bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics, sediment transport, and morphology in a tide‐dominated embayment
Authors: Sternberg R. W. , Marsden M. A. H. 
Published: February 2007

AbstractWestern Port, Victoria, Australia is a tide‐dominated embayment with an unusual and complex shape. Bottom currents and circulation and their effects on sediment processes were examined using instrumented tripods to measure currents, tides and wave activity, and to estimate sediment transport at nine locations in the bay. Overall bottom water movement patterns were determined by use of seabed drifters.The characteristics of the bay reflect a small catchment and low freshwater and sediment input. A complex system of channels is flanked by extensive intertidal areas.Tidal range varies up to more than 3 m, generating bottom currents up to 70cm s−1. Flow directions generally conform to channel alignments but major deviations are important. Net circulation in the bay is clockwise around the large central island. The ratio of tidal range to half‐tidal period (ΔH/ΔT) when compared with measured currents gave a method of prediction of the annual frequency distribution of maximum bottom current velocities.Determination of threshold current velocities enabled prediction of annual frequency of bedload movement (generally 50–100 per cent of tide cycles). Bedload mass transport for all observed tide cycles was calculated, and estimates of annual mass transport capacity (between 102 and 106 g cm−1 a−1( were obtained from a relationship between predicted tidal conditions and mass transport.Seabed drifters delineated the major bottom water movements in the bay and adjacent Bass Strait, and also detailed circulation patterns. This linked the data from the tripod stations, in particular patterns of ebb‐ and flood‐dominance.A coherent picture of the processes operating in Western Port is presented by integrating these studies with corroborative studies of sediment distribution and morphology, hydrochemistry, and mathematical modelling. Some morphological characteristics related to tide‐dominance are discussed.
The evolution of fluviatile sediments as demonstrated by QDa‐Md analysis
Authors: McManus J. 
Published: February 2007

AbstractThe modification of scree sediments entering a stream is examined by QDa‐Md methods. Loss of fine or coarse subpopulations or both in combination from an initially symmetrical grain size distribution is shown to result in the dispersion of the QDa‐Md plots throughout an envelope typical of fluvial sediments. Natural plots from the Rivers Earn and Tay provide live examples of the transenvironmental trend patterns demonstrated.
Geometry of alluvial fans: Effect of discharge and sediment size
Authors: Le Hooke Roger B. , Rohrer William L. 
Published: February 2007

AbstractThe slope of an alluvial fan increases with increasing debris size and sediment concentration in the flow, and decreases with increasing discharge. Laboratory studies suggest that the discharge which controls this slope, or dominant discharge, is that which is equalled or exceeded one quarter to one third of the time that flow occurs on the fan. In contrast, the dominant discharge in perennial alluvial rivers is equalled or exceeded only about 5 per cent of the time that flow occurs in the river. The dominant discharge on fans increases with increasing debris size, reflecting the importance of threshold stress.The slope of some natural and most laboratory alluvial fans is steepest on the flanks and gentlest along the axis. Consideration of the momentum of water debouching onto a fan at its apex suggests that the difference in slope between axis and flank should be greatest on steep fans composed of relatively non‐cohesive materials because on such fans higher discharges tend to flow down the axis, whereas lower discharges can be turned to course down the flanks. On fans with gentle slopes or composed of more cohesive material the higher discharges can also be turned toward the flanks, so on such fans the difference in slope between the axis and flank is less pronounced. Field and laboratory observations support this interpretation.Because deposition at any one time on an alluvial fan is localized, some areas aggrade while others remain at a fixed elevation. This process is treated as a Markov process with the probability of diversion from an area of active deposition into an adjacent lower area increasing as the height of the active area above the mean or ‘ideal’ surface increases. Analysis of data from laboratory and natural fans suggests that the amplitude of such surface irregularities is greater on fans composed of coarser material. The data on natural fans also suggest an increase in amplitude of the irregularities with increasing fan area.
Causal and functional relations in fluvial geomorphology
Authors: Hey Richard D. 
Published: February 2007

AbstractThe concept of causality has been a fundamental principle of scientific investigation for many centuries. Recently, however, there has been a significant reappraisal of the philosophical basis of the concept of causality and this has important implications for future geomorphological research.It is now recognized that there are two approaches to the study of relations between variables. Conventionally knowledge was divided into classes and, on the basis of time precedence, causal relations were defined. While this approach enables static systems to be analysed it does not apply to dynamic systems which exhibit mutual causality. This traditional view of knowledge became obsolete with the introduction of the concept of the continuum. Algebraic techniques now enable the solution of systems of simultaneous equations, provided that there are as many equations as unknowns. Significantly this approach applies to dynamic as well as static systems.Further advances in fluvial geomorphological research are dependent on the adoption of mathematical reasoning. This will concentrate research on the mode and rate of operation of channel processes and feedback mechanisms. Given this information it will be possible to develop a static process‐response model to explain and predict channel response to a set of input conditions, and a dynamic model to simulate channel development through time and space.
Ground retreat and slope evolution on regraded surface‐mine dumps, waunafon, gwent
Authors: Haig Martin J. 
Published: February 2007

