Author(s): Christoph Hauer; Peter Flodl; Tobias Mayer; Helmut Habersack
Keywords: No Keywords
Abstract: River catchments in the northern part of Upper Austria are characterized by granite/gneiss geology. The sedimentological composition of bed material is based on coarse substrate (cobbles) and the weathering products of granite and gneiss, described as fines in the coarse sand and fine gravel fractions (diameter=1mm–10 mm). Especially, those weathering products caused severe ecological problems over the last decades (spawning habitats/macroinvertebrates) on the one hand due to a fill up of the gravel matrix and on the other hand due to mobile bed forms. Therefore, studies to investigate the causes of the increased sedimentation problem have been conducted in the crystalline catchments on various scales. The results showed that the impacts of climate change were responsible for an increase in fine sediment deposition in the rivers of the Bohemian Massif. This has to be related on the one hand to an increase in precipitation and intense precipitation rates respectively with an increase of erosion in small tributary catchments. On the other hand a decrease of the annual numbers of days of active fine sediment transport could have been detected for the various rivers by numerical modelling. The date of trend change could have been determined for the beginning of the 1990s and thus to the statistically significant increase in global warming. Moreover, habitat modelling of target fish species showed, that due to the increased sedimentation of weathering products of granite and gneiss key habitats have been reduced (e. g. fill up of pools).