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Desert Geomorphology
... Besides, the sand particles carried by the upwind flow are deposited when flow decelerates close to the building. The upwind deposition gradually grows, and eventually forms the so-called echo dune shape (Bagnold, 1941;Tsoar, 1983;Cooke et al., 1993;Qian et al., 2011;Jackson and Nordstrom, 2011). In addition, deposition occurs along the lateral faces of the building and continues somewhat downstream, approximately following the shape of the horseshoe vortex shown in Figure 1.3 (Poppema et al., 2021). ...
... The upwind deposition is similar to the so-called echo dunes that also develop in front of the vertical natural obstructions, e.g. cliffs, in sandy environments (Tsoar, 1983;Cooke et al., 1993;Jackson and Nordstrom, 2011;Qian et al., 2011). The sedi- ment accumulation in front of the building grows in size until its slope stands at the angle of repose of dry sand, approximately 34 • (Bagnold, 1941). ...
... Previous studies have examined morphological changes around buildings, while little attention has been paid to how and to what extent these changes depend on the positioning of buildings at the beach. The incident wind direction with respect to the buildings strongly influences the characteristics of the secondary flow patterns in the near-wake region which, in turn, determine the generation and development of sand shadows in the lee of buildings (Cooke et al., 1993;Becker et al., 2002;Luo et al., 2012;Unnikrishnan et al., 2017). In real beach conditions, buildings are mainly positioned close to each other due to the growth of beach tourism and high demand for centralized facilities on the limited land space at the beach. ...
Coastal zones worldwide have always been attractive to human populations because of their rich resources and recreational values. This leads to an increasing number of buildings at the beach-dune interface, such as hotels, restaurants, vacation houses and pavilions. Buildings at the beach locally change the airflow patterns in their surrounding area depending on their size, shape, orientation and positioning with respect to neighbouring buildings. These building-induced changes in wind flow field (speed and direction) alter aeolian sediment transport which, in turn, influence the morphologic patterns around buildings. For beach buildings placed in front of the dunes, these forced bedforms around buildings could negatively affect the dunes by e.g. trapping the sediments upwind of the buildings slowing down the dune growth. Furthermore, a large amount of sediment deposition or an intense erosion around buildings cause malfunctions in buildings. Coastal managers are responsible to define regulations for the design and placement of buildings at the beach. Understanding the airflow patterns and aeolian sediment transport around buildings could help to gain most benefits from buildings at the beach in regard to steering more sediments to dunes, or minimising their negative influence on dunes growth. To achieve this aim, a numerical model is developed using OpenFOAM and the influence of several parameters on airflow structures, aeolian sediment transport patterns and bedform development around buildings is investigated.
In Chapter 2, we quantified the influence of systematic changes in building dimensions, i.e. length, width and height, on airflow patterns around buildings. The divergence of the cubed horizontal wind velocity field was used as a proxy for wind-driven erosion and deposition patterns. Our results showed that the near-bed airflow structures and sediment transport patterns around buildings depend most on the building width perpendicular to the wind direction, whereas they are least dependent on the building length parallel to the wind direction. Numerical simulations showed sediment deposition at a small distance upwind of the buildings and two deposition tails starting from some distance away from the lateral sides of the building to downstream of the buildings. Strong scour occurs around the upwind corners of the buildings. However, less intense eroding regions have been found directly in front of the upwind face of the building and close to the lateral faces of the building. Our findings showed that relations exist between building characteristics and the size and intensity of the erosion-deposition patterns around buildings.
In Chapter 3, the influence of buildings positioning at the beach relative to the neighbouring buildings, and the orientation of a row of buildings with respect to the wind direction on near-bed airflow patterns was examined. The wind-induced bed shear stress calculated via the OpenFOAM model was used in Bagnold's equation to evaluate the sediment transport flux around buildings. The Exner formulation was used to estimate the initial rate of changes in bed elevation around buildings. Results showed that there is a critical gap size between adjacent buildings of 2w, where w is each building width, beyond which the airflow and sediment transport patterns form almost independently from patterns developed around neighbouring buildings. In that case, the adjacent buildings have minor impacts on each other and the resulting airflow and sediment transport patterns can be considered as more individual patterns around buildings. We also found that the orientation of buildings at the beach relative to the incident wind direction plays a key role in the formation of the vortices developing around buildings as well as their location, size and orientation. The characteristics of these vortices determine the sediment transport patterns in the vicinity of buildings. Next, the average sediment transport rates across along-shore lines downstream of the buildings were computed to gain insight on the influence of buildings on duneward sediment transport.
Finally, in Chapter 4, we investigated the influence of buildings placed on poles, and examined the systematic changes in building pole height on horizontal and vertical wind field as well as the sediment transport patterns. The Exner equation together with Bagnold's sediment transport formula were used to determine the initial bed level changes. Next, we developed a new model that couples the airflow model, OpenFOAM, with an existing sediment transport model, AeoLiS, to model the morphological evolution of the wind-driven bed patterns. The results of the average sediment transport rates across along-shore lines revealed that depending on pole height, the elevated buildings could both steer more sediments to the dunes hence enhancing the dunes growth, or they could block sediments upwind of the buildings therefore slow down the dunes growth.
Overall, this thesis provided new insights in the influence of buildings on potential duneward sediment transport and bed level changes in their surrounding. The guidance provided by this research could help coastal managers to decide on regulations in regards to beach buildings.
... The upwind deposition is similar to the so-called echo dunes that also develop in front of the vertical natural obstructions, e.g. cliffs, in sandy environments (Tsoar, 1983;Cooke et al., 1993;Jackson and Nordstrom, 2011;Qian et al., 2011). The sediment accumulation in front of the building grows in size until its slope stands at the angle of repose of dry sand, approximately 34 ...
... Previous studies have examined morphological changes around buildings, while little attention has been paid to how and to what extent these changes depend on the positioning of buildings at the beach. The incident wind direction with respect to the buildings strongly influences the characteristics of the secondary flow patterns in the near-wake region which, in turn, determine the generation and development of sand shadows in the lee of buildings (Cooke et al., 1993;Becker et al., 2002; Fig. 1. Examples of some buildings at the a, b) Kijkduin, and c, d, e) Katwijk beach, the Netherlands. ...
... In the lee of the gap, the air decelerates as it flows in a larger space and joins the undisturbed flow sufficiently downstream of the buildings. As a result, the sediment will deposit and form the so-called sand drift at a small distance downstream of the gap (Bagnold, 1941;Pye and Tsoar, 1990;Cooke et al., 1993;Luo et al., 2014;Luo et al., 2016;Poppema et al., 2022). First attempts to systematically study the impact of building positioning with respect to neighboring buildings and the prevailing wind on flow characteristics and the implications for sediment transport go back to the wind-tunnel studies by Luo et al. (2012), Luo et al. (2014) and Luo et al. (2016). ...
Buildings at the beach change the near-bed airflow patterns in the surrounding area. This induces alterations in wind-induced bed shear stress and wind-induced sediment transport which, in turn, affect the bed topography in the vicinity of buildings. Three-dimensional computational fluid dynamics simulations using OpenFOAM have been performed to understand how and to what extent the buildings at the beach influence the sediment transport from the beach to the dunes. Herein, we explicitly account for the positioning of the buildings with respect to each other and the dominant wind direction. Also discussed are the airflow mechanisms that are responsible for sediment transport, and how they alter due to systematic changes in the gap spacing between buildings and the wind incidence angle. Simulations were performed, in which we model flow and initial sediment transport around a repeating row of ten parallel full-scale beach buildings when the gap spacings and wind incidence angles were systematically varied. The horizontal near-bed streamline patterns showed that there is a critical gap spacing, below which the neighboring buildings significantly affect each other. Furthermore, the airflow in the near-wake region behind the row of buildings is quite complex. The shape and the extent to which the sand drifts develop behind the gaps between buildings are largely influenced by the wind direction, relative to the buildings. We also computed the average sediment transport flux along different lines downstream of the buildings. Our findings showed that, depending on the buildings’ positioning at the beach, they could have negative effects on dune growth by obstructing the sediment particles from moving downstream, or they could have positive effects on dune growth by steering the airflow and supplying more sediment downstream.
... Livingstone and Warren (1996) classified dune field patterns as transverse dunes, linear dunes, and star dunes. In our study region, the patterns also included crescent dunes and chains, coppice dunes, and sand sheets (Cook et al., 1993). For the desert and oases boundary were not our main research aims, we used HJ-1A/B remote-sensing images with 30 m spatial resolution obtained from the China Center for Resources Satellite Data and Applications (http://www.cresda.com/n16/n92006/n92162/ ...
... Dunes in this desert include crescent dunes, coppice dunes, reticulate dunes, linear dunes, star dunes, and so on. Reticulate dunes are also known as "dune networks," "dune reticules," "aklés," "rhombic waffle patterns," or "alveolar dunes" (Cook et al., 1993). They develop under a wind regime with a bidirectional wind regime where the dominant wind directions are perpendicular (Cook et al., 1993;Livingstone and Warren, 1996;Hasi et al., 1999;Ewing et al., 2006;Zhang et al., 2015) and are characterized by network patterns (Zhang et al., 2015b, Zhang et al., 2015c. ...
... Reticulate dunes are also known as "dune networks," "dune reticules," "aklés," "rhombic waffle patterns," or "alveolar dunes" (Cook et al., 1993). They develop under a wind regime with a bidirectional wind regime where the dominant wind directions are perpendicular (Cook et al., 1993;Livingstone and Warren, 1996;Hasi et al., 1999;Ewing et al., 2006;Zhang et al., 2015) and are characterized by network patterns (Zhang et al., 2015b, Zhang et al., 2015c. Crescent dunes and chains develop under a unidirectional wind regime or a bidirectional wind regime with dominant winds in opposite directions. ...
