Evidence to be submitted at each stage of planning Appendix B SuDS Treatment Train Discharge Hierarchy Sustainability Hierarchy Dickie, S, McKay, G, Ions, L, Shaffer, P (2010) DISCHARGE CHOICE SUSTAINABILITY CHOICE Planning for SuDS making it happen, C687, – Discharge SuDS Type Sustainability SuDS Technique Flood Pollution Wildlife & Hierarchy Level Reduction Reduction Landscape CIRIA, London (ISBN: 978-0-86017-687-9). Benefit MOST Source Control    MUST BE SUSTAINABLE Roofs & Walls CONSIDERED (PREFERRED) Infiltration: FIRST Infiltration    OPTION 1 trenches & Infiltration To basins Ground Soakaways: (standard or crate Appendix C system) Climate change allowances Filter strips and    OPTION 2 Swales Attenuation and Basins and Discharge: ponds: In February 2016 there was a change to the EA    Wetlands climate change advice to modify the allowance levels To Pond, Balancing Ponds Ordinary for rainfall when designing surface water drainage: to Detention Basins Watercourse or Retention Basins 20% CC allowance for 1 in 100 year events but with a Main River Conveyance 40% sensitivity test. (please note the advice for river swales flow levels also changed please contact the OPTION 3 – Attenuation and Environment Agency for more details) Discharge Permeable Surfaces & filter   Applicants should design the discharge rates and a) To Surface drains: attenuation on site to accommodate the 1:100 Water Sewer Gravelled areas Porous paving year +20% CC event and understand the flooding b) To Combined implications for the +40% CC event. Sewer OPTION 4 If the implications are significant i.e. the site contains Attenuation and Tanks & Piped vulnerable” or infrastructure” “highly “critical Discharge Systems:  receptors, could flood another development or put Crated ONLY IF ALL To Foul or people at risk then a view should be taken to provide Attenuation OPTIONS ARE LEAST Highways Tanks UNVIABLE SUSTAINABLE more attenuation to meet the 40% CC event. This will (only in Oversize pipes exceptional tie into designing for exceedance principles. circumstances)
Evidence to be submitted at each stage of planning Appendix B SuDS Treatment Train Discharge Hierarchy Sustainability Hierarchy DISCHARGE CHOICE SUSTAINABILITY CHOICE Discharge Hierarchy SuDS Type Sustainability Level SuDS Technique Flood Reduction Pollution Reduction Wildlife & Landscape Benefit MUST BE CONSIDERED FIRST ONLY IF ALL OPTIONS ARE UNVIABLE Source Control MOST SUSTAINABLE (PREFERRED) LEAST SUSTAINABLE Roofs & Walls    OPTION 1 Infiltration To Ground Infiltration: Infiltration trenches & basins Soakaways: (standard or crate system)    OPTION 2 Attenuation and Discharge: To Pond, Ordinary Watercourse or Main River Filter strips and Swales    Basins and ponds: Wetlands Balancing Ponds Detention Basins Retention Basins Conveyance swales    OPTION 3 Attenuation and Discharge a) To Surface Water Sewer b) To Combined Sewer Permeable Surfaces & filter drains: Gravelled areas Porous paving   OPTION 4 Attenuation and Discharge To Foul or Highways (only in exceptional circumstances) Tanks & Piped Systems: Crated Attenuation Tanks Oversize pipes  Dickie, S, McKay, G, Ions, L, Shaffer, P (2010) Planning for SuDS – making it happen, C687, CIRIA, London (ISBN: 978-0-86017-687-9). Appendix C Climate change allowances In February 2016 there was a change to the EA climate change advice to modify the allowance levels for rainfall when designing surface water drainage: to 20% CC allowance for 1 in 100 year events but with a 40% sensitivity test. (please note the advice for river flow levels also changed – please contact the Environment Agency for more details) Applicants should design the discharge rates and attenuation on site to accommodate the 1:100 year +20% CC event and understand the flooding implications for the +40% CC event. If the implications are significant i.e. the site contains “highly vulnerable” or “critical infrastructure” receptors, could flood another development or put people at risk then a view should be taken to provide more attenuation to meet the 40% CC event. This will tie into designing for exceedance principles.
SCC-SuDS-ProForma-2017.docx