2021; 13: 27–38

Open Geosciences 2021; 13: 27–38 Applied Geomorphology 2019 Filip Bujakowski*, Tomasz Falkowski, and Anna Podlasek Geomorphological immaturity as a factor conditioning the dynamics of channel processes in Rządza River https://doi.org/10.1515/geo-2020-0209 Keywords: river valley, alluvium, channel processes, received July 30, 2019; accepted October 30, 2020 hydrological regime, erosional base level Abstract: A major part of Poland, classified geographi- cally as Polish Lowland, is covered by a layer of loose or cohesive sediments whose thickness increases toward the north. Numerous authors emphasize the impact of the 1 Introduction protrusion of the erosional base level on the course of processes shaping modern river valleys. It has been In the landscape of lowland areas, river valleys are forms - demonstrated, among other things, that the culmination with the highest dynamics of morpho and lithogenetic of the sub-alluvial, cohesive bedrock determines the processes. Their course is closely related to the quality [ ] manner in which the channel zone and the adjacent of the natural environment of the catchment area 1 . [ ] - floodplain are formed, which is associated with the Starkel 2 stated that processes caused by climatic evo fl hydrological system of the river. A number (12) of geolo- lution or changes in valley management are re ected gical documenting holes have been drilled to the bottom very quickly in the course of erosional and depositional of the valley. Also, geological profiles were recorded for processes. Natural sensitivity to changes taking place in fi - 34 natural outcrops. The range of the individual outcrops river valleys imposes a need for very precise identi ca was determined using a geomorphological analysis based tion of natural processes occurring in the catchment area. on, among other things, the data from airborne laser Particular importance is attributed to the interaction ff scanning. The main objective of the research based on between the conditions of water and sediment runo geomorphological criteria was to identify the differences into the valley, and the spatial diversity of erosional ( fi in valley morphology and geological structure as well as and depositional processes formulation de ned by Lane [ ]) fl - the dynamics of currently occurring fluvial processes, 3 . Fluvial processes are in uenced by both the ele along with geological features influencing their develop- ments of the natural environment of the whole catchment ( [ ]) - ment, in particular in the middle course of a river. The area i.e., climatic characteristics 2,4,5 and local phe ( research allowed the distinction of three geologically and nomena i.e., the morphodynamics of zones adjacent to [ ]) - - geomorphologically characteristic sections. This allowed the valley 6 , the occurrence of erosion resistant mate [ – ] - an answer to the question: why is the river in the lowland rials in the bottom of the valley 7 9 , tectonic disconti [ ] similar to a mountain stream. nuities 10 , or the tectonic activity of zones intersected by the river [11]. The abovementioned factors determine the morphodynamic specificity of a given section of a valley or floodplain. It could be reflected by the shape of the valley or the layout of outcrops of alluvial sedi- * Corresponding author: Filip Bujakowski, Department of Water fi Engineering and Applied Geology, Institute of Environmental ments. In Polish Lowland, the speci city of the geological Engineering, Warsaw University of Life Sciences, Nowoursynowska structureofindividualsectionsofthevalleysresults 159, 02-776 Warsaw, Poland, e-mail: fi[email protected] from the morphogenetic immaturity of river valleys Tomasz Falkowski: Department of Water Engineering and Applied [4,12] and the complexity of evolutional processes in Geology, Institute of Environmental Engineering, Warsaw University their bottoms (occurring since the end of the Pleisto- - of Life Sciences, Nowoursynowska 159, 02 776 Warsaw, Poland )[ ] Anna Podlasek: Department of Revitalization and Architecture, cene 2,4,5,13 .ThisiscausedbythePleistocenehistory Institute of Civil Engineering, Warsaw University of Life Sciences, of the analyzed area, including the glacial–interglacial Nowoursynowska 159, 02-776 Warsaw, Poland rhythm of climate changes [14]. During the formation of Open Access. © 2021 Filip Bujakowski et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 International License. 