Identification and assessment of sediment sources and sediment transfer processes in a Mediterranean Agroecosystem in the Northern Apennines, Italy 

Abstract

<p>The management of Mediterranean agroecosystems is crucial to prevent, reduct, and mitigate sediment-related threats like soil erosion, water quality issues, or reservoir sedimentation. Hence, the assessment of sediment connectivity and sediment dynamics at catchment scale is essential for identifying hotspot areas susceptible to sediment loss. Therefore, the identification of type, extent, and location of sediment sources and the analysis of the connectivity between these sources and the channel network are a prerequisite for assessing sediment yield and transport. This study is aimed at elaborating an integrated georeferenced inventory map of sediment landforms and evaluating sediment (dis)connectivity within a Mediterranean agricultural catchment located in Val d’Arda (Northern Apennines, Italy). We performed extensive geomorphic field surveys together with the application of remote and proximal sensing methods in order to identify and characterize the dominant processes involved in the sediment production and transportation throughout the catchment. Based on a detailed terrain analysis using a high-resolution DTM we quantified the physical (structural) linkages between catchment compartments, sediment sources and the drainage pattern following a morphometric connectivity approach. Our study revealed that the Val d’Arda catchment is widely characterized by several large active landslides, in particular complex earthflows and mudflows, but also wide dormant coalescent landslides with small evidence of intermittent reactivation, which are directly linked to the channel network. The terrain analysis highlights clear evidence about the role of such geomorphic processes in shaping the topographic features of the catchment, e.g. their influence on the steepness of the slopes and the lateral morphological evolution of the fluvial system. The processes active in the study area are highly influenced by the structural sediment connectivity and present high spatio-temporally variability. Moreover, we identified several rill-interril, piping and gully systems, whose genesis and evolution appeared to be mainly controlled by lithology and land-use. In some cases these systems have evolved into badlands, with a high potential in terms of soil loss and sediment production. On the other hand, several badlands’ systems are stabilizing, showing revegetation processes, becoming active only due to shallow mudflows. In this study we show that the comparison between the sediment landforms and topography-based connectivity maps allows to highlight the main processes involved in the sediment production and their role in downslope transfer of sediments.</p>