bluuebunny/crossref_metadata_2025_split huggingface dataset:
A discussion of hirano and Aniya's (1988, 1989) explanation of glacial‐valley cross profile development
Authors: Harbor Jonathan M. 
Published: February 2007

AbstractIn A rational explanation of cross‐profile morphology for glacial valleys and of glacial valley development, Hirano and Aniya (1988) present an explanation for the apparent catenary form of glaciated‐valley cross profiles based on the assumption that glacial erosion works towards minimizing friction between a glacier and its channel. However, as there is as yet no convincing justification for the application of such extremum principles to this problem, it is not clear how useful this type of analysis might be. In more detail, Hirano and Aniya's analysis includes assumptions about patterns of basal water pressures and the controls on friction inconsistent with other work in this area. Furthermore, as Hirano and Aniya (1989) point out, the catenary solution they derive is the maximum rather than the minimum friction solution. The underlying reason for this surprising result is that the variational principle Hirano and Aniya use is inappropriately structured for the problem being addressed, as it does not involve a cross‐section area, i.e. ice discharge, constraint.Hirano and Aniya also discuss the progressive development of glacial‐valley cross profiles, but their analysis is hindered by the fact that most of the data they present are purely morphological, and thus cannot be used to assess form development as a function of either time or extent of glacial erosion. The only possible exceptions are Graf's (1970) data, which give morphological parameters as a function of valley order, but these do not unequivocally support Hirano and Aniya's conclusions, and are used with implicit assumptions about the relationship between valley order and time of glacial occupation or magnitude of glacial erosion that are incorrect or uncorroborated, respectively. However, if we accept the common assumption that glacial erosion results in a progression from initial V‐shaped to broadly U‐shaped (parabolic or catenary) forms, Hirano and Aniya's argument that there are two distinct types of form development (incision in alpine situations versus valley widening under ice sheets) is justified, and is an important observation that needs to be addressed in future models of glacial‐valley development.
The influence of debris flows on channels and valley floors in the Oregon Coast Range, U.S.A.
Authors: Benda Lee 
Published: February 2007

AbstractDebris flows are one of the most important processes which influence the morphology of channels and valley floors in the Oregon Coast Range. Debris flows that initiate in bedrock hollows at heads of first‐order basins erode the long‐accumulated sediment and organic debris from the floors of headwater, first‐ and second‐order channels. This material is deposited on valley floors in the form of fans, levees, and terraces. In channels, deposits of debris flows control the distribution of boulders. The stochastic nature of sediment supply to alluvial channels by debris flows promotes cycling between channel aggradation which results in a gravel‐bed morphology, and channel degradation which results in a mixed bedrock‐ and boulder‐bed morphology. Temporal and spatial variability of channel‐bed morphology is expected in other landscapes where debris flows are an important process.
Temperature correction of electrical conductivity values
Authors: Calles Bengt , Calles Ulla Maria 
Published: February 2007

AbstractFor a number of applications in geoscience, electrical conductivity of water is often used as a collective measure of the concentration of dissolved solids. A method for temperature correction of electrical conductivity data based on regression analysis of the actual temperature/conductivity relationship of a number of water samples from natural streams is presented. It is shown that the generally used formulae for temperature correction give corrected results that deviate considerably from the values determined by actual measurements. The error increases with decreasing water temperature and may result in data that deviate by as much as 20 per cent from the true values. The implications are thus especially important for measurements of solute loads and concentrations during periods of low stream water tetaperatures e.g. during snowmelt.
Simulation of the size distribution and erosivity of raindrops and throughfall drops
Authors: Brandt C. Jane 
Published: February 2007

