Using sustainable drainage options on your site can reduce pollution and reduce the risk of flooding. They can save you money compared with the more traditional drainage techniques.
Summary
A well-designed and managed surface water system can:
- save you money
- add to the visual attractiveness of the site.
Planning a site so that water is removed from it as quickly as possible can:
- harm the environment
- increase both water pollution and the risk of flooding to the site itself and elsewhere downstream
- cause damage to wildlife and river habitats.
In areas with combined drainage systems, surface water entering the system causes polluting storm discharges and overloads treatment plants.
Sustainable drainage systems
To make sure your site is not polluting the environment or increasing the risk flooding, you should use the Sustainable Drainage Systems (SUDS) approach to drainage. This approach provides a drainage solution that takes into account the:
- amenity benefits
- quantity of surface water run-off
- quality of surface water run-off.
By doing so it helps to protect and improve the:
- wildlife in the area
- landscape and attractiveness of the site.
SUDS use a wide range of techniques that have been tried and tested on projects throughout England and Wales. They can be applied to a variety of schemes, from small developments through to major residential, leisure, commercial or industrial operations with large areas of hard standing and roof. A particular benefit is that they can be successfully retro-fitted to existing developments.
Our advice
You will get the best results if you consider the use of SUDS options early in the site evaluation and planning process, not just at the detailed design stage. This will ensure drainage costs are adequately considered at the start of the development.
A well-designed SUDS scheme may even save you money. For example, by avoiding the need for gully pots or for constructing surface water sewers. There will be a SUDS technique to suit your site. This could be:
- using infiltration
- swales and ponds
- lined wet ponds
- green roofs.
Factors that will affect your choice
To determine the right technique, first establish the soil conditions and hydrology of the site. Use the results of your investigations to support your drainage proposals. Other factors could be:
- the quality of the land (whether it is affected by contamination)
- the need to protect vulnerable groundwater sources
- the permeability of the soil.
SUDS solutions are most cost effective when designed to work with the natural drainage pattern of your site. For example, you can design them to:
- use existing ditches or natural depressions for swales and ponds, or
- form part of hard and soft landscaped areas.
The Government's planning policy on development in the floodplain highlights the important role that SUDS can play and introduces a general expectation for their use at all sites. Surface water disposal is a material planning consideration. Local authorities increasingly expect developers to submit proposals that incorporate the SUDS approach.
Ponds and green spaces provide habitats for wildlife to flourish, reduce pollution and provide areas for people to enjoy, adding value to your site. Even in the most constrained site you can use green roofs to:
- reduce surface water run-off, or
- collect rainwater for flushing toilets or watering gardens.
Maintaining drainage systems
In the early stages of your site design, consider how the drainage system will be adopted and maintained in the future. It is likely that these decisions will influence the design, just as much as the technical considerations.
