bluuebunny/crossref_metadata_2025_split huggingface dataset:
Debris‐fan constrictions and flood hydraulics in river canyons: Some implications from two‐dimensional flow modelling
Authors: Miller Andrew J. 
Published: February 2007

AbstractRapids in river canyons are frequently found at sites where debris fans constrict flow along the channel. Whereas some fans may have persisted in the same location with unchanging geometry for centuries to millennia, others have changed in response to flow conditions imposed by successive floods. Such a change in boundary conditions may alter local flow hydraulics. This paper utilizes two‐dimensional flow modelling to compare flood hydraulics along two alternative versions of an idealized reach of a river canyon: one with uniform width, gradient and cross‐section, and a second perturbed by a prominent debris fan along the valley wall. The flow pattern along the reach with the fan is far more complex than the pattern along the uniform reach. Maximum velocity along the debris‐fan reach is up to 50 per cent higher than along the uniform reach, maximum bed shear stress is up to three or four times higher, and an area of supercritical flow is predicted extending from the nose of the fan into the zone of flow expansion immediately downstream.Comparison of model output along longitudinal profiles of the two reaches indicates that the backwater effect of the fan extends several valley widths upstream. Predicted flows based on the same stage are as much as 190 to 230 per cent greater along the uniform reach than along the debris‐fan reach. Reconstruction of palaeoflood discharge based on remnant flood marks in the vicinity of the fan would be sensitive to assumptions about boundary conditions that existed in the past; this effect relaxes over a longitudinal distance of several hundred metres. Furthermore there are significant cross‐stream gradients that change slope and direction several times in the vicinity of the fan, calling into question the utility of one‐dimensional step‐backwater hydraulic models for predicting high‐water marks in areas of complex valley morphology.
Gps, gis and geomorphological field work
Authors: Cornelius S. C. , Sear D. A. , Carver S. J. , Heywood D. I. 
Published: February 2007

AbstractThis paper introduces the Global Positioning System (GPS) and considers its role as a technique for use in geomorphological field work. Although valuable on its own, it is apparent that the utility of GPS in geomorphology is enhanced when used alongside Geographical Information Systems (GIS) technology in the field. This paper reviews GPS, considering what it is, the methods available and their relative accuracies, the potential and problems of the technology and its relationship with GIS. Particular attention is given to the application of GPS in geomorphological and related case studies. Examples are presented of the successful use of GPS and GIS to study hydrology and snow patch regime from the recent GeoAltai expedition to Southern Siberia.
The response of coastal marshes to sea‐level rise: Survival or submergence?
Authors: Reed Denise J. 
Published: February 2007

AbstractIn order to maintain an elevation in the intertidal zone at which marsh vegetation can survive, vertical accretion of the marsh surface must take place at a rate at least equal to the rate of relative sea‐level rise. Net vertical accretion of coastal marshes is a result of interactions between tidal imports, vegetation and depositional processes. All of these factors are affected, directly or indirectly, by alterations in marsh hydrology which might occur as a result of sea‐level rise. The overall response of coastal marshes to relative sea‐level rise depends upon the relative importance of the inorganic and organic components of the marsh soil and the impact of increased hydroperiod on net accumulation. The varied combination of factors contributing to sediment supply, and their complexity at the scale of individual marshes, means that predicting the response of suspended sediment concentration in marsh floodwater to any changes which may occur as a result of sea‐level rise, at anything other than the local scale is unlikely to be accurate. The impact of sea‐level rise on net below‐ground production is also complex. The sensitivity of certain species to waterlogging and soil chemical changes could result in a change in species composition or the migration of vegetation zones. Consequently, predicting the net impact of sea‐level rise on organic matter accumulation is fraught with difficulties and requires improved understanding of interactions between vegetation, soil and hydrologic processes.
Modelling the role of climate, vegetation and pedogenesis in shallow translational hillslope failure
Authors: Brooks S. M. , Anderson M. G. , Collison A. J. C. 
Published: February 2007

