Floods on rivers. Floods Floods caused by intense rainfall

Each of us knows at least something about flooding, because this natural disaster is typical for any continent on the planet. Many witnessed the flood firsthand. But do we know the causes of floods?

Main causes of floods

A flood is a large-scale inundation of an area caused by rising water levels in lakes, seas and rivers.

A sea, lake or river can overflow its banks due to:

• wind surge of water onto the shore,
• melting glaciers,
• active snow melting,
• heavy rainfall.

Japan is characterized by floods caused by a tsunami generated by a tidal wave. The extent of flooding depends on the terrain and wave strength. More often than others, areas located in gorges, on mountain slopes, and in coastal zones are subject to floods.

What types of floods are there?

Depending on the causes of occurrence, floods are usually divided into:

• dam,
• surge,
• gluttonous,
• mash.
• Based on scale:
• catastrophic,
• outstanding,
• high and low.

Given the rate of development, floods can develop gradually or abruptly.

Jam flooding occurs most often in early spring or late winter, when ice accumulated in narrowings of the river channel forms jams, which contributes to the overflow of water. A flood of a glacial nature occurs during freeze-up in initial period winter. The causes of dam floods are emergency releases of water from reservoirs or breaches of their dams. Low floods are typical for lowland rivers with small elevation differences.

Particularly dangerous floods

High floods are recorded when large areas are flooded, when human life becomes significantly more difficult. Such floods cause significant moral and material damage. In most cases, the population is evacuated, although many choose to remain in place at their own risk. Covering entire settlements and river basins, an outstanding flood can cause colossal material damage. Depending on the characteristics of the region, large cities suffer, and the vital functions of flooded areas are significantly disrupted.

Catastrophic floods cause many disasters. The population suffers enormous moral and material damage. The percentage of survival in such a natural disaster is directly dependent on the efficiency of evacuation. Despite all the measures taken, the death of people is, as a rule, inevitable. There is complete demoralization, and flooded areas become uninhabitable. Interrupted transport connection, buildings, power lines, and industrial facilities are destroyed.

Flood

Flood in Asheville, North Carolina in July 1916

Flood- flooding of the area as a result of rising water levels in rivers, lakes, seas due to rains, rapid snow melting, wind surge of water to the coast and other reasons, 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 riverbed with ice during ice drift (jam) or due to clogging of the riverbed under a stationary ice cover with accumulations of inland ice and the formation of an ice plug (jag). Floods often occur under the influence of winds, driving water from the sea and causing an increase in the level due to the retention of water brought by the river at the mouth. Floods of this type were observed in Leningrad (1824, 1924), the Netherlands ( 1953 ). On sea ​​coasts and islands, floods can occur as a result of coastal inundation by waves generated by earthquakes or volcanic eruptions in the ocean (see Tsunami). Similar floods are common on the shores of Japan and on other islands Pacific Ocean. Floods can be caused by breaches of dams and protective dams.

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

Congestion, gluttony floods (congestion, gluttony)

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

Surge floods (surges)

Wind surges of water in sea estuaries and on windy areas of the coast of seas, large lakes, and reservoirs. Possible at any time of the year. They are characterized by a lack of periodicity and a significant rise in water levels.

Floods (flooding) resulting from dam failures

An outflow of water from a reservoir or reservoir, formed when a pressure front structure (dam, dike, etc.) breaks through or during an emergency release of water from a reservoir, as well as when a natural dam breaks through, created by nature during earthquakes, landslides, landslides, or glacier movement. Characterized by the formation of a breakthrough wave, leading to flooding of large areas and destruction or damage to objects encountered along its path (buildings, structures, etc.)

Classification of floods depending on the scale of distribution and frequency

Low (small)

They are observed on lowland rivers. Covers small coastal areas. Less than 10% of agricultural land is flooded. They hardly disturb the rhythm of life of the population. Repeatability 5-10 years. That is, they cause minor damage.

High

Cause significant material and moral damage, covering relatively large land river valleys, flood approximately 10-20% of agricultural land. They significantly disrupt the economic and everyday life of the population. Lead to partial evacuation of people. Repeatability 20-25 years.

Outstanding

They cause great material damage, covering entire river basins. Approximately 50-70% of agricultural land and some populated areas are flooded. They paralyze economic activity and sharply disrupt the everyday life of the population. Lead to the need for mass evacuation of the population and material assets from the flood zone and protection of the most important economic facilities. Repeatability 50-100 years.

Catastrophic

They lead to loss of life, irreparable environmental damage, and 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. The economic and production activity, the lifestyle of the population changes temporarily. The evacuation of hundreds of thousands of people, an inevitable humanitarian catastrophe requires the participation of the entire world community, the problem of one country becomes a problem of the whole world.

Types

• Flood is a periodically recurring, rather prolonged rise in water levels in rivers, usually caused by spring melting of snow on the plains or rainfall. Floods low-lying areas.

