Geophysical Investigations of a Paleochannel in the Alluvial Plain of the River Seine, France

The integrated water resources management of the La Bassée alluvial plain is a key point of the current PIREN Seine program (2015-2019), dedicated to the study of the Seine River basin. The understanding of the processes driving the rearrangement of the river network through time is an important issue linked to the hydrogeological and hydrological properties of the basin. This study focuses on a zone located 2 km west of Nogent-sur-Seine (France) in the southern part of the Seine basin. The purpose of this study is to delineate the paleo-channel geometry using geophysical methods on an area of approximately 1 ha. The meander lateral extension has been delineated by electrical conductivity measurements using electromagnetic induction system (EMI). The depth extension of the clayey layer has been constrained and estimated by means of electrical resistivity tomography (ERT) on a 400 m reference profile where a series of auger soundings exist. Both data types have been inverted and interpreted in order to estimate the thickness of the clay layer formed by the paleo-Seine riverbed.