Cape Hatteras

National Seashore
North Carolina

U.S. Department of the Interior
National Park Service

North Carolina State University
1997 Review and Update of the 1988 National Research Council Report

Ad Hoc Committee of Faculty at North Carolina State University: Dr. Arthur W. Cooper, Dr. Leon E. Danielson, Dr. John M. Hanson, Dr. Leonard J. Pietrafesa, Dr. Paul Z. Zia, Dr. Ellis B. Cowling, Chairman.

This Ad Hoc Committee was appointed by Dr. Larry Monteith, Chancellor, North Carolina State University. This report was prepared at the request of Senator Marc Basnight, President Pro Tempore, General Assembly of North Carolina, in consultation with Mr. Russell Berry, Superintendent, Cape Hatteras National Seashore, National Park Service.

Cover photos courtesy of Michael Booher.

January 1997

Foreword
The members of this Ad Hoc Committee to Update the Cape Hatteras Lighthouse Study are grateful for the opportunity to perform a public service for the General Assembly and the people of North Carolina. We hope that this report will serve as an example of how the knowledge and expertise of faculty at North Carolina State University and our sister public and private institutions can be applied to contemporary social, environmental, economic, and cultural issues of importance to our society.

Dr. Ellis B. Cowling, Chairman Ad Hoc Committee

31 January 1997

Introduction and Background
This report has been prepared by a Committee appointed by Dr. Larry Monteith, chancellor of North Carolina State University. In his letter of appointment, Chancellor Monteith stated:

As a public service to the State of North Carolina and at the request of President Pro Tempore Marc Basnight, I am requesting that you serve as an Ad Hoc Committee to review and update, if necessary, the 1988 study conducted by the National Academy of Sciences on the possible options for preserving the Cape Hatteras Lighthouse.

The initial meeting of the Committee was held on December 5, 1996, in the chancellor’s conference room in Holladay Hall. The meeting was attended by Chancellor Monteith; Mr. Russell Berry, superintendent of the Cape Hatteras National Seashore of the National Park Service; and Ms. Norma Ware, representative of Senator Basnight’s Office. Mr. Berry is the official within the National Park Service who has direct administrative responsibility for the lighthouse and the other structures within the Cape Hatteras Light Station Historic District. During this meeting, Chancellor Monteith reviewed his charge to the Committee. In addition, Mr. Berry reported on the history of the lighthouse and various efforts by the National Park Service to maintain the Cape Hatteras Light Station Historic District so that it can be enjoyed by nearly 250,000 visitors each year. Mr. Berry also left with the Committee a series of reports prepared by, or at the request of, the National Park Service since the publication of the 1988 National Research Council (NRC) (The NRC is the working arm of the National Academy of Sciences.) report entitled Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Mr. Berry also offered to arrange for an aerial reconnaissance and on-site inspection of the lighthouse and the historic district. The Committee accepted this offer on December 20, 1996. The site visit included the following events, which were most valuable to the Committee in formulating this report:

