Rekonstrukce murove drahy v povodi Keprnickeho potoka (Hruby Jesenik) na zaklade dendrogeomorfologickych metod

Apical parts of mountain ranges are susceptible to debris flow initiation, if triggered (extreme rainfall events or tectonic movements), and predisposed conditions (e.g. morphometric parameters, lithological conditions, forest cover, anthropogenic factors, etc.) are present. In the case of mid-mountain range (the Hrubý Jeseník Mts.) the debris flows occur at slopes with a minimum inclination of 20° with sufficiently thick weathering mantle, usually formed by weathered parts of mica schist and gneiss bedrock. Large debris flow events that occurred in several parts of the Hrubý Jeseník Mts. are well known from archival records, but there is still a lack of information about chronologies of individual debris flow tracks. Dendrogeomorphology plays important role in spatio-temporal reconstruction of debris flow events in forested catchments. The aim of this study is to reconstruct so far undescribed active debris flow track in the Keprnický catchment (Fig. 1), and to reveal whether it is a new or reactivated track. Using standard dendrogeomorphic methods of sampling trees followed by laboratory processing, we analyzed 61 growth disturbances from 19 sampled trees growing in active debris flow track (Tables 1 and 2) and with applying a weighted dendrogeomorphic index (Wit index) we identified 5 debris flow events (1921, 1965, 1991, 1997 and 2010; Figs 2 and 3). Due to relatively long chronology in the Hrubý Jeseník Mts. (more than 150 years) it can be pointed out that before 1921 no debris flow event occurred, and the last and also the greatest event happened there in 2010, having been triggered by extreme rainfall on May 21 (Šerák meteorological station: 79 mm/day). It is responsible for the current morphological features. This study also confirmed that recent debris flow events are often linked to the previously activated tracks, so that currently become longer and wider. The initiation of debris flows in the Hrubý Jeseník Mts. is still an actual issue and subject for research because of their increasing number during the last decades.

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