bluuebunny/crossref_metadata_2025 huggingface dataset:
Rates of surface processes on slopes, slope retreat and denudation
Authors: Saunders Ian , Young Anthony
Published: February 2007

Results taken from 270 publications on rates are summarized, and collated with those from 149 publications reviewed previously (Young, 1969, 1974). The data are classified by major climatic zone, normal or steep relief, and consolidated or unconsolidated rocks. Representative rates and their ranges are given for soil creep, solifluction, surface wash, solution (chemical denudation), rock weathering, slope retreat, cliff (free face) retreat, marine cliff retreat, and denudation, the last being compared with representative rates of uplift. Solifluction is of the order of 10 times faster than soil creep, but both cause only very slow ground loss. Solution is an important cause of ground loss for siliceous rocks, on which it may be half as rapid as on limestones. Total denudation, brought about mainly by surface wash, reaches a maximum in the semi‐arid and probably also the tropical savanna zones. Acceleration of natural erosion rates by human activities ranges from 2–3 times with moderately intense land use to about 10 times with intensive land use (and considerably higher still where there is recognized accelerated soil erosion). Where there is active uplift, typical rates are of the order of 10 times faster than denudation, although in some high, steep mountain ranges these may approach equality.
Frost action and hydration as rock weathering mechanisms on schist: A laboratory study
Authors: Fahey Barry D.
Published: February 2007

Recently it has been proposed that stress generated by the adsorption of water to clay surfaces in argillaceous rocks may be an important agent of mechanical weathering in polar and alpine environments, implying that long‐held views on the status of frost action in these areas may be in need of revision.

This study documents the response, under controlled experimental conditions, of aggregates of fresh and partlyweathered schist and fresh pre‐cut schist blocks to 500 accelerated (12 hour) freeze‐thaw and hydration‐dehydration cycles. Aggregate samples subjected to freezing cycles produced the largest amounts of material in the less than 2 mm size range (an average of 8 per cent and 16 per cent for the fresh and partly‐weathered aggregates respectively), whereas humidity cycles above and below freezing yielded lesser amounts (3 per cent and 4 per cent respectively). The fresh schist blocks were found to be highly resistant to both mechanisms; only those experiencing freeze‐thaw oscillations produced measurable amounts of detritus.

Although hydration effects were not as effective as frost action in causing particle size reduction in aggregates, the two mechanisms may well reinforce one another in periglacial environments, enhancing the ability of these areas to serve as source regions for loess.
Lichenometric dating of debris‐flow deposits in the Scottish Highlands
Authors: Innes John L.
Published: February 2007

Debris‐flow deposits, dated by lichenometry, indicate that the majority of hillslope debris flows in Scotland have occurred within the last 500 years. Progressive weathering and climatic change can be discounted as the prime cause of the increase in the incidence of debris flows. The timing of the increase suggests that it is related to landuse changes in the Scottish Highlands during the 19th and early 20th centuries. Both burning and overgrazing can be cited as potential causal factors.
The temporal and spatial development of landslides in the axmouth‐lyme regis undercliffs national nature reserve, Devon
Authors: Pitts John
Published: February 2007

A chronology of landsliding is presented, including suggestions as to a date for initiation. Periods of activity known from historical sources are correlated with known periods of climatic deterioration. The current morphology of the landslide slopes is closely related to the geological succession and structure. These permit the landslides and their development to be differentiated on the basis of whole slope and toe morphology, and much of the whole‐slope activity can be related to conditions at the toe. Examples of geomorphological maps, slope categories maps, and cross sections are presented along with an example of the ‘evolutionary’ maps which may be derived from Ordnance Survey plans and aerial photographs. These generally indicate that weakening of materials by weathering, seepage erosion at the toe, and marine erosion result in frequent mass movement events of a low magnitude. These events ultimately influence the stability of larger slipped blocks behind, which fail less frequently. It is suggested that whole‐slope failures in this region have a maximum frequency of once in 120 to 150 years, and that problems of interpretation of historical accounts may mean that it is very much less frequent than this.
Response of the Ohau River and delta to lake level lowering
Authors: Mosley M. P.
Published: February 2007

The response of the Ohau River to a lowering of Lake Benmore of 4 m was monitored during a three‐month period when the river was carrying mean daily flows between 100 and 400 m3/s from a power station. Initially, the river degraded by up to 0·8 m for a distance of 1·3 km upstream from the lake, but during the 52‐day period of minimum lake level, the delta and lower channel aggraded by up to 0·4 m. During that period, an estimated 225 000 m3 of sediment was supplied to the delta, sufficient for rapid progradation of the delta front into the shallow lake and the observed aggradation of the channel and delta surface. Other factors, in this case receiving‐basin geometry and sediment yield, may thus control the response of a river‐delta system to relative base‐level lowering.
The pre‐glacial evolution of Wales
Authors: Battiau‐Queney Yvonne
Published: February 2007

The classical explanation of the development of the Welsh landscape by the effects of a pulsed ‘eustatic’ uplift during the Cenozoic times is challenged by new data on the geology and geomorphology of Wales and the adjacent regions.

