The summer of 2017 was unusually rainy. Fortunately, this year's heavy rainfall is nowhere near the devastating floods that hit Germany and China centuries ago.

1. Petersburg flood, 1824, about 200-600 dead. On November 19, 1824, a flood occurred in St. Petersburg, which killed hundreds of human lives and destroyed many houses. Then the water level in the Neva River and its canals rose by 4.14 - 4.21 meters above the usual level (ordinary).

Petersburg flood of 1824. The author of the picture: Fedor Yakovlevich Alekseev (1753-1824).

Before the flood began, it was raining in the city and the wind was damp and cold wind. And in the evening there was a sharp rise in the water level in the channels, after which almost the entire city was flooded. The flood did not affect only the Foundry, Rozhdestvenskaya and Karetnaya parts of St. Petersburg. As a result, the material damage from the flood amounted to about 15-20 million rubles, and about 200-600 people died. One way or another, this is not the only flood that occurred in St. Petersburg. In total, the city on the Neva was flooded more than 330 times. Commemorative plaques have been erected in memory of many floods in the city (there are more than 20 of them). In particular, a sign is dedicated to the largest flood in the city, which is located at the intersection of the Kadetskaya line and Bolshoy Prospekt of Vasilyevsky Island.

Commemorative plaque on the Raskolnikov House. Interestingly, before the founding of St. Petersburg, the largest flood in the Neva delta occurred in 1691, when this territory was under the control of the Kingdom of Sweden. This incident is mentioned in the Swedish chronicles. According to some reports, that year the water level in the Neva reached 762 centimeters.

2. Flood in China, 1931, about 145 thousand - 4 million dead. From 1928 to 1930, China suffered from a severe drought. But at the end of the winter of 1930, heavy snowstorms began, and in the spring - incessant heavy rains and a thaw, which caused the water level in the Yangtze and Huaihe rivers to rise significantly. For example, in the Yangtze River in July alone, the water rose by 70 cm.

As a result, the river overflowed its banks and soon reached the city of Nanjing, which at that time was the capital of China. Many people drowned and died from infectious diseases waterborne, such as cholera and typhoid. Cases of cannibalism and infanticide among desperate residents are known.

Flood victims, August 1931.

According to Chinese sources, about 145,000 people died as a result of the flood, at the same time, Western sources claim that the death toll was from 3.7 million to 4 million. By the way, this was not the only flood in China caused by the overflowing waters of the Yangtze River. Floods also occurred in 1911 (about 100 thousand people died), in 1935 (about 142 thousand people died), in 1954 (about 30 thousand people died) and in 1998 (3,656 people died).

3. Flooding on the Yellow River, 1887 and 1938, about 900 thousand and 500 thousand dead, respectively. In 1887, heavy rains fell for many days in Henan province, and on September 28, rising water in the Yellow River broke through the dams. Soon the water reached the city of Zhengzhou located in this province, and then spread throughout the northern part of China, which occupies approximately 130,000 km². The floods left about two million people in China homeless and about 900,000 people died. And in 1938, a flood on the same river was provoked by the Nationalist government in Central China at the start of the Sino-Japanese War. This was done in order to stop the Japanese troops advancing rapidly into the central part of China. The flood has subsequently been called "the largest act of environmental warfare in history". So, in June 1938, the Japanese took control of the entire northern part China, and on June 6 they captured Kaifeng, the capital of Henan Province, and threatened to capture Zhengzhou, which was located near the intersection of important railways Beijing-Guangzhou and Lianyungang-Xi'an. If the Japanese army succeeded in doing this, such large Chinese cities as Wuhan and Xi'an would be under threat. In order to prevent this, the Chinese government in Central China decided to open dams on the Yellow River near the city of Zhengzhou. Water flooded the provinces of Henan, Anhui and Jiangsu adjacent to the river.

Soldiers of the National Revolutionary Army during a flood on the Yellow River in 1938. The floods destroyed thousands of square kilometers of agricultural land and many villages. Several million people became refugees. According to China's initial figures, about 800,000 people drowned. However, nowadays researchers studying the archives of the disaster claim that many less people- about 400 - 500 thousand.

Refugees who appeared after the 1983 flood.

Interestingly, the value of this Chinese government strategy has been questioned. Since, according to some reports, the Japanese troops at that time were far from the flooded areas. Although their attack on Zhengzhou was thwarted, the Japanese took Wuhan in October.

4. The flood of St. Felix, 1530, at least 100 thousand dead. On Saturday, November 5, 1530, on the day of St. Felix de Valois, most of Flanders, the historical region of the Netherlands, and the province of Zeeland were washed away. Researchers believe that more than 100 thousand people died. Subsequently, the day when the disaster occurred was called Evil Saturday.

5. The flood of Burchardi, 1634, about 8-15 thousand dead. On the night of October 11/12, 1634, Germany and Denmark were flooded as a result of a storm surge caused by hurricane winds. That night, dykes broke in several places along the coast of the North Sea, flooding the coastal cities and communities of North Frisia.

