Update
GEORGE NEWS - “The heavy, consistent rain on Saturday 21 October that caused the collapse of a seepline on the western slope of the Kaaimans gorge resulting in a landslide leading to the temporary closure of the N2 highway, has left the mountainside scarred with severe loss of indigenous vegetation,” says Cobus Meiring of the Garden Route Environmental Forum (Gref).
Meiring says streams, seeplines and wetlands on mountain slopes play an important role in ensuring the geological integrity of mountain slopes and its 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.”
He says hard infrastructure, such as the N2 highway constructed on a sensitive and geologically unstable mountain slope through Wilderness and the Kaaimans gorge with a history of landslides, will always increase the risk of mountainside collapse under certain circumstances such as torrential rain.
“The impact of invasive alien plants on the landscape and upper catchments effecting river function and health also play a detrimental role in the ability of rivers and streams to cope with large volumes of water flow during floods as it strips river banks of natural vegetation biding river banks and protecting soils.”
Meiring says 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 has in recent years been badly affected by a creeper plant overgrowing forest vegetation and causing the collapse of the forest canopy under its weight.
“Trees are dying off, leaving the seepline and rivulet’s shallow soil structure susceptible to collapse once it becomes water-logged, without sufficient surface vegetation keeping it firmly in place and preventing it from sliding downward under gravity.”
He says 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 a further risk 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.”
Meiring warns that the changing climate and changes in rainfall patterns 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 an unpredictable future.”
The Garden Route Environmental Forum (GREF) is a public platform for landowners and environmental managers in the Southern Cape.
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