Reconstructing sediment distribution in meandering river deposits through a simplified numerical modelling approach, with applications to the Holocene deposits of the Venetian Plain (Italy)

Alessandro Sgarabotto, Elena Bellizia, Alvise Finotello, Andrea D'Alpaos, Stefano Lanzoni, Jacopo Boaga, Giorgio Cassiani, Massimiliano Ghinassi

Research output: Chapter in Book/Report/Conference proceedingChapter (peer-reviewed)peer-review

Abstract

Many present-day alluvial floodplains display traces of abandoned meandering channel belts developed during the past millennia (i.e. mid to late Holocene). Deposits of these ancient rivers represent preferential pathways for groundwater flows and related environmental issues, such as contaminant propagation or saltwater intrusion in coastal areas. However, since formative bankfull flows in such old and abandoned routes are hard to estimate, fossil meanders have not been commonly addressed by morphodynamic numerical models, and most of them have been investigated following classical sedimentological approaches based mainly on punctual data derived from sedimentary cores. This study aims at investigating the sediment distribution within different fossil bends on the southern Venetian Plain (NE Italy), and relating such distribution to numerically modelled bed shear stresses used herein as a proxy of sediment sorting patterns. For this purpose, formative flows in the studied palaeomeanders are first inferred from measured sediment grain size and estimates of bend widths. Then, shear stress distributions are computed along the studied palaeobends using a 2D linearized model. Model results are finally compared with conductivity distributions gauged directly in the field through electromagnetic induction investigations in the frequency domain. Our results suggest significant correlations between shear stress distributions and sediment sorting estimated from conductivity data. We deem that the integration between sedimentological reconstructions and state-of-the-art numerical modelling can provide a solid contribution to predicting the spatial distribution of sediment properties within ancient meandering channel belts, with relevant implications for the understanding of shallow aquifer dynamics and soil management.
Original languageEnglish
Title of host publicationMeandering Streamflows
Subtitle of host publicationPatterns and Processes across Landscapes and Scales
EditorsA. Finotello, P.R. Durkin, Z. Sylvester
PublisherGeological Society of London
Volume540
ISBN (Print)9781786205971
DOIs
Publication statusPublished - 1 Jun 2024

Publication series

NameGeological Society, London, Special Publications
PublisherGeological Society of London
Volume540
ISSN (Print)0305-8719
ISSN (Electronic)2041-4927

Bibliographical note

Funding
This work was supported by the project HYDROSEM (Progetti di Eccellenza CARIPARO 2017, Cassa di Risparmio di Padova e Rovigo): Fluvial and tidal meanders of the Venetian–Po plain: From hydrodynamics to stratigraphy project (PI. M. Ghinassi).

Data availability
The palaeomender data and the scripts developed in this study are available online at: https://doi.org/10.5281/zenodo.7545673

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