Surface Water Drainage Strategies and Designs (SuDS)

Sustainable drainage systems for surface water

Helping you meet the surface water management requirements for your planning application

Increasingly local planning authorities and the national environmental agencies are requesting that developers show how they will manage surface water for their development. The document they require is usually referred to as a surface water drainage strategy or a sustainable urban* drainage systems (SuDS) report. In some instances you may also be required to provide a second-stage report known as a detailed surface water drainage design.

On this page:

  • What is a sustainable surface water drainage strategy?
  • Who needs a sustainable drainage strategy?
  • Our drainage strategies at a glance
  • Why get a surface water drainage strategy report?
  • Our process of producing a surface water drainage strategy
  • Is this the only sustainable drainage report I need?
  • What is the difference between a drainage strategy and a detailed surface water drainage design?


What is a sustainable surface water drainage strategy?

A sustainable drainage system (SuDS) or surface water drainage strategy is a report into how surface water, usually caused by rain, affects a site and the surrounding area. It establishes how water behaves on a site, and determines the runoff rate, flow pathways and infiltration potential (how likely the water will be soaked into the ground).

It then investigates what effect the development will have on these things, and outlines measure the developer can take so that runoff rates meet the requirements for the site set by national and local planning policy.


Who needs a sustainable drainage strategy?

You are likely to need a surface water drainage strategy if you are building a new structure or increasing the built footprint of a site.

As of April 2015 any development of 10+ units (including residential, industrial, commercial and mixed use sites) is required by law to look into the potential use of Sustainable urban* Drainage Systems, often as part of a drainage strategy.

If your development’s is located within an area designated as Flood Zones 2 and 3, or within an area identified as having a surface water flooding problem, you are also likely to need a drainage strategy.

Even, if your development doesn’t meet these criteria, Local Planning Authorities have the final say as to who needs a strategy. It’s best to speak to your local planning office before you submit a planning application.

To check if your site is in Flood Zone 2 or 3, you can contact us or use the country-specific flood zone maps below:


Our sustainable drainage strategies at a glance

Our drainage strategies:

  • Are compliant with the national planning policies for England, Wales, Scotland and Northern Ireland as well with the relevant environmental agency guidance and local planning policy
  • Can be written as separate reports or combined with our Flood Risk Assessments
  • Are suitable for all sizes and types of developments
  • Identify appropriate surface water runoff management options
  • Outline recommendations for sustainable urban drainage systems (SuDS) following consultation with our client
  • Provide initial design parameters for drainage components, such as soakaways and ponds
  • Are produced with the assistance of UKFloodMap4™ – the most complete and up-to-date data set currently available for surface water modelling in the UK.

Surface Water Drainage Strategies

All of our sustainable drainage strategies include visualisations of the recommendations outlined for your site. By incorporating the drainage strategy recommendations into your site plans you can see exactly how the measures will interact with your site.


Why get a surface water drainage strategy report?

  • Improve your chances of achieving planning consent
  • Avoid the costs of later design changes and additional planning applications
  • Reduce the risk of flooding to the site and surrounding area
  • Improve local amenities, reduce the risk of local flooding, and increase bio-diversity


Our process of producing a surface water drainage strategy

  1. Get the site plans and gather information on the site and surrounding area.
  2. Use the latest UK rainfall and flood data and our sophisticated flood modelling software to calculate the runoff rates for the existing site and the proposed site.
  3. Assess the available surface water drainage options:
    • 3a. For previously undeveloped land – “Greenfield” – we take into account the topography of site, the ground conditions and the proximity to public surface water sewers or water courses for discharge potential.
    • 3b. For previously developed land – “Brownfield” – we first look to use existing discharge arrangements where possible.
  4. Propose appropriate elements (such as soakaways or ponds) to meet the runoff rate requirements for the site where necessary and discuss the options with you
  5. Use flood modelling software to verify that these elements will meet the requirements.
  6. Create plans for the recommended surface water drainage strategy using the site plans if available.
  7. Generate visualisations of our recommendations so that you can see how they interact with your design.
  8. Write up the report, either as a standalone document or included within our Flood Risk Assessment for the development.


CAT Modelling Presentation
Download our Drainage Strategy & SuDs Brochure


What is the difference between a drainage strategy and a detailed surface water drainage design?

You may only need a surface water drainage strategy for your planning application. But you may also need a second-stage report known as a detailed surface water drainage design.

The detailed drainage design provides construction details, such as pipe diameters, manhole locations and the results of on-site soil testing. Not all planning applications that need a surface water drainage strategy will need a detailed drainage design though. Whether you will need it or not very much depends on the location, size and type of your development, as well the views of the EA and your local planning authority.

Our team have a wealth of experience in civil engineering, including drainage and infrastructure design, highway alignment, and waterside and marine developments. We use the industry recognised design package Microdrainage for our designs.

We can advise you if you need detailed drainage design  and give you a quote to include it.

Not sure what you need?

Mark Naumann is our Principal Engineer. Call him for advice on a sustainable drainage strategy for your development

Call Mark on 0203 857 8540 or email:


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