The middle areas of China’s Hexi Corridor Desert are distributed within or at the edge of oases in continental river basins in Northern China. Recently, researchers found that rivers can provide sediment material for dune formation and development, but the mechanism has not been investigated in detail. In this study, the relationships among the wind environment, spatial distribution of continental rivers, sand availability, and dune field patterns in the middle area of Hexi Corridor Desert were analyzed. In terms of the wind energy environment, the study area can be divided into three regions: high-energy environment in the north, intermediate-energy environment in the middle, and low-energy environment in the south. The results showed that the resultant drift potential is predominantly from the NW quadrant. The directional variability of wind is intermediate in the northern and middle region and low in the southern region. The directions of winds with critical speed are SW in the northern region, NW and WNW in the middle region, and NW in the southern region. The main dune types are barchans, reticulate dunes, star dunes, linear dunes, and coppice dunes, which differ from previous results (mainly barchans and coppice dunes). Dune field patterns are controlled by the wind energy environment. In addition, the spatial distribution of continental rivers and sand availability are important factors affecting dune formation and development. Sand dunes are distributed downwind of continental rivers, which confirms the hypothesis that rivers can provide sediment material for dune formation. The spatial distribution and different dune types in the middle area of Hexi Corridor Desert reveal that their formation and development are controlled by the wind regime and sediment supply.
... A useful starting point for a discussion of dryland river characteristics is again to stress the great diversity of drylands. Drylands are characterized by varied degrees of aridity, and exist across a wide range of tectonic, structural, lithological, and phytogeographical settings (Cooke et al., 1993;Thomas, 1997a;Parsons and Abrahams, 2009). These environmental factors impact directly and indirectly on dryland river process, form, and behavior through their influence on gross physiography, runoff, and sediment supply. ...
... Generalizations drawn from a small, steep river in a tectonically active catchment underlain by folded and fractured sedimentary rocks most likely will not be applicable to larger, lower-gradient rivers in tectonically stable, granitic catchments. The differences between dryland rivers certainly can be downplayed in the interests of drawing greater contrasts between dryland and humid region fluvial geomorphology (e.g., Rodier, 1985;Graf, 1988a;Frostick, 1994, 1997;Cooke et al., 1993;Thornes, 1994aThornes, , 1994bKnighton and Nanson, 1997;Nanson and Tooth, 1999) but it is vitally important to be aware of the limitations to this approach and to note any exceptions arising. ...
... Variability in transmission losses can be particularly marked in very large catchments and where discrete convective storms are the primary moisture source. Individual convective storms are typically o10-14 km across and therefore are unlikely to wet the entire catchment, and successive storms may wet different parts of the catchment (Cooke et al., 1993;Reid and Frostick, 1997;Bull et al., 1999;Tucker et al., 2006). Some tributaries may flow while neighboring tributaries remain dry, and the active tributaries may contribute flow to the trunk channel before the main floodwave arrives. ...
The idea that dryland fluvial environments are somehow distinctive or even unique compared to fluvial environments in wetter and/or cooler climatic settings has arisen in much of the literature, despite the fact that drylands are themselves inherently diverse, covering a wide range of local climatic, tectonic, structural, lithological, and phytogeographical settings. Focusing on rivers in warm drylands, this chapter outlines the main characteristics of dryland rivers, including flow and sediment transport conditions, channel forms and dynamics, channel and floodplain sedimentology, and equilibrium and nonequilibrium behavior. Although dryland rivers are commonly ascribed a set of restricted characteristics that have been derived mainly from studies in short, steep, tectonically active catchments, investigations in larger, lower-gradient, tectonically stable catchments have revealed much greater diversity in river character both within and between drylands, and have demonstrated overlap with river characteristics in other climatic settings. With this global perspective, I argue that many previous statements regarding the distinctiveness of dryland river characteristics either can no longer be sustained as generalizations, or, at the very least, the geographical and geomorphological contexts for those generalizations need to be clarified. One of the key priorities for future research will be to identify and explain the spatial extent and frequency of occurrence of river styles across different drylands. In particular, research into the controls of meandering, straight, and anabranching rivers characteristic of some moderate-to low-energy Southern Hemisphere drylands has not only contributed to greater appreciation of the global diversity of dryland rivers but is also leading to a better understanding of rivers in general. Technological and methodological developments (especially in geochronology) are enhancing understanding of dryland river process, form, and change, and this will continue to facilitate interdisciplinary work in diverse scientific and applied contexts.
... This created a cohesive shell layer that effectively prevented the transport of underlying sand grains. Despite the difference in residual material, this process is similar to the Saharan "regs" (Cooke, Warren, and Goudie, 1993). Experiments by Cheng et al. (2021) explain the development of surface armoring and show that ripples cannot develop above 15%-20% shell in the sediment. ...
... The rapid and repeated volume changes due to salt growth and subsequent salt solution widen the cracks and facilitate further fracturing of the quartz grains by mechanical marine and eolian impacts. This process of "salt weathering" (or "haloclasty") is known to produce silt from quartz disaggregation (Cooke, Warren, and Goudie, 1993;Goudie, Cooke, and Doornkamp, 1979), but it has never been described in a tidal flat. The frequent presence of euhedral NaCl crystals and tiny silica fragments scattered on the surface of the grains ( Figure 7D,F), but especially their abundance near the salt crystals, suggests the importance of this mechanism, which may be an additional, although minor, source of silt on the tidal flat. ...
Battiau-Queney, Y.; Ventalon, S.; Abraham, R.; Sipka, V.; Cohen, O., and Marin, D., 2024. Bedforms and sedimentary features related to water-depth variations in a sandy tidal-flat environment. Journal of Coastal Research, 40(1), 80-103. Charlotte (North Carolina), ISSN 0749-0208. This study highlighted the variability of a wide sandy macrotidal coastal system on short timescales. Changes in water depth and exposure length were the main drivers of this variability. In the study area, the coastal system consists of three units: a lower ridge-and-runnel beach, a 1000-m-wide tidal flat, and a sandy backshore. This research is based on sedimentary features that can record physical forces, especially the bedforms at the beach surface, and their relationship with beach gradient, exposure length, and changing water depth, according to tidal, weather, and marine conditions. It also demonstrated the ability of scanning electron microscope analysis of quartz grain microtextures to indicate the level of marine and eolian energy in the coastal system. The widespread wave and current sand ripples on the tidal flat showed great variability in time and space. A minimum water depth of 0.30 to 0.50 m was required for their development. The role of wind-induced waves and the frequent interference of tidal, wave, and wind forcing mechanisms are emphasized. The development of some complex sand ripples extended over a complete lunar tidal cycle. Wind-generated sand ripples were observed only on the backshore. Their absence on the tidal flat, despite the high level of eolian energy attested by quartz microtextures, and the poor development of dunes on the backshore are explained by factors impeding eolian sand transport at the beach surface such as extreme fetch segmentation and possible shell armoring of the beach surface during dry periods. This study demonstrated the short-term variability of the beach morphology as opposed to the long-term stability of the coastal system as a whole, in which the ultradissipative tidal flat, characterized by limited sand supply, low wave energy, and high but inefficient wind energy, plays a key role.
... This created a cohesive shell layer that effectively prevented the transport of underlying sand grains. Despite the difference in residual material, this process is similar to the Saharan "regs" (Cooke, Warren, and Goudie, 1993). Experiments by Cheng et al. (2021) explain the development of surface armoring and show that ripples cannot develop above 15%-20% shell in the sediment. ...
... The rapid and repeated volume changes due to salt growth and subsequent salt solution widen the cracks and facilitate further fracturing of the quartz grains by mechanical marine and eolian impacts. This process of "salt weathering" (or "haloclasty") is known to produce silt from quartz disaggregation (Cooke, Warren, and Goudie, 1993;Goudie, Cooke, and Doornkamp, 1979), but it has never been described in a tidal flat. The frequent presence of euhedral NaCl crystals and tiny silica fragments scattered on the surface of the grains ( Figure 7D,F), but especially their abundance near the salt crystals, suggests the importance of this mechanism, which may be an additional, although minor, source of silt on the tidal flat. ...
Battiau-Queney, Y.; Ventalon, S.; Abraham, R.; Sipka, V.; Cohen, O., and Marin, D., 0000. Bedforms and sedimentary features related to water-depth variations in a sandy tidal-flat environment. Journal of Coastal Research, 00(00), 000-000. Charlotte (North Carolina), ISSN 0749-0208. This study highlighted the variability of a wide sandy macrotidal coastal system on short timescales. Changes in water depth and exposure length were the main drivers of this variability. In the study area, the coastal system consists of three units: a lower ridge-and-runnel beach, a 1000-m-wide tidal flat, and a sandy backshore. This research is based on sedimentary features that can record physical forces, especially the bedforms at the beach surface, and their relationship with beach gradient, exposure length, and changing water depth, according to tidal, weather, and marine conditions. It also demonstrated the ability of scanning electron microscope analysis of quartz grain microtextures to indicate the level of marine and eolian energy in the coastal system. The widespread wave and current sand ripples on the tidal flat showed great variability in time and space. A minimum water depth of 0.30 to 0.50 m was required for their development. The role of wind-induced waves and the frequent interference of tidal, wave, and wind forcing mechanisms are emphasized. The development of some complex sand ripples extended over a complete lunar tidal cycle. Wind-generated sand ripples were observed only on the backshore. Their absence on the tidal flat, despite the high level of eolian energy attested by quartz microtextures, and the poor development of dunes on the backshore are explained by factors impeding eolian sand transport at the beach surface such as extreme fetch segmentation and possible shell armoring of the beach surface during dry periods. This study demonstrated the short-term variability of the beach morphology as opposed to the long-term stability of the coastal system as a whole, in which the ultradissipative tidal flat, characterized by limited sand supply, low wave energy, and high but inefficient wind energy, plays a key role. ADDITIONAL INDEX WORDS: Marine energy, wind energy, SEM quartz microtextures, sand ripples, wind waves, sediment supply, French North Sea coast.
... The flow deceleration upwind of the buildings and in the shadow zone just behind the buildings decreases the wind-induced sediment carrying capacity. This results in decreased sediment transport flux and subsequent sediment deposition (Cooke et al., 1993;Qian et al., 2011;Jackson and Nordstrom, 2011;Luo et al., 2012). Conversely, flow acceleration occurs as air moves around and underneath buildings, as well as through gaps between neighbouring structures. ...
