Investigation the stability of reservoir sediments in the lab and field

Institute for Modelling Hydraulic and Environmental Systems, University of Stuttgart, Stuttgart, Germany

^a Corresponding author: markus.noack@iws.uni-stuttgart.de

Abstract

To investigate the erosion stability of reservoir sediments, two measuring strategies were applied. Next to in situ measurements, sediment cores were extracted and analysed in the laboratory. At several sampling points at a reservoir in Germany, the in situ device was used to determine the critical bed shear stresses at the sediment surface. At the same time, sediment cores were withdrawn at each site to perform depth-orientated investigations in the hydraulic laboratory. The objective of this study is to investigate the remobilisation potential of the deposited fine sediments and to compare different methods to determine the erosion threshold. Next to critical shear stresses and erosion rates, additional sedimentary and biological parameters were examined such as bulk densities, particle size distributions, TOC-contents and chlorophylla concentrations. The results show generally a very low erosion stability, especially at the sediment surface and in the upper sediment layers. Deeper sediment layers are characterised by consolidation effects and show a higher erosion resistance. High clay contents result in increased stability while high sand contents show a high remobilisation potential. No significant relation to the parameters TOC-content or chlorophylla concentration are identified. A comparison between the different applied techniques to determine the critical bed shear stresses reveals values in the same order of magnitude; however, some significant variations occur because of different hydromorphological conditions and the different limitations for each device.