Flood risk
National Planning Policy Framework
The National Planning Policy Framework and its associated technical guidance, March 2012, set out national planning guidance for development in relation to flood risk. It takes a risk based approach and categorises land uses into different vulnerabilities, which are appropriate to different flood zones.
This document carries forward the requirement from PPS 25 to undertake a Strategic Flood Risk Assessment (SFRA) to inform the preparation of the Local Plan.
Scott Wilson Ltd were jointly commissioned in July 2007 to undertake a SFRA for Wandsworth, Merton, Croydon and Sutton. The Environment Agency were involved throughout the process.
Note: Since the production of the Strategic Flood Risk Assessment, the River Wandle and Beverly Brook catchments have been remodelled. The Council is aware that the flood zone mapping has changed as a result of this process and clarification regarding the location of the flood zones should be sought from the Environment Agency.
The flood risk guidance within the NPPF technical guidance applies to all forms of flood risk; however, surface water, groundwater and ordinary watercourse flood risks are generally less well understood than fluvial or coastal flood risk. In part this is due to the much faster response times of surface water flooding, a perception that the impacts are relatively minor and the highly variable nature of influences, e.g. storm patterns, local drainage blockages, interactions with the sewer system.
However climate change models are predicting more frequent heavy storms and there is emerging evidence that this is already happening. It is also clear from the flooding that occurred in several parts of England in summer 2007 that surface water flooding can have major impacts. In the heavily urbanised area of London, the risks are significant and it is important that appropriate consideration is given to these risks when new development is proposed. The planning system is a key tool in reducing flood risk, and with this additional information, this can apply to the surface water risk as well as fluvial and tidal risk.
Download the Strategic Flood Risk report and related information
In addition to the flood risk analysis contained within the SFRA, further details of the Sequential and Exception test process can be found in the NPPF technical guidance and associated companion guide. In addition to this the Council has applied the Sequential Test to the sites contained within the preferred options Site Specific Allocations Document.
Read the results in the Flood Risk and Development Sequential Test Report.
Lead Local Flood Authorities
Since April 2011, London Boroughs have been given the roles of Lead Local Flood Authorities (LLFAs) by the Flood and Water Management Act 2010. This means that each borough has new flood risk management duties. The Planning service has an important role to play in delivering these new duties and must ensure that it forms part of authority wide co-ordination of the LLFA role.
As part of the new duties the Council commissioned URS (formerly Scott Wilson) in 2011 to undertake a Preliminary Flood Risk Assessment (PFRA) and a Surface Water Management Plan (SWMP).
The PFRA provides a high level summary of significant flood risk, based on available and readily derivable information, describing both the probability and harmful consequences of past and future flooding. The scope of the PFRA is to consider flooding from the following sources; surface runoff, groundwater, sewers and ordinary watercourses and any interaction these have with main rivers and the sea.
The SWMP outlines the preferred surface water management strategy for Wandsworth and includes consideration of flooding from sewers, drains, groundwater and runoff from land, small watercourses and ditches that occur as a result of heavy rainfall.
Both documents should be used as the basis for Flood Risk Assessment work and to inform decision making in planning proposals in areas of flood risk.
