bluuebunny/crossref_metadata_2025_split huggingface dataset:
The micro‐erosion meter: Use and limitations
Authors: Spate A. P. , Jennings J. N. , Smith D. I. , Greenaway M. A. 
Published: February 2007

AbstractDetection of anomalies in measurements of low rates of limestone surface lowering with a traversing micro‐erosion meter (MEM) led to temperature‐controlled laboratory and field investigations of some sources of error in the method. Regressions for the correction of temperature change in the instrument and in the stud‐rock interface were obtained. Probe erosion tests permitted a correction to be devised and also provided information whereby a measure of operational irregularity was adopted. Corrections and error terms were applied to field measurements from two southern New South Wales karsts and a collection of Australian limestone slabs exposed at one site.Examination of these results and of published MEM rates from other parts of the world validated the MEM method. Marine platforms are lowered at such gross rates that these error sources may be neglected there. However limestone lowering in terrestrial environments cannot be assumed to proceed at rates which permit this and recommendations are made about procedures to ensure that investigations are prosecuted within the limitations of the method.
Lithologic control of bedrock meander dimensions in the appalachian valley and ridge province: A comment
Authors: Abrahams Athol D. 
Published: February 2007

AbstractBraun's finding that the wavelength of bedrock meanders decreases as rock hardness increases is reconciled with Hack's and Tinkler's finding that meander wavelength is greater in bedrock than alluvial channels. In populations of alluvial or bedrock channels, bank resistance controls meander wavelength via its influence on channel shape and is negatively correlated with meander wavelength. In contrast, in mixed populations of alluvial and bedrock channels, bank resistance controls meander wavelength through its effect on the recurrence interval of the channel‐forming discharge and channel size and is positively correlated with meander wavelength.
Hydrostatic‐system palsas at Toolik lake, Alaska: Field observations and simulation
Authors: Outcalt S. I. , Nelson F. E. , Hinkel K. M. , Martin G. D. 
Published: February 2007

AbstractStratigraphic and chemical data from the ice core of an ‘anthropogenic palsa’ at Toolik Lake, Alaska, indicate that the mound formed as a consequence of hydrostatic pressure developed in an isolated hydrologic system within the active layer. Survey data for five palsas over a three‐year period suggest that growth was essentially complete at the time of the initial survey; a net decrease of summit elevation is apparent in all five mounds, but complete degradation of the palsas would require several decades at observed rates.Because accurate field measurements of thermal and hydrologic evolution in such features are extremely difficult, simulation of the environmental conditions and events involved in palsa growth is an important supplement to field observation. Both analytic and finite‐element models yield results that are in substantial agreement with inferences drawn from observational data.
Rock moisture content in the field and the laboratory and its relationship to mechanical weathering studies
Authors: Hall Kevin 
Published: February 2007

AbstractRock moisture content is a major control of mechanical weathering, particularly freeze‐thaw, and yet almost no data exist from field situations. This study presents moisture content values for rocks, taken from a variety of positions and conditions, in the maritime Antarctic. Additional information regarding the amount of water the rock could take up, as observed from laboratory experiments, is also presented. The results show that the approaches used in simulation experiments, particularly that of soaking a rock for 24 hours, may produce exaggerated results. It was found that the saturation coefficient (S‐value) was a good indicator of frost susceptibility (based on water content) but that the derivation of that value may underestimate the potential of some rocks. The distribution of moisture within rocks is seen as an important, but unkown, factor. The results of these field moisture contents suggest that for simulations of freeze‐thaw or hydration to be meaningful then they should have rock water contents based on field observations.
Comparison of the results of quantitative and non‐quantitative tracer tests for determination of Karst conduit networks: An example from the Traligill Basin, Scotland
Authors: Smart P. L. , Atkinson T. C. , Laidlaw I. M. S. , Newson M. D. , Trudgill S. T. 
Published: February 2007

