Floods on the rivers. Floods are natural disasters that affect people living on the banks of rivers.

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 called 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 the release of water far beyond the borders 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 of 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 the shift of lithospheric plates, and huge waves can also 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 quite large land, located in river valleys, 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, 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 a mass evacuation of the inhabitants of the dangerous area is required.

Most dangerous types 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:

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.
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.
Congestion. The blockage is formed in early spring due to blockage of the rivers by an immobile 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.
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.
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.
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 floods in order to correctly calculate their actions in emergency situations. 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 with you a pre-prepared backpack 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 rescuers approach, 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 swim to the right side, 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, the writer A.P. Baschitsky wrote: “The Winter Palace, like a rock, standing in the midst of a stormy sea, withstood the onslaught of waves from all sides, roaring against its strong walls and irrigating them with spray almost to the 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 enormous damage to the city. 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. This creates a need for mass evacuation of people and material assets. 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, jam floods (traffic jams, jams) - floods caused by high resistance water flow, arising from the accumulation of ice material 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 ah 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.

About half of the world's 200 capitals are located in sea estuaries and are threatened by 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. Dam failures are also possible due to poor quality of construction work and improper operation, the impact of earthquakes and the consequences of military operations. Such floods are characterized by the formation of a breakthrough wave, leading to flooding. large territories and to the destruction or damage of objects encountered on the way of its movement (buildings, structures).

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 the main reason for the fall in productivity or the death of 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.

Tasks 4. Geoecological problems

Global climate change can lead to the melting of ice sheets and, as a result, an increase in the level of the World Ocean. Which of the listed cities in Russia could suffer the most in the event of such a development of events?

1) Kemerovo

2) Kaliningrad

3) Novosibirsk

Such unfavorable climatic phenomena as droughts, dry winds and dust storms make it difficult economic use territory. For which of the following territories of Russia are they most typical?

1) Kirov region

2) Kamchatka Territory

3) Astrakhan region

4) Komi Republic

Permafrost has an impact on human economic activities: mining, construction of roads and buildings. In which of the following regions of Russia is it necessary to take into account the consequences of permafrost thawing?

1) Samara region

2) Krasnoyarsk region

3) Rostov region

4) Chuvash Republic

4. Global climate change can lead to the melting of sheet glaciers and, as a result, an increase in the level of the World Ocean. Which of the listed cities in Russia could suffer the most in the event of such a development of events?

1) Smolensk

2) Yekaterinburg

3) Arkhangelsk

4) Novosibirsk

Seismicity and underwater volcanism are closely associated with the danger of huge sea waves- tsunamis, under the threat of which are the territories of coastal cities and towns. Which of the following territories of Russia needs the work of special services to warn the population about the tsunami?

1) Chukotka Peninsula

2) Kola Peninsula

3) Kuril Islands

4) archipelago New Earth

For the safety of people in earthquake-prone areas, a special construction technology is used. In which of the following regions is it necessary to conduct earthquake-resistant construction?

1) Tula region

2) Smolensk region

3) Leningrad region

4) Sakhalin region

Such unfavorable climatic phenomena as droughts, dry winds and dust storms significantly complicate the economic use of the territory. Which of the following areas are the most typical?

1) Republic of Kalmykia

2) Perm region

3) Khabarovsk region

4) Republic of Karelia

For many countries, monitoring of volcanic activity and the work of services to alert the population about upcoming volcanic eruptions are relevant. For which of the following countries is it important to constantly monitor volcanic activity?

1) Finland

2) Iceland

4) Australia

Mud flow - mud or mud-stone flow, characterized by destructive power, suddenness of occurrence. In which of the following regions of Russia is the occurrence of mudflows most likely?

1) Kabardino-Balkarian Republic

2) Smolensk region

3) Republic of Kalmykia

4) Kaliningrad region

Earthquakes are natural disasters that often affect people. Timely notification of the population by special services can prevent catastrophic consequences of earthquakes. Which of the following countries requires such special services?

1) Australia

2) Mexico

3) Ireland

4) Netherlands

Seismicity and underwater volcanism are closely related to the danger of huge sea waves - tsunamis, which threaten the territories of coastal cities and towns. In which of the listed regions of Russia is the work of special services necessary to warn the population about the approaching tsunami?

