Longshore drift from longshore current is a geological process that consists of the transportation of sediments along a coast parallel to the shoreline, which is dependent on the angle of incoming wave direction. Oblique incoming wind squeezes water along the coast, and so generates a water current which moves parallel to the coast. Longshore drift is simply the sediment moved by the longshore current. This current and sediment movement occur within the surf zone. The process is also known as littoral drift.
Provincetown Spit, at the northern end of Cape Cod, was formed by longshore drift after the end of the last Ice age.
Timber groyne from Swanage Bay, UK
Picture showing the use of artificial headlands and detached breakwaters in a coastal system
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange. The time-scale of swash motion varies from seconds to minutes depending on the type of beach. Greater swash generally occurs on flatter beaches. The swash motion plays the primary role in the formation of morphological features and their changes in the swash zone. The swash action also plays an important role as one of the instantaneous processes in wider coastal morphodynamics.
Swash
Figure 1. Beach classification by Wright and Short (1983) showing dissipative, intermediate, and reflective beaches.
Figure 2. Swash zone and beachface morphology showing terminology and principal processes (Modified from Masselink & Hughes 2003)
Figure 3. Beach cusp morphology. Uprush diverges at the cusp horns and backwash converges in the cusp embayments. (Modified from Masselink & Hughes 2003)