The post‐Caledonian surface developed over most of Wales in the upper Westphalian plays a major role in landform development. Since its emergence before mid‐Cretaceous times, the Welsh Massif has suffered a long subaerial evolution which favoured a powerful chemical weathering. In Anglesey and St. David's Land, residual hills were formed by a process of differential weathering, and downwearing in saprolites. The Millstone Grit quartzites have been deeply weathered and dolines or flat‐bottomed basins have been developed.

From Cretaceous to Miocene times, a morphotectonic equilibrium has existed between uplift and denudation, so that, in the major part of Wales, the original planation surface was constantly maintained by lowering on itself and in some places it is possible to prove that no more than a few dozen metres of rock thickness disappeared during that period. Several main escarpments were produced by the warping of the planation surface along sharp flexures, during Neogene times. The Cenozoic vertical movements were controlled by the Caledonian or pre‐Caledonian tectonic pattern which has divided the continental crust into major structural units.

Welsh tectonic development is related to the opening of the North Atlantic, associated stresses reactivating ancient lines of weakness in the heterogeneous lower crust or upper mantle.
Rate of soil erosion processes on vineyards in central Piedmont (NW Italy)
Authors: Tropeano Domenico
Published: February 2007

The ‘Tertiary Basin of Piedmont’ is a hilly region, mainly composed of marine sediments, such as marls, silts and sands. The slopes, largely devoted to grape production, are usually kept bare of vegetation and are thus prone to soil erosion processes. For two years we have measured soil loss in relation to rainfall on experimental plots located in vineyards. In all the plots considered erosion started with low rainfall intensities (0·07 mm/min), and above 0·4 mm/min the amount of soil loss dramatically increased (to over 1800 g/m in one event). Most of the erosion occurs during summer rainstorms, but the behaviour of the soil under erosive rainfalls is very different from one site to another, depending only in part upon the various rainfall rates, soil and geometrical characteristics of the plots. It can be seen that soil loss varies from nearly negligible values (20 g/m/yr) to unacceptably high levels (to over 4·7 kg/m/yr), according to the different types of land cultivation. Deep ploughing and heavy herbicide treatment give rise to accelerated erosion processes leading to soil losses much higher than in other vineyard plots in Europe.
Frost weathering and the saturation of coastal rocks
Authors: Trenhaile A. S. , Mercan D. W.
Published: February 2007

Measurements were made of the water content in coastal rocks, by simulating tidal oscillations in the laboratory, and by field measurement in eastern Canada. If rapid freezing takes place upon exposure to the air, saturation levels may be high enough to permit frost weathering in fine grained rocks in the lower portions of the intertidal zone. Near the high tidal level, however, it may be dependent upon a supply of water from the ice foot and from melting snow. If freezing is slow, frost action may be inhibited by desorption of the rocks while they are exposed by the ebb tide. There was no evidence of a level of permanent sea water saturation within the intertidal zone. Ambient temperature and humidity may affect the rate of rock desorption.
Diffusion models of slope development
Authors: Trofimov A. M. , Moskovkin V. M.
Published: February 2007

This paper represents a systematic investigation of slope evolution diffusion models and has the following sections: (1) The model of slope development with linear coefficient k = k0x; (2) The model of slope development with quadratic coefficient in x; (3) Slope development model with vertical lowering of base level (downcutting); (4) Slope development model with the base level a horizontal variable (undercutting); (5) Steady‐state regime of undercut slopes; (6) Model of a pediment and scree slope formation.

The comparison is made between mathematical and classical methods of slope evolution analysis.
The influence of soil properties on the erodibility of Belgian loamy soils: A study based on rainfall simulation experiments
Authors: Verhaegen Th.
Published: February 2007

Twenty soils from the Leuven region were tested in the laboratory with a rainfall simulator. Their texture varied from loam to loamy sand. On the basis of the results obtained, they were classified as a function of the runoff and splash erodibility. For every soil, several properties were determined and tentatively used to explain the classifications based on the runoff and splash erodibility.

Significant negative correlations were found between silt content, aggregate stability, C5–10 index, water content at saturation, and cohesion on the one side and erodibility on the other; a positive correlation was found between sand content and erodibility.
Formation of afterflow silt loam deposits and structural modification due to drying under warm conditions: An experimental and micromorphological approach
Authors: Mücher H. J. , De Ploey J.
Published: February 2007

In earlier papers the authors discussed several micromorphological and textural characteristics of loamy afterflow deposits derived from loess material and formed during overland flow without splash. This discussion is completed by considering the critical load concentrations ccr for the start of sedimentation, taking into account the hydraulic properties of laminar flow. Furthermore, a remarkable combination of clayey and medium coarse, sandy laminae was observed in the deposits produced under laboratory conditions. Mechanisms are proposed to explain the affinity of these fractions for simultaneous deposition.

