- this is a significant flooding of the area with water as a result of a rise in the water level in a river, reservoir, lake or sea, caused by an abundant influx of water during the period of snowmelt or heavy rains, wind surges of water, as well as during traffic jams, ice jams and other phenomena.

Flooding is dangerous natural phenomenon, a possible source of emergency, if the flooding of the area causes material damage, damages the health of the population or leads to the death of people, farm animals and plants.

In terms of frequency, distribution area and total average annual material damage of floods in the territory Russian Federation occupy the first place in a number of natural disasters, and in terms of the number of human casualties and specific material damage (per unit of the affected area) - the second place after earthquakes.

Rivers are different various conditions formation of water runoff (water runoff is the amount of water flowing through the closing section of the river for any time interval).

According to the conditions of runoff formation and the occurrence of floods, the rivers of the Russian Federation are divided into four types (Table 1).

Table 1

Types of rivers of the Russian Federation depending on the conditions for the formation of the maximum runoff

Formation conditions maximum flow	Distribution areas on the territory of the Russian Federation
Spring snowmelt on the plains	European part of the Russian Federation and Western Siberia
Melting mountain snows and glaciers	North Caucasus
Heavy rainfall	Far East and Siberia
Combined effect of snowmelt and precipitation	Northwestern regions of the Russian Federation

The variety of floods can be reduced to five general groups that combine various floods according to the causes of occurrence and the nature of their manifestation (Table 2).

Within the Russian Federation, floods of the first two types prevail (about 70 - 80% of all cases). They are found on the plains, foothills and mountain rivers, in the northern and southern, western and eastern regions of the country. The remaining three types of floods have a local distribution.

The classification of floods depending on the scale of their distribution and frequency is presented in Table. 3.

table 2

Types of floods depending on the causes and nature of the manifestation

Types of floods	Causes	The nature of the manifestation
high water	Spring snowmelt in the plains or spring-summer snowmelt and rainfall in the mountains	Repeat periodically in the same season. Characterized by a significant and prolonged rise in water levels
high water	Intense rains and snowmelt during winter thaws	There is no clearly defined periodicity. It is characterized by an intense and relatively short-term rise in the water level.
Jam, zazhorny floods (jamming, zazhora)	High resistance to water flow, in certain sections of the river channel, arising from the accumulation of ice material in narrowings or bends of the river during freeze-up (jamming) or ice drift (jamming)	Jam floods form in late winter or early spring. They are characterized by a high and relatively short-term rise in the water level in the river. Jam floods form at the beginning of winter and are characterized by a significant (but less than during a jam) rise in the water level and a longer duration of the flood.
Surge floods (surges)	Wind surges of water in sea mouths of rivers and on windy sections of the coast of the seas, large lakes, reservoirs	Possible at any time of the year. Characterized by the absence of periodicity and a significant rise in the water level
Floods (flooding) formed when dams break	An outflow of water from a reservoir or reservoir, which is formed when a pressure front structure (dams, dams, etc.) breaks or during an emergency discharge of water from a reservoir, as well as when a natural dam breaks through, created by nature during earthquakes, landslides, collapses, glacier movement	They are characterized by the formation of a breakthrough wave, leading to the flooding of large areas and the destruction or damage of objects encountered on the way of its movement (buildings, structures, etc.)

Table 3

Classification of floods depending on the scale of distribution and frequency

Classes floods	Scale of distribution floods	Repeatability
Low (small)	They do relatively little damage. Covers small coastal areas. Less than 10% of agricultural land is flooded. Almost do not break the rhythm of life of the population.	5-10 years
High	They cause significant material and moral damage, cover relatively large areas of river valleys, and flood approximately 10-15% of agricultural land. Significantly violate the economic and everyday life of the population. Lead to the partial evacuation of people.	20-25 years old
Outstanding	They cause great material damage, covering entire river basins. Flood approximately 50-70% of agricultural land, some settlements. They paralyze economic activity and drastically disrupt the way of life of the population. Lead to the need for mass evacuation of the population and material assets from the flood zone and protection of the most important economic facilities	50-100 years old
catastrophic	They cause enormous material damage and lead to death of people, covering vast territories within one or more river systems. More than 70% of agricultural land is flooded, many settlements, industrial enterprises and engineering communications. Economic and industrial activity is completely paralyzed, the way of life of the population is temporarily changed	100-200 years

The main characteristics of the water flow are given in table. 4.

During flooding, secondary damaging factors may occur: fires (due to breaks and short circuits in electrical cables and wires); collapse of buildings, structures (under the influence of water flow and due to erosion of the base); diseases of people and farm animals (due to contamination of drinking water and food), etc.

Buildings that periodically fall into the flood zone lose their solidity: wood is damaged by rot, plaster falls off, bricks fall out, metal structures corrode, due to erosion of the soil under the foundation, uneven settlement of buildings occurs and, as a result, cracks appear.

