The 2002 rock/ice avalanche at Kolka/Karmadon, Russian Caucasus: assessment of extraordinary avalanche formation and mobility, and application of QuickBird satellite imagery

Abstract

Abstract.A massive rock/ice avalanche of about 100×10 6 m 3 volume took place on the northern slope of the Kazbek massif, North Ossetia, Russian Caucasus, on 20 September 2002. The avalanche started as a slope failure, that almost completely entrained Kolka glacier, traveled down the Genaldon valley for 20 km, was stopped at the entrance of the Karmadon gorge, and was finally succeeded by a distal mudflow which continued for another 15 km. The event caused the death of ca. 140 people and massive destruction. Several aspects of the event are extraordinary, i.e. the large ice volume involved, the extreme initial acceleration, the high flow velocity, the long travel distance and particularly the erosion of a valley-type glacier, a process not known so far. The analysis of these aspects is essential for process understanding and worldwide glacial hazard assessments. This study is therefore concerned with the analysis of processes and the evaluation of the most likely interpretations. The analysis is based on QuickBird satellite images, field observations, and ice-, flow-and thermomechanical considerations. QuickBird is currently the best available satellite sensor in terms of ground resolution (0.6 m) and opens new perspectives for assessment of natural hazards. Evaluation of the potential of QuickBird images for assessment of high-mountain hazards shows the feasibility for detailed avalanche mapping and analysis of flow dynamics, far beyond the capabilities of conventional satellite remote sensing. It is shown that the avalanche was characterized by two different flows. The first one was comparable to a hyperconcentrated flow and was immediately followed by a flow with a much lower concentration of water involving masCorrespondence to: C. Huggel ( chuggel@geo.unizh.ch) sive volumes of ice. The high mobility of the avalanche is likely related to fluidization effects at the base of the moving ice/debris mass with high pore pressures and a continuous supply of water due to frictional melting of ice. The paper concludes with implications of the Kolka/Karmadon event for worldwide glacial hazard assessments. It is emphasized that situations with large glacierized high-mountain walls with potentially unstable glaciers within impact distance need special attention and monitoring efforts.

Review Article: Potential geomorphic consequences of a future great (<i>M</i><sub>w</sub> = 8.0+) Alpine Fault earthquake, South Island, New Zealand

“…The main part of the glacier detached during a major rock avalanche and cascaded down the valley for a total distance of ∼ 20 km, at which point a mudflow was generated flowing a further 15-17 km downstream. The average velocity of the main flow is thought to have been close to 50 m s −1 (180 km h −1 ) (Petrakov et al, 2008) with maximum velocity estimates ranging from 70 m s −1 (250 km h −1 ) (Drobyshev, 2006) to 90 m s −1 (325 km h −1 ) (Huggel et al, 2005). Until this event collapse of an entire valley-type glacier had not been considered possible.…”

“…They involve collapse of all or part of a glacier due to significant rock avalanching and involve extraordinary velocities, long-distance run-outs, and superelevations (Petrakov et al, 2008). From the few examples studied, they begin as rock and/or ice avalanches/slides before gradually transforming into ultra-high speed flows (> 30 ms −1 ) and often finish as debris flows (Huggel et al, 2005;Petrakov et al, 2008). They can travel for distances of tens of kilometres (Huggel et al, 2005;Petrakov et al, 2008).…”

The extremely long-runout Komansu rock avalanche in the Trans Alai range, Pamir Mountains, southern Kyrgyzstan

“…Rock-ice avalanche deposits resemble those of slurry flows 418 in their distal regions (Fig. 10); photos from the Kolka-Karmadon (Huggel et al, 2005) and 419 corresponds to the total volume of the Komansu event, at least 6-10 km 3 of ice would have been 436 required to generate a rock-ice avalanche; correspondingly more would be needed to cause the 437 inferred 5-10 km 3 event into a rock-ice avalanche. It is difficult to explain the availability of such 438 a large volume of ice, especially given that the age of the deposit appears to correspond to a time 439 after the region's glaciers began to retreat.…”

Monitoring topographic changes in a periglacial high‐mountain face using high‐resolution DTMs, Monte Rosa East Face, Italian Alps

“…Barla et al, 2000;Noetzli et al, 2003;Cola, 2005;Oppikofer et al, 2008;Fischer, 2009), Canada and Alaska (e.g. Evans and Clague, 1994;Geertsema et al, 2006), the Caucasus (Huggel et al, 2005) and New Zealand (e.g. Cox and Allen, 2009;Allen et al, 2009).…”