River channel response to climate- and human-induced hydrological changes: Case study on the meandering Hernád River, Hungary

Abstract The increasing extent of human activities and climate change may have notable effects on river systems; therefore, a comprehensive knowledge of these effects is essential to mitigate their unfavourable consequences. The aim of the present study is to analyse the hydromorphological changes caused by climate change and human impacts on the Hungarian section of the Hernad River and to evaluate the morphological responses of this river from a flood prevention perspective. Over the past 60 years, considerable morphological changes were measured in the studied river sections, caused by the alteration of their hydrology. The main morphological change was the evolution of secondary bends on large meanders. This process was driven by extrinsic factors, as the morphometric changes were determined by an altered water regime caused by precipitation change and engineering works. Further mean discharge decreases caused the propagation of this process on smaller meanders as well. Meanwhile, the cross-sectional area of the channel also decreased, primarily as a result of narrowing. This altered morphology enhances the flood risk in the short run, as the narrow channel is not sufficient to drain the rapid flood waves. In the twenty-first century, climate change may cause decreasing mean discharge while also increasing the frequency of rapid floods, further increasing flood risk. However, the projection of the geomorphological effects of future precipitation changes is very uncertain.

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