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More or less flooded

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Flooding - the personal costs

1.4 million properties in Great Britain are at risk from river flooding and up to three times that number from surface water flooding. Add to that the approximately 98,000 properties that could be deluged by the sea – not counting all those that would flood if the sea came over and beyond the defences (as occurred last winter) and it is clear that the UK needs to take flooding seriously.  Apart from the obvious economic cost associated with flooding there is the human cost.  The plight of flood victims can often lead them into depression and occasionally even to suicide.  The misery of seeing one’s home and treasured possessions destroyed by flood water and sewage is difficult to comprehend by those who have never experienced it.  The personal cost to individual people is immense. But the wider social impact should not be underestimated.  Flood victims have to move to temporary accommodation, which is often unsuitable, for long periods of time.  As they disperse far and wide to try and settle into life elsewhere, they leave behind them a community with its heart torn out. 

What's happening?

Flooding and its consequences cannot be ignored. So we must ask questions in order to try and manage it better.  This article will address some of those questions.  Are we being flooded more often than we used to be? What types of flooding have caused our recent floods? Why are they happening? And finally, what does the future hold?

The floods that inundated the UK during the winter and spring of 2013-2014 were a combination of four flood types. Windstorm Xaver battered our coastlines when low pressure at sea combined with strong winds and high tides, creating unusually large and invasive waves.  Excessive rainfall filled our river channels to overflowing causing them to flood; it also proved too much for our drainage systems which, as a result of either low capacity or poor maintenance, could not cope with the quantity of water running off the land. This led to wide-spread surface water flooding.  Meanwhile, in the chalky southern regions the surplus water saturated the ground until it could hold no more. This groundwater started to bubble up from below, flooding people's homes. So, within the space of a few months our land was flooded by the sea, by rivers, by surface water runoff and by groundwater. That was quite a flood cocktail and with home repairs taking many months to complete, people are still suffering the effects.  Flooding can also occur when hydraulic structures fail - for example, dams and canals; all of these flood types are modelled in JBA’s Comprehensive Flood Map of the UK and Ireland, but for now, we'll concentrate on weather-related flooding because of its unpredictability. While we can predict with reasonable certainty that engineers will try to ensure the safety of our dams, canals and aqueducts, we cannot predict how the weather is going to impact the country from one month to the next.

The UK certainly seems to have had more than its fair share of floods over recent months and years.  But is this part of a trend or just a few random occurrences?  If it is a trend, why is flooding on the increase?

First of all, is flooding really becoming more frequent? What is the evidence?

Trends

The river gauge data from JBA's Great Britain event set, which covers the period from 1960 to 2008 shows some interesting trends.  All the events with a return period of at least 10 years at a minimum of one gauge were counted, for each year of the analysis period, and they are increasing in number (Figure 1).  So within this time period, flood events have become more frequent. 

Figure 1

What about the severity of the events? Has that increased as well? To get an idea of that, we looked at the number of events each year with a return period of either 25, 50 or 100- years and calculated for each, what percentage they made up of the total number of events that year.  Yet again, the trend shows that the proportion of higher return period events is gradually increasing which means that flood severity is worsening as well (Figure 2).

Figure 2

So if, as the data suggests, flooding is becoming both more frequent and more severe, there must be reasons for this. What are they and what factors are contributing to it?  Most of these can be grouped under two headings: climate change and land use.

What are the causes?
1. Climate change

Let’s begin with climate change and how it is contributing to the growing number and severity of flood events. There is overwhelming agreement within the scientific community that our global climate is changing.  Data gives evidence of rising sea levels, rising temperatures and more severe weather patterns and it seems likely that this pattern will continue. For example, the Intergovernmental Panel on Climate Change in their fifth report published in September 2013, made this statement:"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased."

On a global scale, the economic effects of this are colossal as has been shown in a new report from the World Meteorological Organization. The research demonstrates that between 1970 and 2012 the global economy suffered a huge £1.4 trillion of losses as a result of weather, climate and water related disasters. Sources speculate that this may be even higher than indicated by earlier estimates. In Europe, economic losses totalled £5.5 billion and these are predominantly the result of floods and storms.

Views vary on whether or not the causes are man-made but that is not the issue in discussion here. Whatever the reasons, the fact that the climate is changing is what we need to build into our thinking. In the UK, the winter storms of 2013/14 led to the wettest December to January period since records began, and while the Met Office noted that climate change could not be definitively blamed for this, they did go on to comment that extreme daily rainfall rates are becoming more intense, and that the rate of increase is consistent with what is expected from the fundamental physics of a warming world.

Furthermore, a recent report by the Committee on Climate Change (CCC) in the UK claims that the greatest threat posed by climate change in the UK is increased flood risk. Models of the climate system suggest floods of the type experienced in England and Wales in autumn 2000 and between December 2013 and February 2014 have become more likely as a consequence of increased concentrations of greenhouse gases in the atmosphere.

