Table Of ContentFLUVIAL PROCESSES
IN
GEOMORPHOLOGY
Luna B. Leopold
United States GeologicalSurvey
M. Gordon Wolman
TheJohns Hopkins University
John P. Miller
lateofHarvard University
DOVER PUBLICATIONS, INC.
New York
Copyright
Copyright © 1964,1992 byLuna B.Leopold and M. Gordon Wolman.
All rights reserved.
BibliographicalNote
This Doveredition, first published in 1995,isan unabridged and unaltered
republicationoftheworkfirst publishedbyW.H.Freemanand Company,San
Francisco,in 1964.
Library ofCongress Cataloging-in-Publication Data
Leopold,Luna Bergere,1915-
Fluvial processes in geomorphology / Luna B. Leopold, M. Gordon
Wolman, John P.Miller.
p. em.
"An unabridgedand unaltered republicationoftheworkfirst published by
W.H. Freemanand Company,San Francisco,in 1964"-T.p. verso.
Includes index.
ISBN0-486-68588-8(pbk.)
I. Physical geography. 2. Rivers. I. Wolman, M. Gordon (Markley
Gordon), 1924- . II. Miller, John P. (John Preston), 1923-1961.
III. Title.
GB55.L4 1995
551.3'5-dc20 95-20080
CIP
Manufacturedin the UnitedStates byCourierCorporation
68588807
www.doverpublications.com
Preface
THIS BOOK deals primarily with landform development under processes
associated with running water. The bias of the book is dictated by our ex
perience and interest and also by our belief that there is a great need at
the present time for a review of geomorphic processes.
We have emphasized those things which are best known to us (and
about which wefeel most is known). Many subjects we have included are
by no means treated completely, for they are discussed only from one
viewpoint. Others that are treated lightly, such as the evolution of slopes,
are ones for which little comprehensive quantitative data are available.
Rather than present amere rehash ofpublished materialwhich wecould
not adequately discuss, we decided to omit entirely subjects we have not
studied ourselves in the field or laboratory. Some summary monographs
are available for wind, shore, and glacial processes, and we have not at
tempted to cover those subjects here. Combining process and stratigraphy
for wind, shore, and glacial morphology would only have enlarged this
book to unmanageable bulk; and, as Penck argued many years ago, a case
can be made for the thesis that river and hillslope processes provide the
central theme of geomorphology.
Our emphasis on process is not intended to minimize the importance
of the historical aspects of geomorphology. Unfortunately, because of the
limited understanding of geomorphic processes and their associated land
forms, we ourselves are unable at present to make a truly satisfactory
translation from the dynamics of process to historical interpretation. Bet
ter future understanding of the relation of process and form willhopefully
contribute to, not detract from, historical geomorphology.
Despite its omissions, we hope that our treatment of geomorphology
in this book will provide a logical framework for the subject as a whole,
viii PREFACE
within which students and other readers can integrate material appropriate
to their own interests or local physiographic environments.
We have sorely missed our compadre and co-author, John Preston
MilJer, during the last two years when this book was actively being con
structed. Those portions which he prepared were perforce revised during
that time. We hope that his principal ideas have been retained and that
wehave not allowed either divergent viewpoints or errors to creep into his
work. Though we can put a book together without him, we can not view
the high mountains nor can we pitch a camp in just the same spirit as
when he was along.
We are indebted to colleagues and friends too numerous to name who
helped in a variety of ways-in technical review of portions of the manu
script, in furnishing data and information, in preparation of copy and il
lustrations, and in our field work. But some should be noted specifically.
First, Mae E. Thiesen, although this is not the first manuscript which
she has prepared for us. It is a pleasure to be able here to acknowledge
her thoughtful and untiring help in all aspects of manuscript preparation,
without which this book would not have been brought to completion.
We are particularly indebted to A. O. Woodford and James Gilluly for
their overall review, and to Ralph A. Bagnold, Ivan K. Barnes, John T.
Hack, Meyer Rubin, and Estella B. Leopold for their suggestions on por
tionsofthework.
To the other river boys, William W. Emmett and Robert M. Myrick,
our thanks not only for help in the field and in preparing the manuscript,
but for their company at many delightful campfires beside many distant
rivers.
Particular thanks we owe to William H. Freeman, who encouraged us
when wemostneededsuchencouragement.
And finally, we wish to mention two men who long have been close
friends, admired colleagues, and friendly advisors, Walter B. Langbein and
Thomas Maddock, JI., whose influence on this work has been perhaps
deeper andmore significantthan that ofanyothers.
