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Mitigating Shore Erosion Along Sheltered Coasts MITIGATING SHORE EROSION ALONG SHELTERED COASTS Committee on Mitigating Shore Erosion Along Sheltered Coasts Ocean Studies Board Division on Earth and Life Studies NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES THE NATIONAL ACADEMIES PRESS Washington, D.C. www.nap.edu
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Mitigating Shore Erosion Along Sheltered Coasts THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This study was supported by a contract between the National Academy of Sciences and the following entities: purchase order no. 2W-0373-NANX from the Environmental Protection Agency, purchase order numbers W19HQ-04-P-0132 and W912HQ-05-P-0064 from the U.S. Army Corps of Engineers, contract numbers 04-891 and 05-927 from the Cooperative Institute for Coastal and Estuarine Environmental Technology, and purchase order no. FC133CO5SE6428 from the NOAA Coastal Services Center. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number-13: 978-0-309-10346-6 (Book) International Standard Book Number-10: 0-309-10346-0 (Book) International Standard Book Number-13: 978-0-309-66651-0 (PDF) International Standard Book Number-10: 0-309-66651-1 (PDF) Library of Congress Catalog Card Number 20006941054 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Copyright 2007 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.
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Mitigating Shore Erosion Along Sheltered Coasts THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council. www.national-academies.org
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Mitigating Shore Erosion Along Sheltered Coasts COMMITTEE ON MITIGATING SHORE EROSION ALONG SHELTERED COASTS JEFF BENOIT, Chair, SRA International, Arlington, Virginia C. SCOTT HARDAWAY, JR., College of William and Mary, Virginia Institute of Marine Science, Gloucester Point DEBRA HERNANDEZ, Hernandez and Company, Isle of Palms, South Carolina ROBERT HOLMAN, Oregon State University, College of Oceanic Atmospheric Sciences, Corvallis EVAMARIA KOCH, University of Maryland, Center for Environmental Science, Horn Point Laboratory, Cambridge NEIL McLELLAN, Shiner Moseley and Associates, Houston, Texas SUSAN PETERSON, Teal Partners, Rochester, Massachusetts DENISE REED, University of New Orleans, Department of Geology and Geophysics, New Orleans, Louisiana DANIEL SUMAN, University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, Florida Staff SUSAN ROBERTS, Study Director AMANDA BABSON, Christine Mirzayan Science and Technology Policy Graduate Fellow SARAH CAPOTE, Senior Program Assistant
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Mitigating Shore Erosion Along Sheltered Coasts OCEAN STUDIES BOARD SHIRLEY A. POMPONI, Chair, Harbor Branch Oceanographic Institution, Fort Pierce, Florida LEE G. ANDERSON, University of Delaware, Newark JOHN A. ARMSTRONG, IBM Corporation (retired), Amherst, Massachusetts WHITLOW AU, University of Hawaii at Manoa ROBERT G. BEA, University of California, Berkeley ROBERT DUCE, Texas A&M University, College Station MARY (MISSY) H. FEELEY, ExxonMobil Exploration Company, Houston, Texas HOLLY GREENING, Tampa Bay National Estuary Program, St. Petersburg, Florida DEBRA HERNANDEZ, Hernandez and Company, Isle of Palms, South Carolina CYNTHIA M. JONES, Old Dominion University, Norfolk, Virginia WILLIAM A. KUPERMAN, Scripps Institution of Oceanography, La Jolla, California FRANK E. MULLER-KARGER, University of South Florida, St. Petersburg JOAN OLTMAN-SHAY, NorthWest Research Associates, Inc., Bellevue, Washington ROBERT T. PAINE, University of Washington, Seattle S. GEORGE H. PHILANDER, Princeton University, New Jersey RAYMOND W. SCHMITT, Woods Hole Oceanographic Institution, Massachusetts DANIEL SUMAN, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida ANNE M. TREHU, Oregon State University, Corvallis Staff SUSAN ROBERTS, Director FRANK HALL, Program Officer SUSAN PARK, Associate Program Officer ANDREAS SOHRE, Financial Associate SHIREL SMITH, Administrative Coordinator JODI BOSTROM, Research Associate NANCY CAPUTO, Research Associate SARAH CAPOTE, Senior Program Assistant
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Mitigating Shore Erosion Along Sheltered Coasts Preface Sheltered coasts, and the bodies of water they surround, are increasingly popular places for people to live, work, and recreate. This is partially due to a preference for a serene setting that is afforded some protection from the full fury of coastal storms. The same sheltered nature of these areas also creates some of the most biologically productive and ecologically valuable resources of the coastal region. But sheltered coasts are indeed subject to erosion and sea level rise, and suffer chronic land loss as a result. The common response by landowners to the loss of their increasingly valuable land has been to “harden” the shoreline by construction of fixed structures such as bulkheads, revetments, or groins. This response can easily create a “bathtub” effect and fundamentally change the character of the coastal environment; in some cases actually worsening the erosion and inundation, and in most cases causing a loss or shift in ecological values. As a better understanding is gained of the physical and ecological impacts of hardening the shoreline, new approaches are being developed for managing eroding sheltered shorelines. This report reviews options available to mitigate erosion of sheltered coasts; explores why certain decisions are made regarding the choice of erosion mitigation options; provides critical information about the consequences or altering sheltered shorelines; and, provides recommendations about how to better inform decisions in the future. Integrating broad societal and ecological considerations into erosion mitigation strategies is a continuing challenge. Practitioners are slowly moving in that direction and are encouraged to continue on that course. We suggest that more focused research on sheltered coasts, and long-term regional planning early in the process, are key solutions to this chronic issue.
