Wayanad landslides (2024)

Topic: Natural Hazards and Disaster Management in India · NCERT: Beyond NCERT

Meaning

The Wayanad landslides (2024) were a series of landslides and debris flows on 30 July 2024 in the villages of Mundakkai, Chooralmala and Punchirimattom in Wayanad district, Kerala. They were set off by extreme rain on soil that weeks of monsoon rain had already soaked, and over 200 people died.

This is one of India's deadliest recent landslide disasters. It shows that the Western Ghats can fail badly even though their rock is hard. It also brought back the debate on protecting the Ghats as Ecologically Sensitive Areas (ESAs).

Explanation

How it happened: cause → process → result

• Wet soil first
• Weeks of monsoon rain had already soaked the soil and rock on the slopes.

• Wet ground is heavier, so gravity pulls harder on it.

• Extreme rain on top

• More water soaked in and reduced the friction that holds soil grains and rock blocks together.

• The slope broke along a failure plane, also called a shear plane (a weak surface where the upper mass breaks away from the ground below).

• Debris flow

• The loose mass mixed with water.
• Mud, boulders and uprooted trees rushed down the stream valleys like a river of debris.
• The flow hit the villages of Mundakkai, Chooralmala and Punchirimattom.

Type: a debris flow

• A landslide is any large mass of rock, soil and debris that moves quickly down a slope because of gravity.
• A debris flow is a fast, wet kind of landslide. The material has so much water in it that it flows like a liquid, not like a solid block.
• Debris flows follow stream valleys, so they can travel far and bury settlements on the valley floor.

Why the Western Ghats slide even though the rock is hard

• The Western Ghats are part of the old, stable block of the Peninsular plateau, and they are made of hard crystalline rocks.
• They still lie in the very high landslide vulnerability zone for three reasons:
• Steep cliffs on the western face.
• Very intense monsoon rain. Moist wind hits the Ghats and is pushed up. The rising air cools, its water vapour condenses, and heavy rain falls on the side facing the wind (orographic rain).

• Mechanical weathering from temperature change: rock heats by day and cools by night, so it cracks and breaks apart.

• Human pressure on the slopes adds to this. Examples are quarrying, road cuts, unplanned building and poor drainage.

Warnings and policy link

• The Union Home Minister told Parliament that the Centre sent early warnings to Kerala on 23, 24 and 25 July 2024 [3].
• On 26 July, the Centre warned of more than 20 cm of rain and of possible landslides that could kill people [3].
• After the disaster, people again debated two reports on making parts of the Ghats ESAs (zones where mining, quarrying and big building projects are restricted):
• Gadgil Committee report (2011), from the Western Ghats Ecology Expert Panel.
• Kasturirangan Committee report (2013), from the High-Level Working Group.

Where it occurs

• Exact place: Mundakkai, Chooralmala and Punchirimattom, in Wayanad district, Kerala. Wayanad sits on the Western Ghats.
• Landslide zone: the high-rainfall, steep-sloped Western Ghats and Nilgiris are in the very high landslide vulnerability zone (NCERT, Figure 6.9).
• Similar belts in India: the young, unstable Himalaya, the north-eastern region and the Andaman and Nicobar Islands are also in the very high zone.
• National extent: about 0.42 million sq km, or 12.6% of India's land area (not counting snow-covered areas), is prone to landslides [1].
• Monitoring that covers this region:
• NLSM (National Landslide Susceptibility Mapping) by GSI maps the Western Ghats at 1:50,000 scale [4].
• The Landslide Atlas of India by NRSC (ISRO) covers the Himalaya and Western Ghats. It includes event-based inventories, for example of Kerala [2].
• GSI's National Landslide Forecasting Centre (NLFC) was inaugurated on 19 July 2024, just eleven days before Wayanad. It warns of rain-triggered landslides using rainfall thresholds (the amount of rain beyond which slopes usually fail) and Numerical Weather Prediction (NWP) models (computer weather forecasts) [4].

Don't confuse with

• Malpa landslide (1998): happened in the Himalaya, in the Kali valley of Pithoragarh, Uttarakhand. It was a rockfall and debris event that hit Kailash Mansarovar pilgrims. Wayanad (2024) happened in the Western Ghats, Kerala, and was a debris flow.
• Joshimath land subsidence (2023): the ground sank slowly in Chamoli, Uttarakhand, because the town is built on old landslide debris and has poor drainage. At Wayanad, ground did not sink. Rain-soaked debris flowed fast down the slopes.
• Rockfall: dry blocks of rock fall from a cliff, as on the Konkan Railway. A debris flow like Wayanad is a wet mix of mud, boulders and trees that moves like a river along stream valleys.
• Gadgil (2011) vs Kasturirangan (2013): both reports deal with Western Ghats ESAs. Gadgil came from the Western Ghats Ecology Expert Panel. Kasturirangan came from the High-Level Working Group.

Prelims Hooks

• Wayanad, Kerala, 30 July 2024: Mundakkai, Chooralmala and Punchirimattom. The type was debris flows.
• Trap: the Western Ghats are made of hard crystalline rock but are still in the very high landslide zone, because of steep cliffs, intense rain and weathering caused by temperature change.
• Early warnings from the Centre were sent on 23, 24 and 25 July 2024. On 26 July the warning was for more than 20 cm of rain [3].
• GSI's NLFC was inaugurated on 19 July 2024, eleven days before Wayanad [4].
• Pair the place with its state: Wayanad is in Kerala (Western Ghats). Malpa is in Pithoragarh (Himalaya). Joshimath is in Chamoli (Himalaya).
• Gadgil = 2011, Kasturirangan = 2013. Both are about Western Ghats ESAs.

Mains Points

• Causes (GS-I/GS-III): natural and human factors worked together.
• Natural: steep western scarps (cliff faces), intense orographic rain and soil already soaked by weeks of monsoon rain.

• Human: quarrying, road cuts and unplanned building on fragile slopes weaken the slope and block drainage.

• Development versus fragility (GS-III): Wayanad (2024), like Joshimath (2023), shows that hill development can push unstable slopes past their limit.

• Answer frame: carrying-capacity studies for hill settlements, ESA zoning based on the Gadgil (2011) and Kasturirangan (2013) reports, and stricter environmental clearances for quarries, roads and buildings.

• From warning to action (GS-III, Sendai Framework): the Centre sent warnings [3], yet over 200 people died. Better planning needs four steps:

• Map the risk with GSI's NLSM at 1:50,000 and NRSC's Landslide Atlas [4][2].
• Forecast rain-triggered landslides through the NLFC [4].
• Follow the NDMA landslide guidelines (2009) when planning land use in very high zones.
• Turn warnings into timely evacuations at the village level.

Related concepts

• Landslide
• Landslide vulnerability zones
• Landslides in the Himalayas and Western Ghats
• Landslide mitigation
• Malpa landslide
• Landslide Atlas of India
• Land subsidence
• Joshimath land subsidence (2023)

Read more

• Landslides and land subsidence