Geography Unit 1

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.

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.

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.

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

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.

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

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

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.

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

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

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.