Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications [1 ed.] 9780309583077
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Copyright © 1987. National Academies Press. All rights reserved.
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i
Saving Cape Hatteras Lighthouse from the Sea Options and Policy Implications
Committee on Options for Preserving Cape Hatteras Lighthouse Board on Environmental Studies and Toxicology Commission on Physical Sciences, Mathematics, and Resources National Research Council
NATIONAL ACADEMY PRESS Washington, D.C. 1988
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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ii 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 report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of 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. Frank Press 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. Robert M. White 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. Samuel O. Thier 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 of 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. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council. Support for this project was provided by contract no. CX-5000-7-0040 between the National Academy of Sciences and the National Park Service, an agency of the U.S. Department of the Interior. Library of Congress Catalog Card Number ISBN Available from: Board on Environmental Studies and Toxicology National Research Council 2101 Constitution Ave., N.W. Washington, D.C. 20418 Printed in the United States of America Cover Photograph by David Policansky
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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iii
COMMITTEE ON OPTIONS FOR PRESERVING CAPE HATTERAS LIGHTHOUSE Rutherford H. Platt, Chairman, University of Massachusetts, Amherst Milner Ball, University of Georgia, Athens Ben Gerwick, Jr., Ben C. Gerwick, Inc., San Francisco, California Eugene Harlow, SOROS Associates, New York City Francis Ross Holland, National Park Service (retired) Valerie I. Nelson, The Lighthouse Preservation Society, Rockport, Massachusetts Dag Nummedal, Louisiana State University, Baton Rouge Charles Henry Peterson, University of North Carolina, Morehead City Alan Yorkdale, Brick Institute of America, Reston, Virginia (deceased November 1987) Paul Zia, North Carolina State University, Raleigh Staff David Policansky, Project Director Sylvia Tognetti, Research Assistant Lee Paulson, Editor Leah S. Gales, Project Secretary
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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iv
BOARD ON ENVIRONMENTAL STUDIES AND TOXICOLOGY Donald Hornig, Chairman, Harvard University, Boston, Massachusetts Alvin L. Alm, Thermal Analytical, Inc., Waltham, Massachusetts Richard N. L. Andrews, University of North Carolina, Chapel Hill David Bates, University of British Columbia Health Science Center Hospital, Vancouver Richard A. Conway, Union Carbide Corporation, South Charleston, West Virginia William E. Cooper, Michigan State University, East Lansing Benjamin G. Ferris, Harvard School of Public Health, Boston, Massachusetts Sheldon K. Friedlander, University of California, Los Angeles Bernard Goldstein, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey Donald Mattison, University of Arkansas for Medical Sciences, Little Rock Philip A. Palmer, E. I. Dupont de Nemours & Co., Wilmington, Delaware Duncan T. Patten, Arizona State University, Tempe Emil Pfitzer, Hoffman-La Roche Inc., Nutley, New Jersey Paul Portney, Resources for the Future, Washington, D.C. Paul Risser, University of New Mexico, Albuquerque William H. Rodgers, University of Washington, Seattle F. Sherwood Rowland, University of California, Irvine Liane B. Russell, Oak Ridge National Laboratory, Oak Ridge, Tennessee Ellen Silbergeld, Environmental Defense Fund, Washington, D.C. I. Glenn Sipes, University of Arizona College of Pharmacy, Tucson Staff Devra L. Davis, Director James J. Reisa, Associate Director Jacqueline Prince, Staff Associate
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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v
COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND RESOURCES Norman Hackerman, Chairman, Robert A. Welch Foundation, Houston, Texas George F. Carrier, Harvard University, Cambridge, Massachusetts Dean E. Eastman, IBM T. J. Watson Research Center, Yorktown Heights, New York Marye Anne Fox, University of Texas, Austin Gerhart Friedlander, Brookhaven National Laboratory, Upton, Long Island, New York Lawrence W. Funkhouser, Chevron Corporation (retired) Phillip A. Griffiths, Duke University, Durham, North Carolina J. Ross Macdonald, The University of North Carolina, Chapel Hill Charles J. Mankin, The University of Oklahoma, Norman Perry L. McCarty, Stanford University, Stanford, California Jack E. Oliver, Cornell University, Ithaca, New York Jeremiah P. Ostriker, Princeton University Observatory, Princeton, New Jersey William D. Phillips, Mallinckrodt, Inc., St. Louis, Missouri Denis J. Prager, MacArthur Foundation, Chicago, Illinois David M. Raup, University of Chicago, Chicago, Illinois Richard J. Reed, University of Washington, Seattle Robert E. Sievers, University of Colorado, Boulder Larry L. Smarr, National Center for Supercomputing Applications, Champaign, Illinois Edward C. Stone Jr., California Institute of Technology, Pasadena Karl K. Turekian, Yale University, New Haven, Connecticut George W. Wetherill, Carnegie Institution of Washington, Washington, D.C. Irving Wladawsky-Berger, IBM Corporation, White Plains, New York Staff Raphael G. Kasper, Executive Director Lawrence E. McCray, Associate Executive Director
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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vi
Copyright © 1987. National Academies Press. All rights reserved.
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PREFACE
vii
Preface
The Committee on Options for Preserving Cape Hatteras Lighthouse was formed in July 1987, under the auspices of the Board on Environmental Studies and Toxicology (BEST) of the National Research Council's Commission on Physical Sciences, Mathematics, and Resources. The committee was established at the request of the National Park Service (NPS), which since 1980 has tried to protect the lighthouse--a national historic landmark--from destruction by shoreline retreat. The committee's task was unusual for the NRC in its specificity and urgency. The NPS requested definitive, achievable advice on how to save the lighthouse. Furthermore, it required the committee's preliminary evaluations within 90 days from the contract inception and the final report 6 months later, a short time frame that placed considerable pressure on the committee and its NRC staff. The NRC usually does not undertake narrowly defined, site-specific projects; however, the committee also was asked to review the implications of the Cape Hatteras options for other sites and historic structures affected by shoreline erosion, especially those within national park facilities. It was asked to evaluate specific measures to preserve the lighthouse and simultaneously address the broader issues of coastal erosion, historic preservation, public recreation, and environmental protection. The committee was an outstanding and diverse group that included a coastal geomorphologist, a coastal ecologist, a law professor, a geographer, a lighthouse historian, an economist
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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PREFACE
viii
specializing in lighthouse preservation, and four civil engineers. In its research and four meetings, the group generously contributed its expertise and time. David Policansky, the NRC project director, was crucial to the committee's work. As a trained ecologist and avid saltwater angler, he brought an extraordinary level of interest and dedication to the committee's deliberations and report preparations. He was persistent in identifying and resolving factual and analytical inconsistencies and tirelessly assisted with the report preparation. As chairman, I relied heavily on his guidance. The committee also thanks the other NRC staff members who contributed to the project. They include James Reisa, associate director of BEST; Charles Bookman, director, and Donald Perkins, associate director of the Marine Board; John Eberhard, director of the Building Research Board; Lee Paulson, editor; Sylvia Tognetti, research assistant; and Leah Gales, project secretary. We also thank Devra Davis, director of BEST, for her encouragement and support. The committee gratefully acknowledges several outside experts who gave generously of their time and expertise. They include Ellis Cowling of North Carolina State University, who was instrumental in originating this study; David Stick, historian; Limberios Vallianos, of the U.S. Army Corps of Engineers Waterways Experiment Station at Vicksburg; William Dennis, U.S. Army Corps of Engineers; David Fischetti and Barrett Wilson, Move the Lighthouse Committee; Spencer Rogers, Sea Grant Marine Advisory Service; and Rudi Van Leeuwen, Spencer, White, & Prentis, Inc. In addition, the committee thanks the staff of the National Park Service's Southeast Region, including Robert Baker, director; Dominic Dottavio, chief scientist; Patricia Patterson, resource management specialist; and Tom Hartman, superintendent of the Cape Hatteras National Seashore.
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
Copyright © 1987. National Academies Press. All rights reserved.
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Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
ix
Committee member Alan Yorkdale, vice president of engineering and research, Brick Institute of America, died on November 15, 1987. His personal and professional contributions to the committee and the report are appreciated and highly valued. The committee dedicates this volume to his memory. Rutherford H. Platt, Chairman Committee on Options for Preserving Cape Hatteras Lighthouse
Copyright © 1987. National Academies Press. All rights reserved.
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Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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Copyright © 1987. National Academies Press. All rights reserved.
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CONTENTS
xi
Contents
PREFACE EXECUTIVE SUMMARY Background Rate of Shoreline Retreat Relevant Public Policies The Preservation Options and Evaluations Incremental Relocation of the Lighthouse Intact Seawall/Revetment Rehabilitation of Groinfield with Revetment Other Options Broader Issues
PART I. 1.
vii 1 1 2 3 5 5 6 7 7 8
INTRODUCTION Historical Background Recent Proposals The Present Study
9 9 13 13
BACKGROUND CONSIDERATIONS The Physical Setting Structural Geology of the Hatteras Shore Origin of the Outer Banks Island Morphodynamics Storms Changes in Sea Level Historical Trends
15 17 17 17 19 23 24 24
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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CONTENTS
xii
2.
3. PART II. 4.
5.
Estimated Future Trends Shoreline Retreat Trend Analysis Summary of Shoreline Retreat Estimates Relevant Public Policies Protection of Navigation National Park Service Mandate Protection of Historic Structures Coastal Barrier Recession Flood-Hazard Mitigation Enhancement of Recreation and Tourism Public Education Federal Consistency with State Law Wetlands Protection Economic Effectiveness Environmental Protection Use and Protection of the Coast Concepts of Historic Preservation THE CRITERIA, OPTIONS, AND EVALUATION Preservation Options and Evaluation Criteria The Options Criteria to Evaluate Preservation Options Evaluation of the Options Incremental Relocation: The Preferred Option Overview Cost of First Move Cost of Future Moves Evaluation Site Selection Ecological Consequences of Moving the Lighthouse Recent Legislation Summary Protection of the Lighthouse In Situ
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
25 27 29 29 33 34 34 34 35 36 36 37 37 37 38 38 39 41 45 47 47 47 53 54 54 55 59 60 63 67 70 71 72
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CONTENTS
xiii
Groinfield Rehabilitation Without Revetment Groinfield Rehabilitation With Revetment Seawall/Revetment Artificial Reefs Offshore Breakwaters and Groins Artificial Seagrass Beach Nourishment No Action New Lighthouse Practical Considerations Contracting Considerations Insurance Interim Measures Rehabilitation of the Lighthouse Site Design
72 74 79 86 88 89 90 91 92 95 95 97 97 98 99
Major Shoreline Protection Measures General Measures Taken in Cape Hatteras Vicinity The NPS Decision Process and the Value of Open Planning Actions to Protect Cape Hatteras Lighthouse Since 1980
101 101 102
APPENDIX B:
Additional Analyses of Shoreline Retreat Trend Analysis for Shoreline with No Protection The Bruun Rule
111 111 112
APPENDIX C:
Partial List of National Park Structures Moved by the National Park Service
117
APPENDIX D:
Biographical Sketches of Committee Members
119
References
125
6.
APPENDIX A:
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EXECUTIVE SUMMARY
1
Executive Summary
BACKGROUND Cape Hatteras Lighthouse, the tallest brick lighthouse in the U.S., faces eventual destruction due to coastal erosion. The lighthouse was built in 1870, 1,500 feet (460 meters) from the shoreline, replacing a lighthouse built near the present site in 1803. It is 200 feet (61 meters) tall and weighs approximately 2,800 tons (2,540 metric tons). Protective measures to reduce the rate of beach erosion in front of the lighthouse have provided a temporary respite, but by late 1987, the lighthouse stood only 160 feet (49 meters) from the sea. The motivation for protecting the lighthouse and its associated structures is to preserve a famous and historic landmark; modern navigational aids have outmoded its original function of protecting shipping in the stormy waters off the Outer Banks. Cape Hatteras Lighthouse is on one of the barrier islands that constitute North Carolina's Outer Banks. These islands are subject to powerful currents and storms that, in general, cause erosion of east-facing shorelines and accretion of south-facing shorelines. Thus, the east-facing shoreline in front of the lighthouse is expected to continue to recede until storm-driven waves undermine the tower's foundation and topple the lighthouse. The lighthouse now stands close enough to the water's edge to be vulnerable to damage by a severe hurricane. At the request of the National Park Service (NPS), the Board on Environmental Studies and Toxicology of the
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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EXECUTIVE SUMMARY
2
National Research Council's (NRC) Commission on Physical Sciences, Mathematics, and Resources formed the Committee on Options for Preserving Cape Hatteras Lighthouse in July 1987. The committee's task was to evaluate and develop several options for preserving Cape Hatteras Lighthouse from the encroaching Atlantic Ocean. It is important to note that the committee's charge was how best to preserve the lighthouse, not whether to preserve it. Political feasibility of the various options or the nature and extent of public sentiment associated with them were not within the scope of the charge, and the committee did not critically assess them. NPS's decision on how to preserve the lighthouse will have to be made in the context of its mission to provide historic preservation, the various public policies relating to U.S. coastlines, and scientific and engineering constraints. In an interim report to NPS on October 14, 1987 (NRC, 1987a), the committee tentatively concluded that relocation was the best option for preserving the lighthouse. This final report reaffirms and expands on that evaluation. Rate of Shoreline Retreat The rate of beach erosion (and hence shoreline retreat) is affected by changes in sea level, among other factors. Sea level has been rising for at least the past 10,000 years, during which the barrier islands of the Outer Banks have been migrating westward. The committee concludes that a conservative estimate of sea-level rise for the next few decades would be a continuation of the rate of the past century--a relative rise of about .08 inch (2 mm) yearly at Cape Hatteras. Recently, another NRC committee also considered three possible scenarios of sea-level rise, accelerating at different rates from the present to the year 2100 (NRC, 1987b). If present trends continued, sea-level rise would be 2.4 inches (60 mm) by the year 2018; the high NRC (1978b) scenario would yield 6.1 inches (155 mm) by 2018. Based on this range of values, the committee estimates that the shoreline in front of the lighthouse would retreat 157-407 feet (48-124 meters) by the year 2018. By the year 2088, the retreat might reach 525-3,280 feet (160-1,000 meters).
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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EXECUTIVE SUMMARY
3
Relevant Public Policies Numerous national, state, and local policies bear upon decisions concerning the preservation of historic structures and the management and protection of coastal areas. The committee considered these in evaluating the options for preserving the lighthouse. In particular, it identified potential conflicts between national and state policies concerning hardened structures on coasts and NPS policies concerning historic preservation and management of national parks. Historic Preservation Historic preservation has always been part of NPS's mission. The NPS organic act of 1916 (16 U.S.C., Sec. 1 et seq.) stated that the purpose of the agency is “to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.” In 1935, the Historic Sites, Buildings, and Antiquities Act (16 U.S.C. Sec. 461-467) broadened the NPS role in historic preservation. It authorized the Historic American Buildings Survey, the Historic American Engineering Record, and the National Survey of Historic Sites. It also provided for establishment of national historic sites, preservation of properties “of national historic or archeological significance,” and designation of national historic landmarks. The National Historic Preservation Act of 1966 (16 U.S.C. Sec. 470) involved NPS in the preservation of historic and archeological sites at the state and local levels. The act declared a national policy for historic preservation by providing for the expansion of the National Register of Historic Places, matching grants to the states and the National Trust, and the Advisory Council on Historic Preservation. The act defined historic preservation as “the protection, rehabilitation, restoration, and reconstruction of districts, sites, buildings, structures, and objects significant in American history, architecture, archeology, and culture.” Congress amended the act in 1980 (94 Stat. 2987), expanding the roles of federal,
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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EXECUTIVE SUMMARY
4
state, local, and private sectors and providing new mandates for federal land managers. Management and Protection of the Coast The U.S. has 80,560 miles (129,621 kilometers) of coast (excluding the Great Lakes), of which 19,240 miles (30,957 kilometers) is erosional (U.S. Army Corps of Engineers, 1971). Marine shorelines generally are retreating in response to sea-level rise (May et al., 1983). This natural process of shoreline migration clashes with demographic growth and development pressure in the coastal zone. Coastal development has increased dramatically in recent decades (Dolan and Lins, 1986; Nordstrom, 1987). Population pressure on the coast is a severe test of environmental and land-use planning capacities (Platt et al., 1987). An array of federal statutes and regulations govern development and protection of the coast as well as contiguous marine areas. North Carolina's Coastal Area Management Act (1974) discourages efforts to harden or artificially stabilize retreating shorelines. Notwithstanding these measures and historic concern for the American coast, the nation and its coastal states have yet to formulate an adequate response to the increasing problems of a shoreline moving landward and a population moving seaward. Resolving the Conflicts In selecting an option or combination of options to preserve the lighthouse, NPS will need to comply with public policies concerning historic preservation as well as those concerning coastal management and protection. The main conflict in the present case--between policies that would preserve the historic lighthouse and policies that would allow natural processes to occur unimpeded-is representative of a large class of conflicts between historic preservation and natural conservation. With its dual mandates of historic preservation and conservation of natural areas, NPS must deal with such conflicts frequently. The committee was mindful of this conflict and its general nature, and is confident that the favored option--relocation
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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EXECUTIVE SUMMARY
5
of the lighthouse--is consistent with preservation and conservation policies. Further, the committee hopes that a solution that resolves the conflict in the present case will serve as an example for other similar decisions. THE PRESERVATION OPTIONS AND EVALUATIONS The committee evaluated 10 options for preserving the lighthouse and associated buildings. Three were considered in depth and the rest more briefly. Incremental Relocation of the Lighthouse Intact This option--the committee's preferred option--involves moving the lighthouse complex 400-600 feet (122-183 meters) southwest of its present position to a new site near the far side of the existing parking lot and landscaped area. The committee estimates that this relocation would cost approximately $4.6 million and take approximately 1 year, including planning and site preparation. The committee estimates that a future move of an additional 500 feet in the same direction as the first would cost approximately $1,600,000 in 1988 dollars. Despite the apparent difficulty of moving a large brick structure, the operation entails minimal risk. Many structures larger and older than Cape Hatteras Lighthouse have been moved successfully, and the technology for such operations is well established. The committee envisions that subsequent moves eventually will be required and, therefore, suggests that the steel lifting beams that would be inserted through the lighthouse foundation be left in place for use in future moves. Incremental relocation would provide the most reliable, cost-effective, and prudent long-term protection for the lighthouse by allowing it to be moved away from the approaching sea as the need arises. This option best satisfies public policies regarding historic preservation, conservation, and coastal management; minimizes ecological damage; and involves little risk to the lighthouse. The committee also believes that moving the
Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
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EXECUTIVE SUMMARY
6
lighthouse would attract much attention and, therefore, would provide an opportunity to educate the general public concerning problems of coastal erosion and the value of historic preservation. Seawall/Revetment The design for a seawall and revetment considered by the committee was prepared for NPS by the U.S. Army Corps of Engineers in 1985. The proposed design involves four elements: a concrete seawall encircling the lighthouse, a sheetpile cutoff wall below the seawall, an underground stone revetment fronting the seawall, and a compacted earth fill behind the seawall (U.S. Army Corps of Engineers, 1985). The crest of the wall would be 23 feet (7 meters) above mean sea level and 15 feet (4.6 meters) above grade at the base of the lighthouse. The underground revetment would reach 208.5 feet (63.6 meters) seaward of the lighthouse. The U.S. Army Corps of Engineers estimated a construction time of 20 months from award of the contract at a total cost of $5,575,000 in 1985 dollars. The committee accepts the U.S. Army Corps of Engineers' estimates of construction time and cost. Although the committee judges that the seawall/revetment probably would protect the lighthouse for 20-30 years or more, it does not favor this option. The seawall would obstruct the view of the lower portion of the lighthouse, and thus would change the appearance of the historic landmark. The associated lighthouse keepers' dwellings and other structures would be separated from the lighthouse, which would degrade the historical integrity of the site. Constructing a large, hard, defensive structure around the lighthouse would conflict with several national, state, and NPS policies. In addition, the beach in front of the seawall would be lost when the shoreline eroded to the seawall, impeding movement along the beach. Eventually, the encircled lighthouse would become a tombolo or an island, which would further degrade the historical integrity of the site and make it difficult for the public to visit the lighthouse. During construction, the lighthouse's vulnerability to storms would be increased; thus, this option presents the greatest construction-related risk of
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EXECUTIVE SUMMARY
7
all the options considered. Finally, the seawall/revetment effectively would foreclose future relocation of the lighthouse. Rehabilitation of Groinfield with Revetment This option involves repairing and shortening the existing three groins, constructing one or two new groins south of the lighthouse, and building a below-grade, reinforced concrete revetment around the lighthouse. The revetment would protect the lighthouse from the undermining effects of storms, but not from the battering of waves. The rehabilitated groinfield would stabilize the beach in front of the lighthouse, and the beach would prevent storm waves from directly battering the lighthouse, except during the most severe storms. The committee estimated that this option would cost $4.76.7 million and would require less than 1 year to construct. This option would protect the lighthouse for 20-30 years, barring a disastrous storm. Eventually, as the shoreline outside the groinfield continued to retreat, it would become increasingly expensive, and perhaps impossible, to maintain a beach in front of the lighthouse, which would become increasingly vulnerable to wave damage in severe storms. The groinfield/revetment option would make future relocation of the lighthouse more difficult and expensive. In addition, placing hardened defensive structures on the beach, even below ground, is not in accord with state and national coastal policies. Because of these disadvantages, the committee did not favor this option. However, of the options that would preserve the lighthouse in situ by defensive means, this offers some protection to the lighthouse at relatively low cost. Other Options Other options considered by the committee were rejected for a variety of reasons. The primary reasons included excessive cost (continuing beach renourishment), uncertain
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EXECUTIVE SUMMARY
8
effectiveness and cost (artificial reefs), failure to protect the lighthouse for any period (artificial seagrass and no action), failure to provide either long-term protection or reliable short-term protection (rehabilitation of the groinfield without a revetment), violation of various coastal policies (offshore breakwaters and rehabilitation of the groinfield), and failure to preserve the historic lighthouse (new lighthouse). BROADER ISSUES In addition to evaluating options to preserve Cape Hatteras Lighthouse, the committee was asked to address the broader context of national policy concerning historic preservation versus conservation and coastal issues. Indeed, as sea level continues to rise, additional decisions will need to be made concerning whether and how to protect coastal structures. Moreover, NPS faces decisions concerning historic preservation versus ecological conservation for its properties far from the coast. The committee believes that the present study offers guidance for future decisions on historic preservation and conservation. Although the conclusion itself--to relocate the lighthouse--may not be applicable directly to other cases, the decision process could be emulated. The essence of this process is that options are identified and evaluated against the criteria of natural and engineering constraints, public policy, cost, and effectiveness. Full review of those factors will allow sound public policy to be developed regarding historic preservation and conservation. The committee commends NPS for its willingness to reconsider its initial decision to build a seawall.
