Sel definition. Reasons for the formation of mudflows. The most catastrophic mudflows in human history. Flood forecasting. Flood prevention measures. Engineering measures for protection. When snow melts due to radiation, it captures

Landslides- This is a sliding displacement of rock masses down a slope under the influence of gravity.

They are formed in various rocks as a result of an imbalance or weakening of their strength. Caused by both natural and artificial (anthropogenic) reasons. Natural ones include: increasing the steepness of slopes, eroding their bases with sea and river waters, seismic tremors. Artificial is the destruction of slopes by road cuttings, excessive removal of soil, deforestation, unreasonable management Agriculture on the slopes. According to international statistics,up to 80% of modern landslides are associated with human activity. A significant number of landslides occur in mountains at altitudes from 1000 to 1700 m (90%).

Landslides can occur on all slopes, starting from a steepness of 19°. However, on clay soils they also occur at a slope steepness of 5-7°. For this, excessive moisture of the rocks is sufficient. They come at any time of the year, but for the most part in spring and summer.

Landslide classification

Landslides are classified: according to the scale of the phenomenon, speed of movement and activity, mechanism of the process, power and place of formation.

By scale Landslides are classified into large, medium and small scale.

Large ones are usually caused by natural causes and form along slopes for hundreds of meters. Their thickness reaches 10-20 meters or more. The landslide body often retains its solidity.

Medium and small-scale ones are smaller in size and are characteristic of anthropogenic processes.

Scale is often characterized by the area involved. In this case, they are divided into grandiose - 400 hectares or more, very large - 200-400 hectares, large - 100-200 hectares, medium - 50-100 hectares, small - 5-50 hectares and very small - up to 5 hectares.

By speed very diverse, as can be seen from table. 2.3.

By activity Landslides are divided into active and inactive. The main factors here are the rocks of the slopes and the presence of moisture. Depending on the amount of moisture, they are divided into dry, slightly wet, wet and very wet. For example, very wet ones contain such an amount of water that creates conditions for liquid flow.

According to the mechanism of the process are divided into: shear landslides, extrusion landslides, viscoplastic landslides, hydrodynamic landslides, and sudden liquefaction landslides. Often have signs of a combined mechanism.

By process power landslides are divided into small - up to 10 thousand m 3, medium - from 11 to 100 thousand m 3, large - from 101 to 1000 thousand m 3, very large - over 1000 thousand m - the mass of rock involved in the process.

By place of education they are divided into mountain, underwater, adjacent and artificial earthen structures (pits, canals, rock dumps).

Landslides cause significant damage to the national economy. They threaten the movement of trains, road transport, residential buildings other buildings. When landslides occur, the process of land removal from agricultural use is intensive.

Table 2.3. Characteristics of landslides based on movement speed

They often lead to human casualties. Thus, on January 23, 1984, as a result of an earthquake in the Gissar region of Tajikistan, a landslide 400 m wide and 4.5 km long occurred. Huge masses of earth covered the village of Sharora. 50 houses were buried, 207 people died.

In 1989, landslides in Ingushetia led to destruction in 82 settlements. 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural, trade and consumer services facilities were damaged.

A type of landslides are snow avalanches. They are a mixture of snow crystals and air. Large avalanches occur on slopes of 26-60°. They are capable of causing great damage, resulting in loss of life. Thus, on July 13, 1990, on Lenin Peak in the Pamirs, as a result of an earthquake, a large derailment snow avalanche demolished the climbers' camp, located at an altitude of 5300 m. 40 people died. It was the biggest tragedy in domestic mountaineering.

Mudflow

Mudflow (mudflow)- a rapid mud or mud-stone flow, consisting of a mixture of water and rock fragments, suddenly appearing in the basins of small mountain rivers.

It is characterized by a sharp rise in water level, wave movement, short duration of action (on average from one to six hours), and a significant erosion-accumulative destructive effect.

Mudflows pose a threat to populated areas, railways and highways and other structures located on their way.

The immediate causes of mudflows are showers, intense snow melting, breakthrough of reservoirs, less often earthquakes, volcanic eruptions.

Classification of mudflows

All ifs, according to the mechanism of nucleation, are divided into three types: erosive, breakthrough And landslide.

