Późnovistuliański i holoceński rozwój dolin dorzecza Małoszówki

Evolution of valleys in the Małoszówka Stream catchment during the Late Vistulian and Holocene

Summary: The article presents the evolution of valleys in the Małoszówka Stream catchment during the Holocene. The study area is located on the Proszowice Plateau which is a sub-unit of the Nida Basin and was among the Polish regions most early settled by the prehistoric man. Most of this area is mantled by a loess cover which was deposited after the formation of hills and main valleys. The density of valley network is relatively high, reflecting high erodibility of loess and the history of human impact. The evolution of valleys is explained on the basis of morphological analysis, sedimentological analysis of valley fills and the evolution of such forms in the neighbouring areas, documented in scientific literature. The following valley types were recognised in the Małoszówka Stream catchment: dells, flat-bottomed valleys and gullies (all of them representing denudational valleys) as well as river valleys. Of the 596 investigated valley, 298 were classified as dells formed during the Holocene and such forms constitute 24.4% of the total length of the mapped valleys. After the accumulation of loess deposits had finished, the loess cover in the area was subject to intensive erosion which resulted in the exhumation of older flat-bottomed valleys and the exposure of pre-Quaternary substratum. The intensity of degradation phenomena considerably increased at the time of colonization of the area by the Neolithic communities. The delivery of sediment from slopes was accelerated with progressive deforestation of the area. As a result, a complex of mineral and organic deposits accumulated in the valleys, with the thickness of 5.8 m in Małoszówka valley. In the Late Neolithic, a change from permanently settled to pastoral nomadic communities resulted in the reduction of the intensity of slope processes and conservation of valley forms. Since the beginning of the Subatlantic period, the climate got colder and wetter and severe rill erosion has resulted in a significant dissection of slopes. This has led to the formation of gullies and deepening of the existing valleys. At present, geomorphic processes are activated in the area due to the occurrence of extreme rainfall events and human activity. In deforested denudational valleys, an important role in their transformation is played by agricultural degradation, linear and surface wash and rill erosion, whereas in those under forest soil creep is important. To reduce the intensity of soil erosion and unfavourable effects of slope degradation, cultivation practices parallel to contour lines and slope terracing are necessary.

Słowa kluczowe: suche doliny, ewolucja dolin, denudacja agrotechniczna, zdarzenia ekstremalne

Słowa kluczowe (w języku angielskim): dry valleys, valley evolution, agricultural degradation, extreme rainfall events

Prace Geograficzne, 2010, z. 123, s. 63-81.

Instytut Geografii i Gospodarki Przestrzennej UJ

ISSN 1644-3586

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