Environment Agency briefing 21 July 2021 - Updating peak river flow allowances in 'Flood risk assessments: climate change allowances'

The Environment Agency issued the following update 21 July 2021:

"This update is for local planning authorities (LPAs) and developers preparing Strategic Flood Risk Assessments (SFRAs) and site-specific flood risk assessments (FRAs), and has been sent to LPA development management and planning policy team generic email addresses.

Peak river flow allowances

Further to our previous update in May 2021, we are pleased to inform you that the peak river flow allowances in ‘Flood risk assessments: climate change allowances’ were updated on GOV.UK on 20 July 2021, so they reflect the latest projections in UKCP18 and subsequent research that models how the latest rainfall projections are likely to affect peak river flows.

The updated guidance will come into immediate effect from 20 July 2021, and the main changes are as follows:

Peak river flow allowances are provided for ‘management catchments’ rather than river basin districts.
The central allowance for peak river flow will be used to assess most developments, however, the higher central and upper end will be important for some assessments still.

Given that we do not expect a significant increase in allowances used in most assessments in the large majority of locations, and our provision of specific advice prior to the pending update in cases with a significant change in allowance, we don’t expect the update to present significant or unexpected issues for developers or LPAs.

We will usually only base our advice on the previous guidance in the following circumstances:

For local plans submitted for examination on or before 20 July 2021.
For planning applications validated on or before 20 July 2021.

Peak rainfall allowances

We previously mentioned that we were awaiting the publication of a research project which will be the basis for updating peak rainfall allowances. The research is due to be published in summer 2021, and once available we will work to understand if and how the peak rainfall allowances need to be updated. It is unlikely updates to the peak rainfall allowances will happen until late 2021 at the earliest.

If you require advice, or have any queries, in relation to the above, please email Cumbria and Lancashire Sustainable Places team at CLPlanning@environment-agency.gov.uk / contact the Environment Agency planning officer for your area."

When do I need to provide a site specific flood risk assessment?

A site specific flood risk assessment is required to be submitted with any of the following planning application types:

All proposals of 1 hectare or greater in Flood Zone 1
All proposals for new development in Flood Zones 2 and 3
All proposals within Flood Zone 1 where the site has critical drainage problems (as notified to the local planning authority by the Environment Agency)
All proposals within the buffer zone of a main river
All proposals on land at risk of surface water flooding

If proposal falls within one of these categories, you must provide a site specific flood risk assessment before we can validate your application.

Who's responsibility is it to undertake a site specific flood risk assessment?

The Government expects developers to undertake a site specific flood risk assessment. You may need to employ a suitably qualified consultant or flood engineer to do this for you.

Where can I find further advice about site specific flood risk assessment?

The Government's National Planning Practice Guidance provides further information and links about the consideration of flood risk flood risk assessments in the planning process.

What information does a site-specific flood risk assessment need to include?

The Government's National Planning Practice Guidance explains that the objectives of a site- specific flood risk assessment should be to:

establish whether a proposal is likely to be affected by current or future flooding from any source
establish whether a proposal will increase flood risk elsewhere
establish whether the measures proposed to deal with flood effects and risks are appropriate
provide the evidence for the local planning authority to apply the Sequential Test where necessary
establish whether the development will be safe and pass the Exception Test if applicable

Your site specific flood risk assessment should demonstrate how flood risk will be managed now and over the development's lifetime, taking climate change into account, and with regard to the vulnerability of the development's users. The Government publishes a checklist of the information they expect your flood risk assessment to include in National Planning Practice Guidance.