bluuebunny/crossref_metadata_2025 huggingface dataset:
The hydraulics of sheet flow on a smooth surface and the effect of simulated rainfall
Authors: Savat Jan
Published: February 2007

If the hydraulics of a flow is to be understood, then at least a few parameters must be known accurately. When the depth and the unit discharge are measured correctly, many other parameters can be calculated, e.g. the mean velocity of the flow, the friction, the Reynolds Number, the Froude Number, and, if the study is to be connected with erosion measurements, the shear stress. A method is therefore developed for the direct measurement of the depth of disturbed water films, by weighing the entire run; the depth of the flow is thus equal to the weight of the water contained in it, one gram being the equivalent of one cm3, divided by the area of the run. Corrections to the measurement are, however, necessary because the water accelerates along the run to a steady state velocity, because the weight drops due to an acceleration in the gravity field, because the weight of the spattered drops has to be known if simulated rainfall is applied, and because the impact of the drops causes a weight. The accuracy of the method is 10 μ if the flow conditions are not to be studied on too steep slopes and if the discharge used is not too great. The main results are plotted in Figure 6 which combines the formulas for laminar, transitional and turbulent flow that are obtained. A comparison with available literature suggests mat sheet flow can either be laminar or purely turbulent, but that mixed flows prevail on low slopes, under 0.5 per cent combined with greater water depths. Since the flow equations on steep slopes obey physical laws, sin S is to be used instead of S, which stands for tan S.

The experiments have shown that the effect of the rainfall impact on the Darcy‐Weisbach f does not exceed 20 per cent in the case of laminar flow on gentle slopes. This influence diminishes when the discharge increases, or when the Reynolds Number increases, as well as when the slope angle increases.
Measurements of rainsplash erosion and the formation of colluvium beneath deciduous woodland in the Luxembourg Ardennes
Authors: Kwaad F. J. P. M.
Published: February 2007

In wooded dry valleys in the Luxembourg Ardennes a gravelly and slightly organic colluvial deposit occurs. The depositionary nature of the material is ascertained by its micromorphological characteristics and its position on top of a truncated argillic horizon of an older soil. Pollen analysis revealed the colluvium to have been formed in the last 500 years, the lower 37 cm in the Haarts valley under non‐forest (presumably arable land) conditions and the upper 10 cm under today's oak woodland. A formation of the colluvium by Horton overland flow is ruled out by permeability and infiltration capacity measurements of the forest soil. The importance of rainsplash erosion for the formation of the upper part of the colluvium is demonstrated with simplified Ellison type splash boards. Two modes of transport, induced by raindrop impact, may be distinguished, one through the air (particles up to 6.3 mm) and one across the soil surface (particles up to and above 1 cm). The overall grain size distribution of the trapped soil strongly resembles that of the colluvium, and the gravel sized rock fragments in the colluvium certainly do not exclude an origin by rainsplash erosion.
Nature and importance of mass‐wasting by rock glaciers in alpine permafrost environments
Authors: Barsch Dietrich
Published: February 2007

Active 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

Measurements 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

During 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

The 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

The 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

The 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

Observations 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

A 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

Wischmeier'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

A 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

Reduced 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

Variation 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

The 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

Needle 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

The 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

In 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

The 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

Recent 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

Karst 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.
Stability of composite river banks
Authors: Thorne Colin R. , Tovey N. Keith
Published: February 2007

The stability of a river bank depends on the balance of forces, motive and resistive, associated with the most critical mechanism of failure. Many mechanisms are possible and the likelihood of failure occurring by any particular one depends on the size, geometry and structure of the bank, the engineering properties of the bank material, the hydraulics of flow in the adjacent channel and climatic conditions.

Rivers flowing through alluvial deposits often have a composite structure of cohesionless sand and gravel overlain by cohesive silt/clay. Bank erosion occurs by fluvial entrainment of material from the lower, cohesionless bank at a much higher rate than material from the upper, cohesive bank. This leads to undermining that produces cantilevers of cohesive material. Upper bank retreat takes place predominantly by the failure of these cantilevers. Three mechanisms of failure have been identified: shear, beam and tensile failure.

