bluuebunny/crossref_metadata_2025_split huggingface dataset:
A stochastic distributed model of soil erosion by overland flow
Authors: Wright A. C. , Webster R. 
Published: February 2007

AbstractA model has been built to simulate runoff and erosion on slopes of varying form with soil of varying hydraulic conductivity, porosity, storage capacity, and particle size distribution. The model is based on known physical laws and takes into account spatially dependent random variation in the initial conditions of the soil. The rainfall is similarly both random and autocorrelated in space.Detailed results show how runoff is generated as a result of slow conductivity and high water table, how this leads to erosion, the degradation of the land surface, the capture of flow lines, and the development of networks of rills. The last accords well with results from laboratory experiments. Changing the initial conditions produces results that accord with intuition and reality.
Sediment yield and delivery in the blanket peat moorlands of the southern Pennines
Authors: Labadz J. C. , Burt T. P. , Potter A. W. R. 
Published: February 2007

AbstractIn contrast to much previous research on blanket peat moorland, which has concentrated upon studies of the form and causes of gully erosion, this paper attempts to investigate sediment transport and to estimate both short‐term and long‐term sediment yields in such terrain. The research was conducted on Wessenden Head Moor to the west of Huddersfield, Yorkshire, where automatic stream sampling continued over a period of two years. Use of corrected rating curves (Ferguson, 1988) provided a mean estimate of sediment yield over this period of 55 t km−2 yr−1.In addition an estimate of longer‐term sediment yield was derived from four reservoir sediment surveys in the Wessenden Valley. Total yield was 203.69 t km−2 yr−1, including an organic fraction of 38.82 t km −2 yr−1. Stream sampling at three sites on Shiny Brook, including headwaters and the outflow to the reservoir, suggested that there is great temporal and spatial variability in mineral and organic inputs to the reservoirs. Although not excessive in gravimetric terms, the low density of peat means that there is a serious erosion problem. Estimates of erosion rates for the peat gully network at Shiny Brook appear to confirm earlier evidence concerning the relatively recent occurrence of this erosion, within the last two centuries.
Spatial and seasonal aspects of shoreline changes at Forcados Beach, Nigeria
Authors: Oyegun C. U. 
Published: February 2007

AbstractThe influence of the seasons of the year on beach changes is well documented in the literature. One generalization which has emerged is that beaches are ‘combed down’ in winter and ‘built up’ in summer. Some workers have disagreed with this dictum because field evidence does not necessarily support the assertion.This study, located in the humid tropics, shows, with the aid of graduated pegs emplaced perpendicularly to the shoreline, that the magnitude and frequency of beach changes are greater in the wet, than in the dry season. Furthermore, there is a net loss of beach materials in the wet season and a net gain in the dry season, even though erosion and accretion occur throughout the year with no statistically significant difference in their magnitudes.Erosion prevails at the northern half of the beach while accretion is dominant to the south. The upper and lower foreshore zones are more prone to changes than the mid‐tide level.
Comments on Allison's (1990) developments in a non‐destructive method of determining rock strength
Authors: Campbell Ian A. 
Published: February 2007

AbstractIn Developments in a non‐destructive method of determining rock strength, Allison (1990) compares data collected using an ultrasonic apparatus with data obtained from Schmidt hammer tests. He concludes that the Schmidt hammer data shows a wide degree of scatter and that its accuracy as field technique is questionable. No discussion is made of how the Schmidt hammer was used or of the total number of readings taken and the range of values. The graphs presented comparing data derived from some samples using ultrasonic equipment do not appear markedly at variance from the Schmidt hammer‐derived data but true comparison is not possible because the graphs use different measurement criteria. No information is given on comparative time and financial costs, which must be significantly different for the two techniques.
Effects of peat content, rainfall duration and aggregate size on soil crust strength
Authors: Ekwue E. I. 
Published: February 2007