Painting depicting the Burchardi flood.

According to various estimates, from 8 to 15 thousand people died during the flood.

Maps of North Frisia in 1651 (left) and 1240 (right). Author of both maps: Johannes Mejer.

6. The flood of St. Mary Magdalene, 1342, several thousand. In July 1342, on the feast day of the myrrh-bearing Mary Magdalene (the Catholic and Lutheran churches celebrate it on July 22), the largest recorded flood in Central Europe occurred. On this day, the waters of the rivers Rhine, Mosel, Main, Danube, Weser, Werra, Unstrut, Elbe, Vltava and their tributaries flooded the surrounding lands. Many cities such as Cologne, Mainz, Frankfurt am Main, Würzburg, Regensburg, Passau and Vienna were severely damaged.

According to the researchers of this disaster, after a long hot and dry period, heavy rains followed for several days in a row. As a result, about half of the average annual precipitation fell. And since the extremely dry soil could not quickly absorb such an amount of water, surface runoff flooded large areas of the territories. Many buildings were destroyed and thousands of people died. And although the total number of deaths is unknown, it is believed that about 6 thousand people drowned in the Danube region alone. Besides, summer next year It was wet and cold, so the population was left without a crop and suffered greatly from hunger. And to everything else, the plague pandemic that took place in Asia, Europe, North Africa and the island of Greenland (Black Death) in the middle of the XIV century, reached its peak in 1348-1350, taking the lives of at least a third of the population of Central Europe.

Illustration of the Black Death, 1411.

Late summer 2013 on Far East a powerful flood hit, which led to the very massive flood over the past 115 years. Flooding swept five regions of the Far East federal district, the total area of ​​flooded territories amounted to more than 8 million square kilometers. In total, since the beginning of the flood, 37 municipal districts have been flooded, 235 settlements and more than 13 thousand residential buildings. Over 100 thousand people were affected. More than 23 thousand people were evacuated. The most affected were the Amur Region, which was the first to receive the blow of the elements, the Jewish Autonomous Region and the Khabarovsk Territory.

On the night of July 7, 2012 the flood flooded thousands of residential buildings in the cities of Gelendzhik, Krymsk and Novorossiysk, as well as in a number of villages Krasnodar Territory. Energy, gas and water supply systems, road and rail traffic were disrupted. According to the prosecutor's office, 168 people died, two more were missing. Most of the dead - in Krymsk, which accounted for the most swipe elements. In this city, 153 people died, more than 60 thousand people were recognized as victims. 1.69 thousand houses are recognized as completely destroyed in the Crimean region. About 6.1 thousand houses were damaged. The damage from the flood amounted to about 20 billion rubles.

April 2004 V Kemerovo region there was a flood due to a rise in the level of the local rivers Kondoma, Tom and their tributaries. More than six thousand houses were destroyed, 10 thousand people were injured, nine died. In the city of Tashtagol, located in the flood zone, and the villages closest to it, 37 pedestrian bridges were destroyed by flood waters, 80 kilometers of regional and 20 kilometers of municipal roads were damaged. The element also disrupted telephone communications.
The damage, according to experts, amounted to 700-750 million rubles.

In August 2002 V Krasnodar Territory there was a quick tornado and torrential rains. In Novorossiysk, Anapa, Krymsk and 15 other settlements in the region, more than 7 thousand residential buildings and office buildings fell into the flood zone. The elements also damaged 83 housing and communal services, 20 bridges, 87.5 kilometers highways, 45 water intakes and 19 transformer substations. 424 residential buildings were completely destroyed. 59 people died. By the forces of the Ministry of Emergency Situations hazardous areas 2.37 thousand people were evacuated.

In June 2002 Catastrophic flooding as a result of past heavy rains affected 9 subjects of the Southern Federal District. 377 settlements were in the flood zone. The elements destroyed 13.34 thousand houses, damaged almost 40 thousand residential buildings and 445 educational institutions. The elements claimed the lives of 114 people, another 335 thousand people were injured. Specialists of the Ministry of Emergency Situations, other ministries and departments saved a total of 62 thousand people, more than 106 thousand residents of the Southern Federal District were evacuated from dangerous areas. The damage amounted to 16 billion rubles.

July 7, 2001 in the Irkutsk region due to heavy rains a number of rivers overflowed their banks and flooded seven cities and 13 districts (a total of 63 settlements). Sayansk was especially affected. According to official figures, eight people died, 300 thousand people were injured, 4.64 thousand houses were flooded.

May 2001 The water level in the Lena River exceeded the maximum flood and reached a mark of 20 meters. Already in the first days after the catastrophic flood, 98% of the territory of the city of Lensk was flooded. The flood practically washed Lensk off the face of the earth. More than 3.3 thousand houses were destroyed, 30.8 thousand people were injured. In total, 59 settlements were affected in Yakutia as a result of the flood, 5.2 thousand residential buildings were flooded. The total amount of damage amounted to 7.08 billion rubles, including 6.2 billion rubles in the city of Lensk.

