Abstract
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 1951–2003. 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.
Highlights
Flood generation and magnitude are the result of a complex interaction between meteorological conditions, such as the amount and spatial distribution of precipitation or the inflow of warm air masses, and pre-event hydrological catchment conditions, such as soil saturation and snow water equivalent (Merz and Bloschl, 2008, 2009; Brocca et al, 2008; Parajka et al, 2010; Marchi et al, 2010)
As soil moisture is a key variable of hydrological catchment conditions, we examine whether flood initiation in the Elbe River basin can be linked to specific soil moisture pattern types
Flood generation and magnitude are the result of a complex interaction between the meteorological situation and pre-event hydrological catchment conditions
Summary
Flood generation and magnitude are the result of a complex interaction between meteorological conditions, such as the amount and spatial distribution of precipitation or the inflow of warm air masses, and pre-event hydrological catchment conditions, such as soil saturation and snow water equivalent (Merz and Bloschl, 2008, 2009; Brocca et al, 2008; Parajka et al, 2010; Marchi et al, 2010). As far as hydrological catchment conditions are concerned, several studies identified soil moisture pattern types on the local or regional scale applying an automated classification (Kim and Barros, 2002; Jawson and Niemann, 2007; Korres et al, 2010; Ibrahim and Huggins, 2011; Perry and Niemann, 2007; Wittrock and Ripley, 1999). The analyzed soil moisture data (remotely sensed or groundbased point measurements) are either limited in their spatial extent covering a small (< 1 km2) study area (e.g. Perry and Niemann, 2007) and/or in their temporal resolution (monthly/annual values or a small number of subsequent days)
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