Environmental Geology

542 Pages·2010·65.629 MB·English

by  Carla Montgomery

ninth edition
Environmental
Geology
Carla W. Montgomery
Professor Emerita
Northern Illinois University
TM
TM
ENVIRONMENTAL GEOLOGY, NINTH EDITION
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Library of Congress Cataloging-in-Publication Data
Montgomery, Carla W., 1951-
Environmental geology / Carla W. Montgomery.—9th ed.
p. cm.
Includes bibliographical references and index.
ISBN 978–0–07–352408–5 — ISBN 0–07–352408–5 (hard copy : alk. paper) 1. Environmental
geology—Textbooks. I. Title.
QE38.M66 2011
550—dc22
2009041010
www.mhhe.com
I n Dedication
Environmental Geology is aff ectionately
dedicated to the memory of Ed Jaff e, whose
confi dence in an unknown author made the
fi rst edition possible.
–CWM–
Preface
b o u t t h e ACourse cannot, for instance, use a resource that is not there, or build a
secure home or a safe dam on land that is fundamentally un-
stable. Geology, then, is a logical place to start in developing an
Environmental Geology Is Geology Applied
understanding of many environmental issues. The principal
to Living
aim of this book is to present the reader with a broad overview
The environmentt is the sum of all the features and conditions
of environmental geology. Because geology does not exist in a
surrounding an organism that may infl uence it. An individual’s
vacuum, however, the text introduces related considerations
physical environment encompasses rocks and soil, air and wa-
from outside geology to clarify other ramifi cations of the sub-
ter, suchfactors as light and temperature, and other organisms.
jects discussed. Likewise, the present does not exist in isolation
One’s social environment might include a network of family
from the past and future; occasionally, the text looks both at
and friends, a particular political system, and a set of social
how the earth developed into its present condition and where
customs that affect one’s behavior.
matters seem to be moving for the future. It is hoped that this
Geology is the study of the earth. Because the earth pro-
knowledge will provide the reader with a useful foundation for
vides the basic physical environment in which we live, all of
discussing and evaluating specifi c environmental issues, as
geology might in one sense be regarded as environmentalgeol-
well as for developing ideas about how the problems should be
ogy. However, the term environmental geology is usually re-
solved.
stricted to refer particularly to geology as it relates directly to
human activities, and that is the focus of this book. Environ-
Features Designed for the Student
mental geology is geology applied to living. We will examine
how geologic processes andhazards infl uence human activities
(and sometimes the reverse), the geologic aspects of pollution This text is intended for an introductory-level college course. It
and waste-disposal problems, and several other topics. does not assume any prior exposure to geology or college-level
mathematics or science courses. The metric system is used
Why Study Environmental Geology? throughout, except where other units are conventional within a
discipline. (For the convenience of students not yet “fl uent” in
One reason for studying environmental geology might simply
metric units, a conversion table is included on the inside back
be curiosity about the way the earth works, about the howand
cover, and in some cases, metric equivalents in English units
why of natural phenomena. Another reason is that we are in-
are included within the text.)
creasinglyfaced with environmental problems to be solved and
Each chapter opens with an introduction that sets the
decisions to be made, and in many cases, an understanding of
stage for the material to follow. In the course of the chapter,
one or more geologic processes is essential to fi nding an ap-
important terms and concepts are identifi ed by boldface type,
propriate solution.
and these terms are collected as “Key Terms and Concepts” at
Of course, many environmental problems cannot be fully
the end of the chapter for quick review. The Glossary includes
assessed and solved using geologic data alone. The problems
both these boldface terms and the additional, italicized terms
vary widely in size and in complexity. In a specifi c instance,
that many chapters contain. Most chapters include actual case
data from other branches of science (such as biology, chemistry,
histories and specifi c real-world examples. Every chapter con-
or ecology), as well as economics, politics, social priorities, and
cludes with review questions and exercises, which allow stu-
so on may have to be taken into account. Because a variety of
dents to test their comprehension and apply their knowledge.
considerations may infl uence the choice of a solution, there is
The “Exploring Further” section includes items that might
frequently disagreement about which solution is “best.” Our
serve as ideas for projects or research papers building on text
personal choices will often depend strongly on our beliefs about
material.
which considerations are most important.
Each chapter includes one or more case studies relating
to the chapter material. Some involve a situation, problem,
About the Book
or application that might be encountered in everyday life.
Others offer additional case histories or relevant examples.
