Aeolian Sand and Sand Dunes Kenneth Pye · Haim Tsoar

Aeolian Sand and Sand Dunes

123 Kenneth Pye Associates Ltd., Crowthorne Enterprise Centre, Crowthorne Business Estate Old Wokingham Road, Crowthorne, Berksire RG45 6AW, UK

Haim Tsoar Ben-Gurion University of the Negev Department of Geography and Environmental Development POB 653, Beer Sheva 84105, Israel

ISBN 978-3-540-85909-3 e-ISBN 978-3-540-85910-9 DOI 10.1007/978-3-540-85910-9

Library of Congress Number: 2008935393

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987654321 springer.com Preface to the 2009 Reprint

Our decision to produce a reprinted version of Aeolian Sand and Sand Dunes has been based on several factors. The original version, published by Unwin Hyman in 1990, has been out of print for several years and we have received frequent en- quiries about the availability of ’spare’ copies of the book, either new or second- hand! A measure of the book’s success is provided by the fact that it was one of the top ten most cited books in the journal Geomorphology over the period 1995–2004 (Doyle & Julian, 2005, ‘The most cited works in Geomorphology’, Geomorphol- ogy 72, 238–249). Another indicator is provided by the fact that there are only two books identified by Google Scholar related to aeolian geomorphology which have a larger number of citations, namely Bagnold’s classic The Physics of Blown Sand and Desert Dunes, originally published by Methuen in 1941, and Pye’s Aeolian Dust and Dust Deposits, published by Academic Press in 1987. During the 20 years since we first wrote the book there have inevitably been many new developments in the field, notably relating to aeolian sand transport processes, numerical modelling of dune development, the effects of climate change and other factors on the mobil- ity and stability of sand dunes, and on dune management and conservation. In our opinion, a revised edition of the original book would not have allowed full justice to be done to this new work while at the same time retaining the essential character of the original version. We have therefore opted for a reprinted and re-styled version of the original, leaving open the prospect of a totally new book with different focus some time in the future. In choosing this route we have effectively followed Bagnold, whose 1941 book has been reprinted several times with only minor modifi- cations, most recently in 2005, and which continues to provide an invaluable source of information. In preparing this reprint of Aeolian Sand and Sand Dunes, a number

v vi of errors and omissions in the original text have been corrected, and the book has been given a more attractive layout by the new publishers (Springer), to whom we are most grateful for their help and support. We hope that the reprinted version will continue to be a useful aid to aeolian geomorphology researchers and a wider com- munity of scientists and environmental managers concerned with problems of sand, wind and dunes.

October 2008 K. Pye H. Tsoar Preface

It is more than half a century since the publication of R.A. Bagnold’s classic book The physics of blown sand and desert dunes, and it is a tribute to the quality of Bagnold’s work that many of the fundamental principles which he developed re- main valid today. His book continues to be essential reading for any serious stu- dent of aeolian processes. However, the past two decades have seen an explosion in the scale of research dealing with aeolian transport processes, sediments, and landforms. Some of this work has been summarized in review papers and edited conference proceedings, but this book provides the first attempt to review the whole field of aeolian sand research. Inevitably, it has not been possible to cover all as- pects in equal depth, and the balance of included material naturally reflects the authors’ own interests to a significant degree. However, our aim has been to provide as broad a perspective as possible, and to provide an entry point to an extensive multi- disciplinary scientific literature, some of which has not been given the attention it deserves in earlier textbooks and review papers. Many examples are drawn from existing published work, but the book also makes extensive use of our own research in the Middle East, Australia, Europe, and North America. The book has been written principally for use by advanced undergraduates, post- graduates, and more senior research workers in geomorphology and sedimentology. The emphasis is therefore on physical processes and sediment properties rather than ecology, human usage, and management. However, we believe that the book will also prove useful to many botanists, agriculturalists, engineers, and planners who have an interest in sand dunes. Following a short introductory chapter which outlines the nature and importance of aeolian sand research, the physical background to airflow is discussed in Chap. 2. The basic properties and formation of sand grains, together with the textural and mineralogical properties of aeolian sediments, are considered in Chap. 3. Chap- ters 4, 5, and 6, which lie at the heart of the book, deal with the mechanisms of aeolian sand transport, the formation of sand seas, and the dynamics of aeolian bed forms, respectively. Chapter 7 provides a summary of the internal structures found in aeolian sand deposits, and weathering and early post-depositional modification of dune sands are considered in Chap. 8. Chapter 9 examines the interactions between

vii viii Preface the physical properties of sand and dune vegetation, the problems arising from the human use of dune areas, and techniques used to stabilize windblown sand. The ﬁnal chapter (Chap. 10) provides further information about some of the main techniques currently used in aeolian research. Where possible, SI units of measurement have been used in the text. However, since many older papers present data in c.g.s. units, a conversion table is presented in Appendix 1. Acknowledgements

