Bigger cities mean bigger concrete surfaces, which in turn leads to reduced natural infiltration of rain water. And this is not something we can ignore, says Rachel Wray Thompson, Chicago-based architect and LEED Accredited Professional: “While asphalt and concrete have been the go-to outdoor surfaces for years, they really have very few benefits other than being one of the least expensive options.”

“A better choice would be a pervious material — something that allows water to drain through the material itself, or through the joints of the construction.”

Terracrete in square pattern at the new control gate at Cape Town harbour

The blocks are laid on spun bounded geofabric and plants are taking hold

Locally, Terracrete, a product developed by Terraforce, local and international licensor of concrete blocks, is an example of a permeable paving block. As an alternative to impermeable urban surfaces, the block allows for unrestricted water penetration and can help manage storm water run-off by temporarily storing rainwater runoff before filtering it back – cleaned of impurities – into the soil. As a result, rainwater that would normally run off into rivers and streams is returned directly into the soil.

The incorporation of drainage lines along edges of roadways assist with storm water management

The handling of storm water runoff from sealed traffic areas is made less complicated with permeable paving

Another benefit – and one not to be scoffed at – is that permeable surfaces just look better. Says Thompson: “Instead of boring concrete or high maintenance, ugly and smelly asphalt, permeable surfaces come in a variety of styles that pretty much always look better.”

This is a point Holger Rust, Owner of Terraforce, also strongly emphasizes in the design of the Terracrete block: “From an aesthetic point of view, the blocks are user-friendly and versatile. Homeowners want their property to look good. A grassy driveway, a rustic gravel driveway, or an attractive pattern of pavers can add the finishing touch to a custom home looking to stand out. Permeable grass pavers can add a park-like or pastoral feel to areas normally needing hard paving.”

He adds that the blocks are suited to create attractive walkways, storm water run-off channels for a garden or golf course, grassy parking areas and rustic roadways: “They can be laid in different patterns and may also be used with or without ground anchors for the lining of riverbanks and other areas subjects to soil erosion. As a finishing touch the pavers can be filled with gravel or planted with hardy grass to create a softer surface.”

This, says Thomson, reduces overall irrigation demand: “By allowing the water to seep into the ground, the direct and surrounding areas will need much less man-produced irrigation. This will save you money and reduce the amount of water used for your everyday irrigation needs.”

By allowing the water to seep into the ground, the direct and surrounding areas will need much less man-produced irrigation

As a finishing touch the pavers can be filled with gravel or planted with hardy grass to create a softer surface

Not only can newly developed areas be paved to create permeable surfaces.  Rust also suggests using the block to upgrade drainage in existing paved areas or in areas that are to be paved with asphalt or interlocking clay/concrete pavers: “The incorporation of drainage lines along edges, around perimeters and at fixed centres across parking/storage areas or roadways makes it possible to up-grade existing ones or enhances drainage of new installations. This method can also be applied when new service or irrigation lines have to cut across existing parking areas while trees are established at the same time.”

Many industry experts agree that permeable pavers can offer a good solution to increased storm water run-off.  Says Dr Sönke Borgwardt, self-employed landscape architect and consulting engineer and leading expert on the subject in Germany: “the use of permeable paving is an important contribution to a sustainable and environmentally useful management of drainage systems. The handling of storm water runoff from sealed traffic areas is made less complicated and more affordable when it is decreased considerably by the application of infiltratable pavements.”