Coastal erosion occurs when sand is removed from shorelines in one way or another.
Coastal erosion causes the shapes of shorelines to change due to the removal of sand from shores and beaches. A variety of factors moves sand from beaches to other beaches, further inland, into the deep sea and into ocean trenches. Currents and waves can return sand from the ocean to the shoreline, but replacement generally occurs at a slower rate than removal. The rate of erosion varies by location. The southern shore of Rhode Island, for example, retreats between 1 and 2 feet per year. Rocky West Coast beaches only experience several inches of erosion per year.
Natural Causes
Waves, ocean currents and tides all contribute to coastal erosion. Waves are caused by the rotation of the earth and wind blowing over the surface of oceans. When waves hit beaches, sand is removed from the shore as the water retreats back to the ocean. Ocean currents are like rivers within oceans. The Gulf Stream is a current that travels from Florida along the eastern coast of the U.S., then towards Europe. Currents push sand from shorelines to other locations. Tides are normal increases in sea levels caused by the gravitational pull of the sun and moon. They also pull sand from beaches into the ocean.
Catastrophic Events
Catastrophic events are major storms or natural disasters, such as hurricanes and earthquakes. These events exacerbate the effects of the natural causes of erosion. The high-speed winds and large waves generated during hurricanes, for instance, can take a large toll on coastal regions. A powerful hurricane could cause the shoreline to recede up to 30 feet at Matanuck beach in South Kingston, Rhode Island. Tsunamis are extremely large waves caused by earthquakes that can severely damage shorelines. A tsunami that struck Sri Lanka carried beach sand 500 feet inland.
Man-Made Structures
Levees and dams are often constructed to protect coastal property from the effects of catastrophic events. These structures, however, contribute to coastal erosion by preventing sand from being redeposited on shorelines. For instance, more than 3,000 square miles of coastal wetlands in Louisiana have disappeared since 1900 because of levees constructed where the Mississippi River meets the Gulf Coast.
Sea-Level Rise
Changes in sea levels have been apparent throughout human history, but sea levels have been rising at an accelerated pace recently due to global warming. Sea-level rise is not technically a cause of coastal erosion, but can be viewed as a contributing factor. Oceans have risen 16 inches over the past century and are predicted to rise another 24 over the next century. Sea-level rise has a direct effect on the appearance of shorelines, causing them to retreat. Sea-level rise can also minimize the effects of geological structures near shores that prevent erosion.
Tags: sand from, coastal erosion, Coastal erosion, contribute coastal, contribute coastal erosion
