FREE ESSAY ON WAVES IN THE SHORELINE

WAVES IN THE SHORELINE

When waves approach shore and feel the bottom, water piles up and breakers form. This
process proves that a shoreline is not static. Primarily these waves, breaking at an
angle to the shoreline, are what generate a long shore current that parallels the shore.
The long shore current not only moves water in the surf zone, it also moves sediment
parallel to the shoreline. Long shore current is a function of the angle of wave
approach. For example, if the waves approach the shoreline from the south, long shore
current moves from south to north 
Although, long shore current and the resulting transport of sediment is only one of the
dynamic processes that constantly alter the shoreline. As waves repeatedly hit the shore,
water moves onto the beach and then retreats in a continuous cycle. However, the waves
are not all that moves on the shoreline. In fact, the sediment on the shore is also
always on the move. Great energy is expended on the beach as waves crash against the
shoreline. This energy allows the water to transport sediment. The grains are lifted as
the waves in the swash zone move onto the beach, and then the grains are deposited again
as the water retreats. As long as the waves hit the shoreline "straight on", the wave
crests are parallel to the shoreline, the sand grains will be picked up and redeposit in
the same general area. In this case, no real net movement of sand occurs in the swash
zone. 
Waves generally do not form parallel to the shoreline, and thus, usually approach the
shore at an angle. Consequently, beach sand will have a net movement up or down the
beach, depending on the direction of incoming waves. Sand grains are transported as the
waves move onto the beach. Therefore, the sand grains are being carried in the same
direction that the waves are moving. However, when the water retreats, due to gravity it
goes straight back perpendicular to the shoreline and not back in the opposite direction
from which it came. Since grains are redeposit as the water retreats, the grains are
actually deposited further down the beach or down long shore current. The net overall
movement of sand is down current. The sediment that has moved down shore is replaced by
sediment from further up shore, as long as sediment is available there. If the waves hit
the beach from the south, the net movement of sand will be to the north as we saw last
week at the Loyola beach. Net beach sediment movement can change back and forth with
shifts in wave direction. In spite of this, along any particular shoreline one direction
for incoming waves usually dominates resulting in a preferential net movement of
sediment. 
Sand and water work together consistently on the shore. Many years of this procedure of
waves movement will result in one side with more sand than the other. The side with less
sand, in conclusion, will be replaced with sand poured in by humans.