Download the presentation of mudflows and their characteristics. Presentation on the topic "Natural disasters. Mudflows." Carrying out protective work

tightly close doors, windows, ventilation and other openings. Turn off electricity, water, gas. Remove flammable and poisonous substances from the house and, if possible, bury in pits or cellars. In the event of an emergency evacuation, go to a safe, elevated place on your own (the evacuation route must be studied in advance). Have documents, stock of food, water, clothes and medicines. A situation is possible when people, buildings and structures are on the surface of a moving landslide stream. In such a situation, leaving the premises, one should move as far as possible upwards and, acting according to the situation, beware of boulders, stones, fragments of structures, an earthen rampart, and screes rolling down from its rear part when braking a landslide. After the end of collapses, landslides and mudflows, before returning to their homes, you need to make sure that there is no second threat. Since these phenomena most often occur in mountainous regions, where external assistance is often delayed due to the destruction of roads, the survivors should immediately begin to search for and extract the victims, provide them with first aid, clear roads and priority restoration work.

What is sel? Mudflow is a rapid channel flow, consisting of a mixture of water, earth and rock fragments, which occurs in mountain river basins. Mudflows are characterized by the advancement of its frontal part in the form of a shaft of water and sediment, or more often by the presence of a series of successively shifting shafts. The passage of the mudflow is accompanied by significant reformations of the channel.

A potential mudflow source is a section of a mudflow channel or mudflow basin, which has a significant amount of loose clastic soil or conditions for its accumulation, where mudflows arise under certain flooding conditions. Mudflow foci are divided into mudflow cuts, potholes and foci of dispersed mudflow formation. The causes of mudflows are powerful downpours, heavy melting of snow and ice, disturbances in economic activity (deforestation, non-compliance with the rules for blasting), as well as volcanic eruptions and earthquakes. Sometimes mudflows occur in the basins of small mountain rivers and dry ravines with significant slopes of the thalweg and in the presence of large accumulations of weathering products. The causes of mudflows are powerful downpours, heavy melting of snow and ice, disturbances in economic activity (deforestation, non-compliance with the rules for blasting), as well as volcanic eruptions and earthquakes. Sometimes mudflows occur in the basins of small mountain rivers and dry ravines with significant slopes of the thalweg and in the presence of large accumulations of weathering products. thalweg causes.

Mudflow protection. To protect against mudflows, protective networks, dams, cascades of dams are built to release streams from solid material, drainage ditches to divert water. Observation of mudflow hazardous areas and forecasting of these phenomena is of great importance. To protect against mudflows, protective networks, dams, cascades of dams are built to release streams from solid material, drainage ditches to divert water. Observation of mudflow hazardous areas and forecasting of these phenomena is of great importance.

Mudflow classification. Seismic mudflows Seismic mudflows As a result of earthquakes, broken fragments of glaciers or rocks can block the path of rivers, forming very unstable dams. When such a dam is destroyed, water is not discharged from it gradually, but instantly, which contributes to the accumulation of unimaginable kinetic energy by the flow. As a result of earthquakes, broken fragments of glaciers or rocks can block the path of rivers, forming very unstable dams. When such a dam is destroyed, water is not discharged from it gradually, but instantly, which contributes to the accumulation of unimaginable kinetic energy by the flow. Lahars Lahars are mudflows of volcanic origin. As a result of the ejection of lava or the descent of pyroclastic flows, the snow cover and glaciers on the slopes of the volcano rapidly melt, and the resulting water mixes with ash and rocks. During the eruption of Vesuvius in 79, under the ashes of which Pompeii was buried, the city of Herculaneum was filled up with a three-meter layer of mud-stone mass brought by the lahar. During excavations, it was found that the mudflow shell of Herculaneum is much denser than the ash layer of Pompeii. VesuviusPompeiiHerculaneum

Cohesives Coherent streams include mud-stone streams, in which water practically does not separate from the solid part. They have a large volumetric weight and great destructive power. Water-stone flows are classified as incoherent. Water transports clastic material and, as the speed decreases, deposits it in the channel or in the area of the alluvial fan on the foothill plain. Mudflow classification.

