A beach is the area of land along the edge of a body of water, usually made of sand or other material such as gravel or shingle. They are often part of a wider coastline and can be hundreds of kilometers long or very short, depending on the location. They are most commonly associated with the sea but can also be found next to lakes or rivers.
Beaches can be large or small, and are often a popular recreational destination for both locals and tourists. They can be public or private and are regulated by local governments.
Coastal beaches are shaped by natural processes and have to deal with human influences such as pollution, plastic pollution, and coastal erosion. These changes can impact the overall character of a beach and the ability of it to support a variety of uses.
The sand or gravel on a beach accumulates during periods of accretion (growth) and moves away during periods of erosion. Grain size determines the slope of a beach and affects its formation. Fine sand absorbs less water than coarse sand. When waves break on a beach, some of the water flows up into the sand (a process called swash), but most of it flows back down, forming a backwash that flattens the slope and moves the sand in a direction that is parallel to the sea.
At high tide, the ocean completely covers a beach. This is because of the way that tidal currents move the water. However, at low tide, the water retreats and reveals more of the beach.
Wave swash, backwash and longshore drift are natural processes that shape and stabilize beaches worldwide. These processes, which occur in tandem with each other, move sediment comprising a beach in a flow direction that is parallel to the beach.
Sand is the most important material for beaches, but it is also important to consider the flora and fauna that live on them. These organisms provide important ecosystem services, such as filtering pollutants and nutrients from rainwater. In addition, they play an essential role in stabilizing the sand dunes and foredunes that form the top of the beach.
Flora and fauna on a beach can also protect it from erosion. For example, beachfront flora with network root systems, such as creepers and grasses, trap and hold sand particles and prevent the erosion of the beach head.
These flora and fauna can also help to control the growth of marine algae. If a lot of algae grows on a beach, it can cause the water to become murky or cloudy. In some locations, these algae can be toxic to humans and wildlife.
Beaches are also affected by storms, which can erode sand bars that have formed offshore and moved onto the beach. In some places, the sand that forms these offshore bars can move inland and even to other beaches.
Some people build sand berms on beaches to keep the sand in place. These structures are based on the idea that a sand bar, or a layer of sand deposited by the sea, is an indicator that the beach has been gaining sand in recent weeks or months.