An introductory text cannot explore all aspects of environmen- The tone is occasionally light, but the underlying issues are
tal concerns. Here, the emphasis is on the physical constraints nonetheless real. (While some case studies were inspired by
imposed on human activities by the geologic processes that actual events, and include specific factual information, all
have shaped and are still shaping our natural environment. In a of the characters quoted, and their interactions, are wholly
real sense, these are the most basic, inescapable constraints; we fi ctitious.)
iv
Nwe and Updated Content of such retreating of alpine glaciers for water supplies in
many areas.
Chapter 10 This chapter, new to the last edition, has been
Environmental geology is, by its very nature, a dynamic fi eld in
considerably expanded, refl ecting ever-growing interest
which new issues continue to arise and old ones to evolve. Every
in global climate change. The relatively greater warming
chapter has been updated with regard to data, examples, and
of the polar regions, and its signifi cance, is examined
illustrations.
more fully. New information from the IPCC 2009 report
Geology is a visual subject, and photographs, satellite
is incorporated. Additional effects of climate change,
imagery, diagrams, and graphs all enhance students’ learning.
observed and postulated, are described: changes in
Accordingly, this edition includes more than two hundred new
phytoplankton productivity, changing ocean chemistry
illustrations, with revisions having been made to dozens more.
and its effect on corals, changing patterns of rainfall and
In addition each chapter now features one or two Case Studies
drought such as may have contributed to the recent
to present contemporary issues.
devastating Australian fi res. The role of oceans as
Signifi cant content additions and revisions to specifi c
thermal reservoir is further examined. Discussion of
chapters include:
paleoclimates and the evidence for them has been
Chapter 1 A new case study examines models of lunar expanded. A case study addresses the problem of how,
origin to illustrate hypothesis-testing in science. in fact, the earth’s temperature is measured, and how
Population statistics have been updated, with increased some of those measurements support the connection
focus on China and India. between warming and GHG. Some proposed
Chapter 2 The asbestos case study has been expanded to “geoengineering” solutions to moderate climate change
include some of the complexities of the Libby, Montana, are noted.
vermiculite mine. Chapter 11 New information includes data showing that
Chapter 3 Discussion of evidence supporting plate-tectonic evaporation losses from reservoirs exceed human water
theory has been expanded, and a case study added to consumption worldwide, and evidence that use of
illustrate how this theory supplanted the previous model desalinated water may cause defi ciency disease in crops
of mountain-building. if not in people. Case studies of the High Plains Aquifer
Chapter 4 Discussions of fault types, of moment magnitude, System and the Aral Sea are updated.
and of tsunami monitoring have been expanded. New Chapter 12 Impact of expansion of biofuel crops on
case studies describe applications of short-term soil-conservation efforts are noted. A case study has
earthquake early-warning systems, and studies related to been added to explore forensic geology as it involves
the San Andreas Fault Observatory at Depth (SAFOD). soils and sediments.
Chapter 5 Information has been added on the Mammoth Chapter 13 Data and graphs on mineral consumption,
Lakes tree kills and the hazards of magmatic CO , as well reserves, recycling, etc., have been fully updated.
2
as on new evidence of links between earthquakes and Discussion of global mineral demand now includes
volcanic activity. The status of activity at Kilauea and specifi c focus on the impact of China’s development. A
Mount St. Helens has been updated. A new case study case study examines cell-phone e-cycling from a
examines the threats posed by the reawakening of mineral-resource perspective.
Redoubt volcano. Chapter 14 As with minerals, tables and graphs of fossil-
Chapter 6 Updated case studies examine more broadly the fuel consumption and reserves have been updated.
problem of characterizing fl ood frequency, and that of Expanded analysis of factors affecting possible oil
controlling fl ooding on the Mississippi River system via exploration in ANWR now includes information on the
levees. time factor in oil-fi eld development. New/additional
Chapter 7 Discussion of tides has been improved and information on mountaintop-removal coal mining,
expanded. The case study involving the vulnerability of hazards of ash impoundments, and usefulness of
coastal regions to hurricanes now addresses Hurricane coal-to-liquid technology has been included.
