Drainage divide dynamics modulated by erosion-driven landscape adjustment in a low-deformation setting

Abstract

The Vosges Mountains (northeast France) are a mid-altitude mountain range with peaks reaching ∼1500 m a.s.l., in a low-deformation setting. Despite this, they maintain significant topographic relief (up to ∼1000 m), characterized by deeply incised valleys and broad, rounded upland summits (“ballons”). This heterogeneous landscape reflects the interplay of long-term tectonic inheritance, extensive Quaternary glaciation, and ongoing fluvial incision. This study investigates the dynamics of the main drainage divide of the Vosges, a key marker of ongoing erosion-driven landscape adjustment, through a comprehensive analysis integrating morphometric indices, denudation rates derived from terrestrial cosmogenic nuclide concentrations ( 10 Be and 26 Al) in small catchments, and hilltop curvature as a proxy for denudation rates. By focusing on small-scale, second-order basins to quantify denudation rates in the vicinity of the divide, we minimize complexities related to sediment routing, lithological heterogeneities, and basin-scale averaging in large catchments that could confound geomorphic signals. Using a calibrated relationship between hilltop curvature and these local denudation rates, we provide a region-wide assessment of the erosional contrasts across divides and identify the processes governing the ongoing divide migration. Results reveal that the main drainage divide is predominantly migrating westward, away from the Upper Rhine Graben. Transient geomorphic processes, evidenced by knickpoints and river captures, drive rapid, episodic adjustments of the divide intertwined with a slow long-term migration. These findings emphasize that even in low-deformation settings, subtle and transient processes can maintain relief and reconfigure drainage networks. Comparison with published datasets from tectonically and climatically diverse regions places the inferred divide mobility within the range expected for erosion-dominated landscapes. In the Vosges, the ongoing divide migration therefore reflects a long-term geomorphic adjustment to inherited uplift patterns and episodic base-level changes, underscoring that mountain landscapes can remain dynamic well beyond the cessation of tectonic forcing.