A beach is a landform along the shore of a body of water, most commonly the sea. The term is most often used to refer to sandy shores, but beaches can also be found at the edges of lakes, rivers and even large ponds. The main feature of a beach is the presence of loose particles such as sand, pebbles and shells that lie scattered across the surface of the water. Beaches are a common sight along many of the world’s coastlines and are popular locations for recreational activities including swimming, sunbathing and playing beach games.
A wild sand or shingle beach is shaped and maintained naturally by wave actions. The composition of the particles forming a beach varies with local geological conditions. In some parts of the world, beach sand is made up of very fine quartz grains while in others it contains heavier minerals such as feldspars. Beach sand can also contain calcite or calcium carbonate from the skeletal remains of marine organisms. The size of the particles composing a beach determines its texture, colour and structural characteristics.
The shape of a beach is determined by the nature and volume of the sediments in the area, the speed of wind and water flow and the degree to which they are compacted by mud or established vegetation. A well-established vegetative cover (especially species with thick, tenacious root systems) will reduce the erosional potential of a beach by slowing fluid flow at the surface layer. Sands of different types will tend to form a variety of distinct geomorphic features including beach ridges, troughs and barges.
Coastal erosion processes are not necessarily invariable, but the dominant factors at any given time are the strength of waves and the composition and distribution of the sediments on a beach. A beach with a high proportion of fine-grained sand tends to be more stable than a beach with coarser grained sediments as the particles have a greater tendency to stick together and resist erosion.
The upper part of a beach is usually above sea level and may be comprised of a series of parallel beach ridges or berms. Below this is a low-tide terrace and at the lowest tide level is a trough or swash line. Beyond this is one or more longshore bars: submerged ridges of sand formed where the swirling turbulence of breaking waves excavates a channel into the sandy beach bottom. The sand in these structures is fed by wave action and the backwash of the trough and by the accretion of sand from a beach berm or by the crumbling of nearby sand cliffs. This feeding process is sometimes referred to as beach nourishment.