Ike as well as Katrina, and illustrates the role of the Chapter 15 The Chernobyl case study has been updated, as
Galveston seawall. have statistics on U.S. and global nuclear reactors
Chapter 8 Landslides in the Pacifi c Northwest in the winter operating and under construction. Analysis of energy loss
of 2008–2009 are now discussed. Coverage of landslide in generation of electricity has been expanded. New
monitoring and prediction is expanded to illustrate issues include mineral-resource availability as a potential
relationships of slide hazard to precipitation history. constraint on expanded use of photovoltaics, and the
Chapter 9 Historic and modern photo pairs illustrate effect that widespread cultivation of biofuel crops can
dramatic changes in several alpine glaciers. The case have on food supplies, land use, and carbon sinks.
study considering glaciers as a water source has been Chapter 16 Data on municipal waste generation and
expanded to explore more specifi cally the implications nuclear-waste handling in various parts of the world
Preface v
have been updated, as has discussion of Superfund. The realities. The section on surface processes concludes with a
problem of toxic elements in e-cycling is highlighted. chapter on climate, which connects or affects a number of the
The case study examining “life cycle” comparison of surface processes described earlier in Section III.
simple objects to assess environmental impact has been A subject of increasing current concern is the availability
expanded. of resources. A series of fi ve chapters deals with water re-
Chapter 17 Mercury pollution is more fully examined. A sources, soil, minerals, and energy, the rates at which they are
new case study on DDT highlights the environmental being consumed, probable amounts remaining, and projections
persistence of bioaccumulative pesticides. New data on of future availability and use. In the case of energy resources,
water quality in wells are presented. we consider both those sources extensively used in the past and
Chapter 18 Data on emissions of EPA’s criteria air pollutants new sources that may or may not successfully replace them in
have been updated, as have acid-rain maps. Expanded the future.
discussions include the role of aerosols in weather, and Increasing population and increasing resource consump-
carbon-sequestration strategies and experiments; new tion lead to an increasing volume of waste to be disposed of;
information on residual lead in soils along highways has thoughtless or inappropriate waste disposal, in turn, commonly
been added to the discussion of lead pollution. creates increasing pollution. Three chapters examine the inter-
Chapter 19 “Cap-and-trade” as a strategy for reducing related problems of air and water pollution and the strategies
pollution is now discussed. Discussion of seabed mining available for the disposal of various kinds of wastes. The intro-
rights and the EEZ is expanded to include new legal duction to this section presents some related concepts from the
developments and effects of global warming. fi eld of geomedicine, linking geochemistry and health.
Chapter 20 Three Gorges Dam is now a major case study, The fi nal two chapters deal with a more diverse assort-
with more information on hazards and concerns associated ment of subjects. Environmental problems spawn laws intended
with the project, and problems already experienced. to solve them; chapter 19 looks briefl y at a sampling of laws,
policies, and international agreements related to geologic mat-
At chapter ends, the old “For Further Thought” questions have
ters discussed earlier in the book, and some of the problems
been expanded and modifi ed under the revised heading “Ex-
with such laws and accords. Chapter 20 examines geologic con-
ploring Further” to include a number of activities in which stu-
straints on construction schemes and the broader issue of trying
dents can engage, some involving online data, and some
to determine the optimum use(s) for particular parcels of land—
quantitative analysis. For example, they may be directed to ex-
matters that become more pressing as population growth pushes
amine real-time stream-gaging or landslide-monitoring data, or
more people to live in marginal places.
information on current or recent earthquake activity; they can
Relative to the length of time we have been on earth, hu-
manipulate historic climate data from NASA to examine trends
mans have had a disproportionate impact on this planet.
by region or time period; they may calculate how big a wind
Appendix A explores the concept of geologic time and its mea-
farm or photovoltaic array would be required to replace a con-
surement and looks at the rates of geologic and other processes
ventional power plant; they can even learn how to reduce sul-
by way of putting human activities in temporal perspective. Ap-
fate pollution by buying SO allowances.
2 pendix B provides short reference keys to aid in rock and min-
eral identifi cation, and the inside back cover includes units of
Organization
measurement and conversion factors.
Of course, the complex interrelationships among geologic
T he book starts with some background information: a brief processes and features mean that any subdivision into chapter-
outline of earth’s development to the present, and a look at one sized pieces is somewhat arbitrary, and different instructors
major reason why environmental problems today are so may prefer different sequences or groupings (streams and
pressing—the large and rapidly growing human population. ground water together, for example). An effort has been made
This is followed by a short discussion of the basic materials of to design chapters so that they can be resequenced in such ways
geology—rocks and minerals—and some of their physical without great diffi culty.
properties, which introduces a number of basic terms and con-
cepts that are used in later chapters.
