Guidance Document – Cost- Benefit-Analysis in freshwater ecosystem restoration (09/2025, revised 10/2025)

Key messages:

1. Cost-Benefit Analysis (CBA) is essential for evidence- based freshwater restoration planning. CBA can support both public and private investment.

2. Freshwater ecosystem restoration delivers multiple co-benefits (or ecosystem services).

3. Valuing ecosystem services in a freshwater context requires tailored approaches.

4. This guidance complements existing CBA frameworks, focusing on how to assess the costs and benefits of freshwater ecosystem restoration.

5. Seven ecosystem services are included: biomass provision; flood risk mitigation; carbon sequestration; nutrient retention; drought mitigation; recreation and habitat provision.

6. A coupled biophysical – economic modelling tool developed by MERLIN enables users to assess the effects of restoration on flood risk mitigation and nutrient retention using EU-wide datasets

7. Real-world case studies - including the use of CBA on 5 MERLIN Case Studies - are presented to show how the methods work in practice.