Search

Kellerer-Pirklbauer, A., Slupetzky, H. and Avian, M., 2012. Ice-avalanche impact landforms: the event in 2003 at the glacier Nördliches Bockkarkees, Hohe Tauern Range, Austria. Geografiska Annaler: Series A, Physical Geography, 94, 97-115. doi:10.1111/j.1468-0459.2011.00446.x ABSTRACT The hanging glacier Nördliches Bockkarkees (47° 07′ 21″ N; 12° 44′ 00″ E) represents the only Austrian glacier that formed large and hazardous ice avalanches over the last decades. Only one major ice avalanche was released between August 1993 and July 2011 underlying the rareness of such large ice avalanches in the Austrian Alps. The ice avalanche happened on 26 June 2003 and was very unusual for two reasons: First, the ice avalanche occurred suddenly without major signs of glacier instabilities even a few days before the event. Second, the ice avalanche was released very early in the season. Ice and debris with a volume of 300 000 m3 avalanched over a vertical distance of 1200 m. The main deposits with a volume of 250 000 m3 and a debris content of 10% formed a flat avalanche cone in the Käfer Valley covering 82 000 m2. This paper focuses on geomorphic and glaciological field measurements and observations at and below the ice avalanche deposit and its vicinity after the event. Studies were made (a) at the deposited material itself, (b) at the reshaped land surface below the deposit after ice melt, (c) at the front and margin of the deposit, and (d) outside the deposit. Our study reveals different types of ice-avalanche impact landforms comparable to landforms caused by snow avalanches. It is shown that ice avalanches charged with debris at the Nördliches Bockkarkees are important in forming and reshaping erosional and depositional landforms along the track. However, the conservation potential of these landforms is low. [ABSTRACT FROM AUTHOR]

Sass, O., Haas, F., Schimmer, C., Heel, M., Bremer, M., Stöger, F. and Wetzel, K.-F. 2012. Impact of forest fires on geomorphic processes in the Tyrolean Limestone Alps. Geografiska Annaler: Series A, Physical Geography, 94, 117-133. doi:10.1111/j.1468-0459.2012.00452.x ABSTRACT We investigated geomorphic processes on two slopes (Arnspitze and Bettelwurf) burned by wildfire in the region north of Innsbruck. Both burned in 1946 and both are still characterized by severe vegetation destruction. Sparsely grass-covered rock and debris slopes have developed replacing the former dwarf pine ( Pinus mugo) shrub stands. Our aim was to establish disturbed and undisturbed erosion rates and to decide whether recent debris flows can be assigned to these historical wildfires or not. We measured fluvial erosion by means of collectors, estimated the amount of post-fire erosion from stratigraphic exposures in the adjacent talus, modelled bedload discharge with a statistical model developed in a nearby study area and quantified recent debris flow activity by combining airborne and terrestrial laser scans. We measured erosion rates of 3-30 g m−2 a−1, which is roughly ten times higher than the undisturbed sediment yields. Slopewash was higher than linear fluvial transport in the four years of our investigation. Surplus material was removed from the channels by avalanches and debris flows; both being more important for the sediment budget than fluvial action. The modelling approach allowed measured sediment yields to be transferred to larger slope parts and to calculate scenarios of pre-fire conditions. The concordance of measured and modelled yields was reasonably good; deviations may be explained by differing amounts of precipitation. Our results support the impression that current debris flow activity at the Bettelwurf was enhanced by the aftermath of the 1946 wildfire. [ABSTRACT FROM AUTHOR]

Laimer, H.J. and M¨llegger, M., 2012. Geomorphological and geotechnical causes of anthropogenically induced rockmass falls in theWachau-Danube Valley (Bohemian Massif, Lower Austria). Geografiska Annaler: Series A, Physical Geography, 94, 157-174. doi:10.1111/j.1468-0459.2012.00451.x ABSTRACT The Wachau-Danube Valley represents a transverse valley, intersecting the Variscian Bohemian Massif. Weakened rocks along fault structures led to accelerated river erosion, forming relatively steep rock slopes. The exceptional cultural position of the region generated an increasing demand for building materials. Over the centuries quarrying had a sizeable impact on slope morphology. Interdependences between quarrying and construction caused unstable rock slopes and four rock-mass falls have occurred at two quarries near Spitz (1961, 1984, 2002) and Dürnstein (2009). Rock mechanical analysis at these quarries has shown that the combination of existing geological discontinuities and artificially modified morphology is fatal in terms of slope stability. In Spitz the bedding planes within the marble had been undercut by the mining face. Additionally, two conjugated, steeply dipping joint sets formed large scale blocks sliding on bedding planes. In three major rockslides/rock-mass falls, each triggered by heavy rainfalls, a total mass of 170 000 m3 of rock failed. At the quarry near Dürnstein the geotechnical characteristics of the gneiss are also unfavourable in relation to the exposition of the mining face. After several rockfalls, 65 000 m3 were blasted away in 1909 to remove unstable rock slopes. The residual rock face was destabilized and rockfall activities culminated in an event with a total volume of approximately 15 000 m3. Remedial measures for both locations are essential to maintain transport infrastructure. Sufficiently stable conditions can only be achieved by extensive reshaping of the mining faces, which involves adapting slope geometries to naturally stable joint faces. [ABSTRACT FROM AUTHOR]