Supplements
The next several chapters treat individual processes in de-
tail. Some of these are large-scale processes, which may involve
motions and forces in the earth hundreds of kilometers below Supplements for this edition include: Instructor’s Manual, Pre-
the surface, and may lead to dramatic, often catastrophic events sentation Center, PowerPoint Lecture Outlines, and Student
like earthquakes and volcanic eruptions. Other processes—such Quizzing. The “NetNotes” previously included at the end of
as the fl ow of rivers and glaciers or the blowing of the wind— each chapter have been expanded and moved to the website.
occur only near the earth’s surface, altering the landscape and They continue to highlight a modest collection of Internet sites
occasionally causing their own special problems. In some cases, that provide additional information and/or images relevant to
geologic processes can be modifi ed, deliberately or acciden- the chapter content. These should prove useful to both students
tally; in others, human activities must be adjusted to natural and instructors. An effort has been made to concentrate on sites
vi Preface
with material at an appropriate level for the book’s intended Thomas B. Boving, Ernest H. Carlson, Elizabeth Catlos, Dennis
audience and also on sites likely to be relatively stable in the DeMets, Hailiang Dong, Alexander Gates, Chad Heinzel,
very fl uid world of the Internet (government agencies, educa- Edward Kohut, Richard McGehee, Marguerite Moloney, Lee
tional institutions, or professional-association sites). The end- Slater, and Dan Vaughn, and additional comments by Nathan
of-chapter “Suggested Readings/References” have likewise Yee. Like its predecessors, this ninth edition has also been
been updated and moved to the website, and the appendix on strengthed through the careful reading and thoughtful sugges-
maps and satellite imagery included in previous editions has tions by r eviewers: Christine Aide, Southeast Missouri State
been moved there also. University; James Bartholomew, University of South Carolina;
Thomas Boving, University of Rhode Island; Jim Constanto-
poulos, Eastern New Mexico University; Mark Groszos,
Acknowledgments
Valdosta State University; Duke Ophori, Montclair State
University; Bianca Pedersen, University of Wisconsin–Eau
A great many people have contributed to the development of Claire; John Rockaway, Northern Kentucky University; Kevin
one or another edition of this book. Portions of the manuscript Svitana, Otterbein C ollege; and Clifford H. Thurber, University
of the fi rst edition were read by Colin Booth, Lynn A. Brant, of Wisconsin–Madison.
Arthur H. Brownlow, Ira A. Furlong, David Huntley, John The input of all of the foregoing individuals, and of many
F. Looney, Jr., Robert A. Matthews, and George H. Shaw, and the other users who have informally offered additional advice, has
entire book was reviewed by Richard A. Marston and Donald substantially improved the text, and their help is most grate-
J. Thompson. The second edition was enhanced through sug- fully acknowledged. If, as one reviewer commented, the text
gestions from Robert B. Furlong, Jeffrey J. Gryta, David Gust, “just keeps getting better,” a large share of the credit certainly
Robert D. Hall, Stephen B. Harper, William N. Mode, Martin belongs to the reviewers. Any remaining shortcomings are, of
Reiter, and Laura L. Sanders; the third, with the assistance of course, my own responsibility.
Susan M. Cashman, Robert B. Furlong, Frank Hanna, William M. Dalecheck, C. Edwards, I. Hopkins, and J. McGregor
N. Mode, Paul Nelson, Laura L. Sanders, and Michael A. Velbel; at the USGS Photo Library in Denver provided invaluable as-
the fourth, through the input of reviewers Herbert Adams, sistance with the photo research over the years. The encourage-
Randall Scott Babcock, Pascal de Caprariis, James Cotter, Dru ment of a number of my colleagues—particularly Colin Booth,
Germanoski, Thomas E. Hendrix, Gordon Love, Steven Lund, Ron C. Flemal, Donald M. Davidson, Jr., R. Kaufmann, and
Michael McKinney, Barbara Ruff, Paul Schroeder, Ali Tabidian, Eugene C. Perry, Jr.—was a special help during the develop-
Clifford Thurber, and John Vitek. The fi fth edition was im- ment of the fi rst edition. The ongoing support and interest of
proved thanks to reviews by Kevin Cole, Gilbert N. Hanson, fellow author, deanly colleague, and ecologist Jerrold H. Zar
John F. Hildenbrand, Ann E. Homes, Alvin S. Konigsberg, has been immensely helpful. Thanks are also due to the several
Barbara L. Ruff, Vernon P. Scott, Jim Stimson, Michael thousand environmental geology students I have taught, many
W hitsett, and Doreen Zaback; the sixth, by reviews from Ray of whom in the early years suggested that I write a text, and
Beiersdorfer, Ellin Beltz, William B. N. Berry, Paul Bierman, whose classes collectively have provided a testing ground for
