Collinear wave-current shear interactions are often assumed to be the same for currents following... more Collinear wave-current shear interactions are often assumed to be the same for currents following or opposing the direction of regular wave propagation; with momentum and mass exchanges restricted to the thin oscillating boundary layer (zero-flux condition) and enhanced but equal wave-averaged bed shear stresses. To examine these assumptions, a prototype-scale experiment investigated the nature of turbulent exchanges in flows with currents aligned to, and opposing, wave propagation over a mobile sandy bed. Estimated mean and maximum stresses from measurements above the bed exceeded predictions by models of bed shear stress subscribing to the assumptions above, suggesting the combined boundary layer is larger than predicted by theory. The core flow experiences upward turbulent fluxes in aligned flows, coupled with sediment entrainment by vortex shedding at flow reversal, whilst downward fluxes of eddies generated by the core flow, and strong adverse shear can enhance near-bed mass tr...
The object of this work is to study and to describe the mobility of various types of non-cohesive... more The object of this work is to study and to describe the mobility of various types of non-cohesive sediment considering the hydrodynamic conditions in the channel of Treporti in the lagoon of Venice.<br> To reach this aim the study has been subdivided into one experimental phase and one modeling phase. In the experimental phase, a campaign of sampling and the granulometric analysis of the Treporti channel sediments were done in order to obtain a detailed map of the grain size distribution, which was compared with reported data. In the modeling phase a sediment transport model Sedtrans96 has been applied for 4 different grain sizes (500, 250, 200, 150 μm) and two different periods. First the total sediment transport through the 8 sections has been calculated on a period of 12 hours using ideal values of wind (bora, scirocco) and tide. A second set of simulations were carried out for one year (1987) and forced with real values of wind and tide. The results obtained from granulome...
The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused ... more The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton Water, UK. It was found that the profile containing a seawall had a very different profile form to the undefended sites, and that this seawall profile could not be accurately represented in the model. The model was extended to include wave reflection from the seawall, producing a new prediction with a much improved resemblance of the observed profile. It was concluded that the likely cause of the different profile form at the site of the seawall in this case, is due to incident and reflected wave interaction.
ABSTRACT Amos, C.L.; Kassem, H.; Bergamasco, A.; Sutherland, T.F., and Cloutier, D., 2021. The ma... more ABSTRACT Amos, C.L.; Kassem, H.; Bergamasco, A.; Sutherland, T.F., and Cloutier, D., 2021. The mass settling flux of suspended particulate matter in Venice Lagoon, Italy. Journal of Coastal Research, 37(6), 1099–1116. Coconut Creek (Florida), ISSN 0749-0208. A multidisciplinary study of the stability of the tidal flats of Venice Lagoon has provided field and laboratory data on the factors influencing the mass settling rates of material in suspension. This work was performed using two in situ benthic flumes (Sea Carousel and Mini Flume) in association with a wide range of physical and biological measurements undertaken during the summer of 1998 and the subsequent winter. Also, controlled experiments on erosion/sedimentation of prepared beds were carried out using Lab Carousel, a laboratory equivalent of Sea Carousel. Particle size and mass settling rates were found to be largely independent of suspended sediment concentration but strongly controlled by the antecedent bed shear stresses that led to the suspension. Results between the three flume types differed because of differences in the induced stress history created in each case. Comparable results were obtained by normalizing mass settling rate to the mean friction velocity of the flow during settling, i.e. the Rouse parameter () , and by use of the mean dimensionless particle diameter (D*). Results fell in line with results on carbonate and silica sands of the inlets of the lagoon. The mean particle diameter (df) varied in proportion to the applied shear stress and shear rate (G) suggesting that the suspended particles were eroded aggregates not floccules. The effective density of these aggregates was least (∼16 kgm–3) at the largest sizes (df > 1 × 10–4 m) and greatest (∼160–1600 kgm–3) at the smallest sizes (df < 1 × 10–4 m). The lack of an increase in df at low shear rates suggests that flocculation was not taking place. The mean deposition threshold (all experiments) was 0.68 Pa, which is less than the mean erosion threshold from these sites (0.78 Pa).
... on continental shelves (Smith and Hopkins, 1972; Butman et al., 1979; Swift et al., 1986a,b),... more ... on continental shelves (Smith and Hopkins, 1972; Butman et al., 1979; Swift et al., 1986a,b), but th magnitude and direction of storm transport are ... current shear velocity, M^cs&amp;gt; wave shear velocity, s, combined wave-current shear velocity, u^ws (s in the sub-script here denotes ...
... These data show that the critical wave mobility number and Shields parameter for sheet flow a... more ... These data show that the critical wave mobility number and Shields parameter for sheet flow are not constant, but rather their values decrease with an increase in grain size. The critical sheet-flow Shields parameter under combined ...
Sea surface temperature (SST) trends in the coastal zone are shown to be increasing at rates that... more Sea surface temperature (SST) trends in the coastal zone are shown to be increasing at rates that exceed the global trends by up to an order of magnitude. This paper compiles some of the evidence of the trends published in the literature. The evidence suggests that urbanization in the coastal hinterland is having a direct effect on SST through increased temperatures of river and lake waters, as well as through heated run-off and thermal effluent discharges from coastal infrastructure. These local drivers of SST are compounded by regional drivers manifest as changing weather patterns (latent heat exchange) and direct radiative heating of shallow coastal waters (particularly in restricted embayments and seas). Thus the impact of urbanization on SST may extend well beyond the much-popularised impact of “greenhouse gasses”. The Marine Climate Change Impacts Partnership Report [37] stated that our capacity to define and predict long-term coastal changes due to anthropogenic causes is “un...