A flood can become catastrophic if the infiltration properties of the soil have significantly decreased due to its oversaturation with moisture in the fall and deep freezing in the harsh winter. Increased floods can also lead to spring rains when its peak coincides with the peak of the flood.

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

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

• Zazhor is an accumulation of loose ice during freeze-up (at the beginning of winter) in narrowings and bends of the river bed, causing water to rise in some areas above it.
• Wind surge is a rise in water level caused by the action of wind on the water surface, occurring at the mouths of large rivers, as well as on the windward shores 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 large masses water.

Causes

Long rains

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

Summer rains falling on the Abyssinian Highlands cause the Nile to overflow every year, flooding the entire valley in its lower reaches.

Snow melting

Intensive snow melting, 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 inundation of the coastal strip by waves generated by earthquakes or volcanic eruptions in the ocean. Similar floods are common on the shores of Japan and other Pacific islands.

Bottom profile

One of the causes of floods is rising seabeds. Each river gradually accumulates sediments, in riffles, in mouths and deltas.

Flood Prevention Methods

The most effective way to combat river floods is to regulate river flow by creating reservoirs. To combat floods on the seashore, protective dams are used.

One of the ways to combat floods is to deepen riffles and other shallows.

History of floods in Russia

Floods in the Krasnodar region

An almost annual natural disaster, the scale 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 river bed, 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 often occurred (in the spring, they also happened in summer time) and brought great disaster to the city. Thus, the chronicle speaks of a severe frosty winter, heavy snows and great floods. 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 18th century six floods are mentioned: , , , , and ; in 1783 the supports of the Bolshoi were damaged by floods Stone Bridge. During the 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 rate was 2140 m³/s, the water rise above the low-water period was 7.3 m. The next and last flood was in (water rise 6.8 m). Nowadays, in the upper part of the Moscow River basin, Istrinskoye, Mozhaiskoye, Ruzskoye and Ozerninskoye reservoirs have been built, which regulate the flow. In addition, the river bed within the city has been widened in places, sharp bends have been straightened, and the banks are reinforced with granite embankment walls. After this, floods within the city passed almost unnoticed.

Floods often occurred on the river. Yauza during spring floods and heavy summer rains. The modern Elektrozavodskaya, Bolshaya Semyonovskaya, Bakuninskaya streets, Preobrazhenskaya, Rusakovskaya, Rubtsovskaya, Semyonovskaya embankments suffered especially often and severely. An additional reason for flooding on the river. The Yauza was served by the presence of bridges in the form of brick vaulted pipes of insufficient cross-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). To replace the 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 enclosure in a brick pipe (in the first half of the 19th century in the area from the mouth to Samotyochnaya Square, in - above Samotyochnaya Square). The pipes were designed to carry only 13.7 m³/s of water, and almost every year during heavy rainfalls it burst out of the ground and flooded Samotechnaya and Trubnaya Squares and Neglinnaya Street. The water on Neglinnaya Street rose by 1.2 m. After a heavy rain, Neglinnaya Street turned into a seething 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. Neglinnaya Street, Trubnaya and Samotyochnaya squares were flooded somewhat less, twice - on June 8 and 22, and on August 7 and 9; this happened in . A new pipe has now been laid, designed to carry a water flow of 66.5 m³/s. However, the increasing intensity of rainfall in Moscow again leads to severe floods: on June 26, 2005 in the area of ​​Neglinnaya Street and on June 9, 2006 on Entuziastov Highway, when the first floors of buildings were flooded with water.

Flooding also occurred on the Khapilovka, Rybinka, Presnya and other rivers, which also arose due to heavy rainfall and insufficient cross-section of pipes (large cross-section pipes are now installed).

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 intensifies 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 ones). - St. Petersburg. , 1890-1907.

Links

	Flood in Wiktionary
	Flood on Wikimedia Commons
	Flood in Wikinews

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

If the risk was great, a person either refused to use floodplain lands or tried to reduce the danger by building simple protective structures. Sooner or later these protective measures it turned out to be not enough and the person again faced the need to choose. Human activities leading to floods. Man has struggled with floods throughout his entire existence and for his centuries-old history There have been many such natural disasters.

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Plan:

Introduction…………………………………………………………………………………..3

1. Types and causes of floods………………………………………….4

2. Examples of floods in Russia and the world……………………………..8

3. Problems of floods and safety of hydraulic structures.12

Conclusion…………………………………………………………………………………14

List of references………………………………………………………15

Introduction.

It is well known that the state, development and vital activity of the biosphere and human society are directly dependent on the state water resources, but water does not always play a positive role in the functioning of all living things. Unfortunately, sometimes it becomes a powerful element capable of destroying everything in its path.

