bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature and importance of mass‐wasting by rock glaciers in alpine permafrost environments
Authors: Barsch Dietrich 
Published: February 2007

AbstractActive rock glaciers are forms of and indicators for alpine permafrost. On average every individual transports a volume of 1.2‐1.6 × 106 m3 of talus and ice with a speed of 5‐100 cm/yr. The amount of talus in a rock glacier is about 40‐50 per cent of the total volume. Active rock glaciers are therefore an important talus transport system of the periglacial zone of high mountains. They form below talus slopes and beneath small glaciers, and they resemble therefore talus transport systems in continuation of the talus slope or the glacier transport system.According to our estimation (Tables II, III and IV) the total volume of all 994 active rock glaciers in the Swiss Alps is 1,200‐1,600 × 106 m3. The total amount of talus on the move is estimated to be 500‐800 × 106 m3, and the mass‐wasting by active rock glaciers per year is then 450‐600 × 106 m × t (horizontal) and 140‐190 × 106 m × t (vertical) for a movement of 0.3 m/yr and a slope of 30 per cent (= 17°). In relation to the unit of area (km2) these values represent 20 per cent of the total mass‐wasting in the eastern Swiss Alps according to Jäckli (1957) or 160 per cent of the mass‐wasting in Kärkevagge according to Rapp (1960).
Soil erosion processes and their measurement in the german area of the Moselle river
Authors: Richter Gerold , Negendank Jörg F. W. 
Published: February 2007

AbstractMeasurements and observations of soil erosion processes in vineyards on steep slopes in the German portion of the Moselle valley‐are described. Rates of erosion caused by gravitational mass movements and the action of running water differ. Catastrophic geomorphic events since 1972 are described qualitatively while quantitative data on precipitation, runoff, soil and solute loss during one year (1974‐5) from 13 plots in old and new vineyards (measuring 2m × 8, 16, 24, 32 and 48m) are presented. On the 20° slope plots erosion rates were 2.7cm/1,000 years in the old vineyard and 4.4 cm/1,000 years in the new vineyard.These results compare favourably with rates of 0.75‐4‐4 cm/1.000 years calculated from geological evidence. Both values are lower than those from many other agricultural plots and probably reflect the relative stability of the stony loams.
Erosion of fixed dunes in the Sahel, Central Niger
Authors: Talbot M. R. , Williams M. A. J. 
Published: February 2007

AbstractDuring the 1974 rainy season gullies of the order of 150–300 m long were active on the flanks of fixed Pleistocene dunes in the vicinity of Janjari, central Niger. The gullies terminate on small (0.5–1 × 104m2) alluvial fans, where sand deposition had occurred below the intersection point. Gully activity was probably the result of a particularly severe storm. Comparison between fixed dunes subject to differing climatic conditions suggests that gullying and alluvial fan formation may be characteristic of a restricted morphoclimatic zone.
The analysis of drainage network composition
Authors: Smart J. S. 
Published: February 2007

AbstractThe Horton method of analyzing drainage network composition is reviewed, with the conclusion that it has not been very effective either in improving understanding or in developing useful methods of characterizing drainage basins. New methods which are based on the link rather than the Horton (or Strahler) stream are described. A number of detailed examples of the application of these new methods to the topologic and geometric properties of networks are provided. The results are compared with the predictions of the random model.Data used in the analysis were obtained from 1:24,000 U.S.G.S. topographic maps of eastern Kentucky. Thirty drainage basins were selected and their channel networks were outlined first by the contour‐crenulation (CC) method and then by another, more objective, method (SC) in which stream sources were identified by a quantitative slope criterion. The CC and SC samples comprise about 8,700 and 1,700 links, respectively.The three most important results of the analysis are: (1) the channel networks are slightly but significantly more elongated than predicted by the random model, (2) there are fewer second magnitude links than predicted, and (3) the length distribution for interior links depends upon the kind of link (interior or exterior) joined downstream. These features are found in both CC and SC networks.
The assessment of sediment sources: A field experiment
Authors: Lewin J. , Wolfenden P. J. 
Published: February 2007