The main characteristics of the consequences of floods are as follows:

The number of the population that ended up in a zone prone to floods (here the following stand out: the number of victims, the number of victims, the number of people left homeless, etc.);
the number of settlements that fell into the zone covered by the flood (cities, urban-type settlements, rural settlements, completely flooded, partially flooded, caught in the flood zone are distinguished here);
the number of objects of various sectors of the economy that ended up in the zone, floods;
the length of the iron and highways, power lines, communication and communication lines caught in the flood zone;
number of bridges and tunnels flooded, destroyed and damaged by flooding;
the number of residential buildings flooded, destroyed and damaged as a result of flooding;
the area of ​​agricultural land covered by the flood;
the number of dead farm animals, etc.

Generalized characteristics of the consequences: the magnitude of the damage caused by the flood.

Table 4

Characteristics of the main damaging factor of floods

Basic striking factor	Characteristics of the main damaging factor	Units measurements characteristics
water flow	Maximum water level during the flood (in the considered section of the river)	m or cm
	Maximum water flow during the flood (in the considered section of the river)	m 3 / s
	Current speed (in the considered section of the river)	m/s
	Area of ​​flooded area	km 2
	Duration of area flooding	weeks, days, hours
	Repeatability maximum level water	years, months
	Provision of the maximum water level
	Water temperature during a flood	degrees Celsius
	Start time (season) of the flood	month, date
	The rate of rise (intensity of rise) of the water level during the flood	m/h, cm/h
	Layer (depth) of terrain flooding at the considered point	m, cm

The main features of the situation that occurs during floods are: the destructive nature of the emergency, the rapid increase in the parameters of damaging factors, the limited survival time of the victims affected by them; the difficulty of access to the victims, the need to use special floating equipment for this, as well as difficult weather conditions (heavy rains, ice drift, mudflows, etc.).

The main goal of emergency rescue and other urgent work in flood conditions is the search, assistance and rescue of people who find themselves in the flood zone as soon as possible, ensuring their survival in the current situation.

The success of rescue and other urgent work in the aftermath of floods is achieved by:

Carrying out systematic, advance preparation of command and control bodies and units of civil defense troops, search and rescue formations and services for conducting emergency rescue operations; rapid response to the occurrence of a natural disaster, alerting and advancing necessary forces and means, organizing effective reconnaissance and deployment of a command and control system;
application effective ways and technologies for search and rescue of victims, as well as ways to protect the population and economic facilities;

Flood and catastrophic flood rescue operations include:

Search for victims;
ensuring access of rescuers to victims and rescue of victims;
providing victims with first aid medical care;
evacuation of victims from the danger zone.

Immediate emergency response to floods includes:

Strengthening (construction) of enclosing dams and ramparts;
construction of drainage channels;
elimination of congestion and congestion;
equipment of berths for life-saving equipment;
protection and restoration of road structures;
restoration of power supply;
localization of sources of secondary damaging factors.

The main ways to protect people from the damaging factors of floods are the evacuation of the population from flooded areas, the placement of people in non-flooded parts, undamaged structures and terrain.

Depending on the location of the settlement, the time before the start of its flooding, the state of transport communications and other factors, evacuation can be carried out immediately before receiving a signal about the possible flooding of this area or only with an immediate threat of flooding, on foot or using Vehicle. In addition to the evacuation of the population, the export of farm animals, material and cultural values ​​can also be carried out in an organized manner.

The effectiveness of evacuation as a way to protect the population during floods depends mainly on the timely warning of the danger, the degree of preparedness of the population and routes.

To this end, a public warning system is being created in areas of possible flooding, information is provided in advance about the location of settlements regarding a possible danger zone and evacuation routes, training is conducted with the population and evacuation authorities to practice evacuation issues, including the independent exit of people to a non-flooded area. .

In addition to the direct impact of the water flow, aspiration (getting into Airways) water, long stay in cold water, neuropsychic overstrain, as well as flooding (destruction) of systems that ensure the vital activity of the population, especially the failure of water supply and sewerage systems.

With prolonged forced stay of people in water with a low temperature, hypothermia (hypothermia) of the body occurs. When a person gets into the water, hypothermia is possible even at a relatively high temperature (Table 5).

Placement of people in non-flooded parts, non-destructible structures and areas of the terrain is used in cases where the high speed of the water flow causes its rapid arrival in settlements and (or) the population cannot be evacuated to a safe area. In this case, the implementation of such protective measures, as a rule, requires the further implementation of rescue operations to evacuate people from temporary accommodation in the danger zone. At the same time, it should be borne in mind that the population can also use the upper parts of trees as a place of temporary residence (shelter).

