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... 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...
Research Interests: Geology, Physics, Mechanics, Water, Turbulence, and 6 moreMultidisciplinary, General, Shear Stress, Vortex, Eddy, and Boundary Layer
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... 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 extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton... 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.
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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... 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).
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... 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... 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 ...
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... 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 ...
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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.... 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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Publisher Summary In this chapter the term “Tidal Flats”, defines tidal flat as “sandy to muddy or marshy flats emerging during low tide and submerging during high tide”. This definition can be ambiguous as the positions of low and high... more
Publisher Summary In this chapter the term “Tidal Flats”, defines tidal flat as “sandy to muddy or marshy flats emerging during low tide and submerging during high tide”. This definition can be ambiguous as the positions of low and high tides are time-variable. The frequency of tidal flat inundation, Waves play a strong role in the resuspension of sediments on tidal flats. A series of papers are written on the effects of storms, hurricanes and typhoons on tidal flats. The non-periodic occurrences of wave magnitude means that even sheltered regions are subject to wave influence at times. The degree of this influence is often visible across the tidal flats in the form of erosion of the seaward edges of salt marshes and mud flats, in the development of sandy beaches on top of the salt marsh at the mean high water spring tides (MHWST) level. The varying influences of waves are often apparent in the tidal flat zonation and associated sediment texture.
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... Chapter 10 Siliciclastic Tidal Flats. Carl L. Amos. Available online 19 August 2007. Geomorphology and Sedimentology of Estuaries. Developments in Sedimentology 53 edited by GME Perillo 1995 Elsevier Science BV All rights reserved. ...
Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring tide) in the Mediterranean Sea. Presently, the Lagoon is suffering from a sediment loss of ~1 million m 3 /a seawards. The consequence of... more
Venice Lagoon is the estuary with the largest area and the greatest microtidal range (1 m spring tide) in the Mediterranean Sea. Presently, the Lagoon is suffering from a sediment loss of ~1 million m 3 /a seawards. The consequence of such a deficit in the sediment budget is the progressive destruction of salt marshes and tidal flats. It is estimated that all the salt marshes will have disappeared by 2040 if this trend continues (Consorzio Venezia Nuova, 1992; 1996). In this study, a multidisciplinary investigation was undertaken at two different spatial scales (regional and local) to determine the factors controlling the stability and evolution of Venice Lagoon. Relationships between the critical erosion threshold of the lagoonal sediments and their biological properties (PATERSON, 2000) reveal that complex feed-back mechanisms exist which enhances the accretion of the intertidal areas in the northern part of the Lagoon.
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Research Interests: Geology and Sedimentology
... &amp;quot; &amp;quot; ~ooo v&amp;lt;&amp;gt; _a r~ ZD .,fo EASTERN SHOAL ~,&amp;#39;~w~^- ~ ~ SABLE ISLAND BANK or) #,~&amp;quot; AMOS ) o SABLE ISLAND BANK /&amp;quot; (EVANS-HAMILTON) (B) #/ GEORGES BANK... more
... &amp;quot; &amp;quot; ~ooo v&amp;lt;&amp;gt; _a r~ ZD .,fo EASTERN SHOAL ~,&amp;#39;~w~^- ~ ~ SABLE ISLAND BANK or) #,~&amp;quot; AMOS ) o SABLE ISLAND BANK /&amp;quot; (EVANS-HAMILTON) (B) #/ GEORGES BANK D BAY OF FUNDY I00 II II IIIIIII &amp;#39; ai | i . | | O. I IO IO SAND RIDGE HEIGHT (m) 192 SAND WAVES AND ...
