Presentation on the topic of mudflows and their characteristics. Presentation on the topic "Natural Disasters. Mudflows". IV. Homework check

Mudflow, or mudflow, is a stormy temporary mountain stream, consisting of a mixture of water and a large amount of rock debris from clay particles to large stones and boulders. This formidable phenomenon occurs in mountains with a continental climate, where sharp temperature changes intensively destroy rocks and many products of destruction (loose rocks) accumulate on the slopes of the mountains. During heavy rains or amicable melting of snow, loose rocks are washed away by the formed water and turn water flows into mud or mud-stone flows of mudflows.

The sources of the solid component of the mudflow can be loose rock materials resulting from talus, landslides and landslides, as well as blockages and blockages formed by previous mudflows. For high-mountainous regions with developed glaciers, the sources of the solid component of mudflows are glacial moraine deposits. They consist of a mixture of a wide variety of rock debris, from large boulders to sand and clay. The sources of water supply for mudflows are rains and downpours, and in high-mountainous regions, water formed during the intensive melting of glaciers and snow, as well as during the breakthrough of glacial or moraine lakes.

Mudflows form in the mountains Kabardino-Balkaria, North Ossetia, Dagestan, Kamchatka, Primorye, the Kola Peninsula and the Urals. The impact of mudflows on various structures depends on the total volume of mudflow. On this basis, mudflows are subdivided into low-power, medium-power, powerful and catastrophic. The total volume of mudflow is: in a thin village, m 3; in a medium-sized village, m 3; in a powerful village m 3; in a disastrous village more than m 3.

Questions 1. What conditions are necessary for mudflow occurrence? 2. List the main components of the mudflow. 3. How are mudflows divided according to the power of their impact on environment? List the main criteria that determine this division. 4. Why is a mudflow dangerous?

Close doors, windows, vents, and other openings tightly. Cut off electricity, water, gas. Remove flammable and toxic substances from the house and, if possible, bury in pits or cellars. In the event of an emergency evacuation, go to safe high places on your own (the evacuation route must be studied in advance). Have documents, food, water, clothing and medicine. A situation is possible when people, buildings and structures find themselves on the surface of a moving landslide stream. In such a situation, leaving the premises, one should move upward as much as possible and, acting according to the situation, beware of blocks, stones, debris of structures, earthen ramparts, debris rolling from the rear of the landslide when braking. After the end of landslides, landslides and mudflows, before returning to their homes, you must make sure that there is no repeated threat. Since these phenomena most often occur in mountainous areas, where external assistance due to the destruction of roads often comes with a delay, the survivors should immediately begin to search for and extract the victims, provide them with the first medical care, road clearing and priority restoration work.

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

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VILLAGE

Mudflow (in hydrology from the Arabic Sayl - "stormy stream") - a stream with a very high concentration of mineral particles, stones and debris (up to 50-60% of the volume of the stream), which suddenly appears in the basins of small mountain rivers and dry logs and caused, as a rule, by heavy rainfall or rapid melting of snow. Mud is a cross between liquid and 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 of up to 50-100 km².

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CHARACTERISTIC

The speed of movement 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 the foothill plains. Mudflows are characterized by the advancement of its frontal part in the form of a rampart from water and sediments or, more often, by the presence of a series of successively shifting ramparts. The passage of the mudflow is accompanied by significant reformation of the channel.

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CAUSES OF OCCURRENCE

Mudflow occurs as a result of intense and prolonged downpours, rapid melting of glaciers or seasonal snow cover, as well as due to the collapse of large amounts of friable 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 the trees hold the upper part 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. By the mechanism of origin, erosion, breakthrough and landslide mudflows are distinguished.

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Classification

Seismoseli As a result of earthquakes, breakaway 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 unthinkable kinetic energy by the flow.

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LAHARA

Lahars are mudflows of volcanic origin. As a result of the ejection of lava or the descent of pyroclastic flows, a rapid melting of snow cover and glaciers on the slopes of the volcano occurs, and the resulting water mixes with ash and rocks... During the eruption of Vesuvius in 79 years, under the ashes of which Pompeii were buried, the city of Herculaneum was covered with a three-meter layer of mud-stone mass brought by the lahar. During excavations, it was discovered that the mudslide 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 a great destructive force. Water-stone streams are classified as incoherent. Water carries debris and, as the velocity decreases, deposits it in the channel or in the fan area on the foothill plain. Volumetric weight of water-stone mudflows.

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According to the degree of saturation with sediments and their fractional composition

Mud mudflows - a mixture of water with fine earth with a small concentration of stones, volume 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 Water-stone (sedimentary) mudflows - a mixture of water with mainly large stones, y = 1.1-1.5 t / m³

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The following zones are distinguished in the mudflow basin:

Nucleation (feeding) zone Transit zone Accumulation zone

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Mudflow control

Mudflows can cause 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 carried out. The use of certain methods of struggle is determined by the zones of the mudflow basin. Preventive measures are taken to prevent the occurrence of mudflows 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 forbidden to cut down the forest and disturb the sod cover. Here, it is advisable to increase the stability of slopes by terracing, to intercept and divert water by upland ditches, earthen ramparts. In mudflow channels, dams have the greatest effect. These structures of stone and concrete, installed across the channel, stop the mudflow and take away part of its solid material. Semi-ponds squeeze the stream towards the bank, which is less prone to rupture. Debris traps are used in the form of pits and basins, laid on the path of the movement of streams; they build bank-protecting retaining walls to prevent the erosion of the channel banks and protect buildings from the impact force of mudflows. Directional dams and mudflows are effective. Dams direct the flow in the desired direction and weaken its effect. On plots settlements and separate structures located in the zone of sedimentation of the proluvium, they arrange branch channels, directing dams, the river bed is taken into high stone banks, limiting the spread of the mudflow. To protect road structures, mudflows are most rational in the form of reinforced concrete and stone trays that let mudflows over or under structures.

