Flood and tsunami announcement. Tsunami

"Tsunami" means "wave in the harbor" in Japanese. This is a fairly accurate transfer of the essence of this phenomenon.

Away from the coast, in the open ocean, tsunamis are invisible. And as we know them, the waves become near the coast and in the harbors.

Let's look at what a tsunami is, what are the causes of a tsunami and their consequences?

In most cases (about 85%), tsunamis are caused by vertical displacements of the seabed at . At the same time, the underthrust (subduction) of one lithospheric plate under the other causes a sudden rise of the latter, and with it the rise of huge masses of water.

Surface waves diverge from the place of uplift. They reach the nearest coasts and are called local tsunamis. These waves can reach a height of 30 meters and cause great destruction on the coast near the epicenter of the earthquake.

But the uplift of the sea floor generates a series of underwater waves similar in nature to sound or shock waves.

They spread in the water column from the surface to the bottom of the ocean at a speed of 600-800 km/h. When such waves approach distant shores, their energy is concentrated due to a decrease in depth. There are surface waves, which fall on the shore. These tsunamis are called remote.

Such waves are capable of crossing the Pacific Ocean from Chile to Japan at a speed of 200 m/s in 22-23 hours.

In the ocean, due to its length of 200-300 km and a height of only 0.5 meters, they are not noticeable from the surface of the water and from the air.

Another cause of tsunamis is landslides above or below the water level. Such waves occur in 7% of cases and have local meaning. But their height at the same time can reach more than 20 meters and cause corresponding destruction. And under certain conditions, such as during the earthquake in Alaska and the landslide in Lituya Bay in 1958, the wave that reached the opposite shore of the bay had a height of 524 meters.

Approximately 5% of tsunamis are caused by volcanic eruptions. A classic example is the explosion of the Krakatoa volcano near the island of Java in 1883. The resulting waves caused the death of 36,000 people, and their effect was felt in all the harbors of the world.

In addition to the death of people, tsunamis cause flooding of significant coastal areas and soil salinization, destruction of buildings and structures, soil erosion, damage to ships moored near the coast.

To reduce the damage from the consequences of the tsunami, construction should be carried out outside the zone of their impact. If this is not possible, build buildings so that they take the blows of their short side, or place them on strong columns. In this case, the wave will pass freely under the building without damaging it.

If there is a threat of a tsunami, ships moored near the coast must be taken out to sea.

Unfortunately, there are few of them. This is, first of all, an earthquake, even if it is weak. We cannot know where it happened, on land or under the seabed, how powerful it is, and whether it caused a tsunami. Therefore, being on the seashore, any earthquake should be considered a tsunami harbinger.

In some cases, before the arrival of the tsunami, atypical, untimely low tides are observed lasting from several minutes to half an hour.

The occurrence of such a low tide after an earthquake should alert. (a photo)

Eyewitnesses often note the atypical behavior of animals that show concern, try to leave the coastal strip and, allegedly, climb to elevated places.

The combination of all the listed tsunami harbingers should not be in doubt, and the only correct action in this situation is to take rescue measures.

What to do in the event of a tsunami.

Areas along the coast, sea bays, harbors, the height of which does not exceed 15 meters above sea level, are considered to be tsunami hazardous. And if local tsunamis are expected, then areas with a height of less than 30 meters.

Being in such areas, you should think over in advance the sequence of your actions in case of danger.

Care must be taken to ensure that the documents necessary minimum things and products were always at hand.

Arrange with family members for a rendezvous point after a disaster, consider evacuation routes from a dangerous coastal area, or designate places to escape if evacuation is not possible. It can be local hills or high capital buildings. It is necessary to move to them by the shortest route, avoiding low places. A distance of 2-3 km is considered safe. from the shore.

Remember that when observing tsunami warnings, tremors, or local tsunami warnings, the time to rescue can be measured in minutes.

The occurrence of distant tsunamis is recorded by warning systems and the forecast is reported on radio and television. Such messages are preceded by the sounds of sirens.

It is impossible to predict the number, height of waves, as well as the interval between them. Therefore, after each wave, it is dangerous to approach the shore for 2-3 hours. It is advisable to use the gap between the waves to find the safest place.

Any earthquake felt on the seashore should be considered a tsunami hazard.

You can not approach the coast to look at the tsunami. It is believed that if you see a wave and are in a low place, it is too late to save yourself.

Compliance with these simple rules of conduct, knowledge of tsunami precursors could reduce the number of victims of the tsunami in the Indian Ocean in 2004. Indeed, according to eyewitnesses (this can also be seen on the recorded videos), many people used such a tsunami harbinger as the ebb before the arrival of the waves to walk along the seabed and collect marine animals. (a photo)

With the right behavior, the number of people who survived could reach tens of thousands.

Knowing the causes of a tsunami, as well as ways to reduce the damage from the consequences of a tsunami, can one day help you save your life, the lives of your loved ones and property.

Tsunami video. (Japan, Fukushima, 2011 Earthquake of magnitude 6.6 on)

Flood

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 altitude 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. Flooding can occur suddenly and last from a few hours to 2 to 3 weeks.

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 the immediate vicinity of 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 act 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 the back 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 cloth lined with a pole, and in dark time- light signal and periodically 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 person drowns. Throw a floating object to a drowning person, encourage him, call for help. When swimming to the victim, take into account 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.

What to do 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 use food products that have been in contact with water. Organize the cleaning of wells from the applied dirt and remove water from them.

Tsunami

A tsunami is a dangerous natural phenomenon, which is a shock ocean waves, resulting mainly from the upward or downward displacement of extended sections of the seabed during submarine and coastal earthquakes. Tsunami-prone areas are the Kuriles, Kamchatka, Sakhalin, Japan, and the Pacific coast. To counteract the tsunami today is impossible.

Having formed in any place, a tsunami can spread at high speed (up to 1000 km/h) over several thousand kilometers, while the height of the tsunami in the area of origin is from 0.1 to 5 meters.

When reaching shallow water, the height of the tsunami increases sharply, reaching a height of 10 to 50 meters. Huge masses of water thrown ashore lead to flooding of the area, destruction of buildings and structures, power transmission and communication lines, roads, bridges, moorings, and death of people and animals.

In front of the tsunami water shaft, an air shock wave is also formed near the coast. It acts like a blast wave, destroying buildings and structures.

The tsunami wave may not be the only one. Very often it is a series of waves rolling ashore with an interval of 1 hour or more. The possible scale of destruction is determined by the range of the tsunami: weak (1-2 points); average (3 points); strong (4 points); destructive (5 points).

