Post on 21-Jun-2020
VIRGINIA BARRIER ISLAND BACKGROUND
Virginia's barrier islands are part of a barrier island chain extending 2,700 miles from Maine to
Texas. These thin strips of sand provide valuable habitat for wildlife, protect the mainland from
the storm-driven fury of the ocean, and attract thousands of vacationers in the summer. For these
varied reasons, the barrier islands of Virginia are important natural resources. If improperly
managed, these islands could be lost; therefore, they are an ecosystem that deserve our attention.
The Islands and Their Location
Virginia's barrier island system is composed of 13 islands stretching 75 miles along the
oceanside of the Eastern Shore. The southernmost island is Fisherman, at the mouth of the
Chesapeake Bay. Fisherman Island is the smallest of the barrier islands, only 1 mile in length.
Although crossed by the Chesapeake Bay Bridge Tunnel, the island is not generally open to
visitors. It is a national wildlife refuge managed for the benefit of nesting shorebirds that spend
the spring and summer there.
Smith, Myrtle, and Ship Shoal islands are the next three islands to the north of Fisherman. They
are owned by The Nature Conservancy, a private conservation organization. As part of the
Conservancy's Virginia Coast Reserve, these islands are maintained as undeveloped natural
areas. Although there are some restrictions, the islands are open to the public. Access is not easy,
however, because the islands are not connected to the mainland and the only way to get to them
is by boat. The purpose of keeping these areas undeveloped and of limiting public access is to
preserve a natural beach system for future generations to enjoy.
Wreck Island is owned by the Virginia Division of Parks. It is also maintained as an undeveloped
natural area with limited public access.
To the north of Wreck Island are Cobb, Hog, and Parramore islands. They are natural areas in the
Virginia Coast Reserve. These islands at one time had thriving communities, but were
abandoned when shoreline erosion began to take its toll. Domestic animals such as goats and
cattle, left behind by the residents, survived in the wild on the islands. Many of these animals
were finally rounded up and removed to the mainland by the Nature Conservancy. The domestic
animals were disturbing the natural habitats and native animal species on the islands.
In contrast to the islands of the Coast Reserve, Cedar is a privately owned island that has been
developed. Beach cottages line the oceanfront where grass-covered dunes would otherwise stand.
It resembles the resort beaches of the East Coast rather than its neighboring barrier islands.
Beyond Cedar Island is Metompkin, the northernmost island in the Virginia Coast Reserve. With
Metompkin, Parramore, Hog, Cobb, Ship Shoal, Myrtle, and Smith islands, the oceanfront
property managed by The Nature Conservancy totals 50 miles.
The other privately owned island in Virginia's chain is Assawoman Island. The Nature
Conservancy is working to purchase this island for the Coast Reserve.
Wallops Island is owned by the federal government and is used by NASA as a rocket-launching
area. Although a bridge to the mainland makes access possible, Wallops Island is off-limits to the
public because of the government activities there.
Assateague is the northernmost, longest, and probably the most well-known of the barrier
islands. It extends north to Ocean City, Maryland. Although 33 miles in length, only 14 miles lie
within Virginia's borders. The entire island is federally owned. Part of i t is designated a
national seashore. Most of the Virginia section is a national wildlife refuge. This
island is the most familiar to the public because it can be visited by car. The area is managed
with both the wildlife and the public in mind. The beaches, marshes, and woodlands that are
inhabited by a variety of flora and fauna are easily observed from .well-maintained trails
and roads.
Formation of the Islands
When and how did Virginia's barrier islands form? Scientists believe that the islands formed
within the last 18,000 years when the last Ice Age ended and sea level began to rise. They
propose several theories for the formation of the islands:
Beach ridges became islands when rising water broke through and flooded the area behind
them. The new islands remained above sea level by migrating westward as sea level
continued to rise.
Offshore sand bars became islands after being built up above sea level.
Spits became islands after being breached by storms.
It seems as if the barrier islands do not have a common origin; each island is unique. The islands
probably formed under a combination of conditions.
Present Morphology
However the barrier islands were first formed, they are all now shaped by winds, waves, and
currents. The wind sculpts dunes from sand deposited above the water line. Waves work the sand
at the beach face and are responsible for the onshore-offshore movement of sand. Gentle waves
push sand onshore, building up the beach and providing sand for the dunes. Rough storm waves
erode the beach, carrying sand offshore where it is stored as bars. When gentle conditions return,
the bars move back toward the beach. The longshore current is generated by the waves that break
on the beach at an angle. The current flows within the surf zone parallel to the beach and carries
sand suspended by the waves. Longshore transport of sand along the East Coast is generally to
the south.
As a result of the wind, wave, and current actions, Virginia's entire barrier island system
migrates south and west. Sand, transported by the longshore current, moves south through the
system barrier by barrier. Sand also moves west, pushed by the continually rising sea level.
