Assessing multi-temporal river-floodplain dynamics as baseline for process-oriented restoration in a large river: the Duero River, Spain

The time-based perspective of river-floodplain processes plays a key role in understanding its evolution until its present situation and in guiding process-based river restoration. However, despite the wide range of approaches to eco-hydromorphological characterization, the analysis of fluvial dynamics and their drivers under a temporal perspective requires more investigation. For the present study, a historical analysis of river-floodplain dynamics has been undertaken in a study section of the Duero River upstream of Zamora (Spain), within the framework of the DRAINAGE project for the integral management of flood risk. Aerial imagery for the period 1945-2017 was used to create habitat maps that were subsequently intersected to identify trajectories of habitat change (anthropization, changeless, progression, and regression). In addition, a Natural Trajectory Index (NTI) and an Anthropization Ratio (AR) were proposed as a way to assess the balance of natural trajectories (progression vs. regression) and the weight of anthropization versus the sum of natural trajectories, respectively. Results show a system with a high degree of stability and anthropization, and a current imbalance of natural trajectories with a predominance of progression in the ecological succession. Rejuvenation processes have to be reactivated through nature-based solutions, allowing for more sustainable water management practices. This perspective aims at promoting a more resilient system. The diachronic analysis presented is widely exportable to other river-floodplain systems as a basis for process-based restoration practice.