The floods of Summer 2007: 10 years on

Whilst the UK has been enjoying very hot temperatures recently, 10 years ago it was a different story.

The Summer of 2007 was the wettest since rainfall records began in 1766.  Heavy rain triggered two extreme rainfall events; on 25th June and again on July 20th.  The Met Office reported that from May through to July 2007 more than 387mm of rain fell across England and Wales which is double the average for the period. Despite a relatively dry April, by mid-June the ground was saturated and low sunshine levels meant that there was little evaporation.

On 25th June, intense rainfall led to severe flooding in parts of the North East including Sheffield, Doncaster and Hull; areas in which the level of penetration of insurance is low compared to other parts of the UK.  In Hull, over 6,000 properties were flooded and more than 10,500 homes evacuated as flash flooding led to drainage and sewage systems being overwhelmed.  The flooding caused major disruption to homes and businesses with almost half a million people without a water supply for up to 3 weeks and left many residents unable to return to their homes for up to a year.

More heavy rain on July 20th caused flooding in many parts of England and Wales with some areas hit particularly bad such as Gloucestershire, Cambridgeshire, Wiltshire, Hampshire and Oxfordshire where properties were flooded for the second time in less than a month.

 The impact on the insurance industry

The Environment Agency (EA) estimated the total costs of the 2007 floods to be £4 billion.  Around £3 billion of this loss was covered by insurance, making this one of the costliest events to date for the UK insurance industry.   In terms of insurance claims, the ABI reported around 165,000 claims with 132,000 of those claims for damage to domestic households.   Thankfully this was a rare event and believed to be somewhere between a one in 500 years and a one in a 1000 years event. This estimate though is very much a guess given the amount of data used to base this estimate on and with a changing climate calling into question the assumptions underpinning the analysis.

How flood risk mapping has changed since 2007

Whilst it is not unusual for the UK to experience extreme rainfall in the Summer, a much higher proportion of the flooding of Summer of 2007 was due to surface water flooding rather than any other type of flood risk (e.g. river flooding). By its very nature, surface water flooding is very localised and is caused by large volumes of rain water, making it very difficult to accurately predict exactly where flooding will occur geographically.

At the time, there were no surface water flood maps and insurers did not factor it into their ratings.  Today over 3 million properties are estimated to be at risk of surface water flooding in the UK.

Following the 2007 floods, the Pitt Review found that work was needed to improve the management of flooding from surface water and poor drainage.  It also identified the need for surface water flood maps for England and Wales. Subsequently, JBA Consulting developed the first nationally produced model of surface water flooding to supply to the EA.

The Flood Map for Surface Water (FMfSW) in England and Wales was developed in 2009 and included:

  • an additional rainfall probability
  • the influence of buildings
  • reduction of effective rainfall through taking account of drainage and infiltration
  • a better digital terrain model that incorporated the Environment Agency’s high-quality LIDAR data.

In 2013, an updated Flood Map for Surface Water (uFMfSW) was produced.  The new surface water flood map for England and Wales shows the worst-case flood extents, depths, velocities and hazard ratings for the 30, 100 and 1,000-year return period storm events of one, three and six-hour durations.

The EA maps were not intended to be used for insurance purposes to assess the risk to a particular property but were intended to provide an indication of whether your area may be affected by surface water flooding and to what extent.

Lessons learned for the future?

Recent flooding events have revealed the UK’s vulnerability to extreme rainfall events.  Peter Stott, Head of the Met Office’s climate monitoring and attribution team, believes there is strong evidence that extreme rainfall events are increasing and are likely to become more frequent in future years.

The general scientific consensus is, however, that the summer 2007 floods were not a “climate change event” but rather were a consequence of a combination of unusual (but normal) events such as prolonged heavy rainfall and saturated soil which made it unable to absorb the additional rainfall.

One thing that is clear is that this problem is not going away anytime soon. The NFRR (National Flood Resilience Review) concluded in September 2016 that it was plausible that rainfall experienced over the next ten years could be between 20% and 30% higher than normal.

Insurers are ensuring they are better equipped to deal with the impact of extreme weather events by using data models that are based on up-to-date information and that take account of changing risk patterns to better predict, assess and monitor risk. However, this is not just an insurance issue; it involves government, house builders, local authorities and insurers all working together to ensure the UK becomes more resilient to flooding. With a changing climate and potentially more frequent and more severe flood events in the future, we need to make sure that we take action considering what could happen – failure to adapt is not an option.

Current research indicates that if we are not able to control the average rise in global temperatures then we will subsequently see a significant increase in the risk of flooding. For example, failure to constrain average global temperature rises to within 4 degrees will see the overall risk of UK flooding increase by 150%. It’s a problem that won’t go away and one that needs to be addressed now, not after the next cluster of events.


Flood, building on flood plains and the profile of those at risk

It is estimated that there are currently 1 in 6 properties or 4.7 million properties in Great Britain at risk from flooding, with 2.7 million properties at risk from flooding from rivers and sea alone.  Between 2001 and 2011, around 200,000 new homes were built on land that has a significant chance of flooding, either from a river or the sea. During the 1990s, this figure was even higher as there was less focus on flood and no obligation on planners to carry an analysis of flood risk at the time.

After the devastating effects of last winter’s storms and the subsequent costs to the insurance industry, building residential properties on flood plains continues although admittedly not in the same volumes.

