Study of the mudflow hazard and glaciation decrease in Central Caucasus

This is a previous project which was run at SPRI within the former Remote Sensing Group. The content below was written in November 2001.

Collaborating groups: the University Centre for Engineering Geodynamics and Monitoring, Moscow - UCEGM (Sergey Chernomorets); Scott Polar Research Institute - SPRI (Dr Olga Tutubalina); Faculty of Geography of the Moscow State University - MSU (Dr Alexander Aleinikov, Anna Aleinikova, Ivan Krylenko, Inna Krylenko, Dmitry Paramonov, Dr Dmitry Petrakov, Dr Eugene Zolotarev and others); Dr Irina Seinova

Background

On 18-25 July 2000 the small mining town of Tyrnyauz in the mountains of Central Caucasus was struck by a series of severe glacial mudflows. According to official records, eight people were killed when one of the first waves knocked down a section of a 9-storey building; several other multi-storey buildings were destroyed.

Tyrnyauz is marked on the map by the red dot.
Source: Nationalgeographic.com and ESRI's Map Machine

The mudflows came from the Western Kayaarty glacier through the Kayaarty-Su and Gerkhozhan-Su river valleys, through a protective dam (destroyed by a mudflow a year before) in the lower Gerkhozhan-Su, and blocked the course of the Baksan River in the main valley. As a result, a large lake of muddy water appeared and persisted for two months. Tyrnyauz was bitterly nicknamed "the Caucasian Venice" at the time, because the town's inhabitants travelled around in boats, trying to retrieve belongings from their flooded apartments. A large fan of mudflow deposits, 2 to 18 m thick, filled the space between the destroyed buildings. By September 2001 the area along the course of Gerkhozhan-Su within the town remained empty, except the protective walls that were restored along the river banks. The layer of fresh mudflow deposits was easily visible where it was intersected by an artificial channel created to restore the course of the Baksan River.

Mudflows had been recorded in this area in 1937, 1960, 1961, 1962, 1977, and 1999. However, the 2000 mudflows were by far the most catastrophic. They occurred after a long period of hot and dry weather, which accelerated the melting of glacial ice. It is not known what provided an initial impulse for the mudflows, sudden precipitation or glacial melt water.

Immediately after the 2000 disaster the government of this region (the Republic of Kabardino-Balkariya) initiated a research campaign to study the origins of the mudflow hazard in the Gerkhozhan-Su basin and establish a monitoring network. Members of our research group took part in reconnaissance trips in July and September 2000, compiled analytical reports and specialised maps of the basin in winter 2000/2001 and performed extended fieldwork in June-September 2001. The scope of this research is now being widened to the whole of Central Caucasus.

Aims of the project

• to establish the key factors of mudflow formation in the Central Caucasus;
• to analyse changes in mudflow structure and formation as conditioned by the current glaciation decrease in this region;
• to map mudflow potential* in several key areas;
• to enhance existing techniques for forecasting mudflows.

* mudflow potential refers to the capacity of an area to produce a mudflow, as defined by a number of environmental factors (availability of mudflow material, water, specific weather conditions etc).

Methodology

The project is based on integrated field research, which involves hydrological and glaciological observations, geomorphological analysis and photogrammetric mapping. Examples of particular activities are: short-term monitoring of ground movement and micro-mudflows in the areas of current mudflow development, stereophotography to monitor active mudflow channels and potentially hazardous glacial lakes, GPS-located geomorphological descriptions, and observation-based mass balance estimations for selected glaciers.

Field data are being integrated with recent aerial and satellite imagery to create maps of mudflow formation factors for several key basins. Once this is completed a pool of historic imagery and field data will be used to analyse changes in mudflow character caused by a decrease in regional glaciation. This includes changes in sources of mudflow material, in prevailing factors causing mudflows, and in predominant height levels where mudflows originate. Modern geoinformation technologies are used throughout the project to ensure efficiency of analysis.

Results of field research and change analysis will provide information to understand fundamental mechanisms of mudflow formation in periglacial areas, to improve existing forecasting techniques and ultimately to reduce the hazard for populated areas in Central Caucasus.

Current results

Four study areas comprising seven key mudflow basins are being investigated (see map below). These basins have been selected on the basis of their recent (XX century) mudflow activity and of their proximity to vulnerable populated areas. The research group has drawn upon recent fieldwork (1987-2001), and results of long-term research by Drs Irina Seinova and Eugene Zolotarev which they have summarised in a new book.