The fight against mudflows. Mudflows can produce enormous destruction. The fight against mudflows is carried out mainly by fixing the soil and vegetation cover, building special hydraulic structures. Mudflows can produce enormous destruction. The fight against mudflows is carried out mainly by fixing the soil and vegetation cover, building special hydraulic structures. To combat mudflows, preventive measures and the construction of engineering structures are being carried out. The use of certain methods of control is determined by the zones of the mudflow basin. The use of certain methods of control is determined by the zones of the mudflow basin.

Where in Russia mudflows occur. Many mountainous regions are characterized by the predominance of one or another type of mudflow in terms of the composition of the solid mass carried by it. So, in the Carpathians, water-stone mudflows of relatively small thickness are most often found, in the North Caucasus - mainly mud-stones, in Central Asia - mud flows.

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1. Sel. 2. Characteristics of mudflow. 3. Cause of mudflow. 4. Classification. 5. Zones sat down. 6. Fight against mudflows. 7. Mudflow in Almaty in 1921 and 1973.

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SEL

Mudflow (in hydrology from Arabic ‎‎sail - “turbulent stream”) is a stream with a very high concentration of mineral particles, stones and rock fragments (up to 50-60% of the volume of the stream), suddenly arising in the basins of small mountain rivers and dry dens and caused, as a rule, by heavy rainfall or rapid snowmelt. Sel is a cross between a liquid and a solid mass. This phenomenon is short-term (usually it lasts 1-3 hours), typical for small streams up to 25-30 km long and with a catchment area up to 50-100 km².

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CHARACTERISTIC

The speed of mudflows is on average 2-4 m/s, sometimes 4-6 m/s, which causes their great destructive effect. On their way, the streams cut deep channels, which are usually dry or contain small streams. Mudflow material is deposited in foothill plains. Mudflows are characterized by the advancement of its frontal part in the form of a shaft of water and sediment, or more often by the presence of a series of successively shifting shafts. The passage of the mudflow is accompanied by significant reformations of the channel.

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CAUSES

Mudflow occurs as a result of intense and prolonged showers, rapid melting of glaciers or seasonal snow cover, as well as due to the collapse of large amounts of loose-clastic material into the channel (with terrain slopes of at least 0.08-0.10). Deforestation in mountainous areas can serve as a decisive factor in the occurrence - the roots of trees hold the top of the soil, which prevents the occurrence of a mudflow. Sometimes mudflows occur in the basins of small mountain rivers and dry ravines with significant (at least 0.10) thalweg slopes and in the presence of large accumulations of weathering products. According to the mechanism of origin, erosion, breakthrough and landslide mudflows are distinguished.

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Classification

Earthquakes As a result of earthquakes, broken fragments of glaciers or rocks can block the path of rivers, forming very unstable dams. When such a dam is destroyed, water is not discharged from it gradually, but instantly, which contributes to the accumulation of unimaginable kinetic energy by the flow.

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LAHARS

Lahars are mudflows of volcanic origin. As a result of the ejection of lava or the descent of pyroclastic flows, the snow cover and glaciers on the slopes of the volcano rapidly melt, and the resulting water mixes with ash and rocks. During the eruption of Vesuvius in 79, under the ashes of which Pompeii was buried, the city of Herculaneum was filled up with a three-meter layer of mud-stone mass brought by the lahar. During excavations, it was found that the mudflow shell of Herculaneum is much denser than the ash layer of Pompeii.

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Connected streams include mud-stone streams, in which water practically does not separate from the solid part. They have a large volumetric weight (up to 1.5-2.0 t/m³) and great destructive power. Water-stone flows are classified as incoherent. Water transports clastic material and, as the speed decreases, deposits it in the channel or in the area of the alluvial fan on the foothill plain. Volumetric weight of rock mudflows.