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Mitigating Shore Erosion Along Sheltered Coasts These findings would not have been possible without the hard work, collective action, and perseverance of this committee. I would like to thank my colleagues on the committee for their efforts. Some members are knowledgeable practitioners with hands-on experience working with landowners on the design or permitting of erosion mitigation strategies; others are among the leading researchers in the field of estuarine ecology. I have been honored to serve with such an eminent group and to learn from their wisdom. More importantly, it was a pleasure to get to know them and work alongside them all. The committee and I gratefully acknowledge and thank the staff of the Ocean Studies Board for their tireless support. Dr. Susan Roberts served as project director for the majority of the project after Dr. Dan Walker was called on for service to another committee. Dan was invaluable for getting us off to a well thought out start and assisting with preparation of the final report. Frank Hall and Susan Park provided valuable assistance during the review process of this report. Sarah Capote was always there for us and provided critical research and logistical support. Amanda Babson also conducted helpful research for the workshop during her internship with the Board. We hope that the conclusions and recommendations of this report provide meaningful advice to state and federal agencies, local communities, and landowners to guide a new management approach in the planning, design, and construction of erosion mitigation strategies for sheltered coasts. Jeffrey R. Benoit, Chair
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Mitigating Shore Erosion Along Sheltered Coasts Acknowledgments This report was greatly enhanced by participants at the two meetings held as part of this study. The committee would like first to acknowledge the efforts of those who gave presentations at the meetings. These talks helped set the stage for fruitful discussions in the closed sessions that followed. ROBERT BRUMBAUGH, U.S. Army Corps of Engineers BETH BRYANT, University of Washington, School of Marine Affairs CHARLES CHESTNUTT, U.S. Army Corps of Engineers SCOTT DOUGLASS, University of South Alabama KATHLEEN KUNZ, U.S. Army Corps of Engineers ROBIN LEWIS, Lewis Environmental Services, Inc. DAN MILLER, New York State Department of Environmental Conservation, Hudson River National Estuarine Research Reserve DOUG MYERS, Puget Sound Action Team KAREN NOOK, U.S. Army Corps of Engineers NEVILLE REYNOLDS, Vanasse Hangen Brustlin, Inc. SPENCER ROGERS, North Carolina Sea Grant HUGH SHIPMAN, Washington Department of Ecology JAY TANSKI, New York Sea Grant JOHN TEAL, Teal Partners and Woods Hole Oceanographic Institution JIM TITUS, Environmental Protection Agency DWIGHT TRUEBLOOD, National Oceanic and Atmospheric Administration DON WARD, U.S. Army Corps of Engineers PHIL WILLIAMS, Phillip Williams Associates, Ltd.
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Mitigating Shore Erosion Along Sheltered Coasts The committee is also grateful to Hugh Shipman, Washington Department of Ecology, and Jeff Parsons, University of Washington, for organizing the committee field trip in the Seattle area. Assistance with conceptual diagrams in Chapter 4 was provided by the Integration and Application Network (ian.umces. edu), University of Maryland Center for Environmental Science. This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for the participation in their review of this report: BERNARD O. BAUER, University of British Columbia-Okanagan, Kelowna, Canada MARK BRINSON, East Carolina University, Greenville, North Carolina ROBERT DALRYMPLE, Johns Hopkins University, Baltimore, Maryland MARGOT GARCIA, Tucson, Arizona JORDAN LORAN, Maryland Department of Natural Resources, Annapolis HUGH SHIPMAN, Washington Department of Ecology, Bellevue CLIFF TRUITT, Coastal Technology Corporation, Sarasota, Florida S. JEFFRESS WILLIAMS, U.S. Geological Survey, Woods Hole, Massachusetts Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by Norbert Psuty, Rutgers University. Appointed by the National Research Council, the reviewers were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.
