Implementing SUDS contributes significantly towards achieving sustainable development. Many planning authorities will expect planning applications, whether outline or detailed, to demonstrate how a more sustainable approach to drainage is to be incorporated into development proposals. Planning authorities will set a limit to the rate of stormwater flow from a site via sewers as a condition of planning consent. In recognition of this, Local Plans increasingly state that all applications should, in the first instance, aim to incorporate SUDS into development proposals. SUDS are also considered suitable for mitigating adverse impacts and supporting water conservation objectives. SUDS incorporate cost-effective techniques that are applicable to a wide range of schemes, from small developments to major residential, leisure, commercial or industrial operations with large roof areas and hardstanding. They can also be successfully retrofitted to existing developments. Planning policy guidance on development and flood risk emphasises the role of SUDS and introduces a general presumption that they will be used. As with other key considerations in the planning process - transport, landscape, heritage and nature conservation - incorporating SUDS needs to be considered early in the site evaluation and planning process, as well as at the detailed design stage.
The Building Regulations Approved Document H3, Rainwater Drainage, which came into effect on 1 April 2002, prioritises drainage requirements. In short, it requires that rainwater from the roof of a building or from a paved area may either be gathered for reuse or be discharged into one of the following, listed in order:
(a) an adequate soakaway or some other adequate infiltration system; or, where that is not reasonably practicable,
(b) a watercourse; or, where that is not reasonably practicable,
(c) a sewer.
In other words, the traditionally preferred method of rainwater disposal, ie totally discharging to a sewer, may now only be considered after other forms of reuse or drainage have been considered. The Building Regulations also provide guidance on the construction of rainwater harvesting systems for the first time.
In the early stages of design, consideration should be given to the arrangements for adoption and future maintenance of the system. This is likely to influence the design just as much as technical considerations. For private, or non-adopted systems, maintenance will be the responsibility of the owner and future developments may be affected by covenants. For systems serving more than one residential property it is recommended that maintenance should be the responsibility of a publicly accountable body, which will often necessitate the payment of a commuted sum or a legal agreement, possibly backed by the deposit of a financial bond. The adopting organisation should approve the design before construction.