south

Updated: Aug 26, 2019 01:00 IST

Western Ghats are vulnerable to environmental disasterssimilar to Kerala’s Kavalappara, where heavy rains triggered a mudslide this month and wiped away the entire village, according to the India Meteorological Department (IMD) data. The frequency of extreme rainfall events (more than 15 cm in 24 hours) during the monsoon there is the highest along with parts of the northeast.

A book titled Observed Climate Variability and Change over the Indian Region (2017) is based on the data from 9,294 weather stations from 1901-2010 and shows how climate change is impacting the country.

The data shows that light-to-moderate rainfall (less than 64.4 mm) days from June to September have reduced over Peninsular India, including Karnataka, Tamil Nadu, and Kerala. But the frequency of “very heavy rainfall (124 to 244.5 mm)” is also going up over Karnataka, Goa, and Tamil Nadu.

Extremely heavy rainfall (more than 244.5 mm) events are going up over Maharashtra, Goa, and Karnataka, which are anyway high precipitation zones, along with Uttar Pradesh, Odisha, and Chhattisgarh and parts of the northeast. Goa is particularly vulnerable to extreme rainfall events.

“While overall rainfall is decreasing in Kerala, we can see that the frequency of extreme rainfall events was high in the Western Ghats during the past decades. So, it is definitely a vulnerable region. Out of 122 days of rains during the monsoon, the average annual frequency of extremely heavy rain days is more than 50 in the Western Ghats. This trend is increasing in the Konkan-Goa region. It is very heavy rain in a few number of days,” said Pulak Guhathakurta, head of IMD Pune’s Climate Application and User Interface Group.

Former IMD director general K J Ramesh said the Ghats are not aligned to the coastline in Kerala. “The catchments of most rivers are in the Ghats. We need granular data to understand how extreme rain is impacting the ghats,” said Ramesh.

The elevation in Kerala ranges from -48 m below sea level in the backwaters and other low-lying areas, to +2,692 m in the hills above mean sea level. Around 35% area is between 0-50m, 39.82 % between 50-500 m and 24 % of the area is above 500m making its topography vulnerable, Ramesh has highlighted.

The problem exacerbates to dangerous levels when soil and forests are not managed accordingly. For example, pit-making for monoculture plantations using heavy machinery, quarrying, mining, constructing buildings or resorts on the hill slopes aggravate impacts from extreme rainfall.

“Rampant rain-pit making in slopes of 30% (gradient) or more need to be regulated. Pits for monocultures should be done carefully and not with JCBs that displace a lot of soil,” said V Nandakumar, a scientist at the National Centre for Earth Sciences, who assessed the mudslide at Kavalappara, which killed at least 50 on August 8.

Madhav Gadgil, an ecologist and the head of a panel that submitted a report on declaring parts of Western Ghats as eco-sensitive zones in 2010, said more such disasters can be expected.

“In 2018, many thought that this was a calamity that strikes just once in a century and we will get back to normality soon and can merrily continue business as usual. But the probability of two such back to back events [landslides in Kerala] is only 1 in 10,000… landslides are under check-in areas with intact natural vegetation because of the binding of the soil by roots. However, any disturbance to natural vegetation would render a locality with high rainfall and steep slopes susceptible to landslides,” he said.

“We expect that in the areas assigned by us to ESZ1 (eco-priority regions) any such disturbance of natural vegetation and soil would mean the greater danger of landslides. The fact that these have all been occurring in 2018 and 2019 in ESZ1 as designated by us is, therefore, to be expected,” he said.