bluuebunny/crossref_metadata_2025 huggingface dataset:
Beach erosion as a function of variations in the sediment budget, Sandy Hook, New Jersey, U.S.A.
Authors: Allen James R.
Published: February 2007

Many of the world's beaches have recently been eroding, even on progradational landforms. This study uses the sediment budget approach to identify and rank the causes of the hazard along Sandy Hook spit where the primary recreational beach has been eroding at about 10 m/yr since 1953 and 23 m/yr in the 1970s.

Large spatial variations in longshore sediment transport are found to result from differences in refracted wave energies and intersegmental sediment transport. Erosion results from a 60 per cent deficit (‐270,000 m3/yr) in the sediment budget that is primarily caused by (1) refraction induced locally high waves that increase the transport rate by 100,000 m3, and (2) shore protection structures that have lessened the longshore sediment inputs by an additional 100,000 m3/yr. A storm index is presented to analyse secular climatic variation. It suggests that the annual sediment transport rate may vary by as much as ±50 per cent about the mean and that recently, above normal storm wave energies are responsible for about 60,000 m3/yr of the budget deficit. Rising sea levels and storm overwash each account for only about one per cent of the sediment loss.

Pulses of sediment, induced by accelerated erosion at the feeder beach locale of spit segments, are found to move downdrift. They alter the geomorphology of the spit through episodic extensions of the spit segments with lag times exceeding one year per segment.
Soil loss variation within a Colorado Alpine area
Authors: Bovis Michael J. , Thorn Colin E.
Published: February 2007

The areally weighted surface erosion for Niwot Ridge, an alpine interfluve in the Colorado Front Range, is 10−1 mm/y. This may be subdivided into rates for three generalized cover types: tundra meadow, 10−2 mm/y; dry tundra, 10−1 mm/y; late‐lying snow patches, 10° mm/y. Tundra meadow (about 50 per cent of the interfluve area) yields about 5 per cent of the eroded material; dry tundra (35 per cent of the area) contributes slightly less than 50 per cent of the eroded material; while nivation hollows occupied by late‐lying snow patches occupy only about 3 per cent of the area they contribute 50 per cent of the eroded material. The bulk of the surficial erosion is accomplished between June and September, primarily by rainsplash, except where snowmelt is important. The overall estimated surface lowering rate presented here is substantially higher than those reported previously.
Evidence of flandrian valley alluviation in staindale, North York Moors
Authors: Richards K. S.
Published: February 2007

The Dovedale Griff has incised into valley fill deposits in Staindale to expose sub‐fossil wood at the base of a meander cut bank. The wood includes oak (Quercus sp.) driftwood, and apparently in situ stumps of willow (Salix sp.) and alder (Alnus sp.). An alder stump is dated at 6270 radiocarbon years BP. Fluvial gravels approximately 1±5 m thick have accumulated above the wood, which has been exposed by renewed incision.
Horton's slope function
Authors: Church Michael
Published: February 2007

An error is pointed out in Robert Horton's (1945) presentation of his ‘slope function’. The history of its apparent non‐detection provides an interesting perspective on the development of geomorphology as a science.
Recent trends of experimental geomorphology in the field
Authors: Richter G.
Published: February 2007

Experimental geomorphology is a part of functional geomorphology. It tries to reach an exact analysis of the processes and to give statements on their importance for the recent relief forming. In all cautiousness the results may be transformed into more extensive areas and other time periods. Experimental geomorphology plays a differing role within the geomorphological research of the European countries. Most of the investigations deal with process studies and the quantification of weathering, mass movement, deflation, surface runoff, sediment transport in stream channels and denudation of watersheds. Experimental geomorphology should not be a goal in itself, but should be used as an applied geomorphology and for the examination of geomorphological theories as well.
Some aspects of the regional variation in the amount of available sediment produced by isopods and porcupines, northern negev, israel
Authors: Yair A. , Rutin J.
Published: February 2007

A recent study conducted in the Sde Boqer experimental site drew the attention to the possible influence of the burrowing and digging activity of some desert animals on the spatial variation of erosion rates over arid limestone slopes. Such activity provides loose soil aggregates which are easier to remove by shallow overland flows, than is the compacted and crusted loessial soil.

In order to study the regional extent of available sediment amounts produced by the biological activity, six plots were selected in the northern Negev in the range of 65 mm to 310 mm average annual rainfall amount. All plots had the same, north facing, aspect and the same lithologic composition. Their size varied from 1110 m2 to 5470 m2. Available sediment produced was found to vary from 3 g to 70 g/m2, increasing with rainfall amount. The distribution of available sediment within each plot was not spatially uniform depending greatly on the spatial distribution of bedrock surfaces and soil cover. The overall possible influence of the biotic activity on short term cycles of soil erosion over limestone arid slopes in the Negev is discussed.
Work done by Splash: Laboratory experiments
Authors: Savat J.
Published: February 2007

Laboratory experiments, based on the theory proposed by van Heerden (1967) that net splash discharge equals the difference between yMiVi and miyi, where M and Y denote downslope masses and projected distances and m upslope projected distances and masses, demonstrate that the work done by splash is a function of the slope angle to (sin a)1.9.

