What are Sustainable Drainage Systems (SuDS)?

National environmental agencies and local planning authorities are increasingly asking developers and planners to demonstrate how they intend to manage water drainage. Sustainable Urban Drainage Systems are becoming a popular alternative to conveying water away to close-by watercourses from our towns and cities through traditional surface water channeling systems, including sewers and a network of pipes.

SuDS are a great way to improve the spaces and places where we live and work by managing rainfall close to where it falls. They mimic natural drainage regimes to reduce surface water runoff and flooding while improving water quality. SuDS also have benefits for the environment and support wildlife and biodiversity by creating suitable habitats.


How SuDS Work

Local authorities, construction companies, and development companies are looking for sustainable ways to tackle the environmental challenges created by population growth and climate change. Sustainable urban drainage systems are vital where existing sewerage systems are running close to full capacity.

SuDS work by reducing flow rates, increasing soak rates, and increasing water storage capacity. They increase evaporation from the surface and boost the uptake of water by vegetation. There is also the added benefit of lowering the amount of pollution that is transported to the water environment.

From the outset, considerations are needed to understand the ground conditions, drainage potential, groundwater protection, infiltration constraints, and ground stability. Through these considerations, sustainable drainage systems may be chosen. They can include rainwater harvesting systems, infiltration systems, green roofs, ponds and wetlands, bio-retention systems, filter drains, proprietary treatment systems, swales, attenuation storage tanks, and detention basins.


The Principals of Sustainable Drainage

There are six principals that SuDS use to mimic natural drainage. They do this by:

  • Harvesting rainwater close to where it falls
  • Filtering out pollutants
  • Storing runoff water and releasing it slowly (attenuation)
  • Allowing sediment settling through controlling the flow of the watercourse
  • Allowing water to soak back into the ground (infiltration)
  • Slowly transporting water on the surface (conveying)


Why Sustainable Drainage Surveys are Important

Sustainable drainage surveys and flood risk assessments are vital elements that will support the planning applications of developers. Drainage surveys will identify water pathways and show opportunities to reduce run-off rates to the greenfield.

The drainage strategy in areas designated as flood zones is important to avoid the expense of later design changes or the need to make additional planning applications. To be effective, the project may require the knowledge and collaboration of landscape architects, engineers, and planners. However, the results delivered by SuDS are inspirational, and they provide excellent value for money.