When laminated silt loam deposits are found in the Pleniglacial Middle loess deposits in the southern part of The Netherlands or in the Belgian Hesbayan loess, showing structural modifications, for example cracks formed after sedimentation, it is not always clear whether these modifications were the results of cold or relatively warm conditions. This paper describes micromorphological and laboratory investigations aimed at identifying criteria representative of warm conditions. The experiments examined the effect of drying on the structure of laminated silt loam deposits produced by afterflow and enabled the characterization of the modifications formed.

Drying could be done at room temperature, with circulating warm air, or at temperatures below 0°C. Elsewhere (see Coutard and Mücher, 1985), the influence of drying at temperatures below 0°C on the structures of an afterflow silt loam deposit will be discussed.

In comparison with the deformation in laminated silt loam deposits due to freeze‐drying, these new formations are small and have only locally influenced the sedimentary structures. These structure modifications are:

formations of cracks dominantly in clay layers and less (about 25 per cent of the cracks) in very fine silt layers, consisting of grains smaller than 10 μm in diameter, with only very locally deformations of the laminated structure;

only incidentally the cracks are partly refilled by a subsequent overland flow deposit, mostly only followed by sealing of cracks;

only incidentally the cracks are partly refilled by a subsequent overland flow deposit, mostly only followed by sealing of cracks;

curling or argillaceous laminae, maximum 5 mm in upward direction;

only very locally, formations of the tiny waved laminae, with a vertical amplitude between 100 and 400 μm, in combination with the occurrence of vesicles.
The potential use of pollen in the identification of suspended sediment sources
Authors: Brown A. G.
Published: February 2007

Pollen and spores form a significant part of the suspended organic load of a New Forest stream. Flood concentrations reach 230 grains ml−1 while baseflow carries under one grain ml−1. Hydrographs from different seasons show differing hysteretic loops for pollen and spore concentrations against discharge and suspended sediment. These variations reflect not only factors of production, but the type and distance of the contributing sources. This investigation suggests that variations in flood pollen and spore concentrations may be used to trace such suspended sediment sources as: eroding bedrock, channel banks, or hillslopes under specific vegetation covers.
The incidence and nature of bedload transport during flood flows in coarse‐grained alluvial channels
Authors: Reid Ian , Frostick Lynne E , Layman John T
Published: February 2007

A continuous record reveals that the incidence of bedload in a coarse‐grained river channel changes from flood to flood. Long periods of inactivity encourage the channel bed to consolidate sufficiently so that bedload is largely confined to the recession limb of the next flood‐wave. But when floods follow each other closely, the bed material is comparatively loose and offers less resistance to entrainment. In this case, substantial amounts of bedload are generated on the rising limb. This is confirmed by values of bed shear stress or stream power at the threshold of initial motion which can be up to five times the overall mean in the case of isolated floods or those which are the first of the season. This produces a complicated relationship between flow parameters and bedload and explains some of the difficulties in establishing bedload rating curves for coarse‐grained channels. Besides this, the threshold of initial motion is shown to occur at levels of bed shear stress three times those at the thresholds of final motion. This adds further confusion to attempts at developing predictive bedload equations and clearly indicates at least one reason why equations currently in use are unsatisfactory. Bedload is shown to be characterized by a series of pulses with a mean periodicity of 1.7 hours. In the absence of migrating bedforms, it is speculated that this well‐documented pattern reflects the passage of kinematic waves of particles in a slow‐moving traction carpet. The general pattern of bedload, including pulsations, is shown to occur more or less synchronously at different points across the stream channel.
Lake catchment based studies of erosion and denudation in the merevale catchment, Warwickshire, U.K.
Authors: Foster I. D. L. , Dearing J. A. , Simpson A. , Carter A. D. , Appleby P. G.
Published: February 2007

Sediment yields estimated from contemporary stream monitoring of suspended sediment in the Merevale forested catchment, North Warwickshire, were compared with the sediment yield record obtained from analysis of lake sediment in the downstream reservoir. Total sediment volume and mass for nine periods since 1861 were calculated by extrapolation of synchronous levels in 54 cores, identified from magnetic susceptibility and other magnetic measurements, and by using 210Pb and 137Cs analysis to provide an absolute sediment chronology. Sediment yield estimated from the two methods show comparable but low (50‐200 kg ha−1 yr−1) levels of sediment loss. While suggesting that lake sediments can be a useful means for extending the period over which contemporary monitoring exists, the study stresses the need for detailed historical records of land use and climate against which long term sediment yield records can be evaluated.
Salt marsh cliff stability in the oosterschelde
Authors: Van Eerdt Martha M.
Published: February 2007

