THE USE OF AIRBONE REMOTE SENSING DATA IN DETECTION OF PRONIVAL RAMPARTS IN THE TATRA Mts.

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1 THE USE OF AIRBONE REMOTE SENSING DATA IN DETECTION OF PRONIVAL RAMPARTS IN THE TATRA Mts. Helena Sedláková, Gabriel Bugár Department of Ecology and Environmental Sciences, Faculty of Nature Sciences, Constantine the Philosopher University in Nitra, Trieda A. Hlinku 1, Nitra, Slovakia Correspondig author: Abstract Data from remote sensing are widely used in various analyses of high-mountain landscape concerning with land cover, vegetation types or specific object detection. Pronival ramparts are one of the less investigated landforms at least within the Tatra Mts. territory. They represent a specific phenomenon indicating the postglacial development of the alpine environment and, more precisely, the existence of permanent or perennial snowfields and relating implications on local climate and hydrological regime. The aim of the paper is to present theoretical-methodological approaches of pronival rampart identification and classification based on airborne image data and digital elevation model analyses. Preliminary results from the study of eight ramparts detected so far show that they occur at the elevations from 1700 to 2050 m a.s.l., mostly at the head of glacial valleys, following a parallel direction of the major valley axis. The younger accumulations consist of bare boulders and debris while the older ones are covered with vegetation (Pinus mugo scrubs, grasslands, lichens) appropriate to the age and position (elevation and aspect) of the landform. Key words: pronival rampart, Tatra Mts., airbone image data, debris material. 1 Introduction High relief amplitudes of glacially formed mountain areas are usually reflected in a high variability of both biotic and abiotic landscape elements by means of climatic gradient effects and gravity-induced processes. The Tatra Mts. represent an excellent example of highmountain landscape where the above mentioned phenomena were explored and summarised in several scientific monographs (e.g. Lukniš, 1973, Konček et al., 1974, Midriak, 1983, Vološčuk, 1994). A catena principle of the occurrence of present geomorphic processes in high-mountain landscape was used in classification of morphodynamic systems (Hreško, 1996, 1997). Bizubová and Škvarček (1999) referred the nature of slope processes in deglaciated landscape such as transportation and accumulation of clastic sediments. The patches of debris material of various particle sizes and genesis represent one of the major land cover types in alpine zone of the Tatra Mts. (Boltižiar, 2007). They are a product of glacial weathering and erosion, gravitational and hydro-gravitational processes with specific landforms (e.g. talus piles, talus cones, debris-alluvial fans, moraine sediments, glaciers etc.). Raczkowska (2007, 2008) investigated the accumulation of debris material in surroundings of perennial firn patches and created a detailed geomorphological map of the Medená Kotlinka Valley (a hanging valley in the Veľká Zmrzlá Valley in the Tatra Mts.) with additional information on the occurrence of gravitational and periglacial processes and snow avalanche activity included. Direct deposition measurements of clastic material from debris falls can indicate the occurrence of permafrost (Gadek, Raczkowska, Źogala, 2009). A specific type of coarse angular debris accumulation occurs usually at the foot of steep talus slopes with perennial snowbeds in a form of debris ridges or ramps, known as protalus ramparts (e.g. Ballantyne, 1987, Shakesby, Mathews, McCarroll, 1995, Shakesby, 1997). The term protalus rampart is widely used especially in Anglo-Saxon literature. In the Tatra Mts., the similar landforms are named as nival ramparts (wał niwalny, Kotarba, 2007, Raczkowska, 2007) or nival (firn) debris ramparts (snehový/firnový sutinový val, Lukniš, 1973). These terms seem to be more fitting to describe the genesis of the landforms. 172

