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Determination of bottom boundary layer parameters at two shallow sea sites using the profile method
546
D. Submarine Geology and Geophysics
typical of the thickness of the crust. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA. (hbf)
D70. Coasts, beaches, marshes 88:3423 Coe Neto, R., J.-M. Froidefond and Bruno Turcq, 1986. Coastal geomorphology and chronology of recent sediments. Example: the east coast of Rio de Janeiro (Brazil). Bull. Inst. G~ol. Bassin Aquitaine, 40:67-83. (In French, English abstract.) Univ. Fed. de Fluminense, Inst. de Geochim., Niteroi R.J., Brazil. 88:3424 Liu, Cangzi, Licheng Wu and Min Cao, 1987. Sedimentary characteristics of eheniers in southern Changjlang Delta and their origin and age determination. Acta oceanol, sin. (English version), 6(3):405-412. Inst. of Estuarine and Coastal Res., East China Normal Univ., Shanghai, People's Republic of China. 88:3425 Maa, P.-Y. and A.J. Mehta, 1987. Mud erosion by waves: a laboratory study. Continent. Shelf Res., 7(11-12): 1269-1284.
Two types of cohesive sediment, a commercial kaolinite and an estuarial mud, were used to study the mechanism by which soft muds erode under progressive waves in a flume. A multi-layered hydrodynamic model which considers the mud to be viscoelastic was used to evaluate bed shear stress at the oscillating mud-water interface. The viscoelastic property of the mud was confirmed by rheological measurements, and model results on velocity, pressure and wave attenuation verified against flume data. Concentration profiles indicate an evolutionary pattern resulting in a highly stratified suspension. Just above the bed, a thin layer of fluid mud is generated; above this layer, the suspension concentration is significantly lower. This two-layered feature is related to the oscillatory response of the mud and water layers, and the associated momentum exchange and mass diffusion characteristics. An expression relating rate of erosion to bed shear stress in excess of bed shear resistance was developed. VIMS, Coll. of William and Mary, Gloucester Point, VA 23062, USA. 88:3426 Parker, W.R., 1987. Observations on fine sediment transport phenomena in turbid coastal environments. Continent. Shelf Res., 7(I 1-12): 1285-1293.
OLR (1988) 35 (6)
Measurements using new technology highlight unsteady behaviour and the importance of the cohesive boundary--a time-dependent transition between moving fluid and stationary bed. Discrepancies between various techniques for describing the properties and behaviour of the cohesive boundary become clear when the purpose of the description is considered. Although transport processes are described in physical terms, the impact of biological processes is now widely recognized. Non-intrusive measurement techniques offer a route to more realistic quantification of fine sediment transport phenomena in these environments. Sci. and Engng Res. Council, c/o Blackdown Consultants Ltd., 8, Fore St., Taunton, Somerset TA3 75H, UK. 88:3427 Sahl, L.E. and M.A.H. Marsden, 1987. Shelf sediment dispersal during the dry season, Princess Charlotte Bay, Great Barrier Reef, Australia. Continent. Shelf Res., 7(10): 1139-1159. 68 Bellewood Ave., South Setauket, NY 11720, USA. 88:3428 Salomons, W. and W.G. Mook, 1987. Natural tracers for sediment transport studies. Continent. Shelf Res., 7(11-12): 1333-1343.
Differences in chemical, mineralogical and isotope geochemical composition of marine and fluvial sediments can be used as tracers, provided that three criteria are met: conservative behaviour during transport, with time, and after deposition. Examples of the utility of natural tracers are presented, including their use for the interpretation of pollutant patterns in estuaries. The application of natural tracers shows marine sediments may be transported past the freshwater boundary in estuaries, and thus contribute to the sedimentation in freshwater tidal areas. Delft Hydraulics Lab., c/o Inst. for Soil Fertility, P.O. Box 30003, 9750 RA Haren, Gr, Netherlands. 88:3429 Schauer, Ursula, 1987. Determination of bottom boundary layer parameters at two shallow sea sites using the profile method. Continent. Shelf Res., 7(10):1211-1230.
