bluuebunny/crossref_metadata_2025 huggingface dataset:
Limited modification of mid‐latitude landscapes by ice sheets: The case of northeast Scotland
Authors: Hall Adrian M. , Sugden David E.
Published: February 2007

The paper uses a case study in Scotland to examine the amount and processes of landscape modification by Quaternary ice sheets. There is an inverse correlation between the distribution of landforms of glacial erosion and pre‐glacial landscape remnants in northeast Scotland. The implication is that in places ice sheets can preserve a pre‐glacial landscape unscathed, while elsewhere they remove the pre‐glacial weathered rock. The location of glacial protection or erosion is strongly influenced by the topography and its influence on former ice sheet flow and basal thermal regime. The classic glacially eroded landscape of areal scouring can be produced by the removal of only 10–50 m of weathered rock. Furthermore rock basins, often regarded as the hallmark of glacial erosion, may be directly inherited from the pre‐glacial pattern of deep weathering.
Limestone landform studies and their curriculum applications
Authors: Paterson Keith
Published: February 2007

This paper reviews the educational merits and application of limestone landform studies in British secondary schools and considers these in the context of recent developments within geomorphology and the geography curriculum. The relevance of both traditional and newer approaches to the field study of karstforms is highlighted together with developments in classroom activities. School‐based work is shown to have benefitted considerably from advances in educational technology.
Dissipative systems: Implications for geomorphology
Authors: Huggett R. J.
Published: February 2007

A recent revolution in the study of nonlinear dynamical systems in the physical sciences has shown the worth of regarding systems as dissipative. The nature of dissipative systems in equations, bifurcations, and fluctuations. Some speculations are then made concerning the implications of dissipative system theory for geomorphology. It is suggested that geomorphological systems containing bifurcations will have both deterministic (universal and necessary) and probabilistic (historical happenstance) elements; they will have more than one solution (configuration) and this fact calls into question notions of process domains leading to the development of characteristic forms; they will possess varying degrees of susceptibility to change induced by fluctuations; and they will respond differently to local, regional, and global fluctuations.
Thin surface soil layers attributable to rain‐flow transportation on low‐angle slopes: An example from semi‐arid tropical Queensland, Australia
Authors: Coventry R. J. , Moss A. J. , Verster E.
Published: February 2007

Particle‐size analyses have been made on surface soils and a thin, overlying sandy pavement at 16 sites along a gently sloping transect at Torrens Creek in North Queensland. The transect is 1590 m long and has a maximum gradient of 0.018 (less than 1°). The sandy pavement is enriched in coarse components due to the sorting and differential downslope transport of the finer soil fractions. Particle movement is ascribed to the action of raindrops impacting very shallow, flowing water. The process, referred to as ‘rain‐flow transportation’, is active wherever overland flow is too weak to generate rills and channels and occurs in areas of very low slope with permeable surface soils that allow rapid infiltration during storms. Rain‐flow transportation is discussed with particular reference to the development of soil profiles in an old, subdued landscape of semi‐arid tropical Australia.
A unified theory of particulate flows in geomorphic settings
Authors: Culling W. E. H.
Published: February 2007

Particle aggregates can be regarded as a fourth state of matter which with differing energy levels can display behaviour associated with the other three. This provides the basis for a unified theory of particulate flow in the land scape, ranging from the solid‐like soil creep, through plastic flows like solifluction to fluidized phenomena exemplified by fluvial sediment flows wherein bed and suspended loads relate to dense and dilute phases of fluidized beds and therefore to liquids and gases respectively.

The theory of the liquid state is central to any unified theory and this is presented with the aid of Eyring's rate process theory and Frenkel's theory of holes. Applications to geomorphology are noted, to be given detailed treatment on a subsequent occasion.
Historical development of the saltmarsh at Wells, Maine
Authors: Jacobson Heather A.
Published: February 2007

Comparisons of maps and aerial photographs dating from the late 1700s to the present document the recent development of an 8 km2 saltmarsh that is situated behind a barrier spit in southern Maine. Tidal channels that were relatively narrow in 1794 became wider by 1872. The reduction of marsh bordering tidal channels is interpreted as evidence that marsh accretion could not keep pace with rising sea‐level. This suggests that the rate of sea‐level rise had increased, although a change in discharge or sediment load caused by extensive settlement and land clearance may also have been involved.

Meander patterns of the tidal streams changed considerably throughout the time period covered by the maps, demonstrating that the streams of this marsh are more dynamic than some others that have been widely reported in the literature. These differences in stream dynamics are probably related to the differences in sedimentological structure of the marshes.

Between 1872 and 1956 the barrier spit eroded on its inside (shoreward) edge, probably in response to the construction of riprapping and houses along the spit, and the subsequent reduction of overwash and aeolian transport of sediment.