16 and 17 May 1998 in the area of ​​the city of Lensk, Yakutia, there was a severe flood. It was caused by an ice jam along the lower reaches of the Lena River, as a result of which the water level rose to 17 meters, while the critical level of flooding in the city of Lensk was 13.5 meters. More than 172 settlements with a population of 475 thousand people were in the flood zone. More than 50 thousand people were evacuated from the flood zone. The flood killed 15 people. The damage from the flood amounted to 872.5 million rubles.

Edited 08/11/2019

Flooding is flooding certain territory land as a result of a rise in the water level in a river, lake, reservoir or sea, causing material damage to the economy, social sphere and the natural environment.

Causes of floods

snowmelt

Intensive snowmelt, especially when the ground is frozen, can lead to flooding. The strength of such a flood is highly dependent on many factors, so it can be different - from the most insignificant to catastrophic. Most often combined with other factors.

Long rains

Floods due to this most often occur in exceptionally humid regions with high level rainfall, dry regions (deserts and steppes) experience this problem extremely rarely, as well as regions with moderate humidity.

tsunami wave

On the sea coasts and islands, floods can occur after a tsunami, as a result of the flooding of the coastal strip by a wave - formed during earthquakes or volcanic eruptions in the ocean.

Similar floods are not uncommon on the shores of Japan and other Pacific islands.

In lakes and bays, such waves can occur as a result of large landslides.

Bottom lifting

One of the causes of floods is the rise of the bottom. Each river gradually accumulates sediments, in riffles, in estuaries and deltas. Flooding in this case occurs several years after the start of the process, is slow in nature, but easily predictable and eliminated by dredging and cleaning.

Breaking dams or reservoirs

Occurs when a reservoir or dam (including natural ones) located on water body upstream, they can no longer hold back due to some circumstances (for example, earthquakes) a strong pressure of water.

The reason may also be an emergency discharge of water through the reservoir, bypassing the structure, made for some reason (flooding on the reservoir, for example). In this case, the flood turns out to be very powerful, destructive (it demolishes everything in its path in the valley, regardless of weight) and uneven (in terms of destructive power, the flow of water can be stronger than a tsunami wave), but, as a rule, short-term.

Other natural causes

The causes of floods can be: storm surges, surge phenomena, seiches, as well as landslides blocking river beds.

Additional factors

An additional negative factor in the conditions of the city can be the clogging of the rain sewer system, which, in conditions, for example, of heavy rains or active snowmelt, can lead to flooding of entire urban areas.

flood types

high water

High water is a periodically repeating, rather long rise in the water level in rivers. Usually accompanied by the release of water from the channel and the flooding of low areas.

The high water is repeated annually in the same season of the year - a relatively long and significant increase in the water content of the river, causing a rise in its level.

High water can take on a catastrophic character if the infiltration properties of the soil have significantly decreased due to its oversaturation with moisture in autumn and deep freezing in severe winter.

High water is caused by increased prolonged inflow of water, which may be due to:

• spring snowmelt on the plains;
• summer melting of snow and glaciers in the mountains;
• abundant rains.

Floods caused by spring snowmelt are typical for many lowland rivers, which are divided into 2 groups:

• rivers with a predominance of spring runoff (for example, the Volga, the Urals)
• rivers with a predominance of summer flow (for example, Anadyr, Yukon, Mackenzie).

Floods caused by the summer melting of mountain snows and glaciers are typical for rivers Central Asia, Caucasus, Alps.
Floods caused by summer monsoon rains are typical for rivers South-East Asia(Yangtze, Mekong).

high water

Flood - intense and relatively short-term (from an hour to several days) rise in the water level in the river, caused by heavy rains, downpours, sometimes rapid snow melting during thaws.

Unlike floods, floods can be repeated several times a year, at any time of the year.

Flash floods associated with short-term, but very intense downpours, which also occur in winter due to thaws, pose a particular threat.

Resistance to water flow in a riverbed

Congestion

Congestion is the accumulation of ice floes in the riverbed during the spring ice drift, causing constraint water current and the associated rise in water levels.
Congestion usually occurs in the narrowing and bends of rivers, on the shallows and in other places where the passage of ice floes is difficult. Jam floods are characterized by a high and relatively short-term rise in the water level in the river.
As a result of congestion, the water level rises, sometimes causing floods. Usually large congestion occurs in the spring on major rivers flowing from south to north. The opened southern sections of the river in their course are dammed up by the accumulation of ice in the northern regions, which often causes a significant increase in the water level.

The backwater of the water level in the rivers due to clogging of the living section with sludge is called a zazhor.

Zazhor

Zazhor - accumulation of sludge, bottom ice and other types of inland ice in the riverbed during the autumn sludge run and at the beginning of freeze-up, restricting the living section of the stream and leading to backwater (water level rise), decrease bandwidth channel, or openings of the culvert and possible flooding of the coastal sections of the river.