2 Shakesby, Mathews and McCarroll (1995) suggested using term pronival as a widely applicable descriptor suitable for any debris accumulations forming ramps or ridges at the downslope margins of snowbeds irrespective of location in relation to slope position. Their arguments have been supported by the observations of active protalus ramparts forming by debris flows moving over the snow surface (Ono and Watanabe, 1986) and by snow or slush avalanching (Ballantyne, 1987). The lack of qualitatively and quantitatively sufficient information about the terrain characteristics desired for large-scale mapping belongs to the main problems in research tasks dealing with the high-mountain landscape. On the one hand, any fieldwork concerned with the monitoring or regular measurements in hard accessible locations (steep rocky slopes, chutes etc.) is the most time-consuming activity therefore the research is usually limited to spatially smaller areas. On the other hand, the progress in remote sensing techniques and high-resolution data accessibility, together with improving GIS tools allows spreading the area of interest from scattered spot observations to areal extent at once, and process spatial data quickly with adequate precision. Usage of satellite or aerial high-resolution images and digital elevation models can support and partly substitute the fieldworks. In case of spatiotemporal analyses of landscape changes, there are many opportunities to achieve appropriate remote sensed datasets, starting from historical aerial images to the newly commissioned very high-resolution multispectral satellite images. So far, the research on changes in the landscape structure within the Tatra Mts. region has been conducted in several representative areas (valley systems, transects) delimited in compliance with the aims of research tasks; e.g. the changes in landscape structure and development of erosional landforms (Boltižiar, 2007) or land cover changes affecting biodiversity (Olschofsky et al., 2006). Our research is focused on pronival ramparts (protalus ramparts) as a specific landform that can indicate the activity of morphodynamic processes connected with the occurrence of perennial or long-term snowfields in the Tatra Mts. This paper brings out the theoretical and methodological background and preliminary results from the existing data sources and current observations. 2 Methods Historical panchromatic aerial photographs from 1949 and 1955 (archived in the Topographic Institute in Banská Bystrica) are used for the interpretation of historical landscape structure in surroundings of the identified ramparts. The original 16x16 cm analogue negatives at a scale of 1:15000 approximately have been scanned at the resolution of 1200 DPI into a raster file format TIFF. Then the resulting spatial resolution of the orthorectified images could be better than 0.5 m per pixel. Colour aerial photographs from 2002 are used for the comparison and change analysis within the study areas. They are available as orthophoto images distributed by GEODIS Slovakia, s.r.o.in a compressed raster file format JFIF (JPEG File Interchange Format) with spatial resolution of 1 metre per pixel and radiometric resolution of 8 bits per pixel. It is convenient that the aerial photography of investigated region took place in cloudless weather in midsummer when the shadows are at minimum. The image classification procedure is based on visual on-screen vectorisation and interpretation of delimited objects using photointerpretation signatures. In case of pronival ramparts, the following interpretation features have been chosen: 1. Shape slightly curved linear feature, often in crescent-shaped with horns oriented towards the adjacent talus slope or rock wall; 2. Texture in the meaning of visual perception of surface roughness the spotted texture is typical for debris cover and the size of individual spots depends on the diameter of rock fragments; 173

3 3. Colour on panchromatic photographs, the tonal variety of debris cover is in the range from white to light grey (the lighter tone usually indicates younger accumulations while the older ones are darker as they are usually covered by lichens or sparse vegetation and reflect less radiation); the light grey colour prevails on colour photographs as well, with yellow-green tinge in case of older accumulations; 4. Position often at the foot of rock walls and steep talus slopes or at the base of dividing crests in lower parts of the valley. In the first phase, the photo interpretation is carried out on colour orthophoto images. In the second phase, the results are compared with historical aerial images by means of overlay function to identify significant changes. Additional data from the existing publications (i.e. historical ground photographs, geomorphological maps) as well as the current photographs taken during field trips are an important part of the process. 3 Study area The Tatra Mts. represent the highest range within the Carpathians, with a concentration of unique natural values, for instance, a diverse glacial relief with a high number of alpine lakes, numerous autochthonous (endemic) plant and animal endemic species, and spatially largest alpine vegetation zone. Topographically, the Tatra Mts. are usually divided into two main orographic sections: the Western Tatra Mts. and the Eastern Tatry Mts. The second one is further divided into two subsections (from the west): the High Tatra Mts. and the Belianske Tatra Mts. (Mazúr, Lukniš, 1978). The main ridge of the High Tatra Mts. is 26,5 kilometres long, with the mean elevation of 2357 metres a. s. l. and maximum at 2654,4 metres a. s. l. (the Gerlachovský Peak). The mean values of the other two orographic parts are lower; 1957 m a. s. l. in the Western Tatra Mts. and 2011 m a. s. l. in the Belianske Tatra Mts. (Lukniš, 1973). The Tatra Mts. were glaciated several times during the Pleistocene when the structure of cirques, U-shaped valleys with typical erosional and accumulation glacial landforms had been formed. Base on the previous research, the existence of 21 individual mountain glaciers with the High Tatra Mts. and 18 glaciers within the Western Tatra Mts. has been proved by means of lithological-geomorphological surveys (Lukniš, 1973). The glaciation in the Belianske Tatra Mts. was much weaker; nevertheless, there were several smaller cirque glaciers with short tongues (or without them) formed on the northern slopes. Lukniš (1968) have mapped 10 such small glaciers from the last glacial oscillation in this territory. 4 Results and discussion 4.1 Occurrence of pronival ramparts in the Tatra Mts. The occurrence of debris ramparts in the High Tatra Mts. is sporadic, while none has been detected in the Western Tatra Mts. and the Belianske Tatra Mts. (Raczkowska, 2007). These landforms are visually similar to frontal moraines and sometimes they are named as firn pseudo-moraines (Bizubová, Škvarček, 1999). They are postglacial landforms formed usually at the heads of the glacial valleys. Unlike the transverse orientation of the frontal moraines towards the valley axis, their orientation is horizontally parallel to the lateral slopes and the position is usually predisposed in a certain distance from the base of the rock wall, below the adjacent snowfield on talus slope. Debris falls supply the material for the formation of rampart accumulation (Fig. 1). 174

