bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developments in monitoring and modelling small‐scale river bed topography
Authors: Lane S. N. , Richards K. S. , Chandler J. H. 
Published: February 2007

AbstractRecent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography, flow hydraulics and sediment transport. Although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within‐channel process studies, less attention has been given to the accurate monitoring and terrain modelling of river channel form using three‐dimensional measurements. However, such information is useful in two distinct senses. Firstly, it is one of the necessary boundary conditions for a physically based, deterministic modelling approach in which three‐dimensional topography and river discharge drive within‐channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change. Secondly, research has shown that an alternative means of estimating the medium‐term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel. This paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey. The availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface. Intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition. A detailed assessment is undertaken of the quality of the morphological information acquired. This allow some general comments to be made concerning the use of more traditional methods to monitor and represent small‐scale river channel morphology.
Diurnal freeze–thaw depth in rockwalls: Field measurements and theoretical considerations
Authors: Matsuoka Norikazu 
Published: February 2007

AbstractRock temperatures were monitored for a year at two alpine rockwalls in the Akaishi Range, Japan, where permafrost is absent. Diurnal frost and thaw penetration depths were evaluated from subsurface isotherms drawn on the basis of the temperature records at 0, 10 and 40 cm depths. The surface of the rockwalls experienced more than 100 diurnal freeze‐thaw cycles, most of which accompanied a frost or thaw penetration shallower than 50 cm, and several long duration cycles with deeper frost or thaw penetration. Theoretical frost and thaw depths were also calculated by incorporating the surface freezing indices into the modified Berggren equation, the results from which were then compared with the actual values. The modified Berggren equation provided values that showed a strong correlation with observed depths, despite somewhat underestimating the actual values. Using the modified Berggren equation, the seasonal frost depth in the observed winter was estimated to be about 4·5 m. The frost and thaw depths are considered to give the maximum estimation of the depth to which frost‐induced cracking can propagate in the bedrock.
Holocene valley aggradation and gully erosion in headwater catchments, south‐eastern highlands of Australia
Authors: Prosser Ian P. , Chappell John , Gillespie Richard 
Published: February 2007

AbstractLate Quaternary stratigraphy of a 50 km2 catchment on the south‐eastern highlands of Australia reveals processes and history of denudation, and helps resolve a long‐standing debate about factors controlling episodic valley aggradation and degradation during Holocene times. Valley sedimentation occurred when swampy vegetation fully colonized valley floors and obliterated all channels, promoting aggradation for periods of several thousand years, with most incoming sediment being trapped in swampy meadows. Much of the sediment was reworked from late Pleistocene alluvial fan and valley fill deposits, and primary hillslope erosion was minor during the Holocene. Differing sedimentation patterns between the Late Pleistocene, Holocene and Post‐European settlement periods reflect regional changes in sediment supply and transport capacity as a result of major environmental change. Within the Holocene, however, valley fill stratigraphy is controlled by massive, episodic gully erosion terminating aggradation. Gully initiation appears to be controlled more by thresholds of incision into vegetated valley floors than by changes to sediment supply. Whether the thresholds are exceeded because of climatic change, autonomous change or extreme events cannot yet be determined. Overall, the Holocene history represents continuing complex response to events of the Late Pleistocene, and does not support the K‐cycle concept, which has strongly influenced late Quaternary geomorphology in Australia.
Estimate of long‐term sediment discharge at tidal inlets using water level data from a tide gauge
Authors: Gao Shu , Collins Michael 
Published: February 2007

AbstractA simple approach to the estimate of long‐term sediment discharge through an entrance to a tidal basin is described. Using the method, cross‐sectional mean current speeds are derived, on the basis of the definition of an ‘apparent tidal basin area’, from records of water level data from a single tide gauge. The obtained time‐series of current speeds are then used to define ‘local’ current speeds, through the use of a sectional distribution function for the currents. Sediment transport formulae are then applied, using the obtained speed data and other relevant parameters contained within the formulae and frequency distribution functions with regard to wave and tidal current characteristics, to estimate sediment discharge through the entrance. Analytical procedures of the method are described in detail, in an example from Christchurch Harbour (southern England).
Explorations into the formal structure of drainage basins
Authors: Werner Christian 
Published: February 2007