AbstractGround retreat was monitored on two vegetated and two unvegetated profiles over a five‐year period. The average annual retreat of the two unvegetated profiles was 5.84 mm and 3.62 mm; that of the two vegetated profiles 2.34 mm and 2.07 mm. Slope evolution was controlled by the mid‐slope‐ward migration of two zones of accelerated erosion and the resulting replacement of a central rectilinear slope segment by the upper and lower slope elements.
Stone chute development on a limestone scree
Authors: Loughran Robert J. , Loughran Ann I. 
Published: February 2007

AbstractThe modification of limestone scree slopes in North Yorkshire takes the form of downslope trains of finer stones. These features, termed stone chutes, usually coincide with a narrow defile in the limestone scar above. Investigations of four stone chutes below Raven Scar in Twisleton Dale revealed intermittent downslope movement of stones. On these coarse limestone screes, where there is insufficient fine material for debris flow formation, stone chutes are the visible evidence of slope evolution.
‘Bedload’ dynamics: Grain‐grain interactions in water flows
Authors: Leeder M. R. 
Published: February 2007

AbstractOwing to experimental difficulties, the transport stage at which collisions between moving ‘bedload’ grains might become significant has never been investigated, yet the existence or otherwise of such collisions is of some importance in the understanding of the mechanics of sediment transport, in particular the theory developed by Bagnold. Application of the basic principles of gaseous kinetic theory to ‘bedload’ grains moving in saltant trajectories and the adoption of a ‘characteristic’ saltation path leads to the prediction that grain‐grain collisions should dominate in the transport of coarse sands over plane beds in water flows above a transport stage of about 2, i.e. when the mean boundary fluid shear stress exceeds the critical boundary shear stress for grain motion by about 4 times. Above this stage interrupted saltations should always occur, with the ‘bedload’ grains held above the stationary bed by a combination of fluid and solid momentum transfer mechanisms. A classification of the types of grain motions is given and evidence is presented for the existence of an upward decrease in grain collision frequency and of grain concentration at the top of the ‘bedload’ zone.
Discriminant analysis as a possible tool in landslide investigations
Authors: Reger James P. 
Published: February 2007

AbstractAs part of an investigation of mass movement on outslopes of contour surface‐mines in West Virginia, discriminant analysis was used to determine whether selected spoil properties could statistically distinguish failed and unfailed embankments. The analysis utilized the variables degree of saturation, liquid limit, and shrinkage limit, and the a priori assignment of samples into either actively failing, unfailed, or regraded categories.Results were encouraging, with seventy‐four percent of the samples being correctly classified. All misclassifications involved samples from active or regraded landslides, suggesting the method was conservative.Performance of discriminant analysis could probably be improved by modifying the sampling plan.
Sorted stripes orientated by wind action: Some observations from sub‐antarctic marion island
Authors: Hall Kevin 
Published: February 2007

AbstractSorted stripes found on the volcanic scoria and glacial deposits of sub‐Antarctic Marion Island indicate a distinct preferred orientation. Despite uniformity of slope and material, the stripes are predominantly aligned parallel to the wind. It is suggested that melting of needle ice by the early morning sun is of only limited importance in the sub‐Antarctic owing to the almost continual overcast conditions. The effect of the wind is so great that in exposed situations stripes are formed on horizontal surfaces.
Laboratory simulation of salt weathering processes in arid environments
Authors: Cooke R. U. 
Published: February 2007

AbstractThe equipment and techniques being used at Bedford College, London to simulate salt weathering processes in deserts are described in the context of a general discussion of the nature of salt weathering processes and approaches to studying them. An experiment based on the equipment and techniques is described: it is designed to test the durability of three building stones in the presence of several different saline solutions under conditions of surface temperature and relative humidity that are considered typical of hot deserts. The experiment, the first of a series, shows that Na2SO4 is the most effective of the salts used, and that susceptibility of the rocks to weathering is related to such rock properties as porosity, microporosity and water absorption capacity.
PLAN FORM AND PROFILE FORM OF HILLSLOPES
Authors: Parsons A. J. 
Published: February 2007

