Between 1971 and 2007, the area surrounding Counters Creek, London, lost around 20 percent of its permeable green space. This, along with the loss of all open watercourses in the locality, has led to a rise in surface water run-off, which, increases the risk of flooding in the local sewer network.
In order to manage the flood risk in this area, Thames Water has worked with partners to pilot an innovative retrofit scheme which monitors and assesses the effectiveness of several surface water management systems. Taking place across three London streets – Mendora Rd, Melina Rd and Arundel Gardens – the scheme uses the Permavoid geocellular system to reduce the flow of surface water into the sewer system. However, each street uses a slightly different system that is tailored to that specific environment. At Mendora Rd, Permavoid cells have been installed beneath the paving on both sides of the street, forming 136 cubic meters of storage for excess water. Prior to entering the storage tank, the water also passes through a Permafilter geomembrane to remove any oil and other vehicle pollutants.
A different approach has been taken at the Melina Rd scheme, with four separate storage tanks installed beneath the street’s rain gardens. These tanks contain over 2,000 Permavoid Permafoam cells, which collect rainwater and can be used to irrigate the vegetation above. This technique is viewed as a ‘blue-green’ solution, reducing flood risk during heavy rainfall while also providing additional urban green space and promoting plant growth.
The next stage of the project will see a third system design implemented at Kensington’s Arundel Gardens. For this scheme, Permavoid will be installed beneath the road surface, with the stored rainwater being used to irrigate established magnolia trees on either side of the street.
At all three sites there has been a commitment to maintaining residents’ quality of life and preserving biodiversity, and it’s great to see green infrastructure solutions being showcased in this way.