With erosion, saturation occurs first water stream debris material due to the washout and erosion of the adjacent soil, and then a mudflow wave is formed.

Breakthrough is characterized by an intensive process of water accumulation, at the same time rocks are eroded, a limit is reached and a breakthrough of a reservoir (lake, intraglacial reservoir, reservoir) occurs. The mudflow mass rushes down the slope or river bed.

During a landslide, a mass of water-saturated rocks (including snow and ice) is torn away. The flow saturation in this case is close to maximum.

Each mountain region has its own causes of mudflows. For example, in the Caucasus they occur mainly as a result of rains and downpours (85%).

IN last years added to the natural causes of mudflow formation technogenic factors, violation of the rules and regulations of mining enterprises, explosions during the construction of roads and the construction of other structures, logging, improper conduct of agricultural work and violation of soil and vegetation cover.

When moving, a mudflow is a continuous stream of mud, stones and water. The steep leading front of a mudflow wave with a height of 5 to 15 m forms the “head” of a mudflow. The maximum height of the water-mud flow shaft sometimes reaches 25 m.

The classification of mudflows based on the causes of occurrence is given in Table. 2.4.

In Russia, up to 20% of the territory is located in mudflow zones. Mudflows are especially active in Kabardino-Balkaria, North Ossetia, Dagestan, in the Novorossiysk region, Sayano-Baikal region, in the area of ​​the Baikal-Amur Mainline, in Kamchatka within the Stanovoy and Verkhoyansk ranges. They also occur in some areas of Primorye, Kola Peninsula and in the Urals. Back in 1966, more than 5 thousand mudflow basins were registered on the territory of the USSR. Currently, their number has increased.

Table 2.4. Classification of mudflows based on the root causes of occurrence

Based on the main factors of occurrence mudflows are classified as follows: zonal manifestation - the main formation factor is climatic conditions(precipitation). They are zonal in nature. The convergence occurs systematically. The paths of movement are relatively constant; regional manifestation (the main formation factor is geological processes). The descent occurs episodically, and the paths of movement are not constant; anthropogenic - this is the result of human economic activity. Occur where there is the greatest load on the mountain landscape. New mudflow basins are formed. The gathering is episodic.

Classification by power (based on transferred solid mass):

1. Powerful (strong power), with the removal of more than 100 thousand m 3 of materials. Happens once every 5-10 years.
2. Medium power, with removal from 10 to 100 thousand m 3 of materials. Happens once every 2-3 years.
3. Weak power (low-power), with the removal of less than 10 thousand m 3 of materials. They happen every year, sometimes several times a year.

The classification of mudflow basins by the frequency of mudflows characterizes the intensity of development or its mudflow activity. Based on the frequency of mudflows, three groups of mudflow basins can be distinguished:

• high mudflow activity (with recurrence once every 3-5 years or more);
• average mudflow activity (with recurrence once every 6-15 years);
• low mudflow activity (with a frequency of once every 16 years or less).

Mudflows are also classified according to their impact on structures:

• Low-power - small erosion, partial blocking of openings in culverts.
• Medium power - severe erosion, complete blocking of holes, damage and demolition of foundationless buildings.
• Powerful - great destructive force, demolition of bridge trusses, destruction of bridge supports, stone buildings, roads.
• Catastrophic - complete destruction of buildings, sections of roads along with the road surface and structures, burial of structures under sediments.

Sometimes a classification of basins is used based on the height of the sources of mudflows:

• alpine. The sources lie above 2500 m, the volume of removal from 1 km 2 is 15-25 thousand m 3 per mudflow;
• mid-mountain. The sources lie within the range of 1000-2500 m, the volume of removal from 1 km 2 is 5-15 thousand m 3 per mudflow;
• low mountain. The sources lie below 1000 m, the volume of removal from 1 km 2 is less than 5 thousand m 3 per mudflow.

Landslides (mountain collapse)- detachment and catastrophic fall of large masses of rocks, their overturning, crushing and rolling down on steep and steep slopes.