Table 5

The safe time for a person to stay in the water

Water temperature, °C	Time of safe stay, min
	420-540
5-15	10-270
	10-15
Up to 2

The decision to carry out emergency rescue and other urgent work in case of floods is made on the basis of intelligence data, which is organized during floods to identify the situation in disaster areas in order to minimize damage.

Determining the boundaries of flooding;
control of flood development dynamics;
establishing the locations of people and farm animals in need of help;
identification of material values ​​to be removed from the disaster zone;
selection and reconnaissance of routes for the evacuation of people, animals and material assets by watercraft, equipment of berths;
selection and equipment of landing sites for helicopters in the disaster area.

To carry out emergency rescue operations, units of the civil defense troops, search and rescue detachments (services), reinforced with amphibious assault vehicles, are assigned. To perform other urgent work, taking into account their nature, engineering, engineering and technical, road units and formations are assigned.

When searching for and rescuing victims in the water and in flooded areas, aviation technologies using aircraft and helicopters should be widely used.

The use of certain technologies for eliminating ice blockages (blockages) and landslides depends on the scale of floods and the consequences associated with them. Explosives are the main method of destroying the ice cover, eliminating ice blockages (blocks), as well as rock falls. The work is carried out by pyrotechnic units equipped with watercraft and vehicles equipped for the delivery of explosives and explosives. During catastrophic floods, especially on the large rivers of the North and North-East of Russia, flowing from south to north, the destruction of the ice cover, ice jams and ice jams is practiced using bomber aircraft.

Measures to prevent floods and eliminate their consequences are provided for in action plans for the prevention and liquidation of emergency situations, developed at all levels by emergency commissions.

The organization of interaction between the forces of liquidation, the consequences of floods and catastrophic flooding of territories is one of the critical factors that ensure the success of rescue and other urgent operations.

Interaction is organized primarily in the interests of rescue units, the implementation of these works in the shortest possible time.

The experience of recent years in eliminating the catastrophic consequences of floods (Yakutia - 2001, the Southern Federal District - 2002) suggests that in order to improve the protection of the population and territories from floods, the executive authorities of the constituent entities of the Russian Federation, local governments can be recommended:

Accelerate the formation of territorial systems for monitoring, laboratory control and forecasting of emergency situations;
to take measures to develop warning systems for the population, paying special attention to rural areas;
take measures to create and strengthen bank protection structures, repair dams, deepen and clean river beds;
intensify work on the creation of search and rescue units financed from the budgets of the constituent entities of the Russian Federation;
based on this experience, rework action plans for the prevention and elimination of emergency situations;
create full reserves of financial and material resources for the liquidation of emergency situations;
consider the issue of the need (expediency) of redistributing the budget funds of the constituent entities of the Russian Federation in the direction of increasing funds for urgent measures aimed at the safe functioning of the water management complexes of the regions.

behavior emergency fire

Flood - this is a significant flooding of the area as a result of a rise in the water level in a river, lake or sea during the period of snowmelt, showers, wind surges of water, during traffic jams, ice jams, etc. Floods caused by wind surge of water in the mouths of rivers are of a special type. Floods lead to the destruction of bridges, roads, buildings, structures, cause significant material damage, and at high water speeds (more than 4 m/s) and high water rise (more than 2 m) cause death of people and animals.

Causes:

• · - heavy rainfall, rains;
• - intensive snow melting;
• - formation of congestion (ice floes in spring), ice jams (light snow, ice in autumn);
• - destruction of hydraulic structures;
• - underground earthquakes (cause giant waves - tsunamis)
• · - strong surge wind on sea coasts and estuaries of rivers flowing into the sea.

Floods passing along the rivers are divided by height:

• · On low or small (low floodplains are flooded);
• · Medium (high floodplains are flooded, partially populated);
• Strong or outstanding (cities, communications are partially flooded, evacuation of the population is required);
• · Catastrophic (cities are significantly flooded, major rescue operations are required, mass evacuation).

If the area often suffers from floods, you need to study and remember the boundaries of possible flooding, as well as elevated, rarely flooded places located in close proximity to places of residence, the shortest routes to them. Familiarize family members with the rules of conduct during organized and individual evacuation, as well as in the event of a sudden and rapidly developing flood. Remember where boats, rafts and building materials for their manufacture. Prepare in advance a list of documents, property and medicines taken out during the evacuation. Put valuables, necessary warm clothes, a supply of food, water and medicines in a special suitcase or backpack.

Flood instructions:

Upon a warning signal about the threat of flooding and about evacuation, immediately, in accordance with the established procedure, leave (leave) from the danger zone of possible catastrophic flooding to the designated safe area or to elevated areas of the terrain, taking with you documents, valuables, necessary things and a two-day supply of non-perishable food. At the final evacuation point, you must register. Before leaving the house, turn off the electricity and gas, put out the fire in the heating stoves, secure all floating objects located outside the buildings, or place them in utility rooms.

