CONICET | Buscador de Institutos y Recursos Humanos

A re-analysis of historical data from two field campaigns was undertaken to examine the accuracy of measurements ofbed 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 controlledunidirectional flow conditions. These results were compared with Helley-Smith sand trap measurements of bed load offine to medium sand in a tidal inlet of Venice Lagoon, Italy. Ripple migration rates in Sea Carousel were similar to thosemeasured in rivers and shallow marine settings at similar flows. Accuracy of sand transport rate (derived from ripplemotion) was assessed by comparison to fundamental methods presented in the literature. Some of the scatter incorrelations with earlier methods was removed by using a nondimensional form of total sand transport and correlating itto 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 graindiameter. Total immersed (normalized) sand transport (Q00tot) in Sea Carousel correlated with excess stream power in afashion similar to results reported in the literature: Q00tot¼ 0.288(x ? xcr)1.65 kg m1 s1, where the immersed total sandtransport 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 literaturefrom a wide variety of flume and field settings and for a wide variety of grain sizes. It is concluded that annular benthicflumes offer a reasonable and reliable method of assessing sand transport under controlled conditions of flow. The resultsfrom 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 theseabed, and due to the arbitrary conditions of flow to which they are subjected when deployed.