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http://www.geol-amu.org/notes/be1a-3-9.htm

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https://www.getprepared.gc.ca/cnt/hzd/vlchs-eng.aspx

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emergency preparedness planning how to prepare natural disaster avalanche facts safety what to do during mountain snow collapse

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Thousands of avalanches occur in Canada each year. They happen in all regions of Canada, but are more frequent in the mountains of British Columbia, Yukon and Alberta.

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1. Damage to Life and Property: A large number of casualties takes place after avalanches hit heavily populated areas. Infrastructure is damaged and the blockage caused, impacts the livelihood of many. People who enjoy skiing, snowboarding and snowmobiling are at a greater risk of losing their lives. A powerful avalanche can even destroy buildings and power supplies can be cut off.

2. Flash floods: When an avalanche occurs, it brings down all the debris with it and can cause havoc in low lying areas. Flash floods are seen to happen after avalanches, which is a long term problem many villagers and townspeople have to deal with. They can also change weather patterns and cause crop failure in farms present on the lower fields.

3. Economic Impact: An avalanche can block anything in its path and even restrict the normal movement of traffic. Various ski resorts depend on tourists to run their business successfully. Ski resorts and other businesses are forced to close until the avalanche decreases and weather conditions become suitable.

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Three Instruments Used In Avalanche Hazard Forecasting : Snow Settlement - Temperature, Snow Collector for Recording Rain Gauge, Temperature Telemeter | Alta Avalanche

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The purpose of this report is to provide a short description of these instruments and furnish sufficient technical data that they may be duplicated when needed at future stations yet to be established.

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Radar technology

distance from the flow,
Recently, radar has been used in broadly two ways in snow avalanche research:

- (a) To derive a general picture of avalanche movement by installing the radar at some
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- (b) To measure the avalanche velocities near the ground by installing radar in the track.

An important advance that has occurred in the last decade is the use of pulsed Doppler radar for measuring the velocity remotely. This type of system, which will be used in the SATSIE project, operates on two separate frequencies.

This allows measurement of the velocity characteristics of the powder cloud as well as the denser layer of snow beneath it. The existing radar of this type is able to provide velocity estimates averaged over 50m sections of the avalanche path.

More detail on the pulsed Doppler radar system can be found by clicking [ here ].

By installing pairs of radar within the avalanche track itself that point upwards into the flow it is possible to use the correlation in the signal between the radar to measure avalanche velocities at the bed.

Furthermore, the depth of snow before, after and during the avalanche can also be determined. These data are extremely important because many of the processes occurring within an avalanche (erosion of the underlying snow, the nature of grain-to-grain collisions) are related to behaviour near the bed.

Load sensors

Load plates can be used to determine both normal and tangential stresses. This means that they can be installed on instrument towers and within the avalanche track.

Plates that are installed to measure tangential forces must have similar roughness characteristics to the rest of the path to ensure that the stresses are transmitted from the avalanche to the sensor in an appropriate manner.

Electronic sensoring equipment means that stresses can be measured at high frequency. Thus, the possibility arises that the nature of collisions within the avalanche can be inferred from the plates. However, because snow becomes squashed against the sensor, interpreting these results (which are also sensitive to the area of the plate) is rather difficult.

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xxxxxxLoad plates on an instrument tower at Ryggfonn.

For some images showing installation of load plates at Ryggfonn, which will be used in the SATSIE project click [ here ].

For some images showing load plate measurements from the Großer Gröben avalanche in Austria, click [ here ].

Video recording of avalanches

If there is good visibility this simple method can provide useful information on the dynamics of the avalanche front and of the powder cloud. Stereo-imaging can help to provide accurate surface velocity information.

However, the techniques used to analyse this video data seem to need improving.

To see some videos of avalanche events, please click [ here ]

Seismic studies of avalanche behaviour

Much of the recent work that uses seismic methods to determine avalanche flow properties has been undertaken by the Department of Geodynamics and Geophysics at the University of Barcelona [ link ].

Attempts have been made to interpret such measurements with respect to the processes occurring within an avalanche, although such research is hampered by the damping effect that the snowcover has on the passage of seismic waves.

Hence, research is needed into optimising this method for avalanche analysis.

Pitot tubes

These sensors measure changes in pressure and can be used to infer velocity. They have been used effectively when making measurements around ping-pong ball avalanches, for the research homepage click [ here ].

They have the potential to enhance our understanding of the dynamics of the powder cloud, but cannot be used for making measurements within the denser layers of the flow.

LED sensors

This technique has been successfully implemented at both Ryggfonn [ link ] and at Montana State University's Revolving Door site [ Research home page ].

It is another technique that determines velocity by correlating signals; in this case the light emitted from LEDs and reflected by the snow is recorded at neighbouring photocells. These sensors are mounted on a tower in the avalanche path (or at Revolving Door are protected by a large boulder in the path).

The problem with using simple pairs of sensors is that vertical fluctuations can result in decorrelation of the signal. However, these sensors are cheap to construct and thus, have some real potential.

Capacitance probes

The main restriction with this type of sensor is that the devices are highly sensitive to the presence of free-water, which makes their use in wet-snow avalanches highly problematic.