AbstractFor 27 hillslope profiles located within four first‐order drainage basins on the dip slope of the South Downs in East Sussex, contour curvature (P), measured in degrees per 100 m, is highly variable within any one hillslope. Hillslopes may be described as wholly concave in plan where P is less than −40, wholly convex in plan where P is greater than +40 and convexo‐concave in plan where P lies between −40 and +40. One measure of P taken at the profile sampling line is found to give a better estimate of P than measuring P at the steepest point on the hillslope. P is found to be significantly negatively correlated with slope in 38 per cent of cases, correlated with distance from the divide in 55 per cent of cases (positively where P<0 and negatively where P<0) and positively correlated with profile curvature in 70 per cent of cases. Implications of these correlations for hillslope process‐response models are discussed.
Experimental test of autosuspension
Authors: Southard John B. , Mackintosh Michael E. 
Published: February 2007

AbstractThe concept of autosuspension implies that if, in a flow transporting suspended sediment down a slope, the sediment adds more energy to the flow than it extracts, the concentration can rise to an indefinitely high level. This was tested in a small closed duct, with variable slope, connecting two free‐surface reservoirs. The sediment‐carrying flow could be recirculated continuously from the downstream end of the duct to the upstream end. For each of five sediment sizes ranging from 14 μm to 96 μm, two flows at the same discharge were run, one with zero slope and one with a slope chosen so that autosuspension should have been in effect. Something is wrong with the autosuspension criterion: in each set of runs, equilibrium suspended‐sediment concentrations were virtually identical in the two cases. Analysis of the term in the autosuspension criterion expressing work done by the flow to suspend sediment shows that this quantity is much smaller than is assumed in autosuspension, and so the criterion should have been even more strongly oversatisfied in our tests. Although both the energy‐expenditure form and energy‐contribution form in the criterion have a physical reality, comparison of the two has no relevance to the equilibrium state of the flow; autosuspension is based on an irrelevant system of energy bookkeeping. Suspension must be viewed as limited by factors involving alterations in turbulence structure leading to changes both in boundary resistance and in the ability of the flow to entrain and suspend sediment.
Beach erosion as a function of variations in the sediment budget, Sandy Hook, New Jersey, U.S.A.
Authors: Allen James R. 
Published: February 2007

AbstractMany of the world's beaches have recently been eroding, even on progradational landforms. This study uses the sediment budget approach to identify and rank the causes of the hazard along Sandy Hook spit where the primary recreational beach has been eroding at about 10 m/yr since 1953 and 23 m/yr in the 1970s.Large spatial variations in longshore sediment transport are found to result from differences in refracted wave energies and intersegmental sediment transport. Erosion results from a 60 per cent deficit (‐270,000 m3/yr) in the sediment budget that is primarily caused by (1) refraction induced locally high waves that increase the transport rate by 100,000 m3, and (2) shore protection structures that have lessened the longshore sediment inputs by an additional 100,000 m3/yr. A storm index is presented to analyse secular climatic variation. It suggests that the annual sediment transport rate may vary by as much as ±50 per cent about the mean and that recently, above normal storm wave energies are responsible for about 60,000 m3/yr of the budget deficit. Rising sea levels and storm overwash each account for only about one per cent of the sediment loss.Pulses of sediment, induced by accelerated erosion at the feeder beach locale of spit segments, are found to move downdrift. They alter the geomorphology of the spit through episodic extensions of the spit segments with lag times exceeding one year per segment.
Soil loss variation within a Colorado Alpine area
Authors: Bovis Michael J. , Thorn Colin E. 
Published: February 2007

AbstractThe areally weighted surface erosion for Niwot Ridge, an alpine interfluve in the Colorado Front Range, is 10−1 mm/y. This may be subdivided into rates for three generalized cover types: tundra meadow, 10−2 mm/y; dry tundra, 10−1 mm/y; late‐lying snow patches, 10° mm/y. Tundra meadow (about 50 per cent of the interfluve area) yields about 5 per cent of the eroded material; dry tundra (35 per cent of the area) contributes slightly less than 50 per cent of the eroded material; while nivation hollows occupied by late‐lying snow patches occupy only about 3 per cent of the area they contribute 50 per cent of the eroded material. The bulk of the surficial erosion is accomplished between June and September, primarily by rainsplash, except where snowmelt is important. The overall estimated surface lowering rate presented here is substantially higher than those reported previously.
Evidence of flandrian valley alluviation in staindale, North York Moors
Authors: Richards K. S. 
Published: February 2007

AbstractThe Dovedale Griff has incised into valley fill deposits in Staindale to expose sub‐fossil wood at the base of a meander cut bank. The wood includes oak (Quercus sp.) driftwood, and apparently in situ stumps of willow (Salix sp.) and alder (Alnus sp.). An alder stump is dated at 6270 radiocarbon years BP. Fluvial gravels approximately 1±5 m thick have accumulated above the wood, which has been exposed by renewed incision.
Recent trends of experimental geomorphology in the field
Authors: Richter G. 
Published: February 2007

