in coastal regions and in small islands
Coping with shoreline erosion in
changes due to natural processes and human intervention represent a major concern
of coastal planners the world over, and indeed of ordinary citizens who have
real or potential interests in beaches and seaside property. While beaches may
be the substance of vacation dreams for some, their disappearance through erosion
can lead to nightmares for those who live, work, relax and build close to the
shore. In the Caribbean region, one collaborative research activity has focused
since the mid-1980s on issues related to coast and beach stability. One recent
product has been guidelines to help coastal
planners and stakeholders to establish their own specific measures for dealing
with coastline instability.
Shorelines are areas of
continuous change where the natural forces of wind and water interact with the
land. Though the shifts between water and land have been taking place for centuries1
- and are the result of both natural forces and human activities such as sand
mining and beach construction - these changes have taken on paramount importance
in the Caribbean islands since tourism became the major industry in the 1970s.
Despite their economic value in a region where tourism is dependent for the
most part on sun, sea and sand, beaches have unfortunately not been perceived
as areas needing management, protection and funding, but rather as permanent
features of the landscape.
has been growing slowly. International events, such as the United
Nations Conferences on Environment and Development (Rio de Janeiro, 1992)
and on Sustainable
Development of Small Island Developing States (Barbados, 1994), have helped
to focus public attention on the need for environmental management. Yet is was
the dramatic events of 1989 and 1995 that gave the region the most direct demonstration
of the need for beach management; Hurricane Hugo in 1989 and the numerous hurricanes
in 1995 brought home to everyone the impermanence and vulnerability of the region's
Within such a context, UNESCO
has been involved in the search for answers to coastal problems for well over
two decades. Under the auspices of its Coastal Marine programme, a project was
developed and eventually entitled Coast and Beach Stability
in the Caribbean (COSALC)2.
Since 1993, the project has benefited from the co-sponsorship of the
Sea Grant College Program of the University of Puerto Rico. More recently,
UNESCO's support for the project's activities has been provided through the
Organization’s platform for cross-sectoral action: Environment
and Development in Coastal Regions and in Small Islands (CSI). One tangible
output of a decade and a half of co-operation and field studies is a practical
guide on shoreline protection and other management measures. The 119 page illustrated
guide, Coping with Beach Erosion 3,
presents environmental background and practical guidelines on what can be done
in response to disappearing and degrading beaches. The information is organized
in terms of eleven generic cases:
- Countering the effects
of high seas in winter
- When a hurricane occurs
- When stones have replaced
a sand beach
- Assessing the impact
of coastal structures
- Adding more sand to the
- When sand has been mined
from the beach
- When sand dunes have
- When vegetation has been
removed from behind the beach
- Stabilizing the river
mouth or tidal inlet n Conserving reefs
- New ways to reduce beach
This article provides glimpses
into some of these situations, and to the sorts of approaches that have commended
to those concerned with erosion-prone beach areas. While the focus is on the
Caribbean, many of the conclusions and measures may also be relevant to beach
systems elsewhere in the world and especially in small islands.
A HURRICANE OCCURS
a hurricane, wind circulates counter-clockwise around a central eye,
shown in black in this satellite view of Hurricane Iris in September
1995. In the eye, the winds are calm. Source:
US National Geophysical Data Center.
such as hurricanes are the major cause of shoreline changes in the Caribbean.Many
hurricanes originate as tropical waves off the west coast of Africa and travel
across the Atlantic Ocean gaining strength from the warm ocean waters. As tropical
waves streng then, they pass through several stages, including tropical depression
and tropical storm before reaching hurricane strength. Once a system reaches
tropical storm strength, it is named. Hurricanes are further classified into
five categories based on wind speed. The wind speeds in categories one to five
refer to sustained wind speeds. Actual gusts may be much higher. Most hurricanes
are experienced in September in the Caribbean .
and wind speed
||118 - 152
||74 - 95
||153 - 176
||96 - 110
||177 - 208
||111 - 130
||209 - 248
||131 - 155
Most of hurricanes
affecting the Caribbean islands move in a westerly to northwesterly
direction. As the hurricane approaches, winds usually blow from the
east and north. Once the centre, or eye, of the hurricane has passed,
the wind blows from the west and south.
from Bacon (1978).4
Based on study of weather
patterns and climate records over the past hundred years, it appears that
hurricane generation in the North Atlantic Ocean occurs in 20-25 year alternating
cycles of activity and relative in activity. The evidence indicates that we
have now entered an active hurricane cycle, which is expected to continue
for the next two decades. The years 1995 and 1996 were especially active,
1995 registering as the second-most active year on record with nineteen named
storms. However, even within an active cycle, there are years with below -
average hurricane activity, such as 1997. Tropical storms and hurricanes are
such intense, well - organized systems that they generate waves which move
out of the immediate vicinity of the hurricane to a ffect other islands as
swell waves. Considerable damage may occur to beach systems as a result of
high seas, raised water level (known as a storm surge), high winds and heavy
rain fall. Hurricane waves erode the beaches and penetrate farther into the
land behind the beach causing flooding, erosion of sand dunes and destruction
of coastal highways and buildings.
