Present-day denudation rates in postglacial landforms of the Polish Lowlands

The young-glacial relief of the Polish Lowland, together with the retouching of Holocene morphogenesis, is one of the youngest in Poland. Three landscape features clearly distinguish the young glacial zone: significant hypsometric diversity (-1.8 m b.s.l. - 328.6 m a.s.l.), a developing and genetically complex valley/river network and the presence of a dense network of post-glacial troughs and undrained depressions, including those filled with lakes. This zone is represented by complexes of post-glacial, slope, fluvial, aeolian and denudational landforms. The most characteristic complexes of forms in the young glacial landscape are hypsometrically diversified hills and frontal moraine embankments, extensive gently undulating areas of bottom moraine plateaus, flat outwash areas, sometimes deeply incised subglacial channels, river valleys usually with a meridional course and often with a gap character, and ice-marginal valleys with a latitudinal course. Late-glacial and Holocene retouching mainly includes erosional edges remodeled by periglacial denudation basins, erosional cuts of different ages with alluvial fans at their outlets, as well as dune plain areas. The contemporary relief of the young glacial zone is shaped primarily by chemical denudation predominating over mechanical denudation, erosion and accumulation of water flowing down the plains and slopes, intense deep erosion in the upper reaches of rivers, processes of building up flood terraces and lateral erosion in the lower reaches of rivers, as well as processes degradation and aggradation, caused by human activity.

Attempts to estimate the intensity of mechanical and chemical denudation have been developed on a large scale since the 1970s. The main denudative morphogenetic processes in upland and outwash areas today include: chemical denudation, water erosion and aeolian deflation, and to a lesser extent suffusion.

Recognition of contemporary slope morphogenesis indicates that mass movements and gully erosion play a minor role in it, with soil washing predominating. The lowest wash-out values occur within turf areas (meadows, grassy fallows). Wash-out in agricultural crops has quite wide ranges of values for cereals, potatoes and black fallow, respectively. On surfaces with an inclination of 0-2º, wash-out associated with water runoff occurs extremely rarely and has little morphogenetic significance. The amount of dispersed wash-out was determined to be larger compared to forest areas. The range of variability of wash-out volumes is usually very seasonal, although the highest wash-out values are usually caused by heavy rainfall in spring and early summer. Concentrated wash-out processes, characteristic of upland edge zones, are repeated on the same fragments of slightly converging slopes and, together with plow erosion, result in the formation of wash-out basins. The analysis of these forms shows that on average there are several of them per 10 square km. The average density of road gulches is very low. There are much fewer of them than gullies, the average density of which is much higher. Intensive linear erosion, under favorable conditions, may lead to the formation of deep grooves and furrows, which are not leveled as a result of normal agrotechnical procedures and may give rise to gullies.