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INTRODUCTION
9
Introduction
HISTORICAL BACKGROUND Cape Hatteras Lighthouse, the tallest and best-known brick lighthouse in the U.S. (Figure 1), faces destruction due to coastal erosion. It is 200 feet* (61 meters) tall and weighs approximately 2,800 tons (2,540 metric tons). The present lighthouse was constructed in 1870 to replace a masonry tower built near the present site in 1803 (Holland, 1968). The principal purpose of the lighthouse and its predecessor was to protect shipping from the dangerous Diamond Shoals that extend 13 nautical miles (24 kilometers) seaward--the “Graveyard of the Atlantic”--where at least 600 ships have been lost. In 1870, the lighthouse was approximately 1,500 feet (460 meters) from the water's edge. By 1935, this distance had diminished to approximately 100 feet (30 meters) due to shoreline erosion. Today, partly due to temporary shoreline protection measures, the lighthouse is approximately 160 feet (49 meters) from the water's edge.
* This height was estimated from the engineering drawings obtained from the National Archives (e.g., Figure 1) and information from the Coast Guard's Light List (1971). The lighthouse is approximately 200 feet (61 meters) from its base at grade level to the platinum tip of the rod above the roof of the lantern. The focal plane of the light is 190.8 feet (58.2 meters) above mean low water, approximately 181 feet (55.2 meters) above the ground.
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FIGURE 1 Elevation and vertical section of Cape Hatteras Lighthouse. Adapted from engineering drawing, late 1860s. Photograph courtesy United States National Archives.
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INTRODUCTION
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Several remedial and emergency measures were taken during the past 50 years to protect the lighthouse and other structures in its vicinity (Appendix A). These measures included an artificial dune constructed along Hatteras Island by the Civilian Conservation Corps in the 1930s; a field of three groins abreast and north of the tower constructed in 1969-70, repaired in 1975, and now deteriorating; nourishment of the beach north of the lighthouse with 200,000 cubic yards (153,000 cubic meters) of sand in 1971 and with 1,250,000 cubic yards (955,000 cubic meters) of sand in 1973; a semicircle of nylon sandbags seaward of the lighthouse installed in the late 1960s and again in 1980; a 150foot (46-meter) landward sheetpile extension of the southern groin constructed in 1980 to prevent flanking; and artificial seagrass installed in 1981, 1982, and again in 1984. Some of these measures, notably the groinfield, have reduced the rate of retreat of the shoreline and may temporarily have promoted accretion of the beach (Figure 2; U.S. Army Corps of Engineers, 1985). However, they do not provide any long-term (100 years) protection to the lighthouse, and prolonging their short-term (20 years) beneficial effects would require costly repairs and new construction. Since 1870, the shoreline has receded approximately 1,600 feet (490 meters; U.S. Army Corps of Engineers, 1985), except for a small promontory at the lighthouse. The apparent reduced rate of shoreline retreat near the lighthouse since the 1930s may provide an unfounded sense of security. Research by coastal geomorphologists during the past two decades has clarified the migratory nature of coastal barriers, including the influence of gradual sealevel rise. The beach gradient in front of the Cape Hatteras Lighthouse is steep and narrow, which suggests that the shoreline is poised to return to equilibrium through sudden recession in the event of a major storm or series of storms (Leatherman, 1985, 1987; Everts, 1987). At present, even without further shoreline erosion, the lighthouse is vulnerable to damage from major storms. A storm surge or abnormal increase in sea level due to a “100-year storm” (having a 1% probability of occurring in any year) is estimated to be 8.8 feet (2.7 meters) (MTMA Associates, 1980). This temporarily would raise sea level to the base of the lighthouse, which stands 8 feet (2.5 meters)
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FIGURE 2 Aerial view of lighthouse and beach showing effect of groinfield on beach erosion. Photograph by D. Policansky, August 1987.
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INTRODUCTION
13
above mean sea level (MSL). At high tide, such a storm surge would engulf the base of the lighthouse. To make matters worse, the “average height of the one-third highest waves” breaking above the storm surge elevation would be 15.5 feet (5 meters) (MTMA Associates, 1980, Table 5). Thus, storm surge and breaking waves would directly attack the lighthouse, undermine its shallow footings, and probably demolish its accessory buildings as well. RECENT PROPOSALS Since 1980, the National Park Service (NPS) has considered diverse measures to protect the lighthouse and associated buildings--two keepers' dwellings and an oilhouse. One proposal, approved by NPS in 1985, involved construction of an octagonal revetment and seawall that would encircle the tower and reach a height of 15 feet (4.6 meters) above grade level. Alternative proposals considered by NPS involved relocation of the lighthouse--either in one piece or in segments--to a new site approximately 2,800 feet (850 meters) southwest of the present location. This would place it about 2,400 feet (730 meters) from the nearest shoreline. Other proposed or attempted options include rehabilitating and expanding the groinfield (with or without a partial revetment), submerging objects offshore to create an artificial reef, constructing offshore breakwaters with rehabilitation of the groinfield, installing artificial seagrass, continuing beach nourishment, and taking no action. Several studies and reports prepared since 1980 addressed the preservation of the lighthouse; examples are cited throughout this report and are described in Appendix A. THE PRESENT STUDY The Committee on Options for Preserving Cape Hatteras Lighthouse was formed by the National Research Council in July 1987 at the request of NPS. The committee's charge was to
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INTRODUCTION
14
. . . evaluate the scientific, engineering, environmental impact, and policy aspects of alternative options for preserving the lighthouse from the encroachment of the sea. The feasibility, likelihood of success, long-term dependability and monetary cost of each option will be considered. The study will emphasize the broader context of national policy concerning preservation versus conservation and coastal issues.
The committee also was charged with providing an interim report summarizing its initial findings within 3 months or as soon as possible thereafter. The interim report was submitted to NPS on October 15, 1987. The committee contained within its membership a broad array of experience and disciplinary specialties pertinent to the Cape Hatteras problem. The committee studied many relevant documents, met at Cape Hatteras with additional technical experts and local community spokespersons, visited the site, inspected the lighthouse, and flew over the Cape Hatteras area. Science cannot adjudicate the legislative mandates and public policies under which NPS manages national seashores. The committee recognizes that the final decision concerning options for preserving Cape Hatteras Lighthouse will involve important factors outside its purview--public sentiment and politics in particular. Political feasibility of the various options or the nature and extent of public sentiment associated with them were not within the scope of the charge, and the committee did not critically assess them. The committee was not charged with evaluating the wisdom of a national policy that would preserve this particular lighthouse. Congress has appropriated more than $4 million to preserve the lighthouse (U.S. Senate, 1986). Many issues must influence any decision concerning Cape Hatteras Lighthouse. Part II discusses the options considered by the committee and the associated costs, engineering technology, and reliability of protection. Factors discussed in Part I of this report include coastal barrier-island migration sediment transport; rising sea level; historic preservation--aims, methods, and constraints; and relevant public policies.
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15
Part I
Background Considerations
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THE PHYSICAL SETTING
17
1 The Physical Setting
STRUCTURAL GEOLOGY OF THE HATTERAS SHORE The entire east coast of North America forms part of a trailing edge coast in the global plate-tectonic scheme (Inman and Nordstrom, 1971). Although such a trailing edge is seismically passive compared with the west coast of North America, trailing edge coasts subside in response to gradual cooling of the underlying oceanic crust. The generally level appearance of the east coast of North America owes its topography to this passive accumulation of sediments eroded from the Appalachian mountains since the beginning of the Jurassic, more than 200 million years ago. Subsidence rates along the American east coast, however, have not been uniform. ORIGIN OF THE OUTER BANKS The Outer Banks of North Carolina is one of the longest continuous barrierisland systems in the world. The Outer Banks includes all the barrier islands from Bogue Banks in the south to Currituck Banks in the north (Figure 3). Striking repetitive morphological patterns at all the Carolina capes and the location of all the Outer Banks islands on the Carolina Platform permit patterns identified in the Cape Lookout to Cape Fear region to be extrapolated northward to the Cape Hatteras region.
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FIGURE 3 The Outer Banks of North Carolina (figure does not include Bogue Banks).
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THE PHYSICAL SETTING
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The best Holocene (the past 10,000 years) sea-level curve on the Outer Banks is for Cape Lookout (Heron et al., 1984). This curve--a function of sea level over time--is based on carbon-14-dated peats in island cores (Figure 4) and demonstrates that the rate of sea-level rise has declined. A particularly sharp decline in the rate of sea-level rise occurred about 4,000 years ago. Before this, all barrier-island shorelines probably were moving landward. As a consequence of the sharp decline in rates of sea-level rise 4,000 years ago, some segments of the coast began moving seaward (prograding). Other coastal segments, perhaps nearby, might have continued to erode. Along the North Carolina coast, this pattern meant that shorelines facing south--west of capes such as Cape Hatteras, Cape Lookout, and Cape Fear-began to accrete. Therefore, the most landward beach ridges at Bogue Banks are about 4,000 years old. The pattern of progradation at Buxton Woods on Hatteras Island (Figure 5) suggests that this area, too, is no more than 4,000 years old. This maximal age has been recorded for many barriers along the U.S. coastline (Nummedal, 1983a). The east-facing shorelines, however, continued retreating, so they are much younger. ISLAND MORPHODYNAMICS The capes evolved through a complex pattern of longshore, offshore, and onshore sediment transport. This transport is controlled by longshore currents driven by some of the highest wave energies along the East Coast. The mean annual wave height at Cape Hatteras is 4.9 feet (1.5 meters), and deepwater waves in excess of 6.6 feet (2 meters) are present 25% of the time (Nummedal et al., 1977). This high wave energy drives powerful and persistent longshore currents along the Atlantic shore of the barriers. The resulting longshore transport rate along the east-facing barrier shoreline is calculated at 2.3 million cubic yards (1.7 million m3) of sand per year toward the south (Langfelder et al., 1968). Tides are small at the Outer Banks because of the narrow adjoining continental shelf. The mean tide range at Cape Hatteras is only 3.6 feet (1.1 meters), and the associated currents are weak except at tidal inlets. Consequently, the
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FIGURE 4 Relative sea level at Cape Lookout during the past 9,000 years. Adapted from Heron et al., 1984.
FIGURE 5 Complex pattern of dune ridges at Cape Hatteras indicating pattern of progradation. From Dolan and Lins, 1986.
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THE PHYSICAL SETTING
21
morphology of the Outer Banks barrier-island chain is that of a wavedominated barrier characterized by long, thin barrier islands, frequently overwashed in their natural state, and subject to rapid landward migration. These islands are separated by migrating, widely spaced tidal inlets (Nummedal et al., 1977). The morphology at Cape Hatteras is controlled by dramatic differences in physical processes along the two flanks of this cuspate foreland. Due to the dominance of northeasters, the directional distribution in wave power is such that 75% of the total onshore power strikes the east-facing flank, but only 25% strikes the south-facing shore (Nummedal et al., 1977). As a consequence, the east-facing shore generally is exposed to erosional waves; waves approaching the south shore cause accretion. Therefore, the history of Cape Hatteras has been one of shoreline retreat at the eastern shore and accretion to the south (see, e.g., Dolan and Hayden, 1983; Dolan and Lins, 1986). The average rate of erosion at the northern part of Hatteras Island, which faces east, is 6.4 feet (1.94 meters) per year. The accretion of the southern part of the island, which faces south, has progressed at 1.2 feet (37 cm) per year (Dolan and Lins, 1986). If sea level continues to rise at its current rate, this pattern will be maintained. If sea level rise accelerates, as has been suggested recently (NRC, 1987b), the southern shore could become erosional, and the eastfacing shore could erode more rapidly. Not all the sand that converges on Cape Hatteras accretes along the southern shore. Most of it is carried offshore onto the extensive Diamond Shoals (Figure 6). These and related shoals along the Atlantic seaboard define zones of long-term sediment convergence during the Holocene retreat of the East Coast barrier islands. Much of the sand once contained in the barriers probably has been lost to these extensive shoals and the associated smaller, linear shelf sand ridges (Swift, 1976).
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FIGURE 6 Diamond Shoals. From the U.S. Army Corps of Engineers, 1985. Details of the shoreline (black) are in Figure 7 and Figure 11.
