Seriously wet: a metre of water is bad news for farmers and for wildlife (Image: David Woodfall)
Can we prevent a repeat of the disastrous floods that hit south-west England last winter – and keep both farmers and conservationists sweet at the same time?
FROM the top of the hill, the Somerset Levels appear green and calm. Rain clouds scud across the summer sky as we look out at the rivers Parrett and Tone, snaking over the flat land in thin threads.
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It is August and the rivers are safe within their banks. “Six months ago, this view was rather different,” says Richard Bradford, an ecologist who has worked here for 20 years.
Last winter, both rivers burst their banks, flooding more than 120 square kilometres of this low-lying coastal plain. At one point, the Levels contained 100 million cubic metres of water, according to the UK’s Environment Agency, the government body charged with managing the rivers. Angry farmers gathered on the few spots of dry land to buttonhole the world’s media with stories of a conspiracy between Agency scientists and environmentalists to flood their land. “Is this David Cameron’s Hurricane Katrina?” asked The New York Times.
The British prime minister’s response was to declare: “We cannot let this happen again.” But now, with the land largely dried out, the questions remain. Can his promise be kept during this winter and beyond? And given that the Somerset Levels are a world-renowned habitat for water birds, should his promise be honoured at all?
Even in normal winters, the Levels flood. This is because of the landscape’s topography: the rivers that cross the Levels are higher than much of the land, held back behind banks first raised in medieval times to turn tidal marshes into grazing pastures. And when the rivers reach the sea, they are confronted by one of the highest tidal ranges in the world.
High tide in the Severn estuary is more than 7 metres above mean sea level. For more than 6 hours a day, the sea towers over the rivers, tides flood far inland and the rivers back up. And when, as last winter, those rivers are in spate, they back up for tens of kilometres. Once the rivers breach their banks and flood the surrounding moors, only evaporation by the sun – or pumps – can shift it.
Local farmers are used to this regular inundation. Their meadows are nibbled by cattle in summer, and left waterlogged in winter. The Levels contain the largest surviving area of wet lowland grass in the UK, so their conservation value is high. Birds like the wet, and environmentalists like the birds. And this is a landscape where nature and cattle can happily coexist. The biggest landowner is the Royal Society for the Protection of Birds, which employs Bradford as its farm liaison officer. It has 900 hectares, where cattle graze and wildfowl and wading birds such as snipe and lapwings roost and feed.
But last winter was exceptional: it rained and it rained. For a month, daily Atlantic storms dumped their loads on south-west England. Draining rain-soaked hills to the west, the Tone burst its banks, spilling on to two adjacent low-lying marshes – Curry Moor and North Moor. That is their role in the Levels’ drainage system (see map) and between them they have a capacity of more than 20 million cubic metres. This capacity is normally sufficient, but last winter the Tone sometimes overflowed at a rate of 100 cubic metres a second, enough to fill both moors in little more than two days.
The problem was made worse because the Tone also drains into the river Parrett, which at the time had its greatest recorded flow, according to the Environment Agency’s flood manager for the region, Graham Quarrier. The agency’s engineers had to make space in the Parrett by diverting part of its flow into the Sowy, a flood-relief channel that bypasses Bridgwater – the main town on the Levels – and joins the river again near the coast.
Soon the Sowy was full. The moors overtopped, roads flooded and one village, Moorland, submerged so rapidly that an evacuation alert was delivered by helicopter.
Now they have dried out, most farmers on the Levels can only scoff at Cameron’s promise to prevent future floods: this is a floodplain, after all. The main problem was people seduced by a few years without major floods, building houses where they shouldn’t. Bradford says pastures have recovered well but arable land is taking longer.
Yet last winter’s inundation was not unique, says Quarrier. Floods on the Somerset Levels in 1960 and 1929 lasted just as long. Going back to 1919, about 280 square kilometres flooded, more than twice the 2014 figure.
That didn’t stop the blame game. “We thought we were dealing with experts,” the government minister in charge, Eric Pickles, told a TV interviewer. That rankles with the Environment Agency, the experts Pickles had in mind. In fact, the agency had a shopping list of things to alleviate floods but all had been rejected by ministers as they did not meet spending rules.
High on this shopping list was dredging the rivers Tone and Parrett. As the waters covered their land, farmers complained long and loud that dredging would have reduced the floods. They had a case. Dredging silt brought upstream from the Severn estuary by the tides had historically been a routine part of keeping the rivers clear. It is done “as and when the perceived risk of flooding has been high”, according to a 2012 Environment Agency technical report. But the last major dredging was half a century ago, in 1960. The agency says that as a result, the parts of the Tone and Parrett that spilled over had only two-thirds of their former capacity.
According to Quarrier, dredging would not have reduced the flooding much. But it would have allowed the land to be drain faster. The floods on Curry Moor and North Moor would have lasted weeks rather than months. But there are, he says, risks. Dredging could have simply moved the worst flooding downstream towards Bridgwater, or even cleared the way for more water to rush upstream during high tides on the Severn.
This is the crux of the matter. There are two competing views about how to manage floods. They played out in the debate about the Levels, as they have in floods on heavily managed rivers everywhere, from the Mississippi and the Rhine to the Yellow River in China.
In the blame game on the Somerset Levels, there are two popular theories about what went wrong. One is the “fast water” argument. It says you should fight floods by rushing water to the sea as quickly as possible. That means deepening and widening rivers and cutting out meanders. Above all it takes dredging. That is the conventional solution, and most farmers on the Levels say that is where government policies failed.
