Identification of the fluvial sediment source areas in the Burano catchment basin (Cantiano, PU)

Climate change and increasing anthropogenic pressure are two of the major drivers of increased frequency and the intensity of highly disastrous events like flash-floods in the drainage network. This is the case of Burano watercourse flooding, a tributary of the Metauro river, in the northern Marche region where high flow rates were recorded in a few hours in September 2022. This event resulted in about 13 fatalities, 50 injuries and critical damages to infrastructure during the disastrous inundation. In this scenario, the current strength also generates solid transport of large amounts of sediments, increasing the hydrogeological risk of flooding in densely populated areas located close to the river bank. Therefore, the main purpose of this work is understanding solid transport, focusing on the identification and characterization of the sediment sources and sink areas by a GIS-based remote sensing approach. Source material comes from both linear zones, where the detritus moves along a well-defined direction, and areal sources understood as landslides along slopes and extensive erosion zones (e.g. gullies), which demonstrate a connection with the hydrographic network. Through new geomorphometric approaches, it is possible to characterize spatial patterns of sediment connectivity by enabling the quantitative modeling of sediment discharge. The proposed methodology consists of a study of the current geomorphological framework as well as an analysis of morphological variations in the riverbed that result in changes in width, profile and pattern of the river, and a characterization of the sediment along the water network. Preliminary analysis of satellite imagery among different time periods (1977, 1987 and 2022) are performed to study the evolutionary trends of river network and longitudinal profiles of channels are also used to highlight anomalies in steepness (knickpoints or kinckzones). Landslide and areas characterized by an intense erosion, provided by various databases (e.g. Hydrogeological Basin Plans - PAI, Italian Landslide Inventory - IFFI) and collected during fieldwork, are joined in a database in GIS environment allowing to create a new geomorphological map of the upper part of the Metauro basin. Moreover, lithology (substrate and quaternary deposits), slope, presence of vegetation, the sources and the distance of hydrographic network are some of geomorphological features taken into consideration for the estimation of the sediment. The results obtained during the process allowed to define the source sediment areas and to create a landslide susceptibility map, with the union of all the data it was possible to analyze sediment connectivity along the riverbed. The applications demonstrate that a reliable assessment of sediment connectivity via geomorphometric approach, especially when integrated with a sediment sources inventory, is useful for giving management priorities by the competent authorities in reducing hydrogeological risk.