Coasts - Facts and Case Studies (copy)

• 4.7km straight line sea wall (£1000/m)

• Revetments combined with sea wall in some areas

Population: 35,000 (most populous)

Avg. House Price: £180,000

→ due to long term defences + accessibility

Number of Tourists: 5mil (lots)

• 2.7m/year of erosion

Population: 2,500

→ vs. Mappleton - low vote turnout

Avg. House Price: £90,000

Number of Tourists: less than 1000

Other Key Areas to Protect: Caravan sites, church lost, 35 homes and 4 businesses lost

• 3km curved sea wall (£4000/m)

• 1km rock armour (£2000/m)

• 7 groynes (£15,000 each)

• Concrete revetment at the caravan park

Population: 9000

Avg. House Price: £202,000

Number of Tourists: 1 million

Other Key Areas to Protect: Trans Pennine Trail, caravan park and the gas terminal

• 10 rock armour - groyne hybrids (£2mil total)

Population: 342

→ though less than Skipsea, they voted tory = they protect

Avg. House Price: £200,000

Number of Tourists: less than 1000

Other Key Areas to Protect: Mappleton Beach, grade 3 agricultural land, B1242 Main Road

• Some groynes + rock armour

• Salt marsh + sand dune succession = negative feedback that maintains spit

• Small sea wall around life boat station

Population: 10 families (lifeboat workers - RNLI)

Number of Tourists: ~ 40,000

Other Key Areas to Protect: Protected (SSSI) by RSPB + National Trust, lifeboat station = tugboat for River Humber

Low Relief

• 50% live 10m below sea level

  • = susceptible to even minimal sea level rise

Tropical Climate

• Increased rainfall

• Weather events such as typhoons and monsoons also bring increased volumes of water

  • monsoons flood lands = worsened storm surges with decreased infiltration

Himalayas

• Relief rainfall

• Glacial melt = more water in rivers = worsened storm surges

• Prevent typhoons moving further inland past Bangladesh = more rainfall

Bay of Bengal

• Triangular shape = water channels into Bangladesh

• Causes monsoon rains + regular high tide + storms to travel and concentrate around Bangladesh

Deforestation

• 70% mangroves deforested (for shrimp farms and tourist access to beaches)

  → mangroves absorb wave energy + slow water so without them good coastal defence removed

The Gangas Delta

• Lots of rivers → 3 biggest in Asia

  • leads to lots of deposition = sediment builds up (accretion) = subsidence under weight

Population: 114,000

Location: Oceania

Land Size: 811 sq km

Mean Elevation: 2m

Physical Factors

• islands are low lying sands and mangrove atolls

• coral atoll island

  • bikini atoll - lots of holes = water enters and ocean acidification worsens solution (eroding from underneath)

Globalisation

• loss of culture + way of life if island is lost

• loose national identity

Climate Change

• sea level rise → 1.2cm/yr in places (4x global average)

  → 60% thermal expansion / 40% ice melt

  • many islands could submerge in 50yrs + 2 already gone

  • food insecurity → sea water contaminates ground water and surface water (salt) = cannot subsistence farm and less drinking water

Managing the Risk

• environmental refugees

  → if needed in future people can move to Fiji (agreement = can establish a quasi-state within their borders by buying land off them for resettlement)

  BUT wouldn’t have rights as citizens + seen as immigrants

  → gov launched ‘migration with dignity’ policy to allow people to apply for jobs in neighbouring countries (e.g., NZ)

• Land will be used in immediate future for agriculture +fish farming

  • VN Kiribati Food Insecurity Project (adaptation)

South- west of England due to long fetch across atlantic

Anticlines and Syncline Formation

→ tectonic forces compressed, bending strata

• collision margin: African plate and Eurasian plate

Flooding

Sea level rise at end of glacial period caused flooding of synclines

This produced lines of narrow islands parallel to the coast by projecting sections of anticlines.

