SuDS Technical Roundup

August 2021

What is SuDS?

SuDS refers to Sustainable Drainage Systems. Before looking at SuDS, we must identify what is a drainage system? According to schedule 3 of the Flood and Water Management Act, 2010, a drainage system is:

“A structure designed to receive rainwater, except a public sewer or a natural watercourse”

Therefore, any proposed development, or redevelopment will have a drainage system, whether it is guttering, discharge to sewers, green or blue roofs or ponds. As of April 2015, it became a pre-requisite for SuDS to be implemented in major development applications. SuDS may also be required, or at least be considered for any minor development, permitted development or conversion within Greater London in accordance with the London Plan.

SuDS philosophy

“The SuDS approach involves slowing down and reducing the quantity of surface water runoff from a developed area to manage downstream flood risk, and reducing the risk of that runoff causing pollution. Yhis is achieved by harvesting, infiltrating, slowing, storing, conveying and treating runoff on site and, where possible, on the surface rather than underground. Water then becomes a much more visible and tangible part of the built environment, which can be enjoyed by everyone.”

-CIRIA SuDS manual, 2015

SuDS Design

What does SuDS do?

The idea of SuDS is to promote design practice which responds to rainfall in a way that mimics the natural environment or catchment response. If you are developing a greenfield site, then your proposed development should mimic the natural response of what was there before. In basic terms this might be:

  • Manage water close to where it falls

  • “Slow the flow” – reduce the speed at which water exits your site (either to the sewer or a watercourse).

  • Promote natural principles like discharging water to the ground through infiltration, evaporation and;

  • Develop drainage systems that can cope with increasing large or intense rainfall “both now and in the future”.

If you want to learn more detail about SuDS systems, then consult the CIRIA SuDS documentation.

How do I incorporate SuDS into my development?

At the most basic level, you need to make space for it, both in physical area and within your design principles. That means you need to know a lot of information about your site and the potential measures that you can put in place. You don’t want to get close to a planning application only to find that your mitigation measures won’t work or are not appropriate.

That means looking for opportunities early in the planning process and engaging with experts who can guide your decision making, offer alternative solutions and work with you to ensure that your drainage strategy is an effective one.

To see how Aegaea can help, get in contact with or call 02081641282.

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