OCSC were appointed to conduct a Flood Risk Assessment for a new development comprising residential, retail, office and leisure facilities over an undercroft car-park. The site of the development, which comprises 5.8 hectares close to Newry City Centre, is located immediately adjacent to the Newry River on lands defended from flooding by earthen embankments. The Flood Risk Assessment dealt with all possible sources of flooding including fluvial, tidal, off-site infrastructure, groundwater, development runoff and failure of the existing flood defence embankments.
The Finished Floor Levels for the development were determined by the Flood Risk Assessment to provide the required level of protection from fluvial and tidal flooding. The proposed drainage system for the development was altered to mitigate flood risks identified in the Flood Risk Assessment. Flood risks associated with overland flow were identified and the vertical alignment of the proposed roads for the development was amended to provide routes for flood waters to safely exit the site.
The site of the development is in an area of Newry defended from tidal flooding by a 2.6km-long earthen embankment. The Flood Risk Assessment identified residual flood risks arising from catastrophic failure of the defences and considered the potential failure mechanisms, such as erosion, piping, settlement and rotational slip. To mitigate this residual flood risk to the undercroft car-park, OCSC identified flood evacuation routes to safe-havens and prepared a Flood Evacuation Plan for the on-going management of the development.
The Flood Risk Assessment was conducted in accordance with Northern Ireland’s Planning Policy Statement PPS15 and CIRIA’s C624. The Flood Risk Assessment and the Flood Evacuation Plan were approved by Northern Ireland’s Rivers Agency.