Is-it Worth Investing in NBS Aiming at Reducing Water Risks? Insights from the Economic Assessment of Three European Case Studies

Economic narratives are largely put forward as an argument for the promotion of Nature Based Solutions (NBS). However, integrated economic evidence, taking into account direct and opportunity costs, avoided damages and the multiplicity of co-benefits generated by NBS are still needed to support this argument and convince decision makers to invest in these solutions. To address this gap, we develop a methodological framework for the economic assessment of NBS for water related risks and present its application to three European case studies. We find that the cost of implementation and maintenance is lower for NBS strategies than for grey solutions for the same level of risk reduction, thereby confirming the cost-effectiveness advantage of these solutions. Benefits in terms of avoided damages are however generally not sufficient to cover these costs. Co-benefits represent the major share of the monetary value generated by NBS strategies. Finally, the results of the cost-benefit analysis reveal context-specific results on the overall economic efficiency of NBS. These results urge decision makers to tailor funding strategies to the specificity of NBS economic value.