Survay and prevention of extreme glaciological hazards in european montainous regions (GLACIORISK)

The database/computer atlas gathers information on all the main glaciers (total of 2192) in Norway. It provides basic geographical and dimensional information for each glacier. Where appropriate, glaciers are classified according to risk. Information on each event is documented (total of 76 events). Mass balance information on glaciers is included, where available (a total of 453 mass balance years). This database is an addition to the Gridbase, and was created in order to complement the hydrological database already used at NVE.

"Atlas of hazardous glaciers in Austria" is a web site on Austrian contribution to the GLACIORISK project. It is on line at http://www.glaciorisk.at.tf. The web site contains a general overview of the project, links to GRIDABASE, to the main page of the GLACIORISK and to other project partners' contributions. It is possible to choose one of Austrian counties to search for risky glaciers on the area or pick the glacier directly out of an alphabetical list. By choosing particular options, more data, pictures and maps become accessible giving detailed information on each event.

An educational film was produced and largely diffused to make glacial risks known to a larger audience and to make public and local organisations more responsible. This 14-minute film presents real events like serac falls, water pocket sudden draining and examples of prevention, protection and mitigation. French and English versions have been realised. A CD-copy of this film has been sent to every participant of GLACIORISK and every end-user (around 100 copies).

The inventory includes 82 glaciers, which in the past inflicted damage on persons or property or for which a potential danger was recognised. Of these 82 glaciers, 55 are located in the canton of Valais, 18 in canton of Berne, 2 in the cantons of Vaud, Uri and Grisons, and one in the cantons of Obwalden, Glarus and Ticino respectively. According to the present assessment, 51 of these 82 glaciers can expect potential damage to settlements (22 cases), traffic routes (28 cases) or other man-made installations (water intake, farm buildings, agricultural land, hiking trails, mountain cabins, tourist facilities) (49 cases) within the next 10 to 20 years. A large number of people pursue various activities within the potential risk zones. At present there is a monitoring scheme for only 12 of the 51 glaciers, whereas for the remaining glaciers such a scheme has still to be devised. A compilation of all inventoried events showed that since 1595 at least 440 persons have lost their lives in 21 glacial disasters (approximately one event every 20 years, or one victim per year). In 146 events, collateral damage was caused to various human infrastructures (approximately one event every 3 years). This inventory contains all the information about glacial events and potential risks the team could gather from local chronics, glacier reports, publications and newspapers. However, it does not claim to be exhaustive because some events may have escaped the observers attention or gone unrecorded. As the risk potential changes with glacier fluctuations (in the context of potential climate changes), the results of this evaluation will have to be revised and updated regularly. In the first section of the inventory, the governing processes of the three risk types are examined. The methods known for early recognition of these dangers are also explained. In the second section, the collected events are presented and illustrated for each glacier by means of maps, figures and photos.

This work is a first attempt of a precise inventory of the glaciers in the French Alps, with some catastrophic events (glacier falls, outburst of glacial lakes, internal water pockets). The Atlas presents the glaciological scientific works of the century. An analysis of the observed climat warming (since 1850) is also developed. This work has been carried out in 1999, for the French Ministry in charge of Environment. The data of this inventory has been included into the Gridabase database at the beginning of the Glaciorisk project.

The altas provides an overview of locations of risky glaciers in Iceland. Risky glaciers in Iceland are mainly connected with glacier floods due to: - Release of meltwater from subglacial lakes at geothermal areas, - Sudden volcanic eruptions under the glaciers or - Drainage of ice dammed marginal lakes. The altas provides an overview of the past events, their nature and frequency. The damage caused by the events is mainly due to the disruption of the road system. Although the events are frequent, thanks to alert monitoring of the risky areas and to a successful warning system few human lives have been lost. Further information is available on the web-site: http://www.raunvis.hi.is/glaciorisk which was established for the project. All the results are accessible for the general public and for all authorities and institutes dealing with glacier hazard studies, prediction, migtation and rescue workers in Iceland. The team aims to update the altas regularly on the web-site and integrate its information into the data bases of its partners.

Gridabase is a database storing all the information and data about glacial hazard -events known in European mountainous regions. After a period of feeding (during the project) from all the European project partners, Gridabase was made public on the internet. The archive is available on line and accessible to anyone interested in glacial hazards (planners, geologists, local managers, tourists, mountaineers). The web address is http://www.nimbus.it/glaciorisk/gridabasemainmenu.asp It contained, end of February 2004, a total of 671 events and it is constantly updated by each partner with new events.