Otto, J.-C., Keuschnig, M., Götz, J., Marbach, M. and Schrott, L., 2012. Detection of mountain permafrost by combining high resolution surface and subsurface information - an example from the Glatzbach catchment, Austrian Alps. Geografiska Annaler: Series A, Physical Geography, 94, 43-57. doi:10.1111/j.1468-0459.2012.00455.x Abstract Permafrost distribution in mid-latitude mountains is strongly controlled by solar radiation, snow cover and surface characteristics like debris cover. With decreasing elevation these factors have to counterbalance local positive air temperatures in order to enable permafrost conditions. We combine high resolution surface data derived from terrestrial laser scanning with geophysical information on the underground conditions using ground penetrating radar and electrical resistivity tomography and ground surface temperature data in order to understand the effects of surface characteristics on permafrost distribution in an Alpine catchment, Austrian Alps (Glatzbach, 47°2′23.49″ N; 12°42′33.24″ E, 2700-2900 m a.s.l.). Ground ice and permafrost is found above an elevation of 2780 m a.s.l. on north-east facing slopes in 2009, previous studies detected permafrost at the same site at 2740 m a.s.l. in 1991. Analysis of surface roughness as a proxy for grain size distribution reveals that the lower boundary of discontinuous and sporadic permafrost is lowered on rough surfaces compared to fine-grain zones. At the same location modelled potential summer solar radiation in coarse grain zones is reduced by up to 40% compared to surfaces of fine grain sizes. The mostly patchy permafrost distribution at the Glatzbach can therefore be attributed to local surface cover characteristics, particularly regolith grain size and its influence on solar radiation. We conclude that the analysis of ground surface characteristics using very high resolution terrain data supports the assessment of permafrost in Alpine areas by identifying rough surface conditions favouring permafrost occurrence. [ABSTRACT FROM AUTHOR]

Mergili, M., Kopf, C., Müllebner, B. and Schneider, J.F., 2012. Changes of the cryosphere and related geohazards in the high-mountain areas of Tajikistan and Austria: a comparison. Geografiska Annaler: Series A, Physical Geography, 93, 79-96. doi:10.1111/j.1468-0459.2011.00450.x ABSTRACT This paper quantifies recent glacier changes and possible future permafrost retreat in the Austrian Alps and the Pamir and Alai Mountains of Tajikistan (Central Asia), two mountainous areas with striking differences in climate and hypsometry, but also in economy and research history. The aim of the comparative study is to improve the understanding of regional differences as a baseline for further research and for a differentiated evaluation of possible socio-economic implications. Besides a review of the available literature, multi-temporal remote sensing of glaciers of selected areas as well as additional helicopter and field surveys were conducted. The Tajik glaciers displayed a differentiated behaviour during the investigation period 1968-2009, with a strong trend to retreat - at least since 2002. More than 100 pro- and supraglacial lakes have been forming or growing in the southwestern Pamir. Destructive outburst floods of such lakes have occurred there in the recent past. Almost all Austrian glaciers are in an advanced stage of retreat, a trend which continues at enhanced rates. Comparatively few glacial lakes exist in the direct forefields of the glaciers. Potential permafrost distribution maps for the present and the future were produced for Tajikistan and Austria by adapting an empirical model developed in Switzerland. In absolute terms, the highest loss was predicted for the Pamir. The expected relative loss in the same area is moderate compared to the rest of Tajikistan and particularly to Austria, where the model predicted the disappearance of more than 90% of the potential permafrost until the end of the twenty-first century. [ABSTRACT FROM AUTHOR]

Bell, R., Petschko, H., Röhrs, M. and Dix, A. Assessment of landslide age, landslide persistence and human impact using airborne laser scanning digital terrain models. Geografiska Annaler: Series A, Physical Geography, 94, 135-156. doi:10.1111/j.1468-0459.2012.00454.x ABSTRACT Landslides occur worldwide and contribute significantly to sediment budgets as well as to landform evolution. Furthermore, they pose hazards and risks to people and their goods. To assess the role of landslides, information on their age or persistence (i.e. the length of time the morphological characteristics of a landslide remain recognizable in the terrain) is essential. In this study, the potential of airborne laser scanning digital terrain models (ALS DTMs) is analysed for estimating landslide age, landslide persistence and human impact. Therefore, landslides in two study areas, Swabian Alb in Germany and Lower Austria in Austria, are mapped from hillshades of ALS DTMs and combined with historical information on landslide occurrence. It is tested whether the modification of the geomorphological features of landslides can be used to assess landslide age. In the Swabian Alb older landslides might show fresher features than younger ones because of different degrees of human impact, natural erosion and different histories of landslide reactivation. Estimated persistence times range between 27 and 320 years but are minimum values only. In Lower Austria four landslides show estimated minimum persistence times between 4 and 28 years. In Lower Austria 27 landslides disappeared in less than 7 years after occurrence mainly because of planation by farmers. The results show no clear trend in landslide persistence, neither regarding landslide magnitude, nor regarding land use. However, it is evident that human impact plays a major role in landslide persistence. [ABSTRACT FROM AUTHOR]

Embleton-Hamann, C. and Slaymaker, O., 2012. The Austrian Alps and paraglaciation. Geografiska Annaler: Series A, Physical Geography, 94, 7-16. doi:10.1111/j.1468-0459.2011.00447.x ABSTRACT There is some confusion in the geomorphological literature with respect to the usage of the term 'paraglacial'. We review the meaning of the term as defined in the Anglo-Canadian literature between 1972 and the present. We then show that many of these ideas were implicit in the early-twentieth-century German literature but were never, to our knowledge, synthesized into an overarching framework for the study of post-glacial glaciated landscapes. It was not until the end of the twentieth century that the paraglacial model was directly applied to the interpretation of the European Alps. The first decade of the twenty-first century has seen a growing appreciation and some critique of that model in research in the Austrian Alps. The post-glacial glaciated landscape is interpreted as a landscape of transition between the full glacial of the Last Glacial Maximum and the present almost entirely deglaciated landscape. It provides a conceptual framework and a challenge to determine exactly how far any specific glaciated landscape has evolved in response to non-glacial processes and whether it remains a disturbance regime landscape. [ABSTRACT FROM AUTHOR]