Geophysical and Sedimentological Investigations Integrate Remote-Sensing Data to Depict Geometry of Fluvial Sedimentary Bodies: An Example from Holocene Point-Bar Deposits of the Venetian Plain (Italy)

Giorgio Cassiani,Alessandro Fontana,Andrea D’Alpaos,Elena Bellizia,Massimiliano Ghinassi,Jacopo Boaga

doi:10.3390/rs12162568

Abstract

Over the past few millennia, meandering fluvial channels drained coastal landscapes accumulating sedimentary successions that today are permeable pathways. Propagation of pollutants, agricultural exploitation and sand liquefaction are the main processes of environmental interest affecting these sedimentary bodies. The characterization of these bodies is thus of utmost general interest. In this study, we particularly highlight the contribution of noninvasive (remote and ground-based) investigation techniques, and the case study focuses on a late Holocene meander bend of the southern Venetian Plain (Northeast Italy). Electromagnetic induction (EMI) investigations, conducted with great care in terms of sonde stability and positioning, allowed the reconstruction of the electrical conductivity 3D structure of the shallow subsurface, revealing that the paleochannel ranges in depth between 0.8 and 5.4 m, and defines an almost 260 m-wide point bar. The electrical conductivity maps derived from EMI at different depths define an arcuate morphology indicating that bar accretion started from an already sinuous channel. Sedimentary cores ensure local ground-truth and help define the evolution of the channel bend. This paper shows that the combination of well-conceived and carefully performed inverted geophysical surveys, remote sensing and direct investigations provides evidence of the evolution of recent shallow sedimentary structures with unprecedented detail.

Highlights

Modern coastal landscapes are widely shaped by meandering fluvial, fluvio-tidal and tidal channels, which over the late Holocene accumulated complex and extensive sedimentary bodies
The study area is located at the boundary between the Venetian Plain and the Po River Delta, in a zone which is characterized by a dense network of alluvial ridges and sand bodies that are the geomorphological products of the complex interaction between the Adige and Po Rivers during the late Holocene (Figure 1a) [25,54]
This paper presents a successful integrated approach to analyze the distribution of sedimentary facies ooff aappaalleeoommeeaannddeerrininththeeSSoouuththerenrnVeVneenteiatinanPlPailnai,nN, oNrothrethaestaesrtnerIntaIltya.lTy.hTehaepparpoparcohaicshbiassbeadsoedn aoncoma bicnoamtiobninoaftiroenmootef -sreenmsiontge-(saeenrisailnagnd(aseartieallitea)nddatas,agtelolipthe)ysidcatlai,nvgeestoipgahtyiosincsal(eliencvtreosmtigaagtnieotnics s(eulrevcetryosm) aangdnedtiircescut rsvedeyims)eanntdardyicroecrtinsge.dimentary coring

Summary

Introduction

Modern coastal landscapes are widely shaped by meandering fluvial, fluvio-tidal and tidal channels, which over the late Holocene accumulated complex and extensive sedimentary bodies. These bodies today often define subsoil permeable systems [1] that are often exploited as water reserves for agricultural, industrial and civil uses [2], and are extremely sensitive to saltwater intrusion [3,4] as well as to contamination [5,6]. In locating the position of these surficial bodies, and possibly distinguishing between tide- and fluvial-generated meanders [22], remote sensing alone is not capable of providing information at depth, remaining essentially a qualitative tool for the characterization of 3D geological structures. Regardless, a 3D reconstruction is still difficult with these means only [26], if not as a result of interpolation of scarce scattered data

Objectives

Methods

Findings

Conclusion