From Green Roofs to Rain Gardens

by Rich Howorth Author - Ben Kimpton Urban

From Green Roofs to Rain Gardens: “Green Infrastructure” for our towns and city We are fortunate that our urban areas contain a rich network of green spaces, from large Victorian parks with unique elm trees through to road verges with wildflowers and tree-lined railway corridors. Increasingly people are trying to design and retrofit the hard-surfaced environment of buildings, roads and other built infrastructure to be more natural and permeable, by incorporating vegetation to shade us, absorb rainfall, and sustain wildlife. These green spaces and buildings are our “green infrastructure”, providing us with many benefits that are as vital to our urban life as the more conventional “grey infrastructure” with which we are more familiar. For us to live better in the future as an international Biosphere demonstration area, then we will need to integrate the green and grey to cope with more extreme weather events from climate change, ranging from heat episodes to flooding. Green Infrastructure (GI) provides a multi-functional range of benefits – so-called “ecosystem services” – to people, especially those living in urban areas of our Biosphere, such as, enabling wildlife to move along ‘green corridors’ between the surrounding countryside and city centres, countering the ‘Urban Heat Island Effect’, and reducing storm water flooding from climate change. The UK is predicted to experience a 40% increase in peak rainfall events in the future from global climate change. Since 75% of rainfall in built-up areas ends up as surface water run-off, in heavy storm events our predominantly Victorian drainage systems can quickly be overwhelmed, resulting in localised flooding and thus inevitable costs and disruption. Our infrastructure will have to evolve to cope with future challenges if we are to avoid a significant increase to the risk of flooding. Sustainable Drainage Systems, or ‘SuDS’, can help us to address climate change by providing more natural ways of managing surface water run-off than conventional systems of drains, pipes and sewers. Different systems such as rain gardens, filter strips, green roofs, permeable paving, swales, and wetland features aim to mimic natural drainage processes and help to reduce the amount and rate of surface water leaving a site. A “rain garden” is a small low-lying area of wetland plants designed to receive and hold rainfall from surface run-off or diverted from roofs via down-pipes, with surplus water returned to the conventional drainage system.   Rain Garden in London (BK-EC)

A rain garden in an urban park near London Bridge © Ben Kimpton

The great thing about rain gardens is that they not only hold back storm water and reduce flooding, they can also help to filter pollution, attract wildlife to your neighbourhood and look colourful at the same time – making them multi-functional. We are currently carrying out a Biosphere feasibility study (funded by Natural England) in the urban area of Portslade to see if new rain gardens could help to alleviate recent flooding here. Reducing the rate of discharge from heavily built-up areas is one of the most effective ways of managing localised flood risk, reducing the amount and cost of the overall drainage infrastructure required to support urban development. Furthermore, if planned properly from the outset, SuDS need not cost any more than conventional drainage systems. The concepts of GI and ecosystem services, whilst not new, are now set to become an important planning tool in the UK. They have been recently embedded in the National Planning Policy Framework, and in regions such as the All London Green Grid (ALGG). At a local level, Local Development Frameworks, Neighbourhood Plans, Surface Water Management Plans, Open Space and Tree Management Strategies are all carrying the GI torch. For sustainable drainage, the Lead Local Flood Authorities in South East England have produced guidance for development. Other recent publications that set out the process and benefits of GI implementation include those by the Department for the Environment and Rural Affairs, Natural England, The Landscape Institute, Town and Country Planning Association and Wildlife Trusts. Brighton has one of the oldest and largest pieces of green infrastructure in the form of the Green Wall along Madeira Drive. The local interest group ‘Brighton and Hove Building Green’ has successfully championed this poorly understood historic feature as a proposed new Local Wildlife Site. The green wall is approximately 1.2km long and up to 20m high in places, with Japanese spindle planted along its length 140 years ago to provide a green backdrop to the built-up seafront environment. Today this is now host to a hundred different plant species! Green Wall Madeira Drive (BK-EC)

Madeira Drive Green Wall - eastern end (Duke’s Mound) © Ben Kimpton

The uptake of Green Roofs in our urban Biosphere area has been quite slow – when compared to cities like London, Manchester and Sheffield – despite the huge benefits that they can deliver to us. Interest is growing in greening our rooftops however, with large local examples at: the University of Brighton, in the New England Quarter of Brighton, at the Linklater Pavilion in Lewes, and on the container flats at Richardson’s Yard and the new Velo Café as part of the landmark regeneration of The Level park in Brighton. These last examples were installed by local company Organic Roofs, who now plan to launch a habitat roof design competition that reflects our Biosphere here, using plants of local provenance that provide food for target pollinator species, set upon a hay base that represents a low embodied energy system. Richardson Yard Brighton Organic Roofs green roof James Farrell building-green.org 12 rev

Richardsons Yard, Brighton by Organic Roofs © James Farrell

So, the future could be brighter for the urban areas of our Biosphere area – if we choose to use green infrastructure as part of a better way of living. Ben Kimpton, The Ecology Consultancy - January 2015

Comments

  • Jackie Seaman:

    What a lovely idea having ponds everywhere. I also like the new thing of digging up the tarmac around pavement trees and replacing it with wood mulch. I would also like to suggest that it would be wonderful if the council stopped spraying glyphosate on the pavements to kill ‘weeds’. I have heard that a salt solution may also kill weeds – maybe this would not be a problem in terms of ‘run-off’ as we live near the coast. Could this be investigated as an alternative.
    Could there also be a move to educate about alternatives to tarmac on front gardens/driveways. It seems many people pour down concrete etc to make a flat surface for laying patio slabs etc., where as sand is just as effective but still allows water to drain into the earth. Is tarmac on driveways part of planning legislation?

    28 Jan 2015 11:15:38

  • Dave Turner:

    Brighton has some earlier examples of green roofs, The Diggers Selfbuild Housing Coop built 1994 and Hedgehog Selfbuild Housing also built in the 1990s.

    03 May 2015 14:20:35

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