Characteristics

• submergent landscape

• eustatic forces: sea level rises, land stays the same

• Croatia = 1240 islands

→ form where deposition produces unconsolidated geological structures parallel to the coastline

Formation

• sea level during glacial was 100m lower than today

  • water retained in ice sheets

• Meltwater rivers deposited thick layers of sands/gravels onto outwash plains beyond the ice front

• During the Interglacial period, constructive waves these transported sands/gravels landwards as sea levels rose

• Sand ridge formed bars across some bays and river mouths → trapped water behind = lagoon

Examples

• Neman Haff → behind the bar running from the Kaliningrad in Russia to the Lithuanian coast at the mouth of river Neman

→ FAST

Geology

Boulder Clay:

• Unconsolidated

  • less resistant to destructive waves

  • slumps when wet

• Easily transported by suspension = doesn’t accumulate as beach sand = waves can erode cliff base

• 7-10m eroded per year

Chalk:

• more resistant than boulder clay

• sedimentary = not the most resistant though

  • many bedding planes/fractures

  • vulnerable to solution

Powerful Waves

• Long fetch → 500-800km over North Sea + length of Atlantic

  • increased energy of destructive waves

Weather

• Low pressure weather system = raised sea level = waves reach higher up the cliff

• Winter storms pass over North Sea = locally strong winds and waves

Naturally Narrow Beaches

• less friction = wave power isn’t reduced as much = higher energy waves erode cliffs

→ Mainly mechanical + biological

• mechanical: freeze-thaw from constant wetting and drying of boulder clay

→ mainly slumping

1. alternate wetting and drying of boulder clay = expansion + shrinkage that produces cracks during dry periods

2. rain then enters cracks, percolates into cliff, becoming heavier (higher pore pressure)

3. weakened cliff slides down under gravity

4. slumped material at cliff base removed by sea (boulder clay vulnerable to suspension) = cliff retreat

• Positive feedback mechanisms caused by human management is risking erosion in south (L.S.D = N→S) with sediment starvation

  • e.g., Spurn Head at risk of erosion (esp. due to groynes)

    = essential services such as coastguard/lifeguard will have to move or be lost

  • e.g., conflict at Aldbrough (settlement south of Mappleton) as no defences + cliffs rapidly eroding

    → believe defences at Mappleton worsening their erosion

• Conflict between different stakeholders developing (e.g., Aldbrough) due to different beliefs in what should be managed

  • UK national gov coastal defence budget in Norfolk being £9mil (2023) = can’t hold the line across entire coastlines

Raised Beaches

→ Lendalfoot, Ayrshire, west Scotland

• raised beach surface used for A77

→ Isle of Arran

• 5m raised beach

• 3 levels of raised beaches produced at different stages of post-glacial adjustment. 

Fossil/Relict Cliffs

→ Isle of Arran

• 40m raised cliff now 200m inland

• caves

Rias

→ Kingsbury, south Devon

• 6m long

• main channel 1m wide near its mouth at Salcombe

• 2 large drowned tributaries extend on east side

  • Frogmore Creek = 2km long, 500m wide

Fjords

→ Sognefjord, west Norway

• 205km long

• 1.3km deep

• main branch 4.5km wide

Ice Formation/Melt - 40%

→ Greenland’s ice sheet looses 250bn tonnes of ice per year

→ Cyclic climate change due to Milankovitch Cycles (change in Earth’s orbit) = glacial periods (90,000 year phases) and Inter-glacial periods (10,000 year phases)

• changing distribution of water within the hydrological cycle = sea level changes

Thermal Expansion - 60%

→ Pacific Ocean expanded by 30-55% in last 50 years

→ Also linked to cycle of glacial and inter-glacial periods (warmer inter-glacial period = expansion)

• changing temperature of seawater = sea level changes

Post Glacial Adjustment - local rise/fall

→ UK: northern half during Devensian Glacial period covered by 2km thick ice sheet = weight of ice depressed the crust below + rigidity of crust = see saw effect

→ UK: now, after ice melted, Scotland rising 2mm per year and adjacent southern half falling by 2mm per year

Accretion - local rise

cause:

