SuDS are drainage solutions that mimic natural drainage patterns, thus reducing the impact of flooding and pollution on receiving water bodies. SuDS utilise drainage principles that are well established but they are often perceived to be innovative solutions to drainage problems (a paper, ‘SuDS – Innovation or a Tried and Tested Practice?’ examines these issues and can be downloaded below).

This perception is based on the preference for piped drainage systems in the past, because of the simple design criteria which aims  to remove surface water from developed sites as quickly as possible, while ignoring water quality and its amenity value. There is also a well established framework for adoption of these systems and developers, local authorities, water companies and other interested parties often prefer to take this route because the risks are well known and understood. However, times are changing and there is now a much greater appreciation of the need for development to become much more sustainable.  The Floods and Water Act 2010 also changes the way in which drainage of new development will be assessed and permitted.

SuDS are designed to mimic the natural drainage regime of an area, thus minimising impact on receiving watercourses. The term SuDS covers a range of sustainable urban drainage techniques, from end of pipe facilities such as wetlands or retention ponds, to source control systems such as soakaways and permeable surfaces. Where possible, it is recommended that surface water is controlled at source so that the water is returned to the natural drainage system as close to where it falls as possible, maintaining the drainage regime.

Using SuDS for the disposal of surface water run-off from impermeable areas has the following advantages:

• Reduced impact on watercourses;
• Reduced diffuse pollution;
• Reduced flows in combined sewers;
• Improved amenity value;
• Increases infiltration to soil thereby maintaining soil health
• Increasing groundwater recharge
• Reduced construction costs.
• Safety concerns

SuDS often utilise the natural landscaping to attenuate surface water flows. Although open SuDS techniques such as ponds do present a potential danger to children, SuDS design principles take this into account with designs that aim to minimise this risk. This is achieved through the use of gently sloping sides and barrier planting to prevent easy access to the water along with shallow water depths and avoiding sudden depth changes.

Where appropriate, open water may also be fenced to prevent access, although this can present its own risks. Individual developers and local authorities need to decide on their approach to this issue.