Flood Risk & SuDS Policy in Westminster
Westminster's City Plan Policy 35 addresses flood risk, vulnerable uses, flood management infrastructure, and sustainable drainage requirements for development in the capital.
The City of Westminster adopted their City Plan 2019-2040 in April 2021.
What is Policy 35?
Policy 35 relates to flood risk and sustainable drainage within the City of Westminster, consisting of over 10 separate statements covering development safety from flooding, site-specific assessments, vulnerable uses in flood zones, flood management infrastructure protection, and sustainable drainage systems requirements.
Vulnerable Uses
Highly vulnerable uses are restricted in Flood Zone 3. Essential Infrastructure and More Vulnerable Uses must pass the Exception Test. More Vulnerable Uses should be directed away from Surface Water Flood Risk Hotspots. Flood Warning and Evacuation Plans are required for certain uses in tidal breach areas.
Flood Management Infrastructure
Existing flood management infrastructure must be protected with maintenance access. A 16-meter undeveloped buffer zone should surround flood defence structures. Development should not limit future raising of flood defences outlined in the Thames Estuary 2100 Plan.
Sustainable Drainage
New development must incorporate Sustainable Drainage Systems to manage surface water flood risk and achieve greenfield run-off rates.
How Does Policy 35 Affect My Development?
Given building density in Westminster, exceptions exist. Developers must engage early regarding SuDS statements and London Drainage Hierarchy requirements. Basement expansions face specific restrictions in Rapid Inundation Zones.
Aegaea holds fluvial and tidal models for Westminster, enabling analysis of rapid inundation zones and flood zones. The team has successfully delivered flood risk assessments across Westminster, which has 15 critical drainage areas.