bluuebunny/crossref_metadata_2025 huggingface dataset:
Bank erodibility of shallow sandbed streams
Authors: Pizzuto James E.
Published: February 2007

Cross‐sections were surveyed at straight reaches of 16 sandbed streams in the midwestern U.S. Two stratigraphic horizons are found in the banks at each site, an upper cohesive unit usually composed of silt and clay, and a lower unit composed of sand.

Bank erosion on these rivers occurs when the upper cohesive unit is undercut by scour at bends. The overhanging cohesive block fails by toppling forward into the channel. During failure, the soil is primarily in tension rather than compression or shear. Analysis of this failure mechanism leads to a field method for measuring the tensile strength of riverbanks. Measured values of the tensile strength are not correlated with the channel geometry. Thus, the erodibility of the cohesive bank sediments does not influence the geometry of the rivers studied.
Sedimentation within a regulated river
Authors: Petts Geoffrey E.
Published: February 2007

Channel change induced by tributary sediment injection to a regulated, gravel‐bed river is described for the River Rheidol, U.K., eighteen years after dam closure. Morphological and sedimentological data are presented for an aggrading reach. A primary lobate bar appears to have initiated flow separation and the subsequent construction of channel‐side berms. Hydraulic sorting has operated to produce both longitudinal and lateral particle‐size reduction, and selective particle‐size dispersal appears to be an important process influencing channel change. The channel is adjusting to a lower width‐depth ratio form, of smaller capacity, and with a steeper slope.
Isovolumetric weathering and silcrete formation, southern Cape Province, South Africa
Authors: Summerfield M. A.
Published: February 2007

Calculations of absolute elemental gains and losses based on isovolumetric bedrock alteration are applied to deep weathering profiles and silcrete developed on Dwyka Tillite and Bokkeveld Shale. Bedrock weathering to kaolinite and illite yields sufficient SiO2 to account for observed thicknesses of associated silcrete. Absolute accumulation of SiO2 in silcrete is complemented by substantial absolute depletion of Al2O3. Absolute accumulation of TiO2 in both silcrete and associated weathered material together with authigenic anatase concentrations in silctete recorded during micromorphological investigations indicate TiO2 mobilization in a low pH environment (pH < 3·75) during silcrete formation. Under these low pH conditions increased Al2O3 solubility led to replacement of kaolinite and illite by a proportion of SiO2 retained in the weathering profile through restricted drainage.
River channel change: Problems of interpretation illustrated by the river derwent, north Yorkshire
Authors: Richards K. , Greenhalgh C.
Published: February 2007

Some inherent limitations of the spatial interpolation method of identifying and interpreting channel adjustment are illustrated by a study of the River Derwent in Yorkshire. Here, cross‐sections downstream from a river diversion appear to have contracted in size when compared with predictions based on upstream relationships between channel form variables and basin area. However, these sections are slightly larger than expected for their diminished discharge, suggesting that they have not fully adjusted to altered environmental conditions and are still in a transient state.
Stone movement on hillslopes in the Mojave Desert, California: A 16‐year record
Authors: Abrahams Athol D. , Parsons Anthony J. , Cooke Ronald U. , Reeves Richard W.
Published: February 2007

Previous research has shown that either hydraulic action or creep may be the dominant process transporting coarse debris down hillslopes in the American Southwest. This study analyses the movement over 16 years of painted stones on two hillslopes in the central Mojave Desert to ascertain which of these two processes dominate in this region. The distance moved (M) is found to be directly related to length of overland flow (X) and hillslope gradient (S), and inversely related to particle size (D). The fact that M is more highly correlated with X than with S suggests that hydraulic action rather than creep is the dominant process. It is concluded that this is probably the case over most of the Mojave and Sonoran Deserts on slopes up to at least 24°, and that it is only at higher elevations where winters are more severe that creep may become dominant.
Surface runoff and sediment yield in the Ardèche rangelands
Authors: Roels J. M.
Published: February 2007

This paper presents a case study of runoff and sediment generation under Submediterranean rangeland conditions (Ardèche drainage basin, France). Measurements indicate that on a rough hillslope interrill runoff and sediment are not produced uniformly over the slope surface. It is observed that runoff concentrates immediately in non‐permanent interrill flow paths, which under average storm conditions vary in length from 1.0 to 12.5 m. Long interrill flow paths may eventually become permanent. These permanent flow paths, called pre‐rills, are introduced as a new source area, and are considered to be the initial stage in the development of rills. Along pre‐rills considerable quantities of runoff and sediment are carried away.

