Modelling a century of soil redistribution processes and carbon delivery from small watersheds using a multi-class sediment transport model

Florian Wilken,Kristof Van Oost,Peter Fiener

doi:10.5194/esurf-5-113-2017

Abstract

Abstract. Over the last few decades, soil erosion and carbon redistribution modelling has received a lot of attention due to large uncertainties and conflicting results. For a physically based representation of event dynamics, coupled soil and carbon erosion models have been developed. However, there is a lack of research utilizing models which physically represent preferential erosion and transport of different carbon fractions (i.e. mineral bound carbon, carbon encapsulated by aggregates and particulate organic carbon). Furthermore, most of the models that have a high temporal resolution are applied to relatively short time series (< 10 yr−1), which might not cover the episodic nature of soil erosion. We applied the event-based multi-class sediment transport (MCST) model to a 100-year time series of rainfall observation. The study area was a small agricultural catchment (3 ha) located in the Belgium loess belt about 15 km southwest of Leuven, with a rolling topography of slopes up to 14 %. Our modelling analysis indicates (i) that interrill erosion is a selective process which entrains primary particles, while (ii) rill erosion is non-selective and entrains aggregates, (iii) that particulate organic matter is predominantly encapsulated in aggregates, and (iv) that the export enrichment in carbon is highest during events dominated by interrill erosion and decreases with event size.

Highlights

Numerical models of soil detachment, transport, and deposition are important tools for improving our understanding of soil systems and the linkages between the terrestrial and aquatic ecosystems
A detailed model description can be found in Van Oost et al (2004) and Fiener et al (2008); here we focus on its main features and modifications made in order to continuously simulate long-term soil and carbon erosion
The model predictions were only consistent with field observations when (i) interrill erosion was simulated as a process that entrains primary particles, (ii) rill erosion is unselective, and (iii) low-density particulate organic matter (POM) is encapsulated within soil aggregates and cannot be entrained by interrill erosion

Summary

Introduction

Numerical models of soil detachment, transport, and deposition are important tools for improving our understanding of soil systems and the linkages between the terrestrial and aquatic ecosystems. A wide range of erosion models are available Conceptual models, such as the RUSLE (Römkens et al, 1997), focus largely on the prediction of long-term sediment production under various environmental and management conditions. Physically oriented models have been developed to simulate the routing of soil over complex topographies, taking hydrological and sediment-sorting processes into consideration (e.g. WEPP: Nearing et al, 1989; EROSION-3D: Schmidt, 1991; LISEM: De Roo et al, 1996). These models operate over relatively short timescales, typically one to several events, and are concerned with modelling the detachment and movement of mineral particles. Over the last few decades, they have been instrumental in improving our understanding of erosion processes and currently serve as tools for landscape management

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