Many people and organizations have provided practical and financial assistance during the preparation of this book. Useful comments on earlier drafts of some chapters were made by J. D. Iversen, D. Skibin, A. Danin, V. Goldsmith, N. Lancaster, A. S. Issar, B. B. Willetts, P. Nalpanis and D. Hartmann. Any remaining errors or inaccu- racies are, of course, the sole responsibility of the authors. A. Cross and J. Watkins provided invaluable assistance with the drafting and photography. Special thanks are due to Roger Jones of Unwin Hyman for his patience and fortitude during the book’s long gestation period, and to Andy Oppenheimer for assistance during the final stages of preparation. Most of all, we wish to thank our long-suffering families for their unfailing support in trying circumstances. The following organizations, individuals and publishers kindly provided illustra- tive material or gave permission to reproduce copyrighted figures and tables (some in modified form): J. R. Riley (Fig. 2.9); D. H. Krinsley (3.24); J. Shelton (6.17, 6.19, 6.22); K. W. Glennie (6.23); D. Ball (6.35); A. Warren (6.27); V. P. Wright (8.18, 8.25); V. Goldsmith (6.21); D. Blumberg (10.8); W. G. Nickling (10.2); Beach Protec- tion Authority of Queensland (9.19); C.S.I.R.O. (Australia) (10.10); Endecotts Ltd. (10.15); American Society of Civil Engineers (4.19, 4.20, 9.11, 9.28, 9.31), U.S. Army Coastal Engineering Research Center (9.29); O. E. Barndorff-Nielsen (3.7, 6.30, 6.32, 10.9); Department of National Mapping (Australia) (6.44, 6.45, 6.48); U.S. Geological Survey (3.13, 3.14, 5.4, 7.20); Surveys and Mapping Department of South Africa (6.53); D.S.I.R. (New Zealand) (5.8); Royal Meteorological Soci- ety (2.24); Geological Society of America (5.11, 5.12, 5.5, 6.6); Soil Science So- ciety of America (4.12); International Association of Sedimentologists (4.10, 6.26, 6.32, 6.36, 7.2.1, 7.3, 7.4, 7.6, 7.7, 7.12, 7.15, 7.29, 7.30); Geografisker Annaler (6.17, 6.46, 6.47, 7.2.4, 7.10, 7.11, 7.13, 7.2.6); Society of Economic Paleontologists and Mineralogists (3.10, 3.20, 6.5, 6.41, 8.6.3); The Royal Society (3.7); Episodes Secretariat (5.19); American Association of Petroleum Geologists (8.19); Gebruder Borntraeger (5.4); Longman Ltd. (6.58, 6.59); Macmillan Journals Ltd. (4.7, 4.22, 6.20, 8.12); Blackwells Ltd. (8.16); Oxford University Press (3.16, 3.17, 3.4.2); John Wiley Ltd. (7.31); University of Chicago Press (3.8, 3.30, 6.50); Elsevier Scientific

ix x Acknowledgements

Publishers (3.21, 3.22, 5.2, 5.5, 5.8, 6.32, 10.3); Unwin Hyman Ltd. (5.7, 5.16, 6.56, 7.19, 8.1, 8.5.6, 9.4, 9.25); Van Nostrand Reinhold (2.5); McGraw-Hill Book Com- pany (2.19, 2.21); Martinus Nijhoff Publishers (2.26); Chapman and Hall Ltd. (4.15, 7.5); Edward Arnold Ltd. (4.21); D. Reidel (2.25, 9.20); SPB Academic Publishers (9.27); W. H. Freeman and Company (6.17, 6.19); Pergamon Press (5.5). Contents

1 The Nature and Importance of Aeolian Sand Research ...... 1 1.1 Deﬁnitions...... 1 1.2 PreviousWork...... 3 1.3 FutureResearchRequirements...... 6

