Monte Rosa east face and Belvedere Glacier:

Transcription

1 Monte Rosa east face and Belvedere Glacier: Glacier surge, glacier lake, slope instabilities and related emergencies Christian Huggel, Luzia Fischer Glaciers in an Environmental Context: Case Studies

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3 C. Rothenbühler

4 2000

5 2001

6 2000

7 2001

8 July 2001 February 2002

9 Tourist trails had to be closed : Uplifted highly crevassed glacier surface Ice and rock fall from uplifted glacier

10 Glacier surface velocities Automatic matching of orthophotos Time periods: Sept-Oct 2001

11 Vertical glacier surface changes DEM subtraction: October 1999 July 2002

12 Vertical glacier surface changes DEM subtraction: July 2002 September 2003

13 Vertical glacier surface changes Jörg, Fischer et al.

14 Vertical glacier surface changes Jörg, Fischer et al.

15 Effects on moraine stability Following downwasting of Belvedere Glacier

16 1996

17 2001

18 Lago Effimero June 2002

19 Lago Effimero June 2002

20 Intervention of Italian Civil Protection Activation of National Civil Protection with subsidies : military, police, fire brigades, guardia civil, etc. Massive media invasion

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22 July 2002

23 Critical situation Volume > 3 Mio m 3 Rapid increase of lake level (~ 1 m/d) Damming by glacier ice (water pressure!) Close to buoyancy Monitoring Emergency measures Lake lowering by pumping

24 Damming and outburst flood characteristics

25 J. Alean July 2002

26 October 2002

27 June 2003

28 June 2003

29 C. Rothenbühler

30 Lake volume changes and discharge

31 Tracer studies

32 The Monte Rosa east face Haeberli Fischer General decrease of ice thickness At some locations very strong or complete loss of ice

33 Multiple mass movement activity Many active initiation zones Which are the factors leading to slope instabilities? Since about 1990 increased mass movement activity observed

34 Factors influencing high-mountain slope stability

35 Methods for analysis of high-mountain slope stability

36 Geology Several rock fall initiation zones are located in transition zone between orthogneiss and paragneiss

37 Permafrost modeling Lower permafrost limit between about 3200 and 3700 m asl (depending on aspect) All rock fall initiation zones located in modeled permafrost. Many failure zones located in lower, warm permafrost Gletscher kein Permafrost Permafrost Modeling: J. Nötzli Anrisszone

38 Loss of entire hanging glacier Sella Detachment of underlying rock layer Röthlisberger 1990 One of the most active 2002 recent rock fall zones Haeberli Haeberli

39 Changes of glaciation on east face Many failure zones of rock fall and debris flows are located in areas that have recently become ice-free

40 Generation and analysis of high-resolution DEMs 2001 Photogrammetrically derived DEM 3D view of hillshade

41 Generation and analysis of high-resolution DEMs 2005 Lidar DEM 2005 lidar 3D view of hillshade

42 DEM - Differences Vertical terrain changes Röthlisberger Haeberli

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44 Ice avalance August 2005 Failure volume: > 1mill. m 3 One of the largest ice avalanche events in the Alps Entrainment of material (mostly debris) along the trajectory

45 DEM - Differences Vertical terrain changes

46 Ice avalanche runout: Most of the material reached (and stopped) at depression of former Lago Effimero Lateral moraines exerted a protection function Pressure and airborne finer material reached Rifugio Zamboni consider strong pressure waves

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49 Rock failure and avalanche April 2007

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51 Possible effects of anomally warm periods

52 Predisposing and trigger factors

53 Conclusions for mass movement activity Most failure zones located where surface ice has disappeared in past years & decades permafrost is in warm conditions transition zone between orthogneiss and paragneiss Complex failures, an integrative analysis of multiple factors is necessary Distinguish between predisposing and trigger factors Ice and permafrost are currently changing at highest rate, shear strength can fall below critical value, resulting in failure

54 Cascading processes Rock fall Ice avalanche Glacier lake Erodible sediment Flood Debris flow Inundation

55 General conclusions for hazard assessments & management Consider cascading processes that typically increase magnitude and reach of mass movements Thus, in such complex cases an integrative process analysis is highly needed Rapid overview in case of emergencies is required; based on that identification of more detailed studies; continuous monitoring Responsibilities and decision-making process among scientists and different kinds of authorities should be clear