AbstractThe effect of peat on crust strength was investigated using ten soils with organic matter levels ranging from 1‐50 to 18‐23 per cent. As peat content increased, the crust strength reduced. This occurred in spite of the inability of peat to increase the stability of soil aggregates. Peat reduced crust strength by acting as a mulch on the soil surface, thereby reducing breakdown of soil aggregates. Peat also formed a source of weakness on the soil, reducing crust formation.Using a factorial experiment involving a further seven soils with different levels of peat treatment, exposed to four rainfall durations and with two aggregate sizes, crust strength was described in terms of the direct effects and the interactions of these factors. Most of the crust strength values reduced with increasing peat content. For each soil, crust strength increased significantly with increasing rainfall duration. Crust strength was greater for the smaller aggregate size.The most significant interactions affecting crust strength were between soil and aggregate size, rainfall duration and aggregate size, and soil and rainfall duration in that order. These interactions were used to describe the effect of organic matter in form of peat on crust strength. For each soil and aggregate size, polynomial relationships were established to relate crust strength to total kinetic energy of rainfall.
Time‐dependency of runoff velocity and erosion the effect of the initial soil moisture profile
Authors: Govers Gerard 
Published: February 2007

AbstractThe paper reports on experiments carried out to evaluate the effect of the initial soil moisture profile on temporal variations in runoff erosion rate. The moisture profile was varied by applying infrared heating to the soil sample surface over various time periods, while runoff erosivity was varied by varying the slope of the flume. The experiment confirms that dry loamy soils are very erodible: on a slope length of only 4.3 m long sediment concentrations are near transporting capacity in case of a dry soil sample. It appears that temporal variations in sediment concentrations can be well simulated using a simple relationship between runoff erosion resistance and initial soil moisture content, thereby implicitly assuming that the effect of initial moisture content is persistent over the whole duration of the experiment. The implications of these findings with respect to the modelling of sediment output from larger catchments and the design of experiments on rill erodibility are discussed.The experiments also show that, under the present circumstances, mean velocities in the rills appear to be independent of slope. This finding may be of importance with respect to overland flow routing and deterministic erosion modelling.
A reappraisal of the significance of obstacle clasts in cluster bedform dispersal
Authors: De Jong Carmen 
Published: February 2007

AbstractThe dispersal of cluster bedforms is examined in a short, partially braided reach of the River Quoich, northeast Scotland, after minor flood events in 1989 and 1990. In all cases, the eventual dispersal of clusters occurred without prior removal of the obstacle clast. Since none of the obstacle clasts was dispersed in 1989 and only two‐thirds by 1990, obstacle clasts probably form a less significant delay to sediment entrainment than previously assumed and represent a relatively immobile component of bed sediment.
The influence of rock mass strength on glacial valley cross‐profile morphometry: A case study from the Southern Alps, New Zealand
Authors: Augustinus Paul C. 
Published: February 2007

AbstractThe erosional morphology in the vicinity of the Main Divide of the Southern Alps, and Fiordland, New Zealand, appears to be a product of the interaction between Alpine Fault‐induced tectonic processes, rock mass strength of the uplifted and eroded bedrock, and the processes acting to denude the developing mountain landscape. The magnitude of the effects of glacial erosion on the landscape is directly controlled by the size and physical properties of the glaciers, whilst the form of the trough is a direct consequence of the rock mass strength (RMS) properties of the slope rock. Realistic models of development of the cross‐profile shape of glacial valleys must take into consideration the RMS properties of the eroded substrate.
Gradient irregularity in the herbert gorge of Northeastern Australia
Authors: Wohl Ellen E. 
Published: February 2007