Modification of the tidal inlet and adjacent marsh during the 1960s, including jetty construction, dredging, and filling of portions of the marsh surface, affected the marsh only locally. One tidal stream has been migrating rapidly apparently in response to compaction of peat by dredge spoils and consequent local disruption of the marsh hydrology. Except for this migration, erosion of the marsh edge occurred immediately after the inlet modifications; planimetric changes in the marsh and its streams have been minor since then.
Application of a diffusion‐erosion model to alluvial channels which degrade due to base‐level lowering
Authors: Begin Ze'ev B.
Published: February 2007

The applicability of a diffusion‐erosion model that predicts transient longitudinal profiles of degrading alluvial channels has already been demonstrated in laboratory experiments, and is here applied to some field examples. By fitting simulated longitudinal profiles to measured ones for several streams (with discharge 0.04<Q5<680 m3s−1) diffusion‐erosion coefficients, K, were determined which are well correlated to discharge and drainage area.

Headward knickpoint migration which results from base‐level lowering was also treated through the diffusion‐erosion model. Theoretically, the distance of a knickpoint from the mouth of a tributary should be proportional to the square root of the time that elapsed since the base‐level was lowered. Field observations are in accordance with these theoretical considerations.

Use of the model is discussed for prediction of erosion and for assessment of the age of alluvial fault scarps crossed by streams.
The complex nature of creep movements on steeply sloping ground in Southern Rwanda
Authors: Moeyersons Jan
Published: February 2007

Long term soil creep motion is often represented as a type of laminar flow, with velocity vectors parallel to the slope and constant in time. Records on a hillslope in Southern Rwanda reveal that creep movements there compare more with turbulent flow, characterized by a A1 humic horizon superlayer, creeping over a subsoil affected by more irregular creep deformation.
Sediment size variation in a braided reach of the Sunwapta River, Alberta, Canada
Authors: Dawson Martin
Published: February 2007

The downstream diminution in sediment size in a braided reach of the proglacial Sunwapta River, Alberta, Canada, was examined statistically to identify the sources of the observed variation about an expected exponential relationship between clast size and distance. Major deviations from this hypothetical relationship, such as a relative increase in grainsize, may be attributed to the effects of tributary sediment inputs and downstream changes in channel behaviour, whilst local variation is associated with complex patterns of sediment deposition observed at a bar scale. A comparison of diminution coefficients, calculated for separate lithologies and for subreaches along the river, with those obtained from previous studies, is used as an indicator of river behaviour and sediment transport processes. It is shown that rates of diminution vary within the reach in response to differing rates of aggradation and to the backwater effects created by tributary alluvial fans. The relatively high values for the calculated diminution coefficients indicate that processes of differential transport are the main cause of the grain size decrease.
Settling‐velocity distributions and sorting processes on a longitudinal dune: A case study
Authors: Hartmann Daniel , Christiansen Christian
Published: February 2007

The processes acting on a longitudinal dune are inferred from the response in the area size‐sorting characteristics of the sediment of the active layer. The sediment size distributions are determined by settling and are best described by a log‐hyperbolic model which provides the most information on size‐sorting processes. Size‐sorting characteristics are markedly different across the low round‐crested part of the dune from cross‐sections of the high more sharp‐crested part. This results in changes in textural parameters along the lee‐side consistent with changes in the lee‐side separation vortex. This is the first time that the effect of wind speed up on the lee‐side is observed to be reflected in the sediment; it can only be detected with the very sensitive log‐hyperbolic parameters.
Bedload transport in two gravel‐bedded streams
Authors: Carling P. A.
Published: February 2007

Bedload transport measurements in two upland streams are considered as a function of the excess stream power exerted on the bed by the flow.

During low flows when the framework gravels remain undisturbed, fine sediments are winnowed from the bed‐surface layer once a threshold of 3·4 W m−2is exceeded and the transport rate is strongly supply limited. However for stream powers in excess of 15 W m−2framework gravels are mobilized and the efficiency of the transport process approaches a local maximum of about 1 per cent for discharges up to 2/3 of bankfull.

An inverse depth dependence in the efficiency of the transport process was noted but although bedload calibre increased as a function of discharge its influence on efficiency could not be demonstrated. However it was suspected that the size‐sorting relationships of the bed‐material in a number of rivers in relation to the transport efficiency might profitably be examined further.
Tree ring information and rainfall characteristic for landslide in the Kobe District, Japan
Authors: Kashiwaya Kenji , And Takashi Okimura , Kawatani Takeshi
Published: February 2007

Heavy rainfall on the south side of the Rokko Mountains has often caused severe landslides and debris flows. Analysis of the annual summation of rainfall in excess of 100 mm/day shows that the rainfall in this area has dominant periodicities of about 25–30, 10–13, and 5–7 years. The period of about 25–30 years corresponds to that of occurrence of the natural disasters produced by heavy rainfall; years when the maximum rainfall correspond to years when there have been severe landslides and debris flows in the area. Temporal change in this rainfall may provide a first approximation for erosional force. Analyses of tree ring width from these mountains indicate that the sequences have a dominant periodicity of about 25–30 years. Cross‐spectral analyses for rainfall and ring width in this area show high coherency for the periods of about 25–30 years; evidence that variations in the ring width may be used as proxy data for erosional force.
The effect of forestry drainage operations on upland sediment yields: A study of two peat‐covered catchments
Authors: Francis I. S. , Taylor J. A.
Published: February 2007

