Dredging the rivers Parrett and Tone would have significantly reduced the extent of the flooding in the Somerset Levels this winter, ICE past president Jean Venables has told NCE.
Venables also said that a long-term solution could be achieved with a £60M investment in dredging and pumping.
Venables was speaking to NCE in her capacity as Association of Drainage Authorities chief executive before giving evidence to the House of Commons environment, food and rural affairs committee on Wednesday.
“We’re not saying that these areas should not flood,” she said. “They are flood plains and they should flood - but for a day or two, not for weeks on end.”
Venables explained that some simple engineering measures costing around £60M would allow the floodwaters to be cleared more quickly without increasing the flood risk in the towns of Taunton andBridgwater, both of which lie on the edge of the Levels.
Two severe flood warnings remain in place for the Levels, while the Environment Agency oversees the country’s largest ever pumping operation. Ninety six pumps, many imported from the Netherlands, are working to remove 7.3Mt of water daily.
Construction of a permanent pumping station close to where the Parrett meets the River Severn at the village of Dunball is key said Venables.
The station, along with a new tidal gate, would allow water to be pumped from the Parrett around the clock.
The tidal nature of the Parrett means water only drains naturally at low tides.
There are currently eight temporary pumps installed at this location. These high capacity pumps have been brought in from the Netherlands, but Venables said it was too risky to rely on this as a long-term solution.
“We ought to have our own pumps,” she said. “If the Netherlands had had its own emergency, they would not have been available.”
She added that dredging the rivers Tone and Parrett close to their confluence at Burrowbridge was also important, as this would allow their conveyance capacity to be returned to historic levels.
Working in combination with the new pumping station at Dunball this would allow much greater volumes of water to flow through the area before floodwaters overspill onto the Levels.
“It is not simply a case of too much rain,” she said. “It is possible to design a system that can cope.” Venables cited as evidence the neighbouring Axe and Brue water catchments that are not flooding.
Some engineers have questioned the scientific and financial justifications for dredging the Levels, which has been seen in some quarters as a move to appease voters (NCE 6 February).
But Venables insisted that there was a clear role for dredging. “This [prolonged] flood has been caused by a lack of maintenance,” she said.
Venables added that the cost of implementing such measures should not come out of the Environment Agency’s existing maintenance budget or the extra £130M promised by the government in response to this winter’s floods.
“We are focusing on the Somerset Levels,” she said. But a lot of other areas of the countries are close to this situation. So I would be very concerned if the repair costs came out of the maintenance budget.”