The massive landslip at Shirur, Uttara Karnataka, calls for a relook into the construction and road widening activities along hillslopes.
In a recent letter to the Ministry of Road Transport and Highways, the National Environment Care Federation has highlighted the threat of landslips occurring frequently in various parts of the country due to unscientific development activities, including road widening and tunnel constructions, especially in ghat and hill regions.
“Different countries have different protocols that determine the most appropriate angle of a cutting and suitable stabilisation measure for a cutting. In general, the road cutting should be characterised according to the geometrical, material, and hydrological conditions of the specific site. It is important to design road cuttings to be stable and resilient under the present day extreme climatic events,” says S. Sreekumar, former professor, Department of Geology and Environmental Science, Christ College, Irinjalakuda.
Dr. Sreekumar is at present the Disaster Risk Management expert at the Kerala Institute of Local Administration (KILA). Now, the disaster management plans are prepared at the local body level in Kerala and capacity development training is carried out by the KILA to consider all the negative aspects that can result from a development project.
The density of the road network has more than tripled in the past three decades in the country. This growth has been rapid, extensive and in many places haphazard.
“The problem faced in our country is the limitation of available land for acquisition, mostly under forest areas. So, they are forced to design the cuttings with steeper slopes than actually permitted, within the space constraint. Due to budget constraints, protective measures that have lower construction costs are opted,” Dr. Sreekumar, also a resource person for the United Nations Development Programme-Government of India vulnerability reduction project, says.
The burst of water flow carrying huge debris from high elevated to low elevated points during extreme rainfall events is often disastrous. The situation worsens with continuous heavy rain. There has been a sharp increase in the road network in high lands in Idukki and Wayanad, connecting tourism villages.
Dr. Sreekumar, who was part of a team which did a mapping of landslip-prone areas after the 2019 floods, says most of the minor and major soil slips and rockfalls were associated with road cuttings.
Studies carried out a few years back have identified several high hazardous stretches along the Kottayam-Kumily road.
“The concave areas along the hilly ghat region, which are more spacious, are popular spots among tourists and travellers. They may have refreshment centres and sometimes even a minor spring. However, these concave areas are mostly formed due to paleo slide scars and chances of further soil slides have to be foreseen during intense rainfall episodes,” says Dr. Sreekumar.
Precautions
“Geological and geotechnical analysis of slopes, which are at high risk, should be done for stability assessment before the development process. Appropriate site-specific stabilisation measures have to be taken,” says Dr. Sreekumar.
Maintenance of road drainage and weepholes, without permitting build-up water pressure, is important. Decayed roots should be removed from the slopes of the forest-acquired land and grouting should be done to prevent soil piping. Monocrop plantation along slopes should be discouraged and deep-rooted trees of indigenous species should be planted, he says.
Published - July 26, 2024 07:43 pm IST