  • A flight over the long reach of open water in Pamlico Sound before reaching the thin line of barrier islands that constitute the Outer Banks and Hatteras Island (Figure 1).
  • An aerial view of the Cape Hatteras National Seashore, the Cape Hatteras Light Station Historic District, and the lighthouse itself... now only about 120 feet from the Atlantic Ocean. From the air and the lighthouse gallery, we noted the remarkable patterns of erosion that have occurred immediately to the south of the most southerly of the three steel groins that jut out into the ocean perpendicular to the beach in the vicinity of the lighthouse. We also noted the approximate location of the two sites to which the NRC recommended that the lighthouse might be moved incrementally in order to protect it from the sea.
  • A meeting with representatives of various groups who have a special interest in the preservation and maintenance of the lighthouse, the historic district, and the Visitor Center of the Cape Hatteras Light Station Historic District.
  • An on - the - ground inspection and a further examination of the lighthouse and its setting from the windows and the gallery near the top of the lighthouse. These inspections included an assessment of the exterior and interior condition of the lighthouse, its proximity to the waves, the action of those waves on the three steel groins, the nearby assemblage of sandbags and rubble that have been placed over and near the foundation of the lighthouse, the artificial dunes that have been created by the bulldozing of sand near the lighthouse, the “snow fences” that have been erected to discourage visitor trampling of the dune vegetation near the lighthouse, the exterior condition of the lighthouse keeper’s home and visitor center, and the two sites to which the NRC committee recommended that the lighthouse might be moved incrementally in order to protect it from the sea. It was obvious, especially to the Committee’s structural engineers, that the 136-year-old lighthouse is still a very sturdy brick masonry structure. Its center of gravity is at about one-third of its height.
  • A lunch meeting and general discussion with Senator Basnight and several of the Dare County commissioners who also have a special interest in the preservation and maintenance of the lighthouse, the historic district, the Cape Hatteras National Seashore, and the vitality of the nearby communities of Avon, Hatteras, Buxton, and other settlements.
  • A meeting with Superintendent Berry to summarize and share our initial and more studied impressions of the options and policy implications outlined in the 1988 NRC Report. These options and policy implications were considered in the light of additional documents which were provided to the Committee in connection with our initial meeting. The most useful of these documents are listed at the end of this report. Some Committee members also consulted with other experts and officials within the North Carolina Coastal Resources Commission about some of the policy implications and practical considerations involved in the four general and ten specific options for protecting the lighthouse and associated structures detailed in the 1988 NRC report. We have organized this report in substantially the same way and with substantially the same headings and subheadings as were used in the 1988 NRC study. Our charge is generally similar to and congruent with the charge to the NRC committee, which presented the following statement of purpose:

    The [NRC] 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 [and societal justification for the cost] 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 assess them.

    Review and Update of The Physical Setting
    Since 1988, scientists have increased our understanding of the lighthouse’s physical setting and of the influence of storms and continuing sea-level rise on the physical dynamics of the barrier islands on which the lighthouse was erected in 1870. More specifically, researchers have learned a great deal about the following topics:
  • The underlying geology, morphodynamics, and westerly retreat of Hatteras Island;
  • Current and future estimates of the rate of sea-level rise; and
  • The genesis, frequency, and severity of storms in the vicinity of Hatteras Island
  • both tropical cyclonic storms (some of which become hurricanes) and extra-tropical cyclonic storms (some of which become "nor’easters").

    The major and minor scientific conclusions drawn from research in these three fields support the strong body of evidence that was already available in 1988 and that led to the single most important conclusion of both this Committee and the 1988 NRC report:

  • The Atlantic Ocean will destroy the Cape Hatteras Lighthouse and the other structures of the Cape Hatteras Light Station Historic District unless actions are taken soon to move these structures farther from the sea.

    In what follows, we summarize, by research topic, some of the most important of the above-mentioned results and conclusions.

    Geomorphology of the Hatteras Coastline and Shoreline Retreat

    At present, the shoreline in the vicinity of the Cape Hatteras Lighthouse retreats at a rate of about 10 feet per year. This rate applies to all portions of the eastern shore of Hatteras Island, from about 0.7 miles south of the lighthouse to about 3 miles north of it. The annual rate varies considerably, however. For example, in 1993 the North Carolina Division of Coastal Management published the results of their most recent measurements: The average annual rate of shoreline retreat for the area between Cape Point to the south of the lighthouse and Oregon Inlet to the north varied from a minimum of 6 feet per year to a maximum of 11 feet per year.
    In contrast to the east-facing, westerly retreating shore of Hatteras Island, the south-facing shore of Hatteras Island below Cape Point is accumulating sand and thus is gradually extending farther southward. Three steel groins were built near the Cape Hatteras Lighthouse in 1969. They extend about 500 feet into the ocean perpendicular to the east-facing shore of Hatteras Island. Their intended purpose was to decrease the rate of shoreline retreat in front of the nearby U.S. Naval Facility (now used by the U.S. Coast Guard) immediately to the north of the lighthouse. As has been found with virtually all hardened structures at the edge of the sea, however, these groins have slightly modified but not greatly or permanently altered the general dynamic patterns of sand erosion in some areas and accumulation in other areas along the shores of Hatteras Island. When intact, these groins decreased the rate of shoreline retreat in front of the Naval facility. A "headland beach" did accumulate to the east of the groin field as the adjacent shoreline continued to retreat westward. At the same time, however, the groins accelerated the rate of sand erosion immediately to the south of the southernmost groin, which, unfortunately, is just to the southeast of the lighthouse. As a result, the third groin (the one closest to the lighthouse) has been repeatedly breached by wave action. These breaches, coupled with the proximity of the southernmost groin to the lighthouse, have accelerated the rate of shoreline retreat immediately to the south of the lighthouse (Figure 2). The minimum distance between the ocean and the lighthouse at the time of the 1988 NRC report was about 160 feet. In 1995, this distance was reported to be about 135 feet. In January 1997, this distance had further decreased to about 120 feet.

