On August 25th, 2022, the Environment Agency released a substantial update to the Planning Practice Guidance flood risk, aligning it with the modifications made to the National Planning Policy Framework (NPPF) in 2021.
The councils are applying these changes at different speeds. For instance, the London Boroughs are applying these changes while the midlands and northern councils are still in the process of getting up to speed with these changes.
A development at risk of surface water requires a Sequential and Exception Test
The Sequential and Exception Tests which used to evaluate fluvial (river flooding) only. It now applies to sites at risk of surface water flooding or other flood risks such as groundwater flooding and the impact of climate change. This reflects the growing concern and recognition of the impact of surface water on new developments and the change in rainfall patterns. As a result, there is now a stronger emphasis on considering surface water flood risk in a more comprehensive and earlier manner in the planning process. This means that surface water should no longer be treated as an afterthought but should instead be factored in from the start to ensure a more sustainable and resilient development. Areas at ‘medium’ risk of surface water flooding may require modelling to determine the impact of climate change.
Change of Use and Permitted Development rights. Local Planning Authority can request a Flood Risk Assessment.
The new planning practice guidance flood risk recognises that change of use has a greater impact on flooding and as such should be treated differently. The flood risk vulnerability and flood zones’ compatibility will determine if the change of use requires a flood risk assessment. The flood risk vulnerability classification table will determine the viability of the development. Moreover, the council has the freedom to request flood risk assessments for permitted developments should there be flood issues within the site.
Flood zone 3b (Functional Flood Plain) has become bigger. The 1 in 30 storm event is now applicable instead of the 1 in 20.
The functional floodplain (Flood Zone 3b) has been altered. The previous requirement of an annual probability of 1 in 20 (5%) or greater has been updated to 1 in 30 (3.3%) or greater. As a result of this change, a larger portion of land is likely to be considered a functional floodplain, and it is typically not deemed suitable for development unless the flood risk vulnerability classification is water-compatible.
Sustainable Drainage Systems are required for all developments and are a must for sites within the flood zone or at risk of any type of flooding.
Multifunctional Sustainable Drainage Systems (SuDS) are to be applied to all development affected by flooding. This includes surface water flooding. SuDS are now expected to be standard in new developments. However, an emphasis has been placed on utilising above-ground multifunctional SuDS, which provide benefits for biodiversity, amenities, and water quality, in addition to their traditional role of managing water quantity. Moreover, the use of SuDS is required in order to pass the sequential test of your development.
Safe Evacuation must be provided to the 1 in 1000 (0.1%) + CC storm event.
The evacuation should be provided to the 1 in 1000 + CC storm event. It will be challenging to meet as most of the modelling does not contain this level. The Planning Practice Guidance flood risk also makes allowances for developers to cover the full cost of emergency services when this requirement is not met. The cost of emergency services is also applied when a development is at risk of reservoir inundation.
Promotion of Natural Flood Management within the developments
The promotion of Natural Flood Management (NFM) in new developments has been increased. The revised guidance provides comprehensive information on how NFM techniques can be carried out, with a focus on de-culverting and re-naturalizing watercourses. In cases where these measures cannot be achieved, and there are offsite impacts, the developer may be required to provide additional funding to maintain such structures.
