The downslope movement of rock, soil or debris triggered by heavy rain, earthquakes or human activity. A major monsoon hazard in the Himalayas and Western Ghats.
PhenomenaWhat is a Landslide?
A landslide is the downslope movement of rock, soil, or debris under the force of gravity. The term covers a wide range of events:
- Rockfall — Loose rocks tumbling down steep cliffs.
- Rockslide — Whole rock mass sliding along a fracture plane.
- Debris flow / mudslide — Saturated soil and rocks flowing rapidly down a slope.
- Earthflow — Slow flow of saturated fine-grained soil.
- Slump — Rotational failure of a slope.
- Creep — Imperceptibly slow downhill movement.
In South Asia, the most deadly type is the rain-triggered debris flow — when intense monsoon rainfall saturates a steep hillside, the soil loses cohesion and rushes downhill as a torrent of mud, rocks and uprooted trees, often burying entire villages in minutes.
What causes landslides
The fundamental cause is gravity acting on an unstable slope. Triggers:
Weather-related:
- Heavy or prolonged rainfall — saturates soil, increases pore-water pressure, lubricates failure planes. Triggered 79% of fatal non-seismic landslide events worldwide in 2004–2016.
- Cloudbursts — sudden 100+ mm/hour events can trigger flash-flood debris flows.
- Snowmelt — combined with rain in spring.
- Cyclone-driven rainfall — heavy rain hundreds of km inland can trigger landslides.
Non-weather:
- Earthquakes — Nepal 2015, Sikkim 2011, Pakistan 2005 triggered thousands of co-seismic landslides.
- Human activity — road-cutting, slope undercutting for construction, deforestation, unplanned terracing.
- Volcanic activity — rare in mainland South Asia, but possible.
Where landslides hit hardest in South Asia
Indian Himalayan states (highest frequency):
- Uttarakhand — Kedarnath 2013 (5,700+ deaths), Chamoli 2021, Rudraprayag yearly.
- Himachal Pradesh — Kullu, Manali, Mandi 2023.
- Jammu & Kashmir — Pir Panjal range during monsoon.
- Sikkim — South Lhonak GLOF 2023 (at least 55 deaths).
- Arunachal Pradesh — Sino-Indian border road slides.
Western Ghats:
- Kerala — 2018 floods (483 deaths, many from landslides); Wayanad 2024 (~400 deaths).
- Karnataka — Kodagu, Madikeri.
- Maharashtra — Konkan slopes, Talie, Raigad 2021.
- Tamil Nadu — Nilgiris, Coonoor.
Northeast India:
- Assam, Meghalaya, Tripura, Mizoram — annual monsoon landslides.
Nepal:
- Most landslide-prone country in South Asia per capita.
Pakistan:
- Khyber Pakhtunkhwa, Gilgit-Baltistan — Karakoram Highway frequently blocked.
- Murree, Galyat in northern Punjab and Khyber Pakhtunkhwa during heavy rain.
Bangladesh:
- Chittagong Hill Tracts — Rangamati, Bandarban — annual fatal landslides during monsoon.
Historic South Asian landslide disasters
- 1968 Kalimpong, India: landslides after extreme rainfall in early October.
- 2010 Attabad, Pakistan: rockslide killed 20 people and created a lake that submerged Ayeenabad and lower Shishkat.
- 2010 Leh cloudburst: 200+ deaths from debris flows.
- 2013 Kedarnath, Uttarakhand: cloudburst + glacial moraine collapse — 5,700+ deaths.
- 2014 Malin landslide, Maharashtra: village wiped out, 151 deaths.
- 2017 Rangamati, Bangladesh: 118 deaths in the district after heavy rain, and 162 across five districts.
- 2018 Kerala floods: 483 deaths including many from landslides.
- 2021 Chamoli, Uttarakhand: glacier-rock avalanche, 200+ deaths.
- 2023 Himachal monsoon disaster: 556 lives lost to hydro-meteorological disasters in 2023-24 (provisional state figure).
- 2024 Wayanad, Kerala: ~400+ deaths in a single debris flow.
Warning signs of an imminent landslide
If you live in or are visiting a mountainous area during monsoon, watch for:
- Cracks appearing in ground or walls
- Doors and windows that suddenly stick or jam
- Tilting trees or fence posts
- Unusual sounds — rumbling, cracking
- Sudden change in stream flow (clear water becoming muddy)
- New springs or wet patches on a hillside
- Bulging slopes
- Vehicles or buildings sliding even slightly
If you observe these, evacuate immediately to higher, stable ground — do not wait for official warnings, which may be too late.
Landslide safety
Before:
- Avoid building or living below steep slopes, especially loose-soil ones.
- Know your area’s landslide history.
- Plant deep-rooted vegetation to stabilise nearby slopes.
During heavy monsoon rainfall:
- Listen to weather bulletins and government warnings.
- Move to higher, level ground if rain has been intense for hours.
- Do not cross flooded valleys — they may carry debris flows.
After:
- Stay away from the slide area — secondary slides are common.
- Help check for trapped persons only if safe.
- Report damaged utilities (gas, water, electricity).
- Document damage for compensation.
Early warning and Indian system
The Geological Survey of India (GSI) operates a National Landslide Forecasting Centre. The centre issues landslide forecast bulletins for high-risk districts.
Newer technologies include:
- Satellite InSAR monitoring of slow ground movement.
- Doppler-radar rainfall thresholds for nowcast warnings.
- Smartphone landslide-alert apps in Sikkim and Uttarakhand.
Climate change and landslides
Four trends are increasing landslide risk:
- More intense rainfall events as the atmosphere warms (Clausius-Clapeyron: ~7% more water per °C).
- Glacial retreat and GLOFs — newly exposed slopes are unstable.
- Permafrost thaw in the high Himalayas — destabilising rock-ice slopes.
- Population pressure pushes settlements onto steeper, more vulnerable land.
Climate models project an increase in landslide-triggering rainfall events in Himalayan regions.
Frequently asked questions
How much rain triggers a landslide? Thresholds vary by slope, soil and vegetation. Typical triggers: 70–100 mm in 24 hours, or 30–50 mm in 1 hour on already-saturated ground. A single dry-season storm rarely triggers slides; cumulative monsoon rainfall is more critical.
Are landslides predictable? Short-term triggers are increasingly predictable using radar-based rainfall nowcasting and slope-monitoring sensors. But the exact location and timing of slides remain difficult to forecast. Most warnings are area-wide, not pinpointed.
What’s the difference between a landslide and a mudslide? A landslide can involve any material (rock, soil, debris). A mudslide (or debris flow) specifically involves saturated fine-grained material flowing rapidly. Most fatal South Asian “landslides” are technically debris flows.
Can deforestation cause landslides? Yes — tree roots stabilise soil. Removing trees increases landslide risk on steep slopes. Many recent landslide disasters (such as Wayanad 2024) occurred in areas where forest had been cleared for plantations.
Where can I check landslide risk for my area? GSI publishes hazard maps. Mausam Online displays precipitation forecasts on every city page — useful as a leading indicator during monsoon. See Shimla, Dehradun, Kohima, Munnar.