MORPHOLOGICAL IMPACT AND POST-STORM RECOVERY OF HURRICANE IVAN ALONG NW FLORIDA BARRIER-ISLAND COAST

Hurricane Ivan induced substantial morphological impacts along NW Florida’s barrier-island coastline stretching from St George Island westward to the landfall site of its eastern eyewall in Pensacola. This strong category three hurricane, a one time Category 5 Hurricane in the Gulf of Mexico, had a widespread impact on the barrier islands of NW Florida. Dramatic morphological impact was measured more than 250 km from landfall of the eastern eyewall. Regional barrier inundation, overwash, dune scarping, and back beach erosion were observed extending from west to east for over 250 km. The purpose of this study is to quantitatively document the Ivan impact and short-term post-storm recovery for a large area of over 250 km.

On September 14, the day before landfall of Hurricane Ivan, ten pre-storm beach profiles were surveyed at four barrier-island locations extending from Ft. Walton Beach to St. George Island. A week later, on September 22-23, these same locations were surveyed and a baseline for damage and recovery measurements was established. Overall, dramatic beach/dune erosion was measured as far east as St. George Island. The post-storm surveys will continue monthly through August 2005 as part of a longer term study of the Ivan impacts. A series of aerial photos were taken from the eastern eyewall landfall site to St. George Island two months after the impact. The purpose is to examine the regional characteristics and extent of barrier inundation and overwash, in addition to the beach profiles. This visual imagery was used to determine the percentage of inundation, overwash, and dune scarping.

Data collected through the middle of December indicates a relatively rapid initial beach recovery in the form of ridge-runnel growth and attachment to the shoreline. In addition, it is apparent that recovery of back beach erosion by Hurricane Ivan is proceeding much more slowly than the foreshore and that one of the fresh overwash deposit areas have undergone considerable erosion by eolian transport, losing as much as 0.5 m overwash platform elevation in one month.