Flood hazard in Slovenia and assessment of extreme design floods

Abstract

Due to the lack of hydrological measurements in the torrential areas and smaller catchment areas of Slovenian rivers, in accordance with the European Floods Directive, we used an empirical equation to estimate the magnitude of a 500-year flood (Q500). In this paper, we critically evaluate the proposed empirical equations for estimating the Q500 discharge, as defined in the Slovenian Rules on the methodology for determining areas at risk of floods and related erosion of inland waters and the sea, and on the method of classifying land into risk classes. In this assessment, we use publicly available measured data from Slovenia’s hydrological monitoring network and data on extreme flows for selected Slovenian high dams, and thus compare the database with empirical equations for determining extreme flows in Europe and elsewhere in the world that are used for planning high dams. Although the reach of the Q500 flood line determines the area of residual flood danger, it makes sense to abandon the determination of extreme flows in Slovenia using empirical equations and move to a hydrological-hydraulic modelling system using modern software tools.