Landslides of natural origin are observed in the mountains, on sea shores and cliffs of river valleys. They occur as a result of a weakening of the cohesion of rocks under the influence of weathering processes, erosion, dissolution and the action of gravity. The formation of landslides is facilitated by: geological structure terrain, the presence of cracks and rock crushing zones on the slopes. Most often (up to 80%) modern collapses are associated with the anthropogenic factor. They are formed mainly during improper work, during construction and mining.

Landslides are characterized by the power of the landslide process (volume of falling rock masses) and the scale of manifestation (involvement of area in the process).

According to the power of the landslide process, landslides are divided into large (rock detachment of 10 million m3), medium (up to 10 million m3) and small (rock detachment of less than 10 million m3).

According to the scale of manifestation, landslides are divided into huge (100-200 ha), medium (50-100 ha), small (5-50 ha) and small (less than 5 ha).

In addition, landslides can be characterized by the type of collapse, which is determined by the steepness of the slope of the rockfall masses.

Landslides, mudflows, and avalanches cause great damage to the national economy, the natural environment, and lead to casualties.

The main damaging factors of landslides, mudflows and landslides are impacts from moving masses of rocks, as well as the collapse and flooding of previously free space by these masses. As a result, buildings and other structures are destroyed, settlements, economic facilities, agricultural and forest lands are hidden by rock layers, river beds and overpasses are blocked, people and animals die, and the landscape changes.

Landslides, mudflows and landslides on the territory of the Russian Federation occur in mountainous regions North Caucasus, Ural, Eastern Siberia, Primorye, Sakhalin Islands, Kuril Islands, Kola Peninsula, as well as along the banks of large rivers.

Landslides often lead to large-scale catastrophic consequences. Thus, a landslide in Italy in 1963 with a volume of 240 million m3 covered 5 cities, killing 3 thousand people.

In 1982, a mudflow 6 km long and up to 200 m wide hit the villages of Shiveya and Arenda in the Chita region. As a result, houses, road bridges, 28 estates were destroyed, 500 hectares of cropland were washed away and covered, and people and farm animals also died. The economic damage from this mudflow amounted to about 250 thousand rubles.

In 1989, landslides in Checheno-Ing Ushetia caused damage to 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural and public service facilities in 82 settlements.

Consequences of mudflows and landslides

Sel is a temporary flow of water that suddenly forms in the beds of mountain rivers with a large content of stones, sand and other solid materials. The cause of mudflows is intense and prolonged rainfall, rapid melting of snow or glaciers. Mudflows can also form from the collapse of large amounts of loose soil in river beds.

Unlike ordinary flows, mudflows, as a rule, do not move continuously, but in separate waves. At the same time, hundreds of tons, and sometimes millions of cubic meters of viscous mass are carried out. The sizes of individual boulders and fragments reach 3-4 m in diameter. When encountering obstacles, the mudflow passes through them, continuing to increase its energy.

Possessing a large mass and high speed of movement, up to 15 km/h, mudflows destroy buildings, roads, hydraulic engineering and other structures, disable communication and power lines, destroy gardens, flood arable land, and lead to the death of people and animals. All this lasts 1-3 hours. The time from the occurrence of a mudflow in the mountains to the moment it reaches the foothills is often calculated as 20-30 minutes.

To combat mudflows, they fix the surface of the earth by planting forests, expand the vegetation cover on mountain slopes, especially in places where mudflows originate, periodically drain water from mountain reservoirs, build anti-mudflow dams, dams and other protective structures.

Active snow melting is reduced by arranging smoke screens using smoke bombs. 15-20 minutes after the smoke, the temperature of the surface layer of air decreases, and the water flow is reduced by half.

The level of water accumulated in moraines (mountain lakes) and mudflow reservoirs is reduced using pumping units. In addition, in the fight against mudflows, such simple structures as cotton wool, ditches and terraces with a wide base are widely used. Protective and retaining walls, semi-dams and dams are built along river beds.

For the timely adoption of measures and the organization of reliable protection of the population, a clearly organized warning and warning system is of paramount importance. In areas threatened by mudflows, an anti-mudflow service is created. Its tasks include forecasting mudflows and informing the population about the time of its occurrence. In this case, a route is provided in advance along which the population is evacuated to higher places. There, if time permits, livestock is driven away and equipment is brought out.