Jam floods are characterized by a significant, but less than during a jam, rise in the water level and a longer duration of the flood.

wind surge

Wind surge is a 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.

Other types of floods

Less common are such types of floods as the spill of water from a reservoir, a reservoir, which is formed when a structure of the pressure front of hydraulic structures (dams, dams, etc.) breaks through, or when water is released from an emergency reservoir, as well as when a natural dam breaks, formed during earthquakes, landslides, landslides, etc.

It is characterized by the formation of a breakthrough wave with subsequent uncontrolled movement of large masses of water, leading to the flooding of large areas and the destruction or damage of buildings (buildings, structures, etc.) encountered on the way of its movement.

This type of flood, however, is very short-lived.

Classification of floods by damage

Low (small)

They are observed mainly on flat rivers. Almost do not break the rhythm of life of the population, but cause minor material damage. The frequency of their repetition is approximately once every 5-10 years.

tall (large)

Cause tangible material damage, cover relatively large land river valleys. Significantly violate the economic and everyday life of the population. May lead to partial evacuation of people. The repeatability is about 20-25 years.

Especially dangerous

They cause great material damage, covering entire river basins. Some settlements are flooded. Paralyze economic activity and drastically disrupt the way of life of the population. They lead to mass evacuation of the population and the protection of the most important economic facilities. The recurrence is about 50-100 years.

catastrophic

They lead to death of people, irreparable environmental damage, cause material damage, covering vast territories within one or more water systems. Many settlements, industrial enterprises and utilities are flooded. At the same time, the economic and production activity temporarily changing the way of life of the population.

The evacuation of hundreds of thousands of people, an inevitable humanitarian catastrophe.

In the case of a city close to a flooding river, in a not very high place, as a rule, it is also flooded. The repeatability is about 100 - 200 years.

What to do before a flood

• in the event of a risk of flooding, warning messages may be given on radio and television. It indicates the approximate time of the approach of water, flood zones, order.
• if your house falls into a flood zone, study and remember the boundaries of possible flooding, as well as elevated, rarely flooded places located in the immediate vicinity of the places of residence, the shortest routes to them
• collect . Collect valuables. Separately collect stocks of food and medicines. All this must be compactly placed in a backpack or bag.
• if a flood is planned in advance, it is best to evacuate to a safe place ... on your own or with the help of rescuers. How to do this is described in the article.
• before leaving the house/apartment, check and turn off the gas, electricity, turn off the water taps, close the windows and doors, and put out the fire.
• material assets (valuables, furniture) must be moved to a safe place. If this is not possible, they should be placed as high as possible, for example, on the upper floors or attic.
• animals must be released from the premises, dogs must be unleashed
• all items that can float away when the water rises (for example, firewood), it is better to transfer to the room (barn)
• together with family members, you should study the evacuation plan and find out the places of the evacuation gathering.
• the actions of the population in case of a flood threat should be coordinated, so you should familiarize yourself with the location of the boats in case of a sudden onset of flooding
• it is advisable to come to the meeting place for temporary accommodation and registration
• when living on the lower floors, strengthen the windows with boards and plywood, other strong materials that can hold back water pressure
• if possible, get a boat (only not an inflatable one!, because it can be punctured) and for each family member

What to do in a flood

Try to do everything that is written above in "What to do before the flood."

• in the absence of an organized evacuation, until help arrives or the water subsides, stay on the upper floors and roofs of buildings.
• If the flood was unexpected and/or there was no organized evacuation, try to protect yourself by climbing on the upper floors or roofs of buildings, trees or other towering objects until help arrives or the water subsides.

Keep in mind that trees, poles and structures of dubious strength are best not used - they can be washed away by water flows and fall.

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. It is even better if you have some signaling means for this... at least.
If you don’t have it, then gather some necessary things for the first hours: blankets, boots, warm and practical clothes, energy-rich and baby foods (chocolate, water, milk), documents, money and valuables, which, unfortunately, are often necessary when everything else is carried away under the pressure of water.
Water, like food, should be at the rate of 2-3 days for each person. If there are animals - do not forget about them.

• 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
• try to collect everything that can come in handy - watercraft, lifebuoys, ropes, ladders, signaling means
• if possible - save people cut off by the elements from the rest, provide first aid to the victims.
• 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.
• before you hit the water, take a breath of air, grab the first thing you see and go with the flow, trying to stay calm
• if you get into a strong current in the water, then try to grab hold of any object floating by - a tree trunk, a door, a fence opening. It will be better if you can climb it. Keep in mind that under certain conditions you may well control your watercraft - with your feet or a stick using them instead of a keel, you can try to swim out from the middle or get to the island.
• if you still decide to get out of the water on your own, then remember about the laws of physics: you will inevitably be carried downstream, swim obliquely towards the goal.
• if the area is already flooded, do not drive your vehicle through it. You don't know what's underwater and you can get stuck. If this happens and water starts to get into the car, leave immediately.
• do not drink water from a contaminated source. best source immediately after the spill - bottled water. Floods usually contaminate the water layer with oils, fats, and all sorts of things that make the water unhealthy to drink.

