Physical Landscapes In The Uk-[optional] Coastal Flashcards
What is a coast?
A part of land that joins the sea.
What causes waves to form?
Wind blowing over the sea
Waves form as a result of the water’s motion, gravitational forces, and winds. The most common waves we see are created by wind.
What does the size and strength of waves depend on?
- How strong the wind is
- How long it blows for
- How far it travels
Define swash?
Water rushing up the beach
Define backwash?
Water draining back down the beach
Define fetch?
The distance a wave has travelled
What are constructive waves?
Waves that have a very strong swash and a weak backwash.
They build up the beach.
How do constructive waves build beaches?
They deposit material with the swash as the backwash is weak and leave sand and pebbles behind
What are destructive waves?
Waves that have a weak swash and a strong backwash.
They pull pebbles and sand back down the beach as the water retreats
Name the features of constructive waves?
- Low
- Wave crests far apart
- Gentle sloping wave front
- 6 - 8 per minute
- Gentle beach created
Name the features of destructive waves?
- Steep beach created
- High
- Break close together
- Up to 15 per minute
What are marine processes?
The base of cliffs being eroded by hydraulic action and abrasion
Which waves are associated with coastal erosion?
Destructive waves
Define ‘weathering’
Weathering is the breakdown of rock at or near the surface by the weather
List the 2 main types of weathering?
- Mechanical weathering
- Chemical weathering
What is mechanical weathering?
Mechanical weathering is caused by physical changes such as changes in temperature, freezing and thawing.
Water gets into cracks in rocks, freezes when the temperature drops below 0’c, prising the rock apart. When the water melts, a larger crack develops. Overtime this causes rocks to break apart.
What is chemical weathering?
The weathering of rocks by chemicals is called chemical weathering. Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Minerals in rocks may react with the rainwater, causing the rock to be weathered
Define erosion
Wearing away of rocks by water, weather or ice
List the 4 main types of erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
Define ‘hydraulic action’
Water being forced into cracks in the rock and breaking it up.
Define ‘abrasion’
Loose rocks (sediment) are thrown against the cliff by waves. This wears away at the cliff and chips bits of rock off.
Define ‘attrition’
Loose sediment that has been knocked off the cliff is swirled around by waves, colliding with other pieces wearing them into smaller smoother pieces.
Define ‘solution’
Seawater dissolves material from the rock.
What is mass movement?
When rocks loosened by weathering move down slope under gravity. They can slide or slump
What is slumping?
This is common where cliffs are made of clay. The clay becomes saturated during heavy rain and oozes down towards the sea.
What is sliding?
This is when large chunks slide down slope quickly without any warning
What is ‘rock fall’?
A type of mass movement where material breaks off the cliff and falls down the slope.
How is sediment transported along the coastline?
Longshore drift
Describe how longshore drift works.
- Waves approach the beach at an angle
- As waves break the swash carries material up the beach at the same angle
- The backwash carries material straight back down the beach under gravity
- This causes the material to move along the beach in a zig-zag pattern
What is deposition?
When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition.
Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.
Defne ‘landform’
A feature in the landscape that has been formed by erosion, transportation and/or deposition.
What factors influence the landforms found along a coastline?
Hard rock (resistant rock) - does not erode easily - likely to find headlands
Soft rock (less resistant rock) - erodes easily - more likely to be a bay
List some coastal landforms that result from erosion
- Headlands and bays
- Cliffs
- Wave cut platforms
- Caves, arches, stacks and stumps
How do headlands and bays form?
Where coasts are made from alternating bands of hard and soft rocks, destructive waves will erode the less resistant (softer rock) more to form bays and coves. The more resistant (harder) rocks sticks out into the sea to form headlands.
Describe how a wave-cut platform is formed?
- The sea attacks the base of the cliff forming a wave-cut notch.
- The notch increases in size causing the cliff to collapse.
- The backwash carries the rubble towards the sea forming a wave-cut platform.
