Graduation Maikel Berg

Nature-based Solutions (NbS) is an increasingly popular concept referring to actions that harness nature
to address major societal challenges. Implemented in river landscapes, NbS have the potential to play
an important role in restoring many of the ecosystem services that are lost as result of human
interventions and global warming. Despite its exponential growth, there are still many barriers to
successful implementation of NbS, including the lack of a global and common framework with
guidelines for its implementation and evaluation. In an attempt to develop such a framework, the
International Union for Conservation of Nature (IUCN) published the IUCN Global Standard for NbS.
Even though the IUCN Standard has been designed to be applicable to NbS in all sectors and over the
entire globe, knowledge on its applicability and usefulness to specific sectors is still limited. Therefore,
this research aims to identify the challenges that occur in ex-post application of the IUCN Standard to
river restoration projects with a focus on flood risk mitigation, and the added value that this application
could provide to stakeholders.

At first, a literature study was conducted in which the content of the IUCN Standard was related to
twenty-two other assessment frameworks for NbS and compared in-depth to the frameworks of
Andrikopoulou (2020), Dumitru & Wendling (2021a) and Huthoff et al. (2018). These comparisons
indicate that that the IUCN Standard has a relatively large broadness in scope of application, provides
limited flexibility in assessment to its users and is descriptive, as it requires semi-quantitative input and
qualitative rationale. Furthermore, the comparisons provide the insight that the IUCN Standard can be
used as a tool to evaluate the extent to which the essential processes of a NbS, established by the IUCN
(e.g. regular monitoring, inclusive stakeholder engagement and continuous adaptive management), have
been incorporated in the project. The IUCN Standard can, however, not be used to evaluate project
results, including both biophysical and social results.

In the next part of the research, the IUCN Standard has been applied to three case studies of river
restoration projects with a focus on flood risk mitigation, of which at least two differ significantly in the
surface area, position in the catchment, kinetic energy of the river, data accessibility, resources and the
type of riverine NbS measures that were implemented. The selected case studies are the Eddleston Water
Project, the “Room for the River” Deventer Project and the Missouri River Levee Setback Project.
Despite facing challenges in the interpretation of indicators, data accessibility, a relatively coarse scale
for evaluation, and tensions between the project objectives and the use of the IUCN Standard, the
Standard could successfully be applied to all case studies. The case study results consist of (1) a total
percentage match to the IUCN Standard and a statement on being in adherence to the standard, which
could provide credibility to the project processes, (2) the strengths and weaknesses of a project, which
could be used to inspire and/or guide projects and strengthen (future) projects, respectively, and (3) a
radar chart, which could provide possibilities to compare to and learn from other projects. Based on
these results, it can be concluded that, despite of a few challenges, the IUCN Standard is applicable to
river restoration projects with a focus on flood risk mitigation, and that application of the Standard could
provide added value in various ways, although restricted by the limited evaluation of flood risk
mitigation.

As the field of research is very dynamic, the results of the literature study could be significantly different
when conducted at another point in time. Furthermore, there are several factors that could have
influenced the case study results, although these are of less importance compared to the main objective
of analysing the applicability and usefulness of the IUCN Standard. As the IUCN Standard cannot be
used for the evaluation of project results, it is recommended that the Standard is used in combination
with a framework that can be used to evaluate the results of a project. Lastly, in order to build on the
evidence with regard to the applicability and usefulness of the IUCN Standard obtained in this research,
a number of recommendations for interesting applications of the IUCN Standard are proposed.