This study also shows that calculations based on interrill, pre‐rill, and rill runoff will only have significance if storm and soil conditions are specified in detail. It is concluded from a correlation analysis between the runoff volume and the amount of soil loss on a storm‐by‐storm basis that the runoff volume alone cannot explain the amount of sediment that is generated in each source area; soil availability is an additional factor that must be taken into account.
Flow and grainsize pattern in a sharply curved river bend
Authors: Van Alphen J. S. L. J. , Bloks P. M. , Hoekstra P.
Published: February 2007

The main characteristics of river flow and grainsize in a bend of the sand bedded meandering river Dommel, The Netherlands, are presented. Measurements were carried out at a relatively low discharge in a sharply curved bend following a long straight reach. In the studied bend, secondary circulation is restricted to the thalweg area; only in the downstream part of the bend it exists over the entire cross‐section. Therefore, on the entire pointbar platform, which comprises the larger part of the bend, the median sedimentation diameter of the bedload material is governed by the distribution of the longitudinal components of the bed shear stress only.
Ventifacts distribution in Qatar
Authors: Babikir A. A. A. , Jackson C. C. E.
Published: February 2007

This study attempts to investigate the distribution of ventifacts in Qatar. It is believed that ventifacts are confined to the areas within about 5 km of the Miocene or Mio‐Pliocene Hofuf formations and the spreads of continental gravels derived from them. Three hypotheses were formulated: (1) Ventifacts in Qatar are confined to areas within about 5 km of the Hofuf formations and the spreads of continental gravels derived from them. The distribution of ventifacts within these areas varies according to the nature of the ground surface; (2) The most active ventifaction areas are where the continental gravels merge with the Eocene limestone because of the increase in saltation particle speed in these areas where bedrock or bare limestone is exposed; (3) The unit area ratio of ventifact to non‐ventifact pebbles varies inversely with the total amount of pebbles. To test these hypotheses, nine land class categories were identified in the three major Hofuf formations. Line transects were carried out from randomly selected stations near the middle of the Hofuf formations. Along each transect systematic sampling was carried out at 200 m intervals. The data were processed using a WANG MVP 2200 computer with software developed for the project. It was found that ventifacts tend to concentrate on the outer edges of the continental gravels in areas of limestone outcrop and limestone pavement. Higher areas have big gravel counts and a low ratio of ventifacts while the low‐lying plains have small gravel counts and a higher ratio of ventifacts. In certain areas ‘ventifact fields’ were found where the density of ventifacts was as high as 30 per m2. Many of the ventifacts in these fields were buried beneath the surface suggesting that the ventifaction predates the present site conditions. Other high ventifact density areas were discovered where the ventifacts have collected in shallow depressions or hollows on the limestone plateaux. Water action has washed these ventifacts, a high proportion of which are dreikanters, into the hollows, where they have been partially buried in fine alluvial silts. These ‘ventifact graveyards’ are generally only a few metres wide but contain large numbers of fine specimens.
Drop shape and erosivity part II: Splash detachment, transport and erosivity indices
Authors: Riezebos Hans Th. , Epema Gerrit F.
Published: February 2007

The relevance of drop shape for erosivity was tested for different combinations of drop sizes and fall heights. For all test combinations together the introduction of the observed drop shape in erosivity parameters only produces minor improvements in the relation between erosivity and detachment and transport by splash. This result is attributed to the dominance of oblate shapes in high velocity conditions. Using small fall heights and low fall velocities as in many rainfall simulators and drop tests it is shown that prolate drops produce a splash detachment which is 2 to 3 times higher than that produced by drops with an oblate shape at impact. As drop production in rainulators or for aggregate stability drop tests may result in more or less uncontrolled variations of drop shape, it is concluded that in addition to other test conditions drop shape should be specified. Moreover it is noted that the erosive capability of prolate drops can explain partly the high splash erosion amounts below vegetation.
Changes in river regime after the construction of upstream reservoirs
Authors: Chien Ning
Published: February 2007

This article presents and analyses many years of investigations in China on the fluvial processes downstream of impounding and detention reservoirs. The study covers the change in hydrograph, the recovering of sediment concentration along the river course, the degradation of stream bed, the adjustment of longitudinal profile, the coarsening of bed material, the change in channel width, and the trend of channel pattern variation for alluvial streams downstream of impounding reservoirs. Without confluence of major tributaries, the degradation may extend to a great distance below the dam. In the process of reducing the sediment carrying capacity of the flow to match the diminished sediment supply, the coarsening of bed material is a factor of equal, if not greater, importance as compared with the flattening of channel gradient. In places where the flow has not been sufficiently cut down and the bank is erosive non‐resistant, a receding of banklines may take place in concurrence with the deepening of the river bed. Below detention reservoirs, even if the total runoff and sediment supply remain essentially unchanged, the modification of the hydrograph is sufficient to enhance the deterioration of the downstream channel.
A palaeovalley system in the floodplain of the Mark River (Central Belgium)
Authors: Huybrechts Willy
Published: February 2007