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THE PHYSICAL SETTING
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STORMS Cape Hatteras Lighthouse is on a coast subject to numerous storms. The most powerful are hurricanes; however, the most frequent are extratropical storms (northeasters), which sometimes have winds of hurricane force. The Outer Banks region has an annual hurricane landfall probability of about 20% (Simpson and Lawrence, 1971), the highest along the East Coast north of southern Florida. Yet, northeasters dominate the annual wave-energy distribution (Nummedal et al., 1977). The mean annual wave power at Cape Hatteras is 23 × 103 watts/m, among the highest along the East and Gulf coasts (Nummedal, unpublished). Although an individual hurricane track is difficult to predict, documented hurricanes historically follow a well-defined path across the Cape Hatteras region from south to north (Neumann et al., 1978). Northeasters at Cape Hatteras are most frequent during November through March (Dolan and Lins, 1986). Storms threaten the lighthouse in two major ways. First, erosion is accelerated. Storms generate powerful longshore currents that transport large quantities of sand. Such transport results in erosion of the east-facing shoreline at Cape Hatteras, while the south-facing shoreline accretes. Second, waves and storm surges caused by severe storms can wash over the barrier island, break open new inlets, and threaten land structures. Storm centers are areas of low barometric pressure and are associated with a local rise in sea level known as a storm surge. A storm surge of 8.8 feet (2.7 meters) above normal high tide has approximately a 1% probability of occurrence per year (MTMA Associates, 1980). The cumulative effects of storm surge, storm waves, and spring tide during the Ash Wednesday storm of March 5-8, 1962, produced waves more than 30 feet (9 meters) high along the mid-Atlantic coast (Dolan and Lins, 1986). Hurricane Diana produced sustained winds of 75 knots (138 kilometers per hour) and a modest storm surge of 5.5 feet (1.7 meters) at Carolina Beach in September 1984. Yet it probably was responsible for shoreline retreat of as much as 50 feet (15 meters) (NRC, 1986). The primary danger of a severe storm to the lighthouse is that the foundation would be undermined, and the structure
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THE PHYSICAL SETTING
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would collapse. An extremely severe storm could produce waves large enough to damage the lighthouse directly by their battering. The probability of such a severe storm, however, is very low. The most likely combination of events that would damage the lighthouse is a series of two or three moderately severe storms within a few weeks. In this case, the effects of the first storm would render the lighthouse more vulnerable to the effects of later storms. If the shoreline continues to retreat and protective measures are not taken, the lighthouse will become increasingly vulnerable to the effects of storms during the next few decades. Individual storms cannot be predicted reliably more than a few days in advance, much too late for any major protective measures. In addition, many years might pass with no major storms; in other years, several major storms might occur. The frequency and severity of storms also affects the rate of shoreline retreat, which has not been uniform. Therefore, it is impossible to make precise predictions concerning the survival of the lighthouse. CHANGES IN SEA LEVEL The rate of change in sea level (the first derivative of sea level with respect to time), and changes in the rate of sea-level change (the second derivative of sea level with respect to time) have profound influences on the formation and behavior of barrier islands. They are also critical in estimating the risk to Cape Hatteras Lighthouse and effectiveness of options for protecting the lighthouse. Even if the second derivative is 0 (i.e., sea-level rise is not accelerating), the lighthouse is at risk because the barrier island will continue to migrate westward. There is no reason to believe that the first derivative will become 0; an overwhelming body of evidence indicates that sea level will continue to rise for at least the next several hundred years (NRC, 1987b). Historical Trends Global (eustatic) sea level has fluctuated throughout geologic history in many cycles of different frequencies and
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THE PHYSICAL SETTING
25
amplitudes (Nummedal, 1983b; Haq et al., 1987). Processes such as varying rates of sea-floor spreading, waxing and waning of ice-sheets, and changes in global ocean temperature all cause sea-level changes. Of greatest concern is a continuing eustatic sea-level rise caused by melting of midlatitude glaciers and thermal expansion of ocean waters (Gornitz et al., 1982). Increasing concentrations of so-called “greenhouse gases” in the atmosphere are likely to cause global warming (NRC, 1983), which probably will increase the rate of rise in eustatic sea level (NRC, 1987b). Observed sea-level rise along a coastline equals the sum of land subsidence and eustatic sea-level rise. This relative sea level controls the actual position of the shoreline; the rate of change in relative sea level affects the rate of shoreline erosion. Tide gauges located at most major harbors of the world are the principal source of data for changes in local relative sea level. For the east coast of North America, local rates of change vary greatly (Braatz and Aubrey, 1987). Because Wilmington and Cape Hatteras are located on the Carolina Platform, the value for Wilmington is representative of the whole North Carolina coast. From 1920 to 1983, the rise in relative sea level at Wilmington averaged about .08 inch (2.0 mm) per year. Of this, .04 inch (1.0 mm) per year (Braatz and Aubrey, 1987) or .05 inch (1.2 mm) per year (Gornitz and Lebedeff, 1987) is probably the eustatic component. The North Carolina coast, therefore, appears to be subsiding at a rate of .03-.04 inch (0.8 to 1.0 mm) per year. The rates used in calculations that follow are .05 inch (1.2 mm) per year for eustatic rise and .03 inch (0.8 mm) per year for local subsidence. Estimated Future Trends Eustatic sea-level change and subsidence are influenced by anthropogenic factors. Subsidence rates increase in response to withdrawal of fluids, such as groundwater and shallow oil and gas (Allen and Mayuga, 1970); eustatic sea level increases in response to global warming (NRC, 1983). With continued residential development along the Outer Banks, rates of subsidence are likely to increase due to groundwater use. However, in the absence of solid data to the contrary,
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the committee assumes that this factor will remain insignificant for the next few decades. Consequently, future changes in the rate of relative sea-level rise are assumed to be strictly a function of changes in the rate of eustatic rise. The current best estimate is that eustatic sea-level rise will follow a power-function law (NRC, 1987b) of the form: E(t) = 0.0012t + bt2 (Equation 1), in which E(t) is the additional eustatic component (in meters) above present sea level, t is the time in years from the present, and b is a coefficient of the change in the rate of sea-level rise. The first term in this equation represents a simple linear extrapolation of the average rate of rise for the past century, and the second term represents an increasing rate of rise (quadratic) in response to greenhouse warming. Subsidence must be added to E(t) to obtain the relative or observed rise in sea level, as described below. The NRC (1987b) recognized the uncertainties in projecting rates of rise and evaluated the engineering implications of sea-level rise in terms of three scenarios involving eustatic rises by year 2100 of a low rate, L, of 1.6 feet (0.5 meter); a medium rate, M, of 3.3 feet (1.0 meter); and a high rate, H, of 4.9 feet (1.5 meters). The associated b factors are summarized in Table 1. The choice of three scenarios for future sea-level rise is based on a series of analyses published during the past 5 years (Revelle, 1983; Hoffman et al., 1983, 1986; Robin, 1986; and NRC, 1983). These studies were summarized by the NRC (1987b), but the original studies should be consulted for an appropriate understanding of the complex array of assumptions that their models involve. The data are too scant and the models too uncertain to justify assigning probabilities to the three sea-level rise scenarios. Using the NRC estimates for rates of eustatic rise combined with the assumed steady subsidence for the Cape Hatteras area of .03 inches (0.8 mm) per year, the local relative sea-level rise can be calculated for any desired future date, T(t), as: T(t) = E(t) + S(t) (Equation 2),
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where S(t) is the change due to ground subsidence. Using the numbers above and combining equations 1 and 2 yields: T(t) = 0.002t + bt2 (Equation 3). Calculated magnitudes of sea-level rise are summarized in Table 1. SHORELINE RETREAT Estimates of the rate of shoreline retreat in response to rising sea level can be obtained by different methods that apply varying levels of sophistication. The committee emphasizes, however, that so many unpredictable factors affect shoreline retreat (e.g., frequency and magnitude of storms and measures taken to protect the shoreline) that no method can provide a precise estimate. Common approaches for such estimates include extrapolation of historical trends and use of the Bruun rule (NRC, 1987b). Several factors complicate any predictions of shoreline retreat. First, there are the four estimates of rates of sea-level rise: a continuation of historic trends and the three NRC scenarios. Second, various methods can be used to estimate the rate of shoreline retreat for any estimated rate of sea-level rise. Third, the rate of shoreline retreat would be much greater for an unprotected coast than for a protected one; the coast in front of the lighthouse is partially protected. The committee did not choose between the four rates of sea-level rise. However, the most reliable estimates for shoreline retreat were believed to be those provided by trend analysis (Leatherman, 1984) assuming some shoreline protection. Analyses of estimated shoreline retreat by Bruun's rule and trend analysis in the absence of shoreline protection are provided in Appendix B for comparative purposes. They predict greater shoreline retreat than trend analysis assuming protective structures for all rates of sea-level rise.
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TABLE 1 Estimated Future Sea Levels for Cape Hatteras Based on Four Estimates of Sea-Level Rise Rate of b Eustatic Rise by Year in Rise at Cape Hatteras Eustatic Inches/ Inches (mm) Observed2 by Year Seayear2 in Inches (mm) Level Rise1 Inches/ year (mm/yr) (mm/ 2000 2018 2088 2000 2018 2088 yr2 ) 0.05 0 0.55 1.4 4.7 0.94 2.4 7.9 (1.2) (14) (36) (120) (24) (60) (200) NRC low 0.001 0.71 2.4 16 1.1 3.3 19 (0.028) (18) (61) (400) (28) (85) (480) NRC 0.0026 0.94 3.7 31 1.3 4.6 34 medium (0.066) (24) (95) (780) (34) (119) (860) NRC high 0.004 1.2 5.2 46 1.5 6.1 49 (0.105) (30) (131) (1170) (39) (155) (1250) 1.05 inch per year is a continuation of present trends; the NRC scenarios are accelerating rates of sealevel rise (acceleration rate b) taken from NRC, 1987b. 2The observed rate of sea-level rise is eustatic sea level rise plus subsidence of .03 inch (.8 mm) per year.
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THE PHYSICAL SETTING
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TREND ANALYSIS The following discussion uses the observed retreat rates at Cape Hatteras during the past 50 years, over which time various engineering interventions were implemented (see Appendix A). It is assumed that the existing groins will continue to have some effect in maintaining the present rate of retreat during the next few decades, although their effect for the next 100 years will be minimal without major reconstruction. It is difficult to determine a typical shoreline retreat rate since the 1930s, because various shoreline engineering measures were implemented at different times. The rate of retreat at Cape Hatteras has decreased steadily since the 1930s (Everts et al., 1983; Figure 7). To determine a relationship between shoreline retreat and sea-level rise for this period, therefore, becomes somewhat arbitrary. The average retreat rate at the lighthouse from 1945 to 1983 reported by the U.S. Army Corps of Engineers (1985) was 5.2 feet per year (1.6 meters per year; Figure 8); during this time, short periods of accretion occurred. Assuming a past local rate of sea-level rise at Wilmington of .08 inch (2.0 mm) per year, .39 inch (1 cm) of sea-level rise corresponds to 26 feet (8 meters) of shoreline retreat, a ratio of 1:800. Table 2 summarizes future shoreline retreat based on the four estimates for sea-level rise and assuming a ratio of sea-level rise to shoreline retreat of 1:800. It is clear that even with intervention, the shoreline at Cape Hatteras will continue to recede. SUMMARY OF SHORELINE RETREAT ESTIMATES 1. The local relative sea level at Cape Hatteras 30 years from now will be 2.4 inches (6.0 cm) higher than it is now, if the trends of the past century continue unchanged; in 100 years it will have risen 7.9 inches (20 cm). With the high NRC (1987b) scenario, the corresponding values are 6.1 inches (15.5 cm) in 30 years and 49 inches (125 cm) in 100 years. 2. Predictions of shoreline retreat are rough estimates because of uncertainties in future rates of sea-level rise and
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FIGURE 7 Position of the shoreline at Cape Hatteras 1852-1980. SOURCE U.S. Army Corps of Engineers, 1985.
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TABLE 2 Predicted Shoreline Retreat at Cape Hatteras in the Presence of Continued Mitigative Measures for Four Sea-Level Rise Scenarios (The Estimates of Shoreline Retreat Take Subsidence Into Account.) Shoreline Retreat by Year, in Feet (meters) Eustatic Sea-Level Rise* in Inches (mm)/yr 2000 2018 2088 .05 (1.2) 62 (19) 157 (48) 525 (160) NRC low 72 (22) >223 (68) 1,260 (384) NRC medium 89 (27) 315 (96) 2,260 (688) 102 (31) 407 (124) 3,280 (1,000) NRC high *.05 inch per year is a continuation of present trends; the NRC scenarios are accelerating rates of sea-level rise as presented in Table 1.
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inadequately quantified models of shoreline response and storm frequency. 3. The committee believes that the most realistic projections of shoreline retreat are those based on trend analysis of the past 40 years because existing structures will continue to have some effect for the next few decades. Accordingly, continuation of the present erosion rate will move the shoreline 157 feet (48 meters) landward in the next 30 years. With NRC's (1987b) high scenario, the retreat would be 407 feet (124 meters).
FIGURE 8 Cumulative shoreline change at Cape Hatteras Lighthouse, 1945-1983. SOURCE U.S. Army Corps of Engineers, 1985.
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RELEVANT PUBLIC POLICIES
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2 Relevant Public Policies
In selecting an option or combination of options to preserve the lighthouse, the NPS is guided by a complex series of public policies that address diverse public concerns. The policies are declared by different levels of government and, in some cases, these policies conflict. Conflicts also may arise among different programs and agencies of the same level of government. Many laws affecting the coastal zone, such as the National Flood Insurance Program, are conceived in response to actual disasters or other events and trends perceived to be harmful. Public policies seldom anticipate and mitigate future harms whose time of occurrence is unknown. Similarly, public policies commonly focus on the short term. Deciding how to preserve Cape Hatteras Lighthouse is not easy, as it involves numerous and various public policies. And it is not possible to wait until the lighthouse is about to fall to a storm; by then it will be too late. The changes that will lead to that vulnerability are unpredictable and will occur over decades rather than months or years (aside from an unlikely storm of great severity, which could affect the lighthouse now). The decision requires a longterm view, as NPS recognizes. With these considerations in mind, the committee identified the following public policies as being relevant to the lighthouse preservation decision.
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PROTECTION OF NAVIGATION The original purpose of the lighthouse--to prevent shipwrecks on Diamond Shoals--is of little significance to the question of how the lighthouse should be preserved. The present light is visible on a clear night for 24 nautical miles (44 kilometers) and is supplemented by a beacon on a “Texas tower” 13 nautical miles (24 kilometers) seaward at the outer edge of Diamond Shoals. Modern shipping relies chiefly upon LORAN and other electronic navigational systems; the lighthouse is chiefly of navigational value to small craft. NATIONAL PARK SERVICE MANDATE The National Park Service Organic Act of 1916 (16 U.S.C., Sec. 1 et seq.) charges NPS with a dual mandate to preserve and facilitate public enjoyment of NPS facilities, namely: “to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.” In the case of Cape Hatteras Lighthouse, this mandate applies equally to the lighthouse as a historical artifact of great importance and to the beach, dunes, wetlands, and other natural resources of the national seashore. Options that compromise natural resources in the interest of preserving the lighthouse presumably are disfavored. PROTECTION OF HISTORIC STRUCTURES The National Historic Preservation Act of 1966 (16 U.S.C. Sec. 470) and Executive Order 11593 (U.S. President, 1971) declared a national policy favoring the preservation of historic structures. Cape Hatteras Lighthouse is on the national and state registers of historic landmarks. This public objective of preservation is articulated further in NPS Management Policies (U.S. National Park Service, 1978): “Historic structures constitute a major component of the cultural resources entrusted to the National Park Service. The continued integrity of these resources, based upon their classification,
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appropriate treatment, management, and use, is a primary concern of the Service.” Relocation of a historic structure that individually possesses national significance in terms of criteria for evaluating proposed national historic landmarks is not permitted under NPS policies. Although a memorandum from the NPS associate director for cultural resources (J. L. Rogers, 1987) implies that relocation of Cape Hatteras Lighthouse is permissible, relocation would require the NPS director to waive the guideline (R. J. Beallus, National Park Service, personal communication, 1988). NPS management policies further indicate that “no historic structure shall be moved if its structural integrity or preservation would be adversely affected thereby.” In addition, “every effort shall be made to reestablish its historic orientation, immediate setting, and general relationship to its environment.” COASTAL BARRIER RECESSION The Coastal Barrier Resources Act (CBRA) of 1982 (16 U.S.C., Secs. 3501-3510) demonstrated congressional recognition of the migratory and dynamic nature of coastal barriers. The CBRA prohibits federal subsidies for infrastructures and other actions that would encourage development of undeveloped, nonpublic coastal barriers. The Cape Hatteras site is federally owned and is not within the direct purview of the CBRA. Nevertheless, the CBRA reflects a broader national policy. Public investment decisions should be consistent with that policy, rather than contradict it. NPS generally favors letting nature take its course with respect to sites under its auspices. However, NPS does distinguish between natural zones and historic zones. In the latter, NPS management policy (U.S. National Park Service, 1978) provides that “control measures, if necessary, will be predicated on thorough studies taking into account the nature and velocity of the shoreline processes, the threat to the cultural resource, the significance of the cultural resource, and alternatives . . . and how control measure[s] would impair resources and processes in natural zones.” It is further provided that “where erosion control is required by law, or where present developments must be protected to achieve
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park management objectives, the Service will employ the most natural appearing and effective method feasible.” State policy to similar effect is expressed in North Carolina's constitution, Article XIV, Table Section 5 (1973; conservation and protection of lands and waters); the Coastal Area Management Act of 1974 (natural shoreline preservation); and the 1987 Guidelines of its Coastal Resources Commission (policy against permanent shoreline stabilization). FLOOD-HAZARD MITIGATION The National Flood Insurance Act (NFIP) of 1968 as amended (42 U.S.C., Secs. 4001-4128) reflects a national policy that coastal and riverine flood losses should be reduced by discouraging activity in flood-hazard areas, in contrast with past reliance upon structural flood-control projects. The NFIP has mapped inland and coastal flood-hazard areas and set minimum standards for local management of new development in such areas. Executive Order 11988 (U.S. President, 1977) further provides that the federal government will avoid investing in identified flood-hazard areas when reasonable alternatives exist. Recent amendments to the NFIP are discussed with reference to relocating the lighthouse in Part II. ENHANCEMENT OF RECREATION AND TOURISM Cape Hatteras Lighthouse is a symbol of the Outer Banks and a focal point of the Cape Hatteras National Seashore. Although the lighthouse is not open to the public, approximately 140,000 people visited the lighthouse site in FY 1986 (1.6 million visited the entire national seashore in that year). Such tourism provides an important contribution to the economy of the area. Maintenance of continuity of the beach along Hatteras Island in its unobstructed state is important to the recreational function of the national seashore.
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RELEVANT PUBLIC POLICIES
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PUBLIC EDUCATION Cape Hatteras Lighthouse and its site are resources for public education, an important component of the NPS mission. Topics that may be studied at the site include the maritime and settlement history of the Outer Banks, the physical and ecological nature of coastal barriers, the phenomena of hurricanes and coastal storm hazards, and the design and operation of this lighthouse and of U.S. lighthouses generally. FEDERAL CONSISTENCY WITH STATE LAW The Federal Coastal Zone Management Act of 1972, as amended (16 U.S.C., Secs. 1451 et seq.) declared “a national interest in the effective management, beneficial use, protection, and development of the coastal zone” (16 U.S.C., Sec. 1451) and further noted that “important ecological, cultural, historic, and aesthetic values in the coastal zone . . . are being irretrievably damaged or lost.” To implement national coastal policy, the act facilitated development of state coastal zone management programs under federal guidelines and partial funding and provided that “each federal agency conducting or supporting activities directly affecting the coastal zone shall conduct or support those activities in a manner which is, to the maximum extent practicable, consistent with approved state management programs” (16 U.S.C., Sec. 1456 (c) (1)). In addition, state law predating the Coastal Zone Management Act may regulate activities on federal coastal lands (California Coastal Commission et al., 1987). WETLANDS PROTECTION Section 404 of the Clean Water Act (33 U.S.C., Sec. 1344) reflects a broad policy favoring the protection of tidal and freshwater wetlands and establishes a permit program to regulate dredging or filling of wetlands under the joint administration of the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency. In general, disturbance of natural wetlands is discouraged if a suitable, nonwetland site
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is available. Executive Order 11990 (U.S. President, 1977) similarly prohibits federal actions that disturb wetlands if alternative sites are available. ECONOMIC EFFECTIVENESS Since the Flood Control Act of 1936 (33 U.S.C., Sec. 701a et seq.), Congress has required that certain flood-control and other water-resource projects be justified by a cost/benefit analysis demonstrating that anticipated benefits would exceed costs “to whomsoever they may accrue.” The requirement for a cost/benefit analysis applies chiefly to projects proposed by the U.S. Army Corps of Engineers and certain other federal construction agencies but not to NPS. Although a proposed seawall/revetment would be constructed by the U.S. Army Corps of Engineers, NPS is the deciding agency, and a cost/ benefit analysis is not required. Nevertheless, this long-standing provision indicates the importance of selecting an option whose anticipated short- and long-term benefits are optimal compared with short- and long-term costs. ENVIRONMENTAL PROTECTION Numerous statutes embody a federal policy of commitment to environmental protection. For example, Section 101 of the National Environmental Policy Act of 1969 recognized “the profound impact of man's activity on the interrelations of all components of the natural environment” and declared a federal policy to “assure for all Americans safe, healthful, productive, and aesthetically and culturally pleasing surroundings; preserve important historic, cultural, and natural aspects of our national heritage.” The act requires an environmental impact statement be prepared concerning any “major federal action significantly affecting the quality of the human environment” (Section 102 (c)). The foregoing policies do not suggest the most favorable option for the preservation of the lighthouse. Indeed, policies do conflict as applied to the problem. For instance, the need to preserve a historic structure may conflict with a laissez faire approach to coastal barrier erosion. In addition,
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policy-oriented criteria to select a preferred option must be viewed in light of scientific, engineering, and other technical factors. USE AND PROTECTION OF THE COAST The United States has 80,560 miles (129,621 kilometers) of coast excluding the Great Lakes, of which 19,240 miles (30,957 kilometers) is erosional (U.S. Army Corps of Engineers, 1971). At present, the sea is rising, so the shoreline is moving landward (May et al., 1983). This natural compression from the sea clashes with outward demographic growth and development pressure in the coastal zone; the population of coastal areas has grown faster than that of the U.S. as a whole (West, 1987), and coastal development has increased dramatically in the past few decades (Dolan and Lins, 1986; Nordstrom, 1987). Population pressure on the coast is a severe test of environmental and spatial planning capacities (Platt et al., 1987). An array of federal statutes and regulations govern the development and protection of the coast as well as the contiguous marine areas. North Carolina has adopted a singular approach to its migratory coastline: its policy is to discourage attempts at permanent stabilization of the shore. Notwithstanding these measures and historic concern for the American coast, the nation and the coastal states have yet to formulate an adequate response to the increasing problems of a shore moving landward and a population moving seaward. Cape Hatteras Lighthouse stands on the line of compression. Resolution of its future might act as a signal to the country of the problems confronting the coast and illuminate approaches to solving the problems of living with a rising sea.
