Assessing the effect of climatic forcing on the landscape evolution of a mountainous setting: A case study of the northern flank of Sierra de Gredos (Central Spain)

Glaciers in mountainous landscapes reshape the topography by forming wide-open valleys. Besides valley excavation, the amount of available glaciogenic sediment stored after deglaciation is paramount since this is used by rivers to incise and transport the sediment further downstream. Although glacial erosion is traceable from the preservation of glacial landforms and deposits, knowledge of its effects after deglaciation and differences with the non-glaciated landscape are necessary to assess the contribution of glacial processes in the evolution of mountainous landscapes. For this purpose, we consider the effects of the Quaternary post-glacial erosion of Sierra de Gredos, a Mediterranean mountain range found in Central Spain, where we analyze the fully glaciated, moderately glaciated, and fluvial catchments of the northern flank of the mountain range. Results from morphometric analysis show that the mean basin normalized channel steepness index (k(sn)) correlates with the basin morphometry regardless of its glacial inheritance; water divides separating parallel valleys are stable. Knickpoints are present in the glaciated and non-glaciated river valleys, confirming the tectonic control of this region. We found that block size, connectivity and bedrock exposure are comparable in fully and mildly glaciated basins, and are greater than in fluvial basins. Local relief of glaciated and mild glaciated basins is similar to 30 % more than that of fluvial basins and a large amount of glaciogenic sediment is still stored in the formerly glaciated landscape. Linearized profiles (Chi plots) of fully glaciated valleys are distinctive for their numerous irregularities that are observed as steps in fluvial profiles. Glacial inheritance has not produced, however, a significant difference in the trend observed for the long-term evolution of the landscape that is tectonically controlled and modulated by Mediterranean climatic conditions.