A borehole programme on the floodplain of the River Mark has revealed an important fossilized fluvial system, now invisible in the present landscape. The palaeovalley meanders gently and is up to 200 m wide and 8 m deep. It is eroded in older fluvial sands, probably of Pleniglacial age, overlain by an aeolian cover of varying thickness. As indicated by several radiocarbon dates of the valley fill deposits, the erosion of the system took place in the pre‐Holocene period. The filling proceeded in three phases. The morphological implications of each phase and their spatial extension are demonstrated. Most of the vertical fill consists of a sandy loam to loam. Around 9000 yr BP, the accumulation of an organic facies (mainly woodpeat) started, followed by the deposition of a weak fluvial clay. At 1400 yr BP the filling of the palaeovalley was complete.
Chemical denudation on a magnesian limestone hillslope, field evidence and implications for modelling
Authors: Crabtree R. W. , Trudgill S. T.
Published: February 2007

The pattern of relative denudation at the soil‐bedrock interface over a wooded Magnesian Limestone hillslope was investigated using micro‐weight loss bedrock tablets. The resulting pattern of weight loss after emplacement for one year indicated a consistent upslope increase in solutional denudation. Results from tablets emplaced for two years confirmed this. Dye tracing and gypsum sphere weight loss results showed that water movement over the slope was by vertical percolation and not by throughflow. The pattern of solutional denudation was related to changes in soil type and associated changes in soil pH. Continued slope development by solutional denudation will ultimately lead to slope decline. Comparison with a similar study suggests that a general soil chemistry based model of hillslope solutional denudation can be proposed.
Turbidity and suspended solids variations downstream of a regulating reservoir
Authors: Gilvear D. J. , Petts G. E.
Published: February 2007

A controlled reservoir release from Llyn Celyn to the Afon Tryweryn, Wales, U.K., has been used to study suspended load and turbidity variations. Turbidity was monitored continuously at two sites and 235 suspended solids samples were obtained at these and three additional sites during the passage of the release wave. The results are compared with data for a natural tributary flood event. The reservoir release data relate to sediment source depletion and reflects changing sources along the channel. Close to the dam, fine organic matter dominates the seston which scanning electron microscopy revealed to be predominantly allochthonous organic matter, with algal fragments and inorganic diatom frustules, derived from the periphyton of the channel bed. Coulter Counter analysis showed the seston to be relatively coarse with a median particle‐size of 20 μm. Within 3 km of the dam, however, minerogenic particles dominate the sediment load of which more than 90 per cent is finer than 10 μm. This represents the flushing of channel‐bed accumulations derived from tributary sources. The relationships between suspended sediment concentration and turbidity during the release are characterized by a marked, anticlockwise hysteresis. This contrasts with the clockwise hysteresis for the tributary flood event, but the different relationships cannot be explained by particle‐size variations alone; seston composition also appears to be an important control.
Application of photogeological mapping to studies of glacial history of south spitsbergen
Authors: Lindner Leszek , Marks Leszek , Ostaficzuk Stanisław , Pękala Kazimierz , Szczęsny Ryszard
Published: February 2007

The aim of this paper is to describe a study of Quaternary landforms and sediments of selected areas in South Spitsbergen by means of field observations supplemented by photogeological mapping from air photos. The results of these investigations are presented in the form of four geological‐geomorphological maps at a scale of 1:10000. These maps are also analysed in terms of the glacial history of South Spitsbergen.
The effect of road construction on sediment deposition in Loch Earn, Scotland
Authors: Duck Robert W.
Published: February 2007

In 1982 an unmetalled road was constructed in a Scottish Highland glen, Glen Ogle, crossing several left bank tributaries of the Ogle Burn, one of the main influents to Loch Earn. As a result, at least 1824 tonnes of sediment were deposited over an area of 4‐6 ha of loch bed in less than 2 months. This was over 20 times as much material by weight than had passed a temporary gauging station, near the confluence with the loch, during an earlier 12 month monitoring period. The mean thickness of the resultant deposit should, under normal circumstances, have taken some 20 to 25 years to accumulate. Thus, this study provides a quantified illustration of the potential impact of a specific human activity on the acceleration of erosion and deposition rates.
A medium‐term estimate of bedload yield in allt A'Mhuillin, Ben Nevis, Scotland
Authors: Richards Keith , McCaig Mike
Published: February 2007

The 13‐year average bedload yield of Allt a'Mhuillin is estimated from accumulations in boulder traps to be about 261 km−2 yr−1. This represents a minimum estimate of the highest average bedload yields likely to be generated from natural British catchments of the order of 10 km2 in area.
Mountain bedload yields in the United Kingdom: Further information from undisturbed fluvial environments
Authors: Newson M. D. , Leeks G. J.
Published: February 2007

Further medium‐term estimates of bedload yield are derived from gravel traps formerly operated to keep watercourses open in the Lake District of England. They are compared with the results presented by Richards and McCaig (preceding communication).
Regional variation of mechanical and chemical denudation, upper Colorado River Basin, U.S.A.
Authors: Schmidt Karl‐Heinz
Published: February 2007

The variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0‐2 1/s km2 ( = 6 mm p a) to 151/s km2 ( = 475 mm p a). The hydrological‐geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0‐221/s km2 = 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per year.
The adjustment of the meandering pattern of the lower Jordan River to change in water discharge
Authors: Klein Micha
Published: February 2007