- The process repeats and the cliff continues to retreat.
How do caves, arches, stacks and stumps form?
- Resistant rock headlands have faults and joints
- Abrasion and hydraulic action widens the joints
- Waves make the joint wider to form a cave
- Waves erode the cave until it cuts through the headland to form an arch
- The arch is eroded until the roof collapses leaving a stack
- The stack eventually collapses leaving a stump
List some coastal landforms that form as a result of deposition
- Beaches
- Sand dunes
- Spits
- Bars
How do beaches form?
- The material may come from eroded cliffs or have been moved from a beach somewhere else
- Waves transport the material by longshore drift and deposit it
What is a bar?
A narrow ridge of sand or shingle that grows across a bay
How is a bar formed?
Longshore drift carries sediment along from a headland, depositing sediment further out from the headland. Over time, this line of sediment joins two headlands together; a bar is formed, cutting the bay off from the sea.
Which feature lies behind a bar?
A lagoon
Why do spits have a hooked or re-curved end?
This is caused by the wind and waves changing the direction of the spit
What are spits?
Lond narrow ridges of sand and shingle stretching out from the coast
How a spit is formed?
- Longshore drift moves material along the coastline
- A spit forms when the material is deposited further out from the coastline
- Over time the spit grows and develops a hook as wind blows off the sea.
- Waves cannot get past the spit and a sheltered area develops behind it where silt is deposited to create mud flats and salt marshes
Which feature lies behind a spit?
A saltmarsh and mudflats
How are sand dunes formed?
- Wind carries sediment up the beach
- Obstacles on the beach encourages sand to build up
- Vegetation begins to stabilse the dune, encouraging more sand to deposit
- Overtime, the dunes migrate backwards, away from the sea
Which grass grows on sand dunes and holds them in place?
Marram grass
Name an example of a UK coastline that has major erosional and depositional landforms
Dorset coast
Name some coastal features you would find at the Dorset coast
- Arch - Durdle Door
- Bay - Swanage Bay and Studland Bay
- Cave, Arch, Stack, Stump - Old Harry
- Bar and Lagoon - Chesil Beach and Fleet Lagoon
Name a coastline that is at risk of erosion and has coastal management strategies in place.
The Holderness Coast
Why is the Holderness Coast at risk of coastal erosion?
- Strong prevailing winds creating longshore drift that moves material south along the coastline.
- The cliffs are made of a soft boulder clay.
Why does the Holderness coast need protecting?
- Fast eroding cost (nearly 2m lost each year)
- Strong prevailing winds carries sediment south
- Made of soft boulder clay
- Lots of towns along the coastline
- Important gas terminal located there
What management strategies are being used at Holderness?
Mappleton - rock armour along base of cliffs and rock groynes to trap sediment
Hornsea - sea wall and groynes
Withernsea - sea wall, groynes and rock armour
What are the impacts of the management of the Holderness coast?
+ Mappleton is successfully protected from erosion
- Towns south of Mappleton have lost sediment due to groynes, therefore they are experiencing increased erosion
- Increased need to protecting at the Easington Gas terminal which has cost £6 million
What is meant by hard engineering of coastlines?
Man made structures that are used to reduce coastal erosion and flooding.
Name a range of hard engineering strategies used to manage coasts
- Groynes
- Sea walls
- Gabions
- Rock armour
What are the benefits of hard engineering strategies?
- Usually immediately effective
- Long lasting
What is a sea wall?
Concrete or rock barriers placed at the foot of cliffs or at the back of the beach
They are curved to reflect waves back to the sea
What are the advantages of sea walls?
- Effective at stopping the sea
- Provides a promenade for people to walk along
What are the disadvantages of sea walls?
- Can look obtrusive and unnatural
- Very expensive and high maintenance at £10,000 per metre
What is a groyne?
- Wooden or rock structures built out to sea at 90 degrees to the coast
- They trap sediment moved along the coast by longshore drift
What are the advantages of using groynes?
