Landslide, Avalanche and Glacier Lake Outburst Flood

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.

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:

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 .

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.