... These considerations should account for both recreational demands and nature-based flood defense strategies. Previous studies on the morphological impacts of beach buildings have mainly focused on identifying erosion and deposition patterns that form around buildings on the sedimentary bed (Bagnold, 1941;Pye and Tsoar, 1990;McKenna Neuman and Bédard, 2015;Tominaga et al., 2018), and how these patterns depend on buildings characteristics such as geometry and size (Iversen et al., 1991;Cooke et al., 1993;Poppema et al., 2021;Pourteimouri et al., 2022) as well as buildings positioning such as orientation and spacing from each other (Luo et al., 2012;Luo et al., 2014;Luo et al., 2016;Poppema et al., 2022;Pourteimouri et al., 2023). However, scientific research investigating the impact of elevated buildings on bed level changes and the subsequent influence on duneward transport, based on varying pole heights, is lacking. ...
... The flow deceleration upwind of the buildings and in the shadow zone just behind the buildings decreases the wind-induced sediment carrying capacity. This results in decreased sediment transport flux and subsequent sediment deposition (Cooke et al., 1993;Qian et al., 2011;Jackson and Nordstrom, 2011;Luo et al., 2012). Conversely, flow acceleration occurs as air moves around and underneath buildings, as well as through gaps between neighbouring structures. ...
... These considerations should account for both recreational demands and naturebased flood defense strategies. Previous studies on the morphological impacts of beach buildings have mainly focused on identifying erosion and deposition patterns that form around buildings on the sedimentary bed (Bagnold, 1941;Pye and Tsoar, 1990;McKenna Neuman and Bédard, 2015;Tominaga et al., 2018), and how these patterns depend on buildings characteristics such as geometry and size (Iversen et al., 1991;Cooke et al., 1993;Poppema et al., 2021;Pourteimouri et al., 2022) as well as buildings positioning such as orientation and spacing from each other (Luo et al., 2012;Luo et al., 2014;Luo et al., 2016;Poppema et al., 2022;Pourteimouri et al., 2023). However, scientific research investigating the impact of elevated buildings on bed level changes and the subsequent influence on duneward transport, based on varying pole heights, is lacking. ...
... Dong et al., 2018, Figure 1). Hack (1941) proposed the concept of climbing dunes when describing dune landforms in the western part of the Navajo tribal lands in the southwestern United States, and surmised that climbing dunes were formed by sand particles deposited along rising slopes when sand carried by aeolian transport encounters a topographic barrier, These features can be classified as topographic barrier dunes (Cooke et al., 1993;Haney & Grolier, 1991;Lancaster & Tchakerian, 1996;Meng et al., 2018;Qian et al., 2012;Tsoar, 1983). Lancaster and Tchakerian (1996) found that large amount of sand often accumulates on the windward flanks of mountain ranges. ...
... Previous studies have explored the formation processes, influential factors, morphological characteristics and development of barchan dunes, pyramid dunes, and shrub dunes in wind-tunnel experiments (Cai et al., 2021;Yang et al., 2019;Zhao et al., 2019). Wind-tunnel experiments by Cooke and Warren (1973) and Cooke et al. (1993) showed that when the windward gradient is small, the sand particles were able to climb the slope primarily by saltation under the action of airflow, thus forming climbing dunes. However, when the surface gradient is steep, echo dunes form at the foot of the slope due to eddy currents along the sloping surface. ...
Climbing dunes are typical aeolian landforms. The study of their formation and development mechanisms is necessary for the prevention and control of dune migration. The gradient and shape are important geomorphic factors affecting the formation of climbing dunes, but their influencing mechanism is not clear at present. In this work, wind speed and sand deposition on a sloping surface were monitored at a constant wind speed of 8 m s⁻¹ in wind‐tunnel experiments, under six gradients (8°, 15°, 25°, 35°, 45°, and 55°) and five shapes (planar, concave, convex, concave‐convex, and stepped). The results show that (a) The flow field structure was affected by gradient and shape of the surface. The influences of flow field expanded both horizontally and vertically as the gradient increased; while at the 25° gradient, the horizontal range of influence was similar, but the vertical influence varied with different shapes. (b) The development of the sand deposition on a sloping surface could be divided into two stages. First, sand deposition occurred rapidly and climbing height, deposition area and deposition amount increased. After the surface was filled, the deposition on the surface slowed down and stabilized. (c) When the surface shape is flat, 25°–35° is the easiest gradient to form climbing dunes. Concave and stepped surfaces were more prone to form climbing dunes than were surfaces of other shapes. Those preliminary findings may enhance our understanding the formation of climbing dunes as well as provide useful references for reducing their influences upon the arid environment.
... Nebkhas are unique biogeomorphological features that are formed by aeolian sand accumulating around clumps of vegetation or single shrubs in arid and semi-arid environments (Cooke et al., 1993;Tengberg and Chen, 1998;Lancaster et al., 2013;Wang et al., 2017). They usually have the form of a mound and are also called coppice dunes or hummock dunes in arid and semi-arid environments (Fig. 1). ...
... In recent years, nebkhas have drawn considerable attention in the aeolian research community due to their biogeomorphological origin and potential connection with environmental change. It is recognized that the formation of nebkhas is related to the interaction of plant growth, aeolian sand accumulation, and flow structures over the dunes (Cooke et al., 1993;Wang et al., 2010;Hesp and Smyth, 2017;Zhao et al., 2021). Many factors including the wind regime, sediment supply and plant traits have been identified as key factors that influence nebkha formation (Tengberg, 1995;Tengberg and Chen, 1998;Wang et al., 2008Wang et al., , 2010. ...
Nebkhas, also known as nebkha dunes or coppice dunes, are a unique biogeomorphological aeolian landform that is common in arid and semi-arid regions. They are often regarded as a signal of regional desertification and could be potential dust sources due to their relatively large content of fine sediments, but they also serve as “fertile islands” that enhance biodiversity at a micro-habitat. How the interactions between plant growth and aeolian sand deposition affect the formation and development of nebkhas has not been well documented, though. In this study, the chronology and morphological features of nebkhas in the Mu Us dune field, north-central China were studied using radionuclide (¹³⁷Cs) dating and unmanned aerial vehicle (UAV) photogrammetric survey. The results show that the nebkhas are mainly distributed around lake basins and dry river valleys with relatively flat topography. Most nebkhas have heights around 0.5-1.5 m, and according to a new integrated age-height model, they mostly formed in the last fifty years. Widespread nebkha growth over that time is interpreted as a response to both desiccation of lake beds and river valleys and a pronounced decline in strong wind frequency. The regular rounded shape of the nebkhas in the study area may reflect the growth form of prostrate, extensively branched Nitraria tangutorum, the dominant formative shrub, and response to the low-energy wind environment. A nebkha’s height and horizontal length increase synchronously in the early stage of the development, while the increase in horizontal length and projected area accelerates when the dunes become larger. Feedbacks involving both aeolian sand transport and shrub growth can explain a decline in growth rate with increasing height and an apparent height limit of about 4 m. This study also implies that nebkhas are important biogeomorphological features demonstrating how biotic and abiotic interactions can shape landforms and influence ecological functioning in arid and semi-arid environments.
... Deserts are one of the major land-cover types, covering approximately one-third of the terrestrial area of the earth [1]. Due to topography, atmospheric circulation, latitude, ocean currents, etc., deserts, as a product of arid climatic conditions, are mostly located on the western coasts of continents near 30˚north and south latitude [2,3]. There is still no universally accepted common or technical definition for deserts, only distinguished by characteristics (e.g., climate, weather, and hydrology) [4]. ...
... And it has been widely used in analyses of NDVI trends [39,[61][62][63]. The Mann-Kendall test was computed using Eqs (2)(3)(4). ...
Vegetation, which is a good indicator of the impacts of climate variability and human activities, can reflect desert ecosystem dynamics. To reveal the vegetation variations in China’s deserts, trends in the monthly, seasonal, and annual normalized difference vegetation index (NDVI) from 2000 to 2017 were measured both temporally and spatially by the Theil-Sen estimator and Mann-Kendall test. Additionally, correlation coefficients and residual analysis were employed to evaluate the correlations between the NDVI and climatic factors and to distinguish the impacts of climate variability and human activities. The results showed that China’s deserts underwent greening. The annual NDVI showed a significant increasing trend at a rate of 0.0018/yr, with values of 0.094 in 2000 and 0.126 in 2017. Significant increasing trends in NDVI were observed in all four seasons. The NDVI were higher in summer and autumn than in spring and winter. Both the monthly NDVI and its trends showed an inverted U-shaped curve during the year. Spatially, the greening trends were mainly distributed on the southern edge of the Gurbantunggut Desert, in the northwestern part of the Taklimakan Desert, and in the Kubuqi Desert. The correlations between the NDVI and climatic factors at the monthly and seasonal scales were stronger than those at the annual scale. Temperature and precipitation had positive effects on NDVI at the monthly and seasonal scales, but only precipitation had a positive effect at the annual scale. Human activities, especially oasis expansion and sand stabilization measures, were two major causes of large increasing areas of desert greening in China indicated by the NDVI.
... Por otra parte, la presencia de flujos granulares (litofacies Smg(Ae)) indica que la cara de avalancha tenía una pendiente entre 32°-34° (Mountney, 2006;Bristow y Mountney, 2013), por lo que el ángulo de la cara de avalancha fluctúa temporalmente. La geometría sinuosa de la cresta se relaciona a dunas tridimensional o 3D (Rubin, 1987a, Mountney, 2006) y se clasifican como dunas activas si se consideran las superficies de reactivación (Cooke et al., 1993). Estas últimas se producen por (i) variación en la morfología y escala de la duna, produciendo una redistribución en la estratificación (Rubin, 1987a;Mountney, 2006); (ii) cambio de velocidad o de la dirección del viento (Brookfield, 1977;Kocurek, 1981); y (iii) únicamente por cambio de la dirección del viento (Hunter, (Rubin, 1987a,b;Mountney 2006). ...
... La falta de separación de flujo se evidencia por la ausencia de láminas tangenciales y asintóticas al pie del depósito (Hunter, 1977). Cuando la cresta de la duna es recta se la clasifica como bidireccional o 2D (Rubin, 1987a,b) y si se encuentra limitada por superficies de reactivación se la denomina activa (Cooke et al., 1993). El origen de las superficies de reactivación se interpreta asociada a los mismos procesos que afectan a las dunas eólicas de cresta sinuosa. ...
