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Fluvial Flooding Case Study

Abstract

Historically, flood risk management in the United Kingdom has mainly concentrated on river and coastal flooding, yet flooding from surface water runoff is a risk to urban areas. A comprehensive study of the causes, the impact and the consequences as well as the management of serious pluvial flooding in Heywood, Greater Manchester, in 2004 and 2006 revealed that the victims of the floods were unprepared, ill-informed and confused as to responsibilities before, during and after the event. Householders had to rely on their insurers for loss mitigation, but the response of the insurance industry was varied and inconsistent, and there were difficulties in building in resilience after the event. In 2006, only one property was on the Office of the Water Regulator DG 5 Register on the basis of previous flooding. Thus the area falls between the responsibilities of the Local Authority (LA), the Environment Agency and the water utility. The people affected do not know whom to turn to for assistance. A way forward may be through the establishment of an overriding agency to provide a coherent voice and strategic guidance, supported by dedicated flooding experts within LA planning departments, the adaptation of buildings for flood resilience and through changes within the insurance industry.

Flooding Case studies

Cockermouth, UK - Rich Country (MEDC)

Causes: Rain 
A massive downpour of rain (31.4cm), over a 24-hour period triggered the floods that hit Cockermouth and Workington in Cumbria in November
2009
 
What caused all the rain?
The long downpour was caused by a lengthy flow of warm, moist air that came down from the Azores in the mid-Atlantic. This kind of airflow is
common in the UK during autumn and winter, and is known as a ‘warm conveyor’. The warmer the air is, the more moisture it can hold.

What else helped to cause the Cumbrian Floods?
·        The ground was already saturated, so the additional rain flowed as surface run-off straight into the rivers
·        The steep slopes of the Cumbrian Mountains helped the water to run very rapidly into the rivers
 ·       The rivers Derwent and Cocker were already swollen with previous rainfall
·        Cockermouth is at the confluence of the Derwent and Cocker (i.e. they meet there)

 The effects of the flood
·       Over 1300 homes were flooded and contaminated with sewage
 ·      A number of people had to be evacuated, including 50 by helicopter, when the flooding cut off Cockermouth town centre
·       Many businesses were flooded causing long-term difficulties for the local economy
·       People were told that they were unlikely to be able to move back into flood-damaged homes for at least a year. The cost of putting right the damage was an average
  of £28,000 per house
·       Insurance companies estimated that the final cost of the flood could reach £100 million
·       Four  bridges collapsed and 12 were closed because of flood damage. In Workington,  all the bridges were destroyed or so badly damaged that they were declared
  unsafe – cutting the town in two. People faced a huge round trip to get from one side of the town to the other, using safe bridges
·      One man died– PC Bill Barker

Responses to the flood
 ·     The government provided £1 million to help with the clean-up and repairs and agreed to pay for road and bridge repairs in Cumbria
·      The Cumbria Flood Recovery Fund was set up to help victims of the flood. It reached £1 million after just 10 days
·      Network Rail opened a temporary railway station in Workington     
The ‘Visit Cumbria’ website provided lists of recovery services and trades, and people who could provide emergency accommodation

Management of future floods at Cockermouth
£4.4 million pound management scheme
New flood defence walls will halt the spread of the  river
Funding from Government and local contributors
River dredged more regularly to deepen the channel 
New embankments raise the channel height to reduce the likelihood of extra floods
New floodgates at the back of houses in Waterloo street


Pakistan, Asia - Poor Country

At the end of July 2010 usually heavy monsoon rains in northwest Pakistan caused rivers to flood and burst their banks. The map below shows the
huge area of Pakistan affected by flooding. The floodwater slowly moved down the Indus River towards the sea.

Continuing heavy rain hampered the rescue efforts. After visiting Pakistan, the UN Secretary General, Ban Ki-moon, said  that this disaster was worse than anything he’d ever seen. He described the floods as a slow-moving tsunami.


The effect of the floods

·   At least 1600 people died
 ·  20 million Pakistanis were affected (over 10% of the population), 6 million needed food aid
·   Whole villages were swept away, and over 700,000 homes were damaged or destroyed
·   Hundreds of thousands of Pakistanis were displaced, and many suffered from malnutrition and a lack of clean water
·   5000 miles of roads and railways were washed away, along with 1000 bridges
·  160,000km2 of land were affected. That’s at least 20% of the country
·   About 6.5 million acres of crops were washed away in Punjab and Sindh provinces

The responses to the floods
 ·        Appeals  were immediately launched by international organisation, like the UK’s Disasters Emergency Committee – and the UN – to help Pakistanis hit by the
  floods
·         Many charities and aid agencies provided help, including the Red Crescent and Medecins Sans Frontieres
·        Pakistan’s government also tried to raise money to help the huge number of people affected
·        But there were complaints that the Pakistan government was slow to respond to the crisis, and that it struggled to cope
·        Foreign Governments donated millions of dollars, and Saudi Arabia and the USA promised $600 million in flood aid. But many people felt that the richer foreign governments didn’t do enough to help
·        The UN’s World Food Programme provided crucial food aid. But, by November 2010, they were warning that they might have cut the amount of food handed out, because of  a lack of donations from richer countries


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