Groundwater Flooding at Barn Meadow
Hampshire’s underlying chalk geology becomes saturated after prolonged periods of rain, making the water table rise. This is the source of winterbournes, the seasonal streams we see in places like Bishop’s Sutton, and groundwater flooding – like that in our video of Barn Meadow.
The map below shows precisely where our video was taken; in the supposedly drier part of Barn Meadow away from the river. So why don’t the Environment Agency’s flood risk maps show this flooding?
We asked the EA’s Groundwater, Hydrology & Contaminated Land Team just that. Their reply was very helpful:
“Unfortunately, the flood maps for planning do not show groundwater risk, only river and sea flooding data” and “they do not show the risk of groundwater flooding on a site. The surface water flood map does not cover groundwater flooding.”
Going on to say, “when you check long term flood risk on our website … the ‘other flood risks’ does have a groundwater section, but the risk is based on our flood alert areas. These groundwater flood alert areas do not cover all areas that suffer from groundwater flooding, so again are not adequate for assessing groundwater flood risk at every site.“
It stands to reason that if the Environment Agency doesn’t have sufficient resources to tackle river pollution adequately, it won’t be measuring groundwater flooding on every acre of farmland in the country.
The EA Technical Specialists also told us that “any anecdotal evidence is really useful when it comes to sites as we don’t have data everywhere.”
We shared the Environment Agency’s guidance with the council and asked them to consider our video as evidence ahead of the Community Consultation, so the community could properly understand the risks of building on Barn Meadow; an offer they refused without explanation.
From the wessex rivers trust
Devastation from Groundwater at Chalk River Floodplain Development
Our friends at the Wessex Rivers Trust sent us these photographs of the ongoing pollution from chalk river development on the River Were at Warminster. They told us:
“We’re dealing with the consequences of unsustainable new development on the floodplain of the River Were; like the Arle, a chalk river headwater. Winter groundwater inflows and surface water run off during heavy rainfall is resulting in large quantities of soil running off the building site and into the river. Once the soil is lost to the river, these low energy chalk streams cannot wash it away, resulting in long term ecological damage.”
That site is some distance from the River Avon SAC. Barn Meadow shares its banks with the River Itchen SAC, so any such impact on its protected habitat would be immediate.
Barn Meadow is the only site put forward for housing in Alresford within the medium and highest risk Flood Zones 2 & 3, with much of it in the highest risk Flood Zone 3
All the other proposed housing sites are well away from Zones 2 + 3 in the lowest risk Zone 1
Flood Map
Much of Barn Meadow is recognised as being part of the highest risk Flood Zones 3 and 2.
Groundwater Flooding
The red triangle on the Flood Map shows where our video of groundwater flooding was taken – in the middle of the supposedly ‘driest’ part of the floodplain.
Climate Change Model
Water levels are projected to rise due to the impact of climate change. This will effect all low-lying areas, including Barn Meadow.
It is essential to make responsible planning decisions ahead of these changes.
