What landforms can result from longshore drift?
Waves and longshore drift are important in controlling the formation of beaches, as well as spits, tombolos, baymouth bars, and barrier islands. Beaches can be divided into zones, such as foreshore and backshore, and beach shapes typically change from season to season.
What are the negative effects of a longshore drift?
Longshore drift plays a large role in the evolution of a shoreline, as if there is a slight change of sediment supply, wind direction, or any other coastal influence longshore drift can change dramatically, affecting the formation and evolution of a beach system or profile.
How does longshore drift affect sediment size?
The size of the sediment particles moved by the wave is determined by what is available on the sea bed, and by the power of the wave. Each wave can move the sediment a little further across the beach. Groynes are effective at trapping material as it is moved along along the coast by longshore drift.
Does long shore drift occur along the Sussex coast?
Longshore drift along the Sussex and Kent coast is usually from west to east because most of the coast is exposed to storm winds and waves advancing up the Channel from the west or south-west. As a result of this longshore drift, shingle tends to accumulate on the west side of groynes and harbour arms.
What causes long shore drift?
Longshore (littoral) drift is the movement of material along the shore by wave action. It happens when waves approach the beach at an angle. The backwash (waves moving back down the beach) carries material back down the beach at right angles. This is the result of gravity.
What causes swash and backwash?
When a wave breaks, water is washed up the beach. This is called the swash . Then the water runs back down the beach, which is called the backwash . With a constructive wave, the swash is stronger than the backwash.
How can human activity affect sediment cells?
Human activity can interfere with the processes within a sediment cell by disrupting the supply of sediment and therefore the sediment budget of the cell. Groynes, jetties and harbour walls will block the movement of sediment, which can lead to beach erosion further downdrift.
How do waves affect beach morphology?
Constructive waves alter beach morphology by causing net movement of sediment up the beach, steeping the beach profile. Swash carries sediment of all sizes up the beach, but weaker backwash can only transport smaller particles down the beach.
Is deposition fast or slow?
Remember, faster moving water causes erosion more quickly. Slower moving water erodes material more slowly. If water is moving slowly enough, the sediment being carried may settle out. This settling out, or dropping off, of sediment is deposition.
How is longshore drift related to the longshore current?
Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle) along a coast parallel to the shoreline, which is dependent on oblique incoming wave direction.
How much is longshore drift on the Sussex coast?
The beaches were re-seeded at regular intervals, and the depth of transport (“active layer”) was estimated from laboratory experiments. The volume of longshore drift eastwards over a 22 week study period was determined to be about 880 tons per week and over a 52 week period about 590 tons per week, i.e. about 31,000 tons a year.
How are spits formed in a longshore drift?
Spits are formed when longshore drift travels past a point (e.g. river mouth or re-entrant) where the dominant drift direction and shoreline do not veer in the same direction. As well as dominant drift direction, spits are affected by the strength of wave-driven current, wave angle and the height of incoming waves.
How are flood shoals affected by longshore drift?
The majority of tidal inlets on longshore drift shores accumulate sediment in flood and ebb shoals. Ebb-deltas may become stunted on highly exposed shores and in smaller spaces, whereas flood deltas are likely to increase in size when space is available in a bay or lagoon system.