AbstractThis paper presents a model that simulates the size distribution and erosivity of raindrops and throughfall drops. It utilizes existing models of rainfall drop size distribution and fall velocity and combines them with newly collated evidence of throughfall drop size distributions. A sensitivity analysis reveals that the model is sensitive to parameters that are easily measured or estimated: rainfall intensity, the mean volume drop diameter of the intercepted throughfall, canopy cover, and canopy height.The results of the model may be used at two levels. Firstly, to calculate specifically the size and fall velocity of individual drops, parameters that are needed in studies examining the response of soil surfaces to forces applied by rainfall. Secondly, to produce erosivity indices, based on rainfall intensity but which take account of the effects of a vegetation canopy. The paper shows that while the kinetic energy of rainfall (E(0), J mm−1 m−2) may be calculated from an equation of the familiar form:

the kinetic energy of throughfall under any canopy may be calculated by combining this equation with another that relates the energy of drops under a 100 per cent canopy cover (E(100)) and the canopy height:

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The chronology and stratigraphy of the alluvial terraces of the river Dane Valley, Cheshire, N.W. England
Authors: Hooke J. M. , Harvey A. M. , Miller S. Y. , Redmond C. E. 
Published: February 2007

AbstractThree groups of alluvial terraces together with the modern floodplain mark the Postglacial development of the middle part of the Dane Valley, Cheshire. These are a High terrace group of late Pleistocene age, a Middle terrace group of late Pleistocene to early Holocene age, a Low terrace of mid–late Holocene age, and a modern (post ca. 1840 AD) floodplain. A chronology of erosion, deposition, and landform development since mid‐Holocene times is established in this paper on the basis of terrace morphology, stratigraphy, sedimentology, soil analysis, magnetic mineral analysis, and four radiocarbon dates. After dissection of the Middle terrace during the early to mid‐Holocene, a long period of lateral activity by the river was followed by a major aggradation phase, which formed the Low terrace surface. This was followed by dissection during the last ca. 300 years and the development of the modern floodplain since ca. 1840 AD. Various explanations for the changes during the Holocene are considered; the Low terrace aggradation appears to be related to a major phase of mediaeval soil erosion.
The influence of microform bed roughness elements on flow and sediment transport in gravel bed rivers
Authors: Hassan Marwan A. , Reid Ian 
Published: February 2007

AbstractPebble clusters are reported widely as characteristic of gravel river beds and are known to influence the initial entrainment of bedload. A field assessment suggests that their distribution is not ubiquitous, favouring channel bars, but also reveals a tendency towards a preferred stream wise spacing. A series of laboratory flume experiments shows that flow resistance rises to, and falls from, a peak value as the longitudinal spacing of pebble clusters decreases, in a manner similar to that shown by others for strip roughness, isolated blocks, and simulated ripples and dunes. The experiments also reveal a strong inverse relationship between bedload flux rates and the flow resistance induced by the concentration of pebble clusters. It is concluded that pebble cluster spacing tends towards an equilibrium that is regulated by a feedback process involving sediment transport rates and that the spatial concentration of these microforms will adjust to the point where they induce maximum flow resistance.
An appraisal of the velocity‐reversal hypothesis for stable pool‐riffle sequences in the river severn, England
Authors: Carling P. A. 
Published: February 2007

AbstractThe ‘velocity‐reversal hypothesis’ is the linchpin for a number of recent conceptual models pertaining to sediment sorting and the maintenance of pool‐riffle sequences in gravel‐bedded streams. The literature in support of the hypothesis together with published adverse criticism is reviewed. It is concluded that convincing evidence for the ubiquitous occurrence of such a reversal in a range of channel geometries is currently unavailable. Continuity considerations indicate that riffles need to be considerably wider than pools for a reversal in the mean velocity to occur under conditions of subcritical flow, high stage, and stable morphology. These observations are substantiated by a detailed study of the hydraulic geometry of stable pool‐riffle sequences in the River Severn, England. Neither the sectionally‐averaged velocity nor the near‐bed shear velocity is sensibly greater in the pools than over the riffles during bankfull or near bankfull flow. Instead a tendency towards equalization of the values of average hydraulic variables is noted as discharge increases. A detailed investigation of the three‐dimensional character of the flow is required to demonstrate whether the entrainment forces within pools can locally exceed those over neighbouring riffles. Unusual behaviour of the energy gradient over riffles during moderate discharges is related to backwater effects as mediated by the spacing of the riffles. The hydraulic data are used to comment on the stability of the test reaches in the context of the development of the River Severn in the vicinity of Shrewsbury.
Automated recognition of valley heads from digital elevation models
Authors: Tribe Andrea 
Published: February 2007