What to do after a flood

• wait for permission from the authorities that you can return to your homes.
• do not drive out on the road immediately after a flood. The road can be destroyed or weakened due to cavities under the road. In this case, the road may collapse under the weight of your vehicle.
• Before entering a building, check if it threatens to collapse or fall any object, if there are cracks in the walls and damage to the floors, there are no gaps in and around the house, glass is not broken and there are no dangerous debris and debris.
• ventilate the building (open all doors and windows) to remove accumulated gases. This will also help to ventilate the room.
• pump water out of the house
• clean up: remove silt and dirt from walls, floors
• disinfect contaminated dishes and household items and the area around the house
• 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 electrical wiring, gas supply pipelines, water supply and sewerage, do not use them until you verify their serviceability with the help of specialists
• floods tend to damage septic tanks, sewer basins and sewer systems. If this has happened to your property, be sure to fix these leaks as quickly as possible. If one of your neighbors has this problem, try to help him. These leaks can be a health hazard if not addressed promptly.
• do not eat food that has been in contact with water
• on the way to anywhere, be careful of broken and sagging electrical wires
• wells must be drained by pumping
• be sure to boil drinking water, especially from water sources that have been flooded
• if you want to help with flood relief, ask the authorities what you can do. If not, don't get in the way and let them do their job.

The first and most important precaution you can take is to not build your home in an area that is easily flooded. If you don't have a choice and you must build your house on a floodplain, make sure the foundation is strong and high enough. Also, avoid building a basement: water will flood it all the time.

After the Great Flood flooded the entire surface of our planet, floods in the world are considered one of the most dangerous natural disasters. Maybe they do not look as grandiose and impressive as a sudden tornado or typhoon, and often give people time to leave dangerous territory, the consequences of floods are no less deplorable.

Thus, the largest documented flood in the world occurred in China in the thirties of the last century, when the longest and full-flowing river of the country, the Yangtze, together with the neighboring Huang He, burst their banks after heavy rains, destroying dams and flooding more than 300 thousand hectares of fertile land ( in some areas, the water did not descend for about six months). When the river waters calmed down, the consequences of the flood were so catastrophic that the world shuddered: only according to official figures, the death toll exceeded 3.7 million people.

Flooding is the flooding of vast areas, which was caused by a rise in the water level in lakes, rivers, seas after heavy rainfall, snowmelt, dam break, which led to water flowing far beyond the coastline.

Although in most cases the population can be warned about the approach of a natural disaster, warnings are often ignored due to the fact that local residents refuse to leave their homes in the hope that the disaster will bypass them. And completely in vain: the advancing water does not spare anyone and not only destroys buildings (especially buildings with a shallow foundation and constructed of wood), but often leads to human casualties.

Speaking about the causes of floods, hydrologists distinguish the following factors:

• Long rains - this type of flooding occurs only in humid areas, which are characterized by a large number of precipitation. For example, numerous showers that often fall in the summer on the Abyssinian Highlands, supplying the Nile with water, lead to the fact that the river annually floods the entire valley of the mouth. Despite the fact that the soil here is ideal for the development Agriculture, it is impossible to delay the harvest, otherwise it will be destroyed by the arriving waters.
• Snow melting - the cause of the flood is the intense melting of the snow cover, when the water entering the ground quickly goes to nearby rivers, sharply increasing the amount of water in them, as a result of which even a very small river increases many times in size.
• Tsunamis - the floods that tsunamis carry with them most often become catastrophic, often flooding the entire coast and going deep into four kilometers. A tsunami is formed in the ocean as a result of a shift lithospheric plates, also huge waves can form in lakes and bays after large landslides fall into them from a height.
• Raising the bottom - any river over time accumulates sediments in places of folds, which are the causes of flooding. The depth of the river in these places decreases, but the flow expands, flooding the coastal strip.
• Breakthrough of reservoirs - the element is extremely destructive, since the flow of breaking water is extremely strong, and therefore it is not inferior in strength to a tsunami: it demolishes everything that is in its path, regardless of the weight of the object.

What are floods

Naturally, not all types of floods lead to catastrophic consequences. Those that occur most often are not as devastating as those that occur once every few decades, but the effects of such floods are felt for a significant period. Therefore, hydrologists, focusing on the consequences of floods, classified the elements into four groups and gave them a description.

Small floods created by lowland rivers cover small coastal areas, occur once every five to ten years, and the population easily copes with the consequences of floods of this type.

Much more serious floods are classified as "Hazardous". They happen less frequently, once every 20-25 years. Covering rather large land plots located in river valleys, they cause significant material damage, flooding from 10 to 20% of crops. In some cases, even a partial evacuation of the population is required.

