Detecting landslides: Expert panel for installation of alert monitoring system

Ambika Sharma

Solan, November 2

Installation of an alert monitoring system for detecting landslides, sinking events, etc., at critical locations has been recommended by an expert committee, which examined the 20-km critically damaged stretch (Parwanoo-Dharampur) on the National Highway-5.

Major observations

• The panel questioned the economic viability of adopting four-lane standards in hill areas like Himachal and went ahead with the suggestion of adopting two two-lane corridors on different alignments
• The National Highways Authority of India could not execute adequate slope protection works while the highway was being four-laned owing to its high cost vis-à-vis the total project cost
• “The panel has suggested short-term, long-term and immediate measures to be adopted to ensure smooth flow of traffic on the road,” said Anand Dahiya, Project Director, NHAI, Shimla

Damage could have been contained

Damages could have been minimised by taking actions from the stages of planning, by including and implementing protection measures at the time of execution. Expert panel

The committee headed by RK Pandey, former ADG, Ministry of Road Transport and Highways, made detailed recommendations for containing damages on the NH-5.

As many as 176 defects were identified over an area of 6,485 m, which was affected by the landslides due to torrential rains. The existing slope angle varied from 50 to 85 degrees with the slope height varying from 10 to 100 metres. The committee had visited the highway on September 9.

The panel has also flagged the inadequacies in the detailed project report (DPR), which serves as a guide for executing the project. It questioned the economic viability of adopting four-lane standards in hill areas like Himachal and went ahead with the suggestion of adopting two two-lane corridors on different alignments.

This aspect should be included as part of the scope of the DPR consultant while planning a corridor in the hills, observed the committee in the report. The report has exposed glaring shortcomings in the DPR.

Few damages were triggered due to blockage of culverts, absence of the energy dissipation mechanism on downstream side and inadequate size of the culverts, proper inlet and outlets.

“The committee has suggested short-term, long-term and immediate measures to be adopted to ensure smooth and uninterrupted flow of traffic on the road,” said Anand Dahiya, Project Director, NHAI, Shimla.

It is also noted that the stretches where some protection works have been executed have survived. However, taking note of the cost of the protection work, which exceeds the cost of road, the user requirement should be brought out in the schedule B.

Notably, the National Highways Authority of India could not execute adequate slope protection works while the highway was being four-laned owing to its high cost vis-à-vis the total project cost. It has been noted that the detailed project report (DPR) lacked key aspects like absence of valley-side retention measures, which could have prevented slope failure at several points.

Several modifications were suggested in the DPR like using self-drilling anchors, muck removal and proper maintenance of weep holes, adequate slope protection system, use of additional rockfall arresters at sites where sliding of debris and rolling down of huge boulders are observed, conducing agronomic soil testing for sites where sliding incidents and water run-off has occurred.