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CONCEPTS OF HISTORIC PRESERVATION
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3 Concepts of Historic Preservation
Sande (1984) describes the purposes of historic preservation as continuity-the conservation of physical evidence of the past; integrity--the accuracy of restoration and interpretation; plausibility--the recreation of a true feeling of an earlier time; and meaning--the hopes, dreams, and satisfactions nurtured in those who visit the site. From the standpoints of continuity and historic integrity, Cape Hatteras Lighthouse ideally should be preserved at its original site. The tower first was constructed 1,500 feet (460 meters) from the ocean, but since 1919, it has been close to the water's edge; preservationists have the choice of which era to restore. Plausibility and meaning depend on nonscientific sentiment. Yet, they are a force behind the decision to save the lighthouse. Cape Hatteras Lighthouse stands about 200 feet (61 meters) tall on a flat and narrow island, is painted with black and white stripes, and has a rotating beacon of 250,000 candlepower (U.S. Coast Guard, 1971). It is a forceful presence in the surrounding community and can be seen from great distance on land and at sea. Citizens of Hatteras Island and many visitors want to save the lighthouse at its original site for as long as possible. However, this might not be a realistic, long-term solution to preservation. Historic preservation has been a mission of the National Park Service since its beginning. The National Park Service Act of 1916 (16 U.S.C. Sec. 1 et seq.) stated that the purpose of the agency is “to conserve the scenery and the natural and historic objects and the wildlife therein and to
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CONCEPTS OF HISTORIC PRESERVATION
42
provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.” The word “historic” was included deliberately. Horace Albright, second director of the NPS and a drafter of the legislation, explained that he and Stephen Mather, the first director, always envisioned the inclusion of historic parks and sites in the NPS domain (Albright, 1971). The election of Franklin D. Roosevelt as president afforded an opportunity to realize this vision. Roosevelt issued a presidential order transferring to NPS more than 60 national battlefields, national monuments, and other historic sites then under the care of other government agencies. In 1935, the Historic Sites, Buildings, and Antiquities Act (16 U.S.C. Secs. 461-467) broadened the role of NPS in historic preservation. It authorized the Historic American Buildings Survey, the Historic American Engineering Record, and the National Survey of Historic Sites. It also provided for establishment of national historic sites, preservation of properties “of national historic or archeological significance,” and designation of national historic landmarks. The National Historic Preservation Act of 1966 (16 U.S.C. Sec. 470) involved NPS in the preservation of historic and archeological sites at the state and local level. The act stated a national policy for historic preservation by providing for the expansion of the National Register of Historic Places, matching grants to the states and the National Trust, and the Advisory Council on Historic Preservation. The act defined historic preservation as “the protection, rehabilitation, restoration, and reconstruction of districts, sites, buildings, structures, and objects significant in American history, architecture, archeology, and culture.” Congress amended the act in 1980 (94 Stat. 2987), expanding the roles of federal, state, local, and private sectors and providing new historic preservation mandates for federal land managers. Numerous other laws and executive orders affect the preservation of historic or archeological properties and apply to NPS. A 1987 list of all “water-related” properties on the National Register of Historic Places comprises 750 entries, approximately half of which are historic vessels. Of the
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remaining half, most are lighthouses or lifesaving stations. It is reasonable to assume that no more than seven or eight individual historic coastal properties might be endangered by rising sea level and erosion during the coming years. A primary threat to all historic structures is lack of funds and associated neglect. A recent report (U.S. Department of Interior, 1987) estimates that $100 million is needed to repair historic structures in the national parks administered by the Southeast region alone. Because of past and recent development patterns along the barrier islands and ocean bluffs, historic structures probably are not considered the most pressing public policy issue posed by erosion and rising sea levels. Rather, beach houses and roads are pressing concerns, followed by concern for coastal cities.
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Part II
The Criteria, Options, And Evaluation
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PRESERVATION OPTIONS AND EVALUATION CRITERIA
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4 Preservation Options and Evaluation Criteria
THE OPTIONS The committee identified and evaluated ten principal options, some of which foreclose others. For example, relocation would eliminate from immediate consideration the construction of a seawall, and a seawall would make subsequent relocation difficult or impossible. Other options, such as beach nourishment or breakwater construction, could be used in combination. The committee did not evaluate every possible option, but selected the following as worthy of consideration: • • • • • • • • • •
Incremental relocation of the lighthouse intact Rehabilitation of the groinfield without revetment Rehabilitation of the groinfield with revetment Seawall/revetment Artificial reefs Offshore breakwaters and groinfield rehabilitation Deployment of artificial seagrass Continuing beach nourishment No action New lighthouse CRITERIA TO EVALUATE PRESERVATION OPTIONS
To evaluate the options, the committee developed a set of criteria or tests against which to judge the options. The
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committee then discussed and listed those criteria that appeared relevant. Each option was then discussed with respect to each criterion. The criteria the committee used are: Technical feasibility. Can the option be implemented successfully from a technical or engineering standpoint? Long-term reliability. Will the option protect the lighthouse for at least 100 years? Short-term reliability. Will the option protect the lighthouse for at least 20 years? Initial cost. What is the approximate cost to implement the option? Long-term cost. What are the likely recurrent future costs to maintain the effectiveness of the option? Protection of natural resources. What are the potential effects on ecological, hydrological, geomorphological, and related natural systems and processes in the vicinity of Cape Hatteras Lighthouse? Aesthetic impact. What is the visual effect of the option? Local public considerations. How are residents of the Outer Banks, specifically Buxton, N.C., likely to view the option? Protection of historical values. What is the implication of the option for preserving the lighthouse, its associated buildings, and its historical milieu? Will a precedent be set for protection of other historic structures similarly endangered? Public access and recreation. What is the effect of the option on public enjoyment of the lighthouse site, including the beach in front of it?
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Risk of damage to the lighthouse during implementation. What is the likelihood of damage to or destruction of the lighthouse due to or during implementation of the option? Preservation of other options--short term. To what extent does the option immediately foreclose alternative preservation options? Preservation of other options--long term. Are other preservation options foreclosed after 20 years? Construction time. How long will it take to achieve effective protection after an option is chosen? Coastal Barrier Resources Act. Although NPS is not covered by the CBRA, to what extent is the option consistent with the act? NPS shoreline-management policies. Is the option consistent with NPS policy not to obstruct natural processes on coastal barriers? North Carolina coastal policies. Is the option consistent with state policy on response to shoreline retreat? Flood-hazard mitigation. How does the option relate to the national goal of reducing flood hazards through adjustment of land use in floodplains, the National Flood Insurance Act, and Executive Order 11988? Wetlands effects. What is the potential effect of the option on wetlands and other U.S. waters regulated under Section 404 of the Federal Clean Water Act? Fisheries. What are the potential effects of the option on commercial and recreational fish habitats? Navigation. How would the option affect commercial and recreational navigation? The criteria fit into four general categories. The first contained crucial criteria: if an option failed to meet these
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criteria, it was not considered further. The crucial criteria were technical feasibility, short-term reliability, initial and long-term cost, protection of historical values, and risk of damage to the lighthouse during implementation. Options that met the criteria in category 1 then were considered against criteria in category 2. This category contained important criteria but not so important that failure to meet one of them automatically excluded an option from further consideration. Some of these criteria are relative--although no option would guarantee protection under all circumstances, some would offer better protection than others. All options that would provide at least some protection would cost a substantial amount of money, but some would cost more than others. The criteria in category 2 were long-term reliability, initial and long-term cost, protection of natural resources, aesthetic impact, public access and recreation, preservation of other options in the short and long term, construction time, and NPS shoreline-management policies and North Carolina's coastal policies. The third category consisted of criteria that overlapped with one or more in category 2: Coastal Barrier Resources Act, flood-hazard mitigation, and wetlands effects. Although these criteria were not identical to any in category 2, every time the relevant category 2 criteria--i.e., protection of natural resources and relevant coastal-management policies--were met, these criteria also were satisfied. Category 4 contained two criteria that did not appear to be affected much by any option--fisheries and navigation--and one criterion, local public considerations, which is important to decision makers but outside the committee's purview. Six options failed criteria in category 1. Deployment of artificial seagrass is not technically feasible in that it does not work, and the committee was uncertain of the effectiveness of artificial reefs at this site. Building a new lighthouse would not protect historical values as required by NPS's mandate. Beach renourishment would incur excessive long-term costs, and no action or rehabilitation of the groinfield without a revetment would not provide reliable short-term protection for the lighthouse. The committee's evaluations of the remaining four options were based largely on criteria in category 2 and are discussed in detail in Chapter 5. In brief, relocation would not
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fail any criterion. The seawall/revetment option would conflict with coastal management policies, historic preservation, long-term cost, public access and recreation, aesthetic considerations, risk of damage during implementation, and preservation of other options. Rehabilitation of the groinfield with a revetment and offshore breakwaters with groinfield rehabilitation would not satisfy criteria concerning long-term reliability and shoreline management policies. The types of conflicting considerations faced by the committee (such as conflicting public policies and the desirability of minimizing cost while maximizing protection) also might arise in other NPS decisions regarding historic preservation and conservation. The committee suggests that an approach similar to one it used--developing a set of relevant criteria and studying options against those criteria--would prove useful for other decisions that involve conflicting considerations.
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EVALUATION THE OPTIONS
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5 Evaluation the Options
The committee provides cost estimates for the options discussed below (except for artificial reefs, for which too many variables are involved, and artificial seagrass, for which no effective level of application can be determined). In some cases, estimates from other sources were used as the basis for the committee's estimates. In other cases, the committee developed its own estimates. The committee's cost estimates are conservative, and should be considered as guides, within a range of perhaps ±20%. The actual cost of each option can be determined only by receiving a specific proposal from a contractor. Variables not included in the committee's cost estimates include competition, experience, expertise and equipment already owned, and time involved in obtaining necessary permits and insurance. Several options imply costs of maintenance and repair or of rebuilding or choosing another option in the future. In addition, an appropriate discount rate must be applied when considering future costs. For example, if OMB's current discount rate of 10% per year is applied, a cost of $5 million 30 years in the future is minor compared with a similar cost next year. Except in the case of beach nourishment, the committee did not attempt to account for inflation in future costs, and all estimates of future costs are in present dollars. In addition, the committee made no attempt to adjust previous cost estimates from other sources. Thus, the dollar values of all previous estimates are valid for the dates of the estimates.
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INCREMENTAL RELOCATION: THE PREFERRED OPTION Overview The committee concluded that the best option is to relocate the lighthouse a minimal distance--400-600 feet (122-183 meters)--to the southwest, which will ensure protection for approximately 25 years. Thereafter, the lighthouse should be moved further as advance of the sea requires. Steel lifting beams for the move would be left in place (concealed by sand) to facilitate future moves. Subsequent moves would be less expensive than the first, because much of the work required need be done only once. The current groinfield would not be repaired under this option.* Choice of the initial resting site should be made by NPS; the committee favors an area close to the southwest corner of the present parking lot. This and other areas are discussed under “Site Selection.” The committee recognizes that methods for relocating the lighthouse other than the rail and track method described below are available. However, based upon the information currently available to it, the committee believes this method will minimize cost and ecological damage. Detailed confirmation of the correctness of this approach and the technical details of any relocation must be determined by a contractor, retained by NPS. A conceptual description of the committee's suggestion is outlined below. In preparation for the move, the building's structure would be assessed and minor repairs and reinforcements made as needed. The foundation of the lighthouse would be tunneled for insertion of a series of needle beams. Then the lighthouse (minus part of its below-surface foundation and
*The three groins were constructed by the Naval Facilities Engineering Command to protect the U.S. Navy facility north of the lighthouse, although the south groin was installed south of its originally planned location to extend protection to the lighthouse (U.S. Army Corps of Engineers, 1985). The present committee was asked to consider options to protect the lighthouse, not the Navy facility. If the groins were maintained, they would probably continue to reduce beach erosion in front of the Navy facility and the lighthouse.
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the timber mat) would be vertically raised by hydraulic jacks to clear the belowsurface foundation that remained. The lighthouse would be lowered onto rollers that rest on multiple horizontal steel-rail beams supported by precast concrete piles. The entire lighthouse structure would be moved on the tracks with hydraulic jacks and pulled to its new site, where it would be placed on a newly constructed foundation, such as a pile-supported concrete mat (Figure 9). The total time estimated for the move, including engineering analyses, is approximately 1 year; preparation and relocation of the lighthouse would take fewer than 3 months. The actual relocation should not occur during hurricane seasons-summer and fall. It is expected that the light will be nonfunctional during this 3month period. The keepers’ quarters could be moved using standard housemoving techniques. Before relocation, the external structure would be strengthened and reinforced as an integral unit by vertical and circumferential prestressing as discussed in “Risks to the Lighthouse,” and as shown in Figure 10. The foundation tunneling would involve no movement of the tower. Needle beams would be inserted immediately into 3-foot (91 cm) tunnels; thus, the base of the lighthouse would not be weakened. During lifting, hydraulic jacks would be equipped with mechanical locknuts, and cribbing would be placed close behind; this would limit vertical displacement to less than ½ inch (1.3 cm) in case of jack failure. Were a jack to fail, the center of gravity would move about 1¼ inches (3.2 cm) horizontally. The top would move more, but such displacement should have little effect on the stability of the lighthouse. Cost of First Move The MTMA Associates report (1980) described relocation of the lighthouse in one piece to an area approximately 2,800 feet (850 meters) southwest of the present location at a cost of $2.7 million. The NPS Environmental Assessment (1982) estimated $5.9 million, and the Move the Lighthouse Committee (Fischetti et al., 1987) estimated $3.2 million to move the lighthouse to the same area.
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FIGURE 9 Schematic drawing of proposed lighthouse relocation. Plan view.
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FIGURE 10 Schematic drawing of proposed lighthouse relocation, showing some external reinforcing of the structure. Cross section of A - A from Figure 9.
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The committee estimates that relocation of the lighthouse and its associated structures 500 feet (150 meters), including design and construction of a new site, would cost approximately $4.6 million. The marginal cost of moving the lighthouse an additional distance is estimated at approximately $600 per foot ($1,970 per meter). The committee's cost estimates were based on the following: • Current site Sheet piling around excavation; dewatering and excavation; piling; concrete reaction/support beams; concrete ring reinforcement; prestressing rods; main support beams; end-support trusses; prestressing; installation of beams, including, tunneling; jacks; cribbing; raising of the structure $ 750,000
• Rail/track Pile supports, concrete caps, steel beams/plates, rollers or sliding surfaces (steel on polytetrafluoroethylene) 660,000
• New foundation Pile supports; excavation; material for new concrete foundation; removal of trusses and beams; patching of lighthouse base; backfilling, grading, and landscaping area 280,000
• Existing structure: strengthening and repairs Joint-bonding of masonry; circumferential stressing; vertical prestressing; repairing the gallery, stairs, and windows; removal of external coating and recoating 470,000
• Site restoration Demolition of concrete track and old site, cutting off or removing piles, restoration of old site, removal of present parking lot, landscaping of site
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200,000
• Moving the keepers' dwellings
360,000
• Engineering
400,000
• NPS administration • Insurance Replacement of lighthouse Professional liability
200,000 55,000 400,000
• Contractor's profit
600,000
• Contingency Total
$ 4,585,000
Cost of Future Moves By leaving the needle beams in the base of the lighthouse, the cost of a future move is much reduced. Also, the lighthouse would not need to be cut from its stone foundation a second time. The committee estimates the cost of a future move of 500 feet (150 meters) at approximately $1,600,000 (current dollars) if the move continues in the same direction as the first move. The estimate is based on the following: • Reinstallation of external strengthening (i.e., tendons and bands) $150,000
• Uncovering the needle beams, rejacking the lighthouse 105,000
• Railbeams, piles, etc.; construction of 500-foot move track 500,000
• New foundation, and site preparation (e.g., landscaping) 115,000
• Engineering 100,000
• Insurance 150,000
• Contractor's profit
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• Contingency 200,000
Total $ 4,585,000
Evaluation Structural Integrity: Can the Lighthouse be Moved? The lighthouse is structurally sound (Hasbrouck Hunderman Architects et al., 1986). Small cracks visible in the structure do not compromise its integrity. The committee concludes that the risk of damage in a properly performed relocation would be minimal and certainly less than that involved in building a seawall/revetment or leaving the lighthouse at its present site. To further reduce the risk of damage to the lighthouse, the committee recommends structural repairs and a variety of measures to strengthen the structure temporarily that are discussed below. The Move the Lighthouse Committee (Fischetti et al., 1987) estimated the weight of the lighthouse at 2,600 tons (2,360 metric tons); the present committee judges that the weight of the granite in the 45-foot (13.7-meter) diameter base was underestimated and estimates the weight of the structure at 2,800 tons (2,540 metric tons). Success in moving structures depends on careful, detailed study and design of each case. However, many large, heavy structures--some larger and older than Cape Hatteras Lighthouse--have been moved successfully (Appendix C). Examples include a 3,000-ton (2,720-metric ton) masonry wing moved 260 feet (80 meters) in 1949 and the five-story, 2,350-ton (2,130-metric ton) brick Willard Parker Hospital building, moved 60 feet (18 meters) in 1941 (Prentis and White, 1950); a 3,200-ton (2,900-metric ton) brick and frame church moved 20 feet (6.1 meters) in 1923 (Anonymous, 1923); a 12,000-ton (10,900-metric ton) 14th century church moved 2,400 feet (730 meters) in Czechoslovakia in 1975 (Curtis, 1979); and oil-related structures as much as 200 feet (61 meters) tall and weighing up to 35,000 tons (31,700 metric tons) that were moved onshore before being loaded onto barges (Gerwick, 1986).
