Landslides in the Mailuu-Suu Valley, Kyrgyzstan—Hazards and Impacts

Mailuu-Suu is a former uranium mining area in Kyrgyzstan (Central Asia) at the northern border of the Fergana Basin. This region is particularly prone to landslide hazards and, during the last 50 years, has experienced severe landslide disasters in the vicinity of numerous nuclear waste tailing dams. Due to its critical situation, the Mailuu-Suu region was and still is the target area for several risk assessment projects. This paper provides a brief review of previous studies, past landslide events and a discussion on possible future risk scenarios. Various aspects of landslide hazard and related impacts in the Mailuu-Suu Valley are analyzed in detail: landslide susceptibility, historical evolution of landslide activity, size-frequency relationship, river damming and flooding as well as impacts on inhabited areas and nuclear waste storage zones. The study was carried out with standard remote sensing tools for the processing of satellite imagery and the construction of digital elevation models (DEMs). The processed inputs were combined on a GIS platform with digital landslide distribution maps of 1962, 1977, and 2003, digitized geological and geographic maps, and information from landslide monitoring and geophysical investigation. As a result, various types of landslide susceptibility maps based on conditional analysis (CA) are presented as well as predictions of future landslide activity and related damming potential and their possible impact on the population. For some risk scenarios, remediation and prevention measures are suggeste

Geophysical investigation and dynamic modelling of unstable slopes: case-study of Kainama (Kyrgyzstan)

The presence of massive Quaternary loess units at the eastern border of the Fergana Basin (Kyrgyzstan, Central Asia) makes this area particularly prone to the development of catastrophic loess earthflows, causing damages and injuries almost every year. Efficient disaster management requires a good understanding of the main causes of these mass movements, that is, increased groundwater pressure and seismic shaking. This paper focuses on the Kainama earthflow, mainly composed of loess, which occurred in 2004 April. Its high velocity and the long run-out zone caused the destruction of 12 houses and the death of 33 people. In summer 2005, a field survey consisting of geophysical and seismological measurements was carried out along the adjacent slope. By combination and geostatistical analysis of these data, a reliable 3-D model of the geometry and properties of the subsurface layers, as shown in the first part of the paper, was created. The analysis of the seismological data allowed us to point out a correlation between the thickness of the loess cover and the measured resonance frequencies and associated amplification potential. The second part of this paper is focused on the study of the seismic response of the slope by numerical simulations, using a 2-D finite difference code named FLAC. Modelling of the seismic amplification potential along the slope confirmed the results obtained from the seismological survey—strong amplifications at the crest and bottom of the slope where there is a thick loess cover and almost no amplification in the middle part of the slope. Furthermore, dynamic slope stability analyses were conducted to assess the influence of local amplifications and increased groundwater pressures on the slope failure. The results of the dynamic modelling, although preliminary, show that a combination of seismic and hydrologic origin (pore pressure build-up during the seismic shaking) is the most probable scenario responsible for the 2004 failur

Tien Shan geohazards database: Earthquakes and landslides

In this paper we present new and review already existing landslide and earthquake data for a large part of the Tien Shan, Central Asia. For the same area, only partial databases for sub-regions have been presented previously. They were compiled and new data were added to fill the gaps between the databases. Major new inputs are products of the Central Asia Seismic Risk Initiative (CASRI): a tentative digital map of active faults (even with indication of characteristic or possible maximum magnitude) and the earthquake catalogue of Central Asia until 2009 that was now updated with USGS data (to May 2014). The new compiled landslide inventory contains existing records of 1600 previously mapped mass movements and more than 1800 new landslide data. Considering presently available seismo-tectonic and landslide data, a target region of 1200 km (E–W) by 600 km (N–S) was defined for the production of more or less continuous geohazards information. This target region includes the entire Kyrgyz Tien Shan, the South-Western Tien Shan in Tajikistan, the Fergana Basin (Kyrgyzstan, Tajikistan and Uzbekistan) as well as the Western part in Uzbekistan, the North-Easternmost part in Kazakhstan and a small part of the Eastern Chinese Tien Shan (for the zones outside Kyrgyzstan and Tajikistan, only limited information was available and compiled)..

Development of Petrov glacial-lake system (Tien Shan) and outburst risk assessment

Global climate warming causes an intensive melting and retreat of glaciers in the Tien Shan mountains. Melting water of glaciers causes overfilling of high mountain lakes. The increase of the surface and volume of the Petrov Lake accompanied with the decrease of stability of the dam represents an extremely dangerous situation that can produce a natural disaster. Failure can happen due to erosion, a buildup of water pressure, an earthquake or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base. In case of the lake dam rupture, flooding of a disposal site of highly toxic tailing from the gold mine Kumtor is a threat. If this happens, the toxic waste containing cyanides would contaminate a large area in the Naryn (Syrdarya) river basin. Even if the flooding of the disposal site does not occur, the damage after lake dam fracture will be immense due to the glacial lake outburst flood may be a devastating mudslide. In order to prevent or reduce the risk of this event we recommend performing engineering surveys for the development and implementation of the project for the controlled reduction of water level in the Blue Bay of the Petrov Lake to a safe volume

Past and potential future socioeconomic impacts of environmental hazards in Kyrgyzstan

This chapter presents an overview on the past socioeconomic impacts of natural hazards, locally combined with severe ecological consequences, in Kyrgyzstan, starting with the end of the 19th century. It will also provide a prospective view on the type of natural events that could have major impacts with nationwide consequences. The analysis of past events shows that compared, e.g., to countries in Western Europe the environmental situation of this relatively small Central Asian country is clearly aggravated through the regular occurrence of multiple geological hazards. Those hazards include numerous disastrous landslides that occur almost every year, and strong (M > 6.3) to very strong (M > 7) earthquakes that are observed once per decade or once per quarter-century, respectively. The review of past events will show that some past earthquakes had fundamental impacts on the governmental structure; this is exemplified by the change of name of the present capital of Kyrgyzstan, Bishkek, in connection with the reconstruction of the city after major impacting seismic events. In this regard, it is important to situate Kyrgyzstan in the general Central Asian context as similar governmental impacts occurred also in the neighbouring countries. The second factor increasing environmental hazards at local or subregional scale is related to the presence of mining and nuclear waste tailings and dumps in several areas distributed all over the country. Here, we will focus on some hotspots such as the Mailuu-Suu River valley. In those areas, ecological disasters are closely depending on natural hazard impacts. Due to the combined presence of multiple types of waste and of active landslides that can be reactivated by earthquakes, most efforts of environmental hazard remediation are presently concentrated on those areas, partly with support of multi-million USD projects. Finally, a third point will be highlighted as it will have the most predictable future negative impacts in many parts of the country - those related to climate change on the water resources and multiple highmountain hazards (snow avalanches, glacier lakes, landslide dam stability and outburst floods). Those impacts can be considered as the most predictable ones as climate change cannot be denied anymore; therefore, related hazards are less aleatory than those induced by geological hazards, earthquakes, in particular. Some changing high-mountain hazards are also likely to impact more and more the aforementioned environmental hotspots in Kyrgyzstan, including also dam structures and reservoirs, through the intermediate of increased flood hazards. Providing a quantitative verification of social and economic impacts of geological, climatic and general environmental hazards is not always possible. Therefore, part of the chapter will be dedicated to a critical analysis of available statistics describing those impacts. This is necessary in order to make reliable predictions of future consequences of hazards that also need to take into account the social changes to which Kyrgyzstan is exposed: rural exodus, decreasing general population, changing economic situation of private persons and public institutions, as well as the changing risk perception in the population. © 2017 Nova Science Publishers, Inc