Wet unpleasant land (Image: Adam Gray/SWNS.com)

Much of southern England is underwater thanks to a record-breaking deluge that has fallen over two months. More than 5000 homes have flooded in the Thames valley and Somerset. Many of the people affected complain that rivers should have been dredged to allow the water to escape faster. But hydrologists say dredging alone would have made little difference. The only way is to manage entire catchment areas, or in the case of Somerset, perhaps build an artificial lagoon.

Rainfall in England and Wales in December and January has been the heaviest since records began 240 years ago. The rains have been exacerbated by conditions in Indonesia and the tropical west Pacific, according to the UK Met Office. Heavy rains there in November, plus warm seas, combined to redirect and strengthen the North Atlantic jet stream, the air current carrying the downpours to the UK.

As the waters rose, residents blamed the Environment Agency and its embattled chief Chris Smith for failing to allow floodwater to escape by adequately dredging rivers.


But hydrologists contacted by New Scientist say that dredging alone would not have stopped the flooding. “Given the amount of rain that has fallen, you could have doubled the carrying capacity of every drainage channel in Somerset, at huge cost, and large parts would still have flooded,” says Hannah Cloke at the University of Reading.

Large-scale thinking

Instead, we must manage drainage throughout entire river systems. “You need to help slow down the flow of water into rivers, and help water infiltrate into the ground instead,” says Cloke. This could mean placing debris like tree stumps in tributaries near the river source, to slow the flow into the main river.

We could also build “balancing” ponds alongside rivers, or install temporary barriers to hold water until it soaks away, says Cloke. “But you’d need to use these measures at many places.”

Sustainable drainage systems are key, especially for new housing estates near rivers, says a flood engineer at the Environment Agency who preferred to remain anonymous. “They could be simple things, like requiring water butts, plus porous driveways and balancing ponds to hold back excess water and drain it gradually.”

Artificial lagoon

For Somerset, one long-term solution might be to build a dammed artificial lagoon at the mouth of the River Parrett, the main source of drainage from the flooded areas. “It would divide the sea from the river, and serve as an enormous valve to control drainage from the river,” says Roger Falconer of Cardiff University.

A scheme like this, called the Bridgewater Bay Lagoon scheme and estimated to cost £4 billion, was rejected in 2010 by the Welsh Assembly. Falconer says it would have generated tidal energy as well as controlling the risk of flood.

The plan was to build a 20-kilometre-long semicircular dam around the mouth of the river. The dam would allow water to drain out when tides fell, but stop it coming back in. Such a structure would allow the waters of the lagoon to be lowered by as much as 8 metres below the river, speeding up drainage from the land. Up to 640 million cubic metres of water could be drained every day, says Falconer. “It would also stop the tide pushing the water back in again.”

Cloke says the scheme could help Somerset. “It’s a unique system, with no gradient, so it could work for that area.” But it would take years, and is expensive.

The trouble is, the recent deluge has been so sustained that nothing could have prevented all the flooding, says Cloke. “I’ve just been down to the Thames, and it’s really full. It would be unrealistic to think you can control these enormous floods with any measures.”

“The solution for residents and communities is to adapt to living with it,” Cloke says. “They shouldn’t expect the government or the Environment Agency to protect them from a flood that’s impossible to protect against.”