FRA Addendum and Drainage Strategy – Tooting and Mitcham Football Club

Project Brief

Metis were engaged to produce a Flood Risk Assessment addendum and Drainage Strategy for a part of the Tooting and Mitcham Football Club site in the London Borough of Merton. The development proposal was for a new residential apartment block comprising 73 new homes for shared ownership.

Our approach

• Produce a cost-effective addendum to the existing Flood Risk Assessment to assess the risk of flooding to the site from all sources.
• Produce a Drainage Strategy to determine the storage and disposal of surface water runoff from the site, which complies with national, regional and local policy.

Project outcomes

• The FRA addendum found that the risk of flooding from fluvial and tidal sources, surface water, ordinary watercourses, sewers, reservoirs and canals to the site was considered to be low, with a potential risk of flooding from fluvial and groundwater sources.
• Mitigation measures were proposed for the site, including SuDS to mitigate surface water flood risk and raising finished floor levels and locating vulnerable development away from certain areas to mitigate fluvial flood risk. No basement development was proposed to mitigate groundwater flood risk.
• The drainage strategy proposed several SuDS features including permeable paving, a green roof, tree pits and water butts. The features provide wider benefits above and beyond flood risk, with the strategy providing environmental and ecological benefits. All features were considered with value for money and buildability in mind to ensure feasible solutions were put forward.
• The development is designed to prevent all on-site flood risk as a result of events up to and including the 1 in 30 year event, and prevent the flooding of buildings as a result of all events up to and including the 1 in 100 year event (with a climate change consideration).
• The development proposals are consistent with the aims of the National Planning Policy Framework, alongside relevant regional and local policies, and were accepted with no detrimental impact on programme.