|
|
Information on Beach Erosion and Re-nourishment Nearly half of the United States population lives within eighty kilometers of the coast. The beach is the boundary between the water and the land; it is an area for human settlement and agriculture. Our beaches form the shapes of bays and harbors and provide fresh water for coastal towns. The beaches of the US and the rest of the world are teeming with economic and ecological growth. The United States has 19,000 miles of beaches, 500 miles of which have been set aside in ten national seashores. Each national seashore is protected by its own legislation and managed by the National Park Service. Recently, erosion has become one of the most alarming threats to regional, national and international beaches. Erosion is the wearing away, or corrosion, by which material is taken away from the earth's surface. Most erosion results from the combined activity of several factors: heat, gases, water, wind, gravity and plant life. GREENHOUSE WARMING Lately, one of the leading causes of beach erosion has been greenhouse warming. Greenhouse gases such as carbon dioxide, nitrous oxide, methane and chlorofluorocarbons are generated by human activity (like the combustion of wood and fossil fuels). These gases are accumulating in the atmosphere and trapping the sun's radiation heat. Trees are also being cut down in massive quantities, leaving fewer forests to recapture the chief greenhouse gas, carbon dioxide. The onslaught of global warming is likely to increase the frequency of tropical storms which tear sand away from beaches. The increasing concentrations of greenhouse gases in the atmosphere are likely to raise the average temperature of the earth from 2.5 degrees Celsius to 5.5 degrees Celsius over the next century. The level of the sea is also expected to rise with warming seas and the melting of polar ice caps. The EPA (Environmental Protection Agency) estimates that the seas could rise by 2100 anywhere from half a meter to two meters. A one meter rise by the year 2075 could result in widespread economic, environmental and social disruption. SUBSIDENCE The beaches of the world are the continents' defense against the rising sea. The coasts can absorb the storms by changing their shapes and then rebuilding themselves during periods of gentle waves. Human activity however interferes with the natural cycles of the ocean. When ground water is over pumped and sedimentation interferes with ground water and rivers, subsidence occurs and the land begins to sink. The more populous a region becomes, the more likely subsidence will occur. America's population is growing by about 2.6 million people every year. Where humans interfere with river systems, sediment shoots past lowlands and is taken out to sea or blocked upriver, creating more severe shoreline erosion and a relative increase in sea level. The heavy development of beach resorts and other coastal areas means that few wetlands have the means and time to slowly reestablish themselves upland. THE PROCESS OF EROSION During a storm, a beach gives up to the water sand it has been storing in the dunes. The waves carry the sand to the sea and leave the sand on the bottom floor of the ocean. During calm periods, erosion reverses. The sand is moved offshore and slowly land ward by the orbital motion of gentle waves. The ocean currents and waves keep the beach in perpetual motion. The existence of cliffs on a coast indicates that erosion is taking its toll on the beach. Waves hurl themselves at the cracks in the cliff wall. The pressure of the water and the compressed air creates a wider crack, causing the earth to break off into pieces. More waves grind the pieces of earth together to make sand. The chemical reaction of salt water and oxygen breaks down rocks which come into contact with sea water. Most of the sand movement about a beach occurs in and just beyond the surf zone: waves and currents hold particles of earth in suspension until the weight of the particles causes them to sink. When every wave breaks on the beach, a thin layer of sand is carried along. When the wave retreats, the sand is taken back to the surf zone. After a storm, a vertical cut in the high point of the beach (the berm) and a steeper, sloping beach face shows that large waves have claimed a great deal of the shore. Big waves have more power to hold more sand particles in suspension and take sand off the beach than smaller waves. Both the energy and the steepness of a large wave carry the sand seaward. Calm seas have waves which have enough energy to carry sand away but they leave more sand on the berm than they carry away to sea. MASSACHUSETTS BEACHES The beaches of the Atlantic are broad, long and straight. The slope of the beaches is so shallow as to be all but imperceptible; a series of small rises in sea levels can add up to a dramatic retreat from shore. The EPA estimates that Northeast sea levels will double in the next century due to global warming. The beaches of the Massachusetts shore are pummeled by hurricanes and Nor'easters, the frequency of which has declined recently. The number of severe storms on the other hand has risen in the past several years. The beaches of Cape Cod, developed and trodden upon by tourists and residents, retreat further each year. The islands of Nantucket and Martha's Vineyard face a more uncertain future that anyone would have imagined fifty year ago; if the coast of Nantucket retreats thirty feet per year, the island will be gone in 600 years. CAPE COD Cape Cod's oldest lighthouse, the Highland Light, is moving. The Atlantic Ocean has swallowed 400 feet of the lighthouse's front yard since its construction in 1797. In the past seven years, a series of harsh winter storms has eaten up forty feet of the coast, leaving the lighthouse 100 feet from the ocean. More than a year ago, a $1.5 million Army Corps of Engineers project began. A new foundation was created 150 yards west of the falling bluff. In Eastham, the Nauset Light also needs to be moved; it stands 45 feet away from the Atlantic surf. The lighthouses of the cape are less essential but are still beloved landmarks. 