Benthic control upon the morphology of transported fine sediments in a low‐gradient stream

Fox, James F.; Ford, William I.; Strom, Kyle; Villarini, Gabriele; Meehan, Michelle

doi:10.1002/hyp.9928

Cited by 23 publications

(22 citation statements)

References 52 publications

(84 reference statements)

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“…Flocs are present in nearly every type of waterbody and flow that contains fine sediment with some amount of clay (Droppo & Ongley, ; Fox et al, ; Hill et al, ; Mikkelsen et al, ). Yet it is rare for changes in floc size and their impact on settling velocity to be accounted for in larger hydrodynamic and sediment transport models such as those used to predict water quality or morphologic change (Caldwell & Edmonds, ; Sanford, ; Xia & Jiang, ); with the exception to this norm being the study of Sherwood et al ().…”

Section: Discussionmentioning

confidence: 99%

A Shear‐Limited Flocculation Model for Dynamically Predicting Average Floc Size

2018

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The accuracy of sediment transport models depends on the selection of an appropriate sediment settling velocity. In general, settling velocity is primarily dependent on the size and density of the particles in the water column. Determining this value for mud suspensions can be difficult because the small cohesive particles can aggregate to form flocs whose sizes and density are a function of hydrodynamic and physiochemical conditions of the suspension. Here we present a new model for predicting floc size as a function of hydrodynamic conditions and inherited floc sizes. The new approach is a simple modification to the existing Winterwerp (1998, https://doi.org/10.1080/00221689809498621) floc size model. The modification is significant in that it yields predictions that are more inline with observations and theory regarding the upper limit on floc size. The modification we propose is to make the ratio of the applied stress on a floc, over the strength of the floc, a function of the floc size relative to the Kolmogorov microscale. The outcome of the modification is that flocs are not allowed to surpass the Kolmogorov microscale in size and that calibrated aggregation and breakup coefficients obtained at one suspended sediment concentration can be used to predict floc size under other concentrations without recalibration. In this paper, we present the motivation for the modification, the functionality of the modification, and we make a comparison of the updated model with laboratory and field data. Overall, the modification shows promise as a tool for improved prediction of cohesive mud transport.Plain Language Summary Rivers deliver muddy sediment to coastal regions. Upon arrival, mud can deposit in or move through the rivers, bays, marshes, and deltas of the region. Forecasting where the mud goes when it arrives is important for society. For example, accurately forecasting the movement and deposition of mud is important for predicting and evaluating the effectiveness of river diversion projects aimed at using sediment deposits to build deltaic landscape. Yet predicting the movement of mud is difficult because small mud particles tend to clump together and form aggregates, or flocs, which grow or shrink depending on turbulence levels and other water column properties. When these flocs grow or shrink in size, the rate at which they settle out of the water changes, creating dynamic settling speeds that are difficult to model. Here we present a new method for predicting floc size as a function of hydrodynamic conditions and inherited floc size. The new model is a simple modification to an existing method that yields predictions more inline with observations and theory. The model also performs better outside of the conditions for which it was calibrated than the previous method.

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Section: Discussionmentioning

confidence: 99%

A Shear‐Limited Flocculation Model for Dynamically Predicting Average Floc Size

2018

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“…Currently, R qual assumes high or low quality depending on substrate type; however, bio-stabilization of recalcitrant SOM has been recognized to improve its bioavailabilty (Lane et al, 2013). Future improvements to R qual are needed to incorporate these recent advancements in sediment aggregate composition in which the surface area of transported sediment can be higher during summer months due to algal and bacterial excretion of exopolymeric substances that result in aggregation of recalcitrant SOM particles (Fox et al, 2013). Furthermore, this current study assumes that the stable isotopic signature of algal FPOC is conservative over the 5-year study.…”

Section: Ability Of δ 13 C and R Qual To Reflect Fpoc Qualitymentioning

confidence: 99%

Impact of extreme hydrologic disturbance upon the sediment carbon quality in agriculturally impacted temperate streams

