Abstract
A high-frequency monitoring station was implemented at the outlet of the small catchment of the Pommeroye (0.54 km2) 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.
Highlights
In the North-Western European loess plateau and in particular in the North of the Paris Basin, erosion of agricultural land is a serious environmental issue (Evrard et al, 2007; Delmas et al, 2012)
This study reports on a detailed record of the hydro-sedimentary response to rainfall events in the small agricultural catchment of the Pommeroye in Northern France
The research was based on a high-frequency (6 min) monitoring of rainfall, runoff, and suspended sediment transport over a period of two hydrological years (April 2016eApril 2018), in a challenging context where the studied catchment is a lacking a perennial hydrographic network
Summary
In the North-Western European loess plateau and in particular in the North of the Paris Basin, erosion of agricultural land is a serious environmental issue (Evrard et al, 2007; Delmas et al, 2012). Classical survey methods to evaluate sediment production on small catchments are aerial photography (Nachtergaele and Poesen, 1999; Marzolff et al, 2011), terrestrial photography (Frankl et al, 2011), terrestrial laser scanning (Li et al, 2017), airborne laser scanning (Goodwin et al, 2017), or direct measurements of channel volumes (Valcarcel et al, 2003). These methodologies are not suitable for quantifying the sediment yield at the catchment scale (Vandaele and Poesen, 1995). Catchment monitoring was successfully used by several authors (Nadal-Romero et al, 2008; Estrany et al, 2009; Nu-Fang et al, 2011; Gimenez et al, 2012; Sherriff et al, 2015) to quantify erosion processes in
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