Investigating the temporal dynamics of suspended sediment during flood events with 7Be and 210Pbxs measurements in a drained lowland catchment

Marion Le Gall,Irène Lefèvre,Olivier Cerdan,Olivier Evrard,Sébastien Salvador-Blanes,Anthony Foucher,J Patrick Laceby,Sophie Ayrault,Louis Manière

doi:10.1038/srep42099

Abstract

Soil erosion is recognized as one of the main processes of land degradation in agricultural areas. High suspended sediment loads, often generated from eroding agricultural landscapes, are known to degrade downstream environments. Accordingly, there is a need to understand soil erosion dynamics during flood events. Suspended sediment was therefore sampled in the river network and at tile drain outlets during five flood events in a lowland drained catchment in France. Source and sediment fallout radionuclide concentrations (7Be, 210Pbxs) were measured to quantify both the fraction of recently eroded particles transported during flood events and their residence time. Results indicate that the mean fraction of recently eroded sediment, estimated for the entire Louroux catchment, increased from 45 ± 20% to 80 ± 20% between December 2013 and February 2014, and from 65 ± 20% to 80 ± 20% in January 2016. These results demonstrate an initial flush of sediment previously accumulated in the river channel before the increasing supply of sediment recently eroded from the hillslopes during subsequent events. This research highlights the utility of coupling continuous river monitoring and fallout radionuclide measurements to increase our understanding of sediment dynamics and improve the management of soil and water resources in agricultural catchments.

Highlights

To cite this version: Marion Le Gall, O
Hydrosedimentary parameters were recorded at seven locations in the Louroux catchment, including five stations installed on the main streams draining to the Louroux pond located at the outlet: Conteraye (CO), Picarderie (PI), Beaulieu (BE) on the northern tributaries of the pond, and Masniers (MS) and Grand Bray (GB) stations on the southern tributary
On February, 13, 2014, the 3rd flood event was more intense (Fig. 2) and characterized by the highest water discharge recorded during the study period, with a maximal value of 1.1 m3 s−1 measured at the BE station, corresponding to a maximal export of sediment of 66 t

Summary

Introduction

To cite this version: Marion Le Gall, O. Results indicate that the mean fraction of recently eroded sediment, estimated for the entire Louroux catchment, increased from 45 ± 20% to 80 ± 20% between December 2013 and February 2014, and from 65 ± 20% to 80 ± 20% in January 2016. These results demonstrate an initial flush of sediment previously accumulated in the river channel before the increasing supply of sediment recently eroded from the hillslopes during subsequent events. This research highlights the utility of coupling continuous river monitoring and fallout radionuclide measurements to increase our understanding of sediment dynamics and improve the management of soil and water resources in agricultural catchments. These substances are mainly associated with the

Methods

Results

Conclusion