1. Introduction
According to UNO data the floods cause the greatest economic damage to mankind from all natural disasters, being second by number of victims only to earthquakes. The basic floods on the rivers of Russia are connected not to rains, but to spring ice jams. The floods formated as a result of ice jams on the rivers of Yakutia, on which territory a half of all large rivers of the North of the Earth flow, are especially large-scale and have considerble consequences for the population and agriculture.
Yakutia has up to 450 000 rivers more than 10 kms long. The total length of rivers exceeds 1,5 mln km. Thirteen rivers have length of more than 1000 km . The density of the river network makes about 0,5 km per 1 sq km, the total flow reaches 900 cubic km per year.
The approximate estimation show that total amount of ice freezing on the rivers exceeds 120 cubic km. In the main the Lena river-bed it makes more than 20 cubic km. Hence, in the winter more than 14 % of annual water flow from the territory of Yakutia is kept in kind of ice in the river-beds. Besides the main rivers of Yakutia flow from the south to the north, and the ice on their mouth breaks later than the upper reaches.
Therefore the jams of rivers in Yakutia are widespread. The larger river is the more powerful jams are. On the Lena river they cause especially catastrophic rising of water.
For last 115 years the maximal peak charge of water on the Lena river has been equaled to 137 thousand cubic metre per second (near Kyusyur in 1960) that is equal to the sum of peak charges of three largest rivers of Russia - Yenisei, Ob and Amur. In 1960 for 7 seconds the Lena river carried through one million tons of water, and for one day - 12 billions tons. At such planetary productivity the Lena river develops capacity about one million horsepower, transport for one day about billion tons of ice at the rate of 8- 12 km per hour, and after fast destruction of a jam the rate on the first kilometers increases up to 20 km per hour.
On the rivers of Yakutia ice drifting practically does not happen without ice jam. From Vitim settlement to Sangar settlement only along the Lena river the constant places of jam formation number about 54. And jams formation on a number of sites threatens large settlements, including the capital of the republic Yakutsk with a flooding.
In Republic on the rivers, including small, every year there are floods of first three classes, tab. 1.1.
The table 1.1.
Classification of floods depending on scale of distribution and repeatability
Flood classes |
Scale of flood distribution |
Repeatability ( years ) |
1 |
2 |
3 |
High |
Bring appreciable material and moral damage, cover the rather large ground areas of river valleys, flood approximately 10-15 % agricultural grassland. Essentially disturb economic and household way of life of the population. Cause partial evacuation of people. |
20-25 |
Highest |
Bring large material and moral damage, covering the whole river basins. Flood approximately 50-70 % agricultural grassland, some settlements. Paralyse economic activity and sharply disturb way of life of the population. Cause necessity of mass population evacuation and valuable property from a zone of flooding and protection of the most important economic objects. |
50- 100 |
Disastrous |
Bring huge material damage and cause death of people, covering vast territories within the limits of one or several river systems. Flood more than 70 % agricultural grassland, a great number of settlements, industrial enterprises and engineering communications. The economic and industrial activity is completely paralysed, the way of life of the population temporarily changes. |
100 - 200 |
2. Review of high water in 1998 and 2001 (damage)
In 1998, 1999 the floods have been marked by several record indicators. So in 1998 in Lensk the level of water rising - 17,5 m – has been record not only for the Lena river and Yakutia but also for Russia as a whole, in the same year the record rising of water has been marked on the Aldan river.
In 1999 the level of water in Yakutsk has made 911 с m and on 2 с m has not reached a record, and the level of water above critical (when the low parts of the town begin be flooded) has held for 10 day. Earlier duration of flooding has not exceed 5 day.
The level of a high water on the Kolyma river in the Kolymskoye settlement has reached a record mark - 10,65 m (in 1974 - 10,13 m ).
The flood in 1998 falls under the catastrophic class.
135 settlements in 20 uluses and towns of the republic have been damaged. The number of suffered population has made 47 326 men, as a result of flood 15 men have been lost. More than 13 thousand dwelling houses have been flooded, 746 houses of them have been completely destroyed, including 657 private houses, where 3 158 men have been living.