2. Urban land use

Land use is the second and probably the least disputed cause of flooding. Whether the land is agricultural or urban, some of the uses to which we currently put it contribute greatly towards flooding. The spreading of urban terrain is not only a cause, but it is also an exacerbating factor on the impact of floods. Local government is under pressure to meet central government targets for increasing the nation's housing stock.  Additional funding is available to local authorities if they reuse brownfield sites for housing development – an obvious incentive to do so – but many brownfield sites are in the floodplains.  However, such riverside locations can be very desirable, making houses easy to sell. This is an immediate advantage for developers and councils alike. Another attraction for developers is that floodplains are flat, making them easier and cheaper to build on than hilly terrains.  According to figures obtained by The Independent on Sunday in its 2 February 2014 issue, local councils allowed at least 87 planning developments involving 560 homes to proceed in England and Wales in areas at such high risk of flooding that the Environment Agency formally opposed them. 

3. Drainage

Besides the building of housing on floodplains, another major issue in the advance of urbanisation is our drainage systems.  Many of these are ageing and in a poor state of repair.  Blocked, collapsed and leaking drains are not uncommon, all of which can cause flooding.  Besides the state of the pipes, there is the additional issue that many of our existing drains are typically designed to cope with only a 1 in 10-year flow.  Newer drains should have a capacity for a 1 in 30-year flow but as we have seen, the higher return period events are increasing in frequency.

The drainage problem is compounded by our need for, and obsession with, impermeable ground cover. Concrete, tarmac, and fashionable paving stones used for roads, car parks, pavements, buildings, driveways and patios, are covering more and more of our land that was formerly fields, common land, woodlands or gardens. Every inch of impermeable surface gained is another inch of natural water storage lost. For example, in a ten year period, ten per cent of all the permeable ground in London was lost in this way. Our drains are simply unable to cope with the extra quantity of rainfall runoff that our concrete lifestyle is producing.  The seriousness of urbanisation really came to the fore after the floods in the summer of 2007 in England; two-thirds of the properties flooded were affected because drains and sewers were overwhelmed. In other words, surface water flooding became our new greatest enemy.

4. Agricultural land use

Even agricultural land use has a part to play. This became a hot topic last winter / spring when the Somerset Levels lay underwater for nearly three months.  Farmland (in this case the Levels) was deemed to be a lower priority for flood relief expenditure than densely populated urban regions. Arguments raged over the value of dredging; whether or not to relax soil protection rules; and winter sowing of crops such as maize, which leaves soil bare before and after harvesting. Bare soil after harvesting is often compacted by heavy machinery causing rainwater to run off the ground and down to the river. Any soil it brings with it adds to the river’s silt bed; the extra water and silt both contribute towards flooding. 

Deforestation was also cited as a contributory factor towards the Somerset floods.  The removal of trees further up a catchment is known to cause flooding further down the valley because rain, which would have percolated into the ground around the tree roots, simply runs down into the river – or town, if it reaches that first! Even such a seemingly minor matter as the direction in which a farmer ploughs his hillside fields can cause flooding. If the furrows run up and down the hill instead of around it, they can act as excess water channels and flood any properties below them.

By contrast, a very successful flood management demonstration project, delivered by the National Trust, JBA Consulting and Penny Anderson Associates, was shortlisted at the 2014 Climate Week Awards for having shown the benefits of managing floods in harmony with the natural landscape.

What does the future hold?

So, what about the future?  If, as the evidence suggests, we are to expect more of the same, what options are open to us?  Allowing the land to be inundated is the natural solution and in certain areas this course of action is advisable.  For example, some of the old sea defences along Britain's coastline are actually being removed as they are no longer fit for purpose.  Coastal waters will be able to inundate the land naturally but residents will be forced to move further inland. Implementing the policy of defence removal elsewhere in the country would require homeowners whose houses are at risk of flooding to abandon their homes - an unrealistic notion.  All that remains as a viable policy is to bolster our defences. At a micro level, property flood barriers are effective and moving possessions to an upper floor can lessen the damage to a property's contents.  But at a macro level, we need to consider the role of flood defences. Can we rely on these to improve the situation? Let's look at the facts.

Flood defences

According to House of Commons Standard Note SN/SC/5755, 12 February 2014, "Flood defence spending in England," annual flood damage costs in England are in the region of £1.1 billion. These costs could rise to as much as £27 billion by 2080. It has been estimated that maintaining existing levels of flood defence would require flood defence spending to increase to over £1 billion per year by 2035. This is just to maintain existing levels of flood defence.  No figure is given for actually extending the level of defence. The Note also comments that Central Government spending on flood defences will reduce in real terms over the spending review period but that the Government hopes to attract funding from local investors.

So it seems that the prospect of improved flood defences rests on the combined will and ability of local investors to provide substantial funds.  Whether or not this scheme will work remains to be seen.

If the scheme fails to attract investors, flooding in the UK is set to become an even greater threat than it already is.  And if sufficient measures are not taken to defend us from an ever-increasing flood risk, we might ask what effect this will have on the property market. Some home owners fear that their homes will depreciate in value if they are known to be in an area susceptible to flood – even if affordable insurance is available to them. Will this result in a blighted subset of the property market? Or will it perhaps kick-start a general lowering of house prices across the UK?  On the other hand, if the details of Flood Re turn out to be satisfactory to everyone, perhaps nothing will happen to house prices. Who knows? But one thing we can be sure of: flooding in our land is not about to dry up.

 

Note 1: Indicative flood assessments are available from JBA Risk Management and detailed flood risk assessments are available from JBA Consulting.

Note 2: This article is an updated version of an article that was originally written for and first published by Lexis Environmental PSL.

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