1) Transbaikal region

2) Yamalo-Nenets Autonomous Okrug

3) Primorsky Krai

4) Arkhangelsk region

Seismicity and underwater volcanism are closely related to the danger of huge sea waves - tsunamis, under the threat of which are the territories of coastal cities and towns. Which of the following countries requires the work of special services to warn the population about the approaching tsunami?

2) Bulgaria

3) Turkmenistan

4) Philippines

13. Snow avalanches are one of the most formidable and dangerous natural phenomena. In which of the following regions of Russia do snow avalanches pose the greatest danger?

1) Chuvash Republic

2) Kaliningrad region

3) Arkhangelsk region

4) Republic of North Ossetia - Alania

Floods are natural disasters that affect people living on the banks of rivers. Which of the following rivers floods most often in summer time?

Earthquakes are natural disasters that often affect people. Timely notification of the population by special services can prevent catastrophic consequences. Which of the following countries requires such special services?

1) Finland

3) Netherlands

People have long built cities near rivers, seas and other large bodies of water. They served as transport, a source of fish, natural protection. Modern settlements have been preserved in place of the old ones. But at the same time, some of them have become flood areas that occur on a regular basis. Why is this happening and what does it mean?

Essence

Most probably know the biblical story about the Great Flood, in which almost all of humanity perished. Perhaps this in itself is an indicator that flooding is extremely dangerous phenomenon bringing destruction, chaos and death to all living things. Perhaps they do not look as impressive as earthquakes or typhoons, but their power should not be underestimated.

Flooding is, in fact, the flooding of vast areas due to various reasons. They can be both quite rapid and occur gradually. In other words, huge volumes of water end up where they should not be - on land. There are several classifications of floods, both according to the criterion of danger or scale, and according to the consequences.

Quite often, floods accompany other natural disasters. Thus, an earthquake may be accompanied by a tsunami and subsequent flooding of coastal areas. After Hurricane Katrina, New Orleans also experienced flooding, leaving hundreds of thousands of people homeless.

Causes of floods

They can occur due to different events, and this affects their character. If we talk about more or less common causes of floods, they can be as follows:

Long rainfall. Abundant and prolonged rains in lowland areas create a situation where moisture simply has nowhere to go. If she does not have time to leave, it turns out flooding.
Rapid melting of snow. Sometimes in spring the temperature rises very quickly and abruptly. At this time, all the snow that has fallen over the winter begins to melt. If its volume is large, there is a danger of both local and fairly extensive flooding.
Raising the bottom of reservoirs. In any river or lake, over time, some deposits appear in the form of the remains of dead organisms and plants, silt, and sometimes even garbage. This can cause the bottom to rise and, accordingly, change the coastline, sometimes with flooding of areas that were previously out of danger.
Reservoir breakthrough. Any engineering structures built by man have their own margin of safety. Sometimes, due to some events, dams do not withstand, and then destructive, but rather short-term flooding can be expected.
Tsunami. A wave that forms in the ocean after strong tremors quite regularly devastates coastal areas, for example, in the countries of Southeast Asia.

An additional contributing factor to flooding can be clogging of drains in the city's sewer system, with the result that the consequences can be much more devastating than they could be in the absence of malfunctions. And what they can be in general?

Consequences

Flooding is, as it has already become clear, no joke. It has some damaging factors. As you know, water is a universal solvent. With prolonged exposure to some materials, it can completely destroy them. Cracks appear in the walls of houses, agricultural plantings perish. Another serious danger is the wave itself, if the flood is fast enough. It literally demolishes the walls of buildings, leaving behind the rubble, under which people remain. There is a special classification that indicates the scale and danger of each particular flood:

small or low. They are observed during the flooding of large rivers in lowland flat areas. They are distinguished by a relatively small scale, they practically do not affect the rhythm of the life of the population.
Dangerous. They cover up to 20% of agricultural land and fairly large areas. Often lead to partial evacuation.
Particularly dangerous. Violate the usual way of life, paralyze Agriculture covering up to 70% of crops. lead to mass evacuations.
catastrophic. They cause enormous moral and material damage, one or several settlements are flooded, there are victims. Hundreds of thousands of people are being evacuated, a humanitarian and environmental catastrophe is being observed.