Se presenta un estudio sedimentológico de una sucesión eólica-fluvial de 29,5 m de
potencia perteneciente a la Formación Santa Cruz (Mioceno medio) en afloramientos
del Cañadón Ferrays, ubicados a 35,5 km al noroeste de Comodoro Rivadavia y sobre la
Ruta Nacional Nº 3. Se identificaron catorce (14) litofacies, ocho (8) asociadas a
procesos de transporte subáereos y seis (6) a procesos subácueos. De acuerdo con su
agrupación, se definieron nueve (9) asociaciones de litofacies: 1) duna eólica de cresta
sinuosa, 2) duna eólica de cresta recta, 3) interduna seca, 4) laguna de interduna
húmeda, 5) lóbulo de descarga proximal de interduna húmeda, 6) lóbulo de descarga
distal de interduna húmeda, 7) canal fluvial de régimen efímero, 8) canal fluvial de
régimen permanente, y 9) manto de arena. Se interpretaron dos sistemas
depositacionales eólicos (SD I y SD II) con sub-sistemas (o secciones) establecidas en
base a la arquitectura eólica, formas depositacionales, y relación del nivel freático con la
superficie. El SD I se interpreta como un sistema eólico húmedo, y el SD II como un
sistema eólico seco, separados entre sí por una supersuperficie.
El SD I inferior se compone principalmente por dunas eólicas 3D con dirección de
paleoflujo hacia el ENE, y constituye un sistema de draa compuesto. En este subsistema se reconocieron lagunas de interduna húmeda y canales fluviales de régimen permanente y efímero. Hacia arriba evoluciona a un campo de dunas estabilizadas,
asociadas a un estadío con nivel freático situado próximo a la superficie, que permitió el
desarrollo de actividad biológica y la cementación de los estratos.
El SD I superior está compuesto por depósitos de interduna húmeda, con escasas
dunas eólicas de cresta recta y sinuosa, con paleoviento dominante al NO y subordinado
al SO, y canales fluviales de régimen efímero. Se registran lóbulos de descarga
proximal y distal que desembocan en lagunas, asociadas al incremento máximo del
nivel freático luego de precipitaciones inusuales que provocan inundaciones. El límite
del SD I superior y SD II inferior está definido por una supersuperficie, que se interpreta
asociada a un cambio climático hacia condiciones más áridas.
La sección inferior del SD II se inicia con un manto de arena asociado a un período
de estabilización que controló la deflación, producto del nivel freático próximo a la
superficie y estable. Por encima, el tramo alto de la sección inferior del SD II contiene
elementos arquitecturales de interduna seca, dunas de cresta recta y dunas de cresta
sinuosa, con paleovientos hacia el SSE y NO. Estos depósitos son atravesados por
canales fluviales de carácter efímero, producto de precipitaciones inusuales y períodos de alta descarga. Este sub-sistema presenta escasa continuidad lateral y vertical, y se
interpreta como un período de transición con la sección superior del SD II. Este último
se caracteriza por dunas de cresta sinuosa, y en menor proporción dunas de cresta recta,
con leve aumento de la potencia de las dunas, aumento de su continuidad lateral, y
ausencia de zonas de interduna. Los paleovientos presentan sentido dominante al NO, y
subordinado al SSO. La ausencia de depósitos de interduna del sub-sistema superior del
SD II se asocia a altas tasas de migración de las dunas eólicas en relación a la tasa de
agradación del sistema depositacional. Las dunas eólicas conforman un draa con formas
sobreimpuestas, que en conjunto definen dunas lineales sinuosas. La sección superior
del SD II se caracteriza por un nivel freático por debajo de la superficie, disminución o
nula deflación, aumento del aporte sedimentario y condiciones de aridización
progresiva. La variación del régimen eólico de húmedo a seco se asocia a un cambio
climático de húmedo a seco durante el Mioceno medio, aunque su real extensión dentro
de la cuenca es actualmente desconocida.
Se complementó la información sedimentológica mediante la realización de 77
perfiles de rayos gamma total (GR) y espectral (SGR), utilizados para establecer
relaciones entre la radioactividad y litología, granulometría, y asociaciones de
litiofacies. Se realizaron perfiles con 50 cm de resolución vertical y separación lateral de
1 m, 5 m y 10 m. Pese a la homogeneidad litológica de la sucesión analizada, los datos
del contenido radioactivo ajustados con los datos de litofacies permiten diferenciar
algunas de las asociaciones de litofacies, particularmente aquellas con contraste
granulométrico, aunque el solapamiento estadístico de las lecturas es elevado. La
confección de mapas 2D de la distribución del contenido radioactivo utilizando
diferentes separaciones laterales muestra una adecuada correspondencia con las
asociaciones identificadas, especialmente cuando existe contraste litológico. Además,
los mapas 2D permitieron analizar de forma cualitativa la distorsión en el curveo del
contenido radioactivo en relación a la continuidad real de los depósitos, destacando que
mientras mayor es la separación las extrapolaciones son más imprecisas. Debido a la
granulometría relativamente homogénea (areniscas medianas a muy finas) de la mayoría
de los depósitos eólico-fluvial, la diferenciación de litofacies y asociaciones de
litofacies no es concluyente. Este estudio sedimentológico, de carácter local, ha
incrementado el conocimiento sedimentológico de la Formación Santa Cruz, alentando
la realización de estudios regionales que permitan integrar estos resultados en un
contexto regional.
... These two aeolian deposits differ 57 from each other as TSS do not display well-defined dune formation, instead, they 58 have minimal dunes or slipface-less dunes on their surface, whereas TDf can 59 present various types of dunes and may present sand sheets, various depositional 60 units such as nebkha fields and gegenwalle ridges, and erosional remnant knobs 61 (Hesp, 2013). Nebkhas are discrete dunes formed by aeolian deposition among 62 individual plants or a group of plants (Cooke et al., 1993;Hesp and Smyth, 2019). 63 They are common in arid regions and may comprise a foredune zone or be 64 scattered thoughout dunefields (Hesp et al., 2021;. ...
Transgressive sand sheets (TSS) and transgressive dunefields (TDf) over time often present multiple phases of development and a variety of morphologies controlled by biogeomorphological interactions related to abiotic processes, vegetation, and human interference. While dunefileds have experienced an increase in vegetation cover over the last decades worldwide, a few places have shown an increase in dune mobility. In this study, a GIS analysis was conducted using aerial photographs and satellite imagery to investigate the evolution of a TDf, foredune collapse, TSS formation and vegetation cover in a Holocene coastal barrier in southern Brazil over the last 75 years. Vegetation cover exhibited an increasing trend, and both increase and decrease in TDf and TSS movement were concurrent. Correlation analyses revealed a strong negative correlation between vegetation cover and TDf movement. Three phases of transgressive sand sheet formation were identified between 1948 and 2023 (1964 to 1975,1996 to 2000 and from 2010 until 2023). Post-2003, a poorly vegetated nebkha-dominated foredune subsequently collapsed and was replaced by a TSS in less than a decade, being fully formed in 2010 and continuing to move inland at rapid rates. In the third phase, the highest total TSS movement exceeded 700m in 12 years (from 2010 to 2022). Possible drivers for TSS formation include an increase in sand drift potential (DP), climatic modes, negative precipitation anomalies and groundwater level depletion in addition to anthropogenic actions that might cause negative feedback in foredune sand-biding vegetation.
... Barchan dunes are crescentic dunes classically formed in a supplylimited environment, uni-directional wind and no vegetation (Bagnold, 1941;Cooke et al., 1993;Elbelrhiti, 2012). They are usually discrete although sometimes merged with another dune (Assis et al., 2022), and they occur in both coastal and continental regions (Finkel, 1959;Hesp & Hastings, 1998). ...
Barchan dunes do not often coexist with grasslands. However, in Gonghe Basin, northeastern part in Qinghai-Tibetan Plateau (QTP), China, many barchan dunes are distributed on the grassland at high altitude. Identifying celerity and morphodynamics of barchan dunes and exploring the interaction between barchans and grassland landscape can help us better understand aeolian system sand mitigate damages. In this work, we tracked dune celerity and observed three-dimensional changes of symmetrical and asymmetrical barchan dunes in Ertala based on high-resolution UAV-SfM reconstruction in short-term monitoring and discussed the factors influencing dune celerity and deformation at high altitude. The results revealed that the barchan dunes are highly mobile with an average celerity of 0.85 m/M for the whole study area. Based on observations of dune morphology and dynamics, we found the following: (1) The dune deformation degree in a short time is not large but is widespread, especially in the elongated arm of asymmetric dune. The deformation of symmetric dune is symmetrical, whereas that of dune with extended horn is asymmetrical; (2) the sand supply, vegetation and airflow at low air density all influence the celerity and deformation degree in the development of barchan dunes; (3) the asymmetric airflow and sediment supply are important cause of dune asymmetry. The above results help us understand the deformation of barchan dune from the three-dimensional, especially the difference reflected by the symmetry of barchan dune at high altitude. K E Y W O R D S asymmetrical and asymmetrical barchan dunes, deformation, dune celerity
... Yardangs are aeolian erosional features in the form of wind-abraded ridges of cohesive material (Cooke et al. 1993, Parsons and Abrahams 1994, Goudie 2004. These aeolian landforms are composed of alternating ridges and corridors and have been reported from numerous arid regions on Earth and other planets, including Mars, Titan and Venus (Ward & Greeley 1984, Greeley et al. 1995, Ding et al. 2020, Paillou & Radebaugh 2013. ...
In many localities on earth and other solid planets, yardangs as the most spectacular aeolian landscapes. In the region of Dakhla (Morocco), yardangs are hills with a « teardrop » shape and a typical orientation NNE as it the orientation expressing prevailing winds. The conjunction of deflation and abrasion in a desert zone with sparse vegetation such as our study area, may be up the formation and evolving reliefs into these regular morphologies.
This study presents the first identification of the yardangs sculpted into Quaternary and Plio-quaternary formations during the Holocene in the Moroccan Sahara. In addition, this primary work focus on their geomorphological and lithological characteristics. The statistical results made on morphometric parameters provide valuable information for further investigations. Several data (lithology, topography, climate, etc.) and the comparison with other localities in the world have allowed discussing the factors and phases of the evolution of this wind erosion landscape.
