Human impact on fluvial morphodynamics and contaminant dispersion in small river catchments – case study Wurm, Lower Rhine Embayment

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Michael Buchty-Lemke

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  Sampling of the sediments at the Wurm River P. Winandy PhD student Michael Buchty-Lemke, Professor Frank Lehmkuhl, and Roy Frings work on the Wurm River. The alluvial sediment serves as an archive for human impact on the river system.

Modern river systems in Central Europe are humanized fluvial systems. The influence started with the beginning of agriculture and increased since the medieval time, especially by forest clearing, mill ponds, and sealing. In addition, with the industrialization the contamination of water and sediment increased. Furthermore, the regulation of rivers induced significant changes in fluvial morphodynamics. This project focuses on human impact in a small catchment.

  Sunken tank trap of the Siegfried Line M. Buchty-Lemke Tank traps of the Siegfried Line are sunken into the floodplain sediments. This is both a document for mining subsidence and a time marker, that helps to estimate sedimentation rates.

Case studies

As a case study area we chose the Wurm River in the Lower Rhine Embayment with a catchment size of 345 square kilometers. Due to a long tradition in coal mining in parts of the river mining subsidence occurred. This is a result of collapsed mine galleries, which causes depressions at the surface and in the floodplain. In addition, industry and wastewater sewage polluted water and sediments.

Methods

The sedimentation rates in time and their spatial distribution in the floodplain and in the depressions can be detected by using different methods – amongst others, analyses of heavy metals, organic geochemistry, and cesium 137. Source-specific substances allow a historic and spatial classification as well as the determination of point sources, remobilization and downstream dilution effects. The effects of mining subsidence and transverse structures like weirs on the fluvial morphodynamics can be shown by using physical and numerical models.

  Incision of the Wurm River M. Buchty-Lemke The Wurm River is deeply incised into its own sediments due to extensive sealing in the upper catchment and the import of drinking water from the Eifel mountains.

Relevance

The results of this interdisciplinary approach involving landscape reconstruction, geochemistry and fluvial modelling will show the effects of direct and indirect human influence on fluvial dynamics and spatial distribution and remobilization of contaminants in floodplains. The transfer from results of this project on other comparable fluvial systems show challenges for environmental and social problems.

 
Duration 07/2015 - 07/2018
Funding DFG Sachbeihilfe
Project partners Dr. Roy Frings – Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen
Prof. Dr. Holger Schüttrumpf – Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen
Prof. Dr. Jan Schwarzbauer – Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen