A specific form of natural conditions is represented by the internal adverse dangerous natural phenomena (ADNP) or natural disasters inherent to certain localities. In specialized literature, the concept of a natural disaster is interpreted as a dangerous natural phenomenon that causes an emergency situation.
The concept of an emergency situation is associated with such concepts as danger and risk (quantitative assessment of danger).
In Kyrgyzstan, according to specialists, there are more than 75 varieties of dangerous processes and phenomena of natural, technogenic, ecological, biological, and social nature. However, monitoring and forecasting cover no more than 10 types of disasters that occur most frequently and pose a significant threat to humans.
By genesis, all the main known types of ADNP in the Chui Valley are divided into hydrometeorological and geological-geomorphological. Some of them occur in the form of sudden and short-lived events (earthquakes, landslides, avalanches, collapses, mudflows, etc.), causing significant material losses and loss of life. Others, such as floods and erosion, develop over a long time, rarely leading to human casualties, but can cause colossal material damage.
The treachery of natural phenomena has been known to humanity for millennia. Traces of past destructions, descriptions, legends, paintings, and much more remind us of the catastrophes that have occurred in the world as a result of natural phenomena.
Earthquakes are the most significant geological phenomenon in terms of their consequences. Every year, according to specialists, about 10,000 people die from them worldwide, and the material damage, based on incomplete data, reaches 400 million dollars.
Earthquakes are caused by seismic waves and elastic vibrations of the Earth's crust. The destructive power of earthquakes is characterized in conditional intensity points. In the Chui Valley, a 12-point intensity scale is adopted to describe the forces of earthquakes.
The destructive effect of an earthquake is determined by the energy and depth of its focus or hypocenter, the amplitude and period of seismic wave oscillations, and the distance from the epicenter, where seismic energy is absorbed. The radial projection of the hypocenter on the surface of the Earth is called the epicenter of the earthquake - this is the area where the greatest destruction occurs.
An earthquake represents a complex disaster due to its numerous direct and secondary manifestations on the Earth's surface. The main disasters caused by earthquakes are associated with enormous physical damage, casualties, as well as fear of this disaster, which leads to the destruction of housing, fires, and accidents. For example, the Suusamyr earthquake of 1992, according to the Ministry of Emergency Situations and Civil Defense specialists, caused enormous damage to the Chui Valley, approximately 1.5 billion rubles.
Within the Chui Valley (and adjacent areas), significant catastrophic earthquakes are known, such as the Belyvodskoye earthquake in 1865, the Vernensky earthquake in 1887, and the Kemin earthquake in 1911. The most powerful devastating earthquake, a 10-point Suusamyr earthquake, occurred on August 19, 1992. It claimed many lives and reminded us once again of the danger. The main shock of the earthquake was felt by people throughout Kyrgyzstan with a force of 4.5 points and higher, depending on the distance to the epicenter. The zone of maximum tremors covered the northern part of the Suusamyr Ridge, partly the Ketmen-Tyobon and Talas valleys. According to residents, at the moment of the earthquake, "waves" ran across the ground, as if the surface of the soil became bumpy and then straightened out. In the epicentral zone, cracks appeared on the surface of the ground, and massive collapses and landslides were noted in the mountains. It became clear that one of the strongest earthquakes of the year had occurred, which is the largest in the Tian Shan since the post-war period.
As a result of a comprehensive analysis of geological and seismic data (working program for the protection of buildings and structures "Saktoo," Bishkek, 1992) and seismic zoning of the territory of Kyrgyzstan, conducted in 1977 and 1995, seismogenic zones were identified. All the strongest earthquakes are associated with the Northern Tien Shan zone, as it is located along edge faults at depths ranging from 20-40 to 60 km, with the speed of recent movements along them reaching 5-7 mm per year.
To preserve the lives of people living in seismically hazardous areas, to ensure the stability and resistance of buildings against the destructive impact of earthquakes, norms and rules are being created and applied in practice, providing for various measures aimed at increasing their seismic resistance.
Mudflows and floods. It is often very difficult to draw a line between a mudflow and a flood, as both can form in the same basin.
