Landslides in Western Ghats

Landslides in Western Ghats

Context

Heavy monsoon rainfall recently triggered widespread landslides, mudslides, and flash floods across the Western Ghats region, particularly in Kerala. The intense precipitation spell was driven by a strong offshore trough extending along the west coast, coupled with intense south-westerly winds over the Arabian Sea and a steep north-south pressure gradient.

About Landslides

Definition & Nature

• Geological Phenomenon: A landslide is a mass movement event characterized by the rapid downward movement of rock, boulders, earth, or debris along a slope under the influence of gravity.
• Terrain Susceptibility: Primarily occurs in mountainous and hilly topographies where soil, rock mechanics, hydrogeology, and slope angles create conditions favorable for slope failure.

Causative Factors

• Conditioning (Inherent) Factors: Pre-existing environmental conditions including soil depth, rock weathering, geomorphology, structural discontinuities, and natural slope inclination.
• Triggering (External) Factors: Immediate events that disturb slope equilibrium, such as intense or prolonged monsoon downpours, unscientific land-use changes, deforestation, and heavy engineering interventions.

Key Reasons for Vulnerability in Western Ghats

Geographical & Geological Dynamics

• Dual-Layer Stratigraphy: The terrain features a porous upper soil layer resting directly above impermeable, weathered hard bedrock. During intense rain, water infiltrates the soil and flows along the soil-rock interface, reducing friction and severing the cohesive bond binding soil to rock.
• Steep Topography & Weathering: High relief and sharp slope angles accelerate gravitational pull and runoff velocity during cloudbursts or continuous rain.

Human Interventions & Land-Use Alterations

• Unregulated Mining & Quarrying: Expanding stone quarrying and sand mining destabilize fragile slope bases, triggering localized rockfalls and sub-surface fractures.
• Large Hydropower & Construction: High-impact dam developments, hill-cutting for highways, and unscientific infrastructure projects destabilize slope contours and sub-surface hydrology.
• Deforestation & Monocropping: Replacement of deep-rooted native forest canopy with shallow-rooted commercial plantation crops (e.g., tea, rubber, coffee) weakens topsoil anchorage.

Climate Change & Changing Rainfall Patterns

• Extreme Rainfall Events: Rising global temperatures have altered regional precipitation dynamics, leading to frequent short-duration, high-intensity rainfall events that quickly saturate soil capacity.

Key Challenges & Expert Panel Recommendations

Institutional Implementation Bottlenecks

• Gadgil Committee (WGEEP, 2011): Recommended classifying 64% of the Western Ghats into graded Ecologically Sensitive Zones (ESZ 1, 2, and 3), curbing mining, quarrying, and large dams in high-priority zones.
• Kasturirangan Committee (2013): Proposed bringing 37% of the range under an Ecologically Sensitive Area (ESA) framework to balance conservation with local developmental needs.
• Non-Implementation: Implementation of both expert panel recommendations remains stalled across states due to socio-political and economic friction.

Way Forward

• Micro-Hazard Zonation: Prepare granular, panchayat-level Landslide Hazard Zonation (LHZ) maps to restrict human settlements and high-risk construction in critical susceptibility zones.
• Nature-Based Bio-Engineering: Promote slope stabilization through re-vegetation using deep-rooted indigenous flora to anchor topsoil naturally to underlying bedrock.
• Doppler & Early Warning Networks: Deploy localized Doppler Weather Radars and real-time hydrological sensors for precise rainfall-threshold nowcasting and rapid community evacuations.
• Regulate High-Impact Activities: Strictly enforce environmental impact assessments (EIA) for quarrying, tunneling, and road construction along fragile slope gradients.

Conclusion

Managing the escalating landslide crisis in the Western Ghats requires reconciling economic development with ecological conservation. Implementing scientific land-use planning, heeding expert panel frameworks, and deploying micro-level early warning systems are vital to safeguarding fragile hill ecosystems and human lives.