bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flood and vortex scour of the channel bed of the Prosna river, and their depth range
Authors: Młynarczyk Zygmunt , Rotnicki Karol 
Published: February 2007

AbstractFlood and vortex scour were observed in the Prosna channel (Central Poland) in the years 1980–1985. Flood scour increases the thickness of the reworked channel deposits by 30 per cent to 66 per cent, in relation to the thickness determined by the elevation of the normal bed and the bankfull stage. Vortex scour can increase the thickness by as much as 90–95 per cent. Knowledge of these properties of contemporary alluvium allows correct palaeohydrological and stratigraphic interpretation of the alluvial fills of valley floors.
Rates and patterns of bedrock denudation by coastal salt spray weathering: A seven‐year record
Authors: Mottershead D. N. 
Published: February 2007

AbstractRapid surface lowering of bedrock is taking place in the supratidal zone by salt spray weathering. A seven‐year run of data demonstrates a mean rate of lowering of 0·625 mm a−1. Considerable variation exists in annual point lowering values within measurement sites, although between‐site variation is not significant. Aggregate year to year variations in surface lowering are not significant. Spatial variation in individual point values may be compensated by temporal variation over an 11‐year period. There is a marked summer maximum in surface lowering rate, and this is strongly correlated with monthly air temperature. Spatially and temporally episodic swelling of the rock surface is demonstrated. This does not correlate statistically with any available climatic variable and is deemed to be a real and largely stochastic phenomenon. It is interpreted as rock bursting at the granular scale due to haloclasty. The processes most likely to be responsible for the observed rapid denudation are crystallization and thermal expansion of halite, both of which are enhanced by high summer temperatures.
Stemflow and throughfall in a tropical dry forest
Authors: Kellman Martin , Roulet Nigel 
Published: February 2007

AbstractThe rainfall received by a small plot of tropical deciduous forest on sand dunes in Veracruz, Mexico, was partitioned into stemflow and throughfall components to determine whether funnelling by stemflow could reduce soil leaching by transmitting large volumes of water through vertical soil pathways beneath each stem. Although soil infiltration capacities were high, only a very small proportion of incoming rainfall was funnelled by canopy stems. This is attributed to the widely‐branched morphology of mature trees. Smaller trees and shrubs were more effective funnellers of rainfall, and a crude estimate of the magnitude of stemflow in the understorey stratum in one rain event suggested a contribution approximately ten times that of canopy stemflow. However, even if augmented by the understorey stratum in this way, total stemflow is unlikely to have exceeded 10 per cent of gross precipitation, implying that it does not represent an important leaching‐avoidance mechanism in this forest.
Blanket peat erosion in a mid‐wales catchment during two drought years
Authors: Francis I. S. 
Published: February 2007

AbstractThe rate of blanket peat erosion was measured at an upland site in central Wales during the 1983‐1984 drought years. Erosion pins, a peat surface sediment trap, and sediment sampling in the effluent stream, were used to estimate the rate of peat surface recession and the rate of organic sediment loss from the catchment. An overall rate of surface recession of 16 mm y−1 on exposed peat faces was recorded; this differed between faces of different aspects, with the greatest recession on southwest faces. Eroding peat surfaces exhibited maximum recession during the summer, but the peat surface sediment trap indicated that the highest rates of sediment loss from peat faces due to rain wash occurred during the autumn and early winter. Stream sediment sampling showed that the yield of organic sediment from the catchment was 34·4 t km−2 yr−1, with greatest losses also during the autumn and early winter. The evidence suggested that the surface recession, as measured on erosion pins, included a ‘wastage’ or shrinkage component, which possibly accounted for as much as 80 per cent of the apparent loss. Direct and circumstantial evidence suggested that peat wastage during the summer months was the most important agent of surface recession in the study period, which encompassed the two dry summers. Desiccation provided available sediment during the autumn, but organic sediment supply became limited as the winter progressed, despite the occurrence of frost heave.
The weathering effects of the lichen Lecidea aff. Sarcogynoides (Koerb.) on magaliesberg quartzite
Authors: Cooks J. , Otto E. 
Published: February 2007

