Morphoevolution and sediment dynamics in Mediterranean sub-humid badlands through multitemporal UAV-based monitoring

Sub-humid badlands can be found in various Mediterranean regions; locally in Italy, they are known as "calanchi" and "biancane." In Southern Tuscany (central Italy), the morphodynamics of badland areas have been extensively studied in order i) to quantify erosion rates over time, employing both traditional methods like erosion pins and advanced techniques such as UAV-based digital photogrammetry, ii) to investigate the role of chemical and physical characteristics of the parent material or iii) to understand the role of the human impact on the landscape evolution. In Mediterranean regions, sub-humid badland areas exhibit rapid and intricate morphoevolution driven by several geomorphological processes that occur simultaneously, such as sheet, rill, and gully erosion, along with mass movements. The coexistence of gravitational and water erosion processes results in significant sediment mobilization along the catchment, characterized by intermittent transport dynamics. Indeed, mobilized materials often form temporary deposits that are subsequently re-mobilized by future denudational processes in a cut-and-fill cycle. The aim of this study is to analyze the results of 10 years of UAV-based photogrammetric surveys (using Structure from Motion with Multi-View-Stereo technique) conducted in a small badlands hillslope (~0.23 km2) located in Southern Tuscany, within the Orcia River Basin. Highresolution monitoring of this sub-basin leads to the creation of a multi-temporal dataset from which high-resolution Digital Elevation Models (HR-DEMs) are extracted, and subsequently, highresolution thematic maps of topographic predisposing factors (HR-TMs) are derived. Hillslope processes are mapped, through a geomorphological analysis of multitemporal orthophotos, and characterized based on topographic factors and erosion rates obtained from comparison of DEMs (DEM of Difference), aiming to identify the topographical signatures of the denudation processes. Finally, significant focus is dedicated to analyzing connectivity within the sub-basin, including the examination of various indices, and the erosive power of flowing waters. This analysis aspires to understand the transfer of sediment from sources on the hillslopes and low-order streams to the main channel network, taking into account the role of precipitation as triggering factors