Coastal erosion

Coastal erosion is the process in which water, wind, and other forces wear down and carry away sediment from the shoreline, causing loss of land along the coast. Coastal erosion is a natural process that causes beaches to change over time. However, human development along the coast and strong storms exacerbate coastal erosion. Because many cities are situated near the coast and beaches are profitable to the tourism industry, it is often in an area's economic interest to stop natural and unnatural coastal erosion, if possible. However, this can have its own environmental consequences.

Overview

Coastlines are not static, permanent locations. For example, the swelling and shrinking of beaches over time is a natural process. Storms can pull large amounts of sand away from a beach, and eventually smaller waves deposit much of it back. Sometimes beaches disappear completely because the waves take their sand to another place. Other times, beaches are the recipient of sand from another beach. Even rocky shorelines naturally erode, if more slowly, due to the persistent action of waves and tides as well as wind, rain, ice, and other natural forces. At coastal river mouths or deltas, the flow of water and sediment can reshape the shoreline gradually, or more rapidly in major flood events.

Throughout history, such natural coastal erosion was generally not given much consideration by humans. While many population centers arose near shorelines, by necessity they typically prioritized relatively stable ground. Areas known to have frequently shifting shorelines, such as barrier islands, often law limited development. When cities did arise in areas prone to coastal erosion, significant preventative measures such as seawalls and flood control systems were put in place and public attention to the issue was largely limited to major flood or storm surge events. Many societies operated on the belief that humans could and should exercise control over natural processes.

Beginning in the nineteenth century, the rise of the tourism industry led to increasing shoreline development, especially in areas with plentiful beaches. By the late twentieth century and continuing into the twenty-first, some coastal communities were heavily reliant on tourism. If beaches in these places erode, the local economy is significantly threatened. Therefore, coastal erosion earned increasing concern. The rise of the modern environmental movement in the mid-twentieth century also brought more attention to coastal erosion, though for different reasons.

Ironically, the coastal communities that depend on tourism economically in many cases exacerbate coastal erosion. They have removed essential beach plants, such as shrubs and grass, to make beaches look more pristine—but these plants help hold sand in place. Additionally, they have built structures such as buildings and roads too close to the beach. This disrupts the entire coastal ecosystem because these structures press down on the sand and alter how the wind moves along the coast, causing more sand to wash out to sea. Foot traffic from many tourists also contributes to coastal erosion.

Scientists also theorize that many past attempts at combating coastal erosion, while successful in the short term, will accelerate the process in the long term. A common reaction to coastal erosion is to build a seawall, which is supposed to stop or break up large waves to prevent soil from being washed away. However, in a complex reaction, seawalls actually amplify the power of small waves inside the wall. These small waves—the waves that normally deposit sand on beaches—slowly pull the sand from the beach into the area behind the seawall. To make matters worse, sand that would naturally drift toward the beach is stopped at the wall, causing it to accumulate on the outside of the wall. As more sand accumulates there, the area's surface increases and the rate of sand being caught increases with it.

These sudden changes cause some beaches to lose more than forty feet of shoreline per year. Left unchecked, these beaches will shift to other locations or cease to exist entirely. While some environmentalists contend that since these communities caused this, they should be left to fail, others have sought ways to preserve the beaches. One method is known as beach replenishment.

During beach replenishment, thousands of tons of sand are dumped onto a beach in an attempt to replace the sand that has washed out to sea. Sometimes the sand is taken from the bottom of the nearby ocean or from other beaches. Other times, it is artificial and made of crushed glass. The sand is then packed down with bulldozers and large trucks until it appears natural.

While this process replenishes the beach, it is not a perfect solution. For starters, it is expensive—the process costs millions of dollars, and the communities benefiting from the replenished beach often must foot most of the bill. Additionally, replenished sand erodes much faster than naturally deposited sand. This means the expensive replenishment process must be repeated more and more often over time. This has led to questions of whether it is affordable long-term.

Beach replenishment is also considered harmful for the area's wildlife. The sand that is brought in may not be the correct type of sand for the area, causing small animals and corals to be smothered and die off in large numbers. This can seriously disrupt the local food chain, reducing or eliminating populations of wildlife at the beach. Dredging, dragging sand up from the bottom of the ocean, also harms the area where the sand is taken from. Most living things in the seabed are killed in the process.

Many environmental scientists believe that the only way to effectively combat coastal erosion without harming the environment is to stop heavily developing beaches. They advise people to build or relocate houses and large structures off the beach so that these structures do not interfere with the natural environment. Preserving or replanting natural shorelines plant species is recommended to help slow the most destructive coastal erosion. Scientists also insist that when beach replenishment is done, it must be done much more carefully. For example, the types of sand found on beaches could be studied and cataloged so that beaches are replenished only with extremely similar sand.

While progress is being made on combating coastal erosion, scientists warn that coastal erosion may soon become much worse. As global climate change continues to accelerate, more of Earth's polar ice caps and glaciers will melt. This will raise sea levels, engulfing many of Earth's beaches by dragging the sand out to sea or redistributing it in ways that are difficult to predict. This process may also make seasonal storms more common and violent, accelerating the process even more. Scientists warn that if urgent action is not taken, many existing beaches will be seriously threatened. Additionally, it is not only beaches that are at risk. Rising sea levels will accelerate erosion in and around coastal cities worldwide, potentially displacing millions of people and causing other disruptions such as tainted drinking water.

Major Examples of Coastal Erosion

In the United States, coastal erosion has affected many popular beach areas in the late twentieth and early twenty-first centuries, such as Malibu, California; Cape Cod and the island of Nantucket in Massachusetts; and the New Jersey shore. Erosion has been a particular problem for these locations due to their large number of beachfront properties, which can become uninhabitable as erosion progresses. The outer coast of Louisiana has also been especially badly affected, losing approximately fifty feet of beach per year.

Dunwich, England, once the capital of the Kingdom of East Anglia and a major trading port of the medieval era, suffered coastal erosion beginning in the late 1200s. By the twenty-first century, the city had become a small village, most of its former land area lost to the erosion. While, as Dunwich's example illustrates, erosion has always been an issue for the United Kingdom, the rate of erosion has increased with the effects of climate change, such as rising sea levels and increased storms. In addition to beaches, coastal erosion has also affected the UK's chalk cliffs; the famous White Cliffs of Dover were losing about one centimeter per year by the late 2010s.

The islands of Japan underwent significant coastal erosion after World War II due to rapid development during that time period. Erosion has continued in the twenty-first century; the country has made extensive use of concrete structures known as Tetrapods to attempt to slow the disappearance of coastal land.

Bibliography

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