The impact of river incision induced by channelization and gravel mining on the structure of ground beetle assemblages in riparian habitats was investigated on three montane rivers in southern Poland. Ground beetles were collected on three benches of different elevation in 11 incised and 14 vertically stable cross sections of the rivers. In total, 5821 individuals representing 106 species were collected. The effect of river incision on the diversity and abundance of ground beetles depended on bench height. Only on the lowest bench, inundated about once per year on average, species richness of the assemblages was significantly reduced in incised river cross sections. On this bench, the abundance of the specialists of exposed riverine sediments, i.e. small and medium-sized predators with high dispersal power and spring breeding strategy, was highly negatively affected by river incision. On the highest bench, large, brachypterous species with spring and autumn breeding strategy, typical of undisturbed habitats, were more abundant in incised cross sections. As this bench is practically not subjected to flooding even in vertically stable cross sections, these species probably benefited from the occurrence of riparian forest along most incised river sections, whereas the riparian areas along vertically stable sections are subjected to higher agricultural pressure. This study shows that in the mountain region where high precipitation helps to maintain moisture of the riparian habitats, river incision has a negative impact only on the specialists of exposed riverine sediments.
Eco-friendly river restoration structures are a valid solution for river training projects. Among this structure typology, block ramps have been successfully tested to solve problems related to river sediment control, bed stabilization and energy dissipation. Despite the conspicuous literature dealing with block ramps design in straight rivers, there are no studies analysing the erosive process occurring in the stilling basin downstream of a block ramp in a curved river bend. Therefore, this paper represents the first systematic analysis of their behaviour and of the resulting downstream equilibrium morphology in such geometric configuration. A dedicated model was built to simulate a wide range of hydraulic conditions. Experimental data analysis allowed describing the erosion dynamics occurring in the stilling basin and, at the same time, to derive a useful design relationship by which it is possible to estimate the maximum scour depth. Furthermore, the model results were successfully validated by using field measurements collected in the Porębianka river (Poland). Both field data and laboratory experimental results allowed furnishing a comprehensive description of the scour phenomenon. The proposed relationship represents the first trustable and valid tool for hydraulic design of such structure typology in curved rivers.
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