Collinear wave-current shear interactions are often assumed to be the same for currents following... more Collinear wave-current shear interactions are often assumed to be the same for currents following or opposing the direction of regular wave propagation; with momentum and mass exchanges restricted to the thin oscillating boundary layer (zero-flux condition) and enhanced but equal wave-averaged bed shear stresses. To examine these assumptions, a prototype-scale experiment investigated the nature of turbulent exchanges in flows with currents aligned to, and opposing, wave propagation over a mobile sandy bed. Estimated mean and maximum stresses from measurements above the bed exceeded predictions by models of bed shear stress subscribing to the assumptions above, suggesting the combined boundary layer is larger than predicted by theory. The core flow experiences upward turbulent fluxes in aligned flows, coupled with sediment entrainment by vortex shedding at flow reversal, whilst downward fluxes of eddies generated by the core flow, and strong adverse shear can enhance near-bed mass tr...
The object of this work is to study and to describe the mobility of various types of non-cohesive... more The object of this work is to study and to describe the mobility of various types of non-cohesive sediment considering the hydrodynamic conditions in the channel of Treporti in the lagoon of Venice.<br> To reach this aim the study has been subdivided into one experimental phase and one modeling phase. In the experimental phase, a campaign of sampling and the granulometric analysis of the Treporti channel sediments were done in order to obtain a detailed map of the grain size distribution, which was compared with reported data. In the modeling phase a sediment transport model Sedtrans96 has been applied for 4 different grain sizes (500, 250, 200, 150 μm) and two different periods. First the total sediment transport through the 8 sections has been calculated on a period of 12 hours using ideal values of wind (bora, scirocco) and tide. A second set of simulations were carried out for one year (1987) and forced with real values of wind and tide. The results obtained from granulome...
The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused ... more The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton Water, UK. It was found that the profile containing a seawall had a very different profile form to the undefended sites, and that this seawall profile could not be accurately represented in the model. The model was extended to include wave reflection from the seawall, producing a new prediction with a much improved resemblance of the observed profile. It was concluded that the likely cause of the different profile form at the site of the seawall in this case, is due to incident and reflected wave interaction.
ABSTRACT Amos, C.L.; Kassem, H.; Bergamasco, A.; Sutherland, T.F., and Cloutier, D., 2021. The ma... more ABSTRACT Amos, C.L.; Kassem, H.; Bergamasco, A.; Sutherland, T.F., and Cloutier, D., 2021. The mass settling flux of suspended particulate matter in Venice Lagoon, Italy. Journal of Coastal Research, 37(6), 1099–1116. Coconut Creek (Florida), ISSN 0749-0208. A multidisciplinary study of the stability of the tidal flats of Venice Lagoon has provided field and laboratory data on the factors influencing the mass settling rates of material in suspension. This work was performed using two in situ benthic flumes (Sea Carousel and Mini Flume) in association with a wide range of physical and biological measurements undertaken during the summer of 1998 and the subsequent winter. Also, controlled experiments on erosion/sedimentation of prepared beds were carried out using Lab Carousel, a laboratory equivalent of Sea Carousel. Particle size and mass settling rates were found to be largely independent of suspended sediment concentration but strongly controlled by the antecedent bed shear stresses that led to the suspension. Results between the three flume types differed because of differences in the induced stress history created in each case. Comparable results were obtained by normalizing mass settling rate to the mean friction velocity of the flow during settling, i.e. the Rouse parameter () , and by use of the mean dimensionless particle diameter (D*). Results fell in line with results on carbonate and silica sands of the inlets of the lagoon. The mean particle diameter (df) varied in proportion to the applied shear stress and shear rate (G) suggesting that the suspended particles were eroded aggregates not floccules. The effective density of these aggregates was least (∼16 kgm–3) at the largest sizes (df > 1 × 10–4 m) and greatest (∼160–1600 kgm–3) at the smallest sizes (df < 1 × 10–4 m). The lack of an increase in df at low shear rates suggests that flocculation was not taking place. The mean deposition threshold (all experiments) was 0.68 Pa, which is less than the mean erosion threshold from these sites (0.78 Pa).
... on continental shelves (Smith and Hopkins, 1972; Butman et al., 1979; Swift et al., 1986a,b),... more ... on continental shelves (Smith and Hopkins, 1972; Butman et al., 1979; Swift et al., 1986a,b), but th magnitude and direction of storm transport are ... current shear velocity, M^cs&amp;gt; wave shear velocity, s, combined wave-current shear velocity, u^ws (s in the sub-script here denotes ...
... These data show that the critical wave mobility number and Shields parameter for sheet flow a... more ... These data show that the critical wave mobility number and Shields parameter for sheet flow are not constant, but rather their values decrease with an increase in grain size. The critical sheet-flow Shields parameter under combined ...
Sea surface temperature (SST) trends in the coastal zone are shown to be increasing at rates that... more Sea surface temperature (SST) trends in the coastal zone are shown to be increasing at rates that exceed the global trends by up to an order of magnitude. This paper compiles some of the evidence of the trends published in the literature. The evidence suggests that urbanization in the coastal hinterland is having a direct effect on SST through increased temperatures of river and lake waters, as well as through heated run-off and thermal effluent discharges from coastal infrastructure. These local drivers of SST are compounded by regional drivers manifest as changing weather patterns (latent heat exchange) and direct radiative heating of shallow coastal waters (particularly in restricted embayments and seas). Thus the impact of urbanization on SST may extend well beyond the much-popularised impact of “greenhouse gasses”. The Marine Climate Change Impacts Partnership Report [37] stated that our capacity to define and predict long-term coastal changes due to anthropogenic causes is “un...
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