Abstract
Asymmetric morphologies are ubiquitous in many landscapes, but the influence of tectonics, climate or bedrock properties on the development and persistence of this asymmetry is difficult to assess.This study investigates the implications of structurally-controlled relief asymmetry on drainage divide dynamics and network organization.We focus on the French Southern Alps, a tectonically quiescent region where Eocene and Miocene thin-skinned deformation of a well-developed Mesozoic sedimentary series is still strongly imprinted in present-day landscape form, in particular through the presence of asymmetric ridges with steep cliff faces opposite to gently dipping structural surfaces.We build a dataset combining systematic measurements of geomorphological properties of these ridges with available geological information about strata dip direction, to identify eventual systematic correlations between metrics characterizing divide morphology and instability and the structural configuration of the ridge, from a local scale to the larger organization of the river network.We observe a systematic tendency for aggressor basins, according to the χ metric and local slope contrasts, to be located opposite to the dip direction of the strata, with respect to the divide.Such configuration arose from the initial structural asymmetry of the layered landscape, but we propose that it has been maintained over time by an inhibition of fluvial or hillslope erosion processes on the steepest and updip sides of the divide.Such phenomena can have strong implications on the transient evolution of the planform drainage structure, by allowing the persistence of out-of-equilibrium configurations over extended periods of time.