Beaches - Products of
Waves and Sand
are collections of loose sediment deposits, usually consisting of
well-sorted sand, in a coastal zone. They exist between the height
of storm surge waves and the level of the low tide
Beaches - Products of
Waves and Sand
are collections of loose sediment deposits, usually consisting of
well-sorted sand, in a coastal zone. They exist between the height
of storm surge waves and the level of the low tide. A beach consists
of two regions: foreshore and backshore. Nearshore regions are always
underwater, but are still affected by coastal processes such as
storm wave action and currents. The foreshore is comprised of the
normal intertidal region and generally has a 2-10 degree slope.
The angle is controlled by a combination of grain size and typical
wave energy for that shore. The backshore area slopes landward,
is generally wider than the foreshore and may contain one or more
berms, or terrace-like area.
The beach shown to the left is an example of a backshore at Canaveral
National Seashore. If you look closely you may be able to tell
that the beach's angle steepens as it meets the waves - this, depending
on the height of the tide, could be the plunge step, or a slight
Wave energy is determined by a number of factors: prevailing winds,
current, and slope of the shore. Wave
energy increases with increased winds and current. A shorter,
steeper slope will result in more erosive intensity than a long
slope. If the slope is too shallow the waves will break before reaching
the beach, diminishing the erosive power. Longshore
drift, or current that runs parallel to the coast, moves sand
lengthwise down the beach. This drag influences the migration of
sand and, over time, barrier islands.
Assateague Island National Seashore (in the lower half of the image
at right) has moved coastward, or west, in relation to Fenwick Island
since the construction of a sea wall, en placed to protect the channel,
an important shipping conduit. This shift is caused by a combinatio