Boscastle Flood Case Study Responses To How Are You

The effects of and responses to floods vary between areas of contrasting levels of wealth.

 

For this section of the unit you need two case studies, one from a richer area of the world - Boscastle, UK and one from a poorer part of the world - Dhaka, Bangladesh. You need to be able to compare and explain the different effects of and responses to flooding.

 

Boscastle, UK

Dhaka, Bangladesh

16th August 2004

Village built at the confluence of the River Jordan and the River Valency

Video

Severe floods in 1998 and 2004

Confluence of three rivers: Meghna, Ganges, Brahmaputra

Video

CausesNatural
  • Torrential rain: over 500mm rain fell in 4 hours, remnants of Hurricane Alex. Weather system remained stationary over area due to converging winds.
  • Small catchment area (about 23km2)
  • Impermeable upland area (Bodmin Moor)
  • Steep-sided valleys
Extremely wet summer, by August ground was saturated.
  • Confluence of three large rivers
  • Snow melt from Himalayas
  • 70% land area <1m above sea level
  • Cyclones create storm surges
  • Increased surface runoff and more soil erosion means silt blocks river channels reducing carrying capacity of river
  • 80% floodplain and delta makes Bangladesh very susceptible to flooding
Monsoon rainfall
Human
  • Building along river
  • Construction of small bridges across river (trapped material behind them creating small dams)
  • River narrowed through Boscastle reducing capacity
Deforestation in valleys
  • Deforestation in Himalayas
  • Ganges diverted for irrigation increasing silt deposition
  • Rapid unplanned urbanisation in Dhaka
EffectsSocial
  • Destroyed homes
  • Stress and anxiety for local people
Cars belonging to more than 1,000 people washed away
  • Hundreds killed
  • Millions made homeless
Contaminated water led to disease
Economic
  • 25 business properties destroyed
  • Bridges and roads damaged
  • 4 footbridges washed away
  • Visitor centre destroyed
  • Area relies on tourism for 90% income, most of which earned in summer months. Floods dramatically affected earnings.
  • Insurance companies paid out an estimated £20 million to repair damaged property
  • Over 900 bridges destroyed
  • 15,000km road damaged
  • Crops lost leading to food shortages
  • Financial losses for businesses and shops
  • Communications damaged making co-ordinating rescue efforts difficult
Environmental
  • Gardens and pavements destroyed by weight of floodwater
  • Agricultural land flooded and contaminated by polluted water
ResponsesShort-term Major incident declared at 5pm. RAF search and rescue were alerted to rescue trapped people. No-one died mainly due to the rapid response of the emergency services.
  • Farmers provided with free seeds
  • Foreign aid (including £21million from UK)
  • Water purification tablets
  • Food aid
Long-term

To reduce the risk of future floods, a £4.6 million flood defence scheme was completed in 2008.

  • Low bridges removed
  • River widened through Boscastle
  • New flood defence wall built in village centre
  • River bed lowered by an average of 0.75m
  • Trees near to river removed
  • Landowners encouraged to maintain vegetation cover on valley sides

Dhaka Integrated Flood Protection Project

  • Cluster villages (raised by 2m) and raised homesteads (individual homes raised by 2m on earth banks)
  • Flood shelter: about 2ha of raised land where people can bring livestock. Each shelter has space for over 100 families and includes a toilet
  • Radios to issue warnings
  • Embankments to hold back rising water
  • Sluice gates (able to close channel when water rises)
  • Slope protection (to reduce erosion of embankments)

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Case study: Bocastle

Flooding can cause problems in both developed [developed: Refers to a country that has a lot of wealth or a population that is healthy and well educated.]  and developing [developing: Refers to a country that has little wealth or a population that lacks healthcare and education.]  countries.

Boscastle is a small coastal settlement in the south west of England. It flooded in August 2004, washing cars and buildings into the sea and putting peoples' lives in danger.

Causes of flooding in Boscastle:

  • Heavy localised rainfall – 89 mm of rain fell in an hour.

  • Saturated ground from previous rainfall.

  • Topography [topography: The shape of the land.]  of the land. The landscape upstream of Boscastle, a steep-sided valley, acted as a funnel directing vast volumes of water into the village.

  • Narrow river channels in the village itself.

What has Boscastle done to prevent flooding in the future?

  • £4.5 million has been spent on a flood defence scheme.

  • The scheme stretches along the valley, incorporating drainage, sewerage systems and land re-grading.

  • Boscastle car park has been raised in height, which will stop the river from bursting its banks so easily.

  • New drains allow water to run into the lower section of the river quickly.

  • The river channel has been made deeper and wider so that it can accommodate more water.

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