Flood - a high flow of water in a riverbed over a relatively short period. It is a tragedy that causes flooding of nearby areas and significant destruction of economic facilities.
Mudflow (from Arabic - "sayl") - a turbulent mountain stream that suddenly arises in the riverbeds and a temporary muddy flow. Mudflows are rapid mountain streams consisting of semi-liquid mud and rock mass. Such masses contain up to 70-80% of debris material from their total volume, which includes fragments of various sizes, sometimes up to 1 meter or more in diameter. Such muddy rock torrents are formidable forces of the mountains in the Chui Valley that have been known for a long time.
Unlike ordinary streams, mudflows usually move not continuously but in separate waves, according to scientists, at speeds of up to 10 m/s or more.
The most active mudflow activity in the Chui Valley manifests where there is a dense network of river valleys, streams, and ravines with steep slopes, unanchored by soil-vegetation cover. Such conditions are observed in the foothill and low mountain zones of the northern slope of the Kyrgyz Ridge.
Mudflows manifest unevenly and differently by seasons in different parts of the Kyrgyz Ridge. They most often occur in April, May, or June, as a result of heavy rains or melting snow and ice. Mudflows have a rhythmic character and manifest in intervals of 2 to 5 years. Sometimes they occur more frequently, sometimes less frequently, in some areas annually, and in places constantly.
Rainfall plays a primary role in the formation of mudflows. Of the total number of known mudflow cases, about 70% are attributed to rainfall, the frequency of which varies across different parts (districts) of the Chui Valley and is mainly determined by the frequency of rainfall. In nature, it is often the case that one intense spring rain can produce much greater erosive work than precipitation for the entire year. Usually, heavy rains lead to a rapid runoff. And the runoff generates the formation of mudflows in the foothills, which have a catastrophic nature. For example, the heavy rains in the Chui Valley from April 30 to May 3, 2000, produced the strongest mudflows in the valleys of the Kegeti - Jargo, Issyk-Ata, and others. In just the Issyk-Ata Valley, several kilometers of roads from Bishkek to Issyk-Ata and several bridges were destroyed. They cause enormous damage to the national economy. This disaster is beautifully and aptly called by the mountain torrents - the yellow dragon. This is when quiet mountain rivers and streams turn into roaring, muddy monsters that sweep everything in their path within an hour or two.
Mudflows most frequently occur in the Ak-Sai River valley, where they roll through almost every year. Primarily, mudflows are glacial in nature. Between 1960 and 1971, Ak-Sai mudflows were observed ten times. A tragedy occurred in July 1968, resulting in human casualties. A group of students from the geography faculty of KGNU went to the Ak-Sai glacier for field training in Ala-Archa. Three students, returning from the route, crossed the boulder-strewn riverbed of the Ak-Sai and decided to sunbathe. They chose trees that stood equally. At that moment, a huge mudflow occurred. The mudflow wave swept the fir trees and, reaching the river, destroyed everything in its path.
Vivid traces of modern mudflow activity are recorded in the Kyrgyz Ridge, as well as in the valleys of the Kuturgan-Sai (Alamudun basin), Jar-Bashy (Ak-Suu basin), Kara-Balta, and others.
For a mudflow to occur, certain geological, geomorphological, and climatic conditions are necessary. According to M. Jandaev (1966, 1978), the formation of a mudflow is explained by the complex manifestation of many factors, which can be grouped into three categories: hydrological-climatic, geological, and geomorphological. Among these factors, the main ones can be highlighted. Firstly, heavy rains and intense melting of snow cover or glaciers; secondly, the presence and certain physical-mechanical state of debris material in the mudflow basin; and thirdly, the area of the watershed basin and the slope of the riverbeds. The formation of a mudflow is possible only under certain combinations of these three causes, and if at least one of them is excluded, the formation of a mudflow becomes impossible. Therefore, M. Jandaev considers them determining.
The struggle against this formidable force of nature in the conditions of the Chui Valley has become a serious economic problem, on which tens of thousands of soms are already being spent. At the same time, scientific forecasting is one of the important aspects of the complex of anti-mudflow measures.