The annual discharge of the Lower Jordan River has decreased from about 1250 × 106 m3 y−1 to about 300 × 106 m3 y−1 due to water exploitation. The decrease in water discharge was not followed by a similar decrease in the suspended sediment. Evidence from air photographs and maps from 1920s to early 1970s show that the river is adjusting itself by shortening its course. The shortening is not distributed uniformly along the valley length. Local effects obscure the effect of decreasing discharge. Since the early 1970s the channel is becoming longer again due to a change in the dominant flow.
World patterns and amounts of detrital soil carbon
Authors: Meentemeyer Vernon , Gardner John , Box Elgene O.
Published: February 2007

Soil carbon data were collected from published sources for 50 measurement sites spanning the globe's major climate and vegetation types. For each site, climate, vegetation, and land‐use variables were determined and entered into a multiple curvilinear regression program to predict soil carbon. The best model incorporates an estimate of site disturbance, annual actual evapotranspiration, and annual soil moisture deficit, and yields an R = 0‐803. The curvilinear regression equation was coupled with a large climatic database and computer cartography programs to produce first‐generation maps of estimated soil carbon. These maps correctly portray soil carbon as high in boreal and cool temperate zones and low in deserts and tropical zones.

Computer planimetry of maps of soil carbon for an ‘undisturbed’ world and for a ‘disturbed’ world resulted in estimates of 1457 × 109 mtC and 504 × 109 mtC respectively. These estimates compare favourably with recent estimates using other approaches. Clearly, the disturbance factor is critical to future refinements in estimates, suggesting the need for detailed studies of the relationship between land‐use history and the creation and destruction of this important carbon pool.
Climatic control of the assemblages of secondary clay minerals in the A‐horizon of United States soils
Authors: Folkoff Michael E. , Meentemeyer Vernon
Published: February 2007

The concentrations (per cent) of secondary clay minerals (mica, vermiculite, montmorillonite, chlorite and kaolinite) in the A‐horizon of 99 soil sample sites were entered into a cluster program to determine the common clay mineral assemblages found in U.S. soils. Five major assemblages were identified with the most common assemblage consisting of mica, montmorillonite and kaolinite. A suite of climatic variables was determined for each of the 99 sites, including the water balance variables and Arkley's leaching index. A discriminant analysis was then used to predict the occurrence of a clay assemblage from the climate data. Sixty per cent of the sites could be correctly predicted, although not all assemblages could be predicted equally well; two assemblages could be predicted with 88 and 82 per cent accuracy. The precipitation of the wettest month and Arkley's leaching index accounted for most of the predictive power. Thus this study supports theoretical models which suggest that seasonal moisture supply is an important control of clay genesis and persistence. A residuals analysis indicated that many of the palaeosols in the data set and many of the soils from glacial parent materials possessed clay mineral assemblages not expected on the basis of modern climate.
Lithologic control of bedrock meander dimensions in the appalachian valley and ridge province: A comment on a comment
Authors: Braun Duane D.
Published: February 2007

Abrahams' comment relates meander length to channel cross‐section shape and recurrence interval so that meander length can be both directly and inversely proportional to rock resistance. This reply notes that either meander length is directly proportional to rock resistance or it is not; one cannot have it both ways. Many Appalachian Valley and Ridge bedrock meanders are shown to be the same size as alluvial meanders, and appear to be somewhat underfit. A hypothesis is proposed where modest discharge increases may have accelerated bedrock meander cutting although present streams remain capable of slowly cutting the meanders.
The significance of rainsplash in the surficial debris cascade of the colorado front range foothills
Authors: Morris Scott E.
Published: February 2007

The surficial characteristics and precipitation regime of sparsely vegetated hillslopes in the montane zone of the Colorado Front Range suggest that rainsplash may be an important component of the surficial debris cascade. Site sediment flux data from two study periods reveal marked spatial and temporal variability. Comparison of these date with sediment movement data from splashcups suggests the following conclusions: (1) Detachment rates of the rainsplash process appear great enough to account for the sediment flux in the open Gerlach‐type traps; (2) Areal extrapolation of rainsplash transport suggest that 88 per cent of the fine sediment flux in 1982 can be attributed to rainsplash; (3) Estimates of rainfall energy and changes in the potential energy of hillslopes by mass transport suggests a process efficiency of 0.05 per cent for rainsplash. If this procedure is applied to sediment flux values from open traps, the low precipitation‐energy cascade of 1982 appears to be largely rainsplash‐transported sediment. Extrapolation with the 1981 data suggests more aggressive overland flow erosion and transport.
Rates of erosion of till in the nearshore zone
Authors: Davidson‐Arnott Robin G. D.
Published: February 2007

