Farmers and villagers of the Somerset Levels cannot face the misery of flooding year after year. But, as Anth ony Gibson sets out below, there is a permanent solution that won’t cost the earth
The Polden Hills divide the Somerset Levels and Moors in two. To the north lie the valleys of the Axe and the Brue, to the south is the country of the Parrett and the Tone. It was along this ridge that Jesus Christ is supposed to have “walked upon England’s mountains green” with his father Joseph, en route from Combwich on the coast, to do business in the trading centre of Glastonbury.
The A39 now follows the line of the old ridgeway, and if you drive along it right now, you will notice something distinctly odd. Where the moors to the south should be are instead great sheets of water. Yet to the north, where the land is actually slightly lower, and you would expect the floods to be every bit as deep, there is scarcely a puddle.
Why the difference? It is mostly to do with the tide. The rivers to the north of the Poldens – the Brue, the Axe and the Huntspill River – all have sluice gates at their mouths. These are opened when the tide is going down, to let the river water out to sea, and closed as the tide rises, to prevent sea-water pushing up river to meet the land water coming down, with the inevitable consequences.
The Parrett, with its tributaries of Isle, Yeo and Tone, enjoys no such protection. For four-and-a-half hours every tide, nine hours a day, it effectively flows backwards as millions of cubic metres of sea water, driven by some of the highest tides in the world, pushes up through Bridgwater to Burrowbridge and beyond. ‘Tide-lock’, this is called, and it is a huge contributory factor to the flooding problems in the Parrett basin.
It isn’t just that the incoming tide pushes the land-water over the banks when the river is high, it also brings thousands of tonnes of silt with it. That is why it is the tidal stretches of the Parrett and Tone where the need for dredging is most pressing and will do most good. It is also why, if nothing is done about the influence of the tide, dredging will need to be repeated at regular intervals. They took out almost 300,000 tonnes of silt in the last major dredge in the wake of the 1960 floods. A year later, almost a third of that had been replaced by the tide.
The answer seems obvious. Build a sluice near the mouth of the Parrett, to keep the tide out, reduce flood risk, prevent re-silting and save massively on the cost of repeat dredging. It would also protect the 11,400 homes in Bridgwater which are at risk from being flooded from the sea. At the last count, the Environment Agency rated this as a one-in-200-year risk, but with the climate becoming more volatile and tidal surges more severe seemingly with every year that passes, it is a risk that has to be taken seriously (as I was writing this, on the eve of another massive tide, the EA was erecting temporary flood defences in the town).
Over and above that, keeping the tide out of the river would enable it to be held at a constant height through Bridgwater. Instead of being a muddy ditch for half the day, it would become a green and pleasant stretch of water, a focus for urban regeneration and a priceless asset to the town. The potential benefits were valued at almost £400 million in 2005. And you could generate a worthwhile amount of renewable energy as the river emptied itself through the sluice gates on every receding tide.
Ah, if only it were that simple! Money is, as usual, the main problem, but it is by no means the only one. There is a sewage works that will need sorting out, a working dock at Dunball that might be compromised, and the loss of what the ecologists call ‘inter-tidal habitat’ – banks of slimy mud to you and me – to be weighed in the balance.
We would also need to be sure that there was sufficient storage capacity on the landward side of the sluice to remove any risk of flooding upstream when the river was full and the sluice closed. Careful computer modelling will be essential.
As for the cost, a tidal exclusion sluice complete with navigation lock and elver pass – which is really the only sort worth having because of its multiple benefits – would probably set us back around £30 million, according to the most recent estimates. Applying the standard funding formula might see it built by the late 2020s, if we’re lucky.
But there might just be a way around this. The EA/Government would probably come up with a chunk of the cost and the balance could be borrowed, possibly from the European Investment Bank which was specifically created for big infrastructure projects. The debt could be serviced and eventually repaid from a mixture of the roof tax which Sedgemoor District Council is already collecting from developers and the catchment-wide drainage charge which is proposed in the Somerset flooding action plan. It has to be said that history is not encouraging. A Parrett sluice was first proposed in the thirteenth century! But it is now very firmly back on the agenda, and with a bit of imagination, some careful evaluation and a lot of determination, its hour might just finally have come.
Anthony Gibson is chairman of the Somerset Water Management Partnership and the acting Chairman of the Levels and Moors Task Force. He is former communications director of the National Farmers’ Union and a WMN columnist