Mudflow protection measures
ways and means aimed at reducing or eliminating the danger of mudflow. In a general sense, M.z.s. aimed at regulating (managing) the mudflow process. The direct objects of regulation are mudflow, mudflow basin, i.e. mudflow formation factors and, finally, human activity in mudflow-prone areas. From these positions, depending on the objects of regulation, M.z.s. are divided into three main groups. 1. Technical - construction of anti-mudflow structures. The object of regulation is the actual mudflow, and the purpose of the erected structures is to localize or change the path of its descent, stop the flow with the help of dams, canals, dams, etc. 2. Ameliorative - melioration of mudflow basins in order to regulate surface runoff as an essential element of the mudflow process. The methods of hydro- and phyto-reclamation in mudflow basins are afforestation and terracing of slopes, preventive descent of lakes, etc. 3. Organizational and economic - regulation of economic and other activities in mudflow-prone areas in order to prevent human casualties, reduce possible damage and weaken mudflow processes. This includes measures (laws, decisions of executive authorities of the Russian Federation, local governments) aimed at maximizing the preservation of forest cover on mountain slopes, limiting the load on mountain pastures, monitoring and warning in areas of pioneer development and recreation, etc. The best results are obtained by a combination of all groups of protection measures, in particular - ameliorative and technical. The whole complex of M.Z.s is carried out by the anti-mudflow service.
Edwart. Glossary of terms of the Ministry of Emergency Situations, 2010
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Anti-mudflow measures can be divided into two main groups: agro-reclamation and hydrotechnical (engineering).
The first group includes activities carried out in the watershed: improvement of forestry, including afforestation; proper plowing of slopes (across) and their tinning; slope terracing and organization of surface runoff.
Long-term practice of fighting mudflows has shown that agro-reclamation methods are an active means of combating their origin and formation. By creating a grassy and tree-shrub cover, it is possible to significantly strengthen the upper soil layer and significantly reduce erosion processes. Transverse plowing of slopes, as well as their terracing, is also a good way to reduce soil erosion by running water.
Terraces created on steep slopes are divided into trench (terraces - ditches) and stepped.
Trench terraces are ditches dug along contours and earthen ramparts laid along the lower edge of the ditch. They are widely used on slopes with a steepness of not more than 30 0 .
Figure - Ditch tracks
Stepped terraces represent a continuous platform located horizontally or with some allowable slope along the canvas, and the water is discharged from the terrace canvas with the help of trays and storm drains. Arrange them with large slopes (up to 35-40 °). The site is bounded on one side by a continental slope, and on the other side by an artificial slope.
Figure 2 - types of stepped terraces: a) with a horizontal canvas; b) the canvas has a reverse slope; c) the canvas has a slope along the slope.
The most common are terraces with a horizontal canvas, as they reduce the speed of surface waters, however, terraces with a reverse slope (3 ... 6 0) are also used on well-permeable soils; moreover, along the edge of the bulk slope, a roller is made 0.2-0.3 m high and 0.5-0.6 m wide at the base.
The distance between the terraces depends on the steepness of the slope and the width of the terrace canvas, and it is assigned on the basis that the speed of the water flowing down the slope does not reach the maximum eroding speed of the day for this soil.
Hydrotechnical measures are the most rational, and they are carried out by influencing the formed mudflow, since anti-erosion measures carried out on slopes are not always effective and cannot delay the entire surface flow. Therefore, part of it falls into the channel, it is capable of carrying a large amount of solid material and can cause significant damage to cities and found points.
To protect against the channel mudflow, channel hydraulic structures are used, which, according to the nature of the impact on the mudflow, are divided into mudflow-retaining, mudflow-through, mudflow-directing, mudflow-clearing and mudflow-transforming. These structures can solve several problems, in particular, the retention of mudflows above the protective object, the diversion or passage of the flow through the protected object, the stabilization and protection of the channel from erosion, and the protection of the structure from the impact of the flow.
Debris-retaining structures are dams, dammed with nanosoul traps. Mudflow-retaining dams are widely used in the fight against mudflows, which are able to retain large volumes of mudflows.
Dams, which are made of stone, concrete, reinforced concrete, metal in the form of deaf or lattice structures that block the riverbed, can be placed singly or in groups in separate areas or throughout the riverbed.
The main purpose of the dams is to create a new, more gentle, flat slope of the channel than the natural one. As a result, the mudflow velocity decreases, and the destruction of the channel stops, since its energy is lost when it hits the dam. When the sinuses of the dams are completely filled, they can be increased, thus creating additional capacity.
Through mudflow traps are usually inclined grids made of metal and reinforced concrete structures.
Mudflow-retaining structures consist of pits or artificial depressions in the terrain, in which the mudflow is delayed.
Mudflow passage facilities include mudflows and mudflow outlets. The former serve to transfer mudflows through roads, ditches, oil and gas pipelines, etc. Mudflow diverting structures divert the mudflow from a city or settlement and represent retaining walls, dams, etc.
Mudflow-cutting structures (dams, spurs) are arranged to protect the bottom and banks of the channels from erosion or to protect any structures located along the river. Such structures are arranged at an angle to the flow axis (10-20 0). One at their end is embedded in the protected shore and made of stone, reinforced concrete, metal, and other materials.
1. Introduction
2. Sel. Mudflows
3. Initial signs
6. Conclusion
OBJ teacher
Kovalev
Alexander
Prokofievich
Secondary School No. 2
Mozdok
SEL(in hydrology from "sail" - "mudstone stream") - 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, heavy rainfall or rapid snowmelt.
sel- something 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.