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Risks to the Lighthouse A potential, but manageable, risk to the structure would be experienced during the acceleration phase at the start of the move. The initial accelerating force must overcome the static friction between the rollers and the rails. The critical moment in moving the lighthouse occurs when the static friction of the mass resting on its temporary supports is broken and the tower begins to move horizontally. The force required to produce an acceleration is a function of the mass of the tower and its supports, according to Newton's Law: F=m×a where F = force, m = mass, and a = acceleration. However, frictional force must also be overcome. Because static friction is much greater than moving friction, the force required to overcome static friction is much more than that required to balance moving friction. As the force of static friction decreases suddenly to the force of moving friction, the lighthouse will begin to accelerate rapidly. The rate of change in acceleration from 0 to an increasing rate is a “jerk,” a dynamic action that tends to change the stability of the mass. This would tend to cause the lighthouse to rock. To minimize this risk, elasticity in the cables should be minimized and controlled, or short rods should be used. If a contractor were to set up a winch at the far end and use wire ropes to pull the structure, elastic strain energy would build in the wire ropes, resulting in a sudden jerk. Inertial forces during such a jerk could be similar to those of a small earthquake. Rather than wire-rope cables, the current state-of-the-art method uses positive displacement jacks with short strokes, reacting against brackets on the rail beams. The jerk can be minimized further by using roller bearings or steel on polytetrafluoroethylenecoated lubrite surfaces, which minimize starting and moving friction. The accelerating force can thus be limited to negligible values--0.05 times the force of gravity or less.
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Another risk would be settlement of the supporting beams during the move. At each spot along the entire move track, the beams must be able to support the entire weight of 2,800 tons. For this reason, the committee suggests the use of pile-supported beams. The structural integrity of the structure should be positively ensured by a series of steps taken before relocation. Hasbrouck Hunderman Architects et al. (1986) noted the need for a new external tension rod just below the gallery at the top of the lighthouse. The committee suggests temporarily placing a new, heavily reinforced concrete tension ring around the base of the lighthouse. Additional tension bands could be placed as necessary at several elevations of the tower and removed after relocation. The committee also suggests consideration of vertical prestressing for the tower shafts. This would most easily be done by pairs of tendons, one inside and one outside, around the tower's circumference. Alternatively, structural steel bracing could be placed outside for the full height of the tower: this method often has been used successfully. The bracing frame also can be used as a scaffold for repairing the coating and windows. The committee further suggests tying the foundation course together by epoxy injection to bond the foundation blocks into an integral unit. Holes should be drilled and high-strength bars inserted and stressed. The horizontal move of the lighthouse must be level. The cost estimates above do not include significant changes in elevation. In addition to the structural risks, the committee heard and read several comments concerning risks associated with dewatering, which is required for construction that occurs below the water table. One concern was onset of dry rot in the foundation timbers. If dewatering is for a duration of only 3 to 6 months, then the fungus that causes dry rot should not have the opportunity to cause appreciable deterioration. Another concern was settlement of the sands under the foundation, because reduction of the pore-water pressure in the sands could allow them to consolidate. Such settlement generally is uniform and can be reduced to acceptable limits by restricting the depth of dewatering to the elevation of the foundation timbers.
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Site Selection The committee did not assess the merits of all possible sites for lighthouse relocation. Instead, it considered three areas (Figure 11) that met the following constraints: • The route to the site must be a straight line. This would minimize moving costs and the number of times the lighthouse would need to undergo the shock of acceleration. • The move track must not traverse any extensive wetlands. Wetlands are habitats of widely acknowledged ecological value (e.g., Teal and Teal, 1969; Nixon, 1980; Odum et al., 1984) and have broad protection under the Clean Water Act (Platt, 1987). If the move track traversed any large wetland, some disruption--at least temporary--necessarily would take place, perhaps even involving filling of low areas until after the move were completed. This would add economic and ecological costs to the move. • The move track must not encounter any substantial topographic relief, such as the relict dune ridge and swale system along the Buxton Woods nature trail. Substantial excavation and filling would be required to prepare a level move track. Such preparations would add to construction and restoration costs. Furthermore, such a move would disrupt large areas of vegetation, because the move track would need to be substantially wider than the approximately 60 feet (18 meters) required in more level terrain to permit stable sloping transitions to the natural elevation at the edges of the move track. • The lighthouse must remain within the boundaries of the Cape Hatteras National Seashore. This reflects a practical need to avoid costs and political constraints. In addition, the lighthouse should remain in the general vicinity of Cape Hatteras to illustrate its historical role as a warning to mariners.
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FIGURE 11 Cape Hatteras, showing major features and the three potential relocation areas considered by the committee. Adapted from aerial photographs and United States Geological Survey map. (Stippled areas represent marshy areas. Small pockets of wetlands are not shown.)
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• The move should succeed in postponing immediate threat from shoreline retreat for at least 100 years. This follows directly from the National Park Service's request for a long-term solution on this time scale. The only sites that meet these criteria lie within a narrow band extending approximately southwest from the lighthouse's present location and running approximately parallel to the paved road leading from the lighthouse to the parking lot near the nature trail. The committee considered three general areas along this path. The Nearby, Favored Area This area is near the southwest corner of the present parking lot, 400-600 feet (122-183 meters) from the tower's present position. The precise location of the new site would be determined by aesthetic and site-design considerations. Any future moves would be much less expensive if they continue in the same direction as the first move. Factors that aided in the committee's selection of this nearby area were: • • • • •
The move would cost less than a longer move. Ecological damage would be minimized. The historic and aesthetic integrity of the lighthouse site would be preserved. The lighthouse would remain close to the beach and the ocean. The option is a flexible response to a dynamic problem.
This area offers many aesthetic advantages. The tower would remain close to the shore, almost unchanged in appearance to those approaching it, but safe from storms. A move to this area would avoid much ecologically valuable land that an extended move would require, and the beach shoreline would remain a smooth curve. The committee expects that the existing groins would be left in place, but no major repairs would be undertaken.
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The Intermediate Area The committee considered the area broadly described by the Move the Lighthouse Committee (Fischetti et al., 1987). The area is approximately 2,800 feet (850 meters) southwest of the present location of the lighthouse, near the parking lot at the head of the nature trail. At current rates of shoreline retreat, this area would provide protection to the lighthouse for at least 100 years. However, uncertainties associated with estimates of the position of the shoreline increase with the period of the prediction. The committee judges the area east of the paved road that leads to the campground to be preferable to the west, because the vegetation is less dense, the terrain is flatter, and the wetlands are less extensive. Furthermore, a site east of the road would not intrude on the nature trail or the dense and rare maritime forest in the relict dune and swale system of Buxton Woods west of the road. A location near the road would facilitate access during preparation of the move track and probably maximize distance from the eroding east-facing shoreline. A protective fringe of vegetation between the road and the new site of the lighthouse could help preserve the tradition of isolation of the lighthouse and its associated structures from the violation of historic values implicit in the close presence of roads, cars, and parking lots. Public appreciation of the historic, isolated nature of the lighthouse keeper's experience might be achieved best by use of such natural vegetational buffers. The Distant Area The third area considered by the committee is near the south shore of Cape Hatteras, approximately 12,000 feet (3,700 meters) southwest of the lighthouse's present position. A move to this area would place the lighthouse and the associated structures close to the south shore of Cape Point. This shoreline is accreting, so protection against future shoreline erosion likely would be effective for more than 100 years. The area is characterized by flat topography of low vegetation, mostly grasses. If the lighthouse were relocated to this general area, it again would be close to the sea, at
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least until the shoreline accreted some distance farther south; erosion protection would be maximal; and the site would be naturally open. The location is isolated from most other park structures except the nearby campground. However, relocation to this area would cost nearly $7 million more than the move to the near area and would damage ecologically valuable areas. These disadvantages are sufficiently serious that the committee did not consider the area further. Ecological Consequences of Moving the Lighthouse Ecological costs of moving the lighthouse are temporary or permanent habitat alteration in the approximately 60-foot (18-meter) wide path of the move track; potential water-table depletion and saltwater intrusion during the making of concrete for the track and new foundation; and habitat destruction for creating the 6- to 8-acre (2.4- to 3.2-hectare) site for the repositioned lighthouse and associated structures. Habitat Damage Along the Move Track Ecological damage along the move track depends on the precise location and design of the new site for the lighthouse complex and the path taken to reach it. The Near Area If the lighthouse were moved to the near area, little alteration of natural vegetation would occur, because most of the move would proceed across grass lawns and pavement. The Intermediate Area If the lighthouse were relocated to the intermediate area, vegetation in a track of 60 × 2,800 feet (18 × 850 meters) would be disrupted at least temporarily. The ecological damage would not be great, because the sparse dune grasses
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(mostly Spartina patens, but also Ammophila breviligulata, Panicum amarum, and Uniola paniculata), low shrubs (Myrica cerifera, Ilex vomitoria, Juniperus virginiana, Baccharis halimifolia), and low trees (mostly Quercus virginiana) that must be cleared can be reestablished fairly rapidly. Many of these plants are adapted to disturbance, especially from washover (Hosier, 1973; Godfrey and Godfrey, 1976; Hosier and Cleary, 1977). Seeding, transplanting, and fertilizing can be used to speed recovery of the grasses. Because the area of the move track would be surrounded by vegetation and open to salt spray only to the northeast along the move corridor, recovery of natural shrubs should take place quickly. Topsoil would need to be handled carefully during preparation and restoration of the move track, because soil organics accumulate very slowly on coastal barriers. Their absence would greatly retard vegetation recovery (Au, 1974). The most ecologically valuable areas that might be affected in moving the lighthouse to the intermediate area are small areas of wetlands that contain Juncus and other marsh plants, but that total less than one-half acre (.2 hectare). However, relocation of the lighthouse would affect only a small area, and the disturbance would be temporary. After the topography were restored, recovery of wetland plants would proceed and could be aided by transplantation and fertilization (Lunz et al., 1978). Habitat Lost to the New Site The amount and type of habitat lost to provide the new site for the lighthouse complex would depend greatly on the specific site chosen for relocation and its design. The Near Area If the lighthouse were moved only a short distance to the southwest, preparation of the new site would necessitate only clearing of grasses, low shrubs, and pavement. Revegetation of the previous site of the lighthouse would replace the plants lost at the new site with a very similar species composition. Thus, the short move would entail little net ecological .
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loss due to clearing and preparing a new site for the relocated lighthouse complex. The Intermediate Area If the intermediate area were selected, the habitat that would be lost from Buxton Woods would have ecological consequences. NPS holdings in Buxton Woods are only about one-third of Buxton Woods, so any loss would be significant. Furthermore, any loss of Buxton Woods habitat would violate the November 1979 agreement between NPS and North Carolina, which registered all NPS Buxton Woods holdings as a “natural heritage area.” This prohibits any habitat disturbance or alteration in Buxton Woods. However, a site in this area would not involve loss of tall, dense maritime forest but would affect low shrub thicket and sparse taller trees, a common habitat type on coastal barriers. Thoughtful design of the new site would reduce habitat loss. Water-Table Depletion It will be necessary, and not difficult, to ensure that the water table not be lowered in relocating the lighthouse. If too much water were drawn from the narrow lens of fresh water that constitutes the water table of Hatteras Island, consequent saltwater intrusion might endanger the maritime vegetation of the island. Current hydrological estimates (R. Heath, United States Geological Survey, retired, Raleigh, N.C., personal communication, 1987) suggest that fresh water is being tapped at about half the maximal rate that Hatteras Island can provide without saltwater intrusion. This is one reason that much of Buxton Woods has been proposed as an “area of environmental concern” by the North Carolina Coastal Resources Commission to restrict the types and density of development that would create more demand on the limited freshwater resource. Even if all the water needs for concrete used in the move track and the new foundation were met by water-table extractions, the amount--about 242,000 gallons (916,000 liters) for a move of 2,800 feet (850 meters)--probably would be too
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small to have any serious effect on the water table and biota. Nevertheless, the committee recommends that no fresh water be taken from the water table for construction. The concrete slabs needed for the move track could be prefabricated or made with salt water, which is satisfactory when concrete is not expected to be permanent. Water needed for construction of a new foundation (approximately 12,000 gallons (45,000 liters)) could be transported to the new site. These measures would remove all potential risks of ecological damage from water use. Recent Legislation Moving the lighthouse 500 feet is consistent with recent federal legislation and North Carolina's regulations. Section 1306 of the National Flood Insurance Act of 1968 recently was amended (section 544 of Public Law 100-242, the Housing and Community Development Act of 1987) and provides some insurance coverage for buildings that are threatened by erosion to permit them to be relocated before they collapse. Buildings containing four dwelling units or fewer must be relocated landward 30 times the annual erosion rate (30-year setback requirement); larger buildings have a 60-year setback requirement. Furthermore, North Carolina's Administrative Regulation 15 NCAC 7H Rule .0306 requires a 30-year setback for new buildings less than 5,000 square feet in base area and a 60-year setback for larger buildings. Rule .0306(k) requires structures relocated with public funds to conform to the above setback requirements. (Although Cape Hatteras Lighthouse covers less than 1,600 square feet, it clearly is a large building.) North Carolina calculated the erosion rate for Cape Hatteras Lighthouse at 9 feet per year according to rule .0304(1(a)); an updated estimate of 7 feet per year is pending approval. A move of 500 feet would provide erosion protection for slightly more than 55 years according to this value for erosion rate (71 years according to the updated estimate). The Army Corps of Engineers (1985) gives the rate of erosion at the lighthouse at 5.2 feet per year from July 1945 through May 1983. A move of 500 feet would provide erosion protection for 96 years according to this value.
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In addition, the North Carolina Coastal Resources Commission made a declaratory ruling that Cape Hatteras Lighthouse is a unique cultural resource and may be protected in any way that does not interfere with natural migration of the shoreline (June 28, 1985). The committee therefore believes that moving the lighthouse back approximately 500 feet would be in accord with the above legislation and regulations. In addition, it would provide for further moves as the shoreline approaches the lighthouse some time in the future. Summary The committee rated the option of relocating the lighthouse to the near area as the most reliable and involving the fewest risks. This option also rated well in terms of cost-effectiveness, preservation of historic and aesthetic values, and accordance with relevant public policies. By moving the lighthouse and the associated buildings, the entire complex could be preserved and its historical relationships to habitations and service structures left intact at a new setting. The setting might even be improved by relocation: plastic sandbags and trampled dunes from uncontrolled passage could be cleaned up and repaired; remnants of old groins would be less visible. The cost of preparing and relocating the lighthouse, all the associated buildings, the parking lot, and the access trails, estimated by this committee to be $4.6 million, is comparable to the cost of other options and lower than some. Furthermore, long-term costs (other than routine maintenance) do not apply to the relocation option, except those applied to a further move. But even that would cost less than the first move and probably would not be needed for 25 years or more. Relocating the lighthouse after careful consideration of its historic value and the relevant criteria--instead of trying to protect the lighthouse in situ-would be an exemplary response by NPS to the generic problem of shoreline erosion. Relocation is consistent with NPS policies to let natural processes proceed unhindered and to use the national parks as models of wise management of natural and cultural resources. Moving also is consistent with the NPS mandate
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to preserve historical landmarks and structures for future generations and respects policies of the North Carolina Coastal Resources Commission. Relocation probably would attract much media attention, providing NPS an opportunity to educate a large national audience on the nature of coastal barriers. Relocation has some negative aspects. Several local residents expressed strong opposition to relocation, preferring that the lighthouse be preserved in situ, despite the greater risks to the structure that this approach would entail. Relocation also implies a potential loss of several acres of natural habitat, depending on the location chosen. If the short move is chosen, some space already devoted to the lighthouse complex might continue to be used for that purpose. Any habitat loss could be minimized by careful site selection and design. The rarity of maritime forest on the Outer Banks renders a potential loss of habitat at the intermediate area of some ecological and environmental significance. Because NPS owns and controls only about one-third of Buxton Woods, it might be possible to mitigate the loss of this acreage by NPS acquisition of additional Buxton Woods acreage at the park boundary. Such lands are likely to be developed in the future, so acquisition and preservation would be a form of compensation for clearing the new lighthouse site. However, such acquisition would require congressional approval and would add to the cost of this option. PROTECTION OF THE LIGHTHOUSE IN SITU Groinfield Rehabilitation Without Revetment This option involves repairing and shortening the existing three groins, and constructing a fourth groin approximately 500 feet (150 meters) long and 500 feet south of the existing third groin. A fifth groin might be needed another 500 feet to the south to promote beach accretion southeast of the lighthouse. Some beach nourishment would be required at least initially to start accretion between the old and new groin or groins. Subsequent beach nourishment would be determined by the incidence of major storms.
