chihuahua, Mexico". Boletín de la Sociedad Geológica Mexicana 75, n.º 3 (30 de novembro de 2023): A240823. http://dx.doi.org/10.18268/bsgm2023v75n3a240823.
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The Samalayuca Dunes (SMD) (Médanos de Samalayuca), Chihuahua, México, are one of México’s largest and least studied dune fields, now managed as a Protected Area for their ecological characteristics. We present a morphometric characterization of the dune field based on remote sensing and field studies, to advance understanding of its physical environment. SMD’s generally-fine sands originate from shoreline deposits of Paleolake Palomas, transported eastward (downwind) along an aeolian corridor, accumulating primarily as echo dunes upwind of the sierras of Samalayuca and Presidio. A complex wind regime, with northerly and southerly winds complementing regionally-prevailing southwesterlies, modified by topographic effects, shapes the SMD’s morphology. The sand sea covers ~139.7 km2, with ~113.8 km2 in the main eastern body and ~25.9 km2 in a northwestern subfield. We describe six major dune forms: north to south straight-crested dunes, east to west straight-crested dunes, star dunes, vegetated parabolic dunes, relict transverse dunes, and “megastar” (draa) dunes. Mean interdune centroid spacing is 76.5 m. The active dunes, previously described as an “aklé” pattern, are predominantly straight-crested dune sets oriented near-perpendicular to each other with general north-south and east-west crest orientations, 4-5 m high, spaced ~67 m apart for north-south trending crests and ~53 m for east-west trending crests, representing a nearly perpendicular interference pattern in some locations. The active dunes are superimposed in a compound and complex arrangement on relict remnants of much larger north-northwest trending transverse dune ridges fanning out from south to north-northwest, spaced approximately ~1 km apart and ~50 m high. The easternmost dune ridge contains an active set of at least 15 active megastar and reversing dunes up to 120 m tall, increasing in size and complexity from south to north. As a protected area with historical and ecological value, additional geologic investigations should be performed at the SMD, to help conserve this remarkable geologic feature.
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Charbonneau, Bianca, e Brenda Casper. "WIND TUNNEL TESTS OF HOW COASTAL PLANTS FEEDBACK ON DUNE SHAPE". Coastal Engineering Proceedings, n.º 36 (30 de dezembro de 2018): 71. http://dx.doi.org/10.9753/icce.v36.sediment.71.
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Theoretical evolution of a coastal dune system starts at the individual plant level with the formation of bedforms, nebkha and shadow dunes, around plants. Over time, these initial bedforms can evolve into a fully developed foredune and eventually a complex dune system capable of buffering upland coastal areas against high tides and storms. Recent studies suggest that dunebuilding plant species may differ in their sand trapping efficiency and they may support different topographies, building dunes morphologically similar to their own stature – i.e. a taller steeper plant would build a taller and steeper dune. We believe that the bedforms created at the onset of dune evolution, i.e. after a storm or at the backbeach, may carry over through the life of the dune, such that understanding how plant morphology and density affects the initial formation stages of dune morphology is key to optimizing dune management, maintenance, and creation. With ERDC and USGS funding, we built a removable bed unilateral flow wind tunnel to test how the morphology among and within dominant US East coast foredune plants feeds back on bedform creation around individual plants at a baseline of zero (i.e. flat back beach or post storm).
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Naqshband, Suleyman, Bas Wullems, Timo de Ruijsscher e Ton Hoitink. "Experimental investigation of low-angle dune morphodynamics". E3S Web of Conferences 40 (2018): 02056. http://dx.doi.org/10.1051/e3sconf/20184002056.
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Dunes commonly dominate the bed of sandy rivers and they are of central importance in predicting flow resistance and water levels. In the present study, we show that by using light-weight polystyrene particles as substrate in a laboratory setting, promising morphodynamic similarity is obtained between dunes in shallow flow (flume) and deep flow (field) conditions. In particular, results from our flume experiments show that dune lee-side angles, which are crucial in turbulence production and energy dissipation, better approximate dune lee-side angles observed in natural channels. Furthermore, dune height evolution towards upper stage plane bed observed in the present experimental study, closely follows dune height evolution as observed in world’s large rivers.
