Variabilità della portata di picco in fiumi meandriformi: collegamento tra morfodinamica e prodotti sedimentari

The concept of channel planform has traditionally guided sedimentologists and geomorphologists in classifying rivers and understanding the architecture of related sedimentary deposits. However, recent studies indicated that a planform-based approach overlooks the critical role of discharge variability in shaping river evolution and related deposits, prompting a reevaluation of classification methods and facies models for alluvial deposits. In this context, the introduction of inter-annual peak discharge variability led to the development of new models that better account for the often-overlooked variability of fluvial deposits. This study focuses on meandering river systems and adopts a quantitative and integrated approach to i) assess the impact of varying hydrological variability on river morphodynamics, and ii) explore how a high discharge variability affects point-bar deposition, producing features that challenge traditional sedimentological models. Analysis of a global dataset of meandering rivers with contrasting discharge variability reveals that their cutoff regime is primarily driven by overbank discharge variability. Research on point bars in the Powder River (Montana, USA) shows that, in a highly variable hydrological regime, major flood events play a key role in shaping bar geometries, and that significant inter-annual discharge variations result in bar deposits with a cryptic architectural pattern that strongly contrasts with well-preserved macroform architectures described in the literature. By linking morphological and depositional features to specific hydrological regimes, this research provides new insights into the processes shaping alluvial environments and offers an improved framework for interpreting past depositional conditions from the sedimentary record.