Using ALS LIDAR DEM and OpenStreetMap data we visualise in ArcGIS the geomorphic features of a large, lowland river which flows through the area impacted by urbanisation of a big city – the capital of Poland. We present on one map the main geomorphological surfaces and their exact boundaries: valley edge, terrace front and floodplain juxtaposed with buildings and the main transportation corridors. We identify convex aeolian and fluvial landforms: dunes, levees, sandy lobes including crevasse splays, ridges between swales, sandy bars, islands; and concave erosional landforms: floodplain channels, crevasse channels, oxbow lakes, palaeo-meanders, tributary channels, and chute channels. We draw implications for flood management, geo-archaeology geo-heritage conservation. We search for traces of extreme flood events in the Holocene, also on the higher terraces which the river developed by its deposition in the Pleistocene.

River valleys of the Central European Lowlands are the zones of the highest dynamics of morphogenic processes. In the case of areas affected by glacial processes, despite their lowland nature, often they also have a complex geological structure. Sub-alluvial bedrock, composed of erosion-resistant deposits, commonly forms morphological protrusions within them. Their presence significantly affects both the course of flood flows and the valley floor relief. Effective forecasting of fluvial processes in such valley reaches requires conducting research within the entire geomorphologically active zone, both in the channel and the floodplain. The effectiveness of such research should be enhanced by simultaneous use of several different remote sensing methods, including short-range remote sensing. The verification of this hypothesis was the aim of the presented works. Such methods were used in the study of morphodynamics of a Bug valley reach. This area is characterized by a complex geological structure. High-resolution multispectral satellite images (VHRs) and a digital elevation model (DEM) based on aerial laser scanning (ALS) were used to examine the terrain relief. The morphology of the river channel itself was determined based on a series of bathymetric measurements made by a research team. Due to induced climate change and increasing maximum flow values, it can be assumed that the effect of a geological structure in the Central European Lowlands will play an increasing role. The threat and losses associated with floods will also increase. Rational flood prevention requires improvement of remote sensing research methods in lowland river valleys, especially those with complex geological structures. The valley reach presented in this article is an example of such a landform.

Research carried out by the authors’ team in the valleys of many rivers in the Polish Lowlands has shown that the contemporary morphodynamics of channel zones is highly influenced by protrusions of erosion-resistant sub-alluvial bedrock. The article presents the results of analysis of two reaches of the Middle Vistula: near Solec nad Wisłą (km 330-340) and Gołąb (km 382-388), where such protrusions have been found. At each of them, two series of bathymetric measurements were carried out during medium and low water levels in the river channel. The measurements were made using hydrographic sets integrated with a GNSS receiver. The first series of measurements was carried out in July 2004, and the second one in September 2016. In parallel with the bathymetric surveys, low-altitude aerial photographs were taken in 2016 to document the morphology of the channel zone and the condition of the river engineering structures. A comparison of the obtained bathymetric maps shows a high correspondence between the thalweg line from 2004 and that observed twelve years later. This phenomenon proves the significance of the bedrock relief beneath the modern alluvial deposits for the water flow process in the channel. The relief causes the flow to concentrate in specific zones so strongly that it contributes to the damage of river engineering structures that put limits on the channel processes. This trend of concentrating the main thalweg is also accompanied by the diversity of depositional environments of river channel facies, identified along the studied reaches.