Velocities can be derived from these probes using a similar correlation procedure to that for the LEDs, although due to the higher price of these probes, this will not usually be feasible.

However, the main advantage of the capacitance probes is that they have the potential to provide measurements of the density of the flowing snow.

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SATSIE - Current instrumentation techniques for measuring snow avalanche behaviour

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Radar technology distance from the flow, Recently, radar has been used in broadly two ways in snow avalanche research: - (a) To derive a general picture of avalanche movement by installing the radar at somexxxxxx - (b) To measure the avalanche velocities near the ground by installing radar in the track.

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Once the avalanche stops, it settles like concrete. Bodily movement is nearly impossible. Wait—and hope—for a rescue. Statistics show that 93 percent of avalanche victims survive if dug out within 15 minutes. Then the survival rates drop fast. After 45 minutes, only 20 to 30 percent of victims are alive. After two hours, very few people survive.

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Avalanches are most common during and in the 24 hours right after a storm that dumps 12 inches (30 centimeters) or more of fresh snow. The quick pileup overloads the underlying snowpack, which causes a weak layer beneath the slab to fracture. The layers are an archive of winter weather: Big dumps, drought, rain, a hard freeze, and more snow. How the layers bond often determines how easily one will weaken and cause a slide.Storminess, temperature, wind, slope steepness and orientation (the direction it faces), terrain, vegetation, and general snowpack conditions are all factors that influence whether and how a slope avalanches. Different combinations of these factors create low, moderate, considerable, and high avalanche hazards.What to Do in an AvalancheIf caught in an avalanche, try to get off the slab. In most instances, this is not easy. Skiers and snowboarders can head straight downhill to gather speed, then veer left or right out of the slide path. Snowmobilers can punch the throttle to power out of harm's way. No escape? Reach for a tree. No tree? Swim hard. The human body is three times denser than avalanche debris and will sink quickly. As the slide slows, clear air space to breathe. Then punch a hand skyward.

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Avalanches are most common during and in the 24 hours right after a storm that dumps 12 inches (30 centimeters) or more of fresh snow. The quick pileup overloads the underlying snowpack, which causes a weak layer beneath the slab to fracture. The layers are an archive of winter weather: Big dumps, drought, rain, a hard freeze, and more snow. How the layers bond often determines how easily one will weaken and cause a slide.Storminess, temperature, wind, slope steepness and orientation (the direction it faces), terrain, vegetation, and general snowpack conditions are all factors that influence whether and how a slope avalanches. Different combinations of these factors create low, moderate, considerable, and high avalanche hazards.What to Do in an AvalancheIf caught in an avalanche, try to get off the slab. In most instances, this is not easy. Skiers and snowboarders can head straight downhill to gather speed, then veer left or right out of the slide path. Snowmobilers can punch the throttle to power out of harm's way. No escape? Reach for a tree. No tree? Swim hard. The human body is three times denser than avalanche debris and will sink quickly. As the slide slows, clear air space to breathe. Then punch a hand skyward.

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During the afternoon of 25 April 2015, a MW 7.8 earthquake struck Nepal and surrounding countries. Shaking from the quake triggered an avalanche from Pumori into the basecamp on Mount Everest.

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During the afternoon of 25 April 2015, a MW 7.8 earthquake struck Nepal and surrounding countries. Shaking from the quake triggered an avalanche from Pumori into the basecamp on Mount Everest.

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effects

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Avalanches are masses of snow, ice, and rocks that fall rapidly down a mountainside.

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Avalanches are masses of snow, ice, and rocks that fall rapidly down a mountainside.

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Loose snow avalanches are common in steep terrains. They usually occur in snow that has just fallen. ... Loose snow avalanches usually start at the point of the slope and widens as it travels downhill, using more snow. It resembles a teardrop, and large loose snow avalanches can result in slab avalanches.

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Loose snow avalanches are common in steep terrains. They usually occur in snow that has just fallen. ... Loose snow avalanches usually start at the point of the slope and widens as it travels downhill, using more snow. It resembles a teardrop, and large loose snow avalanches can result in slab avalanches.

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One of the worst positions to find yourself is being stuck in an avalanche. Death is a very likely factor when you are entrapped in a snow slide. 90 percent these unfortunate events occur when a human is on a mountain with snow either skiing, snowboarding, or snowmobiling so this is something to consider the next time you decide to do any snow activities.

An avalanche is simply a quick flow of snow down a slope. This happens in a starting zone when the forces on the snow are too heavy for its foundation. The lower they get down the slope, the more they grow in mass because it is accumulating more snow as it goes downhill.

Avalanche Contents

Even though a snow slide is usually composed of air and snow, it can accumulate much more things going downhill such as ice, rocks, trees, and pretty much anything else on the slope making it extremely dangerous for travelers on the mountain that are caught in it.

When Do Occur and How Often?

Avalanches are not rare or random events that occur once in any particular area. They usually happen during winter or spring but movements in the glacier can cause avalanches at any given time. In mountainous terrain, snow slides are one of the most dangerous natural hazards to life and property because they are able to destroy almost anything in its way with an immense amount of snow at high speeds.