Fig. 1 The formation of pronival rampart (Source: http://www.landforms.eu; 2012) The evaluations of the present activity of this process in the Tatra Mts. are disputable.

4 Fig. 1 The formation of pronival rampart (Source: ) The evaluations of the present activity of this process in the Tatra Mts. are disputable. Midriak (1996) estimates the intensity of the current debris falls in a range of 0,01-3,0 mm per year. According to Hreško (1997), the most intensive debris falls occur mainly in early autumn period, during the local sun irradiation of the affected rock face, when the frequency of the process can reach values from 2 up to 3 events per minute. The accumulation effect of snow mass movements on the formation of debris ramparts is evident as well (Hreško, 1997). In case of slide of the whole-profile of snow cover, there is slush or dirty snow avalanche usually generated on smooth grassy slopes or icy rock faces as the shear zones. The avalanche body abrades the base surface and transport released fragments of soil and debris. Subsequently, as soon as the kinetic energy decreases, the material remains on snowfield surface or accumulates below in a form of rampart (Fig. 2). Following the length of the ramparts, it can be assumed that it is a type of slab avalanches developed on planar homogeneous slopes. The pronival ramparts can be formed by rock fragments solely or, in case of some content of soil, they are covered by vegetation of grasslands or Pinus mugo scrubs. Those objects with scrub vegetation are well distinguishable on aerial images (Figs. 3 and 4). Fig. 2 A debris material accumulated on snowfield in the Kotlinka pod Snehovým Štítom (Sedláková, 2011) 175

J. Partsch described the first documented nival debris rampart in 1923 in the Kobylia Valley at the head of the Kôprová Valley (Lukniš, 1973). It is located below the crest of the Tichý Mt. (1979 m a.

5 J. Partsch described the first documented nival debris rampart in 1923 in the Kobylia Valley at the head of the Kôprová Valley (Lukniš, 1973). It is located below the crest of the Tichý Mt. (1979 m a. s. l.) in a form of 800 m long slightly curved strip covered by Pinus mugo scrubs. The rampart is easily visible on aerial images or during the fieldtrip as well (Fig. 3). Smaller ramparts occur below the debris slopes of the Hladký Peak (2065 m a. s. l.) and the Kotolnica crest on the NW slopes of the Tichý Mt. in the Zadná Tichá Valley. Fig. 3 The location of pronival rampart in the Kobylia Valley (marked with white arrows) on aerial image and historical photograph from the 1960s captured from the Temnosmrečianska Valley (colour orthophoto map by Geodis Slovakia, s.r.o., 2002; BW photo: J. Králik, from the 1960s) Another example of the pronival rampart is located on the SW slopes of the Hrubá Veža Mt. (2086 m a. s. l.) in the Litvorová Valley. It appears as two separated crescent-shaped objects with approximately the same length of 120 metres and 300 metres distant from each other (Fig. 4). According to Lukniš (1973), the Hrubá Veža Mt. is a nunatak formed by the removal of the glacial cirque crest and subsequent erosion on the contact with perennial snowfields, where the firn abraded the bedrock. The vegetation reflects lithological differences and probably a different developmental stage of both landforms. Contrary to the higher elevated rampart, Pinus mugo scrubs cover a whole surface of the lower one. However, there is an evident succession progress visible by means of a comparison with the historical aerial images from 1955 (Fig. 4). 176

Fig. 4 Changes of the pronival ramparts on the SW slopes of the Hrubá Veža Peak based on the image comparison (Colour orthophoto map by Geodis Slovakia, s.r.o., 2002; BW aerial image by TOPU Banská Bystrica, 1955) An interesting case of pronival rampart genesis is described by Lukniš (1973).