Yes, a flood is not a sudden earthquake, you can often protect yourself from it. But it is difficult to argue with the fact that this is still an extremely dangerous phenomenon.

High risk areas

Low-lying areas near which there are large reservoirs are the first to be hit. For example, Venice is regularly flooded, despite any countermeasures. The same can be said about the Netherlands. The capital of this country, Amsterdam, has been fighting the elements for a long time, fighting the sea for every meter of land. In Egypt, there are also areas in which the Nile overflows especially abundantly, but this happens regularly and naturally.

There are cities located at the mouths of large rivers or simply along their course. Their inhabitants also may not always feel safe.

Countermeasures

Fortunately, in most cases, scientists can more or less accurately predict flooding. In this case, the number of injured and victims is significantly reduced, since it is usually possible to start the evacuation in time. If the flooding is regular and not too large, it makes sense to build special buildings: dams and locks that can protect the city from rising water levels. When the flooding has already happened, it remains only to dismantle the rubble and save people in anticipation of a decline in moisture.

People who are aware of the increased risk of flooding in their area should also be familiar with the algorithm of action in the event of a disaster. First of all, it is worth studying the location of the hills and the safest places nearby. If there is information about a disaster, you must follow all that the local authorities recommend. If they urge you to stay at home, you should do so. If an evacuation is organised, the instructions must be followed. Before leaving the house, you need to turn off all communications as much as possible and secure light things.

Floods in Russia

Areas in the Russian Federation where flooding occurs most often are St. Petersburg and the Krasnodar Territory. In the latter region, this natural disaster occurs almost every year. The last major event happened in 2012, when the city of Krymsk, which was almost completely destroyed, suffered the most from the disaster.

In 2013, a large-scale natural disaster was observed in Far East. It was due to the fact that in about a month more than the annual rainfall fell over the territory, as a result of which the rivers overflowed their banks. The situation was aggravated by the fact that the previous winter was very snowy, and the spring came late, so the hydraulic systems were already saturated. Despite the huge scale of the flood, no deaths were reported in Russia, while in China the number of victims and missing was almost 200 people.

For many years, hydrologists in St. Petersburg have been closely monitoring the behavior of rivers and canals, monitoring the slightest rise in water level. Fortunately, in last years no major problems were observed.

Flood

Flood in Asheville, North Carolina in July 1916

Flood- 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.

Floods are often caused by an increase in the water level in the river due to blockage of the channel by ice during ice drift (jam) or due to blockage of the channel under the immovable ice cover by accumulations of intra-water ice and the formation of an ice plug (jam). Often, floods occur under the influence of winds that drive water from the sea and cause an increase in the level due to the delay in the mouth of the water brought by the river. Floods of this type were observed in Leningrad (1824, 1924), the Netherlands ( 1953 ). On sea coasts and islands, floods can result from the flooding of the coastal strip by a wave formed during earthquakes or volcanic eruptions in the ocean (see Tsunami). Similar floods are not uncommon on the coasts of Japan and other islands. Pacific Ocean. Floods can be caused by breaks of dams, protective dams.

Flooding occurs on many rivers in Western Europe - the Danube, Seine, Rhone, Po and others, as well as the Yangtze and Yellow Rivers in China, Mississippi and Ohio in the United States. In the USSR, large floods were observed on the Dnieper () and Volga (and) rivers.

Jam, zazhorny floods (jamming, zazhora)

High resistance to water flow in certain sections of the river channel, which occurs when ice material accumulates in narrowings or bends of the river during freeze-up ( behind and ora) or ice drift ( behind T ora). Behind T mountain floods formed in late winter or early spring. They are characterized by a high and relatively short-term rise in the water level in the river. Behind and mountain floods form at the beginning of winter and are characterized by a significant (but less than during a jam) rise in the water level and a longer duration of flooding.

