Barrier erosion Essay

This essay has a total of 1566 words and 7 pages.

barrier erosion

The Erosion of Long Island's Barrier Beaches
The barrier beaches, which line the south shore of Long Island are in a constant state of
change due to factor's such as wind, tides and wave action. "The term 'barrier'
identifies one that protects other features, such as lagoons, salt marshes, and bays from
direct attack from the open ocean" (Leatherman 1). The pebbles and sand of which these
beaches are made constantly lifted and deposited in other areas. Currents created by
tides and waves carry sediment and deposit it on beaches and in shallow water areas along
the shoreline. In this paper I will discuss wave activity, the most prevalent factor of
beach erosion. In addition, I will examine the roll of sand dunes and other ways of
preventing erosion.

The problem which many Long Island beaches face today is the element of erosion. More
sediment is carried away from the shoreline than is deposited. These elements of nature
make the barrier beaches very unstable features of Long Island's south shore. Wave
action, tides, and winds constantly change beaches and shorelines, and are the cause of
the many devastating effects of erosion.

The barrier beach which I have chosen to focus my research on is TOBAY beach, a beach
located just east of Jones Beach. Like TOBAY, barrier beaches are usually the result of a
sandbar which is built up and develops as an islands. They are continuously gaining and
losing sand, and slowly move landward. This is known as barrier island migration. "Sand
from the ocean side of the barrier is transported by water and wind toward the backside of
the island so that the whole landform gradually changes its location" (Leatherman 47). The
constant movement of sediment from the front of the beach to the back is known as
rollover. IF the barrier beaches did not move, they would eventually be covered by water.
In a way, barrier island migration acts against the effects of erosion. (McCormick 23)

Wave action is a major cause of beach erosion. The strength of these waves is determined
by the weather. "Waves are created by the wind blowing over the surface of the water,
transferring the energy of motion from air to water" (Press 421). Calm weather creates
smaller waves which approach the shoreline at regular intervals. Stormy weather creates
large waves which move at high speeds. The power if wind creates the power the waves. If
week winds prevail, small ripples form. However, if heavy winds persist, large,
destructive waves are created. "The height of waves increase as the wind speed increases,
the wind blows for longer times, and the distance over which the wind blows is increased"
(Press 421).

The breaking of waves is an important aspect of wave action. Since waves greatly effect
erosion and the condition of our beaches, it is important to understand how certain waves
"break". As a wave moves closer to a shoreline they break. The wave breaking action
occurs when the wave becomes so steep it can no longer support its weight. "Gently
sloping bottoms cause waves to break further away from the shore, and steeply sloping
bottoms make waves break closer to the shore" (Press 423). Breaking waves fit the
coastline carrying sand away and breaking up solid rocks. After the wave breaks, its
height is reduced. This spreads more water into direct contact with the sand. This is
when erosion takes place. When the water spreads across the sloping front of the
shoreline, it is called swash. Swash creates a backwash of water flowing back into the
ocean. This backwash carries sand along with it. "Fine sand can be moved by wave action
in water up to about twenty inches deep" (Press 423). This process is not only capable of
carrying sand grains, but small rocks as well. At the beach, I built a mound of sand up
near the water's edge. As waves came and smothered my pile, the mound began to get
smaller and smaller. Within 5-6 waves there was no trace of any mound that I had built.
This experiment portrays "swash" and how sand is carried away.

Another important aspect of wave action is refraction. Wave refraction is the bending of
waves as they approach the shoreline from an angle. The shallow bottom, the part of the
wave closest to the shore, hits first causing the wave particles to become more
elliptical. Thus, the wave and its particles are slowed down. This process continues as
the wave approaches the shoreline, and cause the wave to bend its face landward. The
swash then runs up the beach at an angle, and runs down in a similar manner. The
repetition of this process results in the displacement of sand particles. Long shore
drift is the cause of this displacement. Long shore drift and long shore currents working
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