The suspended sediment yields of two adjacent, paired, catchments on blanket peat in mid‐Wales were compared before and after preafforestation drainage works. Catchment A was ploughed whilst an adjacent catchment (B) was left unploughed. After eight months Catchment B was also ploughed. The ploughing strategy in both catchments was designed to minimize sediment loss. However, suspended sediment loss increased 2·5 times following ploughing in Catchment A, whilst no such increase occurred at this time in Catchment B. Subsequently, suspended sediment yields in Catchment B increased 4·8 times after it was ploughed. Organic sediment was lost mainly from furrow sides, and erosion pins showed maximum ground recession in summer, due to peat wastage. Summer desiccation prepared sediment for transport, and organic suspended sediment loads were highest in the autumn. Sediment loads were limited by vegetation colonization and some reduction in sediment loss was due to the presence of unploughed strips adjacent to stream courses.
Morphodynamic and experimental assessments of wave theories in intermediate water depths
Authors: Hardisty J.
Published: February 2007

Although the near‐bed, wave induced currents predicted by the various wave theories are responsible for seabed sediment transport, it is presently unclear which theory should be included in coastal geomorphic models. The theoretical expressions for near‐bed, shorenormal flows are re‐examined and the predictions are tested with morphodynamic and laboratory data. Five wave theories (Airy, Stokes, Cnoidal, Solitary, and Gerstner) are summarized here and arranged to predict the maximum onshore and offshore near‐bed flows and the flow asymmetry as functions of the wave period, the wave height, and the water depth. Morphodynamic argument suggests that only Stokes and Cnoidal wave theories predict the asymmetry required to generate prototype seabed profiles in intermediate water depths. Laboratory measurements of wave induced near‐bed flows are then reported and analysed. The results suggest that Stokes wave theory over‐predicts the observed peak flows. A correction is derived which is shown to be analogous to the pressure attenuation corrections which are routinely applied to wave recording, seabed mounted transducer measurements.
Fractal techniques and the surface roughness of talus slopes
Authors: Andrle Robert , Abrahams Athol D.
Published: February 2007

Linear plots of log N against log G, where N is the number of steps of length G to span a transit, are conventionally used as evidence that geomorphic surfaces are self‐similar fractals (i.e. the surfaces have a constant fractal dimension). In this study 42 transits on talus slope surfaces in Niagara and Letchworth Gorges, western New York, are investigated to ascertain whether they are self‐similar. Log N‐log G plots, which r2 values in excess of 0·99 suggest are linear, are found upon more rigorous testing to be curvilinear. It is concluded that the talus slope surfaces are not self‐similar, and that log N‐log G plots are relatively insensitive to departures from self‐similarity.

The curvilinearity of the log N‐log G plots is explained with the aid of a randomized square‐wave model of the talus slope surfaces. This model is used to extend the range of measurement beyond that which was possible in the empirical analysis. The negative of the gradient of the log N ‐log G relation at a point is the fractal dimension D. Measurements made upon the randomized square‐wave model indicate that the relation between D and scale of measurement has an asymmetrical wave shape with a peak (i.e. maximum D) where the scale of measurement is equal to the characteristic scale of roughness. In other words the value of D for a surface is not absolute but depends on the scale of measurement relative to the scale of roughness.

Linear regression analysis reveals that at the scale of measurement employed in this study, D is positively correlated with particle size. This is because the values of D fall on the right‐hand tail of the wave‐shaped relation between D and scale of measurement. Transects (normal to the direction of slope) are found to have higher values of D than profiles (parallel to the direction of slope), and this is explained in terms of particle orientation, shape, and juxtaposition.

Because D varies continuously with scale of measurement, there are considerable difficulties in using it to characterize and compare the surface roughness of talus slopes. Generalizing from talus slopes to other ground surfaces, it is evident that to the extent that any natural ground surface has a characteristic scale of roughness, it will depart from self‐similarity, and D should be used with caution in quantifying the roughness of the surface. Geomorphologists are therefore urged to be more rigorous in their testing of self‐similarity before employing D to characterize surface roughness.
Monitoring surface change on a Namib linear dune
Authors: Livingstone Ian
Published: February 2007

In tackling the apparently intractable problem of linear dune initiation and maintenance there has been a move away from large‐scale deductive models to smaller‐scale field studies of individual dunes. This paper reports a study of surface change on a large, complex linear dune in the Namib Desert, southern Africa.