AbstractRecent research in geomorphology has considered the significance of progressive pedogenesis and climatic change to slope failure initiation for the Holocene, using physically based models. To date, the significance of vegetation change to slope stability has been largely unexplored through modelling, since available physically based models cannot consider vegetation effects directly. To address the existing deficiency this paper adapts, parameterizes and applies a physically based model of slope hydrology and stability to the combined effect of vegetation change and progessive pedogenesis on slope failure initiation. There is considerable debate in the literature concerning the relative significance of climatic change and vegetation modification to slope failure initiation in the Holocene. This paper uses the model to provide additional evidence for situations in which either climatic or vegetation change is significant to slope failure, depending on the prevailing degree of soil development. The results indicate that young podsols appear to be stable under all the climatic and vegetation conditions considered, but mature podsols may be susceptible to failure. Both climate and vegetation influence slope stability, but their relative significance depends on the stage of soil development. In particular, the stability of young soils is influenced considerably by vegetation, while climate assumes greater significance in mature soils. It is recognized that this conclusion is limited to freely draining podsol profiles, and that more research is needed to consider other soil type and vegetation combinations.
Bed‐material transport estimated from channel surveys: Vedder River, British Columbia
Authors: Martin Yvonne , Church Michael 
Published: February 2007

AbstractThis study investigates the possibility to estimate bed‐material transfer in gravel‐bed rivers by analysis of morphological changes along Vedder River, British Columbia. Data from repeated cross‐section surveys are used to estimate volume changes along the length of an 8 km reach. Gravel budgets are based on a continuity approach. An error analysis is performed to evaluate the uncertainty in the best estimate of transport rates. The mean annual gravel transport into the reach over a 9 year period was estimated to be 36600 ± 5600 m3 yr−1. The sediment transport regime along the length of the river is evaluated and examined in relation to peak flood flows. Significant spatial and temporal variability in transport rates is demonstrated, making dubious the generalization of transport estimates from hydraulic calculations, or from sample measurements at a single cross‐section. The assumptions, procedures and limitations of the ‘morphological approach’ to sediment transport analysis are discussed. It is concluded that this approach provides information of quality comparable or superior to that of direct measurements of transport, yet requires less field effort. It also provides additional information about river morphological changes, making it a preferred method for geomorphlogical investigations and for many river management concerns.
Erosion of a cyclic saltmarsh in Morecambe Bay, North‐West England
Authors: Pringle (Née Phillips) Ada W. 
Published: February 2007

AbstractThis paper presents results of investigations (1983–1992) into rates of change, morphology and processes occurring during the current erosional phase in a Morecambe Bay cyclic saltmarsh, in which it has narrowed from c. 1000 m (1975) to c. 150 m (1992). Monthly monitoring of marsh edge erosion and creek knickpoint retreat has revealed temporal and spatial variations. Highest frequency changes of low magnitude coincided with non‐storm conditions and overmarsh tides above 5·80 m OD, which submerged the whole marsh. Less frequent changes of greater magnitude were associated with both overmarsh tides and strong onshore winds over 15 ms−1, which generated high energy waves. The lowest frequency change of greatest magnitude occurred during an extreme onshore storm event and surge.Morphologically, during the erosional phase, a low angled landward slope was generated as erosion of the c. 0·5 m high active seaward cliff coincided with vertical accretion of 0·07 ma−1 of relatively coarse sediment on the marsh surface immediately landward. Tidal hydrodynamics strongly influence the saltmarsh, which is confined to the upper 2·5 m of the macrotidal range (maximum c. 10·5 m). During overmarsh spring tides (maximum creek flood flow rate 0·13 ms−1, up to bankfull level), flooding begins over lower landward creek banks before submerging the higher marsh edge. During ebb tides, water trapped by this higher edge can escape seaward only via the creeks (maximum ebb velocities 2·07 ms−1 below bankfull level). Wave erosion also is limited to spring tides.Monthly mapping of the Kent Estuary channel pattern seaward of the saltmarsh showed that medium term higher erosion rates were related to the presence of a large channel, which lowered the adjacent creek base level and allowed larger waves to attack the marsh edge than when a sandbank flanked the marsh. Major River Kent channel shifts appear to initiate accretional or erosional phases of cyclic saltmarsh development.
Late‐holocene snow‐avalanche activity in southern norway: Interpreting lichen size–frequency distributions using an alternative to simulation modelling
Authors: McCarroll Danny , Matthews John A. , Shakesby Richard A. 
Published: February 2007