... A barchan dune is a slowly moved crescent-shaped sand body formed by winds that moves the sand on its windward side and forms a slip face on the lee side (Bagnold 1941;Cooke et al. 1993). Barchan has been published under different names, e.g., barcan, barchan, barkan, and barkhan (Glenn 1979). ...
Barchan dunes of the Kharga Depression, Western Desert, Egypt, have been assessed in terms of their morphometry, grain size, and migration rate using remote sensing and GIS techniques and field and laboratory work. Thirty-seven sites were chosen along the Kharga dune belt and subdivided into northern, central, and southern sectors. At each site, several barchans were subjected to morphometric measurements (length, width, height, length of eastern and western horns, and length of windward and leeward sides). The rate and direction of 160 barchans were also measured for the period between 2002 and 2018. Grain size analysis was carried out on sand samples taken from the crest of these dunes. Statistically, significant relationships have been found between the morphometric parameters, dune migration, and grain size attributes. The analysis of the morphology of the barchan dunes, their movement, and the nature of sedimentary materials provide essential information for assessing and evaluating their environmental hazards.
... Yardangs are aeolian erosional features in the form of wind-abraded ridges of cohesive material (Cooke et al. 1993, Parsons and Abrahams 1994, Goudie 2004. These aeolian landforms are composed of alternating ridges and corridors and have been reported from numerous arid regions on Earth and other planets, including Mars, Titan and Venus (Ward & Greeley 1984, Greeley et al. 1995, Ding et al. 2020, Paillou & Radebaugh 2013. ...
Yardangs are among the most spectacular features of aeolian landscapes, occurring in numerous areas on Earth as well as on other solid planets. Yardangs are teardrop-shaped hills whose orientation reflects prevailing winds. The combined action of deflation and abrasion in sparsely vegetated desert areas favours the formation and evolution of these aeolian features, resulting in their characteristic regular
morphologies.
This paper presents the first identification of the yardangs carved in Quaternary formations of the Moroccan Sahara. This preliminary study focuses on describing their geomorphology (length, width, distribution, etc.) and lithology. In addition, the statistical analysis of morphometric parameters provides valuable information for further research in this western region of the Sahara Desert.
... A barchan dune is a slowly moved crescent-shaped sand body formed by winds that moves the sand on its windward side and forms a slip face on the lee side (Bagnold 1941;Cooke et al. 1993). Barchan has been published under different names, e.g., barcan, barchan, barkan, and barkhan (Glenn 1979). ...
Barchan dunes of the Kharga Depression, Western Desert, Egypt, have been assessed in terms of their morphometry, grain
size, and migration rate using remote sensing and GIS techniques and field and laboratory work. Thirty-seven sites were
chosen along the Kharga dune belt and subdivided into northern, central, and southern sectors. At each site, several barchans
were subjected to morphometric measurements (length, width, height, length of eastern and western horns, and length of
windward and leeward sides). The rate and direction of 160 barchans were also measured for the period between 2002 and
2018. Grain size analysis was carried out on sand samples taken from the crest of these dunes. Statistically, significant relationships
have been found between the morphometric parameters, dune migration, and grain size attributes. The analysis of
the morphology of the barchan dunes, their movement, and the nature of sedimentary materials provide essential information
for assessing and evaluating their environmental hazards.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
There are around 2,304 sand dunes scattered within seven dune fields in Kuwait. The longest barchanoid chain dune in Kuwait is 2400 m and 900 m. All the dunes in Kuwait were mapped, sampled, and analyzed. This chapter passes through dunes in Kuwait covering the following: The dunes mapping.
The dune migrations using satellite images.
The chemical properties include Mineralogical properties.
X-ray diffraction (major and minor trace elements).
Micro-inclusions within Aeolian particles.
The physical properties include The particle size analysis.
Statistical properties.
Particle micro-features.
BET surface area.
Perimeter and diameter.
This chapter covers all aspects regarding sand dunes in Kuwait; therefore, this chapter will be a key reference for future studies tackling aeolian landforms in Kuwait and regional areas.
... The literature on aeolian processes and on aeolian morphological and sedimentological features has shown a dramatic increase during the last decade. A variety of textbooks, extensive reviews, and special issues of journal volumes devoted to aeolian research have been published (Nordstrom et al. 1990;Pye and Tsoar 1990;Kozarski 1991;Pye 1993;Pye and Lancaster 1993;Cooke et al. 1993;Lancaster 1995;Tchakerian 1995;Livingstone and Warren 1996;Goudie et al. 1999). However, not surprisingly the majority of these studies discuss aeolian processes and phenomena in the extensive warm arid regions of the world. ...
A distinguished team of Western European scholars has written an advanced, full-length physical geography designed to be a state-of-the-art evaluation of the physical environment of Western Europe, being both retrospective and prospective in its perception of environmental change. The unique natural and regional environments of Western Europe are discussed, as well as the physical geographic framework of the region. Particular emphasis is placed on the impact and responses of human society on the physical environment of the region which is characterized by a very high population density. As an enhanced reference work it will be of enduring value.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
Kuwait marine geology can be directly or indirectly influenced by various environmental, anthropogenic, industrial, and geomorphological factors continuously altering its nature and affecting its numerous compartments like fauna/flora, water chemistry, physical oceanography, etc. In this chapter, we attempted to describe salient characteristics about Kuwait onshore, and offshore marine geology from historical and modern perspectives. It highlights unique and dynamic ecological and geological factors that are continuously influencing its nature concerning local and transboundary environmental impacts in addition to the significantly booming oil industry that is persistently transforming Kuwait’s marine geology.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
Despite the surface geology of Kuwait appears to be scarce and most of the country is covered with Quaternary deposits except for a few outcrops of Oligo-Miocene to Pleistocene age, the subsurface geology of Kuwait is quite unique and astonishing. The discovery of hydrocarbon in Kuwait at the beginning of the last century helped geologists to better understand the structural geology of Kuwait especially by utilizing geophysical methods such as potential field methods (e.g., gravity and magnetic) and seismic reflection. Being part of the Arabian Peninsula, the structural geology of Kuwait shares many of the Arabian Peninsula structural trends. The dominant N-S trending structures of the Arabian Plate are manifested in the Kuwait Arch which is one of the major structures of the country where many of the oil and gas oil fields are associated with. Other dominant structural trends of the Arabian Plate such as NE-SW and NW–SE are resembled in Kuwait as Jal Az-Zor and Dibdibah Trough, respectively. Paleo- and in-situ stress analysis is an important subject for oil and gas exploration, and many studies have been commissioned to better understand them in most of the Kuwaiti fields. The present-day in-situ stress in Kuwait is oriented NE-SW resembling the current tectonic setting of the region due to the collision of the Arabian Plate with the Eurasia Plate since the Oligocene. This chapter will present a thorough review of the previous studies discussing the surface and subsurface structural geology of Kuwait.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
Kuwait has proven conventional oil reserves of about 100 billion barrels which makes it one of the major oil-producing countries worldwide. Most of this reserve is found in Cretaceous and Jurassic with minor quantities in the Paleogene sedimentary successions. Most hydrocarbon production comes from the siliciclastic Burgan Formation which is the most important reservoir in Kuwait. The Jurassic and Lower Cretaceous exhibit good quality source rocks that charged most of the hydrocarbon reservoirs in Kuwait and entered the oil window in Late Cretaceous to Eocene. Most of the hydrocarbon is trapped in very gentle four-way closure structures that are related to the deep-seated fault system of the Arabian Peninsula such as Khurais-Burgan Anticline. Hydrocarbon reservoirs in Kuwait are sealed and capped mainly by shale rocks and to a less extent by evaporites. In the last 15 years, Kuwait Oil Company (KOC) displayed interest in commercially exploiting unconventional hydrocarbon reserves and started laying significant emphasis on the exploration and development of unconventional resources. The aim of this work is to summarize the different petroleum systems of Kuwait including the Paleozoic, Mesozoic, and Cenozoic systems.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
Low magnitude Earthquakes are the most natural hazard facing Kuwait, while other environmental challenges such as flooding, dust fallout, land degradation, and aeolian sand movement often arise from human impact as well as natural factors. Because of the rapid socio-economic development in the last five decades in Kuwait, these issues cause environmental and social problems as well as economic disturbance; they are also considered natural disasters for country. The scale and intensity of the geological environment hazards are considerably increasing especially land degradation, and impacting on the harsh structure of desert ecosystem. Due to fragility of the desert environment, human activities exceeding the carrying capability of the geo-environment system can easily lead to geological and environmental hazards; such as runoff, sand and dunes movements and dust fallout causing serial environmental and health impacts. Geographic Information System (GIS) has been used to evaluate the degrees of geological hazard and risk by producing maps for each hazard; seismic, sand potentiality, hydrologic risk, land degradation, and sand drift severity maps are produced.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
This chapter represents a comprehensive review of Kuwait’s surface geology and stratigraphy from previous works accomplished by numerous geoscience researchers in the past decades. The surface of Kuwait is characterized by nearly flat topography, featureless to gently undulating, apart from a few tens of meters of escarpments in the north and south, and flat low to moderately elevated hills and ridges. It predominantly consists of siliciclastic sediments and sedimentary rock units ranging in age from Middle Eocene to Holocene. The main stratigraphic exposed successions are located in Jal Az-Zor escarpment, Al-Subyiah (Bahrah) area, Ahmadi Quarry, the Khiran Ridges, and the Enjefa Beach. The oldest exposed rock units are represented by the Middle Eocene Dammam Formation, which is exposed at the Ahmadi Quarry, whereas the youngest recent deposits cover most of Kuwait’s surficial area and lie on top of the Kuwait Group’s deposits. This chapter will illustrate the geology and stratigraphy of Kuwait's surface sediments and sedimentary rock strata. Recommendations and future insights were also documented as part of the way forward to improve the presently available work for the surface geology of Kuwait.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
This chapter deals with all the precious documented recently published and unpublished studies that address the seismic situation and earthquakes in the State of Kuwait. Kuwait is geographically and geologically situated in the northeastern part of the Arabian Peninsula. In addition to being close to the famous Zagros belt of earthquakes, the local seismic sources inside Kuwait make it always vulnerable to earthquakes. We will review the instrumental and historical seismic records and the Kuwait National Seismic Network, including Data acquisition, data analysis, and data analysis. This chapter will also highlight all the recent seismic studies conducted in the Kuwait region. The induced seismicity, the seismic sources affecting Kuwait, as well as determining the types of faults using focal mechanism technique, specifying the seismic crustal models and ground motion attenuation inside Kuwait are being reviewed.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
This chapter reviews the subsurface stratigraphy of Kuwait targeting geosciences educators. The lithostratigraphy and chronostratigraphy of the reviewed formations (association of rocks whose components are paragenetically related to each other, both vertically and laterally) followed the formal stratigraphic nomenclature in Kuwait. The exposed stratigraphic formations of the Miocene–Pleistocene epochs represented by the Dibdibba, Lower Fars, and Ghar clastic sediments (Kuwait Group) were reviewed in the previous chapter as part of near-surface geology. In this chapter, the description of these formations is based mainly on their subsurface presence. The description of the subsurface stratigraphic formations in Kuwait followed published academic papers and technical reports related to Kuwait’s geology or analog (GCC countries, Iraq and Iran) either from the oil and gas industry or from different research institutions in Kuwait and abroad. It is also true that studies related to groundwater aquifer systems also contribute to our understanding of the subsurface stratigraphy of Kuwait for the shallower formations. The majority of the published data were covered the onshore section of Kuwait. The subsurface stratigraphic nomenclature description is based on thickness, depositional environment, sequence stratigraphy, the nature of the sequence boundaries, biostratigraphy, and age. The sedimentary strata reflect the depositional environment in which the rocks were formed. Understanding the characteristics of the sedimentary rocks will help understand many geologic events in the past, such as sea-level fluctuation, global climatic changes, tectonic processes, geochemical cycles, and more, depending on the research question. The succession of changing lithological sequences is controlled by three main factors; sea-level change (eustatic sea level), sediment supply, and accommodation space controlled by regional and local tectonics influences. Several authors have developed theoretical methods, established conceptual models, and produced several paleofacies maps to interpret Kuwait’s stratigraphic sequence based on the data collected over time intervals from the Late Permian to Quaternary to reconstruct the depositional history of the Arabian Plate in general and of Kuwait to understand the characteristics of oil and gas reservoirs.
