Author(s): Silke Wieprecht, Lydia Seitz, Stefan Haun
Linked Author(s): Silke Wieprecht
Keywords: Morphology, alluvial form, ecological impact
Abstract:
For the understanding of morphological processes, it is not sufficient to only investigate river sections. On the macro scale, the catchment plays an important role especially for the available quantity of material fluxes and its composition in the river. Intense river works in the last decades and centuries (straightening, reservoirs, dams, dikes etc. ) strongly alter the characteristics of our rivers. In particular, the lack of bed load material severely affects the dynamic processes in rivers and ecological important instream structures. In some examples, the attempt is made to enhance the ecological situation in a river by individual river restoration measures. Depending on the availability of material, very different results can be achieved. These effects can also be proven very well with the help of long-term morphological models. Another option is to bring back sediments into the transport cycle, e. g. by flushing reservoirs. On one hand, this can help to increase the morphological dynamics, but on the other hand the grain sorting effect upstream of reservoirs changes the characteristics of the river bed downstream. Due to changes of material composition, the granular structure on the micro and pico-scale of the river bed may be heavily altered. It occurs that, although the meso-scale structure seems to be good, there are still not enough acceptable habitats for aquatic species available. However, alterations on the micro and pico-scale, like colmation and clogging processes, e. g. due to flushing of reservoirs or changes in wash load fluxes from the catchment, can influence the biological communities in rivers. Depending on sediment texture and content of pollutants and/or nutrients, effects like biofilm growth occur, which then additionally alter sediment transport characteristics
Year: 2017