CGRG Bibliography of Canadian Geomorphology
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Author : Duffy, G.P.; and Hughes-Clarke, J.E.
Date : 2005.
Title : Bedform celerity and sediment transport on a banner bank, Saint John, New Brunswick.
Publication : Proceedings of the 12th Canadian Coastal Conference. Dartmouth, Nova Scotia. November 6-9, 2005.
Issue :
Page(s) :
Abstract
Six monthly repetitive multibeam surveys of Mispec Bay sand bank, the westernmost of a pair of banner banks associated with the headland Cape Spencer, Saint John, New Brunswick, enabled quantification of bedload transported in the form of migrating dunes. A new processing algorithm extracted migration vectors from the repeated surveys of the migrating asymmetric bedforms, which in turn allowed estimation of tidally-averaged bedload transport rate. In this way, the maximum spring-neap averaged bedload sediment transport rate over the sand bank is estimated to be 30 kg/m/tide (2.5E-7 m3/m/s). The banner bank tapers, depth-wise and horizontally, to an end close to Cape Spencer where bedforms are seen to be washed away by increasing bed shear stress, and increasing sediment transport rate, as they move into a zone of maximum net bedload transport around the headland. Comparison of bedform associated sediment transport with numerical predictions based on observed depth-averaged currents and grain size reveal that the observed sediment transport rate is between three – seven times less than predicted rates (depending on the predictor used). The observed value also compared favourably with a pre-existing sediment transport model of the field area. We hypothesise that, in general, the bedform-associated sediment transport rate is an accurate lower boundary to bedload transport rate. Sediment by-passing of bedforms is unmeasured in this research and could possibly cause under-estimation of bedload transport rates.
Bibliography of Canadian Geomorphology