197 welfare objects, 168 industrial objects, motorways 1044 km along have been flooded; 241 bridges, 195 dams and other engineering works have been destroyed and flooded.
The damage on life-supporting objects of settlements of the republic actually requiring financing for reconstruction works has made more than 1,2 billion roubles, ecological damage ~ 2 billion roubles.
In 2001 the conditions of high water formation, usual in the late April – the early May, have been characterized with high thickness of ice on the rivers, low distribution of a snow stock.
On the Lena river in the upper waters in the territory of Irkutsk oblast the intensive thawing of snow has caused powerful inflow of water and the preparedness near the border of the Sakha Republic (Yakutia) has been insufficient. That is one of the factors, which has served to formation of powerful ice jams and accordingly to formation of extremely high levels of water, which have exceeded long-term indicators on 3- 7 m , and in separate cases the record indicators have been recorded.
Formed on the Lena river powerful jam downstream the town of Lensk has caused a real disastrous.
The city with 28-thousand population has turned out under water.
Besides the Lensk town the settlements of Saldykel, Murya, Natora, Nuya, Batamay practically have been destroyed. Last years such disaster has not been at the level of the country.
On the Aldan river an ice jam formed at the mouth of the Tompo river has become a cause of increase of water level above critical in the centre of Tomponsky ulus – the settlement of Khandyga, as a result of which one of the large ulus centres and adjoining to it settlements have been flooded by icy water, dwelling houses and industrial buildings have been destroyed.
The flood in 2001 has brought a serious damage to many settlements of Lensky, Olyokminsky, Khangalassky, Namsky, Ust-Aldansky, Aldansky, Tomponsky uluses, town of Yakutsk and its suburban settlements.
More than 8 thousand dwelling houses, 366 welfare objects, 597 industrial objects have been damaged; 407 kilometers of roads, 160 bridges and dams have been destroyed. The boiler rooms, communication lines and electric power lines, transformers have been put out of operation. Ploughed fields have been flooded, a lot of cattle and birds have been lost.
Damage from a high water in 2001:
- number of suffered population from flood - 46790 men.
- number of population lost their habitation - 12096 men.
- number of flooded dwelling houses – 8139 units.
including destroyed - 3456 units.
- number of dwelling houses to be restored - 4683 units.
At the expense of federal and republican means 8564 apartments have been constructed, 845 state housing certificates have been granted. The summer rehabilitation rest of children who have been in a zone of flooding has been organized.
In 2001 the damage of consequences of disastrous in the Sakha Republic (Yakutia) as a result of spring flood of the rivers of Aldan, Lena has made more than 7 billion roubles or 230 million dollars.
The flood in 2001 is most scale and destructive for last hundred years.
The main causes of such catastrophic consequences of floods are, both a whole complex of negative natural factors (which could not be prevented) and man-caused factors. For example, in May, 2001 there has happen a rare combination of hydrometeorological factors which have caused a high degree of high water and ice jam formation risk on the basin of the Lena river. The severe winters in the territory of Yakutia determine increase of a powerful ice cover on the rivers. From 1970 till 1999 the winters in area of Yakutia has not been severe, and last decade some tendencies to increase of their severity have been emerged. For last 15 years the coldest winter has happened in 2000-2001, especially in the area of Lensk and Olyokminsk.
A thickness of ice, which is one of the important factors of jams formation, downstream Lensk in the spring 2001 has been significantly above the norm. the average thickness of ice on the Lena river from Olyokminsk to Yakutsk has been thickest for the last decade.
Sharp reduction of air temperature during river breaking up has a significant influence on a course of ice jam formation (on the Lena river usually in the second decade of May), what cause additional rising of a water level due to increase of the ice getting frozen. This fact also has played a significant role in formation of a jam on the Lena near Lensk in 1998 and 2001.