Net discharge of sediment (q) therefore increases to (sin a)0.9, It is equally a function of the susceptibility to splash erosion K, which is a complex function of the moisture content of the sands and their grain size distribution.

The technique proposed for the assessment of the mean projected splash distances is rapid and gives very accurate results. When carefully applied, it can also be used for fine material like, for example, loess.

The splash board technique which is currently used for many field experiments, provides none of the basic information necessary for establishing a discharge‐slope relationship.
Drop testing aggregate stability of some soils near Merida, Spain
Authors: Bergsma E. , Valenzuela C. R.
Published: February 2007

The drop test for aggregate stability results in a distribution of destroyed aggregates with increasing drop number. The influence of prewetting time on drop test results is considered. Secondly new indices to describe the drop test results and modifications of the drop test are suggested to avoid undue influence of small numbers of very stable aggregates, and to shorten the test procedure.
A consistency index and rainwash mechanisms on Belgian loamy soils
Authors: de Ploey J. , Mücher H. J.
Published: February 2007

The effects of soil crusting in Belgium are particularly conspicuous on the loamy plateaus and hill‐regions of southern Flanders, Brabant and Hesbaye. Field observations, made at the end of rainy winter seasons, permitted the making of a simple distinction between: (a) ‘stable’ soils showing crusting on less than 50 per cent of their total surface, without any evident slope wash, and (b) ‘unstable’ soils, crusting over more than 50 per cent of the total surface, with evident rainwash and basal colluviation.

The Atterberg limits have been examined for both soil types. It was found that the upslope part of the liquid limit curves, in the range of low consistencies (high water contents), is steeper for stable than for unstable soils. So a distinctive consistency index C2–10was deduced from the liquid limit curves, which may be used for prediction of the relative sensitivity of topsoils for crusting. Stable, well‐structured clods are more hydrophobic than unstable material. This was made clear by wettability tests under a rain simulator. Therefore more water must be added to remolded, stable material to lower its consistency, as is shown by the liquid limit curves.

Crustability decreases and C5–10values increase with increasing clay and organic matter contents, as one would expect. Stable soils are well aggregated. But rain simulator tests also showed that the detachment of this material by raindrop impact is high. Therefore, crumbs and clods of stable soils are relatively more sensitive to splash erosion. Their erosion results from the ejection of stable aggregates. Clods of unstable topsoils are compacted and flattened by raindrop impact, which causes internal liquefaction.

Micromorphological analysis indicates that typical stable topsoils originate from well‐structured Ap‐horizons and from Bt‐horizons of grey‐brown podzolic soils (Alfisols). Laminated silt and mudcrust fragments characterize unstable topsoils which originate, at least partly, from slopewash deposits. The external stability of both stable and unstable clods is increased by compaction and by surficial concentration of gravel, coarse sands, root and other plant fragments. Thin sections of unstable material show the internal collapse of structures, due to liquefaction.

A clear distinction must be made between the structural stability and the erodability of topsoils.
Response of loess materials to simulated translocation by water: Micromorphological observations
Authors: Mücher H. J. , de Ploey J. , Savat J.
Published: February 2007

Structural differences between loess material deposits produced by splash, flow without splash and by rainwash (i.e. combined splash and flow) respectively were reported earlier (Mücher and de Ploey (1977)). Deposits from splash alone proved to be non‐layered and had incurred almost no additional particle sorting. Deposits from flow without splash were well layered, while individual laminae displayed excellent sorting. Rainwash produced poorly layered deposits with poorly sorted individual laminae. Only horizontal and subhorizontal bedding, and no cross bedding, were observed. Similar features appeared in samples from naturally layered loess deposits collected from excavations.

The present paper focuses on the granulometric character of the artificially created layers. Experiments normally involved the combined use of an erosion and a sedimentation flume. Slope angles of the flumes varied mainly form 0.25 to 4 degrees. Precipitation intensities varied from 7 to 120 mm per hour. Unit discharges ranged from 0.2 to 9.2 cm3/cm,s. Flow was laminar or smooth turbulent, either subcritical or supercritical (Froude numbers between 0.5 and 3.8). Raindrop impact had little influence on the flow velocity and thickness of the surficial water film, but it significantly increased transportation capacity and flow competence (Savat (1976, 1977)).

Undisturbed samples were collected during the experiments, and impregnated with unsaturated polyester resin. Thin sections of 20 μm thickness were studied under a polarizing microscope. Comparative observations were made on naturally layered loess materials.

