Rivers & Coasts - Coasts Flashcards
What are the types of coastal weathering/erosion?
Mechanical weathering Chemical weathering Hydraulic action Corrasion Attrition Corrosion
What is mechanical weathering?
Water gets into cracks in rock, when the water freezes it expands and puts pressure on the rock, when it thaws it contracts and releases the pressure. Repetition of this causes the cracks to widen and break apart
What is chemical weathering?
Rainwater has CO2 dissolved in it, which makes a weak carbonic acid, this acid reacts with the rock and dissloves it
What is hyrdraulic action?
Waves crash against the rock and compresses the air inside its cracks, this puts pressure on the rock and the repeated compression causes the rock to break apart
What is corrasion?
Eroded particles in the water scrape against the rock which removes small pieces at a time
What is attrition?
Eroded particles in the water smash against each other and break into smaller fragments, their edges also get rounded off
What is Corrosion?
Weak carbonic acid in seawater dissolves rocks like chalk and limestone
What is a destructive wave?
They have high frequency
They are high and steep
Their backwash is more powerful than swash
The 2 main factors that affect their size and power are wind and fetch (the distance the water has blown to produce a wave)
What is the order of coastal landforms?
Cracks - cave - arch - stack - stump
How do headlands and bays form?
Where there is alternating bands of hard and soft rock
How do coves form?
Where there are parallel bands of hard and soft rock
What is transportation?
The movement of material - waves follow the direction of the prevailing wind, they hit the beach at a non 90 degree angle, the swash carries the material up the beach, the backwash brings the material back down the beach at 90 degree angles, over time material zigzags across the beach
What is traction?
Where large particles like boulders are pushed along the sea bed by water
What is suspension?
Small particles like silt and clay are carried along in the water
What is saltation?
Pebble sized particles bounce along the sea bed by water
What is solution?
Soluble materials dissolve in water and are carried along
What is deposition?
Where material carries by the sea is dropped on the coast - coasts build up when the amount of deposition is greater than the amount of erosion, the amount of material on the beach increases when there is lots of erosion elsewhere, and when there’s lots of transportation into the area
What are constructive waves?
They build up the coast because they deposit more material than they erode
Low frequency
Low and long
The swash is more powerful than the backwash
Made by weaker winds, have a shorter fetch
How are spits formed?
At sharp bends in the coastline
Longshore drift transports material past the bend and deposits it in the sea
Strong winds and waves curve the end
How are bars formed?
When a spit joins 2 headlands together
The bar cuts off the bay between the headlands and the sea - this means a lagoon is formed
What are the economic reasons for protecting coastlines?
Brings in tourism
Businesses near cliffs could be destroyed
Coastal flooding causes farming (agricultural) land damage
Property prices fall
What are the social reasons for protecting coastlines?
Deaths by flooding Water supplies affected Loss of housing Loss of jobs Damage to infrastructure
What are the environmental reasons for protecting coastlines?
Ecosystems affected (salty sea water can damage ecosystems, flooding can uproot and drown trees, plants) Some Sites of Special Scientific Interest are threatened
What are some hard engineering coastal management strategies?
Sea wall Rip rap Groynes Revetments Gabions Breakwaters
What are some soft engineering coastal management strategies?
Beach replenishment
Managed retreat
What is a sea wall and what are its advantages/disadvantages?
A wall made out of hard material that reflects the waves
Advantages - prevents erosion and flooding
Disadvantages - creates strong backwash which erodes under the wall and are expensive to build and maintain
What is rip rap and what are its advantages/disadvantages?
Boulders that are piled up along the beach
Advantages - absorb wave energy and reduce flooding
Disadvantages - can be moved by strong waves so they will need to be replaced
What are groynes and what are the advantages/disadvantages?
Wooden/stone fences that are built at right angles along the coast, they trap material which prevents longshore drift
Advantages - create wider beaches which slow waves, prevents erosion and flooding
Disadvantages - starve beaches of sand further down the coast, which makes them more likely to flood
What are revetments and what are the advantages/disadvantages?
Slanted structures made of concrete/wood/rocks built at the foot of cliffs
Advantages - absorb wave energy so reduce erosion
Disadvantages - Expensive to build, create strong backwash which erodes under the barrier
What are gabions and what are the advantages/disadvantages?
Rock filled cages, built at the foot of cliffs
Advantages - absorb wave energy so reduce erosion
Disadvantages - Ugly
What are breakwaters are what are the advantages/disadvantages?
Concrete blocks/boulders on the sea bed off the coast
Advantages - force waves to break offshore so their power is reduced before they reach the shore
Disadvantages - Expensive and can be broken by storms
What is beach replenishment and what are the advantages/disadvantages?
Adding sand to the beach
Advantages - creates wider beaches which slows waves, protects from erosion and flooding
Disadvantages - expensive and has to be replaced
What is managed retreat and what are the advantages/disadvantages?
Removing an existing defence and allowing the land to flood
Advantages - over time the land will become marsh land, creating new habitats. Flooding and erosion are reduced behind marshland. Is cheap
Disadvantages - People will disagree with what land is allowed to flood e.g. flooding farm land will affect the livelihood of farmers