- Create a wider beach for tourists
- Provide structures for people to fish from
Explain a disadvantage of using groynes?
- Can be seen as unattractive.
- Costly to build and maintain at £150,000 every 200m
- Can have knock-on effects further down the coast.
What are gabions?
Wire cages filled with rocks that can support cliffs or act as a buffer against the sea
What are the advantages of gabions?
- Cheap to produce and flexible in design
- Can improve drainage of cliffs
- Will eventually become vegetated and merge into the landscape
What are the disadvantages of gabions?
- For a while they look unattractive
- Cages last 5 - 10 years before rusting
What is rock armour?
- Piles of large boulders dumped at the foot of a cliff
- The rocks force waves to break and absorb their energy
What are the advantages of rock armour?
- Relatively cheap and easy to maintain
- Can provide interest for people
- Often used for fishing
What are the disadvantages of rock armour?
- Rocks usually come from other parts of the coastline
- Can be expensive at £200,000 per 100 metres
- Rock don’t fit with the local geology
- Can be obtrusive
What is meant by soft engineering of coasts?
Working with the environment or nature to reduce the impacts of the waves.
Name a range of soft engineering strategies used to manage river flooding?
- Beach nourishment and reprofiling
- Dune regeneration
- Dune fencing
Describe beach nourishment?
The addition of sand or shingle to an existing beach to make it higher or wider
What are the benefits of soft engineering strategies?
- Less expensive than hard engineering options.
- Usually more long-term and sustainable
- Less impact on the environment.
What are the disadvantages of beach nourishment?
- Needs constant maintenance unless structures are built to retain the beach
- Becomes costly in the long term
Describe the advantages of beach nourishment?
- Replaces beach or cliff material that has been removed by erosion or longshore drift.
- Beaches are a natural defence against erosion and coastal flooding.
- Beaches also attract tourists.
- Relatively inexpensive option
What is dune regeneration?
Marram grass is planted to stabalise damaged dunes and help them to develop
Fences are used to keep people away from these areas
What are the advantages of dune regeneration?
- Maintains a natural coastal environment that is popular with people or wildlife
- Relatively cheap at £200 - £2,000 per 100 metres
What are the disadvantages of dune regeneration?
- Time consuming
- Can be damaged by storms
- Unpopular with some tourists due to fencing
What is dune fencing?
Fences are built alond the seaward facing dunes to encourage new dune formation
What are the advantages of dune fencing?
- Minimal impact on natural systems
- Can control public access to protect other ecosystems
- Fairly cheap at £400 - £2,000 per 100 metres
What are the disadvantages of dune fencing?
- Can be unsightly
- Needs regular maintenance
Which form of sea defence is built to prevent the effects of longshore drift?
Groynes
What is managed retreat?
Controlled retreat of a coastline by allowing land to flood. This marsh land then becomes a protective strategy, protecting the land behind it.
Describe the advantages of managed retreat?
- Flooded land is land of low value.
- Encourages the development of beaches (a natural defence) and salt marshes (important for the environment)
- Cost is minimal
Why is managed retreat a popular form of coastal management?
- It is more sustainable in the long term as less money is spent on hard engineering
- Sea level rise due to climate change is forcing us to choose this option
Name a managed retreat scheme?
Medmerry near Chichester, West Sussex
Why was the Medmerry managed rertreat scheme needed?
- Low lying flat land used for farming and caravans was threatened by a sea wall needing repair
- Building a new sea wall was a very expensive option
- As the land was of low value it was decided to allow the sea to flood the land
What will the Medmerry managed retreat scheme create?
- A large natural salt marsh acting as a buffer with the sea
- This will protect surronding farmland and the caravan park
- Creates a valuable wildlife habitat which is attractive to visitors
What have been the impacts of cliff management at Mappleton?
- The rock groynes have stopped beach material being moved south from Mappleton along the coast.
- However, this has increased erosion south of Mappleton. Benefits in one area might have a negative effect on another.
