Every day many acres of open ground are brought into use for new residential or commercial development.
A negative consequence of this is that the natural ability of the land to absorb excesss rainfall is lost under new hard landscaping and existing surface water drainage systems are put under pressure, resulting in an increased risk of localised flooding.
Green roofs help to counteract the consequences of increased areas of hard landscaping. They tore rainwater, reduce water run off and delay discharge into the drainage system. This reduces pressure on local drainage provision, whilst water evaporation from green roofs helps to improve the local microclimate.
Based on extensive work by Optigreen's research and development team it has been able to optimise the positive effects of a green roof in terms of water management. The result of this is a clever solution and a patented system for water retention on green roofs using an innovative new drainage board from Optigreen called Meander.
The principle behind the patented Meander Board system is as simple as it is effective – water flows along a winding route from one chamber to another, just like a naturally meandering river or stream. During heavy rainfall the chambers of the board are filled with water and it passes from one chamber to the next causing a long delay in the discharge of excess water. The meander board is available in 30 or 60mm height.
With the standard drainage board, water is stored in individual pockets in the board until a certain level is reached with excess water then draining through small holes in the board to the water storage mat below. With a Meander board in the green roof build-up water is stored in a temporary reservoir and discharged very slowly, the rate to some extent depending on the gradient of the roof.
As an example, during a peak rainfall event, on a roof with a 2 degree fall, and a 60mm depth of substrate up to 99% of the rainfall can be retained using a Meander 30 board.