The territory of the Chui Valley, due to its physical-geographical and natural-geological features, is subject to many other natural processes.
The above-mentioned angles that determine the manifestations or limits of the spread of various natural processes may vary somewhat depending on the exposure and degree of vegetation cover of the slopes, the nature of the soils, and other conditions. However, as a rule, they remain within the specified boundaries. A slope of 1.5° determines the beginning of surface runoff, a slope of 3° - the beginning of linear erosion, and a slope of 6° and more - the beginning of active water erosion (T.V. Zvonkov, 1970).
The spread, frequency, and damage caused by the aforementioned formidable natural phenomena fluctuate from year to year; nevertheless, it can be said that in the long term, the most dangerous for the population and economy of the Chui Valley are earthquakes, mudflows, floods, landslides, collapses, and others.
Water erosion. Erosion is the process of destruction of rocks and washing away of soils by water flow.
The natural prerequisites of the Kyrgyz Ridge and its foothills are favorable for the occurrence and development of erosion. The relief of these areas is characterized by significant slopes and complex dissection, which contributes to intense surface runoff. In addition, the rapid melting of snow and the torrential nature of rains are also significant factors in the development of erosion processes. Finally, intensive human economic activity accelerates the development of erosion.
Water erosion manifests on slopes where rain and meltwater flow down. It is divided into surface (relatively uniform soil washing), rill (formation of shallow channels), and deep (washing away of soils and rocks by water flows).
Atmospheric precipitation flowing down the slopes in a solid veil or in small streams washes away soil particles. As a result, the surface, the most fertile part of the humus horizon of the soil, is carried away. At the same time, small grooves or rill washouts often form on the slope, which can later develop into noticeable channels up to several tens of centimeters deep. In the foothills and lowland plains, washouts often occur in arable fields. When irrigating along the furrows, the stream concentrates in a narrow channel, thereby creating the possibility of washing away in advance.
Washouts can transition into ravines within two or three years as a result of erosion. Such cases have been observed on the slopes of the Kegeti, Issyk-Ata, Norus, Sokuluk rivers, etc., in the zone along the lower shelves, as well as in the foothill step of the Kyrgyz Ridge. Due to the development of ravines, the total area of arable land in the Chui Valley decreases by several thousand hectares per year.
Based on morphogenetic characteristics, four types of ravines have been identified in the territory of the Chui Valley, which are conditionally named: fushovid, flat-bottomed, gorge-like, and cornice-like. Similar ravines have been identified on the slopes of the Zailiyskiy Alatau (M. Jandaev, 1978).
Currently, more than 50% of agricultural lands, mainly in the plain part of the Chui Valley, are subject to erosion. Surface and ravine erosion processes generally do not lead to loss of life, but the economic losses from them can be comparable to the most catastrophic. The republic also loses in that thousands of tons of the fertile part of the soil layer are washed away from arable lands annually due to erosion.
As noted by S.S. Sobolev (1961), it is easier to prevent erosion by preventing the formation of large flows than to fight against its destructive effects later.
Floods are a tragedy for the residents of river valleys. Floods are periodically observed to a greater or lesser extent on most rivers in the Chui Valley. The magnitude of a flood and its frequency are mainly determined by climatic and orographic factors that characterize the area.
Floods have been and continue to be a formidable and treacherous force for humans. According to UNESCO, in the last century, 9 million people have died from them. The material damage they cause is colossal.
Water has always been one of the main elements of human consumption. Therefore, people built their homes near rivers and primarily developed lands adjacent to the river. But the river also brought troubles, washing away homes and crops during floods.
An important prerequisite for effective flood protection is their accurate forecast, the reliability of which, thanks to scientific advancements, is currently very high. Flood protection can be active (construction of dams, dikes, drainage channels, deepening, etc.) or passive (notification and evacuation of people, using places that are unlikely to be flooded, etc.).
However, protective dams and dikes do not completely solve the problem of flood control. Therefore, after the Great Patriotic War, significant attention has been paid to the comprehensive solution of the flood control problem in the Chui Valley, primarily through the construction of reservoirs. Thus, the problem of flood control on the rivers Chui, Ala-Archa, Issyk-Ata, Kara-Balta, and others has been largely resolved.
