Media Release: Collapse of natural infrastructure proves costly in Kaaimans

For Immediate Release
26 October 2023

“Following heavy and consistent rain on Saturday, 21 October 2023, the collapse of a seep-line on the western slope of the Kaaimans gorge caused a landslide leading to the temporary closure of the N2 highway. This left the mountainside scarred with severe loss of indigenous vegetation,” says Cobus Meiring of the Garden Route Environmental Forum (GREF).

Streams, seep-lines and wetlands on mountain slopes play an important role in ensuring the geological integrity of mountain slopes and their ability to direct and absorb water flow. Sand dunes, rivers, streams, mountain catchments, forests and many other examples are referred to as natural infrastructure, and collectively they play an irreplaceable role in ensuring the well-being of nature and the human population it supports.

Hard infrastructure, such as the N2 highway is constructed on a sensitive and geologically unstable mountain slope through Wilderness and the Kaaimans gorge. This type of area is prone to landslides and will always be at risk of mountainside collapse (or partial collaps) under certain circumstances such as torrential rain. The impact of invasive alien plants on the landscape and upper catchments affecting river function and health, also has negative snowball effects on rivers and streams to cope with large volumes of water flow during floods. This is because it strips river banks of natural vegetation binding river banks and protecting soils.

Indigenous vegetation plays a vital and irreplaceable role in ensuring soil stability on steep slopes, and unfortunately, the forests on the western slope of Kaaimans gorge, have in recent years been badly affected by a creeper plant overgrowing forest vegetation. This type of vegetation causes the collapse of the forest canopy under its weight with trees dying off. It then leaves the seep-line and rivulet’s shallow soil structure susceptible to collapse once it becomes waterlogged. Sufficient surface vegetation would have kept it firmly in place and prevented it from sliding downward.

Rehabilitating the damaged water course in Kaaimans will pose a challenge as all the vegetation and topsoil slid down the slope and washed away. It should be considered to investigate the stability of the remainder of the western slope to determine if is stable or posing further risks to the N2 highway.

“Invasive alien plants are very likely to claim the scar left by the landslide as they outcompete indigenous vegetation in terms of new growth,” says Meiring.

Given the changing climate and rainfall patterns, which increase the probability of episodic rain storms along the Garden Route, the region is likely to experience repeated damage to its road and rail infrastructure in the near future.

The Garden Route Environmental Forum (GREF) is a public platform for landowners and environmental managers in the Southern Cape.

Photo: Landslide scar in Kaaimans gorge

Caption: Collapse of indigenous forest poses a further potential threat of landslides

ENDS