AbstractThe effect of the weathering processes generated by Lecidea aff. Sarcogynoides (Koerb.) on the substrate was studied by means of a scanning electron microscope. The elements present in the substrate (Magaliesberg quartzite) and in the lichen thallus were determined by X‐ray fluorescence spectrometry for the purpose of comparison. The elements present were mostly similar although a few were present in the thallus which were not observed in the quartzite. It is possible that those elements present in the lichen thallus which were not present in the substrate may have been extracted from the atmosphere. The occurrence of small hollows (weathering pits) in which the early stages of plant development occurs, and the disintegration of the rock indicate that Lecidea aff. sarcogynoides (Koerb.) contributes to the chemical weathering processes by chelation and mechanically by the penetration and expansion of hyphae. A model is proposed in which a possible mechanism for these weathering processes is suggested.
Velocity‐discharge relationships in three lowland rivers
Authors: Knighton A. D. , Cryer R. 
Published: February 2007

AbstractThe use of different functional forms to describe the variation of velocity with discharge is explored for four cross‐sections, nine short reaches (100‐250 m), and three long reaches (2‐7 km) in three lowland rivers in Lincolnshire. The traditional log‐linear relationship applies to more than half the cases, the degree of correlation never falling below 0‐9. Although probably more valid from a physical standpoint, the log‐quadratic relationship‐is only moderately successful, one problem being the position of the vertex relative to bankfull discharge. Alternative formulations based on a kinematic routing model and a partitioned log‐linear model have restricted application. Rates of change of velocity with discharge are relatively high in these lowland rivers, not only at‐a‐station but also downstream. One explanation is that velocity becomes particularly sensitive to local slope and within‐channel vegetation conditions as discharge decreases, resulting in rather low velocities at small discharges.Cross‐sectional and reach‐based results are compared for neighbouring stretches of river. Velocities in short reaches do not differ appreciably from those at nearby cross‐sections or from those in long reaches with a length of less than 3 km. By integrating within‐reach variability and avoiding the need to chose a representative cross‐section, velocity measurement over short reaches is probably preferable to that at cross‐sections as a basis for at‐a‐station hydraulic geometry.
Effects of vegetation on soil slippage by pore pressure modification
Authors: Terwilliger Valery J. 
Published: February 2007

AbstractInfluences of vegetation on shallow (< 1 m) soil slip formation through modification of soil water was investigated on hillsides covered by verdant chaparral (dense shrubland), and burned vegetation in the Transverse Ranges of California. Per cent available water and hydraulic potentials were obtained from electrical resistance blocks and tensiometers for one year in soils under burned and unburned vegetation on three slopes. Soil remained moister during a dry period under burned vegetation than under unburned chaparral on two of the three slopes studied. Daily increases in per cent available water and hydraulic potential of soils were greatest for a given storm where soil was driest prior to the storm. Furthermore, water levels in soil tended to be greatest for a given storm where soil water levels had been lowest prior to the storm. These two findings were corroborated by laboratory wetting trials on undisturbed soils of vastly differing mechanical properties in that initially drier soils always absorbed water faster and became wetter than initially moister soils. In the field, soil water levels became similarly high under all vegetation after several storms and varied little throughout the remainder of the wet season. These results contradict the common assumption that depletion of soil water by vegetation would result in slower saturation rates and hence greater resistance of a soil mass to slippage.
Developments in a non‐destructive method of determining rock strength
Authors: Allison Robert J. 
Published: February 2007