28 Filip Bujakowski et al. Figure 1: Morphogenetic diversity of sections of river valleys in the Polish Lowland (after [12]).1– Erosion–accumulation section, 2 – post-lake section, 3 – section of the river where the bedrock protrusion is exposed, a – organic soils, b – sands, c – gravels, d – cohesive soils, e – till, f – glacitectonic deformations, g – groundwater level, h – spring. the surface runoff network, rivers often adapted glaci- hydrological regime is also an important factor affecting genic depressions to the sections of their valleys (e.g., the development of river valleys. The conditions of sup- lake basins or thermokarstic depressions),erodingonly plying and draining a watercourse by a groundwater sections placed between them. The fact that lower sec- stream constitute an important aspect. tions of large river valleys often have the youngest relief, Research conducted in many river valleys in Polish contrary to the classical concepts of morphological Lowland [12,16,17] allowed the distinction of several development according to [15],isanothersourceof types of their morphogenetic sections, differing in geolo- their morphogenetic specificity in Polish Lowland (and gical structure, and for which it is possible to define numerous other smaller forms). These zones were the last aspecific type of hydrogeological, geological, and engi- to be released from the cover of a “retreating” ice sheet neering conditions (e.g., the nature of alluvial aquifers sup- (e.g., Vistula, Oder, and many of their tributaries). The plying the riverbed with subsurface runoff;Figure1)[18]. Dynamics of channel processes in small river valley 29 In addition to erosional–accumulational sections 2 Geological background (see 1 in Figure 1), in which a deep erosional base level is filled with a series of alluvia of the channel facies, The source zone of Rządza is located within the morainic forming a clearly visible terrace system (river terraces Kałuszyn upland. The creation of this form is related to and kame terraces; see 1.2 in Figure 1), there are distin- the dissipation of ice sheet from the Warta glaciation (MIS guishable polygenic forms, where glacigenic or thermo- 6)[21]. The surface of the Kałuszyn Upland is made of karstic depressions have been adapted as valley sections. glacial tills of the Warta Glaciation covered by fluviogla- Their size and the supply of clastic material depending on cial sediments (mainly sands). The spring zone of the its hydrological characteristics determined the extent to valley is located within a depression of approximately which the original genesis of a depression is readable in 3.2 km2 filled with organic sediments. The depression is morphology and geological structure. Figure 1 shows sec- delimited by layers made of glacial till and fluvioglacial tions representing different phases and intensity of pro- sands. Numerous dunes occur in the top of sandy sur- cesses of adaptation to valley formation, including wide faces. In a section downstream of Wola Polska (Figures 2 peat forms functioning under the conditions of debris and 3), fluvial erosion has uncovered glacial till in many deficit (see 2.1 in Figure 1), valleys in which the river parts of the uphill slope. The thickness of the Warta mor- was able to build an alluvial dike in a glacial/thermo- ainic sediments in the vicinity of the valley equals 8–10 m karstic depression (see 2.2 in Figure 1), and forms in [22]. These sediments lie directly on the clayey deposits of which changes in the hydrological regime resulting the Odra glaciation. From Rakówiec, going down the from climatic evolution have led to the burial of lacus- river, the erosional base level is formed in morainic sedi- trine sediments under contemporary channel alluvia (see ments of the Odra glaciation. In the area of Mlęcin and 2.3 in Figure 1). A slightly different type is represented by Wola Polska, the influence of the Dobre Structure [23] rivers currently operating in outwash plain areas (see 2.4 uplifted by glacial tectonics is visible in the development in Figure 1). They also use small thaw depressions in and the course of the valley. This structure, documented valleys, but the main factor conditioning their morpho- during the preparation of the Minsk Mazowiecki sheet of dynamics involves very low gradients as well as the pre- the general map of Poland, consists of highly disturbed sence of dune forms limiting the lateral erosion and the Pliocene clays, which locally reveal themselves in the inflow of water into the valley [16,17]. Polygenic segments form of “displaced rock blocks” and “ice drift” on the are connected by sections formed mainly by erosion. surface. According to [23], its upheaval probably led to Within their bottoms, sediments resistant to flowing the displacement of the Rządza valley toward the south- water are often revealed (especially during high water western direction from Wiśniewo to Osęczyzna. Consid- levels – see 3.1 and 3.2 in Figure 1). A typical example of ering the issue of the influence of neotectonic movements such a form is a section of the Vistula River

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