Представлены результаты оценки последствий гипотетического прорывного паводка из озера Дашт (Республика Таджикистан, бассейн р. Шахдара). Расчеты были выполнены с использованием комплекса математических моделей, а именно FLO-2D и FLOVI. Оценка расхода прорывного паводка и селевого потока проводилась в программе FLOVI. В этой программе также оценивалось приращение твердого материала в селевом потоке. Моделирование движения и аккумуляции селевого потока в долине выполнялось в гидродинамической модели FLO-2D. Результаты показали, что внедрение в модель FLO-2D данных, полученных в программе FLOVI с блоком уравнений транспортно-сдвиговой модели, дает более корректные характеристики селя, включая значения расхода, скорости, глубины и площади затопления. The results of modeling the consequences of a hypothetical outburst flood from Lake Dasht (Tajikistan, the Shakhdara River basin) with the use of FLO-2D and FLOVI mathematical models are presented. The discharges of the outburst flood and debris flow and the increment of solid material in the debris flow have been obtained using the FLOVI program. The debris flow movement and accumulation in the valley have been simulated using the FLO-2D hydrodynamic model. The results indicate that the application of data obtained from the FLOVI program with transport-shift equation block in the FLO-2D model gives more correct characteristics of the debris flow, including the values of flow discharge, velocity, depth, and flooding area.

We analyzed multi-time satellite images of the Central Caucasus glacial zone and interpreted more than thirty rock avalanche events in the 21st century with a total damage area of more than 25 km 2 (including the collapse zone of the Kolka Glacier disaster). The highest rock and rock-ice avalanche activity is detected in the section of The Greater Caucasus range (northern and southern slopes) with a length of about 20 km between the Bashkara and Kulaktau peaks (16 rock avalanches) and in the section of the Kazbek-Dzhimaray Massif (series of rock avalanches to the surface of Kolka, Suatisi and Devdoraki glaciers). The feature of the rock and ice-rock avalanches is the large runout distance. For 12 events (about 40%) the distance was more than 2000 m. One ice-rock avalanche from the Mount Kazbek (excluding the Kolka Glacier disaster in 2002) reached the runout distance more than 10 km. In some areas, the rock avalanches occurred several times. In particular, a large number of avalanches were in the cirque of the Kolka Glacier; the last of them at the end of 2019. Thrice шт each case, rock avalanches originated from Mount Bashkara, in the cirques of the Murkvam Glacier, the East Shtulu Glacier, and the Devdoraki Glacier. Ice and rock avalanches were the initial stage of the complex process of the Kolka Glacier disaster and following catastrophic glacial debris flow in the Genaldon/Gizeldon River valley in 2002. Also, they were causes of glacier surges, formation of dammed lakes, and debris flows. As a result of the collapse of the hanging glacier and bedrock, the former right tributary of the Kolka Glacier surged to 200 m in 2006. Ice-rock avalanche from Mount Kazbek in 2014 load up the former right tributary of the Devdoraki Glacier and caused its advancing in 2015–2019, at a distance of more than 400 m. The avalanches caused catastrophic debris flows in the Amilishka/Kabakhi River valley in 2014, the Mestiachala River valley in 2019. Rock avalanches can cause outbursts of lakes and debris flows. Two dammed lakes formed as a result of the rock avalanche from the cirque above the Seri Glacier in the Tviberi River valley of the in May 2016. The lakes (total area was more than 0.05 km 2 ) have outburst at the end of August 2017 after heavy rains. Rock avalanches of the 20th century led to an abrupt deceleration in the retreat of the Yusengi, Bartuytsete, East Shtulu and Mosota glaciers. The formation of rock avalanches in the 21st century took place at high altitudes (an average of about 3900 m). Possibly, the reason was associated with an increase of the «0» isotherm and of the high border of the zone of intense frost weathering due to climate warming. Some rock avalanches in the section of the Kazbek-Dzhimarai Massif have been caused by endogenous factors (seismicity and volcanism).

При сравнении аэрофотоснимков 1983 и 1988 гг. был выявлен факт схода обвала со склона г. Гогутай (3 753 м). На основе анализа рельефа правого склона долины выявлены массивы ополз- ней, которые в литературе отмечены как сейсмогенные. Активность селевых процессов определялась по изменению контуров зон селевых отложений на трех конусах выноса и по изменениям русел на участке широкой поймы. Факты схода лавин устанавливались в результате сравнения разновременных космоснимков и их GIF-анимаций по наличию лавинных снежников в весенне-летний период, по характеру и ареалам растительности, а также по уникальному космоснимку в момент схода лавины. Гра- ницы лавиносборов определялись на основе карты уклонов склонов в сравнении с локальным рельефом местности, фотографиями с маршрутных обследований и контурами лавинных от- ложений на космоснимках. Всего выделено 60 лавиносборов (включающих более 200 путей схода лавин), суммарной площадью 23,4 км2. On the basis of route surveys data in 2008, 2010, 2016 and 2017, decryption of space images from 2015 to 2019 and aerial photographs from 1957 to 1988, the paper considers the activity of dangerous natural processes in the Yusengi Valley: mudfl ows, landslides, avalanches and rockslides. When comparing aerial photographs of 1983 and 1988, the fact of the rockslide from the slope of the mountain Gogutai (3 753 m) is revealed. On the basis of the relief analysis of the right slope of the valley, landslides masses that are known in literature as seismogenic have been identifi ed. The activity of mudfl ow processes was determined by the change in the contours of the zones of the mudfl ow deposits on the three debris cones and by the changes of the stream course in the wide fl oodplain area. The facts of the avalanche collapse were established as a result of the comparison of space images and their GIF animations taken at different times, which carried out in terms of the avalanche snow-patches presence during the spring and summer period, considering the nature and habitat of vegetation, and also the unique space image taken at the very moment of the avalanche collapse. The borders of avalanche catchments were determined on the basis of a map of slopes in comparison with the local terrain, photographs from route surveys and ontours of avalanche deposits on space images. A total of 60 avalanche catchments (including more than 200 avalanche paths), with a total area of 23.4 km2, have been isolated.