Room for the River: An extended cost benefit analysis of integrated river-floodplain management for the Rhine in the Netherlands

Rivers across the globe are under increasing pressure from climatic and anthropogenic threats, which has led to a widespread recognition of the need for integrated, holistic river management and ecological restoration. Economic analyses such as cost-benefit analysis (CBA) often play an important role in the decision-making process. However, (peer-reviewed) information on costs of measures is scarce, existing studies are limited in scope and there is a lack of approaches that integrate biophysical – socioeconomic metrics to allow for spatially explicit scenario analysis. By quantifying and monetising the supply of ten ecosystem services under three integrated river- and floodplain management (RFM) strategies incorporating Nature-based Solutions for the river Rhine in the Netherlands, this study develops such approaches, demonstrates the impact of adopting of a wider scope in CBA and includes an in-depth analysis of investment costs. Of the ten monetized benefits, the amenity value of landscape quality (up to 730 MEUR) and bequest-existence value of wildlife habitats (up to 5030 MEUR) have the highest values. Our results illustrate that expanding the scope of benefits considered can lead to significant changes in the benefit-cost ratio and the ranking of preferred strategies, with potential implications for strategic choices. Overall, our study presents a practical approach for integrating biophysical-economic indicators to support broader valuation of integrated river-floodplain management (RFM) strategies, in line with EC recommendations for water policy and particularly relevant for upcoming Nature Restoration Plans which are being developed under the EU Nature Restoration Regulation.