Measurements of vertical erosion of till in water depths ranging from 1.1 m to 5 m have been obtained using a modified micro‐erosion meter. Measurements in this environment are hindered by poor underwater visibility and losses due to high erosion rates and ice action. There is considerable spatial and temporal variability in the erosion rates measured but average values show a general increase from 11 mm y−1 in 6 m of water to about 35 mm y−1 in 2.3 m of water and even higher rates closer to shore. The measured values in shallow water are in good agreement with long‐term rates extrapolated from shoreline recession. It is suggested that erosion occurs through abrasion and fluid stressing, and that these mechanisms are aided by softening of the upper surface of the till, possibly through cyclic ‘fatigue failure’.
Photo‐sieving: A method for grain‐size analysis of coarse‐grained, unconsolidated bedding surfaces
Authors: Ibbeken Hillert , Schleyer Ruprecht
Published: February 2007

The photo‐sieving method enables the grain‐size analysis of particles > 10 mm from unconsolidated openwork bedding surfaces. The accuracy is equal to the machine‐sieving method. The sediment surface is photographed in the field using a camera stand. The enlarged print is digitized for computer processing by tracing the outlines of the pebbles. From the size and shape of the projection area of the individual pebble images the computer determines the ellipsoids of revolution, classifies these ellipsoids, and establishes their grain‐size distribution in percentage by weight. Thus photo‐sieving differs distinctly from point‐counting techniques. With the aid of photo‐sieving, the surface grain‐size distributions of larger sedimentary systems may be regularly mapped. Alluvial fans, braided rivers, both onshore and offshore coasts or areas of relict sediments and manganese nodules are suitable for this method.
A re‐examination of the evidence for a plio‐pleistocene marine transgression on the Chiltern hills. I. structures and surfaces
Authors: Moffat A. J. , Catt J. A. , Webster R. , Brown E. H.
Published: February 2007

Borehole and surface outcrop data are used to construct sub‐Chalk, sub‐Upper Chalk and sub‐Tertiary contour maps for the Chiltern area. The results show a southwest‐northeast monocline, which coincides with the change of slope at the lower boundary of the morphological bench on the Chalk dipslope that Wooldridge and Linton attributed to Plio‐Pleistocene marine erosion. Younger northwest‐southeast synclines coincide with the main transverse river valleys of the Chilterns. The monoclinal flexuring casts doubt on the value of the bench as evidence for a Plio‐Pleistocene transgression.
An indirect method of determining magnitudes of erosion using the c/p' ratio
Authors: Pitts John
Published: February 2007

An approximate method is described for determining the maximum consolidating pressure in a hard, heavily overconsolidated fissured clay. From this, the overburden thickness producing the observed degree of consolidation has been calculated. The normal method of calculating preconsolidation pressure using an oedometer was not possible. The ratio c/p' is used in conjunction with the undrained shear strength. Values of c/p' are determined using empirical relationships with Atterberg Limit values. The results allow an overburden thickness to be calculated by assuming a value for unit weight.
The permanence of stream networks in Britain: Further comments
Authors: Burt T. P. , Oldman J. C.
Published: February 2007

Previous surveys of the stream network in an area of blanket peat moorland in the Southern Pennines, England, are reassessed with reference to the publication of a new ordnance survey 1:10000 Metric Edition map for the area. It is concluded that a significant number of low order streams are still omitted on the new map, and that the use of field surveys remains essential in such heavily dissected terrain.
Debris from the basal ice of the Agassiz ice cap, Ellesmere Island, arctic Canada
Authors: Gemmell A. M. D. , Sharp M. J. , Sugden D. E.
Published: February 2007

This article describes the characteristics of debris obtained from the basal ice in a borehole in the Agassiz ice cap, Ellesmere Island, Northwest Territories by the Canadian Polar Continental Shelf Project in 1979. The debris appears to have been incorporated by basal freezing at a time when the base of the glacier upstream was near the pressure melting point and some 19°C warmer than at the present site. Such an occurrence may be explained by a different flow regime, by a thicker ice sheet, by the influence of irregular bedrock topography on basal ice conditions at some stage in the past, or by a combination of these factors.
Dynamics of bedload transport in Turkey brook, a coarse‐grained alluvial channel
Authors: Reid Ian , Frostick Lynne E.
Published: February 2007

