Geography Unit 1

It's a brief view about the case studies of impact of flooding 

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Pakistan Floods, 2010- Causes

Causes:

  • heavy & prolonged rains in the monsoon season fill rivers to burstin point
  • at its peak- discharge on river indus was 40 times above normal
  • floods covered one fifth of the country
  • the lowlying central and southern Pakistan mean't it comprised of vast alluvial plains and occupied by millions of poor farmers
  • himalaya mountain range to the north increased precipitation and meltwater from snow 
  • deforestation ?
  • limited protection from flood management schemes.
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Impacts of Pakistan Floods ;)

Impacts:)

  • final death toll of 2000 deaths 
  • 1.2 million homes destroyed and villages swept away
  • 10 million pple displaced
  • 8 million needed emergency relief aid
  • shortages of food & clean drinking water and inadequate sanitation
  • by Sept, outbreak of water borne dzzs e.g cholera
  • economic costs between $3.5 & $5 billion
  • Pakistan's GDP was to fall by 2 %
  • damaged physical infrastructure e.g roads
  • 3.2 million ha of crops lost or badly damaged
  • commercial crops worst affected e.g rice by 20-30 % decline
  • agriculture contributes to Pakistan's GDP by one fifth
  • and also employs 45% of the country's workforce
  • poor farmers & landless labourers wiht few resources were affected
  • concerns of spread of disease and malnutrition after 2 months of the disaster.
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North Devon/Cornwall UK

Causes of flood at Lynmouth in north Devon and Boscastle in Cornwall in 2004:

  • onshore winds bring warm moisture-laden air frm Atlantic ocean which is uplifted as it meets uplands of Exmoor & Bodmin Moor= trigger torrential downpours.
  • steep drainage basins on Lyn,Valency, & impermeable geology & sparse tree cover ??????
  • villages such as Lynmouth & Boscastle occupy the floors of steep,narrow valleys down whc floodwaters are funnelled.
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Lower Severn Floods, Gloucestershire&Worcestershir

Causes:

  • xtreme precipitation on 20 JUly, 135 mm of rain fell at Pershore on Worcestershire in 16 hrs
  • flash floods in several local tributary catchments raised the level of the Severn at Worcester- 6 m above normal
  • heavy antecedent soil moisture- soils were already saturated by record rainfall in June
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Impacts of Lower Severn Floods

Impacts:

  • by 21 July,widespread floodin all along river severn frm Upton to Gloucester
  • floods hit town and villages on River Avon
  • Tewkesbury- floodwaters entered the town's ancient abbey for the first time in 247 yrs.
  • near Glos,foodwaters shut down electricity substation-leavin 50 000 households wiht out power for 2 days
  • tewkesbury, water treatment plant flooded, cuttin water supply to 140 000 households for 5 days
  • 10 000 motorists left stranded on M5- forced to abandon thier cars becoz of floodwater & landslides
  • insured losses were estimated between £1 billion - £1.5 billion
  • large scale damage to property & disruption of businesses
  • 27 000 domestic insurance claims
  • 6 800 business claims made
  • crops were submerged & maize, potatoes were destroyed.
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Coastal Flooding: Eastern England

Causes:

  • low pressure areas/depressions accompanied by gale winds force winds
  • high tides present major flood hazards to the low lying coastal areas
  • breaching of sea defences by elevated sea levels known as storm surges
  • generated hurricane winds moved through the North Sea
  • as it moved south, the shallow funnel-shape of southern part of north sea amplified its height
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Eastern England Floods

IMPACTS:

  • eastern england & southern netherlands were hit by greatest north sea storm surge on record.
  • surge heights reached 3m at Kings Lynn & 3.36m in Netherlands
  • flood embarkments were breached & sea walls crumbled
  • in east and southeast england 307 pple died
  • 75 000 ha of farmland were flooded 
  • 24 000 homes damaged
  • however, in contrast of the 2007 floods in the same area- surge was accurately forecast
  • thames barrier closed & flood warnings issued
  • pple at risk were prepared for evacuation
  • tidal peak passed without incident, though sea level at Great Yarmouth rose to within 10 cm of the top of the sea walls
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Coastal Erosion at Happisburgh, Norfolk

In northeast Norfolk coastal erosion rates often exceed 5 m a year!!!

PHYSICAL CAUSES:

  • coastline comprisin weak sands & gravel & soft clay is easily undercut by wave action
  • the long fetch to north & northeast means that wave energy is high along this coast. 

HUMAN CAUSES:

  • erosion has accelerated since 1990 when 300 m of sea defences (revetments) were destroyed by a storm
  • decision not to repair revetments increased erosion 
  • led to loss of six cliff top homes
  • gorvernment policy of 'no active intervention' the village of Happisburgh cud disappear before end of century.
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Hard Engineering at North Bay, Scarborough

Strengthening hard defences:

  • north bay, surrounded by built up urban environment, is protected by hard defences
  • concrete sea walls extend along the entire length of the bay & protect the narrow promenade, coastal road & steep coastal slope
  • btwn 2000&2005 hard defences were strengthened in southern part of bay
  • thousands of tonnes of rip rap at coast of £26 million were imported by barge & positioned at the foot of the sea wall
  • aim was to prevent wave overtopping, damage to infrastructure on promenade and landslips on coastal slope
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ISSUES:

  • hard defences are controversial apart from cost
  • may cause significant loss of sediment in the Bay
  • advanced line of defences & highly reflective nature of sea walls may have increased energy levels over the remaining upper beach- resulting in sediment being removed offshore
  • without hard defences, north bay wud hve a broader upper beach that wud provide natural protection for the coast
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Soft engineering at Freiston Shore, Lincolnshire

Background&Issues:

  • in 1983, 66 ha of salt marsh at Freiston was reclaimed frm the sea
  • reclaimed land was protected by an earthen flood embarkment and converted to arable farming.
  • costs of maintainin sea defences, with the relatively low value of the reclaimed land- made managed realignment a more cost-effective, and a more sustainable alternative. 

RESPONSES & IMPACT:

  • environment agency, english nature & RSPB produced more sustainable realignment plan which involved breachin flood embarkment- allow the are to return to mix of salt marshes&saline lagoons
  • within 13 months of breachin, inter-tidal area was colonised by 11 species of salt marsh plants, 8 species of fish& numerous waders,geese and ducks
  • Today, Freiston attracts 60 000 visitors a yr, bringin £150 000 a yr to the local economy&creatin four full time jobs.
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