SuDS - sustainable drainage system

SuDS

Surface water run-off should be controlled as near to its source as possible through a sustainable drainage approach to surface water management (SuDS).

SuDS seek to mimic natural drainage systems and retain water on or near to the site, when rain falls, in contrast to traditional drainage approaches, which tend to pipe water off site as quickly as possible.

SuDS offer significant advantages over conventional piped drainage systems in reducing flood risk by reducing the quantity of surface water run-off from a site and the speed at which it reaches water courses, promoting groundwater recharge, and improving water quality and amenity. The range of SuDS techniques available means that a approach in some form will be applicable to almost any development.

Government policy set out in a written statement on the 18 December 2014 by the Secretary of State for Communities and Local Government made it clear that the Government’s expectation is that sustainable drainage systems will be provided in new major developments from 6th April 2015 wherever this is appropriate. Local Planning Authorities should consult the relevant lead local flood authority on the management of surface water and ensure that sustainable drainage systems for the management of run-off are put in place, unless demonstrated to be inappropriate. Furthermore, paragraph 103 of the NPPF expects LPAs to give priority to the use of SuDS in determining planning applications. Further support for SuDS is set out in chapter 5 of the PPS25 Practice Guide and in the document ‘Gloucestershire SuDS Design and Maintenance Guide'.

Local Planning Authorities should ensure their policies and decisions on applications support and complement Building Regulations on sustainable rainwater drainage.

Approved Document Part H of the Building Regulations 2010 establishes a hierarchy for surface water disposal, which encourages a SuDS approach beginning with infiltration where possible for example, soakaways or infiltration trenches. Where SuDS are used, it must be established that these options are feasible, can be properly maintained and would not lead to any other environmental problems. For example, using soakaways or other infiltration methods on contaminated land carries groundwater pollution risks and may not work in areas with a high water table. Where the intention is to dispose to
soakaway, these should be shown to work through an appropriate assessment carried out under BRE Digest 365.

Provision for long-term maintenance should be provided as part of any SuDS scheme submitted to the LPA. Model legal agreements that provide a mechanism for SuDS maintenance can be accessed on CIRIA's website.

Further information and references on SuDS can be found in chapter 5 of the PPS25 Practice Guide. The Interim Code of Practice for Sustainable Drainage Systems provides advice on design, adoption and maintenance issues and a full overview of other technical guidance on SuDS. The Interim Code of Practice is available electronically on CIRIA's website