Automatic and continuously recording samplers are deployed in a Hertfordshire gravel‐bed stream to show that bedload transport is related to stream power. The pattern is similar to that already established for North American channels but, because the record is so detailed, it is possible to identify the cause of the considerable scatter that is normal in such relationships. A major factor is the occurrence of rhythmic pulses in bedload discharge that are not matched by similar fluctuations in hydraulic variables. It is suggested that these pulses reflect downstream differences in the concentration of mobile particles in a slow‐moving traction carpet, and that they may be likened to kinematic waves. The record also reveals that the threshold of sediment transport—always presumed hithero to be associated with incipient motion—is related to the cessation of bedload transport in a river flood. Indeed, the mean value of stream power at the finish of bedload transport is only 20 percent of that prevailing at the moment of incipient sediment motion. Because of this, there is an inevitably poor correlation between actual bedload transport rates and those predicted by bedload equations which rely upon a single traction threshold. These new data show that the general inverse relationship between bedload discharge and water‐depth : grain‐size ratio proposed by Bagnold (1977, 1980) is not universal. Transport efficiency for this gravel‐bed stream is typically 0.05 per cent of available stream power, which compares with 1.6 per cent for a river moving both gravel and sand, and 5 per cent for another channel where bedload is composed predominantly of sand‐sized particles. It is argued that coarse and fine‐grained alluvial channels may need to be considered separately. By allowing for differences in traction threshold at the beginning and end of bedload events, and by averaging bedload discharge flood by flood in order to smooth out the effect of pulses, it is possible to achieve a reasonably good prediction of average bedload transport rate in terms of stream power.
A re‐examination of the evidence for a Plio‐Pleistocene marine transgression on the Chiltern Hills. II. drainage patterns
Authors: Moffat A. J. , Catt J. A.
Published: February 2007

The dry valley pattern of the Chiltern Hills is divided into 55 third order drainage basins which are grouped morphometrically into five groups. The character and distribution of the groups are determined mainly by the lithology of surface deposits and the structure of the underlying Chalk. No evidence has been found for different drainage patterns on the parts of the dipslope equivalent to the ‘Mio‐Pliocene peneplain’ and ‘Plio‐Pleistocene marine platform’ of Wooldridge and Linton (1955), nor for superimposition of drainage from covers of Plio‐Pleistocene or Palaeogene sediments.
Rilling of hillslopes reclaimed before 1977 surface mining law, Dave Johnston Mine, Wyoming
Authors: Soulliere Edward J. , Toy Terrence J.
Published: February 2007

The erosion of hillslopes reclaimed following the surface‐mining of coal is an important geomorphologic concern. However, progress in the design of post‐mining topography and its hydrologic response has been hampered by the paucity of research focusing on the propensity of rill formation on these disturbed surfaces. This investigation is intended to partially rectify this situation through the development of regression equations for the prediction of rill frequency and magnitude based upon site characteristics. Rill width can be estimated using soil bulk density, hillslope age, and hillslope length with a standard error of 0.152 log10 units at this location. Rill depth can be estimated using soil shear strength, hillslope length, and hillslope age with a standard error of 0.114 log10 units. Rill length can be estimated using hillslope length, percent silt in the soil, hillslope age, Bouyoucos Clay Ratio, and soil bulk density with a standard error of 3.515 m. Rill frequency can be estimated using soil bulk density, Bouyoucos Clay Ratio, soil compaction, soil reaction (pH), and hillslope age with a standard error of 0.241 rills/m. The cross‐product of rill width times depth can be estimated using soil shear strength, hillslope length, hillslope age, and soil bulk density with a standard error of 0.260 log10 units. These results must be tested further under various environmental conditions. Nevertheless, prediction of rill formation seems to be a problem capable of solution.
Flow variability and the bankfull depth of sand‐bed streams of the American midwest
Authors: Pizzuto James E.
Published: February 2007

The bankfull depths of 15 midwestern sand‐bed streams increase with increasing variability of flow. Depths are also well represented by a simple one‐dimensional model of vertical floodplain accretion. Thus, the correlation between depth and flow variability may be explained by the ability of deep, sediment‐laden flows to construct high floodplains.

Bankfull depths are also strongly correlated with the average annual maximum flow. Apparently, the average annual maximum flow adequately represents the cumulative influence of varying flows on rivers studied here. These observations further validate the concept of a dominant channel‐forming discharge of moderate return frequency in humid temperate climates.
Sedimentation patterns in a gulf coast backbarrier marsh: Response to increasing submergence
Authors: Delaune R. D. , Smith C. J. , Patrick W. H.
Published: February 2007

The rate of vertical accretion was determined on two backbarrier marshes in the Mississippi River Plain, using 137Cs dating techniques. An average accretion rate of 0‐55 cm yr−1 was found on Grande Terre, and 0.78 cm yr−1 on Grand Isle. Analysis of mineral organic content of the marsh profile shows that the backbarrier marshes accrete through (1) accumulation of low density organic matter, and (2) episodic deposition of high density mineral sediment probably associated with major hurricanes or storm events. The rates of vertical accretion were two to three times less than the rate of submergence due primarily to rapid subsidence in the deltaic plain, and imply that these backbarrier marshes will progressively deteriorate.
Cave sedimentation in the new Guinea highlands
Authors: Gillieson David
Published: February 2007

