BARRIER ISLAND ROLLOVER evidence for rollover see pp

BARRIER ISLAND ROLLOVER evidence for rollover see pp. 24, 26

FACTORS INFLUENCING THE POSITION OF A BARRIER ISLAND • rate of sea level rise • sand supply • sea energy • human intervention

SEA LEVEL RISE • Ice age glaciers retreated 15, 000 years ago, sea levels rose- river valleys floodedsediments from rivers were trapped-sand transported by wind/waves from oceanside to bayside- island retreats inland • sea level rise along the Atlantic Coast has been 1 ft/century - barrier island retreat 100 -1, 000 ft/ century see p 24

SAND SUPPLY • with barrier island retreat sand buries backwater - marshes also retreat and are covered by forest, then dunes , finally coastline • longshore currents form spits through the deposition of sand • see p. 17

SEA ENERGY • storms can break through inlets and overwash, depositing sediments behind the island • see p. 36

HUMAN INTERVENTION • Ocean City Maryland plowed down dunes to build high-rises - dunes store sand, absorb wave energy- wave energy causes washover- sand deposited in backwater areas speeding up barrier island retreat

• dredging the offshore sands to replenish the beachfront • resulted in increased wave energy on the shoreline as offshore sands serve to buffer wave energy.

SUMMARY • BARRIER ISLANDS ALONG THE ATLANTIC COAST CONTINUE TO RETREAT TOWARD THE COASTLINE – SW, IF SEA LEVEL RISE CONTINUES THE RETREAT WILL BE AMPLIFIED