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coastal landscapes and processes - Coggle Diagram
coastal landscapes and processes
Jurassic coast (from East Devon to Dorset)
Studland - dunes
Durndle door - arch
Old harrys rock - stacks
Perveril point - headland
Lulworth cove and stair hole - horseshoe shaped bays
Durston Bay/headland - bay formed from erosion of softer clay and harder chalk
Chesil beach- pebble bar
Erosional Landforms
beaches - deposits of sand and shingles created by constructive waves.
sand dunes - formed by sand blown inland and build up at the back of beach, they're stabilised by vegetation eg marsh grass
Caves, Arches, stacks & stumps - cave formed from erosion, erodes back of the cave = arch, weathering weakens top of arch, collapses to form a stack, stash is eroded by sea = stump
spits - longshore drift transports sand along the coast, spit grows from the land out into sea, end of it curves due to wind and wave direction
wave cut platforms & cliffs - waves erode the base of the cliff, causing wave cut notch and overhanging cliff, notch gets bigger, cliff unstable, collapses, leaving a wave cut platform.
bars - form when longshoredrift causes spits to grow across a bay
headlands & Bays - resistant bands of rocks are eroded slowly to form headlands, weaker rock erodes easily to form bays
Physical processes
transportation
Longshore drift -zig zag movement of sediment dependant on direction of waves and prevailing wind.
deposition
happens when water slows down and waves loose their energy, beaches are formed.
erosion
abrasion - sand papering effect of pebbles grinding over rocky platform
attrition - rock fragments carried by the sea hit each other becoming smaller and rounder.
hydraulic power - waves hit cliff, trapped air forced into cracks.
waves
Destructive- shows wavelength, high hight, weak swash, strong backwash = material removed and erodes beaches
Constructive - long wavelength, low wave, strong swash, gentle backwash = adds material and create big beaches.
mass movement
slumping - permeable rock absorbs lots of water, gets heavier and slumps down
land slide - rock soil and mud move down a slope due to heavy rainfall and gravity.
weathering
chemical - carbonation, rain water absorbs co2 making it acidic, dissolves lime stone.
biological - plant roots grow in cracks, animals burrowing
mechanical - freeze thaw, water collects in cracks, freezes and expands, cracks get bigger, fragments break off.
Lyme Regis
Management strategy - new sea walls, stabilising cliffs, beach nourishment, rock armour, stone groin
resulting effect & conflits - positives: new beaches have increased visitor numbers, harbour is better protected better for fishing industry. negatives: increased visitors cause congestion and litter, new defences spoil the landscape, new sea wall might interfere with natural processes.
Reasons for Management - unstable cliffs, rapid erosion has destroyed many properties, sea wall breached many times.
Coastal defences
gabion - rocked filled wire cage that supports cliffs and is a buffer against the sea. positives - cheap to produced, can improve cliff drainage, can become vegetated and merge into environment. negative - looks ugly at first, cage can rust
groins - rock or timber structures built at right angles to beach, traps sediment moved my long shore drift. positives - create wider beach, cheap negatives -interrupt local Long Shore Drift, can lead to increased erosion elsewhere
rock armour - piles of large boulders at foot of cliff. positives - cheap and easy to maintain, can add interest to the coast. negative - rocks are from elsewhere and do not fit with local geology, expensive to transport rock and can be obtrusive
beach nourishment - sand or shingle is dredged off shore and transport to the coast. positives - cheap and easy to maintain, blends in with the environment. Negatives - needs a lot of maintenance
sea walls - concrete or rock barrier at base of cliffs, curved to reflect waves positives -effective, creates walk way negatives - looks unnatural, expensive and hight matinence costs.
dune regeneration - ma'am grass is planted to stabilise the dunes which helps them to buffer the effects of the sea positive - natural environment, good for wildlife and cheap negatives - time consuming to plant grass, can be damaged by storms
managed retreat /coastal realignment - areas of the coast are allowed to flood and erode naturally (usually low value areas) positives=encourages development of natural beaches and salt marshes, low cost negatives=people have to be compensated for loss of their land
Reasons to defend a coastline
protect people and properties from erosion
protect valuable farmland from flooding and erosion
protect people from flooding
Dune Fencing - fences put up alongside the seaward side of existing dunes to encourage new dunes positives- little impact on natural systems, controlling access protects the ecosystem negatives - unsightedley, needs regular maintenance