2 The Nature of Airflow ...... 9 2.1 PhysicalPropertiesofAirandtheEarth’sAtmosphere ...... 9 2.1.1 TheNatureofAirasaGas...... 9 2.1.2 Composition of the Lower Atmosphere ...... 10 2.1.3 Vertical Gradient of Temperature and Stability of the Atmosphere ...... 11 2.2 NatureandTypesofAirMotion...... 13 2.2.1 HorizontalAirMotion...... 13 2.2.2 TheGlobalAtmosphericCirculation...... 15 2.3 StormTypesthatGenerateSand-TransportingWinds...... 18 2.3.1 TheEnergyofViolentStorms...... 18 2.3.2 Atmospheric Stability and Instability in Subtropical Deserts 21 2.3.3 DustDevils...... 23 2.3.4 Squalls...... 24 2.3.5 WindRegimesintheWorld’sDeserts...... 26 2.3.6 CoastalWindRegimes...... 30 2.4 Flow in the Atmospheric Boundary Layer ...... 32 2.4.1 Viscosity, Reynolds Number andTheirEffectontheAirflow...... 32 2.4.2 VariationofWindVelocitywithHeight...... 35 2.4.3 Continuity of Airflow: Bernoulli Equation andSeparationofFlow...... 40 2.4.4 TheDragForce...... 43 2.4.5 Airflow over Isolated Hills and Complex Terrain ...... 46

xi xii Contents

3 Characteristics of Windblown Sediments ...... 51 3.1 GeneralPropertiesofSedimentGrains...... 51 3.1.1 ConceptsofGrainSize ...... 51 3.1.2 GrainSizeScales...... 53 3.1.3 GrainMassandDensity...... 54 3.1.4 GraphicalPresentationofGrainSizeData ...... 56 3.1.5 GraphicalStatisticalParameters...... 58 3.1.6 MomentParameters...... 60 3.1.7 Bivariate Plots and Statistical Analysis ofGrainSizeParameters...... 60 3.1.8 Log-HyperbolicParameters ...... 61 3.2 GrainShape...... 65 3.2.1 GrainForm...... 65 3.2.2 Grain Roundness ...... 67 3.2.3 GrainSurfaceTexture...... 68 3.2.4 Two-Dimensional Analysis of Digitized Grain Outlines . . . . 68 3.2.5 BehaviouralIndicatorsofGrainShape ...... 71 3.2.6 ControlsontheShapeofSandGrains...... 71 3.3 Porosity, Permeability, and Packing of Sands...... 72 3.4 GrainSizeCharacteristicsofAeolianSediments...... 74 3.4.1 TheNatureofAeolianSediments...... 74 3.4.2 Differentiation Between Aeolian Dune andOtherEnvironments...... 77 3.4.3 Grain Size Variations Within Dune Fields andonIndividualDunes...... 80 3.5 ShapeCharacteristicsofAeolianDuneSands...... 82 3.6 SurfaceTexturesofAeolianSands...... 86 3.7 Porosity and Permeability of Aeolian Sands ...... 89 3.8 Sources and Mineral Composition of Aeolian Dune Sand ...... 89 3.8.1 WeatheringandErosionofCrustalRocks...... 90 3.8.2 Formation of Sand-Size Particles intheNear-SurfaceEnvironment...... 92 3.8.2.1 GypsumSands...... 92 3.8.2.2 ClayPellets...... 92 3.8.2.3 VolcaniclasticSands...... 94 3.8.2.4 Carbonate Ooids and Peloids ...... 95 3.8.3 Formation of Biogenic Carbonate Sand ...... 96

4 Mechanics of Aeolian Sand Transport ...... 99 4.1 ParticleEntrainment...... 99 4.1.1 ForcesExertedonStaticGrainsbytheWind...... 99 4.1.2 ThresholdofGrainMovement...... 101 4.1.3 ImpactThreshold...... 106 4.1.4 Threshold Velocities for Poorly Sorted Sediments ...... 108 4.1.5 EffectofBedSlopeonThresholdVelocity...... 109 Contents xiii

4.1.6 Effect of Moisture Content and Cementing Agents onThresholdVelocity...... 110 4.1.7 Effects of Non-Erodible Roughness Elements andVegetationonParticleEntrainment...... 113 4.2 TransportofParticlesbytheWind ...... 113 4.2.1 AeolianTransportModes...... 113 4.2.2 Suspension ...... 116 4.2.3 Saltation...... 116 4.2.4 WindVelocityProﬁleDuringSaltation...... 124 4.2.5 ContactLoad(SurfaceCreep)...... 127 4.2.6 SandTransportRate...... 128 4.2.7 Avalanching of Sand on Dune Slip Faces ...... 136

