Author(s): Christoph Hauer; Patrick Holzapfel; Diego Tonolla; Guido Zolezzi
Linked Author(s): Christoph Hauer
Keywords: No Keywords
Abstract: The impact of fine sediments and especially the accumulation of fines on the aquatic biology can be significant and partially limiting the habitat use. Both, macroinvertebrate-and fish habitats, especially spawning sites, can be affected. More recently, the impact of hydropeaking is mentioned as one of the decisive factors for fine sediments dynamics in the surface and subsurface layers of gravel bed rivers. Aim of the presented study was to quantify fine sediment concentration in the surface and subsurface layer of rivers with hydropeaking operation. It was of interest, to figure out possible differences in fine sediment concentration in the permanent wetted area (during base and peak flow) and the so called dewatering areas which are only inundated during peak flows. To address this aim freeze-core samples have been used in the study design for different river catchments. The results showed that there is a clear difference in vertical stratification of fine sediment concentration between the permanent wetted area during base flow and the dewatering sites. In contrast to dewatering areas, permanent wetted areas contained no or minor fine sediment concentration on the river bed surface. The consideration of this difference is crucial, especially in estimating the clogging of hydropeaked rivers based on state of the art visual classification methodologies. Moreover, due to a repeated survey of fine sediment concentrations in the gravel matrix based on freeze cores, the de-clogging processes of flood impacts could be quantified.