Erosion is a natural occurrence, but should preferably happen under a state of balance. Holger Rust, the founder and chief executive officer of Terraforce, agrees that high population numbers, bad farming practices and an explosion in urban development, are all aggravating soil loss.
It is estimated that South Africa has already lost at least three-million hectares of productive farm land to soil erosion. Surface water run-off in urban areas is also an increasing problem. It is about four times higher than in rural areas of similar geographical composition. Impermeable buildings, roadways, parking areas and even stormwater drains may cover more than 20% of the total area and cause reduced infiltration, increased run-off velocity and erosion.
“Currently little attention is paid to implementing sensible corrective measures, even though food security is very high on the global agenda,” says Rust.
Soil-stabilisation measures are as simple as implementing re-vegetation with suitable plants such as grass, hydroseeding, mulching, mixing with straw in sandy soils, windbreaks or brush packing, stabilising cylinders, mats made of organic material or logs and hard finishes. “Most of these measures work well, but are not suitable to use on steep slopes,” says Rust.
Embankments that are steeper than one-in-one can effectively be stabilised or retained with interlocking hollow concrete-retaining blocks that are plant-supportive and easy to maintain. Embankments with an inclination of between one-in-one and one-in-two can be stabilised with concrete erosion control or retaining blocks that will not degrade, unlike more cost-effective, soft finishes.
Also, the installation of permeable pavements and the temporary storage of run-off water in detention ponds in the upper reaches of the system need to be implemented as a matter of routine. “Ideally this should take place before man-made disasters strike and not thereafter,” Rust adds as a word of warning.
For more information, refer to concrete solutions for erosion-control problems in the download section at www.terraforce.com.
Tel: 021 465 1907
Fax: 021 465 4047