The southern edge of the lake is attacking by the base of a huge debris cone running from the chutes below the Váhy pass (2340 m a. s. l.)

6 Fig. 4 Changes of the pronival ramparts on the SW slopes of the Hrubá Veža Peak based on the image comparison (Colour orthophoto map by Geodis Slovakia, s.r.o., 2002; BW aerial image by TOPU Banská Bystrica, 1955) An interesting case of pronival rampart genesis is described by Lukniš (1973). It is an accumulation protruding from the Zmrzlé Lake (1760 m a. s. l.) in the Ťažká Valley (Fig. 5). The southern edge of the lake is attacking by the base of a huge debris cone running from the chutes below the Váhy pass (2340 m a. s. l.) and the massif of the Vysoká Peak (2547 m a. s. l.). Additionally, numerous avalanches transport a mixture of snow and debris fragments towards the lake. A certain part of the debris material remains on slope and is being transported secondary by sliding and frost creeping over the snow surface. Extreme topographic characteristics of the cirque (large vertical amplitudes and north aspect) are favourable for the long-term duration of snowpack that creates suitable conditions for continuous formation of the rampart. The progress since 1955 is remarkable especially on the left side of the landform (see the images comparison on Fig. 5). Fig. 5 A debris rampart (indicated with white arrow) in the Zmrzlé Lake (Colour orthophoto map by Geodis Slovakia, s.r.o., 2002; BW aerial image by TOPU Banská Bystrica, 1955; Right bottom photo by Sedlák, 2011) 177

7 Unlike the other crescent-shaped ramparts, in this case the edges are curved downward in the valley direction (reverse crescent shape). This indicates multiple source areas of the transported debris material, with the prevalence of lateral transportation paths at this stage of the rampart development. Other candidates for pronival ramparts have been identified in locations of various elevations and aspects in different parts of the Tatry Mts. (see Tab. 1). So far, eight localities have been identified by means of the visual analysis of aerial images and ground observations. Each landform is described by a set of variables and characteristics defining the position (slope aspect, elevation), dimension (length), shape category and land cover type. Tab. 1 Location and characteristics of the documented pronival ramparts in the Tatra Mts. territory (Sedláková, 2012) Locality Aspect Elevation [m a.s. l.] Length [m] Description of nival debris rampart (shape and land cover) Kobylia dolinka NE-E wavy line shape; Pinus mugo scrub cover Pod Hrubou vežou 1 S-SW crescent shape; Pinus mugo scrub cover Pod Hrubou vežou 2 S-SW crescent shape; bare debris accumulation partly covered by Pinus mugo scrub Zmrzlé pleso N-NE reverse crescent shape; bare blocks, boulders and debris accumulation Važecká dolina W-SW crescent shape; Pinus mugo scrub cover Suchá dolina Važecká NW linear shape; Pinus mugo scrub cover Kotlinka pod Snehovým NW wavy line shape; grasslands and bare debris accumulation Pod Litvorovým štítom N-NW wavy line shape; grasslands, bare boulders and debris accumulation 5 Conclusions The pronival ramparts indicate the existence of perennial snowfields in postglacial landscape development of the Tatra Mts. Some of them are evidently active at present; however, the process of their formation is limited by a seasonal occurrence of snow cover. A rate of the process activity has to be further investigated by image change detection techniques and regular field measurements with a support of climatic data analysis. Using digital elevation models improves the statistical analyses of spatial properties and relationships between the classified landforms. The ambition of our research is to identify and classify all detectable pronival ramparts within the territory of the Tatra Mts. Acknowledgement The research is supported by the VEGA Grant Agency (VEGA 1/0232/12 Súčasný stav využívania krajiny a zmeny kontaktných zón vodných plôch vo vzťahu k biodiverzite). 178