AbstractRecent work by McCarroll (1993, 1994) suggests that a new approach to lichenometry can be used to date diachronous surfaces. Size–frequency distributions of largest lichens obtained from the diachronous surfaces of avalanche boulder ramparts comprise two elements: an equilibrium population growing on boulders deposited throughout the Holocene, and overlapping populations growing on groups of boulders deposited by events during the last 300 years. In this study, almost 10000 lichens were measured on two groups of closely similar ramparts. The number of very large lichens is used to predict the form of the equilibrium distribution, which is then removed, leaving a corrected distribution which reflects the age‐frequency of surface boulders deposited during the ‘Little Ice Age’. The results confirm that maximum avalanche activity occurred during the 19th century, but a minor peak at one site suggests that avalanche activity was enhanced during the mid‐18th century.
Limestone weathering in Eastern Australia. Part 2: Surface micromorphology study
Authors: Moses C. , Spate A. P. , Smith D. I. , Greenaway M. A. 
Published: February 2007

AbstractResults from long term microerosion meter (MEM) studies indicate that microenvironments are characterized by different erosion rates. A complementary study, carried out on the same sites, examines the microscale morphology in each environment. Optical and scanning electron microscopy were used to identify a range of features thought to reflect different processes.Under subaerial conditions micromorphology is dominated by biological weathering features owing to the presence of microflora. Sites permanently covered by soil or stream water have only dissolution etch features, though stream sites may exhibit microfractures. Sites with periodic exposure exhibit both dissolution and biological etch features. The natural environment is more accurately reflected by allowing some microflora colonization of MEM sites rather than preventing colonization by artificial means.
Using gravestones to assess changing rates of weathering in the United Kingdom
Authors: Cooke R. U. , Inkpen R. J. , Wiggs G. F. S. 
Published: February 2007

AbstractWeathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the UK. Comparison of their regression lines and residuals suggested that two of the sites, Portsmouth and Wolverhampton, had similar amounts and rates of weathering over the last 100‐150 years. Gravestones in Swansea appear to have weathered much more and much faster than gravestones at the other two sites. These differences may be the result of the differing pollution and rainfall histories of the three sites.
Play: The handmaiden of work
Authors: Wolman M. Gordon 
Published: February 2007

AbstractThe natural habitat of geomorphologists is at play in the fields of the Lord. Picnics, not the work ethic, often motivate the most productive. As in the field, so too in the mind, creative insights derive from the play of ideas. As in much of science today, Earth scientists are called upon to ‘solve’ immediate problems, but problems whose solutions lie at the cutting edge of the research frontier. The impact of anthropogenic activities in the context of natural processes, the playground where many geomorphologists work, requires continuous reciprocal exchange between research and application. Apologies are not needed for choices of orientation, but only for destructive separation.
The channel‐geometry method: Guidelines and applications
Authors: Wharton Geraldene 
Published: February 2007

