Generally speaking, a beach is a narrow strip of land along the coast of a waterbody. It can be made of various materials, including sand, gravel, rocks, seashells, and cobbles. It is sometimes called a bay. Beaches are very popular for recreation and tourism. They can range in size from a small, rocky beach to hundreds of kilometers in length. Beaches are often polluted, however, and some of the materials they contain may be hazardous to human health.
Beaches are created by waves that pound against the shore. They break down rocks and debris into smaller particles, which are then carried away by the ocean currents. The ebb and flow of the tides then smooth out rough edges and create sand. The ocean currents can move sediment hundreds of kilometers away, or carry it closer to the shore.
In tropical areas, the primary source of beach sand is coral reefs. The coral skeletons contain calcium carbonate, which is the same stuff as shells. In other regions, sand is typically created by weathering. It is made of quartz and feldspar, a mineral that is tan or brown in color. Some sand is also eroded from nearby cliffs or from the rocks in the Gulf of Mexico.
The main threat to beaches is natural coastal erosion. It is caused by storms and longshore currents. In some coastal areas, storms are unable to carry beach sand over dunes. A storm may generate high surf that erodes the beach. The storm may also spread sandbars along the shoreline. This is why most communities want to keep their shorelines in better condition. The process of beach nourishment has been successful at combating erosion. In order to extend the beach, sand is trucked onto the shoreline.
In some coastal regions, such as the Gulf of Mexico, beach nourishment may be combined with the construction of a seawall to protect the shoreline from erosion. The wall may be made of concrete or rock. Depending on the nature of the beach, the wall may also include trees or shrubs to protect the beach.
The coastal zone that is undergoing active sand movement extends to at least 9-12 meters below low tide. This zone is known as the shoreface. It is usually located on the seaward side of a barrier island, and it is intended to strengthen the coastal profile. The most important purpose of beach nourishment is to extend the beach beyond the point of natural erosion. It can also displace the location of breakers farther offshore.
Beach nourishment may also have other benefits, such as improving the habitat for selected species of biota. It is best to perform beach nourishment in a series of small additions at a time, rather than adding a large amount in one go. This may allow natural wave motion to spread the sand more easily. The addition of coarser sediments to a sandy beach may also cause the loss of some species.