8 6 References Ballantyne, C. K Some observations on the morphology and sedimentology of two active protalus ramparts. Journal of Glaciology 33, Bizubová, M., Škvarček, A Geomorfológia. Univerzita Komenského Bratislava, Vysokoškolké skriptá, s. ISBN Boltižiar, M Štruktúra vysokohorskej krajiny Tatier veľkomierkové mapovanie, analýza a hodnotenie zmien aplikáciou údajov diaľkového prieskumu Zeme. FPV UKF Nitra, ÚKE SAV Bratislava Nitra, Slovenský národný komitét pre program Človek a biosféra UNESCO. 248 s. ISBN Gadek, B., Raczkowska, Z., Źogala, B Debris slope morphodynamics as a permafrost indicator in the zone of sporadic permafrost, High Tatras, Slovakia. In Geomorph. N.F., Vol 53, Berlin Stuttgart, 2009, p Hreško, J Morfodynamické systémy vysokohorskej krajiny (Západné Tatry Jalovecká dolina). In: Luknišov zborník 2.Eds. Bezák Anton, Paulov Ján, Zaťko Michal. Vydal Geografický ústav SAV, Bratislava 1996, s Hreško, J Niektoré poznatky o súčasných geomorfických procesoch vysokohorskej krajiny (Západné Tatry Jalovecká dolina). In: Štúdie o TANAP 2 (35). Poprad Slza, s Konček, M. et al Klíma Tatier. Bratislava: VEDA, s. Kotarba, A Lodowce gruzowe i wały niwalne efekt późnoglacjalnej ewolucji rzeźby Tatr. Przegląd Geograficzny 79, 2, 2007, Lukniš, M Zaľadnenie Vysokých Tatier v Pleistocéne a oscilácie ľadovcov vo Würme. (Mapa) In: Geomorfologická mapa Vysokých Tatier a ich predpolia 1: GÚDŠ, Bratislava, Lukniš, M Reliéf Vysokých Tatier a ich predpolia.vydavateľstvo SAV, 375 s. Midriak, R Intenzita súčasných reliéfotvorných procesov jednotlivých typov povrchu územia Tatier. In Luknišov zborník 2. Eds. Bezák Anton, Paulov Ján, Zaťko Michal. Vydal Geografický ústav SAV, Bratislava 1996, s Midriak, R Morfogenéza povrchu vysokých pohorí. Bratislava:VEDA, s. Mazúr, E., Lukniš, M Regionálne geomorfologické členenie SSR. In: Geografický časopis, roč. 30, 1978, č. 2, s. 101 Olschofsky, K., Köhler, R., Gerard, F. (eds.) Land cover change in Europe from the 1950ies to 2000: aerial photo interpretation and derived statistics from 59 samples distributed across Europe. Hamburg, s. ISBN Ono Y., Watanabe T A protalus rampart related to alpine debris flows in the KuranosukeCirque, northern Japanese Alps, Geografiska Annaler, 86A, s Raczkowska, Z Wspólczesna rzeźba peryglacjalna wysokich gór Europy. Polska Akademia nauk, Instytut Geografii i Przestrzennego Zagospodarowania. Prace geograficzne nr. 12. Warszawa s. ISBN Raczkowska, Z Are there geomorphic indicators of permafrost in the Tatra mountains Geographica Polonica, Vol. 81, No. 1, Spring 2008, ISSN Shakesby, R.A Pronival (protalus) ramparts: a review of forms, processes, diagnostic criteria and palaeoenvironmental implications, Progress in Physical Geography 21, Shakesby, R.A., Matthews, J.A., Mccarroll, D Pronival ("Protalus") Ramparts in the Romsdalsalpane, Southern Norway: Forms, Terms, Subnival Processes, and Alternative Mechanisms of Formation. In: Arctic and Alpine Research. Vol. 27, No.3. INSTAAR, University of Colorado, s Vološčuk, I. a kol Tatranský národný park Biosférická rezervácia. Vydavateľstvo Gradus, Martin, 556 s. 179

Changes of vegetation and soil cover in alpine zone due to anthropogenic and geomorphological processes

Landform Analysis, Vol. 10: 39 43 (2009) Changes of vegetation and soil cover in alpine zone due to anthropogenic and geomorphological processes Juraj Hreško*, Gabriel Bugár, František Petroviè Slovak