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
The fresh and brackish groundwater resources in the State of Kuwait are restricted to two main water-bearing formations (aquifers). These are the Dammam Formation and Kuwait Group. The Kuwait Group aquifer is generally unconfined, i.e., water table condition, whereas the Dammam fractured limestone Formation is a confined-semi confined aquifer. The quality of groundwater in Kuwait varies from brackish in the southwest to brine in the northeast of Kuwait. Fresh groundwater bodies of TDS less than 1000 mg/l occur on saline groundwater of TDS 100,000 mg/l in the north and the northeast, e.g. Raudhatain and Umm Al-Aish water fields. Generally, the water table varies from zero at the Arabian Gulf Coast to about 90 m below the surface in the southwest. Significant ongoing and future groundwater projects include monitoring groundwater level and water quality, establishing hydrological, geological and hydrochemical databases, reducing groundwater levels, long-term monitoring for groundwater quality e.g. Raudhtain and Um-Al Aish freshwater reservoirs and environment treatment of groundwater reservoirs. The current study discusses the following parts: groundwater quality, groundwater geology, aquifer systems, Al-Raudhatain freshwater field, groundwater misuse and consequences (case of Wafra Agricultural Area), and Monitoring water ponds and saline soils, Al Wafra Agricultural Area (2008–2011).
... Dune morphology and control lay factors were first mentioned by Beadnell (1910). This was followed by numerous subsequent discussions Folk (1971), Bowler (1973), Breed et al., (1979a, b, 1979b), Nielson et al., (1982, Tsoar (1983aTsoar ( , b, 1986, Greeley and Iversen (1985), Thomas (1986Thomas ( , 1988aThomas ( , b, c, 1989, El-Baz (1986), Cooke et al., (1993). The genesis of the barchan dunes has been described by Bagnold (1941). ...
Satellite Remote Sensing can provide a valuable source of information in different applications and is considered an important tool for disaster management and support for decision-making in the state of Kuwait. This is especially valid for the cloudless atmosphere of Arabia. In this chapter, some examples related to geology ideas are presented. The application of satellite remote sensing techniques using both passive and active sensors is presented over Kuwait desert and marine. This includes academic studies of soil moisture, land subsidence, and operational monitoring of recent flash floods, dust storms, and oil spills detected by optical and SAR instruments from various space satellite platforms over the territory of the state of Kuwait. Operational monitoring of dust storms, especially sever jets from Iraq was performed with MODIS NASA/Terra and Aqua instruments, the oil pollution in the Northern Gulf oil fields was very effectively detected by Sentinel SAR-C instrument of Copernicus/ESA, and some rain floods in urban areas in winter were analyzed by high-resolution instruments of Pleiades.
... However, the flow deceleration in this area also decreases the sediment transport capacity, so if sediment enters the area directly behind the building, this can create deposition (Luo et al., 2012;Poppema et al., 2019). This deposition in the lee of an object is alternatively referred to as a sand shadow (Bagnold, 1941;Luo et al., 2012); shadow dune or lee dune (Hesp, 1981;Cooke et al., 1993;Pye and Tsoar, 2008); or leeward drift (Beyers and Waechter, 2008). ...
Buildings affect aeolian sediment transport and bedform development in sandy environments. Cellular automaton (CA) models have, however, only been used to simulate natural bedform dynamics. This study extends a well-known aeolian CA model to include sediment dynamics around buildings, and uses this model to explore the interaction of building-induced deposition and erosion with natural bedform dynamics. New CA rules are introduced to represent acceleration, deceleration and sideward transport of sediment around obstacles. The simulated deposition and erosion patterns show good agreement with field experiments. The model reproduces the shape and location of the morphological pattern around a single building, and effects of building spacing on this pattern for building groups. Model results further demonstrate that building-induced effects interact with local bedform dynamics and can alter the shape, growth and migration of sand dunes.
... As the dunes grow in height they slowly drift in the direction of the wind. During this accumulation process the slope of the slip face regularly exceeds the angle of repose of dry fine sand (about 35 • ) causing small slumping of the crest (Goudie et al., 1996;Bristow and Mountney, 2022). (Tavernier and De Moor, 1974), and detailed position of cores 1 and 2 on the DEM. ...
The inland dune “Molenberg” (Lys valley, NW Belgium) is an exceptionally well-preserved dune of more than 10 m high. To determine the phases of dune formation and identify possible levels for human occupation, this dune was sampled at closely spaced vertical intervals for Optically Stimulated Luminescence (OSL) dating (every 50 cm) and grain-size analysis (intervals of 10–25 cm) over its entire depth, including the top of the underlying sediments. The resulting ages show dune formation during the late glacial period (GI-1 and GS-1), with a probable extensive deposition during the Allerød (GI-1a-c) and Younger Dryas (GS-1). Interestingly, the OSL dataset for the main body of the dune shows significant cyclical age inversions that may be caused by reworking of sediment causing incomplete bleaching of sand grains. This may further indicate the potential of high-sampling resolution OSL to contribute to the reconstruction of complex dune dynamics.
... Considering the effects and costs . Wind conditions and sand supply lead to different erosion 212 process intensities on the surface so that gravel cover has the dual functions of 213 "catching sand" and "transporting sand" (Bagnold 1941;Cooke et al. 1993). Thus, if 214 the erosion process is stronger than the deposition process, then the function of 215 gravel cover measures is transporting sand. ...
Engineering measures (EMs) are methods to prevent and control aeolian disasters that do not involve plants. Usually, EMs are the preferred prevention and control methods in arid areas, where planting trees is not always possible. In semiarid and dry subhumid areas, EMs are sometimes used in conjunction with other measures, especially in the early stages of biological measures (BMs), for immediate effects. EMs can be divided into four types based on function: sand blocking, sand fixing, sand transporting, and sand guiding. These types of EMs have different forms, such as upright, semiupright, flat, and buried. The materials used in EMs are diverse and include crop straw, degradable nylon mesh, gravel, clay, and synthetic materials. This chapter mainly introduces four forms of EMs and their materials and functions. Chemical measures (CMs) are usually used in regions where both EMs and BMs are not available. CMs can immediately fix the sand surface by spraying chemical materials. Due to their high price and potential pollution, CMs are not extensively used and are introduced at the end of the chapter.KeywordsEngineering measuresFunctionFormsMaterial
Chemical measures
... However, the flow deceleration in this area also decreases the sediment transport capacity, so if sediment enters the area directly behind the building, this can create deposition (see Chapter 2 and Luo et al., 2012). This deposition in the lee of an object is alternatively referred to as a sand shadow (Bagnold, 1941;Luo et al., 2012); shadow dune or lee dune (Cooke et al., 1993;Hesp, 1981;Pye & Tsoar, 2008); or leeward drift (Beyers & Waechter, 2008). ...
Worldwide, many houses, restaurants and other buildings are present at the beach. These buildings alter the airflow and windblown sediment transport in their surroundings. This causes patterns of deposition and erosion around buildings, which can block e.g. roads or beach entrances. Possible repercussions for the larger beach environment arise because deposition around buildings imply that windblown sediment transport is intercepted. This reduces sand influx into the dunes, thereby affecting coastal safety.
Coastal managers are responsible for regulation on beach buildings, and decide where, when and if buildings can be placed. This requires a proper understanding of how beach buildings shape their environment, and especially how this depends on building properties that can be addressed by regulation. Therefore, this thesis aims to determine and understand quantitatively how buildings at a sandy beach affect the wind-driven morphological development of the beach environment.
Using field experiments, the initial deposition and erosion patterns around buildings were examined. By placing cuboid scale models of buildings at the beach, the shape and size of these patterns were linked to building geometry. Next, the field experiments were extended to determine the effect of wind orientation and the bed pattern around building groups at various building spacings. Finally, interactions of building-induced bed patterns with natural bedform dynamics were studied. Hereto building effects were added to an existing cellular automaton computer model for sandy aeolian landscapes. Next, model results were compared to our field experiments, followed by longer-term simulations to explore building-bedform interaction for periods of up to 15 years.
