London Sustainable Drainage Proforma

New requirement – London Sustainable Drainage Proforma

As of April 2019 London’s 33 Lead Local Flood Authorities (LLFAs) now require the London Sustainable Drainage Proforma to accompany any Sustainable Drainage strategy, where required by national or local planning policy, as part of planning application validation requirements.

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The London Sustainable Drainage Proforma sets a clear standard for the information that should be provided as part of the planning validation process for any development. It should be used to summarise the key outputs from the strategy to allow assessing officers at the Lead Local Flood Authority (LLFA) to quickly assess compliance with sustainable drainage (SuDS) planning policy.

The proforma is comprised of four sections which require the following to be outlined:

  1. Site and project information – Details of the current site, development proposals and existing drainage arrangement;
  2. Proposed discharge arrangement – Summary of ground conditions to determine whether infiltration is feasible and outline proposed, post development, drainage arrangements following the drainage hierarchy as set out within the London Plan;
  3. Drainage Strategy – Runoff rates (pre and post development) and proposed SuDS measures. Prioritise SuDS measures that manage runoff as close to source as possible and contribute to the four main pillars of SuDS: amenity, biodiversity, water quality and water quantity;
  4. Supporting information – provide cross references to the page or section of the accompanying drainage strategy where detailed information to support each element can be found. This includes, but not limited to, detailed drainage layouts, utility plans and SuDS maintenance strategy.

The London Sustainable Drainage Proforma is intended to ensure that key information is provided with the initial planning application, reducing the need to request additional information throughout the assessment process and preventing delays in approval.

The proforma initiative is designed to promote a greater consistency in both application requirements and Lead Local Flood Authority information requests throughout the London Councils.


When is the London Sustainable Drainage Proforma required?

The London Sustainable Drainage Proforma is required to accompany any Drainage Strategy prepared for a planning application within the following council areas:


When do I need a Sustainable Drainage Strategy?

A Sustainable Drainage Strategy is required under National Planning Policy in the following circumstances:

  • Developments comprising 10 or more dwellings
  • Developments where the site area is over 1ha
  • Floor space over 1000m2
  • Minor development of less than 10 dwellings located within an area at risk of flooding, or within an area identified as having critical drainage problems or at risk from surface water flooding
  • Any development where there is an increase in impermeable areas and the Local Planning Authority is concerned about the cumulative impact of extensions

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