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Lü, Ping, Clément Narteau, Zhibao Dong, Philippe Claudin, Sébastien Rodriguez, Zhishan An, Laura Fernandez-Cascales, Cyril Gadal e Sylvain Courrech du Pont. "Direct validation of dune instability theory". Proceedings of the National Academy of Sciences 118, n.º 17 (21 de abril de 2021): e2024105118. http://dx.doi.org/10.1073/pnas.2024105118.
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Modern dune fields are valuable sources of information for the large-scale analysis of terrestrial and planetary environments and atmospheres, but their study relies on understanding the small-scale dynamics that constantly generate new dunes and reshape older ones. Here, we designed a landscape-scale experiment at the edge of the Gobi desert, China, to quantify the development of incipient dunes under the natural action of winds. High-resolution topographic data documenting 42 mo of bedform dynamics are examined to provide a spectral analysis of dune pattern formation. We identified two successive phases in the process of dune growth, from the initial flat sand bed to a meter-high periodic pattern. We focus on the initial phase, when the linear regime of dune instability applies, and measure the growth rate of dunes of different wavelengths. We identify the existence of a maximum growth rate, which readily explains the mechanism by which dunes select their size, leading to the prevalence of a 15-m wavelength pattern. We quantitatively compare our experimental results with the prediction of the dune instability theory using transport and flow parameters independently measured in the field. The remarkable agreement between theory and observations demonstrates that the linear regime of dune growth is permanently expressed on low-amplitude bed topography, before larger regular patterns and slip faces eventually emerge. Our experiment underpins existing theoretical models for the early development of eolian dunes, which can now be used to provide reliable insights into atmospheric and surface processes on Earth and other planetary bodies.
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Jarvis, Paul A., Clement Narteau, Olivier Rozier e Nathalie M. Vriend. "The probabilistic nature of dune collisions in 2D". Earth Surface Dynamics 11, n.º 4 (15 de agosto de 2023): 803–15. http://dx.doi.org/10.5194/esurf-11-803-2023.
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Abstract. Dunes are bedforms of different size and shape, appearing throughout aeolian, subaqueous and extraterrestrial environments. Collisions between dunes drive dune field evolution, and are a direct result of interacting dunes of different heights, travelling at different speeds. We perform 2D cellular automaton simulations of collisions between dune pairs migrating in a steady flow. Modelled collisions can result in either ejection, where dunes exchange mass before separating, or downstream- or upstream-dominant coalescence (merging of dunes). For each of these three elementary types of interaction, we identify the mass exchange mechanism and the distinctive intermediate morphologies. Surprisingly, we show that the collision outcome depends probabilistically on the initial dune area ratio r and can be described by a narrow sigmoidal function centred on r=1/2. Finally, we compare our simulations with laboratory experiments of dune collisions, finding good agreement concerning the intermediate morphology and the collision outcome. Our results can motivate further observational or experimental studies that validate our probabilistic collision predictions and fully determine the controls on the coalescence–ejection transition.
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Feyzolahpour, Mehdi, Rouholah Mohamadi e Hasan Ghasemlu. "Analysis of movement and relationships between morphometric components of sand dunes (barchans) in the south-eastern of Iran". AUC GEOGRAPHICA 57, n.º 1 (29 de junho de 2022): 75–84. http://dx.doi.org/10.14712/23361980.2022.7.
