Subscribe
A changing climate means that disasters like the landslides in Kerala’s Wayanad on July 30 will increase in frequency and intensity, an expert has told Down To Earth (DTE).
Also, the poorest and most marginalised sections of society are and will be most affected by such disasters, said Associate Professor Pierre Rognon in the School of Civil Engineering, University of Sydney, Australia.
“The scientific consensus is that climate change will induce even more of such extreme rain events in the future. As extreme rainfalls are a mechanical trigger of landslides, and a direct cause of mud flows like in Wayanad, we should unfortunately expect an increase in frequency and intensity of such landslides globally in the near future,” Rognon, whose area of expertise encompasses landslides and their triggers; social consequences; recovery and rescue; aftermath analysis, added.
He observed that the two major triggers of landslides are rainfall and earthquakes. The landslide that hit Wayanad was most likely triggered and fed by unusual rainfall on the day before the event, and during the week before the event.
Rognon classified the Wayanad landslide as a ‘mud flow’. “It (mud flow) is made of a lot of rain water flowing fast and transporting earth particles, rocks, trees and anything in its path,” he said.
The occurrence of mud flows is directly related to extreme rain events. What happened in Wayanad is a typical scenario, said Rognon.
“Over the course of a few days, significant rainfall fully saturates the porous ground “filling up the ground water tank”; the next heavy rain cannot be stored underground, it then runs off fast on top of the ground and collects in gullies and canyons, where it suddenly forms very powerful streams,” he explained.
These streams, in turn, erode the ground including fine soil particles, boulders and trees.
“This mixture has the devasting consequences that we know on people, buildings and infrastructures that are in its path,” said Rognon.
He also said increasing landslides would hit the weakest.
“In circumstances where the likelihood of having more and larger landslides in any particular area is increasing, the population is divided into two groups: those who can afford relocating to a safer zone and those who cannot,” said the expert.
When relocating is not an option monitoring, early warning systems and protecting structures are available to mitigate, with some limits, the risk of landslides; the question is that of affordability, he reasoned.
“The most vulnerable and marginalised sections of society are sadly these which remain the most at risk,” said Rognon.