Floods, which hydrologists refer to as "Especially dangerous" occur once every fifty to a hundred years. Having overflowed its banks, the waters of the river completely fill the river basins, destroying from 50 to 70% of crops, and in some cases - settlements. As a result, all agricultural activities and the life of the region are paralyzed, the way of life of local residents is sharply disrupted, especially considering the fact that during especially dangerous floods mass evacuation of the inhabitants of the dangerous area is required.

The most dangerous types of floods in the world are classified as "Catastrophic" (it was this type of flood that befell China in the thirties of the last century). They flood the area of ​​one or more water systems, destroying almost all agricultural land, settlements (including cities), causing mass death of people. A country usually copes poorly with the consequences of floods of this magnitude and requires international assistance, since disasters often cause a humanitarian catastrophe.

In addition to the classification according to the consequences of the flood, there are the following types of floods, based on the description of this phenomenon:

1. Floods. This type of flood in the plains floods low areas and occurs in the spring during the melting of snow or after rain. It usually refers to small floods, but in some cases, if the soil was heavily oversaturated with moisture in autumn and severely frozen in winter, the consequences of floods can be catastrophic.
2. Flood. A leash is called a rapid, but short-term rise in the water level in rivers. This type of flood can occur several times a year, as it is primarily affected by heavy rainfall and in some cases by rapid snowmelt during thaws.
3. Congestion. The congestion is formed in early spring due to the blockage of rivers by an immovable block of ice or several ice floes, which slow down the river flow and cause the water to rise above the ice. This type of flood is characterized by a high but short-lived rise in the water level in the river.
4. Zazhor. A glacier flood appears due to an ice plug, which is a concentration of loose ice in the narrowing places of the river. During this flood, the water does not rise as much as during traffic jams, however, this flood is more prolonged.
5. Wind surge. This flood is characterized by a large rise in water and is caused by its wind. Since for this the air currents need to properly disperse the wave, the wind surge is usually fixed on the sea coast, at the mouth of the river, on large lakes, reservoirs. Predicting this flood is not easy, because it is characterized by a lack of periodicity and short duration.
6. Break in the reservoir. Floods of this type are formed due to the breakthrough of the reservoir, dam, dam. Despite their short duration, these floods are dangerous due to their suddenness and unpredictability, as a result of which a significant space is under water, and many objects that are in the way of the water are destroyed.

What to do in case of floods

In order to reduce the risk of occurrence and minimize the consequences of floods, flood protection is created in reservoirs - shallows are poured, rifts are deepened, and to regulate river flow, protective dams are built on the seashore, and reservoirs are built on rivers that equalize the flow of river flow, increasing it in summer, and reducing it. spring.

Unlike other natural disasters, scientists predict the likelihood of a flood quite accurately (unless, of course, they are the consequences of phenomena that are not easy to predict, such as a tsunami or a dam break). By being warned of an impending disaster, people have time to put in place the necessary flood protection.

If a catastrophe of great proportions is coming, special services they begin to evacuate the population (however, these actions are far from always successful, since many refuse to leave their homes).

People living in areas prone to floods should definitely know the rules of behavior in case of a flood in order to correctly calculate their actions in conditions emergencies. To do this, it is necessary to study in advance the boundaries of possible flooding, as well as take into account all the hills and places that are least affected by the elements, and where it will be possible to wait out the flood. It is also worth finding out in advance where boats, rafts or building materials are located so that in case of a disaster you can make a floating vehicle out of them.

The danger zone should be left as soon as there is information about the flood. It is also worth taking a backpack prepared in advance with documents, medicines, valuables, warm clothes and a two-day supply of food. Before leaving the house, you need to turn off the electricity, turn off the gas, put out the fire in the stoves, light objects outside the room so that they do not float away, it is advisable to fix them. Window and door openings must be locked, and if possible, boarded up from the outside with boards or shields.

If you can’t leave the house, you need to get to the roof and attach a banner so that the rescuers know where to look for you. If it is night outside, you need to signal your location with a torch or flashlight. When approaching rescuers, you need to calmly, without sudden movements, go to the rescue boat, and then listen to their instructions.

If there is no help, and the water remains and threatens to flood the shelter, you need to take a raft or an object that can be used instead of a floating facility and sail in the right direction, not forgetting to give distress signals. If people in the water are found along the way, everything must be done to save them. For this drowning person, you need to calm him down, and then throw him a rope. If a person is in a panic state and does not understand anything, you need to swim up to him from behind and tow him by the hair so that he cannot drown the rescuer.