Salt marsh cliff erosion in the Oosterschelde, due to basal scour and small‐scale failure, was monitored during a two‐year period using reference stakes. The composite marsh cliffs have a cantilever profile. Their stability is evaluated from beam failure analysis. A model is proposed, in which the cantilever weight is taken as the motive force; the major resistive force is the tensile strength. By substituting height, undermining width and soil mechanical properties of the cliff in the model, one can identify the cliffs that are likely to fail. Salt marsh cliffs, which combine a large tensile strength due to roots at the top of the profile with a large compressive stress at the cliff base due to the sandy texture of the subsoil, display the highest resistance to beam failure. The critical cliff dimensions, observed in the field, correspond with the values calculated from the proposed model of beam failure.
Thermal properties as controls on rock surface temperature maxima, and possible implications for rock weathering
Authors: McGreevy J. P.
Published: February 2007

Four rock types (basalt, sandstone, granite, and chalk) are examined with respect to the maximum surface temperatures which they experience when subjected to similar conditions of exposure. Rock temperature measurements are reported for an urban environment and for two experimental situations in which an infrared lamp is used to simulate heating under cold and hot conditions. Differences in rock temperatures are discussed with reference to thermal rock properties (albedo, specific heat capacity, and thermal conductivity). Some natural situations are suggested in which thermal rock properties could conceivably play a role in determining the extent to which rocks would be affected by particular weathering processes.
Holocene alluviation in Southeast England and some implications for palaeohydrological studies
Authors: Burrin P. J.
Published: February 2007

Implicit in models of palaeohydrological reconstruction is the assumption that a close relationship exists between climate, hydrological regime, and fluvial systems. Unfortunately, there can be a number of complicating factors involved, some of which are becoming increasingly well known. Research into Holocene alluviation in southeast England has demonstrated some associated difficulties which range from the problem of relating anthropogenically modified drainage networks to an understanding of contemporary rates of floodplain development to the impact of prehistoric societies on valley sedimentation. A theoretical model is presented whereby varying geomorphic domains contributing to floodplain and valley fill construction can be recognized. It is suggested that attempts to apply this framework to palaeohydrological studies may assist in the realization of a more accurate reconstruction in which former hydrological responses are integrated within a broader palaeoenvironmental context.
Trace elements in alluvia of the upper Vistula as indicators of palaeohydrology
Authors: Klimek Kazimierz , Zawilinska Lucyna
Published: February 2007

In the Vistula valley near Góra, at the northern foreland of the Carpathians Mountains, there are young alluvia deposited in the historical period. These alluvia are difficult to date precisely because of the lack of organic interbedded material. In the Vistula drainage basin upstream of Góra since the second half of 18th century small centres of metal, textile, motor, and petrochemical industries have been developed. Concentrations of trace elements such as: Cr, Mn, Co, Ni, Cu, Zn, Cd, Pb, and of some macroelements were used as indicators of the age of different alluvial fills. The main part of the Vistula valley floor was built up by sediment accumulation before the development of industry but after the medieval phase of rural colonization of the Carpathians. Deposits filling the abandoned channels dissecting the valley floor have an increased content of some trace elements and deposits date from the second half of the 18th century, when the first foundries and blacksmith's shops were developed. A drastic increase of concentration of the most abundant trace elements in the youngest alluvial fill indicates that the fill dates from the last decade of rapid industrial development.
A preliminary scanning electron microscope study of honeycomb weathering of sandstone in a coastal environment
Authors: McGreevy J. P.
Published: February 2007

Honeycomb weathering has been observed in a Carboniferous sandstone at a coastal location near Ballycastle on the north coast of Northern Ireland. Specimens of this sandstone have been analysed by X‐ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Results reveal that calcium sulphate (gypsum) is the only salt present and is found only at and immediately below the rock surface. SEM observations suggest that crystallization of salts in pores could easily dislodge quartz grains to promote granular disintegration, whilst etching of quartz grain surfaces attests to chemical weathering activity within the rock However, the reason for the development of the honeycomb pattern is not known.
Laboratory simulation of rock weathering by salt crystallization and hydration processes in hot, arid environments
Authors: Sperling C. H. B. , Cooke R. U.
Published: February 2007

