Policy EN12 

Sustainable Drainage Systems

For major developments, proposals should demonstrate through a surface water drainage strategy that properties will not be at risk from surface water flooding allowing for climate change effects.

Surface water management should be undertaken, wherever practicable through the utilisation of appropriate SuDS techniques which mimic natural drainage patterns, and where appropriate achieve net gains for nature through the creation of ponds and wetlands near watercourses and the introduction of blue green corridors. For SuDS techniques which are designed to encourage infiltration, a site-specific infiltration test will be required to ensure that the water table is low enough.

For sites which lie within or close to groundwater protection zones or aquifers, guidance should be sought from the Lead Local Flood Authority.

Where SuDS are not technically feasible, the applicant is required to provide evidence that a connection to a public surface water sewer is necessary.

All developments will be expected to be designed to achieve, where appropriate, a net decrease in surface water run-off rates, including through green infrastructure provision such as the planting of native trees and bushes and the consideration of using ‘green roofs’. All developments on greenfield sites will be expected to achieve greenfield run-off rates.

All developments will be required to manage surface water through keeping to a minimum the creation of non-permeable areas.

For allocated sites, any surface water management strategy should demonstrate how site-specific guidance in the Strategic Flood Risk Assessment has been implemented.