If time permits, move valuable household items to the upper floors or to the attic of a residential building. Close windows and doors, if necessary and if there is time, clog the windows and doors of the first floors with boards (shields) from the outside. In the absence of an organized evacuation until help arrives or the water subsides, you need to be on the upper floors and roofs of buildings, on trees or other towering objects. At the same time, constantly give a distress signal: during the day - by hanging or waving a clearly visible panel lined with a pole, and in the dark - by a light signal and periodically by voice. When the rescuers approach calmly, without panic and fuss, with the observance of precautionary measures, you need to go to the swimming facility. At the same time, strictly comply with the requirements of rescuers, do not allow overloading of watercraft. During the movement, do not leave the established places, do not board the sides, you must strictly follow the requirements of the crew.

It is recommended to get out of the flooded area on your own only if there are such serious reasons as the need to provide medical assistance to the victims, the continued rise in the water level, and the threat of flooding of the upper floors (attic). In this case, it is necessary to have a reliable swimming facility and know the direction of movement. During self-advance, do not stop giving a distress signal. Help people who are swimming in the water and drowning.

Instructions for actions after the flood:

Before entering the building, it is recommended to check whether it threatens to collapse or fall of any object. Ventilate the building (to remove accumulated gases). Do not turn on electric lighting, do not use sources of open fire, do not light matches until the room is completely ventilated and the gas supply system is checked for proper operation. It is recommended to check the serviceability of the electrical wiring, gas supply pipelines, water supply and sewerage. You can not use them until you check their serviceability with the help of specialists. To dry the premises, you need to open all doors and windows, remove dirt from the floor and walls, pump out water from the basements. Do not eat food that has been in contact with water. It is recommended to organize the cleaning of wells from the applied dirt and remove water from them.

Since ancient times, floods have been perceived by man as the most terrible natural disaster. It is no coincidence that in the religions of many peoples it acts as a "punishment of the Lord." It is enough to remember the Biblical global flood". In all likelihood, this is due to the fact that water shell Earth (hydrosphere) occupies 71% of its surface. The bulk of water (94% of the volume) is contained in the seas and oceans. The water reserve in the rivers is approximately 1200 km3.

In terms of frequency of occurrence, area of ​​distribution, total average annual damage, floods rank first in Russia among dangerous hydrological phenomena and processes. In terms of the number of human casualties and damage per unit area of ​​damage, they rank second after earthquakes.

The absolute record for the magnitude of the effects of floods belongs to the Chinese rivers Huang He and Yangtze. On the river Huang He in 1887, the water in the river rose by 3 m and flooded thousands of settlements, causing enormous material damage. About 1 million people died, more than 7 million people suffered. The spill of the river Yangtze (1911) led to the death of about 100 thousand people. The largest catastrophic flood in China occurred in June-July 1959: flooding of rivers in the northeast led to the death of 2 million people.

The causes of floods are very diverse: spring snowmelt, precipitation in the mountains, winter thaws, ice accumulation in the narrowing of rivers, wind surges of water in sea mouths of rivers, etc. Of particular danger are floods associated with the outflow of water from a reservoir when a dam breaks (accidents at dangerous hydrodynamic objects).

The leading damaging factors in most floods are thermal And biological.

With prolonged forced stay of people in water with a low temperature, hypothermia (hypothermia) of the body occurs. When a person gets into the water, freezing is possible even at a relatively high temperature: at a water temperature of up to 15 0 C, the safe time spent in water at this temperature is about 3 hours; at a temperature of 2-3 0 C - only 10-15 minutes.

When vast areas are flooded, water supply systems, sewage systems, drain communications of bath and laundry facilities can be destroyed. Wastewater, places for collecting garbage and sewage, etc. All this leads to a shortage of good quality water, the emergence and spread of infectious diseases. The conditions for the emergence of epidemics, purulent and anaerobic infections are the most favorable.

In addition to the leading damaging factors characteristic of most floods, in case of accidents at hazardous hydrodynamic objects, the importance of mechanical factor conditioned kinetic energy breakthrough waves. Mechanical damage of varying severity may be the result of:

– direct dynamic impact on the human body of a breakthrough wave;

- the traumatic effect of the fragments of buildings and structures destroyed by a breakthrough wave;

- the damaging effect of various objects involved in the movement of a breakthrough wave.

However, due to flooding, accidents are possible at fire-explosive objects, chemically and radiation hazardous objects, etc. Therefore, exposure of the population to the air shock wave, elevated temperatures, poisoning with AOHV and exposure to ionizing radiation is possible. So, in 1994, in the Egyptian province of Asyut, a flash flood led to a short circuit in a petroleum products warehouse. After a powerful explosion, flaming fuel flooded the village, killing more than 500 people.

