Geomorphic Hazards and their Effects | CUET PG Geography | Notes

Introduction

Geomorphic hazards refer to natural processes operating on the Earth’s surface that pose threats to human life, property, and infrastructure through the sudden or gradual transformation of landforms. These hazards arise from the interaction of endogenic (internal) and exogenic (external) forces acting upon the lithosphere, and their study forms a critical component of applied geomorphology. The major categories include mass movements (landslides), earthquakes, volcanic eruptions, floods, coastal erosion, soil erosion, desertification, and subsidence. Each of these processes has distinct causative mechanisms, spatial distributions, and socio-economic consequences that are of direct relevance to disaster management and regional planning.

Landslides

The movement of a mass of rock, rubble, or dirt down a slope is characterized as a landslide. They are a kind of mass wasting, which refers to any downward movement of soil and rock caused by gravity. Landslides affect 15% of Indian landmass, but their susceptibility may increase in the future owing to climate change and population pressures. This increased magnitude can be addressed by taking a multi-pronged approach that addresses all aspects of disaster governance, including mitigation, preparedness, response, and rehabilitation. 

• A landslide is a fast movement of rock, soil, and plants down a slope caused by gravity.
• It can be produced by natural forces such as severe rain or an earthquake, or it can be caused by human tampering with the slope’s stability.
• Man fractures rocks to build roads, trains, houses, and tunnels, among other things. In such instances, the rocks become loose, resulting in a landslide.
• Landslides are defined as earth flow, mass movement, mudflow, rotating slip, and avalanches.
• Landslides are seldom as large as seismic or volcanic occurrences.
• The severity and scale of the landslide, on the other hand, are determined by the geological structure of the slope, the angle of dip of the slope, the composition of sedimentary materials, and human involvement with the slope.
• When landslides occur on the slopes of a river valley, the sliding mass may reach the valley bottom and partially or completely obstruct the river channel.
• This collected mass of avalanche debris that blocks a river is frequently referred to as a landslide dam.

Landslides in India

• This danger affects at least 15% of the country’s land area in India ( approx 0.49 million square Km.)
• It is highly common in geo dynamically active domains such as the Himalayan and Arakan-Yoma belts in the country’s northeastern sections, as well as in comparatively stable domains such as the Meghalaya Plateau, Western Ghats, and Nilgiri Hills.
• The Nilgiri Hills, located at the confluence of the Eastern and Western Ghats, display numerous landslide scars as a result of their location in a zone of high intensity and prolonged rainfall where the overburden is vulnerable to over-saturation.
• Kerala (2018), Himachal Pradesh (2018), Uttarakhand (2018), Tamenglong-Manipur (2018), and Kalikhola, Manipur (2018) are some recent big events (June 2017).
• The Intergovernmental Panel on Climate Change (IPCC) concluded in its most recent report that a worldwide rise of 1.5 degrees Celsius (from pre-Industrial periods) was unavoidable in the next two decades.
• This would cause greater glacier melt and more water to pour over the steep slopes, resulting in additional landslides.
• The Himalayas are tectonically active mountains formed by the collision of two tectonic plates.
• This increases the likelihood of earthquakes, which might lead to an increase in the number of landslides.
• People Pressure: India accounts for only 2.4 percent of the world’s land area yet houses over 17 percent of the world’s population.
• Furthermore, the population is expected to expand until 2050, necessitating the construction of more infrastructure in vulnerable environments.
• River Characteristics: The rivers in the Himalayan highlands are huge and in their infancy.
• They perform a lot of downcutting, which increases the likelihood of landslides.

Natural Causes

• Earthquakes: They induce a sudden shaking of the earth’s crust, causing stress on materials and, as a result, landslides.
• Heavy Rainfall: The occurrence of major or continuous rainfall may result in heavy landslides on steep slopes.
• Water acts as a lubricant and loosens the material.
• For example, the 2013 Uttarakhand Cloudburst caused massive landslides in the region.

Anthropogenic Causes

• Infrastructure Development: The construction of roads, trains, and dams in hilly areas can cause landslides.
• For example, the construction of Konkan Railways in the Western Ghats is regarded as a major cause of the region’s frequent landslides.
• Mining is the removal of the earth’s surface for mineral discovery, which loosens the material’s hold.
• Explosions are also an element of mining, which can cause landslides.
• Deforestation occurs when trees are taken down for agricultural and industrial purposes, causing soil grip to relax and the region to become more prone to landslides.
• Unsustainable Tourism: As the number of tourists increases in the Himalayan area, more infrastructure and services are required to accommodate them.
• This results in more buildings and more landslides.

Consequences of Landslides

• The loss of irreplaceable human and animal life is the most traumatic effect of a landslide.
• Movement is restricted because the mud, boulders, and debris sliding down the hill create a barrier on vital transportation routes such as highways and railway lines.
• Damage to Infrastructure: When a landslide happens, several residences, buildings, roads, and other infrastructure are affected.
• Economic Losses: A considerable amount of money is spent on rebuilding the destroyed infrastructure, rehabilitating the masses, and giving relief assistance to the affected individuals.
• Water Availability May Be jeopardised: When landslides occur on the slopes of a river valley, the sliding mass may reach the valley bottom and produce a partial or total blockage of the river channel.
• This collected mass of avalanche debris that blocks a river is frequently referred to as a landslide dam.
• It may reduce the availability of water for adjacent residents.

Landslide Management in India

• National Risk Management Strategy for Landslides (2019):
• It encompasses all aspects of landslide disaster risk reduction and management, such as hazard mapping, monitoring, and early warning systems, awareness programmes, capacity building, training, regulations, and policies, landslide stabilisation and mitigation, and so on.
• Guidelines on Landslide Hazard Management issued by the National Disaster Management Authority (NDMA) in 2009:
• It describes the steps that should be done to minimise or reduce the danger caused by landslide risks. Some pointers –
• Identifying regions prone to landslides
• Encouraging the use of effective landslide rehabilitation and mitigation methods.
• Developing institutional capacity and training for geoscientists, engineers, and planners is essential for efficient landslide management.
• The National Organisation of Disaster Management (NIDM) is a prominent institute that provides Capacity Building support to different National and State level authorities in the field of Disaster Management and Disaster Risk Reduction.
• Restriction on building and other development activities such as roads and dams in landslide-prone regions.
• Agriculture is restricted to lowlands and places with modest slopes.
• Control over the growth of big communities in high-vulnerability zones.
• Promoting large-scale afforestation programmes and bund building to minimise water flow.
• Terrace farming should be promoted in the northeastern hill states where Jhumming (Slash and Burn/Shifting Cultivation) is still common.