For many centuries, humanity, making incredible efforts to protect against floods, cannot succeed in this matter. On the contrary, flood damage continues to increase with each passing century. Catastrophic floods and floods quite often occur on the rivers of our country. Vast areas of agricultural land, towns and cities are flooded. Livestock and crops are dying, transport arteries and bridges, residential buildings and industrial structures are being destroyed. Sometimes people die.

Severe floods occur almost every year. Some arise as a result of the rapid melting of heavy snow that covered vast drainage areas, others due to heavy and prolonged rainfall, and others as a result of surge winds that prevent rivers from flowing into their terminal basins.

Catastrophic river floods are perhaps the most significant natural hazard. For centuries and millennia, people have intuitively assessed the risk of floods - they have compared the benefits of developing coastal areas with the potential consequences of their flooding. If the risk was great, people either refused to use floodplain lands or tried to reduce the danger by building simple protective structures. Sooner or later, these protective measures turned out to be insufficient, and the person again faced the need to choose.

1. Types and causes of floods.

Nowadays, rivers have gained importance as a source of energy, irrigation, industrial water supply, Wastewater, and also as a place of mass recreation, tourism and sports. Flood is intense flooding large territory water above annual levels, one of the natural disasters. Occurs during floods, floods, and dam and dam breaks.

A flood is a relatively prolonged rise in water levels in rivers; which repeats annually in the same season and is accompanied by a high and prolonged rise of water, usually its exit from the channel onto the floodplain. During floods, structures in river floodplains are damaged, banks are washed away, and sometimes valuable agricultural land is covered with sand. The greatest floods lead to floods, which are considered natural disasters.

Flood is an intense, relatively short-term rise in the water level in a river, caused by heavy rains, downpours, and sometimes rapid melting of snow during thaws. Unlike floods, floods can occur several times a year. A particular threat is posed by the so-called flash floods associated with short-term but very intense downpours, which also occur in winter due to thaws.

Natural causes of flooding include:

A) Spring-summer melting of snow and glaciers in drainage areas. Such floods can be predicted by season, and based on snow reserves - also approximately by height and duration. It should be borne in mind that the correlation between snow reserves and flood height is not that high. With relatively small snow reserves, a friendly spring can lead to a large flood. The condition of the underlying rocks (frozen or not) on which the site is located is also important. snow cover. And vice versa, with large snow reserves, but not frozen soils and an extended spring, when frosts alternate with thaws, the snow in the catchment areas “rots” to a large extent, preventing runoff.

B) Heavy rains. Here, in the sense of a forecast, we can only talk about a flood season, and in the form of a short-term warning - about calendar dates, approximately - about the duration and height of the expected increase in level. IN climatic conditions In Russia, such rises in level are widespread in the monsoons Far East, in the South-West European territory countries, on the rivers of the Black Sea coast of the Caucasus, etc. It should be noted the peculiarity of the Caucasian rivers, high floods on which can be observed at any time of the year. In mountainous mudflow-prone areas, floods may be accompanied by the movement of water erosion products, as well as bottom sediments, along river valleys.

B) Wind surges of water. They appear on the coasts of reservoirs and in the lower reaches of rivers flowing into these reservoirs. In terms of timing, they are not predictable; in some cases, we can talk about seasons when surges are generally observed more often and are of greater height. In general, we can only talk about a probabilistic description of the height and duration of surge water rises, which can vary greatly along different sections of the coast. On the coasts of marginal seas one has to reckon with the combined manifestation of surge and tidal level rises.

D) Congestion. Congestion - clogging of the riverbed by a stationary ice cover and accumulation of ice floes during the spring ice drift in narrowings and bends of the river bed, restricting the flow and causing a rise in the water level in the place of ice accumulation and above it. Jam floods form at the end of winter or early spring, and arise due to the non-simultaneous opening of large rivers flowing from south to north. The exposed southern sections of the river in its course are being dammed accumulation of ice in the northern regions, which often causes a significant increase in water levels. Jam floods are characterized by a high and relatively short-term rise in the water level in the river.

D) Gluttony. Zazhor - ice plug, accumulation of in-water, loose ice during winter freeze-up in narrowings and bends of the riverbed, causing water to rise in some areas above the level of the main riverbed. Jam floods form at the beginning of winter and are characterized by a significant, but less than jam, rise in the water level and a longer flood duration.

E) Sediment deposition when rivers exit from foothill areas to flat areas with a decrease in flow speed and transport capacity of the flow; At the same time, the riverbed grows, ending up higher than the surrounding area and from time to time “falling” to the side.

J) Fluctuations in the level of closed reservoirs as a result of disturbances in the water balance under the influence of the variability of its components, as is the case, for example, in the Caspian Sea, where the amplitude of the corresponding long-term level fluctuations exceeds 3 m.

The causes of floods are diverse, and each cause or group of causes has its own type of flood. Below we indicate four groups of types of floods.

