Policy 5.12 Flood risk management

Strategic

A The Mayor will work with all relevant agencies including the Environment Agency to address current and future flood issues and minimise risks in a sustainable and cost effective way.

Planning decisions

B Development proposals must comply with the flood risk assessment and management requirements set out in the NPPF and the associated technical Guidance on flood risk^[1] over the lifetime of the development and have regard to measures proposed in Thames Estuary 2100 (TE2100 – see paragraph 5.55) and Catchment Flood Management Plans.

C Developments which are required to pass the Exceptions Test set out in the NPPF and the Technical Guidance will need to address flood resilient design and emergency planning by demonstrating that:

a the development will remain safe and operational under flood conditions

b a strategy of either safe evacuation and/or safely remaining in the building is followed under flood conditions

c key services including electricity, water etc will continue to be provided under flood conditions

d buildings are designed for quick recovery following a flood.

D Development adjacent to flood defences will be required to protect the integrity of existing flood defences and wherever possible should aim to be set back from the banks of watercourses and those defences to allow their management, maintenance and upgrading to be undertaken in a sustainable and cost effective way.

LDF preparation

E In line with the NPPF and the Technical Guidance, boroughs should, when preparing LDFs, utilise Strategic Flood Risk Assessments to identify areas where particular flood risk issues exist and develop actions and policy approaches aimed at reducing these risks, particularly through redevelopment of sites at risk of flooding and identifying specific opportunities for flood risk management measures.

^[1] Technical Guidance to the National Planning Policy Framework, Department for Communities and Local Government, March 2012 or any subsequent guidance on flood risk issued in support of the NPPF

5.54 Proper consideration of flood risk is vital to ensuring that London is and continues to be a sustainable city. Approximately 15 per cent of London is already within a recognised flood risk zone from either tidal or fluvial flooding. The Regional Flood Risk Appraisal (RFRA) produced alongside this Plan, investigates flood risk in more detail and identifies that London is at risk from tidal, fluvial, surface water, sewer, groundwater (see Glossary) and reservoir flooding as sources of flooding. It includes recommendations that will be reported against in the Annual Monitoring Report.

5.55 The Government has endorsed the Environment Agency’s Thames Estuary 2100 (TE2100) Plan, which sets out recommendations for tidal flood risk management for London and the Thames Estuary up to 2100. TE2100 recommends continued maintenance, refurbishment and improvements to the current defences, with some raising of river walls. This should continue to provide London with a high standard of protection from tidal floods. E2100 estimates that the arrangements for major changes to London’s flood defences must be in place by 2070. In order to leave room to raise river walls in a sustainable and cost effective way, some land may have to be safeguarded, and development may need to be set back along the Thames through London. If land is not available, the walls will reduce views across the river and they will be much more expensive to build. There also remains a level of risk, equivalent to 0.1 per cent chance per year – a low risk but not one that could never happen. This means it is still vital at the planning and design stage to consider what would happen to buildings if such a flood were to occur.

5.56 Fluvial flood risk is likely to increase significantly through the century, as a result of climate change. Predictions of increases in peak flows of up to 40 per cent would mean that we would have to expect increased flood risk on all of London’s tributary rivers. The Environment Agency has produced Catchment Flood Management Plans that examine the nature of flood risk and the approaches available to manage it. These reinforce the need to follow the approach of steering development to places with lower flooding risk and that new development and redevelopment can often provide a means of reducing flood risk for example by providing flood storage/conveyance or setting development back from rivers.