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ABSTRACT Geophysical and vibrocore information was used to interpret the distribution, character and evolution of post-glacial sediments in the Minas Basin, Bay of Fundy. Sedimentological evidence provided information on the environment... more
ABSTRACT Geophysical and vibrocore information was used to interpret the distribution, character and evolution of post-glacial sediments in the Minas Basin, Bay of Fundy. Sedimentological evidence provided information on the environment of deposition of the sediments found. Results show that the Minas Basin seabed has not been subaerially exposed since glacial times and that deposition has taken place under continuously marine conditions. During the approximate period 8,600 years B.P.-6,300 years B.P. the Minas Basin was non-tidal and sedimentation occurred predominantly in the deeper parts of the embayment. From 6300 Y.B.P. to the present tidal activity has been increasing linearly; the present tidal activity is the most energetic condition to have occurred in the system. During this period d position was progressively more predominant in the marginal regions, developing the sandflats, mudflats and salt marshes visible today. The progressive inundation of the Minas Basin margins is a function of an increase in tidal range (50%) and a rise in apparent mean sea-level (50%).
Research Interests: Geology and Sedimentary
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... 00221686.2011.583388 Vasiliki Stratigaki a * , Eleonora Manca b , Panayotis Prinos c , Inigo J. Losada d , Javier L. Lara e , Mauro Sclavo ... in the Spanish Mediterranean reduced near-bed turbulence rates more than three times... more
... 00221686.2011.583388 Vasiliki Stratigaki a * , Eleonora Manca b , Panayotis Prinos c , Inigo J. Losada d , Javier L. Lara e , Mauro Sclavo ... in the Spanish Mediterranean reduced near-bed turbulence rates more than three times compared to nearby bare sandy areas, concluding ...
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Abstract The sensitivity of estimated suspended sediment transport rates was studied by applying existing current-wave fields within a coupled numerical model using the Bagnold and the Soulsby-van Rijn formulae. The study area was the... more
Abstract The sensitivity of estimated suspended sediment transport rates was studied by applying existing current-wave fields within a coupled numerical model using the Bagnold and the Soulsby-van Rijn formulae. The study area was the Sylt-Rømø bight, an enclosed back barrier tidal basin located in the North Sea. The bight has an area of some 400 km2 in which sand flats prevail. This work provides numerical estimates of sediment transport rates and shear velocities throughout the Sylt-Rømø tidal basin. Water levels, vertically-averaged two-dimensional current velocities and wave spectra were used as input from validated numerical model calculations. Four days covering a full storm period in April 1997 were selected for the calculations of total bed shear velocities and sediment transport rates. The simulation shows that during moderate wave conditions sediment transport mainly takes place in the tidal channels. However, with high wave energy present, sediment transport becomes more important in shallow areas. The general distribution of shear velocities and suspended sediment concentrations over the basin suggests a large erosion and resuspension of sediment in shallow areas by wave action which may not be so evident in the sediment transport rates because of the low current velocities. This suggests that storms will continue to erode shallow areas, thus increasing the tidal prism and probably the tidal currents which will result in the continuing export of sediment.
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... The sediment transport rate was determined using the numerical model SEDTRANS (Li and Amos 1995). ... (A) Wind speed measured at a height of 10 m on Sable Island; (B) predicted wind-driven and tidal currents; (C) the ware heights and... more
... The sediment transport rate was determined using the numerical model SEDTRANS (Li and Amos 1995). ... (A) Wind speed measured at a height of 10 m on Sable Island; (B) predicted wind-driven and tidal currents; (C) the ware heights and wave lengths measured from the drill ...
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P. S. Balson & M. B. Collins(eds) 2007. Coastal and Shelf Sediment Transport. Geological Society Special Publication no. 274. v + 162 pp. London, Bath: Geological Society of London. Price £65.00, US $130.00; GSL members' price £32.50, US $65.00; AAPG/SEPM/GSA/RAS/EFG/PESGB members' price £39.00, ...more
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Flow-parallel linear ridge–runnel (R–R) bedforms composed of mainly cohesive sediments have been investigated at an intertidal site located at Hills Flats in the Severn Estuary, UK. It is argued that the sequences of sand–mud laminae in... more
Flow-parallel linear ridge–runnel (R–R) bedforms composed of mainly cohesive sediments have been investigated at an intertidal site located at Hills Flats in the Severn Estuary, UK. It is argued that the sequences of sand–mud laminae in the ridge sediments indicate strongly that R–R are depositional bedforms. Faint R–R topography scoured in the underlying soft bedrock and parallel rows of coarser