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Morphology of barchan dunes plays a key role in the rate of movement of barchan dunes and accordingly, the areas that are in the path of barchan dunes can be identified. In this study, morphological parameters of eight barchan dunes in west Lut and movement were investigated. For this purpose, 8 parameters of windward slope length, back-to-wind slope length, right arm length, left arm length, length, width, right width and left width were measured in each barchan dune and Pearson correlation was calculated by SPSS software. In order to better understand the shape of barchan dunes, satellite images were extracted separately from google earth. The results of morphometry showed that barchan dune 6 was in the first place in terms of all morphometric factors. The right arm length to the width had the highest correlation (0.993). The back-to-wind slope length to the right arm length had the lowest correlation (0.815). The right arm length to the width had the highest coefficient of determination (0.9845). The movement during 2005–2019 was extracted from satellite images. It was found that until 2015, the highest movement belonged to barchan dune 3 (225.55 m) and during 2017–2019, the lowest movement belonged to barchan dune 6 (137.49 and 184.66 m). The highest movement during 2017–2019 was 288.24 and 307.67 m for barchan dune 5, respectively.
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Gadal, C., C. Narteau, S. Courrech du Pont, O. Rozier e P. Claudin. "Periodicity in fields of elongating dunes". Geology 48, n.º 4 (31 de janeiro de 2020): 343–47. http://dx.doi.org/10.1130/g46987.1.
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Abstract Dune fields are commonly associated with periodic patterns that are among the most recognizable landscapes on Earth and other planetary bodies. However, in zones of limited sediment supply, where periodic dunes elongate and align in the direction of the resultant sand flux, there has been no attempt to explain the emergence of such a regular pattern. Here, we show, by means of numerical simulations, that the elongation growth mechanism does not produce a pattern with a specific wavelength. Periodic elongating dunes appear to be a juxtaposition of individual structures, the arrangement of which is due to regular landforms at the border of the field acting as boundary conditions. This includes, among others, dune patterns resulting from bed instability, or the crestline reorganization induced by dune migration. The wavelength selection in fields of elongating dunes therefore reflects the interdependence of dune patterns over the course of their evolution.
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Mason, Jasmine, Benjamin T. Cardenas, Mackenzie D. Day, Max Daniller-Varghese, Sarah C. Brothers, Gary Kocurek e David Mohrig. "Pattern evolution and interactions in subaqueous dune fields: North Loup River, Nebraska, U.S.A." Journal of Sedimentary Research 90, n.º 12 (31 de dezembro de 2020): 1734–46. http://dx.doi.org/10.2110/jsr.2020.066.
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ABSTRACT A time series of aerial images of a dune field on a migrating free bar in the North Loup River, Nebraska, is used to generate a quantified dataset that allows analyses of crestline deformation, dune interaction type and spatial density, and impact of spurs. Measurement of dune parameters show that the dune field maintained a dynamic steady-state pattern, despite high rates of deformation, common interactions, and sediment bypassing. Mapped crestlines had a mean migration rate of 8 cm/min. The mean deformation rate, quantified using a partial Procrustes analysis, was 2 cm/min, indicating that along individual crestlines, local migration varied ± 25% from the bedform mean. Dune interactions caused the break-apart and recombination of crestline segments, thus limiting pattern variability caused by deformation. Although most of the 50 documented interactions are comparable to those observed in aeolian dune fields, defect-driven interactions are less common and interactions caused by migration of the convex-downstream nose of the dunes were observed, which has not been reported in aeolian dunes. The spatial density of interactions is consistent with that derived for aeolian crescentic-dune fields, in spite of differences in ambient fluid and dune size. Although spurs were ubiquitous, their presence did not have a quantifiable impact on deformation and interactions as compared to areas where spurs were absent, suggesting that these short-lived features affect instantaneous flux rates only.
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Janssen, Matthew S., Audrey Fanning, Jon K. Miller e Laura Lemke-Verderame. "PARAMETRIZING DUNE RESILIENCE FROM COLLISION THROUGH INUNDATION". Coastal Engineering Proceedings, n.º 37 (1 de setembro de 2023): 161. http://dx.doi.org/10.9753/icce.v37.management.161.
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Numerous studies have identified the protective benefit provided by dunes in shielding upland assets. However, dunes are susceptible to erosion. Breaches, overwash or significant overtopping of a dune are all associated with greater damages to upland infrastructure. Therefore, reliable tools are needed to efficiently assess the likelihood and magnitude of dune erosion during storm events. Existing methods rely on numerical modeling (extensive investment) or insufficiently parameterize the system. To fill this gap, a fragility model using a newly developed dune Engineering Demand Parameter (EDP) was introduced (Janssen and Miller 2022).
