Pressures on conventional drainage systems and high-profile flood events in recent years have contributed to the promotion, in legislation and regulations, of a more sustainable approach to storm water drainage.  The use of sustainable drainage systems (SuDS) provide a multi-beneficial alternative to managing surface water and in controlling diffuse pollutants for improved water quality.

Conventional drainage systems are designed to collect precipitation and discharge it as quickly as possible, usually into a nearby watercourse resulting in a sudden rise in volume and flow rates in watercourses and increased flood risk downstream during and following storm conditions.  Piping this water away from where it has been collected also limits groundwater recharge and limits opportunities to filter diffuse pollutants.

SuDS manage storm events in a way that reduces flood risk in managing water quantity by slowing runoff into receiving watercourses or sewerage systems.  In addition, they serve to provide wider benefits such as reducing pollution and adding amenity value to an area.  There are many examples of successful SuDS schemes in the UK and internationally, which typically manage flood risk by intercepting storm water close to source and mimicking natural processes, such as infiltration.

Nationally, sustainable drainage systems have been encouraged through planning policy which requires the use of SuDS and space to be made for water.  The National Planning Policy Framework (NPPF) requires that sustainable drainage systems should be considered as a priority in all but exceptional circumstances when considering the drainage design of a development.

While national policy requires all major development to implement SuDS, for developments of lesser scale, sustainable drainage requirements vary across local planning authorities.  As specialist flood risk consultants, we ensure your flood risk assessment satisfies all local and national policy requirements for sustainable drainage.