→ sink regions in the sediment cell = net deposition, land is built up, leading to a fall in sea level (in delta regions accretion -> subsidence -> accretion etc)

e.g., Nile Delta

Subsidence - local fall

causes:

→ the weight of deposited of sediment, especially fluvial deposits in large river deltas, overcomes the threshold = very slow 'crustal sag' and delta subsidence

e.g., Nile Delta sinking 5mm per year

→ lowering of water table (increased evaporation climate change or human abstraction) = pore water pressure decreases = overlying sediments settle

e.g., New Orleans, Louisiana - city over-abstracted groundwater for civilian use so displaced rock layers under city

→ heavy buildings

general e.g., Mississippi, Amazon

Tectonics

causes:

→ formation of anticlines/synclines as sedimentary rocks fold under compressive forces

e.g., African-Eurasian plate boundary 60cm fall in the Bakar-Vindol area, Croatia

→ 2004 Boxing Day tsunami: EQ caused the crustal plate to extend and therefore sink at Banda Aceh by 20cm

→ 10.5m storm surge

• Depression moving south across North Sea → reduced pressure (970mb) on sea

  • = sea level rose 0.5m

• Spring high tide

  • = sea level 2m higher than avg.

• Rivers flowing into North Sea in flood due to high sea levels = can’t discharge water

• Extra water surging south couldn’t be transported fast enough due to narrow straight of Dover

  • = sea level rose further 2m

• Anticyclone occurring west of Ireland (high pressure → 1032mb) = large pressure gradient = severe northerly gale (100knots)

  • = 6m waves

• Low lying land between Humber and Thames + some parts of The Walsh below sea level

England - BAD

• 1600km coastline affected

• 24,000 buildings destroyed

• 307 people died

• Canvey Island - Essex worse affected

  • lots of low lying bungalows

  • on an estuary

→ Thames River Locks constructed to stop sea water travelling up the river

Bangladesh - WORSE

• 3500 fatalities caused due to drowning

• Houses, bridges, road and infrastructure were destroyed. Electricity and communications networks were damaged, leaving homes unconnected.

• Drinking water was contaminated with salt water and debris and sanitation infrastructure was destroyed. This increased the risk of diseases spreading in the aftermath of the cyclone.

→ 5m in Hull

• Successions of depressions = especially low pressure

• Spring high tide

  • = sea level 2m higher than avg.

• Strong onshore winds (up to 100mph)

• Unprecedented rainfall

→ Environment Agency said worst since 1953

Social

• 17 died

• Loss of amenity value

  • nature reserve damaged in Skegness

• Loss of livelihood

  • business affected in Lowestoft, Suffolk as harbour area, railway station, and southern town centre flooded → 391 properties flooded

Economic

• Power cuts

  • 40,000 homes in Scotland + N England

• 1400 homes flooded + some fell due to cliff line retreat

• Cost £1bn in damages

• All rail services cancelled in Scotland

• Thames barrier closed to protect London

• Flood defences built protected 800,000 homes in England

• Better forecasting = time to prepare

  • 36 severe flood warnings - the highest category - were issued across the region

• 1000s evacuated

A port city on the Bay of Bengal

Coastal Climate Resilient Infrastructure Project (2012):

→ supported by Asian Development Bank (ADB)

→ aims to ‘climate proof’ area through range of small schemes:

• improving road connections (farmers→markets) + embankments raised (60cm) so roads above normal flood levels = resilient to coastal erosion

• constructing/extending 25 tropical cyclone shelters

  • accounted for future sea level rise + increased wind speeds

• new market areas with sheds on raised platforms above predicted 2050 sea level

• training on climate resilience + adaptation strategies

Positives

• jobs generated = decreased poverty 10%

• reduction in road flooding to 5 days a year from 20 planted trees

Negatives

• 200 people relocated due to road realignment during construction phase

• permanent removal of natural vegetation = disturbed habitats

• embankments slow to be constructed

→ OVERALL: 2015 International Fund for Agricultural Development (a UN agency) rated project satisfactory