The measurement of sand transport in two inlets of Venice lagoon,Italy |
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| Authors: | CL Amos M Villatoro R Helsby CEL Thompson L Zaggia G Umgiesser V Venturini D Are TF Sutherland A Mazzoldi F Rizzetto |
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| Institution: | 1. School of Ocean and Earth Science, National Oceanography Centre, Southampton, Hampshire SO14 3ZH, UK;2. Institute of Marine Sciences, National Research Council, Castello 1364/a, Venezia, Italy;3. SELC SpA, Marghera, Italy;4. DFO-CAER, W. Vancouver, BC, Canada V7V 1N6 |
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| Abstract: | Sand transport in Lido and Chioggia inlets was measured using modified Helley–Smith sand traps equipped with 60-micron nets. The traps had an efficiency of about 4% only but provided enough material for analysis. Very fine sand (0.07 < d < 0.11 mm) only was collected in the traps. Transport of sand was greatest in the bottom 10% of the water column and followed a Rouse profile. Sand extended to a height of about 4 m above the bed during peak flows corresponding to the estimated thickness of the boundary layer; and observed in synoptic ADCP profiles. The sand in the benthic boundary layer was largely inorganic (>95%); above this layer, organic content varied widely and was greatest near the surface. The movability number Ws/U∗ showed a linear relationship to dimensionless grain diameter (D*): (Ws/U∗)=(D∗/10); D* < 10. Sand concentration in suspension was simulated by a mean Rouse parameter of −2.01 ± 0.66 (Lido inlet) and −0.82 ± 0.27 (Chioggia inlet). The β parameter ( Hill et al., 1988) was correlated with D* and movability number in the form: β=2.07−2.03D∗+59(Ws/U∗)2 (r2 = 0.42). Von Karman's constant was back-calculated from a Law of the Wall relationship as a test on the accuracy of U* estimates; a mean value of 0.37 ± 0.1 (compared to the accepted value of 0.41) suggest U* was accurate to within 10%. The constant of proportionality (γ = 3.54 × 10−4) between reference concentration (Ca) and normalized excess bed shear stress was in line with the published literature. |
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| Keywords: | sand transport tidal inlets Venice lagoon |
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