Odra 1997 flood effects on soil properties of cultivated areas in Germany

During the 1997 summer flood of the river Odra, a small cultivated area of 50 km was flooded in the German part of the catchment The flood completely killed the vegetations stands on the fields. Afterwards, the effects of the flood on the ecological properties of the soils and on the conditions for agricultural production had to be evaluated. A study was conducted to estimate the flood effects on heavy metal concentrations and on the nutrient status of the soils. The sediment layer left from the flood had a thickness of less than 3 mm. The heavy metal concentrations within this layer were below legal limits valid in Germany. Thus, no restriction had to be announced for food production purposes. Regarding the nutrient status of the flooded soils, only the mineral nitrogen content was substantially reduced when compared to not flooded soils. This effect could most probably be related to denitrification processes as a result of anaerobic conditions during the flood. Despite the nitrogen losses, the effects of the flood on agricultural management conditons were minor. However, hydrological and land use management concepts have to be developed that help to reduce the probability of such flood events in future.