Signs of a tsunami

An earthquake is a natural tsunami warning signal. Before the start of a tsunami, as a rule, the water recedes far from the coast, exposing the seabed for hundreds of meters and even several kilometers. This low tide can last from a few minutes to half an hour.

The movement of a tsunami may be accompanied by thunderous sounds that are heard before the arrival of the tsunami waves. Sometimes, before a tsunami wave, the coast is flooded with a water "carpet". The appearance of cracks in the ice cover off the coast is possible. A sign of an approaching natural disaster may be a change normal behavior animals that sense danger in advance and seek to move to elevated places.

Precautionary measures before the tsunami

Follow the tsunami forecast messages, remembering their harbingers. Memorize and explain to your family the tsunami warning signals for your area. Plan ahead for what to do during a tsunami. Make sure that all your family members, co-workers and acquaintances know what to do during a tsunami. Assess if your home or place of work is located in the area possible action tsunami.

Remember that the most dangerous places- narrow mouths of rivers, narrowing bays, straits, where the tsunami wave rises even higher. Know the boundaries of the most dangerous areas and the shortest routes to safety. Make a list of documents, property and medicines taken out during the evacuation. It is advisable to put property and medicines in a special suitcase or backpack. Think about the evacuation order in advance.

Decide where your family members will meet if there is a tsunami alert. In the course of daily activities at home and at work, do not clutter the corridors and exits with bulky things, closets, bicycles, strollers. Keep all aisles clear for quick evacuation. Learn the rules of conduct in case of a tsunami hazard.

Think over the sequence of your actions if you find yourself indoors during a tsunami, on open area, in water. Prepare a place in your apartment in advance, in which, in case of a quick evacuation, put the necessary documents, clothes, personal belongings, a two-day supply of non-perishable food.

Support public tsunami preparedness programs, actively participate in planting windbreaks along the coast. Keep up the effort local authorities to strengthen the bays with breakwaters and coastal dams.

What to do during a tsunami

When a tsunami warning is given, react immediately. Use every minute to ensure your personal safety and the protection of those around you. You can have time from a few minutes to half an hour or more, so if you act calmly and thoughtfully, you can increase your chances of being protected from the effects of a tsunami.

If you are indoors, immediately leave it, after turning off the light and gas, and move to a safe place. Take the shortest route to an elevated place 30-40 m above sea level or quickly move 2-3 km from the coast. If you are driving, drive in a safe direction, picking up running people along the way. If it is impossible to hide in a safe place, when there is no time left for moving, climb as high as possible to the upper floors of the building, close windows and doors. If possible, move to the most secure building.

If you take shelter indoors, remember that the safest areas are places near the main internal walls, near the columns, in the corners formed by the main walls. Remove nearby objects that may fall, especially glass ones. If you do find yourself outdoors, try to climb a tree or take cover in a place that is less prone to impact. In extreme cases, it is necessary to cling to a tree trunk or a solid barrier.

Once in the water, get rid of shoes and wet clothes, try to catch on objects floating on the water. Be careful, as the wave can carry with it large items and their debris. After the arrival of the first wave, prepare for a meeting with the second and subsequent waves, and if possible, leave the dangerous area. If necessary, provide the first medical care injured.

What to do after a tsunami

Wait for the alarm signal. On the former place return after making sure that there were no high waves on the sea for two to three hours.

Report the state of your home to the emergency commission. Be actively involved in the team to carry out rescue and other emergency work in damaged buildings, search for victims and provide them with necessary assistance.

I will add from myself. We will not describe in detail the mechanism of tsunami formation here - this is the topic of a separate article. Unfortunately, deliberately unscientific explanations are being circulated on the Internet and the media that a tsunami is supposedly just "very large and very powerful wave after an earthquake", etc. This point of view is fundamentally wrong. Briefly, we can say that a tsunami is a water oceanic shock wave embodied in a real nightmare. The mathematical model of tsunami behavior is described by approximations of delta functions and special Neumann functions.

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INTRODUCTION

In the modern world, there is an acute problem of protecting the population from catastrophic situations, which are associated with both material losses as well as human sacrifice. Such situations include, in particular, such natural disasters as floods, tsunamis and typhoons.

1. FLOOD

Flooding - flooding of the area as a result of a rise in the water level in rivers, lakes, seas due to rain, rapid snowmelt, wind surge of water on the coast and other causes, which damages people's health and even leads to their death, and also causes material damage.

In terms of frequency, distribution area and total average annual material damage, floods in the territory of the Russian Federation rank first 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.

1.1 Flood classification

Depending on the causing causes, floods can be divided into the following types:

High water - a periodically recurring relatively long rise in the water level in rivers, usually caused by spring snowmelt on the plains or rainfall, as well as spring-summer snowmelt in the mountains; its consequence is the flooding of low areas of the terrain.

Flood - an intense periodic, relatively short-term rise in the water level in the river, caused by heavy rains, downpours, sometimes rapid snowmelt during winter thaws. Congestion - a heap of ice floes during the spring ice drift in the narrowings and bends of the river channel, hampering the flow and causing a rise in the water level in the place of ice accumulation and in some areas above it.

Zazhor - an accumulation of loose ice material during freeze-up (at the beginning of winter) in the narrowings and bends of the river channel, causing the water level to rise in some areas above it.

Wind surge is a rise in the water level caused by the action of wind on water surface, which usually occurs in the sea mouths of large rivers, as well as on the windward shore of large lakes, reservoirs and seas.

Dam burst flooding is an intense, usually significant rise in the water level in a river (watercourse) caused by a burst of a dam, dam, or natural barrier in mountainous areas during landslides, rock falls, the movement of glaciers and other extreme events.

Floods caused by underwater earthquakes, eruptions of underwater or island volcanoes occur relatively rarely. They are observed mainly on the coasts of the seas and oceans, in areas of active seismic activity.

Classification by scale of manifestation

global flood

Continental

National

Regional

District

Classification of floods depending on the scale of distribution and frequency

Low floods. 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. Repeatability 5-10 years

Dangerous floods. 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. Repeatability 20-25 years.

Particularly dangerous floods. They cause great material damage, covering entire river basins. Flood about 50-70% of agricultural land, some settlements. They paralyze economic activity and drastically disrupt the way of life of the population. They lead to the need for mass evacuation of the population and material values from the flood zone and the protection of the most important economic facilities. Repeatability 50-100 years.

catastrophic floods. They cause enormous material damage and lead to the death of people, covering vast territories within one or more river systems. More than 70% of agricultural land, many settlements, industrial enterprises and utilities are flooded. Economic and industrial activity is completely paralyzed, temporarily changes way of life population. Repeatability 100-200 years.