AbstractThe possibility of using metals from mining activity as tracers for identifying stream sediment sources is explored. Sampling of monthly bed sediment yield and of the spatial and temporal variation in Pb concentration was undertaken in a 1·02 km2 catchment, and estimates of the sediment contribution from different stream reaches are calculated. The method has considerable limitations, for metal concentrations are notably dependent on sediment size, season, source availability, and the chemical mobility of the metal used. In most natural streams these must preclude the use of pollutants for simple sediment source identification.
After horton
Authors: Kennedy Barbara A. 
Published: February 2007

AbstractThe divergent and yet related problems of post‐Hortonian studies of drainage density and channel network geometry are viewed against the difficulties of defining first‐order channels and basins. It is proposed that the junction of an unbranched perennial (or blue‐line) channel with another perennial channel be taken as the starting point for definitions and that the entire contour‐crenulation network tributary to that point be considered the first‐order stream. It is shown that the concept of network diameter may be used to describe the networks so delimited and that it appears to provide a useful starting point for interregional comparisons. Finally, an analysis of Blyth and Rodda's (1973) data on channel lengths and discharge indicates that network diameter may be as closely related to discharge as is channel length itself.
Drainage density changes during rainfall
Authors: Day D. G. 
Published: February 2007

AbstractObservations of stream behaviour during rainfall indicate that previous notions of a simple expanding and contracting network need review and refinement. In a small rural catchment near Armidale, N.S.W. changes in flowing stream length during rainfall have been depicted on flow length graphs which indicate a varied network response to similar rainfall amounts. Channel flow phenomena include discontinuous flow, the generation of flow points within the channel and movement of water downslope from saturated depression sources. Localized physical controls have a significant effect on stream growth which is a sensitive indicator of the catchment response to rainfall. During rapid changes in stream length total flowing length and discharge are highly correlated. A model of the pattern of network expansion and contraction involves several phases of flow contraction.
Karst depressions in a time context
Authors: Kemmerly Phillip R. , Towe Susan K. 
Published: February 2007

AbstractA study of karst depression enlargement through time on the Western Highland Rim (physiographic province), based on two sets of aerial photography (1937, 1972) and field work, indicates that areal growth rates (dA/dt, m2/a) depend upon the surficial geologic setting. Areal growth rates were calculated from rates of long axis (dL/dt) and mean width (dW/dt) enlargement assuming an elliptical plan shape. Areal growth rates averaged 40, 70, and 100 m2/century for loessial, clayey residual, and silty colluvial surficial material, respectively.Estimates of average apparent age of karst depressions in each of the three surficial materials, based on linear growth rates, varied from 25,000 to 65,000 years B.P. An occurrence of mastodon (Mammut americanum) and ground sloth (Megalonyx jeffersoni) from the Darks Mill depression as well as a pollen record from another depression dating from the Late Wisconsin glacial maximum in the same geomorphic setting yielded dates compatible with estimates of depression age.
The relationship between the soil erodibility factor K (Universal soil loss equation), aggregate stability and micromorphological properties of soils in the Hornos area, S. Spain
Authors: de Meester T. , Jungerius P. D. 
Published: February 2007

AbstractWischmeier's soil erodibility factor K calculated for 10 surface soils in the Hornos area, S. Spain, is compared with 3 aspects of aggregate stability. A significant correlation is found with the percentage of particles < 100 μm after aggregate breakdown, which is used as a measure of the vulnerability of the soil to erosion by overland flow. No significant correlation exists with the number of water drops required to cause breakdown of the aggregates nor with the mean size of the shattered aggregates, both being aspects of the resistance of aggregates to splash erosion. Of the micromorphological and analytical soil properties explaining aggregate stability, only the clay and silt content and the number of closed voids are significantly correlated with the factor K. The aggregate stability of the investigated soils is mainly determined by soil properties inherited from the parent material; the stabilizing effect of pedological features is small.
Chemical weathering in a drainage basin underlain by old red sandstone
Authors: Waylen M. J. 
Published: February 2007

