Morphodynamics of lowland river valley bottoms in the identification of zones convenient for their crossing by heavy military vehicles in the Polish Lowlands

Abstract

An essential factor ensuring freedom of manoeuvre of land forces in lowland areas is the ability to cross water obstacles, especially river channels. For heavy military vehicles to cross river beds, places need to be indentified where both the channel's depth and the alluvial deposits’ resistance to dynamic loads enable safe passage. In the case of many Polish rivers characterized by a predominance of low water levels, the use of Motorized Floating Bridges to ferry armoured vehicles is possible only in brief periods of high water level. Convenient places for crossing channels during low and medium states are zones where sub-alluvial bedrock protrudes. These forms are made of load- and erosion-resistant lithologies. Since the presence of bedrock protrusions determines the morphodynamics of the floodplain, the specific relief, and the outcrop pattern of the valley bottom, may indicate their location. In this study, we indicate specific features of the morphodynamics of river floodplains in the Polish Lowlands, visible in the topographic relief of these forms, that may help identify sections of the riverbed suitable for crossing by heavy military vehicles. Such recognition limits the amount of geological research needed, increases the safety of river crossings, and allows for the optimal use of limited resources of specialist military technology (floating pontoon bridges). We describe research results from river valleys of different sizes in the Polish Lowlands. Geological and geomorphological mapping was carried out using remote sensing, drilling along channels, and bathymetric measurements.