Elbe flood - causes and genesis

The current flood at many rivers in Southern and Eastern Germany, especially at the Elbe, results from an exceptionally long period of winterly conditions with high amounts of snow in the German low mountain ranges. Very cold temperatures with continous frost until mid-March led to the fact that the whole precipitation accumulated in the form of snow. Thus the snow height added up to 1.5 meters at Zinnwald (Ore Mountains) by March 25. A very sudden transition from frosty weather to partially very warm conditions of zonal character led to an increase in temperature of 15 °C within few days. On Monday, March 27, the meteorologial station of Dresden reported just under 20°C while three days before, temperatures were little above the freezing point. This increase in temperature which cooccurred with frequent rain showers let the snow melt rapidly in the low mountain ranges, leading to an increasing runoff.

The cooccurrence of multiple factors (in this case: large amounts of snow, rainfall, thaw) is crucial for the emergence of floods. Therefore spring is generally a flood-prone season, because then the factors rain and thaw cooccurre very often. This year, the amount of snow was exceptionally high, leading to one of the largest spring floods during the past 50 years. However, the impact of the current flood is much lower than it was during the Elbe flood in 2002. This is particularly due to the fact that the genesis of both floods differ entirely: While in August, 2002, a special wheater situation (Vb) led to an enormous amount of precipitation in the whole Elbe catchment area within very short time (up to 50% of annual precipitation within 3 days), with the current flood, unusual prerequisites (snow) played a major role. Precipitation amounts of last March were only litte increased compared to the long-time mean (up to 50%, see. Fig. 1).

Figure 1: Deviation of precipitation in March 2006 from longtime monthly mean (1961-1990) in percent (Source: DWD/Global Precipitation Climatology Centre)

Due to the current prognoses which forecast more moderate conditions and the fact that snow has mostly disappeared in the low mountain ranges, an early relief of the flood situtaion can be expected in all regions.

More definitions of terms you can find in our flood glossary.

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