Dangerous hydrodynamic object(GOO) is a structure or natural formation that creates a difference in water levels before (upstream) and after (downstream) it. GOOs include artificial and natural dams, hydroelectric facilities, and dams.

The most important feature flooding during accidents at the GOO is the formation of the aforementioned breakthrough wave.

A breakthrough wave is a wave formed in the downstream as a result of the rapid fall of water from the upstream during the GOO breakthrough. The breakthrough wave is the main damaging factor of accidents at GOO.

The volume of water and the rate of its fall from the upstream depend on the magnitude of the breakthrough (the location of the damage to the GOO, through which water rushes from the upstream) during the breakthrough of the hydraulic structure. The main parameters of the breakthrough wave (height, width and speed) depend on the size of the breakthrough.

Depending on the height of the wave and the speed of the current in the flooded area, four zones of catastrophic flooding are distinguished:

- the first - the zone of catastrophic flooding is adjacent directly to the hydraulic structure or reservoir, which extends for 6-12 km, the wave height can reach several meters. The wave is characterized by a rapid flow of water with a current speed of 30 or more km/h. The wave passage time is 30 min.

- the second - a zone of fast current (15-20 km / h). The length of this zone can be 15-25 km. The wave passage time is 50-60 minutes.

- the third - the zone of the middle current (10-15 km / h). Length up to 30-50 km. The wave passage time is 2-3 hours.

- the fourth - a zone of weak flow (spill). The speed of the current can reach 6-10 km/h. Its length will depend on the terrain and may be 36-70 km.

Such a conditional division into zones allows rescuers to better navigate the current situation in the disaster area, which, in turn, improves the quality and efficiency of rescue operations.

The total losses of the population located in the zone of action of the breakthrough wave can reach 90% at night, and 60% during the day. Of the total losses, irretrievable losses amount to 75% at night, 40% during the day, and sanitary losses - 25% at night and 60% during the day.

The magnitude and structure of losses among the population during floods can vary depending on the density of the population in the flood zone, time of day, speed and height of the breakthrough wave, water temperature and other factors. An example of large losses from floods as a result of accidents at GOOs can be the destruction of a dam in the state of Idaho (USA) in 1974, which resulted in the death of 150 people. There were 10 cities in the flood zone.

Main characteristics consequences floods are as follows:

- a large number of human casualties and people left homeless;

- flooding of large areas with many settlements;

- in the disaster zone, the functioning of various sectors of the economy ceases;

- in the flood zone are railway tracks, roads, power lines, communications, communications;

- bridges, tunnels are destroyed;

– flood covers large agricultural areas, etc.

FLOODING is a significant flooding of the area as a result of a rise in the water level in a river, lake or sea during the period of snowmelt, heavy rains, wind surges of water, during traffic jams, blockages, etc.

Floods caused by wind surge of water in the mouths of rivers are of a special type. Floods lead to the destruction of bridges, roads, buildings, structures, cause significant material damage, and at high water speeds (more than 4 m/s) and high water rise (more than 2 m) cause death of people and animals. The main cause of destruction is the impact on buildings and structures of hydraulic shocks of water masses, ice floes floating at high speed, various debris, watercraft, etc. Floods can occur suddenly and last from a few hours to 2-3 weeks.

Types of flood

Depending on the cause of the flood, they are divided into 5 types:

• high water - flooding resulting from the melting of snow and the release of a reservoir from its natural banks
• flood - flooding associated with heavy rains
• floods caused by large accumulations of ice that clog the riverbed and prevent water from flowing downstream
• surge floods , occurring due to strong winds that drive water in one direction, most often against the current
• floods resulting from dam break or reservoirs.

high water	high water	Congestion	Zazhor	wind surge
recurring, rather prolonged rise in the water level in rivers, usually caused by spring snowmelt on the plains or rainfall. Floods low terrain.	an intensive relatively short-term rise in the water level in the river, caused by heavy rains, downpours, and sometimes rapid snowmelt during thaws. Unlike floods, floods can occur several times a year. A particular threat is the so-called flash floods associated with short-term, but very intense downpours, which also occur in winter due to thaws.	clogging of the channel by a motionless ice cover and heaping of ice floes during the spring ice drift in the narrowings and on the bends of the river channel, restricting the flow and causing a rise in the water level in the place of ice accumulation and above it. Jam floods are formed in late winter or early spring, and occur due to the non-simultaneous opening of large rivers flowing from south to north. Opened southern sections of the river in its course spring up accumulation of ice in the northern regions, which often causes a significant increase in water levels. Jam floods are characterized by a high and relatively short-term rise in the water level in the river.	ice plug, accumulation of in-water, loose ice during winter freezing in narrowings and on the bends of the channel, causing the rise of water in some areas above the level of the main river channel. Jam floods form at the beginning of winter and are characterized by a significant, but less than during a jam, rise in the water level and a longer duration of the flood.	rise in the water level in the sea mouths of large rivers and in windy areas of the coast of the seas, large lakes, reservoirs caused by the impact of strong winds on the water surface. They are characterized by the absence of periodicity, rarity and a significant rise in the water level, as well as, as a rule, short duration. Floods of this type have been observed in Leningrad (1824, 1924), the Netherlands (1953).
periodically for a long time	fast briefly	ice is standing, piling up water can't get out high level briefly	ice plug loose ice low level for a long time	wind from the sea into the riverbed water can't get out high level brevity