“Many farmers think the floods were the environmentalists’ fault,” says Phil Brewin, a wetlands ecologist at the Somerset Drainage Board Consortium, which manages local drainage. Environmentalists opposed dredging because it might damage river ecosystems. And they insisted on flooding low-lying land for birds, instead of keeping it empty to capture floodwaters when the rivers burst. Many farmers accuse the government of doing the environmentalists’ bidding by abandoning dredging and instead spending some £8 million on water management mainly for the benefit of birds, plus another £3 million a year on payments to farmers willing to maintain their grazing land for wildlife by keeping water levels in ditches high.
Environmentalists say this is a caricature of their position. “There is no evidence that the existing measures to conserve wetland birds contributed significantly to the recent flooding,” says David Leach of the Somerset Wildlife Trust.
Look to the hills
The alternative approach to flood prevention is “slow water”. It says the best thing to do is hold the water in the hills for as long as possible, by plugging drains and planting trees, so the water comes downstream more gradually. Environmentalists like this because it reduces big engineering and can keep the landscape wetter – good news for wildlife.
In reality, neither policy has been pursued on the Levels. If anything, the worst of all worlds has been achieved, as hill farmers add drainage to grow arable crops, while conservationists flood the Levels for birds.
This may not be sensible, says , a government research centre in Wallingford, Oxfordshire. Yet last winter it probably didn’t really matter: there was so much water that neither dredging nor holding it in the hills would have helped. “Soils were saturated. At that point things like drains, land use and afforestation don’t make much difference,” he says. The Environment Agency agrees, and last year one of their studies said: “We do not believe that upstream land use has a significant impact on flooding in Curry Moor or North Moor.”
“Soils were saturated. At that point things like drains, land use and afforestation don’t make much difference”
So what should be done? A government flood-action plan for the Somerset Levels, published in haste in March this year acknowledges that “we will never be able to stop flooding completely”. But it wants to prevent the worst. The first action, which began this summer, was government-funded dredging along 7 kilometres of the two rivers.
The next item is increasing the capacity of the Sowy, the flood-relief channel north of the Parrett. Culverts have been put into road bridges that restricted its flow last winter. Bradford thinks its capacity could be doubled, to 70 cubic metres a second.
But where will the water go then? Some local farmers favour a fast-water option that would involve giant pumps where the Sowy rejoins the tidal Parrett. That way, they could keep emptying even at high tide. The slow-water alternative, favoured by environmentalists, is to set the banks of the Sowy back and let it spill naturally across the fields and moors.
The third major item on the government’s agenda is a barrage on the Parrett, downstream of Bridgwater, with “delivery by 2024”. But there are two options. One would be a flood barrier like that on the Thames that could be raised to prevent occasional tidal surges that might threaten Bridgwater. The second option is a permanent barricade that would keep the tidal waters and silt from coming upstream. This proposal worries environmentalists. They say it would pond up pollution such as nitrates from farms, and that accumulating silt below the barrage would both block navigation and damage mudflats in Bridgwater Bay, important roosting areas for waterfowl and wading birds.
There are plenty of battles ahead but some common ground may be emerging between the farmers and conservationists, the fast-water people and the slow-water people. For one thing, the floods should have put paid to the fiction that what is good for nature is bad for farmers, and vice versa. Environmentalists have seen the downside of floods, says Bradford. “A big flood is bad for both wildlife and the farming community.”
In recent months, environmental groups that once opposed dredging have softened their stance. Some now agree that a lot of water courses have become clogged up, and bird life has done badly as a result.
Meanwhile, more farmers are coming to see the virtue of low-impact farming, which is also low-input, a safe option that seems more attractive after the floods. A middle way would be a more “sustainable” wetland, with farmers grazing the rich and rare pastures that maximise wildlife and bring in ever more tourists. “We need agriculture on the Levels,” says Leach. “Many of the current species assemblages that are internationally important are related to agricultural habitats, such as the wet grasslands and ditches.”
This is a debate that is starting to be played out in wet places around the world. Few wetlands are genuinely natural. Most have embraced human activities over centuries that have profoundly changed their ecology and hydrology. The urge among environmentalists to “rewild” such landscapes may be misconceived when much of the wildlife they want to conserve is dependent on past changes and present methods of management. Equally, the wetlands perform vital services for their human neighbours, not least in absorbing floods by providing space for the waters to go.
Free the flow
A new accommodation between humans and nature is behind efforts in Germany and the Netherlands to prevent a repetition of the floods on the Rhine in 1995, when a quarter of a million people were evacuated as Dutch dykes crumbled and an area of 1500 square kilometres flooded. Even the Dutch, whose country is largely created from drained wetland, now recognise that only by giving some of that land back to rivers can they protect the rest. In the wake of hurricane Katrina, Louisiana is planning to protect existing marshes at the mouth of the Mississippi and also create more. And after hurricane Sandy battered New York City, there is even talk of putting salt marshes back around the edge of Manhattan island.
This summer, massive floods along the Sava river in Slovenia and Croatia concentrated minds there. A major cause of the disaster was that the three-quarters of the low-lying wetlands that the river could once have flooded have become disconnected from it. “The main lesson is that the old flood-protection concept, relying on channelisation, is wrong. We have to work with nature,” says Tibor Mikuska of the Croatian Society for Bird and Nature Protection.
Of course, climate change could wreck even the best-laid plans. Modelling studies used by the Environment Agency suggest that last winter’s floods on the Somerset Levels are a sign of things to come. They predict a future 20 per cent increase in peak flows on the Parrett, seriously increasing the risk of major floods, especially when combined with higher sea levels. More space must be found to accommodate this water.
In this highly artificial landscape, where the Tone was first diverted in the 14th century, giving it all back to nature would not work – even for nature. Management is a necessity. But if there is to be more management, the battle over who controls the sluices and pumps may only intensify.
This article appeared in print under the headline “What to do when the banks bust”
