Monroe County is the southernmost county in Florida and comprises all of the Beach Restoration Management Planning District V. Located at the southwest tip of the Florida peninsula, that portion of the county that is located on the mainland is largely undeveloped and is mostly included in the Everglades National Park. Monroe County also includes most of the Florida Keys which is an elongate, arcuate archipelago over 220 miles in length from Soldier Key at the northeast end of the chain near Miami southwest to the Dry Tortugas. The Florida Keys are separated from the mainland by Florida Bay, a broad shallow marine system which is compartmentalized by numerous carbonate mud banks.

The Gulf of Mexico mainland Coast of Monroe County extends for approximately 54 miles between the southernmost portion of the Ten Thousand Islands region to the East Cape of the Cape Sable region. The mainland shoreline of Monroe County is predominantly characterized by fringing mangrove forests which range in width from 6 to 600 feet. The dominant plant species include the red, black, and white mangroves which are distinctly zoned with red mangroves occurring on the seaward exterior of forests and with black and white mangroves occurring on forest interiors. Numerous mangrove islands and tidal creeks dot this stretch of coast. A number of major tidal channels intersect the coast north of Cape Sable including from north to south: Lopez River, Huston River, Chatham River, Charlie Creek, Lostman’s River, Rodgers River, Broad River, Broad Creek, Harney River, Shark River, Little Shark River, Big Sable Creek, and Little Sable Creek.

The mainland stretch of coast also includes sandy beaches along the Key McLaughlin and Cape Sable. The 4 miles of Highlands Beach along Key McLaughlin and the 12.2 miles of beach along Cape Sable are the longest sandy beach segments in Monroe County and are as yet largely unstudied. These beaches are within the Everglades National Park and the access is difficult given their remoteness. These beaches are predominantly carbonate but their shore processes have not been well researched. The average width of these beaches is approximately SO feet and the estimated direction of net annual
longshore sediment transport is to the southeast.

Sandy beaches also exist throughout the Florida Keys portion of Monroe County fronting on the Straits of Florida and the Gulf of Mexico. Beach and dune formation in the keys is not common, and compared to the Florida peninsula, there is very little quartz sand on the Keys. The sand of the Keys beaches is of carbonate origin derived from the erosion of limestone, from aragonite particles precipitated from seawater, and from the fragmented remains of corals, cast-off shells, and calcareous algae.