bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geomorphology and seismotectonic elements in the giarre area, sicily
Authors: Adorni G. , Carveni P. 
Published: February 2007

AbstractA morphostructural analysis has been performed on the eastern flank of Mt Etna, located between the towns of St. Alfio and Linera and the Ionian Sea. The research has been carried out through analysis of aerial photographs, and has allowed recognition of morphoneotectonic elements such as: some scarps with rectilinear trend, laterally becoming morphological flexures, according to the lithology; anomalies in the hydrographic network, such as rectilinear tracts of drainage, valleys with simple or double bends, hanging valleys and truncated valleys, narrow deeply engraved valleys with meanders and fluvial captures. All these elements are caused by a fault system oriented NNW–SSE, with a mainly vertical component.Seismic events with very shallow foci have been recorded in the study area; these earthquakes triggered several small landslides on the fault scarps and large series of coseismic and coaxial fractures.It is possible to show that the morphostructures examined have been reactivated during many of the seismic events that have occurred in the area. The combination of these elements verifies that the morphostructures have a real neotectonic cause, which is associated with uplifts which have occurred in the area at different times.
Mechanisms responsible for streamflow generation on a small, salt‐affected and deeply weathered hillslope
Authors: George Richard J. , Conacher Arthur J. 
Published: February 2007

AbstractThis paper considers the contributions of overland flow, throughflow and deep seepage to the generation of streamflow in a salt‐affected, deeply weathered landscape.Runoff mechanisms on a small hillslope in south‐western Australia were dependent on the extent and development of variable source areas. In winter, streamflow generation was controlled by returnflow, saturation overland flow and throughflow. In summer, post‐ponding, infiltration‐excess and saturation overland flow dominated. The extent of the variable source area and the magnitude of streamflow were due to antecedent soil moisture, rainfall and slope morphology. Concave hillslope sections accumulated soil moisture due to both saturated and unsaturated lateral flow processes.Throughflow provided the mechanism and vehicle for solute movement from the groundwater discharge area to the stream. However, discharge from the deep aquifer was the primary mechanism responsible for soil salinity and maintaining the core of the variable source area. Estimates of throughflow which only take account of soil‐water movement and disregard returnflow, will underestimate the magnitude of throughflow.
Effects of incorporating two organic materials at varying levels on splash detachment of some soils from Borno state, Nigeria
Authors: Ekwue E. I. , Ohu J. O. , Wakawa I. H. 
Published: February 2007

AbstractSplash detachment by raindrops was measured using a factorial experiment involving three soils (sandy loam, clay loam and clay) and two organic materials (cow dung and groundnut haulms) applied at five levels (0, 2, 4, 6 and 8 per cent by mass). A simulated rainfall intensity of 145 mm h−1 for 10 min duration was used for the tests. Detachment was described in terms of the direct effects and the first and second order interactions of the variables mentioned above. Results indicated that mean splash detachment was reduced significantly (P < 0·01) from 1·97 kg m−2 in the sandy loam to 0·67 kgm−2 in the clay soil. For each soil type, detachment was reduced significantly (P < 0.01) with increasing levels of added organic matter. Groundnut haulms produced lower values of detachment than cow dung. There were also significant interaction effects between the study variables. These interactions were used to describe the effect of added organic materials on splash detachment. For each soil type and organic material, negative exponential relationships were established to relate splash detachment to levels of added organic matter.
Role of in situ cosmogenic nuclides 10be and 26al in the study of diverse geomorphic processes
Authors: Nishiizumi K. , Kohl C. P. , Arnold J. R. , Dorn R. , Klein I. , Fink D. , Middleton R. , Lal D. 
Published: February 2007

AbstractThe central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings. In the light of these general models, we discuss the information that can be derived about geomorphic processes, utilizing concentrations of in situ produced cosmogenic radionuclides 10Be (half‐life=1·5 ma) and 26A1 (half‐life=0·7 ma) in a variety of geomorphic contexts: glacial polish and tills; meteorite impact craters; alluvial fans; paleo‐beach ridges; marine terraces; sand dunes; and bedrock slopes. We also compare 10Be‐26Al data with results obtained by other dating methods. We conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time‐scales in a wide range of geomorphological problems.
Establishing the role of pedogenesis in changing soil hydraulic properties
Authors: Brooks S. M. , Richards K. S. 
Published: February 2007

AbstractChronosequences provide suitable sources for the study of changes in soil hydraulic behaviour as a result of long‐term pedogenesis. For a podsol chronosequence in the Scottish Highlands, data are presented to indicate the changes that have occurred over 13000 years in the saturated hydraulic conductivity (Ksat) in each horizon. As the soil profile has evolved into a differentiated sequence of three horizons, the resulting hydrological changes can be both measured and quantified by relating Ksat to textural properties and bulk density. The results are significant for interpretation of changing runoff processes and slope stability.
Tracing sediment movement in interrill overland flow on a semi‐arid grassland hillslope using magnetic susceptibility
Authors: Parsons Anthony J. , Wainwright John , Abrahams Athol D. 
Published: February 2007