Map of study areas in Central Caucasus. Key: 1 - Upper Adyl-Su basin, 2 - Kamyk-Su and Mukulan basins, 3 - Tutu-Su basin, 4 - Gerkhozhan-Su basin. To check the current state of the work for a particular area, click on it, or scroll down the page.

Current state of work by study area

1. Upper Adyl-Su basin

Field surveying of dammed glacial lakes has been completed, map compilation and analysis of lake development is underway.

2. Kamyk-Su and Mukulan basins

Initial field recoinassance has been completed. A preliminary map of mudflow formation factors is under development.

3. Tutu-Su basin

Initial field recoinassance has been completed.

4. Gerkhozhan-Su basin

Two seasons of field observations and mapping have been carried out. Analysis of digital imagery obtained from a helicopter in September 2001, of topographic maps, and of field data of July-September 2000 and June-September 2001 allowed the compilation of a map of mudflow formation factors at 1:10 000 scale for the whole basin (80 km²). This map and a specially developed map legend will serve as a prototype for the mapping of environmental factors in other mudflow basins. A supplementary map of the mudflow damage in the town of Tyrnyauz and its vicinity (1:7000) has been also compiled.

Results of terrain change analysis are summarised in abstracts in the publications section of this page, and a few selected photographs of this area are also available.

Publications

Our most recent research results for the Gerkhozhan-Su basin are covered in:

1. Krylenko I.V., Petrakov D.A and S.S. Chernomorets. 2001. Perestroika rel'efa v doline Gerkhozhan-Su (Tsentral'ny Kavkaz) posle katastrophicheskikh selei 18-25 ijulia 2000 goda [Change of terrain in the Gerkhozhan-Su valley (Central Caucasus) after disastrous mudflows of 18-25 July 2000]. In Russian with English abstract. In: Ustoichivoe razvitie gornukh territorii: problemy regionalnogo sotrudnichestva i regionalnoi politiki gornukh raionov: tezisy dokladov uchastnikov IV mezhdunarodnoi konferentsii [Proceedings of the IV International Conference on Sustainable Development of Mountain Territories], Vladikavkaz, 23-26 September 2001. Vladikavkaz: Remarko. Pp. 471-472.

   Short abstract in English: Comparison of field observations in July-September 2000 with literature data shows catastrophic incising in the periglacial zone of the Gerkhozhan-Su basin, which captured the headwaters' runoff. Marked changes have occurred in lithodynamic zones and the mudflows have reshaped the entire river channel. The volume of the mudflow canyon near the Western Kayaarty glacier has increased by over 0.5 x 10⁶ m³, and the total debris runoff from glacial mudflows is estimated at over 3.2 x 10⁶ m³. A new 0.7 km mudflow fan has formed within the town of Tyrnyauz, increasing the terrain heights by 2-18 metres.

2. Krylenko I.V., Petrakov D.A and S.S. Chernomorets. 2001. Otsenka usloviy formirovaniya selei v basseine Gerkhozhan-Su i rekomendatsii po zashite goroda Tyrnyauza. [Assessment of conditions for mudflow formation in the Gerkhozhan-Su valley and trecommendations for protection of the town of Tyrnyauz]. In Russian with English abstract. In: Ustoichivoe razvitie gornukh territorii: problemy regionalnogo sotrudnichestva i regionalnoi politiki gornukh raionov: tezisy dokladov uchastnikov IV mezhdunarodnoi konferentsii [Proceedings of the IV International Conference on Sustainable Development of Mountain Territories], Vladikavkaz, 23-26 September 2001. Vladikavkaz: Remarko. Pp. 469-471.

   Short abstract in English: The four series of catastrophic glacial mudflows on 18-25 July 2000 have created a deep canyon in a significant part of the Gerkhozhan-Su river channel, activating and changing the type of exogenic processes. It may be expected that the canyon will gradually widen and fill up with material, but presently the speed and kinetic energy of any new catastrophic mudflows may exceed that of the year 2000 mudflows. The morphology of the canyon allows a partial reconstruction of the mechanisms of the mudflow disaster of 2000. The most important mudflow protection measures are the establishment of mudflow monitoring posts in at least two key places, an early warning system, the reinstatement of the protective flume in the lower Gerhozhan-Su, a ban on construction in and resettlement from the danger zone in Tyrnyauz. An interdisciplinary field expedition is necessary to prepare the basin for mudflow monitoring.