Overall, this study has revealed that systematic relations exist between the geometric characteristics of buildings – individual buildings and building groups – and the induced aeolian deposition and erosion patterns. Quantitative relations were derived for the horizontal extent of the initial deposition patterns and for the asymmetry of the deposition tail lengths. For building groups, three building spacing regimes were identified, each with different morphological patterns around buildings. The long-term simulations illustrate how interactions of building-induced effects with aeolian bedform dynamics can alter dune development. These findings contribute to the much-needed scientific support for regulations for permitting buildings on the beach.
... The principal mode of foredune development in arid environments is nebkha (Hernández-Cordero et al., 2019;Hesp et al., 2021a;Hesp and Walker, 2013). Nebkhas (aka nabkha, coppice dunes, phytogenic mounds) are individual aeolian landforms formed by sand accumulation around and within discrete vegetation (Cooke et al., 1993;Hesp and McLachlan, 2000). The vegetation might comprise herbs, grasses, shrubs or trees, and in the Canaries typically comprises Traganum moquini shrubs. ...
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.
... A sandy hillock around vegetation was referred to as nabkha by Gautier and Chudeau [2]. Bush-mounds, shrub-coppice dunes, knob dunes, phylogenetic hillocks, dune tumuli, rebdou, nebbe, and takouit are some of the words used to describe this Aeolian landform [3]. Several authors have recently investigated the sedimentological and morphological characteristics of the nabkhas in the south and north in Kuwait, also more consideration has been devoted to studying the dominant plant distribution and classification over the last few decades, a special focus has been placed on the preparation of Kuwaiti vegetation maps [4]. ...
Nabkhas are desert and sabkha perennial plants that form stabilized dunes. A total of 23
sediment samples were taken from the surface and subsurface (30 cm depth) of nabkha that formed around Nitraria retusa as the dominant perennial plant species in Ghudai-Kuwait. The morphological and ecological functions of sabkha nabkha are distinguishable. The existence of shallow fresh groundwater that floats atop the saline water bodies and is recharged by rainwater and surface drainage routes is due to the presence of thriving nabkhas within a salty sabkha environment. the selected non-protected Nitraria nebkhas have an elongated dome shape with a height of 1.30 m and an average length of 11.80 m. also, the greatest distances between isolated nabkhas are found in Nitraria dominated coppice dunes. There are three types of Nitraria dominated coppice dunes, namely: single (one plant), coupled (two plants), and complex (three or
more). Nitraria is considered one of Kuwait's most effective plant species for trapping mobile sand, Nitraria can to tarp to 21 m3 of mobile sand and dust. The variations in grain size sediments in Nitraria retusa between surface and root zone, border and crest, upwind and downwind, are efficient for retaining water. Furthermore, Nitraria retusa from the sabkha environment is the most effective in collecting mobile sand in the region.
... A sandy hillock around vegetation was referred to as nabkha by Gautier and Chudeau [2]. Bush-mounds, shrub-coppice dunes, knob dunes, phylogenetic hillocks, dune tumuli, rebdou, nebbe, and takouit are some of the words used to describe this Aeolian landform [3]. Several authors have recently investigated the sedimentological and morphological characteristics of the nabkhas in the south and north in Kuwait, also more consideration has been devoted to studying the dominant plant distribution and classification over the last few decades, a special focus has been placed on the preparation of Kuwaiti vegetation maps [4]. ...
Nabkhas are desert and sabkha perennial plants that form stabilized dunes. A total of 23 sediment samples were taken from the surface and subsurface (30 cm depth) of nabkha that formed around Nitraria retusa as the dominant perennial plant species in Ghudai-Kuwait. The morphological and ecological functions of sabkha nabkha are distinguishable. The existence of shallow fresh groundwater that floats atop the saline water bodies and is recharged by rainwater and surface drainage routes is due to the presence of thriving nabkhas within a salty sabkha environment. the selected non-protected Nitraria nebkhas have an elongated dome shape with a height of 1.30 m and an average length of 11.80 m. also, the greatest distances between isolated nabkhas are found in Nitraria dominated coppice dunes. There are three types of Nitraria dominated coppice dunes, namely: single (one plant), coupled (two plants), and complex (three or more). Nitraria is considered one of Kuwait’s most effective plant species for trapping mobile sand, Nitraria can to tarp to 21 m ³ of mobile sand and dust. The variations in grain size sediments in Nitraria retusa between surface and root zone, border and crest, upwind and downwind, are efficient for retaining water. Furthermore, Nitraria retusa from the sabkha environment is the most effective in collecting mobile sand in the region.
... The sandstones of Cerro Colorado are remarkable morphologies in the landscape, mainly recognizable at the macromorphological scale (Boretto et al., 2021). Tafoni are a form of cavernous weathering (Cooke et al., 1993;Mellor et al., 1997) commonly occurring on granitic and sandstone rocks worldwide (Dragovich, 1969;Mustoe, 1983;C. Ollier, 1984;Sancho & Benito, 1990;Twidale, 1982;among others). ...
Tafoni, produced by physicochemical weathering of sandstones, are abundant in the Cerro Colorado (Córdoba province, Argentina). Many of the rock shelters are decorated with rock art of high heritage significance. This art belongs to semisedentary communities from the Late Prehispanic Period (ca. 1550–350 AP). They include morphologies inherited from more humid ancient climates combined with current weathering processes. Evolutionary relief study established that tafoni formation is a product of inherited past wetter climates. Mineralogical and petrographic analyses were performed on samples collected from the sandstones and from various morphologies, weathering residues, and wall and ceiling concretions at four rock shelters, Cueva del Indio, Ricci, Quitilipi, and La Trampa. Gypsum and other salts that are not part of the unaltered rock but the result of weathering reveal the magnitude of hydroclastic and haloclastic processes. These activities form active granular disintegration, flaking, and spalling, and impinge on some painted panels. Mapping the distribution of weathering features and processes at each rock shelter enables the planning of interventions to mitigate and alleviate the effects caused by infiltration of water through rock discontinuities, fractures, and overhangs. It also allows decreasing the accumulation of dust and minimizing muddy water flowing over the paintings. These actions are aimed at retarding the progression of rock art degradation and the visible loss of some paintings.
... Because of the strong shear, horizontal flow separates along the margins of the plant/nebkha and counter-rotating vortices or eddies form within a flow reversal envelope downwind (McKenna Neuman et al., 2013: Fig. 11). Flow also accelerates over the plant/nebkha and often forms a vertical reversing flow separation cell or region in the lee (e.g., Bagnold, 1941;Cooke et al., 1993;Sutton and McKenna Neuman, 2008a;Hesp and Smyth, 2017). Dong et al. (2008) show that the positions of the reverse vortices move their location in response to changes in shrub density with the reversing vortices situated further downwind at lower densities because the bleed flow pushes the reversal cell downwind. ...
Notable progress has been made in the 80 years following Bagnold's (1941) seminal work on the physics of windblown sand and desert dunes, yet a range of challenges remain for quantifying and modelling wind flow and eolian sand transport over complex dune terrain. These challenges arise from fundamental differences in airflow dynamics over topographically complex surfaces that limit the applicability of conventional boundary layer theory, as well as from a multitude of interactions between dune form, wind flow, sediment transport, and roughness elements, including vegetation, that vary over space and time. In recent decades, significant advances have been made using wind tunnel simulations, detailed field experiments using three-dimensional ultrasonic anemometry, and numerical flow field simulations that, combined, have improved our ability to more accurately model and characterize dune morphodynamics. This chapter provides a comprehensive review of both the fundamentals and recent advances in our understanding of airflow dynamics over a wide range of dune terrain from relatively simple transverse dunes to more complex vegetated dunes such as nebkha and coastal foredunes. New insights from computational fluid dynamics (CFD) modelling approaches are also presented. The review identifies persistent knowledge gaps and opportunities for further research on the measurement and modelling of airflow and sand transport patterns that maintain dune form and function.
... Parabolic dunes (also termed U-dunes, upsiloidal dunes, hairpin dunes, dune plumes) are typically U-and V-shaped dunes characterized by short to elongate, often vegetated trailing ridges which terminate downwind in U-or V-shaped depositional lobes. They occur on all coasts ranging from open coasts and inland seas, to estuaries to lakes (fluvio-glacial, ephemeral pans, and playas; Ritchie, 1972Ritchie, , 1992Pharo and Kirkpatrick, 1994;Langford, 2003;Hansen et al., 2006;Harper and Gilkes, 2004;Roberts et al., 2009;Levin, 2011, Levin et al., 2014Yizhaq et al., 2013;Yan and Baas, 2015;Delgado-Fernandez et al., 2018), and are common in some semi-arid to arid landscapes (Smith, 1965;Cooke et al., 1993;Lancaster, 2013;Wolfe and David, 1997;Hugenholtz, 2010). ...
The initiation mechanisms, geomorphology, and evolution of coastal dunes are examined. The principal coastal dune types, foredunes, relict foredune plains, blowouts, parabolic dunes, and transgressive sand sheets and dunefields are reviewed. The article also attempts to illustrate the morpho-ecological function and diversity of these various dune types by reviewing current research and presenting multiple examples from coastal dune ecosystems worldwide. The accompanying photographs demonstrate the very wide variety of dune morphologies and landform units that exist, and these are used to provide indications of the evolutionary paths of the major coastal dune types.
... processes from both the surrounding drainages and from long-distance dust transport (Cooke et al. 1992;Holliday 1997;Holliday et al. 2008;Bowen andJohnson 2012, 2015;Rich 2013;Adams and Sada 2014;Collins et al., 2018). The ephemeral nature of Harney Basin's small playas makes them highly sensitive to climate change as a consequence of their smaller watersheds, simple hypsometry, and short water residence times, enabling them to record perturbations in the hydrological cycle more rapidly and with shorter lag times than the larger, nearby Malheur Lake system. ...
