The topography of a continental indenter: The interplay between crustal deformation, erosion, and base level changes in the eastern Southern Alps

Greater Alpine river network evolution, interpretations based on novel drainage analysis

The Central European drainage system is dominated by four major rivers (the Danube, Rhine, Rhône and Po). The geometry of these drainage basins has evolved through the history of Alpine and Carpathian orogeny. Analysis of the modern river geometry reveals the geometric stability or instability of the drainage network and enables interpretation of the erosion and exhumation pattern. We characterize the river basin geometry and inter-basin relief through metrics including the quantity χ that relates to the catchment area, and a catchment restricted minimum elevation (CRM) metric. The interpretations from the maps are in agreement with known river captures and morphological features. The χ-map reveals additional systematic, large-scale transients, consistent with ongoing basin changes, mainly manifesting in the Danube losing catchment area. We postulate that the changes are related to the longitudinal initiation of the Danube River in the Alpine foreland, augmented by the formation of the Carpathians and the filling of the Pannonian Basin, which resulted in an elongation of the Danube river basin. We conclude that the Danube has lacked erosional power throughout its history and therefore been victim to capture and area loss.

Abrupt drainage basin reorganization following a Pleistocene river capture

River capture is a dramatic natural process of internal competition through which mountainous landscapes evolve and respond to perturbations in tectonics and climate. River capture may occur when one river network grows at the expense of another, resulting in a victor that steals the neighboring headwaters. While river capture occurs regularly in numerical models, field observations are rare. Here we document a late Pleistocene river capture in the Yimeng Mountains, China that abruptly shifted 25 km² of drainage area from one catchment to another. River terraces and imbricated cobbles indicate that the main channel incised 27 m into granitic bedrock within 80 kyr, following the capture event, and upstream propagating knickpoints and waterfalls reversed the flow direction of a major river. Topographic analysis shows that the capture shifted the river basins far from topographic equilibrium, and active divide migration is propagating the effects of the capture throughout the landscape.

River capture acts as one river steals the neighboring headwaters, which is a dramatic natural process for mountain landscapes evolution. Here the authors show a stream piracy reversed flow in a major river resulting in waterfall formation, bedrock gorge incision, and widespread topographic disequilibrium.