AbstractExperimental geomorphology is a part of functional geomorphology. It tries to reach an exact analysis of the processes and to give statements on their importance for the recent relief forming. In all cautiousness the results may be transformed into more extensive areas and other time periods. Experimental geomorphology plays a differing role within the geomorphological research of the European countries. Most of the investigations deal with process studies and the quantification of weathering, mass movement, deflation, surface runoff, sediment transport in stream channels and denudation of watersheds. Experimental geomorphology should not be a goal in itself, but should be used as an applied geomorphology and for the examination of geomorphological theories as well.
Some aspects of the regional variation in the amount of available sediment produced by isopods and porcupines, northern negev, israel
Authors: Yair A. , Rutin J. 
Published: February 2007

AbstractA recent study conducted in the Sde Boqer experimental site drew the attention to the possible influence of the burrowing and digging activity of some desert animals on the spatial variation of erosion rates over arid limestone slopes. Such activity provides loose soil aggregates which are easier to remove by shallow overland flows, than is the compacted and crusted loessial soil.In order to study the regional extent of available sediment amounts produced by the biological activity, six plots were selected in the northern Negev in the range of 65 mm to 310 mm average annual rainfall amount. All plots had the same, north facing, aspect and the same lithologic composition. Their size varied from 1110 m2 to 5470 m2. Available sediment produced was found to vary from 3 g to 70 g/m2, increasing with rainfall amount. The distribution of available sediment within each plot was not spatially uniform depending greatly on the spatial distribution of bedrock surfaces and soil cover. The overall possible influence of the biotic activity on short term cycles of soil erosion over limestone arid slopes in the Negev is discussed.
Work done by Splash: Laboratory experiments
Authors: Savat J. 
Published: February 2007

AbstractLaboratory experiments, based on the theory proposed by van Heerden (1967) that net splash discharge equals the difference between yMiVi and miyi, where M and Y denote downslope masses and projected distances and m upslope projected distances and masses, demonstrate that the work done by splash is a function of the slope angle to (sin a)1.9.Net discharge of sediment (q) therefore increases to (sin a)0.9, It is equally a function of the susceptibility to splash erosion K, which is a complex function of the moisture content of the sands and their grain size distribution.The technique proposed for the assessment of the mean projected splash distances is rapid and gives very accurate results. When carefully applied, it can also be used for fine material like, for example, loess.The splash board technique which is currently used for many field experiments, provides none of the basic information necessary for establishing a discharge‐slope relationship.
Drop testing aggregate stability of some soils near Merida, Spain
Authors: Bergsma E. , Valenzuela C. R. 
Published: February 2007

AbstractThe drop test for aggregate stability results in a distribution of destroyed aggregates with increasing drop number. The influence of prewetting time on drop test results is considered. Secondly new indices to describe the drop test results and modifications of the drop test are suggested to avoid undue influence of small numbers of very stable aggregates, and to shorten the test procedure.
A consistency index and rainwash mechanisms on Belgian loamy soils
Authors: de Ploey J. , Mücher H. J. 
Published: February 2007

AbstractThe effects of soil crusting in Belgium are particularly conspicuous on the loamy plateaus and hill‐regions of southern Flanders, Brabant and Hesbaye. Field observations, made at the end of rainy winter seasons, permitted the making of a simple distinction between: (a) ‘stable’ soils showing crusting on less than 50 per cent of their total surface, without any evident slope wash, and (b) ‘unstable’ soils, crusting over more than 50 per cent of the total surface, with evident rainwash and basal colluviation.The Atterberg limits have been examined for both soil types. It was found that the upslope part of the liquid limit curves, in the range of low consistencies (high water contents), is steeper for stable than for unstable soils. So a distinctive consistency index C2–10was deduced from the liquid limit curves, which may be used for prediction of the relative sensitivity of topsoils for crusting. Stable, well‐structured clods are more hydrophobic than unstable material. This was made clear by wettability tests under a rain simulator. Therefore more water must be added to remolded, stable material to lower its consistency, as is shown by the liquid limit curves.Crustability decreases and C5–10values increase with increasing clay and organic matter contents, as one would expect. Stable soils are well aggregated. But rain simulator tests also showed that the detachment of this material by raindrop impact is high. Therefore, crumbs and clods of stable soils are relatively more sensitive to splash erosion. Their erosion results from the ejection of stable aggregates. Clods of unstable topsoils are compacted and flattened by raindrop impact, which causes internal liquefaction.Micromorphological analysis indicates that typical stable topsoils originate from well‐structured Ap‐horizons and from Bt‐horizons of grey‐brown podzolic soils (Alfisols). Laminated silt and mudcrust fragments characterize unstable topsoils which originate, at least partly, from slopewash deposits. The external stability of both stable and unstable clods is increased by compaction and by surficial concentration of gravel, coarse sands, root and other plant fragments. Thin sections of unstable material show the internal collapse of structures, due to liquefaction.A clear distinction must be made between the structural stability and the erodability of topsoils.