Causes of floods:

1. Long rains
2. snowmelt
3. tsunami wave
4. bottom profile
5. Dam failure
6. Other natural and man-made causes

Flood classification:

1. storm (rain);
2. floods and floods (associated with the melting of snow and glaciers);
3. jamming and jamming (associated with ice phenomena);
4. overwhelming and breakthrough;
5. surge (wind on the coasts of the seas);
6. tsunamigenic (on the coasts from underwater earthquakes, eruptions and large coastal landslides).

River floods are divided into the following types:
1. low (small or floodplain) - a low floodplain is flooded;
2. medium - high floodplains are flooded, sometimes inhabited or technogenically processed (arable land, meadows, vegetable gardens, etc.);
3. strong - terraces with buildings located on them, communications, etc. are flooded, evacuation of the population is often required, at least partial;
4. catastrophic - vast areas are significantly flooded, including cities and towns; emergency rescue operations and mass evacuation of the population are required.

According to the scale of manifestation, there are 6 categories of floods:
1. The global flood;
2. continental;
3. national;
4. regional;
5. district;
6. local.

Anthropogenic causes of floods:

Direct causes - are associated with the implementation of various hydraulic engineering measures and the destruction of dams.
Indirect - deforestation, drainage of swamps (draining of swamps - natural runoff accumulators increases runoff up to 130 - 160%), industrial and housing development, this leads to a change in the hydrological regime of rivers due to an increase in the surface component of runoff. The infiltrating capacity of soils decreases and the intensity of their washout increases. The total evaporation is reduced due to the cessation of precipitation interception by forest litter and tree crowns. If all forests are reduced, then the maximum runoff can increase up to 300%.
There is a decrease in infiltration due to the growth of waterproof coatings and buildings. The growth of water-resistant coatings in an urbanized area increases floods by 3 times.

Human activities leading to floods:
1. Restriction of the free section of the flow along the channel roads, dams, bridge crossings, which reduces the capacity of the channel and raises the water level.
2. Violation of the natural regime of discharges and water levels, as occurs on the lower Volga as a result of seasonal regulation of the flow by overlying reservoirs: the need for winter energy forced a 2-3-fold increase in water discharges in winter, which, in the presence of ice cover, is accompanied by an increase in water level (winter floods), often higher than in high water.
3. Development of territories in the downstream pools of reservoirs of long-term flow regulation. The economic development of the floodplains increases the maximum runoff.

flood classes

1. Low. They usually do minor damage. They cover small coastal areas. Agricultural lands are flooded by less than 10%. Almost do not knock out the population from the current rhythm of life. Repeatability - 5-10 years.

2. High. Cause significant damage (moral and material). They cover large areas of river valleys. They flood about 10-15% of the land. Violate both household and economic way of life of the population. Partial evacuation of people is very likely. Periodicity - 20-25 years.

3. Outstanding. They cause great material damage, covering river basins. Approximately 50-70% of agricultural land, as well as a certain part of settlements, is under water. Outstanding floods not only disrupt the way of life, but also paralyze economic activity. It is necessary to evacuate material assets and the population from the disaster zone and protect the main objects of economic importance. Repeatability - 50-100 years.

4. Catastrophic. They cause huge material damage, spreading over vast territories within one or more river systems. Lead to human casualties. More than 70% of the land is flooded, many settlements, utilities and industrial enterprises. Industrial and economic activity is completely paralyzed, and the way of life of the population is changing. Periodicity - 100-200 years.

Danger factors:

1. height of water level change;
2. the rate of its change;
3. the duration of the rise period;
4. accompanying phenomena (wind, landslides, soil erosion, turbulent streams, destruction of agricultural products, livestock, death of people, etc.).

