How can we control flooding in the UK?
As parts of Britain suffer terrible flooding, author ofTaming the Flood. Rivers, Wetlands and the Centuries-old Battle against FloodingJeremy Purseglove explores the cause of these flood events and questions whether government policy on flood prevention is fit for purpose.
As the people of Cumbria, Lancashire, Yorkshire and Dumfries and Galloway clean-up after the wreckage of Storm Desmond, it is time to consider how we manage our countryside to minimise flooding. It is clear that climate change is a major cause of these floods as ever warmer winters bring increased rainfall in from the Atlantic. 2014 was the warmest year both globally and in the UK since records began but 2015 seems to have outstripped it.
It is reasonable to assume that this pattern will continue and, as one flood victim stoically remarked on TV, ‘we can’t go on raising walls forever’. As we look for solutions it is useful to consider the history of flood management and to examine the modern farmed landscape. Drainage and river management have been carried out since earliest times. Medieval monks were mad on it. Oliver Cromwell built major flood banks, and river engineering in England reached a crescendo of activity in the post-war years of the twentieth century. This was largely for the benefit of farming – to minimise short grazing seasons and foot-rot in sheep and, above all, to increase cereal crops. When I started working in the water industry in 1977, Flood Defence was known as Land Drainage and the largely agricultural projects were decided by a committee dominated by farmers.
In the 1990s the emphasis of flood defence was changed from rural schemes to urban but the legacy of all that earlier drainage of farmland remains. Farming comprises around 75 per cent of land use. In lowland England you just have to look out of your car window or from a passing train to see huge arable fields with relatively few hedges, wet corners or woodlands. What you cannot see is the damaged soil structure of grassland when over-trampled by cattle and, even worse, the ‘plough pan’ on arable land caused by massive modern machinery. This leads to rain water flowing off the land through the uppermost soil levels rather than filtering vertically into the ground. As a consequence, the water pours into the rivers, which are often closely bounded by raised flood banks. These banks channel the water straight to the downstream towns.
So how do we make space for water to go somewhere rather than flooding us out? The most inspirational flood alleviation project I have seen recently is at Holnicote in Somerset. Here almost all the catchment of a river flowing from Exmoor into Porlock Bay is owned by the National Trust. By owning the land the Trust has been able to work with their tenants to hold the water back along the entire length of the river system. They have put small dams on the moorland headwaters, blocked some of the upper reaches in a steep gorge with tree trunks and have broken out some of the old flood banks on the lower reaches so the water can deliberately spread out over low lying fields at times of heavy rain. Hydrologists regularly measure water flow along the length of the streams.
When there was a one in 70 year storm on Christmas Eve 2013, the downstream villages stayed just above the flood level. As a result, it was possible to prove that the relatively small interventions costing £160,000 prevented £30m property assets from flooding. Of course, the storm was much smaller than the recent one in Cumbria but the land use – saturated moorland, descending through wild upland streams to embanked farmland on the lowest reaches – is not unlike the flashy Eden, Cocker and Derwent river catchments in miniature.
Natural Flood Management schemes such as that at Holnicote can be combined with hard defences together with lagoons, swales and porous surfaces to absorb water in towns. There remains one massive problem if we are to unpick over four centuries of ever-intensively farmed landscape in order to make space for water. Who is going to give their land away to make the space? Town dwellers would be annoyed if they had to surrender their gardens to help save downstream populations from flooding. Even more understandably, farmers are not going to part with land, which earns them a living, unless they get compensation. The Common Agricultural Policy should provide an obvious mechanism to pay appropriate subsidies but 75 per cent of the current payments simply encourage continued intensive farming.
The challenge is massive but so is the chance to change things. Schemes such as Holnicote offer practical hope for reducing flood misery whilst restoring traditional landscapes and habitats. At Pontbren near Welshpool the local farmers instigated tree planting in their upland catchment. Around 20 per cent of the Lake District National Park is owned by the National Trust, which sees the recent floods as an opportunity to carefully re-think land use. Floods will no doubt continue through the rest of the winter but the long term environmental opportunity countrywide is one we cannot afford to miss.
Jeremy Purseglove’s classic book Taming the Flood. Rivers, Wetlands and the Centuries-old Battle against Flooding has been updated in the wake of recent floods and is published by Harper Collins.