W. B. Clapham, Jr., Ralph K. Davis, Brian E. Lock, Gregory many aspects of the presentations herein.
Hancock, Syed E. Hasan, Scott W. Keyes, Jason W. Kelsey, My family has been supportive of this undertaking from
John F. Looney Jr., Christine Massey, Steve Mattox, William the inception of the fi rst edition. A very special vote of appre-
N. Mode, William A. Newman, Clair R. Ossian, David L. Ozsvath, ciation goes to my husband Warren—ever-patient sounding
Alfred H. Pekarek, Paul H. Reitan, and Don Rimstidt. Improve- board, occasional photographer and fi eld assistant—in whose
ments in the seventh edition were inspired by reviewers Thomas life this book has so often loomed so large.
J. Algaeo, Ernest H. Carlson, Douglas Crowe, Richard A. Flory, Last, but assuredly not least, I express my deep gratitude
Hari P. Garbharran, Daniel Horns, Ernst H. Kastning, Abraham to the entire McGraw-Hill book team for their enthusiasm, pro-
Lerman, Mark Lord, Lee Ann Munk, June A. Oberdorfer, Assad fessionalism, and just plain hard work, without which success-
I. Panah, James S. Reichard, Frederick J. Rich, Jennifer Rivers ful completion of each subsequent edition of this book would
Coombs, Richard Sleezer, and Michael S. Smith, and the eighth have been impossible.
edition benefi ted from suggestions by Richard Aurisano, Carla W. Montgomery
Preface vii
Contents
Preface i v
I
Foundations
S E C T I O N
1 2
C H CA HP T E R C HHCA P T E R
An Overview of Our Rocks and Minerals—
Planetary Environment 3 A F irst L ook 23
Earth in Space and Time 4 Atoms, Elements, Isotopes, Ions, and
Compounds 24
The Early Solar System 4
Atomic Structure 24
The Planets 4
Elements and Isotopes 24
Earth, Then and Now 5
Ions 24
Life on Earth 8
The Periodic Table 25
Geology, Past and Present 9
Compounds 25
The Geologic Perspective 9
Minerals—General 26
Geology and the Scientifi c Method 10
Minerals Defi ned 26
The Motivation to Find Answers 10
Identifying Characteristics of Minerals 26
Wheels Within Wheels: Earth Cycles and Systems 11
Other Physical Properties of Minerals 28
Nature and Rate of Population Growth 13
Types of Minerals 29
Growth Rates: Causes and Consequences 14
Silicates 30
Growth Rate and Doubling Time 15
Nonsilicates 31
Impacts of the Human Population 16
Rocks 33
Farmland and Food Supply 16
■ Case Study 2 Asbestos—A Tangled Topic 34
Population and Nonfood Resources 17
Igneous Rocks 35
Uneven Distribution of People and Resources 18
Sediments and Sedimentary Rocks 37
Disruption of Natural Systems 18
■ Case Study 1 Earth’s Moon 20 Metamorphic Rocks 39
The Rock Cycle 39
SUMMARY 21
KEY TERMS AND CONCEPTS 21 SUMMARY 42
EXERCISES 22 KEY TERMS AND CONCEPTS 42
EXERCISES 42
viii
II
Internal Processes
S E C T I O N
3 Earthquake-Related Hazards and Their
Reduction 73
C HHCA P T E R
Ground Motion 73
Plate Tectonics 44
Ground Failure 73
Tsunamis and Coastal Eff ects 80
Plate Tectonics—Underlying Concepts 46
■ Case Study 4.1 Megathrust Makes Mega-Disaster 81
Stress and Strain in Geologic Materials 46
Fire 83
Lithosphere and Asthenosphere 48
Earthquake Prediction and Forecasting 84
Locating Plate Boundaries 48
Seismic Gaps 84
Plate Tectonics—Accumulating Evidence 50
Earthquake Precursors and Prediction 84
The Topography of the Sea Floor 50
Current Status of Earthquake Prediction 84
Magnetism in Rocks—General 50
The Earthquake Cycle and Forecasting 85
Paleomagnetism and Seafl oor Spreading 51
Earthquake Early Warnings? 86
Age of the Ocean Floor 52
