Temporal variation in suspended sediment transport: linking sediment sources and hydro‐meteorological drivers

Abstract

Suspended sediment concentrations (SSCs) in rivers are variable in time due to interacting soil erosion and sediment transport processes. While many hydro‐meteorological variables are correlated to SSCs, interpretation of these correlations in terms of driving processes requires in‐depth knowledge of the catchment. Detailed sediment source information is needed to establish the causal linkages between driving processes and variations in SSC. This study innovatively combined sediment fingerprinting with multivariate statistical analyses of hydro‐meteorological data to investigate how differential contributions of sediment sources control SSC in response to hydro‐meteorological variables during high‐flow events in rivers. Applied to the River Aire (UK), five sediment sources were classified: grassland topsoil in three lithological areas (limestone, millstone grit and coal measures), eroding riverbanks, and street dust. A total of 159 suspended sediment samples were collected during 14 high‐flow events (2015–2017). Results show substantial variation in sediment sources during high‐flow events. Limestone grassland and street dust, the dominant contributors to the suspended sediment, show temporal variations consistent with variations in total SSC, and are correlated with precipitation and discharge shortly prior and during high‐flow events (i.e. fast mobilization to and within river). Contrarily, contributions from millstone and coals grassland appear to be driven by antecedent hydro‐meteorological conditions (i.e. lag‐time between soil erosion and sediment delivery). Riverbank material is poorly correlated to hydro‐meteorological variables, possibly due to weak source discrimination or the infrequent nature of its delivery to the channel. Differences in source‐specific drivers and process interactions for sediment transport demonstrate the difficulty in generalizing sediment transport patterns and developing targeted suspended sediment management strategies. While more research is essential to address different uncertainties emerging from the approach, the study demonstrates how empirical data on sediment monitoring, fingerprinting, and hydro‐meteorology can be combined and analysed to better understand sediment connectivity and the factors controlling SSC. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Linking temporal scales of suspended sediment transport in rivers: towards improving transferability of prediction

“…Furthermore, during the drying period, more urban street dust could have been built up on the streets and then washed away during the event (Old et al 2003). This hypothesis is supported by findings from a sediment fingerprinting study applied to the SS samples collected during this event, which suggest that urban street dust and eroding grassland from the upper part of the catchment were dominant SS sources during the event (Vercruysse and Grabowski 2019). As the event progressed, component 1 became the dominant factor controlling SSC.…”

“…This change can be an indication that soils were increasingly saturated, causing saturation excess overland flow to become the dominant process for erosion and SS transport to and into the river, and is supported by an increase in SS contribution from eroding grassland less connected to the river due to scattered urban areas (Coal Measures area, Fig. 2) (Vercruysse and Grabowski 2019). Similarly, prolonged precipitation in November 2016 (Fig.…”

“…Despite the fact that urban street dust and other particles (e.g. from sewage treatment works) can make-up a significant part of the total SS load (Old et al 2003;Walling et al 2003a;Carter et al 2003;Vercruysse and Grabowski 2019), increased urbanization could have caused a decrease in SSCs due to a decrease in the connectivity of eroding land (i.e. fragmentation of unurbanized land) and riverbanks (i.e.…”

Hydro‐meteorological drivers influencing suspended sediment transport and yield in a semi‐arid mountainous basin

“…However, few studies delve into the relationship of transport processes with hydro-meteorological drivers, which are especially relevant in mountainous environments (e.g. Micheletti and Lane, 2016;Lane et al, 2017;Kumar et al, 2018;Rainato et al, 2018;Vercruysse and Grabowski, 2019). In these areas, the dynamics of suspended sediment are greatly influenced by the torrential nature of rainfall, snow cycles and high local atmospheric and topographic gradients.…”

How do modeling choices impact the representation of structural connectivity and the dynamics of suspended sediment fluxes in distributed soil erosion models?

“…In mesoscale catchments (<100 km²), which correspond to a relevant scale for decision makers, correct modeling of the hydrosedimentary responses requires a good understanding of the interactions between the spatiotemporal dynamics of the rainfall with the spatial distribution of the catchment geomorphological characteristics. Several studies have shown that the contributions of potential sediment sources can differ considerably from one flood event to another and at different times of sampling within a flood event (Brosinsky et al, 2014 ;Gourdin et al, 2014;Cooper et al, 2015;Gellis and Gorman Sanisaca, 2018;Vercruysse and Grabowski, 2019), particularly in Mediterranean and mountainous watersheds (Evrard et al, 2011 ;Navratil et al, 2012;Poulenard et al, 2012;Legout et al, 2013;Uber et al, 2019). Possible reasons for the observed variability of suspended sediment fluxes from one event to another include seasonal variations of the climatic drivers of soil erosion and sediment transport, variability of the spatial distribution of rainfall, land cover changes and human interventions (Vercruysse et al, 2017).…”