To cut landslide risks, NHAI installs slope drain pipe system on Kalka-Shimla stretch, Pg11

Key Highlights:

• NHAI has implemented a slope drainage pipe system at 83 vulnerable points along the Kalka-Shimla NH-5.
• The system aims to mitigate landslide risks and soil erosion by managing rainwater runoff ahead of the monsoon season.
• This intervention was recommended by experts from IIT Bombay and IIT Ropar after previous measures proved inadequate during the 2025 monsoon.
• The project covers 85 km of the highway in Himachal Pradesh, a region prone to frequent landslides.
• Landslides caused an estimated Rs 200 crore in losses to national highway projects in Himachal Pradesh between January 2021 and July 2025.

Detailed Insights:

• The Kalka-Shimla NH-5 is a vital transport link that experienced over 128 landslides in 2019 and 2023, leading to significant disruptions.
• Earlier slope protection methods, such as green mesh netting and anchoring, were found insufficient to control heavy surface runoff during intense rainfall.
• The new drainage system collects water at hilltops and channels it through pipes and cement-lined drains to the slope's base, reducing pressure.
• This approach marks a shift from the shotcrete technique, which, despite its effectiveness, resulted in visually unappealing barren concrete surfaces.
• Highly susceptible sections like Parwanoo-Chakki Mod and Kandaghat-Kaithlighat were prioritized for the initial phase of implementation.
• The initiative is part of a broader NHAI slope stabilization program that also incorporates soil nailing and vegetation-based stabilization for comprehensive protection.

Scientific/Technical Concepts Involved:

• Slope Drainage System: An engineering solution designed to control and divert surface water runoff from slopes to prevent erosion and instability.
• Slope Stabilization: The process of improving the stability of natural or engineered slopes to prevent failures like landslides.
• Soil Nailing: A ground reinforcement technique where steel bars are drilled and grouted into a slope to enhance its shear strength and stability.
• Shotcrete: A method of applying concrete or mortar by spraying it pneumatically at high velocity onto a surface, often used for slope protection.