During rainwash, clay size particles are removed and exported, whereas laminae with particles from 10 to 50 microns are more frequently produced than those with particles from 10 to 30 microns.

Flow without splash produced relatively more laminae with grains smaller than 30 microns diameter.

Striking in all samples is the absence of laminae composed of 30–50 μm grains. Aggregates were only deposited by smooth turbulent flow, either disturbed or undisturbed by raindrop impact.

In view of the experimental results, the naturally formed loess deposits may be interpreted as follows: the bulk of the loess from the excavation near Tongrinne, Belgium, was reworked under influence of turbulent rainwash. Only one sample contained laminae consisting of clay, particles smaller than 10 μm, and of particles from 10–30 μm respectively, suggesting deposition from flow without splash. This was taken from a gully infilling.

A gully fill from the excavation Heverlee near Leuven, Belgium, is characterized by poorly sorted laminae, dominated by the coarser silt fractions. This suggests infilling under influence of turbulent rainwash.
(Re)deposition of loess in southern Limbourg, The Netherlands. 1. Field evidence for conditions of deposition of the lower silt loam complex
Authors: Vreeken W. J. , Mücher H. J.
Published: February 2007

This is the first of five papers on a study clarifying conditions and processes during and between the periods of loess accumulation in the southern Netherlands. The research approach involves studies of the stratigraphic, sedimentological, and paleopedological frameworks, micromorphological and analytical characterization of the deposits, and interpretation of micromorphological data in the light of independent process simulating experiments conducted on comparable test materials.

Lower or Middle Pleistocene Maas terrace Sands and Gravels overlie Middle Miocene Sands, and are separated by a stoneline complex, consisting of four components, from various silt loam units, which have been grouped into the Lower, Middle and Upper Silt Loam complexes. There is also one intra‐silt loam stoneline. The stonelines range from pre‐Saalian to early Middle Pleniglacial Weichselian in age and variably represent periods of deflation, hillslope erosion, and channel erosion. The present paper reports the results of a macroscopic field study of the Saalian, Eemian, and Early Weichselian Lower Silt Loam stratigraphical units and provides a brief overview of the remaining units, which will be detailed in a future paper. The lateral variability of the units is drawn to scale in a profile 475 m long.

The Lower Silt Loam complex comprises an early Saalian channel deposit and a Saalian eolian unit with penecontemporaneous reworking by sheetflow. It is surmounted by the Eemian Rocourt paleosol. This is followed by a Lower Silt Loam unit consisting of older local silt loam material reworked and redeposited by sheet and shallow channel flow, which is in turn surmounted by a paleosol that may be the Early Weichselian (Warneton) or late Eemian in age. The last and largest Lower Silt Loam unit was deposited from channel, and subsequently sheetflow on a major erosional surface, which bevels all older silt loam units. Above this are calcareous Middle Silt Loams.

The geomorphic evolution of a dry valley or del can be traced to an early Saalian channel. But, various paleochannels are no longer evident in the present landscape.
(Re)deposition of loess in southern Limbourg, The Netherlands. 2. Micromorphology of the lower silt loam complex and comparison with deposits produced under laboratory conditions
Authors: Mücher H. J. , Vreeken W. J.
Published: February 2007

In this second of five papers on conditions and processes associated with loess accumulation in the southern Netherlands, micromorphology has been used first to characterize deposits ascribed to eolian, fluvial, overland flow, and masswasting processes, and second to recognize features characteristic of deposits produced by simulated processes using comparable testing materials (Mücher and De Ploey (1977); Mücher et al. (1981)).

The present paper deals with two stratigraphic units of the Lower Silt Loam complex in the Nagelbeek excavation. These are the Saalian Lower Silt Loam A (unit IV). which seems to consist of eolian material, reworked by sheetflow and modified by Eemian pedogenesis, and the Early Weichselian Lower Silt Loam C (unit VIb), which probably results from channel flow deposition and local masswasting followed by sheetflow deposition. Microscopically, lamination in unit IV suggests alternating eolian conditions and deposition from laminar to smooth turbulent afterflow or meltwater flow. Then followed a period in which deposits of rainwash with smooth turbulent flow, alternated with very thin deposits from laminar flow without splash. Unmodified eolian deposition, or colluviation from splash alone, becomes more dominant upwards. Sedimentary lamination has been accentuated by pedogenic clay illuviation.

