Landslides: A Natural Hazard

Let’s begin simply.
A landslide is nothing but the movement of rock, debris, or soil down a slope under the force of gravity.

In geography terms, it is part of “mass wasting”, which includes all down-slope movements driven primarily by gravity — like soil creep, slumping, rock falls, and avalanches.

🧭 Why are landslides common in India?

Because 15% of India’s land area — especially the Himalayas, Western Ghats, and Northeast — lies in zones of steep slopes, fragile rocks, and heavy rainfall.

👉 The Himalayas, in particular, are geologically young and unstable mountains.
They were formed due to the collision of the Indian and Eurasian plates —
and even today, the Indian plate continues to push northward at 5 cm/year, creating constant stress, fracturing rocks, and making the region prone to landslides and earthquakes.

⚙️ Causes of Landslides

Like most disasters, the causes can be natural or anthropogenic (human-induced).

A. Natural Causes

1️⃣ Heavy Rainfall

• The most common trigger.
• Water seeps into soil, increases its weight and reduces cohesion → slope failure.
• Especially common during monsoon in Himalayas and Western Ghats.

2️⃣ Earthquakes

• Tremors shake and loosen rocks, causing them to tumble down slopes.
• Even minor quakes in hilly terrain can destabilize slopes over time.

3️⃣ Volcanic Activity

• Explosions or lava movement disturb slope stability and trigger slides.

B. Anthropogenic Causes

1️⃣ Deforestation

• Roots bind soil particles together. Cutting trees removes this natural binding.
• Bare slopes become exposed to heavy runoff → slope failure.

2️⃣ Road Construction

• Blasting, slope cutting, and dumping debris destabilize slopes.
• Improper engineering without retaining walls is a major issue in Himalayas & NE India.

3️⃣ Shifting Cultivation (Jhuming)

• Common in North-East India.
• Continuous clearing and burning of vegetation loosen soil, increasing slide frequency.

4️⃣ Unplanned Construction

• Rapid tourism and population growth → hotels, houses built without slope analysis.
• Excavation, heavy foundations, and waste dumping on slopes trigger slides.

🇮🇳 Landslide Risk Zones in India

NDMA and GSI have divided India into vulnerability zones based on geology, slope, rainfall, and human pressure.

Vulnerability Zone	Characteristics / Regions
Very High Vulnerability Zone	– Young, unstable mountain regions: Himalayas, Andaman & Nicobar. – Western Ghats, Nilgiris, Northeast hills with steep slopes and high rainfall. – Earthquake-prone and heavily disturbed areas (road & dam projects).
High Vulnerability Zone	– Same as above but with slightly less frequency or intensity. – Excludes Assam plains.
Moderate to Low Vulnerability Zone	– Less rainfall & more stable terrain: Trans-Himalaya (Ladakh, Spiti), Aravallis, rain-shadow areas of Ghats, and Deccan plateau. – Landslides due to mining/subsidence common in Jharkhand, Odisha, Chhattisgarh, M.P., Maharashtra, Karnataka, Goa, Kerala.
Safe/Negligible Zone	– Rajasthan, Haryana, U.P., Bihar, W.B. plains, Assam plains, and southern coasts.

⚒️ NDMA Guidelines: Landslide Hazard Mitigation

NDMA’s approach focuses on prevention, preparedness, and long-term slope stabilization rather than just post-disaster response.

Let’s go through the key strategies 👇

1️⃣ Hazard Zonation and Monitoring

• Identify landslide-prone areas through Landslide Hazard Zonation (LHZ) mapping.
• Use remote sensing, GIS, and field surveys to mark vulnerable slopes.
• Install early warning systems (rainfall thresholds, ground sensors) in selected sites.

2️⃣ Land Use Planning and Restrictions

• Ban or regulate construction on high-slope or unstable terrain.
• Limit agriculture to valleys and moderate slopes.
• Avoid large-scale settlements or tourist infrastructure in high-vulnerability zones.

3️⃣ Afforestation and Soil Conservation

• Promote large-scale afforestation to bind soil and absorb water.
• Construct bunds, check dams, contour trenches to control runoff.
• Encourage terrace farming instead of Jhuming in the North-East.

4️⃣ Engineering and Structural Measures

• Build retaining walls, drainage channels, and gabion walls on unstable slopes.
• Stabilize existing slide zones by slope re-grading, anchoring, and vegetation cover.
• Prepare codes for excavation and grading to ensure safe slope modification.

5️⃣ Insurance and Compensation

• Introduce landslide insurance schemes and define mechanisms for compensation of affected households.

6️⃣ Capacity Building & Awareness

• Integrate landslide risk in DM plans at national, state, and district levels.
• Develop a disaster knowledge network for sharing research and best practices.
• Establish international cooperation for research, forecasting, and monitoring.

⚠️ Existing Challenges in India

1️⃣ Lack of integration of landslide management in DM planning (especially local level).
2️⃣ Fragmented response — usually limited to short-term remediation, not preventive work.
3️⃣ Weak techno-legal regime — poor enforcement of slope protection and zoning laws.
4️⃣ Environmental negligence — unregulated construction and quarrying on fragile slopes.
5️⃣ Limited awareness and data sharing among agencies.
6️⃣ Need for strict regulation and “zero tolerance” towards unsafe practices on slopes.