A plastic modular paving system is being used to help prevent flooding in urban areas by introducing soil structures and tree growth.

The developers of a new tree care and storm management system believe it could contribute significantly to the prevention of flooding in urban areas by introducing soil drainways and vegetation to locations where they would otherwise be absent.

The Silva Cell is a suspended pavement system consisting of modular frames that can be stacked as many as three tiers high and covered with a deck.

Each of the cells measures 1.2 metres in length, 60 centimetres in width and 40 centimetres in depth, making them capable of containing 0.28 cubic metres of soil. The framework of the cell consists of six vertical posts with rounded edges to prevent the concentration of pressure and forestall the possibility of disruptive sinkage.

The decks which cover the paving system consist of hard platforms with a set of six recesses to accommodate the vertical posts of the underlying cells, as well as apertures to permit the ingress of air and water into the soil below.

The cells are manufactured via the injection moulding of a glass and polypropylene compound, with galvanised steel tubes installed to provide additional strength and prevent plastic creep.

The modular paving system provides a firm yet flexible framework for introducing trees and other forms of vegetation to urban areas. It can be made as wide as required by placing individual cells adjacent to each other, and because each framework consists of approximately 92 per cent empty space, also leaves ample room for the installation of utilities-related systems or equipment.

modular cells

When properly placed, the structures can help to prevent flooding in areas which would otherwise be devoid of soil or vegetation by facilitating the absorption, evapotranspiration and interception of storm water.

The system has already been deployed on a significant scale in the UK, where the problem of urban flooding has worsened considerably since the turn of the century.

Welsh Water has invested 15 million pounds in Silva Cells to produce a system of green spaces that draws rainwater into natural local water courses, alleviating the pressure placed on the local sewerage system during severe storm conditions.

At the Stebonheath Primary School in Wales, which is particularly flood prone and subjected to enough storm water each year to fill four Olympic-sized swimming pools, Welsh Water teamed up with civil engineers Arup to retrofit the local playground with Silva Cell installation.

A two-tier Silva Cell configuration was created in the playground to contain a pair of large trees and to produce a catchment area for the reduction of surface water.

The system is expected to divert as much as 3,000 cubic metres of storm water each year – equivalent to nearly a third of the annual total – into the ground and away from the sewerage system.