Flood event July 2021 in North Rhine-Westphalia




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  Flooded floordplains of the Rur River Copyright: © V. Esser Figure 1: Floodplain flooding at the Rur River near the village of Einruhr. View against the direction of water flow.

Extreme flood events can turn small rivers into dangerous torrents. They cause widespread flooding, erode extreme sediment masses in many places and lead to considerable sediment transport and sediment deposition (see Figure 1). Depending on the region, industrial history and naturally elevated trace element contents in soils, strong erosion processes during flood events can cause the remobilization and relocation of sediment-bound pollutants. Often, these are stored from past times in e.g. river floodplains. In addition, there are pollutant inputs from flooded settlements.

  Sampling of suspended sediments and sampled flood sediments Copyright: © PGG / IWW Figure 2: a) Sampling of suspended sediments, b) Sampled flood sediment on parking place, c) Sampled flood sediment on a floodplain of the Rur River, d) Dried sediment samples in the physical-geographical laboratory of the PGG

During and in the aftermath of the extreme flood event in July 2021 in NRW, researchers from the Chair of Physical Geography and Geoecology (RWTH Aachen University) collected a large number of flood samples in collaboration with the Institute of Hydraulic Engineering and Water Resources Management (RWTH Aachen University), Institute for Geology and Geochemistry of Petroleum and Coal (RWTH Aachen University) and the Institute of Ecology, Diversity and Evolution (Goethe University Frankfurt am Main). The aim is to investigate scientifically the effects and processes of this extreme flood event.

Over the next few months, water samples, sediment and sludge samples from river floodplains and from affected settlements will be analyzed for contaminants (see Figure 2b, c and the feasibility study July-floods 2021 – Contaminants in sediments). In addition, water samples from which the suspended sediment is extracted and subsequently weighed will provide information on the sediment transport of the extreme event (see Figure 2a and the research project Humanized River Systems).