The results of a series of experiments are reported in this paper which were designed to differentiate between the forces of crystal growth and hydration in salt weathering, using a single salt‐hydrate system (sodium sulphate), five contrasting rock types, and several diurnal temperature‐relative humidity cycles which permitted or inhibited these processes and simulated ground surface climates in hot, arid environments. It was shown that hydration of sodium sulphate is an effective mechanism of rock disintegration but that it is significantly less destructive than crystal growth pressure. Crystallization of thenardite (Na2SO4) is, in turn, more effective in rock weathering than the crystal growth of mirabilite (Na2SO4.10H2O). In general, rates of disintegration were most rapid where the diurnal temperature range was extreme and relative humidity lowest.
Surface sealing as influenced by slope angle and position of simulated stones in the top layer of loose sediments
Authors: Poesen Jean
Published: February 2007

The influence of five different slope angles and two different positions of simulated stones in the top layer of a sandy and a silty sediment on surface sealing intensity is examined in the laboratory. Sealing intensity is assessed by studying changes of percolation rate through a sediment layer with simulated rainfall duration and by measuring cohesion of the 5 mm thick upper sediment layer, a measure of seal strength, by means of a torvane. Slope has a negative influence on sealing intensity. For a constant per cent of simulated stone cover, sealing intensity is lowest in the case of stones placed on the sediment surface compared to the case of stones pushed into the surface layer. Explanations for these findings are given and some implications are further discussed.
An investigation into the relationship between salt weathering debris production and temperature
Authors: Davison Alan Paul
Published: February 2007

An investigation using laboratory simulation has been made using air temperature data for Tunisia, Antarctica, and southwest England. An experiment with a 50 cycle run produced results which showed significantly greater debris production in the Antarctica and Tunisian simulations than in the southwest England simulation.

Using X‐ray analysts to determine salt penetration, an inverse relationship between salt penetration and debris production was seen to exist. This could be the result of evaporation in the Tunisian simulation and rapid freezing in the Antarctic simulation, concentrating salts in the upper layers of the rock samples. In the southwest England simulation, no freezing, and relatively high humidities allowed greater penetration, thus distributing an equal input of salt over a greater area.

The author tentatively suggests the possible existence of a parabolic relationship between salt weathering and temperature.
Transporting capacity of overland flow on plane and on irregular beds
Authors: Govers G. , Rauws G
Published: February 2007

In this paper the transporting capacity of thin flows, in the laminar and transitional flow regime, is studied. Experiments were carried out on irregular as well as on plane beds, using two totally different set‐ups. The results of these two types of experiment were convergent. In both cases, sediment concentration was clearly related to grain shear velocity and unit stream power, expressed as the product of mean velocity and slope (Yang, 1973). The data agreed with those of Kramer and Meyer (1969). For a sandy bed, the unit stream power relationship was able to predict reasonably well the sediment concentrations measured on a mulched surface. For laminar and transitional flows, both the unit stream power and the shear velocity are related in the same way to slope and unit discharge. The unit stream power is a parameter which in particular can be very easily measured and might therefore become useful in obtaining a quick estimate of the transporting capacity of a thin flow. However, before a sediment transport equation for thin flows can be developed, more information is needed about the influence of the flow regime and grain size and density.
A sediment budget for a forested catchment in Luxembourg and its implications for channel development
Authors: Duijsings J. J. H. M.
Published: February 2007

In the forested catchments of the Luxembourg Keuper area, deeply‐incised valleys have developed in which streambank erosion is a widespread phenomenon. For one of the catchments in this area, the Schrondweilerbaach catchment, a sediment budget was constructed in order to determine the relative contributions of the various channel and valley slope processes to sediment output.

Streambanks contributed 53 percent of the output with bank scour and subsoil fall being the main processes while to a lesser extent bank material was supplied by bank failures, splash erosion, and soil creep. The remaining 47 per cent of the sediment was derived from the valley slopes mainly through the combined action of rainsplash detachment and overland flow transport. During the two years of investigations sediment output from the drainage basin almost equalled sediment input from streambanks and valley slopes. The results of the measurements of the various streambank processes are integrated in a descriptive model for the present‐day widening of valley incisions in the study area and used to hypothesize the palaeohydrological development of the basin. Special attention is paid to the (in)direct effects of the forest vegetation on streambank erosion and sediment transport through the stream channel.
Fractals in Karst
Authors: Laverty Martin
Published: February 2007

The analysis of cave survey data is used to establish that cave length exhibits fractal (self‐similar) behaviour, with dimensions in the range 1–1·5, over a range of measurement resolutions from 1 to 100 m. It is suggested that fractal dimensions, together with their range of applicability, will prove to be useful parameters for the study of caves.
A model of the redistribution of disaggregated soil particles by rainsplash
Authors: Wright Andrew C.
Published: February 2007

A model of the dispersion of splash droplets from a single raindrop impact on a sloping soil surface is combined with a theory of the entrainment of mineral particles from a disaggregated mixture in splash droplets to obtain a model of the dispersion of such particles by a raindrop impact. Stochastic modelling techniques extend this further to a model of the spatial redistribution of soil on a plot after a period of rainfall.