Surge floods (surges)

Wind surges of water in the sea mouths of rivers and on windy sections of the coast of the seas, large lakes, reservoirs. Possible at any time of the year. They are characterized by the absence of periodicity and a significant rise in the water level.

Floods (flooding) formed when dams break

An outflow of water from a reservoir or reservoir, which is formed when a pressure front structure (dams, dams, etc.) breaks through or during an emergency discharge of water from a reservoir, as well as when a natural dam breaks through, created by nature during earthquakes, landslides, collapses, movement of glaciers. They are characterized by the formation of a breakthrough wave, leading to the flooding of large areas and the destruction or damage of objects encountered on the way of its movement (buildings, structures, etc.)

Classification of floods depending on the scale of distribution and frequency

Low (small)

They are observed on flat rivers. 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. That is, they cause minor damage.

High

They cause significant material and moral damage, cover relatively large areas of river valleys, flood approximately 10-20% of agricultural land. Significantly violate the economic and everyday life of the population. Lead to the partial evacuation of people. Repeatability 20-25 years.

Outstanding

They cause great material damage, covering entire river basins. They 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

They lead to death of people, irreparable environmental damage, cause material damage, covering vast territories within one or more water systems. More than 70% of agricultural land, many settlements, industrial enterprises and utilities are flooded. Economic and industrial activity is completely paralyzed, the way of life of the population is temporarily changed. The evacuation of hundreds of thousands of people, the inevitable humanitarian catastrophe requires the participation of the entire world community, the problem of one country becomes the problem of the whole world.

Types

High water is a periodically repeated fairly long rise in the water level in rivers, usually caused by spring snowmelt on the plains or rainfall. Floods low terrain.

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. Spring rains can also lead to an increase in floods, when its peak coincides with the peak of the flood.

Flood - an intense relatively short-term rise in the water level in the river, caused by heavy rains, downpours, sometimes rapid snow melting during thaws. Unlike floods, floods can occur several times a year. A particular threat is the so-called flash floods associated with short-term, but very intense downpours, which also occur in winter due to thaws.
Congestion - a heap of ice floes during the spring ice drift in the narrowings and on the bends of the river channel, hampering the flow and causing a rise in the water level in the place of ice accumulation and above it.

The congestion occurs due to the non-simultaneous opening of large rivers flowing from south to north. The opened southern sections of the river in their course are spring-loaded by the accumulation of ice in the northern regions, which often causes a significant increase in the water level.

Zazhor - an accumulation of loose ice during freeze-up (at the beginning of winter) in the narrowings and on the bends of the river channel, causing the water to rise in some areas above it.
Wind surge is a rise in the water level caused by the action of wind on the water surface, which occurs in the sea mouths of large rivers, as well as on the windward shore of large lakes, reservoirs and seas.
Flooding due to a breakthrough of hydraulic structures (hydrodynamic accident) is an incident associated with the failure (destruction) of a hydraulic structure or its parts, followed by uncontrolled movement of large masses of water.

Causes

Long rains

Flooding in Biysk caused by abnormally long rains (more than 72 hours), 2006

Summer rains falling on the Abyssinian Highlands lead to the fact that the Nile floods every year, flooding the entire valley in its lower reaches.

snowmelt

Intensive snowmelt, especially when the ground is frozen, leads to flooding of roads.

tsunami wave

On sea coasts and islands, floods can occur as a result of flooding of the coastal strip by a wave formed during earthquakes or volcanic eruptions in the ocean. Similar floods are not uncommon on the coasts of Japan and other Pacific islands.

bottom profile

One of the causes of floods is the rise of the bottom. Each river gradually accumulates sediments, in riffles, in estuaries and deltas.

Ways to prevent floods

Most effective method flood control on rivers - regulation of river flow through the creation of reservoirs. Barrier dams are used to control floods on the seashore.

One of the ways to combat floods is to deepen rifts and other shoals.

History of floods in Russia

Floods in the Krasnodar Territory

Almost an annual natural disaster, the extent of which depends on weather conditions. But the reasons lie in the social sphere, including: the development of the floodplain, water protection zones and the littering of the riverbed, which is heavily overgrown in some areas. Catastrophic flood in the Krasnodar region in 2012.

