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Coastal Change & Conflict
- Erosion
- Hydraulic action
- Waves hit the rocks, forcing pockets of air into
cracks. The trapped air is released quickly, which
breaks up the rock.
- Waves hit the rocks, forcing pockets of air into
cracks. The trapped air is released quickly, which
breaks up the rock.
- Abrasion
- Waves pick up stones and hurl them against the cliff
face,wearing it away.
- Waves pick up stones and hurl them against the cliff
face,wearing it away.
- Attrition
- Pebbles become rounder and
smaller as the waves force them to
smash into each other.
- Pebbles become rounder and
smaller as the waves force them to
smash into each other.
- Hydraulic action
- Coastal landforms
- Cave
- Formed when waves
erode a weakness in the
rock
- Formed when waves
erode a weakness in the
rock
- Arch
- Formed when two caves erode from
both side of a headland and meet in
the middle
- Formed when two caves erode from
both side of a headland and meet in
the middle
- Stack
- Formed when the top of an arch collapses
- Formed when the top of an arch collapses
- Stump
- Formed after a stack has been eroded by the wind and/or water
- Formed after a stack has been eroded by the wind and/or water
- Wave-cut platforms
- Waves undercut the cliff face to form a wave-cut notch
- This leaves an overhanging cliff face
- The overhanging rock collapses, and the cliff retreats. This
leaves a wave-cut platform
- The overhanging rock collapses, and the cliff retreats. This
leaves a wave-cut platform
- This leaves an overhanging cliff face
- Waves undercut the cliff face to form a wave-cut notch
- Cave
- Waves
- Swash
- Moves up the beach, depositing sand and gravel
- Moves up the beach, depositing sand and gravel
- Backwash
- Moves back down the beach, carrying sand and gravel away
- Moves back down the beach, carrying sand and gravel away
- Constructive wave
- The swash is stronger than the backwash, so
material is deposited on the beach
- The swash is stronger than the backwash, so
material is deposited on the beach
- Destructive wave
- The backwash is stinger than the swash, so material
is taken away from the beach.
- The backwash is stinger than the swash, so material
is taken away from the beach.
- Deposition
(Longshore drift)
- Waves approach the coast at an angle
- Swash carries material up the beach
- Backwash carries material back down the beach at 90º
- This causes sand and gravel to move
along the beach in a zigzag motion.
- Sand is lighter than gravel, so moves further up
- Sand is lighter than gravel, so moves further up
- This causes sand and gravel to move
along the beach in a zigzag motion.
- Backwash carries material back down the beach at 90º
- Swash carries material up the beach
- Sand spits
- If there is a break in the coastline, such as an estuary, longshore
drift will still continue beyond it. The sand builds up to form a sand
spit.
- The sheltered water behind the spit
becomes a salt marsh.
- The end of the spit becomes curved,
when it meets with strong winds
and waves.
- If a sand spit joins up with the
coastline on the other side, it
forms a bar.
- The sheltered water behind the spit
becomes a salt marsh.
- If there is a break in the coastline, such as an estuary, longshore
drift will still continue beyond it. The sand builds up to form a sand
spit.
- Waves approach the coast at an angle
- Swash
- Geology of coastlines
- Hard rock coasts
- Granite, limestone, chalk
- Resistant to erosion
- High, steep, rugged, bare cliff face
- Some rocks and boulders at the foot of the cliff
- Features such as caves, arches and stacks
- Granite, limestone, chalk
- Soft rock coasts
- Clay
- May be high, but not very rugged or steep
- Piles of mud and clay collect at the bottom
- Very few hard rocks
- Clay
- Lulworth Cove
- Waves cut through a weakness in the resistant
limestone, forming the entrance to the cove.
- Waves erode the soft clay behind.
- Waves erode the soft clay behind.
- Waves cut through a weakness in the resistant
limestone, forming the entrance to the cove.
- Concordant coasts
- Bands of hard/soft rock run parallel
to the coastline
- Bands of hard/soft rock run parallel
to the coastline
- Discordant coasts
- Bands of hard/soft ruck run
perpendicular to the coastline
- Bands of hard/soft ruck run
perpendicular to the coastline
- Hard rock coasts
- Factors effecting coastal erosion
- Rock type
- Number of faults in the cliff
- Fetch
- The length of water over which
the wind has blown
- The length of water over which
the wind has blown
- Cliff exposure
- Storms
- Sea defences
- Rock type
- Coastal management
- Hard engineering
- Sea wall
- Protects cliffs and buildings
- Expensive
- Protects cliffs and buildings
- Groynes
- Prevents longshore drift
- Exposes other
areas of coast
- Prevents longshore drift
- Rip rap
- Rocks absorb wave energy
- Expensive
- Rocks absorb wave energy
- Off-shore reef
- Waves lose power
after breaking on
reef
- Expensive and
interferes with fishing
- Waves lose power
after breaking on
reef
- Sea wall
- Soft engineering
(Holistic management)
- Beach replenishment
- Reduces wave energy and maintains tourism
- Expensive
- Reduces wave energy and maintains tourism
- Managed retreat
- Businesses and people
avoid the effects of
erosion
- Expensive
- Businesses and people
avoid the effects of
erosion
- Cliff regrading
- Foot of cliff is not protected
- Less steep: reduces slippage
- Foot of cliff is not protected
- Beach replenishment
- Hard engineering
- Case study: Coastal retreat
- The Holderness coastline
- 60km long
- Low, easily eroded cliffs
(boulder clay/glacial till)
- Retreating 2m per year
- Management
- Scarborough - soft engineering
- Beach replenishment, £100/m
- Beach replenishment, £100/m
- Mappleton
- Groynes and rip-rap, £2 million
- Groynes and rip-rap, £2 million
- Scarborough - soft engineering
- 60km long
- Recurved sea wall, Robin Hood's Bay
- 500 feet long and 40 feet high
- Built in 1975 for £578,000
- 500 feet long and 40 feet high
- The Holderness coastline
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