Inspection of the Dushanbe-Khujand highway (section 48 - 71km) for avalanche danger
On January 6, 2020, experts of the Glaciology Center of the Agency for Hydrometeorology of the Committee for Environmental Protection under the Government of the Republic of Tajikistan Rakhmonov R, Shoev A, Pirov A., together with experts of the Committee for Emergency Situations and Civil Defense under the Government of the Republic of Tajikistan was surveyed a road section 48–71 km from the village of Khushieri to the Istiklol tunnel for avalanche danger.
The survey showed that a stable snow cover on the track lies with 44 km. The snow thickness on the slopes is 25-30 cm, that is, an underlying snow zone has formed that can lead to the formation of avalanches. The height above sea level in this area is 1480 m. Avalanches are located at heights of 1900 - 2300 m. According to the calculated data, the thickness of the snow cover at these altitudes can reach 120 - 140 cm, depending on the degree of wind transfer of snow. The structure of snow is medium-grained. The snow density reaches 0.25 - 0.27g / cm3. The snow is slightly wet. Traction is high enough to hold snow masses on slopes.
With the rise in the upper reaches of the Varzob River along the route 48 - 50 km. the height of the snow cover increases and reaches 45-60 cm, depending on the wind transport and the exposure of the slopes. The snow is loose, slightly moist with a density of 0.25 - 0.27 g / cm3. At the time of the survey, snowfall increased and visibility worsened, which did not allow us to more accurately determine the snow collection where snow accumulates for the formation of avalanches. But taking into account the intensity of snowfall of 1.2 - 1.3 mm / hour, we can conclude. To achieve the critical value of snow accumulation for the formation of an avalanche, at least 10 to 12 hours are necessary.
At 50 - 55 km of the road, the snow height on the mountain slopes to the bottom of the valley is 70 - 80 cm. Snow density 0.27 - 0.28 g / cm3. The structure of the snow mass is characterized by the following: the surface layer is medium-grained, the upper layer is compacted, freshly fallen. The density of fresh snow is 0.15 - 0.17 g / cm3, that is, with a sufficient amount of precipitation up to 20 mm, a layer of fresh snow can form avalanches.
At 55 - 65 km of Kabut, the mouth of the Maykhura - Ziddy rivers is 1850 - 2000 m above sea level. The height of the snow cover is 120 - 140 cm. The snow structure is medium-grained, compacted. The density of snow is 0.27 - 0.29 g / cm3.
The SLS region (January 3–4, 2020) was characterized by massive avalanches. The number of avalanches is 30. Channel avalanches, the zone of origin is 2600 - 2900 m above sea level. Avalanches reached the bottom of the valley. The poles of power lines in the area of Zidda village were destroyed and the residential building was partially damaged. Under the blow of one of the avalanches were three local residents. They managed to get out of the avalanche snow on their own. According to the calculated data, the snow thickness in the zone of avalanche nucleation was 160 - 170 cm at a density of 0.27 g / cm3. The formation of avalanches was facilitated by overloading the slopes with snow masses and insufficient snow adhesion.
The avalanche volume, according to calculated data, ranges from 80 - 150 m2 to 400 - 600 and more m3. Insufficient snow density did not lead to larger destructive consequences.
At 65 - 73 km, altitude 2300 - 2600 m. Continuous snow cover. Snowfall. Intensity 0.8 - 1 m / h. Strong wind transport of snow. Due to the cloud cover and the intensity of precipitation, it is difficult to visualize the snow collection, where snow accumulation is made for the formation of avalanches. Nevertheless, the avalanche-hazardous situation persists. The thickness of the snow in this area is from 80 to 90 cm. The snow density is 0.28 - 0.30 g / cm3. The structure of snow is medium-grained, fine-grained, wind table. Due to the wind transport of snow in the region, the descent of snowstorms is possible. The strength characteristics of the surface layers create a prerequisite for the formation of avalanches of freshly fallen snow, due to the low density of 0.18 - 0.20 g / cm3 of fallen snow, as well as the rather low (- 40 - 60С) air temperature and wind speed of 7 - 8 m / from.
In the area of the road section 48 - 71 km, a prerequisite has been created for a massive avalanche. This, first of all, is promoted by intensive snowfall, low air temperatures and low density of the snow mass, in which there are practically no adhesion forces.
On January 15, 2020, experts of the Glaciology Center of the Agency for Hydrometeorology Rakhmonov R, Shoev A, Pirov A, together with experts of the Committee for Emergency Situations and Civil Defense, examined a section of the road 48 - 71 km from Hushyori to the Istiklol tunnel for avalanche danger. For the survey period, the weather conditions were characterized by clear, cloudless weather at air temperatures from -80 to 100C. There is no avalanche hazard. Avalanches descended during the snowfall on January 13, 2020. Their volume is from 10 to 25 m3.
At 44 km, the snow height on the slopes is 35 - 38 cm. The height above sea level is 1480 m. Snow density 0.26 - 0.27 g / cm3. The snow is dry, medium grained.
At 48 - 50 km, the snow height on the slopes is 48 - 54 cm. The snow is dry, loose, density 0.26 - 0.27 g / cm3.
At 50 - 55 km, the snow height is 75 - 80 cm. The snow is medium-grained, density 0.27 g / cm3, the top layer is compacted. The density of the upper layer is 0.18 g / cm3.
At 55 - 65 km. height above sea level 1850 - 2000 m. Snow cover height 125 - 145 cm. Medium-grained snow, density 0.26 - 0.27 g / cm3.
At 65 - 73 km. height above sea level 2300 - 2600 m. Snow height from 90 cm to 100 cm, density 0.27 - 0.28 g / cm3. The snow structure is medium-grained, the density of the upper surface of the snow is 0.18 g / cm3. Strength characteristics are weak.
For the period of the survey in the areas of the road, the weather conditions were characterized by clear, cloudless, frosty weather, with air temperature from -80 to -100 ° C. Not avalanche hazard.
It should be noted that from the beginning of January to the present, the Glaciology Center of the Agency for Hydrometeorology of the Committee for Environmental Protection under the Government of the Republic of Tajikistan predicted 5 times warning about avalanches. In general, 41 avalanches were recorded in the republic within 11 days.