DENDROGEOMORPHIC ANALYSIS OF FLASH FLOODS IN A SMALL FOREST CATCHMENT

Abstract

Flash floods represent one of the most significant natural hazards in headwater catchments facing the lack of systematic hydrological monitoring. This study focus on the detection of flash floods on growth disturbances detected at trees of European beech (Fagus sylvatica L.) located in the torrential channel of the Holubi Potok stream in the Jizera Mountains (North Bohemia, Czech Republic). At the injured stems, flood scars were identified and core samples dated by tree ring analysis; the intensity of the disturbance clearly depends on geomorphology of the stream channel. These data were compared with 40 years of hydrometric measurements at the catchment outlet. The flood injuries were detected in the last 65 years, and those flood signs occurred on average every 12-13 years. All of them correspond with intensive summer rainstorms. Flood waves exceeding the gauging capacity or the period of hydrometric observation were reconstructed by HEC- HMS 4.4 and HEC-RAS 5.0.3 tools. The applied approach contributed to the extrapolation and correction of the standard flood frequency curve at the investigated catchment.