Evaluation of extensive floods in western/central Europe

Abstract

Abstract. This paper addresses the identification and evaluation of extreme flood events in the transitional area between western and central Europe in the period 1951-2013. Floods are evaluated in terms of three variants on an extremity index that combines discharge values with the spatial extent of flooding. The indices differ in the threshold of the considered maximum discharges; the flood extent is expressed by a length of affected river network. This study demonstrates that using the index with a higher flood discharge limit changes the floods' rankings significantly. It also highlights the high severity events.In general, we detected an increase in the proportion of warm half-year floods when using a higher discharge limit. Nevertheless, cold half-year floods still predominate in the lists because they generally affect large areas. This study demonstrates the increasing representation of warm half-year floods from the northwest to the southeast.

Spatial patterns and time distribution of central European extreme precipitation events between 1961 and 2013

“…Although the extremity of the EPEs in 2002 and 2013 was almost the same (Table 2), the severity of the 2013 flood seems to be much greater, with the extremity index of Uhlemann et al (2010) reaching the value 1.5 versus 1.09 in 2002 (Gvoždíková and Müller, 2017). While the 2002 and 2013 events are highly ranked according to both the precipitation and flood extremity indices, the two maximum EPEs of 1981 and 1997 are at the 18-19th positions in the list of major floods (Gvoždíková and Müller, 2017). The pre-event soil moisture conditions can explain the difference, but a limitation of the study area may play a role in the case of 1997 event, which also affected parts of the Vistula basin (Kundzewicz et al, 1999).…”

“…It is likely that the WEI rel value of 1997 EPE would increase as well if we consider the Vistula basin. This may also apply to the May 2010 EPE, which is well described by Bissolli et al (2011) as an event of a large extent and high intensity, but it is ranked only as the 50th EPE and it does not appear in the list of major floods (Gvoždíková and Müller, 2017). In contrast, the highly ranked flood events of March 1988 and 1981 do not appear among the 53 maximum EPEs, as probably a combination of soil saturation, rainfall, and snowmelt generated the floods.…”

“…However, the severity of a flood event may be significantly influenced by the pre-event soil moisture content, as it was during the flood of 2013 (Schröter et al, 2015). Although the extremity of the EPEs in 2002 and 2013 was almost the same (Table 2), the severity of the 2013 flood seems to be much greater, with the extremity index of Uhlemann et al (2010) reaching the value 1.5 versus 1.09 in 2002 (Gvoždíková and Müller, 2017). While the 2002 and 2013 events are highly ranked according to both the precipitation and flood extremity indices, the two maximum EPEs of 1981 and 1997 are at the 18-19th positions in the list of major floods (Gvoždíková and Müller, 2017).…”

“…In contrast, some of the five maximum EPEs lasted only 2 days (e.g., the August 2002 event). Nevertheless, they often resulted in rapid runoff increases in the affected rivers (Müller et al, 2009) and severe floods (Müller et al, 2015;Gvoždíková and Müller, 2017 2002 (e.g., Ulbrich et al, 2003;Blöschl et al, 2013). The top 10 EPEs within central Europe are also significant in Czechia alone; however, not all EPEs are included in the list of extreme precipitation presented by Müller et al (2015), which points to the spatial heterogeneity of the study area.…”

“…In contrast, the highly ranked flood events of March 1988 and 1981 do not appear among the 53 maximum EPEs, as probably a combination of soil saturation, rainfall, and snowmelt generated the floods. Generally, the majority of the extreme central European floods occur in the cold half-year (Uhlemann et al, 2010;Gvoždíková and Müller, 2017), especially in the northwest of the area.…”