Water And Oceanography

Beach Erosion



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Where's the Beach?

You've packed your sunscreen, your favorite bikini, a towel, book and lots of bottled water. But before you step one toe onto that beach, stop for a moment and take a good long look at where you are tanning. We tend to take it for granted that the golden sand naturally washed up from the ocean and blanketed out along the shoreline just waiting for our feet and beach umbrellas. But beach dynamics aren't quite that simple.

We live in a world of hurricanes, floods, and droughts, even global warming is said to play a part in our constantly changing shorelines. Residents in beach communities see the changes that occur to their beaches every year. Sometimes it's a steeper bank on the corner of an island where sand has washed up, other times, it is the loss of dunes from storm erosion. Whatever the case, the beach is often like a growing child that changes every year.

In the most unfortunate circumstances, beaches can be lost entirely after a major hurricane or a long storm season. Yet miraculously, that beach comes back and is there to enjoy again years later. Or is it such a miracle? How is that possible after a hurricane pulls away almost every grain of sand, leaving gaping holes or erosion that exposes dangerous underground structures? Perhaps it doesn't happen all by itself.

A closer look at the community of Tybee Island, Georgia can provide some answers. It is a small island located on the Atlantic, at the mouth of the Savannah River. The island has recently undergone a massive Beach Re-nourishment Program after losing a lot of sand over the last ten years due to storms. With one of the top ports on the East Coast only ten miles inland on the Savannah River, Tybee is a vital barrier island which must be well-maintained to protect a busy city and port which in turn affect many other areas of the country which need the items we receive on freighter ships from all over the world. Tybee Island was therefore a very strong candidate for beach re-nourishment.

So, what is Beach Re-nourishment? It is the process in which sand lost from the shoreline and washed out to sea is dredged back up and pumped to its former place on the beach. The cost of re-nourishment is usually over $1 million per mile of beach. But it is not done so the Paris Hilton's of the world will have a pretty spot to tan. Nourishment is an important part of protecting our coastline from storm surges, which extends to protecting homes, roads, bridges, ports, buildings, and of course human and animal life during a storm. On the recreational side, of course, there is the added benefit that re-nourishment increases space along a beach for human use and increases the buffer zone between existing homes and the ocean.

One issue that is critical in re-nourishment, is that the sand which is returned to the shoreline from the ocean, should be the same texture and color as the current beach sand. This is not for looks alone. The porosity of the sand must match what is already there so it all sticks together and holds in place. You can't just dump ultra-fine sand onto coarse sand or it will soon wash away. So re-nourishment should always involves returning the beach's own native sand back to land, rather than trucking in sand from other places.

However, there are some concerns for marine biology in this process. Dredging can affect some marine organisms, because it changes the seafloor where they live. This can include sand dollars, mollusks, coral and aquatic plants. In particular, coral needs light to survive and deepening the habitat where it grows as you remove sand from the seafloor, can make it harder for light to reach the coral.

Great care must be taken in the re-nourishment process to ensure that the dredging is not done too close to shoreline, as this can cause further erosion. The beach is also a habitat for sea turtles to nest in summer, so work is often done in winter to minimize the threat to these beautiful endangered creatures. A variety of sea birds can also temporarily lose their home, so working fast is a key to protecting various species from being affected. Re-nourishment efforts carry on day and night, to make the most out of the low tide times. Even over holidays, such as Thanksgiving 2008 when Beach Re-nourishment Technicians at Tybee Island worked on through Turkey Day to protect the beach as quickly as possible, so it would have the smallest possible impact on marine life. Not all beaches are good candidates for beach re-nourishment. If erosion has occurred for man made reasons (building too close and removing dunes to increase human areas) then the beach is not a good candidate and the human factors should be dealt with first. Beaches which are long and straight are better at maintaining re-nourished sand, as do beaches in inlets (pocket beaches). Those with rocky seawalls and shorelines, which do not have a lot of native sand, present a serious problem for re-nourishment efforts as the natural state is not suited for a sandy beach and it is unlikely that the sand pumped in will stay on shore. Nourishment is the best option when the erosion is mild to moderate. Other options are usually explored for severely eroded areas.

So remember before you lay down that towel on the warm golden sand this summer, take a good look up and down and the beach. There may be a lot more to appreciate than sun, waves, frozen drinks and warm smiles.

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