1. Floods associated with the passage of very large water flows for a given river. Such floods occur during the period of spring snowmelt, with heavy rainfall and rainfall, in the event of dam failures and dammed lakes breaking out.

2. Floods caused mainly by the great resistance that the water flow encounters in the river. This usually happens at the beginning and end of winter due to jams and ice jams.

3. Floods caused by both the passage of large flows of water and significant resistance to water flow. These include mudflows on mountain rivers and water-snow flows in gullies, ravines and hollows.

4. Floods created by wind surges of water on large lakes and reservoirs, and direct causes are associated with various hydraulic engineering measures and the destruction of dams. Indirect - deforestation, drainage of swamps, industrial and residential development, this leads to a change in the hydrological regime of rivers due to an increase in the surface component of runoff. Evapotranspiration is reduced due to the cessation of interception of precipitation by the forest floor and tree crowns. If all forests are removed, the maximum flow can increase to 300%. There is a decrease in infiltration due to the growth of impervious pavements and buildings. The growth of waterproof coatings in urbanized areas increases floods 3 times.

Human activities leading to floods:

1. Restriction of the living cross-section of the flow by roads, dams, bridges, which reduces the throughput of the riverbed and increases the water level.

2. Disruption of the natural flow regime and water levels.

It should be emphasized that in a particular water body, floods are usually caused by several reasons, and therefore, in order to determine the calculated characteristics of possible flooding, a comprehensive analysis should be carried out and a composition of the probability distribution laws that are characteristic of certain species floods.

2. Examples of floods in Russia and the world.

Man has struggled with floods throughout his entire existence, and many such natural disasters have occurred over its centuries-old history. In Russia, between 40 and 68 crisis floods occur annually.

Floods with catastrophic consequences on the territory of modern Russia over the past 20 years have occurred:

In 1994 In Bashkiria, the dam of the Tirlyansk reservoir broke and an abnormal release of 8.6 million cubic meters of water occurred. 29 people died, 786 were left homeless. There were 4 settlements in the flood zone, 85 residential buildings were completely destroyed;

In 1998 near the city of Lensk in Yakutia, two ice jams on the Lena River caused the water to rise by 11 m. 97 thousand people were in the flood zone, 15 died;

In 2001 Lensk was again almost completely flooded due to flooding, which led to the death of 8 people. 5 thousand 162 houses were flooded; in total, over 43 thousand people suffered from the flood in Yakutia;

In 2001 V Irkutsk region because of heavy rains a number of rivers overflowed their banks and flooded 7 cities and 13 districts (63 settlements in total). The city of Sayansk was especially affected. 8 people were killed, 300 thousand people were injured, 4 thousand 635 houses were flooded;

In 2001 There was a flood in the Primorsky Territory of the Russian Federation, as a result of which 11 people died and more than 80 thousand were injured. 625 square meters were flooded. kilometers of territory. 7 cities and 7 districts of the region were in the disaster zone, 260 km of roads and 40 bridges were destroyed;

In 2002 As a result of severe flooding in the Southern Federal District of the Russian Federation, 114 people died, of which 59 were in the Stavropol Territory, 8 in Karachay-Cherkessia, 36 in the Krasnodar Territory. In total, more than 330 thousand people were affected. 377 settlements were in the flood zone. 8 thousand residential buildings were destroyed, 45 thousand buildings, 350 km of gas pipelines, 406 bridges, 1.7 thousand km of roads, about 6 km of railway tracks, over 1 thousand were damaged. km of power lines, more than 520 km of water supply and 154 water intakes;

In 2002 on Black Sea coast The Krasnodar region was hit by a tornado and heavy rains. 15 were flooded settlements, including Krymsk, Abrau-Durso, Tuapse. Novorossiysk and the village of Shirokaya Balka suffered the greatest destruction. The disaster claimed the lives of 62 people. Almost 8 thousand residential buildings were damaged;

In 2004 As a result of the flood in the southern regions of Khakassia, 24 settlements (1077 houses in total) were flooded. 9 people died;

In 2010 In the Krasnodar region there was a major flood caused by powerful torrential rains. 30 settlements were flooded in the Tuapse and Absheron regions and in the Sochi region. 17 people were killed, 7.5 thousand people were injured. As a result of the natural disaster, almost 1.5 thousand households were destroyed, of which 250 were completely destroyed;

In 2012 year, heavy rains led to the devastating flood throughout the history of the Krasnodar region. 10 settlements were affected, including the cities of Gelendzhik, Novorossiysk, Krymsk, and the villages of Divnomorskoye, Nizhnebakanskaya, Neberdzhaevskaya and Kabardinka. The main blow of the disaster fell on the Krymsky region and directly on Krymsk. As a result of the flood, 168 people died, of which 153 people were in Krymsk, three in Novorossiysk, 12 in Gelendzhik. 53 thousand people were recognized as affected by the disaster, of which 29 thousand completely lost their property. 7.2 thousand were flooded. residential buildings, of which over 1.65 thousand households were completely destroyed.