LUNA B. LEOPOLD
M. GORDON WOLMAN
May 1963
Contents
PART I. THE EVOLVING LANDSCAPE
Chapter 1. The Changing Scene 3
Chapter 2. Geomorphology and the Field Problem 10
Introduction 10
A Mountain Block in a Semiarid Climate 10
A Meandering River Cut into Bedrock 18
Benches along a Sea Coast 22
PART II. PROCESS AND FORM
Chapter 3. Climate and Denudational Processes 27
Introduction: Processes of Upbuilding and of Downwasting 27
Characteristics and Classification of Processes 29
Erodibility 37
Morphogenetic Regions 40
Interaction of Vegetation, Runoff, and Sediment Yield:
an Example 46
Effective Climate in Geomorphology 49
The Annual Water Budget 49
Distribution of the Total Water Supply 51
Frequency Distribution of Climatic Events 52
Streamflow Fluctuation 58
Flood Frequency 63
The Frequency Concept and Geomorphic Processes 67
Landforms in Relation to Frequency of Climatic Events 80
Chapter 4. Weathering 97
Rocks and Water-the Components of Weathering 97
Materials Subject to Weathering 99
x CONTENTS
Composition of Rain and Snow in Relation to Weathering 101
Mineral-waterReactions 104
Products of Chemical Weathering and Some Determining
Factors 107
Products of Weathering-Clay Minerals 107
Effects of Removal by Erosion 108
Effects of Weathering Sequence 109
Effects of Transport of Materials 110
Effects of Precipitation and Temperature 111
Organic Matter 112
Processes of Physical Weathering 113
Products of Physical Weathering 114
Rates of Weathering 116
Soils: Introduction 116
Factors That Affect SoilFormation 118
Precipitation 121
Parent Material 123
Topography 126
Biologic Factors 127
Chapter 5. The Drainage Basin as a Geomorphic Unit 131
Numbers, Lengths, and Orders ofStream Channels 134
Drainage Density and Texture 142
Description of the Drainage Basin in Cross Section 149
Chapter 6. Water and Sediment in Channels 151
Introduction 151
Forces Acting in Channels 152
Velocity and Its Distribution 153
Factors Controlling Flow Velocity 156
Energy Losses in Streamflow 160
Measurement of Velocity and Discharge 166
The Debris Load of Rivers: Introduction 169
The Nature of Fluid Force and Its Relation to Debris
Movement 173
Bed Load and Suspended Load 180
Computation of Sediment Load 181
Measurement of Sediment Load 185
The Stream Bed and Its Description 188
CONTENTS xi
Chapter 7. Channel Form and Process 198
Shape of the Channel 198
Riffles and Bars 203
Variation of Hydraulic Characteristics at a Given Cross
Section 215
River-bed Scour DuringFloods 227
Variation of Hydraulic Characteristics in a Downstream
Direction 241
Longitudinal Profile of the River Channel 248
Observations on Artificial Base Level 258
Equilibrium, River Profiles, and Channel Geometry 266
Channel Pattern: Introduction 281
Straight Channels 281
Braided Channels 284
Geometry of Meanders 295
Flow in Meanders 298
Initiation and Development of Meanders 301
Meandering Valleys 308
The River Flood Plain: Introduction 317
Floods and the Flood Plain 319
Flood Plain Formation 322
Chapter 8. Hillslope Characteristics and Processes 333
Features of Slopes 333
Controls of the Form of Hillslopes 336
Relation to Lithology and Environmental Controls 337
Mass Movements: Introduction 337
Landslides and Rockfalls 338
Rapid Flows of Wet Debris 341
Creep 344
OverlandFlow: General 353
Runoff 354
Erosion 357
Lithology and Form 363
Climate and Form 367
Examples of Slope Forms in Different Regions 370
Spitzbergen and Scandinavia 370
Central Appalachian Mountain Region 372
m
CONTENTS
Hawaii 374
Southern Sudan 377
SouthwesternUnited States 379
South Africa 381
SomeGeneralizations on the Forms of Hillslopes 383
PART III. THE EFFECTS OF TIME
Chapter 9. Geochronology 389
Introduction 389
Historical Records 389
Dendrochronology 393
ArcheologicalMethods 396
Varves 397
Pollen Analysis 398
Radioactivity 402
An Example of GeochronologicProblems 405
Chapter 10. Drainage Pattem Evolution 411
Development of Rill Systems 411
Effectof Longitudinal Profileon Tributary Junctions 414
Probability and the Drainage Network 416
Evolution ofthe Drainage Net 420
Modes of Drainage Extension 428
Limits of Drainage Development 430
Chapter 11. Channel Changes with Time 433
Channel Aggradation and Accumulation of ValleyAlluvium 433
Degradation: Headcuts and Gullies 442
The Discontinuous Gully 448
Degradation of Channels as a Result of Changes in
Hydrologic Regimen 453
River Terraces 458
Terrace Sequences and Correlation of Terrace Remnants 465
Paleosols 468
River Terraces and the Field Problem 474
CONTENTS xiii
Chapter12. Evolution of HiUslopes 486
Divergent Viewsof HiIlslopeEvolution 486
Types of Evidence Supporting Some Postulates on
Landscape Evolution 487
Ultimate Forms: Pediments and Peneplains 494
Models of Slope Evolution 500
APPENDIX A.
Conversion of Units and Equivalents 505
APPENDIX B.
Symbolsand Nomenclature 506
INDEX 509
THE EVOLVING
Part I
LANDSCAPE
