Surface water management and SuDS

The ongoing growth of our towns and cities increases flood risk and may exacerbate spills from combined sewer overflows. Sustainable drainage systems (SuDS) and green infrastructure help to mitigate these risks using natural drainage features that can slow, store and clean runoff, delivering climate resilience, improved water and air quality, improved water security, biodiversity net gain and social and community value.

Through our detailed understanding of hydrological and hydraulic processes (plus water quality management and treatment) and our many years of experience in surface water management, we have developed industry-wide guidance, tools and designs. We provide expert support across the development and water management industry.

We carry out a broad range of SuDS projects, including advising developers on surface water management and SuDS requirements - often as part of broader flood risk assessment support. We produce conceptual SuDS designs for developments, regularly using our online UK SuDS tools, created to support SuDS designers. 

All our activities are underpinned by our ongoing SuDS research.

We assess existing and/or proposed drainage systems and advise on the benefits and requirements for SuDS. Examples of our projects include: 

• Kintbury, Berkshire, UK  Incorporating the site topography and landscape features into a SuDS conceptual design for a residential housing development - including a swale and a storage basin;
• National Trust, Oxfordshire, UK  Developing SuDS proposals which incorporate a wetland / basin with flow control, for the storage of excess runoff from a car park;
• Ballymun surface water, Dublin, Ireland  Detailed hydraulic modelling of a surface water drainage system, identifying requirements for storage and flow controls, for a large-scale urban regeneration project.

With our unique expertise and national recognition as leaders in this field, we are often appointed as expert witnesses on projects related to urban drainage systems, including SuDS.

We’ve carried out research into SuDS for over 20 years, including:

• UK government research on the hydraulic and water quality performance of SuDS components, and maximising the ecological value of SuDS 
• UK water industry research on economics and whole life costs, and the recording and mapping of SuDS assets
• regulatory research into design methods and best practice. 

We developed and host UK SuDS, an Environment Agency approved website which provides SuDS evaluation and design tools. The tools are used by many organisations to develop SuDS proposals, are familiar to Lead Local Flood Authorities and are accepted in planning submissions. They address issues such as:

• pre-development greenfield runoff rates
• storage volumes required to meet flow rate controls
• suitability of SuDS for treating site runoff
• infiltration
• rainwater harvesting
• types of SuDS applicable to specific site constraints.
   

We are the lead authors for the SuDS Manual - the UK’s key technical guidance for the design, construction and maintenance of SuDS. This was recognised at the Institution of Civil Engineers and the Landscape Institute Awards, reflecting the principle of integrating drainage with site landscaping to deliver multiple benefits.

We also author and contribute to many other national and international SuDS and stormwater management guides and standards, including providing support to English and Welsh governments in developing National Standards and supporting guidance.

We provide classroom and online SuDS training for drainage consultants, housebuilders and planning authorities to help them design and deliver, or approve, SuDS schemes that meet the appropriate standards. We also offer bespoke courses for organisations with large numbers of delegates to train.

We have extensive expertise in drainage modelling of foul, surface water and combined sewer networks. We use the Innovyze ICM software to represent SuDS within wider networks, evaluating the potential benefits of different retrofit and new build strategies.