The dune surface responds to a markedly seasonal wind regime. In summer westerly winds erode sand from the west flank of the dune and deposit it on the easterly lee side of the dune crest. In winter this pattern is reversed. Easterly winds erode sand from the east slope and deposit it on the west slope. The crest therefore moves back and forth some 15 m each year returning at the end of a year's cycle to its position at the beginning. The position of the base of the dune appears to remain fixed, even though sand is moving throughout the dune system. The dune does extend northward along some resultant of the westerly and easterly winds.

Despite relatively high levels of activity, especially at the dune crest, there is no evidence of the breakdown of the linear dune form. The conclusion must therefore be that linear dunes can be maintained in bimodal wind regimes and are not necessarily related to unidirectional parallel regimes as others have suggested.
Assessment of visual interpretation of thematic mapper (TM) images for land use and cover in Sudan
Authors: Ali Abdalla Elsadig
Published: February 2007

Three thematic mapper (TM) images, a band 3 image, a band 4 image and a 432 colour composite image of Khartoum were compared for detection, identification and recognition of land use and cover classes in hydrology in Sudan. Simple visual interpretational techniques were employed for this purpose. The results show that visual interpretation procedures can be very useful for an inventory of hydrologic land use and cover using Landsat TM photographic products. This is an important conclusion for developing countries where digital techniques are very expensive at the present and many developing countries cannot afford to make use of them.
Error in polygon overlay processing of geomorphic data
Authors: Smith James W. F. , Campbell Ian A.
Published: February 2007

Predictive models for calculating sediment yield and discharge require accurate areal data. Such models may be unrealistic when using digitized data given the potential error involved in compiling and digitizing thematic polygon maps.

The estimation of boundary variability for digitized polygon maps of a 0·34 km2 area of badlands in Dinosaur Provincial Park, Alberta shows the effects of positional errors introduced during mapping and digitizing processes. Polygon overlay of maps of surface features and slopes produced high frequencies of very small polygons and some unlikely combinations of slopes and surface features, and decreased reliability in areal measurements in the composite map. At an epsilon band width of 0·7 m, a reasonable estimate of boundary variability, 31·7 per cent of the resultant overlaid map can be considered unreliable.
A Markov model for beach changes on the holderness coast of England
Authors: Mason Susan J. , Hansom James D.
Published: February 2007

Markov models offer an objective and quantitative method of assessing beach changes. For a stretch of the Holderness coast a beach classification scheme was devised and a probabilistic first order matrix model based on surveyed profile data was produced. This could describe and predict transitions between beach types and between different time periods. Different profile types dominated different coastal locations and seasonal variations were seen. In order to improve the accuracy of prediction throughout the year a second, ‘winter’, model was added to the original ‘summer’ one. Although the models had been prepared independently of wave conditions, a comparison of the wave record and beach transitions revealed that waves under 0·3–0·5 m high produced fairly static beaches; when waves were between 0·5 and 1·0 m the beach was more dynamic and variable, while waves over 1·0 m led to the depletion of the upper beach. This was broadly in accordance with published theory. Markov models have the advantage that they can be adjusted periodically if conditions change, and are thus useful for prediction on coasts for which no wave records exist.
Geomorphological effects of catastrophic flooding on a small subtropical Estuary
Authors: Cooper J. A. G. , Mason T. R. , Reddering J. S. V. , Illenberger W. K.
Published: February 2007

The Mgeni Estuary is situated on the east coast of South Africa. Tidal salinity changes commonly extend 2.5 km upstream from the mouth. The subtropical climatic regime causes seasonal flooding, the geomorphological effects of which are increased by a steep river gradient. A 120‐150 year flood event during September 1987, with an estimated peak discharge of 10800 cumecs, resulted in the erosion of 1.86 × 106 m3 of sediment from the estuary. The normal high tide volume of the estuary (0.35 × 106 m3) increased to 1.85 × 106 m3 after the flood. The post‐flood intertidal volume (tidal prism) of the estuary was 0.43 × 106 m3 compared to 0.19 × 106 m3 before the event.

The nature and extent of erosion in the estuary was controlled by the composition of the estuary banks and bed material. Gravel and sand substrates were preferentially eroded from the estuary bed before the cohesive bank materials were undercut in sections of the estuary. Mud and fine sand were deposited on overbank areas when the flood waned and a lag of coarse sand and gravel was produced on the estuary bed. Approximately 46 per cent of the bedload sediment supplied to the estuary since 1917 was retained in the estuary until the 1987 flood. The remainder was transported through the system and into the Indian Ocean. Results show that catastrophic floods play an important role in sedimentation in small estuaries.
Design and installation of a combined automatic tensiometer‐piezometer system
Authors: Anderson M. G. , Kemp M. J. , Lloyd D. M. , Othman A.
Published: February 2007

Currently available systems for monitoring both negative and positive pore pressures have certain restrictions as to their use. A system design is described that seeks to overcome some of the potentially more restrictive elements insofar as site investigations in tropical slopes are concerned. In particular, the system uses an integrated approach to both pore pressure and ancillary (e.g. raingauge) monitoring. Initial trials of the instrumentation suggest its suitability for pore pressure recording where high temporal resolution is needed in both negative and positive pressures.
Evaluation of grain shear stresses required to initiate movement of particles in natural rivers
Authors: Petit F.
Published: February 2007

Shear stresses were evaluated at different sites on two rivers. The first (the Rulles) is characterized by a pebbly bedload and a meandering bed with riffles and pools. The second (the Rouge Eau) has mainly a sandy rippled bed where meandering is well developed but also flat gravelly sectors without meandering system.

