The distribution of trace metals in alluvial sediments depends on their natural background concentrations, and on the dynamics of contemporary depositional and erosional (mainly flood-induced) processes. Geological and geochemical investigations were carried out in the valley of Vistula River near Magnuszew (central Poland). Sediment samples were collected from a depth of 35 cm and comprise sediments of all defined geomorphological features. Identification and geological interpretation of the morphodynamic sediment features was supported by aerial photographs and high-resolution satellite images. These studies revealed that the distribution of trace metals is closely linked to the morphogenesis of the alluvial floodplain. The highest concentrations of Cu, Co, Zn, V, Cr and Ni were observed in crevasse-splays deposits. By contrast, Sr, Pb and As were concentrated in deposits which fill oxbow lakes (partly infilled with organic deposits). The lowest concentrations of trace metals were detected in flood sediments deposited within erosional troughs. The geomorphological and sedimentological history of the fluvial features explains the pattern of heavy metal distribution on the current floodplain surface.

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We aim to answer a question: how does the evolution of fluvial environment affect to risk of embankments failure in lowland rivers and how can we identify and describe places at risk of levees failure using the remote sensing data? The study was carried out in the Vistula River valley near Magnuszew (middle Vistula course, central Poland). 24 geological boreholes were drilled to a depth of 2.0–8.5 m and groundwater table observations were conducted in a monitoring network consisting of 22 wells, 5 piezometers (screened within the Holocene alluvial aquifer) and 2 temporary water gauges. Identification of the diversity of the geological structure of the floodplain was supported by airborne laser scanning imaging, as well as high resolution satellite images and aerial photos. This remote sensing study allowed the creation of a conceptual model of hydrogeological conditions. Study takes into account the effects of the land forming activity of flood waters resulting from the evolution of the fluvial environment in the Holocene. Created conceptual model subsequently fed into the construction and calibration of a mathematical groundwater flow model using MODFLOW software. The study allowed the identification and characterisation of intensified groundwater flow zones. Concentrated flow in the substrate of flood protection levees constitutes a threat to their stability. Documented in many publications climate change will induce in future climate scenarios an increase in rainfall and prolongation of dry periods. The implementation of the methodology of identifying the geological forms with the use of presented techniques allows the identification of sections of flood embankments potentially at risk of failure.

We explored the background of differences in long-term stability between two parts in an undisturbed mire system (Rospuda fen, NE Poland). We re-constructed the Holocene history of the mire and compared it with current vegetation, water level dynamics, water chemistry and nutrient availability in two basins: A, where the mire terrestrialised a deep gyttja-filled lake, and B, where peatland developed directly on fluvial sands. The current vegetation of sedgemoss fens was described in 10 relevés from each basin, groundwater was sampled from piezometers and analysed for major ions, while its relative water level was recorded during three years. N and P content was measured in above ground vascular plant samples collected within the relevés. Fens in basin A were stable in the past, whereas fens in basin B switched between open and wooded or reed-dominated phases. In basin B, where trees are more abundant, we found higher water fluctuations, occurrence of river floods and a higher N:P ratio than in basin A. Our interpretation follows that the subsurface geology of fen basin may govern mire stability by determining its hydrological-buffering capacity, which may affect N:P ratios. Our results suggest that Plimited fens are more vulnerable for changes in water level.