Identification of floodplain and riverbed sediment heterogeneity in a meandering UK lowland stream by ground penetrating radar

Rebwar Dara, Nicholas Kettridge, Michael O. Rivett, Stefan Krause, David Gomez-Ortiz

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Complex spatial heterogeneity in riverbed and floodplain sediments control the spatio-temporal exchange of groundwater and surface water in the hyporheic zone, inducing hot spots of microbial activity and biogeochemical cycling. However, the characterization of hyporheic exchange dynamics has thus far failed to adequately account for the complex subsurface heterogeneity of river bed sediments in a spatial explicitly manner, in particular for highly complex lowland river bed sediments. Here we demonstrate the ability of ground penetrating radar (GPR) to efficiently map floodplain and river bed sediment structures within a lowland meandering river. The aim of this study was to delineate the type and spatial extent of complex, texturally heterogeneous facies of high and low conductive streambed materials. GPR surveys in this study involved not only state-ofthe-art terrestrial applications but also an aquatic survey conducted from a floating rig. The surveys revealed substantial sub-surface heterogeneity of depositional materials in the streambed and riparian zone. Eight characteristic radar facies were identified through the floodplain and groundtruthed against core samples and exposures of bank deposits. The majority of GPR profiles were dominated by trough-shaped depositional elements with erosional, curved, concave upward bounding surfaces, indicative of abandoned and chute stream channel structures. The identified abandoned channel structure was found to extend into the riverbed and to be filled by suspension fall-out fine-grained deposits (mud with organic matter and interbedded clay as indicated by observed signal attenuations). GPR proved to be a successful method to identify the spatial patterns of low conductivity peat and clay structures in the streambed and riparian zone of the investigated meander bend, highlighting its potential for larger scale analysis of these structures that have shown to control the exchange flow patterns between groundwater and surface water in lowland rivers.
Original languageEnglish
Article number103863
Number of pages15
JournalJournal of Applied Geophysics
Volume171
Early online date17 Oct 2019
DOIs
Publication statusPublished - 31 Dec 2019

Keywords

  • ground penetrating radar
  • lowland meandering
  • ground truth
  • permeability field
  • radar facies
  • hydrogeological model

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