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  • Barchan-shaped ripple marks in a wave flume
  • Aeolian features ; Barchan ; Comparative study ; Dune ; Earth surface processes ; Experimentation ; Geomorphology ; Wave
  • The formation of barchan morphologies under the action of purely oscillatory wave motion has not yet been fully investigated. This study attempted to form barchan topography in a wave flume and to compare this with barchans in the field. Barchan
  • morphologies of ripple size, called the barchan ripples, were generated from a flat bed by the action of waves. This study will examine the migration speed of these laboratory and field morphologies through dimensional analysis.
  • Barchan dunes on the Kuiseb River Delta, Namibia
  • Barchan ; Delta ; Desert ; Dune ; Earth surface processes ; Namibia ; Spatial variation
  • The shape and behaviour of the barchan dunes on the Kuiseb River delta, south of the town of Walvis Bay, and the temporal and spatial variability of those characteristics are the focus of this study. - (AJC)
  • Width, height and slope relationships and aerodynamic maintenance of barchans
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; Dune ; Earth surface processes ; Geomorphometry ; Namibia ; Wind
  • The allometric relationship between the height of barchan dunes and horn to horn widths is re-examined. The addition of new data from barchans in the Namib Desert and elsewhere confirms the relationship that the height of a barchan is approximately
  • one-tenth of the width of the dune. The AA. attempt to assess the factors (particularly slope and aerodynamics) that act to produce and maintain the barchan dune shape.
  • The shape of the barchan dunes of southern Morocco
  • Aeolian features ; Aeolian transport ; Barchan ; Dune ; Earth surface processes ; Model ; Morocco
  • The AA. present detailed shape measurements of several barchan dunes in southern Morocco, near Laâyoune. Using these data, they disprove the concept of shape invariance of barchan dunes of different sizes. A further objective is a detailed
  • investigation of the scaling of barchan dunes using data from entire profiles instead of simple length, width and height relationships. Finally, they are interested in a simple geometric model in order to describe a barchan dune by only one parameter, which
  • Barchan ripples under unidirectional water flows in the laboratory : formation and planar morphology
  • Arid area ; Barchan ; Comparative study ; Desert ; Experimentation ; Geomorphogenesis ; Ripple-mark ; Runoff
  • This study investigates the formation and planar shape of barchan ripples generated by laboratory unidirectional water currents and compares the morphology with that of barchans formed by laboratory waves and flows in natural environments. A thin
  • veneer of sand as a sediment source was placed initially at the upstream part of a recirculating flume and the change in bed configurations by the flow was recorded by a video camera. Two types of formative process were observed : one was that barchan
  • Observations regarding the movement of barchan sand dunes in the Nazca to Tanaca area of southern Peru
  • Aeolian features ; Aerial photography ; Barchan ; Coastal dune ; Coastal environment ; Peru ; Photointerpretation ; Sand ; Wind
  • To understand, and perhaps predict, something of the movement of these barchan sand dunes, the A. undertook a study of the dunes using aerial photographs. This led to a general study of sand movement in the surrounding region.
  • The formation of seif dunes from barchans-a discussion
  • Bagnold's model for the formation of seif dunes from barchans supported by Lancaster (1980), is reviewed. A new model was developed based on field work done in the northern Sinai desert that does not differentiate between the effects of strong
  • A continuous model for sand dunes : review, new developments and application to barchan dunes and barchan dune fields
  • Aeolian features ; Barchan ; Dune ; Geomorphogenesis ; Model ; Sediment transport ; Wind speed
  • validated and able to simulate realistic barchan dunes, which are the basic solution of the model in the condition of unidirectional flow and scarce sediments. From the simulation, the AA. extract new relations describing the morphology and dynamics
  • of barchans that compare very well with existing field data. Next, the AA. revisit the problem of the stability of barchan dunes and argue that they are intrinsically unstable bed-forms. Finally, the AA. perform more complex simulations : first, a barchan dune
  • under variable wind strength and, second, barchan dune fields under different boundary conditions. The latter has important implications for the problem of the genesis of barchan dunes.
