BRIEFING FOR NORMAN BAKER MP: THE LEWES TO NEWHAVEN STUDY
Update on flood defences 12th January 2004Following the initial submission of the Ouse Strategy, Defra's response in February 2003 agreed to further investigations into the benefits of downstream storage. Babtie Brown & Root were commissioned by the Agency to undertake a more detailed feasibility for a storage area downstream of Lewes in the Lewes Brooks area. This was a staged approach, with the first stage looking at the impacts of increased flow on the river bed and banks between Lewes and Newhaven. The downstream boundary of the Ouse Strategy stopped at Southease, and it was important that the impacts at Newhaven were also considered.
The first stage report was completed in May 2004. This showed that the reason the tidal embankments on the Lower Ouse were suffering erosion and slips was that the river was already constrained for the current flows. Increasing the flow in the river through the creation of a tidal storage area of the size originally envisaged in the Ouse Strategy, would triple the amount of water flowing through this stretch of river and would result in the failure of some of the banks and potential flooding at Newhaven. The creation of a fluvial storage area remains a possible option, but is dependent on the long-term stability of the tidal earth embankments.
The main outcome of the study was that it became apparent that the Lewes downstream storage option could not be considered in isolation from the river between Southease and Newhaven. This length of river was already being considered as part of the Ouse to Seaford Head Coastal Defence Strategy. As areas in Newhaven are at flood risk from both the river and the sea, they need to be considered together to ensure that benefits were not double-counted. It was therefore determined that the best way forward was to extend the boundary of the Coastal Defence Strategy up to the A27. This will enable the future of the tidal embankments to be considered holistically, and the feasibility of flood storage below Lewes to be fully investigated.
The preferred option for reducing flood risk in Lewes recommended in the Ouse Flood Risk Management Strategy is wall raising without making any allowance for an additional reduction in flood risk by the provision of downstream storage. This recognised the potential difficulties in delivering a downstream storage solution. This option is still being considered through the Coastal Defence Strategy, which is programmed for completion in autumn 2005, however, in the light of the studies feasibility cannot be assured.
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