Impact of value-driven scenarios on the geomorphology and ecology of lower Rhine floodplains under a changing climate

The biogeomorphological functioning of lowland floodplains will be altered strongly due to future landscaping measures that are necessitated by climate change. For many industrialized and urbanized river basins, the layout of the fluvial area depends on the human choices for landscaping measures, which reflect the dominant value system of the actors. We aimed at (1) designing scenarios for the future layout of the floodplains of the River Waal in the Netherlands for 2050 using a new value-based methodology, and (2) assessing the floodplain biogeomorphology under these scenarios and climate change. The scenarios are driven by transitions in human value systems and they are color-coded: green (personalistic-consensual), orange (scientific-rational), and yellow (integrated-systemic). Per scenario, the landscaping measures were translated into a future topography and ecotope distribution. Using various spatially explicit simulation models, we evaluated the scenarios regarding the biogeomorphology in 2050: (1) flood peak reduction (green 0.11, orange 0.65, and yellow 0.37 m), (2) year-average floodplain suspended sediment deposition (+114, +148, +143%), (3) food web exposure to heavy metals (4–5 out of 10 species for all scenarios) and (4) biodiversity value (+23, −4, +39%). We conclude that (1) analysis of value systems provides a broad interpretive framework for scenario development, which guides the choices for transitions and (2) the biogeomorphology is affected by climate change (+58% deposition), but the effects of the local landscaping measures are even stronger. None of the scenarios shows the ideal combination of high flood peak reduction, low sedimentation, and high biodiversity. Ecotoxicological risks seem less discriminative.