Unit VIb starts with reworked pedorelicts from Eemian and Early Weichselian paleosols, deposited from rainwash with smooth turbulent flow. Lamination resulted from smooth turbulent to laminar flow without splash. This is followed by intercalations originating from either eolian deposition or splash deposition, and overland flow deposits with evidence for a finely‐branched system of very small rills. Microscopic examination of lobate portions of mass movement deposits within unit VIb does not confirm this origin because of the scale limitations of thin sections. It merely reveals structures that predate the mass movement.
The development of blowouts in ‘de blink’, a coastal dune area near Noordwijkerhout, The Netherlands
Authors: Jungerius P. D. , Verheggen A. J. T. , Wiggers A. J.
Published: February 2007

Surface changes in six blowouts in the coastal dunes near Noordwijkerhout between s‐Gravenhage and Zandvoort were measured weekly over a period of two years at 80 erosion pin sites. Readings were correlated with wind variables derived from nearby Valkenburg airbase for the same weekly periods. The values of the wind variables is determined by the number of hours that specific average wind speeds and directions were recorded.

The first part of this paper deals with the process of wind erosion. Special attention is given to the relationship between surface changes and wind speed, wind direction, season and rain. Surface changes are associated with wind speeds as low as 1.25 m/s, but net lowering, i.e. erosion, is best correlated with wind speeds between 8.75 and 10 m/s. At higher wind speed there is a tendency for the blowouts to be filled in. Winds from an easterly direction generally correlate with accumulation, whereas winds from the west correspond with accumulation at low speeds and with erosion at high speeds. Springtime and autumn are the most important seasons for blowout development. The effect of rain seems to be limited: the correlations are not improved by excluding rainy days, perhaps because wet sand will be dried rapidly by strong winds.

In the next part of the paper, the response of blowouts to the erosion process is discussed. Wind erosion is dominant at the windward side because contrarily to what is often assumed the erosivity decreases as soon as the air is loaded with sand. As a result, blowouts grow southwestwards against the prevailing wind. Nevertheless, much sand is also shifted by winds from other directions. The forms of the blowouts determine in their turn the efficacy of the wind. The errosivity of the wind is most pronounced in circular blowouts, it decreases as the blowout grows in length.

Finally, a model of blowout development is proposed which is controlled by width, depth and length ratios.
Reddening of dune sands—evidence from southeast India
Authors: Gardner Rita A. M.
Published: February 2007

Thin section, SEM, and TEM analyses have indicated that the red ‘teri’ sands of southeast India have formed from weathering in situ of coastal dune sands. The data does not support a detrital origin for the red sands. C14 dates indicate that dune deposition and weathering, to a maximum depth of 10 m, leading to the formation of a hematite, koalinite and illite rich matrix has taken place rapidly over the past 25,000 years. It is postulated that garnet was a major source of hematite (ferric oxide).
Influence of porefluid salinity on instability of sensitive marine clays: A new approach to an old problem
Authors: Carson M. A.
Published: February 2007

The geographic association between earthflow occurrence, sensitivity of the sediment and salinity of the interstitial fluid has been examined in an area of exposed marine (Champlain Sea) deposits in the Lachute region northwest of Montreal, Quebec. Mapping of earth resistivity, as a means of calculating porefluid salinity, revealed that areas of large earthflows (>20 ha) coincided with sediment of very low porefluid salinity. Earthflow scars were absent from intervening areas of higher salinity (>5 gl−1). Mapping of the thickness of the clay deposit by seismic refraction showed, furthermore, that low porefluid salinity occurred only in areas of relatively thin (<25 m) deposits resting upon more permeable drift or rock. Finally, laboratory tests confirmed that high sensitivity was restricted to areas of low porefluid salinity. The study thus provides a geomorphological verification of the importance of ‘salt depletion’ as a prerequisite for earthflow occurrence, and, by implication, presents mapping of porefluid salinity as a method of delineating zones which should be safe from landslide retrogression in this type of sediment.
Heathland vegetation, soil moisture and dynamic contributing area
Authors: Gurnell Angela M.
Published: February 2007

Gurnell (1978) demonstrated the potential of the composition of wet heathland vegetation as an indicator of hydrological processes in a small heathland catchment. The present paper investigates this potential and demonstrates that on a hillslope in the study catchment simple prediction equations for pressure head based entirely on position on the slope can be substantially improved by the inclusion of vegetation related variables. It is suggested that in this context the vegetation composition is largely reflecting soil permeability and that the remaining scatter around the prediction equations results from other factors controlling micro‐scale variations in the vegetation pattern.
The influence of organic debris on channel morphology and bedload transport in a New Zealand forest stream
Authors: Mosley M. Paul
Published: February 2007