5 The Formation of Sand Seas and Dune Fields ...... 141 5.1 Deﬁnition of Sand Seas and Dune Fields ...... 141 5.2 GlobalDistributionofSandSeas...... 141 5.3 Factors Controlling the Distribution andMagnitudeofSandSeas...... 147 5.3.1 SandSourcesandDuneFieldDevelopment...... 147 5.3.2 RelationshipBetweenSandDepositsandClimate...... 153 5.3.3 Time Required for the Development ofErgsandDuneFields ...... 155 5.4 Development of Sand Seas in Relation to Topography ...... 156 5.5 WindRegimeandRegionalSandFlowPaths ...... 159 5.6 Evolution of Ergs in Response to Climatic Changes ...... 168 5.7 EffectofSea-LevelChangesonCoastalDuneFields...... 170 5.8 EffectofSea-LevelChangesonContinentalDuneFields ...... 172

6 Aeolian Bed Forms ...... 175 6.1 Types of Aeolian Sand Accumulation and Bed Form Terminology . . 175 6.2 Ripples...... 176 6.2.1 TheGeneralNatureofSandRipples...... 176 6.2.2 Effect of Wind Velocity and Grain Size onAeolianRippleDevelopment...... 178 6.2.3 ModelsofRippleFormation...... 180 6.2.4 AdhesionRipples...... 184 6.3 SandDunes...... 185 6.3.1 Classiﬁcation of Sand Dunes andOtherAeolianSandAccumulations...... 185 6.3.2 Dune Accumulation Inﬂuenced by Topographic Obstacles . . 190 6.3.2.1 LeeDunes...... 190 6.3.2.2 EchoDunes...... 192 6.3.2.3 Cliff-TopDunes...... 195 6.3.3 FormationofSelf-AccumulatedDunes...... 195 6.3.3.1 Dune Initiation ...... 195 xiv Contents

6.3.3.2 Development of a Steady-State Dune Proﬁle . . . . . 197 6.3.3.3 Flow Separation and the Development ofaDuneSlip-Face...... 200 6.3.4 SimpleBarchansandTransverseBarchanoidRidges...... 201 6.3.5 LinearDunes...... 206 6.3.5.1 DevelopmentofSeifDunes ...... 209 6.3.5.2 ObliqueDunes...... 216 6.3.6 StarDunes...... 219 6.3.7 DomeDunes...... 223 6.4 VegetatedDunes...... 224 6.4.1 HummockDunes...... 225 6.4.2 Parabolic and Elongate Parabolic Dunes ...... 229 6.4.3 PrecipitationRidges...... 237 6.4.4 LunetteDunes...... 238 6.4.5 VegetatedLinearDunes...... 239 6.5 SandSheets...... 245 6.5.1 WarmClimateSandSheets...... 245 6.5.2 Zibar ...... 247 6.5.3 ColdClimateSandSheets...... 248 6.6 Summary of Factors Determining the Morphology ofAeolianSandAccumulations...... 251

7 Internal Sedimentary Structures of Aeolian Sand Deposits ...... 255 7.1 Introduction ...... 255 7.2 InternalStructuresofSandDunes...... 258 7.2.1 Primary Structural Features Common to Most Dune Types. . 258 7.2.2 InternalStructureofBarchans ...... 262 7.2.3 InternalStructureofTransverseDunes...... 266 7.2.4 InternalStructureofSeifDunes...... 266 7.2.5 InternalStructureofUnvegetatedDomeDunes...... 270 7.2.6 Internal Structure of Reversing Dunes and Star Dunes . . . . . 270 7.2.7 InternalStructuresofShadowDunes...... 273 7.2.8 InternalStructuresofVegetatedCoastalDunes ...... 275 7.2.9 InternalStructureofParabolicDunes ...... 275 7.2.10 Nature and Origin of Bounding Surfaces ...... 277 7.3 Secondary Sedimentary Structures in Dunes ...... 280 7.4 Sedimentary Structures of Inter-dune Areas and Sand Sheets ...... 284 7.4.1 Inter-dune Areas ...... 284 7.4.2 Extra-DuneSandSheets...... 289 7.5 Niveo-Aeolian Deposits and Cryogenic Structures inCold-ClimateDunes...... 290 Contents xv

