Impacts of 2021 revised NPPF and Climate Change Allowances
We are writing to provide an update and the potential impacts of two recent changes that are likely to affect the assessment of flood risk within England.
On Tuesday 20 July 2021, the Ministry of Housing, Communities & Local Government, released an updated version of the National Planning Policy Framework (NPPF), and on the same day the Environment Agency released an update to climate change allowances for Flood Risk Assessments. The impacts of these changes on individual projects is yet to be determined. However, the purpose of this article is to raise an early warning that the changes in the NPPF and the Climate Change guidance could have an impact on the outcomes of your project(s).
Summary of 2021 NPPF Changes: Flood Risk and Coastal Change
The main change to the NPPF within the Flood Risk and Coastal Change context is related to the scope of study and the requirements for the Sequential Test. The updated text in the NPPF states that:
“All plans should apply a sequential, risk-based approach to the location of development – taking into account all sources of flood risk and the current and future impacts of climate change – so as to avoid, where possible, flood risk to people and property.”
Paragraph 161, NPPF 2021
The inclusion of all sources means that the need for a Sequential Test may be triggered if a site is located in an area at high risk of surface water or groundwater flooding. However, the guidance on the process for applying the Sequential Test has not yet been updated and still only refers to the Flood Zones (fluvial and tidal flood risk).
For sites which are currently subject to a Sequential Test, the scope of the study may need to be increased to consider the flood risk posed by surface water, groundwater, and other flood sources.
For sites which are not currently subject to a Sequential Test, the Local Planning Authority may require that this is undertaken so that the risk from all sources of flooding can be Sequentially Tested.
The NPPF states that for sites allocated through local plans then provided a Sequential Test was undertaken at the plan making stage, it is not necessary to undertake a Sequential Test.
Applications for some minor developments and change of use should not be subject to the sequential or exception test.
Summary of 2021 Climate Change Allowance Changes
There are a number of changes introduced by the latest guidance from the Environment Agency relating to which climate change allowances are relevant in which area and also clarification on which allowance to use. The Surface Water and Tidal allowances remain the same as previously provided. However, the river flow allowances have significantly changed.
Where previously England had been split into ten River Basin Districts, the new approach divides these ten River Basin Districts into 92 smaller Catchment Management areas, each of which has its own climate change allowance value.
For example, within the Thames River Basin District a 70% allowance has been used to determine the design flood level for the majority of developments. This was based on the Upper end allowance for the 2080’s. However, the new guidance states that for the majority of developments the Central allowance should be used. Within the Thames River Basin District, there are 17 Catchment Management areas, the Central allowance for which ranges from 10% to 35% with an average allowance of 21%.
At present there is no guidance on how to implement this change when a site is located within a Catchment Management area which is downstream of another Catchment Management area with a different predicted response to climate change.
Furthermore, as a result of this change, we are not aware of any current flood models held by the Environment Agency that contain the new climate change allowances. Many of the models had not been updated to reflect the previous update. Consequently, determining the crest levels of flood defences or the design finished floor levels for habitable use, they may be at risk of being based on an interpolation of previously provided flood level information.