Seven sediment cores from Rimrock Lake (n = 4) and Hay Lake (n = 3) playas (Harney Basin, northwest Great Basin, Oregon, USA) were used to characterize their stratigraphic relationships through time. End-member mixing analysis, conducted on grain-size distributions, identified five end-members (EM), which explain 97.23% of total variance across all samples and represent two major environments of deposition, lacustro-eolian and fluvio-lacustrine. Normalized differences between finest and coarsest EMs were calculated to serve as a visual proxy for comparison of changes in energy within the playas. Playa and watershed morphometric analysis, using GIS, indicates both playas are relatively large (* 54 ha) compared to other wetlands within Harney Basin. Both playas were established as marshy environments during the late Pleistocene, ca. 19,500-18,500 cal yr BP, and experienced increased fluvial activity during the early Holocene, between ca. 9000 and 8000 cal yr BP. Rimrock Lake playa continued to experience a lacustrine environment with alternating lake levels well into the middle Holocene, even during times of increased regional aridity, whereas Hay Lake playa did not seem to have experienced an expanded lacustrine environment into the middle Holocene. Digital elevation models, aerial imagery, and documented late Quaternary tectonic activity, suggest that tectonics may have played a role in diverting ephemeral channels toward Rimrock Lake and away from Hay Lake.
... As for the site, the gullies follow the general slope of the area to the southwest ( (Havholm and Kocurek, 1994). Sand dunes deposit due to the occurrence of natural or human obstacles in the path of the sand-loaded wind or because of the decrease in speed (Cooke, 1993). Sand dunes are clearly present in large parts of the study area along the middle strip of the study area extended North-west to the southeast. ...
This work aims to evaluate the predictive capability of three bivariate statistical models, namely information value, frequency ratio, and evidential belief functions, in gully erosion susceptibility mapping in northeastern Maysan Governorate (Ali Al-Gharbi District) in southern Iraq. The gully inventory map, consisting of 21 gullies of different sizes, was prepared based on the interpretation of remotely sensed data supported by field survey. The gully inventory data (polygon format) were randomly partitioned into two sets: 14 gullies for build and training the bivariate model, and the remaining 7 gullies for validating purposes. Twelve gully influential factors were selected based on data availability and the literature review. The selected factors were related to lithology, geomorphology, soil, land cover, and topography (primary and secondary) settings. Analysis of factor importance using information gain ratio proved that out of 12 gully influential factors, eight were of more importance in developing gullies (the average merit was greater than zero). The most important factors and the training gully inventory map were used to generate three gully erosion susceptibility maps based on the three bivariate models used. For validation, the area under the operating characteristics curves for both success and prediction rates was used. The results indicated that the highest prediction rate of 82.9% was achieved using the information value technique. All the bivariate models had prediction rates greater than 80%, and thus they were regarded as very good estimators. The final conclusion was that the bivariate models offer advanced techniques for mapping gully erosion susceptibility.
... One of these indicators, consistent with the data available from the study area, is the activity index of sand masses, developed by Lancaster (1988). Equation 3 shows how to calculate this index (Cooke et al., 1993;Lancaster, 1988). ...
Coastal plains are prone to various degrees of wind erosion due to their characteristics. This study aimed to investigate the effect of climatic factors in the western region of Makran coastal plain in a southeastern region of Iran on the wind erosion potential. The study period was 1993-2018. First, the data related to wind velocities, relative humidity and precipitation, and the granulometric data of plain surface sediments were obtained. Then, the wind erosion threshold velocity in humid air conditions was determined. Finally, the Mann-Kendall test was applied to analyze the probability of wind erosion and its temporal variability. The results indicated that the wind erosion threshold, in terms of humidity changes, varied from 7.21 to 12.31 meters per second during the study period. The highest probability of wind erosion was in February, March, and April, with 24.69%, 21.51%, and 20.41%, respectively. The lowest probability of wind erosion was in October, November, and September with 4.00%, 4.12%, and 6.00%, respectively. Finally, the erosion trend analysis indicated that wind erosion was a temporal phenomenon that increased significantly in January (winter solstice) and July (summer solstice). These months were characterized by an increase in the wind blowing at speed above the threshold. Otherwise, the months were not different from other months of the year in terms of precipitation or the number of dry days. Therefore, wind erosion is expected to maximize in the early winter and the early summer.
Megafans are partial cones of river sediment that reach unexpectedly large dimensions, with the largest on Earth being 700 km long. Due to recent developments in space-based observations, global mapping efforts have shown that modern megafan features cover vast landscapes on most continents. This book provides a new inventory of nearly 300 megafans across five continents. Chapters focus on regional studies of megafans from all continents barring North America and Antarctica. The major morphological attributes of megafans and multi-megafan landscapes are discussed, and the principal controls on megafan development are examined. The book also compares megafans with alluvial fans, deltas, floodplains and the recently recognised 'major avulsive fluvial system' (MAFS). The final part of the book discusses the application of megafan research to economic geology, aquifers and planetary geology including layered deposits on Mars. This is an invaluable reference for researchers in geomorphology, sedimentology and physical geography.
Megafans are partial cones of river sediment that reach unexpectedly large dimensions, with the largest on Earth being 700 km long. Due to recent developments in space-based observations, global mapping efforts have shown that modern megafan features cover vast landscapes on most continents. This book provides a new inventory of nearly 300 megafans across five continents. Chapters focus on regional studies of megafans from all continents barring North America and Antarctica. The major morphological attributes of megafans and multi-megafan landscapes are discussed, and the principal controls on megafan development are examined. The book also compares megafans with alluvial fans, deltas, floodplains and the recently recognised 'major avulsive fluvial system' (MAFS). The final part of the book discusses the application of megafan research to economic geology, aquifers and planetary geology including layered deposits on Mars. This is an invaluable reference for researchers in geomorphology, sedimentology and physical geography.
Megafans are partial cones of river sediment that reach unexpectedly large dimensions, with the largest on Earth being 700 km long. Due to recent developments in space-based observations, global mapping efforts have shown that modern megafan features cover vast landscapes on most continents. This book provides a new inventory of nearly 300 megafans across five continents. Chapters focus on regional studies of megafans from all continents barring North America and Antarctica. The major morphological attributes of megafans and multi-megafan landscapes are discussed, and the principal controls on megafan development are examined. The book also compares megafans with alluvial fans, deltas, floodplains and the recently recognised 'major avulsive fluvial system' (MAFS). The final part of the book discusses the application of megafan research to economic geology, aquifers and planetary geology including layered deposits on Mars. This is an invaluable reference for researchers in geomorphology, sedimentology and physical geography.
This chapter discusses the major types of sand dunes and sand seas (ergs). It examines the following dune types: barchans, transverse ridges, reversing dunes, zibars, parabolics, linears, stars, domes, topographic (obstacle) dunes, lunettes, shadow dunes and nebkhas.KeywordsDunesSand seasTranverse dunesLinear dunesTopographic dunes
Shell middens are conspicuous manifestations of the exploitation of rich, sustainable, easily seen and harvested marine resources that, worldwide, enabled hunter-gatherers to reduce mobility and increase population and social complexity. Globally, known sites tend to cluster chronologically around 6 k BP, after slowing eustatic sea-level rise, although the Pacific coast of South America offers some rare earlier exceptions.
We report investigations of La Yerba II, a Middle Preceramic shell matrix site on the Río Ica estuary, south coast Peru. These show how, beginning around 7000 Cal BP, over 4.5 m of stratigraphy accumulated in less than 500 years. Consisting of prepared surfaces, indurated floors and the ashy interiors of wind shelters and their associated midden deposits, alternating with phases of abandonment, this was the outcome of an intense rhythm of repeated occupations by logistically mobile marine hunter-gatherers. Final phases, dominated by Mesodesma surf clams, mark change towards more task-specific activities.
La Yerba II's topographic position and well-preserved cultural and environmental markers provide insight into the local history of relative sea level change and changing marine hunter-gatherer lifestyles during a period critical to the transition to sedentism and the formation of new estuarine and beach habitats following the stabilisation of eustatic sea-levels.
Soils of arid and semi-arid environments are characterized by scant moisture conditions, low clay and organic matter contents, low water holding capacity and low inherent fertility, and hence various management practices including foliar fertilization is essential. The present study aims at assessing the effect of integrated soil and foliar application of nitrogen, phosphorus, and potassium (NPK) fertilizers on growth, yield, and contents of some osmoprotectants, antioxidant, and nutritional status of Capsicum annuum (L.) in sandy soil under semi-arid condition. A pot experiment was conducted with five NPK application treatments: 100% added to the soil + 0% foliar spray, 75% soil + 25% foliar spray, 50% soil + 50% foliar spray, 25% soil + 75% foliar spray, and 0% soil + 100% foliar spray. The results of the study indicate that the integrated treatment of 50% soil + 50% foliar spray proved to be the best treatment compared with other treatments. This treatment significantly increased growth components (leaf area plant‒1, shoot fresh and dry weights) and yield (number of fruits plant‒1, average fruit weight, and fruits weight plant‒1), and the contents of soluble sugars, free proline, and nutrients (NPK); while significantly reduced the contents of ascorbate and glutathione compared to other treatments, including the control. The combined treatment of 75% soil + 25% foliar spray was the second-best treatment with respect to all tested parameters. The study concludes that the recommend integrated treatment of 50% soil + 50% foliar spray minimizes nutrient loss and achieves higher growth and yield of hot pepper plants under semi-arid condition.
Cliff-related talus accumulations are often highly affected by post-depositional processes, and the sedimentological characteristics are poorly documented, especially in arid settings. In the southern margin of the Fergana Valley, Kyrgyzstan, the Obishir-I is an archaeological site of the Epipaleolithic Obishirian industry, located within a talus cone. Archaeological excavations have allowed us to study the internal structure, chronology, and depositional history of the cone as well as the relationship between the slope processes and the archaeological assemblage. We applied a multiproxy approach, including sedimentological studies supported by the basic geochemistry of sediments, luminescence dating, paleoecology of fossil mollusks, and archaeological analyses. The Obishir-I rockfall talus accumulated from the Last Glacial Maximum to the early part of the Middle Holocene. The talus onlaps the bedrock at the foot of a limestone cliff, and its chronology is coherent, spanning from ca. 19–8 ka B.P. The material is an unconsolidated, poorly sorted mixture of angular rock fragments accumulated by rockfall and fine-grained materials accumulated by aeolian processes, illuviation, and in situ weathering. The sequence bears an archaeological collection attributed to two settlement phases: unidentified Upper Paleolithic and the Obishirian. Both assemblages are affected by post-depositional relocation within the slope.
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