The stability of a cantilever may be analysed using static equilibrium and beam theory, and dimensionless charts for cantilever stability constructed. Application of the charts requires only a few simple measurements of cantilever geometry and soil properties. In this analysis the effects of cracks and fissures in the soil must be taken into account. These cracks seriously weaken the soil and can invalidate a stability analysis by affecting the shape of the failure surface.

Following mechanical failure, blocks of soil must be removed from the basal area by fluvial entrainment if rapid undermining and cantilever generation are to continue. Hence, the rate of bank retreat is fluvially controlled, even though the mechanism of failure of the upper bank is not directly fluvial in nature.

This cycle of bank erosion: undermining, cantilever failure and fluvial scour of the toe, operates over several flood events and has important implications for river engineering, channel changes, and the movement of sediment through fluvial systems.
A note on topological matrices and characteristic polynomials of fourth‐magnitude drainage net maps
Authors: Coleman Neil L.
Published: February 2007

I suggest that a connection matrix and a characteristic polynomial, which can be formed for any drainage net, using Shreve link magnitudes, may be used in studying drainage nets. I show how the matrix and the polynomial can be formed, using selected drainage nets as examples.
Asymmetry of river channel cross‐sections: Part I. Quantitative indices
Authors: Knighton A. D.
Published: February 2007

Most river cross‐sections display some degree of asymmetry for which there is no adequate quantitative definition. Indices of asymmetry are derived using two principles based on areal differences and maximum depth displacement relative to the channel centreline. The indices are assessed firstly by comparing values for a set of constructed channel shapes which are ranked in order of increasing visual asymmetry, and secondly by analysing a series of 50 cross‐sections from a small mountain stream. Two indices, A* and A2, are probably the most valuable, and could be used to test and generate hypotheses regarding the related changes to cross‐sectional and planimetric form which occur during the transition from a straight to a meandering channel, particularly if parallel measures of flow asymmetry are defined.

Part II of this paper, concerned with ‘Mode of Development and Local Variation’ will be published in a subsequent issue of this journal.
Drainage area and the variation of channel geometry downstream
Authors: Klein Micha
Published: February 2007

Recent geomorphological studies tend to deal with small basins. The understanding of small basin dynamics provides important information for the understanding of large basin dynamics assuming that the extrapolation of small basin data to larger basins is valid. This work tests the validity of this extrapolation of data with reference to channel geometry.

An analysis of the variation of channel width downstream reveals that the value b =0.5 (W = aQb) is a ‘good’ average. However, the use of a one‐line model consisting of a simple power function incurs a loss of a considerable amount of relevant information concerning the channel form and hence the channel processes. It has been shown that the –b– value for small basins and very big basins is lower than the one for the intermediate basins.
Prediction of limestone solution rates from rainfall and runoff data: Some comments
Authors: Gunn John
Published: February 2007

Recent work by Láng (1977) on solutional erosion rates in limestone drainage basins in relation to rainfall contains serious errors and has a questionable logical basis. Although much sounder, Smith and Atkinson's (1976) work on erosion rates in relation to runoff also requires modification as it greatly overestimates erosion rates in two areas of New Zealand. Greater resolution could probably be obtained by relating autogenic runoff to the rate of solution by autogenic waters and by computing separate relationships for areas where solution takes place under open and closed system equilibrium conditions. These factors should be taken into account in the experimental design of future studies.
Observations in a cavity beneath grinnell glacier
Authors: Anderson R. S. , Hallet B. , Walder J. , Aubry B. F.
Published: February 2007

During a 3‐year period, several aspects of the glacier‐rock interface were studied in a cavity beneath 5–8 m of ice near the terminus of Grinnell Glacier, Montana, U.S.A. Continuous week‐long records of the summer sliding rate revealed a very uniform speed of about 12 m a−1 during the summer, a value about 20 per cent higher than the average annual sliding rate. Several decimetre‐sized rock fragments were broken from the glacier bed near the lee sides of bedrock ledges and transported down‐glacier. In the course of a two‐week long experiment, the glacier abraded its bed significantly and non‐uniformly. It is of interest that significant quarrying and abrasion occurred under thin ice with relatively little entrained debris.
Slope profile variability in first‐order drainage basins
Authors: Parsons A. J.
Published: February 2007

