A beach is a rocky coastline where waves break and sand, pebbles and other sediment are deposited. Beaches are found in many bodies of water, including lakes, rivers and some large ponds. A beach may have a varying extent of sandy and gravelly material but is always characterized by a water’s edge with loose materials like sand, cobbles and shells. A beach is not only an environment for humans to enjoy, it also provides habitats for marine life, such as fish, crabs, clams and sea turtles.
Beaches are dynamic natural features that change over time. The process of beach formation involves a complex interplay between wind, waves and currents, weathering (breaking down of rocks into smaller fragments), erosion, deposition, and accretion. Beaches are constantly changing in size, shape and composition, sometimes on very rapid time scales of a few weeks, days or even hours during major storms.
The most familiar beaches are found on the ocean coast, but they can also be found along rivers, ponds and lakes. The most common type of beach is a coarse sand beach that is composed of terrigenous [1] siliceous sand, derived from the erosion of other rock types and transported by rivers. Beaches may also be composed of biogenic[2] sand, derived from the skeletal parts and shells of marine organisms, that are washed out to sea from inland deposits.
Waves and tidal currents continuously transport sand and other fine sediments from offshore to the beach, where it is deposited between ripple crests by wave action. The sediments are also eroded and carried to deeper waters by longshore and rip currents, where they can be transported a great distance from the source area.
Beach erosion, transport and deposition are controlled by a variety of factors, including the size of the sediments, their angularity, coastal morphology and bathymetric slope, the production of biogenic sand, the dynamics of longshore and rip currents, the frequency and energy of storms and their duration, and the direction and intensity of wind.
Many natural and human-induced processes are influencing the shape of today’s beaches, including erosion and transport of sediment by sea and river currents, the loss of beach vegetation, the removal of trees by people for building and firewood, and pollution from human activities. Some of the most obvious beach pollutants are sewage and other raw wastes washed ashore by storms and collected in the debris on the beach, while some plastics and other man-made materials may be trapped between the sand dunes or buried beneath the sand. Beaches are also being shaped by climate change, with rising sea levels potentially exposing a greater area of land that could eventually form a new coastline.