beach cross-section before and after a hurricane. The hurricane waves
overtopped the seaward dune and the building on the dune collapsed. Sand
was moved offshore and inland. Figure adapted from Bush et al. (1995).5
after a hurricane may vary from slight to severe. In Barnes Bay, Anguilla,
pre - hurricane beach conditions in 1994 featured a wide sandy beach
backed by palm trees . Post hurricane, in 1995, the sand had been
stripped from the beach during Hurricane Luis, leaving rocky outcrops
exposed and just a few pockets of sand. The palm trees were lost.
THE EFFECTS OF HIGH SEAS IN WINTER
Waves, tides and ocean
currents are among the several natural forces that cause beach changes. One
cause of considerable beach erosion are swell waves - waves that travel out
of the area in which they were generated. In the Caribbean, such swell waves
are usually caused by intense midlatitude storms in the North Atlantic Ocean,
which travel thousands of kilometres south affecting the west, north and east
coasts of the islands in the winter months from October to April.
the summer months, when the seas are calmer and the waves smaller, beaches
tend to build up. This process is known as accretion. If the amount of winter
erosion exceeds summer accretion, there is overall erosion with the land behind
the beach being eroded as the beach retreats inland. The rate of retreat is
called the erosion rate. Overall erosion may be due to one or more factors:
for example, a particularly severe winter swell, a recent hurricane, the death
of an adjacent coral reef or interference in the supply of sand. Conversely,
if accretion exceeds erosion, the beach gets wider over time and accretionary
features, such as cupsate forelands, tombolos, spits and bars, may develop.
Figure adapted from
|Winter beach conditions at Folkestone (Barbados). Following
a seve re winter swell, the waves have eroded the beach and cut into
the edge of the land, leaving tree roots exposed. In the background,
one large tree has fallen as a result of erosion.
Summer beac h conditions Folkestone, Barbados, 1980.
The dead trees have been removed and the beach has shown significant
build-up of sand. However, the exposed roots of the tree in the
fore ground indicate that the beach has not fully recove red from
winter erosion .
||STRUCTURES FOR BEACH PROTECTION
are three main groups of solid structures
which protect land and/or beaches : structures built parallel to the shore (seawalls
, bulkheads, revetments); structures built at right angles to the shore (groynes
and jetties); and offshore structures like offshore breakwaters .
Structures built parallel
to the shore are generally made of steel, concrete, rock or wood, and are
designed to protect land and buildings from erosion by the sea. They are the
most common means of protection found on island beaches. They come in all shapes
and sizes. It is important to remember that these structures only protect the
land. They do not promote beach accretion. In this sense, they can only be regarded
as a means of buying time, since erosion will continue in front of the seawall
and the beach will narrow or even eventually disappear.
walls are often built to separate private property from the beach.
are designed to protect land from wave action. Neither type of structure
promotes beach build-up. Figure adapted from Bush et al. (1995) 5
structures built at right angles to the shore, designed to trap the moving
sand transported in longshore currents which move parallel to the shore.
Their main function is to promote beach build-up by trapping sand or slowing
down its movement along the beach . Groynes are usually constructed of rock
or concrete and usually result in sand accretion on one side and erosion
on the other. Groynes function most effectively along coastlines where the
direction of longshore transport is constant. In the Caribbean islands with
their prevailing North easterly Trade Wind regimes, the predominant longshore
transport direction is from east to west. Experience has shown that groynes
work best along north or south facing coast lines. For
example, groynes have worked reasonably effectively on the north coast of
Nevis. Similarly, much of the south coast of Barbados has been stablized
from US Army Corps of Engineers (1981) 7
and groynes, Cock- burn Town, Grand Turk , 1995. The seawall and
groynes are protecting the coastal highway and buildings from inundation
by the sea. Note the absence of any beach in front of this seawall.
||ADDING MORE SAND TO THE BEACH
consists of adding large volumes of sand to the beach . The sand may be obtained
from an inland or offshore source. Since land sources of sand are limited in
the Caribbean, the sand is usually obtained from the offshore zone. The sand
and water mixture is then pumped via a floating pipeline onto the shore. Beach
nourishment has been little used in the Caribbean islands, unlike in North America
and other parts of the world. Generally speaking, it is an expensive technique
and not an option individuals choose, since it includes an entire beach. In
the islands, the cost of dredged sand ranges from US $ 5-16m
- 3. In addition, mobilization costs for the dredge may range from US$100,000
to US$300,000 depending on the location of a suitable dredge .
dredged sand in beach nourishment. A sand and water mixture is pumped
from the offshore zone into a settling pond on the beach, from which the
water will drain back into the sea. The sand in the settling pond is then
spread along the beach. Figure adapted from Cambers (1996). 8
- beach nourishment conditions , Pinneys Beach, Nevis, 1995. One week
after Hurricane Luis, the beach had been severely eroded.