1.2 Causes of floods

The main causes of flooding are:

Spring-summer melting of snow and glaciers in the catchment areas. Such floods are amenable to forecasting by seasons, and based on snow reserves - approximately also in height and duration. It should be borne in mind that the correlation between snow reserves and the height of the flood is not so high. With relatively small snow reserves, a friendly spring can lead to a large flood, as was the case on the river. Lower Tunguska in 1955. The condition of the underlying rocks (frozen or not) on which the snow cover is located is also of importance. And vice versa, with large snow reserves, but not frozen soils and extended spring, when frosts alternate with thaws, the snow on the watersheds "rots" to a large extent, not giving runoff. In case of floods from floods, it is most correct to refrain from developing territories subject to flooding more often than 1 time in 20-50 years; it is possible to create reservoirs upstream of flooded areas in order to cut the peaks of floods. However, it should be taken into account that the hydraulic resistance decreases, leading to the spreading of the flood wave *; in the zones of backwater wedging out, the level will increase constantly in time due to the deposition of sediments, and also periodically rise during ice jams during the spring opening of the river. In some cases, it is necessary to go to the resettlement of people and the transfer of economic facilities.

Shower rains. Here, in the sense of the forecast, we can only talk about the flood season, and in the order of a short-term warning - about calendar dates, approximately - about the duration and height of the expected rise in the level. In the climatic conditions of Russia, such level rises are widespread in the monsoons of the Far East, in the southwest European territory countries, rivers of the Black Sea coast of the Caucasus, etc. It should be noted the peculiarity of the Caucasian rivers, high floods on which can be observed at any time of the year. Measures to minimize damage here are generally similar to those discussed above. In mountainous mudflow-prone areas, floods may be accompanied by movement along river valleys products of water erosion, as well as bottom sediments. But mudflows are an independent problem, which we do not consider now.

Wind surges of water; appear on the coasts of reservoirs and in the lower reaches of the rivers flowing into these reservoirs. In terms of timing, they are not amenable to foreseeing; in some cases, we can talk about seasons when surges are generally observed more often and have great height. In general, we can only talk about probabilistic description the height and duration of surges of water, which can vary greatly in different parts of the coast. The processing of published materials on surges is hampered by the fact that reference publications usually provide data for a single year highest promotion level; as a result, data on high surges, which turned out to be not the highest in their year, drop out of processing. It should be noted that surge statistics have not been developed in sufficient detail: confident ideas about the type of probability distribution have not yet been formed, as well as about numerical parameters that cannot be sampled. On the coasts of the marginal seas, one has to reckon with the joint manifestation of surge and tidal level rises.

Congestion during the spring breakup of the ice cover. They are caused by heaps of ice with partial or almost complete overlapping of the free flow section, which entails an increase in the water level: major rivers, flowing from south to north, the height of jammed level rises can exceed 10 m. The duration of jammed floods can vary in a wide range - from several hours to 10-15 days. Bomb attacks on ice accumulations are not always effective, and timely short-term resettlement of people from areas of possible flooding is often required. One feature of powerful traffic jams should be noted: when the traffic jam breaks, powerful masses “cut off” the centers, small islands, and cut the banks of the rivers.

Congestion. Unlike ice jams, they form at the beginning of winter during the formation of an ice cover by clogging the under-ice space with sludge. The duration of the sludge formation period is related to the flow velocity; mountain rivers sometimes do not freeze all winter, being a kind of sludge factory. An effective way to reduce the ice material that forms ice jams is to create a backwater regime in the relevant areas to reduce the flow rate and freeze formation, which stops the formation of sludge.

Sedimentation at the exit of rivers from the foothill areas to the plains with a decrease in the flow rate and the transporting capacity of the flow; the channel at the same time grows, being higher than the surrounding area and from time to time "falling" to the side. The creation of dike dams to prevent such floods of water leads to an acceleration of the growth of the channel, since the strip of sediment deposits remains narrower than during a flood. The river can be up to 8-10 m higher than the surrounding area, which makes the task of maintaining dams difficult and exacerbates the consequences of dam failure. Such is the situation on the Huang He and, to a lesser extent, on the Kura and Terek. Compound protective measures includes: afforestation and terracing of the catchment area to reduce the erosion processes that feed the river with sediment, the creation of sediment-retaining reservoirs and flow regulation aimed at reducing flow rates and the erosion effect of river flow on protective dams.

Fluctuations in the level of drainless water bodies as a result of disturbances in the water balance under the influence of the variability of its components, as is the case, for example, in the Caspian Sea, where the amplitude of the corresponding long-term fluctuations in the level exceeds 3 m. In this situation, one should refrain from developing territories subject to even rare floods or flooding. Otherwise, there is a need for protective structures and resettlement of people. This happened in the Caspian Sea, where in the process of a long 40-year decrease in the level from ~ 26 m abs. up to ~28.5 m abs. vast areas (about 40 thousand km2) dried up only on the seashore; in addition, the drying appeared along the hydrographic network of river deltas, primarily in the Volga delta. Creeping development of drained lands has begun

Flooding caused by underwater earthquakes. They are characterized by the appearance of giant waves of great length - tsunamis (in Japanese - " a big wave in the harbour). Tsunami propagation speed up to 1000 km/h. The height of the wave in the area of its occurrence does not exceed 5 m. huge force crashing on the coast. At flat coasts, the wave height does not exceed 6 m, and in narrow bays it reaches 50 m ( tunnel effect). The duration of a tsunami is up to 3 hours, and the coastline affected by them reaches a length of 1000 km. In 1952, the waves almost washed away Yuzhno-Kurilsk.

In various regions of the globe, the causes of flooding depend on the specifics of natural conditions. For example, in most areas, floods are caused by prolonged, intense rain and downpours resulting from the passage of cyclones. Floods on the rivers of the Northern Hemisphere also occur due to the rapid melting of snow, ice jams, ice jams. Foothills and high-mountain valleys are exposed to floods associated with outbursts of intraglacial and dammed lakes. In coastal areas, strong winds surge floods are not uncommon, and during underwater earthquakes and volcanic eruptions, floods caused by tsunami waves.

AT recent centuries, especially in the twentieth century, all big role in frequency increase and destructive power floods are played by anthropogenic factors.

