Coasts Physical Geography

• Beaches are an important temporary store where beach accretion, the process of depositing sediment, occurs after consecutive constructive waves.
• Destructive waves remove large amounts of sediment.
• Drift-aligned beaches are formed when waves approach at an angle.
• Swash-aligned beaches move up the beach with little transfer of energy-aimed sediment.
• Drift-aligned beaches move up the beach with sediment transferred from the coast.
• Beaches can extend from the backshore to the offshore zone.
• Large pebbles tend to be near the top of the beach and small ones at the bottom.
• The pebbles at the bottom of a beach are more rounded due to waves causing abrasion and attrition.
• Scree means pebbles at the top of a beach are more angular.
• Pebble size and angularity changes along the beach.
• Summer profile is when more constructive than destructive waves so energy is deposited over a wide area, weakening backwash, forming berms like in figure 7.
• Winter profile is when more destructive waves than constructive so berms can be eroded.
• Strong backwash from winter profile transports sediment offshore sometimes making a rip current.
• Spits form when prevailing winds cause longshore drift along a drift-aligned beach.
• The sediment from spits extends to an estuary where a second dominant wind takes over.
• Soil conditions improve and shrubs and trees colonise.
• A recurved end is a feature of a river that prevents a spit from extending across an estuary.
• Sand dunes form when large amounts of sand are deposited by constructive waves, there is a large tidal range, and dominant onshore winds.
• Offshore bars form when destructive waves erode the sand and deposit it offshore.
• Sand dunes like the ones in figure 13 are formed by these steps: sand is initially trapped by debris, vegetation grows and stabilises sand, and over hundreds of years vegetation succession occurs.
• Mudflats develop into salt marshes when mud is deposited at high tide line causing flocculation where particles of mud stick together so they can sink.
• Mud level rises above high tide mark so a lower saltmarsh develops so plants no longer need to be adapted to salty conditions.
• As soil pH decreases, bigger vegetation can grow like trees compared to marram grass.
• Depressions in between dunes can form dune stacks where the water table is closer to the surface.
• Bars on the south coast are due to rising sea levels in the glacial period.
• Sand dunes grow over time with embryo dunes being the first to develop.
• River estuaries are important sediment stores that can develop into saltmarshes.
• Offshore bars can absorb wave energy reducing the impact of waves and erosional processes like hydraulic action on the coastline.
• Offshore bars are submerged ridges formed by offshore waves.
• Saltmarshes need multiple factors to form including sheltered areas, estuaries, no strong tides, and vegetation succession.
• Bars are beaches which extend two headlands, for example, Start Bay in Devon.
• Pioneer plants can help trap further deposits of mud.
• Wave refraction carries material around a sheltered water behind a spit.
• Lagoons can form behind bars.
• A saltmarsh can form behind a spit.
• An example of a recurved end is Poole harbour in Dorset where a double spit is present.
• Barrier beaches are beaches separated by the mainland.