AbstractMaterial strength is an important variable for any study of the relationships between rock mass geomechanical characteristics and landform development. Standard field and laboratory tests for measuring strength present a variety of problems to the geomorphologist. Recent studies (Allison, 1988) have described a laboratory based non‐destructive method for indirectly determining material strength, by measuring Dynamic Young's Modulus. Data presented here suggest that the same apparatus can be used as a field technique. Tests have been conducted on the Devonian limestone of the Napier Range, Western Australia. Laboratory results obtained using the non‐destructive ultrasonic apparatus have a high correlation with triaxial Hoek Cell tests. Results from on‐site tests have much greater accuracy than data collected using the Schmidt hammer, which is currently the most widely used geomorphological field technique for determining rock strength.
Topography and ice sheet growth
Authors: Payne Antony , Sugden David 
Published: February 2007

AbstractThis paper uses a numerical ice sheet model to investigate the role of topography in influencing ice sheet growth. The model is applied to the maritime, mid‐latitude uplands of Scotland and relies on a series of assumptions about mass balance, topography, and ice flow. It is driven by an imposed pattern of temperature change. The model is able to predict effectively the extent and thickness of the Loch Lomond ice sheet, using a palaeotemperature curve based on Coleoptera assemblages.A series of experiments with a stepped, constant July air temperature depression suggests that in Scotland a change in excess of −3·0°C is necessary to initiate ice sheet growth; that steady state ice caps build up at changes of −3 to − 6·5°C; and that large ice sheets build up at changes of more than − 6·625°C. The bifurcation revealed by the last two types of behaviour is the result of topography. Both the vertical amplitude and the spatial distribution of bedrock basins and ridges are important in determining the pattern, rate, and extent of ice sheet growth. The implication is that topography plays an important role in determining the dynamics of ice sheet growth.
Differential weathering of feldspar and pyroxene in an arctic‐alpine environment
Authors: McCarroll Danny 
Published: February 2007

AbstractThe relative relief of adjacent plagioclase and pyroxene minerals was accurately measured on a recently‐exhumed outcrop of gabbroic rocks in Leirdalen, southern Norway. Above the level of the former soil surface the feldspars protrude above the pyroxenes whereas below that level the pyroxenes are higher. Differential relief declines with increasing depth of burial down to 80 cm. On exposed surfaces the mean loss of pyroxene relative to feldspar is 103 cm3 m−2 of rock surface. With burial down to 50 cm in an arctic‐alpine Brown Soil the mean loss of feldspar relative to pyroxene is 179 cm3 m−2. These figures represent minimum amounts of weathering over about 9000 years. The results confirm the importance of chemical weathering in arctic‐alpine environments and the techniques may provide useful physical measures of degree of weathering for use in rate studies and relative‐dating.
Experimental frost and salt weathering of chalk—II
Authors: Jerwood L. C. , Robinson D. A. , Williams R. B. G. 
Published: February 2007

AbstractExperiments are described in which chalk cubes were soaked in solutions of either sodium chloride, sodium sulphate, or magnesium sulphate at concentrations of 5·5 per cent and 12·5 per cent, or in a mixed solution of sodium chloride and sodium sulphate or in distilled water. After removal of excess liquid, the cubes were subjected to six freeze–thaw cycles with temperatures ranging from either +15 to −10°C or +15 to −30°C. The results confirm that frost weathering can be enhanced by the presence of certain salts, but the extent of weathering was much less than that previously reported for samples frozen totally immersed in the same liquids. Evidence is presented which suggests that salt crystallization is the major weathering process operative when non–immersed samples are frozen but a combination of frost and salt weathering operates when fully immersed samples are frozen.
Influence of lithologic erodibility on alluvial fan area, western white mountains, California and Nevada
Authors: Lecce Scott A. 
Published: February 2007

AbstractDifferences in lithologic erodibility and sediment storage within a drainage basin affect the relationship between alluvial fan area and drainage basin area along the western White Mountains. Large fans are produced by basins underlain by resistant rocks, which have steep and narrow trunk stream canyons with little sediment in storage. Small fans are produced by basins composed of erodible lithologic units, which have wider valley floors, lower valley‐side slopes, and considerably more sediment stored along trunk stream canyons than is the case in basins underlain by resistant rocks.
The weathering rates of some sandstone cliffs central Weald, England
Authors: Pentecost Allan 
Published: February 2007