Recent figures obtained by the i newspaper under the Freedom of Information Act show permission has been given to build more than 1,200 new homes on flood plains despite official objections from the Environment Agency about the risk of flooding on such sites. With all the publicity and available data relating to flood risk, it does seem slightly unbelievable that construction even at these levels is allowed to proceed, or at least without an obligation on builders to ensure that properties are built to be flood resilient.

New housing built in areas thought to be protected by flood defences may also be more at risk than first thought. Flood defences are built to withstand a certain magnitude of event, e.g. a flood with an estimated return period of 1 in 200 years, yet the underlying techniques modelled from relatively small data samples are based on extreme value theory which is sensitive to the underlying assumptions. I know there are still some people in senior roles in the world that are sceptical about climate change, however it does undermine the accuracy of these models and mean that defences may be more vulnerable than when first built or constructed. A good recent example being in Carlisle which flooded in 2005 (1925 homes and businesses) with flood defences that were breached. The defences were improved at a cost of £38 million yet these failed again in 2015 following a more extreme event than had been considered in the planning.

Profiling those areas hardest hit by flooding
We used our geodemographic risk profiling tool Resonate© to analyse the demographic profile of those affected by the Winter floods in 2015 in Carlisle and areas of Cumbria.   Our analysis revealed that there was an over-representation of properties flooded from working class and disadvantaged rural areas across the distribution of those hit.

Further analysis of these areas revealed a large number of properties flooded were from the Resonate lifestyle group ‘Rural & Village Survivors’ and those worst affected were predominantly from ‘Blue Collar Heartlands’; which are characterised by blue-collar workers in pre-war terraced properties where the proportion of terraced properties is almost thirteen times the UK average percentage. There is a high proportion of this type of neighbourhood in Carlisle.

Looking at all the areas across the UK that have a high risk of flooding does reveal that there is an over-representation of older, disadvantaged and more vulnerable neighbourhoods. In the future, we will no doubt continue to see more occurrences similar to that of Carlisle with poorer and more deprived neighbourhoods being disproportionately hit.

As long as there is still a demand for new houses, building on flood plains will continue. There is an increased demand for new housing particularly in the South East in areas where flood defences do exist, though climate change may limit the level of protection envisaged when some of these defences were built. A geodemographic analysis of the make up of the high-risk flood areas is quite startling – higher volumes of older, more disadvantaged and more vulnerable members of society dominate.

This highlights the important role that insurance plays and how the availability of affordable flood insurance for everyone is essential.  The introduction of Flood Re goes some way towards offering flood-prone properties a degree of cover but does not yet guarantee affordable insurance for everyone. The Government will need to put more investment in maintaining and improving flood defences and will need to look at helping make properties in the highest risk areas more resilient to damage from flooding.

The next big climate risk?

supervolcanoes and climate change1816 – the year with no Summer, dramatic climate change and a worldwide recession.  What caused it and could it happen again?

Exactly 200 years ago there was a dramatic change in the earth’s climate. It snowed heavily in July, the River Thames was frozen over, crops failed and there was a worldwide recession. Similar events are believed to have also brought about a dramatic change in climate during the Middle Ages often referred to as the ‘Little Ice Age’. What caused this and more importantly could it happen again?

Scientist believe that the ‘Little Ice Age’ was caused by the cooling effect of a large volcanic eruption or ‘super eruption’.   The last recorded supervolcanic eruption was 201 years ago at Mount Tambora in Sumatra, Indonesia in 1815. It had a massive impact on the world economy due to damage to human life, property, machinery and agriculture and severely impacted the world’s climate for many years afterwards.

Tens of thousands of people were killed by the eruption and in subsequent months, thousands more people died in the surrounding areas from starvation due to the resulting crop failures and disease.    Twenty-four hours after the eruption, the ash cloud that had formed is reported to have covered an area approximately the size of Australia.  This ash cloud took years to clear, changing the climate dramatically and causing a ‘volcanic winter’ that blocked out the sun for between six to eight years.

With the resulting lowering of temperatures, 1816 became known as the year without Summer; with snow drifts on hills until late July and it is reported that the Thames was completely frozen over in September.  There was a subsequent worldwide recession. A similar event happening today would be catastrophic.

supervolcanoesYellowstone National Park, Wyoming, USA has one of a number of active supervolcanoes, although the last eruption is believed to have been over 70,000 years ago.   The United States Geological Survey (USGS) conducted a study on Yellowstone. The study used a program called ‘Ash 3D’ to model the effects of a Yellowstone super eruption, focusing on how much ash would fall, how far it would travel and the major effects it would have on infrastructure.

The study found that cities up to 300 miles away from Yellowstone would be covered by up to three feet of ash.  With the sun not able to penetrate the thick blanket of ash and particles in the atmosphere, the average global temperature would drop by an estimated 10ºC for about a decade which would have a dramatic impact on Earth.  Scientists think that a succession of large volcano eruptions had a similar impact on the climate in the Middle Ages when very severe winters were more frequent.

NASA have also been using state-of-the-art climate models to simulate the response to a major volcanic eruption.  They found that some types of evergreen and deciduous trees virtually disappeared for a number of years due to the lack of sunlight.  However, despite all the scaremongering from the press, the Earth’s climate is more resilient than once thought to a supervolcanic eruption. The research from NASA showed that the climate returned to near normal conditions within a decade in most simulations.

Scientists are continuing to monitor the pressure of underground magma.  From these observations, they have concluded that a large scale eruption is not imminent.  Using various factors and calculations, they suggest a confidence of at least 99.9% that 21st century society will not experience a Yellowstone super eruption.