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Comprehensive approach to the reduction of river flood risk: Case study of the Upper Vistula Basin

Wyżga, Bartłomiej, Kundzewicz, Zbigniew W., Konieczny, Roman, Piniewski, Mikołaj, Zawiejska, Joanna, Radecki-Pawlik, Artur
The Science of the total environment 2018 v.631-632 pp. 1251-1267
bank erosion, basins, case studies, channelization, climate models, ecological restoration, flood control, floodplains, risk, risk reduction, rivers, roads, runoff, sediments, watersheds, Carpathian region, Poland
The paper examines options for river flood risk reduction in the Upper Vistula Basin located partly in the Carpathian Mountains in Poland. Projections of high-flow indices for the periods 2021–2050 and 2071–2100 generally indicate small future increases, although the projected flow changes vary highly both across the study basin as well as among climate models. An overview of twentieth-century catchment and channel changes indicates that some of them decreased and others increased the rapidity of runoff but they largely reduced availability of sediment for fluvial transport, hence inducing bed incision and bank erosion that create risk to roads and bridges. Traditional methods of flood protection in the basin encompassed large structural defences such as river channelization and flood embankments. These have limited floodwater retention within floodplains and accelerated flood runoff, shifting flood hazard downstream rather than reducing it. A range of alternative approaches to reducing future flood risk are thus proposed and examples of their application in southern Poland are described. These approaches include river restoration measures aimed to reduce erosional potential of flood flows and increase channel and floodplain retention of floodwater, as well as grassroots initiatives promoting preparedness for flooding at the community level. There is an increasing need to change the existing paradigm that flood-control measures should be based on fast evacuation of floodwater that, in turn, was associated with a significant reduction in floodwater retention on the valley floors. Alternative approaches discussed in this paper extend the roster of flood risk reduction strategies and contribute to a gradual paradigm change.