Flood Risk Assessment
Cranfield Mill Student Accommodation FRA
Keywords: Flood Risk Assessment, Extreme Surge Analysis, Tidal Breach, TUFLOW
TUFLOW – Flood Hazard Mapping
Client, Architect & Other Organisations
Alan Baxter Associates Ltd
Wharfside Regenerations (Ipswich)
Description
The Cranfield Mill development comprises two separate sites lying between Star Street and Key Lane in Ipswich. To the south of the development are the Orwell Quay wet dock and the river Orwell. The Environment Agency’s flood risk mapping indicated that the site was within Zone 3a as defined by PPS25 and considered therefore to be at high risk of inundation from tidal / surge. The development incorporates a ground floor allocated for retail development The seven upper floors are reserved for student accommodation.
Scope of Work
The primary flooding mechanism for the site was a combination of tides and storm surge propagating up the Orwell to Ipswich. The flood risk assessment considered a range of twelve tidal / surge inundation scenarios which included breaching, overtopping and inundation due to operational failure of the existing lock gates. These scenarios included assessment for a range of climate change scenarios for 0, 60 and 100 years for a 1 in 200 year event for the pre and post development situation.
Tidal / surge and pluvial / rainfall modelling were assessed using TUFLOW using filtered LiDAR data to define the digital terrain model. Buildings in the urban environment were modelled using areas of high roughness and tidal flood defences incorporated with crest levels commensurate with the information contained in the Strategic Flood Risk Assessment. An evaluation of hazard was also undertaken to assess the viability and safety of the flood evacuation route from the student accommodation.
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