SPATIO-TEMPORAL ANALYSIS OF DECADAL-SCALE PATTERNS IN BARRIER ISLAND RESPONSE TO STORMS: PERDIDO KEY, NW FLORIDA

This investigation employed a suite of coastal data-topographic maps, high-resolution satellite imagery, aerial photography and lidar survey data to establish decadal trends of shoreline movement along a barrier island located on the wave dominated and microtidal northwest Gulf of Mexico coast. Perdido key is a narrow, 24 km long, sandy barrier island located in escambia county, florida, and baldwin county, alabama. The island is of low topographic relief and has an average width of approximately 0.35 km. The barrier is composed of undeveloped areas with minimal anthropogenic modifications along the island’s eastern section while the western portion is characterized by residential and tourism-related infrastructure. An extensive collection of shoreline data was assembled for the project, comprising nearly two dozen historic shoreline positions dating from the mid-19^th century to the present.the usgs dsas and a more recently developed tool, ambur techniques were used to evaluate the shoreline data and detect morphologic change over time. The results show that the barrier shoreline is a highly dynamic feature with distinct zones of erosion and accretion. For a significant period in the mid-to late 19^th century, the shoreline was moderately stable. Over the 93 year time interval (1920 – 2013), approximately 54 percent of the perdido key shoreline experienced erosion with the remaining 46 percent of the shoreline advancing. The average rate of change along retreating shorelines over the long-term (1920-2013) was found to be -0.52 m/yr, while the mean rate of change along advancing shorelines was +0.44 m/yr. A cluster of four major storms had a significant effect on the coastal morphology and stability of the island over the recent period of unusual storminess (1998 – 2013) with an average rate of erosion of -2.33 m/yr during that interval. The eastern, undeveloped portion of perdido key is dominated by retreat, while the western, developed segment is advancing. These trends appear to be strongly associated with the presence of offshore bathymetric features. The historic shoreline data reveal that periods of rapid retreat have been associated with the occurrence of major storms and emphasize the dominant influence of storm intensity and frequency in determining coastal change