Kodagu landslips a result of natural and man-made causes

The Geological Survey of India has made an inventory of over 150 landslip-prone spots in Kodagu alone.

August 22, 2018 11:00 pm | Updated August 23, 2018 03:33 pm IST - Bengaluru

 A house balances precariously following a landslip, near Madikeri on Saturday.

A house balances precariously following a landslip, near Madikeri on Saturday.

The hand of man through deforestation and concretisation, the wrath of the rain clouds, and an earthquake may have all played a part in the immense devastation seen in Kodagu district this month.

On July 9, after a gap of nearly five years, a mild tremor shook parts of southern Kodagu, with the epicentre being 10 km below the ground between Madikeri and Sampaje. The Karnataka State Natural Disaster Management Centre (KSNDMC) noted the quake to have registered 3.4 on the Richter scale. Incidentally, it is this stretch that has seen the most landslips this month.

“Following the earthquake, most residents could hear sounds, almost like soft blasts, even as cracks appeared. There could be a connection between the mild earthquake and the landslips. The hard rock might have loosened in the tremors and this might have been washed away in the rains,” said C.G. Kushalappa, Dean of Forestry College at Ponnampet.

 

Statistics accrued independently by the college — through a network of rain gauges —show that this nature of rainfall was last seen in 1961, when intense rainfall was concentrated in a few weeks. “There is definitely a human factor of deforestation along the slopes and construction along floodplains that may have contributed to the floods. But, the natural factor should be studied too,” said Mr. Kushalappa.

While the lower number of landslips in Talacauvery area — which has received the most rains — is explained by the thick forest cover there, the devastation has been most prominent in the dense human habitations along the Madikeri-Sampaje road.

KSNDMC officials said the sounds heard could have been of the formation of “hydrological cavities” in the slopes, which collapse with the onset of rains. “This is a common precursor to landslips. The formation of hydrological cavities can be seismic (that is, due to the earthquake) or be part of a natural process before monsoons when the soil is dry,” said an official.

K.V. Maruthi, senior geologist at the Geological Survey of India (GSI) who is in the district with a team to study the cause of landslips, said they would look at all the angles, including the possibility of geological causes. “We can’t be sure now, because landslips are caused by numerous factors, natural and man-made... Generally, only stronger earthquakes contribute to landslips, but we will look at this too,” he said.

The GSI has made an inventory of over 150 landslip-prone spots in Kodagu alone. They make up nearly 20% of the 704 spots in Karnataka’s Western Ghats region.

In a previous assessment by the GSI, they had studied eight landslips in Kodagu following the immense rains in June. Seven were found to be aggravated by human interference, including roadwork with inadequate retaining walls, lack of drainage, clearing of vegetation, and weakening of slopes through unscientific construction of houses. The report shows that diversion of traffic on the Bengaluru-Mangaluru highway owing to landslips at Shiradi Ghat had increased the traffic load on the Madikeri-Sampaje road, and it may have contributed to landslips in the area.

Forest loss

However, this is not to negate the changes in land use Kodagu has seen over the years or factor in poor design of roads and layouts. This is anecdotally seen in the places of devastation: while Talacauvery, which is surrounded by natural forests, received the most rains, it had the least number of landslips. The relatively dense habitations along Madikeri-Sampaje road saw the most number of landslips.

The Forest Survey of India’s State of Forest Report shows that since 2007, Kodagu has lost 88 sq. km of forests. While very dense forests remain well-protected and have risen dramatically, moderately dense and open forests — many of which fall in private property — have come down by 654 sq. km since 2015. Many researchers have pointed out that the replacement of native trees with Silver Oak has led to greater soil erosion, while studies have shown that Kodagu has lost 30% of its dense tree cover in three decades.

Meanwhile, the Coorg Wildlife Society, which is a collective of citizens who have been fighting against “unnecessary” development projects, has found out through RTI queries that more than 2,800 acres of paddy fields, coffee plantations, and highlands were converted into residential layouts, sites, commercial complexes, and resorts between 2005 and 2015.

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