Sustainable water management in towns and cities is now essential. 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 in some areas is at or above capacity. Heavy downpours result in the system being overwhelmed leading to flooding and associated pollution and damage.
However, it is possible to deliver sustainable and resilient SuDS systems that mimic natural drainage, allowing surface run-off to be managed as close to the surface and as close to its source as practicable.
GreenBlue Urban worked with Arup to install SuDS features into 13 streets in Grangetown, Cardiff. Arup’s water engineers and placemaking team designed solutions that integrated SuDS with public realm improvements, with GreenBlue advising on the tree pit installations.
Prior to the commencement of this scheme, 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, Dwr Cymru Welsh Water has 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.
The Arup design team, working alongside tree officers at the City of Cardiff Council, urban tree and soil science specialists at Natural Resources Wales and GreenBlue Urban Ltd, put a design emphasis on long-term sustainable tree planting for the rain gardens 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 in 2001.
The Client Project Lead from Cardiff Council and instigator of the scheme Ian Titherington stated: "Green Blue’s input into the project has been a critical element, in delivering a truly green environment into streets previously largely devoid of such advantages. Working alongside our excellent design team from Arup, they have helped to already transform the street scene and peoples’ perceptions of the area; this being achieved before the trees have been located for more than two seasons."
The results so far have been overwhelmingly positive. The team are pround to have delivered such a broad spectrum of environmental and social benefits through this well-planned scheme.
For more information on the details about the tree and shrub planting, and the additional benefits of the project, click 'Visit website' opposite.