The behaviour and form of, and bedload sediment transport through, a 3.5 m wide forest stream have been monitored for nearly three years. Bedload transport is highly episodic and spatially variable, and is controlled less by water discharge than by sediment availability. Organic debris in the channel creates temporary base levels and sites at which coarse sediment may remain stored for long periods; collapse or disruption of log and debris jams makes sediment available for transport in only a small proportion of the runoff events that are actually competent to move the material. Even then, sediment travels only a short distance before being redeposited, frequently behind debris accumulations further downstream. Rates of sediment transport during a given runoff event can vary markedly over short distances along the stream, again depending on whether sediment was made available for transport by log jam collapse upstream. Organic debris is therefore a major constraint on the application of physical laws and theories to explaining sediment movement in, and the morphology of, this stream.
Bed‐form‐dependent pulsating flow in medano creek, southern colorado
Authors: Schumm S. A. , Bean D. W. , Harvey M. D.
Published: February 2007

Some sand‐bed streams exhibit unsteady supercritical flow in the form of periodic bores that propagate downstream. The bores are formed by unstable antidunes, which store water while growing in amplitude and then release the stored water, when the antidunes wash out to form a plane bed. A cyclic process of antidune growth, oversteepening, antidune breaking, then bed‐form washout produced bores on regular periodic intervals of roughly 15 s in Medano Creek, Great Sand Dunes National Monument, Colorado. This periodic bore‐generating pulsating flow, is bed‐form dependent, and it requires sufficiently high flow velocities and sediment transport rates to form unstable breaking antidunes. The Froude number maximum is 1.8, below that required for slug flow.

Pulsating flow has been observed in flumes, arroyos, and rivers, and it may be more common than initially anticipated. Its high erosive capacity can influence both channel morphology and the character of associated sedimentary deposits.
Environment and provenance in the development of recent alluvial deposits in epirus, nw greece
Authors: Macleod D. A. , Vita‐Finzi C.
Published: February 2007

The valleys of Epirus, in NW Greece, are floored by alluvium laid down in historical times. In an attempt to evaluate the relative importance of diagenesis and of parent material in determining its local character, the alluvium was compared with the principal source deposits, namely the red beds of the late Quaternary Kokkinopilos Formation and the brown Mediterranean soils that have developed on flysch outcrops. Rehydration of the haematite pigment after deposition coupled with silt‐clay depletion during redeposition of the red beds is responsible for the drab colour of the valley‐floor deposits in limestone catchments. Where the alluvium was derived from brown soils, little mineralogical change has occurred. Some reduction and mobilization of iron has affected Kokkinopilos beds still in place, possibly during periods of seasonal waterlogging under oak forest, to produce a veining pattern akin to that found in pseudo‐gley soils.
Rapid deglaciation as an initiator of volcanic activity: An hypothesis
Authors: Hall Kevin
Published: February 2007

Volcanic activity on sub‐Antarctic Marion Island is found to have occurred only during the interglacials. The present volcano distribution is associated with a radial and peripheral fault system, the location of which appears to be related to the former glacier distribution. An hypothesis is presented suggesting that the faulting is a result of deglaciation and that the specific location of the faults is due to the differential stresses occurring between ice‐covered and ice‐free areas during isostatic uplift. The faulting initiates volcanism due to the location of the island within a volcanic region.
Automatic sampling of stream water during storm events in small remote catchments
Authors: Martin R. P. , White R. E.
Published: February 2007

In order to study the relationship between water composition and stream flow rate, it is desirable to sample at a frequency related to flow rate, especially during storm events. In a rural catchment of 18 ha near Oxford, the rate of rainfall was found to be linearly related to discharge on the rising limb of the stream hydrograph. A sampling system was therefore designed in which electrical pulses from a tipping‐bucket raingauge were used to initiate and control the action of an automatic water sampler. A threshold rainfall intensity is set above which sampling commences. Sampling then continues at regular increments of rainfall until the intensity drops below the threshold, after which sampling occurs at regular intervals during the period that the stream flow reverts to normal.

The CMOS electrical circuits which control the sampling also operate a cassette tape recorder which records the time of each tip of the raingauge and operation of the sampler. Since the sytem is designed to impose very little additional load on the battery which powers the water sampler, and can operate unattended for at least a fortnight, it is ideal for use in small, remote catchments. The system has been extended to include measurements of water temperature and could provide other measurements as well.
Erosion of strip‐mine dumps in la salle county, illinois: Preliminary results
Authors: Haigh Martin J. , Wallace William L.
Published: February 2007

Direct measurement of slope retreat on three unvegetated slope profiles on unmodified, pre‐1939, strip‐mine dumps revealed average ground losses ranging from 29 to 33 mm/year. Measured ground losses are twice those estimated from the Universal Soil Loss Equation. Slope length seems less significant than frost action in influencing erosion on these slopes.
Flow variability and hillslope hydrology
Authors: Huff D. D. , O'Neill R. V. , Emanuel W. R. , Elwood J. W. , Newbold J. D.
Published: February 2007

