Unravelling the recent dynamics of headwaters based on a combined dendrogeomorphic approach (a case study from the Sudetes Mts., Czech Republic)

Abstract

ABSTRACT Headwater catchments are frequently prone to debris flows/floods. Dendrogeomorphic methods allow for the accurate dating of the frequencies and spatial patterns of these events. Nevertheless, a combined approach based on the sampling of increment cores from tree stems and the extraction of cross-sections of scarred roots has been rarely used together at one site to determine the headwater dynamics. Such sampling strategy was performed in the Rudohorský potok catchment (the Hrubý Jeseník Mountains, Eastern Sudetes, Czech Republic) to compile the debris flow/flood chronology and to describe the detailed spatial patterns in the studied sub-catchments. In total, 44 events of increased hydrogeomorphic activity during the last 110 years were identified based on the analysis of 860 growth disturbances from 322 trees and 85 roots. The largest events (debris flows) occurred in 1921, 1951, 1965, 1975, 1991, 1997, 2001 and 2010. Higher dynamics of hydrogeomorphic processes were investigated in the sub-catchment affected by deep-seated rockslides. The inclusion of root analyses facilitated the completion of the event chronology mainly during the last 20 years. With respect to the decreasing sensitivity of tree stems with increasing age to the recording of geomorphic disturbances, the root analysis helped to better illustrate the spatial imprint of recent debris flow events (especially the most recent one in 2010).