Nature-based solutions (NBSs) are increasingly implemented to mitigate natural risks in urban and rural contexts, from coastal to mountainous areas. Nevertheless, the lack of quantitative approaches to assess NBSs’ effectiveness limits their technical, social and cultural acceptance. Within the PHUSICOS project (EU H2020 Innovation Action; Grant Agreement nr. 776681) a comprehensive assessment framework tool (AFT) has been developed to fill this gap. This paper presents an ex-post analysis with the PHUSICOS AFT applied to the Isar River case study. The restoration of the urban reach of the Isar River, in the city of Munich, was implemented in the early 2000s and represents a successful example of ecosystem and user-friendly flood risk management plan. The performance of the NBS measures implemented to manage the flood risk and improve the ecological status of the river (NBS scenario) is assessed in comparison with an alternative scenario with traditional hard engineering measures (grey scenario, GS). Results underscore the NBS as a competitive alternative. The ex-post analysis shows the potential of the PHUSICOS AFT for NBS performance assessment, providing guidance on indicator selection, stakeholders’ management and performance assessment. The application discussed here is expected to aid professionals and researchers involved in the design, implementation, monitoring and evaluation of NBSs.

This paper describes an assessment framework tool to analyze the performance of nature-based solutions (NBS) for hydro-meteorological risk management. The tool is based on multi-criteria decision analysis within the context of NBSs, an umbrella concept currently in focus that promotes nature and provides ecological and socio-economic benefits. The proposed tool includes the selection and application of key performance indicators (KPIs) for the co-benefits and costs associated with the implementation of NBSs. To ensure high societal impact, the tool relies on a participatory approach. Stakeholder preferences are taken into account within the assessment process. As such, the assessment framework can be used as a design and selection tool for NBSs and other alternative measures, including grey and hybrid solutions. The proposed procedure can be adapted to the specific socio-environmental context and hydro-meteorological risk by tailoring the set of relevant KPIs. The assessment framework is useful for monitoring the implemented measures and to document their effectiveness. The methodology provides quantitative and transparent documentation of hydro-meteorological risk management processes, useful for decision- and policy-makers, and stakeholders dealing with NBS measures. Graphical Abstract

This work reports the results of a study on the effects of an earth levee in flow depth and velocity reduction found by mapping the flood hazard for the baseline and Nature-Based Solution scenarios for one of the case studies of the H2020 Phusicos Project, namely, the Jorekstad site, in the town of Lillehammer (Norway). To achieve this target, the study employed various modelling procedures. These included climate, GIS, hydrological and hydraulic modelling structured in an integrated workflow. By running the FLO-2D model, the flooded areas were computed, and maximum flow depth and velocity were assessed by varying the return period with reference to different settings of the antecedent moisture conditions.