bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractCurrently 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

AbstractShear 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

AbstractThe 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

AbstractRivers 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

AbstractA 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

AbstractIn 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

AbstractAndrle 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

AbstractLaboratory 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

AbstractThe 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

AbstractChannel 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.
Development of miniature sorted patterned ground following soil erosion in East Falkland, South Atlantic
Authors: Wilson Peter , Clark Richard 
Published: February 2007

AbstractMiniature 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

AbstractThe 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

AbstractIn 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

AbstractIn 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

AbstractAccurate 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

AbstractThis 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

AbstractA 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

AbstractChanges 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

AbstractAt 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.