Returning after the flood, before entering the house, you need to make sure that the building stands firmly and does not collapse, and then ventilate the room. Before turning on electrical appliances, or even lighting a match, be sure to check the gas pipeline, electrical wiring, as well as water supply and sewerage for serviceability (it is advisable to do these actions with specialists). After making sure that everything is in order, you need to pump out water from the basements, dry the rooms, clean the wells from dirt.

| Origin and types of floods. Their consequences

Fundamentals of life safety
7th grade

Lesson 16
Origin and types of floods. Their consequences

FROM THE HISTORY OF FLOODS

Not even four months had passed since the founding of St. Petersburg, when a flood happened. On the night of August 30-31, 1703, the water in the Neva rose by more than 2 m and flooded the camp of Russian troops. Food warehouses were flooded, part of the forest prepared for the construction of the Peter and Paul Fortress was blown away.

The head of the garrison, A. I. Repnin, reported to Peter I: “Great, sir, we have severe weather from the sea, and fills in our place, where I stand with regiments, water right up to my camp, overnight in the Preobrazhensky regiment at midnight at taverns of many sleepy people and junk helped them ... "

Two years later, on the night of October 15-16, the same warehouses were again flooded. Under the onslaught of violent waves and gale-force winds, the walls of houses collapsed, roofs flew off, uprooted trees fell.

An eyewitness to the flood, writer A.P. Baschitsky wrote: “ Winter Palace, like a rock, standing in the middle of a stormy sea, withstood the onslaught of waves from all sides, with a roar crashing against its strong walls and irrigating them with spray almost to top floor. On the Neva, the water boiled like in a cauldron, and with incredible force reversed the flow of the river ... "

The flood of September 21, 1777 took the city by surprise on a dark autumn night. A fierce storm and an extremely rapid rise in water greatly aggravated the situation. Due to the disorganization of the population and the indiscretion of the authorities, the flood of 1777, despite its short duration, caused the city huge damage. Many fences and fences were overturned, wooden houses squinted. The water washed away the prison, which was located on the seaside, along with 300 prisoners. The fountains in the Summer Garden turned out to be destroyed (later they were never restored).

Catherine II in her diaries described the storm on that memorable night in the following way: merchant ships. The stock exchange has changed its place... My cellars are flooded with water, and God knows what will become of them.”

The flood of 1824 brought huge losses to the city. 208 people died (according to other sources - 569 people). The Neva remained restless until the middle of the winter of 1824/25. 324 houses were completely destroyed, 3257 various other buildings were damaged (that is, half of all existing ones). Of the 94 ships that were in the harbor, only 12 were saved. 3,600 heads of cattle drowned, 900,000 poods of flour and a large amount of other food were spoiled. For a long time after this flood, colds raged in the city. Prices for food and firewood skyrocketed. For more than half a century, this flood was called the "Flood".

Origin and types of floods

Flooding is a significant flood of water in the area adjacent to a river, lake, sea or reservoir, which damages the health of people or even leads to their death, and also causes material damage.

From 1900 to 2006 there were 2855 major floods in the world. They killed 7 million people.

Depending on the scale, recurrence and damage caused, floods are divided into low, high, outstanding and catastrophic.

Low (small) floods occur mainly in lowland rivers. At the same time, water floods low places (less than 10% of agricultural land). Such floods almost do not disturb the rhythm of life of the population and cause minor damage. They repeat once every 5-10 years.

high floods significantly disrupt the well-established life of people, cause significant material damage. In densely populated areas, it is often necessary to partially evacuate the population. Such floods occur once every 20-25 years.

outstanding floods cover entire river basins. They cause great material damage, flood settlements and cities. In this case, there is a need for mass evacuation of people and material values. Occur once every 50-100 years.

catastrophic floods completely change the way of life of the population and lead to huge material losses. More than 70% of agricultural land is flooded. Such floods occur no more than once every 150-200 years.

Floods rank first in the world in terms of the number of natural disasters they create and second or third in terms of the number of victims.

Let's turn to the history of our country. The Ipatiev Chronicle recorded a terrible flood in the south of Russia in 1145, which was caused by heavy rains ... Another chronicle (Troitskaya) says that in 1403, due to heavy rains, floods were noted from Pskov to Paris.

Depending on the causes of floods, they are divided into several types.

Floods - floods caused by spring snowmelt on the plains or melting of snow and glaciers in the mountains. They repeat annually in the same season with different intensity and duration, which depend on meteorological conditions. Floods are characterized by a significant and prolonged rise in the water level.

Floods - floods caused by rain and heavy rains or rapid snowmelt during winter thaws. An intense, but relatively short-term rise in the water level is characteristic. Unlike floods, floods occur at any time of the year.

Jam, zazhorny floods (jamming, zazhory) - floods caused by high resistance to water flow that occurs when ice material accumulates in narrowings or bends of the river during freeze-up (jamming) or during ice drift (jamming).

jam floods formed in late winter or spring. They are characterized by a high and relatively short-term rise in the water level in the river.

zagorny floods formed at the beginning of winter. They are characterized by a significant, but smaller than during a jam, rise in the water level and a longer duration.