    Many emergency efforts have been made to stop the breaching of this southernmost groin. These include repairing the groin; building steel and rock bulkheads; placing many layers of nylon sandbags near the breached groin and in front of the lighthouse; and even tearing up and dumping parking lot asphalt into the area of maximum erosion just to the south of the lighthouse. So far, these stop-gap measures have protected the lighthouse from the accelerated erosion that has been occurring south of the third groin.

    The experience at Cape Hatteras Lighthouse illustrates very well the problems with groins and why the North Carolina Coastal Resources Commission ruled in 1984 that hardened structures are not permitted along the North Carolina coastline except under extraordinary circumstances.

    Sea-Level Rise
    Sea-level rise is the underlying cause of the westerly retreat of Hatteras Island and a problem with which barrier islands must contend for their very existence in many parts of the world. In almost all portions of the eastern shore of North America, east-facing shores slowly retreat west while south-facing shores extend farther to the south. This is exactly the pattern observed along the east-facing shore of Hatteras Island north of Cape Point and the south-facing shore south of Cape Point: The east-facing shore is retreating westward while the south-facing shore is accumulating sand and thus extending or expanding southward. During most of the past 18,000 years, the average annual rate of sea-level rise along the North Carolina coast was about 0.26 inches per year. Thus, the mean sea level of the Atlantic Ocean along the North Carolina coast is today about 389 feet higher than it was about 18,000 years ago - the time of the last ice age in the northern hemisphere. During the past 4,000 years, however, the annual average rate of sea level rise has decreased nearly ten-fold and is now only about 0.024 inches per year. It is not known why this comparatively slow rate of sea- level rise along the North Carolina coast is less than the 0.039 to 0.078 inches per year observed in other parts of the world.

    If we project these presently observed rates of sea-level rise for about 100 years, it becomes clear that the mean sea level at the eastern shore of Hatteras Island could be at least 10 inches higher than at present. The Polar Research Board of the NRC and other authoritative scientific organizations have estimated that the mean sea level of the Atlantic Ocean in the year 2100 could be even higher — from 24 to 95 inches higher - than at present. No matter what authoritative estimate we choose, however, this much is clear: Sea-level rise will continue to threaten the Cape Hatteras Lighthouse unless it is moved farther from the sea.

    Coastal Storms
    During the passage of major storms along the Atlantic coast, Cape Hatteras is frequently buffeted by strong winds; heavy rains; larger - than - usual waves in the surf along the beach; and “storm surges,” which are really wind-induced temporary increases in the elevation of the ocean in the immediate area of the storm. When these large cyclonic storms originate near the equator, they are called tropical cyclones, and when their winds reach speeds in excess of about 74 miles per hour, they are called hurricanes. When these large cyclonic storms originate over North America or over the near-continent portions of the Atlantic Ocean, they are called extra-tropical cyclones or nor’easters. Figure 3 shows a view of the Atlantic Ocean from the gallery of the Cape Hatteras Lighthouse during a nor’easter in March 1990.

    Hurricanes usually pass over the eastern coast of North America in one or two days, most often during June to November. Nor’easters, on the other hand, sometimes produce sustained gale force winds in excess of about 39 miles per hour for two to four days. Nor’easters occur most frequently from October through April.

    Cape Hatteras is subjected to an unusually high frequency of both tropical cyclones and extra-tropical cyclones (Figures 4 and 5). Many ships have been sunk in the treacherous waters that develop during these large cyclonic storms.

