Integrating Biophysical and Economic Assessment: Review of Nature-Based Adaptation to Urban Flood Extremes

Over the last decade, the potential of nature-based solutions (NBS) has been recognized to support climate change adaptation, by promoting sustainable urban planning. Nevertheless, a wider uptake of such solutions in urban areas faces different challenges and barriers. A comprehensive mapping of available NBS impact assessment methods could help to accelerate this process. There is, however, a lack of comprehensive systematization of economic analysis. This research aims to provide an overview of NBS impact evaluations by assessing how the scientific literature integrates such economic analysis into urban planning adaptation. A systematic review approach has been used to discuss the role of NBS in climate change adaptation. This review presents two main stages. Firstly, it identifies the biophysical–economic assessment of NBS adaptation measures to reduce urban flood extremes in coastal cities. Secondly, the NBS approaches were categorized based on the biophysical benefits (in terms of flood-risk reduction) related to each specific solution and the subsequent economic evaluation of such implementations. This research review revealed a low-level gap of integration between climate change issues and NBS analysis (i.e., it is commonly used as background condition). Most publications provide NBS biophysical impacts assessment, without combining these results with economic evaluation of the flood damages to finally achieve the avoided cost due to the implementation of such solutions. This work shows the growing interest on further research to develop spatially integrated environmental–economic assessment of NBS implementation, by highlighting the needs and opportunities of a trans-disciplinary approach to support policy-making in the framework of urban climate change adaptation.