Original paper

Small catchments as sediment archives of past human activities, the example of Sudetes Mountains (SW Poland)

Latocha, Agnieszka

Abstract

Small catchments in the depopulated upper parts of the mountains, with declined agriculture and with stabilised hillslope covers (due to secondary vegetation succession), are able to store the sedimentological record of past agricultural activity, which led to formation of fine-grained colluvial and alluvial covers. Such areas were formerly seen only as sediment sources for downslope erosion, transport and accumulation in the mountain foreland. However, in the six study catchments, both within the slopes and valley floors, up to 825 and 780 m a.s.l. respectively, the accumulation zones of human-induced fine-grained colluvial and alluvial sediments are also present, which is much higher than previously assumed. It proves that small catchments in upper parts of the mountains are able to store most of the material, which was eroded from higher elevation and that the sediment transport is, in most cases, only local and on short distance. Therefore small catchments, as sediment archives, can reveal valuable information regarding the direct and indirect linkages between slope and channel coupling, especially that the source of the transported material is relatively close to its deposition site. The most striking feature of all the deposits (colluvium and alluvium), which can be linked with former agricultural land use, is a high variability of their thickness even at short distances. The main factors responsible for these variability, and thus the final record of human-induced morphological processes, are lithology, local topography, including microrelief on slopes, slope length and inclination, shape of valley floor, valley gradient and initial thickness of slope regolith. No individual factor appears to control this process. It is the combination of various factors at one site, which can have diverse outcomes at different sites. In some places the role of slope inclination is dominant, while in others the lithology seems to be crucial for sediment formation. The complexity of the environmental factors and their mutual linkages, both enhancing and weakening their various effects, makes it very difficult to connect human impact with its strict environmental effect in an explicit way. Nevertheless, small catchments are one of the few areas where it is possible to quantify the impact of past human activity. The like Sudetes area is an appropriate place to demonstrate the impact of past land use change.

Keywords

human impactsoil erosionslope-channel couplingsediment archivesmall catchmentsudetes mountains