Public Response to Earthquake Hazards 86
Polar-Wander Curves 52
■ Case Study 4.2 Understanding Faults Better—Parkfi eld and
Types of Plate Boundaries 54 SAFOD 87
Divergent Plate Boundaries 55 Earthquake Control? 88
Convergent Plate Boundaries 56
u Fture Earthquakes in North America? 89
Transform Boundaries 58
Areas of Widely Recognized Risk 89
How Far, How Fast, How Long, How Come? 59 Other Potential Problem Areas 90
Past Motions, Present Velocities 59 SUMMARY 91
KEY TERMS AND CONCEPTS 92
Why Do Plates Move? 61
EXERCISES 92
l Pate Tectonics and the Rock Cycle 61
5
■ Case Study 3 New Theories for Old—Geosynclines and
Plate Tectonics 62 C HHCA P T E R
SUMMARY 63 Volcanoes 93
KEY TERMS AND CONCEPTS 64
EXERCISES 64
Magma Sources and Types 94
4
Styles and Locations of Volcanic Activity 96
C HHCA P T E R
Continental Fissure Eruptions 96
Earthquakes 65 Individual Volcanoes—Locations 97
Shield Volcanoes 97
Earthquakes—Terms and Principles 67
Cinder Cones 98
Basic Terms 67
Composite Volcanoes 98
Earthquake Locations 69
Hazards Related to Volcanoes 99
Seismic Waves and Earthquake Severity 70
Lava 99
Seismic Waves 70 Pyroclastics 102
Locating the Epicenter 71 ■ Case Study 5.1 Living with Lava on Hawaii 103
Magnitude and Intensity 72 Lahars 105
Contents ix
Pyroclastic Flows—Nuées Ardentes 106 Response to Eruption Predictions 114
Toxic Gases 108 More on Volcanic Hazards in the United States 115
Steam Explosions 110 CascadeR ange 115
Landslides and Collapse 110 Alaska and The Aleutians 115
Secondary Eff ects: Climate and Atmospheric Chemistry 110 Long Valley and Yellowstone Calderas 116
■ Case Study 5.2 Redoubt Volcano, Alaska 117
Issues in Predicting Volcanic Eruptions 111
SUMMARY 121
Classifi cation of Volcanoes by Activity 111
KEY TERMS AND CONCEPTS 121
The Volcanic Explosivity Index 112 EXERCISES 122
Volcanic Eruption Precursors 112
III
Surface Processes
S E C T I O N
6 7
C HHCA P T E R C HHCA P T E R
Streams and F looding 124 Coastal Zones and
Processes 150
The Hydrologic Cycle 125
Streams and Their Features 125
Nature of the Coastline 151
Streams—General 125
Waves and Tides 151
Sediment Transport 126
Sediment Transport and Deposition 153
Velocity, Gradient, and Base Level 127
Storms and Coastal Dynamics 153
Velocity and Sediment Sorting and Deposition 128
mEergent and Submergent Coastlines 155
Channel and Floodplain Evolution 130
Causes of Long-Term Sea-Level Change 155
Flooding 131
Signs of Changing Relative Sea Level 156
Factors Governing Flood Severity 131
Present and Future Sea-Level Trends 158
Flood Characteristics 133
Coastal Erosion and “Stabilization” 159
Stream Hydrographs 133
Beach Erosion, Protection, and Restoration 160
Flood-Frequency Curves 135
Cliff Erosion 161
■ Case Study 6.1 How Big Is the One Hundred-Year Flood? 137
sEpecially Diffi cult Coastal Environments 163
Consequences of Development in Floodplains 139
Barrier Islands 163
Strategies for Reducing Flood Hazards 140
Estuaries 165
Restrictive Zoning and “Floodproofi ng” 140
■ Case Study 7 Hurricanes and Coastal Vulnerability 166
Retention Ponds, Diversion Channels 141
Channelization 141 Costs of Construction—and Reconstruction—
in High-Energy Environments 168
Levees 142
Recognition of Coastal Hazards 168
lFood-Control Dams and Reservoirs 142
SUMMARY 170
■ Case Study 6.2 Life on the Mississippi: A History of Levees 144
KEY TERMS AND CONCEPTS 170
Flood Warnings? 146 EXERCISES 170
USMMARY 148
KEY TERMS AND CONCEPTS 149
EXERCISES 149
x Contents