Since the model is probabilistic and physically based it enables the incorporation of further advances in the understanding of splash erosion at all stages and can simulate the effect of the stochastic nature of rainfall and soil properties on the process. Several different situations are simulated. These include the movement of marked soil particles from point sources and the spatial patterns of erosion on a sloping plot. The model can also simulate the differential erosion of different soil particle size fractions.
Intermittent surging movements of a coastal landslide
Authors: Grainger P. , Kalaugher P. G.
Published: February 2007

Since the late 1960s there has been a large mudslide in coastal cliffs of Permo‐Triassic strata (conglomerate overlying mudstone) at West Down Beacon, 2 km west of Budleigh Salterton, Devon. A total displacement of 100 m was achieved between 1981 and 1985 as the lobate toe of the mudslide pushed forward across the beach in eleven surges of movement. Each surge involved a displacement of between 5 and 15 m and was completed within a few hours. The toe moved by planar sliding, possibly on more than one seaward‐dipping shear surface or zone. Occasionally there were additional relatively minor displacements (less than 1 m), but normally the mudslide was stationary between the major surges. After each surge high‐oblique aerial photographs were obtained for stereoscopic interpretation. Debris falls from the cliff appear to have triggered some of the mudslide surges. A displacement recording of one surge has indicated that the rate of movement of the mudslide may have been partly controlled by variations in sea level during the tidal cycle.
Bedload transport and sediment yield in the Onyx River, Antarctica
Authors: Mosley M. P.
Published: February 2007

Bedload transport measurements were made in a braided reach of the Onyx River, Wright Valley, Antarctica, during summer 1984/85. Transport was predominantly of sand in the form of dunes, which moved in a band down the centre of the channels, the perimeters of which were composed of a gravel pavement created during short duration high flows in earlier years. Transport rates at‐a‐point and past‐a‐cross‐section were highly variable in space and time, even under conditions of constant discharge, and it was inferred that many factors other than hydraulic conditions—particularly sediment supply—control transport rates.

An empirical power function relationship between sediment discharge and water discharge was used to predict an average annual total sediment discharge of 3400 t y−1 past the study reach. This gives a specific sediment yield of 5.9 t km−2 · y−1, which is two orders of magnitude less than values for Arctic and Alpine proglacial rivers, and confirms earlier conclusions that sedimentation rates on Antarctic sandur are much lower than in the arctic.
Late quaternary monsoon patterns on the Loess Plateau of China
Authors: And Li Jijun , Zhaodon Feng , Lingyu Tang
Published: February 2007

China's Loess Plateau was formed under special conditions. The tectonic movement, topographical characteristics, and monsoon patterns combined to create a favourable environment for the accumulation of thick loessic deposits. The Loess Plateau itself is part of the ‘Monsoon Triangle’ of China, a region very susceptible to climatic changes. Throughout the Upper Pleistocene the palaeoenvironment on the Loess Plateau alternated from steppe, to deciduous forest and coniferous forest, in response to shifts in the atmospheric circulation. Three monsoon patterns appear to be indicated: (1) a full glacial monsoon pattern (18000–15000 yr BP) which induced a cold and dry climate favouring loess accumulation in steppe conditions; (2) an interglacial monsoon pattern (last interglacial and Holocene) in which a warm humid climate prevailed with deciduous forests, leaving palaeosols interbedded within the loess sequence; and (3) a transitional or interstadial monsoon pattern (50 000–23 000 yr BP) in which the climate was cold and humid in the Loess Plateau, encouraging the development of coniferous forest.
A preliminary electron probe study of microchemical variations in desert varnish in Western New South Wales, Australia
Authors: Dragovich D.
Published: February 2007

Examination of desert varnish samples from Australia by electron microprobe and energy dispersive spectrometry has shown that gross layering of iron‐ and manganese‐enrichments is variable. Surface (upper) varnish may be similar to lower varnish, or be relatively enriched in either iron or manganese. When viewed in sections cut parallel to the varnished surface, microlaminations with high manganese content (up to 30 per cent) were sometimes found in concentrically zoned patterns around grains.

Dorn et al. (1986) have proposed that chemical changes occur with increasing varnish age. In this study, the possibility of such changes was examined at the within‐varnish scale by comparing near‐surface and deeper (upper and lower) portions of the same varnishes. Variations in elemental ratios (K + Ca:Ti) at this scale were shown to be largely unsystematic, suggesting either that samples were unrepresentative; that element inputs to varnish have varied over time; that the varnish was too young for differentiation by weathering into an upper and lower layer; that varnish cover formed rapidly and at one time; or that existing varnish cover represents the coalescence of numerous individual patches of varnish, each of which formed over a relatively short period.
A contour‐based topographic model for hydrological and ecological applications
Authors: Moore I. D. , O'Loughlin E. M. , Burch G. J.
Published: February 2007

A digital model for discretizing three‐dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described. From this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area, element area, slope, and aspect. This form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon. The model therefore has wide potential application for representing the three‐dimensionality of natural terrain and water flow processes in the fields of hydrology, sedimentology, and geomorphology. Three example applications are presented and discussed. They are the prediction of zones of surface saturation, the prediction of the distribution of potential daily solar radiation, and the prediction of zones of erosion and deposition in a catchment.
A laboratory simulation of rock breakdown due to freeze‐thaw in a maritime Antarctic environment
Authors: Hall Kevin
Published: February 2007

Results of freeze‐thaw simulations on three large blocks of quartz‐micaschist are presented. Three types of water to ice phase change were identified from temperature and ultrasonic measurements. It is suggested that the type of phase change results from a particular combination of rock moisture content, solute concentration, freeze amplitude, and rate of fall of temperature. The temperature at which ice thawed inside the rock (−0.7 to −1.9°C) was also found, and this indicates the possibility of freeze‐thaw effects without positive temperatures. Approximately 80 per cent of the water that will freeze under natural conditions, in the Maritime Antarctic environment under study, appears to have done so by −6°.
Erosion of the eastern United States observed with 10Be
Authors: Brown Louis , Pavich Milan J. , Hickman R. E. , Klein Jeffrey , Middleton Roy
Published: February 2007

The problem of identifying areas of accelerated erosion in a dynamic landscape is complicated. The limited history of sediment yield measurements makes this task difficult even if geomorphic evidence is available. Beryllium‐10, a cosmogenic isotope produced by cosmic rays interacting with the earth's atmosphere and surface, has chemical and physical properties that make it useful as a tracer for erosion and sediment transport processes. The rarity of the stable isotope, 9Be, allows 10Be to be detected with accelerator mass spectrometry in natural materials at extremely low levels. Backgrounds for rocks and sediments below 105 atom per g are now attainable, a value to be compared with an average deposition rate of 1.3 × 106 atom cm−2 yr−1. The affinity of Be for the components of soil and sediment is sufficiently high that it is effectively immobilized on contact, thereby allowing 10Be to function as a tracer of sediment transport. To a good approximation all the 10Be transport out of a drainage basin is on the sediment leaving it. The number of 10Be atoms passing the gauging station can be determined by measuring the concentration of the isotope in the sediment, if the annual sediment load is known. The ratio of the 10Be carried from the basin by the sediment to that incident upon it, called the erosion index, has been determined for 48 drainage basins within the same physiographic province, which allows them to be reasonably compared, all of which have sediment yield data. Basins located in the Atlantic coastal plain have an average index of 0.3 with the maximum observed being 0.9. Basins located between the fall line and the mountains, a region called the Piedmont, have an average value of 2.2 with individual values ranging from 0.6 to 6.7; this marked difference is thought to result from two centuries of farming on land of moderate gradient. Basins in the highland regions reflect local conditions with low indices for those in grass and timber and high indices associated with destructive land use. The data allow an estimate of the erosion index for the pre‐colonial Piedmont, which then allows the pre‐colonial sediment yield to be calculated. A number of basins have also been examined world wide with similar conclusions derived. An important deviation from the rule is noted for rivers that erode large regions of loess, such as the Mississippi, Hwang Ho, and Yangtze. Large aeolian deposits were laid down during the ice age in these basins, deposits that brought inherited 10Be with them and that are easily eroded.
Holocene debris cone evolution in Glen Etive, Western Grampian Highlands, Scotland
Authors: Brazier Vanessa , Whittington Graeme , Ballantyne Colin K.
Published: February 2007

Stratigraphic investigations, radiocarbon dating of buried soils and pollen analyses were employed to reconstruct the history of development of a fluvially‐reworked debris cone in Glen Etive. Paraglacial aggradation of debris flow deposits resulted in cone formation between c. 10000 yr B.P. and c. 4000 yr B.P. until supplies of sediment from upslope were effectively exhausted and debris flow activity ceased. There ensued a prolonged period of stability and soil development on the cone surface. This ended sometime after c. 550 yr B.P. when human interference (including burning) resulted in destruction of the natural vegetation cover and triggered fluvial incision and the development of an alluvial fan of reworked sediment that buried the lower part of the debris cone. The wider implications of these findings are discussed.
Hydraulic geometry and changes in flow velocity at a river confluence with coarse bed material
Authors: Roy André G. , Roy René , Bergeron Normand
Published: February 2007

A survey of flows was conducted at a river confluence with coarse bed material. Bridges were installed on both tributaries, at the confluence and farther downstream on the receiving stream. At these stations, flow velocities were measured over a dense grid for seven conditions ranging from very low flows to the bankfull stage. Hydraulic geometry relationships established at all four stations revealed that flow is accelerated through the confluence as stage rises. At bankfull discharge, average velocity is 1.6 times higher at the confluence than on either tributary. Flow acceleration occurs at and above intermediate flow stages and is concentrated at the centre of a linear pool located at the confluence. The development of a zone of high shear stress is also associated with the cell of high flow velocity. Flow acceleration is dissipated at the exit of the pool where water surges over boulder ribs. The acceleration is not related to the development of flow separation zones as observed by Best and Reid (1984) for wide junction angles, nor is it explained by the reduction of the friction exerted by the banks. Acceleration is associated with the plan geometry of the confluence, with the lateral slopes which permit water to converge, and with a reduction in grain roughness at the confluence. Owing to the curvature of the tributary and to the acute angle of entry, relative power losses through the confluence decrease with increasing stages.
Bed load transport in braided gravel‐bed stream models
Authors: Ashmore Peter E.
Published: February 2007

Bed load transport rate was measured in ten self‐formed small‐scale gravel braided streams developed in a laboratory flume at several different values of steady discharge and flume gradient. The streams are approximate Froude models of typical prototype braided streams but of no particular river. Slight viscous effects may be present in the models because particle Reynolds numbers are close to 70. Total bed load discharge was measured every fifteen minutes throughout each 60 hour run. In addition, 80 channel cross‐sections were measured in each run to establish the average channel geometry.

Total bed load transport rate correlates well with total discharge and total stream power, although at a given stream power bed load discharge is greater when braiding is less intense and the width/depth ratio is lower. Analysis using unit stream power and cross‐section average bed shear stress reveals that the laboratory data conform to existing empirical bed load transport relationships. However, comparison with field data from gravel‐bed rivers shows discrepancies that may be due to differences in bed material size gradation and bed sediment structure.

At constant discharge, wide fluctuations in bed load discharge occur with some regularity. Periods range from 2 to 10 hours in the models, which is equivalent to several tens of hours in a prototype. The presence of these long‐period fluctuations compounds the problems of field measurement of bed load in braided streams.
A rational explanation of cross‐profile morphology for glacial valleys and of glacial valley development
Authors: Hirano Masasgige , Aniya Masamu
Published: February 2007

The fact that the cross‐profile of the glacial valley could be well approximated by parabolas (Y = aXb, b = 2.0) is explained by the variation principle, assuming that the glacier erosion works towards minimizing thefriction between ice and bedrock. The variation principle proves that the ideal or fully‐developed morphology of the glacial valley should be a catenary, the curve which a chain hanging from two fixed points forms. Maclaurin's series expansion of the catenary equation shows that a parabola is a very good approximation of the catenary; hence, the good approximation of the cross‐profile by parabolas.

Different catenaries are generated by changing the form ratio (depth/rim width) and are then approximated by Y = aXb by the method of last‐squares. The b values obtained become only fractionally larger than 2.0 with invreasing form ratios of up to 1.0, indicating that b values would range, in practice, between 1.0 and about 2.0 Two types of trend in the relationship between b values and the form ratio were obtained from several glaciers. For one type the b value becomes larger with increasing form ratios, and for the other the opposite. The first type is called the Rocky Mountain model after its source of data and represents overdeepening of the glacial valley development. The second type is caalled the Patagonia‐Antarctica model, representing a widening, instead of a deepening, process of development. These differences are attributed to the nature of the glaciers which produced these valleys, i.e. alpine glaciers and continental ice sheets.
Particle dislodgement from a flat sand bed by wind
Authors: Willetts Brian B. , Rice And M. Ann
Published: February 2007

The rate, with respect to area and time, at which grains are dislodged from a sand bed for given wind conditions is an important factor in determining the grain transport rate and the intensity of grain activity in each of the transport modes. The literature of the subject contains little direct information about particle dislodgement.

The paper describes a series of experiments in which dyed sand grains, spread on the surface of quartz dune sand in a wind‐tunnel, were photographed at five second intervals while the sand was exposed to wind. The data on rate of loss of coloured grains was used, for two of three chosen size fractions, to deduce the dislodgement rate for each size fraction. The variation of this dislodgement rate with shear velocity is shown graphically for values of u* between 24 cm s−1 and 50 cm s−1. Because of the artificial method of distribution of the coloured sand grains, the results should be applied with caution to natural conditions.

The interpretation of the observations of dyed grain loss involved the numerical simulation of the process which comprises removal of coloured grains, slightly offset by replenishment as upwind coloured grains settle briefly in the observed zone. An estimation of grain excursion length has to be incorporated in the simulation. This estimation was made by trial, but general corroboration was found from earlier work.

Comparisons are made between dislodgement rates obtained thus and rates estimated by Anderson (1986) and by Jensen and Sorensen (1986). Reasonable agreement with the latter is found in the u* range 30 cm s−1.