Deciphering flood event information from tree-ring data in the Tatra Mountains: Implications for hazard assessment

Abstract

Mountains and their foothills are areas where intense floods are characterized by high discharge and where they occur more often than in lowlands. Furthermore, due to the fact that they are mainly caused by short-lasting heavy rainfall events, they are difficult to predict. The dense network of meteorological stations and river gauges is crucial to understand hydrological processes and to forecast floods. Most mountain regions suffer from a scarcity of instrumental data that are long enough for scientific purposes. In such cases where historical data or instrumental records are lacking, floods in forested catchments can be analysed by using growth series from trees growing along stream channels. In the streams draining the northern slopes of the Tatra Mountains, it was possible to reconstruct the occurrence and magnitude of paleofloods using tree-ring data. More than 1100 increment cores were sampled from 218 Picea abies and Abies alba trees growing at 6 stream sectors and allowed determination of 480 growth disturbances and a definition of the magnitude of 47 flood events between A.D. 1866 and 2012. In this region, floods are triggered by intense and prolonged rainfall events in spring and summer. These paleoflood records also allowed construction of a regional flood analysis and to reduce the uncertainties in the flood frequency assessment.