Depave our city? A lesson from Portland, Oregon

We know that some parts of Brighton & Hove are ‘risky’ when it comes to flooding and depaving may provide part of the answer. Don’t worry, we aren’t advocating digging up the whole city! 

Building Green was speaking on the subject recently at a Hove Civic Society meeting, and reflecting on the July 2014 floods – 100 properties flooded in Portslade and 300 emergency calls to East Sussex Fire and Rescue in a single morning. Now, this is ‘surface water flooding’ we are talking about – the kind where very heavy rainfall runs and collects in the hollows in the hard surfaces in our towns and cities.

Cities tend to be impermeable places – and we know that where we can increase permeability at scale, for example through landscaping, retaining front and back gardens, green roofs and other ‘sustainable drainage’ approaches, we can reduce the risk of flooding.

Come and learn more about it all this weekend – and how you can help by ‘doing it yourself’ at the workshops run by Building Green, Organic Roofs and Brighton Permaculture Trust. Not too  late to book a place!

Portslade is home to two of the first ‘rain gardens’ in Brighton & Hove. Building Green and partners have completed a study that has found enough flat roofspace in 9km2 of central Brighton – 87 football pitches worth in fact – to hold back 100 Olympic swimming pools of rainwater that our street drainage networks might struggle with during heavy rainfall events.

As we’ve reported before, there are other places that do this much, much better. Let’s learn from them.

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Victoria Recreation Ground rain garden, Portslade

One such place is Portland, Oregon – and in this blog Dusty Gedge writes about a new initiative to ‘depave Portland’ – ripping up the hard surfaces and planting stuff.

Good for sustainable drainage – but also good for visual amenity, and even crime rates potentially. A study in Chicago Illinois in 2001 in one public housing development found that robberies were down by 48% and violent crime by 56% in areas where buildings had been ‘greened’ with green walls and landscaping. Poster below. Those are big numbers – what if we could achieve 1 or 2% – still worth doing? Building Green thinks so.

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Huge potential for green roofs to improve the centre of Brighton

The first feasibility study and audit of the potential for green roofs in Brighton has been published.

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Green roof on the Velo cafe, The Level, Brighton – image by Building Green

The study examined a study area in Central Brighton, to assess the potential benefits of establishing green roofs.

It finds that 61 hectares of roofs in Central Brighton are suitable for retrofitting with green roofs, in a way which brings nature, summer cooling and storm water management benefits and improves the attractiveness of the cityscape.

This is equivalent to 87 football pitches-worth of new green roof space in the 9km2 area of the city that runs between the West pier and Dyke Road, and from Bear Road to Kemptown.

This area is highly urbanised, is susceptible to surface water flooding, and has limited open green space.

More on the benefits:

  • In terms of urban drainage benefits, it is estimated that 61ha of ‘biodiverse’ green roofs could attenuate between 3507.5m³ and 244,000m3 of storm water. In other words, up to 100 Olympic swimming pools of water would be held back from the city’s roads and drains at peak times. This could have a significant combined effect in reducing flooding and the need for additional, costly, engineering infrastructure.
  • Approximately 2.3MWh of electricity could be saved every year on cooling costs for buildings – via reduced or avoided air conditioning.
  • Greening roofs would also reduce the Urban Heat Island Effect, potentially providing an additional saving in cooling costs in the region of 1.3million kWh per annum.
  • The centre of Brighton would be far more attractive at roof level.

This work should be of interest to planners, architects, developers, environmentalists, householders and city businesses.

Download the Brighton Green Roof Audit

The study was prepared by Ben Kimpton (Senior Ecologist – The Ecology Consultancy) and The Green Roof Consultancy, it was supported by Matthew Thomas (former Ecologist – Brighton & Hove City Council), James Farrell (Chair – Brighton and Hove Building Green), Dusty Gedge (Founder – Livingroofs.org and Director – The Green Roof Consultancy) and Lee Evans (Director – Organic Roofs).