Dangers of Landslide

Sub: Geography

Sec: Physical geography

Tags: Landslides

Cyclone Remal impact:

West Bengal: Six fatalities and damage to 27,000 houses due to Cyclone Remal.
Northeast India: Cyclone-triggered landslides in Meghalaya, Mizoram, Assam, and Nagaland resulted in at least 30 deaths, including 14 from a stone quarry collapse in Aizawl, Mizoram.
Cyclone Aila in May 2009 also triggered landslides in the Northeastern region.

Need for Resilience:

Multi-Hazard Disasters: India faces multiple interconnected disasters such as heavy rainfall causing glacial lake breaches and flash floods, leading to landslides.
- One event can trigger another and can lead to multiple disasters simultaneously.
Infrastructure and Services Impact: Resulting in power outages, transport and communication failures, and disruption of health services, complicating rescue and relief efforts.

Landslide Vulnerability in India

0.42 million sq km, or 13% of India’s landmass, is landslide-prone, covering 15 states and 4 Union Territories.
0.18 million sq km, or 42% of the vulnerable area, is in the Northeast, a hilly and earthquake-prone region.
The Northeast recorded 378 major landslides during 2015-2022, constituting 10% of all major landslides in India. Kerala witnessed the highest number, largely post-2018 floods.

Risk Management Efforts:

The Disaster Management Act, of 2005 provides a comprehensive legal and institutional framework for the management of various disasters including landslides.
The National Landslide Risk Management Strategy (2019) covers all aspects of landslide disaster risk reduction and management, such as hazard mapping, monitoring, and early warning systems.
- Early Warning Systems: Trial-based systems linked to IMD rainfall forecasts to predict soil displacement. Few systems deployed, with installations in Nagaland, Sikkim, Uttarakhand, and Kerala.
The National Disaster Management Authority (NDMA) has issued Guidelines on Landslide Hazard Management (2009) that outline the steps that should be taken to reduce the risk of landslides.
The National Institute of Disaster Management (NIDM) has been providing capacity building and other support to various national and state-level disaster management authorities.
Efforts have been made towards better prediction of weather. E.g. Ensemble Prediction System. This will help predict disasters like landslides.

What is Landslide?

A landslide is defined as the movement of a mass of rock, debris, or earth, down a slope due to the action of gravity.
Areas with steep slopes, for example, mountainous regions, are particularly susceptible to landslide hazards.
Earth flow, mass movement, mudflow, rotational slip, and avalanches are all examples of landslides.

Causes of Landslide:

Geological causes	Morphological causes	Human causes
Weak or sensitive materials Weathered materials Sheared, jointed, or fissured materials Adversely oriented discontinuity (bedding, schistosity, fault, unconformity, contact, and so forth) Contrast in permeability and/or stiffness of materials	Tectonic or volcanic uplift Glacial rebound Fluvial, wave, or glacial erosion of slope toe or lateral margins Subterranean erosion (solution, piping) Deposition loading slope or its crest Vegetation removal (by fire, drought) Thawing Freeze-and-thaw weathering Shrink-and-swell weathering	Excavation of slope or its toe Loading of slope or its crest Drawdown (of reservoirs) Deforestation Irrigation Mining Artificial vibration Water leakage from utilities

Types of Landslides

Falls: It happens due to the abrupt movements of the mass of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs.
Topples: It happens due to the forward rotation of a unit or units about some pivotal point, under the actions of gravity and forces exerted by adjacent units or by fluids in cracks.
Slides: In this type, rocks, debris, or soil slide through slope forming material.
Spread: It usually occurs on very gentle slopes or flat terrain.