Sediment Deposition in Apalachicola Bay, Florida: a 200 Year Chronicle

Abstract

ABSTRACT Apalachicola Bay, Florida is the terminus of the state's largest river system. Economically, the bay is of considerable value and provides a significant income to a large proportion of the nearby population by virtue of its fishing industry. As such, any changes in sediment depositional patterns are important, whether the result of natural processes or those abetted by man. Bottom sediment maps compiled from recent and historic data over the past 150 years reveal that the bay is a truly dynamic system. Hurricanes have significantly altered the bay's bottom sediments on several occasions, both by scouring and re-distribution of sediment and by breaching of the fringing barrier island. Equally striking are changes directly traceable to the construction of dams on the contributory river system. Initially, dam construction resulted in a decrease in the coarse sediment load provided to the bay by trapping of sediment behind the dams; subsequently, accelerated erosion of Neogene-age sediments and widening of the flood plain below the lowermost dam have caused a recent increase in the quantity of coarse sediment now being supplied to the bay. An innovative method is described using examples from the bay that allows users to quickly, and quantitatively, identify significant changes in bottom sediment maps of bays, basins, estuaries, etc. The procedure makes use of readily available commercial software and provides the scientist with geological and environmental information that heretofore was either unavailable or obtainable only with a great deal of effort.