Keywords

1 Introduction

Central Asia region embracing Pamir, Tien Shan and Dzungarian mountain systems located in six states—Afghanistan, China, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan, is one of the global landslide hotspots (Nadim et al. 2006). Unique combination of rugged terrain, arid climate and lack of vegetation, active tectonics and high seismicity provides conditions quite favorable both for landslides formation and for their identification, mapping and detailed study at both regional and site-specific scales. It is fully applied to the study of large-scale rockslides and rock avalanches—the most destructive and most hazardous types of landslides in mountainous regions.

Complex study of these hazardous phenomena, compilation of the regional inventory of rockslides exceeding 1 million cubic meters in volume, and organization of an annual two-week field training course for students and young researchers interested in studying these natural phenomena are the main aims of the multi-year joint project of the JSC “Hydroproject Institute” (Moscow) and Institute of Seismology of National Academy of Sciences of Kyrgyz Republic. These organizations were awarded as World Centre of Excellence on Landslide Risk Reduction (WCoE) since the 1st World Landslide Forum in 2008.

Seventeen years of development and progress of these activities as well as our future plans are described in brief hereafter.

2 Field Training Course—The Kokomeren Summer School

The Kokomeren Summer School on Rockslides and Related Phenomena started in 2006. It was skipped in 2010 due to political crisis in Kyrgyzstan and in 2020–2021 due to the COVID-19 pandemic but was resumed in 2022. The Kokomeren Summer School (KSS) is a two-week long field training course during which the entire group led by the author visit rockslides, rock avalanches and rockslide dams where various peculiarities of these natural phenomena are demonstrated and explained in detail.

The first KSS was preceded by the 2005 special field reconnaissance during which most interesting and didactic sites were selected and studied. Data collected during this field trip as well as those collected by organizers during their previous work in the study area were summarized in the full-color detailed guidebook. These activities were performed within the frames of the IPL M-111 project supported by the International Consortium on Landslides (ICL) and followed later by the C-106-2/IPL-106-2 projects. In 2017–2019, and in 2022, the KSS was supported partially by the Central Asian UNESCO office that covered the expenses of four participants, one each from Kyrgyzstan, Kazakhstan, Uzbekistan and Tajikistan. Almost each year some new study sites or new field routes have been found and included in the new versions of the Guidebook. The latest one is available at the ICL and IPL websites.

During fourteen years of the KSS, 159 students, young researchers, and several experienced experts from Argentina, Austria, Belgium, China (including Hong Kong), Chinese Taipei, Czech Republic, France, Germany, Great Britain, Italy, Japan, Kazakhstan, Korea, Kyrgyzstan, New Zealand, Poland, Russia, Slovakia, Slovenia, Switzerland, Spain, Tajikistan, USA and Uzbekistan have attended this field training course (Table 1). Some of them attended two courses.

Table 1 Number of participants attending the KSS
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This area (Fig. 1) was selected for field training course due to quite favorable combination of several factors: (1) unique variability of rockslide morphological types and subtypes (Strom 2021); (2) excellent exposure of both morphology of the studied features and of their internal structure; (3) impressive manifestation of neotectonics and active faulting in the study area that form the prerequisites of large-scale rockslides formation; (4) attainability of almost all study sites that require up to two hours driving and several kilometers long hiking to reach them; and (5) closeness of the area to Bishkek—route from Bishkek airport to base camp takes 5–6 h, depending on weather conditions.

Fig. 1
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Large landslides, rock avalanches and caldera-like collapses in the Kokomeren River basin and adjacent part of the Naryn River basin. Suu, Dj and K-T—the Suusamyr, the Djumgal and the Ketmen-Tiube intermountain depressions. Selected features most of which are demonstrated during the training course: 1—Seit; 2—Ak-Kiol; 3—Mini-Köfels; 4—Kashkasu; 5—Northern Karakungey; 6—Southern Karakungey; 7—Chongsu; 8—Sarysu; 9—Ming-Teke; 10—Lower Ak-Kiol; 11—Snake-Head; 12—Lower-Aral; 13—Kokomeren;14—Ornok; 15—Displaced Peneplain; 16—Kyzylkiol caldera-like collapse; 17—Karachauli; and 18—Lower Kokomeren

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During daily field trips the attendees visited numerous rockslides and rock avalanches, the largest of which—the Kokomeren rockslide was about 1.5 km3 in volume and formed the dam up to 400 m high, nowadays completely dissected by erosion (Fig. 2). There are also impressive evidence of river damming (Fig. 3) and of the subsequent outburst floods (Fig. 4)—the secondary and the tertiary effects of large-scale rock slope failures that can be even more destructive than rockslides themselves.

Fig. 2
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Overview of the Kokomeren Rockslide whose ca. 400 m high body had been completely dissected by erosion

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Fig. 3
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Succession of lacustrine sediments accumulated in the lake dammed by the Kokomeren rockslide (above) and composition of its basal unit—mixture of dark-grey Paleozoic metasediments rubble and red Neogene claystone

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Fig. 4
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Terrace-like body downstream from the breached 70 m high Lower Aral rock avalanche dam. These deposits left by the final phases of the outburst flood are composed of layers of angular unrounded clasts

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The KSS attendees also have a chance to be acquainted with the traditional lifestyle of very friendly and hospitable local people and to taste local food and traditional drink of nomads—kumis—fermented horse milk (Figs. 5 and 6).