AbstractA hydrochemical budget is used to quantify the rate of chemical weathering and solutional denudation on Old Red Sandstone in East Twin drainage basin (0.2 km2) on the Mendip Hills for the 1972–73 Water Year. Net nutrient uptake by the biomass and precipitation inputs are subtracted from stream solute outputs to give an estimate of the solutes released to the system by weathering. The mineralogies of the sandstone and the soil are compared to predict possible weathering reactions for the primary and secondary minerals. Tentative estimates of primary mineral alteration and secondary mineral formation are then made by substituting the hydrochemical balances into the formulated weathering reactions. Finally the rate of solutional denudation (0.8 tonnes/a or 1.6 mm/100 a) is compared with other estimates of solutional and mechanical denudation at East Twin and with similarly derived results for other lithologies.
Bedrock freeze‐thaw weathering regime in an alpine environment, colorado front range
Authors: Thorn Colin E. 
Published: February 2007

AbstractReduced major axis analysis is used to describe monthly temperature averages for daily maxima, minima, means and ranges at a sequence of bedrock microenvironments in the alpine zone of the Colorado Front Range. Seven thermistors buried at 1 cm in bedrock provide comparative data on easterly, southerly and westerly aspects, and also upon the impact of snow accumulation (⩽0.5m to ≥4.0m deep) against an east‐facing rock wall. Intersite temperatures commonly differ by less than 5°C and, rarely, by more than 10°C. The freezing intensity of freeze‐thaw cycles occurring within the confines of a seasonal snow patch rarely dropped to −5°C, while at snowfree, vertical faces freezing dropped to −5°C quite commonly. Comparison with laboratory established criteria for effective freeze‐thaw weathering (abundant moisture and freezing to at least −5°C) suggests that moisture rich microsites lack adequate freezing intensity, while adequately frozen sites lack moisture. Available data suggest that the overlap between freeze‐thaw and hydration weathering requires careful re‐evaluation.
The relationship between throughflow generation and the solute concentration of soil and stream water
Authors: Burt T. P. 
Published: February 2007

AbstractVariation in solute concentrations of soil and stream water during throughflow events was studied at Bicknoller Combe, Somerset, England. The main hydrological process acting in the catchment involves a delayed throughflow discharge pulse a day or two after the rainfall event. During the period of storm runoff, coincident with the rainfall, the solutes in the stream are diluted, but their concentration in the throughflow remains unchanged. During the delayed throughflow pulse, concentrations of both soil and stream water increase. This is due to additional leaching from the soil in hollows where saturated moisture conditions prevail. The results suggest that two distinct erosional environments may exist: on the spurs, leaching seems to be related solely to infiltration processes, whilst in the hollows, saturated throughflow also contributes to the solute removal. This contrast in erosional processes may perhaps account for the difference in slope form and development between the hollow and spur zones.
Drainage‐basin evolution and aquifer development in a karstic limestone terrain South‐Central Texas, U.S.A.
Authors: Woodruff C. M. , Abbott Patrick L. 
Published: February 2007

