Variation in suspended sediment yield across the UK – A failure of the concept and interpretation of the sediment delivery ratio

Worrall, F.; Burt, T.P.; Howden, N.J.K.; Hancock, G.R.

Abstract

The sediment delivery ratio (SDR) has been a common approach developed to understand change in sediment yield and flux through a catchment. In this study we propose that the underlying concept of the sediment delivery ratio is flawed for a number of reasons: its linear extrapolation is physically meaningless; there is no evidence of the magnitude of storage required by the SDR approach on annual to decadal timescales; and the SDR approach assumes suspended sediment transport is conservative yet it is known to undergo both loss and production in-channel. This study considers the sediment yield from 192 UK catchments from 1974 to 2010 for catchment areas between 4 and 9948 km2 and shows that linear extrapolation of the SDR approach overpredicts source terms and underpredicts fluxes for large catchments. The SDR approach hides a range of behaviours of suspended sediment flux within catchments with patterns of net deposition, net increase or no change all apparent in UK catchments. The approach proved to be self-correlated which meant that it can result in spurious correlations when compared to catchment area. The change in yield with catchment area can be just as well understood as a change in sediment supply from channels rather than as a change in delivery from hillslope sources. We propose that suspended sediment flux change with catchment area be modelled as a more physically-meaningful Gompertz function (step function) rather than using the traditional SDR approach.

Citation

Worrall, F., Burt, T., Howden, N., & Hancock, G. (2014). Variation in suspended sediment yield across the UK – A failure of the concept and interpretation of the sediment delivery ratio. Journal of Hydrology, 519(Part B), 1985-1996. https://doi.org/10.1016/j.jhydrol.2014.09.066

• Journal Article Type: Article
• Acceptance Date: Sep 24, 2014
• Publication Date: Nov 27, 2014
• Deposit Date: May 1, 2015
• Publicly Available Date: May 1, 2015
• Journal: Journal of Hydrology
• Print ISSN: 0022-1694
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 519
• Issue: Part B
• Pages: 1985-1996
• DOI: https://doi.org/10.1016/j.jhydrol.2014.09.066
• Keywords: Suspended sediment flux, SDR, Particulate organic matter, Rivers.
• Public URL: https://durham-repository.worktribe.com/output/1439450