Nature-based solutions for hydro-meteorological hazards: Revised concepts, classification schemes and databases

Hydro-meteorological hazards (HMHs) have had a strong impact on human societies and ecosystems. Their
impact is projected to be exacerbated by future climate scenarios. HMHs cataloguing is an effective tool to
evaluate their associated risks and plan appropriate remediation strategies. However, factors linked to HMHs
origin and triggers remain uncertain, which pose a challenge for their cataloguing. Focusing on key HMHs
(floods, storm surges, landslides, droughts, and heatwaves), the goal of this review paper is to analyse and
present a classification scheme, key features, and elements for designing nature-based solutions (NBS) and
mitigating the adverse impacts of HMHs in Europe. For this purpose, we systematically examined the literature
on NBS classification and assessed the gaps that hinder the widespread uptake of NBS. Furthermore, we critically
evaluated the existing literature to give a better understanding of the HMHs drivers and their interrelationship
(causing multi-hazards). Further conceptualisation of classification scheme and categories of NBS shows that
relatively few studies have been carried out on utilising the broader concepts of NBS in tackling HMHs and that
the classification and effectiveness of each NBS are dependent on the location, architecture, typology, green
species and environmental conditions, as well as interrelated non-linear systems. NBS are often more cost-effective
than hard engineering approaches used within the existing systems, especially when taking into consideration
their potential co-benefits. We also evaluated the sources of available data for HMHs and NBS,
highlighted gaps in data, and presented strategies to overcome the current shortcomings for the development of
the NBS for HMHs. We highlighted specific gaps and barriers that need to be filled since the uptake and upscaling
studies of NBS in HMHs reduction is rare. The fundamental concepts and the key technical features of past
studies reviewed here could help practitioners to design and implement NBS in a real-world situation.