How does beach sand migrate as a result of longshore drift? Explain the sediment budget of a coast.

Longshore drift is a geographical process that transports sand and sediment along the coast. It is caused by waves that approach the shore at an angle. The energy from the waves pushes the sand up the beach at the same angle. However, gravity pulls the sand straight back down the beach, creating a zigzag movement of the sand particles in the direction of the prevailing wind. This results in the overall movement, or 'drift,' of sand and sediment along the coast. #

As the sand particles on the beach are transported in a zigzag motion by the longshore current, they slowly move along the coastline. This zigzag path makes the sand 'drift' steadily down the beach, resulting in migration of beach sand. This migration of sand changes the shape of the beach over time, which may lead to the formation of various coastal features such as spits and bars. Moreover, during storms, the longshore drift might increase dramatically which can result in greater, more noticeable changes to the coastline. #

A sediment budget of a coast is an assessment of the sources, sinks, and storage of sediment within a coastline system. It is a balance between sediment being added to and removed from a certain coastal area. The sediment can be added by processes like river deposition, cliff erosion, human activities etc., and removed by processes such as longshore drift, sea level rise, or human interference. A sediment budget can be positive (more sediment added than removed, leading to increase in land), negative (more sediment removed than added, leading to coastal erosion) or balanced. #

In a coastal environment, sediment is constantly being added and lost. River deposition adds sediment to the coastline whereas wave erosion removes sediment from it. Longshore drift then transports the sediment along the coast. The amount and type of sediment present at a particular coastline depends on these factors of addition and removal along with geological features and human activities. For example, if more sediment is added than removed by processes such as erosion, sea level rise or longshore transport, the coast will grow (positive sediment budget). Conversely, if more sediment is transported away from the coast than is added, the coast will erode and shrink (negative sediment budget). A balanced sediment budget, on the other hand, means that sediment input and output are more or less equal. This understanding of sediment budgets is critical for coastal management and conservation. #