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Calafat, Antoni, Sara Vírseda, Raúl Lovera, Joan Ramon Lucena, Carme Bladé, Lluís Rivero e Josep M. Ninot. "Assessment of the Restoration of the Remolar Dune System (Viladecans, Barcelona): The Resilience of a Coastal Dune System". Journal of Marine Science and Engineering 9, n.º 2 (22 de janeiro de 2021): 113. http://dx.doi.org/10.3390/jmse9020113.
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The Remolar beach-dune system (700 m long and more than 100 m wide, 070N direction) borders a campground that was closed (2003), due to the Barcelona airport expansion. In order to recover and restore the dune ecosystem, a series of soft measures were performed. After 10 years, a study of the morphology, sedimentology, and vegetation of the ecosystem was carried out to evaluate the results of these measures. For this purpose, a series of topographic and ground-penetrating radar (GPR) profiles, grain-size analysis, and an analysis of plant communities found along the profiles were carried out. The data obtained were compared with data from a former 2004 study. The results show that the morphology of the dunes recovered, and a new primary dune has arisen. The system now has a greater process of aggradation than of progradation. The vegetation has recovered the global composition of dune systems, with a typical community of embryo dunes and others of primary dunes that are set in strips parallel to the coast. Despite this improvement, the opportunistic and ruderal component in the primary dune vegetation evidences a strong anthropic inheritance in the system.
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Wilson, Kat, e David Mohrig. "Signatures of Pleistocene Marine Transgression Preserved in Lithified Coastal Dune Morphology of The Bahamas". Geosciences 13, n.º 12 (28 de novembro de 2023): 367. http://dx.doi.org/10.3390/geosciences13120367.
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The morphology of some lithified wind-blown, carbonate dunes in The Bahamas preserves the signature of erosion from paleo-marine processes: wave-induced swash, scarping, and longshore transport. Digital elevation models were used to distinguish between two dune morphotypes—those disconnected versus connected to beach processes. Dune sinuosity and upwind slope were quantified and used to interpret which dunes remained beach-attached and subject to marine erosion and processes versus dunes that became disconnected from the shoreline via inland migration or shoreline regression. Disconnected dunes possess low slopes over stoss surfaces with sinuous planforms mimicking their crestlines. Beach-connected foredunes preserve steep, kilometers-long linear upwind faces, which are interpreted to be signatures of beach-dune morphodynamics. Foredune morphology serves as a proxy for shoreline position during past sea-level high-stands, while the basal elevations of their stoss dune toes provide an upper limit on the beach and adjacent sea level. A growing library of digital topography will allow for this tool to be used to interpret global paleo-shoreline positions through time and space.
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Manzolli, Rogério Portantiolo, Luana Carla Portz, Angela Fontán-Bouzas, Volney Junior Borges Bitencourt e Javier Alcántara-Carrió. "Contribution of Reverse Dune Migration to Stabilization of a Transgressive Coastal Dune Field at Lagoa do Peixe National Park Dune Field (South of Brazil)". Remote Sensing 15, n.º 14 (10 de julho de 2023): 3470. http://dx.doi.org/10.3390/rs15143470.
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Coastal dunes that transgress typically move landward, while their reverse movement is not well understood. The article discusses the study of barchan and barchanoid dunes in the Lagoa do Peixe National Park in the coastal plain of Rio Grande do Sul, Brazil. The aim of the study is to analyze seasonal patterns and long-term trends in the direction and migration rates of these dunes, which can pose a threat to the lagoon if they invade its space. The crest migration of 12 dunes was monitored by satellite images between July 2003 and December 2018, and DGPS topographic surveys were performed on five dunes between 2010 and 2018. The migration rates obtained were combined with an analysis of the meteorological data and calculations of the drift potential for eolian sediment transport. The wind regime in the study area shows a multidirectional pattern, with the predominant wind direction being from the NE, followed by the ENE direction. The wind direction also exhibits a seasonal behavior, with the winds from the first quadrant being dominant during spring and summer months and a gradual increase in winds from the second and third quadrants from the end of summer to winter. The dune crest migration rates in the Lagoa do Peixe National Park show an average of 16.55 m·yr−1 towards WSW–W, mainly controlled by the direction of the effective winds. However, intense SSW–WSW winds caused by cold fronts in the past generate the reverse migration of dunes towards ENE–E. The reverse migration of dunes explains the steadiness of the dune fields at CPRGS and is a factor controlling dune stabilization and the geomorphological evolution of transgressive coastal dune fields. The article highlights the importance of monitoring dune movement to understand their responses to natural and anthropogenic stressors and to protect sensitive ecosystems.
