Southampton City Council Local SuDS Design Guidance FINAL V1.0 2017 � [Page intentionally left blank] � Contents � Contents � 1. Introduction .................................................................................................................................................... 1 � 1.1 Sustainable Drainage Systems.................................................................................................................. 1 � 1.2 Planning context ....................................................................................................................................... 1 � 1.3 Purpose of this document ........................................................................................................................ 2 � 1.4 Structure of this document ...................................................................................................................... 3 � 1.5 Further guidance and useful information ................................................................................................ 4 � 2. SuDS and the Southampton environment ..................................................................................................... 5 � 2.1 Geology and soils ...................................................................................................................................... 5 � 2.2 Topography ............................................................................................................................................... 5 � 2.3 Rivers and watercourses .......................................................................................................................... 6 � 2.4 Flood risk ................................................................................................................................................... 7 � 2.5 Groundwater levels .................................................................................................................................. 7 � 2.6 Water quality ............................................................................................................................................ 7 � 2.7 Rainfall and climate .................................................................................................................................. 8 � 2.8 Landscape and biodiversity ...................................................................................................................... 8 � 2.9 Historic environment ................................................................................................................................ 9 � 2.10 Land contamination and land use .......................................................................................................... 9 � 2.11 Urbanisation and land availability ....................................................................................................... 10 � 2.12 Unexploded ordnance .......................................................................................................................... 10 � 2.13 Proximity to airfields and flight paths ................................................................................................. 11 � 3. Site constraints and opportunities ............................................................................................................... 12 � 3.1 Geology and soils .................................................................................................................................... 12 � 3.2 Topography ............................................................................................................................................. 13 � 3.3 Rivers and watercourses ........................................................................................................................ 13 � 3.4 Flood risk ................................................................................................................................................. 14 � 3.5 Groundwater levels ................................................................................................................................ 14 � 3.6 Water quality .......................................................................................................................................... 15 � 3.7 Rainfall and climate ................................................................................................................................ 15 � 3.8 Landscape and biodiversity .................................................................................................................... 15 � 3.9 Historic environment .............................................................................................................................. 16 � 3.10 Land contamination and land use ........................................................................................................ 16 � 3.11 Urbanisation and land availability ....................................................................................................... 17 � 3.12 Unexploded ordnance .......................................................................................................................... 18 � Southampton SuDS Guidance Page | i � Contents � 3.13 Proximity to airfields and flight paths ................................................................................................. 18 � 4. Design and selection criteria ........................................................................................................................ 20 � 4.1 The SuDS management train .................................................................................................................. 20 � 4.2 Discharge location .................................................................................................................................. 21 � 4.3 Water quantity ........................................................................................................................................ 22 � 4.4 Water quantity: climate change ............................................................................................................. 23 � 4.5 Water quality .......................................................................................................................................... 23 � 4.6 Design for flood risk ................................................................................................................................ 23 � 4.7 Design for exceedance ............................................................................................................................ 24 � 4.8 Design for low flows ............................................................................................................................... 24 � 4.9 Maintenance and Adoption .................................................................................................................... 25 � 4.10 Biodiversity ........................................................................................................................................... 26 � 4.11 Integration with public space: visual impact, amenity and multifunctional spaces .......................... 26 � 4.12 Detailed design and materials .............................................................................................................. 27 � 4.13 Construction method and phasing ....................................................................................................... 28 � 4.14 Health and safety .................................................................................................................................. 29 � 4.15 SuDS features: key design criteria ........................................................................................................ 32 � 5. Planning for SuDS .......................................................................................................................................... 36 � 5.1 Pre-planning advice ................................................................................................................................ 36 � 5.2 Outline application ................................................................................................................................. 36 � 5.3 Full application ........................................................................................................................................ 37 � 6. Standing advice for minor development ..................................................................................................... 39 � Southampton SuDS Guidance Page | ii � 1. Introduction � 1. Introduction � 1.1 Sustainable Drainage Systems For many years developers have dealt with surface water through the use of piped systems that collect and convey water away from the site as quickly as possible, discharging it directly into the nearest watercourse or sewer. Although this method may work in the reduction of surface water at the site, it can result in the increase of flood risk downstream, as well as pollution of watercourses from oil, silt and other pollutants carried directly from a development. In order to help reduce the risk of surface water flooding to development sites across the city, we are now looking for opportunities to move away from traditional piped drainage towards softer engineering solutions which seek to mimic the natural drainage regime. This can be achieved through the use of Sustainable