The Government has accepted that it has been underestimating the amount of damage inflicted by groundwater and other long-term flooding when deciding whether to fund alleviation schemes.
A study commissioned by Hampshire County Council found that flooding lasting weeks or even months resulted in up to three times the amount of damage than predicted by the Department for Environment, Food and Rural Affairs’ current model.
The research, ordered after a £2M scheme to tackle groundwater flooding from a chalk aquifer in mid-Hampshire failed to attract a government grant, found that the effect of the duration of flooding had largely been neglected. Carried out by Middlesex University’s flood hazard research centre – which drew up the Government’s tables for estimating potential flooding damage – it concluded that a flood of two weeks would cause 2.6 times the amount of damage a 12-hour-long flood would inflict. In 2000/20001, a ‘river’ formed along the main street of the Hampshire village of Hambledon for more than two months following prolonged rainfall, which had caused the chalk aquifer to rise above ground level.
David Richardson, Hampshire principal engineer for highways, said the issue would strengthen the case for any schemes drawn up for alleviating groundwater or other long-term flooding. ‘Hopefully, this will encourage engineers to make a case for funding.’
DEFRA's current flood-management strategy switched focus away from purely looking at fluvial and coastal flooding, and embraces flooding from other sources, including groundwater, as well as from overloaded drains and sewers. It estimates that 1.7M properties in England are vulnerable to the increasing problem (Surveyor, 18 November 2004). The Environment Agency said it would improve the justification for the scheme to install culverts at Hambledon when it was considered by the regional flood defence committee. DEFRA accepted the principle that the damage was greater in reality than assumed, but questioned how the consultants arrived at the exact amounts of damage.
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