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The northernmost two groins, 530 feet (162 meters) long, are 1,200 feet (366 meters) and 550 feet (168 meters) north of the tower. The south groin, 610 feet (186 meters) long, is about 100 feet (30 meters) south of the lighthouse (U.S. Army Corps of Engineers, 1985). Cost MTMA Associates (1980) estimated an initial construction cost of $3.2 million for groinfield expansion and beach nourishment. The estimate included $235,000 to construct a new 450-foot (137-meter) groin and $2,934,000 to pump 500,000 cubic yards (380,000 cubic meters) of sand. No money was budgeted to repair existing groins. The subsequent costs for repair, maintenance, and renourishment were estimated at $63 million over 100 years. NPS (1982) estimated the construction cost of a new groin and replacement of existing groins without beach nourishment at $4 million with a 50-year additional cost of $12 million. The committee estimates the initial cost of this option to be $3.7-$4.7 million. This includes $1 million for one new groin, $1.9 million to repair the existing groins, and $800,000 for 300,000 cubic yards (230,000 cubic meters) of beach nourishment. A fifth groin, if constructed at the same time as the fourth, would add another $1,000,000. This does not include additional costs for renourishment, even in the absence of major storms. Evaluation Deprivation of sand to the downdrift shoreline resulting from expanding the groinfield is not viewed as a problem. Unlike developed shorelines with multiple owners, the area that would be affected is owned by NPS and is unimproved, so a slight increase in the rate of shoreline retreat in such areas is acceptable. Despite the favorable conditions for groins at this site, construction of groins departs from NPS policy by interfering with natural processes and is contrary to the policies of the North Carolina Coastal Resources Commission. However, natural
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processes already have been interrupted at the site, and variances can be obtained from the coastal regulations when public benefits are high and adverse consequences are minimal. Continued use and expansion of the groinfield would have some advantages as a short-term measure for protecting Cape Hatteras Lighthouse. The visual obtrusiveness of the structures would not be much worse than that caused by the three present groins and might be lessened if the dysfunctional outer segments of the groins were removed. The groins would continue to create wave characteristics favored by surfers. The lighthouse could remain at its present location in its historical conjunction with the other structures at the site. Although groinfield improvements are a possible short-term approach to the problem of preserving the lighthouse, this option merely postpones the need to make a long-term choice. And, unlike relocating the lighthouse, it does not make future protective measures easier or less expensive. Groins on this high-energy shoreline will need frequent attention unless they are very well constructed. The groins initially installed in 1969-70 were damaged seriously in the early 1970s; they were repaired in 1975, but they are again in need of repair and modification (Figure 12). The committee's estimates for this option were based on groins that are likely to last 20 years without repair. Even an expanded and well-maintained groinfield cannot ensure protection of the lighthouse against the storm surge and wave action of a 100-year storm or hurricane. The groins and beach could be overwhelmed by such an event. The committee does not favor this option because it would not protect the lighthouse against severe storms, recurrent maintenance costs probably would be needed, and it would not ensure long-term protection for the lighthouse. Groinfield Rehabilitation with Revetment This option includes all aspects of the previous option. It also entails construction of a below-grade-level concrete caisson revetment to prevent undermining of the lighthouse (Figure 13). This would be constructed by the established
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Saving Cape Hatteras Lighthouse from the Sea : Options and Policy Implications, National Academies Press, 1987. ProQuest
FIGURE 12 The south groin at Cape Hatteras Lighthouse in moderate seas, November 1987. Photograph by D. Policansky.
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FIGURE 13 Schematic diagram of proposed caisson revetment.
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“slurry-trench diaphragm-wall” technique, in which a full-depth concrete wall would be constructed in six 12-foot (3.7meter) segments. In this application, the joints between segments would need to be reinforced (several proprietary methods are available to accomplish this). The segments would be cast in trenched slots and kept open with bentonite slurry. Then, a thick, horizontal, reinforced concrete slab would be constructed between the top of the wall and the base of the lighthouse. The joint would be unbonded to accommodate differential displacements caused by differential settling. Recharging wells would be installed around the base to prevent dry rot of the existing timber-mat foundation under the lighthouse; such wells would be 1½-inch (3.8 cm) diameter perforated pipes, with a cap that periodically would be filled with water. They could be either inside the lighthouse structure or around the outside, whichever the architect thought would be least noticeable. This caisson revetment is not a substitute for the seawall/revetment of the U.S. Army Corps of Engineers, because it does not protect the lighthouse from battering by large storm waves that would occur after the shoreline retreated to the lighthouse. Therefore, the caisson revetment would have to be accompanied by rehabilitation of the groin field to maintain the protective beach in front of the lighthouse. Several lighthouses survive indefinitely in the face of violent waves that batter them directly, for example, Minot's Ledge Lighthouse in Cape Cod Bay and the Eddystone Lighthouse in the English Channel. Those lighthouses, however, are constructed of massive, interlocking granite blocks specially designed to withstand such assault (Hague and Christie, 1975). The brick Cape Hatteras Lighthouse, constructed conventionally, would not survive such conditions. Thus, although this option would protect the lighthouse against undermining and would provide some protection against storm surges and waves, it might not protect against a major hurricane.
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Cost MTMA Associates (1980) estimated a construction cost of $2.6 million for partial revetment, one new groin, modest repairs to existing groins, and initial beach nourishment with 235,000 cubic yards (180,000 cubic meters) of sand. This option costs less than the previous option because it provides less beach nourishment. Maintenance, repair, and renourishment costs were estimated at $31 million over 100 years. The committee estimates the initial construction costs to be $4.7-6.7 million, including initial beach nourishment of 300,000 cubic yards of sand. Renourishment costs could not be quantified. The committee's cost estimates include construction of a modern groin that is likely to last for 20 years without repair and thorough repairs of the three existing groins. The committee's estimates are as follows: • Revetment wall (caisson): materials, design, construction • Construction of two new groins at $661,500 each • Repair of 3 existing groins at $242,670 each • Five trestles for construction and repair, reusing the materials five times at $376,000 each time • Overhead and profit • Engineering and design • Beach nourishment with 300,000 cubic yards (229,000 cubic meters) of sand Total
$529,000 1,323,000 728,000 1,880,000
934,000 500,000 800,000
$6,694,000
If only two groins were repaired and one new one constructed, the cost would be reduced by approximately $2 million. Evaluation The caisson revetment would protect the lighthouse against undermining and to some extent against storm surges and waves. However, this option might not provide protection
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against a major hurricane and would not provide long-term protection for the lighthouse. Depending on the frequency and severity of storms, maintaining the shoreline in front of the lighthouse would become increasingly costly, and perhaps impossible. The lighthouse would need to be moved, which probably would cost 50% more (in constant dollars) than it would today, when the lighthouse and its structures are still some distance from the sea. This option conflicts with national and state policies concerning barrier coastlines, because the proposed revetment places a new, hard structure on the coast--albeit below ground. Because of these disadvantages, the committee did not favor this option. However, of the options that would preserve the lighthouse in situ by defensive means, this offers some protection to the lighthouse at relatively low cost. Seawall/Revetment This option was developed by the U.S. Army Corps of Engineers (1985). The lighthouse and the adjacent oilhouse (but not the keepers' dwellings) would be encircled by an octagonal reinforced concrete seawall constructed symmetrically with the base of the lighthouse. The design has four major structural components: a gravity-mass concrete seawall, a prestressed concrete sheetpile cutoff wall extending from the toe of the seawall to 16 feet (4.9 meters) below mean sea level (MSL), a stone revetment fronting the seawall, and a compact earth fill backing up the seawall (Figure 14). The top of the seawall would rise 23 feet (7 meters) above MSL (15 feet (4.6 meters) above grade at the base of the lighthouse), with a public promenade encircling the interior edge of the seawall 20 feet (6.1 meters) above MSL-approximately 12 feet (3.7 meters) above the existing ground elevation around the lighthouse base. The earth fill would begin at the granite fence base 48 feet (14.6 meters) from the base of the lighthouse and would rise toward the promenade at a moderate 25% grade. Each segment of the seawall would be 129 feet (39.3 meters) along its toe face, which would be 157 feet (47.9 meters) from the center of the lighthouse. The stone revetment would extend 51 feet (15.5 meters)
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FIGURE 14 Revetment and seawall section. Redrawn from U.S. Army Corps of Engineers, 1985.
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beyond the outer edge of the seawall, reaching a distance of 208.5 feet (63.6 meters) from the center of the lighthouse (Figure 15). Initially, only the six seaward sides of the seawall would be constructed, leaving the west and the northwest landward sides open to facilitate public access to the lighthouse. However, the entire revetment and the sheetpile cutoff wall below ground level would be constructed to encircle the base of the lighthouse. Upon encroachment of the sea, flood walls would be constructed, eventually closing off the two open faces of the seawall on the landward side (Figure 16). In constructing the seawall/revetment, excavation and dewatering would be required to place the base of the revetment 10.5 feet (3.2 meters) below MSL and the base of the seawall 1 foot (30.5 cm) above MSL. To facilitate this operation, a temporary sheetpile coffer cell probably would be constructed. The cell would be confined to the immediate area of excavation or constructed to encircle the entire structure. After the initial excavation reached the prescribed top elevation of the concrete sheetpile cutoff wall +3 feet (91 cm) MSL along the seaward faces and +5.5 feet (1.7 meters) MSL along the landward faces, the sheetpiling would be placed by jetting and driving. Thereafter, additional excavation and dewatering would be necessary on both sides of the sheetpile to permit geotextile filter fabric and stone revetment to be placed. This excavation would need to be at least 60 feet (18 meters) wide and would need to extend 10.5 feet (3.2 meters) below MSL--approximately 11.5 feet (3.5 meters) below the top of the timbermat foundation of the lighthouse. The center of the excavated area would be approximately 175 feet (53 meters) from the center of the lighthouse. The water table at the excavated area is estimated at +1 foot (30.5 cm) MSL. Cost MTMA Associates (1980) estimated a cost of $4.5 million initially, $1.1 million in maintenance cost over 100 years, and a total cost of $5.6 million. The U.S. Army Corps of Engineers (1985) estimated a $5.72 million construction cost
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FIGURE 15 Plan view of seawall and revetment. From U.S. Army Corps of Engineers, 1985.
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FIGURE 16 Artist's impression of Cape Hatteras Lighthouse surrounded by seawall 10-20 years after construction. SOURCE1 U.S. National Park Service, 1982.
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(including closing the seawall in response to recession of the shoreline) with an annual maintenance cost of $16,000. (This estimate was vague regarding details of the project; no dimensions were provided, and “seawall” and “revetment” were used interchangeably.) NPS (1982) estimated a cost of $5.3 million, with no maintenance costs. The Move the Lighthouse Committee (Fischetti et al., 1987) estimated a construction cost of $6.7 million, with a 100year maintenance cost of $54 million, based on the U.S. Army Corps of Engineers (1985) specifications. This committee estimates approximately $6 million in construction costs to construct the seawall/revetment proposed by the Army Corps of Engineers, with substantial but unquantifiable maintenance and repair costs. Evaluation The seawall/revetment option would require a long construction phase--19 to 20 months--during which the lighthouse would be exposed to potentially serious risks. The extensive excavation required to install sheetpiling and the stone revetment could endanger the foundation of the lighthouse if a severe hurricane with surging waves hit the widely exposed area and breached the temporary cofferdam. This presents the greatest construction-related risk to the lighthouse of all the options evaluated. The committee judges that the U.S. Army Corps of Engineers's estimated annual maintenance cost of $16,000 was unrealistically low. Seawalls and revetments constructed in areas of high wave energy often need maintenance and repair after a time, as illustrated by experience with structures at South Padre Island, Texas; Seabrook Island, South Carolina; Sines, Portugal; Island Esther off Seal Beach, California; Pacifica, California; and other California examples discussed by Fulton-Bennett and Griggs (1987). The committee judges that, to ensure long-term reliability, the proposed seawall/revetment probably would need expensive maintenance and repair. Interlocking concrete sheetpiling behind the toe revetment might move if stones in the toe revetment were rearranged during a major storm. Sand could leak rapidly, followed by undermining and local seawall collapse. The
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potential scour adjacent to this seawall, exposed to the Cape Hatteras stormwave climate, could threaten the structure during its design life. Such partial failures would require expensive repairs. In preserving the nation's historical heritage, NPS assigns significance to the total setting of the landmark, including aesthetic values. The seawall would greatly alter the setting; a seawall would compete visually with the lighthouse, especially from nearby. The octagonal lighthouse base, with its distinctive redbrick panels framed in granite, would be obscured from outside the seawall. In addition, the lighthouse keepers' quarters would be separated from the lighthouse. As the shoreline receded and the enclosed lighthouse became a tombolo or completely separated from land, preservation of the other buildings would require relocation landward, away from the lighthouse. Construction of a seawall/revetment probably would accelerate loss of the beach in front of the structure. In any event, when the eroding beach reached the structure, the structure would interrupt continuity of the beach and pose an obstacle to passage along the water's edge. The initial construction cost estimated by the U.S. Army Corps of Engineers (1985)--$5.6 million--is high but not out of line with other options for a permanent solution. However, the committee found the estimate for maintenance--$16,000 per year--to be unrealistic, because of periodic requirements for replacement of riprap at the seaward toe. Some localized failure related to storm and scour damage would probably occur within the next few decades. If this damage were not repaired, large-scale structural collapse would ensue. Although surrounding Cape Hatteras Lighthouse with a seawall/revetment is technically feasible, the committee does not favor this option because: (1) the risks to the lighthouse during the construction phase would be serious; (2) reliability would be uncertain in the long-term; (3) the integrity of the historic site would be destroyed; (4) a major coastal structure of this kind is not in accord with the letter or spirit of local, state, and federal coastal guidelines; and (5) the unknown maintenance costs for this option likely would be high.
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Artificial Reefs This option involves submerged obstructions seaward of the lighthouse to diminish wave energy and promote beach accretion in front of the lighthouse. Such artificial reefs could consist of rubble mounds, concrete caissons weighted with sand and stone, concrete or steelpile structures of various configurations, or surplus ships filled with sand and stone, as considered by the committee in its interim report. The latter allows construction to proceed intermittently, vessel by vessel, as weather permits. Construction could be extended as advisable and economic. The number of obstructions required would depend on their size, condition, and distance offshore. The committee envisioned placing obstructions far enough offshore to be entirely submerged, so a large number of them might be required. Cost In view of the many uncertainties associated with this option, the committee is unable to estimate costs. Evaluation Any submerged object of sufficient size could serve as an artificial shoal that reduces wave energy by causing the waves far from shore to break and dissipate energy in turbulence, rather than moving beach sand. The Hatteras offshore is strewn with more than 100 submerged wrecks; these probably have contributed to the longevity of this protruding section of coastline. Deliberate sinking of ships would require some costly preparation and cleaning to rid them of oil and other contaminants, a disadvantage that could be avoided by constructing artificial reefs from other materials. In a major hurricane, very large waves can occur in deep water. As they approach the shore, their height is limited by water depth. In 30 feet (9 meters) of water, with an expected storm surge of 9 feet (2.7 meters) when the astronomical
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tide is 4 feet (1.2 meters), a wave could be 32 feet (9.8 meters) high from trough to crest. If allowed to proceed to the beach, the run-up and turbulence would be disastrous to groins and foreshore. If a storm lasted long enough, it probably would undermine and destroy the lighthouse foundation and topple the tower. A submerged artificial reef constructed in a suitable depth and location and strong enough to withstand the turbulence would cause such waves to break, expending most of their energy on the lee side. A depth of 16 feet (4.9 meters) would support a wave about 12 feet (3.7 meters) high. Such a wave might be reduced by vortex effects in the lee of the reef before breaking on the beach. The beach would increase in width with time because of the sheltering effect of the reef. Time-lapse photographs illustrate how a discontinuous offshore impediment has caused shoaling and widening of beaches on other coasts (U.S. Army Corps of Engineers, 1984). Consequently, the more time passes after reef construction before a major storm, the better the protection that is afforded to structures near the shore. The reef would not protrude above water level at any time and would be visible only during normal heavy weather as a line of foam and breakers. Suitable navigation aids supplementing the Diamond Shoals beacon and bell would serve to warn small boats and shallow draft vessels. Thousands of miles of shoreline in many parts of the world are so protected by natural coral formations. The high wave energy of the east-facing shoreline at Cape Hatteras might reduce the effectiveness of artificial reefs as offshore breakwaters. In the wave conditions near the lighthouse, artificial reefs would not be expected to retain their structural integrity or position indefinitely. Therefore, large but unquantifiable maintenance costs are associated with this option. The committee is unable to cite an example of artificial reefs in areas with wave energy as high as that at Cape Hatteras. Although construction of submerged artificial reefs is attractive in many aspects, it would require substantial study to produce reasonably precise estimates of the size and number of obstructions needed, the cost of construction, and probable effectiveness.
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The many uncertainties concerning construction, functional lifespan, initial and continuing costs, and effectiveness constrains the committee from favoring this option. Offshore Breakwaters and Groins Under this option (NPS, 1982), four breakwaters constructed of rock and rubble would be constructed within 200 feet (61 meters) of the shoreline. Three breakwaters would be perpendicular to each of the existing three groins; the fourth would be placed about 500 feet (150 meters) south of the southernmost groin. An additional short groin would be constructed about 500 feet south of the fourth breakwater. The breakwaters would be visible from the shore. Cost The breakwater system described by NPS (1982) was estimated to cost $4.4 million and did not include maintenance costs. The committee estimated this option would cost $5 million, with unknown maintenance costs. Evaluation This option would interfere with natural processes, which would violate NPS policy and alter the beach contrary to the regulations of the North Carolina Coastal Resources Commission. Because the shoreline is expected to retreat during the next 100 years, this solution would be effective only for a limited period. The breakwaters would be visible from shore and might pose hazards to surfers, swimmers, and boaters. At an estimated cost of $5 million, this solution does not compare well with other short-term measures. Furthermore, this option does not conform to relevant policy guidelines and affords uncertain long-term protection of the lighthouse.
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Artificial Seagrass This option involves installation of commercially manufactured artificial seagrass in the surf zone to trap sand and induce beach accretion or reduce erosion. Natural and artificial seagrasses have been employed successfully elsewhere as baffles to current flow, resulting in enhanced sediment deposition and bottom stabilization (Ginsburg and Lowenstam, 1958; Orth, 1977; Peterson et al., 1984). However, seagrass was installed in 1981, 1982, and 1984 at Cape Hatteras without these results (U.S. Army Corps of Engineers, 1984; Rogers, 1986). Cost Because the previous installations of seagrass at Cape Hatteras proved ineffective, a cost estimate for this option is irrelevant. Evaluation Artificial seagrass (“Seascape”) was installed three times in the lighthouse vicinity without the desired results (Appendix A). This method has been applied successfully only under conditions of far less wave and current energy, less turbulence, and less intense oscillatory water flow than are present at Cape Hatteras. In southern California, a carefully controlled and monitored experimental installation of artificial seagrass did not effectively alter beach dynamics (Jenkins and Skelly, 1987). None of the applications of Seascape at Cape Hatteras promoted beach accretion. In addition, Seascape fabric and its anchoring mechanism clearly are unable to withstand the strong bottom shear forces characteristic of the surf zone at Cape Hatteras Lighthouse (Rogers, 1986). The committee acknowledges the appeal of a solution that contains no visible intervention. Nonetheless, application of artificial seagrass would not build up the beach, significantly reduce erosion at Cape Hatteras, or protect the lighthouse.