AbstractEvery basin of higher than first order is drained by a channel network composed of two subnetworks. Their basins are separated by a drainage divide line, called the basin divider, which is the primary organizing feature of the main basin. Each basin of magnitude n contains n – 1 subnetworks of higher order, and is therefore organized by a set of n – 1 dividers. The dividers and the basin boundary are interconnected in a graph called the divider network of the basin; in graph‐theoretic terms this network forms a tree and has the same magnitude and link numbers as the channel network draining the basin. While the subbasins and subnetworks of a drainage basin form a nesting hierarchy, the corresponding dividers do not; indeed, any two dividers share at most one node in common, and whether they do so is independent of whether the corresponding subbasins are nesting or disjoint. However, the dividers of nesting basins are linked by recursive relationships which permit the derivation of a set of algebraic equations; these equations relate the dividers of a basin to other basin components; for example, their combined length is equal to half the length of all first‐order basin boundaries minus the length of the main basin boundary.The second part of the paper explores the dependence of the divider length on other basin parameters. The expected length, as predicted by the assumption of topological randomness, is clearly rejected by the data. An alternative approach (regression) is based on the observed magnitudes of the subbasins separated by each divider, and is reasonably successful in estimating divider length. The last section introduces the concept of the standardized basin defined by a boundary length of unity; the estimated lengths of the basin divider and the basin boundary permit an approximate reconstruction of the idealized basin shape and the location of the divider in it.
Measurement of bedload gravel transport: The calibration of a self‐generated noise system
Authors: Rouse H. L. 
Published: February 2007

AbstractSelf‐generated noise (SGN) is a passive acoustic technique for the measurement of bedload transport through the acoustic detection of intergranular collisions using a submerged hydrophone system. SGN is of interest because of the possibilities it offers to the measurement of transport parameters at the frequencies of turbulent or oscillating current scales. This paper describes the background of the technique, and reports the results from laboratory experiments on the relationship between SGN and the absolute transport rate.
Processes and timescales by which a coastal gravel‐dominated barrier responds geomorphologically to sea‐level rise: Story head barrier, Nova Scotia
Authors: Orford J. D. , Carter R. W. G. , Jennings S. C. , Hinton A. C. 
Published: February 2007

AbstractSea‐level rise (SLR) is considered to be important for barrier behaviour when barriers are swash‐aligned and single‐crested, which is typical of only one part of a barrier's lifeterm. Under such conditions gravel‐barrier retreat rate correlates with mesoscale (sub‐decadal: <101 a) SLR rate. Barrier crest overwashing, depending on surge frequency/magnitude, is recognized as the dynamic element that controls barrier retreat rate. Surge characterization of the Halifax tide gauge (using an annual forcing coefficient derived from tide gauge surge residuals) is shown to have high correlation with Story Head (Nova Scotia) barrier retreat rate between 1945 and 1987. Barrier response appears to vary as a function of mesoscale (sub‐decadal) SLR and antecedent barrier conditions in combination with the forcing coefficient. Mesoscale (100 a–102 a) rather than macroscale (> 102 a) SLR rate is the critical control on barrier retreat, as mesoscale SLR variation in combination with surge potential is able to raise water level to the elevation threshold sufficient for barrier overwash and hence drive barrier retreat.
Coastal slope terracing and relative sea‐level changes: Deductions based on computer simulations
Authors: Cinque A. , De Pippo T. , Romano P. 
Published: February 2007

AbstractAlthough a traditional geological survey of terraced coastal slopes is an essential part of studies aimed to reconstruct relative sea‐level changes, the stratigraphic and chronological data so obtained frequently prove inadequate to completely unravel the sometimes very complex history of sea‐level fluctuation, especially where erosion has prevailed over deposition and/or deposits are difficult to date.On the basis of our experience we think that much additional information can be gained through geomorphological interpretation of the profiles of those slopes. In order to facilitate such interpretation, a computer simulation model is developed that is able to predict the morphogenic response to a variety of possible relative‐sea‐level histories. The results can be used to envisage some new interpretation keys for the analysis of real situations and, hopefully, as bases for the conception of general models of coastal slope evolution under the action of a variable sea level.Though preliminary, the results so far obtained permit identification of the geomorphological consequences (in terms of resulting slope profile) of ordered successions of transgressions and regressions of different amplitude, rate, order and style. Moreover they provide interesting insights into the role that different styles of tectonic uplift may play in the phenomenon of multiple terracing of coastal slopes.
Salt ramps: Wind‐induced depositional features on Tunisian playas
Authors: Millington Andrew C. , Drake Nicholas A. , White Kevin , Bryant Robert G. 
Published: February 2007

