Sediment Yields and Sediment Budgets

Abstract

This article aims to provide a broad overview of the topic across spatial scales ranging from small catchments to a global perspective. The two elements of the topic (i.e. sediment yields and sediment budgets) are closely related, with the former treating the catchment or river basin essentially as a black box. The latter looks into the black box to consider the importance of sediment sources, and sediment mobilization, transport, and storage in influencing sediment yields. Attention is directed firstly to the key features of sediment yields, by considering fluvial sediment loads, measurement techniques, the magnitude of sediment yields, and associated global and regional patterns and key controlling factors. Information on spatial variability of sediment yields is complemented by consideration of medium‐ and longer‐term temporal variability in response to natural factors and, more importantly, the impact of anthropogenic activity and climate change. Sediment budgets are introduced by considering the important role of internal storage in influencing the sediment yield from a catchment or river basin and the concepts of the sediment delivery ratio and connectivity, as well the need to take account of the sediment sources involved. Examples of sediment budgets are provided and available techniques for assembling the information necessary to establish a sediment budget are reviewed.

Effect of historical land‐use change on soil erosion in a Mediterranean catchment by integrating 137Cs measurements and WaTEM/SEDEM model

“…Alatorre et al (2012) demonstrated that the use of catchment sediment yield data alone is not enough to allow for a robust calibration and despite it could provide reasonable predictions of sediment yield, it could offer no insight into the spatial patterns of soil erosion. Overall, similar concerns were raised by Walling (2019) who stated that by focusing on the amount of sediment exported, values of sediment yield effectively view the catchment as a black-box and no account is taken of the processes or where the sediment originates. Thus, our grid calibration enables to identify the areas that generate most sediment.…”

A reconnaissance survey of channel bank particulate phosphorus concentrations, controls and estimated contributions to riverine loads across England

“…Up to 90% of the TP load of some Danish rivers has been reported to originate from bank erosion (Kronvang et al, 1997 ). Similarly, Walling, Webb, et al ( 2008 ) and Walling, Collins, et al ( 2008 ) reported that up to 43% of the PP flux in 12 agricultural sub‐catchments in the UK originated from channel bank or subsurface source erosion. On the basis of existing studies reported in the international literature, eroding channel banks have been estimated to account typically for between 10% (Sekely et al, 2002 ) and 40% (Howe et al, 2011 ) of the total P load in any individual river catchment, although this can be upwards of 90% (Kronvang et al, 1997 ).…”

“…Within most catchments in temperate landscapes, the erosion of agricultural topsoils is the dominant source of fine‐grained sediment, and therefore of the PP, delivered to freshwaters. However, eroding channel banks can also contribute a large proportion of riverine sediment load and therefore potentially of the total PP load (Collins et al, 1997 ; Collins et al, 2012 ; De Rose et al, 2005 ; Evans, 2019 ; Evans et al, 2003 ; Imeson et al, 1984 ; Kronvang et al, 2013 ; Laubel et al, 2003 ; Lu et al, 2015 ; Miller et al, 2014 ; Neal & Andera, 2015 ; Owens et al, 2000 ; Rode et al, 2018 ; Walling et al, 1999 ; Walling & Collins, 2005 ; Walling, Collins, et al, 2008 ; Walling, Webb, et al, 2008 ; Wilkinson et al, 2005 ; Zaimes et al, 2008a ). For example, 7%–10% of the total P load of the Blue Earth River in Minnesota, USA, originated from channel bank erosion (Sekely et al, 2002 ) compared with up to 56% of the P load in rivers in central Illinois, USA (Roseboom, 1987 ).…”

“…More recent work has employed the key physical factors controlling channel bank erosion processes, including upstream area, channel confinement and sinuosity to both evaluate and update the original index (Janes et al, 2017 ; Zhang et al, 2014 ). By relating these composite indices to mapped channel bank positions in different time periods or estimated bank erosion yields produced using sediment source apportionment procedures and either measured (e.g., Walling & Webb, 1987 ; Walling, Webb, et al, 2008 ) or extrapolated (Cooper et al, 2006 ) catchment suspended sediment yields, bank erosion rates in river catchments can be estimated (Janes et al, 2017 ). By combining the updated version of the Collins and Anthony ( 2008 ) bank erosion index with the typical TP concentrations of channel banks, Zhang et al ( 2014 ) generated estimates of the channel bank‐derived proportions of riverine TP loads for all inland Water Framework Directive surface waterbodies (WFD waterbodies hereafter) across England and Wales.…”

“…Mapped strategic scale TP concentration data exist for topsoils in the UK and these have been used as proxy values for the TP contents of channel banks in some previous research (Deuthmann et al, 2009 ). Alongside the topsoil data, limited published TP content data is available as a by‐product of sediment source apportionment work where source‐specific geochemistry analysis included measurement of TP content (e.g., Walling, Webb, et al, 2008 ). These and additional data (Collins pers.…”