AbstractThe Edwards artesian aquifer occurs in cavernous limestones of Cretaceous (Albian) age within the Balcones fault zone in south‐central Texas. The major recharge and discharge zones of the aquifer are contained within the upper reaches of three river systems: the Nueces, the San Antonio, and the Guadalupe. Within these watersheds, recharge dominates in the semiarid Nueces basin to the west while most discharge occurs farther east from wells in the subhumid San Antonio basin and from springs in the subhumid Guadalupe basin. This long‐distance transfer of ground water (up to 240 km) is a result of several factors: depositional and early diagenetic history of the limestone host rock, geometry and magnitudes of fault displacement, and physiographic responses to faulting.The loci of greatest discharge from the aquifer occur in an area that was exposed subaerially with concomitant porosity enhancement due to dissolution of limestone during late Early Cretaceous time. This area also was subjected to the greatest fault displacement during Miocene time. Thus, faults and associated joints superimposed additional avenues for porosity and permeability development onto an area that already had considerable secondary porosity. Further determinants on aquifer properties resulted from late Tertiary and Quaternary drainage evolution in response to faulting along the Balcones trend. The strike of the fault zone lay at acute angles to the courses of the main trunk streams in the ancestral Guadalupe and San Antonio River systems, whereas in the Nueces basin the trend of the fault zone was normal to the courses of the main streams. Thus, as a fault‐line scarp began to form in the eatern basins, scarp‐normal streams were incised rapidly into northwest‐trending canyons. These steep‐gradient streams captured the eastward‐flowing major streams in the easten watersheds. These pirate streams incised into the aquifer at the lowest topographic levels within the region because of: 1. The sudden acquisition of extensive catchment areas in a subhumid area; and 2. Steep stream gradients that reflected the larger fault displacement in the east. The low topographic points of discharge became the loci of major springs.Recharge is dominant in the Nueces basin mainly because streams cross permeable limestone units at higher topographic levels than in the San Antonio and Guadalupe basins. The topographic characteristics of the Nueces watershed resulted from a combination of diverse factors: lesser fault displacement, no major stream piracy, and less vigorous erosion because of a semiarid climate.
Soil moisture and texture controls of selected parameters of needle ice growth
Authors: Meentemeyer V. , Zippin J. 
Published: February 2007

AbstractNeedle ice was grown in the laboratory to determine the limits of soil moisture and texture on the growth of needle ice. As the percentage of fines in the soil increases the lower limit of soil moisture required for growth decreases and may be defined by a linear boundary. The efficiency of conversion of soil water to needle ice in soil samples used, peaked at about 16 per cent soil fines. Contrary to expectations the finer textured soils produced significantly thicker ice crystals. Quantity of soil lifted by needle ice was related to ice height, the ice mass to atmospheric void ratio, soil texture and moisture and soil surface roughness. However, no definite, quantitative relationships could be determined. A test to determine if needle ice is selective in the grain sizes of particles lifted suggested no selectivity.
Dissolved material transport—the flushing effect in surface and subsurface flow
Authors: Klein M. 
Published: February 2007

AbstractThe study deals with the relationship between specific conductance and water flow in a small catchment.Three flow types were studied: (a) channel flow; (b) overland flow; (c) subsurface flow.The study of the three flow types demonstrates the important role of the flushing effect in small basins. The flushing effect is seen as an increase in water conductivity in the early stage of an event.Flushing is probably a function of accumulation in the basin. Accumulation is best defined as a function of time elapsing since the last heavy rain.The study has been carried out in the School of Geography at Leeds University, Leeds LS2 9JT, England.
The exposure of forest soil to erosion by earthworms
Authors: Hazelhoff L. , van Hoof P. , Imeson A. C. , Kwaad F. J. P. M. 
Published: February 2007

AbstractIn mixed oak‐beech forests in the undulating Keuper region of Luxembourg extensive areas of the forest floor are litter‐free or covered with worm casts during many months of the year. This creates an opportunity for splash erosion or erosion by (saturation) overland flow. A systematic investigation of the occurrence and seasonality of the litter‐free areas resulting from the action of the earthworm species Lumbricus terrestris, L. was undertaken in a forest with poorly to imperfectly drained, silty clay loam soils. This forest exhibits microtopographic depressions of a few hundred square metres which are damper than the immediate surroundings and which seem to favour the activity of L. terrestris. A vegetation survey showed that the depressions also have a slightly different vegetation from the immediate surroundings. The activity of L. terrestris, which pulls leaves from the surface into its hole, was followed by establishing 11 plots, 5 × 5 m in size, and surveying these with monthly intervals during a year. The percentage of bare soil ranged from zero during the winter for all plots to a maximum of 60 per cent in July and August for some plots. Rates of leaf removal were found to follow trends in soil moisture content. The relationship observed between the occurrence of bare soil and composition of the understorey vegetation allowed the vegetation map of the forest to be used to estimate the area of exposed soil.The effects of the cast producing species Allolobophora nocturna, Sav. and A. longa, Ude. were studied in a mixed oak‐beech forest with sandy loam to sandy clay loam soils. These soils are moderately well drained. Cast production was measured within a fenced‐off area of 50 × 45 m, in which 10 plots of 1 m2 each were located at random. A fine nylon netting 30 cm above the soil surface prevented splash erosion of the newly formed casts between the monthly visits. The cast material was collected, dried and weighed. Splash erosion of the casts was investigated with 50cm high splash collectors. The percentage of bare soil in front of the splash boards was estimated from photographs. From the limited data available the yearly rate of cast production appears to be approximately 1.5 kg/m2 (15 ton/ha). No significant correlations were obtained so far in most cases between amount of soil caught in the splash traps and percentage of soil covered with worm casts.
Wind tunnel experiments on dune sands
Authors: Logie Marleen 
Published: February 2007

