Anthropogenic activities [human intervention] have enhanced the severity of high intensity rain-induced landslips in the Talacauvery-Bhagamandala belt of Western Ghats in Kodagu district last month, said a geologist, after a physical inspection of the region and collating satellite imagery data.
Hejmady Gangadhara Bhat, professor of marine geology at Mangalore University, said that about 500 mm rain for 24 hours preceding the landslip triggerred the activity, while saturated thick soil layer [about 20m] in the region compounded the intensity.
Prof. Bhat told The Hindu that human interventions such as cutting hill slopes for development activities, including roads and buildings, as well as digging trenches on hill slopes for rainwater harvesting, intensified the impact of the landslips.
While Kodagu witnessed massive landslips in 2018, not many incidents were seen in 2019.
He said that routine landslips on the steep slopes of the Western Ghats in Kodagu, Hassan, Dakshina Kannada, and Chikkamagaluru districts are aggravated by anthropogenic activities.
There was no doubt that high-intensity rains within a short duration had triggered the Bhagamandala landslips. The region received over 65 cm rain in August first week. Rainwater infiltration into the soil has changed the soil’s absorption and moisture levels.
Upon examination of the rocks in the debris, he found two to three sets of joints and the weathering of rocks.
The soil got saturated following heavy rains thereby gaining weight and slipped fast as the steepness of the hillock was nearly 55 degree, Prof. Bhat said.
Though there were reports of digging trenches on Gajagiri at Talacauvery, Prof. Bhat said he could not trek the mountain owing to heavy rains.
However, there were vertical trenches that were dug up behind the residence of priests, which naturally amplified soil weight, he said. Indiscriminate digging of trenches on hillocks would prove hazardous, he cautioned.
The government should immediately undertake risk assessment in the Ghats region and undertake hazard zonation mapping. It was also necessary to shift residents on the foot of hillocks to safer places. The government should exploit all the advanced systems of geo mapping for the same, he suggested.