2014

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The impact of extreme hydrologic disturbances on the quality of fine particulate organic carbon (FPOC) associated with sediments in low-gradient, agriculturally impacted streams remains poorly understood despite the significance of the FPOC pool to benthic food webs, organic matter budgets and nutrient cycles. We estimated immediate and long-term impacts of an extreme flow disturbance on FPOC quality using a 5-year dataset of the stable carbon isotopic signature and a new metric for carbon quality. Results of the study show that the stable isotopic signature of sediment carbon is significantly enriched in the year following the extreme event, which reflects the streams response to accrual of degraded soil carbon. Further, our FPOC metric was found to be inversely proportional to the isotopic signature, suggesting an immediate shift of the benthic ecosystem to lower quality carbon that is retained for more than 1 year before recovering to the pre-disturbance state. Following recovery, results show that the benthic ecosystem exports FPOC with quality that oscillates seasonally -the lowest quality observed in late spring and the highest quality in late fall. Although studies have addressed the response of high-quality algal biomass to fluvial shearing, this study is the first to assess the response of high-quality FPOC to an extreme hydrologic disturbance characterized by sediment deposition in an agriculturally impacted stream.

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“…Traps that were removed, sieved, and refilled with clean gravel more frequently (i.e., the traps installed for shorter time periods) collected more fine sediment than traps, which were resident for several months. This may be associated with renewed connectivity of substrates associated with vertical hydrological pathways, an increase in initial storage capacity and the removal of benthic algae (Potamogeton spp and Cladophora spp ) that may inhibit sediment accumulation and ingress (Bo et al, ; Fox, Ford, Strom, Villarini, & Meehan, ; Papanicolaou, Diplas, Evaggelopoulos, & Fotopoulos, ). Hydraulic conductivity, and associated sediment transport, is also strongly linked to the time since the last streambed disturbance (Boano et al, ; Stewardson et al, ) and, as such, longer trap residence times are able to capture this natural decay in infiltration rates that may be a function of bed turnover (or in this instance trap removal).…”

Section: Discussionmentioning

confidence: 99%

The complexities of measuring fine sediment accumulation within gravel‐bed rivers

Harper

Foster

Lawler

et al. 2017

River Research & Apps

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Fine sediment storage within gravel beds is a key component of catchment sediment budgets and affects the health of benthic and hyporheic habitats. Here, we assess the performance of two substrate infiltration traps for the characterization of fine sediment (<2 mm) accumulation. One design, the vertically extending sediment trap, permits both lateral and vertical exchange in the sediment column, whereas the second type, a more traditional fixed-area sediment trap with impermeable side walls, permits only vertical exchange. Traps were deployed at three sites on the River Tame, Birmingham (UK), over varying installation periods (14-401 days). Results indicate that the facilitation of multiple pathways of exchange within the vertically extending sediment traps (vertical and lateral) resulted in a significantly greater amount of fine sediment being accumulated than in adjacent fixed-area sediment traps. This suggests that lateral transport is an important component contributing to fine sediment accumulation. However, there are notable and inherent problems associated with the use of different types of sediment trap and in the way the data should be presented and interpreted. This paper discusses the practical implications of the study findings and reflects on the complexities of undertaking accurate sediment deposition measurements in the field. Excessive quantities of fine sediment stored within river networks is an important driver of aquatic habitat degradation (Descloux, Datry, & Marmonier, 2013;Packman & MacKay, 2003;Phillips & Walling, 1999), which poses a serious long-term threat to in-stream ecosystems (Négrel et al., 2014;Prosser et al., 2001). Fine-grained sediment affects the entire aquatic ecosystem from reducing primary production (Jones, Duerdoth, Collins, Naden, & Sear, 2014;Wagenhoff, Lange, Townsend, & Matthaei, 2013) and altering macroinvertebrate diversity via enhanced drift and direct burial (Larsen & Ormerod, 2010;Wood, Toone, Greenwood, & Armitage, 2005), through to reducing habitat heterogeneity and limiting oxygen exchange within interstitial pore spaces (Huston & Fox, 2015;Owens et al., 2005). Understanding fine --------------------------------------------------------------------------------------------------------------------------------This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Benthic control upon the morphology of transported fine sediments in a low‐gradient stream

Cited by 23 publications

References 52 publications

A Shear‐Limited Flocculation Model for Dynamically Predicting Average Floc Size

A Shear‐Limited Flocculation Model for Dynamically Predicting Average Floc Size

Impact of extreme hydrologic disturbance upon the sediment carbon quality in agriculturally impacted temperate streams

The complexities of measuring fine sediment accumulation within gravel‐bed rivers

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