Fig. 5
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Participants of the 2018 KSS with local family

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Fig. 6
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Drinking kumis in the shepherd’s yurt

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Such field training proved its efficiency—many unclear or controvercial peculiarities of the studied phenomena can be explored and explained directly on site. Several participants of the KSS from the European and Asian countries came to Kyrgyzstan again with their own research projects to continue studying excellent manifestations of rock slope instability, both in the same parts of the Tien Shan and in other parts of this mountain system.

3 Central Asian Rockslide Database—Compilation and Analysis

Preparation of the Summer School Guidebook along with the study of numerous rockslides, rock avalanches and deep-seated gravitational slope deformations (DSGSD) performed in different parts of the Central Asian mountains, was a starting point for compilation of the complete large-scale rockslide inventory and database of the entire Central Asian region (Strom and Abdrakhmatov 2017) (Fig. 7). This database includes ca. 1000 case studies in the Djungaria, Tien Shan and Pamir Mountain systems, for about 600 of which quantitative and qualitative parameters characterizing their headscarps, deposits and the dammed lakes are provided. Results of these studies have been summarized in the monograph “Rockslides and rock avalanches of Central Asia: distribution, morphology, and internal structure” (Strom and Abdrakhmatov 2018) published by Elsevier (ISBN: 978-0-12-803204-6). The database is available as an Excel spreadsheet at the Elsevier website (https://www.elsevier.com/books/rockslides-and-rock-avalanches-of-central-asia/strom/978-0-12-803204-6) as part of the supplementary material and can be provided by the author upon the request as well.

Fig. 7
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Spatial distribution of large rockslides, rock avalanches and DSGSDs’ in the Central Asian region

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Unique and didactic examples of rockslides, most of which converted into flow-like rock avalanches (Fig. 8), of the existing, silted and breached rockslide dams (Figs. 9, 10 and 11) and of the DSGSDs (Fig. 12) have been identified throughout the entire Central Asia Region—from the Djungarian Range in the North to Pamir and Afghan Badakhshan in the South and from Eastern Tien Shan in Xinjiang, China, to its westernmost part in Uzbekistan and Tajikistan. Some of case studies are really unique due to their size and expressiveness (Fig. 13).

Fig. 8
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The 7.5 km long Chukurchak rock avalanche, Tien Shan, Kyrgyzstan. Headscarp is marked by elevation marks 2970 and 2250 m a.s.l., while other elevation marks are placed at the front of rock avalanche branches

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Fig. 9
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Rockslide (rock avalanche) dam of the Big Almaty Lake, Kazakhstan. Red arrows mark the headscarp at 3000–3300 m a.s.l.; yellow arrows—rock avalanche front. Lake level was raised by small earthfill dam

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Fig. 10
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Rockslide dam in Chinese Pamir and completely silted and forested dammed lake

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Fig. 11
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Gigantic breached natural dam ca. 500 m high at the junction of the Dura and Munjiang River in the Kokcha River basin in Afghanistan. It was formed by the Pazhuk rockslide about 3 km3 in volume

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Fig. 12
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Ca. 5 km long DSGSD at the northern slope of the Peter the First Range, Tajikistan

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Fig. 13
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Oblique view of the tremendous Padjvar rockslide in Afghan Badakhshan ca. 6 km3 in volume. The entire ridge about 6 km long collapsed in the adjacent valley of the left tributary of the Pianj River and filled it almost completely with the deposits up to 650–700 m thick that cover 19.72 km2, while the total affected area is about 27 km2

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Large number of the quantified rockslides and rock avalanches allowed establishing statistical relationships between parameters, characterizing the collapsed rock massif—its volume and height drop and parameters that are used to describe their mobility (runout, angle of reach, affected area) (Strom 2018; Strom and Abdrakhmatov 2018; Strom et al. 2019). These relationships, some of which are characterized by very high correlation coefficients (R2 > 0.9), can be used for fast assessment of the landslide hazards and associated risks if the potentially unstable slope is identified and its height and volume are estimated.

Parts of the entire database were used for testing new software developed for automatic generation of landslide profiles (Li et al. 2020) and for elaboration of the more strict determination of landslide longitudinal shape (Li et al. 2022).

The Central Asian rockslide database serves as a reference point for various regional and site-specific studies of natural hazards and risks associated with rockslides, rock avalanches and rockslide dams (e.g. Fomenko et al. 2020; Jones et al. 2021). It has been also used for the landslide susceptibility assessment of the Central Asian states performed within the frames of the ongoing World Bank funded project. In future, the database will be enlarged by quantifying those case studies whose parameters have not been measured yet.

4 Conclusions

Activities of the World Centre of Excellence (WCoE) of JSC “Hydroproject Institute” and of Institute of Seismology of National Academy of Sciences of Kyrgyz Republic are focused on the study of the most disastrous types of landslides in mountainous regions—large-scale rockslides and rock avalanches.

WCoE performs both scientific (compilation of the Central Asian rockslide database and study of the most informative features) and educational (Kokomeren Summer School) tasks. Besides, results of our studies have been used and will be used in future for practical purposes—to assess landslide and seismic hazards of the particular sites and associated risks.