Collapses and landslides. A landslide, in the broadest sense of the word, refers to all types of slope movement under the influence of gravity. In a narrower sense, this term refers to the movement of rock or soil masses down a slope along one or more sliding surfaces. According to I.V. Popov (1951), a landslide is defined as the displacement of blocks of rock on slopes with an inclination exceeding 15° as a result of saturation of the sliding surfaces by groundwater. Landslides occur rarely at smaller angles. Landslide processes are always hydrologically conditioned.
Landslides are one of humanity's oldest problems. Protection against landslides has remained one of the most significant issues for humanity for centuries. Many articles and books have been published on the origin and manifestation of landslide processes in the republic. Thus, a certain experience has been accumulated in studying this process.
Landslide flows are formed in loess-like rocks, which belong to the group of structurally unstable rocks that can reduce their strength and collapse under intense wetting and certain stress conditions; this causes subsidence of the rocks and subsequent horizontal displacements. Large landslide flows are most often formed in the upper reaches of streams and are associated with areas where loess-like rocks cover depressions or erosional cuts in the bedrock - troughs, which serve as a continuation of the stream beds upwards. The majority of landslide flows are observed in years with a high amount of atmospheric precipitation, when the groundwater level rises 2-3 times. Landslides can occur on all slopes with an inclination of 10° or more. They are formed and widely distributed in the foothills and low mountains of the Kyrgyz Ridge. Landslides can occur at any time of the year. However, landslide movements are mainly associated with the spring-summer season, as their activation is primarily linked to the intensification of feeding by groundwater and surface water. Landslides are characterized by slow movement (from several millimeters to 1-2 meters per year), which is sometimes replaced by faster movements.
It should be noted that currently, in the Kyrgyz Ridge - river valleys, the number of landslide cases on slopes and sides of excavations is increasing, including large ones, associated with the influence of technogenic factors. An example of this is the vicinity of the settlements of Bordu, Aktyuz, and others.
A collapse is the process of detaching large blocks from the main mass of rock and their subsequent movement down the slope. More expressively, a collapse refers to the free or vertical fall of fragments of any size of the composing rock from a cliff or another very steep slope.
Collapses occur suddenly on steep mountain slopes, often composed of various other fractured sedimentary, metamorphic, and volcanic rocks.
The danger of collapses, as well as other slope processes in the Chui Valley, should be assessed from two perspectives: as a direct threat to populated areas and individual engineering structures, and as a possibility of damming rivers and forming lakes, which, in the event of a breach, can flood the lower-lying areas.
Collapses of small masses of rock, consisting of fragments no larger than one cubic meter, are referred to in literature as rockfalls. Rockfalls most often occur due to uneven heating of the surface of rocks or earthquakes. Sometimes, especially in the morning hours, one can observe how individual fragments of rock fall with a roar into the river gorges. However, larger-scale rockfalls are associated with earthquakes.
Natural factors that contribute to the occurrence of mountain collapses and rockfalls are divided into two groups: passive - geological structure, features of the region's relief, climate.
Active - seismic shocks, the activity of atmospheric agents associated with the weathering of rocks, the activity of surface and groundwater, soil moisture, hydrodynamic pressure. According to specialists, a seismic event of 4 points is sufficient for the formation of mountain collapses. As a result, sudden collapses occur.
Snow avalanches. Snow avalanches are defined as the rapid and sudden sliding and flow of usually unconsolidated and unsorted snow, ice, and rock material. There is a shorter and more expressive definition by G.K. Tushinsky (1963); avalanches are sliding and cascading masses of snow.
Snow avalanches are an integral element of the mountain landscape. Just as it is impossible to imagine the ocean without storms, the desert without heat, or the Arctic without ice, it is also inconceivable to have the highlands of the Kyrgyz Ridge without snow avalanches. Mountains generate avalanches.
The material for avalanches is the snow itself, which usually accumulates over one winter season or even one snowfall. Avalanches do not unload or slow down while moving, unlike mudflows, but, rushing down a snow-covered slope, they increase in volume and accelerate their movement until they reach a horizontal surface, where they stop their rapid run.