A great influence on the behavior and actions of the population during mudflows and landslides is provided by the organization of timely detection and registration of signs of these natural disasters and the organization of notification (warning) about a disaster.
In most cases, the population about the danger of a mudflow can be warned just for tens of minutes and less often for 1 - 2 hours or more . The approach of such a stream can be heard by the characteristic sound of boulders and stone fragments rolling and colliding with each other, resembling the roar of a train approaching at high speed.
The initial sign of the beginning of landslide movements is: the appearance of cracks in buildings, gaps in roads, coastal fortifications and embankments, bulging of the earth, displacement of the base of various high-rise structures and even trees in the lower part relative to the upper one.
The average speed of mudflows is 2-4 m/s, reaching 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.
How to prepare for a village
Usually, the places where mudflows can go are known. Before going to the mountains, study these places on your route and avoid them, especially after heavy rains.
Always remember that it is almost impossible to escape when caught in a mudflow. You can save yourself from a mudflow only by avoiding it. Before leaving the house, in case of early evacuation, turn off electricity, gas and water supply. Close doors, windows and vents tightly.
Affecting factors
landslides, mudflows, landslides
- Leave the mudflow-prone channel if there is heavy rainfall in the upper reaches of the mudflow-prone basin.
- Do not approach a moving mudflow closer than 50-70 m.
- Do not stop near sheer cliffs and steep slopes, as a landslide or rockfall may occur from the shaking during the passage of mudflows.
- Move along mudflow channels at intervals of at least 20-30m. between people.
- Do not stop for rest and do not set up a camp near mudflow channels, on lake dams (dams) and under them.
- If you see signs of a mudflow, immediately move as far as possible from the channel up the mountain slopes.
7. Do not go down into the mudflow channel after passing the mudflow shaft - another shaft may follow it.
8. Exercise maximum caution when descending into the channel and when moving along it after the passage of a mudflow, especially in areas of mudflow incision and potholes.
9. It is recommended to stay on the moraine-glacial complex and move along it during periods when there is no danger of mudflows or is unlikely, it is better at negative air temperatures.
10. Do not move across the bridges of lakes composed of unstable lying debris, as well as formed by a moving glacier
11. Constantly follow the media reports about the situation in the mountains.
Homework § 4.5 pp. 102-104
Protection of the population from the consequences of mudflows is carried out in various ways. Organizational, economic and protective and restrictive measures provide for the prohibition of the construction of industrial enterprises, residential buildings, railways and roads in the channels of mudflow basins without the organization of reliable protection against mudflows.
Protective measures include the construction of anti-mudflow engineering and hydraulic structures.
Anti-mudflow structures, according to the nature of the impact on mudflows, are divided into mudflow control, mudflow dividing, mudflow containment and mudflow transforming.
Such structures are designed to retain mudflows above the protected object, to divert the mudflow from the object, and also to protect the object from the impact of the mudflow.
Detention of debris flows can be carried out by the construction of dams, dams (dams) or pits-nano-catchers. Dams can be made of stone, concrete, reinforced concrete, metals and other materials in the form of blind or lattice walls blocking the channel. Mudflow-retaining dams are designed to retain a large volume of solid mudflow runoff. The supporting surface of the dam is located perpendicular to the surface of the mountain slope. Pit-nano-catchers reduce the speed of the mudflow.
The simplest structures were also erected: ditches and terraces with a wide base. Shafts-ditches are located strictly horizontally on slopes with a steepness of not more than 10 °. On slopes with a steepness of 10 to 30 °, stepped terraces 3.5-4 m wide are arranged.
Preventive measures are also taken to protect the population from the consequences of mudflows. Such activities include:
- elimination of artificial or natural reservoirs, the breakthrough of which can lead to the formation of mudflows;
- installation of sewer channels and preliminary discharge of water from mountain lakes before the onset of a mudflow hazard period;
- reduction of the water component of the mudflow due to the regulation of the rate of snowmelt. The acceleration of snowmelt in certain places is achieved by spraying coal dust, soot, and ash over the snow cover in these places. This accelerates snowmelt by 15-20 days in pollinated areas, and the total surface runoff of water is reduced due to its discharge in small volumes;
- strengthening the land on the slopes of the mountains by planting trees.
If necessary, a warning system and evacuation of the population from dangerous areas will be organized.
In addition, specialists from the EMERCOM of Russia have developed recommendations for the population living in mudflow-prone areas.
Let's take a look at some of them.
Before leaving for the mountains, study the places on your route where mudflows can go, and avoid them, especially after heavy rains.
Hearing the noise of a suddenly approaching mudflow, you should immediately climb from the bottom of the hollow up the slope by at least 50-100 m.
From the mudflow, you should quickly go up the slope
Remember
- From a mudflow moving at high speed, stones of enormous size and weight can be thrown out over considerable distances, which is life-threatening.
When leaving the house during an early evacuation, turn off the electricity, gas, and water supply. Close doors, windows and vents tightly.
To protect the population from the consequences of mudflows, the forecast of mudflow formation is of great importance.
The rain mudflow hazard forecast is based on the meteorological forecast of the amount of precipitation, and in high-mountainous areas - on the identification of processes that affect the rate of snow and glacier melting.
Test yourself
- What method of protecting the population from mudflows do you consider the most effective? Justify your answer.
- Name the main reason for mudflows.
After school
Think over and write down in the safety diary the order of your behavior in case of a threat of a mudflow in several situations (while you are indoors, in the mountains, etc.).
