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Dendrogeomorphological analysis of the Sawicki Landslide in the Beskid Niski Mountains (S Poland)

Krąpiec Marek, Nawrocka Natalia, Margielewski Włodzimierz, Szychowska-Krąpiec Elżbieta

Geological Quarterly

2019

Vol. 63, No. 4

801--810

We applied dendrochronological analysis to study an extensive (~2.5 km long) complex-type landslide in the Beskid Niski Mountains (Polish Flysch Carpathians), which was rejuvenated in historical time (the earliest transformation occurred in 1913). We used three complementary methods (dating of eccentricity of annual growth rings, eccentricity indices, and analysis of reaction wood), based on seven species of deciduous and coniferous trees. A total of 204 trees were sampled and 408 cores collected using a Pressler increment borer. Based on the dendrochronological analysis, the activity of various parts of the landslide in the past century is presented, which appears to have been diverse and influenced mostly by precipitation. The upper part of the landslide was active from the 1920s until the 1940s. In the middle section of the landslide, intensifications of gravitational movement were repeatedly recorded after intense rainfalls throughout the entirety of the last century. The highest landslide activity was dendrochronologically detected in the 1980s and 1990s. Increasing landslide activity during so-called “dry years” may have been related to quick drying of the bedrock, resulting in changes in rock strength parameters. Our results indicate significant susceptibility of this particular slope-valley geosystem in response to even slight hydrogeological changes (including dryness), which can trigger ground movement.

Analiza dendrogeomorfologiczna ruchów masowych na obszarze polskich Karpat fliszowych

Krąpiec M., Margielewski W.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

2000

T. 26, z. 2

141-171

W obrębie Karpat fliszowych wydatowano okresy aktywizacji 23 osuwisk. Do analizy wykorzystano zaproponowaną przez autorów analizę par krzywych dendrochronologicznych drzew porastających analizowane osuwiska. Sygnały diagnostyczne dla uruchamiania podłoża, uzyskiwano zestawiając krzywe dendrochronologiczne odstokowych i dostokowych partii pnia tego samego drzewa. Zliczanie uśrednionych sygnałów dla okresów 5 letnich, pozwoliło na wykreślenie krzywej aktywizacji poszczególnych form osuwiskowych i pasm górskich, a także Karpat zachodnich. Analiza przebiegu tej krzywej wskazuje na korelację jej maksimów z powodziami i nawalnymi deszczami oraz wstrząsami sejsmicznymi, szczególnie tymi związanymi z końcem małej epoki lodowej

Periods of activity of 23 landslides in the area of the Polish Flysch Carpathians, were dated with the dendrochronological method. The research was performed with a new, proposed by the authors, method of analysis of pairs of tree-ring patterns of trees growing on the landslide areas. The analysed pairs of dendrochronological curves, representing upper and lower sides of trunks of inclined trees overgrowing the investigated landslides, yielded signals diagnostic for the ground movements. These diagnostic signals, averaged for successive five-years' periods, were used for construction of activity curves for individual landslides, for mountain ranges, the Western Flysch Carpathians. Analysis of shapes of these curves demonstrated high correlation of its maxima with the floods, heavy rainstorms and earthquakes, particularly those related to the Little Ice Age