Based on the nature of movement, T.K. Tushinsky (1963) distinguishes three types of avalanches: snow avalanches (snow slides), channel avalanches, and jumping avalanches.
The main causes of avalanche formation and measures of protection against them are laid out in the work of T.K. Tushinsky. However, the distribution and regime of avalanches in each mountain system have their own characteristics. The study of this issue by Kyrgyz researchers has allowed for the establishment of the peculiarities of avalanche formation and movement in the Tenir-Too, including in the Kyrgyz Ridge.
The upper reaches of the valleys of the Kyrgyz Ridge are usually narrow, with slopes cut by numerous couloirs and gullies. In addition, at the ridges, there are destroyed ancient cirques and catchment funnels with steep slopes. It has been noted that avalanche-prone slopes have inclinations of 30-50°.
The most dangerous period when mass avalanches occur is spring - March, April. During this time, the overload of slopes with snow is combined with a sharp thaw, forming so-called wet or ground avalanches, which have the greatest destructive power. However, not every avalanche is dangerous for the Chui Valley and its mountainous surroundings. Most avalanches occur in uninhabited areas. The most affected are the roads Bishkek-Osh, power lines and poles, forested areas, civil structures, and others.
It is known that natural disaster processes occurring in mountainous areas are subject to at least three general laws: firstly, for each type, a specific spatial association can be established; secondly, a certain frequency, in particular, the greater the intensity of the phenomenon, the less frequently it recurs with the same force; and finally, thirdly, with greater or lesser reliability, a dependence of the destructive effect of natural disasters can be established based on the scale, duration, and intensity of a particular type of natural phenomenon, and its possible manifestation can be predicted.
Dangerous hydrometeorological phenomena. At least 10 types of dangerous hydrometeorological phenomena that adversely affect humans and the economy have been identified in the territory of the Chui Valley. Among them, strong winds, precipitation and snowfalls, hail, frosts, and others occur frequently.
Strong wind. A wind is considered strong if its speed reaches 15 m/s. The criterion for wind as a dangerous phenomenon is a speed of 20 m/s or more. The greatest number of days with winds of 15 m/s or more has been recorded in the foothill and mid-mountain zones, at stations located at the entrance to narrow valleys.
At stations located on the plains (Bishkek, Tokmok), the greatest number of days with strong winds does not exceed 50, and winds with speeds of 30 m/s or more are extremely rare. Strong winds cause damage to the national economy. For example, in January 2001, the wind tore off roofs in Kemin (Bystrovka), Kemin district. The damage caused to the economy was measured in thousands of soms.
Significantly heavy precipitation. Heavy precipitation is defined as precipitation that exceeds 12 mm in 12 hours or less for rain and 5 mm for snow /Climate of the Kirghiz SSR, 1964/. The corresponding criterion for determining precipitation as heavy is a fall of 30 mm in the spring period for rain, 20 mm for snow, and 30 mm in 1 hour or less for torrential rain.
In most of the Chui Valley, the maximum number of days with significant precipitation occurs in the spring months. In March - in the plains and foothills, in April in mountainous areas at altitudes of 1500-2000 m. In high-altitude areas, the maximum number of days with significant precipitation shifts to the summer months. In late July 2001, a torrential rain fell in the Chui Valley for several days, causing significant damage to farming and peasant households in the region.
Hail - precipitation in the form of specific particles or pieces of ice, with a diameter of 5 to 50 mm or more, falling from powerful cumulonimbus clouds. In the Chui Valley, the frequency of hail events ranges from 1 to 13 days. At the same time, according to the Tyo-Ashuu meteorological station, the maximum number of days with hail in the Chui Valley reaches 22, while the minimum is 6. Thus, certain areas are also characterized by significant recurrence of hail events. The occurrence of hail that causes damage to agriculture is referred to as hailstorms /Climate of the Kirghiz SSR, 1965/. The degree of damage depends on the size of the hailstones, their density, the intensity of the fall, as well as the type of agricultural crops.
