Table Of ContentPhysics of desertification
Physics of desertification
Edited by
FAROUK EL-BAZ
ltek Optical Systems
Lexington MA
USA
M.H.A. HASSAN
University of Khartoum
Khartoum, Sudan
1986 MARTINUS NIJHOFF PUBLISHERS
a member of the KLUWER ACADEMIC PUBLISHERS GROUP
DORDRECHT / BOSTON / LANCASTER
Distributors
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Falcon House, Queen Square, Lancaster LAI lRN, UK
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P.O. Box 322, 3300 AH Dordrecht, The Netherlands
Library of Congress Cataloging in Publication Data
Papers of desertification.
Papers presented at a workshop held in Trieste,
Italy, Nov. 10-28, 1980, under the auspices of the
International Center for Theoretical Physics.
1. Desertification--Congresses. 2. Geomorphology--
Arid regions--Congresses. 3. Arid regions--Congresses.
4. Arid regions agriculture--Congress€s. I. EI-Baz,
Farouk. II. Hassan, M. H. A. III. International
Centre for Theoretical Physics.
GB611.P476 1986 551.4 86-762
ISBN-13: 978-94-010-8451-2 e-ISBN-13: 978-94-009-4388-9
001: 10.1007/978-94-009-4388-9
ISBN-13: 978-94-010-8451-2
Copyright
© 1986 by Martinus Nijhoff Publishers, Dordrecht.
Softcover reprint of the hardcover 1s t edition 1986
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means, mechanical,
photocopying, recording, or otherwise, without the prior written permission of
the publishers,
Martinus Nijhoff Publishers, P.O. Box 163, 3300 AD Dordrecht,
The Netherlands.
PREFACE
Deserts are parts of the Earth that receive little or no
rain; 25 cm or less per year. The physical processes that act
upon these parched lands are vastly different from those that
shape the more humid parts of the terrestrial landmasses. In
the desert, wind is a major agent of erosion and transportation.
As the results of recent space missions have indicated,
this is also true in the case of the planet Mars. Thus, our
understanding of desert processes sheds light on fundamental
planetary processes that may apply on any planetary body that
is enveloped by a windy atmosphere.
An understanding of the physical layout of arid lands, and
the nature of processes that initiate changes therein is also
fundamental to thoughtful utilization of these lands for the
benefit of mankind. It is with this in mind that we prepared
this book for publication.
We believe that the collection of articles in this book
will be useful to scientists who are interested in desert
landforms and processes, and to planners of economic develop-
ment of arid lands. The book also serves as a guide for
students as to the state of our knowledge in this field as
well as to the topics that require additional research.
Special thanks are due to three staff members of the
Smithsonian Institution's Center for Earth and Planetary
Studies: Ellen Lettvin for her help in preparing the manu-
script for publication; Rose Aiello for drafting the figures;
and Donna Slattery for typing the manuscript. We are also
indebted to the Itek Optical Systems Publications Department
personnel for their help in preparing the manuscript.
Farouk El-Baz
M. H. A. Hassan
v
TABLE OF CONTENTS
List of Contributors . . . . . . . . . . . . . . . . . . XI
Report on Workshop on Physics of Desertification 1
M. H. A. Hassan
Desertification of Arid Lands • • • • • • • • • • • • • • 4
H. E. Dregne
Wind Versus Water Erosion in the Context
of Desertification • • • • • • • • • • • 35
Michael M. Verstraete and Jean-Pascal van Ypersele
The United Nations Organization and the
Issue of Desertification 42
Michel M. Verstraete
The Impact of Desertification on Land
Productivity in Sudan • • • • 52
M. O. H. El-Karouri
Desertification Problems in a Humid Region 59
Jens Tyge M~ller
The Formation and Motion of Dunes and Sand Seas • • • • • 70
Farouk El-Baz
Two-Dimensional Analysis of Dune Profile and the
Effects of Grain Size on Sand Dune Morphology • 94
Haim Tsoar
VII
Stabilization and Afforestation of Sand Dunes
Through Biosaline Culture Technique • 109
R. Ahmad
Some Aspects of Sand Stabilization in Egypt • • • • • •• 118
S. S. Tag El Din
Eco-Technique--Magic Formula for Reclaiming
Desertified Semiarid Crop Land • • • • • 127
Hans-Joachim Spaeth
Monitoring the Sand-Moving Desert Winds • • • • • • • •• 141
Farouk El-Baz
Aeolian Activity as a Planetary Process • • • • • • • •• 159
Ronald Greeley
On the Reddening of Quartz Grains in Dune Sand 191
Farouk El-Baz
The Wind and Desertification Processes in the
Saharo-Sahelian and Sahelian Regions 210
Monique Manguet
The Advance Mechanism of Longitudinal Dunes • • • • • •• 241
Haim Tsoar
Production of Dust 251
Dale A. Gillette
Soil Erosion by Wind: An Overview • • • • • • • • • • • • 261
E. L. Skidmore
Wind Erosion in the Interior Delta of the
Niger in Mali ••••••••• • • • • • • • • 274
H. K. Barth
Aeolian Processes and Features at
