Is it time to deliver more with sustainable drainage?

The challenges of having either too much, or too little water as well as concerns about the impact of drainage systems on the quality of our streams and rivers means that water management is, increasingly, never very far from our minds.

SuDS have a crucial role in overcoming these challenges and delivering better outcomes for society and the environment. SuDS as defined in The SuDS Manual (CIRIA, 2015) is drainage designed to mimic natural systems in delivering effective surface water management together with key environmental and social benefits.

Different SuDS components are used to harvest, absorb, infiltrate, convey, store, treat and control runoff – integrating these processes through the development and its landscape. Good quality SuDS schemes help manage local flood risk and water quality as well as improve amenity and biodiversity – commonly referred to as the four pillars of SuDS. SuDS components can take many forms, both at the surface, and underground, but SuDS that are designed to be multi-functional, manage and use rainwater close to where it falls, are on the surface and incorporate vegetation, provide the most opportunities for multiple benefits.

The current English Non-Statutory Technical Standards (NSTS) for SuDS focus solely on delivering the hydraulic control of surface water runoff from new developments. However, research to date suggests that their limited scope is constraining the ability of the industry to push for far broader outcomes.

Initiatives like CIRIA’s Benefits Estimation Tool (B£ST), The Ignition Partnership and work undertaken by the University of Sheffield have highlighted the value that blue-green infrastructure and SuDS can offer business and society in terms of health and wellbeing, reducing flood risk, improving climate resilience, improving habitats and biodiversity, and providing better quality places and spaces.

The opportunity for multiple benefits is also increasingly recognised in national policy with the National Planning Policy Framework (NPPF), 25 Year Environment Plan making explicit reference to SuDS, and/or green infrastructure and multifunctionality. There is also increased recognition of multifunctionality and the role of SuDS within green infrastructure in the National Design Guide. New SuDS standards provide an opportunity to respond to this shift in the regulatory landscape and help deliver the Biodiversity Net Gain sought by the future Environment Bill.

And there is already precedent for a change in approach. The Welsh Government already has Statutory Standards for SuDS that cover the four pillars of SuDS and multiple benefits, developed as part of the implementation package for Schedule 3 of the Flood and Water Management Act in 2019.

With climate and ecological emergencies, increasing pressures on our water resources from urbanisation and population growth, and a rising recognition of the value of blue and green space for our health and wellbeing, it is crucial that we recognise the value of surface water and deliver more from our drainage.

What does the industry want?

The Department for Environment, Food and Rural Affairs (Defra) commissioned HR Wallingford, with support from CIRIA, McCloy Consulting, Illman Young and others, to explore whether updating the NSTS could help deliver SuDS that provide multiple benefits.

A key part of this work has been understanding how the current NSTS are used, and considering how the standards could be updated to improve consistency in SuDS delivery. An online survey was carried out earlier in the summer and 667 responses were received. The majority of respondents (89%) agreed that the NSTS should be updated to include multiple benefits. ‘Management of water quality’ came out top as the most desired benefit not currently in the NSTS, closely followed by ‘improvements in biodiversity’ and ‘climate resilient development’.

Surveys undertaken by CIWEM, ICE, CIC and susdrain suggest that while there are frustrations with the process for delivering SuDS there is also greater ambition across all stakeholders for high quality SuDS that deliver the four pillars of SuDS.

The potential for future updates

As well as engaging industry through the survey and online focus groups, the Defra project has reviewed evidence and relevant policy to understand potential enablers and challenges for the delivery of SuDS with multiple benefits. The project has also obtained views from Welsh stakeholders about the challenges and opportunities of implementing their new SuDS standards.

The project team has drafted a new set of Standards that could provide the framework industry is looking for to help deliver better surface water management schemes. They now need your input to critically review and refine these proposals.

Have your say

A consultation has started to obtain stakeholder views on the proposals. Stakeholders are invited to provide feedback on each of the six standards and associated clarification statements as well as views on ease of delivery and assessment of the standards. The new standards cover prioritising where runoff should be discharged, the management of both everyday and extreme rainfall, water quality, amenity and biodiversity. The consultation has now closed.

To make it easier to review the proposals, you can download and review a copy of the consultation document and then respond to the survey online .

The results from this survey will contribute to the evidence base for recommendations to Defra on how the NSTS should be updated.