Location: Cardiff, Wales
A Genuinely Innovative Answer to an Escalating Urban Storm Water Challenge
For many older cities and towns, stormwater management has been steadily rising up the agenda for years. Existing ageing infrastructure built for a different era and population, coupled with increased hardscape areas and roads for today’s living means that drainage infrastructure is at or above capacity. Heavy downpours result in the system being overwhelmed resulting in flooding and associated pollution and damage.
The harsh reality is that there are few affordable options to improve existing drainage pipe networks. What can be done however is to ‘un plug’ or disconnect areas from that network.
‘Greener Grangetown’ does just that, by re-landscaping the urban realm with soft landscape and SUDS interventions.
Greener Grangetown in Cardiff is a very interesting example of the successful retro installation of SUDS features into an existing urban streetscape. Working with Arup, GreenBlue were closely involved with advising on the tree pit installations, and assisting the GG team from concept through to completion.
The Greener Grangetown project covers the roads; Aber St, Abercynon St, Bargoed St, Blaenclydach St, Coedcae St, Clydach St, Cymmer St, Ferndale St, Llanbradach St, Taff Embankment, Taff Terrace and Ystrad St.
Prior to the commencement of this scheme, the rainwater flowed into the sewer, mixed with wastewater from kitchens and bathrooms and was pumped around 8 miles to the Vale of Glamorgan, before being treated and released out to sea. By removing this rainwater from the sewer, Welsh Water have reduced the energy used for pumping and treating the wastewater. At the same time, by doing this, they have freed up some space in the sewer to help the region adapt to more extreme weather conditions which are caused by climate change.
A Solution with Multiple Physical, Social and Economic Benefits
The goal was to ensure that Greener Grangetown delivered a wide range of benefits for the environment and the local community. The new street designs included installing attractive rain gardens and kerbside planting areas. These not only enhance local biodiversity and wildlife, but deliver important improvements to water quality in the River Taff, and encourage water efficiency.
One of the great advantages with this is that by creating more green areas it opens up new opportunities for people to enjoy walking, cycling and other recreation close to where they live and work. More greenery and tree planting also means noise and pollutants are better absorbed, and air will be cleaner too.
As well as forming part of the rain garden strategy, the trees and shrubs bring a cohesive identity to the Greener Grangetown area.
The layout, species, shapes and colours of the planting gives each street an individual look. In total, 135 trees have been planted – and a total of 19 different species.
All the trees share certain characteristics. They are:
- Generally deciduous so that natural light is maximised during the winter.
- ‘Street trees’ that can tolerate urban environments.
- Trees that provide interest all year round either due to leaf colour, bark or flowers.
- All trees are UK sourced.
- Trees with appropriate root volume provision, and designed for long term tree health
- Trees with a 2.5 metre clear stem to deter vandalism.
- Tree species with a high biodiversity value.
The Tree Pit and Rain Garden Design team at Arup, working with GreenBlue Urban Ltd, put a design emphasis on long term sustainable tree planting for the raingardens and tree pits. Where possible, tree pits were linked below ground, increasing available soil volume for the trees, and simultaneously increasing water attenuation capacities, a true win-win.
Load bearing soil cells from GreenBlue, were used extensively to provide load bearing soil volume, and maintain uncompacted aerated soil conditions, perfect for root growth, water attenuation and transport, and air supply in the root zone.
Uncompacted soil media is vital in these situations – as tree health depends on the macro and micro pore structure within the soil. The structural components such as RootSpace and Stratacells look after the physical structure of the soil, enabling the soil to look after the tree. This simple philosophy has served urban tree planting projects very well since first introduced globally by GreenBlue Urban back in 2001.
GreenBlue Urban have enjoyed being part of the team making this scheme happen. From the earliest concept stage, experienced design consultants contributed to detailed drawings, and followed through, working with the contractor and providing active ‘on site’ support during construction. We continue to be involved as the project planting establishes and matures, for no other reason other than it inspires us! The GreenBlue mission is to ‘enable sustainable cities through Green and Blue Infrastructure’. Greener Grangetown is an exemplar of this vision and mission fulfilled.
The results so far have been overwhelmingly positive. The team have been hugely enthused about delivering such a broad spectrum of both physical ecosystem and social benefits through this well-planned scheme. As a GreenBlue representative put it
“the trees and landscaping in this project are raising the living standards for so many people, and the nice thing is that because the Greener Grangetown team have invested in appropriate volume tree pits, the value is going to increase year on year for decades to come.”