Landslides: Waiting in the wings

High rainfall and steep slopes render localities susceptible to landslides; hence regions of highest ecological sensitivity (ESZ1) in the Western Ghats are susceptible to landslides. Further, any disturbance to natural vegetation - construction of buildings and roads, quarrying or mining, replacement of natural vegetation by plantations, or levelling of the land using heavy machinery - renders an ESZ1 locality susceptible to landslides. Had our recommendations (Western Ghats Ecology Expert Panel report submitted in 2011) been accepted, there is no doubt that the extent and intensity of landslides in the region would have been much lower.

Unfortunately, the pace at which these disturbances are taking place has increased over the last 9 years.

There are other compounding factors as well. There are now many rock quarries afflicting the hilly regions of Kerala. Even if they are not close to the landslide site, shock waves from blasting of rocks in quarries slowly weaken the rocks in the surrounding areas, enhancing chances of landslides. Regrettably, the Pettimudi landslide tragedy is no surprise.

The Western Ghats force moisture laden winds coming from Arabian Sea to rise, resulting in high levels of rainfall on the western slopes and the crest line of the Ghats. Elsewhere, air may rise if the ground below is locally heated. This happens wherever the original vegetation cover of the land is replaced by the cement-concrete jungles of cities, highways and rocks exposed due to mining and quarrying.

Moreover, India is characterised by the highest levels of aerosols. As water vapour in air laden with aerosols begins to condense, it initially forms myriads of small water droplets, which then coalesce to form larger heavy water drops that lead to intense rain over shorter periods.

So, what would otherwise have constituted a gentle drizzle lasting 6 hours, now pours down as an intense lashing of rains, ranging from 30 minutes to 3 hours. The result is intense floods and increased chances of landslides, breaching of bunds, and collapse of buildings.

The extensive forest cover of Switzerland has developed only over the last 160 years. Before that, only about 4% of that country’s lands had retained forest and there were disastrous landslides. This led to a public awakening and a restoration of the tree cover. This regeneration was managed by local communities, not by government departments. Working together, communities of Switzerland, practising genuine participatory democracy, have revived the country’s ecology. Such participatory democracy is the only way forward.

(The writer was the chairman of Western Ghats Ecology Expert Panel)