Overwash during storms carries the sand to the backside of the islands, allowing them to migrate
to the west.
Valuable Coastal Buffers
Barrier island systems are dynamic. Sand comes and goes, and the islands migrate; yet, they
maintain their identity above sea level. Because of their ability to withstand the power of the
ocean, barrier islands are valuable coastal buffers. They protect the mainland from the full
impact of storm winds, waves, and tides.
Valuable Coastal Habitats
Barrier islands provide habitats for wildlife. Because the islands have often been inaccessible to
man, the animals have been left undisturbed, which is particularly important during nesting
season. A walk across an island will take you through several habitats:
1. Beach
The beach is not an easy place to live. It can be quite hot during the day and cold at night. The
waves stir the sand, preventing rooted plants from growing. Salt in the water and in the air has an
adverse effect on many organisms. To survive here, animals must protect themselves from the
waves and tolerate salt water. Mole crabs and coquina clams are well adapted to life here. Their
streamlined shapes allow them to burrow quickly when a wave approaches. Other creatures live
higher up on the beach away from the waves. They protect themselves from the heat by hiding
under debris or by being more active at night. Ghost crabs are common inhabitats of the beach at
the base of the dunes. Many animals visit the beach to feed. Gulls, terns, and shorebirds eat crabs
and fish, or scavenge debris. These birds also nest on the beach.
2. Dunes
The dunes are far enough from the water that they are not normally worked by waves; therefore,
rooted plants can grow there. In Virginia, the common dune grasses are sea oats and American
beach grass. More animals can live in the dunes where they are protected from the waves and salt
water and can find shade among the grasses. Insects dominate the animal community in the
dunes. On the backside of the dunes shrubs such as wax myrtle and live oak appear. Perching
birds and small mammals inhabit the shrub thicket.
3. Swales
Swales are low areas between dune lines on a barrier island. Swales are often filled with fresh
water, creating a pond habitat where freshwater plants and animals live. The ponds are important
sources of fresh water for the animals that live in an environment otherwise surrounded by salt
water.
4. Maritime Forest
The maritime forest grows behind the dunes and the shrub thicket. The trees need as much
protection from salt spray as possible. In Virginia, loblolly pines, live oak, yaupom holly, and
black cherry grow in the maritime forest.
5. Marsh
Marshes are found along the backside of barrier islands. They fringe the shoreline of the sounds
that separate the islands from the mainland. The marsh grasses such as big cordgrass and
saltmarsh cordgrass can take root in the quiet waters of the sound. The grass provives food and
protection for many small animals. About 95% of the commercial fish and shellfish species in
Virginia spend some part of their lives in a marsh.
Man's Influence on the Barrier Islands
The Indians used the barrier islands as places to gather food. They recognized the potential
hazards of living on the open coast and only made seasonal hunting trips to the islands. When the
colonists arrived in Virginia, they did not initially settle on the islands. They were used by pirates
as hide outs and staging areas for raids. People who needed to escape from the growing society
found refuge on the barrier islands. Eventually, small communities, often founded by victims of
shipwrecks, popped up on some of the islands. These early inhabitants recognized the dynamic
nature of the islands and would simply pick up and move if the settlement were threatened by the
encroaching beach. Many settlements were completely abandoned when residents moved back to
the mainland.
In more recent times, the barrier islands have been viewed as ideal vacation spots. As the pace of
daily life increased, people went looking for an escape. Barrier islands, offered not only peace
and quiet but a variety of recreational opportunities, the perfect place to build a vacation home.
But, there was a catch to all of this - beach migration. Barrier islands are not stable. They are in
dynamic equilibrium with the present set of wind, wave, and current conditions. Although an
island looks the same from day to day, it has actually moved. The movement is imperceptible in
the short term, but is very obvious year-to-year or after a storm. This movement is natural beach
migration, but, to the oceanfront landowner, it is beach erosion!
What does the landowner do? Suddenly finding the ocean at the doorstep, the landowner wants
to protect and preserve the home. Barrier island residents of the past would move inland or back
to the mainland, but this resident thinks he or she has too big an investment to abandon the
property. So, groins, bulkheads, or riprap are installed. These structures may provide temporary
relief for the immediate area, but they are not a long-term solution. In fact, is there any longterm
solution? Remember, the culprit behind beach migration is the continuing rise in sea level. So
far, man has been unable to halt this force.
Most attempts at stabilizing the barrier islands for the sake of private homes have come at the
expense of the islands themselves.. Structures placed on the beach and in the dunes for
stabilizing the sand interfere with the natural onshore-offshore and longshore movement of sand
that maintain the islands against the forces of the ocean. When that system is interfered with, the
result is often a net loss of sand. The island can no longer maintain its identity in a steadily rising
sea and begins to disappear.
