V Geography - Coasts + Coastal Hazards

Landscapes and Physical Processes

Constructive Waves

Constructive Waves

Waves with strong swash and weak backwash

Destructive Waves

Waves with strong backwash and weak swash

Longshore Drift

The movement of sediment along the coast

Formation and change of: Wave-cut Platforms (Wave-cut Notch and Rock Pools)

Created as cliffs retreat and the base rock remains. As water and rock enters bedding planes and joints on the wavecut platform, the cracks will be eroded and increase in size creating pools. When the tide is high the pools will fill with water that remains as the tide retreats. This is a rockpool, an important coastal habitat.

Formation and change of: Headlands

Erosion in cliff → forms caves → cave gets bigger → sea arch forms → sea arch collapses → stack is formed → stack collapses → stump is formed

Formation and change of: Spits

Prevailing wind approaches the beach at an angle → swash pushes sediment up the beach at an angle → gravity means the backwash returns at a 45 degree angle to the sea → when the coast changes direction sediment continues to be moved by longshore drift and is deposited when the sea loses energy → this process continues and sediment is moved along the beach by longshore drift creating a spit → the area behind the spit is sheltered from the power of waves so silt is deposited, and seeds begin to germinate forming salt marshes → if the wind changes direction for a period of time the direction of sediment movement will change and a recurved end form

Formation and change of: Bars

A bar is formed like a spit only connecting two headlands

Discordant Coastline

Where the rocks run perpendicular to the sea - forming headlands and bays

Concordant Coastline

Where the rocks run parallel to the sea - forming a more uniform looking coastline

How does geology affect the rate of coastal landform change?

Relative structure/resistance of rocks

How does climate affect the rate of coastal landform change?

Prevailing wind direction, fetch and extreme weather events

How does human activity affect the rate of coastal landform change?

Management to reduce erosion and unintended consequences e.g. groynes on longshore drift

Coastal Hazards

• Erosion

• Extreme weather events

Cost Benefit analysis

Weighing up of the cost of coastal protection against its benefits

Hold the Line

Used in high risk and high benefit areas - the use of coastal protection to hold the coastline at its current position - most likely using hard engineering

Managed Retreat

Used in low risk and low benefit areas - allowing the coastline to flood to a certain point (soft engineering)

Do Nothing

Used in very low risk and benefit areas - allowing the coastline to flood without management

Advance the Line

Used in high risk high benefit areas - building the coastline further out to create more land and make up for what has been lost and reduce the risk of erosion

Groynes

Long planks that are used to reduce the amount erosion by decreasing the wave energy and limiting the movement of sediment (hard engineering)

Advantages

• Builds a beach - which encourages tourism.

• They trap sediment being carried by longshore drift.

Disadvantages

• The beaches further down the coastline from the groynes are starved of sediment meaning that they loose their natural barrier from erosion and it occurs there instead

• They look unattractive

Sea Wall

A concrete wall that is built along a coastline in order to reduce risk of erosion (hard engineering)

Advantages

• Effective at protecting the base of the cliff.

• Sea walls usually have promenades so people can walk along them.

Disadvantages

• Waves are still powerful and can break down and erode the sea wall.

• Expensive - approximately £2,000 per metre.

Rock Armour

A barrier of large boulders placed in front of a cliff or sea wall to absorb wave energy and reduce backwash

Advantages

• Cheaper than a sea wall and easy to maintain.

• Can be used for fishing.

Disadvantages

• They look different to the local geology, as the rock has been imported from other areas.

• The rocks are expensive to transport.

Beach Nourishment

Sand is pumped onto an existing beach to build it up

Advantages

• Blends in with the existing beach.

• Larger beaches appeal to tourists.

Disadvantages

• Needs to be constantly replaced.

• The sand has to be brought in from elsewhere, starving other areas of sediment

Reprofiling

The sediment is redistributed from the lower part of the beach to the upper part of the beach.

Advantages

• Cheap and simple.

• Reduces the energy of the waves.

Disadvantages

• Only works when wave energy is low.

• Needs to be repeated continuously.

Dune Nourishment

Marram grass planted on sand dunes stabilises the dunes and helps to trap sand to build them up.

Advantages

• Relatively cheap.

• Maintains a natural-looking coastline.

Disadvantages

• Can be damaged by storm waves.

• Areas have to be zoned off from the public, which is unpopular.

Rockfalls

Mass movement when rocks fall down cliffs after being unsupported

Landslides

Mass movement when slabs of land fall down cliffs after being unsupported

Shoreline Management Plan

The plan that details how a local authority will manage each stretch of coastline in the UK in the future