    Thus, Cape Hatteras deserves its nickname: the "graveyard of the Atlantic." Although the frequency of Atlantic hurricanes varies greatly from year to year, the Cape Hatteras area has as high a frequency of hurricane - force storms as any comparably long stretch of shoreline from Texas to Nova Scotia. In November 1993, the National Park Service appointed an advisory committee to conduct a site visit to the Cape Hatteras Lighthouse, assess the beach erosion problem in the area, and estimate the short-term and long-term risks of damage associated with erosion and storm surge. In 1995, Superintendent Russell Berry asked this same advisory committee (Robert Dean of the University of Florida, Robert Dolan of the University of Virginia, and John Fisher of North Carolina State University) to update the 1993 report and recommend further actions as needed. In 1995, the advisory committee concluded that:
      The present situation places the lighthouse at higher risk than at any time in the past... This past winter’s experience confirms the higher likelihood of serious risk of damage... The south flank of the lighthouse is now less than 135 feet from the ocean. This area, which is immediately downdrift of the groin field, was termed the “Achilles heel” in our last report and we remain convinced that this area could lead to problems in the future... The lighthouse is vulnerable to direct frontal attack by high waves and storm surge. A storm with a return interval of about 30 to 50 years (Class 3 hurricane or Class 4 northeaster), with a 16% chance of occurring, could lead to this threat depending upon its track and duration... Two less powerful storms back-to-back could lead to similar results.
    In any given year, Simpson and Lawrence (1971) have estimated that there is an 18% probability that a tropical cyclone will occur in the vicinity of Cape Hatteras. Predictions for 1997 are for 11 Atlantic tropical cyclones with 7 becoming storms of hurricane force. Although the tracks for both tropical and extratropical cyclonic storms cannot be predicted, a general shift appears to have occurred: from a greater frequency of storms ending up in the Caribbean to a greater frequency of storms ending up in the Atlantic Ocean, although some of the latter eventually track to the lighthouse as well. Obviously, storms on "Atlantic" tracks are much more likely to have a "close encounter" with Cape Hatteras than storms on "Caribbean" tracks. History suggests that the current "Atlantic" pattern is likely to be sustained for several more years. This reinforces the Ad Hoc Committee’s conclusion that if the lighthouse is to be preserved by moving it farther from the sea, the move should be accomplished as soon as possible.

    Review and Update of Relevant Public Policies
    The 1988 National Research Council report reviews a wide variety of public policies that address a diverse array of public concerns regarding the lighthouse, its use, and its preservation. These include:

  • Protection of navigation, the original purpose of the lighthouse;
  • The National Park Service mandate 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"
  • Protection of historic structures - especially those which, like the Cape Hatteras Lighthouse, are on the national and state registers of historic landmarks;
  • The Coastal Barrier Resources Act, which codifies congressional recognition of the migratory and dynamic nature of coastal barrier islands;
  • Flood hazard mitigation;
  • Enhancement of recreation and tourism;
  • Public education;
  • Federal consistency with state laws;
  • Wetland protection;
  • Economic effectiveness;
  • Environmental protection; and
  • Use and protection of the coast.


    Figure 4. Tracks of 1996 tropical cyclones passing near Cape Hatteras.
    (Data obtained from the National Oceanic and Atmospheric
    Administration’s National Hurricane Center.)

    No significant changes have occurred in these policies that might impact the protection options relating to the National Park Service mandate, the enhancement of recreation and tourism, public education, economic effectiveness, and environmental protection. Thus, the policy narrative on these issues within the NRC report is still valid and appropriate. Meteorological and other events since the late 1980s have enhanced the credibility of the NRC analysis of policies relating to shoreline protection and the preservation of historic structures near the sea. Major hurricanes, particularly those which damaged the southern coast of North Carolina in 1995 and 1996, emphasize the fragility of the Outer Banks and the highly vulnerable situation of the lighthouse. Furthermore, North Carolina’s Coastal Resources Commission has strengthened its commitment to prevent the use of hardened structures as a means of protecting the state’s shore. This places an even heavier burden on the National Park Service... if it were to choose hardening as its preferred protective measure — to prove that hardening is the only feasible alternative. Given what is known about the defects of hardening as a beach-protection measure and the Coastal Resources Commission’s current position on hardening, any proposal to protect the lighthouse by hardening has a low probability of approval. Recent changes in federal wetlands protection requirements also place a burden on the National Park Service to minimize, if not eliminate, damage to wetlands which might occur as a result of efforts to move the lighthouse. Although wetlands protection policies do constrain the direction and distance of such a move, the Ad Hoc Committee is satisfied that the site currently preferred by the National Park Service (very near the so-called “intermediate latitude aeria” shown in Figure 11 of the NRC report) will not violate current federal or state wetlands policy. Therefore, the Ad Hoc Committee concludes that the proposal to move the Cape Hatteras Lighthouse to the National Park Service preferred site is not only consistent to the maximum extent possible with all relevant federal and state policies, but also supports them in ways that none of the other nine NRC alternatives do.

