As a rule, high floodwaters are of a short-term nature, but cause huge damage to settlements and the national economy. As a whole, during 1960s-1990s, an increase in the number of days with disastrous floods was observed. During the period under research, the highest number of disastrous floods was observed in 1969, 1970, 1985 and 1988. Between 1991-2000, several disastrous floods were experienced in the republic in 1993 and 1998, which destroyed many sites (Rogun hydropower station dam under construction, roads, houses in Khatlon and Sogd regions) and huge damage was caused.

The southeast slopes of Gissar range, northern slopes of Turkestan range and southern slopes of Kuramin range are the areas with greatest flood activity, particularly in the basins of Yakhsu, Varzob, Vakhsh, Zeravshan and Obihingou rivers. The high-mountain area of the Eastern Pamirs and the lower reaches of rivers are not threatened with mudflows. The highest mudflow risk is in April and May. In foothills and middle mountains, the mudflow period occurs mainly in spring, while in high-altitudes in summer. Intensive precipitation is the main reason of mudflow formation (80%).

High air temperatures lead to rapid snow melting and ice thawing thereby creating conditions for formation of glacial-born mudflows. Sometimes mudflows happen as a result of a glacial lake outburst formed by a surging glacier.

Snow avalanches. Basic conditions for the formation of avalanches are slopes with a gradient of 30-50°, snow cover more than 30 cm, and relevant meteorological conditions. In Tajikistan's conditions, the major reason of avalanches is fresh snow formation (60-70%). Many avalanches are registered in Zeravshan-Gissar and Darvaz mountains. The biggest occurrence of avalanches has been reported on the slopes with a northern exposition. Most avalanches are observed in February and March. The biggest number of days with avalanches was indicated in 1978, when mass avalanches occurred in all highland areas. It caused traffic jams; many communication and power supply systems were damaged. In 1969, extraordinary avalanche activities were indicated in the Western Pamir. The number of days with avalanches exceeding twice the average was indicated in 1976, 1984 and 1987. In the period of 2001-2003, avalanches resulted in 10 deaths; in individual regions, the infrastructure was destroyed and other serious damage caused to the economy.

Landslides are common in Tajikistan due to the favorable geological, climatic, and geodynamic environments, formed due to the presence of a thick sequence of Quaternary deposits and heavy showers in a winter-spring period. The areas at elevations 700 to 2,000 masl are most exposed to the risk of landslides. Some 50 thousand landslide events, 1,5 thousand of which are threatening to settlements and industrial constructions, have been reported all over the republic. Seismic landslides are generally associated with earthquakes. Non-seismic landslides mostly result from man-made factors or extreme hydrometeorological conditions. Glacier landslides (surging movements) are typical for high-altitude zone. The anthropogenic impact results in the formation of irrigation landslides on the slopes of hills, crossed with irrigation cannels, as well as in river sides, terrace slopes, etc. They are common in Gissar, Yavan, and Obikiik valleys. Such landslides reduce the area of irrigated lands, destroy water management constructions, villages, and roads, and cause many deaths.

Earthquakes are typical for Tajikistan, where potential earthquake magnitude can be as high as 9 of Richter scale. The most drastic earthquakes in their consequences occurred in 1911 and 1946, when hundreds of people died and numerous economic objects were destroyed. Earthquake epicenters are located almost everywhere. Earthquakes are seriously dangerous, since they cover broad areas and are able to cause a considerable damage to reservoir dams, buildings and communications. According to expert estimates, 70 to 100 thousand people suffered from earthquakes in Tajikistan in the last century. A few moderate and strong earthquakes 5-6 of Richter scale, with considerable economic damage, were experienced in Tajikistan in 2002.

Dangerous meteorological phenomena include heavy snowfall, rainfall, dust storms, hails, and other events assigned to natural disasters and causing damage to the national economy.

High temperatures. The zone of an adverse thermal regime (equal to and higher than 40°C) covers the entire plain areas of the republic. On the basis of the analysis of observational data, an upward trend of 30% in the number of days with temperature above 40°C has been identified in almost all the plains of the republic. In 1984, a period of 48 days with temperatures above 40°C was observed in Shaartuz. The least number of days with temperatures above 40°C was observed in 1972.

Low temperatures. Daily mean temperatures of air equal and below -10°C are also considered dangerous weather events. The least average number of days in one year with low temperatures is observed in the territory's plains (0.2-0.8 days), although in some years this number increases up to 5-15 days. The greatest reoccurrence of low temperatures is observed in mountainous areas, especially in low depressions, mountain passes, and tops of high mountain ranges. In foothill areas, the average number of days with low temperature changes from 6 to16 days, and in some years, between 25 and 80 days. In general, the number of days with a daily average temperature below -10°C shows a downward trend by 30%.

Heavy snowfall and rainfall. Intense precipitation is one of the most dangerous hydrometeorological events in terms of its consequences. The average number of days with intense precipitation in the republic is insignificant and varies from 0.1 to 6 days per year. In some areas, intense precipitation does not occur at all. In some years, for example in 1969, the number of semidiurnal intense precipitation exceeded the average value by 3.5-5.5 times. The maximum number of days with intense precipitation is accounted for mainly in spring months and in summer months in high-altitude areas. During the last 30-40 years, the number of days with intense hard precipitation tended to reduce. The change in the number of days with intense liquid precipitation is ambiguous: they increased in some areas, while decreased in others.

Heavy snowfall create snowdrifts on the roads resulting in traffic disturbance, increasing loads on the roofs of buildings, breaking fruit and adornment trees, worsening conditions for feeding animals, decreasing the visibility during plane taking off and landing and avalanches in mountain areas. Heavy rainfall, over 30 mm a day, contribute to the erosion processes, cause serious damage to the agriculture and provoke mudflow and landslide events and floods.

Dust storms are observed in Tajikistan for 1-4 months in a spring-summer period. They raise thousands of tonnes of soil and sand into the air, thereby considerably increasing the concentration of suspended particles in the atmosphere. A lot of farms suffer from this event, when the crop productivity decreases. Long-lasting dust storm and haze in Tajikistan was registered in 2001.

Hailstones frequently cause damage to agriculture. The centre of most hail events is located along the Gissar range, primarily in the foothills. The number of days with hail grows as the altitude increases. At the same time, the maximum reoccurrence of hail ranges from 0.7-1 days in lowland areas to 4-8 days in high altitudes. Gissar valley is known for its large frequency of hail events, where the number of days with hailstone averages to 1.9-3.5 days per year. In the last 30-40 years, the number of days with hailstone in lowland and foothill areas has decreased. In mountainous areas, the occurrence of hail has not changed, and in some areas has increased. In 2002, hails caused damage to many farms in the Gissar Valley and other regions of Tajikistan.

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Last update 03/03/2003
V. Novikov, N. Safarov