Nova data o reaktivacich vybranych svahovych deformaci na Vsetinsku

Landsliding is a dangerous geomorphic process frequently occurring in the Vsetínské vrchy Mts. Predisposition, triggers or inner structure of many landslides were studied in the past. Unfortunately, the knowledge about historical reactivations is only very scarce. Furthermore, only large reactivations, which often caused damage of infrastructure or human estates are known. The reason is the remote position of many landslides or selective human memory. The most appropriate approach to acquire data on landslide reactivations is the use of dendrogeomorphic methods. They enable dating of a few centuries old landslide movements with annual precision. Three landslides (Mikulůvka, Křížový vrch, and Miloňov) were selected in the Vsetínské vrchy Mts. for dating of their reactivation using dendrogeomorphic methods. Individual trees of common spruce – Picea abies (L.) Karst. – were sampled at each locality using the Pressler increment borer. Two increment borer cores were extracted from each tree. All samples were processed following standard procedure. Individual steps included drying of samples, gluing onto woody supports, sanding, tree-ring counting and measuring using TimeTable, cross dating with reference chronology, identification and dating of growth disturbances (onset of reaction wood) (Fig. 1). Nineteen trees were sampled at the Mikulůvka landslide. Altogether eleven years of landslide reactivation were dated (three proven, and eight presumable events; Fig. 3A). Seven trees were sampled at the Křížový vrch landslide and five reactivations were dated (two demonstrable, and three probable; Fig. 3B). Nine trees were sampled at the Miloňov landslide and five reactivations were dated (one demonstrable, and four probable; Fig. 3C). Finally, this study brings one of the first information about landslide reactivation from the Vsetínské vrchy Mts. The number of studied landslides should be greatly extended in future in order to acquire more relevant data, and to achieve more representative results in the study area.

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