AbstractExperiments were undertaken to determine the feasibility of tracing sediment movement in interrill overland flow. Crushed magnetite was introduced as a source‐line 10 cm wide by 8 m long on a runoff plot 18 m wide by 29 m long located in southern Arizona. Initial magnetic susceptibilities along this source line, and along three transects located 0·25, 2·95 and 5 m downslope of the source‐line, were measured. Movement of the magnetite in response to three rainfall simulation experiments was monitored. During the first two experiments, overland flow discharge was sampled at miniature flumes located along two cross sections on the plot downslope of the source‐line, and at a supercritical flume at the plot outlet. Magnetic susceptibilities along the source‐line and transects were measured after all three experiments. Results show that the magnetite moves very early in the experiments and that it reaches one of the flumes 2 m downslope of the source‐line in 3 min. Most of the tracer moves a very short distance: 29·7 per cent is deposited within 25 cm of the source‐line and only 2·2 per cent is deposited 2·95 m away. The deposition rate appears to decrease exponentially away from the source‐line. Very little magnetite is recorded in the flow through the miniature flumes: in general it makes up less than 1 per cent of the total sediment load. No temporal pattern in these percentages is observed. Magnetite appears to be an effective tracer of sediment movement in interrill overland flow, though its higher density than natural soil may affect its detachment and transport.
Velocity‐reversal hypothesis: A model approach
Authors: Keller E. A. , Florsheim J. L. 
Published: February 2007

AbstractHydraulic modelling of a riffle‐pool‐riffle sequence in a straight reach of Dry Creek near Winters, California, indicates that while at low flow the mean (section average) velocity at riffles exceeds that of an adjacent pool, during high flow the mean velocity of the pool exceeds that of adjacent riffles. This supports the velocity‐reversal hypothesis which is based on limited field measurements of near‐bed flow velocity. A velocity reversal does not occur at the same discharge in both riffle‐pool sequences modelled, and a more detailed explanation is necessary to account for complex aspects of channel form and process in riffle‐pool sequences. Nevertheless, the velocity‐reversal hypothesis helps to explain many of the observations and processes that operate in the riffle‐pool environment.
The application of confocal microscopy to the study of stone weathering
Authors: Rautureau Michel , Cooke Ronald U. , Boyde Alan 
Published: February 2007

AbstractConfocal scanning light microscopy is a valuable new method for examining the nature and progress of stone weathering at a level of resolution between optical microscopy and scanning electron microscopy. Not only is it non‐destructive, but it can also create three‐dimensional images.
The soil erosion bridge: A device for micro‐profiling soil surfaces
Authors: Shakesby Richard A. 
Published: February 2007

AbstractThe soil erosion bridge is a simple, robust, cheap, lightweight device comprising a bar which, when mounted on two stakes, provides a stable datum for micro‐profiling the soil surface beneath. Its main advantage over similar devices is the unique combination of mounting clamps, which allow for variation in the distance and angle with respect to the vertical of the mounting stakes without loss of accuracy. The design, installation and measurement procedures are described. Applications and limitations are discussed.
Automated water sampling in ephemeral hydrological systems
Authors: Vivian B. J. , Quinton J. N. 
Published: February 2007

AbstractA wide variety of sampling programmes may now be considered practical with the recent developments in data logger and water sampler technology. In ephemeral systems the water sampler remains idle for long periods between events. Two approaches are described which overcome the problems of sampling in ephemeral systems: short interval time dependent sampling (TDS) and automated flow proportional sampling (FPS). Both approaches utilize the data logger's ability to perform intermediate operations on incoming data to control the initiation of water sampling. The logger programs are described and allow many recorder/water sampler units to be controlled from one device. The relative merits of the two approaches are discussed in terms of experimental requirements and data precision.
Controls on bedrock channel incision along nahal paran, Israel
Authors: Wohl Ellen E. , Greenbaum Noam , Schick Asher P. , Baker Victor R. 
Published: February 2007