Heavy snowfalls. Snowfalls are also among the dangerous weather phenomena that cause damage to the economy. They lead to the formation of snow drifts on roads, resulting in disrupted regular transportation, breaking of fruit and decorative trees, burying crops, etc. For example, in 2001, an early autumn snowfall caused damage to the economy in the Chui Valley.
Snowfalls with an intensity of 31-40 cm are observed on the slopes of the Kyrgyz Ridge at altitudes of 1200-2400 m. At altitudes above 2500 m, with an intensity of 41-50 cm.
Frosts. Frost is defined as a drop in air temperature to 0° or lower on the surface of the soil or in the vegetation during the growing season against a background of positive average daily temperatures.
The entire agricultural zone of the Chui Valley is subject to the effects of frosts. The greatest danger to agriculture is posed by late spring frosts, which are observed in the valley's lowland bottoms, although they end here significantly earlier than in the Kyrgyz Ridge.
The first autumn frost in the air is most likely to occur in the Chui Valley during the second and third decades of October. The greatest recurrence is observed for frosts with a minimum air temperature of -10°.
Thus, various natural disaster processes are intensively manifested in the Chui Valley. These processes often arise unexpectedly, catching the population of mountainous areas off guard, causing significant damage to the national economy - transportation communications, industrial enterprises, agricultural facilities, settlements, and others. Agriculture suffers the most from these phenomena.
Therefore, knowledge of the nature of these natural processes, at least in general terms, is useful for all who live and visit the mountains. The damage caused by the natural disaster that occurred this year in the Chui Valley is already measured in tens of millions of soms. According to specialists, the elimination of the consequences of just one landslide requires an average of 6 million soms.
According to specialists from the Ministry of Ecology and Emergency Situations of the republic, we cannot avoid natural destructive phenomena, but it is within our power to forecast (anticipate) them and do everything to minimize possible consequences. The staff of the Ministry of Ecology and Emergency Situations has done a lot of work. We now have maps (cartographic schemes) of all potentially dangerous zones in Kyrgyzstan, including the Chui Valley, possible shifts of landslides, collapses, avalanches, breaches of lakes, rivers threatening floods. All this, along with timely warnings of possible timelines for the manifestation of natural disaster processes, are successful steps in combating them. Protecting land and economic facilities from natural disasters is a nationwide task.
As is known, the negative impact of natural disaster processes increases with the intensification of human economic activity. Humans constantly change, expand, and improve the ways and forms of their impact on the natural environment and transform it, as V.I. Vernadsky said. In doing so, established connections in nature are often disrupted, leading to the intensity of natural disaster processes. Therefore, the tasks of prevention, forecasting, and combating these natural phenomena are becoming increasingly relevant. In recent years, special efforts have been directed towards studying and forecasting rare movements of glaciers and possible shifts of landslides in the Kyrgyz Ridge, as well as earthquakes, mudflows, and their dangerous consequences.
In studies of natural disaster processes, it is important to highlight the following aspects: studying the mechanism and causes of their occurrence, as well as their distribution in the area; forecasting the timing and scale of their manifestation; studying the seasonal rhythm of mudflows, landslides, and other processes; determining the impact of human anthropogenic activity on the development of these disaster processes, and developing measures to prevent or mitigate the destructive effects of these processes. It is necessary to organize preventive measures to protect economic facilities from floods, mudflows, earthquakes, landslides, and others. Here it is appropriate to recall the French researcher Jacques-Yves Cousteau, who said: "Nature used to frighten humans, but now humans frighten nature." The time has come to stop frightening each other and to improve our common home, the biosphere, through the joint efforts of all living on Earth.
It should be noted that all manifestations of natural disasters are a physical constant of our mountains, changing from year to year depending on climatic features. Moreover, most natural cataclysms have a clear seasonal-spatial attachment. This facilitates the work. We know where, with what force, and with what probability a particular dangerous phenomenon will occur. And we can predict it with varying degrees of accuracy.
Snow avalanches can be predicted several hours before they occur, while the prediction of earthquakes has long-term (5-10 years) and medium-term (up to 5 years) forecasts by the Ministry of Emergency Situations and Civil Defense, with short-term forecasts provided by the Institute of Seismology of the National Academy of Sciences of the republic.