Anthropogenic causes of floods can be divided into two types:

Direct causes - associated with the implementation of various hydrotechnical measures and the destruction of dams: improper implementation of flood protection measures leading to a breakthrough of embankment dams, destruction of artificial dams, emergency drawdown of reservoirs, etc.

indirect reasons. Among them, first of all, it is necessary to name deforestation (maximum surface runoff increases by 250-300%), irrational agriculture (as a result of a decrease in the infiltration properties of soils, according to some calculations in central regions In Russia, from the 9th to the 20th century, surface runoff increased 4 times and the intensity of floods increased sharply). A significant contribution to the increase in the intensity of floods and floods was made by: longitudinal plowing of slopes, overconsolidation of fields when using heavy equipment, overwatering as a result of violation of irrigation norms. The average flood discharge in urban areas has approximately tripled due to the growth of impermeable coatings and development. A significant increase in the maximum flow is associated with the economic development of floodplains, which are natural flow regulators. During the construction of roads, dams, the free section of the flow is constrained, which reduces throughput channels and raises the water level.

1.3 Flood consequences

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

* the number of people who find themselves in a zone prone to floods (here they 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;

* length of iron and highways, power lines, communication and communication lines caught in the flood zone;

* the number of bridges and tunnels flooded, destroyed and damaged as a result of 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.

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 facilities for this, as well as complex weather(heavy rains, ice drift, mudflows, etc.).

Direct damage includes death, hypothermia and injuries to people, damage and destruction of residential and industrial buildings, roads, power lines and communications, death of livestock and crops, destruction and damage to raw materials, fuel, food, feed and fertilizers, costs for temporary evacuation of the population, destruction of the fertile soil layer. In this case, the death of people may be the result of drowning, severe injuries and hypothermia (Table 1); hypothermia can also be the cause of many diseases, injuries can be caused by heavy floating objects or occur from hitting obstacles when moving in a fast stream.

The secondary consequences of floods are the loss of strength of various kinds of structures as a result of erosion and washing, the transfer of water from the damaged harmful substances and pollution of vast territories by them, complication of the sanitary and epidemic situation, swamping of the area, as well as landslides, landslides, the cost of acquiring and delivering food, feed and necessary material resources, reduction in production due to flooding of enterprises, deterioration in the living conditions of the population, the impossibility of rational use of territories in the flood zone, accidents in transport and industrial facilities. The magnitude of the consequences of flooding depends on the duration of dangerous water levels, the speed of the water flow, the area of flooding, the season, population density and intensity economic activity in flooded areas, the presence of protective hydraulic structures and specific flood preparation measures, the level of preparation and organization for actions in flood conditions of the management staff, personnel of enterprises and organizations, emergency rescue forces. In a generalized form, the consequences of the flood are expressed through indicators of material and financial damage. Losses among the population are estimated by the number of dead, injured, missing.

1.4 Flood protection measures, flood rescue

Floods in most cases are available for forecasting, which helps to prevent mass casualties among the population and reduce damage. For forecasting is used hydrological forecast- science-based prediction of the development, nature and extent of floods. The forecast also indicates approximately the time of the onset of any element of the expected regime, for example, the opening or freezing of the river, the expected maximum flood, the possible duration of high water levels, the likelihood of ice jam, and more.
Forecasts are divided into short-term - up to 10-12 days and long-term - up to 2-3 months or more. They can be local (for individual sections of rivers and reservoirs) or territorial, containing information generalized over a large area on the expected size and timing of the phenomenon. Many years of experience have shown that material damage from floods is significantly reduced in the presence of a forecast, a well-established information and warning service, and high organization and education of the population. Unfortunately, even today, not all people living in the zone of potential flooding treat forecasts with due attention.

Important flood protection measures are:

Reducing the maximum water flow by redistributing the flow over time;

Flood flow regulation with the help of reservoirs;

River straightening:

Construction of enclosing dams (shafts);

Carrying out bank protection and dredging works, filling low places;

Plowing land across slopes and planting windbreaks in river basins;

Terracing of slopes, preservation of tree and shrub vegetation.

Flood prevention measures:

1. During the economic development of flood-prone territories, both in river valleys and on sea coasts detailed economic and environmental studies should be carried out. Their goal is to identify ways to obtain the maximum possible economic effect from the development of these territories and, at the same time, to minimize possible damage from floods.

2. When developing flood control measures in river valleys, the entire watershed should be considered, and not its individual sections, since local flood control measures that do not take into account the entire flood situation in the river valley can not only not give an economic effect, but also significantly worsen the situation as a whole. and result in more flood damage.

3. It is necessary to skillfully combine engineering methods protection with non-engineering. First of all, these include: restriction or complete prohibition of such types of economic activity, as a result of which floods may increase (forest harvesting, etc.), as well as the expansion of measures aimed at creating conditions leading to a decrease in runoff. In addition, in flood-prone areas, only such types of economic activity should be carried out, which, if flooded, will cause the least damage.

4. Engineering structures for the protection of lands and economic facilities must be reliable, and their implementation must be associated with minimal disturbance to the natural environment.

5. A clear zoning and mapping of floodplains should be carried out with drawing the boundaries of floods of various probability. Taking into account the type economic use territory, it is recommended to allocate zones with 20% flood security (for agricultural land), 5% security (for buildings in rural areas), 1% security for urban areas and 0.3% security for railways. It goes without saying that in different natural zones and ecological areas the number of zones and the principles of their allocation may change to some extent.

6. The country should have a well-functioning system for forecasting floods and for notifying the population about the time of the onset of the flood, about the maximum possible levels of its level and duration. Flood forecasting should be carried out on the basis of the development of a wide, well-equipped modern appliances monitoring services for hydrometeorological conditions.

7. Importance should be given to early informing the population about the possibility of flooding, explaining its likely consequences and measures to be taken in case of flooding of buildings and structures. To this end, television, radio and other media should be widely used. Flood knowledge should be widely promoted in flood-prone areas. All state structures, as well as each resident, must clearly understand what they should do before, during and after the flood.

8. It is very important to develop and further improve methods for calculating both direct and indirect damage from floods.

9. Regulation of the use of flood-prone areas should be the prerogative of the republics, territories, regions, districts and cities. The state can direct and stimulate their activities only by adopting certain laws on the regulation of land use.

10. The system of flood protection measures should include both state and public organizations as well as private individuals. Successful work such a system should be coordinated and directed central authority at the federal level.

11. The best tool for regulating land use in flood prone areas may be a flexible flood insurance program that combines both compulsory and voluntary insurance. The main principle of this program should be as follows: in case of adopting a rational type of use of the territory from the standpoint of flood protection, the insured is paid a significantly larger sum insured than if he ignores the relevant recommendations and norms.

12. A set of measures in flood-prone areas, including forecasting, planning and implementation of work, should be carried out before the onset of a flood, during its passage and after the end of a natural disaster.

main goal rescue and other urgent work in flood conditions are 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 a systematic, advance preparation command and control bodies and troops civil defense, search and rescue formations and services to conduct emergency rescue operations; quick response to the occurrence of a natural disaster, alerting and deploying the necessary forces and means, organizing effective reconnaissance and deploying 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;

* provision of first aid to victims;

* evacuation of victims from the danger zone.