AbstractThe seventy‐kilometre‐long Herbert Gorge of northeastern Australia preserves a record of past floods in slackwater deposits and palaeostage indicators. Step‐backwater modelling of water‐surface profiles indicates that discharges ranging from 11000 to 17000 m3s−1 have occurred six times in the gorge during the last 900 years. These flood reconstructions provide insight into the role of extreme flows in shaping bedrock channel morphology. In particular, the hydraulics of extreme flows can be related to boulder transport, and to the location of large boulder bars.Large boulder bars occur throughout the Herbert Gorge, being best developed at loci of stream power minima along the inside of bends, at tributary junctions, and at obstructions in the channel caused by bedrock highs. Only the flows exceeding approximately 8000 m3 s−1 are competent to transport the boulders which constitute the bars. In the straight channel reaches, the boulder accumulations and bedrock highs have a fairly regular spacing which appears to be independent of lithologic or structural controls. The bars provide an efficient means of energy dissipation, and they are interpreted as a result of the inherent high turbulence of flow in a steep channel. The regular spacing of the bars, and their correspondence with the hydraulics of large flows, suggest that the bars and associated bedrock highs may represent a self‐regulating mechanism akin to the pool‐riffle sequence of alluvial channels. It may therefore be appropriate to view bedrock channels as deformable on the timescale of extreme discharges.
The relations between modulus of elasticity and temperature in the context of the experimental simulation of rock weathering by fire
Authors: Goudie A. S. , Allison R. J. , McLaren S. J. 
Published: February 2007

AbstractFires occur frequently in many biomes and generate high temperatures on the ground surface. There are many field examples of fire causing rock disintegration. The simulation of fire in the laboratory (using a furnace) and the monitoring of changes in rock modulus of elasticity (with a Grindosonic apparatus), reveal that different rocks respond differently to heating. Significant decreases in elasticity occur at temperatures as low as 200°C and granites display particularly marked reductions. Extended periods of heating are not required for significant reductions to occur. It is postulated that the degree of change in elasticity as a result of simulated fire is such that rock outcrops subjected to real fires are likely to be sufficiently modified as to increase their susceptibility to erosion and weathering processes.
Accuracy of two sampling methods used to estimate sediment concentrations in runoff from soil‐loss plots
Authors: Lang R. D. 
Published: February 2007

AbstractThe use of a bottle sampler and a soil pipette to quickly and accurately sample soil‐water mixtures of known sediment concentrations was tested. Both devices failed to sample adequately soil‐water mixtures containing 1–187 gl−1 of solid particles. Poor sampling ability was attributed to rapid settlement of larger particles and to innate deficiencies in the sediment trapping ability of the samplers. These sampling devices should not be used to estimate sediment loads in runoff from soil‐loss plots, and erosion data from plot studies which have used a sediment sampling procedure should be treated with caution.
Morphological, sedimentological and tectonic features of diamante‐m. Carpinoso Marine terrace flight (tyrrhenian coast of northern Calabria, Italy)
Authors: Carobene Luigi , Ferrini Gianluca 
Published: February 2007

AbstractMarine terrace flights resulting from the interaction of Quaternary glacio‐eustatic fluctuations and tectonic uplift are a typical feature of the Tyrrhenian coast of Calabria in Southern Italy; in particular a térrace flight with four orders of terraces is evident in the Diamante area. The lowest terrace levels (fourth order: Diamante‐Cirella terrace) are typified by a calcarenitic deposit with Cladocora caespitosa which give a Th/U age > 300,000 years. The third order terrace has a sedimentary cover formed of a basal discontinuous level of well rounded pebbles which underlies a deeply weathered coarse‐grained sand horizon. The deposit ends with a paleosol locally cut by erosional scours filled by yellowish tuff deposits. The formation of this terrace dates from the Middle Pleistocene. The second order terrace presents a sedimentary cover composed of two generations of soils and is attributed to Middle Pleistocene age. The first order terrace (M. Carpinoso terrace) presents a wave‐cut platform covered by a clastic deposit of marine and continental origin; this deposit consists of superimposed depositional events separated by unconformities, bounded by two diachronous surfaces. The formation of the wave‐cut platform could be related to several sea‐level stands during a long‐lasting slow subsidence phase of the coastal area during the Lower Pleistocene. The uplift following terrace formation displaced the first order terrace most markedly; tectonic lineations controlled the hydrographic pattern and erosion of the surfaces.
The relationship between geology and landforms along a coastal mountain front, northern Calabria, Italy
Authors: Sorriso‐Valvo Marino , Sylvester Arthur G. 
Published: February 2007