This paper investigates the nature and processes of sedimentation of allogenic cave deposits in the high relief, everwet karsts of montane New Guinea. Under the high intensity rainfall regime, episodic mass movements in small karst catchments provide a wide range of sediment textures from clayey gravels to fine clays. These allogenic sediments are deposited into pools of water within the caves, giving sedimentary structures analogous to turbidites. Diamictons within the cave relate to episodic mudflows in the catchment. These deposits move as fluidized masses in a manner similar to some esker deposits. Cross‐stratified sediments are formed by dumping of pulses of sediment laden water into deep pools. Extremely fine‐grained clays and muds accrete parallel to underlying surfaces following flood pulses. These deposits represent the last phase of catchment instability, when a small amount of slopewash occurs. Catchment processes are dominated by solution and episodic mass movements. When the thick root mat which masks the ground is disrupted, some slopewash occurs but it is not a major component in catchment processes.
The headward extent of fluvial landforms and associated vegetation on massanutten mountain, Virginia
Authors: Hupp Cliff R.
Published: February 2007

Variation in fluvial landforms and associated vegetation in the headward (upstream) direction has received little study and the controlling factors are not well understood. The relations among channel gradient, basin area, stream order, and the headward extent of fluvial landforms and vegetation was studied in 18 small basins and larger nearby stream reaches in the Massanutten Mountain area, northern Shenandoah Valley, Virginia. Low‐order streams were traversed to their basin heads. Notice was made of the point or region of the disappearance of fluvial landforms. Indicator species were used to confirm landform identification. The studied landforms include the channel bar, channel shelf, floodplain, and terraces. Basin geomorphic characteristics were determined from topographic and geologic maps and ground surveys. Results suggest that gradient is the most important factor controlling the development of fluvial landforms. Floodplains have not developed along stream reaches where average channel gradients exceed 0.15. Channel shelves and associated vegetation occur farther upstream than floodplains.
Interception, drop size distributions and rainfall kinetic energy in four colombian forest ecosystems
Authors: Vis M.
Published: February 2007

Interception losses, rain and throughfall drop size spectra and kinetic energy were studied in four relatively undisturbed tropical forest ecosystems along a transect across the Central Andean Cordillera of Colombia at altitudes between 3000 and 1000 m above sea level. Interception amounts ranged from 11 to more than 20 per cent of the total rainfall and fell within the normal range of interception figures observed in natural tropical forests.

Drop size spectra were established using the filter paper method; the drop size distributions of the open field rainfall were unimodal while the throughfall had bimodal distributions, with a higher percentage of the volume of rain falling as large drops.

Disturbance of the natural forests, for example by logging activities or cattle grazing, will further increase the throughfall kinetic energy and may lead to higher splash erosion rates inside the forests than in the open field.

The kinetic energy of the throughfall was higher than that of the open field rainfall (20‐70 per cent), even after correcting for interception losses (4‐30 per cent). Splash‐cup experiments, conducted both in the field and in the laboratory, indicated that the kinetic energy is a good index of rainfall erosivity. Inside the forests the amounts of sand splashed from the splash‐cups was, after correction for interception losses, 2‐16 per cent higher than outside the forests.
Secondary flows and the pool‐riffle unit: A case study of the processes of meander development
Authors: Thompson Alan
Published: February 2007

The major bedforms of gravel bed rivers, whether braided, meandering or straight, may be usefully resolved into pool‐riffle units, each comprising a single scour pool together with an associated depositional shoal downstream. At low flow, the latter may be characterized by a single emergent bar‐head and submerged riffle, or by a variety of remnant braid bars, depending upon the type of channel.

Identification of pool‐riffle units and observation of associated flow structures on a small meandering stream in northwest England has demonstrated important links between bedforms, flow patterns and channel change.

Each unit appears to be associated with a systematic pattern of secondary flows, which are able to modify the bedforms and initiate meander development. Feedback links between plan morphology, flow patterns and erosive and depositional forces within these units ensure that each stage of meander growth has a characteristic style of channel change. Consequently, meanders tend to evolve by regular cycles of increasing curvature and complexity.
Reply to—comparison of taxon calibrations, modern analogue techniques, and forest‐stand simulation models for the quantitative reconstruction of past vegetation a critique by A. M. Solomon
Authors: Delcourt Hazel R. , Delcourt Paul A.
Published: February 2007

Three points raised by Solomon's discussion are clarified, a conservative approach is preferred, using pollen‐vegetation relationships based on all taxa potentially involved for a given site. The use of techniques for comparison with modern analogues is defended, provided that appropriate methods such as Standardized Euclidian Distance are used. The model ‚FORET’︁ used by Solomon is based on half hectare plots and is not considered ideal for aggregation to the forty hectare lake site or to the same area for pollen grains entering it.
Towards the use of catchment geomorphology in flood frequency predictions
Authors: Beven Keith
Published: February 2007

A further development of a topography‐based model of catchment hydrology (TOPMODEL) is described and applied to the problem of predicting flood frequency characteristics. The model can simulate infiltration excess, saturation excess, and subsurface runoff contributions to peak flows. Catchment geomorphology plays a central role in predicting the nature of the hydrological response. Using stochastic rainfall and initial condition inputs based on measured data, the model satisfactorily reproduces the mean hourly flow flood frequency growth curve for the Wye catchment, but not the mean number of peaks greater than 3mm h−1 each year. Suggestions for further improvements are made.
The physical properties of quartz‐micaschist and their application to freeze‐thaw weathering studies in the maritime antarctic
Authors: Hall Kevin
Published: February 2007