Immediate emergency response to floods includes:

* strengthening (construction) of protecting dams and ramparts;

* construction of drainage channels;

* elimination of congestion and congestion;

* equipment of berths for life-saving equipment;

* protection and restoration of road constructions;

* 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 territory 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.

1.5 Flood rules

Flooding is one of the major natural disasters. The actions of the population during floods are carried out taking into account the time of anticipation of the flood, as well as the experience of observing the manifestation of this element in past years.

With a significant time to prevent flooding, measures are taken to erect appropriate hydraulic structures on rivers and other places of expected flooding, to prepare and carry out early evacuation of the population and farm animals, and to remove material assets from areas of possible flooding.

Flood evacuation is usually announced by special order of the emergency commission.

The population of flooded areas is informed about the beginning and procedure for evacuation via local radio broadcasting networks and television; workers, in addition, are notified through the administration of enterprises, institutions and educational institutions, and the population not employed in the sphere of production and services - through housing maintenance sites and house management. If there is sufficient time, the population from the threatened areas will be evacuated along with their property. To this end, each family should be provided with transport.

At enterprises and institutions, when there is a threat of flooding, the mode of operation changes, and in some cases, work stops. Protection of some part of material assets is sometimes carried out on the spot, for which pits, entrances and window openings of basements and lower floors of buildings are sealed. In areas of possible flooding, schools and preschool children's institutions temporarily stop working.

The suddenness of the flood causes the need for special behavior and actions of the population. If people live on the ground floor and there is a rise in water on the street, it is necessary to leave the apartments, go up to the upper floors, if the house is one-story, take the attic.

The search for people in the flooded area is organized and carried out immediately, for this, crews of swimming facilities and equipment are involved.

During rescue work, it is necessary to show restraint and self-control, strictly comply with all the requirements of the rescuers. Do not overload life-saving equipment, as this threatens the safety of rescued and rescuers.

Once in the water, you should throw off heavy clothes and shoes, look for objects floating nearby and use them until help is received.

When saving a drowning person, you need to help him even if he does not have visible signs life. The fact is that the victim may be in a state clinical death and it can still be saved. Revival can be stopped only if there are clear signs of true, or biological, death.

If your home is in a flood zone.

Turn off gas, water and electricity; put out the fire in the furnaces; transfer to the upper floors and attics, valuable items and things; close the windows and doors, if necessary, upholster the windows and doors of the first floors with boards or plywood.

Until help arrives or the water subsides, stay on the upper floors and roofs or other hills. In order for rescuers to find victims more quickly, it is necessary to hang a white or colored canvas on a high place during daylight hours, and to give light signals in the dark. When the rescuers approached, you need to jump into the boat, you need to get into the helicopter one at a time, without causing a panic.

If an evacuation warning is received:

prepare warm clothes, boots, blankets, money and valuables;

wrap your passport and other documents in a waterproof bag;

collect a three-day supply of food; prepare a first aid kit and medicines that you usually use;

bring toiletries and bed linen.

All things and products are best placed in a backpack, suitcase or bag. You will be told where and how (by special transport or on foot) you should go from the danger zone. At the final point of evacuation you need to register.

2. TSUNAMI

Tsunami is a dangerous natural phenomenon, which is sea waves, arising mainly as a result of the upward or downward displacement of extended sections of the seabed during underwater and coastal earthquakes. Now it is a common international scientific term, it comes from Japanese word, which means "a big wave flooding the bay."

Tsunami waves in the open ocean propagate at speeds up to 1000 kilometers per hour. But there they are very gentle, since the wavelength (the distance between the crests) reaches 100-300 kilometers, and the height from the bottom to the top is only a few meters, and therefore they are not dangerous for navigation. When waves enter shallow water, near the coastline, their speed decreases sharply to 50-100 kilometers per hour, and their height increases. Near the coast, a tsunami can reach several tens of meters. The highest waves, up to 30-40 meters, are formed near steep coasts, in wedge-shaped bays and near capes protruding far into the ocean. Coastal areas with closed bays are less dangerous. Huge masses of water thrown ashore lead to flooding of the area, destruction of buildings and structures, power transmission and communication lines, roads, bridges, piers, as well as to the death of people and animals. An air shock wave propagates in front of the water shaft. It acts like a blast wave, destroying buildings and structures. The tsunami wave may not be the only one. Very often it is a series of waves rolling ashore with an interval of 1 hour or more.

Over 80% of tsunamis originate in the periphery of the Pacific Ocean, including the western slope of the Kuril–Kamchatka Trench.

2.1 Causes of a tsunami

The most common causes of tsunamis include: underwater earthquakes, landslides, volcanic eruptions. Let's consider each of them in more detail.

Underwater earthquake (about 85% of all tsunamis). During an earthquake, underwater vertical movement bottom: part of the bottom goes down, and part of the bottom rises. The surface of the water comes in oscillating motion vertically, trying to return to baseline, -- mean sea level, -- and generates a series of waves. Not every underwater earthquake is accompanied by a tsunami. Tsunamigenic (that is, generating a tsunami wave) is usually an earthquake with a shallow source. The problem of recognizing the tsunamigenicity of an earthquake has not yet been solved, and warning services are guided by the magnitude of the earthquake. The strongest tsunamis are generated in subduction zones (the place where the oceanic crust sinks into the mantle).

Landslides. Tsunamis of this type occur more frequently than was estimated in the 20th century (about 7% of all tsunamis). Often an earthquake causes a landslide and it also generates a wave. On July 9, 1958, as a result of an earthquake in Alaska, a landslide occurred in Lituya Bay. A mass of ice and terrestrial rocks collapsed from a height of 1100 m. A wave formed, reaching a huge height on the opposite shore of the bay. Such cases are very rare and, of course, are not considered as a standard. But much more often underwater landslides occur in river deltas, which are no less dangerous. An earthquake can cause a landslide and, for example, in Indonesia, where shelf sedimentation is very large, landslide tsunamis are especially dangerous, as they occur regularly, causing local waves over 20 meters high. Landslides can generate localized waves, but are unlikely to generate large ocean-wide waves.

Volcanic eruptions (about 5% of all tsunamis). With strong volcanic explosions, calderas are formed, which are instantly filled with water, resulting in a long and low wave. However, during the eruption of an underwater volcano, the formation of powerful tsunami. The classic example is the Krakatoa eruption (when about 36,000 people died from the tsunami). But this case cannot be considered evidence of the tsunamigenicity of volcanic eruptions, since during the eruption of Krakatau several nearby islands sank under the water. The sinking of the islands suggests that during the eruption of Krakatoa, part of the earth's crust sank. And, most likely, it was this rapid lowering of one section of the crust and the rise of another that caused the tsunami during the Krakatoa eruption.