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Beach Nourishment Sand from nearby sources could be pumped to the beach in front of the lighthouse. Beach nourishment has been applied to eroding shorelines north of the lighthouse in amounts of 312,000 cubic yards (240,000 cubic meters) in 1966, 200,000 cubic yards (153,000 cubic meters) in 1971, and 1.25 million cubic yards (960,000 cubic meters) in 1973 (MTMA Associates, 1980; U.S. Army Corps of Engineers, 1985). Cost MTMA Associates (1980) estimated an initial cost of $2.9 million to pump 500,000 cubic yards (380,000 cubic meters) of sand to the beach in front of the lighthouse. Supposing a need for an additional 300,000 cubic yards (230,000 cubic meters) every other year and 300,000-500,000 cubic yards after every major storm, the long-term cost was estimated at more than $120 million (not discounted) over 100 years. NPS (1982) estimated an initial cost of $3 million and a 50-year cost of $60 million. To nourish the beach with 1,000,000 cubic yards, the committee estimated an initial cost of approximately $2 million and further estimated that the maintenance cost--initially about $700,000 per year-would increase with time. Even applying OMB's discount rate of 10% per year, a maintenance cost of $700,000 per year over the next 20 years is worth more than $5,000,000 in present value. Evaluation Beach nourishment, achieved by transporting sand from near Cape Hatteras or from Diamond Shoals, is one technically feasible response to the erosion problem at the lighthouse. This approach has the merit of requiring no visually obtrusive structures at the lighthouse except those related to pumping sand. Furthermore, the sand to be taken for placement at the lighthouse is not needed to maintain a developed downdrift shoreline. Nevertheless, the virtually permanent
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pipeline and pumping equipment necessary for the repeated nourishments would intrude upon the natural setting and interfere with beach use by visitors to the seashore. If sand were taken from the beach near Cape Hatteras, the huge borrow pits might interfere with beach access and reduce nesting sites for birds. However, the benefits of beach nourishment are short lived. Therefore, large quantities of new sand must be applied frequently to counteract erosion. The decisive criterion that this option fails is cost. The costs of beach nourishment are prohibitive, as described above, and, as the shoreline continues to retreat, the costs of maintaining an increasingly large artificial promontory at the lighthouse would grow disproportionately. Within 50 years, this option may become technically unfeasible as well as prohibitively costly. Furthermore, this option to control erosion at the lighthouse does not ensure against loss of the lighthouse during a major storm. No Action Although the committee was charged with evaluating options to preserve the lighthouse, it included no action as a management alternative, consistent with the National Environmental Policy Act. No action would lead to loss of the lighthouse within the next few decades, or possibly sooner, in the event of a direct hit by a severe hurricane or series of lesser storms. The option of doing nothing was eliminated from consideration because it would expose the lighthouse to a high risk of loss. The lighthouse probably would not be standing today without the present groin system. An additional risk is deterioration of the lighthouse foundation if no action is taken. The top of the existing timber mat is now approximately +2 feet (61 cm) MSL. When the lighthouse originally was constructed, the fresh groundwater level was above the top of these timbers, protecting them from dry rot. As the sea approaches, the groundwater level will continue to drop closer to MSL, exposing the timbers to dry rot and the lighthouse to serious settlement and possible collapse, if it remains in its present location (Lisle, 1985).
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Because no action probably will lead to loss of the lighthouse, this option is not satisfactory. New Lighthouse This option was not considered in the interim report. A new lighthouse would be built a suitable distance inland from the shoreline. A replica of the present lighthouse would be one possibility; another would be to hold a design competition. Cost It is impossible to provide a cost estimate for this option, because the committee could not predict the designs that would be considered. Evaluation Building a new lighthouse would be consistent with the history of the first lighthouse at this site, which was destroyed when the present one was built (Holland, 1968). When the original 1803 lighthouse at Cape Hatteras became endangered by the sea in the 1860s, it was replaced by the current structure. The original tower was destroyed. When the present tower appeared to be endangered in 1936, it was abandoned temporarily, and a steel tower was erected farther inland. When shoreline erosion was reversed in the 1940s, the steel tower was abandoned, and the 1870 lighthouse was reactivated. This option has several advantages. The beach would not be affected by any new structure, and natural processes would not be impeded. Historical precedent would be followed. An example would be set for other problems in coastal-zone management elsewhere, teaching the value of adapting to ecological forces rather than trying to hold fast to difficult positions. However, NPS's purpose is to preserve Cape Hatteras Lighthouse as required by its mandate to preserve historic
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structures. Construction of a new lighthouse, however imaginatively designed or built to resemble the original, would not serve the purpose of historic preservation. Reconstruction merely suggests the form and materials of the old structure. To replicate the lighthouse in all its detail, using original construction methods and materials, would be prohibitively expensive and might not be possible. For this reason, this option does not meet NPS's needs.
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6 Practical Considerations
The committee discussed a variety of practical matters related to moving the lighthouse. Some would apply to any option chosen by NPS; others are specific to the relocation option. CONTRACTING CONSIDERATIONS Because of the unusual nature of lighthouse relocation and the intricacies of federal procurement regulations, the committee believes it prudent to comment on the potential NPS contracting process. NPS must comply with the Federal Acquisition Regulations System (1987), as well as its own agencyspecific procurement regulations and policies. Within those constraints, two considerations are of great importance in this matter: • The need to select a well-qualified contractor from the small number of firms technically capable of performing such a project successfully. • The need to allow appropriate flexibility regarding specific methods to be used by the contractor to accommodate realities such as local availability and cost of materials, as well as geological, structural, and engineering factors that will be inherent to the methods employed.
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A suitable way to select a contractor is a two-stage, negotiated procurement process such as that used by the U.S. Army Corps of Engineers on similarly complex projects involving potential risk, such as the Wolf Creek Dam cut-off wall in Kentucky. Offerors would submit qualifications (e.g., experience in similar projects, technical and engineering capabilities, and proposed supervisory staff). NPS would carefully screen the technical qualifications of potential contractors (with an independent advisory board if necessary) before specific technical and cost proposals for the actual work were solicited. Qualified offerors would provide a detailed technical proposal for carrying out the lighthouse relocation. This would include the following: • Prepare detailed plans to strengthen the lighthouse to give it full structural integrity. • Prepare detailed plans for the permanent foundation of the relocated lighthouse. • Prepare detailed specifications for repairs to the gallery, lantern, stairs, windows, and masonry coatings. • Prepare detailed plans for moving the lighthouse. • Prepare detailed performance criteria for the move, including raising the structure, temporary dewatering and excavation, jacking procedure and controls, allowable tilt, allowable accelerations and restrictions on jerk, control during the horizontal move, and final set down. With the advice of a board of consultants (and an independent engineering consultant with structural and geological expertise), NPS would review all submitted materials and select qualified contractors and request a financial proposal. NPS would be permitted to suggest minor modifications in any offeror's technical plans. Selected contractors would submit competitive cost proposals for the total project, which would include assumption of responsibility, and an appropriate insurance policy.
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PRACTICAL CONSIDERATIONS
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Allowing flexibility in methods to be used implies the need to develop and specify performance criteria for the lighthouse relocation--rather than detailed methodological requirements--in the NPS request for proposals. The committee emphasizes that no set of detailed methods, including the committee's own example of a relocation concept, should be specified at the outset. Rather, performance criteria, such as the desired lighthouse site location, structural and architectural rehabilitation and strengthening, measurable damage limitations, allowable displacement of structural components, and other criteria suggested above are preferable for this type of project. INSURANCE Builder's risk insurance is available to cover any physical damage to a structure that results from external events, such as tornadoes and hurricanes during the contract period. Insurance also is available to cover contractor's errors or omissions. Maximum coverage would be limited to replacement value of the structure. Professional liability insurance is available to protect the relocation contractor and the engineering consultant from errors in design or specifications, including omissions. Limits are specified, but usually have a maximum of $5,000,000. Project wrap-up insurance can be obtained on a case-by-case basis, which includes the professional liability of all parties involved in design. An insurance company usually will insist on an independent review. INTERIM MEASURES The committee was asked to comment on interim measures for protecting the lighthouse. Such measures should be taken as soon as possible to reduce the possibility of damage or destruction of the lighthouse before long-term protective measures can be completed. However, no interim measure would provide enough protection to justify postponement of a long-term solution.
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The immediate danger to the lighthouse is the destructive erosion that might occur during a single storm or series of storms, rather than gradual, longterm retreat of the beach. A storm or storms might occur at any time of year, and would provide at most a few days' warning of their arrival. The most cost-effective interim measure--and one that could be implemented quickly--is beach nourishment in the bight immediately south of the southernmost groin. The committee suggests adding sand along 1,000 yards (910 meters) of beach south of the southernmost groin. This would require a volume of sand 3 yards (2.7 meters) deep and 40 yards (37 meters) wide, totalling 120,000 cubic yards (92,000 cubic meters). The estimated cost of pumping this quantity of sand from the vicinity of Cape Point is $530,000. It should be recognized that this measure would be sacrificial--the new sand would be lost in a major storm. But its purpose would be served if it buys enough time to implement a long-term protective option. REHABILITATION OF THE LIGHTHOUSE Constructed of mass brick masonry, the lighthouse is structurally sound. However, long vertical cracks are evident in the interior brick wall on the north and south sides of the lighthouse from the first landing level to the sixth landing level, extending intermittently for 150 feet (46 meters). These cracks pass through many points where stair stringers are anchored to the wall and through the sections that contain the window openings. Thermal effects probably caused these long cracks. When the outer cylindrical masonry wall of the lighthouse expands, high tensile stresses are induced in the inner cylindrical wall, because the two are tied together by a series of large, brick ribs. Cracks would be expected to occur in the interior wall along its weakest vertical sections. Movement of these cracks under thermal changes was confirmed by field instrumentation measurements. Additional cracks also have been observed at various locations where metal attachments are fastened to the interior wall. These cracks likely have developed as the result of corrosion of the anchorage for the attachments.
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Although these cracks do not adversely affect the structural integrity of the lighthouse, the committee recommended that they be cleaned and sealed with a high quality, flexible joint sealant to prevent further deterioration and intrusion of moisture into the wall. These necessary rehabilitation efforts and other preservation measures have been thoroughly defined by an architect/engineer team (Hasbrouck Hunderman Architects et al., 1986) and should be implemented as soon as feasible, regardless of the option chosen for long-term protection of the lighthouse. The committee hopes it will be possible to open the lighthouse to public access on completion of relocation or other long-term protective measures. SITE DESIGN Before the lighthouse is moved, the future location of the dwellings and other structures that form the lighthouse complex must be considered carefully. It would be best to place these structures at the new lighthouse site so that their physical relationship to the tower will continue as it has been in the original location. The present visitor parking and picnic areas impinge on the historical setting of the lighthouse. The committee suggests that additional parking and other visitor facilities should be separated from the lighthouse complex and screened by natural vegetation. Every effort should be made to recreate the sense of isolation of the original 1870 lighthouse setting.
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APPENDIX A
101
Appendix A Major Shoreline Protection Measures
GENERAL MEASURES TAKEN IN CAPE HATTERAS VICINITY* 1930 1930s 1933 1966 1967 1969
One thousand feet (300 meters) of interlocking steel sheet pile groins were installed along the beach. The Civilian Conservation Corps built a major barrier sand dune system along the entire length of Hatteras Island. Installation of additional sheet-pile groins. Three hundred thousand cubic yards (230,000 cubic meters) of sand was pumped from Pamlico Sound onto the beach in front of Buxton, north of the lighthouse. A revetment of large nylon sand-filled bags was placed in front of the lighthouse. The U.S. Navy built three reinforced concrete groins to protect the U.S. Navy facility and the lighthouse.
*Data from MTMA Associates, 1980; U.S. Army Corps of Engineers, 1985.
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APPENDIX A
1971 1973 1974 1980 1981 1982 1982 1983 1984
102
Two hundred thousand cubic yards (150,000 cubic meters) of sand was dredged from a borrow pit at Cape Hatteras to beach at Buxton Motel area. Beach nourishment again was undertaken; 1,250,000 cubic yards (960,000 cubic meters) of sand was dredged from a pit at Cape Hatteras to the beach north of the U.S. Navy facility. Major repairs made to the 1969 groins. Emergency measures were implemented to protect the lighthouse foundation. These included a landward sheetpile extension of the lighthouse groin and emplacement of rubble riprap at the foot of this extension. Offshore artificial seagrass was installed. More extensive artificial seagrass was installed. Seven hundred sandbags were placed around the base of the lighthouse. A protective scour-mat apron was installed at the toe (landward end) of the lighthouse groin. A third, even larger installation of artificial seagrass was implemented.
THE NPS DECISION PROCESS AND THE VALUE OF OPEN PLANNING Since 1980, the National Park Service has sought a long-term, technologically feasible, and cost-effective solution to the problem of preserving Cape Hatteras Lighthouse. In the process, it has shifted its focus from piecemeal stopgaps to larger-scale, more permanent options. Numerous federal, state, and private entities have participated in the quest. The documentary legacy of this process has been prodigious, including professional studies, workshop reports, interagency
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APPENDIX A
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communications and agreements, resolutions, permits, and appropriations. NPS diligently undertook efforts to obtain a diversity of opinions and expertise. On July 29, 1982, on the basis of an environmental assessment, NPS announced its preference for the seawall/revetment option. This was adopted as a final decision on November 26, 1985; Congress appropriated $4,070,000 to preserve the lighthouse October 30, 1986 (H.S. Res. 738, P.L. 99-591). The relocation option initially was discussed by MTMA Associates (1980) report and briefly in the environmental assessment (U.S. National Park Service, 1982). After the April 1, 1982, NPS workshop at Manteo, North Carolina, relocation was dropped from further consideration in favor of the seawall/ revetment. New information from various sources provided the impetus to reexamine the various options, and the desire to reexamine the options led to the formation of this committee. NPS is to be commended for its willingness to reconsider its earlier decision. The value of public input to agency decisionmaking, although time-consuming and even abrasive at times, is thus demonstrated. ACTIONS TO PROTECT CAPE HATTERAS LIGHTHOUSE SINCE 1980 October 28, 1980 Emergency protective measures for Cape Hatteras Lighthouse were initiated after a severe storm in March 1980. The storm destroyed the ruins of the original lighthouse and flanked the beach anchor point of the southern groin (nearest the current lighthouse). This allowed storm-driven or high-tide waves to flow between the steel and concrete jetty and the softer sand dunes and erode sand. The protective measures included: • Placing rubble at the base of the eroding escarpment nearest the lighthouse. • Extending the southern groin 150 feet (45.72 meters) landward.
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APPENDIX A
104
• Placing additional sandbags. Six to 24 months of protection were expected, during which alternative long-term protective measures were to be evaluated, a course of action selected, and funding for implementation obtained. December 2, 1980 NPS presented five options to preserve the lighthouse for 100 years (MTMA Associates, 1980): • • • • •
Relocation Full revetment Partial revetment and groinfield with beach nourishment Groinfield rehabilitation with beach nourishment Beach nourishment
March 5, 1981 After evaluating the options, the North Carolina Coastal Resources Commission determined that moving the lighthouse was the approach most consistent with state guidelines. The approach preferred next was seawall construction (Benton, 1981). May 5, 1981 Five hundred units of artificial seagrass were installed in front of the lighthouse as a demonstration project by the manufacturer. This probably why not effective in building up the beach (U.S. Army Corps of Engineers, 1984). July 15, 1981 A letter from NPS was sent to the U.S. Army Corps of Engineers requesting assistance in developing a long-term (30-50 year) protection plan (Baker, 1981). December 16, 1981 The U.S. Army Corps of Engineers completed analyses of two protection alternatives: a stabilization scheme involving construction of four inshore breakwaters and a southern terminal groin, and construction of a seawall/ revetment (Hughes, 1981).
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APPENDIX A
105
January 18, 1982 The North Carolina Department of Natural Resources and Community Development pointed out to NPS that the U.S. Army Corps of Engineers review only addressed alternatives within its purview to execute and urged NPS to develop comparable information on other alternatives (Flourney, 1982). April 1, 1982 NPS held a workshop in Manteo, NC, to obtain public input on how to protect the lighthouse. The workshop conclusions were that: • The proposals were difficult to evaluate because of the range in quality and detail. NPS should develop selection criteria and ask again for public input. • Given the three NPS constraints--saving the lighthouse, a permanent solution, and no major recurring costs--short-term interim protective measures would be needed. A basal revetment was favored as the long-term solution. Relocation was opposed because it addressed only safety of the lighthouse and not the problem of shoreline erosion. The MTMA feasibility study was not considered reliable. The U.S. Army Corps of Engineers proposed another feasibility study. May 31, 1982 A study by Lee Wan & Associates, Inc. was completed for NPS (Lee Wan & Associates, 1982). July 29, 1982 NPS issued an environmental assessment and requested comments by August 31, 1982. NPS also proposed seawall/ revetment as the preferred alternative (National Park Service, 1982). August 27, 1982 The North Carolina Coastal Resources Commission passed a resolution supporting the NPS preferred alternative to build a seawall, based on the NPS environmental assessment and discussions with NPS personnel, which indicated potential problems
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APPENDIX A
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with moving the lighthouse (Chesson, 1982). Commission staff were informed that “the lighthouse is a double-walled structure which makes a moving alternative particularly difficult and hazardous to the structure” (Benton, 1982). In a memo accompanying the resolution, relocation was ruled out on the basis of projected cost and time efficiency (Willett, 1982). The commission indicated that final plans would be reviewed for consistency with state plans, as required under federal law (Coastal Zone Management Act of 1972). September 13, 1982 NPS designated funds to the U.S. Army Corps of Engineers for protection work, including testing at the Waterways Experiment Station and monitoring the seagrass to determine its effectiveness as an interim measure (Guse, 1982). September and October, 1982 Additional artificial seagrass was installed (U.S. Army Corps of Engineers, 1984). July, 1984 The U.S. Army Corps of Engineers completed Report on Generalized Monitoring of Seascape Installation at Cape Hatteras Lighthouse, North Carolina (U.S. Army Corps of Engineers, 1984). October, 1984 More artificial seagrass was installed (Rogers, 1986). April 9, 1985 NPS requested a declaratory ruling from The North Carolina Coastal Resources Commision on the consistency of the seawall with the state coastal management program. The commission held that relocation and beach nourishment were preferred under the coastal management regulations [15 NCAC 7H .0308(a)(1)] but concluded that a seawall was consistent with state policy, because there would be no adverse effect on marine productivity, it would allow natural erosion processes to continue, there would be no adverse effect on adjacent property, and there was a “clear statement of need for structural rather than nonstructural erosion control methods.” The seawall plan also was consistent with the Dare
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APPENDIX A
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County Land Use Plan (North Carolina Coastal Resources Commission, 1985.) July 3, 1985 The Department of the Army (DOA) issued a public notice that NPS applied for a permit under section 404(b) of the Clean Water Act to place fill material in the Atlantic for long-term shoreline protection in conjunction with the seawall plan. Approval of the DOA permit hinged on required state and local permits and authorizations, which include: • Water quality certification (Clean Water Act Section 401) from the NC Division of Environmental Management • Issuance of a dredge/fill permit from NC Division of Coastal Management [NC General Statute 113-229] • State permit (unspecified type) from NC Division of Coastal Management or its delegates • Easement to fill or occupy state-owned submerged land (NC General Statute 143-341(4), 146-6, 146-11, and 146-12) from NC Department of Administration and NC Council of State • Submission of Erosion and Sedimentation Control Plan to Land Quality Section, Division of Land Resources (State Sedimentation Pollution Control Act of 1973 (NC General Statute 113 A-50-66)) (Warren, 1985). September 9, 1985 A letter from the North Carolina Department of Natural Resources and Community Development to the U.S. Army Corps of Engineers commented on the public notice and concurred that the project was consistent with the North Carolina Coastal Management Program, providing that temporary material and debris were removed at completion. The letter also requested that NPS contact the following offices 2 weeks before beginning the project to ensure that critical fisheries resources and turtle-nesting activities would not be affected adversely:
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APPENDIX A
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• Mr. Paul Raymond, National Marine Fisheries Endangered Species Branch (813)893-3366 • Mr. John Friddel, U.S. Fish and Wildlife Service, Office of Endangered Species (704)259-0321 • Mr. Harrell Johnson, N.C. Division of Marine Fisheries (919)338-1558 (Rhodes, 1985). According to Mr. Hugh Heine at DOA, the necessary authorizations (listed above) were obtained, and a permit was issued (personal communication, November 4, 1987). November, 1985 The U.S. Army Corps of Engineers completed Seawall and Revetment Design for Long-Term Protection of the Cape Hatteras Lighthouse, N.C. for NPS (U.S. Army Corps of Engineers, 1985). November 26, 1985 NPS announced selection of the seawall revetment alternative and found no significant impact (NPS, 1985b). March, 1986 A comprehensive structural analysis was completed by Hasbrouck Hunderman Architects et al. for NPS (Hasbrouck Hunderman Architects et al., 1986b). July, 1986 A comprehensive preservation program was completed by Hasbrouck Hunderman Architects et al. for NPS. (Vertical cracks were found in interior masonry wall.) (Hasbrouck Hunderman Architects et al., 1986a.) August 17, 1986 Dr. Orrin Pilkey of Duke University claimed a wall would seal the fate of the lighthouse, because it would enhance erosion, ensuring that the lighthouse eventually would fall (Minehart, 1986).