If a person is captured by a moving mud flow, it is necessary to provide assistance to him by all available means. Such means may be poles, ropes or ropes. It is necessary to remove rescued people from the stream in the direction of the stream, gradually approaching its edge.

Landslide- sliding mixing of earth masses under the influence of its own weight - occurs most often along the banks of rivers and reservoirs and on mountain slopes. The volume of rocks displaced during landslides ranges from several hundred to many millions and even billions of cubic meters. Landslides are caused by various reasons: erosion of rocks by water, weakening of their strength due to weathering or waterlogging by precipitation and groundwater, unreasonable economic activity person, etc.

Landslides can destroy populated areas, destroy agricultural land, create danger during the operation of quarries and mining, damage communications, tunnels, pipelines, telephone and Electricity of the net, water management structures, mainly dams. In addition, they can block the dam, form a dam lake and contribute to flooding. Thus, the economic damage they cause can be significant.

The most effective protection against landslides is their prevention. A landslide does not usually start suddenly. First, cracks appear in the ground, ruptures in roads and coastal fortifications, buildings, structures, telegraph poles are displaced, and underground communications are destroyed. At the same time, it is very important to notice these first signs in time and make a correct forecast about further development landslide. It should also be taken into account that landslides move at maximum speed only in the initial period, then it gradually decreases.

In landslide areas, constant monitoring of soil movement, water levels in wells, drainage structures, wastewater disposal systems, boreholes, rivers, reservoirs, precipitation and precipitation is organized. Such observation is organized especially carefully in the spring-autumn periods, when the most precipitation falls.

If a landslide occurs, it is necessary, firstly, to warn the population, and secondly, as the situation worsens, organize the evacuation of the population to safe areas.

In the event of destruction of buildings and structures as a result of a mudflow or landslide, rescue operations are carried out, victims are removed from the rubble, and people are helped to leave the danger zone.

Protection of the population in case of threat and during landslides, mudflows and landslides

The population living in landslide-, mudflow- and landslide-hazardous zones should know the sources, possible directions and characteristics of these dangerous phenomena. Based on the forecast data, residents and enterprises are informed in advance about the danger of identified landslides, mudflows, collapse sources and possible zones their actions, the periods of passage of mudflows, as well as the procedure for sending signals about the threat of these phenomena. Such early informing of people about possible outbreaks natural disaster reduces the impact of stress and panic that may subsequently arise when transmitting emergency information about the immediate threat of these phenomena.

The population of these dangerous mountainous areas is obliged to take measures to strengthen houses and the territory on which they are built, as well as to participate in the construction of protective hydraulic and other engineering structures that protect against landslides and mudflows.

Primary information about the threat of landslides, mudflows and avalanches comes from landslide and mudflow stations, parties and hydrometeorological service posts. It is important that this information is communicated to the destination in a timely manner. Warning of the population about these natural disasters is carried out in the prescribed manner through sirens, radio and television, as well as through local warning systems that directly connect hydrometeorological service units with populated areas located in threatened zones.

If there is a threat of a landslide, mudflow or landslide, and if there is time, advance evacuation of the population, farm animals and property from threatening zones to safe places is organized.

Before leaving a house or apartment for early evacuation, they are brought into a state that promotes weakening damaging factors natural disaster, preventing the occurrence of secondary factors and facilitating subsequent possible excavations and restoration. Therefore, moved property from the yard or balcony must be removed into the house; the most valuable property that cannot be taken with you must be protected from moisture and dirt. Doors, windows, ventilation and other openings are tightly closed. Electricity, gas, and water supply are turned off. Flammable and toxic substances are removed from the house and, if possible, buried in remote pits or separate cellars. In all other respects, citizens act in accordance with the procedure established for organized evacuation.