In addition to those discussed above, there are other possible reasons tsunami occurrence: human activity, the fall of a large celestial body. In addition, there are so-called meteorological tsunamis. Let's take a closer look at these reasons.

Human activity. In our age atomic energy man had in his hands a means to cause concussions, previously available only to nature. In 1946, the United States carried out an underwater atomic explosion in a 60 m deep sea lagoon with a TNT equivalent of 20,000 tons. The wave that arose at a distance of 300 m from the explosion rose to a height of 28.6 m, and 6.5 km from the epicenter it still reached 1.8 m. landslides and explosions are always local. If several hydrogen bombs were simultaneously exploded on the ocean floor, along any line, then there would be no theoretical obstacles to the occurrence of a tsunami, such experiments were carried out, but did not lead to any significant results compared to more accessible types of weapons. At present, any underwater testing of atomic weapons is prohibited by a series of international treaties.

The fall of a large celestial body can cause huge tsunami, since, having a huge falling speed (tens of kilometers per second), these bodies also have colossal kinetic energy, and their mass can reach billions of tons. This energy will be transferred to the water, resulting in a wave. According to calculations, the fall of a relatively small asteroid with a diameter of 300-600 meters into the ocean will generate a tsunami many times greater than all known hitherto.

The wind can cause large waves (up to about 20 m), but such waves are not tsunamis, as they are short-term and cannot cause flooding on the coast. However, the formation of meteorological tsunamis (caused by meteorological reasons) is possible with a sharp change in pressure or with the rapid movement of the anomaly atmospheric pressure. This phenomenon is observed in the Balearic Islands and is called rissaga.

2.2 Main characteristics and consequences of the tsunami

A tsunami, like any sea wave, is characterized by the height, length and speed of the waveform.

The height of a sea wave is the vertical distance between the crest of a wave and its bottom. The height of a tsunami wave above its origin in the ocean is 1-5 m.

Wavelength is the horizontal distance between two peaks (crests) of adjacent waves. The wavelength can be 150--300 km.

The speed of movement of a waveform is the linear speed of horizontal movement of some element of the wave, such as a crest. Tsunami propagation speed ranges from 50 to 100 km/h.

The wavelength of a tsunami, its height and propagation speed depend on the depth of the ocean. The greater the depth of the ocean, the greater the wavelength and speed of its propagation, and the smaller the wave height.

The period of a wave is the time interval between the arrival of two successive waves.

The intensity of the tsunami based on the results of the impact on the coast is estimated on a conditional six-point scale:

1 point - the tsunami is very weak, the wave is recorded only by special instruments (seaographs).

2 points - weak tsunami, can flood the flat coast. It is noticed only by experts.

3 points - average tsunami, noted by everyone. The flat coast is flooded, light ships can be washed ashore, port facilities are subjected to minor damage.

4 points - strong tsunami. The coast is flooded. Coastal buildings are damaged, have weak and strong damage. Large sailing and small motor boats are washed ashore and then washed back into the sea. The shores are littered with sand, silt, tree fragments, human casualties are possible.

5 points - very strong tsunami. The coastal areas are flooded. Breakwaters and breakwaters are badly damaged. Large ships washed ashore. The damage is great and internal parts coast. Buildings and structures have strong, medium and weak destruction depending on the distance from the coast. There are high storm surges at river mouths. There are human casualties.

6 points -- catastrophic tsunami. Complete devastation of the coast and coastal areas. The land is flooded for considerable distances inland. Many victims.

The nature of tsunami propagation inland is naturally determined by land relief. Sometimes waves propagate in depth at a distance of up to 1 km and extremely rarely at a distance of up to 2-3 km or more.

In the event that a river flows through a valley that opens into an open bay or a bay that narrows towards land, a large wave will go up this valley during a tsunami, a water shaft will form on the river, and the rising water will flood the valley.

On the open shores of the Pacific Ocean and sandy capes, the height of the tsunami ranges up to 10 m in the coastal strip and drops rapidly as the wave moves inland.

Tsunamis have the strongest impact on sandbars and spits located not high above the ocean level (shoals and sandbars extending from rocky inclined wedge-shaped bays or lying in the depths of such bays; sandy spits separating the open ocean coast from lagoons or river channels, etc. .P.). From such shores, structures can be washed away by tsunamis, and the shores themselves, composed of loose sediments, often slide down and are washed out by new channels.

In bays with narrow entrances (“gates”), tsunamis manifest themselves as a relatively slow and weak rise in the water level.

On the open coasts of the Pacific Ocean, with a flat coastline and sloping sandy shores, with a width of more than 500 m, as well as on wide sandy capes, tsunamis are usually weak and do not spread further than 300-500 m from the coast.

On the western coast of Kamchatka and the Kuril Islands, tsunamis are very weak, since the waves that arise during an earthquake in the Pacific Ocean quickly attenuate when passing through the straits between the islands of the Kuril chain. For the same reasons, Pacific tsunamis are weakly manifested on the coast of the Sea of Okhotsk and the Sea of Japan.

The movement of the waves may be accompanied by thunderous sounds that are heard before the arrival of the tsunami waves. Sometimes, before a tsunami wave, the coast is flooded with a water "carpet". The appearance of cracks in the ice cover off the coast is possible. A sign of an approaching natural disaster may be a change in the usual behavior of animals that sense dangers in advance and tend to move to higher places.

The scale of the consequences of a tsunami depends on the destructive force of the wave, the nature and natural features coasts and coasts, the effectiveness and timeliness of the measures taken to reduce damage.

Tsunamis are especially dangerous for settlements, cities and structures located on low-lying shores ocean, as well as those located at the top of the bays and bays, wide open to the ocean, where tsunamis catch up a large mass water that floods the mouths and valleys of rivers 2-3 km from the sea. Tsunamis can cause large areas to be flooded with seawater.

Primary damaging factors tsunami: wave impact, hydrodynamic pressure, air wave.

Secondary damaging factors of a tsunami: flooding of the area, destruction of buildings and structures, bridges, power lines, throwing ships ashore, death of people and animals, erosion of coasts and soil cover, destruction of agricultural land, soil pollution, destruction and pollution fresh water, the spread of infections, epidemics.

The dangerous consequences of the destructive effects of a tsunami are fires that occur as a result of damage to oil storage facilities, industrial enterprises and sea vessels. Damage to chemically and radiation hazardous facilities, as well as utility systems, can cause chemical or radiation pollution over vast areas.