AbstractThe relative advantages of fluorescent dyes and Lycopodium spores as tracers are discussed. The major advantage of fluorescent dyes is that they may be detected quantitatively. Thus, in combination with discharge measurements, a dye mass balance can be prepared for tracer tests in karst conduits, which permits elucidation of the underground network. The advantages of this procedure are illustrated by comparison of the networks derived from non‐quantitative (Lycopodium and dye) and quantitative (fluorescent dye) tracer methods in the Traligill Basin, Scotland. These tests also suggest that Lycopodium does not give a true indication of travel time, due to sedimentation underground. This could also cause contamination problems in later tests. For non‐quantitative tracer tests, sensitive methods are necessary if incorrect inferences on conduit networks are to be avoided. In general, however, quantitative tests give much less ambiguous results, and are therefore to be preferred.
The influence of weathering on the geotechnical properties and slope angles of mudstone in the Mineoka earth‐slide area, Japan
Authors: Matsukura Yukinori , Mizuno Keiji 
Published: February 2007

AbstractThree active earth‐slide slopes of Tertiary mudstone were investigated: Slope 1 has an angle of 17 −4°, Slope 2 of 12.9°, and Slope 3 of 11.6°. Infinite slope analysis indicated that the instability of these three slopes can be well explained by using the residual strength parameters of earth‐slide soils near the sliding surface in conjunction with the highest ground water table. The residual angle of shearing resistance, ø'r, plays an important role in the determination of slope angle because it differs greatly among slopes. Mineralogical studies and X‐ray diffraction analyses were performed for the clay minerals included in the slope material. The results showed that illite and chlorite were found in Slope 1, and also in Slopes 2 and 3 together with interstratified illite/montmorillonite and montmorillonite. The degree of weathering is progressive in order of Slopes 1, 2 and 3. The alteration of clay minerals by weathering causes the reduction in ø'r ‐values, i.e., 19.4° in Slope 1 (steep, less weathered) and 12.1‐9.2° in Slopes 2 and 3 (gentle, much more weathered). This result indicates that the degree of weathering has a great influence on the value of ø'r, which in turn determines the slope angle.
Controls of concentration and loadings of major ions in a stream draining intermediate igneous rocks
Authors: Grieve Ian C. 
Published: February 2007

AbstractSome 300 measurements under a wide range of flow conditions were used to construct regression models to predict concentrations of six major ions in a moorland stream draining intermediate‐basic lavas in Scotland. Ca, Mg, and HCO3 were very closely related to discharge in log‐log regressions (r2 > 90 percent). Na and Cl required inclusion of seasonal functions for best prediction (r2 = 76 per cent in both cases). K concentrations were predicted from discharge, direction of stage change, and a seasonal function. Annual losses of Ca, Mg, and HCO3 were 252, 36, and 871 kg ha −1, substantially larger than those for upland catchments on acid rocks. Losses of K, Na, and Cl were of a similar order to other upland sites.
Channel erosion along the Carmel river, Monterey county, California
Authors: Kondolf G. Mathias , Curry Robert R. 
Published: February 2007

AbstractHistoric maps, photographs, and channel cross‐sections show that the channel of the Carmel River underwent massive bank erosion, channel migration, and aggradation in a major flood in 1911, then narrowed and incised by 1939. The channel was stable until 1978 and 1980, when bank erosion affected some reaches but not others. The narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin. Localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation. These events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event (the 1911 flood) or in a low magnitude event, by reducing the resistance to erosion (bank devegetation).The Carmel River is a potentially unstable system. Its discharge and slope characteristics place it near the threshold between meandering and braided. On the Lower Carmel, the presence of bank vegetation can make the difference between a narrow, stable meandering channel and a wide shifting channel with braided reaches.
Rainfall, runoff and erosion on bare arable soils in east Shropshire, England
Authors: Fullen Michael A. , Reed Alan Harrison 
Published: February 2007

AbstractThe magnitude, frequency, and duration of erosive rainfall on bare arable soils is investigated within an area of sandy soils in east Shropshire. Rainfall parameters are compared with runoff and erosion from ten 25 m2 runoff plots, maintained in a bare condition on slopes of varying steepness.On rain‐drop compacted (capped) soils measured erosion rates of ≦ 42.7t ha−1 occur during individual storms. Erosion rates increase markedly with slope and on slopes > ˜ 13° are largely attributable to rill erosion.Prolonged duration, low intensity events cause relatively little erosion; most is accomplished by short duration, high intensity (> 10 mm h−1) convective rainstorms. Comparison of measured erosion‐producing events and long‐term rainfall records indicate that potentially erosive storms are quite frequent, and are most likely to cause erosion in late spring/early summer.
Valley asymmetry: Evidence for periglacial activity in the central North Sea
Authors: Long David , Stoker Martyn S. 
Published: February 2007

AbstractPresent‐day open valleys with distinct asymmetric profiles have been studied from the central North Sea. The bulk of the valleys exhibit steep north‐facing and shallow south‐facing slopes. This asymmetry is ascribed to preferential slumping of the south‐facing slope under periglacial climatic conditions. Exceptions to the regional asymmetric trend are probably the result of more localized factors such as fluvial and microclimatic processes and the effects of local geology. The recognition of this type of within‐valley asymmetry associated with slumping in buried valleys within the Quaternary sequence may be indicative of former periglacial activity.
Some observations on the chemical weathering of the Dartmoor granite
Authors: Williams Andrew G. , Ternan Les , Kent Martin 
Published: February 2007

AbstractThe majority of geomorphological papers about Dartmoor have been essentially speculative, particularly when discussing weathering processes and the evolution of the Dartmoor landscape. In contrast, this article presents a synthesis of several experimental investigations aimed at studying the chemical weathering of Dartmoor granite through the systematic analysis of soil and water samples. This involved the computation of a geochemical budget to determine the amount of erosion in the catchment, as well as more detailed mineralogical investigations within a soil profile.The annual output of solutes due to weathering was 116 kg ha−1 a−1 of which the majority was silica (93 kg ha−1 a−1). From an examination of the soil mineralogy, it was calculated that these solutes were derived from the dissolution of approximately 200 kg ha−1 a−1 plagioclase, 90 kg ha−1 a−1 biotite, and 40 kg ha−1 a−1 orthoclase. As well as the weathering of granite, there was also the production of kaolinite (150 kg ha−1 a−1) and gibbsite (0.02 kg ha−1 a−1). Analysis of the soil water chemistry confirmed that kaolinite was the stable mineral phase in the regolith, although in areas where interflow was the dominant mode of water movement, the solute composition was in equilibrium with both kaolinite and gibbsite. Examination of the clay mineralogy confirmed these results.The microtexture of quartz grains was examined by the scanning electron microscope as another means of investigating the hydrochemical environment in the soil. Silica was found precipitated on all the grains examined but the maximum amount occurred in the Bs horizon. This evidence showed that, firstly, the dissolution of aluminosilicate minerals is greater than that calculated by the chemical budget and, secondly, that models of granite weathering must take localized weathering in the soil profile into account.The final part of the paper highlights the limitations of calculating denudation rates for an entire catchment and stresses the need to consider weathering as a highly localized phenomenon, particularly where there are high volumes of interflow at hill crest sites. Observations on granite decomposition in the future should be quantitative in approach and be related to the local site conditions.
Observations of bedload movement, bar development and sediment supply in the braided Ohau river
Authors: Davoren A. , Mosley M. P. 
Published: February 2007

AbstractRelative bedload transport rate and hydraulic parameters were measured on two occasions in a reach of the braided, gravel‐bedded Ohau River. Each reach contained a deep, fast‐flowing chute leading to an area of diverging, shallow flow which contained a middle bar. The measurements are self‐consistent, and indicate that, where flow is concentrated in a deep chute, shear stress is high, but where flow diverges, depth, slope and shear stress decrease. In the first survey, the bed was scoured in the chute and sediment transport rates were high, but where flow diverged sediment transport rate decreased. It appears that deposition leads to bar growth, bar growth in turn reduces slope and depth, deposition is encouraged, and the bar continues to grow vertically, laterally and upstream. In the second survey no sediment transport was observed, despite hydraulic conditions very similar to the first survey. The absence of sediment transport is attributed to the cessation of sediment supply to the river channel.
Some observations concerning the morphology and sedimentology of a protalus rampart, Okstindan, Norway
Authors: Harris Charles 
Published: February 2007