If there was no advance warning of the danger and residents were warned about the threat immediately before the onset of a natural disaster or noticed its approach themselves, each of them, without worrying about property, makes an emergency independent exit to a safe place. At the same time, relatives, neighbors, and all people encountered along the way should be warned about the danger. For an emergency exit, you need to know the routes to the nearest safe places. These paths are determined and communicated to the population based on the forecast of the most likely directions of arrival of a landslide (mudflow) to a given settlement (object). Natural safe measures for emergency exit are the slopes of mountains and hills that are not prone to landslide processes or between which there is a mudflow-hazardous direction. When climbing to safe slopes, valleys, gorges and recesses should not be used, as side channels of the main mudflow may form in them. On the way, assistance should be provided to the sick, elderly, disabled, children, and the weak. For transportation, whenever possible, personal transport, mobile agricultural machinery, riding and pack animals are used.

In the event that people, buildings and other structures find themselves on the surface of a moving landslide area, they should, after leaving the premises, move upward as much as possible and, depending on the situation, beware when braking the landslide of blocks, stones, fragments of structures, earthenware rolling down from its back part. shaft, scree. It can also take over the thrust of immovable rocks. At high speeds, a strong shock is possible when stopping the landslide. Everything poses a great danger to people in the landslide.

After the end of a landslide, mudflow or landslide, people who had previously hastily left the disaster zone and waited out it in a nearby safe place, making sure that there is no repeated threat, should return to this zone in order to search for and provide assistance to the victims.

Classification

By altitude position

According to the geomorphological structure of the basins

For reasons of occurrence

According to the degree of saturation with sediment and its fractional composition

Mud mudflows

Mud-stone mudflows

Water-rock (alluvial) mudflows

Emergence

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.

Characteristics

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 a mudflow is accompanied by significant reformations of the riverbed.

Mudflows

Debris flows coming from volcanoes are called lahars.

The average speed of mudflows is 2-4 m/s, reaching 4-6 m/s, which causes their great destructive effect. Along their path, streams carve deep channels that are usually dry or contain small streams. Mudflow material is deposited in the foothill plains.

Messengers

Connected people include mud-stone streams, in which water is practically not separated 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 debris and, as its velocity decreases, deposits it in the channel or fan area on the foothill plain. The volumetric weight of water-rock mudflows is 1.2-1.5 t/m3.

The following zones are distinguished in the mudflow basin:

1. Origin zone (feeding)
2. Transit zone
3. Accumulation zone.

Fighting mudflows

Mudflows can cause enormous destruction. The fight against mudflows is carried out mainly by securing soil and vegetation cover and constructing special hydraulic structures.

To combat mudflows, preventive measures and construction of engineering structures are carried out. The use of certain control methods is determined by the zones of the mudflow basin. Preventive measures are taken to prevent the occurrence of a mudflow or weaken its effect at the very beginning of the process. The most radical remedy is afforestation on mudflow-prone mountain slopes. The forest regulates flow, reduces the mass of water, and cuts streams into separate weakened streams. It is forbidden to cut down forests or disturb the turf cover in the catchment area. Here it is advisable to increase the stability of slopes by terracing, intercept and drain water with upland ditches and earthen ramparts. In mudflow channels, dams have the greatest effect. These structures made of stone and concrete, installed across the riverbed, delay the mudflow and take away some of the solid material from it. Half-dams push the flow toward the shore, which is less susceptible to rupture. Mud catchers are used in the form of pits and basins laid in the path of flows; they build bank-protecting retaining walls that prevent erosion of the banks of the riverbed and protect buildings from the impact force of mudflows. Guiding dams and mudflow reservoirs are effective. Dams direct the flow in the desired direction and weaken its effect. At the sites settlements and individual structures located in the proluvium deposition zone, diversion channels are constructed, guide dams are installed, and river beds are taken into high stone banks that limit the spread of the mudflow. To protect road structures, the most efficient are mudflow drains in the form of reinforced concrete and stone chutes that allow mudflows to pass above or below structures.

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See what “Mudflow” is in other dictionaries:

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mudflow, mudflow- mudflow, debris flow mudflow, mudflow is a rapid channel flow, consisting of a mixture of water and rock fragments, suddenly appearing in the basins of small mountain rivers. S.p. characterized by a sharp rise in level, pulsating (wave) ... ...

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SEL, I, m. A stormy mud-stone stream that occurs in the mountains during heavy rains or melting snow. Came down from the mountains. Dictionary Ozhegova. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

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