Predicting changes in groundwater conditions is an important aspect concerning hydraulic engineering on rivers and channels. It plays a major role in environmental impact studies, which research their effect on the hyporheic zone. Hence, it is important to explore the geohydraulic properties of the river bed as accurately as possible. The freeze-core method allows undisturbed sampling of sediments while leaving the structural fabric intact and thus the study of the pore space structure at the interface between groundwater and surface water.

A total of 50 freeze-cores were taken in three sampling campaigns from the Sacrow-Paretz channel near Potsdam. The project’s considerations focused on spatial variabilities of the permeability of the collected sediment samples. Depth and directionally oriented special samples were taken with core cutters to examine the anisotropy by determining their permeability using permeameter tests in the laboratory. The results of the vertically oriented samples are considerably lower compared to empirically estimated values determined with grain-size distribution. This discrepancy can be partly explained by the anisotropy, which points to the presence of hydraulic resistances, such as sealing biofilms. Additionally, the anisotropy was determined in different depths. A maximum anisotropy factor of 20 was found in the upper part of the river bed.

In comparison to other methods, our new approach provides the ability to obtain the permeability of river bed sediments directly and in detailed resolution. Furthermore, this method allows the research of geochemical and microbiological processes within the hyporheic zone on undisturbed samples.