Floods in Moscow

From the history of Moscow, it is known that floods on the Moscow River were frequent (in the spring, they also happened in the summer) and brought great disasters to the city. So, in the annals it is said about a severe frosty winter, big snows and a great flood. In July and August, floods occurred as a result of long continuous rains. In the 17th century three spring floods were noted: in, (the southern wall of the Kremlin was damaged, many houses were destroyed) and in (4 floating bridges across the river were demolished). In the XVIII century. six floods are mentioned: , , , , and ; in 1783, the pillars of the Bolshoy Kamenny Bridge were damaged by floods. During floods in 1788, marks were made on the tower of the Novodevichy Convent and the walls of some buildings. One of the largest floods on the Moscow River was in, during which the maximum water flow was 2860 m³ / s. The water in the river rose 8.9 m above the permanent summer horizon, on the embankments near the Kremlin its layer reached 2.3 m. The river and the Vodootvodny canal merged into one channel 1.5 km wide. 16 km² of the city territory was flooded. During the flood, the maximum flow was 2140 m³ / s, the rise of water above the low water was 7.3 m. The next and last flood was in (water rise 6.8 m). Now, in the upper part of the Moskva River basin, the Istra, Mozhayskoye, Ruzskoye and Ozerninskoye reservoirs have been built, which regulate the flow. In addition, the riverbed within the city has been widened in places, the sharp bends have been straightened, and the banks have been reinforced with granite embankment walls. After that, the floods in the city were almost imperceptible.

Often floods occur on the river. Yauza during spring floods and heavy summer rains. Modern Elektrozavodskaya, Bolshaya Semyonovskaya, Bakuninskaya streets, Preobrazhenskaya, Rusakovskaya, Rubtsovskaya, Semyonovskaya embankments suffered especially often and severely. An additional cause of floods on the river. The Yauza was served by the presence of bridges in the form of brick vaulted pipes of insufficient section. Large spring floods were observed in (the water at the Glebovsky bridge rose by 3.28 m), in (by 2.74 m), in (by 2.04 m), in (by 2.25 m). Instead of old bridges, high reinforced concrete bridges were built, along the banks - reinforced concrete walls (with a margin of 0.5 m above the maximum flood horizon).

Most often, Moscow suffered from floods on the river. Neglinnaya after its conclusion in a brick pipe (in the first half of the 19th century in the area from the mouth to Samotechnaya Square, in - above Samotechnaya Square). The pipes were designed to pass only 13.7 m³ / s of water, and almost every year, during heavy rains, it burst out of the ground and flooded Samotechnaya and Trubnaya Square and Neglinnaya Street. The water on Neglinnaya Street rose by 1.2 m. After a heavy downpour, Neglinnaya Street turned into a raging stream. After a rainstorm on June 25, a lake formed at the intersection of Neglinnaya Street and Rakhmanovsky Lane; the flooded area was 25 hectares. In Neglinnaya Street, Trubnaya and Samotechnaya Squares, it was flooded somewhat less, twice - on June 8 and 22, on August 7 and 9; it happened in . Now a new pipe has been laid, designed for water flow of 66.5 m³/s. However, the increased intensity of showers in Moscow again leads to severe floods: on June 26, 2005 in the area of Neglinnaya Street and on June 9, 2006 on the Entuziastov Highway, when the first floors of buildings were flooded with water.

Flooding also took place on the rivers Khapilovka, Rybinka, Presnya and others, which also arose due to heavy rainfall and insufficient pipe cross-section (large-section pipes are now laid).

Floods in St. Petersburg

Main article: Floods in St. Petersburg

Floods in St. Petersburg are caused by a number of factors: cyclones arising in the Baltic with a predominance of westerly winds cause a surge wave and its movement towards the mouth of the Neva, where the rise of water increases due to shallow water and narrowing of the Neva Bay. Seiches, wind surges, and other factors also contribute to flooding.

Literature

// Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.

Links

Largest Flood Database (in English)
General information and chronology of floods in St. Petersburg on the Neva River

	Flood in Wiktionary
	Flood at Wikimedia Commons
	Flood at Wikinews