Shrinking and Splitting of drainage basins in orogenic landscapes from the migration of the main drainage divide

Stéphane Bonnet (1)

1 GR - Géosciences Rennes

Climate, and in particular **the spatial pattern of precipitation, is thought to affect* *the topographic and tectonic evolution of mountain belts through erosion. Numerical model simulations of landscape erosion controlled **by horizontal tectonic motion or orographic precipitation result in the asymmetric topography that characterizes most natural mountain belts, and in a continuous migration of the main drainage divide. The effects of such a migration have, however, been challenging to observe in natural settings. Here I document the effects of a lateral precipitation gradient on a landscape undergoing constant uplift in a laboratory modelling experiment. In the experiment, the drainage divide migrates towards the drier, leeward side of the mountain range, causing the drainage basins on the leeward side to shrink and split into* *smaller basins. This mechanism results in a progressively increasing number of drainage basins on the leeward side of the mountain range as the divide migrates, such that the expected relationship between the spacing of drainage basins and the location of the main drainage divide is maintained. I propose that this mechanism could clarify the drainage divide migration and topographic asymmetry found in active orogenic mountain ranges, as exemplified by the Aconquija Range of Argentina

Domaines: Géomorphologie

Stéphane Bonnet. Shrinking and Splitting of drainage basins in orogenic landscapes from the migration of the main drainage divide. Nature Geoscience, 2009, 2, pp.766 - 771. ⟨10.1038/ngeo666⟩. ⟨insu-00429309⟩