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Note on Landslide, Avalanche and Glacier Lake Outburst Flood

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Landslide

A landslide is also known as landslip, is the downward movement of soil, rock, debris or vegetation due to gravitational force. A landslide can also occur inside the water, called the submarine landslide. Gravitational force is not only the causes of landslide but there are also other causes of deforestation, earthquake etc. Landslide is also one of the common natural disasters of Nepal. They occur usually in hilly and mountain regions of Nepal.

The landslide causes huge loss of life and human properties. It washes away trees and vegetation. It blocks highways and kills many people. Sometimes it also blocks the river that causes flooding. Lands with less vegetation and forest, weak soil support, and more inclination are like to face landslide.

Source:kathmandupost.ekantipur.com. Fig: Landslide in Sindhupalchok of Nepal
Source:kathmandupost.ekantipur.com
Fig: Landslide in Sindhupalchok of Nepal

Causes of Landslide

  • Heavy rainfall.
  • Deforestation and less vegetation
  • Earthquake and volcanic eruption
  • The weak composition or geological structure of rock or soil formation.
  • Steep sloppy mountains and hills with loosely arranged soil
  • Construction work without caring for natural resources.

Consequences of Landslide

  • It causes huge loss of life, properties, and vegetation.
  • It blocks highways damaging roads, railways, bridges and electrical supply lines in hilly and mountain regions.
  • Landslide causes flooding when it blocks the river.
  • It may cause loss of places of archaeological, historical and cultural importance
  • It imbalances ecosystem

Preventive Measures of Landslide

  • Barriers and strong walls should be constructed where landslide occurs frequently.
  • The government should warn the people where there is a high chance of a landslide.
  • Afforestation and vegetation should be done in naked hills.
  • Awareness programs should be created about the effects and consequences of the landslide.
  • Before building houses the structure of the land should be studied.
  • Terrace farming should be done in hilly regions.

Avalanche

Avalanche is a type of natural disaster that occurs in mountains region. It is the downward flow of the mass of snow, ice, and rocks from the mountain slope. In winter, avalanches are caused when fresh snow falls and slips off the snow surfaces. Similarly, in the spring season, they occur when partly thawed snow rolls down mountain slopes. The avalanche moves at very high speed. Sometimes they achieve velocities as high as 400 km per hour. Avalanches can reach speeds of 80 mph within about 5 seconds. Most avalanches occur between 30 and 45 degrees, on a slope that faces the north, east, and northeast directions.

They also cause huge loss of life and properties when the enter the human civilization in mountain regions. They also kill mountaineers. Each year avalanche kills more than 150 people all over the world. There are various causes of the avalanche. Some of the causes of avalanche are discussed below,

Source:snowbrains.com. Fig: Avalanche
Source:snowbrains.com
Fig: Avalanche

Causes

  • Snowstorm and Wind direction: Snowstorms and wind direction are also one the major causes of the avalanche. Heavy snowstorms cause an avalanche. When the wind blows from one side of the mountain to the other side, it will scour snow off the surface which can overhang a mountain causing an avalanche.
  • Heavy snowfall: When there is heavy snowfall, the amount of snow in the particular area increases causing instability and pressure. In the summer season, when a large amount of snow starts melting it causes wet snow avalanche.
  • Warm temperature: During the summer season, the temperature in mountain region also increases. It creates a warm environment in mountain regions. This may weaken some upper layer of mountains causing the flow of the mass of snow.
  • Human activity: Only nature is not responsible for the natural calamities. Humans are also responsible. Various activities are done in mountain regions like sports, construction of developmental activities etc. And for this, the structure of mountains and snow are changed that may weaken the stability of snow in mountains. This may cause the flow of the mass of snow causing avalanche.

Effects of avalanche

Avalanche also causes loss of life and properties when it enters human civilization areas in mountain regions. People who enjoy skiing, snowboarding and snowmobiling are at a greater risk of losing their lives. Powerful avalanche can block roads and may damage power supplies. It also causes flash floods. It also economically affects the tourism sector that is associated with mountain regions.

Preventive Measures

  • The government should warn the people where avalanche occurs frequently.
  • Developmental activities should be carried out carefully in mountains regions.
  • The snow packs with high possibility of avalanche should be disposed of by artificial triggering
  • Prediction and forecasting should be done about the occurrence of the avalanche.

Glacier Lake Outburst Flood ( GLOF)

A glacier is a persistent body of dense ice that is constantly moving under its own weight. It forms where the accumulation of snow exceeds. In our country Nepal there are lots of mountains which is cover by snow. About 15 % of the mountain are susceptible to Glacial Lake Outburst Floods ( GLOF ). The most of the mountain are with the average elevation of 4 ,500 m above which are mostly covered with snow. The high glacier mountains have been experiencing fast melting, result in the formation of a large number of glacial lakes .

When the water come down from the mountains and start to make a lake. The glacial lake outburst makes the flood. It occurs when it contains a glacial lake fails. As we know during the flood thousand of people, hundred of villages and basic infrastructure such as house bridges, building etc are in danger during the flood. All the climate or global change invited environment in trouble and disasters in the Hindu-Kush Himalayan region including Nepal .

Source:floodinhumla.wordpress.com. Fig: Glacier Lake Outburst Flood
Source: floodinhumla.wordpress.com.
Fig: Glacier Lake Outburst Flood

Cause of GLOF

There are various factors that are trigger the GLOF events in the snow peaked mountain region, Some of them are given below:

  • Nuclear test and explosion
  • Climate Change
  • Volcanic Eruption
  • Earthquakes etc.