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Niu, Zhenmin, Nai’ang Wang, Nan Meng, Jiang Liu, Xueran Liang, Hongyi Cheng, Penghui Wen, Xinran Yu, Wenjia Zhang e Xiaoyan Liang. "Contribution of Lake-Dune Patterning to the Dune Height of Mega-Dunes in the Badain Jaran Sand Sea, Northern China". Remote Sensing 13, n.º 23 (3 de dezembro de 2021): 4915. http://dx.doi.org/10.3390/rs13234915.
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Mega-dunes in the lake group area of the Badain Jaran Sand Sea, China, are generally taller than dunes in the non-lake group area. This spatial distribution of dune heights may provide a new perspective on the controversy regarding the dunes’ formation mechanism. In this study, we calculated the relative heights and slopes of individual dunes based on a digital elevation model, and we confirmed the height distribution of abnormally tall dunes in the lake group area of the sand sea. It was also found that slopes of more than 10° in the lake group area are more common than those in the non-lake group area. Based on meteorological observations, coupled with the measurement of water content in the sand layers, we propose a conceptual model demonstrating that moisture exchange between the lakes and soil via non-rainfall water will humidify dune slopes and form a more favorable accumulation environment for aeolian sand, thus increasing dune heights. Although long-term observations are yet to be carried out, the present study can be used as evidence for understanding the basis of dune formation in the lake group area and assessing groundwater utilization in deserts.
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McCann, S. B., e M. L. Byrne. "Stratification models for vegetated coastal dunes in Atlantic Canada". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 96 (1989): 203–15. http://dx.doi.org/10.1017/s0269727000010939.
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SynopsisThe principal types of stratification and some characteristic sedimentary sequences found in vegetated coastal dunes in Atlantic Canada are described. Four examples are selected to show a range of dune types and depositional settings. In each case the documentation and interpretation of the internal structure and stratification has made an important contribution to understanding the evolution of the dunes. Stratification and depositional models are presented for:(1) a single, continuous, transgressive foredune ridge which maintains its form during transgression;(2) a discontinuous transgressive foredune ridge, interrupted by washover passages;(3) a “precipitation” dune, which buries an existing stable dune; and(4) complex dunes produced by two or more phases of aeolian activity characterised by different plant associations.
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Bierstedt, Svenja E., Birgit Hünicke, Eduardo Zorita e Juliane Ludwig. "A wind proxy based on migrating dunes at the Baltic coast: statistical analysis of the link between wind conditions and sand movement". Earth System Dynamics 8, n.º 3 (17 de julho de 2017): 639–52. http://dx.doi.org/10.5194/esd-8-639-2017.
