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.