Other factor causing formation of powerful ice jams is simultaneous ice drifting on the main river and on its inflows. It is necessary to emphasize that one of key factors caused the catastrophic scenario of course of flooding in area of the town of Lensk is first of all rising from upper reaches of the Lena river in the territory of Irkutsk oblast of the second high water wave.
The cause of formation of the second high water wave has become early sudden warming (up to +30 degrees С elsius), fall of heavy rains and intensive thawing of snow in Irkutsk oblast (in the basin of the upper Lena river and its inflows) on May 13-16, 2001. The exceeding of average long-term indications of air temperature in the territory of Irkutsk oblast in this period has made from 190 % up to 210 %, on May 13 in the territory adjoining to the upper Lena river more than 20 settlements, including towns of Kirensk, Ust-Kut, have been flooded. On May 17-18 the second high water wave from the upper reaches of the Lena river has reached Lensk. At approach of the second high water wave the second jam block of the Lena river has taken place, the level of water in the area of Lensk sharply has risen and has reached 20,12 m .
However, besides the natural causes of the catastrophic emergency situation conditioned by nature, it is necessary to note a number of man-caused actions, which considerably have furthered such large-scale emergency.
3. Conditions of formation of powerful jams.
The process of formation of jams is influenced by many factors such as:
Sharp transition from severe climatic conditions of the winter to the spring. The fast rising of heat in the beginning of the spring causes intensive inflow of thawed waters in the rivers, as which result the main role in the process of river breaking up belongs to heat and mechanical factor dynamically influencing on a firm winter ice cover of the rivers.
The most of the large rivers of Yakutia flows from south to north. On the rivers of such kind in middle and down current the heat influence has only preparatory character, the river breaking up on these sites usually is accomplished under influence of mechanical forces of ice drifting process. In this case thickness plays an important role.
The sites of jams formation, their sizes, capacity, extent, terms of formation and duration of existence, size of rising of jam levels of water and risk of flood of the rivers, repeatability depend on many factors.
The main of them are as follows:
- Morphological features of a structure of a channel and valley;
- Hydrological mode;
- Invariancy of hydrometeorological conditions in the period of freeze-up and breaking up of the rivers;
- Man-caused activity;
- Amount of autumn and winter sediments; character of spring (early, late); time and simultaneity of breaking up of inflows of the main river and their high level; temperature of air; thickness of ice.
It is first of all caused by a difference of climatic conditions. If on the rivers of the center of Russia the ice is drifting under daily average temperatures above zero, the thickness of ice does not exceed 0,5- 0,7 m , and in Yakutia daily average temperature frequently is below zero, the thickness of ice reaches 2,5 m , the ice has high strength. From this the methods of prevention of ice jams are significantly differ, and frequently are simply inapplicable for conditions of Yakutia.
4. The experience of realization of preventive measures on reduction of the risk of floods in the settlements through prevention of large ice jams.
In Yakutia for last 10 years the specialists of Hydrometservice, EMERCOM of Russia and UE "Vzryvstroy" has accumulated certain experience of forecasts and prevention of ice jams on the Lena, Aldan, Kolyma rivers. To destruct jams it is used energy of explosion, ice breakers, bombs and mines, to destruct ice fields - manual and machine drilling and explosions. Since 2002 the methods of easing of ice by means of covering with coal and sawing up are successfully applied, the research works on study of ice jams and methods of regulation are carried out: the sites of potential jams and character of jam formation are revealed, the measures of protection of settlements are developed, organizing of preventive measures are organized at a proper level, long before a high water the plans and estimation of forces and means are made. On the basis of the data of the Yakut Hydrometeorological Service the Centre of Monitoring and Forecasting makes the forecasts on jams and rise of water.
Since 2002 under the program "Reduction of risks and mitigation of consequences of emergency situations of natural and man-caused character in the Sakha Republic (Yakutia) till 2006" the purposeful work on study of jams and measures of their prevention is conducted.
By the order of the Ministry the Institutes of the republic have conducted works on the given subjects and works on prevention of jams are simultaneously conducted during preparation for safe high water passing.  back
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