Trend of GLOF Events in Nepal

The scientists from the UNEP and ICIMOD identified 3,252 glaciers lakes in Nepal. It has at least 24 GLOF events in the past and 14 are said or believed to have occurred by Nepal itself and 10 were the result of flood overspills across the China-Nepal border. Nepal was conducted to an aim of development for the adoption of GLOF's trouble in Nepal which gives to develop overall risk from GLOF in the upcoming days .

Table : Glacier Lake Outburst Flood ( GLOF ) Events in Nepal in Different Time Period:

SN Date River basin Lake Cause Losses
1 450 years ago Seti Khola Machha puchchhre Moraine collapse Pokhara valley covered by 50-60 meter deep debris
2 3rd Sep 1977 Dudh Koshi Nare Moraine collapse Human live bridges other
3 23 rd Jun 1980 Tamor Nagma pokhari Moraine collapse Villages destroyed 71km from source
4 4thAug 1985 Dudh Koshi Dig Tsho Moraine collapse Human lives, Namche small hydropower station , 14 bridges etc.
5 12th Jul 1991 Tama Koshi Chubung Moraine collapse House , farmland , etc.
6 3rd Sep 1998 Dudh Koshi Chubung

Moraine collapse

Human lives and more than Rs.156 million
7 15th Aug 2003 Madi River Kabache Lake Moraine collapse Not known
8 8th Aug 2004 Madi River Kabache Lake Moraine collapse Not known
9 Unknown Arun Barun Khola Moraine collapse Not known
10 Unknown Arun Barun Khola Moraine collapse Not known
11 Unknown Dudh Koshi Chokarma Cho Moraine collapse Not known
12 Unknown Kali Gandaki Unnamed (Mustang ) Moraine collapse Not known
13 Unknown Kali Gandaki Unnamed (Mustang ) Moraine collapse Not known
14 Unknown Mugu Karnali Unnamed (Mustang ) Moraine collapse Not known
15 5th May 212 Seti River Unnamed (Annapurna) Avalanche 20 human lives and damage to property

Precautions

  • Awareness programs should be created about the consequences of glacier lake outburst.
  • Regular monitoring and survey of the glacier lakes should be done.
  • Necessary things like pure drinking water, food, sanitation services, clothing, medicines etc should be provided very fastly to the affected people.
  • There should be proper evacuation system for the affected people in the safe place in advance in the case of accidental GLOF events.

  • A landslide is also known as landslip, is the downward movement of soil, rock, debris or vegetation due to gravitational force.
  • The landslide cause huge loss of life and human properties.
  • Avalanche is a type of natural disaster that occurs in mountains region. It is the downward flow of mass of snow, ice and rocks from the mountain slope.
  •  Snowstorms and wind direction are also one the major causes of avalanche.
  • A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds .
  • Glacier lakes should be regular monitoring and survey.
.

Very Short Questions

Some of the causes of landslide are as follow : 

  • Heavy rainfall.
  • Deforestation and less vegetation
  • Earthquake and volcanic eruption
  • Weak composition or geological structure of rock or soil formation.
  • Steep sloppy mountains and hills with loosely arranged soil
  • Construction work without caring for natural resources

Following are the various factors that trigger the GLOF :

  • Nuclear test and explosion
  • Climate Change
  • Volcanic Eruption
  • Earthquakes etc.

0%
  • The downward movement of soil,rock or vegetation due to gravitational force is called

    Flood
    Avalanche
    Earthquake
    Landslide
  • Landslide is also known as

    Soilslip
    Flood
    Landflow
    Landslip
  • A mass of snow, ice, and rocks falling rapidly down a mountainside is considered as

    Snowquake
    Snowslide
    Avalanche
    Snowflood
  • Which one of the following is not the cause of Avalanche?

    Human Activity
    Less snowfall
    Snowstorm and Wind Direction
    Warm temperature
  • Which one of the following is not the preventive measures for landslide?

    Awareness should be created
    Trees should be planted
    Deforestation should be done
    Overgrazing should be stopped
  • The avalanches sometimes achieve velocities as high as _________.

    50km/hour
    250 km/hour
    300 km/hour
    400 km/hour
  • Which one of the following is not the cause of landslide?

    Afforestation
    Intense heavy rainfall
    Volcano
    Earthquake
  • What is the full form of GLOF?

    The fullform of GLOF is Glacier Lake Outburst Flood
  • How many percentage of land is covered by mountain region in Nepal?

    13%
    16%
    15%
    17%
  • Which one of the following are the causes of GLOF?

    Climate change
    Nuclear test and explosion
    All of the given
    Avalanche and Earthquake
  • How many glacial lakes are identified by the UNEP and ICIMOD in Nepal?

    2323
    3256
    400
    200
  • When was glacier lake outburst event occurred in Seti River (basin)?

    5th May 2012
    6th June 2015
    8th July 2013
    7th July 2012
  • When did glacier lake outburst event occurred in Kabache Lake?

    8th Aug 2004
    12th Jul 1991
    15th Aug 2003
    3rd Sep 1998
  • When did glacier lake outburst event occurred in Tama Koshi?

    12th Jul 1991
    3rd Sep 1998
    8th July 2013
    15th Aug 2003
  • When did glacier lake outburst event occurred in Nare lake?

    8th July 2013
    3rd Sep 1977
    15th Aug 2003
    3rd Sep 1998
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