Time series of mean current profiles within 3.5 m of the bottom were obtained in two hydrographically different regions. The shear velocity reached maximum values of u. = 6 cm/s. Values of z 0 are very high (0[cm]) and show a systematic variability with the velocity. The profiles are slightly concave, thus z 0 and u. decrease with the profile height considered. Both results indicate differences between observations and the Prandtl theory. Factors influencing the
D. Submarine Geology and Geophysics
typical of the thickness of the crust. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA. (hbf)
D70. Coasts, beaches, marshes 88:3423 Coe Neto, R., J.-M. Froidefond and Bruno Turcq, 1986. Coastal geomorphology and chronology of recent sediments. Example: the east coast of Rio de Janeiro (Brazil). Bull. Inst. G~ol. Bassin Aquitaine, 40:67-83. (In French, English abstract.) Univ. Fed. de Fluminense, Inst. de Geochim., Niteroi R.J., Brazil. 88:3424 Liu, Cangzi, Licheng Wu and Min Cao, 1987. Sedimentary characteristics of eheniers in southern Changjlang Delta and their origin and age determination. Acta oceanol, sin. (English version), 6(3):405-412. Inst. of Estuarine and Coastal Res., East China Normal Univ., Shanghai, People's Republic of China. 88:3425 Maa, P.-Y. and A.J. Mehta, 1987. Mud erosion by waves: a laboratory study. Continent. Shelf Res., 7(11-12): 1269-1284.
Two types of cohesive sediment, a commercial kaolinite and an estuarial mud, were used to study the mechanism by which soft muds erode under progressive waves in a flume. A multi-layered hydrodynamic model which considers the mud to be viscoelastic was used to evaluate bed shear stress at the oscillating mud-water interface. The viscoelastic property of the mud was confirmed by rheological measurements, and model results on velocity, pressure and wave attenuation verified against flume data. Concentration profiles indicate an evolutionary pattern resulting in a highly stratified suspension. Just above the bed, a thin layer of fluid mud is generated; above this layer, the suspension concentration is significantly lower. This two-layered feature is related to the oscillatory response of the mud and water layers, and the associated momentum exchange and mass diffusion characteristics. An expression relating rate of erosion to bed shear stress in excess of bed shear resistance was developed. VIMS, Coll. of William and Mary, Gloucester Point, VA 23062, USA. 88:3426 Parker, W.R., 1987. Observations on fine sediment transport phenomena in turbid coastal environments. Continent. Shelf Res., 7(I 1-12): 1285-1293.
OLR (1988) 35 (6)
Measurements using new technology highlight unsteady behaviour and the importance of the cohesive boundary--a time-dependent transition between moving fluid and stationary bed. Discrepancies between various techniques for describing the properties and behaviour of the cohesive boundary become clear when the purpose of the description is considered. Although transport processes are described in physical terms, the impact of biological processes is now widely recognized. Non-intrusive measurement techniques offer a route to more realistic quantification of fine sediment transport phenomena in these environments. Sci. and Engng Res. Council, c/o Blackdown Consultants Ltd., 8, Fore St., Taunton, Somerset TA3 75H, UK. 88:3427 Sahl, L.E. and M.A.H. Marsden, 1987. Shelf sediment dispersal during the dry season, Princess Charlotte Bay, Great Barrier Reef, Australia. Continent. Shelf Res., 7(10): 1139-1159. 68 Bellewood Ave., South Setauket, NY 11720, USA. 88:3428 Salomons, W. and W.G. Mook, 1987. Natural tracers for sediment transport studies. Continent. Shelf Res., 7(11-12): 1333-1343.
Differences in chemical, mineralogical and isotope geochemical composition of marine and fluvial sediments can be used as tracers, provided that three criteria are met: conservative behaviour during transport, with time, and after deposition. Examples of the utility of natural tracers are presented, including their use for the interpretation of pollutant patterns in estuaries. The application of natural tracers shows marine sediments may be transported past the freshwater boundary in estuaries, and thus contribute to the sedimentation in freshwater tidal areas. Delft Hydraulics Lab., c/o Inst. for Soil Fertility, P.O. Box 30003, 9750 RA Haren, Gr, Netherlands. 88:3429 Schauer, Ursula, 1987. Determination of bottom boundary layer parameters at two shallow sea sites using the profile method. Continent. Shelf Res., 7(10):1211-1230.
Time series of mean current profiles within 3.5 m of the bottom were obtained in two hydrographically different regions. The shear velocity reached maximum values of u. = 6 cm/s. Values of z 0 are very high (0[cm]) and show a systematic variability with the velocity. The profiles are slightly concave, thus z 0 and u. decrease with the profile height considered. Both results indicate differences between observations and the Prandtl theory. Factors influencing the