AbstractApplications of landform recognition in map‐making, geographical information systems, and in improving the storage and representation of earth surface information are described. Reasons are given for the use of digital elevation models for landform recognition: increasing availability of data, easier data integration, and automation of landform recognition.An automated technique for recognizing valley heads from digital elevation models is presented. The technique has been developed for valley head recognition because valley heads are known locations of geomorphological activity and because areal features have been largely ignored in the automated landform recognition literature. The problem of valley head recognition is divided into valley head location and valley head delineation, and the technique is developed using a DEM representing a simple artificial landscape.Two methods are given for valley head location. In the first, valley heads are located at valley ends. In the second, valley heads are located at cells which would have water flowing into them from many directions if water was flowing over the terrain. The latter method locates all the valley heads on the artificial landscape. The cells locating valley heads are iteratively ‘grown’ to adjacent cells that are concave in plan and not flat, to delineate the valley head. At best, 82 per cent valley head cells on the artificial landscape are correctly recognized with a 43 per cent commission error.The method is tested on real data where it is less successful because of the variability of real landscapes and the inadequacy of the methods chosen for valley network delineation. Machine learning of thresholds and a method involving inspection of profiles across a DEM cell are suggested as methods to improve the automated valley head recognition technique.
Patterns of development of lavaka, Madagascar's unusual gullies
Authors: Wells Neil A. , Andriamihaja Benjamin , Rakotovololona H. F. Solo 
Published: February 2007

AbstractLavaka (Madagascar's abundant gullies) show a complex pattern of development. Fourteen independent measures of size and shape in 93 lavaka were investigated by principal components analysis and discriminant function analysis. Typical lavaka start either as wounds and raw patches on mid‐hillside that develop step‐like head scarps, or as toe slopes collapsed by seepage, slumping, or undercutting. They become deep, raw, vertical‐sided, teardrop‐ to heart‐shaped gashes that may be deepest and broadest uphill. As the walls retreat, slump, and become overgrown, lavaka become longer, broader, gentler, and partly filled concavities. They can grow to reach from the valley floor to the hill crest (or even beyond the crest) before healing over. Unless excessive erosion creates tors and inselbergs, they heal over and end up as unremarkable hillside reentrants and side‐valleys.
High flow events and sediment transport in small streams in the ‘tertiary basin’ area in piedmont (Northwest Italy)
Authors: Tropeano Domenico 
Published: February 2007

AbstractRainfall, peak discharges, and suspended sediment transport were surveyed for 280 events in three small (0.8 to 10 km2) catchments in a hilly area derived from Neogene marls, silts, and sands.Under similar hydrological input conditions, stream flow behaviour and sediment delivery differed considerably from one catchment to another, depending on topography, lithology, land use, and especially sediment availability. Analytical treatment of data showed a good fit between sediment yield and peak flow discharge. Less good, although still significant, was the correlation between sediment concentration and discharge values for different flow stages. Rainfall peak/basin lag time and rainfall/discharge showed poor or no correlation, mainly due to strong variations in rainfall distribution.Sediment concentration in the catchments varied enormously according to season, from zero up to 334 g 1−1; sediment yield was 160‐900 tonnes km−2 yr−1 in the two major catchments, and over 5200 tonnes km−2 yr−1 in the headwater catchment, stressing the importance of small tributaries not only in inducing floods in downstream channels, but also in sediment supply.
Formation of stationary alternate bars in a steep channel with mixed‐size sediment: A flume experiment
Authors: Lisle Thomas E. , Ikeda Hiroshi , Iseya Fujiko 
Published: February 2007

