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

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

SEA LEVEL RISE Ice age glaciers retreated 15,000 years ago, sea levels rose- river valleys flooded- sediments from rivers were trapped-sand transported by wind/waves from oceanside to bayside- island retreats inland Ice age glaciers retreated 15,000 years ago, sea levels rose- river valleys flooded- sediments 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 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 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 longshore currents form spits through the deposition of sand see p. 17 see p. 17

SEA ENERGY storms can break through inlets and overwash, depositing sediments behind the island storms can break through inlets and overwash, depositing sediments behind the island see p. 36 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 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 dredging the offshore sands to replenish the beachfront resulted in increased wave energy resulted in increased wave energy on the 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 BARRIER ISLANDS ALONG THE ATLANTIC COAST CONTINUE TO RETREAT TOWARD THE COASTLINE – SW, IF SEA LEVEL RISE CONTINUES THE RETREAT WILL BE AMPLIFIED