AbstractThe effect of the dry bulk density, time and the presence of roughness elements at the surface on the wind erodibility of a dry dune sand (D50 = 230–250 μm) were evaluated in a laboratory study.There is no significant correlation between the dry bulk density of the dune sand and the corresponding deflation threshold. During the experiments, a variation of the fluid threshold in time was noticed. It increased to a value 11 per cent higher than the lowest threshold velocity. Selective eroding of the wind cannot be responsible for this time‐effect, for threshold velocities do not work selectively on non‐uniform sands. It can be explained by thinking of a dynamic surface which evolves towards a configuration of lower surface roughness.The size of roughness factors e.g. gravel, marbles, placed on a sand surface, and the density of the cover seem to be important factors influencing the erodibility of the underlying sand surface. Small cover densities are related to values of the deflation threshold, which are below the fluid threshold of the sand surface. Furthermore, dense covers protect the ground against wind erosion by increasing the threshold. The size of the roughness factors determines the inversion point at which a cover becomes protective.
Overwash processes along a gravel beach in south‐east Ireland
Authors: Carter R. W. G. , Orford J. D. 
Published: February 2007

AbstractRecent overwashing, and to a more limited extent overtopping, has occurred on a gravel‐dominated beach just west of Carnsore Point in south‐east Ireland. At relatively low points swash excursions have breached the duneline and extensive gravel fans have formed on landward‐facing slopes. Also, at interbreach positions, swash ramps have been built‐up in front of previously eroding dune cliffs, allowing overtopping at heights of up to 5 m above MHWOST, spreading a veneer of sediment over the adjacent dune ridge. In both cases events appear to be preceded by erosion and backbeach sand and gravel deposition. Stratigraphic, textural and fabric analyses assist in identifying environmental conditions that prevailed during overwash throat and fan, and overtopping ramp, sedimentation.
Limestone solution rates and processes in the Waitomo District, New Zealand
Authors: Gunn John 
Published: February 2007

AbstractKarst solution processes are investigated on Oligocene limestones in the Waitomo district, west central North Island, New Zealand. Estimates of the inputs, throughputs and outputs of water and dissolved calcium and magnesium in two drainage basins were used to establish the rate of limestone solution by autogenic waters. The best estimate for solution loss from the basins during the study year is 69 m3/km2. The potential measurement errors inherent in each parameter used in the erosion rate computations were assessed and the probable maximum and minimum erosion rates were estimated to be 88 and 61 m3/km2. In both basins approximately 67 per cent of the annual solute load is transported by flows greater than the mean annual discharge, over 15 per cent being transported by flood flows that are exceeded only 5 per cent of the time. Almost half of the annual load is transported during the three winter months (June‐August), but no one month accounts for more than 18 per cent or less than 2.7 per cent of the annual total. Approximately 37 per cent of solution takes place within the soil profile, and most of the remainder is concentrated in 5–10 m of weathered bedrock (the subcutaneous zone) beneath this. Thus, it is likely that at least 85 per cent of the total solutional erosion contributes to the surface lowering of soil and bedrock.