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Mitigating Shore Erosion Along Sheltered Coasts Contents SUMMARY 1 1 INTRODUCTION 11 Study History, 11 Scope of the Problem, 12 Mobile Bay, Alabama, 14 Raritan Bay, New Jersey, 15 Terminology of Sheltered Coasts, 16 Shore, 16 Erosion and Inundation, 18 Sheltered Coasts, 18 Beaches and Dunes, 22 Bluffs, 22 Mudflats and Vegetated Communities, 22 Study Organization, 23 2 UNDERSTANDING EROSION ON SHELTERED SHORES 25 The Physics of Coastal Erosion, 25 Understanding Sediment, 26 Conservation of Sediment Volume, 27 Threshold of Sediment Motion, 28 Sediment Transport Processes, 30
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Mitigating Shore Erosion Along Sheltered Coasts Spatially and Temporally Variable Factors Controlling Coastal Erosion, 31 Wave Climate, 31 Sediment Type, 32 Sources and Sinks, 33 Littoral Cells, 33 The Role of Changes in Sea Level, 34 Implications of Geomorphic Setting for Erosion Mitigation Strategies, 37 Understanding the Physical Setting, 37 Human Elements of Shoreline Character, 42 Findings, 42 3 METHODS FOR ADDRESSING EROSION 44 Approaches to Erosion, 44 Manage Land Use, 45 Vegetate, 46 Harden, 49 Sills, 57 Trap or Add Sand, 57 Composite Systems, 62 Headland Control, 66 Nontraditional and Innovative Methods, 66 Design Elements and Criteria, 67 Level of Protection, 68 Damage and Risk Assessment, 69 Erosion Control Strategies in Application, 70 Homeowner’s Dilemma, 71 Consultant’s Site Analysis, 71 Options for Addressing Erosion, 73 Findings, 76 4 MITIGATING ERODING SHELTERED SHORELINES: A TRADE-OFF IN ECOSYSTEM SERVICES 78 Ecosystem Services Provided by Natural Coastal Systems, 80 Beaches and Dunes, 80 Mudflats and Vegetated Communities, 83 Bluffs, 89 Ecosystem Services Provided by Techniques to Mitigate Shoreline Erosion, 92 Cumulative and Secondary Impacts of Techniques to Mitigate Shoreline Erosion, 95 Case Studies, 96 Ecological Impacts of Low-Crested Breakwaters in Europe, 96 Mills Island, Chincoteague Bay, Maryland, 97 Findings, 97
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Mitigating Shore Erosion Along Sheltered Coasts 5 THE EXISTING DECISION-MAKING PROCESS FOR SHORELINE PROTECTION ON SHELTERED COASTS 98 Decision-Makers, 98 Strategies Available to Address the Problem, 103 Permitting Requirements for Shoreline Protection on Sheltered Coasts, 104 Federal Permits, 104 State and Local Permits for Shoreline Protection Activities, 108 Intergovernmental Coordination, 111 Variability Among States, 112 Influence of the Regulatory Process, 114 Cost Considerations, 115 Transaction and Administrative Costs of Shoreline Management, 116 Criteria to Assess the Costs of Shoreline Protection Measures, 116 Who Performs This Assessment and How?, 117 Potential Use of Mitigation Banks for Shoreline Erosion Control Permits, 117 Planning Considerations, 119 System Planning, 120 Cumulative Impact Analysis, 121 Findings, 122 6 A NEW MANAGEMENT APPROACH FOR SHELTERED SHORELINES 124 Regional Approaches, 125 Developing a Regional Plan, 125 Findings and Recommendations, 130 Establishing a New Management Approach, 130 Conclusion, 136 REFERENCES AND BIBLIOGRAPHY 138 APPENDIXES A Committee and Staff Biographies 153 B Acronyms 159 C Workshop Agenda and Participants List 161 D Potential Federal Regulatory Requirements 167 E Glossary 170
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