AbstractA protaius rampart up to 4.75 m high and consisting largely of angular clasts up to boulder size is described. Bulk samples contained up to 35 per cent fines by weight, compared with up to 68 per cent fines in adjacent till. Although the rampart material was clast dominated, fines filled much of the void space, in contrast with most other protalus ramparts described in the literature.
Comparison of taxon calibrations, modern analogue techniques, and forest‐stand simulation models for the quantitative reconstruction of past vegetation: A critique
Authors: Solomon Allen M. 
Published: February 2007

AbstractTaxon calibrations based on eastern North America or on the southeastern United States alone suggest a different forest composition from that based on Wisconsin/Michigan, which is argued as preferable. Questions are raised about how well comparison with modern analogues distinguishes forest characteristics. The simulation model used by Delcourt and Delcourt is thought to be inappropriate, partly because it is constrained by faulty climatic data. Models are seen as complementary to other techniques rather than as an alternative methodology.
An erosion criterion for gravel‐bed rivers
Authors: Naden Pamela 
Published: February 2007

AbstractA theoretically‐based erosion criterion is developed for gravel‐bed rivers which incorporates the effect of both grain geometry and turbulent velocity fluctuations. It is derived from a balance of instantaneous drag, lift, and gravity forces operating on individual grains and is calculated for spherical grains arranged in three distinct geometries. To accommodate the temporal variation in bed shear stress, the model includes a stochastic element based on the characteristics of turbulence derived from the flume evidence of McQuivey (1973a, b). In terms of the Shields parameter, results show reasonable agreement with the range of observations quoted from the field and with the experimental data of Fenton and Abbott (1977). Finally, the argument is generalized to cover applications in the wider context of field conditions including a range of grain sizes and flow conditions.
Palaeoflood hydrology of the Salt river, Arizona
Authors: And John Partridge , Baker Victor R. 
Published: February 2007

AbstractGeomorphic evidence along bedrock‐confined reaches of the Salt River in east‐central Arizona provides a record of the river's largest flood events. Fine‐grained flood slackwater deposits accumulated at channel margin irregularities several metres above the low‐flow channel. Discharges associated with flow events responsible for the deposits were estimated by computer flow modelling. These estimates document flood magnitudes in excess of gauged historic streamflows. Relative and radiocarbon dating suggest that a flood record in excess of 600 y is preserved in the slackwater sequences. A prominent flood scar cut into grussy hillslope soils allows the extension of the prehistoric flood record to several thousand years.A maximum discharge estimate of 4600 m3s−1 affixed to the flood scar represents the largest flood event in the record, and is given a minimum recurrence interval of 1000–2000 y. The 1952 flood is the largest historic flow event experienced along the study reach and is estimated at 2900 m3s−1. Two palaeoflood events preserved in the slackwater stratigraphy exceed the 1952 event, and are given recurrence intervals of 300 and 600 y. The latter flood event had an estimated discharge of 3200 m3s−1. It is apparent that discharge estimates affixed to these infrequent, large‐magnitude flood events approach a maximum with decreased probabilities (large recurrence intervals). This suggests that a physical limit on discharge may exist within the Salt River drainage basin and is perhaps directly related to drainage basin size.
River channel adjustments downstream from channelization works in England and Wales
Authors: Brookes Andrew 
Published: February 2007

