Retrofitting Sustainable Drainage Systems Pilot Study - Portslade BHCC Green Infrastructure Briefing 16.04.2015 Ben Kimpton Dip(Hort) BSc MSc MCIEEM - TEC Gary Grant BSc CEnv FCIEEM - GIC Content How do SuDS fit into GI? SuDS in a Nutshell The Findings The Fantastic What is Green Infrastructure? “GI is a strategically planned and delivered network of high quality green spaces and other environmental features. It should be designed and managed as a multifunctional resource capable of delivering a wide range of environmental and quality of life benefits for local communities”. Natural England Green Infrastructure – Key Principles Benefits of Green Infrastructure and SuDS The multiple functions that GI assets provide are underpinned by the concept of ‘ecosystem services’. In the recent UK National Ecosystem Assessment these services were divided into four categories: Supporting Services – ecosystem processes (soils/plants) Regulating Services – control mechanisms (flood control) Provisioning Services – products (water supply) Cultural Services - non-material benefits (visual amenity) Regulating Services Provisioning Climate change – e.g. reducing surface water flooding Services Detoxification/purification in soil, water and air Hazard regulation – water attenuation Pollution control Pollination What are SuDS? Portland Reduces Provisioning ic Surface Flooding Reduce the amount and rate of surface water leaving sites One of the most effective ways of managing flood risk Alternative approach to conventional drainage systems Contribute to climate change mitigation and adaptation Can also improve water quality through bioremediation, increase landscape amenity value, boost biodiversity (Ecosystem Services) Made up of a series of interventions – ‘SuDS train’ The aim is to mimic natural drainage processes Water Sensitive Urban Design SuDS incorporate a range of different techniques: Rain gardens Provisioning Services Filter strips / filter drains Green roofs Permeable paving Stockholm ‘ tree-pits’ Rainwater harvesting – tanks, diverted down-pipes Swales Retention / detention basins Ponds / wetlands NB: A combination of techniques is often the most effective Project Background Provisioning Services Carried out by The Green Infrastructure Consultancy (GIC) and The Ecology Consultancy (TEC) Commissioned by BHCC through the Brighton & Lewes Downs Biosphere programme Funded by Natural England under the Green Infrastructure Challenge Fund (2014/15) Supports Brighton & Hove’s work as a Lead Local Flood Authority Feasibility Study of the potential to retrofit Urban SuDS in Portslade Focussed principally on the creation of ‘rain gardens’ on public land Scale Services selected on the basis they are prone to Provisioning 7 areas (sub-catchments) surface water flooding and historic flooding events have occurred. Method Provisioning Services 7 Survey Areas (sub-catchments) selected on the basis they’re prone to surface water flooding and historic flooding events have occurred. natural gradient - direction of surface water flow? evidence of standing water - where would water collect? building and greenspace features - down pipes, existing GI assets etc. drainage - how and where does water enter and exit the site? access and use - who uses the site and what is the level of use? visibility - is the site in the public domain and highly visible? services - what services are present and where are they located? SURVEY AREA 4 Street Name/s: Buckler Street Description: Densely developed area of housing located in gently sloping valley running north-south through south Portslade. Buckler is a short section of road joining Bamfield Street (to the north) with Elm Road (to the south). The central section is pedestrianised. Problem/flood history: Surface water flows both east and west down Bampfield Street and Elm Road, collecting in the lowest point where Buckler Street is located. As Bampfield Street is on higher ground water also flows into Buckler Street from the north. Buckler Street is indicated by the Environment Agency on their uFMfSW as being susceptible to a 1:30 year flood event with c.6 properties in the location experiencing flooding in 2014. Constraints: Narrow pavement and road on both Bampfield Street and Elm Road. Parking bays in frequent use. Opportunities: Pedestrianised central section provides a relatively large area for attenuation. Rainwater down-pipes from three adjacent properties could be diverted. SuDS Solutions: The use of a Stockholm tree pit across the whole pedestrianised area to increase water storage capacity. Mature trees/shrubs could be retained and incorporated. Area to be covered with both permeable paving and rain gardens, subject to detailed design. Water flow from Bampfield Street end to be diverted into the SuDS via a drop kerb at northern end. Indicative cost: Potential (max.) area: £20-40K 220m2 Potential attenuation: Other GI benefits: Will vary according to final size/depth of SuDS feature. Could provide biodiversity and visual amenity benefits. The greatest social benefits would be derived from community involvement in managing (gardening) the planting scheme. Priority Medium General Findings Provisioning Services 0.5 hectares of SuDS could potentially be delivered. Significant improvements can be made through the first phase of micro-projects, which will reduce the risk of flooding. SuDS features identified are located in the middle / lower catchment of the valley that runs north-south through west Portslade. Always consider the SuDS management (treatment) train. Appropriate land-use planning and management in the upper catchment must prevent and control the source of water and SuDS features will become overloaded. In Portland, rain gardens very similar to those proposed in Portslade can reduce the volume of surface water run-off by 80% (1:25 event). Actual volumes that can be attenuated will depend on the type and size of the interventions, installed at each site. More detailed estimates or models can only be provided following detailed design. ‘Urban-creep’ is prevalent. Long-term programme to promote and incentivise ‘de-paving’ and/or the use of domestic rainwater harvesting should be launched. Site Specific Findings Provisioning Services Survey Area 2 (Portslade Village) offers the greatest opportunity in terms of the number of SuDS options and their combined surface area. Three Survey Areas have public open spaces that could be utilised for SuDS features i.e. Survey Area 2 (Victoria Recreation Ground), Survey Area 3 (Lock’s Hill Recreation Ground) and Survey Area 7 (Vale Park). Survey Area 2a(1) - Lock’s Hill Potential Rain Garden Survey Area 2a(1) - Lock’s Hill Potential Rain Garden Portland Rain Gardens Portland Rain Gardens Portland Rain Gardens Portland Rain Gardens Portland Rain Gardens Lyon Rain Gardens Lyon Urban Wetlands London Park Rain Garden Hackney Urban Swale Hackney Urban Swale Case Study Greening The BIDS (London Bridge) Tyers Estate Rain Garden Planter Rain gardens that are cost-effective and without any major barriers to development have been targeted as flagship projects • Location: Tyers Estate – Leathermarket JMB, off Bermondsey Street • Partners: Leathermarket JMB, Peter De Hann Charitable Trust, Groundwork London, residents, volunteers, Southwark Council • Delivery: Spring 2013 Cost: £5K • Provides an exemplar for local residents • Forms part of a 3 year community garden project on Tyers and Whites Ground Estates • Potential to be rolled out across the BID and other social housing estates Estates Greening Rain Garden Estates Greening Rain Garden Fair Street Rain Vertical Rain Garden • Location: Junction of Tooley Street and Fair Street • Partners: Fair Street Housing, GLA, CRP • Delivery: Spring 2013 Cost: £10K • Multiple options including hanging green walls/screens, vertical rain garden and ground level rain gardens • Under-utilised space under housing block. Space could also be used for public seating • Downpipes and below pavement drainage strips are both present for diversion/use • Provides a green link between Potters Field Park and St. John’s Churchyard Fair Street – Option 1 Tooley Street, London Tooley Street, London Thank You Any Questions? [email protected] [email protected]
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