Quantificazione dell’Influenza della Confinazione Laterale della Valle sulla Morfodinamica dei Fiumi Meandriformi

This study investigates the impact of valley lateral confinement on floodplain age distribution and sediment storage time in meandering river systems. Understanding how valley width influences floodplain development is crucial for assessing ecological processes, flood risk, and sediment transport. Despite its importance, limited research has focused on quantifying the effect of valley confinement on meandering river floodplains using numerical simulations. This research aims to address this gap. Numerical simulations were used to generate floodplain rasters for seven different valley widths and one unconfined floodplain, following the methodology of Ielpi et al. (2023). These simulations modeled single-thread meandering rivers, prone to neck cutoff events, allowing the study of floodplain evolution over time. Three datasets were generated: distribution of floodplain age, sediment storage time, and pixel visit frequency. Statistical analysis was performed to identify the best mathematical models to describe the relationship between valley width and floodplain age and storage time. The findings reveal that valley width significantly influences floodplain morphology and sediment dynamics. In narrow valleys, floodplains predominantly consist of young deposits due to frequent surface reworking, with minimal preservation of older sediments. As valley width increases, a more balanced mixture of young and older deposits emerges. In very wide and unconfined valleys, substantial preservation of older surfaces occurs, resulting in a complex landscape where some areas remain undisturbed for long periods. Statistical analysis shows that the relationship between valley width and floodplain age follows a power law, highlighting a non-linear interaction. Additionally, the study finds that sediment storage times increase with valley width. Narrow valleys experience rapid reworking, resulting in short storage times, while wider valleys allow for longer sediment storage, with unconfined valleys exhibiting the longest durations. The pixel visit frequency analysis further emphasizes how valley confinement influences the spatial distribution of channel migration. This research fills a key gap in the study of meandering river floodplains, highlighting the importance of understanding floodplain age distribution. It provides valuable insights into flood risk management, carbon cycling, and river restoration efforts, emphasizing the role of valley confinement in influencing sediment preservation and ecological function.