AbstractAll river engineering schemes require flood discharge estimates as part of the design and appraisal process. Unfortunately, continuous measurement of flood discharges is limited to those river sites with instrumented gauging stations, which constitute only a small proportion of channel reaches where information is required. Therefore, considerable research effort has been devoted to the development of reliable indirect techniques of flood discharge estimation. Research on the interrelationship of stream channel geometry and river discharge has provided the basis for an indirect method of flood estimation – the channel‐geometry method – which employs river channel dimensions alone to estimate discharge characteristics at ungauged river sites. Channel‐geometry equations are developed empirically by relating streamflow data from gauging stations and channel dimensions measured from natural river reaches in the vicinity of the gauge, and take the form of power function relations. Once regional channel‐geometry equations have been defined, a channel width or channel capacity measurement is the only variable needed to estimate the flood flow characteristics at a specified river site. The method is useful as an alternative to traditional catchment‐based approaches or as a rapid reconnaissance technique. In addition to the application for flood discharge prediction, channel‐geometry equations could prove helpful in the management of river channels, first, by providing a basis for assessing local deviations in the channel form–discharge relation, deviations which could be employed as indicators of the sensitivity of particular stretches of river channel to change, and secondly, in the computation of natural channel dimensions for use in river channel design and river restoration.
A review of mathematical models of river planform changes
Authors: Mosselman Erik 
Published: February 2007

AbstractDifferent mathematical models of river planform changes exist or are being developed. They are reviewed here by discussing a two‐dimensional depth‐averaged model, various meander models and a model for the braided Brahmaputra‐Jamuna River in Bangladesh. Much emphasis is placed on topics where further research is needed. It is concluded that the models help in understanding the underlying processes, but cannot yet be considered generally valid and easy‐to‐use software packages. In the hands of experienced geomorphologists or river engineers, however, some of the models do already form valuable tools which allow better predictions of future river planforms.
Errors in measuring the percentage dry weight change of stone tablets
Authors: Inkpen Rob 
Published: February 2007

AbstractPortland Stone and Monks Park limestone tablets were used to assess weathering loss over a two‐year study. Procedures involved in preparing tablets for exposure, attaching them to the exposure frame and reweighing might have influenced weight changes measured. The impact of each stage in the above procedures was tested to assess how much weight loss was generated and how significant the loss was comparing the two stone types and the final loss sustained upon weathering. Although all the procedures seem to produce a statistically insignificant amount of weight loss, the two stone types do respond differently to the procedures. This suggests that stone properties may be important in determining the accuracy with which tablets can be used to assess spatial patterns of weathering.
The nahal yatir bedload database: Sediment dynamics in a gravel‐bed ephemeral stream
Authors: Reid Ian , Laronne Jonathon B. , Powell D. Mark 
Published: February 2007

AbstractThe Nahal Yatir Bedload Transport Database arises from the Northern Negev River Sediment Monitoring Programme and represents the first body of bedload information to be collected during flash floods in desert gravel‐bed streams. Bedload flux was established automatically with three slot‐samplers of the Birkbeck type. This was complemented by hydraulic measurements that allow sediment transport to be rated against channel average shear stress and specific stream power. Bed material and bedload grain‐size distributions are also provided. The database is given in both printed and electronic tabular format.
A multi‐energy‐level lattice Boltzmann model for the compressible Navier–Stokes equations
Authors: Yan Guangwu , Zhang Jianying , Liu Yanhong , Dong Yinfeng 
Published: February 2007

AbstractIn this paper, we propose a new lattice Boltzmann model for the compressible Navier–Stokes equations. The new model is based on a three‐energy‐level and three‐speed lattice Boltzmann equation by using a method of higher moments of the equilibrium distribution functions. As the 25‐bit model, we obtained the equilibrium distribution functions and the compressible Navier–Stokes equations with the second accuracy of the truncation errors. The numerical examples show that the model can be used to simulate the shock waves, contact discontinuities and supersonic flows around circular cylinder. The numerical results are compared with those obtained by traditional method. Copyright © 2007 John Wiley & Sons, Ltd.
The transmission disequilibrium test and imprinting effects test based on case‐parent pairs
Authors: Hu Yue‐Qing , Zhou Ji‐Yuan , Sun Fengzhu , Fung Wing K. 
Published: February 2007

