Sheffield Flood 2007 Case Study

Flooding — Summer 2007

Torrential downpours in May, June and July 2007 left large swathes of the country under water as the rain was followed by widespread flooding. By accurately forecasting the weather, the Met Office kept people informed on what they could expect.

Unsettled conditions dominated the Bank Holiday in early May, bringing rain and showers to many parts of the country. For the following Bank Holiday there was heavy rain. After a reasonably dry start to June, extremely heavy and prolonged rain fell on to an already soggy UK, leading to serious floods which threatened lives and caused substantial damage to property. Tragically some people died and thousands more had to spend nights in temporary accommodation or were left without power.

Part of the reason for the heavy rain was the jet stream - a band of strong winds in the upper atmosphere that influence how weather systems that bring rain to the UK will develop. As the jet stream was stronger than normal, depressions near the UK were more intense. Some of these depressions pulled in the very warm and moist air to the south of the UK, generating exceptionally heavy and intense rainfall.

What we did

  • We played a vital role throughout the summer, providing highly accurate forecasts and warnings ahead of the heavy rains.
  • Before and during the floods we worked with and advised emergency planners across the UK including the police and military rescue teams, the Environment Agency, the Scottish Environment Protection Agency and COBR (the Civil contingencies committee which leads responses to national crises).
  • We issued early warnings of the severe weather several days ahead to advise the public on the possible impacts.
  • As more heavy rain fell on already flood-hit areas, we kept everyone informed as the downpours deposited well over three times the monthly average rainfall for June in some places.

The results

  • While it is not easy to forecast extreme weather, the heavy rain was well forecast, with Met Office forecasters predicting the heavy and prolonged rainfall.
  • There is no doubt that things would have been much worse without early warnings from the Met Office.

What happened in June

On Monday 25 June prolonged heavy rainfall resulted in many parts of north and east England being flooded.

DatesActions
17 to 20 JuneLocalised torrential downpours continued with many Flash warnings issued.
21 JuneNews Release issued to highlight unseasonable weather.
22 JuneEarly Warning issued to public, government and emergency services giving three days' notice of potential disruption.
23 JuneFurther warnings and update to Early Warning issued for E/NE England.
24 JuneEarly Warning updated with highest probabilities for disruption in an arc from Yorkshire and Humberside to the Welsh Borders, with rainfall totals of 'up to 100 mm or so'.
25 JuneFlash warnings issued for heavy and persistent rain across the high risk areas during the day.

Weather conditions

Days before the actual flooding, the ground around the worst-hit areas became saturated by very heavy rain. Many sites in Yorkshire received at least a month's rainfall in 24 hours.

On Monday 25 June a slow-moving area of low pressure brought a prolonged period of heavy rain to northern and central England. Hitting the already saturated north-east, the water had nowhere else to go and, as a result, led to major flooding.

Impacts

  • Five people died.
  • Surface water flooding in Hull.
  • Widespread disruption and damage to more than 7,000 houses and 1,300 businesses in Hull.
  • River Don burst its banks, flooding Sheffield and Doncaster.
  • Flooding in Derbyshire, Lincolnshire and Worcestershire.
  • Highest official rainfall total was 111 mm at Fylingdales (N Yorkshire). Amateur networks recorded similar totals in the Hull area.
  • There were fears that the dam wall at the Ulley Reservoir near Rotherham would burst.

A heightened alert state was retained during the week 25-30 June, because of the threat of further rain.

What happened in July

The second event caused localised flash flooding across parts of southern England on the morning of 20 July, and later in the day across the Midlands.

Dates Actions
16 JulyMedium-range computer forecast suggests a vigorous weather system could move toward the UK and engage with relatively warm air over northern France.Met Office Executive Board briefed about the chances of this event.
18 JulyEarly Warning issued in the morning, central and eastern areas of England at risk of disruption from 60-90 mm of rain.
19 JulyRisk areas narrowed to south-west Midlands, Gloucestershire and Oxfordshire. Possible rainfall total increased to 75-100 mm.
20 July Flash warnings for southern and central England issued before 9 a.m.

Weather conditions

A slow-moving depression centred over south-east England, drawing warm moist air from the continent across the UK. Heavy and slow moving rainfall moved northwards during the day.

Impacts

  • Widespread disruption to the motorway and rail networks.
  • In the following days the River Severn and tributaries in Gloucestershire, Worcestershire, Herefordshire, Shropshire broke banks and flooded surrounding areas.
  • River Thames and its tributaries in Wiltshire, Oxfordshire, Berkshire and Surrey flooded.
  • Flooding in Telford and Wrekin, Staffordshire, Warwickshire and Birmingham.
  • The highest recorded rainfall total was 157.4 mm in 48 hours at Pershore College (Worcestershire).

The future

  • In August, Sir Michael Pitt conducted an independent review of the flooding. The review recognised our forecasts and warnings had been timely and accurate and also praised the performance of our Public Weather Service Advisors.
  • A key recommendation of the Pitt review, after the floods of summer 2007, was that the Environment Agency and the Met Office should work together, through a joint Flood Forecasting Centre , to improve the capability to forecast, model and warn against flooding.
  • Developments in Met Office capability such as 1.5 km resolution models and probabilistic forecasts will help the UK to be more resilient to severe weather.

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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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