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According to the degree of sediment saturation and their fractional composition

Mud mudflows - a mixture of water with fine earth at a low concentration of stones, volumetric weight y=1.5-2 t/m³ Mud-stone mudflows - a mixture of water, pebbles, gravel, small stones, y=2.1-2.5 t/m³

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The following zones are distinguished in the mudflow basin:

Generation (feeding) zone Transit zone Accumulation zone

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Fight against mudflows

Mudflows can produce enormous destruction. The fight against mudflows is carried out mainly by fixing the soil and vegetation cover, building special hydraulic structures. To combat mudflows, preventive measures and the construction of engineering structures are being carried out. The use of certain methods of control is determined by the zones of the mudflow basin. Preventive measures are taken to prevent the occurrence of mudflow or weaken its effect at the very beginning of the process. The most radical means is afforestation on mudflow-prone mountain slopes. The forest regulates the flow, reduces the mass of water, cuts the streams into separate weakened jets. In the catchment area, it is impossible to cut down the forest and disturb the sod cover. Here it is advisable to increase the stability of the slopes by terracing, to intercept and divert water by upland ditches and earthen ramparts. In mudflow channels, dams have the greatest effect. These structures made of stone and concrete, installed across the channel, delay the mudflow and take away part of the solid material from it. The semi-dams push the flow towards the shore, which is less prone to breaking. Mudflow traps are used in the form of pits and pools laid on the path of flow; bank-protecting retaining walls are built to prevent erosion of the banks of the channel and protect buildings from the shock force of the mudflow. Directing dams and mudflow storages are effective. Dams direct the flow in the right direction and weaken its effect. In the areas of settlements and individual structures located in the zone of proluvium deposition, diversion channels are arranged to guide dams, the riverbed is taken into high stone banks that limit the spreading of the mudflow. To protect road structures, mudflows in the form of reinforced concrete and stone trays are most rational, allowing mudflows to pass above or below the structures.

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PROTECTIVE WORKS

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HOW TO ACT WITH A DERBODOW

Having heard the noise of an approaching mudflow, you should immediately rise from the bottom of the hollow up the drain, at least 50-100 m. At the same time, you need to remember that stones of great weight that threaten life can be thrown out of the roaring stream for long distances.

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ACTIONS AFTER A MURDROW

Provide assistance to the victims and assistance to the formations and bodies that disassemble blockages and drifts along the path of the mudflow and in places where the main mass of the mudflow is removed. If you are injured, try to get yourself first aid. The affected areas of your body, if possible, should be kept in an elevated position, put on them ice (wet matter), a pressure bandage. Contact your doctor.

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MUDDLESHIP IN ALMATY 1921

Serious material damage was caused to the city by a giant mudflow that hit Almaty in July 1921. A mudflow of almost 3 million m 3 swept away on its way and destroyed many buildings and caused great damage to the city. All the efforts of the working people were aimed at overcoming the grave consequences of the natural disaster, at restoring what had been destroyed in the shortest possible time.

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The construction of the mudflow protection dam "Medeo" in the Medeo tract in the valley of the Malaya Almatinka River began in 1964 and was carried out with the help of blasting. The first explosion (right-bank) was made in 1966. The second explosion (left-bank) - in 1967. The rockfill dam of the first stage, 107 meters high, formed a mudflow storage with a capacity of 6.2 million cubic meters and was put into operation in 1972. In 1973, the dam delayed mudflow with a mass volume of 5.3 million cubic meters.

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MUDDLESHIP IN ALMATY 1973

July 15, 1973, 6:15 p.m. The entrance of the first wave of the mud-stone flow into the mudflow storages of the Medeo tract. The mudflow hit the body of the dam and choked, filling the pit with itself.

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PLATINA MEDEO SAVE 1000 LIVES

Alexander Yuryevich Khegay, in July 1973, a member of the government commission for the elimination of the consequences of mudflow, a little later appointed deputy head of the newly created department "Kazselezashchita": "If, God forbid, there was a breakthrough, then the strength of the new stream would have doubled due to the high concentration of mudflow mass. Later, scientists calculated that the strength of the flow in 1973 was 4 times higher than the strength of the flow in 1921. Then a quarter of the entire city behind construction, more than 500 people died. But in the early 20s, Verny was a one-story city with a small territory and a population of about 30 thousand people, and by the mid-70s Alma-Ata had grown several times in territory and twenty times in population - up to 750 thousand, and the center of the city, through which the mudflow passed in 1921, is now multi-storey. So consider what the number of victims and the extent of destruction could be! these calculations are made for today's one and a half million Almaty, then they give the figure - 300 thousand people living or working on a hypothetical mudflow path"

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