Standard 1 – Runoff Destination
- Designs must follow the national runoff hierarchy as per the DEFRA National Standards – reuse, infiltration, surface water body, surface water sewer, combined sewer – and provide evidence when higher-priority options are not feasible.
- KCC expects this hierarchy demonstrated explicitly in all major development submissions.
Standard 2 – Everyday Rainfall Management (Interception)
- Developments must provide on-site retention of the first 5 mm of rainfall, using features such as rain gardens, green roofs, permeable surfaces, and bioretention systems.
- KCC strongly promotes early spatial planning to incorporate these features into layouts.
Standard 3 – Extreme Rainfall & Climate Change
- KCC requires development to apply the Environment Agency’s ‘upper end’ climate change allowances for 30-year (3.3%) and 100-year (1%) storms, unless clearly evidenced as inappropriate.
- Design must manage exceedance safely across site layouts, using defined flow routes.
Standard 4 – Water Quality
- Developers must provide a pollution risk assessment and ensure SuDS offer treatment appropriate to proposed land uses (e.g. car parks need enhanced treatment).
- KCC will expect clear linkage to the CIRIA SuDS Manual treatment stages as a minimum.
Standards 5 & 6 – Amenity and Biodiversity
KCC supports SuDS that contribute to placemaking and ecological value through:
- Wetlands
- Swales
- Naturalistic planting
- Blue–green corridors
This aligns with DEFRA’s expanded biodiversity and amenity expectations.
Standard 7 – Maintenance & Longevity
- KCC requires clear arrangements for the ongoing maintenance of SuDS features for the lifetime of the development, secured by planning conditions/obligations.