How to Read a Florida Gulf Coast Beach; A Guide to Shadow Dunes, Ghost Forests, and Other Telltale Clues from an Ever-Changing Coast by Tonya Clayton. University of North Carolina Press, 2012, paper.
Florida’s beaches vary in structure but, nevertheless, have a common set of characteristics. They can be “read” if you know what you are looking for. Tonya Clayton has made this easier. She describes the beaches lining the Gulf of Mexico but not our more famous Atlantic Coast beaches. There are few beaches in Florida’s Big Bend country. The Cedar Keys, in the middle of the Big Bend, are an exception. Seahorse Key, one of them, is known for is towering, ancient sand dune, the tallest in Florida. The panhandle has wonderful quartz sand beaches, as does the Florida peninsula from Tampa Bay south almost to the Florida Everglades.
Our sand is mostly foreign to peninsular Florida. It is the result of the erosion of the Appalachian Mountains. Rivers brought sediments to the Gulf Coast and waves, tides, and wind contributed to the drift of sand along the coast from north to south. Clayton corrects the oft heard expression, “river of sand.” Rather the beaches are the result of a slow process of sand shifting over short distances, over long periods of time.
Clayton proceeds to name and explain the various forces that have shaped the coast over the millennia. But first, she describes the structure of a Florida Gulf Coast beach. There is a near-shore zone, an over-wash zone, a back beach with its dunes and intervening swales, and commonly a lagoon behind the dunes. The shoreline is always on the make, and you can observe this by the several ridges where there is a slight change in the dip of the beach. Clayton reminds us that beach formation needs room. That is a partial explanation for the absence of beaches along the Big Bend.
Throughout the book there is much talk of threats to our shores, and certainly estuaries are threatened. Estuaries are formed at the mouth of a river where its supple of fresh water mingles with tidal seawater. That mingling has produced a flora and fauna unique to estuaries, and that environment can be easily disturbed.
Sea levels are rising. But that has been so for the last five millennia.
Sea grasses and other flora anchor the shore line, and reduce the movement of sand. We much admire sea oats and applaud conservation efforts. When this normally hardy plant life dies off from various causes, the sand begins to shift around and the beach structure crumbles.
Florida, fortunately, is not prone to tsunamis. But we do have wave surges during hurricanes and tropical storms. Joined with a high tide, they can be devastating. Hurricane Ivan in 2004 caused a storm surge that was ninety-one feet above sea level. It deposited three feet of sediment along twenty-five miles of coast.
Signs of an advancing (moving seaward) shoreline? They include coastal ridges parallel to the shoreline which attest to abundant incoming sand. Sign of a retreating (moving landward) shoreline. Ghost forests: trees dead and dying, drowned in salt water.
The small bluffs measuring from a few inches to a foot, carved into the sand are familiar to beachgoers. Scarps a sure sign that the winds and the sea are in the process of claiming more land.
Looking closely at the wrack line reveals exuberant life amidst piles of debris just behind the wash zone. It often marks the latest high tide line. Sargassum (gulfweed) and various species of algae harbor a universe of flies, beetles, and beach hoppers. They attract shore birds pecking through the wrack. And sadly, they anchor human junk: cigarette butts and filters are the most common, lots of plastic cups, food containers, and beverage bottles. It takes fifty years for a foam cup to disintegrate.
Occasionally there is an outcropping of coquina rock. In the absence of better building stone, coquina was used in earlier centuries as a building material on the east coast, though less commonly on the Gulf side of the peninsula.
“Beach remodeling;” there is a lot of it going on. Coastal engineering includes armoring beaches with sea walls, bulkheads, and retaining walls. Beaches are ‘nourished’ by bringing in sand from distant sources or often by dredging just off shore.
Clayton reminds us that there are both beneficial and dire effects of these efforts to protect the beach from the weather – and man’s folly. One common complaint about beach nourishment is that the new sand doesn’t match the color and texture of the old. It is true that sand comes in various hues and can vary in composition, particularly in its shell content.
Grab your hat, sun screen, insect repellent, drinking water, a towel, and let’s head for the beach.