Abstract

This Florida Geological Survey (FGS) study was funded by the National Oceanic and Atmospheric Administration (NOAA). This study characterizes recently sampled sediments from the beaches of Escambia, Santa Rosa, Okaloosa, Walton, Bay, Gulf, Franklin, Wakulla, Taylor, Dixie, Citrus, Hernando, Levy, and Pasco Counties as well as the extreme northern beaches of Pinellas County. A total of 703 samples, 653 samples from 240 sites along the northwest coast of Florida and 50 samples from 39 sites in Florida’s Big Bend were collected, described and photographed. Selected samples from each location were granulometrically analyzed. Photographs, descriptions and the results of granulometric analyses are provided.

The study area on the northwest coast of Florida was comprised of the beaches of Escambia, Santa Rosa, Okaloosa, Walton, Bay, and Franklin Counties. The study area in Florida’s Big Bend was comprised of the beaches of Wakulla, Taylor, Dixie, Citrus, Hernando, Levy, Pasco and northern Pinellas Counties. These study areas were broken down into 12 and 7 reaches, respectively. On the northwest coast of Florida, where the beaches are more continuous, these reaches are defined by geographic boundaries such as inlets and passes as well as the mouths of rivers, harbors, and bays. The study often showed a correlation between these boundaries and changes in grain size. Progressing eastward along the northwest coast of Florida, as the Big Bend is approached; beaches are occasionally bounded by stretches of coastline where beaches are absent due to coastal erosion. Progressing into the Big Bend and southward through the region, beaches become uncommon. Those beaches that are present are bounded by tidal marshes. Moving further southward across the Big Bend, the barrier island complex of the southwest coast of Florida was reached and beaches again typify the coast.

The trend from west to east along the northwest coast of Florida shows a general eastward decline in mean grain size to Cape St. George. From Cape St. George eastward, there is an increase in mean grain size to the beginning of the Big Bend east of Franklin County.

Changes in grain size, define three regions in the northwest coast of Florida: (1) The first region is defined by the area bounded by sample locations ES-01 and BY-15. This region extends from Perdido Key to just west of the mouth of St. Andrews Bay. In this region, the mean grain size curve generally declines eastward. The curve peaks on Perdido Key, in western Escambia County, on Santa Rosa Island, in eastern Escambia County, and on the mainland beaches of western Bay County. (2) The second region is defined by the area bounded by sample locations BY-16 and FK-15. This region extends from just west of the mouth of St. Andrews Bay to Cape St. George on Little St. George Island. The mean grain size in this region averages lower than that in the regions to either side. (3) The third region is defined by the area bounded by sample locations FK-16, on the east side of Cape St. George, and FK-65, at the mouth of Ochlocknee Bay. Mean grain size generally increases eastward across this region. This region shows the largest variances of mean grain size evidenced in any of the three regions.

As the beaches of Florida’s Big Bend are highly discontinuous, regions based on changes in mean grain size alone could not be defined. Three regions in Florida’s Big Bend were identified within the study area: (1) the beaches of Wakulla County, which owe their existence to being proximal to sand sources on the northwest coast of Florida, (2) beaches in Levy and Dixie Counties, related to the ancestral Suwannee River and relic dunes and (3) the beaches of Pasco County and extreme northern Pinellas County that are more properly considered to be the northern most extension of the barrier island complex of the southwest coast of Florida. All of these beaches are more or less in a natural state. In contrast, the remaining beaches in the Big Bend, lying in Taylor, Dixie, Citrus, Hernando and mainland Pasco Counties, are geographically limited, narrow and frequently man-made.