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Sustainable Drainage Systems


Sustainable Drainage Systems

What are SuDS?

Sustainable Drainage Systems (SuDS) are becoming an integral part of new development planning submissions, driven by Local Authority Water and Flood Management Plans.

SuDS manage peak runoff after a rainfall event to prevent flooding. They try to mimic what would happen if there was no development on site. They can be designed to convey surface water and slow runoff down (attenuate) before it enters watercourses.

Surface water should infiltrate into the soil directly but this may not always be possible as a single solution. This can be due to different soil and rock types, groundwater levels and slope profile.

How does this affect my client?

Local Authorities are now looking for the inclusion of SuDS into new developments. They must now be applied to all major schemes of 10 units or more.

In many instances now, Architects and planning consultants need to demonstrate why a SuDs is not appropriate for the site. If they can’t, then they need to consider how an appropriate SuDS will be integrated to the development so that it does not increase flood risk on site or elsewhere.

Understanding Local Authority Requirements

Planning conditions on SuDS vary considerably across the country. It is crucial that Architects and planning consultants understand these differences, assess the site and design a SuDS scheme that meets planning requirements on behalf of their client.

We have developed a unique catalogue of planning authority SuDS requirements.


Get an Expert View on SuDS

We have many years experience in assessing site drainage and designing suitable SuDS systems as part of Master planning and pre-application submissions.

We have a proven track record of delivering successful schemes through our technical expertise. Our drainage reports provide:

  • an initial view on site infiltration capability for surface water drainage
    more detailed run off calculations
  • Preliminary SuDS design that can be used as part of the pre-planning engagement process
  • We also run a regular series of webinars and can provide in-house seminars


Who are SuDS reports are intended for?

  • House builders and developers
  • Property professionals such as architects, planning consultants, and land agents
  • Private individuals
  • Businesses
  • Insurance brokers and lenders

Why is a SuDS Report required?

  • Validating planning applications at Pre-Planning Stage
  • Planning Conditions
  • Building and flood mitigation design
  • Due diligence
  • Code for Sustainable Homes
  • SuDS approval boards (SABs)
  • Lending, mortgages, and pension funds

How do I know what Level of SuDS Report I need?

For initial screening at the conceptual design stage a SuDSmart or SuDSmart Plus Reports typically support developers and regulators with infiltration drainage advice. This is the preferred method for managing surface water without increasing flood risk downstream.

When infiltration drainage cannot be undertaken at a site due to the underlying ground conditions, other more conventional drainage systems are introduced in our SuDSmart Pro Report (Note: infiltration drainage techniques are also considered when possible).

What does a SuDSmart Pro Report contain?

SuDSmart Pro Reports analyse the potential run-off from a site so that it can be managed effectively to ensure there is no increase in flood risk on or off the site. Post development run-off rates are assessed for a range of storm events including an allowance for future climate change.

A drainage strategy is developed to offset the increase in surface water run-off from the new development using the principles of SuDS and the code for sustainable homes. The hydrological context of the site is assessed, along with any potential issues that may affect the SuDS system.

A range of potential options are assessed including discharge to the ground, surface water courses or sewerage. The report provides sizes and flow rates for a range of sustainable drainage options that may be considered.

Will my report satisfy the Local Planning Office or LLFA?

SuDSmart Reports can be used to support a planning application at Pre-Planning Stage, or alternatively address a Planning Condition prior to planning being granted.

SuDSmart and SuDSmart Plus Reports provide a cursory look at infiltration SuDS which is the preferred method for managing surface water. Whether infiltration techniques are feasible or not will determine the suitability of other SuDS schemes going forward. The level of detail required depends on the specific requirements of your local authority.

You should note that our most detailed report, SuDSmart Pro provides alternative options and preliminary scheme layouts that should be subject to more detailed review at the master planning stage.

In our experience, this level of detail is required for more stringent planning authorities or for more complex sites that warrant more detailed assessment.

How do I know what to do next?

All SuDSmart reports include recommendations for next steps. We will always advise on the most cost effective way to move forward and provide details of how to do this whilst meeting in the needs of the planning department.

What if the Local Authority or LLFA request further information to support my application?

GeoSmart are able to provide access to a range of highly experienced senior consultants, suppliers and engineers, who can provide a more detailed review of your site specifics and planning requirements.

Please contact a member of the GeoSmart team to put you in touch when further detailed assessment is required.

What is GeoSmart’s SuDS Infiltration Map (SD50)?

The GeoSmart SD50 map provides an assessment of the capacity of the ground to receive infiltration depending on the nature, thickness and permeability of the underlying material and the depth to the high groundwater table.

  • Allows preliminary assessment of the site without the need for bespoke SuDS design.
  • Use in conjunction with the SuDSmart report range to identify SuDS infiltration suitability and flow/volume design data.
  • Combination may be sufficient to obtain outline planning.
  • Provides customers with clear site risk profile on drainage cost and land area needed.

To discuss the SD50 SuDS screening map and how it can improve your planning submission for your client, contact us today.








How we can help our clients


Some examples of how our site drainage reports have supported our clients planning submission requirements for SuDs.

GeoSmart was asked to produce a SuDSmart Plus Report to assess how the development of greenfield land into residential properties may impact the flood risk to off-site receptors as a result of the increase in surface water runoff generated.

Read more…

Sustainable Drainage (SuDS) Assessment for a Business Park – Berkshire.
We were asked to assist in gaining planning permission for a new building development at a business park in Berkshire.




The latest videos from GeoSmart Information

Breakfast Briefing: Essential New Drainage Guidance For Lawyers – Highlights

An overview of the key points from each presenter at the Sustainable Drainage Seminar for Lawyers in June 2016 (11 mins).

What are SuDS? Dr Paul Ellis, GeoSmart Information

Our Innovation Director guides you through the role of SuDS, how they are designed and why they are important to manage surface water flooding more sustainably (14 mins).

Drainage Guidance and the Planning Regime. John Bates, Barrister, Old Square Chambers

John shares his insight and expertise to review the history of drainage guidance, the current requirements for developers and assesses how this could impact on a lawyer’s duty of care (18 mins).



We also run a regular series of webinars and can provide in-house seminars to ensure your team is up to speed on the latest requirements and support their CPD needs.