44 drainage & plumbing What are SuDS?
SuDS are a more sustainable approach to surface water management that avoids costly and unsus- tainable transportation of surface water runoff into the local environment or through an over- loaded sewer system. The principles of SuDS are first and foremost to mimic natural drainage paths and processes and deal with rainwater as close as possible to where it falls. SuDS intercept and hold back excess surface
water runoff, then manage it through temporary storage, infiltration, evapotranspiration or reuse. Good SuDS schemes satisfy both quantity and quality objectives and are likely to provide mul- tiple benefits to the community by promoting local amenity and biodiversity.
“SuDS intercept and hold back excess surface water runoff, then manage it through temporary storage, infiltration, evapotranspiration or reuse. Good SuDS schemes satisfy both quantity and quality objectives and are likely to provide multiple benefits to the community”
A good surface water management train can
either use both landscaped and manufactured components taking into account the space available for storage, the ground conditions, the level of pollutants present, the level of infiltra- tion that is possible and so on. Often a combination of above-ground ‘natural’ features and manufactured devices come together to achieve the best result. Given the scale of planned building and need
to implement SuDS, what are the key issues for housebuilders and developers?
Planning
Designing-in surface water features at the very outset of developments, preferably at master- planning stage, and building SuDS into the infrastructure of a site, significantly aids best practice delivery. Stakeholders such as landscape architects and community interests can then be fully consulted.
Land take
Minimising the amount of land used for flood storage is a critical consideration for any housing development. Whether a below-ground storage tank or above-ground pond is designed, best value in land-take and construction costs is para- mount. Carefully thought-out engineering using flow control devices and infiltration technologies can keep costs to a minimum. For example, using an optimising vortex
flow control can save up to 15 per cent in storage compared to similar devices by
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perfecting the all-important design curve that engineers use to calculate the storage required to prevent flooding.
Water quality
The English technical standards are concerned with outcomes, rather than practice and any spe- cific reference to water quality objectives have been removed. Treatment of runoff is, at best, only implied. Water quality will continue to be protected via Environment Agency consultation on planning applications. Local authorities will be driven by their regional catchment plans to meet Water Framework Directive targets for the ‘good status’ of rivers. Developers will want robust, reliable and easily-installed treatment trains for water quality where they are required.
Maintenance
According to the Ministerial Statement, developers will need to demonstrate how SuDS components will be effectively maintained throughout their life to secure planning permis- sion. In theory this should avoid the potential for schemes to be left neglected or rendered ineffec- tive through lack of regular care and inspection.
In practice it remains to be seen how maintenance of SuDs will be interpreted and delivered. A third party such as a local authority, a water company or service company may take on responsibility for maintenance, leading to the potential for residents funding part of the upkeep. This could have particular significance when it comes to social housing. Developers will recognise the benefit of
demonstrating repeatable, measurable perform- ance of SuDS throughout their lifetime and of being able to predict and cost maintenance regimes. In this case, using proprietary devices, with maintenance regimes specified by the man- ufacturer, may help developers demonstrate to local authorities that they are complying.
Enq. 169 Top five tips for SuDS best practice
1. Start early: SuDS plans should be incorporated right from the start of a project, preferably during masterplanning and guided by the Local Plan.
2. Engage the community: Getting local people passionate and involved in sustainable surface water management has been shown to be highly effective in achieving successful schemes.
3.Use the full SuDS toolbox: Create a surface water management train using the most appropriate ‘natural’ and manufactured components taking into account the space available for storage, the ground conditions, the level of pollutants present, the level of infiltration that is possible and so on.
4. Plan predictable and repeatable maintenance: Ensuring that SuDS continue to perform requires skilled ground maintenance, as well as following manufacturers’ schedules for inspection and maintenance of proprietary systems.
5. Insist on Quality Contractors: Construction of a SuDS infrastructure can require a different skillset for contractors from conventional drainage approaches.
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