AbstractNahal Paran drains 3600 km2 of Egypt's Sinai peninsula and Israel's Negev Desert. Much of the channel is alluvial, but a canyon 10·5 km long has been incised into Late Cretaceous chert and dolomite in the lower portion of the basin. Slackwater deposits and paleostage indicators preserved within the canyon record approximately 10 floods of 200 to 2500 m3 s−1 over a period of at least 350 years. Step‐backwater simulations of flood‐flow hydraulics indicate extreme variations in stream power per unit area along the length of the canyon, and associated variability in energy expenditure and sediment transport. These variations reflect channel cross‐sectional morphology. The greatest values of stream power occur along the lower half of the study reach, in association with three pronounced knickpoints and an inner channel. The locations of these features reflect the exposure of thick, resistant chert layers along the channel. The presence of several similar, but buried and inactive, knickpoints along the upper study reach indicates that the locus of most active channel incision has shifted with time, probably in response to baselevel changes associated with tectonic activity along the Dead Sea Rift. Thus, the rate and manner of channel incision along the canyon of Nahal Paran are controlled by lithologic variability and tectonic uplift as they influence channel morphology and gradient, which in turn influence hydraulics and sediment transport.
Ten year remeasurement of chemical denudation on a magnesian limestone hillslope
Authors: Trudgill S. T. , Ferguson R. I. , Ball J. , Crabtree R. W. , Gent R. 
Published: February 2007

AbstractResults from the measurement of microweight loss of Magnesian Limestone rock tablets placed at the soil–bedrock interface on a hillslope over 10 years (1982–1992) gave the same relative pattern of upslope increase in weight loss as did short‐term measurements (1979–1981), but the absolute values were an order of magnitude lower (0·01–0·03 per cent per year long term and 0·1–0·6 per cent per year short term). Microweighed rock tablets may therefore give unreliable absolute rates and can only be used to indicate relative spatial differences rather than to give reliable data on temporal changes.
Fingered flow: The creator of sand columns in dune and beach sands
Authors: Dekker Louis W. , Ritsema Coen J. 
Published: February 2007

AbstractSand columns, sand cones, sand mushrooms and other striking sand forms are frequently observed in the Dutch and German beach and dune sands. This paper aims to clarify the mechanism of sand column formation. Recently it has become evident that homogeneous beach and dune sands often become irregularly wetted by infiltrating rainwater. In otherwise dry sandy soils, wet preferential flow paths (‘fingers’) may develop. At two test sites the volumetric soil moisture content varied between 0·2 and 12·0 per cent. The wet fingers represent the premature state of sand columns. When the dry sand in between these fingers is blown away by the wind, the more resistant wet sand of the fingers will remain in its place and appear as sand columns at the surface. As a result of wind and erosive sand drifts, striking sand forms may be formed.
Critical discharge for entrainment of poorly sorted gravel
Authors: Ferguson R. I. 
Published: February 2007

AbstractEntrainment criteria for gravel‐sized particles on river beds are usually defined in terms of shear stress, but some workers have proposed that critical‐discharge relationships are more reliable and more convenient. The critical shear stress in poorly sorted gravels is known from recent work to depend much more on relative than absolute grain size. It is shown that this effect can be included in a semi‐theoretical equation for the critical unit discharge to move individual grain sizes in a poorly sorted bed. Comparisons with published data on critical discharges in a variety of rivers show that both the sensitivity of critical discharge to grain size, and the absolute levels of critical discharge, are predicted quite well. However, any prediction of critical discharge is sensitive to the assumptions made, first about flow resistance and secondly about the critical stress to move average‐sized particles.
Temporal cycles of karst denudation in northwest Georgia, U.S.A.
Authors: Kiefer Rudi H. 
Published: February 2007

AbstractTime patterns of karst denudation in northwest Georgia (U.S.A.) were investigated at three spring sites for 12 months and at five stream sites for 10 years. Rainfall was evenly distributed and showed no significant seasonality. At the springs, as well as the streams, water hardness was largely controlled by discharge. At the springs, soil pCO2 and water pH were strongly correlated (r + ‐0·69 to ‐0·83). Solute transport in spring waters was highly seasonal, with two conduit flow springs removing more limestone in the winter, and the diffuse flow spring removing more during the growing season. At the stream sites, most denudation occurred during the winter and spring seasons, and least during the summer.Fourier analysis showed that variations in denudation occur on deterministic (long‐wave) as well as stochastic (shortwave) time scales. As contributing variables, discharge varied in short‐wave and long‐wave cycles, whereas soil pCO2 showed only a long‐wave cycle. The 12 month deterministic cycles were the most important, with changes in discharge taking precedence over soil pCO2. Time series regression explains up to 69 per cent of changes in denudation through rain and soil pCO2. Time cycles in available water are the key controlling factor of denudation, and amounts of available soil CO2 may not be as important in the temporal patterns of karst downwearing as has been believed previously.
Prediction of tension crack location and riverbank erosion hazards along destabilized channels
Authors: Darby Stephen E. , Thorne Colin R. 
Published: February 2007