AbstractThe geomorphology of the central Coastal Range, a north‐south trending horst along the west coast of northern Calabria, is governed largely by major faults, fault scarps and the distribution of principal rock types, as well as by a variety of slope processes operative in a Mediterranean climate. Segments of the major rivers and streams have three principal orientations parallel to major faults in the study area: northwest right‐oblique slip faults (oldest); E‐W oblique slip faults; NE left‐oblique slip faults; and north‐south right oblique normal faults (youngest), all of which cut pre‐Tertiary metamorphic rocks, Mesozoic limestone, Miocene molasse and calcarenite. Small, underfit alluvial fans, composed chiefly of locally derived debris flow detritus, are present at the mouths of large, west‐flowing canyons, some of which reach eastward to the crest of the mountain range. Not only do the north‐south normal faults displace rocks and structures of all orientations, but they also make steep scarps in the small alluvial fans and in sediments of the coastal plain. Locally, some of the scarps are buried by recent debris flow deposits.Incipient young rivers utilized the weaknesses along the major faults and cracks as avenues of erosion. Smaller streams and gullies generally flowed westward downflank of the north‐trending horst and incised, thereby, deep, V‐shaped canyons; some of them have captured older, SW‐flowing canyons. Locally, they were guided in other directions where they encountered faults or tectonic fractures.The rocks present a varied resistance to erosion, depending upon the degree of cementation by groundwater salts, upon the orientation of the foliation, and upon the rocks themselves. Thus, mica schist with a relatively flat foliation forms nearly vertical sea cliffs, but the sea cliffs are more gentle where the foliation is steep or dips towards the sea. Therefore, downslope movements are facilitated by seaward slip on foliation, schistosity, bedding and fault surfaces, and are evinced especially by large and deep pre‐Holocene landslides (Sackung) in phyllite having areal dimensions up to 2 Km2. Other downslope processes include surficial creep and soil slip, particularly of highly fractured phyllite and schist, block sliding and rock falls.
Spatial variability of infiltration and related properties of tropical soils
Authors: Jetten V. G. , Th. Riezebos H. , Hoefsloot F. , Van Rossum J. 
Published: February 2007

AbstractThe levels of variance associated with measuring the infiltration process and modelling it by means of a regression model are compared to see which approach yields the best results in terms of effort and accuracy. A nested sampling scheme has been used in the three major physiographic units of central Guyana, South America: ‘White Sands’; (Haplic and Ferralic Arenosols), ‘Brown Sands’ (Haplic Ferrasols) and ‘Laterite’ (Xanthic and Dystric Leptosols). Cluster analysis yields three sample groups that reflect the sharp landscape boundaries between the units. Multiple regression analysis shows that each unit has a different combination of soil properties that explains the variance in final infiltration rate and sorptivity satisfactorily. Nested analysis of variance indicates that clear spatial patterns with distances of variation of several hundred metres exist for final infiltration rate in White Sands and Laterite. Infiltration rate in Brown Sands and sorptivity in all units have large short‐distance variabilities and high ‘noise’ levels. The correlated independent variables behave accordingly. For the majority of the soil properties, sampling at distances of 100 to 200 m results in variance levels of more than 80 per cent of the total variance, which indicates that only a detailed investigation can assess spatial variation in soil hydrological behaviour. The use of simple soil properties to predict infiltration is only possible in a very general sense and with the acceptance of high variance levels.
The effects of hurricane hugo on suspended‐sediment loads, Lago loíza Basin, Puerto Rico
Authors: Gellis Allen 
Published: February 2007

