Evaluating morphological quality and scale effects in a Mediterranean river using IDRAIM methodology: The Jerte river (Spain)

Study region The upper-middle section of the Jerte River (39.4 km, Tagus River Basin, Spain), a mountain water body with a Mediterranean pluvio-nival regime. The primary disturbances to the river’s natural regime are driven by intense agricultural activity (specifically terraced cherry cultivation), recurrent wildfires, and seasonal recreational river uses. Study focus The research addresses the need for standardized tools to evaluate fluvial systems under the Water Framework Directive in Europe. Specifically, we examine the applicability of the Italian IDRAIM framework and its core tool, the Morphological Quality Index (MQI) in an Iberian-Mediterranean environment. The Jerte river was segmented into 21 reaches to assess geomorphological functionality, artificiality, and channel adjustments. Additionally, a statistical sensitivity analysis was carried out at both reach and water body scales to evaluate MQI stability to indicator variations and expose local critical conditions. New hydrological insights for the region While the length-weighted water body assessment shows an overall moderate morphological quality (MQI = 0.67), the multiscale approach reveals high spatial heterogeneity, demonstrating that aggregated estimations mask localized degradation. For instance, reaches near towns exhibit constraints on lateral mobility, deficient riparian vegetation, and extensive riverbed modifications. Reaches with poor quality account for 52% of the river length. Integrating IDRAIM with sensitivity analysis successfully identified unstable reaches and indicators driving perturbation, providing an objective tool for regional river management and restoration prioritization.