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ninth edition Environmental Geology Carla W. Montgomery Professor Emerita Northern Illinois University TM TM ENVIRONMENTAL GEOLOGY, NINTH EDITION Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020. Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved. Previous editions © 2008, 2006, and 2003. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. Some ancillaries, including electronic and print components, may not be available to customers outside the United States. This book is printed on acid-free paper. 1 2 3 4 5 6 7 8 9 0 WDQ/WDQ 1 0 9 8 7 6 5 4 3 2 1 0 ISBN 978–0–07–352408–5 MHID 0–07–352408–5 Vice President, Editor-in-Chief: M arty Lange Vice President, EDP: Kimberly M eriwether David Director of D evelopment: K ristine Tibbetts Publisher: R yan Blankenship Executive Editor: Margaret J . Kemp Senior Marketing Manager: L isa Nicks Senior Project Manager: Vicki Krug Senior Production Supervisor: S herry L. Kane Designer: Michelle D. Whitaker (USE) Cover Image: © Doug Sherman/Geofi le Lead Photo R esearch Coordinator: C arrie K. Burger Photo Research: J erry Marshall/pictureresearching.com Compositor: Aptara, Inc. Typeface: 10/12 Times Roman Printer: Worldcolor Photos not credited on page provided by author, Carla W. Montgomery. All credits appearing on page or at the end of the book are considered to be an extension of the copyright page. 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

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