Geography Topic 4: Coastal Landscapes

1.1 Coastal processes and landforms

a. types of wave: constructive and deconstructive

Deconstructive Waves 8d4062a22a73715eb6abc6e21c88bbbba5eebf8c.gif

  • High wave (>1m)
  • High wave energy
  • High wave frequency (10 waves/min)
  • Erodes material
  • Backswash > Swash

Constructive waves

903cb89096e5824a7b28b5172135498d5bc2a193

  • Low wave (>1m)
  • Low wave energy
  • Low frequency (<10 waves / min)
  • Deposits material
  • Swash > Backswash

b. the impact of weathering, erosion and mass movement on the coast: cliffs and wave cut platforms, headlands and bays, caves, arches, stacks and stumps

Erosional Processes

  • Hydraulic action
  • Abrasion
  • Attrition

Weathering Processes

  • Biological weathering
  • Chemical weathering
  • Physical weathering

Mass Movement

  • Rock fall
  • Slumping
  • Soil creep

Wave cut platforms

Erosional landforms

Concordant geology

Discorncodrant geology

Wave refraction

large.png

impacts on geology, people and vegetation

  • Contamination of the water
  • Increased flooding
  • Change of typography of the land
  • The amount of sand on the beach affects the waves of the beach
  • Biological beings (plants, trees and animals) will be destroyed
  • Plants roots prevent vegetation
  • Houses, tourism and industrial sites are lost due to erosion on the coast
  • Economy is damaged for repairs

c. the process and impact of longshore drift on the coastline

 229b24d65359ae54d2a2c757e8987a7a061050d9.png

d. the formation of beaches, spits and bars

  • Beaches –  formed by the deposition of sand, gravel, rocks and pebbles
  • Spits – formed by longshore drift moving material across the coastline. Spits form where material is deposited. The spit may grow to form a hook, providing a sheltered area. Behind that is a salt marsh, which plays host to many rare plants and animals
  • Bars – by the process of LSD, a spit will become a bar if the spit connects with the other headland. From there, it will form a lagoon.

 

1.2 coastal landforms are subject to change

a. differential rates of cliff recession due to factors such as fetch, geology and coastal management

Geology –

  • Coastline with less resistant rock are eroded at a rate of 1-2m/year, as opposed to more resistant rock which typically erode at only a couple mm/year.
  • Hard rocks form high, rugged and steep cliffs
  • Soft rocks form slighter, less steep cliffs and often have evidence of slumping

Vegetation

  • Vegetation prevents and protects against erosion

Sea level change

  • Submergent coastline – they have rising sea levels with drowned valleys (vias) and drowned glacial valleys (fjords)
  • Emergent coastline – falling sea levels with raised beaches and relict cliffs

Fetch

  • The distance of sea over which winds blow and waves move towards the coastline
  • Longer fetch = more destructive waves = more erosion – an example of this would be the south west coast of England ‘getting the fetch’ from the atlantic ocean

Coastal management

  • If coastal defences protected weak geology, the rate of erosion would have been much slower

b. the effects of coastal recession on people and the environment

  •  Cliff recession has negative effects on both people and the environment

CASE STUDY: Durlston Bay, near Swanage – 1968-1988

  • Cliff recession up to 12m a year, ending up 25m away from an apartment block
  • Iconic park (Durlston Country Park) is home to 250 species of bird, their habitats are threatened by cliff recession which could affect the breeding of these rare species

 

  • Property loss by cliff recession is not yet covered by UK insurance
  • In the USA, about $80 mil is paid out for insurace due to coastal recession.

c. prediction and prevention of the effects of coastal flooding by forecasting, building design, planning and education

  • Prediction – Suggesting what flooding is likely to happen in the future
  • Prevention – Relates to the stopping of the impacts of flooding

Coastal flooding – Caused by strong winds and storms, increasing the height of waves and tide. The Environment Agency monitors the sea’s conditions 24/7, and the Storm Tide Forecasting service provides the Environment Agency with forecasts of flooding.

