What are sustainable drainage systems?
The aim of a sustainable drainage system is to mimic the response of the existing catchment and its surfaces, ultimately with some betterment, negating any increased off-site flood risk that the development could cause, ie. maintaining the surface water characteristics of the catchment to pre-development levels or better.
Sustainable drainage systems is a term that is now applied to all drainage systems that are sustainable whether urban or rural and including natural and engineered structures.
A contemporary sustainable drainage methodology for managing surface water runoff should use Best Management Practices to focus on three key areas:
Quantity
Controlling surface water (reducing off-site flow rates)
Quality
Improving surface water
Amenity
providing added development amenity value
Provision of all three areas in equal measures will not always be possible or necessary.
Three key objectives should be developed as part of an integrated and sustainable surface water management strategy:
- Maximise a reduction in natural runoff by the use of infiltration techniques wherever feasible.
- Manage the residual flood risk as well as reducing the total volume of surface water runoff discharged.
- Maximise quality improvements in surface water runoff.
These can all be satisfied using natural or proprietary techniques either alone or in combination.
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