Shear stresses calculated from friction velocities (τ*) using a redefined y1 roughness height parameter were compared with total shear stresses calculated from the energy grade line and the hydraulic radius (τ), Divergence between these shear stresses seems to increase in the presence of bedforms and large‐scale irregularities of the channel. The τ*/τ ratio is close to 0·5 in the gravelly sector of the Rouge Eau and reaches 0·65 in the riffles of the Rulles (generally located at the inflexion point of the meanders), while it is less than 0·3 in the pools of the same river (located in the loops) and only 0·2 in the sandy rippled sector of the Rouge Eau.

Grain and bedform shear stresses were evaluated at these same sites by different methods. The grain shear stress (τ') represents on average 30 per cent of the total shear stress in the riffles of the Rulles and the gravelly sector of the Rouge Eau, but less than 15 per cent in the pools in the Rulles and the sandy sectors of the Rouge Eau. However, it emerges from experiments conducted with marked pebbles and in situ observations of erosion and transport of sandy and gravelly particles, that the grain shear stresses are underestimated and cannot explain the movements and modifications actually observed.

Conversely, shear stresses calculated from friction velocities at the sites where erosion actually occurred (or failed to occur despite very high velocities) provide a better explanation of the observed movements.
Effect of organic matter on splash detachment and the processes involved
Authors: Ekwue E. I.
Published: February 2007

The influence of organic matter on splash detachment was investigated using soils with grass and peat treatments. The relationship between organic matter and aggregate stability to water disruption was positive for soils with grass treatment while it was negative for those with peat treatment. Organic matter from both treatments, however, reduced splash detachment by rainfall. Soils with grass did this by increasing aggregate stability while peat acted as a mulch on the soil surface. This implies that though organic matter always reduces splash detachment, different processes may be involved, depending on the form of the organic material.

Because of the different processes involved, both negative and positive relationships between splash detachment and aggregate stability as reported in literature were obtained for the soils with grass and peat respectively.
Minimum froude number and the equilibrium of alluvial sand rivers
Authors: Jia Yafei
Published: February 2007

Rivers adjust towards an equilibrium condition, the stability of which depends upon a set of controlling factors expressed by the Froude number. As alluvial river channels approach stable conditions, the Froude number of the channel flow will tend to attain a minimum value which reflects minimum bed material motion and maximum channel stability, under the constraints imposed by water discharge, sediment load, and particle size. Computer simulations for sand bed rivers show that the Froude number of the flow tends to a minimum value when the equilibrium river tends to a certain hydraulic geometry. Evidence from 57 alluvial sand material rivers and stable canals shows that this simulated hydraulic geometry with minimum Froude number corresponds to the natural equilibrium state.
Styles of subglacial glaciotectonic deformation within the context of the anglian ice‐sheet
Authors: Hart Jane K. , Hindmarsh Richard C. A. , Boulton Geoffrey S.
Published: February 2007

A substantial proportion of the glacial sediments of East Anglia, England, are chaotic and highly deformed. This has been attributed to (a) direct glaciotectonic deformation or (b) slumping of glaciomarine sediments. We show that interpretation (a) leads to a classification of subglacial glaciotectonic deposits into sites of ‘constructional deformation’, where little or no erosion of the preglacial deposits has occurred and styles of deformation are preserved moving up in the sequence, and ‘excavational deformation’, where substantial erosion of preglacial sediments has occurred and deformational styles are superimposed on each other.

By using glaciological and geotechnical theory, we show that the expression of these deformational styles in East Anglia is a natural response to the stress fields imposed by the ice‐sheet, and that in consequence their spatial relationships are explicable. The depth of deformation is related to the geotechnical properties of till and substrate, the stress and effective stress fields, and found to be consistent with observations.
Aerodynamic entrainment thresholds and dislodgement rates on impervious and permeable beds
Authors: Williams Jon J. , Butterfield Graeme R. , Clark David G.
Published: February 2007

