A beach is a narrow gently sloping strip of land that lies along the edge of a body of water such as an ocean lake or river. Beaches are composed of materials such as sand pebbles rocks and seashell fragments that have been washed to the shore by waves currents and winds.
Beaches are popular recreation spots for humans and animals. They are often surrounded by a variety of facilities such as lifeguards, changing rooms, showers, shacks and bars. Beaches also play important economic and cultural roles in some areas by driving local tourism industries. In some places beaches are protected by man-made structures like sand dunes and seawalls.
The sand, gravel and silt that cover a beach is called a beach substrate. It varies in thickness depending on the environment and the type of sediment that forms it. Coarse sand forms in zones of high current and wave activity, while fine sand silt and mud cover the seabed in more sheltered zones. Beaches are constantly changing over time due to natural beach processes, including erosion and deposition.
Long-term erosion of a beach is sometimes caused by a structural imbalance between the supply and export of sediment. This may be the result of a change in littoral drift (see: Littoral drift). Erosion can also occur because of a shift in the flow of sediment, such as an increase in cross-shore currents or a decrease in longshore currents.
A beach berm is a nearly horizontal and shore-parallel ridge formed on the beach by the transport of the coarsest fraction of the sediments ejected by the wave uprush. The berms are a characteristic feature of beach morphology and they form over the backshore and tidal flats. Beach berms are a common feature of barrier islands and barrier spits.
An offshore sand bar is a sand ridge that extends seaward of a beach and is connected to the beach by tidal deltas and submarine sand bars. The sandbars are typically elongated in the direction of the current and they develop in convergence zones where tidal currents meet. They are also found in estuaries and tidal lagoons.
An offshore sandbar that stretches out into the sea between two points of equal depth is called a double sandbar. Double sandbars are not uncommon and they can be created by a number of different factors such as tide currents wind etc. They can be very dangerous for swimmers because they often create rip currents which lead to drowning incidents. Rip currents are strong offshore-directed currents that are discharged through gaps between nearshore sandbars when high incident waves break over them.