14,000 years ago, Cape Cod and Martha's Vineyard were formed by melting glaciers. The two areas have no bedrock to anchor them and prevent the ocean from pushing around their beaches. In Chatham, nine homes have fallen victim to the sea in recent years. Cape Cod is protected as part of the National Seashore. Development is regulated, but the feet of humans and the warming of the world's and the seas are still causing destruction on the beaches of the Cape. The Province Lands is an expanse of dunes, woodland and seashores compromising the outermost hook of Cape Cod. The Lands are teeming with wildlife- red fox, coyote, white-tailed deer, hog-nosed snakes, great horned owls, marsh hawks, piping plovers, blue herons and herring gulls. It takes as few as twenty human footsteps to destroy the beach grass Amophila breviligulata. Amophila grows up through new layers of sand and stabilizes dunes with its elaborate root system. Poison ivy is everywhere on the Province Lands; an efficient soil-binder, it covers large areas as a trailing vine or low shrub. NANTUCKET Since colonial times, the South Shore of Nantucket has retreated a half mile. The eastern shore has lost some hundred feet of beach in the last decade. Muskeget Island off Nantucket has moved more than 1,000 feet eastward since the 1800s. Nantucket has nothing to slow down breaking waves except the Nantucket Shoals to the east, which are the sandy remains of what was dry land several thousand years ago. These shoals have most likely caused a dramatic increase in erosion at Codfish Park on Nantucket. Storms might have shifted the shoals so that waves are funneled through the breaks in the sand and concentrated on Codfish Park. Erosion on Nantucket's South Shore is at a rate of about fifteen feet a year. At least 25 buildings have either been condemned or destroyed since the 1980s. If nothing is done to curb erosion, fifty to sixty more homes could be destroyed in the next ten years. OTHER US AREAS IN DANGER Some EPA estimates claim that between eighty and ninety percent of America's shoreline is eroding. The cities of New York, Miami and New Orleans are in perilous danger. Not only is land being lost but so is expensive real estate and housing on these highly developed coasts. Most of greater Miami lies at or below sea level on reclaimed land from the Everglades. Fifty percent of New Jersey's famous beaches have been reduced to mere rubble. North Carolina's Topsail Island, located one mile off the mainland, is listed by geologists as one of the most storm vulnerable barrier islands off the Atlantic Coast. Topsails' three townships were built on not much more than sand. INTERNATIONAL EROSION Egypt, Thailand and the US are just a few of the countries where extensive coastal land degradation, with very small changes in global sea level, is contributing to large-scale land loss. The Netherlands is a nation built on the river deltas of the Meuse, Rhine and Scheldt Rivers. The country contains 250 miles of carefully maintained dikes and 120 miles of sand dunes. The Netherlands spends heavily to protect itself from the onslaught of erosion. The Nile and Bengal river deltas are other areas where human activities are interfering with the normal earth processes that could balance out the effects of rising water levels. These low-lying regions are normally in a dynamic equilibrium, forming and breaking down in a constant pattern of acceleration and subsidence. In England, the cliffs along the Yorkshire Coast (which encompasses farm and residential land as well) are swallowed by the sea at a rate of nine feet per year. The British 1,100 miles of seawalls and other coastal defenses are also failing. In 1991, the United Kingdom spent fifty-eight million pounds on maintenance and reconstruction to protect its shores. SOLUTIONS- ATTEMPTS, FAILURES AND THE FUTURE Because of the continuing development of the planet's coasts and the long lead time involved in the building of dikes and other structures, decisions on solutions regarding erosion must be made fairly soon. Measuring the real environmental cost is difficult because traditional economic models don't show that barriers built to hold back the sea can contribute to the decline of ecosystems vital to wildlife and ultimately humans. The choices regarding the future range from establishing de-watering systems, planting soil-binding plants, retreating from the coasts or building extensive protection devices. RENOURISHMENT PROJECTS "Beach renourishment projects" are programs supplying coastal towns with piles of sand, artificial beaches and dune-lines. These projects are carried out and largely paid for by the US Army Corps of Engineers. The Corps has spent billions of dollars to carry out its engineered solutions to natural depredations on all of the country's shorelines. Additional sand makes the beach flatter and forces waves to shoul and break earlier, lessening erosion. The solutions provided by the renourishment programs include jetties, revetments, seawalls, groins, bulkheads and breakwaters. Coastal geologists have given a name to the results of the renourishment attempts: Newjerseyization. New Jersey was the first state to undertake intensive development and fortification of its beaches. 