HIGH-ENERGY MODIFICATION TO LANDSCAPES BY HURRICANE ISABEL AT FISHERMAN ISLAND, VIRGINIA

Fisherman Island is an emergent barrier island in the entrance to the Chesapeake Bay. Initially, elements of the island emerged from the shallow shoreface about 200-250 years ago. In 1865, Fisherman Island had a total land and marsh area of about 60 ha. In 2002, the combined marsh-land surface area exceeded 900 ha. Fisherman Island is the most rapidly accreting barrier island on the Virginia coast. The island is not the result of rapid spit progradation but rather the collection of sediments in the entrance to the Chesapeake Bay caused by converging wave crests. Wave refraction sweeps sandy material to a focal point where it is driven ashore by shoaling waves. Bipolar currents along the Fisherman Island shoreline have produced a regular pattern of dune ridge sets expanding the south west corner of the island and a chenier plan of hammocks lengthening the east edge of the island. The sequence of ridges and cheniers reveal patterns of island development over the past 150 years. Each set of dune ridges and cheniers represents a temporal stage in a chronosequence of island development. Fisherman Island is a low-profile island with elevations generally less than 3 meters above high water. In September 2003, hurricane Isabel made landfall in northern North Carolina. Northeast winds from the storm pushed water into the entrance of the Chesapeake Bay producing storm-surge estimates of 2-3 meters. Much of the island surface was submerged during elevated water levels. The southeast corner of the Fisherman Island received the full impact of storm winds causing significant overwash for the first time in over 100 years. The overwash caused major modifications to the landscape and eradicated many geomorphic features that provided a sequential record of island development. Although a large percentage of the island was flooded during the storm, not all surfaces revealed the same degree of modification after re-emergence. Terrain modification by overwash was significant at submerged surfaces wind windward exposures. Submerged surfaces with leeward and oblique exposures to the wind had only minor modifications following re-emergence.