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Project: The Airfields, Deeside Enterprise Zone - "Northern Gateway"
Type: Commercial Development


The former RAF Sealand site forms part of the Northern Gateway development at Deeside, also comprising part of the former Corus site to the south.

The site is located entirely within Zone C1 under Technical Advice Note 15 (TAN15): Development and Flood Risk, which is defined as an area of the floodplain which is developed and served by significant flood defence infrastructure.

Weetwood was instructed to assess the flood risk issues relating to the proposed redevelopment of the site and in doing so help secure planning permission for safe, insurable and saleable development opportunities.


What We Did

Weetwood prepared a Flood Consequences Assessment (FCA) encompassing the entire Northern Gateway site to demonstrate how the proposed development could be reasonably delivered.

The FCA was undertaken in accordance with TAN15 and in consultation with Environment Agency Wales (EAW), Welsh Government and Flintshire County Council.

In order to identify and assess the level of flood risk from both fluvial and tidal sources (from a number of local watercourses and the River Dee), Weetwood developed a 1D-2D hydraulic model.

This included an assessment of the risk and consequences associated with both overtopping and breach of the River Dee northern embankment.

Weetwood subsequently developed and assessed a site wide flood risk mitigation and surface water drainage strategy.

Outcome and Value Delivered

The FCA demonstrated that the Northern Gateway site could be redeveloped sustainably, delivering the aspirations of the landowners, as well as meeting the requirements of TAN15 over the lifetime of the development.

Outline planning permission for the site was granted in April 2012 for a mixed use generation scheme comprising the following:

• Up to 205,000m2 of storage and distribution floorspace;
• Up to 31,000m2 of other employment uses (offices, shops, etc);
• Up to 725 residential dwellings;
• Public open space and landscaping

The flood risk mitigation measures and surface water drainage system developed by Weetwood maximised the development potential of the site and provided a cost-effective solution.