    Review and Update of Preservation Options and Criteria of Evaluation
    The NRC committee developed and defined an elaborate system of 22 criteria for evaluating each of the ten Tropical Storms - Cape Hatteras - North Carolinaoptions that were published in the 1988 NRC report. We reviewed these criteria and their associated definitions, and found them to be appropriate for our assigned task to “review and update” the 1988 NRC report.

    Review and Update of Evaluation of Options
    Among the several documents provided to the Ad Hoc Committee was a 300-page Comprehensive Structural Analysis Report prepared in 1986 for the National Park Service by Hasbrouck Hunderman Architects of Chicago, with Wiss, Janney, Elstner Associates, an engineering consulting firm in Northbrook, Illinois. This study was also cited in the 1988 NRC report. The study includes copies of many of the original architectural drawings used in constructing the lighthouse. It also describes, in detail, many aspects of the masonry, above-ground steel work, foundation structure, paints and coatings, and many other features of the materials and construction techniques used in building the lighthouse in 1870. Among the potentially important, and apparently less well-known, construction features discussed in the Comprehensive Structural Analysis Report is that the deepest part of the foundation is a two-layered 12-inch-thick mat of "timber lagging" under the lighthouse’s rubblestone foundation. Hasbrouck Hunderman obtained fragments of this mat by drilling though the soil directly adjacent to the lighthouse. These fragments were sent to the Center for Wood Anatomy Research at the Forest Products Laboratory in Madison, Wisconsin. The laboratory’s timber pathologist determined that "no evidence of decay or deterioration of the timber was apparent." The report concludes:

    In summary, the timber lagging is in good condition... This can be attributed to the fact that the timber lagging has apparently remained submerged beneath the fresh groundwater for that entire period of time... As long as the timber remains submerged below fresh water, no decay or deterioration should take place. Presently [1986] the top of the timber foundation is 6 feet 8 inches below the ground, and approximately 3 feet 3 inches below the water table measured by STS Consultants. We strongly recommend that permanent well points be installed adjacent to the lighthouse on all four sides, and that the water table be monitored at those points for the continued life of the structure.

    In the 1988 NRC report, the Committee on Options for Preserving the Cape Hatteras Lighthouse evaluated ten options that were deemed worthy of consideration as means of saving the lighthouse from destruction by the sea or by loss of integrity of the foundation if the water table were not maintained above the timber lagging as discussed above:

      1. Incremental relocation of the lighthouse intact
      2. Rehabilitation of the groin field without revetment
      3. Rehabilitation of the groin field with revetment
      4. Seawall with revetment
      5. Artificial reefs
      6. Offshore breakwaters and groin field rehabilitation
      7. Deployment of artificial seagrass
      8. Continuing beach nourishment
      9. No action
      10. New lighthouse.
    Five criteria were considered crucial by the NRC Committee in their evaluation of these ten options:
  • Technical feasibility
  • Short-term reliability
  • Initial and long-term cost
  • Protection of historic values
  • Risk of damage to the lighthouse during implementation. In applying these five crucial criteria to the ten options listed above, the NRC Committee concluded that:
  • Only the first four options met all five crucial criteria, and
  • Incremental relocation of the lighthouse was the preferred option. The National Park Service has subsequently completed or commissioned a series of studies that have further elaborated on the themes developed and the options considered in the 1988 NRC report. The first of these follow-on studies was entitled Protection Alternatives / Development Concept Plan / Environmental Assessment. This study was completed by the National Park Service in June 1989. It gives detailed consideration to the first and fourth options considered in the NRC report and reached the following conclusions:
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