AbstractShort‐term (1‐30 months) weathering rates were obtained for steep cliffs of Cretaceous Ardingly Sandstone in southern England, using a new photographic method. Mean rates for an exposed and a sheltered outcrop were 0.11 and 0.033 mm a−1 respectively. Significant (p < 0.1) positive correlations were obtained with illumination and algal biomass and a significant negative correlation (p < 0.05) with slope angle. There was no correlation with grain size, porosity, or mean surface temperature. Highest weathering rates were observed on south‐ and west‐facing exposed cliffs. The results are discussed with reference to algal growth, climate, and wind direction.
Statistical analysis of factors influencing Cliff erosion along a section of the West Wales coast, U.K.
Authors: Jones D. G. , Williams A. T. 
Published: February 2007

AbstractCliff erosion along a section of the West Wales coastline is described. Rockfalls, mudslides, and retreating fencelines are evidence of current activity. Measurements over a two‐year period (1983‐85) gave mean annual recession figures of up to 0.25 m yr−1 for glacial embayments. Wave refraction modelling and longshore beach surveys confirmed the existence of ‘high’ and ‘low’ beaches. Factors influencing variation in recession rates were identified and measured. Regression analysis suggested that the volume of beach‐face material was the dominant explanatory variable in short‐term cliff erosion.
Behaviour of beach profiles during accretion and erosion dominated periods
Authors: Thom B. G. , Hall W. 
Published: February 2007

AbstractBeach profiles have been surveyed at monthly intervals between 1972 and 1988 at Moruya on the South Coast of New South Wales, Australia. Four profile sites have been used as a data set to provide an understanding of changes to beach volume, width, and shape. Moruya beach represents a moderately high energy, microtidal environment, which responds in a dramatic way to major storm events such as those experienced in the mid‐1970s. This study distinguishes between profile characteristics associated with such a period (erosion‐dominated or EDP) compared with periods when accretion dominated (ADP) accompanied by foredune expansion in both height and width.
Sediment transport by burrowing mammals, Marin County, California
Authors: Black Thomas A. , Montgomery David R. 
Published: February 2007

AbstractField observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in Marin County, California. Spatial concentrations of the 1150 gopher mounds surveyed vary from 0‐16 mounds m−2 on interfluves to 0.32 mounds m−2 on sideslopes and in the topographic hollow, with localized concentrations of up to 2.88 mounds m−2 on the margins of the colluvial deposit. Simple models of sediment transport by burrowing activity yield estimates of between 0.91 and 2.33 cm3 cm−1 yr−1 for the basin as a whole, with absolute minimum and maximum rates of 0.48 and 631 cm3 cm−1 yr−1. These values are similar to those previously estimated for this area (Lehre, 1982) and are nearly an order‐of‐magnitude less than average long‐term sediment transport rates at the same site (Reneau, 1988).
GIS techniques and statistical models in evaluating landslide hazard
Authors: Carrara A. , Cardinali M. , Detti R. , Guzzetti F. , Pasqui V. , Reichenbach P. 
Published: February 2007

AbstractGeographical Information Systems (GIS) and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard.From a small drainage basin located in Central Italy, relevant geological and geomorphological factors were collected and processed by applying GIS technology. In particular, modules were used which both generate high‐fidelity digital terrain models and automatically partition the terrain into main slope‐units. The resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope‐unit. Although not lacking drawbacks, the method proved to be a feasible and cost‐effective approach to landslide susceptibility assessment and mapping.
Assessment of the sensitivity of the landscape in a sample area in Hungary for climatic variability
Authors: Kerényi Attila , Csorba Peter 
Published: February 2007