Amboy Lava Field, California • • • • • • • • • • • • • 290
Ronald Greeley and James D. Iversen
Aeolian Processes in the Environmental Wind
Tunnel and in the Atmosphere •••••• 318
J. D. Iversen
Threshold Velocities for Dust Production 322
Dale A. Gillette
VIII
Formation of Ripples, Dunes, and Antidunes in
River Beds •.•.•.••..•.•... 327
J¢rgen Freds¢e
Saltation Threshold Mechanics • • • • • • • • • • • • • • 344
J. D. Iversen
Dust Production by Wind Erosion: Necessary
Conditions and Estimates of Vertical Fluxes of
Dust and Visibility Reduction by Dust • • • 361
Dale A. Gillette
The Aeolian Wind Tunnel--Saltation Similitude • • • • • • 372
J. D. Iversen
Shape and Dimension of Dunes in Open
Channel Flow • • • • • • 385
J¢rgen Freds~e
The Stability and Propagation of Sand Ripples
and Dunes • • • • •• •••• 398
I. A. Eltayeb and M. H. A. Hassan
Turbulent Flow Over Topography With Applications
to Sand-Wave Development ••••••••••••••• 435
K. J. Richards
INDEX ••••••••••••••••••••••••••••••••• • •• " ••••••.••••• . • . 46 3
IX
LIST OF CONTRIBUTORS
Professor R. Ahmad Dr. I. A. Eltayeb
Faculty of Science School of Hathematical
University of Karachi Sciences
Karachi 32, Pakistan University of Khartoum
Khartoum, Sudan
Dr. Hans Karl Barth
Universitaet Bremen Dr. J~rgen Freds~e
FB1-Schewertukt Geographie Institute of Hydrodynamics
Post Fach 330440 and Hydrolic Engineering
D-2800 Bremen 33 Technical University
Federal Republic of Germany of Denmark
KD-2800 Lyngby
Denmark
Professor Harold E. Dregne
International Center for Arid
and Semi-Arid Land Studies Dr. Dale A. Gillette
Texas Tech University Cires Program
P. O. Box 4260 University of Colorado
Lubbock, Texas 79409 USA Boulder, Colorado 80307 USA
Dr. Farouk El-Baz Dr. Ronald Greeley
Itek Optical Systems Department of Geology
10 Haguire Road Arizona State University
Lexington, Hassachusetts 02173 Tempe Arizona 85281 USA
USA
Dr. H. H. A. Hassan
Dr. M. O. H. El-Karouri School of Hathematical
Agricultural Research Council Sciences
P. O. Box 6096 University of Khartoum
Khartoum, Sudan Khartoum, Sudan
XI
Dr. J. D. Iversen Dr. Hans-Joacnim Spaeth
Aerospace Engineering Department of Geography
Department University of Oklahoma
304 Town Engineering Building at Norman
Iowa State University Norman, Oklahoma 73069 USA
Ames, Iowa 50010 USA
Dr. S. S. Tag EI Din
Professor Monique Mainguet Desert Institute
Laboratoire de Geographie Al-Matreya, Cairo
Physique Zonale at d'Etudes Arab Republic of Egypt
des Pays ages en Roches
Sedimentaires
Universite de Reims Dr. Haim Tsoar
57, rue Pierre Taittinger Department of Geography
51100 Reims, France Ben-Gurion University
Beer-Sheeva 84105, Israel
Jens Tyge M~ller
Institute of Geology Dr. Michel M. Verstraete
c/o Institute of Physics Desertification Unit
Bygning 521 United Nations Environmental
Langelandsgade Programme
DK 8000 Aarhus C P. O. Box 47074
Denmark Nairobi, Kenya
Dr. K. J. Richards Jean-Pascal van Ypersele
Department of Applied Desertification Unit
Mathematics and United Nations Environmental
Theoretical Physics Programme
University of Cambridge P. O. Box 47074
Silver Street Nairobi, Kenya
Cambridge, United Kingdom
Dr. E. L. Skidmore
U. S. Department of
Agriculture
Wind Erosion Research Unit
Room 204, East Waters Hall
Kansas State University
Manhatten, Kansas 66506 USA
XII
REPORT ON
WORKSHOP ON PHYSICS OF DESERTIFICATION
By
M. H. A. Hassan
BACKGROUND AND OBJECTIVES:
Al though deserts and arid lands comprise nearly one-third
of the Earth's land surface, the physical processes taking
place in these regions are far from being fully understood. In
certain places these processes result in severe degradation of
soil and lead to desertification and human suffering. It is
estimated that nearly 80 million people are threatened by
desertification, particularly those living near desert bound-
daries and around oases that are surrounded by active sand
dunes. In recent years and particularly after the Sahelian
drought and famine, the problems of arid lands have received
wide international attention. Most of this attention, however,
has been directed towards ecological, socioeconomic, and
management problems.
It is now generally accepted that a fundamental
understanding of the problems of deserts and arid regions can
only be achieved through a broadly based interdisciplinary
approach. In this approach, it is essential to consider the
desertification mechanism as a complicated combination of both
physical and ecological processes--a clear understanding of
which must be based on physical and mathematical modelling.
A workshop on the Physics of Desertification was held in
Trieste, Italy, from the 10th to the 28th of November 1980,
under the auspices of the International Center for Theoretical
Physics. The workshop was attended by approximately 80 scien-
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