Changes in the IDF curves of short-term rainfall in mountainous and lowland areas of Slovakia

Abstract

Rainfall intensity-duration-frequency (IDF) curves are of great practical importance in the water resources management, e.g., for the design of hydraulic structures and urban drainage systems, and for the estimation of flash flood risks and flood protection design. Due to the impacts of climate change, there is an evidence that short-term rainfalls have been observed to occur at a higher frequency than before in Europe; the need for a re-evaluation of the design values of short-term rainfall has therefore become important. This study analyzes observed and projected changes in the short-term rainfall events during the warm season (April – October) in an ensemble of a set of Regional Climate Model (RCM) simulations. The analysis was aimed at the seasonality and changes in the scaling exponents that influence the estimation of IDF curves on ungauged sites. The analysis was performed for the selected stations in southern lowland and northern mountainous parts of Slovakia. The characteristics of maximum rainfall events were analyzed for two scenario periods, i.e., one past and one future (1960 – 2000 and 2070 – 2100) and compared to the characteristics of the actual events observed in the past. The main findings from the analysis show a shift in the seasonality, which is different for the rainfall durations and also for the stations analyzed. It can be observed from the comparisons of the IDF that the derived design short-term rainfall values are higher for mountainous regions. A significant difference can be seen in the duration of 240 min. This finding reveals that in the future, very extreme short-term rainfall can be expected in the mountainous areas of Slovakia.