27% of South Carolina's developed shoreline is armored, as is 80% of Georgia's and nearly 100% of New Hampshire's. Many people feel that hardened structures such as those provided by renourishment programs are too expensive, will eventually fall prey to raising sea levels and make problems worse. Over the past 45 years, more than 200 cubic yards of sand has gone to re-nourish America's beaches. Sand can cost as much as $5 per cubic yard; a new beach can cost $2 million per square miles. For a typical Corps project, 65% of the cost is undertaken by federal taxpayers and the remainder of the cost is paid by state and local governments. In the US, $10 million- $15 million is spent annually on beach renourishment projects and more on hard structures. Renourishment must be done again and again, as the process replaces only limited parts of the whole beach system. The construction of hardened structures may save real estate but it actually accelerates beach erosion. The presence of a seawall may concentrate the power of waves breaking in the surf zone, because the waves have less room to expend their energy than they do when rolling over a natural beach. In recent years, the further construction of hardened structures has been banned by Maine, North Carolina and South Carolina. INTERNATIONAL STRATEGIES Worldwide development has increased dramatically during the past several decades, especially in developing countries who look for cheap, quick means towards wealth. Poorer countries partake in water projects leading to subsidence, policies that encourage deforestation and development programs based on fossil-fuel intensive technologies. All such activities lead directly or indirectly to beach erosion. The world has offered anti-erosion proposals such as raising energy efficiency, curtailing fossil fuel use, finding substitutes for CFCs and stopping rampant deforestation. Another option for coastal countries is to retreat people and buildings from the shore. Abandoning shores is not practical, however, with large coastal cities and certainly not popular with coastal home owners. In the UK however, "managed retreat" has become increasingly more popular. The British government has a list of forty areas, where, as an experiment, the sea will be allowed to follow nature's directions. MASSACHUSETTS' ATTEMPTS In the sands of Salisbury Beach State Reservation, volunteers are planting the shoots of American beach grass in an effort to preserve the state's dunes. The beach grass is barricaded by fences in an attempt to prevent people from walking on it. Storms do not only sweep away chunks of the earth but also threatened species of sea grasses vital to holding the sand in place such as swamp oats, sea lyme and sea beach needle grass. The Massachusetts Task Force handles areas of high priority concern while the Volunteer Conservation Corp takes care of low priority plants. On Nantucket, artificial reefs to large amounts of new land are being considered as possible erosion solutions. A "Beach De-watering" System was buried under Siasconset Beach; the system is supposed to reduce the water content of the beach on the hypothesis that a drier beach acts as a magnet for sand. This system however gets knocked out by storms and costs $1.3 million in private money and $600,000 in state and federal money. As the dunes retreat, their sands are blown inland over the forests and marshes behind them. As the level of the oceans rise, the tides carry more of the shore out to sea. Scientists bicker over the actual severity of the greenhouse effect and global warming. Some experts deny that worldwide temperatures and seas are rising. But every year the land becomes a little smaller and the oceans a little bigger. Human activity certainly plays some role; over the past 100 years, global sea level rose ten to fifteen centimeters. The rise used to be one to ten centimeters per century. Sooner or later, if erosion is not curbed, human populations may be faced with only one choice: retreat from the sea and leave the beaches to nature. BIBLIOGRAPHY Allen, Scott. "Losing Ground Against All Odds, Nantucket Is Trying To Hold Back The Sea." The Boston Globe. June 30, 1996, pg. 29. Associated Press. "Erosion-Fighting Army Digs In Volunteers Plant Grass To Protect Massachusetts Dunes From Wind and Waves." The Boston Globe. April 21, 1996. Carroll, Matt. "Split Views On Rivers Protection Law Realtors Resigned, Environmentalists Thrilled." The Boston Globe. August 25, 1996. Graham, Wade. "Beaches." The New Yorker. December 16, 1994, v40, pg. 58. Griffin, Rodman D. "Threatened Coastlines." CQ Researcher. February 17, 1992, vol. 2, No. 5, pp 99+. Henderson, Keith. "Mean Nor'easters Brew In A Complex Stew of Winter Weather." Christian Science Monitor. March 9, 1994, pg. 15. Henson, Robert. "Hurricane In Disguise: Some Winter Storms Sport a Tropical Look." Weatherwise. December/ January 1995-1996, pp 12-17. Howe, Peter. "A Moving Landmark Traveling Light With 450 Tons." The Boston Globe. June 30, 1996, pg. 29. Jacobson, Jodi L. "Holding Back The Sea." Futurist. September/ October 1990, pp 20-27. Jacobson, Jodi L. "A Really Wosrt-Case Scenario." Oceanus. Summer 1989, vol 32, No. 2, pp 37-45. McLaughlin, Jeff. "Boston's Treasure Islands National Park Designation Has Officials Discussing Management, Funding." The Boston Globe. October 13, 1996. Peters, Robert and Reed Noss. "America's Endangered Ecosystems." Defenders. Fall 1995, pp 16-27. Rezendes, Paul. "The Province Lands." Yankee Magazine. March 1995, vol 59, pg. 64. Stuller, Jay. "On the Beach." Sea Frontiers. December 1994, pp 28-34. Stutz, Bruce and Katharine Whittemore. Audubon. May/ June 1994, pp 38-59. Watson, Ben. "New Respect For Nor'easters." Weatherwise. Dec 1993/January 1994, pp 18-23.
This page was researched by a senior environmental science students at Needham High School. Students chose topics that were of interest to them and concerned an environmental issue. The project was overseen by Mr. McDonald, the environmental science teacher at NHS. These kids have class ;-) Related Links: |
|
"Serving Destin, Ft. Walton Beach, Panama City, Pensacola, Crestview, Eglin AFB, Hurlburt Field and all points in-between..."
|
