Tuesday, 2 April 2013

DCC's Strategic Flood Risk Assessment - will it protect Ottery St Mary?

DCC has just finalised its Strategic Flood Risk Assessment (SFRA), as required by the NPPF. This informs mineral planning in relation to flood risk and supersedes the unambiguous advice - "mineral development that would reduce storage capacity in areas functioning as floodplain or increase the risk of flooding of sensitive areas will not be permitted". The NPPF and SFRA do still make it clear that:
Inappropriate development in areas at risk of flooding should be avoided by directing development away from areas at highest risk, but where development is necessary, making it safe without increasing flood risk elsewhere
Quarrying activity can increase surface water run-off and therefore flood risk if the area of hard surface is increased, by the compaction of soil, or through the breaching of water and silt storage lagoons. The potential for groundwater flooding may be influenced where mineral extraction impact on local hydro geological characteristics and the interface with the hydrogeological regime, for example through increased transmissivity.
Yet the SFRA says (4.11) that when considering flood risk we must remember that "mineral working is a temporary (albeit often long term) activity that entails the subsequent restoration of the site to a beneficial after-use". Leaving aside the arguments on restoration, mineral working may be temporary but quarrying millions of tonnes of sand and gravel from an aquifer would permanently - not temporarily - change the hydrogeological characteristics on the slopes above a town prone to flooding.

The SFRA acknowledges the history of flooding in Ottery St Mary (6.48), and the ongoing risks it faces as one of Devon's 32 high risk communities. It refers to the flooding in 2008, as resulting in:
an estimated 350 properties flooding from main rivers, ordinary water-courses and surface water, with 25 people requiring assistance from the fire service. The incident is considered to be the worst flood event to have occurred in Devon in the past 25 years.
So why, with an unstable climate, does DCC still consider the removal of millions of tonnes of ground-water storage, exacerbating run-off at the head of streams flowing into Ottery, such a good idea?

And on the subject of groundwater, groundwater flooding may be "considered relatively rare within the Plan Area" (5.31), but despite what the SFRA says, detailed information is available on groundwater flood risk. In fact, such a map has been on this blog since it was set up. Contrary again to the SFRA, there are areas that are considered to have a high susceptibility to groundwater flooding - indeed, some in very close proximity to Straitgate Farm.

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