How is success or failure in river restoration projects evaluated? Feedback from French restoration projects

• 44 French restoration projects that included an evaluation were documented.
• Evaluation strategies (monitoring frameworks, metrics and references) were studied.
• Results underline short-term monitoring and a lack of site control in the monitoring framework.
• Results underline the importance of the references used in the evaluation.
• The subject of scientific evaluation is discussed as well as the social values attributed to rivers.

Since the 1990s, French operational managers and scientists have been involved in the environmental restoration of rivers. The European Water Framework Directive (2000) highlights the need for feedback from restoration projects and for evidence-based evaluation of success. Based on 44 French pilot projects that included such an evaluation, the present study includes: 1) an introduction to restoration projects based on their general characteristics 2) a description of evaluation strategies and authorities in charge of their implementation, and 3) a focus on the evaluation of results and the links between these results and evaluation strategies. The results show that: 1) the quality of an evaluation strategy often remains too poor to understand well the link between a restoration project and ecological changes; 2) in many cases, the conclusions drawn are contradictory, making it difficult to determine the success or failure of a restoration project; and 3) the projects with the poorest evaluation strategies generally have the most positive conclusions about the effects of restoration. Recommendations are that evaluation strategies should be designed early in the project planning process and be based on clearly-defined objectives.