Geomorphological controls on the evolution of a new streamflow in the piedmont of the southern of Sierras Pampeanas: A case study of the Río Nuevo, West-central Argentina

Abstract

Our understanding of the geomorphological processes that drive river formation and hydrological settings that favour them is still under development, facing the difficulties of knowledge fragmentation and the mismatch of temporal scales, particularly in arid or semi-arid regions. In this study, we provided new evidence on the link between river formation and hydrological settings by analysing the extremely rapid development of a new river (Rio Nuevo) network in the Morro basin, San Luis, West-Central Argentina. The geomorphology and the morphoevolution of the new hydrographic basin were documented in view of its morpho-litho-stratigraphy and structural characteristics of the river valley. Six main geomorphological units in relation with the formation of the new river were identified. Three of these units predated such formation, two other geomorphological units accompanied the onset of river formation and were also subject to rapid expansion while the last one (lagoons and wetlands) is still stable due to the river rapid expansion as a result of water table level rise. The evaluation of these geomorphological characteristics has provided a better understanding of the process that governs the formation of rivers in semiarid areas, contributing to the prediction and management of future transformations. Further geomorphological controls associated with topographic configuration and tectonic processes were also inferred.