To the most known cases tsunamis include:

June 15, 1896 in the Sanriku region (Japan). At 8 pm, a mighty hiss and whistle was heard, as if dozens of trains were approaching at full speed. Soon the hiss turned into a roar, and the ocean hit the shore in six or seven waves about 35 m high. The fishermen who were in the ocean near the epicenter did not notice the tsunami due to the small amplitude of the waves over deep water. But when they returned to the port, a picture of terrible destruction appeared before their eyes. Entire villages were leveled to the ground. Almost all the coastal villages and towns of the three provinces, stretching for 800 km, ceased to exist. More than 27,000 people died in the tsunami waves. This catastrophe was included in the Guinness Book of Records as one of the most severe tsunami-related disasters in terms of the number of victims.

On April 14, 1923, a strong earthquake occurred in the Kamchatka Bay. In 15-20 minutes after the ground shaking, a wave approached the top of the bay. On the coast, two fish factories were completely destroyed, buildings on the Dembievskaya Spit and in the village of Ust-Kamchatsk, located closer to the mouth of the Kamchatka River, were damaged, the ice on the river was broken for 7 kilometers. At 50 kilometers southwest of the village, the maximum height of water rise on the coast was observed and was equal to 20-30 meters.

Tsunami in Japan:

On September 1, 1923, a massive earthquake struck the Japanese cities of Tokyo and Yokohama. The earthquake was accompanied by an invasion sea waters. Huge tsunami waves over 10 meters high did what the forces of the Earth, hidden in its bowels, did not do. About a million people lost their homes, 100 thousand people died.

In 1933, a 20-meter giant wave hit the shores of the island of Honshu - higher than a five-story building. Thousands of houses were washed into the sea, sunk and hundreds of ships were wrecked. About 3,000 people died as a result of this intrusion of the waters. Everywhere were traces of a terrible tragedy.

November 5, 1952 On the night of November 5, at about 4:00 local time, the residents of Severo-Kurilsk were awakened by a 7-magnitude earthquake. 45 minutes after the earthquake began, a loud rumble was heard from the ocean, and after a few seconds, a huge wave hit the city, moving at high speed and having the highest height in the central part of the city, where it rolled along the river valley. A few minutes later, the wave receded into the sea, taking with it everything destroyed. After 15-20 minutes, a second, even larger wave, reaching a height of 10 meters, hit the city. It caused especially strong destruction, washing away all the buildings in its path, only the cement foundations of the houses were preserved. The wave that passed through the city reached the slopes of the surrounding mountains, after which it began to roll back into the basin, located closer to the city center. A few minutes after the second wave, a weaker, third wave arrived, which washed a lot of debris ashore. All this was scattered throughout the city and along the banks of the strait. This tsunami covered almost 700 km of the Far East coast. At the same time, the highest waves were noted in the bays of Piratkova (10-15 meters) and Olga (10-13 meters) in Kamchatka.

Crescent City (California, USA) March 1964. The most significant for recent decades A tsunami hit the shores of the Pacific Ocean after the strongest March earthquake in Alaska. In San Francisco Bay, a wave about a meter high was noted at the Golden Gate. Damage caused to the California coast amounted to $10 million. Two seismic sea waves penetrated Crescent City Harbor, while a third and fourth caused destruction in the low-lying areas around the south-facing beach. The third wave splashed over 500 meters ashore, flooding 30 blocks of the city, while one-story wooden houses were seriously damaged or completely destroyed.

June 17, 1998 Papua New Guinea. After 7 p.m., residents felt the earth tremble under their feet. A minute later, a wave 10 meters high hit the coast, flooding coastal zone where about 10,000 people lived. More than 1500 people died.

2.3 Tsunami Prevention

The Tsunami Warning System (TWS) in the Pacific includes 25 states, including Russia, whose coastal areas are affected by tsunamis.

The Far East Tsunami Warning Service is interregional and consists of three regional services: Kamchatka, Sakhalin regions and Primorsky Krai. In the Kamchatka region, tsunami warning is carried out by the tsunami station of the Kamchatka Territorial Administration for Hydrometeorology and Monitoring environment and a seismic station of the Institute of Physics of the Earth, Russian Academy of Sciences.

The Pacific Tsunami Warning Center (TPTC) is located on Hawaiian Islands USA in the city of Honolulu.

When a strong earthquake occurs in the Pacific Ocean, the Pacific Center informs all members of the SOC of the time, coordinates and strength of the earthquake. The first information about the tsunami comes from sea level observation stations located in the immediate vicinity of the earthquake epicenter. If confirmation of the formation of waves is received, then in the case of approach devastating tsunami and to bring operational services to a state of readiness, the TTsPTs transmits a warning.

The tsunami station, after analyzing this information and real threat tsunami in Kamchatka, announces the alarm.

When a strong near earthquake off the coast of Kamchatka and a possible threat of a tsunami, a seismic station announces an alarm and transmits it according to the notification scheme. The tsunami station distributes this message throughout the region, as well as beyond its limits, performs calculations of tsunami parameters (height and time of arrival of waves), analyzes information about the observed height of their waves received from hydrometeorological stations, and transmits an end to the alarm. The tsunami station also transmits information about the height of the waves on the peninsula to the TCPC, on the basis of which the Center makes an assessment of the tsunami hazard for other areas of the Pacific Ocean.

Measures for partial protection against tsunamis include: the creation of artificial coastal structures (hvilioriziv, breakwaters, embankments), planting forest strips along the coast.

2.4 Rules of conduct during a tsunami

When a tsunami warning is given, react immediately. If you are indoors, immediately leave it, after turning off the light and gas, and move to a safe place. Take the shortest route to an elevated place 30-40 m above sea level or quickly move 2-3 km from the coast. If you are driving, drive in a safe direction, picking up running people along the way. If it is impossible to hide in a safe place, when there is no time left for moving, climb as high as possible to the upper floors of the building, close windows and doors. If possible, move to the most secure building. If you take shelter indoors, remember that the safest areas are places near the main internal walls, near the columns, in the corners formed by the main walls. Remove nearby objects that may fall, especially glass ones. If you do find yourself outdoors, try to climb a tree or take cover in a place that is less prone to impact. In extreme cases, it is necessary to cling to a tree trunk or a solid barrier.

Once in the water, get rid of shoes and wet clothes, try to catch on objects floating on the water. Be careful, as the wave can carry large objects and their fragments. After the arrival of the first wave, prepare for a meeting with the second and subsequent waves, and if possible, leave the dangerous area. If necessary, provide first aid to the injured.

Wait for the alarm signal. Return to your original place after making sure that there were no high waves on the sea for two to three hours.