AbstractAlternate bars were formed by sediment transport in a flume with Froude‐modelled flow and relative roughness characteristic of gravel‐boulder channels with steep slopes. The flume (0.3 m wide × 7.5 m long) was filled with a sand‐gravel mixture, which was also fed into the top of the flume at a constant rate under constant discharge. Channel slope was set at 0.03. Initially, coarse particles accumulated on incipient bar heads near one side of the flume and diverted flow and bedload transport across the flume toward a pool scoured against the opposite flume wall downstream. Sorting in the pool directed coarse particles onto the next bar head downstream. Alternate sequences of pools and coarse bar heads were thereby linked down the entire flume by interactions of sediment sorting, flow, and channel morphology. During episodes of bar construction, unsorted bedload invaded interior bar surfaces and was deposited. Persistent deposition of coarse particles on bar heads prevented downstream migration of bars by inhibiting bar‐head erosion and bedload transport over bars. Likely factors leading to bar‐head stabilization in modelled gravel‐bed channels are coarse mixed‐size sediment, steep channel gradients, and shallow depths.
Empirical relations for the sediment transport capacity of interrill flow
Authors: Everaert Wilfried 
Published: February 2007

AbstractExperiments were carried out in order to measure the sediment transport capacity of interrill flow with and without rainfall and to relate the transport capacity to selected hydraulic parameters, such as effective stream power and shear velocity. Different sediments were used in order to study the effect of grain size. The proposed relationships show considerable variations with grain size and there is only a minor effect of rainfall on the transport capacity which also seems to be grain size dependent.The proposed relationships can be used to predict sediment transport capacity of interrill flow and can therefore contribute to the development of physically based erosion models.
Summer and winter regimes of runoff generation and soil erosion on cultivated loess soils (The Netherlands)
Authors: Kwaad F. J. P. M. 
Published: February 2007

AbstractMonthly runoff and soil loss data of three fallow experimental plots are presented, comprising a summer and following winter season. The fallow plots were only tilled once, at the end of April. Summer runoff appeared to be controlled by rainfall intensity and conforms to the Horton model of overland flow generation. Winter runoff was primarily controlled by rainfall amount and conforms to the saturation or storage control model of runoff generation. Summer runoff volume was one fourth of winter runoff volume. Summer soil loss was twice as high as winter soil loss and was caused by high intensity, high energy rainfall. Winter soil loss was due to detachment limited erosion, caused by low intensity, low energy rainfall. Mean sediment concentration of winter runoff was one seventh of that of summer runoff. Implications for runoff and erosion of climatic change, involving increased rainfall amounts or intensities in summer or winter, are given.
Estimation of flow resistance in gravel‐bedded rivers: A physical explanation of the multiplier of roughness length
Authors: Clifford N. J. , Robert A. , Richards K. S. 
Published: February 2007

AbstractThe need to estimate velocity and discharge indirectly in gravel‐bedded rivers is a commonly‐encountered problem. Semilogarithmic friction equations are used to estimate mean velocity using a friction factor obtained from depth and grain size information. Although such equations have a semi‐theoretical basis, in natural gravel‐bed channels, an empirical constant (6.8 or 3.5) has to be introduced to scale‐up the characteristic grain size (D50 or D84) to represent the effective roughness length. In this paper, two contrasting approaches are used to suggest that the multiplier of characteristic grain size is attributable to the effect of small‐scale form resistance, reflecting the occurrence of microtopographic bedforms in gravel‐bedded environments. First, spatial elevation dependence in short, detailed bed profiles from a single gravel‐bedded river is investigated using semivariogram and zero‐crossing analyses. This leads to objective identification of two discrete scales of bed roughness, associated with grain and microtopographic roughness elements. Second, the autocorrelation structure of the three‐dimensional near‐bed velocity field is examined to identify regularities associated with eddy shedding and energy losses from larger grains and microtopographic bedforms. Apart from improving the capacity to determine friction factors for velocity and discharge estimation, the findings have implications in general for the initial motion of gravelly bed material.
Bedload entrainment, travel lengths, step lengths, rest periods—studied with passive (iron, magnetic) and active (radio) tracer techniques
Authors: Schmidt Karl‐Heinz , Ergenzinger Peter 
Published: February 2007