The flow of water as a damaging factor

Characteristics of the water flow as a damaging factor:

1. The highest water level.

2. The highest water consumption.

3. The speed of the current.

4. Area of ​​flooding.

5. Repeatability of the value of the highest water level.

6. Duration of flooding.

7. Water temperature.

8. Security of the highest water level.

9. Time of start of the disaster.

10. The rate of rise in the water level during the entire time of the flood.

11. The depth of flooding of the territory in the area under consideration.

Damaging factors:

The combined effect of waves, wind, rainfall causes flooding of the area. This is accompanied by a significant erosion of the coast, leads to the destruction of buildings and structures, the erosion of railways and roads, accidents on utility networks, the destruction of crops and other vegetation, casualties among the population and the death of domestic animals and natural ecosystems. After the water falls, buildings and land sag, landslides and landslides begin.

Flood consequences:

The main features of the environment arising from such natural disasters are: the rapid increase in the strength of the damaging factors, the difficulty of access to the victims, the destructive nature of the situation, the low survival rates of the victims, as well as the presence of complex weather conditions(mudflows, ice drift, heavy rains, etc.).

The amount of damage depends on:
1. - lifting heights;
2. - speed of water level rise;
3. - areas of flooding;
4. - timeliness of the forecast;
5. - availability and condition of protective structures;
6. - the degree of population and agricultural development of the river valley;
7. - the duration of standing flood waters;
8. - the frequency of floods (with repeated rises in the water level, the damage is less than with the initial one).

The passage of floods (flooding of agricultural land) after harvesting leads to less damage than before harvesting.
The severity of emergencies during channel floods depends not so much on the absolute value of the rise in the water level, but on its value relative to the altitude of settlements.

How to prepare for a flood?

If your area often suffers from floods, study and remember the boundaries of possible flooding, as well as elevated, rarely flooded places located in close proximity to places of residence, the shortest routes to them. Familiarize family members with the rules of conduct during organized and individual evacuations, as well as in the event of a sudden and rapidly developing flood. Remember the places where boats, rafts and building materials for their manufacture are stored. Prepare in advance a list of documents, property and medicines taken out during the evacuation. Put valuables, necessary warm clothes, a supply of food, water and medicines in a special suitcase or backpack.

HOW TO PROCEED DURING A FLOOD

At the warning signal of the threat of flooding and evacuation, immediately, in accordance with the established procedure, leave (leave) the danger zone of possible catastrophic flooding to the designated safe area or to elevated areas of the area, taking with you documents, valuables, necessary things and a two-day supply of non-perishable food. Register at the final evacuation point.

Before leaving the house, turn off the electricity and gas, put out the fire in the heating stoves, secure all floating objects that are outside the buildings, or place them in utility rooms. If time permits, move valuable household items to the upper floors or to the attic of a residential building. Close the windows and doors, if necessary and have time, board the windows and doors of the first floors from the outside with boards (shields). In the absence of an organized evacuation, stay on the upper floors and roofs of buildings, on trees or other towering objects until help arrives or the water subsides. At the same time, constantly give a distress signal: during the day - by hanging or waving a clearly visible panel lined with a pole, and in the dark - by a light signal and periodically by voice. When the rescuers approach, calmly, without panic and fuss, in compliance with the precautionary measures, go to the swimming facility. At the same time, strictly follow the requirements of the rescuers, do not overload the boats. During the movement, do not leave the assigned places, do not board the sides, strictly follow the requirements of the crew. It is recommended to get out of the flooded area on your own only if there are such serious reasons as the need to provide medical assistance to the victims, the continuing rise in the water level with the threat of flooding of the upper floors (attic). In this case, it is necessary to have a reliable swimming facility and know the direction of movement. During self-advance, do not stop giving a distress signal.

Help people who are swimming in the water and drowning.

IF A MAN DROWNS

Throw a floating object to a drowning person, encourage him, call for help. When reaching the victim by swimming, consider the course of the river. If the drowning person does not control his actions, swim up to him from behind and, grabbing him by the hair, tow him to the shore.

HOW TO ACT AFTER A FLOOD

Before entering a building, check to see if it is in danger of collapsing or falling.

Ventilate the building (to remove accumulated gases). Do not turn on electric lighting, do not use open flames, do not light matches until the room is completely ventilated and the gas supply system is checked for proper operation. Check the serviceability of the electrical wiring, gas supply pipelines, water supply and sewerage. Do not use them until you have verified that they are working properly with the help of specialists. To dry the premises, open all doors and windows, remove dirt from the floor and walls, pump out water from the basements. Do not eat food that has been in contact with water. Organize the cleaning of wells from the applied dirt and remove water from them.

5.1. Flood - this is a temporary flooding of a vast territory as a result of a rise in the water level in a river, lake, or sea. Floods occur as a result of intense melting of snow (glaciers), heavy rainfall, traffic jams and ice dams, destruction of hydraulic structures, and tsunamis.

Congestion- this is the accumulation of ice in the riverbed, limiting its flow, as a result, the water rises and spills. The jam is formed during ice drift and consists of large and small ice floes.

