Modelling desert dune fields based on discrete dynamics

Bishop, Steven R.; Momiji, Hiroshi; Carretero-González, R.; Warren, A.

doi:10.1080/10260220290013462

Cited by 62 publications

(59 citation statements)

References 27 publications

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“…The CA approach has been particularly productive in the context of dune-field patterning (e.g., [21][22][23]172]), and the spatial nature of CAs lends itself well to analysing ecogeomorphic systems [173]. The strength of CA models lies in their capacity to represent key processes underlying complex systems, using a far smaller number of parameters and assumptions than many detailed reductionist models [171].…”

Section: Cellular Automaton (Ca) Modellingmentioning

confidence: 99%

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Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

Mayaud

Webb

2017

Land

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Drylands are characterised by patchy vegetation, erodible surfaces and erosive aeolian processes. Empirical and modelling studies have shown that vegetation elements provide drag on the overlying airflow, thus affecting wind velocity profiles and altering erosive dynamics on desert surfaces. However, these dynamics are significantly complicated by a variety of factors, including turbulence, and vegetation porosity and pliability effects. This has resulted in some uncertainty about the effect of vegetation on sediment transport in drylands. Here, we review recent progress in our understanding of the effects of dryland vegetation on wind flow and aeolian sediment transport processes. In particular, wind transport models have played a key role in simplifying aeolian processes in partly vegetated landscapes, but a number of key uncertainties and challenges remain. We identify potential future avenues for research that would help to elucidate the roles of vegetation distribution, geometry and scale in shaping the entrainment, transport and redistribution of wind-blown material at multiple scales. Gaps in our collective knowledge must be addressed through a combination of rigorous field, wind tunnel and modelling experiments.

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Section: Cellular Automaton (Ca) Modellingmentioning

confidence: 99%

“…Wind regime and sediment supply are known to largely control the formation of bare-sand dunes (e.g., [20][21][22][23]), but the complicating effects of vegetation, which form part of a wider, multi-scaled interplay of biophysical and anthropogenic factors, are less well understood [24][25][26].…”

Section: Introduction: the Drylands Contextmentioning

confidence: 99%

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

Mayaud

Webb

2017

Land

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“…See text for discussion. dynamics, the transport of sand by the wind gives rise to the evolution of dunes as emergent behaviour (Werner, 1995;Nishimori et al, 1998;Bishop et al, 2002). Dune type is a function of only the direction(s) and magnitude of the winds, in which the specific classes of dunes (i.e.…”

Section: Defect Densitymentioning

confidence: 99%

Pattern analysis of dune‐field parameters

Ewing

Kocurek

Lake

2006

Earth Surf Processes Landf

165

203

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As a basic form of pattern analysis, the parameters of dune spacing, defect density, crest orientation and crest length are measured from remote images and treated statistically for dunes at White Sands in New Mexico, the Algodones in California, the Agneitir in Mauritania, and the Namib in Namibia. Statistical populations are identified from frequency plots of dune spacing and crest length, field-scale calculations of defect density, and rose diagrams of crest orientation. Single populations characterize simple dune fields (White Sands), whereas multiple populations characterize compound/complex dunes (Algodones, Namib), and complex dune fields (Agneitir). As time increases, dune fields show an increase in dune spacing and crest length, a decrease in defect density, more tightly clustered crest orientation, and a reduction in the variance associated with measurements of these parameters. The results are consistent with models of dune fields as self-organizing complex systems in which a characteristic pattern emerges as a function of constructional time. Because pattern evolution is a function of time, it may be possible to use pattern analysis to augment current methods of age determination. Statistically defined populations can be used in geomorphic backstripping to unstack generations of simple patterns that give rise to complex patterns, and to reconstruct each generation in terms of construction time and palaeo-wind regime.

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“…Besides, very little is known about the dune morphology resulting from bimodal winds under conditions of low sand availability. In spite of many theoretical advances in the past, a model that solves both the three dimensional equations of aeolian sand transport and computes the evolution of dunes under bimodal wind regimes was lacking (12)(13)(14)(15)(16)(17).In the present work, we extend a well-developed and tested dune model (18,19) to investigate the formation of dunes under bimodal wind regimes. This model, which combines a set of well-established analytical equations for the turbulent wind field over the topography (20) with a continuum model for saltation (18)-the motion of grains in ballistic trajectories producing a splash of new ejected particles after grain-bed collisions (21-23)-reproduces quantitatively the shape of barchans and transverse dunes (24-26) and has become a powerful tool in the investigation of the large time scale processes involved in the formation of aeolian landscapes.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Dune formation under bimodal winds

Parteli

Durán

Tsoar

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

112

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The study of dune morphology represents a valuable tool in the investigation of planetary wind systems-the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle θ w between the wind directions is larger than 90 • . Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the "wedge dunes" observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability.pattern formation | critical phenomena | aeolian transport | erosion and sedimentation T he majority of the world's sand dunes are formed by winds blowing from more than one wind direction: bimodal winds, which oscillate seasonally between two main directions, are typical of the largest sand deserts of our planet (1-7). Whereas the well-known barchans and transverse dunes appear under unimodal winds for low and high sand availability on the ground, respectively, seif dunes ( Fig. 1) are the prevailing dune type under bimodal wind regimes. These dunes form in the absence of vegetation and align parallel to the resultant wind trend, developing a sharp crest which explains the term "seif" ("sword" in Arabic) and an intriguing meandering shape which has challenged geomorphologists for decades. In recent years, understanding the dynamics of seif dunes has become an issue of major interest also for planetary scientists: fields of seif dunes occur seldom on Mars (8, 9), which led to the hypothesis that Mars wind systems are essentially unidirectional. Is the appearance of seif dunes, indeed, related to the wind regime only? Moreover, are seif dunes the only dune type shaped by bimodal winds? The results of the present work provide insights into these challenging questions.It is still unknown whether other factors rather than wind directionality could also be relevant for dune alignment (10, 11) and which factors determine the meandering shape of seif dunes. Besides, very little is known about the dune morphology resulting from bimodal winds under conditions of low sand availability. In spite of many theoretical advances in the past, a model that solves both the three dimensional equations of aeolian sand transport and computes the evolution of dunes under bimodal wind regimes was lacking (12)(13)(14)(15)(16)(17).In the present work, we extend a well-developed and tested dune model (18,19) to investigate the formation of dunes under bimodal wind r...

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Modelling desert dune fields based on discrete dynamics

Cited by 62 publications

References 27 publications

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

Pattern analysis of dune‐field parameters

Dune formation under bimodal winds

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