Developers see the islands as prime oceanfront property for resort and residential development.
Conservationists see the islands as unique biological and geological systems that should be left in
their natural state. How should the barrier islands of Virginia be managed?
Cross-section of a Barrier Island
Beaches, Sand, and Currents
The United States coast from New Jersey to Florida has many sandy beaches. But these
beaches are not all alike. Where wave action against the beach is heavy, the sar.d grains are
large. The beach itself slopes sharply into the sea. Less exposed beaches tend to have wide,
shallow shores with gentle slopes.
The most common mineral in sandy beaches is quartz, which comes from Inland on the
continent. Rock fragments are eroded away by rivers and carried down to the ocean. When these
pieces of rock reach the ocean, they are pounded into tiny grains by the movement of waves
against the shore. Other sources of materials for sand are rock outcroppings along the shore and
the shells of marine animals. Along the coast of North Carolina, for example, as much as 10% of
the beach materials are ground-up shells. Farther south the sands are made from weathered rocks
carried by rivers from the Appalachian Mountains. Still farther south the eastern beeches of
Florida can be almost pure quartz or quartz mixed with shell and coral.
Some of the most beautiful and valued beaches in
this region are on barrier islands. These are islands
of sand built up by the ocean and parallel to the
mainland. Barrier islands are formed along gently
sloping sandy coasts where the water remains
shallow far from the shore. Their name comes from
the fact that these stretches of sand are between the
ocean and the mainland. Figure A shows barrier
islands, the lagoon behind, their inlets, and a river
that empties into the lagoon.
Once formed, barrier islands are far from
permanent. Giant winter storms with their huge
waves can form new inlets or close older ones. During these storms, lave amounts of sand can be
dug from one place and deposited elsewhere along the beach. Even during the calmer weather of
summer, the ever-present surf is constantly reshaping the islands. Breaking waves carry sand
wish them as they run back into the sea. Longshore currents pick up this sand and move it down
the coast Since the Longshore Currents in this area usually move southward, they are slowly
carrying the barrier islands in that direction. Where there is an arm of land into the ocean or an
Inlet, sand is deposited on the north side and eroded away on the south side. This constant
migration of sand can cause entire sections of beach to disappear or the mouths of inlets to move
as much as 25 meters a year.
Because barrier islands are such splendid areas, many
people want to live and work on them. To do so, they try
to change the Island to fit their needs. Figure B shows
how the people who live In Fishville plan to change Blue
Inlet. They want to stop the migration of the inlet by
putting in jetties, or walls, along the inlet. Should this
plan be carried out? Look at the diagrams and the
information, and then answer the following questions.
BARRIER ISLAND STUDY
Objective
Analyze the natural and political forces that may influence the existence of barrier islands and
beaches
Background Information
Sea level was much lower during the last ice age, so deposits of sand on the continental shelf
were exposed to the action of wind and waves. Blown by the wind and moved toward shore by
the waves, the sand was piled up into large dunes. Submerged sandbars broke the surface and
moved toward shore as barrier islands. Some merged with the mainland while others formed
islands offshore.
Severe storms cause 'washover' on the barrier islands carrying sand into the bays on the landward
side. As sand is removed from the ocean and deposited into the bay, the island migrates slowly
landward.
Barrier islands also move parallel to the coast due to the longshore currents, in the direction that
the current is moving. One side of the barrier builds up while the other is eroded-both due- to the
movement of the long shore currents.
Vocabulary
Shoals – submerged sandbars
Lagoon – quiet body of water separating barrier islands from the mainland
Longshore current – current moving parallel to the shore caused by waves striking the beach at
an angle
Materials
Student copies of Barrier Island Study Map of Virginia’s Eastern Shore
Procedure
A. Using the background information and the map provided, answer the following questions:
1. Why are the Virginia barrier islands a valuable natural resource
2. Are all barrier islands formed in the same manner?
3. What shapes the barrier islands today?
4. Where does the Virginia’s barrier island migrate?
5. Label the missing parts of a beach in diagram 1. Then label the different zones in
diagram 2.
6. What are 2 reasons that barrier islands are so valuable?
7. Explain your trip over a barrier island starting at the beach and working your way bact
into the bay.
8. What is the most common mineral in a sandy beach?
9. How far can an inlet move each year? Why?
10. Complete the analysis questions. Yes you have to think- these may be your opinion!
Analysis
1. How does the Blue River contribute to the formation of barrier islands?
2. Why do you think people at Fishville are concerned about the movement of Blue inlet?
3. If you were the State Park Director how would you react to the plan? Why?
4. If you were in charge of the Coast Guard Station explain how would you react to the plan?