Around the world you can note:

December 1999 - Severe flooding in Venezuela was caused by rain that continued for a week. A state of emergency was declared in 5 northwestern states and the capital federal district. The death toll, according to Western news agencies, exceeded 10 thousand people;
- February - March 2000 - The largest flood in Mozambique was caused by Cyclone Eline. The disaster destroyed hundreds of thousands of houses, huge areas of farmland and caused the death of more than 700 people. About 2 million people, more than 10% of the country's population, were left homeless as a result of the floods;

March 2000 - in Hungary heavy rains and melting snow caused some of the worst flooding in years. A state of emergency was declared in the eastern regions of the country. More than 200 thousand hectares of land were under water;

September 2000 - in India, the cause of a natural disaster was prolonged and very heavy monsoon rains, which caused a ten-meter rise in water in the rivers. The death toll in the Indian states of West Bengal and Bihar has reached almost 800. In total, up to 15 million people were affected. About 600 settlements were flooded, crops and food storage facilities were completely destroyed;

October 2000 - an emergency in Vietnam was caused by the worst floods in the country's history. Heavy rains in southern Vietnam continued for more than 2 months. The water level in the Mekong River within the city of Ho Chi Minh City exceeded the permissible level and reached 1.26 m. According to official data, 727 people died as a result of the floods, including 239 children. About 45 thousand families were evacuated;
- August 2002 - heavy rains in the summer in northern and central Europe caused catastrophic flooding in August. 250,000 people were directly affected;

2005 - Hurricane Katrina in the United States causes widespread flooding in Louisiana, Mississippi and Alabama. The levees around New Orleans, Louisiana were breached and the entire city was flooded, causing much of the city's population to be evacuated. 1193 people died;

May 2008 - The Ayeyarwaddy Delta in Myanmar floods due to Cyclone Nargis, the largest cyclone ever recorded in the Bay of Bengal. The United Nations reported that 2.4 million people were affected, with about 146,000 dead or missing;

2008 - Haiti. Four tropical disasters Tropical Storm Fay, Hurricanes Gustav, Hanna and Ike, which occurred within 1 month, caused flooding that led to the death of 425 people, destroyed crops throughout the country, up to 600,000 people require international assistance;

2009 - in the Philippines, after two tropical downpours within a week, mudflows and severe flooding occur. The President declares a national disaster. At least 3 million people were affected and more than 540 died;

2009 - Samoa Islands. An earthquake in the sea led to the formation of a wave up to 6 m in height, which washed away all villages up to 1 km inland on the coast of Samoa, American Samoa and Tonga, on the Pacific Islands, killing more than 189 people;

July August 2010 - About 2,000 people died in Pakistan. The flood caused a mass exodus of spiders: they fled from the flow of water on the trees, entangling their crowns with a thick layer of cobwebs, giving the coastal landscapes an ominous look;

July 2011 January 2012 - Thailand was flooded for six months, entire provinces went under water. The flood claimed the lives of more than 600 people.

3. Problems of floods and safety of hydraulic structures.

Floods are among the most destructive and frequently recurring natural disasters. IN Russian Federation The area of ​​flood-prone areas is about 400,000 km². An area of ​​about 150,000 km², where more than 7 million hectares of agricultural land is located, is subject to floods with catastrophic consequences. Regions most at risk from flooding include: Krasnodar region, Volgograd, Astrakhan, Amur and Sakhalin region, Transbaikalia, Stavropol Territory, Buryatia, Primorsky Territory, Dagestan, Kabardino-Balkaria. Last years in the south of Russia, in the Primorsky Territory, the Republic of Sakha (Yakutia), there is an increase in floods with catastrophic consequences for the population and economic facilities.

The main reasons for the occurrence and increase in the risk of floods are climate change and the occurrence of abnormal weather phenomena, as a result of ice jams in river beds, intensive development and construction of drainage and flooded areas, insufficient provision of settlements and agricultural land, reliable engineering protection. Risk factors are measures to restrict (reduce) the flow of the river, economic development of flood-prone areas in the lower reaches of hydroelectric facilities, with the placement of residential and economic facilities.

The aggravation of the flood problem in Russia is directly related to the aging of the main production assets of the country's water sector. With deterioration technical condition hydraulic structures, the risk of their destruction during floods increases. Of the total number of hydraulic structures, over 90% are built from soil and stone-soil materials, for which the service life is about 30 years. However, the share of hydraulic structures with a service life of more than 30 years is about 50%. The fight against floods in the Russian Federation consists mainly of fencing the territory with dams, increasing the capacity of rivers, redistributing flow and other engineering measures.