Ten Deadliest Avalanches in History

In January of 1954, Blons, Austria saw one of its worst avalanches to date. 118 people were buried. While rescue workers were trying to get them out, another unexpected avalanche came and wiped them out.

In World War II, the Italian and Austrian military had bases in the Alps. On what is now known as "White Friday", the Alps witnessed a series of avalanches claiming the lives of 10,000 soldiers, none of which guessed that enemy fire or bombs would be the least of their worries.

One of the most Ironic cases is the one that took place in Wellington, Washington on 1910. Three trains that were carrying 119 people were delayed at a station house so that they didn't have to travel in poor weather. Unfortunately, an avalanche defeated the whole purpose of the stop when it swept the trains over a 150-foot cliff.

In 1970, Mount Huascaran was devastated by rock ice and snow cascading swiftly which caused 80,000 people to die and left around one million people homeless.

In the Rhone Valley of Switzerland and France, in 1720 the Galen Avalanche took 88 lives and 100 buildings. This avalanche caused numerous fires that led to the destruction of the town.

In 1618 on September 4, The Rodi Avalanche in Switzerland ripped through an entire city burying 2,500 people alive. No one survived the avalanche, however, 4 people who were away returned home only to find their entire community, homes, and friends destroyed.

The famous "Winter of Terror" which plagued the Swiss-Austrian Alps in 1950-1951 consisted of almost 650 sub-avalanches that claimed 265 lives. These events were caused by warm air currents combining with polar air currents, causing much more precipitation than the area could manage.

Instigated by blizzard conditions of wind and snow, the Lehaul Valley Avalanche in the Himalayas buried 200 people under 20 feet of snow in 1979. This was the only avalanche in the Himalayas to make it to the top ten list of most dangerous avalanches in the world.

Leaving only 50 people alive, the avalanche in Ranrahirca, Peru happened several years before the Great Peruvian Earthquake. Snow, mud, rock, and frozen debris fell down from Mount Huascaran smothering the whole village of Ranrahirca, leaving over 2,700 people dead and destroying every house in its path.

In 1965, construction on the Mattmark Dam, which is the biggest dam on earth, caused 12 men to lose their lives. A part of the Allalin Glacier broke off and fell onto the building site destroying everything in its path.

Natural Causes of Avalanches

Even though humans usually instigate avalanches, they obviously happen other ways as well. They can happen when there is an increased load of snowfall. Melting from solar radiation is another natural way that avalanches happen. Rain, icefall, rock fall, earthquakes trigger avalanches as well, depending on the circumstances. It is always important that you pay attention to weather reports if you are planning on doing any snow activities where there is a possibility that an avalanche can occur.

Different Types of Avalanches

There are different avalanches that are categorized by the characteristics of the avalanche. Knowing what areas are prone to certain types of avalanches can be helpful when planning to go on a ski trip or any activity involving being on a mountain with snow.

Loose Snow Avalanches

Loose snow avalanches are common in steep terrains. They usually occur in snow that has just fallen. Also, they can happen in old surface snow that was moistened by heavy solar radiation. Loose snow avalanches usually start at the point of the slope and widens as it travels downhill, using more snow. It resembles a teardrop, and large loose snow avalanches can result in slab avalanches.

Slab Avalanches

Slab avalanches are formed when snow is deposited, or re-deposited by wind factor. They look like a block of snow cut out from its environment by fractures. These slab avalanches vary in thickness. They can be from a few centimeters to a few meters. Slab avalanches cause 90 percent of avalanche-related fatalities.

Powder Snow Avalanches

Powder snow avalanches form currents of turbulent suspension, in which they are the largest. This is a cloud of powder that lies over an avalanche that is dense. These form from any type of initiation structure or snow, but most of the time happens with dry, fresh powder. These types of avalanches can go move faster than 300km/h carrying a mass of 10 million tones. They can also travel long distances on a flat surface and uphill for a short amount of time.

Wet Snow Avalanches

Wet snow avalanches tend to be low in velocity suspension and consist of water and snow. The low speeds are caused by friction between the sliding surface of the track and saturated water flow. Although these types of avalanches tend to move slowly, they can still cause great damage with powerful destructive forces because of its large mass and density. Wet snow avalanches can consume boulders, earth, trees and other things in its path. These avalanches can be triggered by loose snow releases, or slab releases occurring only in snow packs that are saturated by water and equilibrated isothermally to the melting point of water. These types of avalanches usually happen towards the end of a winter season, when there is an immense amount of daytime warming.

In the end, any of the above avalanches could cause you to lose your life. With that being said, when you are out on the slopes trying to catch major footage, keep in mind that if a mountain is feeling too much pressure, you could be making your final recording.

Avalanche Related Articles

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One of the worst positions to find yourself is being stuck in an avalanche. Death is a very likely factor when you are entrapped in a snow slide. 90 percent these unfortunate events occur when a human is on a mountain with snow either skiing, snowboarding, or snowmobiling so this is something to consider the next time you decide to do any snow activities.