coastal change and conflict Flashcards
what is weathering?
breakdown of rock and material in situ by elements of the weather, chemicals and living organisms
what is mass movement?
large-scale movements of material down a slope due to gravity e.g. rockfall, landslide, slumping
describe the processes of wave action on coasts
- Hydraulic action – water is forced into cracks in the rock which compresses the air. When a wave breaks the compressed air blasts out and can force the rock apart
- abrasion – sediment is thrown against cliff by waves which wears the cliff away and chips off bits of rock
- attrition – loose sediment is swirled around by waves and collide with other sediment which get worn down into smaller around sediment
- Corrosion – salts and other acids in sea– water slowly dissolves a cliff
what is a discordant coast and give an example
swanage Coast, dorset
•alternating hard and soft rocks at right angles to the coastline
•hard rock- difficult to erode forms headlands
•soft rock-easy to erode forms bays
what is a concordant Coast and give an example
Lulworth coast, Dorset
•alternating hard and soft rocks parallel to the Coast
•one rock type evident at Coast
•if waves erode through hard rock a narrow entrance allows waves to erode soft rock forming a cove
what are joints?
cracks in rocks where there is no displacement of the rock. Caused by cooling when rocks are formed or unloading when weight is taken off them as material above erodes
what are faults?
cracks in rocks where there is displacement of the rock. Often caused by tectonic movements
describe hard rock coasts and give an example
chalk cliffs, swanage bay, Dorset •20m tall almost vertical •smooth, cracks, some vegetation •Wave cut notch and platform •Lower rate of erosion
describe soft rock coasts and give an example
sand and clay cliffs, Christchurch bay, Dorset •15m tall, Low angle 45° steeper at top •Uneven, some vegetation •Beach, slumped material •Wave action weakens base •High rate of erosion
describe a constructive wave
- Strong swash
- Week backwash
- Small wave amp
- Long wavelength
- Sand transported up beach and deposited on beach
- gently sloping beach
- Depositional landform
describe a destructive wave
- Weak swash
- Strong backwash
- large wave amp
- short wavelength
- Sand is transported out to sea and eroded from beach
- Steep beach
- Erosional landform
what is erosion?
breakdown of rock and sediment and its removal by wind, running water, glacier and wave action
what is a spit?
when longshore drift pushes sediment out onto river it is deposited forming a long neck of sand and shingle
what is a bar?
where a spit grows across a bay and can enclose the bay to create a Lagoon
describe and explain the stages of longshore drift
- Wind – prevailing wind blows at oblique angle to coastline
- waves – causes waves to arrive at coast at a similar angle
- Swash – transport material up beach at oblique angle
- Backwash – transports material down beach at perpendicular angle
- repeated many times
- Overall movement – results in material being transported along shoreline
describe and explain the conflicting views on how the coast should be managed for a named location
in favour –
• residence of Barton on Sea whose homes are in danger
• local tourism businesses like caravan parks, hotels - put in danger leading to a poor income liable for payment of clearance
• local politicians who want to support residents and businesses
against –
•Hampshires taxpayers who don’t live on the coast – paying for something which doesn’t help them and less money towards other services
•Environmentalists – all management destroys nature causing visual pollution
explain the erosion of cliffs at the named location
- as it rains on the cliffs the rain percolates through the sand and is absorbed by the clay
- this weakens the clay and causes slumping
- The base of the cliff weakens as abrasion occurs
explain the costs and benefits of hard engineering structure -seawalls
Wall of concrete at base of cliff or behind a beach \+ • reflects waves back out to sea • effective in preventing erosion •Easy to maintain and repair - • prevents easy access to beach •Seawalls will have to be higher to cope with the rising sea levels in future – expensive
explain the costs and benefits of hard engineering structure -groynes
wooden fences that run down the beach at right angles to the coast
+
•Larger beach – dissipates wave energy reducing erosion
-
• May increase erosion down drift
•Beaches disappear as sediment is prevented from reaching other locations
explain the costs and benefits of hard engineering structure -rip rap
pile of hard rock boulders placed along base of cliff \+ • natural – less visually polluting • easy and cheap - •Doesn't prevent longshore drift
explain the costs and benefits of soft engineering structure – Cliff grading
Cliff angle is lowered and profile smoothed out vegetation is planted
+
•Prevents slumping and degradation of cliff
• visually pleasing
-
• doesn’t prevent 100% erosion
• Long time to implement
explain the costs and benefits of soft engineering structure – Cliff drainage
drainage pipes incorporated into cliff face
+
•Prevents saturation of the cliff – preventing slumping
-
• expensive
•Requires expert engineering to fit
explain the costs and benefits of soft engineering structure – Beach nourishment
additional sand added to beach making it larger
+
• widens beach
• natural form
-
•Sediment removed from other parts of coastline