AbstractRunoff generated from large storm events, such as hurricanes, is expected to transport large quantities of suspended sediment. Observations of suspended‐sediment loads transported during Hurricane Hugo in the Lago Loìza (Lake Loiza) basin, Puerto Rico, indicate that loads were lower than expected. In the two main tributaries that enter Lago Loìza, Rio Grande de Loìza and Rio Gurabo, 99 600 tonnes of suspended sediment was transported by 58·2 × 106 m3 of runoff in a 48 h period.The storm‐average suspended‐sediment concentration in the Río Grande de Loìza for Hurricane Hugo was 2290 mgl−1, the second lowest for the 12 storms that have been monitored at this site. In Río Gurabo the storm‐average suspended‐sediment concentration was 1420 mgl−1, the sixth lowest recorded out of 15 monitored storms. In Quebrada Salvatierra, a small tributary to Río Grande de Loìza, suspended‐sediment concentrations were as low as 33 mgl−1 during the peak runoff of 20 m3 s−1. Normally the suspended‐sediment concentrations at this discharge are 3000 mgl−1.Hurricane force winds seem to be the most important factor contributing to the lower than expected suspended‐sediment loads in the Lago Loìza basin. The high winds caused vegetation and debris to be dislodged and displaced. Debris accumulated on hillslopes and in small channels, blocked bridges and formed debris dams. These dams caused local backwater effects that reduced stream velocities and decreased suspended‐sediment loads.
Geometrical simulation studies of coastal cliff failures in liassic strata, South Wales, U.K.
Authors: Williams A. T. , Davies P. , Bomboe P. 
Published: February 2007

AbstractThree numerical models of cliff failure have been developed, based on analyses of rockfalls along the 22 km Liassic coastline of the Glamorgan Heritage Coast, U.K. Detailed field investigation of the bucklandi (limestone dominated) and angulata (mudstone dominated) Lias series at four locations confirm the veracity of the models. Translation failure was correctly predicted at the mainly limestone buttressed cliff sites in the bucklandi and at locations where the angulata series formed a high proportion of the cliff mass. Toppling was predicted for vertical and overhanging cliffs with basal undercutting. The factor of safety reduces as the ratio of undercutting depth (d) to tension fracture distance (D) from the cliff face increases. Instability can be triggered by thrust forces generated by wave/tide impact, freeze/thaw and expansion/contraction associated with clay infill. Thrust forces can be modest, ranging from 1·7 to 2·7 MN m2, but can exceed the cross‐joint strength as weathering proceeds.
Geomorphic effects of a large flood on fluvial fans
Authors: Scott Pamela F. , Erskine Wayne D. 
Published: February 2007

AbstractThe response of 12 fluvial fans near Sydney, Australia to a large storm between 2 and 4 February 1990 was determined by repeating previously surveyed longitudinal profiles and by undertaking detailed field observations of erosion and deposition. Peak rainfall intensities occurred on 3 and 4 February when between 173 and 193·8 mm were recorded. Return periods for 24 h duration peak rainfall ranged between 5·7 and 11·0 years on the annual maximum series at six stations within the study area and return periods for 48 h peak rainfall ranged between 13·5 and 29·4 years.Of the 12 fans, seven were trenched and five untrenched. The most significant geomorphic effects of the storm were recorded on the proximal region of the fans. However, fan response was highly variable, with one fan exhibiting no detectable change, three fans localized deposition, two fans spatially disjunct erosion and deposition, two fans channel avulsions, and seven fans fanhead trench reworking. Some fans exhibited more than one type of response.A four‐stage, tentative cyclical model of fanhead development was constructed from the field data. Stage 1 refers to the episodic aggradation of the fanhead by localized deposition, spatially disjunct erosion and deposition and/or channel avulsions. Stage 2 represents the initiation of a fanhead trench when progressive aggradation locally exceeds a threshold slope leading to localized erosion. This erosion initially creates one or more discontinuous flow‐aligned scour pools. Over time, the scour pools widen, deepen and extend both up‐ and downfan. Stage 3 refers to the coalescence of discontinuous scour pools into a continuous trench by the removal of intervening log and boulder steps. Stage 4 represents the backfilling phase of the trench once it has been overwidened and/or slope reduced. Aggradation then continues as for stage one.