Examination of spatial variability of streamflow in headwater areas can provide important insight about factors that influence hillslope hydrology. Detailed observations of variations in stream channel input, based on a tracer experiment, indicate that topography alone cannot explain flow variability. However, determination of changes in channel input on a small spatial scale can provide valuable clues to factors, such as structural geology that control subsurface flows.
Equilibrium and time scales in geomorphology: Application to sand‐bed alluvial streams
Authors: Howard Alan D.
Published: February 2007

Equilibrium is defined as a single‐valued, temporally invariant functional relationship between the values of an output variable and the values of the input variable(s) in a geomorphic system. Disequilibrium occurs if the output deviates from the functional relationship by more than a consensual degree. Natural geomorphic variables are characterized by a relaxation time. Output variables are insensitive to cyclical inputs with frequencies much greater than the relaxation time, but can respond completely for sufficiently low frequencies. Rapid trends, recent step changes or pulse inputs, and intermediate frequency inputs can cause disequilibrium.

The gradient of sand‐bed alluvial channels (the output variable) is determined by sediment and water delivery from slopes (the input variables), and changes in this hydraulic regime require regrading by erosion and deposition. Initial stages of adjustment to changed regime in a long, unbranched channel with sediment and water delivery only at the upstream end propagate downstream, but later stages of adjustment occur simultaneously throughout the reach. In a dendritic channel network the gradient responds rather uniformly throughout the network to changes in regime during all stages of adjustment. The time scale of adjustment to changed regime depends upon the size of the channel network (or stream length), the sediment and water discharges, and to a lesser degree upon the magnitude of the change.

Grade as defined by Mackin (1948) is synonymous with equilibrium as used in this paper if ‘a period of years’ is replaced by ‘a time period commensurate with the relaxation time of the gradient’. The use of the term grade is best restricted to a single‐valued relationship between channel gradient and the hydraulic regime.
The permanence of stream networks in britain: Some further comments
Authors: Burt T. P. , Gardiner A. T.
Published: February 2007

The conclusions of Ovenden and Gregory (1980) are reviewed in the context of a stream network on the blanket peat moorland of the Southern Pennines. The very great disparity between the 1:10560 map network and the present channel system suggests that the original survey only included the major tributaries. Map accuracy in areas of peat moorland must therefore be treated with some caution particularly if no air photograph or field checking can be done. Some problems of network definition in the peat moorlands are also briefly discussed.
Reexamination of the rate of desert varnish formation reported south of barstow, California
Authors: Elvidge Christopher D.
Published: February 2007

Desert varnish is reported to have formed in 25 years on desert pavement stones in an abandoned road south of Barstow, California. It has been discovered that stones buried close to the surface of the roadbed and adjacent desert pavement bear the same dark desert varnish as the exposed stones at the surface. This and other observations refute the claim of 25 year old varnish.
Pedogenic zones in postglacial sediment of lake manitoba, Canada
Authors: Teller James T. , Last William M.
Published: February 2007

The postglacial sediment record of Lake Manitoba is composed dominantly of silty clay to clayey silt with little variation in most physical, chemical, and mineralogical properties. Distinct in the sedimentary sequence of this large lake, however, are four zones that have a low moisture content, blocky to pelletal structure, and gleyed colour. All of these zones formed during the warmest and driest postglacial period in the region, 9500 to 4500 years ago. Although several possible hypotheses can be formulated regarding the origin of these zones including changes in sedimentation rate, clay mineralogy, lake chemistry, and depth of winter freezing, the most likely explanation is that they represent pedogenic horizons. Formation by pedogenesis during dry or extremely low water conditions is not mutually exclusive of the other hypotheses, and several are favoured by low water conditions.
The role of sidewall processes in gully development; some N.S.W. examples
Authors: Blong R. J. , Graham O. P. , Veness J. A.
Published: February 2007

Little attention has been paid to the role of sidewall processes in gully development. Simple estimates of linear incision/sidewall erosion ratios at two localities in New South Wales, Australia suggest that sidewall erosion is responsible for more than half the gully volume. Studies at three localities where overland flow and throughflow are limited to only one sidewall indicate that these processes are responsible for 10‐30 per cent of gully volume. These observations have important implications for gully management.
Controls on the stability and inclinations of hillslopes formed on hard rock
Authors: Selby M. J.
Published: February 2007

In identifying controls on rock slope form a distinction is made between: (1) rock slopes with joints which dip steeply out of a cliff and hence are subject to mass failure of the rock mass above a critical joint; and (2) rock slopes with inclinations which are either in equilibrium with the mass strength of their rocks, or have profiles which will develop towards strength equilibrium as cross joints open. In the first class of slope, stability results not just from the basic frictional resistance of the rock but also from the frictional roughness along the critical joint and from the normal stress acting across that joint. Stability may be reduced by weathering and loss of strength of the joint wall rock. As a result of normal stress variations with depth, induced by overburdens, high cliffs which are not undercut have a concave profile. The second group of slopes includes those with inclinations controlled at the scale of individual joint blocks, buttressed slopes and those on unjointed rock masses. Buttressed and unjointed rock masses develop towards a condition of mass strength equilibrium as cross joints open. Strength equilibrium slopes may be recognized by application of a rock mass strength classification proposed for geomorphic purposes. Eleven propositions are formulated which identify controls on rock slope development and some consequences of these controls.
‘frost and salt’ weathering: Further experimental results
Authors: McGreevy J. P.
Published: February 2007

