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OCR for page 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). Protec-
tive 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
t~unchon 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
OCR for page 2
2
Saving Cape Hatteras Lighthouse
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 light-
house, 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, 1 987a),
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, dur-
ing 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 continua-
tion 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 ( 1 97Sb)
scenario would yield 6.1 inches ( 155 mm) by 2018. Based on
this range of values, the committee estimates that the shore-
line in front of the lighthouse would retreat 157-407 feet
(48- 124 meters) by the year 2018. By the year 208S, the
retreat might reach 525-3,280 feet (160-1,000 meters).
OCR for page 3
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 pre-
serving 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 mis-
sion. 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 en iovment 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 author-
ized 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
arcneo~og~ca~ sites at the state and local levels. The act
declared a national policy for historic preservation by provid-
ing 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, rehabilita-
tion, restoration, and reconstruction of districts, sites, build-
ings, 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,
~. .. ... . . ..
OCR for page 4
4
Saving Cape Hatteras Lighthouse
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
level rise (May et al., 1983~. This natural process of shore-
line migration clashes with demographic growth and develop-
ment 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 capaci-
ties (Platt et al., 1987~.
An array of federal statutes and regulations govern devel
1n response to sea
opment and protection ot 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 pre-
serve 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
OCR for page 5
Executive Summary
s
of the lighthouse--is consistent with preservation and conser-
vation 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 approxi-
mately $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 founda-
tion 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
OCR for page 6
6
Saving Cape Hatteras Lighthouse
lighthouse would attract much attention and, therefore, would
provide an opportunity to educate the general public con-
cerning 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 ele-
ments: a concrete seawall encircling the lighthouse, a sheet-
pile 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 construc-
tion 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 struc-
tures 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 tombola 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
OCR for page 7
Executive Summary
7
all the options considered. Finally, the seawall/revetment
effectively would foreclose future relocation of the light-
house.
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 con-
crete revetment around the lighthouse. The revetment would
protect the lighthouse from the undermining effects of
storms, but not from the battering of waves. The rehabili-
tated 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 $4.7-
6.7 million and would require less than 1 year to construct.
This option would protect the lighthouse for 20-30 years,
barring a disastrous storm.
· ~.. . I. . . .
Eventually, as the shoreline out
slae one groins 1ela continued to retreat, it would become
increasingly expensive, and perhaps impossible, to maintain a
beach in front of the lighthouse, ~ ~ ~
· · ~. .& . . -
W~lCh WOU1d 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.
committee did not
favor this option. However, of the options that would pre
serve the lighthouse in situ by defensive means, this offers
some protection to the lighthouse at relatively low cost.
Because of these disadvantages, the
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
OCR for page 8
8
Saving Cape Hatteras Lighthouse
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 revetments, 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 Hat-
teras Lighthouse, the committee was asked to address the
broader context of national policy concerning historic preser-
vation 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 struc-
tures. Moreover, NPS faces decisions concerning historic
preservation versus ecological
far from the coast.
The committee believes that the present study offers guid-
ance for future decisions on historic preservation and con-
servation. 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 his-
toric preservation and conservation. The committee com-
mends NPS for its willingness to reconsider its initial deci-
sion to build a seawall.
conservation t~or its properties
Representative terms from entire chapter:
cape hatteras
