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Flood in London: A Mission Impossible?

Major floods in London have always been a part of London life

Key Ideas

Climate change poses potential risks of flooding in London

London is not very well prepared for major flooding

Major floods could devastate London and kill many people

The government and relevant agencies need action plans in place to prepare for such a disaster


The risk of flooding in London

Major floods in London have always been a part of London life. A tidal surge in 1953 caused the Thames and the East coast to flood, killing 300 people. This resulted in a review of flood defences - most notably the building of the Thames Barrier. Climate change poses potential threats to London, where 1,250,000 people live/work on the floodplain worth an estimated £80 billion. The likelihood of tidal flooding is increasing because sea level is rising. It is estimated that climate change could increase fluvial and coastal risk by a factor of eight to 12 times. Research for the London Climate Change Partnership estimated that by the 2080s, winters will be 30% wetter, heavy winter rainfall could occur twice as frequently and the number of storms crossing the UK each winter could increase from five to eight. Relative sea level in the Thames Estuary with extreme sea levels experienced more frequently. 

London is at risk of flood by:

  • Tidal - overtopping of existing defences due to a severe storm surge in the North Sea. Also if the tidal defences fail to operate

  • Fluvial - due to freshwater flows in a tributary that exceeds the capacity of the channel especially if undefended or breached

  • Surface water - usually as the result of intense rainfall in a summer thunderstorm that exceeds the capacity of the drainage system

  • The following may also increase flood risk: sewage, water main burst, groundwater, contained water, for example reservoirs

London's flood prevention measures

The Thames Barrier provides good protection for London at present but should there be a major flooding event, the barrier could be breached. In addition, the Thames Barrier was constructed with a life expectancy spanning until 2030. The Environment Agency along with several London water companies have been drafting up plans to reduce the likelihood of major floods in London between 2015 and 2030 which is estimated to cost in the region of £4 billion. Among the ideas to protect Londoners include: raising homes on stilts, Bangladesh-style escape roads, using large areas of Kent and Essex farmland to flood waters during a tidal surge. Some property owners along the River Thames have already put up temporary flood barriers for when waters are particularly high. However, in the future this may not be enough. Building more defences is not always the answer and is not always a sustainable solution. The Environment Agency is also conducting a feasibility study for a new barrier to be sited down river. A barrier there would halt the surge before it reached central London.

The impact of flooding in London

The designers of the Thames Barrier claim that only a tidal surge severe enough to occur only once in 1,000 years could currently flood London. However, this seemingly small risk is increased due to climate change. In January 2003, the barrier had to be lowered a record 19 times to prevent flooding during heavy rains. The impact on Londoners would be huge: there are 38 underground stations that could fill with water, eight power stations, 16 hospitals, 400 schools and 500,000 properties. This would also cause a huge amount of economic disruption to businesses in the city. In addition, there could be sludgy water ponding in low lying areas, damaged homes would not be inhabitable and services and emergency services would not be able to function properly.

The London Assembly Environment Committee (2005) said that 'fragmented responsibility for maintaining flood defences and lack of clarity over planning are putting London at risk.' Clear and strong planning policy is crucially needed to protect London. See BBC News article Warning over flood defense for more information.

To see the roles of various organisations in the incidence of a major flood see: Pages 18 to 27 of the government report London Flood Response Strategic Plan


What if London really flooded?

Imagine what it would be like if London really flooded. Watch this film trailer for the 2007 film Flood. Whilst this film is a story and many scientists believe that London is unlikely to flood in this way, a major flood in London is what students will have to deal with in this lesson.

As a class, discuss initial thoughts about the film trailer and what it would be like if London flooded.

Main Activity

Mission Impossible?

Climate change has the potential to cause increased flood risks in the London area. The aim of this exercise is to imagine what it would be like if there was a storm surge which threatened London and what could be done to help prevent damage to the city and loss of life.

The activity is based on the film Mission Impossible. You will need to work in groups, as teams of agents, to decide on an action plan to save London from a devastating storm surge. You will need some large paper, copies of a London flood map and a stopwatch. The London population density map from UK National Statistics may also help.

Download the "Mission Impossible" PowerPoint. Read each slide carefully and follow the instructions as given. This is a fast-paced, timed exercise. To ensure you keep to time use a stop watch and make sure you spend no longer that 5 minutes writing your three recommendations to the Prime Minister and 10 minutes to write your action plan.

Once you have finished the task had in your ideas to the Prime Minister (otherwise known as your teacher).


Share your finished action plans with the class. Refer to the questions posed at the end of the Mission Impossible PowerPoint. Reflect on how well you worked together as a group and whether your ideas would have actually worked.


The Thames Barrier was designed to be operational until 2030. Since climate change threatens to cause sea level rise, and there is the increased likelihood of surges reaching the Thames, design a new Thames Barrier to take London through the rest of the century.

The links below concerning the Thames Barrier may be useful for help.