severn estuary forum flood risk and the severn barrage 19 th september 2009 nick lyness wessex flood...
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Severn Estuary ForumFlood Risk and the Severn Barrage19th September 2009 Nick Lyness
Wessex Flood &Coast Erosion Risk Manager
UPSTREAM DOWNSTREAM
habitat
defences
drainage
de-commissioning
coastal development
channel morphology
80,000 ha low lying land
Flood risk
A barrage should decrease overall flood risk from storm surges, but……
Existing defences, and new strategies, will manage the flooding impacts of climate change without a barrage.
SDC report recognises that flood risk is an emotive subject, but it is not a show stopper or promoter.
Flood Defence issues
Tidal flap valve at Windmill Reen, Redwick
Blackwall West Reen, Magor
Seawall near Goldcliff Point
A barrage should decrease overall flood risk from storm surges, but……
~ 100 drainage schemes will need upgrading.
Up to £60m to sort the pumping stations and tidal outfalls
Thousands of people are protected by defence systems
Flood Defence issues
Flood Defence issues
Flood Defence issues
Effective life of the barrier
100 yrs? 200 yrs? For the foreseeable ever? Higher seas, bigger seas - how effective is it? Climate change impacts?
Coastal development behind the barrier - depending on barrier
Who maintains the “defence”?
De-commissioning
Severn Estuary SPA
Our view Nature and scale of barrage proposals would cause
irreversible impacts to features, species and habitats.
Direct impact on Severn Estuary Special Protection Area (SPA), proposed Special Area of Conservation (pSAC) etc.
Difficult to envisage how required compensatory habitats could be provided to replace those that would be lost.
The case for a barrage needs to take account of other renewable options which might give similar benefits, at lower financial and environmental cost.
Shad Facts
• No breeding populations of Allis shad known in UK• Only 4 sustainable breeding populations of Twaite shad known in UK
AND 3 are in the Usk, Wye & Severn
(the 4th is in Tywi)• All are SAC Listed
Our view
Major environmental impacts due to the vast amounts of materials required.
Discharge consents / permits would need reviewing.
Substantial ancillary and infrastructure development including the need to modify or build new port facilities.
Lots of work to understand how the proposal would fit with the requirements of the Water Framework Directive.
A major programme of predictive environmental studies will be needed, which could take several years to complete.
Thank you
Nick Lyness
Wessex Flood &Coast Erosion Manager