A beach is a landform along the shore of an ocean, river or lake, made from granular material such as sand, gravel, pebbles, cobbles and shells. A beach may also contain other materials, such as organic matter and human-made objects such as plastics. Beaches can be used for recreation and are often the focus of tourism industries.
The term beach can be applied to a large area of coastline, but a more precise definition refers to a sandy shore that is relatively shallow and has little wave action. Its slope is usually gradual and it is backed by a dunes of natural or man-made materials, such as timber jettys or vegetation.
A sandbar is a submerged ridge of sand or coarse sediment that is built offshore from a beach. It forms when the swirling turbulence of waves breaks off a beach and excavates a trough in the sand. Sand suspended in backwash and rip currents adds to the bar, as does sand moving shoreward from deeper water.
Geological sand comes from the weathering of rocks, while biological sand is made up of the broken pieces of coral skeletons and other shells from marine plants and animals. Many beaches are composed of a mixture of these two types of sand.
As sand moves through the water, it is sorted by size and density, with lighter, less dense grains being carried away by waves and currents. Over time, these grains will accumulate to create a beach. The size and composition of the beach can be influenced by local factors such as the shape of the coastline, wind direction, tidal movements, the type of seabed rock on which the sand is deposited, and whether a river or stream feeds the area.
Beaches provide habitat for a range of organisms, including sea grasses, coral reef fish, clams and oysters. They are important sources of nutrients, as runoff from the beach carries silt and organic matter to coastal waters. This may help to sustain coastal ecosystems by supplying food for fish and other aquatic life. Beaches are also vital as a source of sediment to build up barrier islands, lagoons and deltas.
Since the 19th century, the popularity of beaches has grown, with a variety of activities taking place there, from swimming and sunbathing to recreational boating, fishing, surfing, windsurfing and diving. They are also a major location for a variety of leisure activities and can serve as an amenity for residential developments. A beach can also be the site of a variety of recreational and commercial facilities, including lifeguards, showers, changing rooms and shacks. Many beaches are supervised by government agencies, in order to maintain public safety and environmental conditions. Those beaches that have not been developed for commercial purposes may be protected by legislation to safeguard their environmental quality and natural character. These beaches are often called wild or natural beaches. Some are even protected under international law, such as the United Nations World Heritage Convention.