A laboratory experiment has been conducted to examine the effects of ‘frost and salt’ weathering (i.e. physical breakdown by the freezing of salt solutions) on a limestone. Results show that the presence of certain salts in solution can inhibit frost damage. These findings are in direct conflict with those presented by Goudie (1974) and, more recently, Williams and Robinson (1981).

Comparison of the experimental methods used in each of these three studies suggests that opposing results can be explained in terms of the different experimental procedures which were employed. If salt supply is frequent and plentiful then it seems likely that rock breakdown will be enhanced‐this is the case represented by the experiment of Williams and Robinson. Conversely if the salt supply is limited and the amounts of salt remain more or less constant then rock breakdown will be inhibited‐the case of the present experimental study. Caution is therefore advocated when attempting to extrapolate laboratory‐derived results to infer on the behaviour of rocks under natural conditions.

Several environmental situations in which ‘frost and salt’ weathering may be a possibility are dsiscussed, but it is concluded that further field data, especially concerning temperature regimes and salt availability at and below rock surfaces in cold regions, would be necessary before more definite statements could be made about the efficacy of this process.
A model of two‐phase bedload transport in an oregon coast range stream
Authors: Jackson W. L. , Beschta R. L.
Published: February 2007

A descriptive model for bed material routing in small sand and gravel bedded channels with sequences of pools and armoured riffles was developed. Aspects of the model are demonstrated at Flynn Creek, a 202‐ha, third‐order drainage in the Oregon Coast Range. Assuming that channel geometry, sediment transport competence, and the availability of sediments for transport are all non‐uniform in the downstream direction, the model described bedload transport as occurring in two phases. Phase I involves the transport of fine, predominantly sand‐sized bed materials over stable gravel‐armoured riffles. Phase II occurs at higher flows that can entrain riffle armour and transport riffle sediments, in addition to Phase I sediments. Phase I bedload transport was sampled during three moderate flow events. A power function related Phase I bedload transport to water discharge. The relationship was consistent between storms and between two successive years. Phase II bedload transport, sampled during a 1.8‐yr return period streamflow event in February, 1979, proved non‐uniform in a downstream direction and unsteady over time at a given stream discharge. Transport rates closely correlated with the rapid scour and redeposition of the riffle at the bedload sampling cross‐section; transport peaks corresponded to scour and transport decreased greatly during deposition. The transport of large (> 12.5 mm diam.) bed material increased up to 12‐fold during riffle scour.
Medium‐term effects of two landsliding episodes on channel storage of sediment
Authors: Pearce Andrew J. , Watson Alex
Published: February 2007

Two landsliding episodes between late 1973 and early 1975 delivered about 60000 m3 of sediment to six small deeply incised streams draining a 2·7 km2 area. About 4700 m3 of logs in the landslide debris formed major log jams in five streams, which impounded large volumes of landslide‐derived sediment. Five years after the landsliding, 42 per cent (25000 m3) of sediment was still in storage behind 35 log jams ranging from 1·4–8·2 m high. The landsliding episodes have produced multi‐stepped stream profiles, aggradation of channel reaches up to 150 m long to mean depths between 1·2 and 4·1 m, reductions in gradient, fining of bed material size, and related changes in bedforms and channel width:depth ratios that seem likely to persist for at least several decades. Sediment presently stored behind log jams is equivalent to between 50 and 220 years normal supply of sediment from hillslopes to stream channels. Long‐delayed, large magnitude impacts on higher‐order channels may occur if sudden failure of log jams is induced by a large storm at some future date.
On the estimation of spatial autocorrelation in geomorphology
Authors: Cox Nicholas J.
Published: February 2007

Attention is drawn to the existence of different estimators of autocorrelation in one‐dimensional series. It is shown that variation between estimates for series which appear only mildly nonstationary may be of the same order as sampling variation expected under stationarity. Hence it is important that investigators choose estimators carefully and state their choices explicitly.
Pore water pressure and stability conditions on a motorway embankment
Authors: Anderson Malcolm G. , Kneale Pauline E.
Published: February 2007

