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Using historical data to examine the accuracy of sand transport field measurements in two nearshore marine settings

Using historical data to examine the accuracy of sand transport field measurements in two nearshore marine settings
Using historical data to examine the accuracy of sand transport field measurements in two nearshore marine settings

A re-Analysis of historical data from two field campaigns was undertaken to examine the accuracy of measurements of bed load (Qb) and total transport (Qtot) of sand in (1) a wave-dominant shoreface off western Newfoundland, Canada, and (2) a tide-dominant inlet of Venice Lagoon, Italy. Video tapes recorded within Sea Carousel (a benthic annular flume) deployed off Newfoundland were used to determine the transport of medium to coarse sand under controlled unidirectional flow conditions. These results were compared with Helley-Smith sand trap measurements of bed load of fine to medium sand in a tidal inlet of Venice Lagoon, Italy. Ripple migration rates in Sea Carousel were similar to those measured in rivers and shallow marine settings at similar flows. Accuracy of sand transport rate (derived from ripple motion) was assessed by comparison to fundamental methods presented in the literature. Some of the scatter in correlations with earlier methods was removed by using a nondimensional form of total sand transport and correlating it to excess stream power (i.e. above a traction threshold). Better correlations were found between immersed (bed load) transport rate and excess stream power by applying a published adjustment to the observations for flow depth and grain diameter. Total immersed (normalized) sand transport in Sea Carousel correlated with excess stream power in a fashion similar to results reported in the literature: = 0.288(ω-ωcr)1.65 kg m-1 s-1, where the immersed total sand transport is normalized with respect to flow depth and grain diameter. The sand trap data also followed this fit in part (2006 data only) but demonstrated greater scatter. The data herein thus fell in line with those reported in the literature from a wide variety of flume and field settings and for a wide variety of grain sizes. It is concluded that annular benthic flumes offer a reasonable and reliable method of assessing sand transport under controlled conditions of flow. The results from Sea Carousel and the Helley-Smith traps appear to follow the same relationships and so appear compatible. However, benthic sand traps show a higher degree of scatter, perhaps due to the uncertainties in how they sit on the seabed, and due to the arbitrary conditions of flow to which they are subjected when deployed.

Benthic flumes, bed-load transport, ripple migration, sand traps, unidirectional flows
0749-0208
1013-1028
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Kassem, H.
658efa7a-a02c-4b29-9d07-5d57e95a4b51
Townend, I.
f72e5186-cae8-41fd-8712-d5746f78328e
Umgiesser, G.
103345fe-ec36-4a0f-8a27-ade81e739b5a
Madricardo, F.
3edc7f8a-a682-4687-8da8-a40b82887ee2
Zaggia, L.
4e56f35f-00cb-49d0-a3ea-d02fdd0a3ae7
Manfe, G.
38c09606-12b4-444f-87a7-569e3eae2ece
Lorenzetti, G.
7ed89987-0e64-4ad6-af53-a086955fa598
Gomez, E.
c7195f7f-7e77-4e2b-9bac-ce130ecca141
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Kassem, H.
658efa7a-a02c-4b29-9d07-5d57e95a4b51
Townend, I.
f72e5186-cae8-41fd-8712-d5746f78328e
Umgiesser, G.
103345fe-ec36-4a0f-8a27-ade81e739b5a
Madricardo, F.
3edc7f8a-a682-4687-8da8-a40b82887ee2
Zaggia, L.
4e56f35f-00cb-49d0-a3ea-d02fdd0a3ae7
Manfe, G.
38c09606-12b4-444f-87a7-569e3eae2ece
Lorenzetti, G.
7ed89987-0e64-4ad6-af53-a086955fa598
Gomez, E.
c7195f7f-7e77-4e2b-9bac-ce130ecca141

Amos, C.L., Kassem, H., Townend, I., Umgiesser, G., Madricardo, F., Zaggia, L., Manfe, G., Lorenzetti, G. and Gomez, E. (2020) Using historical data to examine the accuracy of sand transport field measurements in two nearshore marine settings. Journal of Coastal Research, 36 (5), 1013-1028. (doi:10.2112/JCOASTRES-D-19-00134.1).

Record type: Article

Abstract

A re-Analysis of historical data from two field campaigns was undertaken to examine the accuracy of measurements of bed load (Qb) and total transport (Qtot) of sand in (1) a wave-dominant shoreface off western Newfoundland, Canada, and (2) a tide-dominant inlet of Venice Lagoon, Italy. Video tapes recorded within Sea Carousel (a benthic annular flume) deployed off Newfoundland were used to determine the transport of medium to coarse sand under controlled unidirectional flow conditions. These results were compared with Helley-Smith sand trap measurements of bed load of fine to medium sand in a tidal inlet of Venice Lagoon, Italy. Ripple migration rates in Sea Carousel were similar to those measured in rivers and shallow marine settings at similar flows. Accuracy of sand transport rate (derived from ripple motion) was assessed by comparison to fundamental methods presented in the literature. Some of the scatter in correlations with earlier methods was removed by using a nondimensional form of total sand transport and correlating it to excess stream power (i.e. above a traction threshold). Better correlations were found between immersed (bed load) transport rate and excess stream power by applying a published adjustment to the observations for flow depth and grain diameter. Total immersed (normalized) sand transport in Sea Carousel correlated with excess stream power in a fashion similar to results reported in the literature: = 0.288(ω-ωcr)1.65 kg m-1 s-1, where the immersed total sand transport is normalized with respect to flow depth and grain diameter. The sand trap data also followed this fit in part (2006 data only) but demonstrated greater scatter. The data herein thus fell in line with those reported in the literature from a wide variety of flume and field settings and for a wide variety of grain sizes. It is concluded that annular benthic flumes offer a reasonable and reliable method of assessing sand transport under controlled conditions of flow. The results from Sea Carousel and the Helley-Smith traps appear to follow the same relationships and so appear compatible. However, benthic sand traps show a higher degree of scatter, perhaps due to the uncertainties in how they sit on the seabed, and due to the arbitrary conditions of flow to which they are subjected when deployed.

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JCOASTRES-D-19-00134_R1 (2) - Accepted Manuscript
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Accepted/In Press date: 9 January 2020
Published date: 1 September 2020
Keywords: Benthic flumes, bed-load transport, ripple migration, sand traps, unidirectional flows

Identifiers

Local EPrints ID: 437371
URI: http://eprints.soton.ac.uk/id/eprint/437371
ISSN: 0749-0208
PURE UUID: 55ac5304-f89b-461f-8b03-4335a414afc9
ORCID for H. Kassem: ORCID iD orcid.org/0000-0002-5936-6037
ORCID for I. Townend: ORCID iD orcid.org/0000-0003-2101-3858

Catalogue record

Date deposited: 29 Jan 2020 17:30
Last modified: 18 Feb 2021 17:22

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