AbstractThis paper reports results from bedload transport investigations with active (radio) and passive (iron, magnetic) tracers in the Lainbach, a step‐pool mountain river, in Bavaria, Southern Germany. The spatial distributions of the iron tracers after flood events can be best described by exponential or Gamma distributions. There is some indication of a tendency of size‐selective transport of the iron tracers, but there is also a considerable amount of scatter in the correlations between weight (size) and travel length owing to the masking influence of other variables, such as the shape of the particles and different positions in the river bed. The experiments with artificial magnetic tracers showed that elongated pebbles (rods) had the longest mean transport distance, platy ones (discs) remained relatively close to the starting points. The particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded.The Pebble Transmitter System (PETSY) consists of transmitters implanted into individual pebbles, a computerized receiver, a stationary antenna system with an antenna switchboard, and a data logging system. The particles do not move continuously but in a series of transport steps and non‐movement intervals. A single value for a given size‐class is not adequate to describe the critical conditions of entrainment under natural circumstances. A probability approach is much more suitable. The critical unit discharges (total discharge divided by active channel width) along the measuring reach are dependent on river bed morphology. In the steps bedload needs higher unit discharges to be entrained. Once entrained, the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods. The distributions of both parameters can be approximated by exponential functions. Applying the stochastic concept proposed by Einstein the mean values of the random variables [step length] and [duration of rest period] measured with the PETSY technique were used for the simulation of spatial distributions of bedload particles from point sources. More field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics.
Bed load transport during rising and falling stages on two small streams
Authors: Kuhnle Roger A. 
Published: February 2007

AbstractBed load transport rates were measured with continuously recording pit samplers on two small gravel‐bed streams in the Goodwin Creek Research Watershed, northern Mississippi, U.S.A. When transport samples were grouped according to whether the stage was rising or falling, significant differences in mean bed load transport rates were found at nearly all flow strengths. At higher flow strengths, mean bed load transport rates were greater during rising stages than during falling stages. The greater transport rates measured during rising stages may be caused by a lag in the formation and destruction of bed roughness elements. One of the streams also showed evidence for greater transport rates for low flows as the stage declined. This may be caused by differences in the stability of the bed material at the beginning and at the end of a transport event.
The fractal properties of topography: A comparison of methods
Authors: Klinkenberg B. , Goodchild M. F. 
Published: February 2007

AbstractIn this study the fractal characteristics of fifty‐five digital elevation models from seven different United States physiographic provinces are determined using seven methods. The self‐similar fractal model tested in this analysis is found to provide a very good fit for some landscapes, but an imperfect fit for others. Thus, outright rejection of this model does not appear to be warranted, but neither does a blind application.The three implementations of the dividers methods considered in this study consistently produce lower dimensions than those produced by the other methods, and those dimensions consistently do not vary much between surfaces. Although the dimensions produced by the cell counting method (applied to the digital elevation model itself) display consistent intersurface variation, the dimensions are generally lower than those produced by the variogram‐based methods. Among the variogram‐based methods, the dimensions of the quarter‐sections of the digital elevation models are generally greater than the dimensions obtained from the other variogram‐based methods. The dimensions produced by the variogram method which considered the surfaces on a directional basis are very similar, on average, to the dimensions produced by the entire‐surface variogram.