Glacier outburst floods (jokulhlaups) are caused by the sudden drainage of glacier-dammed lakes. During such an event, the discharge can increase by more than one order of magnitude within a short time period (from hours to days). Jokulhlaups pose a significant hazard potential and have caused substantial damage in the past in the Alpes and elsewhere. The assessment and prevention of hazards related to jokulhlaups require a reliable prediction of the timing, duration and magnitude of the outburst flood. Despite much progress, several aspects of recent observations were unexpected and highlight the need to improve existing theories. In particular, the rapid rise of discharge during some jokulhlaups indicate that during the start of the drainage different physical processes may be important. Studies should be conducted to address some important open questions of the subglacial drainage process in a combined ?eld and numerical modelling project. In particular, the drainage of different glacier dammed lakes should be analysed with existing and improved models. The second category concerns avalanches. Observations show that ice masses become detached from unstable glaciers by progressive fracture at englacial interfaces. Such events occur all around the year. The main difference between so called hanging glaciers and steep glacier tongues are that for hanging glaciers a progressive motion increase of an instable ice mass always leads to a major break off. For steep glacier tongues this happens only in very rare situations. Results from combined field and modelling studies on hanging glaciers show that a forecast of a major breaking off event is possible in some situations. However, it is still very difficult to predict in advance the breaking off volume. In most cases, an instable ice mass breaks off in many smaller chunks of ice. But even a small volume of falling ice can trigger a huge combined ice/snow avalanche if a thick and unstable snow pack exists around a hanging glacier. Such events can be relevant in the winter season and should be seriously considered by people responsible for the security of roads and railways in regions where hanging glaciers exist. To improve forecasting possibilities of breaking off of instable ice masses, it is necessary to monitor the regular formation and detachment of ice chunks on hanging glaciers by: - Monitoring the breaking off activities at the front of hanging glaciers with regular high quality photographs. - Monitoring the evolution of the motion of the unstable ice mass from the beginning of the instability to the time of breaking off. For hanging glaciers located in regions where the basal ice temperature is close to the melting point, their stability can change in near future because of global warming. This is because the transition of a previously cold to a temperate glacier base, basal sliding can suddenly be induced, leading to a major destabilisation of the hanging glacier. Where such an evolution is expected to happen and if human activities are endangered, a monitoring program for this type of hanging glaciers is extremely important for hazard assessments.

Measurements of the spatial distribution of surface velocity and its changes on various time scales are an important tool for studying deformational and basal processes on glaciers [3]. The surface velocity of glaciers is traditionally measured by repetitive terrestrial surveying of markers on the ice surface. This method allows evaluation of mean velocities over interannual to sub-daily time-scales. A drawback to this method is that usually only a few markers can be monitored, whose spatial distribution is often unable to reveal interesting two-dimensional (2D) features of the velocity field. The traditional method requires ground occupation, which can be expensive and time consuming on large glaciers and ice fields. This work presents a use of SAR interferometry to obtain full 2D-measurements on the displacement field over the Mer de Glace and Argentiere glaciers. The team has used a SAR interferogram obtained from the two European Remote-sensing Satellite (ERS1-2) [1]. Synthetic-aperture radar (SAR) images, acquired on 10 and 11 March 1996. The team has investigated whether the interferometric data are quantitatively consistent with terrestrial velocity measurements along two transverse profiles and two longitudinal profiles. These terrestrial data are from different years (1996 and 1997) and cover the period from 15 September 1996 to 14 September 1997 (a whole year). Terrestrial ice velocity at the date of the SAR imagery was obtained via seasonal and annual corrections that were calculated from other terrestrial velocity measurements available at higher time resolution for selected sites on the glacier. Interferometric and terrestrial velocities are in agreement if a (terrestrially measured) surface-normal velocity component is properly accounted for. This suggests that both the interferometric velocities and the conversions of terrestrial data to the winter period are reliable. Finally, the team showed that the application of repeat-pass SAR interferometry to the glaciers enable precise mapping of ice flow dynamics at a much higher level than the levels usually obtained [2]. References: [1] Hanssen, R. F., Radar Interferometry, Data Interpretation and Error Analysis in Remote sensing and Digital Image Processing, vol 2, Kluwer Academic Publishers, 275 pp, 2001. [2] Massonnet, D., T. Rabaute, Radar Interferometry : Limits and Potential, IEE Trans. Geosci. Remote Sensing, 31, (2), pp. 455-464, 1993. [3] Rabus, B. T., D. R. Fatland, Comparison of SAR-interferometric and surveyed velocities on a mountain glacier : Black Rapids Glaciers, Alaska, U.S.A., J. Glaciol., 46, (152), pp. 119-128, 2000.

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