Entering the house, check its strength, the safety of windows and doors. Make sure that there are no cracks in the walls and floors, there is no undermining of foundations. Carefully check the presence of gas leaks in the premises, the condition of the electric lighting.
Report the state of your home to the emergency commission. Actively join the team to carry out rescue and other emergency work in damaged buildings, search for victims and provide them with the necessary assistance.

3. TYPHOONS

Typhoon is the local name for tropical cyclones that occur in the western Pacific Ocean (up to 170 ° E) north of the equator. These are winds with a force of 12 or more points (speed more than 29 m / s), which produce the strongest destruction.

The typhoon moves at a speed of 10-50 km / h to the west and northwest, reaches the shores of Indochina, China, Korea, Japan, reaches the shores of Russia - Primorye, the Kuril Islands and even Kamchatka. Every year, 20-25 typhoons happen on Earth. They last for several days, and sometimes weeks. About 70% of typhoons form between July and October, when the Intertropical Convergence Zone is displaced far into North hemisphere.

No. 10. Flooding on the rivers Po and Arno (Italy, 1966)

This year, heavy rains dragged on for a whole week. The result: a sharp rise in the water level in the rivers, which the protective dams could not withstand. So Florence and Pisa were flooded. For the first it disaster turned out to be the strongest in the last 500 years. It destroyed:

more than 5 thousand residential buildings;
about 6 thousand enterprises;
caused incredible damage to Florence as one of the cultural centers of the world. Including museum exhibits (collections of books, paintings, manuscripts) that were there.

Source: jeffhead.com

No. 9. Flooding on the Dnieper (Ukraine, 1931)

Once nature made fun of our homeland: it gave Ukraine a rainy autumn of 1930, and a record amount of snow in the winter of 1930-31. This led to the fact that in the spring of 1931 there was more water in the Dnieper than usual. Result: the river flooded the territory with a length of 12 km from Mogilev to Zaporozhye, and with it:

many residential buildings;
2 power plants;
several plants and factories (including food factories, which caused additional terms for hunger).

Source: dnepr.com

No. 8. Flooding in the countries of the North Sea (Denmark, Great Britain, Norway, Belgium, Germany, 1953)

In the winter of 1953, a high tide arose in the North Sea caused by a storm. It turned out to be almost 6 meters higher than expected values. Result: The coasts of Denmark, Great Britain, Norway, Belgium and Germany were flooded. The total death toll is about 2500 people.

But European countries distributed among themselves compensation for damages caused by the elements. Thus, the economic damage did not have too catastrophic consequences. Although the Netherlands, as a country that suffered the brunt of the tide, still had a hard time.

Source: exdat.com

No. 7. Flood on the Pacific coast (Thailand, 1983)

And Thailand in 1983 was tortured by monsoon rains. They poured continuously for almost 3 months, which practically paralyzed the country. Result: damage estimated at $500 million. And a considerable number of dead - 10 thousand people. Plus another 100,000 sick people have contracted water-borne infections.

Source: chime.in

No. 6. Flooding on the Pacific coast (Japan, 2011)

An earthquake occurred in the Pacific Ocean, which generated a tsunami in places up to 40.5 meters high. And this element hit the islands of the Japanese archipelago. Miyagi Prefecture got the most:

local communications were cut off;
the airport is flooded;
water washed away and overturned cars and planes, destroyed buildings.

The total death toll from the earthquake and tsunami is 23,000.

Source: www.moimir.org

No. 5. Surge on the Pacific coast (Bangladesh, 1991)

Today Marian - just beautiful name. And in 1991, it was a terrible cyclone for Bangladesh, which raised a wave 7-9 meters high. The elements hit the southeastern coast of the country, took the lives of about 140 thousand people, and wiped out almost a million buildings. Huge damage was done to agriculture:

crops were destroyed on a gigantic territory;
livestock died;
flooding the area with salty sea water made the land unsuitable for agriculture for a long time.

Source: dantri.com.vn

No. 4. Flooding on the coast of the Indian Ocean (Indonesia, India, Thailand, 2004)

2004 is the year when an incredibly powerful underwater earthquake occurred in the Indian Ocean. The result was a tsunami that hit the coasts of Indonesia, Sri Lanka, South India and even Thailand. The number of dead and missing as a result of the cataclysm exceeded 230 thousand people. But the giant wave did not stop there, and after 7 hours it reached Somalia, having overcome almost the entire ocean. There she took the lives of 250 people.

floods

Flooding - is a temporary flooding of a significant part of the land with water as a result of the action of the forces of nature. Flooding, depending on the causes that cause it, can be conditionally divided into 3 groups.

The first includes floods caused by heavy rainfall or intense snowmelt.

Damage national economy cause floods, which are a combination of flood waters with ice drift. An ice drift is usually accompanied by a jam or jams, which, in turn, cause an additional rise in the water level and the flooding of a new territory. In addition, when water breaks through an obstacle, a rapid wave can form, creating a danger sudden flood downstream area.

The second group consists of floods that occur under the influence of surge winds. They are observed on sea coasts and at the mouths of rivers flowing into the sea. The surging wind retains water in the mouth, as a result of which its level in the river rises.

The third group includes floods caused by underwater earthquakes. As a result of underwater earthquakes, giant waves- tsunami. Their propagation speed reaches 400-800 km/h.

Tsunami

Some earthquakes were accompanied by destructive waves that devastated the coast - a tsunami (a large wave flooding the bay). Tsunamis are long waves of a catastrophic nature, arising mainly as a result of tectonic movements on the ocean floor.

The wavelength of a tsunami ranges from 150 to 300 km. In the open sea, tsunamis are not very noticeable: their height is several tens of centimeters or a maximum of several meters. Having reached the shallow shelf, the wave becomes higher, rises and turns into a moving wall. Entering shallow bays, the wave becomes even higher. At the same time, it slows down and, like a giant shaft, rolls onto land. The speed of the tsunami is the higher, the greater the depth of the ocean. Tsunamis are most often caused by underwater earthquakes. Volcanic eruptions can serve as another source.

There is a tsunami intensity scale:

I - the tsunami is very weak, the wave is noted only by tide gauges.

II - weak tsunami, can flood a flat coast.

III - tsunami of medium strength. Flat coasts are flooded, light ships can be washed ashore. Port facilities suffer little damage.

IV - strong tsunami, the coast is flooded, coastal buildings and structures are damaged. Large sailing ships and small motor ones are thrown onto land, and then washed back into the sea. The shores are littered with debris and debris.

V - very strong tsunami, coastal areas are flooded. Larger ships washed ashore. The damage is great. human sacrifice.

VI - catastrophic tsunami, complete devastation of the coast and coastal areas. The land is flooded. The largest ships are damaged. Many victims.