Flood and Water Management / Drainage

Surface Water Drainage and SUDS: Update to Planning Policy and Statutory Consultee Arranagements

Update to Planning Policy

On 18 December 2014 Government issued a written statement in relation to sustainable drainage systems (SuDS) outlining the strengthening of existing planning policy to make it clear that the Government’s expectation is that SuDS will be provided in new developments. To this effect, it is expected that, where planning applications are for major development, the Local Planning Authority must ensure that SuDS are put in place, unless demonstrated to be inappropriate.

Major development includes:

  1. Residential Development: 10 dwellings or more or residential development with a site area of 0.5 hectares or more where the number of dwellings is not yet known.
  2. Non-Residential Development: Provision of a building or buildings where the total floorspace to be created is 1000 square metres or more, or where the floor area is not yet known, a site area of 1 hectare or more.

The local planning authority (LPA) will therefore determine all major planning applications in accordance with national standards (DEFRA Non-Statutory technical standards for SuDS) and local policy, whilst taking into account technical advice provided by the Lead Local Flood Authority (LLFA) and/or other relevant consultees.

In assessing an application the LPA will need to be satisfied that:

  • Any proposals meet national and local policies;
  • The proposed minimum standards of operation are appropriate;
  • A minimum standard is set out to which the sustainable drainage systems must be maintained;
  • Through the use of planning conditions or planning obligations there are clear arrangements in place for ongoing maintenance over the lifetime of the development, including clearly identifying who will be responsible for maintaining the sustainable drainage systems and that funding for maintenance is fair for householders and premises occupiers.

These changes will take effect from 6 April 2015

Update to Statutory Consultee Arrangements

To co-inside with changes to planning policy, Government also announced on 9 March 2015, that changes would be made to statutory consultee roles in relation to surface water management elements of planning applications. Therefore as of 15 April 2015 the Environment Agency will no longer have a statutory consultee role in this respect. Instead, Lead Local Flood Authorities (LLFA) will now take on the Statutory Consultee role for major applications, so as to reflect the new responsibilities in relation to local flood management which they exercise.

Milton Keynes Council are the LLFA for the Borough area and will therefore be providing technical advice to support the planning process for major applications.

Guidance for Applicants

To assist developers and applicants in designing a suitable SuDS scheme for their site and in providing the relevant information required so as the LPA and LLFA can assess the surface water elements of a planning application, the “Milton Keynes Council Surface Water Drainage; Local Guidance for Planning Applications (PDF, 251KB)” note and pro-forma have been produced to provide standard pre-application advice for any major development. It is expected that developers and applicants follow the guidance provided in this note when preparing a planning application and submit a copy of the related pro-forma as part of their submission (A Word document copy of the pro-forma can be downloaded by following the related link).

Guidance Documents:

Milton Keynes Council Surface Water Drainage; Local Guidance for Planning Applications (PDF, 251KB)

Milton Keynes Surface Water Pro-forma for new development (Word Doc) (DOCX, 34KB)

DEFRA Non-Statutory Technical Standards

Climate Change Allowances Update

The Government have recently changed how the effects of climate change should be assessed when undertaking Flood Risk Assessments for planning, and designing surface water drainage for new developments.

In February 2016, the Environment Agency issued updates to the previous climate change allowances in the NPPF. Previously the NPPF provided recommended national precautionary sensitivity ranges for peak rainfall intensities and peak river flows. The latest updated guidance now includes predictions of anticipated change for peak river flow by river basin, and peak rainfall intensity in small and urban catchments, providing a range of allowances for each, based on statistical probability.

The updated climate change allowances and Environment Agency advice on how to apply them can be viewed at: https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances.

With regard to new developments, developers/applicants are responsible for assessing flood risk, taking into account climate change, and as such, expected to undertake the required assessment to understand the implications of the updated range of climate change allowances on flood risk for their development.

Peak Rainfall Intensity

With regard to peak rainfall intensities, Flood Risk Assessments and Drainage Strategies will now be required to assess both the central and upper allowances to understand their impact on the performance of their proposals.

It is expected that the applicants will design on-site surface water drainage to accommodate the 1:100 year +20% allowance, whilst also assessing the performance of the proposal to fully understand any flooding implications of the 40% CC allowance. Where implications prove to be significant (e.g. the development puts people at risk or has the potential to flood a neighbouring site), the development will be expected to incorporate additional mitigation measures, for example extra attenuation, to ensure no risk to third parties/on-site users for the extreme 40% CC scenario. 


Last Updated: 27 February 2019