Preprints
https://doi.org/10.5194/hess-2021-231
https://doi.org/10.5194/hess-2021-231

  10 May 2021

10 May 2021

Review status: this preprint is currently under review for the journal HESS.

A conceptual model-based sediment connectivity assessment for patchy agricultural catchments

Pedro Batista1, Peter Fiener2, Simon Scheper1, and Christine Alewell1 Pedro Batista et al.
  • 1Department of Environmental Sciences, Universität Basel, Bernoullistrasse 30, 4056, Basel, Switzerland
  • 2Institute for Geography, Universität Augsburg, Alter Postweg 118, D – 86159, Augsburg, Germany

Abstract. The accelerated sediment supply from agricultural soils to riverine and lacustrine environments leads to negative off-site consequences. In particular, the sediment connectivity from agricultural land to surface waters is strongly affected by landscape patchiness and the linear structures that separate field parcels (e.g. roads, tracks, hedges, and grass-buffer-strips). Understanding the feedbacks between these structures and sediment transfer is therefore crucial for minimising off-site erosion impacts. Although soil erosion models can be used to understand lateral sediment transport patterns, model-based connectivity assessments are hindered by the uncertainty in model structures and input data. In particular, the representation of linear landscape features in numerical soil redistribution models is often compromised by the spatial resolution of the input data and the quality of the process descriptions. Here we adapted the WaTEM/SEDEM model using high resolution spatial data (2 m × 2 m) to analyse the sediment connectivity in a very patchy mesoscale catchment (73 km2) of the Swiss Plateau. Specifically, we used a global sensitivity analysis to explore model structural assumptions about how linear landscape features (dis)connect the sediment cascade. Furthermore, we compared model simulations of hillslope sediment yields from five sub-catchments to tributary sediment loads, which were calculated with long-term water discharge and suspended sediment measurements. Our results showed that roads were the main regulators of sediment connectivity in the catchment. In particular, the sensitivity analysis revealed that the assumptions about how the road network (dis)connects the sediment transfer from field-blocks to water courses had a much higher impact on modelled sediment yields than the uncertainty in model parameters. Moreover, model simulations showed a higher agreement with tributary sediment loads when the road network was assumed to directly connect sediments from hillslopes to water courses. Our results ultimately illustrate how a high-density road network combined with an effective drainage system increase sediment connectivity from hillslopes to surface waters in this representative catchment of the Swiss Plateau. This further highlights the importance of considering linear structures in soil erosion and sediment connectivity models.

Pedro Batista et al.

Status: open (until 17 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-231', Anonymous Referee #1, 18 Jun 2021 reply

Pedro Batista et al.

Pedro Batista et al.

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Short summary
In central Switzerland, agricultural catchments have a large number of small fields, which are separated by linear features, such as roads and grass-strips. When eroded sediments are transported out of fields by surface runoff, these features can (dis)connect the sediment dynamics. By use of measured data and a simulation model, we demonstrated how the road network facilitates sediment transport from fields to water courses in a typical Swiss agricultural catchment.