Reservoirs are important because they reduce flood peaks. This is why it is planned to release the reservoirs before the onset of the flood, but this is not enough. In conditions of increasing anthropogenic pressure, pollution and degradation of land and water sources, and the increasing risk of catastrophic floods, the use of an ecosystem approach to environmental management is of decisive importance. It considers environmental, economic and social resources and their interactions. The problem of floods and the safety of hydraulic structures is environmental, socio-economic and technical problem. Along with engineering measures, to solve the problem of floods, it is necessary to analyze factors, the safety of the operation of hydraulic structures and, at the same time, focus on warnings and reductions. negative consequences floods, timely provision of accident-free passage of flood waters, modernization and improvement of the safety of hydraulic structures. The fundamental basis for this is a system analysis of the state of functioning water bodies and hydraulic structures, drainage and flood-prone areas, the causes of the consequences of floods, taking into account natural, social and economic resources.

For warning crisis situations it is necessary to improve the unified state management system, which presupposes the presence of a Federal center, basin, regional, municipal structures and, accordingly, unified information and analytical systems based on monitoring of water bodies and hydraulic structures. The mechanism for implementing measures to solve the problem of floods and the safety of hydraulic structures includes the use of a set of organizational, legislative, regulatory, methodological and socio-economic measures.

Conclusion.

Floods are inevitable a natural phenomenon. The task of humanity is to study the characteristics of floods in as much detail as possible and learn to prevent catastrophic consequences.

From history it is clear that man copes with this problem quite successfully. Hydrological scientists carry out the necessary calculations and forecasts, carry out work aimed at combating floods - agrotechnical, forest reclamation, field protection. However, the accuracy of calculations and the timeliness of activities carried out leaves much to be desired. This can be corrected by the widespread introduction into practice of new technical means of collecting and processing information about the state of the natural environment.

Man continues to build up the banks of rivers and lakes, actively develops river valleys, and storms mountains. For these reasons, the scope of flood control work is increasing. Floods as a natural disaster are becoming increasingly intolerable. Scientific, engineering and socio-economic feasibility studies for flood protection projects are among the most important tasks of specialists in many fields, primarily hydraulic engineers, hydrologists, ecologists and economists.

In the age of technological progress, floods have claimed millions of lives and caused enormous material damage, which tends to increase.

List of used literature.

1. Federal Law “On the protection of the population and territories from natural and man-made emergencies” No. 68-FZ dated December 21, 1994 (as amended on July 21, 2014).

2. Vorobyov Yu.L. Catastrophic floods of the early 21st century: lessons and conclusions. Moscow: Dex-Press, 2003.- 352 p.

3. Oleinik T. F. Great natural disasters: floods, earthquakes, volcanoes, tornadoes. - Rostov-on-Don: Phoenix, - 2006. - 254 p.

4. Chumakov B.N. How to survive natural disasters. Moscow: Eksmo, 2005. - 58 p.

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| Origin and types of floods. Their consequences

Basics of life safety
7th grade

Lesson 16
Origin and types of floods. Their consequences

FROM THE HISTORY OF FLOODS

Less than four months had passed since the founding of St. Petersburg when a flood occurred. On the night of August 30-31, 1703, the water in the Neva rose by more than 2 m and flooded the camp of the Russian troops. Food warehouses were flooded, and part of the forest prepared for the construction of the Peter and Paul Fortress was destroyed.

The head of the garrison, A.I. Repnin, reported to Peter I: “It’s great, sir, our weather from the sea is cruel, and in our place where I stand with the regiments, water is pouring right up to my camp, sleeping in the Preobrazhensky regiment at midnight taverns of many sleepy people and their junk was wet..."

Two years later, on the night of October 15-16, the same warehouses were flooded again. Under the pressure of furious waves and hurricane winds, the walls of houses collapsed, roofs fell off, and uprooted trees fell.

An eyewitness to the flood, writer A.P. Baschitsky wrote: “The Winter Palace, like a rock, standing in the middle of a stormy sea, withstood the onslaught of waves from all sides, crashing with a roar against its strong walls and watering them with splashes almost to the top floor. On the Neva, the water boiled as if 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 extremely rapid rise of water greatly aggravated the situation. Due to the disorganization of the population and the lack of management of the authorities, the flood of 1777, despite its short duration, caused enormous damage to the city. Many fences and fences were overturned and leaned wooden houses. The water washed away the prison, which was located on the seashore, along with 300 prisoners. The fountains in the Summer Garden were destroyed (they were never restored).

Catherine II in her diaries described the storm on that memorable night: “From that moment, everything flew in the air, tiles, iron sheets, glass, water, hail, snow... On the embankment, which is not yet finished, three-masted merchant ships. The exchange has changed its location... My cellars are flooded with water, and God knows what will happen to them.”

