| Coastal Change of Grand Strand Barrier Systems : A Rising Tide Project for Grades 9 and 10
Background |
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Intorduction and Background :
Classroom Activities:
| Short-term coastal processes: Shorter-term processes that contribute to coastal change and sediment movement include waves, winds and currents. Constantly coming into contact with the shoreline, waves can transport sand offshore to form a bar or further onshore helping to feed the dunes growing there. Winds likewise can blow dry sand from the back beach into the landward dunes. While longshore currents, formed by waves approaching the shore at an angle, flow parallel to the beach and carry sediments down the shore. Longshore drift , movement of sediment, is created by wave-action that approaches the shoreline at an angle, slows, and returns down the beach by gravity. This motion creates a sediment transport that flows parallel along the beach (Figure 1). The direction of the wave approach to the beach will determine the direction of the long-shore current and sediment transport along the beach (Figure ??). These sediments are important for nourishing beaches downdrift and building spits at inlets. Net transport along the South Carolina coastline is generally towards the south.
Storms are another major process that modifies the beaches. During storms, sediments along the beach are transported offshore to be stored in bars and during times of fair weather, wave-action causes these sandbars to move back toward the beach to eventually be re-deposited. In some cases, if the waves are large enough during a storm, some may wash over the beach-face and into the areas behind the dune systems. The sediments being carried by the waves in these situations create overwash deposits, or fanlike sand deposits that start at the back of a beach and fan out over the areas behind it . These deposits, which may never be returned, have larger implications for the health of a barrier system as they serve as a bank for future landward migration of the islands. |