AbstractThe transmission disequilibrium test (TDT) based on case‐parents trios is a powerful tool in linkage analysis and association studies. When only one parent is available, the 1‐TDT is applicable in the absence of imprinting. In the presence of imprinting, a statistic is proposed, based on case‐mother pairs and case‐father pairs to test for linkage when association is present as well as to test for association when linkage is present. The recombination fractions are allowed to be sex‐specific in this test statistic. Meanwhile, a statistic based on case‐parent pairs is proposed to test for imprinting. Both test statistics can be extended to include families with more than one affected offspring. A number of simulation studies are conducted to investigate the validity of the proposed tests. The effects of different ratios of the numbers of case‐mother pairs and case‐father pairs on the powers of the proposed tests are studied through simulation. The results show that the optimal ratio is 1:1. How to combine case‐parents, case‐mother pairs, and case‐father pairs jointly in testing for linkage, association, and imprinting is addressed. Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
The determination of the thixotropic limits of sediments
Authors: Boswell P. G. H. 
Published: February 2007

AbstractEfforts to determine the highest thixotropic values that may be reached by sediments have shown that the manner of preparation of the systems is of considerable importance. In particular, the preliminary shaking of the system, instead of the usual procedure of stirring only, results in the production of substantially higher values, even in the case of but moderately thixotropic calcareous and sandy materials. The increase varies from 5 per cent. with weakly thixotropic systems to more than 70 per cent. with fat clays. The significance of the increase, in relation to the theory of thixotropy, is discussed.It has become evident that the lower thixotropic limit cannot be determined by the inverted‐tube method, although its approximate magnitude can be estimated. Some such estimates have been compared with the results obtained in liquid‐limit tests on the same samples, from which it appears that the moisture‐content for flow at 10 bumps in the liquid‐limit test (i.e. about 11 ± 5 per cent. of the liquid limit) approximates to that at the lower thixotropic limit.The necessity for devising more precise experimental methods, and for agreement on definitions of liquid flow and plastic flow, is emphasized. The term rheotropy is suggested to include the phenomena of thixotropy s.s., false‐body, rheopexy, and age‐hardening (i.e. for the isothermal reversible gel/sol‐or‐more‐fluid‐gel transformation).Brief reference is made to certain natural occurrences of thixotropic or potentially thixotropic deposits and to the practical problems to which they give rise. Also, opportunity has been taken to include thixotropic values for a further selection of sediments.
Presidential address to the manchester geological association: Sedimentation facies in the namurian of North‐Western England and adjoining areas
Authors: TROTTER F.M. 
Published: February 2007

AbstractThe correlation links which have been established within the Namurian (Plates VIII & IX) across the sedimentation facies of the Central Province and Northern Province are reviewed. It is possible to portray the palaeogeography during particular sub‐zones and to suggest limits for the various facies (Figs. 1–3). A total of seven facies is recognised—sedimentation facies, of fluvial‐grits, of grit‐shales, of coals, of limestones, of Yoredale‐limestones, of Yoredale‐grits and of marine‐shales.In E1a times a marine‐shale facies lay in the Central Province between the Welsh‐Mercian ridge and an E‐W narrow ridge through the Isle of Man to the Settle district; in the Northern Province, northwards from this ridge to the Midland Valley of Scotland, there is a Yoredale‐limestone facies except in the extreme south‐west where lay a limestone facies.In E1c‐d times a fluvial‐grit facies invaded the Central Province from the east, whilst in the Northern Province a Yoredale‐grit facies occupied much area and passed northwards into a coal facies along the Scottish border.In E2b times marine shales passed northwards into a grit‐shale facies in the Central Province whilst a Yoredale‐grit facies predominated in the Northern Province with land areas emerging in the Isle of Man—Lake District, on the Alston Block and along the Southern Uplands.During H times the Northern Province emerged and remained as land until the close of the Namurian. In the Central Province marine‐shales characterized the western part of the basin, the eastern part having a grit‐shale facies, except during upper R1 times when a fluvial‐grit facies spread eastwards almost as far as Preston.