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CONDUCTING PROTECTIVE WORKS

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HOW TO PROCEED WITH MUD FLOW

Hearing the noise of an approaching mudflow, you should immediately rise from the bottom of the ravine up the drain, not less than 50-100 m. It should be remembered that stones of heavy weight, threatening life, can be thrown from the roaring stream over long distances.

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ACTIONS AFTER MUD FLOW

Provide assistance to the victims and assistance to the formations and bodies that are dismantling debris and drifts along the path of the mudflow and in places where the bulk of the mudflow is carried out. If you have suffered, try to provide yourself with first aid. The affected areas of your body, if possible, should be kept in an elevated position, apply ice (wet cloth) to them, pressing a bandage. See your doctor.

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RURAL IN ALMATY 1921

Serious material damage caused a gigantic mudflow to the city, which fell on Almaty in July 1921. A mud-stone stream of almost 3 million m 3 swept along its way and destroyed many buildings and caused great damage to the city. All efforts of the workers were aimed at overcoming the grave consequences of the natural disaster, at restoring in as soon as possible destroyed.

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

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RURAL IN ALMATY 1973

July 15, 1973, 18:15. The entrance of the first wave of mud-stone flow into mudflow storage in the Medeo tract. The mudflow hit the body of the dam and choked, filling the pit with itself.

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PLATINA MEDEO SAVED 1000 LIVES

Alexander Yuryevich Khegai, in July 1973, a member of the government commission on liquidation of the mudflow consequences, a little later appointed deputy head of the newly created department "Kazselezashchita": Then scientists calculated that the force of the flow in 1973 was 4 times higher than the force of the flow in 1921. Then a quarter of the entire city building was destroyed, more than 500 people died. about 30 thousand people, and by the mid-70s, Alma-Ata expanded several times in territory and twenty times in population - up to 750 thousand, and the city center, through which the village of 1921 passed, is now multi-storey. , what could have been the number of victims and the scale of destruction! When these calculations are made for today's one and a half million Almaty, they call the figure - 300 thousand people living or working melting on a hypothetical mudflow path "

What is mudflow? Mudflow is a rapid channel stream consisting of a mixture of water, earth and rock debris that occurs in the basins of mountain rivers. Mudflows are characterized by the advancement of its frontal part in the form of a rampart from water and sediments or, more often, by the presence of a series of successively shifting ramparts. The passage of the mudflow is accompanied by significant reformation of the channel.

A potential mudflow center is a section of a mudflow channel or mudflow basin that has a significant amount of friable soil or conditions for its accumulation, where at certain conditions flooding, mudflows arise. Mudflow centers are divided into mudflow incisions, potholes and centers of diffuse mudflow formation. The causes of mudflows are heavy rainfall, strong melting of snow and ice, disturbances in economic activity(deforestation, non-observance of the rules for conducting blasting operations), as well as volcanic eruptions and earthquakes. Sometimes mudflows occur in the basins of small mountain rivers and dry ravines with significant thalweg slopes and in the presence of large accumulations of weathering products. The causes of mudflows are heavy rainfall, strong melting of snow and ice, disturbances in economic activities (deforestation, non-observance of the rules for conducting blasting operations), as well as volcanic eruptions and earthquakes. Sometimes mudflows occur in the basins of small mountain rivers and dry ravines with significant thalweg slopes and in the presence of large accumulations of weathering products. talvega Causes of occurrence.

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

Mudflow classification. Seismoseli Seismoseli As a result of earthquakes, breakaway 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 unthinkable kinetic energy by the flow. As a result of earthquakes, breakaway 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 unthinkable kinetic energy by the flow. Lahari Lahari 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 quickly melt, and the resulting water mixes with ash and rocks. During the eruption of Vesuvius in 79, under the ashes of which Pompeii were buried, the city of Herculaneum was covered with a three-meter layer of mud-stone mass brought by the lahar. During excavations, it was discovered that the mudslide shell of Herculaneum is much denser than the ash layer of Pompeii.

Connected Connected are 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 streams are classified as incoherent. Water carries debris and, as the velocity decreases, deposits it in the channel or in the fan section on the foothill plain. Mudflow classification.

Fight against mudflows. Mudflows can cause enormous destruction. The fight against mudflows is carried out mainly by fixing the soil and vegetation cover, building special hydraulic structures. Mudflows can cause 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 carried out. The use of certain methods of struggle is determined by the zones of the mudflow basin. The use of certain methods of struggle is determined by the zones of the mudflow basin.

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