SuDS in London - a guide

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These components are designed to promote infiltration where capacity and permeability of soils and the depth of groundwater allows. However, infiltration systems may not be appropriate in many parts of London due to groundwater extraction issues (see Chapter 2). Benefits Infiltration components allow groundwater to be replenished. They can incorporate marginal and wetland habitat. Planting slows the flow rate by improving the drainage properties of the soil, creating a more effective SuDS component. Infiltration can be used to manage overflows from rainwater collection systems, such as water butts and runoff from small areas (for example, drives and roofs). Design considerations Infiltration components can be retrofitted, designed as a series of small linked elements, or as a single larger one. Runoff flow to be directed to a SuDS infiltration component can be collected laterally along the edge of an impermeable surface. Kerb openings and roadside lateral inlets help to direct, control and reduce flow velocities. A minimum of 1m from the base of the infiltration component to maximum groundwater level is required. Upstream pre-treatment may be needed to remove sediment and silt. Performance of SuDS components may be compromised if surface soils become compacted, so should be designed to withstand high intensity pedestrian use. Performance depends on the capacity of the soils surrounding the component. When rainfall rate exceeds the design capacity, a flow route or temporary storage should be provided. Soil infiltration can be enhanced by: • Managing construction traffic to prevent compaction during construction • Mixing sand with soil to retain its drainage properties • Adhering to tight construction tolerances • Soil decompaction • Reusing existing topsoil to allow the inherent seed bank in the soil to regenerate quickly, reducing erosion and enhancing the potential for infiltration Maintenance This can usually form part of the wider routine landscape maintenance. Control structures require periodic inspection. Existing parkland, particularly in critical drainage zones that are subject to intense use, should be periodically decompacted. Useful design guidance CIRIA C753 The SuDS Manual, Chapter 13 38 3 SuDS components
Case study 3 – Infiltration systems Location Streatham Common South London Borough of Lambeth Date 2013 Images courtesy of Owen Davies SuDS components De-paving Tree planting Kerb inlets Before Objectives Streatham Common South falls within the Streatham Critical Drainage Area (CDA). The project included implementation of a rain garden to alleviate flood risk and was completed within a standard highway maintenance scheme. Outcome Pavement SuDS, where inserted with verges, replaced concrete dished channels. These slow surface water drainage into the sewer system. Modeling undertaken has shown that the grass verge can theoretically remove 6m of surface water runoff in a one in 100 year, six-hour storm event. After Kerb inlet and de-pave detail 39 3 SuDS components
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 and 12: 1.3.1 Water quantity SuDS mitigate
Page 13 and 14: 1.3.2 Water quality Surface water i
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: 3.3 Infiltration systems London’s
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
Page 63 and 64: Design considerations Sedimentation
Page 65 and 66: 4 SuDS in London’s streets
Page 67 and 68: 4.2 Street scenarios Street scenari
Page 69 and 70: Street scenario 3 An important foca
Page 71 and 72: Street scenario 5 A well-connected
Page 73 and 74: Street scenario 7 A local shopping
Page 75 and 76: 5 Case studies
Page 77 and 78: 5.1 Priory Common rain meadow Locat
Page 79 and 80: 5.2 Upminster Bridge swale Location
Page 81 and 82: 5.3 Kenmont Gardens Location Kensal
Page 83 and 84: 5.4 Derbyshire Street Pocket Park L
Page 85 and 86: 5.5 Renfrew Close Location London B
Page 87 and 88: 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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