If the three‐dimensional form of a hillslope is regarded as an infinite population of two‐dimensional slope profiles, values for attributes of the form of the hillslope can be determined by sampling and estimating the means of the attributes of the population of slope profiles. Twelve attributes are examined in seven first‐order drainage basins located on the South Downs in East Sussex to determine necessary sample sizes. Results show that if spatial randomness is assumed the size of sample required varies considerably from one attribute to another but is commonly very large. Of four alternatives to spatial randomness that are tested, consideration of both hillslope plan form and valley asymmetry are shown not to lead to reduction in sample size. However, results do suggest that maximum slope, percentage of profile length in the range 5° to < 10°, and mean angular difference between adjacent slope segments may all be dependent upon distance of the slope profile down valley. Furthermore, initial tests of the effect of spatial autocorrelation suggest that for some attributes consideration needs to be given to this factor when determining sampling strategies.
Sediment yields from a laboratory catchment and their relationship to rilling and surface armouring
Authors: Rowntree K. M.
Published: February 2007

The development and testing of sediment simulation models require continuous monitoring of erosion processes and sediment yields from catchment areas at a wide range of scales. A series of experiments are described in which runoff and sediment yields from a small laboratory catchment were monitored through six consecutive storms applied to each of three soil types. Slope microtopography and the surface particle‐size distribution were surveyed between storms. Pronounced peaks in sediment concentration at the start of each storm were not observed for these conditions, but significant variation in yield through a series of storms was shown to result from the interaction of rilling and armouring processes as the source of sediment shifted from the rills to interrill areas. In view of the experimental findings the validity of experiments reporting average or ‘stable’ erosion rates is questioned. The need for dynamic models capable of simulating rill development and changes in sediment availability is emphasized.
Circular meander pools
Authors: Alford John J. , Baumann Robert H. , Lewis Anthony J.
Published: February 2007

Aerial photographs led to the detection of a previously undescribed type of river meander. These features are characterized by nearly circular pools located at the apex of the bend and are widely distributed on small to medium sized coastal plain streams in the southeastern United States. Bathymetric evidence shows that the structure of meanders containing circular pools is distinctive. Field and laboratory evidence suggests that these features are formed by a short‐lived countercurrent that develops during the flood cycle.
Hydrothermal alteration and earth surface rock weathering: A basalt example
Authors: McGreevy J. P.
Published: February 2007

Geomorphologists have not devoted sufficient attention to the formation of clay minerals by hydrothermal activity. This paper describes the breakdown of freshly‐quarried basalt by cyclic wetting and drying. Breakdown is attributed to the swelling of hydrothermally‐derived smectite, and it is argued that the effects of endogenic processes can exert a significant control upon weathering behaviour under earth surface conditions.
Structure, composition and bulk properties of upland stream gravels
Authors: Carling Paul A. , Reader Nigel A.
Published: February 2007

Upland gravel‐bedded streams in the U.K. have received only scant attention from both hydrologists and sedimentologists, but are worthy of further investigation. The sedimentology of three small streams in Teesdale in the Pennines has been examined in detail. Grain‐size characteristics, bedforms, structure, composition and packing characteristics of these deposits are described, and compared where appropriate with published information.

It is argued that a fuller appreciation of gravel bed composition and morphology should eventually contribute to an improved understanding of sediment transport and deposition mechanisms, and, hence, to improved accuracy in sediment transport and deposition estimates.
Lias clay slope sections and their implications for the prediction of limiting or threshold slope angles
Authors: Chandler R. J.
Published: February 2007