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APPENDIX A
109
December 29, 1986 A letter from the Move the Lighthouse Committee to Secretary of the Interior Donald Hodel requested a review of the decision-making process that led to selection of the seawall/revetment option for saving Cape Hatteras Lighthouse (Fischetti, 1986). February, 1987 The Move the Lighthouse Committee released Move It or Lose It: The Case for Relocation of the Cape Hatteras Lighthouse (Fischetti et al., 1987). March(?), 1987 Limberios Vallianos, coastal engineer with the Army Corps of Engineers, replied to the Move the Lighthouse Committee report (Vallianos, 1987). April 10, 1987 Charles Thomas (former chief engineer on Admiral Hyman Rickover's engineering staff) advised Tom Hartman, superintendent, Cape Hatteras National Seashore, that “the risks of catastrophic structural failure of the lighthouse are so great that relocation must not be attempted” (Thomas, 1987). June, 1987 The U.S. Army Corps of Engineers and the Move the Lighthouse commented to NPS on the work statement for assessment of the lighthouse preservation options. The U.S. Army Corps of Engineers recommended an engineering/cost study of the relocation option comparable to the analysis done for revetment. (Vithalani, 1987; Fischetti, 1987.) April, 1987 NPS requested that the National Academy of Sciences evaluate the options (U.S. Department of the Interior, National Park Service, 1987).
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APPENDIX B
111
Appendix B Additional Analyses of Shoreline Retreat
TREND ANALYSIS FOR SHORELINE WITH NO PROTECTION Numerous studies have been conducted on the rates of shoreline retreat in the immediate vicinity of Cape Hatteras Lighthouse. The long-term rates are not as accurately known as those during the past few decades because of lack of precision of old maps. Nonetheless, rates of retreat before implementation of artificial stabilization measures provide a good base to predict retreat 100 years into the future. The most accurate benchmark for long-term erosion is the lighthouse. The present lighthouse was erected in 1870 at 1,500 feet (460 meters) from the water's edge (MTMA Associates, 1980). It is now about 160 feet (50 meters) from the shore. This produces an average rate of shoreline retreat of 11.5 feet (3.5 meters) per year. However, strictly natural conditions at this site existed only until 1930, when the first groins were installed along the shore (MTMA Associates, 1980). The latest measurement of shoreline location before 1930 was made in 1919, when the shore was 300 feet (100 meters) from the lighthouse (MTMA Associates, 1980). Thus, the best estimate of natural rates of retreat is 1,500 feet (360 meters) in 49 years, or 24 feet (7.3 meters) per year. The U.S. Army Corps of Engineers (1984) determined a retreat of 2,000 feet (610 meters) between 1848 and 1917; this is a yearly rate of 29 feet (8.8 meters). The average of these two rates is 26.5 feet (8.1 meters) a year. Other determinations of long-term retreat rates include data from the post-1930 period. A retreat of 2,400 feet (730
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APPENDIX B
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meters) between 1852 and 1970, corresponding to 20 feet (6.2 meters) a year. Estimates of future retreat rates for a natural Cape Hatteras shoreline for different sea-level rise scenarios can be based on the above numbers. In this simple trend analysis, the rate of retreat is assumed to be linearly correlated with sea-level rise (Leatherman, 1984). Thus, a threefold increase in the rate of sea-level rise would move the shoreline landward three times faster. A yearly retreat rate of 26.5 feet (8.1 meters) for a local relative sea-level rise of .08 inches (2.0 mm) a year yields 133 feet (40 meters) of retreat per centimeter of sea-level rise, or a ratio of 1:4,000 between vertical sea-level change and shoreline retreat. This is an exceptionally small ratio, reflecting the highly exposed shoreline at Cape Hatteras. Table B-1 summarizes predicted shoreline retreat based on this method. It is important to recognize that the island's geomorphology indicates that the materials eroded from the eastern shoreline during the next century will be similar to those cut away in the past. Shoreline retreat at Cape Hatteras in the absence of any form of coastal protection might be rapid. Moreover, the numbers in Table B-1 might be low. They are based on the assumption that the average eustatic rate of rise of 0.5 inches (1.2 mm) per year for the past century (Gornitz et al., 1982) is appropriate for the period before 1930. This number, however, might be too high because of evidence that the global rate of rise has been greater since 1935 than it was before (Braatz and Aubrey, 1987). Therefore, the calculated annual retreat of 26.5 feet (8.1 meters) might have occurred in response to a rate of sealevel rise of less than the .05inch (1.2 mm)per year average. THE BRUUN RULE The Bruun (1962) method to predict shoreline retreat is based on assumed maintenance of an equilibrium shoreface profile during sea-level rise. This requires that sand be removed from the eroding beach and shoreface regions and deposited downdrift or on the offshore continental shelf below the seaward limb of the equilibrium profile (Figure B-1).
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APPENDIX B
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TABLE B-1 Predicted Shoreline Retreat at Cape Hatteras in the Absence of Any Mitigative Measures Eustatic Sea-Level Rise* Inches Shoreline Retreat in Feet (Meters) By Year (mm)/Year 2000 2018 2088 0.5 (1.2) 315 (96) 790 (240) 2,600 (800) NRC low 370 (112) 1,115 (340) 6,300 (1,920) NRC medium 440 (134) 1,570 (478) 11,300 (3,440) 510 (156) 2,030 (618) 16,400 (5,000) NRC high *.05 inch per year is a continuation of present trends; the NRC scenarios are accelerating rates of sea-level rise as presented in Table 1.
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APPENDIX B
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Bruun found reasonable agreement between his model and observed shoreline retreat rates along the coast of Florida. Schwartz (1965) verified the theory with small-scale tests in a wave tank, and Hands (1976) obtained satisfactory correlation between the predictions of this model and observed shoreline retreat on the Great Lakes. In applications in Chesapeake Bay, the Bruun rule also yielded satisfactory results (Rosen, 1978). The Bruun rule is formulated as follows:
where R = shoreline recession due to a sea-level rise of S, B is the height of the berm (the break between the slope of the beach and the flatter shoreline above it) above sea level, h is the water depth at the base of the active profile, and L is the width of the shore zone across which the adjustment occurs. The Bruun model is a strictly geometric relationship that assumes that shoreline retreat is a function only of sea-level rise. However, shorelines also retreat because of differential longshore transport rates, loss of sand into the lagoons by storm overwash, and offshore transport. The “modified Bruun rule” (Dean and Maurmeyer, 1983) is designed to consider a realistic topographic profile explicitly to apply the Bruun rule correctly to beaches that are part of a larger barrier-island system. For the North Carolina coast, the generalized Bruun rule predicts a recession rate about 25% higher than the original Bruun rule (Pilkey and Davis, 1987). In view of the uncertainties associated with predictions of sea-level rise, however, there is little justification for using the slightly more precise but more cumbersome generalized Bruun rule. Values used in this calculation of Bruun rule retreat rates are sea-level rise scenarios predicted by NRC (1987b), as well as one scenario based on no acceleration in the rate of rise; berm height of 3.3 feet (one meter) above mean sea level; and depth of the active shoreface profile of 33 feet (10 meters). The most difficult value to estimate is the width of the active zone of profile adjustment. (For a detailed discussion
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APPENDIX B
115
of this slope, see Pilkey and Davis (1987).) L is a measure of the width of the zone of exchange of beach sand. At Diamond Shoals, sand is exchanged at least 12.5 miles (20 km) offshore; the width of the sand-exchange zone at the lighthouse arbitrarily is set here at half of this value, i.e., L=6.25 miles (10 km). Results of the Bruun rule calculations are summarized in Table B-2. These shoreline retreat values are much closer to those in Table 2 than the ones obtained by trend analysis of the natural erosion data, although whether the shoreline is armored is not stipulated in use of the Bruun rule. Retreat rates at Cape Hatteras computed by Pilkey and Davis (1987) as part of a statewide study of North Carolina shoreline erosion are similar.
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TABLE B-2 Predicted Shoreline Retreat Using Bruun's (1962) Rule Shoreline Retreat in Feet (Meters) By Year Eustatic Sea-Level Rise* Inches (mm)/Year 2000 2018 2088 .05 (1.2) 72 (22) 180 (55) 597 (182) NRC low 82 (25) 253 (77) 1,430 (436) NRC medium 98 (30) 358 (109) 2,562 (781) 118 (36) 459 (140) 3,727 (1,136) NRC high *.05 inch per year is a continuation of present trends; the NRC scenarios are accelerating rates of sea-level rise as presented in Table 1.
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APPENDIX C
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Appendix C Partial List of National Park Structures Moved by the National Park Service* Structure Three World's Fair Houses
Construction Date 1933
Moved To Beverly Shores, Fla.
National Park Inn and Museum, Mt. Rainier Three Sisters Lighthouse (North Atlantic Region) City Point Gazebo
1917 1920
1920 1980 and before
1892
1980
ca 1916
1980s
Future Plans Possible future moves due to shoreline erosion
Move again
*From information supplied by Hugh Miller, Chief Historic Architect of NPS.
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APPENDIX D
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Appendix D Biographical Sketches of Committee Members RUTHERFORD H. PLATT, chairman, is a professor of geography and planning law at the University of Massachusetts at Amherst. He received a B.A. from Yale in 1962, a J.D. from the University of Chicago Law School in 1967, and a Ph.D. from the University of Chicago in 1971. He served on the National Research Council's Committees on Flood Insurance Studies, Federal Water . Resource Research, and National Flood Insurance Program Levee Policy. He is a member of the Urban Ecosystems Directorate of the U.S. Man and the Biosphere Program. Dr. Platt's research interests include land-use management; natural hazards; and management of coastal areas, floodplains, and wetlands. He is co-editor of the book Cities on the Beach: Management Issues of Developed Coastal Barriers, and the author of numerous other publications on floodplain, coastal, and wetland policy. MILNER BALL is Caldwell Professor of Constitutional Law at the University of Georgia Law School. He received an A.B. from Princeton University in 1958, an S.T.B. from Harvard University in 1961, a J.D. from the University of Georgia in 1971, and was a Fulbright Fellow at the University of Tuebingen from 1961-62. He has served as a news reporter for various newspapers and is a minister of the Presbyterian Church, U.S.A. He was editorin-chief of the Georgia Law Review from 1970-71 and staff member on the Secretary of State's Advisory Committee on the U.N. Con-
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Camden, N.J., from 1972-78 and was a senior fellow at the Dean Rusk Center for International and Comparative Law from 1978-81. He is past president of the Athens chapter of the Lawyers Alliance for Nuclear Arms Control, a founding member of the Law and Humanities Institute, and a member of the International Council on Environmental Law. Included in the list of Mr. Ball's wide-ranging interests are environmental law, the law of the sea, and the management and legal aspects of natural resources. BEN GERWICK is a professor of civil engineering at the University of California at Berkeley, where he teaches courses in construction engineering and management. He was an executive in the construction industry for 30 years before taking his present university post in 1971. Since then he also has been involved as a consulting engineer on marine and foundation projects, including major bridges and offshore platforms. He is a member of the National Academy of Engineering and serves on the Commission on Engineering and Technical Systems of the National Research Council. He is past chairman of the Marine Board and a past member of the Polar Research Board. He is a Fellow and Honorary Member of the American Society of Civil Engineers, the American Concrete Institute, the Prestressed Concrete Institute and the Federation Internationale de la Precontrainte. EUGENE HARLOW is a coastal engineer. He received the degrees of B.A. in 1935 and M.S. in 1936 from Harvard University. He is vice president of SOROS Associates, a major engineering firm in New York City, and recently was executive vice president and director of Frederic R. Harris, Inc. He has more than 35 years' professional experience in planning, design, and construction of ports and harbors, including docks, piers, cofferdams, heavy foundations, breakwaters, and offshore structures. He has published numerous technical articles on these subjects. Mr. Harlow is a member of the National Research Council's Marine Board, the American Society of Civil Engineers, the American Association of Port Authorities, the Permanent International Association of Navigation Congresses, and many other national and international professional engineering organizations. He chaired the Marine Board's Technical Panel on Ports, Harbors, and Navigation
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Channels and was a member of the Marine Board's Panel on Harbor/Port Entrance Design. FRANCIS ROSS HOLLAND is a historian. He received a B.C.S. from the University of Georgia in Atlanta in 1950 and an M.A. in history from the University of Texas in 1958. He is writing a history of the Statue of LibertyEllis Island restoration project. Previously, he was the assistant to the President of the Statue of Liberty-Ellis Island Foundation Inc., and has held various positions in the National Park Service since 1950, most recently in cultural resources management. In 1976 he received the Meritorious Service Award from the Department of Interior for his contributions to historic preservation and the Distinguished Service Award in 1983 for his contributions to the National Park Service's Cultural Resource Management Program. His areas of research interest include maritime history, especially shore whaling and lighthouse administration; Spanish explorations, historic preservation, and the cultural resources of the national park system. VALERIE I. NELSON is the executive director of the Lighthouse Preservation Society. She received a B.A. from Radcliffe College in 1969, an M.Sc. from the London School of Economics in 1971, and a Ph.D. from Yale University in 1977. She has been a visiting assistant professor at MIT, and a consultant in public policy for the National Academy of Sciences, the General Accounting Office, and the Center for Employment and Income Studies at Brandeis University. Previously, she was a research associate at University Consultants Inc. from 1972-81, and an instructor and a lecturer at the Kennedy School of Government at Harvard University from 1974-77 and from 1977-79. Dr. Nelson's research interests include adult and vocational education, urban development, and the economics and sociology of employment. DAG NUMMEDAL is a professor of geology at Louisiana State University. He holds B.A. and M.A. degrees from the University of Oslo, Norway, and a Ph.D. from the University of Illinois. His research has concentrated on shallow marine sedimentation, particularly tidal inlet stability and tidal delta sedimentation; barrier island evolution; and shoreline change.
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His current research focuses on sedimentation in modern and ancient continental shelves. Dr. Nummedal has served as consulting geologist to the National Aeronautics and Space Administration and is a member of the Coastal Engineering Board of the U.S. Army Corps of Engineers. He has served on the NRC Committee on Engineering Implications of Changes in Relative Mean Sea Level. CHARLES HENRY PETERSON is a professor of marine science and biology at the University of North Carolina at Chapel Hill, where he has worked since 1976. He received an A.B. from Princeton University in 1968 and an M.A. in zoology and a Ph.D. in biology from the University of California at Santa Barbara in 1970 and 1972. He has taught at the University of California Extension (1970-72), the University of California at Santa Barbara (1971-72), and the University of Maryland (1972-76). He was a Ford Foundation Fellow in 1972 and served on National Science Foundation review panels in biological oceanography in 1980 and 1985-1987. Dr. Peterson's main areas of research are population biology, fisheries management, and community ecology, particularly competition, predation, life history patterns, and species diversity of marine benthic invertebrates and barrier island plants. He is a member of the National Science Foundation's Ocean Sciences Advisory Committee and recently of the North Carolina Marine Fisheries Commission. ALAN H. YORKDALE (deceased) was the vice president for engineering and research at the Brick Institute of America. He studied civil engineering at Montgomery College, George Washington University, and the University of Virginia. He served on the board of directors and was a fellow of the American Society for Testing and Materials, which honored him with an award of merit in 1985. Mr. Yorkdale was also on the board of directors of the Building Seismic Safety Council and authored or coauthored several articles and technical papers on the research, design, and construction of brick masonry. His expertise included earthquake-proof design, building codes, structural engineering, and masonry products.
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PAUL ZIA is a professor and head of the Department of Civil Engineering at North Carolina State University in Raleigh. He received civil engineering degrees of B.S. from the National Chiao Tung University of China in 1949, M.S. from the University of Washington in 1952, and Ph.D. from the University of Florida in 1960. He has taught engineering at the University of California at Berkeley and at the University of Florida in Gainesville. From 1953-55 he was vice president and chief structural engineer at Lakeland Engineering Associates in Lakeland, Florida. Dr. Zia is a member of the National Academy of Engineering, the Prestressed Concrete Institute, and the American Society for Engineering Education. He is a fellow of the American Concrete Institute and the American Society of Civil Engineers and has received several awards for his contributions to civil engineering. His principal areas of expertise are in failure investigation and strength evaluation of reinforced and prestressed concrete structures and the properties and application of high-strength concrete. Staff DAVID POLICANSKY, project director, is a senior program officer with the Board on Environmental Studies and Toxicology. He received his B.A. from Stanford University and his M.S. and Ph.D. in biology from the University of Oregon. Dr. Policansky formerly did research and taught genetics, evolution, ichthyology, and ecology at the University of Massachusetts in Boston, Harvard University, and the University of Oregon. He also has done research on fishes at the Northeast Fisheries Center in Woods Hole and the New England Aquarium in Boston. In his currrent position at the NRC, Dr. Policansky is responsible for oversight several committees. His expertise and intersts include ecology, evolution, fisheries biology, and environmental policy. Dr. Policansky is the author and coauthor of papers on sex changes in plants and animals, the costs of asexual versus sexual reproduction, the inheritance of asymmetry in flounders, and cumulative environmental effects, among others.
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