G.T. Thong
Department of Geology, Nagaland
University Kohima Campus, Meriema
Portions of the Paglapahar area came sliding down early in the morning of 12th August 2011 to cause much disruption, damage to vehicles, and a death. This entire stretch of the highway from the Kuki Dulong Bridge till slightly beyond the Patkai Bridge poses grave threat to all. In August 2002 huge scale devastation took place in the area and the consequences were indeed tragic, with seven slides generated during the month on two days.
The section between Chumukedima and Jharnapani along the NH 29 comprises pervious and unstable rocks and soils, which make this terrain highly landslide-prone during the monsoon.
The other major reasons include steep slopes and heavy rainfall during the monsoon. Most of the landslides in Nagaland have been initiated during intense monsoon precipitation. Severe storms are very common phenomena in this region. Highway widening with no mitigation measures in place too initiated landslides.
With adequate weather forecasting abilities and careful analyses of cumulative rainfall patterns it may be possible to predict to some degree the landslide hazards during a particular rainy season. Those places where sliding has occurred in the past should be closely monitored so that lives and property might be saved in the event of landsliding.
In the Paglapahar area the ground is well saturated by early August. Hence, storms during this period can have devastating effects, as already observed in 2002 and 2011. Low altitude cumulo-nimbus clouds generated during this season slowly come and get trapped by the high hills of Paglapahar, particularly during the cooler periods such as late evening (August 2002) or early morning (August 2011). Such phenomenon causes extreme rainfall that eventually leaves a trail of destruction behind.
The Chathe River is vigorously eroding portions of its banks, including the highway side. Therefore preventive measures to protect against toe erosion should be taken up urgently otherwise bank erosion, though restricted to a few places, will lead to collapse of portions of the already narrow highway.
[This article, now modified, was first published in some of the local papers in August 2011, and again with addition of the last paragraph in July 2023].