Zazhor- this is the clogging of the riverbed with internal ice under a fixed ice cover and the formation of an ice plug. Ice dams form in rivers during the formation of the ice cover.

high water- a relatively long-term increase in the flow of rivers, which is repeated annually in the same season, accompanied by an increase in the water level. May cause flooding.

high water- relatively short-term and non-periodic water level rise. Floods following one after another can lead to floods.

Surge floods arise under the influence of powerful cyclones, when the wind reaches high speed and creates a huge surge wave that blocks the flow of rivers and the natural discharge of water into the sea. Encountering such an obstacle, the water in the river rises sharply and can flood a significant area of ​​the adjacent territory. Surge floods often occur in St. Petersburg, Holland, and England.

Flooding is the most common natural hazard, the damage from which annually amounts to hundreds of millions of rubles in Russia.

Today, most floods are predictable, which allows timely preparatory work. The main methods of flood control are the construction of enclosing dams and reservoirs, the diversion of water into the channels of other rivers and reservoirs, and the carrying out of bank and dredging works.

Those who live in areas prone to frequent flooding should:

build houses on high foundations;

have a floating facility (boat, raft);

store documents and valuables in an accessible and safe place;

stock up on food and medicine.

Actions during a flood:

Before leaving the house, everything that water can spoil should be transferred to the upper floors or other non-flooded places; turn off gas and electricity. Then, taking with you the documents, the most necessary things, a small supply of food and water, arrive at the collection point.

Evacuation is carried out to large settlements that are outside the flood zones.

About the sudden onset of flooding, for example, during the destruction of a hydraulic structure, the population is warned by all available technical means. You should go up to the upper floors, and if the house is one-story, take the attic or go to the roof. The evacuation of the population in this case will be carried out on boats, boats, rafts and other floating facilities. During landing on them, strict discipline must be observed. One should go down into the boat one at a time, stepping on the middle of the flooring, and sit down only at the direction of the elder. During the movement of the boat, you can not change places, get on board; The bow of the boat should be kept perpendicular to the wave. After mooring, one of the passengers must go ashore and hold the boat until all people are on land.

If the flood caught you in a field, in a forest, take the most elevated place: climb a tree, etc.

Remember: the search for people in the flooded area is organized immediately. A drowning person is approached in a boat against the current, and lifted from the stern.

Actions after the flood:

° After the water subsides, keep away from torn and sagging electrical wires, damaged gas lines.

Before entering the house, make sure it is secure. Then dry it: pump out water from cellars and cellars; open all windows and doors. Heavily damaged houses are being demolished.

You can use gas, electricity, sewerage only after obtaining permission from the utilities. It is better not to touch electrical wires and sockets until they are completely dry.

Organize the cleaning of wells from the applied dirt and remove water from them. Strictly observe the rules of hygiene in order to prevent outbreaks of epidemics associated with the mass death and decomposition of animals. Do not eat food that has been in contact with water.

5.2. Tsunami- these are giant sea waves resulting from the upward or downward displacement of extended sections of the bottom during strong underwater and coastal earthquakes, less often volcanic eruptions (Fig. 2.2).

The height of the waves in the area of ​​their occurrence is 0.1-5 m, near the coast - up to 40 m, in wedge-shaped bays and river valleys - over 50 m. Tsunamis can spread inland up to 3 km. The main area where tsunamis appear is the coasts of the Pacific and Atlantic oceans (80% of cases), less often the Mediterranean Sea.

Possessing great energy, tsunamis lead to flooding of the area, destruction of buildings and structures, power transmission and communication lines, roads, bridges, as well as to the death of people and animals. Air is propagated in front of the water shaft. shock wave, which acts similarly to a blast wave, destroying buildings and structures.

A natural tsunami warning signal is an earthquake. Before the start of a tsunami, the water recedes far from the coast, exposing the seabed for hundreds of meters or even several kilometers. Low tide can last from a few minutes to half an hour. The movement of the waves is accompanied by thunderous sounds (they are heard before the approach of the tsunami waves). Before the tsunami, the behavior of animals also changes.

Actions during a tsunami:

Leave the room immediately, after turning off the electricity and gas.

In the shortest way, move to an elevated place 30-40 m above sea level or at a distance of 2-3 km from the coast.

If you are driving, drive in a safe direction, picking up running people along the way.

Once in the water, get rid of shoes and wet clothes, try to catch on floating objects (be careful - the wave can carry large objects and their fragments with it).

Before entering the house after the tsunami, check its strength, the safety of the doors, the condition of the electric lighting, and the absence of gas leaks in the room.

There is no reliable protection against a tsunami. Important for the protection of the population from tsunamis are warning services about the approach of waves, based on the advance registration of earthquakes by coastal seismographs. Tsunamis are not dangerous for ships on the high seas.