The impacts of cities on global climate and ecological systems are very well-known worldwide. Nevertheless, the efforts ofthelast decades focused on reducing the effects of human activities on the environment. Only lately, the idea of mimicking nature as model ofaperfect cycle made its way intothe scientific community and beyond. Hence, the concept of Nature-based Solutions (NbS) has been introduced in the scientific debate in 2009 and since 2015 asacore theme in research and innovation programmes of the European Union. These are defined as living solutions inspired by nature with the aim of addressing societal problems. Implementation of such solutions requires not only a specific expertise, but also many other contextual conditions, such as political will and economic feasibility. Challenges are still present, mainly related to the capacity gap, funding gap, and the lack of a sound accountability framework. The aim of this paper is to focus on the third challenge, i.e. to delineate a possible framework for evaluating the implementation of Nature-based Solutions.This is done by looking at the case study of Hamburg, Germany, which is going to develop NbSintheNeugraben-Fischbek neighbourhood in the frame of the Horizon 2020 Research Project CLEVER Cities. Here,NbSare aimingto re-introducegreen intothe built environment while focusing on the alleviation of both social differences (integration and inclusion of the weaker populationgroups) and technical barriers (big infrastructure caesuras,etc.). These results are reached through a process of co-creation,which seeks the inclusionof local stakeholders and experts in the design and decision on the single interventions to be implemented in the project lifespanThe resulting framework encompassesthe process from the definition of problems and goals in the area of study, through co-creation and the identification of the type of intervention to implement, concluding with the actual realisation of the project.Each of these steps present guidelines and suggestionsfor the determination of indicators through which it is possible to assess both the process and outcomes of the single steps. The article offers an overview of the entire framework,specifying the methodology to build a sound set of indicators as well as reflecting on possible limitations and its future development.
