Worldwide, rivers provide important socio-economic and environmental functions and are essential to human well-being. The growing demand of user-functions and the change in river conditions due to large-scale morphology and climate change, increase the pressure on lowland river systems (e.g. Rhine, Meuse, Danube and Mississippi). To ensure a multi-functional river system, challenges related to uncertain exogenous trends should be tackled. This asks for an integrated approach that accounts for large-scale system behaviour rather than a sectorial approach. This paper proposes a framework that provides support to the river management decision-making process by assessing policy-options against uncertain exogenous processes based on the quantified performance of river functions. Hence, a case study of the Dutch Rhine was carried out, proposing a set of models to simulate river conditions and quantify the performance of the river functions navigation, nature and flood protection. The framework quantifies and monetized the impact of climate change and morphology on the user-functions in 2050. The application of the framework reveals a reduction of shipping efficiency, reduction of floodplain inundation and an increase in flood level. The monetization of river functions allowed an optimization of the policy-options, while dealing with uncertain processes as climate change and morphological changes. We demonstrated the merits of the assessment framework with a case study for the Dutch Rhine, as it provides useful quantitative information to support to decision-making in integrated river management.

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The summer and autumn of 2018 showed the negative drawback of both low-flow conditions and bed degradation over the last century in the Dutch Rhine. This resulted in record-breaking low water levels, extreme low navigation depth and subsequently nautical problems. The Rhine’s long-term bed degradation is the response to river training of the last centuries focused on improvement of navigation and flood protection. Over the past hundred years the river bed of the Upper Dutch Rhine branches degraded 1 to 1.5 m, while a current trend of 1 to 2 cm per year is observed (Blom, 2016). The ongoing bed degradation is problematic since it induces (i) a reduction of navigation depths due to the existence of non-erodible layers, (ii) lowering of ground water levels and dehydration of nature, (iii) lowering of coverage rates of infrastructure (e.g. cables in subsoil, bridges and groynes) and (iv) a gradual shift in discharge distribution at the bifurcation points. As climate change will increase the inter-annual variability of the Rhine’s discharge pattern, low-flow conditions are likely to occur more often, reinforcing the abovementioned impacts on nature and navigation (Sperna Weiland et al., @en