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  • 1
    Electronic Resource
    Electronic Resource
    Particle over-passing on depth-limited gravel bars (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 37 (1990), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An experimental channel is used to examine the transport of mixed sand and gravel bedload over the crestal platform of ‘hump-back’ bars and along the top of planar gravel sheets. Hydraulic processes result in the simultaneous transport of cobbles and pebbles over a static closely packed bed consisting of like-sized and finer particles. For prescribed conditions, flat upper-stage plane sand-beds develop over the crestal location with pebbles rolling easily over the sandy bed. At the brinkpoint, flow separation ensures effective segregation of the gravel from the sand. Over the slip-face the deposition rate of the sand is insufficient to fill fully the interstices within the gravel foresets before rapid deposition of gravel further advances the bed-form. Consequently, distinctive vertical assemblages of open-work and closed contact framework gravels could be generated as another bar migrates over, and preserves, the initial structure.In respect to the observed mechanisms of sorting over the bars, a mathematical expression is developed to explain the critical conditions allowing coarse particle mobility over planar sand or gravel beds under upper-stage plane-bed conditions on the crestal platform. The model then is used to ascertain whether the depositional environment ascribed to certain facies in the Bunter Pebble Beds, described in a recent publication, is appropriate given the distinctive facies assemblages generated in this experiment and the known hydrodynamic control of the particle-segregation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1990.tb00963.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Temporal and spatial variation in intertidal sedimentation rates (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 29 (1982), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Sediment deposition and erosion rates are reported for an intertidal zone in the Burry Inlet, South Wales.Measured deposition rates over the salt marsh are compared with deposition rates calculated from observed suspended sediment concentrations. Notably, it is concluded that residual turbulence at slack water should not be discounted when calculating deposition rates.Grain-size distributions of suspended sediments over the marsh surface, during flood and ebb tides, contrast with the grain-size distribution of deposited marsh sediments, the latter being significantly coarser. These data in conjunction with mass budget calculations are used to relate total annual deposition and sediment supply by tidal action during settled meteorological periods. The analysis suggests that episodic storm-induced sediment transport is probably an important mechanism for introducing coarse sediment on to the marsh surface.Finally, it is noted that seasonal reworking of the sandy non-cohesive sediments may be related to variations in the intensity of wave-breaking throughout the year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1982.tb01705.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Morphology, sedimentology and palaeohydraulic significance of large gravel dunes, Altai Mountains, Siberia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 43 (1996), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Coarse-gravel bedforms which resulted from Pleistocene glacial outburst floods are identified as subaqueous dunes. Comparison of the morphology of these ‘fossil’ structures with modern dunes shows that the form of two-dimensional (2-D) transverse dunes and 3-D cuspate and lunate dunes developed in coarse gravels is comparable with sand-dune morphology within lesser-scale geophysical flows. The similarity of the steepest gravel dunes with equilibrium dunes in sand indicates that grain size is not a major factor in constraining primary duneform.Internal structure indicates that flow over 2-D dunes was relatively uniform but over 3-D bedforms flow was locally variable. Flow separation and complex streaming of flow occurred over the steepest 3-D dunes. Cross-beds are thin and few approach the angle of repose; consequently most dunes did not migrate primarily by avalanching but by stoss-entrained gravel transported over the crests rolling-down and depositing on the lee slopes.Lee-side sediments are often finer than the stoss-slope sediments, which indicates the lee formed when flood power was waning. Some dunes were slightly planed-down during falling stage because lee-side cross-beds tend to be steeper than the angle of the preserved lee slope. However, silt-rich caps indicate that any height reduction was contemporary with the final deposition of foresets. Post-flood modification has been negligible although the modern topography is subdued by loess deposits within the dune troughs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1996.tb02184.x
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  • 4
    Electronic Resource
    Electronic Resource
    Observations on siting, dimensions and structure of salmonid redds (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 34 (1989), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Redds of trout, Salmo trutta L., Atlantic salmon, S. salar L., and rainbow trout, S. gairdneri Richardson, were studied at sites in north-east England, south-west Wales and southern England (Dorset). Spawning females preferred gravels of 20–30 mm diameter and water velocities at 0·6 depth of 〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:00221112:JFB119:ges" location="ges.gif"/〉 15 cm s-1 and 〈c. 2·0 body lengths s-1. After logarithmic transformation the major horizontal dimensions of redds could be related to one another by linear regressions, and redd tail length could, similarly, be related to female fish length. Egg burial depth in upland stony streams in north-east England and south-west Wales could be predicted from a linear regression of mean depth upon female length. Information is also given on gravel composition and redd structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1989.tb02962.x
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  • 5
    Electronic Resource
    Electronic Resource
    Observations on the structure of brown trout, Salmo trutta Linnaeus, redds (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 19 (1981), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper describes the gravel type and structure of brown trout spawning gravels in Teesdale, the flow characteristics of the spawning sites and the size of redds. Factors influencing redd size are investigated and it is concluded that female size is a major factor. Relationships are established between various redd characteristics and the fork length of female fish. The findings are discussed in relation to the existing literature concerning salmonid spawning sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1981.tb03825.x
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  • 6
    Electronic Resource
    Electronic Resource
    Impact of clay particles on the cutaneous exchange of oxygen across the chorion of Atlantic salmon eggs (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 66 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Rates of oxygen consumption for Atlantic salmon Salmo salar embryos approaching hatching were determined. Values were recorded using a ‘closed system’ experimental set-up. A magnetic stirrer was used to ensure that zones of oxygen depletion did not develop in the micro-environment surrounding the respiring eggs. Recorded values of oxygen consumption ranged from 0·0024 to 0·0038 mg O2 egg−1 h−1, with a mean consumption rate of 0·0032 mg O2 egg−1 h−1. The values of oxygen consumption were similar to those reported in other studies using a closed system experimental set-up, however, they were lower than those reported in a study adopting a flow-through system. The introduction of clay-sized sediment to the incubation chamber created a thin film (〈1 mm) of sediment on the egg surface, and resulted in reduced rates of oxygen consumption. The additional 0·3 g of clay sediment reduced oxygen consumption by an average of 41% and the addition of a further 0·2 g of clay sediment reduced consumption by an average of 98%. Two explanations for the recorded reduction in consumption were proposed: (i) the creation of a low permeability seal around the eggs restricted the availability of oxygen to the incubating embryos and (ii) the clay-sized fine sediment physically blocked the micro-pore canals in the egg membrane, thereby restricting oxygen uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00715.x
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  • 7
    Electronic Resource
    Electronic Resource
    An improved conductiometric standpipe technique for measuring interstitial seepage velocities (1986)
    Springer
    Hydrobiologia 135 (1986), S. 3-8 
    Details
    ISSN: 1573-5117
    Keywords: stream-gravel ; seepage ; dilution-gauging ; conductivity ; microcomputer ; data acquisition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The measurement of the seepage velocity through river-bed gravels is required in many biological and chemical investigations concerned with chemical fluxes through the gravel interstices. An improved conductiometric technique is described which is based on an earlier electrolytic method. The apparatus is calibrated for a range of gravel types to yield a spatially-averaged seepage velocity rather than a Darcian bulk velocity. Problems of stratification of the electrolyte and the need for temperature monitoring have been eliminated. The apparatus is compact and, incorporating a micro-computer-based data aquisition system, is easy and rapid to use even in adverse field conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006452
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