AbstractSemicircular and crescent‐shaped accumulations of salt crystals developed on salt crusts were measured on three Tunisian playas in September 1990. These features have been termed salt ramps. Their morphology and chemistry suggest that they are formed in the late stages of shallow ephemeral lake desiccation in playa basins. They form by salt precipitation from shallow brine lakes that are blown across salt‐encrusted playa surfaces by the wind. Moreover, they appear to be short‐lived features and their degradation is related to the flooding of playas with less saline water, and possibly rainfall and deflation.
The multivariate controls of hydraulic geometry: A causal investigation in terms of boundary shear distribution
Authors: Huang He Qing , Warner Robin F. 
Published: February 2007

AbstractMost downstream hydraulic geometry exponents have been found to be very close to the classic values reported by Leopold and Maddock (1953). These have been viewed as the simplified cases to general trends because the hydraulic geometry of alluvial channels is actually the product of ‘multivariate controls’ (Richards, 1982). This paper is an attempt to develop a soundly based foundation for the explanation of the physical mechanisms of these controls. A quantitative relationship between channel shape and boundary shear distribution developed from experimental flume results is found to be applicable in some instances to alluvial channels, particularly to stable canals. On the basis of this relationship, it is shown that downstream hydraulic geometry is determined not only by flow discharge, but also by channel slope, channel average roughness and sediment composition of the channel boundary. This is strongly supported by our analysis of 529 observations from both stable canals and natural rivers in the U.S.A. and the U.K. The difference between regime relations in canals and the hydraulic geometry of rivers appears to be caused mainly by channel slope and average roughness, which can be regarded as constants only in stable canals. The close relationship between discharge and channel average roughness observed in canals is not repeated in natural channels, partly because of the variety of flow values used to define the channel‐forming discharge. Furthermore, it is indicated that the effects of the sediment composition of the channel boundary on hydraulic geometry are significant and need further investigation.
The shoreline preservation index as a relative‐age dating tool for late pleistocene shorelines: An example from the bonneville basin, U.S.A.
Authors: Sack Dorothy 
Published: February 2007

AbstractThis paper evaluates the utility of the shoreline preservation index (s.p.i.) for estimating the age of late Pleistocene palaeolake shorelines, the relative influence of various factors on shoreline preservation, and whether shoreline preservation varies significantly with shoreline aspect. Sampled shorelines from the 3300 km2 study area, which includes the Skull, Tule and Puddle Valley portions of the Lake Bonneville basin, range in age from approximately 26 to 12 ka. Their total s.p.i. values range from 23 to 69 per cent, average 46 per cent, and do not vary significantly with shoreline aspect. The data from Skull and Tule Valleys, where studied shorelines are of known age, are analysed first in order to determine if there are statistically significant associations between variables representing shoreline preservation, age, degree of geomorphic development and duration of subaerial exposure. Pairwise correlation is then repeated using observations from all three valleys in order to determine how data from the Puddle Valley shorelines, whose hypothesized ages are not supported by radiocarbon analyses, affect the results. Results show that s.p.i. is useful as a relative‐age dating tool, that the postulated ages of the Puddle Valley shorelines are ordinally correct, and that geomorphic development is not an important influence on the preservation of these late Pleistocene shorelines. The relative importance of shoreline age and the relative unimportance of duration of subaerial exposure with respect to shoreline preservation suggest that subaqueous processes play a more substantial role in shoreline obliteration than is generally suggested.
Channel form and processes of the flood‐dominated Narmada River, India
Authors: Rajaguru S. N. , Gupta Avijit , Kale V. S. , Mishra Sheila , Ganjoo R. K. , Ely L. L. , Enzel Yahouda , Baker V. R. 
Published: February 2007

AbstractThe 1300 km long Narmada River flows along a structural lineament, alternating between constricting rocky gorges and rapids, and meandering wide alluvial reaches. Channel forms and processes were studied in a 120 km long section of an alluvial reach. Channel size, shape and bedforms in the Narmada River are related to very large floods which have occurred three times in this century. During such floods the entire 400 m wide channel is utilized and 10–15 m high cliffs on both sides operate as riverbanks. Normally, even the high flows of the south‐western monsoon are insufficient to fill the whole channel, and hence their effects are limited to building of discontinuous floodplains between the cliffs and modifying bedforms and bars. A channel‐in‐channel topography is thus created. The very large floods are also responsible for erosion of the rocky stretches and building of point bars. The river meanders, but its movement is restricted because of (1) rocky gorges and scablands operating as anchor points at intervals, and (2) the presence of high alluvial cliffs which are topped on extremely rare occasions. In spite of being located in a tectonically active zone in a monsoon setting, it is the exceptional high‐magnitude floods at irregular intervals which control the form and behaviour of the Narmada River.
Limestone weathering in Eastern Australia. Part 1: Erosion rates
Authors: Smith D. I. , Greenaway M. A. , Moses C. , Spate A. P. 
Published: February 2007