3. D.A Paramonov, O.V.Tutubalina, and S.S. Chernomorets. 2001. Geoinformatsionnoye kartografirovaniye basseina Gerkhozhan-Su (Tsentralny Kavkaz) dlya podgotovki k monitoringu selevykh protsessov [Geoinformation mapping of the Gerkhozhan-Su basin (Central Caucasus) in view of mudflow monitoring]. In Russian with English abstract. In: Ustoichivoe razvitie gornukh territorii: problemy regionalnogo sotrudnichestva i regionalnoi politiki gornukh raionov: tezisy dokladov uchastnikov IV mezhdunarodnoi konferentsii [Proceedings of the IV International Conference on Sustainable Development of Mountain Territories], Vladikavkaz, 23-26 September 2001. Vladikavkaz: Remarko. Pp. 476-477.

   Short abstract in English: A series of digital maps was compiled to assess the state of the Gerkhozhan-Su basin after catastrophic mudflows in July 2000: a map of the mudflow formation conditions in the Gerkhozhan-Su basin (1:10 000 , with a newly developed legend showing over 60 types of features), a map of the mudflow formation conditions in the Kayaarty-Su basin (1:10 000), and a map of the mudflow damage in the town of Tyrnyauz and its vicinity (1:7000). Sources included field observations, aerial surveys in 1997 and 2000, and literature data. All the maps share a common digital base and can be easily integrated with other data to form a geographical information system for mudflow monitoring.

A more general review of recent mudflow and glaciation dynamics in Central Caucasus has been published in Russian:

I.B.Seinova, E.A. Zolotarev. 2001. Ledniki i seli Prielbrus'ia (Evolutsia oledeneniya i selevoi aktivnosti): [Glaciers and mudflows in the Elbrus region (evolution of glaciation and mudflow activity)]. Scientific editor: S.M. Myagkov. Editor: S.S. Chernomorets. Moscow, Nauchny Mir, 220 p.

This book describes the evolution of glaciers and mudflow activity in Central Caucasus over the last two millenia. Chapter 1 covers the geological structure of the region, including its tectonics and the formation of the Elbrus volcano. In Chapter 2 the evolution of glaciers for the last 2000 years is described, including case studies of Bol'shoi Azau and Skhel'da glaciers, as well as the glaciation of Mt. Elbrus. Geological and glacial conditions for mudflow formation are reviewed in Chapter 3. Chapter 4 describes mudflow activity in the key river basins of the Elbrus region, and sources of mudflow material in each basin. Chapter 5 is devoted to patterns of change in mudflow activity over the last two millenia. It is forecast that the current degradation of glaciation may trigger greater mudflow activity in the following decades. Chapter 6 discusses the forecasting of mudflows on the basis of hydrological and meteorological observations. Chapter 7 examines the ecological aspects of protection from mudflows, and which kind of protection is suitable for a particular basin. The Conclusion analyses the mudflow disaster of 2000 in Tyrnyauz in relation to recommendations set out in Chapter 7. Ways of improving the town's protection from mudflows are suggested.

Acknowledgements

This research has been in part funded by the Committee for Natural Resources of the Republic of Kabardino-Balkariya and by Trinity Hall, Cambridge. Assistance in the field has been provided by numerous organisations and people, most notably by the staff of the Vysokogorny Geofizichesky Institut (High-Mountains Geophysics Institute) based in Nal'chik, and staff of the Russian Ministry for Emergency Situations. We are also very grateful to numerous students and friends who participated in the field campaign. Academician A.I. Sheko of All-Russian Research Institute of Hydrogeology and Engineering Geology(VSEGINGEO), O.A.Goncharenko of Northern Osetia's Geological Exploration Enterprize (Sevosgeologorazvedka), E.V. Zaporozhchenko of Northern Caucasian State Planning Institute for Water Infrastructure (Sevkavgiprovodkhoz), Dr V.V. Popovnin of the Faculty of Geography, and M. Yu. Nikitin of the Faculty of Geology, Moscow State University, provided valuable data and help in planning the research. Prof Y. F. Knizhnikov of the Laboratory of Aerospace Methods, Moscow State University, kindly lent a digital camera and Dr R. N. Gelman provided technical assistance.