The Development and Application of a Flood Risk Model for the Czech Republic

106

Abstract. Floods that affect many sites simultaneously can pose great challenges in the co-ordination of flood disaster management actions, as well as for the insurance and reinsurance industry, since this type of flooding leads to an accumulation of losses and the risk assessment needs to be extended to a concept representing the spatial risk of flooding. The assessment of the accumulated risk, especially over large domains, requires an analysis of the spatial and temporal coherence of flooding. For Germany the extent of spatial dependence of flooding is largely unknown and no systematic analysis has been performed so far. In this paper, we present a methodology that is capable of capturing the simultaneous occurrence of flooding using multiple series of mean daily discharge. For the first time we present a complete and consistent set of trans-basin floods in Germany for the period between 1952 and 2002. Each flood is characterised by a specific value for the timing, the location and the magnitude of discharges within the entire river network. We propose a measure for quantifying the overall event severity considering both the heterogeneous spatial extent as well as the locally varying magnitudes of a trans-basin flood. In total, we identify 80 trans-basin floods in the entire time period. The set is dominated by events that were recorded in the hydrological winter (64%); 36% occurred during the summer months. 32 events affected more than one third of the entire river network. These most severe events are predominantly winter events. Dividing the study period into two sub-periods, we find an increase in the percentage of winter events from 58% in the first to 70.5% in the second sub-period. Accordingly, we find a significant increase in the number of extreme trans-basin floods in the second subperiod. A natural extension of this study is the quantification of the spatial and temporal dependencies in a multivariateCorrespondence to: S. Uhlemann (uhlemann@gfz-potsdam.de) framework. This framework needs to be supported by a flood typology based on the analysis of the physical processes relevant in the genesis of trans-basin floods.

Section: Temporal Envelope Wmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A consistent set of trans-basin floods in Germany between 1952–2002

Uhlemann

Thieken

Merz

2010

106

“…Additionally, Rodda (2005) used maximum discharges to express flood extremity in the Czech Republic. He considered the ratio of the maximum mean daily discharge to the median annual flood.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of extensive floods in western/central Europe

Gvoždíková

Müller

2017

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.

“…Several flood identification methods taking the spatio-temporal coherence of flooding into account have recently been proposed by e.g. Rodda (2005), Merz and Blöschl (2003), Keef et al (2009), Uhlemann et al (2010) and Ghizzoni et al (2012). We identified large-scale flood events in the Elbe River basin using an approach proposed by Uhlemann et al (2010) as the method is non-restrictive to a certain return period and takes the simultaneous or time shifted occurrence of peak discharges at many sites into account.…”

Section: Flood Event Identificationmentioning

confidence: 99%

Flood-initiating catchment conditions: a spatio-temporal analysis of large-scale soil moisture patterns in the Elbe River basin

Nied

Hundecha

Merz

2013

Abstract. Floods are the result of a complex interaction between meteorological event characteristics and pre-event catchment conditions. While the large-scale meteorological conditions have been classified and successfully linked to floods, this is lacking for the large-scale pre-event catchment conditions. Therefore, we propose classifying soil moisture as a key variable of pre-event catchment conditions and investigating the link between soil moisture patterns and flood occurrence in the Elbe River basin. Soil moisture is simulated using a semi-distributed conceptual rainfall-runoff model over the period . Principal component analysis (PCA) and cluster analysis are applied successively to identify days of similar soil moisture patterns. The results show that PCA considerably reduced the dimensionality of the soil moisture data. The first principal component (PC) explains 75.71 % of the soil moisture variability and represents the large-scale seasonal wetting and drying. The successive PCs express spatially heterogeneous catchment processes. By clustering the leading PCs, we identify large-scale soil moisture patterns which frequently occur before the onset of floods. In winter, floods are initiated by overall high soil moisture content, whereas in summer the flood-initiating soil moisture patterns are diverse and less stable in time.