Geog 1 - Coastal Environments - Key Flashcards
Abandon line
The strategic withdrawal of human occupation in areas of high risk. Use of less expensive and sustainable methods to “abandon the line” of the coast, often unpopular with farmers and property owners. E.g. National Trust policy Studland Bay.
Abrasion
The wearing away of shoreline by sediment carried by waves. Also erosion by friction scraping, scouring and rubbing of load in contact with banks and bed (Corrasion)
Accretion
The accumulation of marine sediments. Where deposition exceeds erosion.
Advance line
This involves active intervention to produce a defence line that is seaward in some way of the existing line. This would usually involve some form of reclamation, the construction of offshore breakwaters or similar.
Arch
A raised are left when two caves erode back to back on a headland. E.G. Durdle door.
Attrition
The reduction and rounding of particles of sediment carried in water repeated collision with each other and the shore.
Backwash
Movement of water back towards the sea after a wave has broken.
Bar
Coarse grained deposit of sediment extending across the mouth of a bay, sometimes reaching the other side and sealing off the entrance E.g. Looe Bar.
Benefit cost ratio
The ratio of the present value of benefit to the present value of costs. Benefits and costs are compared with the “without project” case for each option
Berm
Low hill of sand or gravel that forms at the upper limit of the swash. They are short-term features and are removed by successive tides and storms.
Beach nourishment
Sand and shingle brought from elsewhere are added to beaches to maintain their breadth and depth to protect from erosion in a natural way E.G. Hengistbury Head.
Blow - hole
A chimney or pipe leading from a cave up through a cliff to the surface. Caused by erosion and often exploitation of joints in the geology.
Breaching
Failure of defences allowing flooding by tidal or storm action.
Char
An island formed from silt deposition in a delta. The land is about at sea level. It is very fertile and attracts settlers desperate for land. However can be easily washed away by monsoon floods and cyclones. Salt water reduces their fertility.
Constructive waves
Low frequency 6 - 8 per minute which have elliptical water motion, with powerful swash and weak backwash. They build up deposition.
Concordant geology
The alignment of geological outcrops which are parallel to the coastline. E.G. Dorset coast at Lulworth.
Corasion
Erosion by friction of load in contact with banks and bed (abrasion)
Corrosion
Includes the dissolving of carbonate rocks (limestone) in sea water and the evaporation of salt crystals which expand on formation and help the rock to disintegrate.
Cusp
Crescent - shaped embayments developed on beaches of mixed sediments.
Cuspate foreland
Is a triangular accumulation of sand an or gravel located alone the coastline. This feature is formed by longshore drift from opposing directions E.G. Dungeness
Defence line
The crest of a sea wall / revetment (man made defences) or the crest of dunes or the cliff edge (natural defences)
Deltas
Form when the amount of sediment delivered at the mouth of a river exceeds the amount removed by waves and tidal currents.
Destructive waves
High frequency 13 - 15 per minute waves which have circular water motion, with weak swash and powerful backwash. They erode.
Differential erosion
Varying rates of erosion relating to geology and energy of coastline. Resistant coastlines have hard rocks massive structure consolidated and not susceptible chemical weathering E.G. Land end (granite)