8 Post-Depositional Modification of Dune Sands ...... 293 8.1 Introduction ...... 293 8.2 Denudation by Rain Splash, Surface Wash, SoilCreep,andGullying...... 294 8.3 Near-SurfaceCompaction ...... 295 8.4 Addition of Allochthonous Components ...... 295 8.5 Weathering and Pedogenesis of Siliceous Dune Sands ...... 297 8.5.1 Leaching of Soluble Salts and Carbonates ...... 297 8.5.2 ChemicalWeatheringofSilicatesandOxides...... 297 8.5.3 HeavyMinerals ...... 298 8.5.3.1 Feldspars...... 298 8.5.3.2 Quartz...... 299 8.5.4 PhysicalWeatheringProcesses...... 301 8.5.5 Chemical Weathering and Reddening of Siliciclastic Dune Sands ...... 301 8.5.6 Silica Coatings and Cementation ...... 307 8.5.7 FormationofSoilProfilesinDuneSands...... 309 8.5.8 PodsolizationandHumateCementation...... 309 8.6 Formation of Carbonate Aeolianites ...... 316 8.6.1 Definition and Occurrence of Aeolianites ...... 316 8.6.2 Controls on Carbonate Cementation in Aeolianites ...... 318 8.6.2.1 Effects of Carbonate Mineralogy ...... 318 8.6.2.2 EffectsofRainfallandEvaporation...... 322 8.6.2.3 EffectsofVegetation...... 324 8.6.3 Calcrete Horizons in Carbonate Dune Sands ...... 325 8.6.4 KarstificationofAeolianites...... 327 8.6.5 RelationshipBetweenAeolianitesandRedSoils...... 327 8.6.6 RegressiveDiagenesisofAeolianites...... 328 8.7 EarlyDiageneticCementationbyEvaporiteMinerals ...... 328

9 Management and Human Use of Sand Dune Environments ...... 329 9.1 Thermal Properties of Sand, Moisture Regime, andVegetationGrowth...... 329 9.1.1 ThermalProperties...... 329 9.1.2 SandMoistureRegime...... 331 9.1.3 OtherFactorsWhichInﬂuenceDuneVegetation...... 336 9.2 WaterCoursesinDuneAreas ...... 338 9.3 Control of Windblown Sand ...... 340 9.3.1 Reduction of Sand Supply ...... 340 9.3.1.1 SurfaceStabilizationbyMulches...... 341 9.3.1.2 PhysicalBarrierstoAirﬂow...... 342 9.3.1.3 Restriction of Human Activity inPotentialSandSourceAreas...... 342 9.3.2 EnhancementofSandTransport...... 343 9.3.3 DiversionofMovingSand...... 344 xvi Contents

9.3.4 Enhancement of Sand Deposition ...... 344 9.3.4.1 SandFences...... 344 9.3.4.2 SandDitches...... 349 9.3.4.3 VegetationPlanting ...... 349 9.3.4.4 Combined Stabilization Methods ...... 354 9.3.5 ControlofMovingDunes...... 355 9.4 HumanUseofSandDuneAreas...... 355 9.4.1 CultivationonDesertSand...... 356 9.4.2 CultivationandGrazingonCoastalDunes...... 358 9.4.3 Urban Development and Recreational Activities ...... 360 9.4.4 SandMining...... 361 9.4.5 Dunes and Water Supply ...... 362 9.4.6 CoastalDunesasNaturalSeaDefences...... 364

10 Aeolian Research Techniques ...... 369 10.1 Wind Tunnel Studies ...... 369 10.2MeasurementofSandMovementUsingSandTraps...... 374 10.2.1 HorizontalSandTraps...... 375 10.2.2 VerticalSandTraps ...... 376 10.2.3 SurfaceCreepTraps...... 381 10.3 Sand Tracer Techniques ...... 381 10.4 Methods of Sample Collection for Grain Size andMineralogicalAnalysis...... 385 10.5 Methods of Determining the Grain Size of Sands ...... 388 10.5.1 Sieving...... 388 10.5.1.1 SamplePretreatment...... 388 10.5.1.2 DrySieving...... 389 10.5.1.3 WetSieving...... 390 10.5.2 Settling Tube Analysis ...... 391 10.5.3 Electro-Optical Methods of Size Analysis ...... 391 10.5.4 Direct Measurement of Grain Size by Image Analysis . . . . . 392 10.6CharacterizationofAirﬂow...... 392 10.6.1 WindVelocityMeasurements...... 392 10.6.2 FlowVisualization...... 393 10.7 Methods of Monitoring Changes in Sand Dune Terrain ...... 393 10.7.1 FieldSurveys ...... 393 10.7.2 RemoteSensing...... 394 10.7.3 Sand Dating Methods ...... 394 Appendix: SI units and c.g.s. equivalents ...... 397

References ...... 399

Index ...... 453