Porous Paving and Green Roofs Urged in New Drainage Plan

The Land Drainage Master Plan (LDMP), published this week by the Ministry of National Infrastructure, recommends moving beyond traditional drain construction to a more holistic approach to storm water management. The report advocates for a three-pronged strategy focusing on source, transport, and end-of-network controls. Porous paving, green roofs, and other innovative techniques are being championed as solutions to urban flooding, according to a new government report.

A key recommendation for urban areas is the use of more permeable materials. The plan encourages the installation of porous paving and other permeable surfaces.

It also suggested that roof water should be directed towards permeable ground, such as lawns or infiltration wells, rather than flowing directly onto impermeable surfaces like pavements or car parks that are connected to the storm water network.

The LDMP also promoted the use of green roofs, provided they are properly designed to prevent prolonged water stagnation.

Temporary water storage on rooftops, acting as a retention basin, is also deemed acceptable under certain conditions.

Surface storage is another recommended technique, using car parks or dedicated zones to regulate flow before water is discharged into the network via a flow-limiting orifice tube.

Other source control measures include bioremediation devices, which simultaneously store and filter storm water, and soil amendments to improve the quality of compacted or nutrient-poor ground.

For controlling water transport in urban areas, the report suggests using improved grassed ditches that promote infiltration and flow regulation.

It also recommends creating oversized channels to both convey storm water and serve as temporary retention structures.

Finally, end-of-network controls, located at the end of the flow path, include infiltration trenches, retention basins, artificial wetlands, and vegetated filter strips.

These measures are designed to improve water quality and reduce flow speed.

Source: l’Express