A beach is a shoreline formation made of sand, gravel, rock, seashell fragments, and other natural materials. Most of these materials are the result of erosion and weathering from water and wind. The waves that beat against cliffs can wear away massive boulders to a few grains of sand.
These materials are then washed into the ocean. These particles remain in the water for a long time before eroding to dust or sediment. Some beaches also contain sediments or soil that has been deposited by a different process. These beaches may also be artificially created to serve as recreational areas for locals and tourists. Artificial beaches may contain sand that is transported from a different location.
The composition of a beach depends on the types of sediments that form upstream of the shoreline. The types of sediments are influenced by their particle size and the degree of compaction. If the sediments are compacted, they are more resistant to erosion. On the other hand, sediments in suspension are prone to erosion, particularly if the duration between wave crests is short.
A beach is also characterized by its shape and size. Some are broad and long, while others are narrow and steep. Some have significant shell content while others do not. Visiting a beach repeatedly will reveal how its width changes as a result of natural forces. You might also notice rocks, tree stumps, or mud layers.
The profile of a beach varies seasonally and hourly due to wave action. During winter, the exposed part of the beach is narrow and may disappear entirely. In spring, the exposed area begins to recover, and the beach reaches its full development in the summer months. It can change by as much as 10 feet or 165 feet in a single day.
The surf zone is the most dynamic part of a beach. Breaking waves occur when water depth is 1.5 times the height of the wave. They break in two different ways: as a plunging wave on a low-gradient slope, or as a surging wave on steeper slopes. The breaking waves release their energy as kinetic waves and travel shoreward as white water. Rip currents also occur along these shorelines.
There are many ways to protect beaches from erosion. Building a seawall, which may be made of plastic, rock, or concrete, may prevent beach erosion. The structures can also help preserve the character of the beach. The Sea Gate community in Coney Island, New York has built several seawalls to protect its neighborhood from hurricanes.
Beach nourishment activities often require the deposit of new sediment in a compacted condition before it can be used for planting and erosion control. Concentrated material on the beach can cause temporary groynes, which can also encourage scouring behind them. Additionally, fine and light sediments may be eroded before they have a chance to compact and integrate with the existing vegetation. Moreover, these sediments can introduce foreign flora and fauna into the environment.