A series of previously published engineering studies of Lias clay slopes in the East Midlands is summarized, along with the description of some further slope sections. All the slopes studied show evidence of landsliding, though some of it may be of periglacial origin. The very disparate nature of the different landslides suggest that various different erosion regimes were responsible for the original slope formation; it is believed that the smaller landslides are more typical of the area. Piezometric observations show that at the present day maximum pore pressures are proportionately less in the larger landslides, the average value of the pore pressure parameter ru varying between 0.48 for shallow landslides to 0.32 in the largest. Stability analyses show that the residual strength is strongly stress dependent, Φr', (c'r = 0) varying from > 16° in shallow landslides to 10° in the case of the largest. These and other factors have important implications for the often used practice of combining laboratory measurements of residual strength with the Infinite Slope method of stability analysis to predict threshold slope inclinations for landsliding.
Storm runoff processes and subcatchment characteristics in a new zealand hill country catchment
Authors: Taylor Colin H. , Pearce Andrew J.
Published: February 2007

The quickflow responses of six subcatchment areas in a small hill country catchment in the Craigieburn Range, South Island, New Zealand, were compared for a range of storm sizes, rainfall intensities and antecedent wetness conditions. Topography and soil characteristics suggested that all subcatchments would receive subsurface stormflow input, but that some would receive larger saturation overland flow inputs than others. Quickflow yields and response ratios were positively correlated with storm size and antecedent wetness conditions in the subcatchment most suited to producing saturation overland flow. In subcatchments more likely to be dominated by subsurface flow, quickflow yields and response ratios were positively correlated with storm size, but were either not correlated, or negatively correlated, with antecedent wetness. Quickflow responses were either not significantly or negatively correlated with rainfall intensity variables. Quickflow from the subcatchment most suited to produce saturation overland flow providing an increasing proportion of total catchment quickflow in larger storms and as antecedent conditions became wetter. Subcatchment responses varied greatly in space and time and there was less pattern to the variation than had been expected. Where topographic and pedologic conditions permit substantial responses to storm rainfall by both saturation overland flow and subsurface stormflow, simple topographic and soil indicators may not be useful guides to the relative importance of runoff mechanisms, or to the identification of runoff‐source areas.
Rock mass strength and the form of some inselbergs in the central namib desert
Authors: Selby M. J.
Published: February 2007

A rock mass strength classification, involving eight parameters, has been applied to selected inselbergs in the Namib Desert. The inselbergs are formed of schists, gneiss, granite and marble. Their slope inclinations are in a strength equilibrium with their rocks. The study suggests that the strength classification is consistent and has a general validity, and that rock slopes, undergoing uniform weathering, retreat to form slopes which are adjusted to their rock mass strength: this is a more general statement than the common hypothesis of parallel retreat. The favoured hypothesis of slope evolution in the Namib is one of retreat rather than downwearing.
Comments on: Experimental test of autosuspension
Authors: Pantin H. M.
Published: February 2007

The experiments of Southard and Mackintosh prove only that autosuspension did not occur under the tested conditions; these were based on the Bagnold (1963) criterion, which is unsound. An alternative criterion is re‐emphasized, and a method for testing its validity suggested. Two separate derivations are given for the power required for sediment suspension.
Concave‐bank benches and associated floodplain formation
Authors: Page Kenneth , Nanson Gerald
Published: February 2007

This paper describes the morphology, sequential development and general sedimentology of concave‐bank benches on the Murrumbidgee River of southeastern Australia, and also notes their important role in floodplain formation on certain meandering rivers in western Canada. Benches form against the concave bank (cut‐bank) of abruptly curving bends immediately upstream of the point of maximum curvature. As a result of flow deflection against the upstream limb of the convex bank, the channel widens here and produces a zone of expanded flow facilitating flow separation near the upstream limb of the concave bank. Sedimentation within this zone starts with a longitudinal‐shaped bar of medium sand forming a platform isolated even at low flow by a narrow secondary channel against the concave bank. Aggradation of the longitudinal‐shaped bar with fine sand, mud and organic matter permits the establishment of trees. Further sedimentation, particularly around the young trees, results in the formation of a fully developed bench isolated by the secondary channel from the remainder of the floodplain only during high flows. Observations on confined meandering rivers in western Canada provide evidence of substantial floodplain formation by concave‐bank bench accretion, a process distinctly different in character to the more familiar mechanism of lateral point‐bar accretion. Furthermore, the preservation of abundant organic debris means that extensive bench deposits may be a source of locally useful natural gas from within floodplain sediments.
Long‐term erosion on granitic roadcuts based on exposed tree roots
Authors: Megahan Walter F. , Seyedbagheri Kathleen A. , Dodson Patrick C.
Published: February 2007

