River rehab: prevention is better than cure

Climate change and growing competition for water are making the protection of South Africa’s valuable water resources more important than ever. Soil conservation engineer Hans King spoke to Glenneis Kriel about how this should be approached.

- Glenneis Kriel

FAST FACTS

The cost of repairing damage done to watercourses via erosion and flooding increases as the situation worsens.

Preventing this damage from ever taking place should be prioritised.

By pooling their resources, riparian owners can achieve the best results in this regard.

It is quick, easy and cheap to damage natural water resources, but difficult and expensive to rehabilitate them. “The highest priority when it comes to river management should therefore be to avoid this damage in the first place,” says soil conservation engineer Hans King.

He points out that it can cost millions of rands to fix such a problem, with the cost increasing significantly over time as the situation worsens and spreads to other areas.

To prevent this damage, the natural flow of the river should be maintained as far as possible.

“Erosion and deposition of sediment in rivers are natural phenomena that should not be interfered with. If a river is unnaturally disturbed by bulldozing or the infestation of woody alien vegetation, such as black wattle, for example, these natural processes become greatly accelerated, and an intervention is often required to return the river to its original state.”

In King’s experience, farmers’ perception of the space a river needs to function tends to be based on very recent flood events of no more than five years beforehand. The disturbed nature of rivers, plus the insufficient space left for rivers to function after such events, results in much higher levels of flood damage in relation to the actual size of the flood.