- beach nourishment conditions, Pinneys Beach, Nevis, March 1996. Three
months after a sand replenishment project, there was a wide beach. However,
it should be noted that the observed sand accretion will also have been
partly due to natural recovery following the hurricane.
||NEW WAYS TO REDUCE BEACH EROSION
Several newer techniques
are now being used to protect beaches, including the use of beach face dewatering
to promote drainage of incoming waves. Beach face dewatering basically consists
of continuously pumping water away from the beach face. The system is based
on the idea that, when the water table under the beach is lower than under the
ocean, sand accretion is enhanced. As each wave rushes up the beach, water from
the wave easily drains through the dry beach, leaving part of its suspended
sand load on the beach. Less water drains back into the ocean taking less sand
with it, and the beach accretes. The technique involves the installation of
a specially designed drainage system under the beach, with pumps removing ground
water from under the beach.
facedewatering system . Figure adapted from Coastal Stabilization Inc.
is another technique that has been tried in the Caribbean, as in other parts
of the world. In one pilot project in Barbados10,
several hundred units of artificial seaweed were placed in the water. These
units consisted of 1.3 m long fronds atta ched to an anchor tube filled with
sand. The seaweed units reduce the speed of the current, there by allowing sand
to be deposited around and on top of the seaweed units. The hoped-for end result
is that the seaweed units are buried by an offshore sand bar, and that this
offshore sand deposit will then protect the beach from wave action. However,
experiments in Barbados with one type of artificial seaweed showed that the
particular material was not suitable for Caribbean waters, since it showed signifi
cant deterioration within eight months of installation .
The example serves as a
conclusion to this short article. A fair amount of progress has indeed been
made in understanding the processes of beach instability and in developing techniques
and technologies for combatting erosion and for rehabilitating degraded beaches.
But much remains to be done to translate scientific understanding into practicable
artificial seaweed units, Barbados, 1985. The fronds floating freely in
the water are designed to slow down the current and promote the deposition
||NOTES AND REFERENCES
|| History provides the example of Cockburn Town in the Turks and Caicos
Islands, where Back Street had to be renamed Front Street at the beginning
of the twentieth century as erosion took its toll.
||Cambers,G. 1998. Coping with Beach
Erosion. With Case Studies from the Caribbean. Coastal Management Sourcebooks
1. UNESCO Publishing, Paris.
|| Bacon, P.R. 1978. Flora and Fauna of the Caribbean, an Introduction to
the Ecology of the West Indies. Key Caribbean Publications Ltd, Port of
Spain, Trinidad .
Bush, D.M.; Webb, R.M.T.; Gonzalez Liboy, J.; Hyman, L; Neal, W.J. 1995.
Living with the Puerto Rico Shore. Duke University Press , Durham, North
||Komar, P.D. 1976. Beach Processes and Sedimentation. Prentice-Hall Inc.,
Englewood Cliffs, New Jersey.
US Army Corps of Engineers. 1981. Low Cost Shore Protection. A Property
Owner’s Guide. US Government Printing Office. Washington D C .
||Cambers, G. 1996. When the beach disappears. Sea Grant in the Caribbean,
Puerto Rico, January - March 1996, pp.3-5.
|| Coastal Stablization Inc. 1989. Stabeach: the Cost - E ffective, Long-Term
Solution for Stabilizing America’s Beaches. Brochure CS 2/89 009 2M. Coastal
Stabilization Inc., Tampa, Florida.
Atherley, K.A. 1989. Seascape ® synthetic seaweed. A failed solution
to erosion in Barbados. In: Coastal Zone ’89: Proceedings of the Sixth
Symposium on Coastal and Ocean Management, (Charleston, South Carolina,
USA), pp. 285-99.
Cambers, pages 43-49 in Nature & Resources Vol. 35 No.4, October-December
is a geographer and geomorphologist by training, with special interests in coastal
processes and in regional activities related to coastal management and research
in the Carribean.
Gillian Cambers, COSALC Coordinator,
Sea Grant College Program (SGCP-UPR), University of Puerto Rico,
P.O.Box 9011, College Station, Mayaguez, Puerto Rico 00681.
Fax: (1) 7872652880;
E-mail: email@example.com or