Assessing temporal variability and controlling factors of the sediment budget of a small agricultural catchment in Northern France (the Pommeroye)

Abstract

A high-frequency monitoring station was implemented at the outlet of the small catchment of the Pommeroye (0.54 km 2 ) in Northern France to study erosion by runoff and hydro-sedimentological responses to heavy rainfall events in the context of Quaternary loess deposits. The aim of this experimental work is to assess the temporal variability of sediment yield and to identify the factors controlling the hydro-sedimentary response. To achieve this goal, statistical and hydro-sedimentary dynamic analyses were performed. During two years of monitoring (April 2016–April 2018), 48 flood events were recorded. The specific sediment yield (SSY) is highly variable and was evaluated to 29.4–70 t km -2 yr −1 which is conventional for the study region. Most of the sediment yield was produced in winter (55%) and autumn (42%). Only 3% of SSY were produced during spring and summer periods. According to our results, only 6% of the erosive events are responsible for the transport of more than 40% of the sediment flux recorded at the outlet. This underlines the temporal variability of the hydro-sedimentary production in small agricultural catchments for which most of the hydro-sedimentary flux is produced during a limited number of events. The results of statistical analyses show that the total amount of rainfall and the duration of a rainfall episode are the main controlling factors on the hydro-sedimentary response. Our results also suggest that the rainfall kinetic energy better reflects the sediment detachment, and that the 48 h-antecedent rainfall is not linked to the hydro-sedimentary response.

Magnetic Fingerprinting of Fluvial Suspended Particles in the Context of Soil Erosion: Example of the Canche River Watershed (Northern France)

“…This study aims to develop a straightforward magnetic proxy parameter to trace the erosion of topsoils at the scale of a catchment in order to quantitatively model spatiotemporal sediment flux. The presented results are akin to the studies of Patault (2018), , and Patault, Alary, Franke, Gauthier, & Abriak (2019) in which other, more routinely used sediment tracer parameters (such as grain size and geochemical elements) were used. We take advantage of the fact that soil particles have been found to carry a distinct magnetic mineral signature (e.g., Maher, 1998Maher, , 2007 compared to the average bedload of rivers.…”