  • Assessment of the planimetric morphology of barchan dunes
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; Data processing ; Dune ; Geomorphometry ; Iran ; Kerman ; Mathematical model ; Remote sensing
  • In this study, high resolution images are combined with field measurements in order to quantitatively study the migration and long term changes in the shape and morphology of barchans. The results indicated a power correlation between height
  • and width of barchans. It also indicated that the outline of barchans can approximately be described by a parabola. Besides, the focal length, the curvatures (windward, leeward) and the brink parabola of the barchans were calculated; using differential
  • geometry and mathematical modeling. Surprisingly, there was no significant difference between focal length and mean curvature of barchan parabola from 2001 to 2011. It seems the general shape of the studied barchans has not changed for long periods of time
  • . The minimum and the maximum annual displacements of the barchans were 9 and 22 m, respectively, in the study area. It was also demonstrated that the best morphologic estimators for migration rate of dunes are in this order : width, mean curvature of windward
  • Aeolian features ; Aeolian transport ; Barchan ; Beach ; Coastal environment ; Dune ; Freezing ; Netherlands (The) ; Wind ; Wind speed
  • This paper describes the existence and maintenance (a day at least) of some unusual crescentic dunes on a frozen beach at Schiermonnikoog. These crescentic dunes displayed a markedly aerodynamic shape, and had a plan view similar to that of barchans
  • , but their morphology was the reverse of that for typical barchans.
  • Barchan migration on the Kuiseb River delta, Namibia
  • A dense concentration of barchan sand dunes in the Kuiseb River delta were examined to ascertain the rate of migration, through the study of aerial photographs taken in 1961 and 1976 and fieldwork in 1988. Wide variations in migration rates were
  • Barchan dunes : why they cannot be treated as solitons or solitary waves
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; Dune ; Experimentation ; Model
  • Schwämmle and Hermann (Nature, 2003, vol. 426, p. 619) have suggested that 2 sub-aerial barchan sand dunes could pass through one another while still preserving their shape in a manner similar to solitons or solitary waves. A wide range of published
  • The barchan dunes of Southern Peru revisited
  • Complex barchans in the libyan desert : dune traps or overtaking solitons ?
  • Africa ; Barchan ; Desert ; Dune ; Egypt ; Grain size distribution ; Physical geography ; Sand ; Sudan
  • The propagation of an error in Long and Sharp's (1964) data on barchan dune movement
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; California ; Data ; Desert ; Earth surface processes ; Error ; United States of America
  • Do swarms of migrating barchan dunes record paleoenvironmental changes ? A case study spanning the middle to late Holocene in the Pampa de Jaguay, southern Peru
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; Coastal environment ; Desert ; Dune ; Holocene ; Palaeo-environment ; Peru ; Quaternary
  • In this paper, a possible use of barchan swarms for paleoenvironmental reconstructions is presented. The approach is based on dune migration. In a case study based on 500 dunes in the Pampa de Jaguay aeolian transport corridor in coastal southern
  • Sediment flux and airflow on the stoss slope of a barchan dune
  • Aeolian features ; Aeolian transport ; Arid area ; Barchan ; California ; Dune ; Grain size distribution ; Sand ; Slope exposure ; United States of America ; Wind speed
  • Measurements of sediment flux on the windward slope of an isolated barchan using an array of 30 sand traps provide new data that can constrain models of dune dynamics. The data show that at low incident wind speeds, flux increases up the dune
  • The statistical analysis of the sand grain size distribution of Al Ubaylah barchan dunes, Northwestern Ar-Rub-Alkhali desert, Saudi Arabia in Saudi Arabia. (L'Arabie Saoudite)
  • Aeolian features ; Australia ; Barchan ; Desert ; Dune ; Grain size distribution ; Sedimentology ; South Australia ; Statistical distribution ; Statistics
  • This technical communication discusses the manner in which spatial granulometric differences for barchan dunes can be confidently and accurately identified using non-parametric statistical methods.
  • A process-based hypothesis for the barchan–parabolic transformation and implications for dune activity modelling
  • Aeolian features ; Barchan ; Biogeomorphology ; Dune ; Earth surface processes ; Impact ; Revegetation ; Vegetation
  • of vegetation on the slipface, which can only occur when slipface deposition rates are less than the deposition tolerance of vegetation. Under a constant vegetation growth regime the transformation of a barchan dune into a parabolic dune is a geometric response
  • to spanwise gradients in deposition rates. Initial vegetation colonization of barchan horns causes shear between the anchored sides and the advancing centre of the dune, which rotates the planform brinkline angle from concave- to convex-downwind. This reduces
  • slipface deposition rate and allows vegetation to expand inward from the arms to the dune centre. The planform inversion of bare barchans dunes into vegetated parabolic dunes ultimately leads to complete stabilization.