In the literature it has been suggested that on permeable, granular beds, both the threshold and rate of aerodynamic entrainment may be affected significantly by seepage flows into and out of the bed induced by fluctuating pressures in the overlying turbulent boundary layer. Using a range of grain sizes and flow conditions, the series of laboratory experiments reported here compares directly the aerodynamic entrainment of loose grains overlying fixed permeable sediment beds with that occuring over fixed impervious beds. For a given granular material, no significant differences in entrainment dynamics on the two types of bed were observed and in the range of flow conditions examined both the threshold shear velocity (U*T) and the aerodynamic entrainment coefficient (k) were found to be independent of bed permeability.
Fractal techniques and the surface roughness of talus slopes: a comment
Authors: Roy Andre G. , Robert Andre
Published: February 2007

Andrle and Abrahams (1989) present the results of a rigourous test of self‐similarity on profiles and transects obtained from talus slopes. The aim of their paper is to show that the self‐similar fractal model (SSFM) is of limited usefulness in describing the roughness of talus slopes and presumably of other geomorphic features. Although their point is well taken and their application provides insight into the controls of the fractal dimension, several issues raised by the authors require further discussion.
The self armouring process under unsteady flow conditions
Authors: Nouh M.
Published: February 2007

Laboratory experiments were conducted to investigate the effect of the original size distribution of sediment and unsteady flow characteristics on the composition of an armour layer in a straight open flume. Bed sediments having different size distribution were subjected to flow hydrographs that varied in depth (D) and duration (T). The sensitivity of the sequence of changed bed sediment compositions to the variation in hydrograph duration was more than that in hydrograph depth. Such sensitivity increased as the geometric mean diameter of the original sediment decreased and as the geometric standard deviation of the sediment increased. The gradation of the armour coat developed under unsteady flow condition was greater than that developed under equivalent steady flow condition (i.e. having the same mean discharge and friction slope), and was found to depend on the value of the parameter P = (D/T)(1/u*) up to the limit of P = 0·01, where u* is the shear velocity. A model is proposed to predict the final composition of the armour layers developed under the effects of unsteady flow conditions.
A reply to ‘a discussion of hirano and Aniya's (1988, 1989) explanation of glacial valley cross profile development’ by Jonathan M. Harbor
Authors: Hirano Masashige , Aniya Masamu
Published: February 2007

The extremum principle is again justified as a valid and relevant approach to cross sectional form of the glacial valley. It is accepted that the extremum previously obtained was a maximum, and not a minimum for friction, but this still appears to be a valid application of the principle. Harbor's more detailed discussion is recognized as valid assuming the presence of appreciable water pressures, and that Hallet's theory is to be preferred over Boulton's, but these assumptions do not always seem appropriate. While the importance of time for valley evolution is fully accepted, the extremum approach is still thought to be useful, for example in maximizing cross section for a given resistance.
Channel avulsion and river metamorphosis: The case of the Thomson River, Victoria, Australia
Authors: Brizga Sandra O. , Finlayson Brian L.
Published: February 2007

Channel avulsion occurred on the Thomson River in Victoria, Australia, in 1952 along a 12 km length of the valley. A comparison of the old and new channels reveals considerable differences in channel characteristics. The old channel was perched above the floodplain on an alluvial ridge such that when bankfull capacity was exceeded, floodwaters concentrated on the lowest part of the floodplain some distance away. This is where the new channel formed. It is an incised channel with larger capacity and longer meander wavelength than the old channel and is also shorter and steeper. The new channel is subject to larger floodflows and a more variable flood regime than the old course because of the differences in the channel/floodplain relationship and channel capacity. The resulting concentration of stream power along the new course is responsible for the contrast in channel characteristics and for the more rapid meander migration.

This example shows that river metamorphosis can occur without major environmental changes. Measures of channel geometry such as gradient, sinuosity, and meander wavelength therefore cannot be used in palaeohydrological work to infer climatic or other environmental changes without independent supporting evidence. Differences in channel geometry can arise simply from changes in the relationship between the channel and its loodplain.
Aeolian sand transport—an optimized model
Authors: Chapman David M.
Published: February 2007

Consideration of the available equations for prediction of aeolian sand transport led to the development of a model which relies on optimization techniques for the production of improved performance. The model has been applied to the characterization of dunesand movement in coastal environments in eastern Australia.
Development of miniature sorted patterned ground following soil erosion in East Falkland, South Atlantic
Authors: Wilson Peter , Clark Richard
Published: February 2007

Miniature sorted patterned ground features (nets and stripes) occur at an elevation of ca. 35 m in the L'Antioja valley, East Falkland. The features have developed following recent soil erosion and display many of the characteristics associated with the operation of frost‐related processes in regolith materials. The patterns are currently active and indicate that in cool oceanic climates the distribution of frost‐sorted patterns is controlled by the presence of bare ground on suitable regolith rather than by altitude.
Sediment budgeting: A case study in the Katiorin drainage basin, Kenya
Authors: Sutherland Ross A. , Bryan Rorke B.
Published: February 2007

