SuDS in London - a guide

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Comparison between runoff rates for greenfield and urban environments Evapotranspiration Evapotranspiration Surface flow Interflow Baseflow Greenfield Urban Higher and more rapid peak discharge Surface flow Interflow Baseflow Flow in river (m3/s) Higher baseflow Lower and less rapid peak Gradual recession Flow in river (m3/s) Steeper recession Lower baseflow Rainfall event Time Rainfall event Time 12 1 Principles of SuDS
1.3.2 Water quality Surface water is often polluted. Runoff from roads, for example, includes contaminants from tyre abrasion such as rubber and soot, nickel and chromium from brake pad linkings and oil, silt and iron oxide from general traffic use. During warm, dry periods, these substances build up on sun-warmed surfaces and heavy showers can wash them into the drainage system. This creates a warm, contaminated, low-oxygen water mix, which flows into watercourses and groundwater. Managing the quality of runoff helps protect the natural environment from pollution and SuDS can be crucial in this respect. The risk of pollution in a SuDS scheme must be assessed and a mitigation strategy proposed to determine the required number of treatment stages to ensure water is clean enough to flow to a watercourse. SuDS can also improve the quality of water entering combined sewers, reducing pressure on sewage treatment plants. Improvements to water quality can also contribute to amenity and the potential for for biodiversity. Reed beds, for example, which naturally slow and treat water, provide an active edge to water features and attract a wide range of birds and insects. Designing for water quality must take account of: • Interception and treatment methods to meet CIRIA standards • The quality of surface water and groundwater receiving run-off • The extent of existing pollution control systems in the catchment • The extent to which risk management measures for spillages of contaminants, such as oil, are in place • The proportion of permeable surfaces, green roofs, and/or surfaces discharging to a rainwater harvesting system or soil-based feature • The proportion of the surface water management system that is on or near the surface to facilitate treatment Reed beds can contribute to water quality • The extent to which the design of the system incorporates sediment retention, such as forebays or hydrodynamic separators • System resilience to cope with future demand, including allowances for climate change and urban intensification 13 1 Principles of SuDS
Page 1 and 2: SuDS in London - a guide November 2
Page 3 and 4: Introduction
Page 5 and 6: II Who is the guidance for? Primari
Page 7 and 8: 1 Principles of SuDS
Page 9 and 10: 1.2 Wider benefits The ambition for
Page 11: 1.3.1 Water quantity SuDS mitigate
Page 15 and 16: 1.3.4 Biodiversity London’s natur
Page 17 and 18: 2.1 What is unique about London? Th
Page 19 and 20: Hampstead Ridge Valley Lea Valley L
Page 21 and 22: • Amenity/biodiversity: the natur
Page 23 and 24: 2.7 Townscape Townscape is the mix
Page 25 and 26: 2.9 London’s green infrastructure
Page 27 and 28: 2.13 Archaeology London’s history
Page 29 and 30: 3 SuDS components
Page 31 and 32: A number of case studies illustrati
Page 33 and 34: 3.2 Structures Roofs and walls can
Page 35 and 36: Case study 1 - Structures Location
Page 37 and 38: 3.3 Infiltration systems London’s
Page 39 and 40: Case study 3 - Infiltration systems
Page 41 and 42: 3.4 Filter strips Filter strips are
Page 43 and 44: 3.6 Wet swales and dry swales Swale
Page 45 and 46: Case study 5 - Swale Location Mill
Page 47 and 48: Maintenance Channel systems require
Page 49 and 50: Case study 6 - Bioretention Locatio
Page 51 and 52: 3.9 Trees Trees in the hard landsca
Page 53 and 54: Street trees: biodiversity Where tr
Page 55 and 56: 3.10 Permeable paving Permeable pav
Page 57 and 58: Case study 9 - Permeable paving Loc
Page 59 and 60: 3.11 Detention basins Detention bas
Page 61 and 62: 3.12 Attenuation and storage tanks
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Design considerations Sedimentation
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4 SuDS in London’s streets
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4.2 Street scenarios Street scenari
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Street scenario 3 An important foca
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Street scenario 5 A well-connected
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Street scenario 7 A local shopping
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5 Case studies
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5.1 Priory Common rain meadow Locat
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5.2 Upminster Bridge swale Location
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5.3 Kenmont Gardens Location Kensal
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5.4 Derbyshire Street Pocket Park L
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5.5 Renfrew Close Location London B
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5.6 Islington Town Hall Location Up
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5.7 Rectory Gardens Location Hornse
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5.8 Talgarth Road Location Talgarth
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5.9 Mile End Green Bridge Location
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5.10 Queen Caroline Estate Location
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5.11 Bridget Joyce Square, Australi
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5.12 Crown Woods Way Location Eltha
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5.13 Hackbridge Location Hackbridge
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5.14 Goldhawk Road Location Shepher
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5.15 Firs Farm Wetlands Location Wi
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5.16 Salmons Brook Glenbrook Stream
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5.17 LuL depot roof, Middlesex Loca
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5.18 A23 Coulsdon Bypass, Farthing
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5.19 London Sustainable Industries
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5.20 Great Kneighton / Clay Farm, C
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5.21 Alnarpsgården Swedish Univers
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5.22 Benthemplein (Water Square) Lo
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5.23 Rue Garibaldi Location Lyon Fr
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5.24 Bo01 Võstra Hamnen Location M
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6 Implementation
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Kings Cross LWT: Camley Street A so
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6.3 Drainage hierarchy SuDS designs
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7 Cost benefit
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7.2 Methodology Cost benefit estima
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4.4 LANDSCAPE WATER MANAGEMENT STRA
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Appendices
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i-Tree Eco Project (2015) Valuing L
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Movement of water from one location
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Heat island Describes urban built u
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Prevention Site design and manageme
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Team The guidance has been produced
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Photo credits 80 Swale sections TfL
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SuDS in London - a guide

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