Changes to the London Plan and How It Will Affect Flood Risk
The London Plan 2019-2041 introduces Policies SL12 and SL13, evolving flood risk management and sustainable drainage requirements for development across the capital.
Flood Risk and Development in London
All developments in Flood Zone 2 or 3 must be supported by a Flood Risk Assessment (FRA) under the National Planning Policy Framework. London’s heavy urbanisation creates elevated surface water flooding risks, with critical drainage areas identified by local planning authorities across Greater London.
What Is the London Plan?
The London Plan serves as London’s planning policy document, distinct from the National Planning Policy Framework. It addresses planning, transport, environment, economic development, housing, culture, and health. Legally binding for all London Local Planning Authorities’ development plans, the current plan spans 2019-2041.
Population Growth and Policy Evolution
London’s population is projected to grow by 70,000 annually, reaching 10.8 million by 2041. This growth necessitates policies supporting sustainable development.
Flood Risk Policy Changes
Policies SL12 and SL13 in Chapter 9 represent evolutions of previous flood management and sustainable drainage policies. Policy SL12 emphasises collaborative flood risk management among London Boroughs, the Environment Agency, developers, and infrastructure providers.
Key requirement: “Development proposals should ensure that flood risk is minimised and mitigated and that residual risk is addressed,” including maintaining setbacks from watercourse banks.
Residual Risk
The Thames Barrier and linear defences protect Central London with a 1,000-year standard of protection. Residual risk refers to potential flooding if these defences fail (breach). The Environment Agency provides models to assess breach risk impacts on specific sites.
Flood Defence Requirements
Paragraph F mandates development setbacks from flood defences to facilitate future maintenance and upgrades, promoting collaboration between developers, the EA, and local authorities.
Natural Flood Management
Major developments must support Thames 2100 Estuary Plan measures, with emphasis on natural flood management methods offering multiple benefits including flood storage and habitat creation.