RATES OF ESTUARINE SHORELINE CHANGE IN EASTERN FLORIDA DURING A PERIOD OF RAPID ANTHROPOGENIC CHANGE, 1940S TO 2009

Using a modified version of an advanced shoreline change analysis geospatial tool (AMBUR, Jackson et al., 2012), we present the first estuarine shoreline change rates for eastern Florida for 1940s-2009, a period of rapid coastal development. The Guana Tolomato Matanzas NERR in NE Florida is one of the fastest growing regions in the state. We digitized and classified 431 km of shoreline from the 1950s (1:2000 scale digitization), 444 km from 1984 (1:1500), and 721 km of from 2009 (1:700). 48% of the transects demonstrate moderate to severe retreat (>0.2 m/y). ~16% of transects had > 1 m/y of retreat. ~ 12 km of retreating shoreline in the northern half of the NERR and ~20 km of retreating shoreline in the southern half of the NERR are along the Intracoastal Waterway that appears to have been modified between 1950s-1984. Larger creeks feeding into the NERR from the west have experienced relatively minimal change in shoreline position. Matanzas Inlet is the most dynamic part of the study area mostly due to flood shoal migration. < 1% of transects had more than 1 m/yr of advance and only 10% of transects could be classified as advancing. Areas of advancing shoreline are <1 km intervals of marsh accretion along the western shoreline of the estuary, usually where there are oyster bars channel-ward of the shoreline. The second study area is the Indian River and Mosquito Lagoons within the Canaveral National Seashore/Merritt Island National Wildlife Refuge. A majority of the study area is undeveloped mangrove and marsh shoreline, with only ~12 km of developed. The majority of the NE IRL was modified before the 1980s by dredging and diking. 316 km of shoreline from the 1950s (1:2000 scale), 299 km of shoreline from 1984 (1:1500 scale), and 336 km of shoreline from 2009 (1:700 scale) was digitized. 75% of the shoreline has no change since 1950. Only 19% of transects had >0.2 m/yr of retreat, and only 3% of transects had > 1 m/yr of retreat, which is most often associated with removal of dikes and wetland restoration since 1984. Other areas of higher shoreline retreat are associated with shoreline modification since the 1940s. < 1% of transects had >1 m/yr of advance and only 7% of transects could be classified as advancing. Areas of shoreline advance are almost all anthropogenically influenced, either through causeway or dike construction.