Storm overwash, rollover migration, and sea-level rise response
Barrier islands migrate landward through rollover: storm overwash carries sand from the ocean-facing beach across the dune crest and deposits washover fans on the back side (lagoon side), simultaneously eroding the seaward face. Sea-level rise accelerates this process by increasing storm surge reach and shrinking the accommodation space. If the rate of sea-level rise exceeds the island's capacity to accrete vertically (through washover and aeolian deposition), the island eventually drowns in place — a fate many Atlantic coast barriers face this century.