AbstractIn the northeastern part of Hungary near the township of Tokaj a landscape research project has been performed in a 9 km2 area. The aim of this study is to examine the possibilities of expressing the climatic sensitivity of the given small landscape unit by analysing the capabilities of such a small sample area and synthésizing the data obtained. The landscape analysis consisted of field and laboratory measurements, theoretical calculations, analyses of maps, as well as the construction of thematic maps (on the scale of 1:10000) and cartograms.In view of climatic sensitivity four of the landscape factors were regarded as crucial: (1) the water budget of the soils, (2) the thickness of the soils and loose sediments, (3) insolation, and (4) land use. By synthesis of these factors a five‐grade climatic sensitivity map was produced. On the basis of the areal proportion of the different classes of sensitivity it was established that the study area is moderately sensitive to climate. Examination of the moisture content of soil clearly indicated different responses of the areas from the different sensitivity classes to changes in temperature and precipitation. The four main landscape factors selected proved to be useful in the rough delineation of the classes on the climatic sensitivity map. However, the use of the other landscape factors improved its accuracy.
The influence of sediment supply on the channel morphology of upland streams: Howgill Fells, Northwest England
Authors: Harvey A. M. 
Published: February 2007

AbstractPrevious work on stream channels in upland areas of Britain has demonstrated a close control over channel morphology and stability by the rate of coarse sediment supply from the hillslopes of the catchment. Streams fed by large amounts of coarse sediment develop unstable, wide, often braided channels, whereas those with limited coarse sediment supply develop stable, much narrower, often meandering channels. The sediment supply from hillslopes is controlled by thresholds of hillslope stability, storm event frequency, and the coupling between the hillslopes and the channel. Climatically‐induced changes in any of these three factors may have implications for channel morphology and stability. This paper examines these implications in British upland fluvial systems, with particular reference to the Howgill Fells, Cumbria, in the contexts of the adjustment of stream channels to sediment supply from erosional gully systems, and their response to and recovery from major flood events.
Simulated aeolian abrasion of Pannonian sands and its implications for the origins of Hungarian loess
Authors: Smith B. J. , Wright J. S. , Whalley W. B. 
Published: February 2007

AbstractQuartz sand from southern Hungary was agitated for 128 hours in an abrasion chamber using a constant airstream. The fines produced by abrasion were collected from the exhaust air using an electrostatic precipitator. Analysis of the fines at set intervals by Coulter Counter show particle size distributions after 16 hours with > 50 per cent in the 20‐60 μm range (the size range normally associated with loess deposits). Results demonstrate the feasibility of a local, abrasion derived contribution to Hungarian loess.
Alluvial cutoffs as indicators of former channel conditions
Authors: Erskine Wayne , McFadden Christopher , Bishop Paul 
Published: February 2007

AbstractAlthough alluvial cutoffs record accurately the geometry, bedforms, and bed material of the channel when last active, few attempts have been made to use cutoffs in studies of channel changes. A detailed record of historical channel changes on the lower Hunter River in southeastern Australia has shown that this channel responds to naturally alternating periods of high and low flood activity, called flood‐ and drought‐dominated regimes respectively. Sinuosity decreased from 3·84 in 1870, to 2·66 in 1893 and to 1·38 in 1970 through the development of eight cutoffs. The channel also aggraded with medium sand burying the former bed material of mixed mud, coarse sand, and gravel. Channel straightening was a response to increased flood frequencies during the flood‐dominated regimes of the late 19th and 20th centuries, combined with localized river engineering works and increased sand load.Detailed stratigraphic studies were carried out on three neck cutoffs and one chute cutoff which were abandoned in 1890, 1950, 1952, and 1956. A comparison of former and present bed elevations and bed material size showed similar trends to those determined by the historical record, confirming the reliability of cutoffs as indicators of former channel conditions.The sedimentary infills of the cutoffs are not uniformly fine grained as recorded previously in the literature. Relatively thin, fine‐grained fills were deposited during the drought‐dominated regime of the first half of this century but thick, coarser‐grained fills were deposited after 1949 during the flood‐dominated regime. All fills fine upwards. Cutoff infills provide a record of changing flood activity and sediment loads.