The flood of 1824 brought the city huge losses. 208 people died (according to other sources - 569 people). The Neva remained turbulent until the middle of the winter of 1824/25. 324 houses were completely destroyed, 3257 various other buildings were damaged (i.e., half of all existing ones). Of the 94 ships docked in the harbor, only 12 were saved. 3,600 heads of livestock drowned, 900 thousand pounds of flour and a large number of other food. For a long time after this flood, colds were rampant in the city. Prices for food and firewood have skyrocketed. For more than half a century, this flood was called the “flood.”

Origin and types of floods

Flood is a significant inundation of water in an 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 2,855 major floods worldwide. 7 million people died in them.

Depending on the scale, frequency and damage caused, floods are classified as low, high, outstanding and catastrophic.

Low (small) floods occur mainly on lowland rivers. At the same time, water floods low-lying areas (less than 10% of agricultural land). Such floods hardly disrupt the rhythm of life of the population and cause minor damage. They repeat once every 5-10 years.

High floods significantly disrupt people's normal lives and cause significant material damage. In densely populated areas, there is often a need for partial evacuation of the population. Such floods occur once every 20-25 years.

Outstanding Floods cover entire river basins. They cause great material damage and flood settlements and cities. In this case, there is a need for mass evacuation of people and material assets. Occurs 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 cause and the second or third place in the number of victims.

Let's turn to the history of our country. The Ipatiev Chronicle recorded a terrible flood in southern 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, floods are divided into several types.

Floods are floods caused by spring melting of snow on the plains or melting of snow and glaciers in the mountains. They are repeated annually in the same season with varying intensities and durations, which depend on meteorological conditions. Floods are characterized by a significant and prolonged rise in water levels.

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

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

Jam floods formed at the end of winter or spring. They are characterized by a high and relatively short-term rise in the water level in the river.

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

On medium-sized rivers, the total length of the jam can be from one to several kilometers. The length of the guzzling section can reach up to big rivers up to 20 km. Ice jams most often occur on rivers flowing from south to north. In Russia it is Northern Dvina, Pechora, Yenisei, Ob, Lena, Irtysh, Vitim, Tom, etc. Icebreakers are used to break up traffic jams, blasting operations and bombing from aircraft are carried out.

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 arise on the windward shore of a reservoir as a result of a rise in water level under the influence of the water surface strong wind cyclone In this case, a surge wave is formed, propagating 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 water levels. The surge wave can spread to large rivers for hundreds of kilometers, for small ones - for tens of kilometers. Flooding usually lasts from several tens of hours to several days.

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

Floods caused by the failure of dams (hydraulic structures). They occur when water overflows over the crest of a dam due to untimely pre-flood drainage of the reservoir, when the dam is destroyed or the dam's spillway capacity is insufficient. Dam failure is also possible due to poor quality construction work and improper operation, the effects of earthquakes and the consequences of military operations. 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 along the path of its movement.

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

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

Consequences of floods

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

Flooding is the covering of the surrounding area with a layer of water, flooding courtyards, streets of populated areas and the lower floors of buildings.

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

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

Secondary consequences of floods: reduction in the strength of structures as a result of erosion and undermining; transfer of harmful substances spilled from damaged storage facilities by water and their contamination of vast areas; complication of the sanitary and epidemiological situation; swamping of the area.

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

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

IN rural areas The timing (season) and duration of flooding are critical. 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 in the soil stops and carbon dioxide enters the water from the roots of the plants, which has a harmful effect on the plants. This circumstance is the main reason for the fall in yields or the death of agricultural crops as a result of floods.

Serious consequences of rare floods are sometimes changes in river channels: new channels appear or old ones deepen. Partially, and sometimes completely, washed away or covered with fertile silt upper layer soils in plowed areas of the floodplain, which significantly worsens land use and reduces productivity.

Measures to reduce flood damage

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

To protect against most floods, the same measures are used to significantly reduce their consequences: they plant shelterbelts in river basins, try to preserve coastal shrub vegetation, carry out special treatment of slopes, build ponds and reservoirs to intercept melt and rainwater.

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

To protect against floods, dikes are built along the banks of many rivers. Straightening of the channels of winding rivers is also carried out, which makes it possible to increase the slope of the water surface and the speed of water flow. As a result, maximum water consumption occurs at a lower level. On newly built-up areas, the method of filling the territory is used.

Work to strengthen river banks reduces the risk of erosion, and to deepen the river bottom allows a larger volume of water to pass through their beds, remove various obstacles from the bottom, and increase the flow speed.

To carry out operational preventive measures (warning the population about the threat of flooding; early evacuation of the population, material assets, animals from potentially flooded areas; construction of simple protective structures to protect populated areas and roads from flooding), a timely and reliable hydrometeorological forecast is important.