AbstractRiverbank erosion, associated sedimentation and land loss hazards are a land management problem of global significance and many attempts to predict the onset of riverbank instability have been made. Recently, Osman and Thorne (1988) have presented a Culmann‐type analysis of the stability of steep, cohesive riverbanks; this has the potential to be a considerable improvement over previous bank stability theories, which do not account for bank geometry changes due to toe scour and lateral erosion. However, in this paper it is shown that the existing Osman‐Thorne model does not properly incorporate the influence of tension cracking on bank stability since the location of the tension crack on the floodplain is indirectly determined via calculation or arbitrary specification of the tension crack depth. Furthermore, accurate determination of tension crack location is essential to the calculation of the geometry of riverbank failure blocks and hence prediction of land loss and bank sediment yield associated with riverbank instability and channel widening. In this paper, a rational, physically based method to predict the location of tension cracks on the floodplain behind the eroding bank face is presented and tested. A case study is used to illustrate the computational procedure required to apply the model. Improved estimates of failure block geometry using the new method may potentially be applied to improve predictions of bank retreat and floodplain land loss along river channels destabilized as a result of environmental change.
Rill erosion along the thalweg of a hillslope hollow: A case study from the cotswold hills, Central England
Authors: Slattery M. C. , Burt T. P. , Boardman J. 
Published: February 2007

AbstractRill erosion is an important erosional form on agricultural soils in England, causing large losses of soil, particularly on cultivated slopes. This paper describes a rill system that developed in a small agricultural catchment in north Oxfordshire during the winter of 1992–93. The rill system comprised two components: a system of ‘feeder rills’ along the valley‐side slopes, which were the result of flow concentration and erosion along wheelings, and a thalweg rill, which formed along a dry valley bottom as a result of surface runoff concentration from the feeder rills. Total volumetric soil loss from the rill system was 32·28 m3, equivalent to 3·01 m3, ha−1 for the rill catchment area, or 3·91 t ha−1. Mean discharge for the thalweg rill and feeder rills, calculated during a storm event, was 31·101s−1 and 1·171s−1, respectively. All flows were fully turbulent and supercritical. We emphasize the need for a spatially distributed approach to the study of runoff and erosion at the catchment scale.
Dimensionless critical shear stress evaluation from flume experiments using different gravel beds
Authors: Petit F. 
Published: February 2007

AbstractFlume experiments were conducted using four different gravel beds (D50 + 12–39 mm) and a range of marked particles (10–65 mm). The shear stresses were evaluated from friction velocities, when initial movement of marked particles occurred. Two kinds of equations were produced: first for the threshold of initial movement, and second for generalized movement. Equations of the type 0c + a(Di/D50)b, as proposed by Andrews (1983) are applicable even if the material is relatively well sorted. However, the values of a and b are lower (respectively 0·050 and ‐0·70) for initial movement. Generalized movement requires a higher shear stress (a + 0·068 and b + ‐0·80).D90 of the bed material and y0 (the bed roughness parameter) were also used as reference values in place of D50. They produced lower values than in natural streams, mainly owing to the fact that the material used in the flume is better sorted: clusters are less well developed and the bed roughness is lower.
Seepage erosion and its implication to the formation of amphitheatre valley heads: A case study at Obara, Japan
Authors: Onda Yuichi 
Published: February 2007

AbstractSeepage erosion was investigated in an amphitheatre with a semicircular valley head, steep slopes, and a flat bottom developed in granodiorite hills at Obara, Aichi prefecture, Japan. A high sediment yield occurred where the measuring sites were located at the base of the landslide debris in the base of the convex slopes, whereas sediment outflows were small where the measuring sites were located at the base of the strong convex slopes. This implies that the seepage erosion was an effective agent for removal of debris deposited at the base of the slope. Small landslides can be found at the lower slopes within the area of the observed amphitheatre. The slope stability analysis and subsurface water observation of the lower slope suggest that the small landslides in this amphitheatre are due to over‐steepened slopes, and relatively insensitive to subsurface water status. Colluvium in the flat valley bottom thinly covers the bedrock surface. Therefore the topography of the amphitheatre was found to be formed by parallel retreat of slopes by the repetition of basal seepage erosion and subsequent small landslides.
Visualization of the turbulent flow structure in a gravel‐bed river
Authors: Kirkbride Alistair D. , McLelland Stuart J. 
Published: February 2007

AbstractA novel technique for visualizing turbulent flow data from a gravel‐bed river is presented. The time development of flow velocity and shear stress at three heights is displayed using a computer program. This can be used to observe how the fluctuations of velocity and shear stress interact both spatially and temporally. We highlight examples of flow events which are important for the understanding of flow dynamics. The visualization suggests that the turbulent flow‐field is characterized not only by coherence over time at a point, but also by spatial interdependence between points. We suggest that this new visualization approach will assist further interpretation of statistical analyses of turbulent signals, as well as focusing future measurement strategies by providing a clearer spatio‐temporal picture of the flow structure.