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dc.contributor.author
Amos, Carl L.
dc.contributor.author
Droppo, Ian G
dc.contributor.author
Gomez, Eduardo Alberto
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dc.contributor.author
Murphy, Tom P.
dc.date.available
2017-12-04T16:42:37Z
dc.date.issued
2003-02
dc.identifier.citation
Amos, Carl L.; Droppo, Ian G; Gomez, Eduardo Alberto; Murphy, Tom P.; The stability of a remediated bed in Hamilton Harbour, Lake Ontario, Canada; Wiley Blackwell Publishing, Inc; Sedimentology; 50; 1; 2-2003; 149-168
dc.identifier.issn
0037-0746
dc.identifier.uri
http://hdl.handle.net/11336/29554
dc.description.abstract
In situ measurements of lakebed sediment erodibility were made on three sites in Hamilton Harbour, Lake Ontario, using the benthic flume Sea Carousel. Three methods of estimating the surface erosion threshold (τ c(0)) from a Carousel time series were evaluated: the first method fits measures of bed strength to eroded depth (the failure envelope) and evaluates threshold as the surface intercept; the second method regresses mean erosion rate (E m) with bed shear stress and solves for the floc erosion rate (E f) to derive the threshold for E m = E f = 1 × 10 -5 kg m -2 s -1; the third method extrapolates a regression of suspended sediment concentration (S) and fluid transmitted bed shear stress (τ o) to ambient concentrations. The first field site was undisturbed (C) and acted as a control; the second (W) was disturbed through ploughing and water injection as part of lakebed treatment, whereas the third site (OIP) was disturbed and injected with an oxidant used for remediation of contaminated sediment. The main objectives of this study were: (1) to evaluate the three different methods of deriving erosion threshold; (2) to compare the physical behaviour of lacustrine sediments with their marine estuarine counterparts; and (3) to examine the effects of ploughing and chemical treatment of contaminated sediment on bed stability. Five deployments of Sea Carousel were carried out at the control site. Mean erosion thresholds for the three methods were: τ c(0) = 0·5 (±0·06), 0·27 (±0·01) and 0·34 (±0·03) Pa respectively. Method 1 overpredicted bed strength as it was insensitive to effects in the surface 1-2 mm, and the fit of the failure envelope was also highly subjective. Method 2 exhibited a wide scatter in the data (low correlation coefficients), and definition of the baseline erosion rate (E f) is largely arbitrary in the literature. Method 3 yielded stable (high correlation coefficients), reproducible and objective results and is thus recommended for evaluation of the erosion threshold. The results of this method correlated well with sediment bulk density and followed the same trend as marine counterparts from widely varying sites. Mass settling rates, expressed as a decay constant, k, of S(t), were strongly related to the maximum turbidity at the onset of settling (S max) and were also in continuity with marine counterparts. Thus, it appears that differences in salinity had little effect on mass settling rates in the examples presented, and that biological activity dominated any effects normally attributable to changes in salinity. Bedload transport of eroded aggregates (2-4 mm in diameter) took place by rolling below a mean tangential flow velocity (U y) of 0·32 ms -1 and by saltation at higher velocities. Mass transport as bedload was a maximum at U y = 0·4 ms -1, although bedload never exceeded 1% of the suspended load. The proportion of material moving as bedload was greatest at the onset of erosion but decreased as flow competence increased. Given the low bulk density and strength of the lakebed sediment, the presence of a bedload component is notable. Bedload transport over eroding cohesive substrates should be greater in estuaries, where both sediment density and strength are usually higher. Significant differences between the ploughed and control sites were apparent in both the erosion rate and the friction coefficient (∅), and suggest that bed recovery after disruption is rapid (< 24 h). τ c(0) increased linearly with time after ploughing and recovered to the control mean value within 3 days. The friction coefficient was reduced to zero by ploughing (diagnostic of fluidization), but increased linearly with time, regaining control values within 6 days. No long-term reduction in bed strength due to remediation was apparent.
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
Wiley Blackwell Publishing, Inc
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dc.rights
info:eu-repo/semantics/openAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
Benthic Flume
dc.subject
Deposition Threshold
dc.subject
Lacustrine Sediments
dc.subject
Mass Settling Rates
dc.subject.classification
Meteorología y Ciencias Atmosféricas
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dc.subject.classification
Ciencias de la Tierra y relacionadas con el Medio Ambiente
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dc.subject.classification
CIENCIAS NATURALES Y EXACTAS
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dc.title
The stability of a remediated bed in Hamilton Harbour, Lake Ontario, Canada
dc.type
info:eu-repo/semantics/article
dc.type
info:ar-repo/semantics/artículo
dc.type
info:eu-repo/semantics/publishedVersion
dc.date.updated
2017-11-30T17:03:54Z
dc.journal.volume
50
dc.journal.number
1
dc.journal.pagination
149-168
dc.journal.pais
Reino Unido
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dc.journal.ciudad
Londres
dc.description.fil
Fil: Amos, Carl L.. Southampton Oceanography Centre; Reino Unido
dc.description.fil
Fil: Droppo, Ian G. National Water Research Institute; Canadá
dc.description.fil
Fil: Gomez, Eduardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina
dc.description.fil
Fil: Murphy, Tom P.. National Water Research Institute; Canadá
dc.journal.title
Sedimentology
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dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3091.2003.00542.x/full
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/doi/http://dx.doi.org/10.1046/j.1365-3091.2003.00542.x
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