Is It Time to Let Go? as Climate Change Takes Hold, Attempts to Control Flooding on the Somerset Levels Will Become Increasingly Difficult, and Other, More Radical Approaches Will Be Needed
Rowe, Mark, Geographical
At the height of this winter's floods, 65 square kilometres of land on the Somerset Levels were under water and 65 pumps were working 24 hours a day to drain 65 million cubic metres of floodwater off the land. In the wettest winter since 1766, the levels had been hit by a one-in-100-year flood for the second time in 14 months.
That much--and the devastation and misery endured by those on the receiving end everyone can agree on. When it comes to the causes--and how to deal with the floods of the future--however, the situation, like the water that overran the fields and villages, is somewhat murkier.
In the short term, the dredging of the bifurcation of the rivers Tone and Parrett, the two major rivers that feed the levels, has already begun. Dredging was at the centre of the fallout over the flooding: farmers, villagers and local and national politicians complained that insufficient dredging had caused the rivers to flood. As a government body, the Environment Agency will dutifully carry out the work.
Yet it's nigh on impossible to identify an expert--geographer, hydrologist, engineer who believes that dredging alone will make much difference. 'There has been an awful lot of garbage, if not untruths and lies, about dredging,' says David Demeritt, professor of geography at King's College London. 'Dredging gives you a bit of extra capacity in the drains, so a little bit more of the rainfall will drain away more rapidly. But it won't make any difference with the order of rain we're talking about. If you dredge, somewhere downstream the water just ends up in someone's kitchen more quickly.'
Instead, the consensus among flooding experts is that dredging and dyke building will make things worse, not better. To seek to tame the floods, they argue, is to miss the point in a climate-changed world of more extreme weather patterns and inexorable sea-level rise.
In a paper issued in February, the Met Office concluded that sea levels around the UK are likely to rise by 11-16 centimetres by 2030, relative to 1990. Daily heavy rain events are also likely to become more frequent--what in the 1960s might have been a one-in-125-day event is now more likely to be a one-in-85-day event.
Dutch experts, meanwhile, have identified one factor at play on the levels that until now has been all but overlooked--subsidence. This has plagued the Netherlands, where land, drained for four centuries, has subsided at a rate of one to two centimetres a year.
'Over the centuries, subsidence has caused some areas, including cities such as Gouda, to go from being at or above sea level to eight metres below sea level,' says Marcel Silvius of Wetlands International.
'When you drain peatland for agriculture, the land compacts,' he continues. Peat is about 90 per cent water, so it subsides under its own pressure. Then the oxygen in the soil starts the biological process of breaking down the organic matter in the peat. This converts the carbon into carbon dioxide, releasing this greenhouse gas into the atmosphere--and making the soil subside even further.'
A TIME FOR PRAGMATISM
So what does all of this mean for the levels? Silvius agrees that all farms and homes could be defended, but the cost would be unfeasibly high. Demeritt, too, believes that the scale of such an undertaking hasn't fully been taken on board. The government seems to be saying that it will protect everything, everywhere,' he says. 'Is that true? It's not right to say that it isn't possible--we can protect every bit of coastline if we want to, if money truly is no object. But in practice, that would mean that your riverside home will never flood only because it has a 15-metre dyke in front of it, so you can't even see the river.'
Defences could, in theory, involve a Thames Barrier-style construction on the levels, but the scale of such a project would, Demeritt argues, be out of all proportion to the benefits. …