The Environment Agency has a 24 hour flood hotline and a website for precautionary advice, stating clearly the main threats to health during a flood (drowning, injuries), the stress of the event and cleaning up, serious danger caused by carbon monoxide fumes from the indoor use of generators and other fuel powered equipment

CASE STUDY: Thames Barrier (Thames Estuary 2010)

  • Who: The Environment Agency
  • What: Installing new flood walls along the river, plans to leave open space for flood plains
  • Why: Insurance companies claim that flooding will be 8-12 times more frequent by 2010

CASE STUDY: Indonesian province of Atech

  • 106 cases of tetanus, 20 deaths reported at the end of 2004, associated with the coastal flood after the tsunami.
  • Why: mixing sea water with sewage in drains and poor healthcare

CASE STUDY: Bangladesh, Coastal embankment project

  • What: This project led to the building of flood walls and 500 flood shelters to house 10,000 people. Local people are being taught on how to deal with a flood and flood warning systems are being put into place.
  • Future: ensuring that the roof of 1-2 storey buildings have accessible exterior stairways so people can escape rising waters.

d. the types of hard and soft engineering used on the coastline of the UK and the advantages and disadvantages of these techniques

  • Hold the line  – Hard engineering
  • Advance the line  – taking the coastline artificially further
  • Retreat the line  – Allowing erosion to happen (doing nothing)
  • Spectrum  – Variety of measures to protect the coastline. You must use a spectrum of measures or the defence will not be effective
  • Sacrificial coastline  – Allowing the coastline to erode for economical reasons and protecting another for the same reason

 

Soft Engineering Method Description Advantages Disadvantages
Beach replenishment Advancing the line by adding sand, rocks and pebbles – £5,000/m
  • Looks completely natural
  • Relatively cheap
  • Beaches are the best form of sea defence
  • Temporary noise pollution
  • Requires constant management
  • May affect plant and animal life
Cliff regrading Cliff cut back to be given a new, gentle slope to prevent slumping
  • Natural, can be covered in vegetation
  • Not effective alone
  • Homes may be disrupted
Managed retreat Doing nothing
  • cheap
  • Upsetting for landowners
Hard Engineering Method Description Advantage Disadvantage
Rip rap/ Rock armour Large rocks placed in front of a cliff – £300/m
  • Cost effective
  • Dissipates wave energy
  • Unattractive
  • Makes  the beach inaccessible
  • Not effective in storm conditions
Gabions Wire cages filled with stones (£11 /m)
  • Cheap
  • Rock cages absorb the energy
  • Wire  cages can break
  • Not as efficient as other coastal defences
Recurved Sea walls Seawalls protect the base of sand dunes (£3,000/m)
  • Reflects and absorbs wave energy
  • Visible – makes the residents feel safe
  • Effective for many years
  • Makes the beach accessible
  • Can be ugly
  • Very expensive
  • Can cause wave scouring if not manufactured properly
Groynes Horizontal planks of wood that stretch from the coast to the sea (£5, 000 each)
  • Prevents LSD
  • Cost effective
  • Keeps the beach in place for tourists
  • Unattractive
  • Geology of the cliff may change
Off shore reef Large concrete/ natural boulders off shore that alter wave direction and energy (about £2,000 / m)
  • Breaks waves offshore to reduce erosive power
  • Allows the sand to build up naturally
  • Difficult to install
  • Requires constant managementMay affect plant and animal life.

1.3 coastal management

a. how the coast is managed in a named location

Case Study: The Holderness Coast

  • Where:  North of England (Flamborough Head –> 8o K of coastline –> Spurn head spit)
  • When: 1991 –> onwards
  • What: Cliffs retreat at an average of 1-2m/year, losing about 8m of land in a single storm
  • Why: Strong prevailing winds create longshore drift, moving material from the North to South coast. Extremely powerful waves and poor geology (cliffs are made from boulder clay, eroded from hydraulic action, abrasion, corrasion and slumping)

 

Key area: Mappleton, 1991

  • £2mil spent on rock groynes and rock armour at the base of a cliff
  • Because of 50 high-end properties, large main road 30m from fast eroding coastline.
  • Properties now increase in value as they are no longer subject to erosion
  • Groynes stop LSD, but did increase erosion towards the south of Mappleton

Key area: Withernsea, 1975

  • £6.3 mil on rock groynes, seawalls and riprap
  • This is because Withernsea is of high economic value (particularly from tourists)

Key area: Bridlington, 2012

  • £1.4 mil sea wall
  • Residents feel much safer

Key area: North Yorkshire, 2001

  • £3mil sea wall
  • Stretch of coast exposed due to powerful waves, weak boulder clay
  • Has a mass value housing development

Key area: Spurn head spit

  • 2 groynes to stabilize the spit
  • Hooked spot at the bottom of the Holderness coast with a triple SSI salt marsh (SSI – special scientific interest)

 

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