The use of short‐lived radionuclides to quantify transitional bed material transport in a regulated river

Salant, Nira L.; Renshaw, Carl E.; Magilligan, Francis J.; Kaste, James M.; Nislow, Keith H.; Heimsath, Arjun M.

doi:10.1002/esp.1414

Cited by 28 publications

(31 citation statements)

References 54 publications

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“…Because of the time required to analyse each sample, it was not feasible to analyse replicate samples at each site or to analyse multiple samples from different locations in the reach. Previous work (Salant et al, 2006b) has demonstrated that variations in 7 Be/ 210 Pb across a channel are generally small (<10%) in these watershed and the variation in 7 Be activity from replicate samples at the same location much less.…”

Section: Fallout Radionuclidesmentioning

confidence: 69%

“…More recently, Salant et al (2006b) . This collection schedule sought to capture the temporal changes in sediment radionuclide activity associated with varying seasonal flow regimes and short-term high discharge events.…”

Section: Fallout Radionuclidesmentioning

confidence: 99%

“…At the laboratory, the sediment was oven dried at 29°C and sieved to collect the fraction between 62Ð5 µm and 2 mm (Salant et al, 2006b). This fraction was packed into a plastic container and weighed in preparation for analysis.…”

Section: Fallout Radionuclidesmentioning

confidence: 99%

“…Previous studies (Bonniwell et al, 1999;Salant et al, 2006b) demonstrated that normalizing 7 Be activity by the activity of the longer-lived fallout nuclide 210 Pb (t 1/2 D 22 years) partially corrects for differential radionuclide sorption between samples due to compositional differences and differences in grain size distributions. Consequently, changes in the 7 Be/ 210 Pb activity ratio primarily reflect the extent of decay, not sorption or grain size effects.…”

Section: Fallout Radionuclidesmentioning

confidence: 99%

“…Sediment transported both in suspension and as bed load is referred to as mixed or 'transitional' load, often defined as having a fluid shear velocity to particle settling velocity ratio (u Ł /w s ) between 0Ð4 and 2Ð5 (Julien, 2002). In previous work, it has been shown that 7 Be activity of streambed sediment in New England traces the movement of transitional bed load (Salant et al, 2006b).…”

Section: Introductionmentioning

confidence: 99%

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Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities

Svendsen¹,

Renshaw²,

Nislow³

et al. 2008

Hydrological Processes

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Abstract:Tributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow-regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long-term discharge and cross-sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short-lived cosmogenic radioisotope 7 Be (half-life 53Ð4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the 7 Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited sediment residence time within the junction. Benthic communities also exhibit a strong seasonal variability. In the spring, neither the 7 Be activity of the sediment, nor benthic communities exhibit clear relationships with sample site location. In contrast, during the late summer the ratio of Ephemeroptera (mayflies)/Trichoptera (caddisflies) decreased significantly below tributary junctions. This decrease in benthic community ratio was driven by increases in caddisfly abundance and was strongly correlated with the presence of recently 7 Be tagged transitional bedload sediment. These observations are probably associated with the presence of coarse, stable, and unembedded substrate downstream of tributaries and the rapid turnover of sediment that may also be associated with a rapid flux in nutrients or seston. The results show that tributaries are impacting the flow-regulated mainstem and that these impacts are reflected in the benthic community structure and in the 7 Be activity of transitional bed load sediment. Moreover, the observed reduction in competence and capacity of the mainstem following flood control suggests that these spatial discontinuities may be a consequence of impoundment.

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Section: Fallout Radionuclidesmentioning

confidence: 69%

Section: Fallout Radionuclidesmentioning

confidence: 99%

Section: Fallout Radionuclidesmentioning

confidence: 99%

Section: Fallout Radionuclidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities

Svendsen¹,

Renshaw²,

Nislow³

et al. 2008

Hydrological Processes

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A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport

Gao

Puckett

2011

Earth Surf Processes Landf

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In this study, we proposed a new approach for linking event sediment sources to downstream sediment transport in a watershed in central New York. This approach is based on a new concept of spatial scale, sub-watershed area (SWA), defined as a sub-watershed within which all eroded soils are transported out without deposition during a hydrological event. Using (rainfall) event data collected between July and November, 2007 from several SWAs of the studied watershed, we developed an empirical equation that has one independent variable, mean SWA slope. This equation was then used to determine event-averaged unit soil erosion rate, Q S/A , (in kg/km 2 /hr) for all SWAs in the studied watershed and calculate event-averaged gross erosion E ea (in kg/hr). The event gross erosion E t (in kilograms) was subsequently computed as the product of E ea and the mean event duration, T (in hours) determined using event hydrographs at the outlet of the studied watershed. Next, we developed two linear sediment rating curves (SRCs) for small and big events based on the event data obtained at the watershed outlet. These SRCs, together with T, allowed us to determine event sediment yield SY e (in kilograms) for all events during the study period. By comparing E t with SY e , developing empirical equations (i) between E t and SY e and (ii) for event sediment delivery ratio, respectively, we revealed the event dynamic processes connecting sediment sources and downstream sediment transport. During small events, sediment transport in streams was at capacity and dominated by the deposition process, whereas during big events, it was below capacity and controlled by the erosion process. The key of applying this approach to other watersheds is establishing their empirical equations for Q S/A and appropriately determining their numbers of SWAs.

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Joint isotopic mass balance: a novel approach to quantifying channel bed to channel margins sediment transfer during storm events

Underwood

Renshaw

Dade

et al. 2015

Earth Surf Processes Landf

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The important role of floodplains and the broader riparian zone in providing temporary storage for a large fraction of the annual sediment load of rivers is well established, but this understanding is largely based on observations of the long-term average behavior of the catchment. Here we combine measurements of the fallout radionuclides 7 Be and 210 Pb and the stable isotopes of hydrogen in water to quantify fine sediment mobilization and storage in a stream and its channel margins during individual intermediate-sized storm events with recurrence intervals of a few months or less. We demonstrate this method using five storm events in a small (~15 km 2 ), undeveloped, gravel-bedded tributary of the Connecticut River (USA). We estimate that in each storm, the mass of sediment deposited onto the margins accounts for almost 90% of the sediment mobilized from the bed, with the remainder of the mobilized bed sediment transported downstream as suspended load. The result that the bed is a net source of sediment to the stream and the margins a net sink is robust, but estimates of the mass of material eroded from the bed and deposited on the margins are less certain. The source of sediment to the bed remains unclear as, consistent with earlier studies, we observe only limited deposition of sediment to the bed during the storm events. The suspended sediment is organic-rich and thus its source may be associated with in-channel organic decay between storm events. Understanding the coupled interactions between discharge magnitude and frequency and sediment resupply at the event time scale has important implications for stream restoration efforts seeking to connect the channel and the broader riparian zone, and for the development of accurate sediment budgets and predictions of sediment flux from a watershed.

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The use of short‐lived radionuclides to quantify transitional bed material transport in a regulated river

Cited by 28 publications

References 54 publications

Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities

Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities

A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport

Joint isotopic mass balance: a novel approach to quantifying channel bed to channel margins sediment transfer during storm events

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