Exposed roots were used to estimate soil and bedrock erosion on the cut slopes of a 45‐year‐old road constructed in granitic soils of the Idaho Batholith. The original roadcut surface was defined by projecting a straight line from the toe of the cut past the end of the exposed root to the intersection of a straight line projected along the surface of the hillslope. A cross‐sectioning technique was then used to determine erosion to the present roadcut surface. A total of 41 exposed root sites were used to estimate erosion on a 1350 m‐long section of road. Average erosion was 1·0 and 1·1 cm/year for soil and bedrock respectively. Buttressing by tree roots caused lower erosion rates for soil as compared to bedrock. Both soil and bedrock erosion rates showed statistically significant correlations with the gradients of the original cut slope. The bedrock erosion data provide a reasonable estimate of the disintegration rate of exposed granitic bedrock exhibiting the weathering and fracturing properties common to this area. The road is located in a study watershed where long‐term sediment yield data are available. Sediment data from adjacent study watersheds with no roads were compared to sediment data from the roaded watershed to estimate the long‐term increase in sediment yield caused by the road. The increase amounts to about 2·4 m3/year. This figure, compared to the average annual on‐site road erosion, provides an erosion to sediment delivery ratio of less than 10 per cent. Based on study results, road construction and maintenance practices are suggested for helping reduce roadcut erosion.
spartina in Mariager Fjord, Denmark: The effect on sediment parameters
Authors: Christiansen Christian , Miller Palle F.
Published: February 2007

The analysis of 3 subsamples from each of 12 sediment cores from a micro‐tidal flat shows that spreading of Spartina effects sediment parameters. The effect diminishes with distance to vegetation.
Geomorphic effects of a 10‐year storm on a small drainage Basin in the Texas Panhandle
Authors: Finley Robert J. , Gustavson Thomas C.
Published: February 2007

Bedded Permian salt in the Palo Duro Basin of the Texas Panhandle is being considered for isolation of nuclear waste. Studies underway to evaluate the geomorphic processes affecting any waste repository that may be sited in the region include studies of the geomorphic events associated with individual storms. On 26 May, 1978, thunderstorms occurred near Canyon, Texas, which received 130mm of rain, and on a small instrumented watershed at Buffalo Lake, 16 km to the southwest, which received 71 mm of rain. Rainfall at Buffalo Lake was concentrated in a period of 3 hours, representing a return period of approximately 10 years and a maximum 30‐minute intensity of 64 mm/hour.

Erosion‐pin fields, topographic surveys, and stakes for headcut monitoring had been established 2 to 3 months before the storm in a 640‐m long tributary canyon to Tierra Blanca Creek downstream of Buffalo Lake. Canyon slopes of moderately to slightly calichified sands and gravels of the Ogallala Formation are capped by well‐indurated caliche on the canyon rim. Erosion‐pin fields showed average net erosion of 2·4 cm (0° to 9° slope) to 2·7 cm (10° to 19° slope) and a single‐pin maximum value of 6·2 cm in the 20° to 29° slope class. Headcuts 1 to 2 m deep in alluvial‐colluvial material on the floor of the canyon migrated as much as 12 m upstream. Canyon floor deposition occurred as a series of elongate bars, 16m long and longer, located at the mouth of tributary gullies, downstream from scours, and at slope breaks. Grain sizes ranged from boulders up to 70cm in intermediate axis deposited in the upper canyon to fine to very fine sand deposited as a sheet up to 25cm thick beyond the mouth of the canyon at Tierra Blanca Creek.

In an adjacent canyon a sequence of irregular beds of caliche gravel, mixed sand and gravel, and fine sand up to 3 m thick is exposed. Comparison of this sequence with deposits resulting from the 26 May, 1978, storm suggests that the coarse fraction of the alluvial sequence is deposited by repetitive major storm events. Cobble and boulder units 30 to 70cm thick can evidently be deposited in a few hours. Under the continental climate of the Texas Panhandle, erosion, deposition, and stream incision are taking place primarily in discrete steps related to episodes of intense rainfall.