AbstractRelatively little attention has been given to river channel adjustments that occur downstream from channelization works. This study is concerned with the nature of channel adjustments downstream from a total of 46 channelization works located in low and high energy environments in England and Wales. Channel changes are identified principally by the method of field survey and by reconstructing the original positions of eroded beds and banks. Use is also made of maps, aerial photographs, and engineering drawings of different dates and the technique of space‐for‐time substitution is applied.Enlargement of channel cross‐sections through erosion had occurred downstream from a variety of types, sizes, and dates of channelization works. The maximum increase of channel size was 153 per cent. Out of a total of 14 sites with enlarged channel cross‐sections, seven had undergone a change of width only, at a further three width increased rather than depth, and at the remaining four sites depth increases were dominant. These sites all have relatively high stream powers.Factors causing spatial variation of erosion included tree roots locally binding bank sediments and the occurrence of bends. Planform change had taken place at only one site. A further three high stream power sites had downstream reaches incised into bedrock and therefore did not exhibit adjustment.Channel enlargement is explained in terms of increased flood flows downstream from channelization works causing higher stream velocities, which in turn cause erosion, thereby increasing channel width and/or depth. Examination of flow records for 35 stations revealed flood events which would formerly have spread overbank but are now confined by the channelization works and are therefore likely to alter downstream flows. At sites with downstream change it is proposed that the energy of increased flows was sufficient to exceed a threshold required for erosion of perimeter sediments. By contrast the absence of change at a majority of sites in low energy lowland areas could be a reflection of both the incompetence of increased flows to erode and resistance provided by perimeter sediments. Sites with erosion features appear not to have yet attained new equilibrium conditions.
Genesis of marine terrace soils, Barbados, West Indies: Evidence from mineralogy and geochemistry
Authors: Muhs Daniel R. , Crittenden Russell C. , Rosholt John N. , Bush Charles A. , Stewart Kathleen C. 
Published: February 2007

AbstractWell‐developed, clay‐rich soils dominated by interstratified kaolinite‐smectite are found on the uplifted coral reef terraces on the island of Barbados. The reef limestone is unlikely to have been the soil parent material however, because it is 98 per cent CaCO3 and geomorphic evidence argues against the 20 m of reef solution required to produce the soils by this process. The mineralogy of the sand, silt, and clay fractions of the soils, and trace element geochemistry, suggest that aeolian materials carried on the trade winds from Africa, volcanic ash from the island of St. Vincent, and quartz from Tertiary bedrock on the island itself are the parent materials for the soils.
A comparison of channel erosion in small urban and rural catchments, Armidale, New South Wales
Authors: Neller R. J. 
Published: February 2007

AbstractFive years after the cessation of housing construction in a small urban catchment in Armidale, New South Wales, the stability of the channel bed and banks was investigated with the use of erosion pins. After eighteen months of monitoring, the rate of channel bank erosion was found to be 3.6 times greater than that of a nearby rural channel and the rate of knickpoint retreat was 2.4 times greater. There was, however, no evidence to suggest that the urban channel was inherently unstable, but that the increased rate of erosion was the product of changed runoff conditions associated with urban development. Both channels are considered to be in a state of equilibrium.
The freeze‐thaw weathering regime at a section of the Niagara escarpment on the Bruce Peninsula, Southern Ontario, Canada
Authors: Fahey Barry D. , Lefebure Todd H. 
Published: February 2007

AbstractThe bedrock freeze‐thaw and moisture regimes at an actively eroding site on the Niagara Escarpment, Bruce Peninsula, southern Ontario, were monitored between December 1983 and April 1984, and the results compared with amounts of debris collected in an adjacent rock trap.Frost wedging in pre‐existing rock fissures is the primary mechanism responsible for the observed rockfall events; hydration effects are negligible. Debris production was more closely related to the duration of the freezing leg of the freeze‐thaw cycle than to intensity or to cycle frequency. Release also coincided with periods of high pore saturation (> 60 per cent) and the seepage of water from cracks and fissures.Fewer freeze‐thaw cycles were recorded in the air than at 1 and 3.5 cm in the bedrock. The number of cycles that could be declared geomorphologically effective according to established temperature criteria was normally less than half the total number of freeze‐thaw cycles recorded in both air and bedrock. Under the current temperature regime at the field site, few effective cycles are capable of penetrating more than 5 cm into the free face.