Most floods can be predicted and, thanks to this, possible losses can be reduced. Residents of cities and towns that periodically fall into flood zones must be informed in advance about this danger, trained and prepared to act in the event of a threat and during floods.

1. In which ocean is the Mariana Trench located? 1) Indian 2) Pacific 3) Atlantic 4) Arctic. 2. Which of the re

numerical sea currents operating in the Pacific Ocean?

1) Gulf Stream 2) Brazilian 3) Guinean 4) Kuroshio.

3. Sable is an animal living in a natural area:

1) steppes 2) taiga 3) deserts 4) tundra

4.One of the main modern species economic activity human in the tundra is:

1) logging 2) mining 3) raising livestock 4) growing grain

5. Among the listed closed lakes are:

1) Baikal 2) Victoria 3) Chad 4) Onega.

6. Which island has the maximum average annual precipitation?

1) Iceland 2) Kalimantan 3) Madagascar 4) Tasmania.

7.What mineral deposits are confined to ancient platforms?

1) oil 2) iron ores 3) copper ores 4) polymetallic ores

8.Which of the listed travelers contributed huge contribution in the discovery and study of Africa?

1) I. Moskvitin 2) D. Cook 3) D. Livingston 4) F. Magellan

9. Moderate maritime climate typical for:

1) Sumatra Islands 2) Iberian Peninsula 3) Great Britain 4) Yucatan Peninsula

10. Which of the following mountain systems the longest?

1) Cordillera 2) Urals 3) Alps 4) Appalachians

11.Which peninsula has monsoons throughout the year?

1) Labrador 2) Alaska 3) Indochina 4) Somalia

12. Which of the following natural zones is characterized by greatest number rodents?

1) taiga 2) tundra and forest-tundra 3) steppes 4) semi-deserts and deserts

13.Which of the listed rivers has a large number of rapids?

1) Volga 2) Amazon 3) Congo 4) Mississippi

14. Sign marine type climate is:

1) summer is dry and hot 2) winter is wet and warm 3) large amplitude of temperature fluctuations

15. Oak, myrtle, wild olive - representatives of the natural area:

1) equatorial forests2) hard-leaved forests3) tropical deserts 4) deciduous forests

1) Cordillera 2) Andes 3) Himalayas 4) Alps.

17.Which continent is the hottest:

1) Africa 2) Australia 3) South America 4) North America

18. Extreme southern point Africa:

1) Cape Agulhas 2) Cape of Good Hope 3) Cape Almadi 4) Cape Ras Hafun.

19. Climate zone Africa with bright pronounced seasonality: dry winter and wet summer:

1) equatorial 2) subequatorial 3) tropical 4) subtropical.

20.The saltiest sea belongs to the basin:

1) Pacific Ocean 2) Atlantic Ocean 3) Pacific Ocean 4) Arctic Ocean

Part B

1. Distribution of climate zones in Africa in order of decreasing density of the river network:

1) equatorial 2) tropical 3) subequatorial.

2. Match.

Natural area: Climatic zone:

1. Rainforests a) subtropical

2. Savannah b) tropical

3. Deserts c) subequatorial

d) equatorial.

3. Distribute the southern continents as their area increases:

1) Antarctica 2) Africa 3) South America 4) Australia.

Part C

1. Why highest point Africa - Kilimanjaro volcano - is located within the platform, not

folded area, like on other continents?

2. Are there glaciers in Africa, and if so, in what part of the continent?

3. Why do platforms usually have plains?

1) In which of the following countries does the majority of the population profess Catholicism: Ukraine; Netherlands; Italy; Greece; Philippines;

Indonesia; Sudan; Argentina?

Which of the following peoples belong to Indo-European family languages: Chinese, Hindustani, Russian, Japanese, 1. With which of the listed states does Russia have a maritime border? 1) Latvia 2) USA 3) Azerbaijan 4) Estonia 2. The extreme northern point of Russia which of the following rocks is metamorphic in origin1) pumice2) marble3) pebbles4) gypsum in humid equatorial forests

South America 1) there is a dry and wet season of the year 2) the vegetation contains many vines of ferns 3) chestnut soils predominate 4) eucalyptus trees predominate in the tree layer

Which of the following countries has the highest average population density1) Canada2) Japan3) Algeria4) Brazil

Which of the following countries has the highest GDP per capita1) Belgium2) Algeria3) Morocco4) Argentina

Which of the following countries does Russia border on the Amur River1) Kyrgyzstan2) Mongolia3) Kazakhstan4) China

in which of the listed regions of Russia are the agroclimatic conditions most favorable for growing sugar beets and corn1) Komi Republic2) Vologda region3) Tver region4) Voronezh region

Which of the following types of minerals is mined in the Volga region1) copper ores2) iron ores3) oil4) coal

in the supply of which of the listed types of products to the world market does Russia have a particularly large share1) semiconductors2) cars3) ships4) metals