ORIGINAL PAPER Investigation of flash flood natural causes of Xirolaki Torrent, Northern Greece based on GIS modeling and geomorphological analysis Konstantinos Tsanakas 1 • Kalliopi Gaki-Papanastassiou 1 • Kleomenis Kalogeropoulos 2 • Christos Chalkias 2 • Petros Katsafados 2 • Efthimios Karymbalis 2 Received: 14 September 2015 / Accepted: 15 July 2016 Ó Springer Science+Business Media Dordrecht 2016 Abstract This paper presents an attempt to evaluate the flood discharge for a severe flood event, which took place on October 25th, 2009. Based on spatial and meteorological data, a simulation of the flood event was established, through hydrological modeling, in a GIS environment. Furthermore, the geomorphological characteristics of the drainage basin and the drainage network were analysed. The results of the modeling such as the peak dis- charge, hydrograph, and volume, derived from the analysis of measured hydrographs in a number of non-flood causing rainfall events with operating stage gauge, were used for calibration and verification of the simulated stage-discharge hydrographs. Drainage basin characteristics such as steepness of the relief combined with a relatively short main channel of the drainage network as well as abnormalities in the hierarchical drainage by stream order are the main natural flood causes amplified of course by the intense human inter- ference at the lower part of the drainage network with a series of constructions such as roads inside the main channel. Geomorphological analysis combined with GIS techniques are fundamental components of flood risk management as they provide the basis for a & Konstantinos Tsanakas ktsanakas@geol.uoa.gr Kalliopi Gaki-Papanastassiou gaki@geol.uoa.gr Kleomenis Kalogeropoulos kalogeropoulos@hua.gr Christos Chalkias xalkias@hua.gr Petros Katsafados pkatsaf@hua.gr Efthimios Karymbalis karymbalis@hua.gr 1 Department of Geography-Climatology, Faculty of Geology and Geoenvironment, National Kapodistrian University of Athens, Athens, Greece 2 Department of Geography, Harokopio University, Athens, Greece 123 Nat Hazards DOI 10.1007/s11069-016-2471-1