Steep slopes secured, Ghat roads in Nilgiris now safe for visitors

COIMBATORE: For tourists negotiating the steep ghat roads in The Nilgiris, a blanket of lush greenery enveloping the slopes in patches is a sight to behold.

Not long before, these spots were marked as vulnerable to landslides, where vehicles moved with caution.

“It’s a remarkable transformation from danger zones into visually delightful areas, where tourists even stop by to have a glimpse and take selfies,” said H Sarath Kumar, who was on a trip to Ooty from Kanyakumari.

Perhaps, such a beautiful transformation also serves another deeper purpose of slope stabilisation to prevent landslides. An innovative solution for slope stabilization; soil-nailing and hydro-seeding being implemented over the last couple of years in The Nilgiris has begun to yield the desired results.

“Along the Ooty-Kotagiri-Mettupalayam Road, where this environment-friendly project was executed, has withstood the vagaries of recent cyclone-induced rains. It has proven to be a cost-effective solution by reducing construction costs by 50 per cent when compared to conventional methods like erecting retaining walls to prevent landslides. Also, the retaining walls aren’t appealing,” said an official of the State Highways Department.

The soil-nailing and hydro-seeding project first took off on a trial basis in the year 2021 in Kotapamandhu and Bhagya Nagar on Ooty-Kotagiri-Mettupalayam Road and as well as on National Highways near Katteri Park.

As it turned out to be a success, similar works were taken up along the ghat road in six more spots in three divisions; three in Ooty, two in Coonoor and one in Kotagiri localities. They all were completed in the year 2024.

After preparing the surface of the slope by removing loose soil with a gradient not exceeding 70 degrees, the soil is nailed using steep rods and cement slurry to strengthen the hills.

Then, hydro-seeding is done by spraying a mix of seed slurry made of grass seed, mulch, fertilizer, seed growth promoters, and water. The soil is also covered with a layer of grass that prevents soil erosion. Following this, the geogrid mats made of polymers are spread over the slopes. After these works, water is sprinkled periodically and maintained for at least three months.

It takes nearly three weeks to carry out earthworks to prepare the ideal gradient for the slope, and then to complete the entire process. In a significant development, the success of this new technology has in turn prompted the highways department to replicate them in Valparai Hills, Kolli Hills and Yercaud Hills.

“Two stretches in Valparai and one spot in Kolli Hills were completed, while in Yercaud, works are likely to commence soon. By the start of next year, plans are afoot to execute soil-nailing technology in Kodaikanal and Palani hills to prevent mud slips. Also, more than 300 spots were identified as vulnerable to landslides in the whole of Nilgiris, where too the works will be taken up on a priority basis on receiving work orders from the highways department,” said Chandran, engineer of Maccaferri, a firm providing solutions to civil, geotechnical and environmental construction, involved in the execution of the soil nailing project in association with the highways department.

There is hope among people that the ongoing slope stabilisation project is expected to give a fillip to the tourism sector, which gets hit every time during rains because of landslides.

Human interventions main cause of most landslides

Large-scale destruction of forest lands, encroachment of water bodies and changes in land use patterns were attributed as major factors behind a spate of incidents of landslides.

“Improper drainage system in urbanised areas is also another cause of landslides. Most of the drainages are blocked as people have constructed houses over them causing diversion of its water course. Also, the natural slopes were cut for developing roads caused along the roads,” said PD Arumairaj, a former professor and head of Geotechnical Division, Government College of Technology in Coimbatore, in his recent study on landslides and its mitigation measures in Ooty.

Landslides are also triggered by climatic changes, increased rainfall, sudden floods, and soil erosion. “Of the 4,170 areas prone to natural calamities in Tamil Nadu, the State Disaster Management has identified 284 spots in Nilgiris as landslide-prone,” said an official of the highways department.

A study by the State government reveals that the number of landslides has accelerated from 1978 onwards and if the present trend continues, the possibility of occurrence of landslides will increase from 70 per to 100 per cent in the next 10 to 20 years.

Since its illustrious past, the scenic Nilgiris district has been prone to natural calamities and landslides. The Avalanche, located almost 26 km from Udhagamandalam, derived its name from a massive landslide in 1824. More than 25 families were killed in a landslide caused by a cloudburst in Ketti on 25, October 1990, while hundreds lost their lives in a cloudburst on the wooden bridge (Marapalam) on November 11, 1993.

A series of landslides in 2009 caused the death of 42 people in 48 hours, while a heavy downpour of 82 cm of rains in 24 hours on August 8, 2019, triggered landslides in 140 places causing heavy damage to infrastructure.

Perhaps, an analysis has revealed that the chances of landslide occurrence are multifold and disastrous. “The frequency of landslide occurrence has increased to alarming levels in the last three decades. Heavy rainfall, deforestation, unplanned construction, and geological factors like the presence of weathered rock, loose soil, and tectonic activity in the district contribute to the region's susceptibility to landslides,” claimed Arumairaj.