The primary objective of this study was to compute a detailed budget for a small semiarid tropical drainage basin in Kenya. Results indicated that transfer of sediments (‘inputs’) from primary source areas was minor in comparison to changes in storage. The major sediment source area within the Katiorin drainage basin was the colluvial hillslope zone. The net change in storage within this zone was approximately 2100 Mg yr−1. Surface wash and rilling were the dominant transport processes responsible for the remobilization of colluvial sediments. Sediment storage within the in‐channel reservoir increased by 60 Mg yr−1, which was minor when compared to the total store of sediment in this reservoir. During 1986, the channel network stored only a small fraction ( < 3 per cent) of the sediment delivered from the hillslope subsystem. Therefore, the in‐channel reservoir had limited influence on sediment conveyance to the basin outlet. These data indicate that a static equilibrium condition cannot be assumed within the Katiorin drainage basin. Such an assumption would result in erosion estimates of approximately 5.5 mm yr−1 for the entire basin (based on a sediment output of 7430 Mg km−2 yr−1 and a measured bulk density of 1.35 Mg m−3). However, this masked the actual rates of 1.2 to 7.1 mm yr−1 in subbasin primary source areas, and rates of 0.6 to 17 mm yr−1 for colluvial material in the various subbasins. The extreme accelerated erosion rates resulted from minimal ground vegetation, steep slopes, soil crust formation, an erodible substrate, and a well‐integrated drainage network for rapid conveyance of sediments from the hillslope subsystem to the basin outlet.
Spatial and temporal variations in temperate forest soil carbon dioxide during the non‐growing season
Authors: Dyer James M. , Brook George A.
Published: February 2007

In the Whitehall Forest of Georgia during the 1985‐86 non‐growing season soil CO2 varied with soil depth, varied spatially at constant depth, and varied temporally with changing environmental conditions. Variations with depth in the upper 1.4 m of the soil were of greater magnitude than temporal variations and spatial differences at 30 cm depth were of lesser magnitude. Mean soil CO2 in evergreen forest was higher (0.207 per cent) than in deciduous and mixed forest (0.157 per cent). There were no trends in soil CO2 along hillslopes or with changes in soil texture, bulk density, moisture content, or temperature. Soil CO2 did increase near trees possibly due to increased root densities and/or more numerous pockets of microbial activity. For CO2 at 30 cm depth, two variables–the mean daily temperature range in the month before measurement and actual evapotranspiration in the week before measurement (AET7)–explained 76 per cent of the variation in mean soil CO2. At the profile site, where soil CO2 was measured at five depths, 66 per cent of the variability in CO2 was explained by soil depth, AET7, and the average daily temperature range in the two months before measurement.
Developments in a non‐destructive method of determining rock strength: A reply
Authors: Allison Robert J.
Published: February 2007

In a previous publication (Allison, 1989), a non‐destructive method for indirectly determining rock strength by measuring Dynamic Young's Modulus was described. Data were presented to assess the Grindosonic apparatus in relation to standard laboratory techniques. A further Short Communication (Allison, 1990) evaluated the non‐destructive test as a field technique, in part achieved by comparing the Grindosonic results with data collected using the Schmidt hammer. The Schmidt hammer is a widely used field technique in geomorphology for determining rock strength (see for example Day and Goudie, 1977; Day, 1981). Allison (1989, 1990) also suggested that the elastic properties of materials are becoming increasingly important in geomorphological studies. The opportunity to provide additional information and comments here is appreciated.
Global energy balance and regional hydrology: A Burgundian case study
Authors: Gunn Joel , Crumley Carole L.
Published: February 2007

Accurate measures of global atmospheric energy balance collected since the International Geophysical Year (1957‐1958) show statistically significant relationships to regional monthly growing season discharge in east central France (also North Carolina, Texas, and Yucatan). The relationships are frequently curvilinear. Transfer functions can be calculated to reconstruct prehistoric and historic regional hydrological balance and project future effects. An astronomical climatology model is used to estimate past global energy balance. The projections appear to fit sediment, diatom, and pollen records. General circulation model estimates of greenhouse warming are used to drive future hydrological balance determinations.
A model for heat and water balance estimation and its application to land use and climate variation
Authors: Olejnik Janusz , Kedziora Andrzej
Published: February 2007

This paper presents a method, which has been recently developed in the Department of Agrometeorology of the Poznań Agricultural University, for estimating heat balance components based on standard meteorological data, plant development stage, and land‐use conditions. Estimates of latent heat flux components made it possible to obtain values of areal evapotranspiration and surface runoff. The method was applied in four catchment areas in Central Poland under present climatic conditions as well as under new, expected climatic conditions caused by an increase of ‘greenhouse gases’ in the atmosphere. Some changes in land use were also considered. The results show significant changes in the water balance when comparing present and future conditions of precipitation and evapotranspiration.
Impact of a CO2‐induced climatic change on river flow variability in three rivers in Belgium
Authors: Gellens D.
Published: February 2007

A hydrological conceptual model developed by the Royal Meteorological Institute of Belgium has been run to assess the potential hydrological impacts of an hypothetical doubling of the atmospheric CO2 concentration. The simulated scenarios were derived from the predictions of climatic change currently provided by General Circulation Models (GCMs).