As part of a study on freeze‐thaw weathering in the maritime Antarctic an investigation was made of the physical properties of the local rock. Tests were made of point‐load compressive strength, Schmidt hammer in situ rock strength, moisture content, indentor resistance and the size range of weathering products. The resulting data were used to consider the form of freeze‐thaw weathering operative in the field and its relationship to laboratory simulations. A distinct difference between ‘massive rock’ and ‘intact rock’ is observed in the field. It is suggested that future studies should generate a greater database pertaining to rock properties as it is an invaluable aid in the study of mechanical weathering.
A study of channel changes in a reach of the North Nashwaaksis stream, New Brunswick, Canada
Authors: Bray Dale I.
Published: February 2007

Repeated surveys of a short channelized reach of the North Nashwaaksis Stream near Fredericton, N.B. over the period 1971‐1981 provide the basis for evaluating the type and magnitude of some physical and botanical changes in the study reach.

In 1967 a 200 m reach of the stream was shortened by about 10 per cent by cutting a new channel through a pasture. The original channel was protected by a dense growth of shrubs along its banks.

The average width of the top of the channel in the channelized reach widened from 11 m to 17 m in response to a major flood in 1973. Rough estimates indicate that as much as 78 per cent of the published suspended‐sediment load associated with the flood could reasonably have been derived from the banks in this short channelized reach.

During the 1973 flood, a mid‐channel bar was formed in the portion of the channel which experienced the most widening. Subsequent to the flood, the mid‐channel bar was first colonized by sedges, and then by alders. By 1981, the width of the low flow channel in the channelized reach was about the same as that for the unmodified upstream reaches.

This case study provides useful information for those planning channelization projects on small to intermediate size streams in humid temperate areas.
The use of small flumes for the determination of soil erodibility
Authors: Verhaegen Th.
Published: February 2007

The objective of this study was to examine the possibility of determining soil erodibility of loamy soils with small flumes. This was done by comparing the classification of soil erodibility obtained in the field with that obtained in the laboratory. Therefore twenty soils with a texture varying from silty loam to sandy loam were selected from the Leuven region. The erosion in the field was determined by measuring the volumetric evolution of the rill pattern. In the laboratory the soils were tested with a rainfall simulator and small flumes.

The conclusion was that for loamy soils the flume experiments are a quick, simple, and reliable method for the determination of the relative soil erodibility.
Effects of time under rain, sampling technique and transport of samples on size distributions of water‐stable aggregates
Authors: Cleary J. L. , Loch R. J. , Thomas E. C.
Published: February 2007

Two methods for sampling aggregates in the soil surface under simulated rain were compared using two soil types. Results showed that aggregate size distributions obtained by spatula sampling were not significantly different from those obtained using rings buried in the soil surface, provided both were sampled to the same depth. The effect of transporting samples over a distance of 60 km was non‐significant when samples were placed in bottles half‐filled with rainwater and transported in an upright position. The per cent aggregates > 0.125 mm was found to be the most suitable index of aggregate stability for both soils.
A quantitative scanning electron microscope study of evidence for lichen weathering of limestone, Mendip Hills, Somerset
Authors: Viles Heather
Published: February 2007

Many saxicolous lichens may cause physical and chemical weathering of limestone substrates, but their geomorphological importance has not been fully determined. A simple method of producing quantitative descriptions of lichen material and petrographic evidence of weathering using the SEM has been developed and tested on samples from the Mendip Hills, England. The technique reveals a variable and often sparse distribution of lichen material and associated weathering effects below a thin, clearly defined lichen thallus.
Slope form, erosion, and hydrology in some Belizean Karst depressions
Authors: Day Michael
Published: February 2007

Detailed slope surveys were made in seven karst depressions in central Belize. Four major slope types were identified—inclined bedrock slopes, staircases, broken cliffs, and talus slopes. Depression bases are dominated by inclined bedrock and talus slopes, midslopes largely by broken cliffs, and near hill summits by staircases. Erosional weight loss tablets deployed in 1975–1981 and 1980–1985 show significant variations between the different slope types, with a maximum near depression bases. Throughfall measurements in 1980 and 1985 show that midslope and near‐summit sites receive 10–20 per cent less water than do depression bases. Surface runoff, monitored using coloured dyes, is of limited distance and duration but still contributes to surface corrosion and morphology. Vadose seepage, monitored by tracing water from the surface to a small, shallow cave, is rapid, and subsurface corrosion exceeds that at the surface.

Overall, near‐surface form and process are consistent with hydrological models of depression development (Williams, 1983, 1985) and surface processes contribute significantly to overall depression form. Moreover, surface activity complements that in the subcutaneous zone by directing recharge into the epikarstic aquifer.