Beaches, Sand and Beach Renourishment
In the interests of understanding the problem created by sand pumped onto beaches for beach renourishment, let us look at the littoral system and understand it. The sand for our Florida beaches comes originally from the erosion of rocks in the southern Appalachian Mountains. The sand resulting from erosion is carried to the seashore by rivers. Some of this is trapped by dams built for hydroelectric energy generation (The first human mistake) The remaining sand is carried south by the large NE waves of winter in a series of zig zag motions collectively called "littoral drift". Anything that interferes with this southward transport hurts our beaches; jetties, groins, etc. (The second human mistake.) Much of this sand is returned during small summer waves, but a portion stays in deeper water. This means a continuous loss, year after year, from our beaches to the shallow offshore. North of Boca Raton there are few "First" and "Second" reefs. They have been covered with sand. The problem is compounded dramatically by all the Inlets along our coast where, in violation of a 1987 State edict, they are not bypassing 100% of the sand coming to the north side of these inlets. Boca Raton Inlet is a particular offender in this respect, but it is not alone.
The result of the State NOT enforcing its 1987 rule means that most beaches lose the sediment transported offshore AND ALSO the sediment trapped in shoals offshore of inlets and on the north sides of jetties, such as north of Port Everglades where a huge area has been filled by sand NOT bypassed to the south to Lloyd State Park. Beaches then either hang on by their teeth, or retreat, sometimes dramatically. So we cure this problem by dredging up some of the sand lost offshore over the last 11,000 years, and placing it back on our beaches. In the meantime marine creatures recolonize areas where hard bottom has been exposed, but more importantly, we have high siltation, because the offshore sand is usually high in the finer sediment (silt) which is washed seaward again by waves. Corals have only modest ability to cleanse themselves of silt and frequently die or are stressed beyond their ability to survive other anthropogenic impacts,: global warming, pollution, noise, anchor dragging etc.
Most of you realize that we must keep our beaches or we lose the tourist dollars that keep Florida "green". When we place offshore sand on our beaches, the fine fraction is carried offshore and aggravates the other impacts. Their are a significant number of "treasures" under our waters that are potentially in danger from this beach renourishment. Locating and video recording these treasures has been a major avocation of Frank Schmidt of Lighthouse Point. Working in conjunction with Coastal Planning and Engineering personnel, and especially with the not for profit group, Vone Research Inc., he has identified some of these treasures and would like to know of more that some reader might have found. His intent is to try to preserve some or all of these from siltation, and in some cases, from direct burial by dredged sediment. We believe that their exposure of at least one such site caused authorities to change plans to place sediment adjacent to an important "treasure".
One long term solution is to import aragonite sand from the Bahamas, where billions of tons blanket the shallow banks. This sand is coarser, so it does not move offshore as easily, has almost no silt in it, because it is washed free of silt and coarse material in the Bahamas. It is beautiful buff colored, with egg shaped grains of calcium carbonate, the same substance as the shell sand on many south Florida beaches. Research proved that turtles DO nest in aragonite sand as readily as in Florida beach sand, that Phragmatopoma worms DO make wormrock using aragonite and we have solved the Buy American and the ship to shore pumping problem. If we can make a suitable arrangement with the aragonite miners, Florida can have beach nourishment at little cost to the environment.
Dr. Ray McAllister