AbstractA traversing microerosion meter (MEM) was used to measure the rates of surface weathering of limestones in southeastern Australia. There were two groups of MEM sites installed in 1978/9. The aim of the experimental design for the first type, the 13 sites at Cooleman Plain and Yarrangobilly Caves, was to obtain erosion rates for limestones of similar lithology exposed under comparable climate conditions. The sites were positioned to measure erosion over a range of microsolutional forms and with exposure to differing forms of erosion, i.e. subaerial, subsoil and instream. The second set, at Ginninderra close to Canberra, consists of nine limestone slabs of differing lithology, collected from different locations but exposed under identical climatic conditions. The number of individual measurement points at each MEM site varied from 24 to 68.There were major differences in erosion rates between subaerial bedrock and instream sites at Yarrangobilly and Cooleman Plain, but no evidence of differential erosion across the micro‐forms. There were differences in the weathering rate for bedrock sites, due to climatic differences, and between the limestone lithologies exposed at Ginninderra. The average rate of erosion for the subaerial bedrock sites at Cooleman Plain and Yarrangobilly over the 13 years was 0·013 mm a−1and at Ginninderra 0·006 mm a−1. At some of the sites microflora (lichens and mosses) caused problems for field measurement. The weathering processes that contribute to the surface lowering are discussed in the accompanying paper by Moseset al.
Challenges and objectives for geomorphology in U.K. river management
Authors: Brookes Andrew 
Published: February 2007

AbstractThis paper reviews some of the challenges and objectives in the application of fluvial geomorphology to improved river management in the U.K. It describes the mechanisms by which geomorphology can be applied to solve problems, including the development of design guidance, policy, management approaches, procedures and training. While it is true that geomorphology is being used increasingly, there remain a number of challenges, such as the need to promote a more professional image and to develop appropriate standards. The scientific basis on which decisions relating to the water environment are made needs to be developed further. Perhaps some of the most significant challenges for fluvial geomorphology in U.K. river management during the next decade will concern river and floodplain restoration.
Sediment‐related river maintenance: The role of fluvial geomorphology
Authors: Sear D. A. , Newson M. D. , Brookes A. 
Published: February 2007

AbstractThis paper addresses the role that fluvial geomorphology might play in the management of sediment‐related river maintenance in the U.K. Sediment‐related river maintenance refers to the operational requirement of river management authorities to remove deposits of sediment or protect river boundaries from erosion, where these compromise the flood defence levels of service. Using data collected as part of a National Rivers Authority (NRA) Research and Development Project it is possible to identify the geomorphic causes of problems, and engineering responses to sediment‐related river maintenance (SRRM) in England and Wales. The Project identified the management problem as widespread and often treated in isolation from the causative processes. Geomorphological guidance is shown to be both relevant and complementary to conventional engineering practice through its ability to identify the cause of a SRRM problem. A methodology for conducting a geomorphological survey, or ‘fluvial audit’, is presented, which synthesizes historical data on the catchment land‐use and channel network, with contemporary morphological maps to present a statement of the location and type of sediment supply, transport and storage within the river basin under scrutiny. The application of geomorphology to two contrasting SRRM problems is explored using case studies from two catchments: the River Sence, a fine sediment system, and the Shelf Brook, a coarse sediment system.
The humber observatory: Concepts, instrumentation and software systems
Authors: Hardisty J. , Rouse H. L. , Middleton R. , Hirst R. S. , Scott T. 
Published: February 2007

AbstractThe role of geomorphological research into sediment flux within modern dynamical systems and the consequent role of geomorphological research in the development of practical environmental management tools are seldom reconciled. Sediment fluxes can be estimated using instruments and numerical models, but problems arise when these results are to be interpreted to inform the environmental management debate. This paper presents one set of solutions in which we describe the work of the Humber Observatory and detail the concepts, instrumentation and software systems which have been developed to address such issues. The design and deployment of a new, automated meteorological station, new multiple sensor, radio‐linked outstations and the collection of associated tidal and bathymetric data are described, together with discussion of the operational problems and data archiving and output issues. We also describe the numerical models based upon the dynamical equations which have been used to estimate water and sediment fluxes through the Humber Estuary, and we describe the design criteria for new semi‐empirical models. Results from the various systems and models are presented as the basis for a regional research capability and in terms of operational delivery for environmental management.