Występowanie i wybrane cechy morfometryczne szlaków spływów gruzowych w Tatrach

Abstract

Debris flows belong to the key geomorphological processes which shape hillslopes in high mountains and steep slopes of medium-altitude mountains located above the timberline. In Poland, debris flows occur frequently in the Tatra Mountains and, less commonly, in the Karkonosze Mountains, while in other mountain ranges they occur incidentally or not at all. This paper presents results of typological and morphometric analysis of debris flow tracks identified in the Tatra Mts by means of orthophotomap (dated 1999) interpretation and measured using ArcGIS 9.2. software, whereas field geomorphological mapping provided raw data for debris flow tracks in the Karkonosze Mts. The entire populations of tracks were subject to analysis, i.e. 418 tracks from the Tatra Mts and 83 tracks from the Karkonosze Mts. Typology of debris flow tracks proposed in this paper includes six categories, reflecting morphological characteristics of source, transfer and depositional areas. We found evident differences between the High Tatra, Western Tatra and the Karkonosze, consistent with the main geomorphic features of each mountainous terrain. In the High Tatra debris flows generated on regolith-covered slopes occur with an almost identical frequency (43.4%) as flows supplied by debris accumulated in ravines dissecting rock slopes (41.5%). In the Western Tatra the respective values are 67.5% and 24%, while in the Karkonosze Mts they are 56.6% and 33.7%. However, in respect to the latter figure, 22 out of 28 tracks of this type occur in one locality – in the Wielki Śnieżny glacial cirque. In the Tatra Mts 26 debris flow tracks exceed 500 m long, whereas in the Karkonosze only one track attains this length. However, the mean lengths are similar, just above 200 m. The problem of hazards posed by debris flows is briefly discussed. The risk is generally very low, but debris flows occasionally damage transport and tourist infrastructure.