Coastal Response to Storms and Sea-Level Rise: Santa Rosa Island, Northwest Florida, U.S.A

The western panhandle coast of northwest Florida is wave dominated and microtidal. Major storms are infrequent but have a significant effect on coastal morphology. Santa Rosa Island, a 75-kilometer long barrier, is the major coastal feature of the region. The island is narrow, with an average width of 500 meters. During most of the historical period, prominent foredunes, ranging as high as 7 meters, have helped keep the island's sediment budget in near equilibrium. This investigation compiled and georeferenced nearly two dozen historical shoreline positions from surveys and aerial photos, dating from the 1850s to the present. Time intervals between shoreline positions ranged from 30 years to multiple datasets per year. The U.S. Geological Survey's Digital Shoreline Analysis System (DSAS) was used to analyze the shoreline data. Analysis of the dataset reveals that storms have heavily influenced shoreline position. Shoreline retreat during the period from 1851-present has averaged less than 1 meter per year. Periods of more rapid retreat have been associated with the occurrence of major storms. A six-decade period of relative quiescence during the mid-20th century resulted in modest advance of the island's coastline. A cluster of three major storms during the period 1995-2005 had a major impact on the morphology and stability of the island. Much of the foredune complex was lost and rates of coastal retreat increased significantly. The historical shoreline data therefore underscore the dominant influence of storm frequency and intensity in determining coastal change. [PUBLICATION ABSTRACT]