Sustainable Drainage Systems are drainage designs that manage rainwater in a way that copies natural processes — infiltrating, storing, filtering and slowly conveying run-off — instead of relying only on underground pipes. They deliver flood risk, water quality, biodiversity and amenity benefits together.
SuDS design is usually described as delivering four benefits: managing flood risk by controlling quantity, protecting rivers and groundwater by improving water quality, creating attractive places, and supporting biodiversity. A well-designed scheme addresses all four rather than just storage volume.
The measures are arranged as a management train, treating and slowing water in stages from the point where rain falls, through conveyance, to any final discharge. Each stage reduces the load on the next, and surface features are generally preferred to buried tanks because they are easier to maintain and provide additional benefits.