On medium rivers, the total length of the jam can be from one to several kilometers. The length of the blockage area can be up to big rivers up to 20 km. Ice jams are most common on rivers flowing from south to north. In Russia, these are the Northern Dvina, Pechora, Yenisei, Ob, Lena, Irtysh, Vitim, Tom, etc. Icebreakers are used to destroy traffic jams, blasting and bombing from aircraft.

Surge floods are caused by wind surges of water onto the shores of large lakes, reservoirs and into the sea mouths of large rivers. They occur on the windward shore of a reservoir as a result of a rise in the water level under the action of a strong cyclone wind on the water surface. In this case, a surge wave is formed, which propagates to the windward shore of the reservoir or up the river. Surge floods are characterized by a lack of periodicity and a significant rise in the water level. A surge wave can spread on large rivers for hundreds of kilometers, on small rivers - for tens of kilometers. Flooding usually lasts from several tens of hours to several days.

Of the 200 capitals in the world, about half are located in the sea estuaries, and they are threatened surge floods. In Russia, St. Petersburg, located in the delta of the river, is most susceptible to this phenomenon. Neva on the low islands. Since its foundation (1703), it has been invaded by waves about 250 times.

Floods caused by dam breaks (hydraulic structures). They occur when water overflows over the crest of the dam, when the pre-flood drawdown of the reservoir is not carried out in time, when the dam is destroyed or when the capacity of the spillway of the dams is insufficient. Breaking dams is also possible due to poor quality construction works and misuse, the effects of earthquakes and the effects of war. Such floods are characterized by the formation of a breakthrough wave, leading to the flooding of large areas and to the destruction or damage of objects (buildings, structures) encountered on the way of its movement.

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

The classification of floods by scale and causes is shown in Scheme 17.

Flood consequences

During a flood, the water quickly rises and the surrounding area is flooded.

Flooding - covering the surrounding area with a layer of water flooding courtyards, streets of settlements and the lower floors of buildings.

Flooding - the penetration of water into the basements of buildings through the sewer network (when the sewer is connected to the river), through various ditches and trenches, and also due to significant groundwater backwater.

Flooding of settlements, agricultural lands and natural complexes accompanied by negative consequences: as a result of the impact of water and its rapid flow, people, agricultural and wild animals die; buildings, structures, communications are destroyed or damaged; material and cultural values ​​are lost; agricultural activities are interrupted; the crop dies, fertile soils are washed away or flooded; the landscape changes.

Secondary effects of floods: decrease in the strength of structures as a result of erosion and undermining; water transfer of hazardous substances spilled from damaged storage facilities and pollution of vast territories by them; complication of the sanitary-epidemic situation; swamping of the area.

Due to the uneven subsidence of the soil during the flood, numerous ruptures of sewer and water pipes, gas mains, electric, telegraph and telephone cables, damage to buildings and roads occur.

The population endures summer flooding and its consequences more easily than spring flooding, and even more so winter flooding.

In rural areas, the time (season) and duration of flooding are crucial. This is primarily due to the seasonality of agricultural work. But any flooding of areas intended for growing crops with water leads to the displacement of air from the soil. At the same time, normal gas exchange stops in the soil and carbon dioxide enters the water from the roots of plants, which adversely affects the plants. This circumstance is main reason the fall in crop yields or the loss of agricultural crops as a result of floods.

Serious consequences of floods of rare frequency are sometimes changes in river beds: new channels appear or old ones deepen. Partially, and sometimes completely, the fertile topsoil is washed away or silted up in the plowed areas of the floodplain, which significantly worsens land use and reduces productivity.

Flood Damage Mitigation Measures

It is almost impossible to get rid of floods completely, but in the power of people to reduce losses from them.

To protect against most floods, the same measures are used to significantly reduce their consequences: forest protection belts are planted in river basins, they strive to preserve coastal shrub vegetation, special treatment of slopes is carried out, ponds and reservoirs are built to intercept melt and rainwater.

On medium and large rivers, a radical means of flood protection is used - regulation of flood flow with the help of reservoirs (this simultaneously allows solving the problem of generating electricity). The essence of this method lies in the fact that the water arriving in the reservoirs is gradually consumed by dumping it through a pressure hydroelectric complex.

Fencing dams are built along the banks of many rivers to protect against floods. The channels of meandering rivers are also straightened, which makes it possible to increase the slope of the water surface and the speed of the water flow in them. As a result, the maximum flow of water occurs at its lower level. On newly built up areas, the method of filling the territory is used.

Work to strengthen the banks of rivers reduces the risk of their erosion, and by deepening the bottom of the rivers, they allow more water to pass through their channels, remove various obstacles from the bottom, and increase the speed of the flow.

Timely and reliable hydrometeorological forecast is important for carrying out operational preventive measures (notifying the population about the threat of flooding; early evacuation of the population, material assets, animals from potentially flooded places; erecting simple protective structures to protect settlements and roads from flooding).

Most floods can be predicted and thereby reduce potential losses. Residents of cities and towns that periodically fall into flood zones should be informed in advance about this danger, trained and prepared to act in case of a threat and during floods.