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-of-the-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 ground-truthed 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.
|Journal||Journal of Applied Geophysics|
|Publication status||Published - Dec 2019|
Bibliographical noteFunding Information:
I wish to express gratitude to higher committee for education development in Iraq (HCED) who provided the funding to make this research possible. We also thank Kevin Voyce (Environment Agency of England and Wales) for providing previous data and scientific report. I would like to thank Prof. Nigel Cassidy and Dr. Jamie Pringle for training provided through the NERC geophysical skills course at Keele University. We are very grateful to the land owners at Helshaw Grange and Heathbrook Farm for permitting access to the River Tern field site.
© 2019 Elsevier B.V.
- Ground penetrating radar (GPR)
- Hydrogeological model
- Lowland meandering
- Permeability field
- Radar facies
ASJC Scopus subject areas