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Abstract. We statistically analyse the relationship between the structure of migrating dunes in the southern Baltic and the driving wind conditions over the past 26 years, with the long-term aim of using migrating dunes as a proxy for past wind conditions at an interannual resolution. The present analysis is based on the dune record derived from geo-radar measurements by Ludwig et al. (2017). The dune system is located at the Baltic Sea coast of Poland and is migrating from west to east along the coast. The dunes present layers with different thicknesses that can be assigned to absolute dates at interannual timescales and put in relation to seasonal wind conditions. To statistically analyse this record and calibrate it as a wind proxy, we used a gridded regional meteorological reanalysis data set (coastDat2) covering recent decades. The identified link between the dune annual layers and wind conditions was additionally supported by the co-variability between dune layers and observed sea level variations in the southern Baltic Sea. We include precipitation and temperature into our analysis, in addition to wind, to learn more about the dependency between these three atmospheric factors and their common influence on the dune system. We set up a statistical linear model based on the correlation between the frequency of days with specific wind conditions in a given season and dune migration velocities derived for that season. To some extent, the dune records can be seen as analogous to tree-ring width records, and hence we use a proxy validation method usually applied in dendrochronology, cross-validation with the leave-one-out method, when the observational record is short. The revealed correlations between the wind record from the reanalysis and the wind record derived from the dune structure is in the range between 0.28 and 0.63, yielding similar statistical validation skill as dendroclimatological records.
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Mayer, James H., e Shannon A. Mahan. "Late Quaternary stratigraphy and geochronology of the western Killpecker Dunes, Wyoming, USA". Quaternary Research 61, n.º 1 (janeiro de 2004): 72–84. http://dx.doi.org/10.1016/j.yqres.2003.10.003.
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New stratigraphic and geochronologic data from the Killpecker Dunes in southwestern Wyoming facilitate a more precise understanding of the dune field’s history. Prior investigations suggested that evidence for late Pleistocene eolian activity in the dune field was lacking. However, luminescence ages from eolian sand of ∼15,000 yr, as well as Folsom (12,950–11,950 cal yr B.P.) and Agate Basin (12,600–10,700 cal yr) artifacts overlying eolian sand, indicate the dune field existed at least during the latest Pleistocene, with initial eolian sedimentation probably occurring under a dry periglacial climate. The period between ∼13,000 and 8900 cal yr B.P. was characterized by relatively slow eolian sedimentation concomitant with soil formation. Erosion occurred between ∼8182 and 6600 cal yr B.P. on the upwind region of the dune field, followed by relative stability and soil formation between ∼5900 and 2700 cal yr B.P. The first of at least two latest Holocene episodes of eolian sedimentation occurred between ∼2000 and 1500 yr, followed by a brief (∼500 yr) episode of soil formation; a second episode of sedimentation, occurring by at least ∼700 yr, may coincide with a hypothesized Medieval warm period. Recent stabilization of the western Killpecker Dunes likely occurred during the Little Ice Age (∼350–100 yr B.P.). The eolian chronology of the western Killpecker Dunes correlates reasonably well with those of other major dune fields in the Wyoming Basin, suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late Quaternary. Similar to dune fields on the central Great Plains, dune fields in the Wyoming Basin have been active under a periglacial climate during the late Pleistocene, as well as under near-modern conditions during the latest Holocene.
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Reddy, Dontireddy Venkat, Vuddaraju Singaraju, Rakesh Mishra, Devender Kumar, Puthusserry Joseph Thomas, Karra Kameshwa Rao e Ashok Kumar Singhvi. "Luminescence chronology of the inland sand dunes from SE India". Quaternary Research 80, n.º 2 (setembro de 2013): 265–73. http://dx.doi.org/10.1016/j.yqres.2013.06.003.
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Records of past climate changes have been preserved variously on the earth's surface. Sand dunes are one such prominent imprint, and it is suggested that their presence is an indicator of periods of transition from arid to less arid phases. We report inland sand dunes from Andhra Pradesh (SE India) spread over an area of ~ 500 km2, ~ 75 km inland from the east coast. The dune sands are examined to understand their provenance, transportation, timing of sand aggradation and their relationship to past climates. The dune distribution, grain morphology and the grain-size studies on sands suggest an aeolian origin. Physiography of the study area, heavy mineral assemblage, and abundance of quartz in the parent rocks indicate that the dune sands are largely derived from first-order streams emanating from hills in the region and from weathering of the Nellore schist belt. It appears that the geomorphology and wind direction pattern both facilitated and restricted the dune aggradation and preservation to a limited area. OSL dating of 47 dune samples ranged from the present to ~ 50 ka, thereby suggesting a long duration of sand-dune aggradation and/or reworking history.