Three typical drainage basins in Belgium have been selected for assessing their common responses and bringing out possible specific behaviours attributable to catchment characteristics.

The study dealt essentially with modifications of the streamflow and with alterations of the flood and low‐flow regimes.

In catchments with prevailing surface flow the considered change in climate could induce:

An increase in flood frequencies during the winter season together with a strengthening of the extreme river stages leading to greater flooding risks;

A decrease in streamflow during the summer season and, as a corollary, increased risks of water pollution;

Possible restraints, in summer and autumn, on water availability from local groundwater storages.

In catchments with high infiltration rate and with strong aquifer the impact could be:

An increase in groundwater storage, bringing about an increase in the base flow throughout the year, which in turn involves increased flood risks;

A reduction of the number of low‐stage occurrences in summer, resulting in reduced river pollution;

A possible increase in water availability from the aquifers.
Sensitivity of the river Rhine discharge to environmental change, a first tentative assessment
Authors: Kwadijk J. C. J.
Published: February 2007

Changes in climatic conditions may have great impact on the distribution of available water in space and time. However the results of models that describe future climate conditions are still insufficient to be used in regional hydrological simulation studies.

This article describes a first tentative estimation of the sensitivity of discharge of the river Rhine to two environmental changes. Firstly, to a change in snow covered area due to a rise of 4°C in winter temperature in the upland part (Alps) of the drainage area and, secondly, to a large land use change in the lowland area (Federal Republic of Germany/France).

‘Worst case’ scenarios for discharge of the river Rhine under warmer conditions give a reduction of 10 percent for the summer discharge at Rees (Dutch/German border). The results of the estimations indicate that the reduction of the summer discharge in a warmer world could be larger.
Classification of rock weathering at writing‐on‐stone Provincial Park, Alberta, Canada: A study in applied geomorphology
Authors: Campbell Ian A.
Published: February 2007

At Writing‐On‐Stone Provincial Park in southern Alberta, Canada, weathering is causing deterioration and loss of archaeologically important Indian rock art. A procedure devised for the use of park personnel identified four classes of weathering ranging from largely unweathered rock to severely weathered. The technique employed simple visual, qualitative assessment and photo interpretation of 50 sample sections of sandstone cliff face covering a total area of 354 m2. Schmidt hammer tests indicated large variations in rock strength and provided a numerical basis for the visual assessment. About 43 per cent of the cliffs are severely to completely weathered, 41 per cent show moderate weathering.
Flow competence: A criticism of a classic concept
Authors: Wilcock Peter R.
Published: February 2007

The largest grains found in samples of transported sediment are commonly used to estimate flow competence. With samples from a range of flows, a relationship between the flow and the largest mobile grain can be derived and used to estimate the critical shear stress for incipient motion of the different grain sizes in the bed sediment or, inversely, to estimate the magnitude of the flow from the largest grain found in a transport sample. Because these estimates are based on an extreme value of the transport grain‐size distribution, however, they are subject to large errors and are sensitive to the effect of sample size, which tends to vary widely in sediment transport samples from natural flows. Furthermore, estimates of the critical shear stress based on the largest sampled moving grain cannot be scaled in a manner that permits reasonable comparison between fractions. The degree to which sample size and scaling problems make largest‐grain estimates of fractional critical shear stress deviate from a true relationship cannot be predicted exactly, although the direction of such a deviation can be demonstrated. The large errors and unknown bias suggest that the largest sampled mobile grain is not a reliable predictor of either critical shear stress or flow magnitude. It is possible to define a single flow competence for the entire mixture, based on a central value of the transport grain‐size distribution. Such a measure is relatively stable, does not require between‐fraction scaling, and appears to be well supported by observation.
Long‐term drainage evolution in the shoalhaven catchment, southeast highlands, Australia
Authors: Nott Jonathan F.
Published: February 2007

The long‐term evolution of streams in the Shoalhaven catchment of southeast New South Wales has been a contentious issue for decades. Several authors have suggested that the Shoalhaven River was captured at the sharp eastward bend near Tallong: this has been used as evidence for the westward migration of the east Australian divide in this area. Other workers, however, have argued that capture did not occur and that the location of the divide has been stable throughout the Tertiary. A vast sheet of sediments which spread across and infill a palaeovalley network cut into a broad undulating plain in the middle Shoalhaven catchment provides a record of stream behaviour since at least the start of the Tertiary. This record shows that the Shoalhaven River and many of its tributaries have maintained almost the same courses since at least the very Early Tertiary. This provides strong evidence against the capture hypothesis. The record further suggests that during the Paleogene these streams were graded to a level within the southeast Australian highlands; their depths of incision thus cannot be used as evidence for the extent of uplift of the southeast Australian highlands during this time.