Prior to the occurrence of a shallow surface slip on a clay embankment a tensiometer system was installed to continuously monitor pore water conditions. It is shown that high pore water pressures can develop in clay embankments after periods of continuous low intensity precipitation. Using stability analyses it is demonstrated that for this first time slide, the clay fill material had a shear strength above residual values and a small but finite cohesion.
The permanence of stream networks in Britain
Authors: Ovenden J. C. , Gregory K. J.
Published: February 2007

Stream networks used in studies of basin morphometry, network topology, flood hydrology, and sediment production should be defined as precisely as possible. Previous work has drawn attention to the way in which stream network definition varies on maps of different scales, on maps employing different conventions devised in relation to the dynamic network, and according to whether maps, remote sensing or field survey sources are used. Networks also vary in extent according to the date of survey and after considering the instructions to surveyors it is shown that such changes, over periods of 100 years reflect changes in network extent. For three areas of Britain, network change can be identified by comparison of maps of different dates, by comparison of these changes with the results of field survey, and by reference to dateable features such as inclosure boundaries. Changes of drainage networks since the nineteenth century are shown to be significant in extent and they have often occurred as a result of the replacement of flushes by clearly defined stream channels. This transformation has often occurred as a result of new or modified systems of stormwater drainage from roads, tracks or farms, and the planning of the future disposal of road drainage should be considered carefully in relation to such stream network changes. The changes of drainage networks identified from maps of different dates and editions can provide a useful data base for studies of network topology and may also be significant in relation to palaeohydrological investigations.
Magnitude and distribution of rates of river bank erosion
Authors: Hooke J. M.
Published: February 2007

Measurements of bank erosion on rivers in Devon over a 2½ year period produced mean rates ranging from 0.08 to 1.18 metres per year and a maximum rate of 2.58 metres per year. These values are compared with rates derived from maps for various time periods between 1840 and 1975. The map rates are generally lower than the field rates and the question of whether this difference is due to the method of measurement, the magnitude‐frequency of events, a change in discharge conditions or the inherent variation in channel activity is discussed. Published data on bank erosion rates are reviewed and the Devon rates are found to coincide with the worldwide distribution. An analysis of factors likely to influence the spatial distribution of erosion rates reveals a square‐root relationship to catchment area and the importance of bank material. Implications of the measured rates for development of flood plains are examined.
Hydrochemical aspects of the negro river, patagonia, argentina
Authors: Depetris Pedro J.
Published: February 2007

Water samples collected in the Negro River drainage basin (Patagonia, Argentina) during two different field trips—the first in May 1972 and the second in January 1973—were analysed for the major dissolved inorganic constituents. Q‐mode factor analyses demonstrate that two factors account for over 98 per cent of the variance in both sample suites. They represent: a) the direct influence of solution of evaporites and associated carbonate rocks in an arid environment‐type; b) the influence of the weathering products of metamorphic, igneous rocks, and varied non‐calcareous sediments. R‐mode factor analyses of the two sets of data suggest that although the main mechanisms controlling water chemistry were essentially the same, the principal sources of dissolved solids differed significantly in each separate occasion. Further, the major mechanisms controlling its water chemistry are within a wide spectrum of the so‐called ‘rock dominance’.
Field studies of sediment transport by overland flow
Authors: Morgan R. P. C.
Published: February 2007

Field studies on sandy soils of the Cottenham Series in mid‐Bedfordshire show that the mean annual rate of sediment transport by overland flow on an 11° mid‐slope is 98 g cm1. The feasibility of using sediment transport equations to predict erosion by overland flow on a storm basis is examined by comparing the observed values of sediment yield with values predicted by four sediment transport equations and a regression equation which relates soil loss to runoff energy and rainfall energy. An expression combining Engelund's sediment transport capacity equation and the Manning equation for flow velocity, as modified by Savat for disturbed flow, best reflects field conditions. Although there is a significant correlation (r = 0.69; n 30) between the observed and predicted values using this expression, the coefficient of determination is too low for predictive purposes. Reasons for this are presented.
Forms of bluffs degraded for different lengths of time in emmet county, Michigan, U.S.A.
Authors: Nash David
Published: February 2007

Distinct differences in morphology are found among bluffs cut and abandoned by Glacial Lake Algonquin and by the Nipissing Great Lakes in Emmet County, Michigan and modern, active bluffs presently being eroded by Lake Michigan in Mason and Manistee Counties, Michigan. The Algonquin, Nipissing, and modern bluffs are all composed of a sandy, morainic material. Because the composition and mode of formation of the three sets of bluffs are similar, it is assumed that the abandoned bluffs had the same initial configuration as the modern bluff. The morphologic differences are likely a function of the different periods of time each bluff has degraded. With time, the angle of the bluff midsection decreased, the extent of the convex crest and the concave base increased, and the angle of the crest increased. This course of hillslope degradation is believed similar to that occurring elsewhere on heavily vegetated hillslopes underlain by cohesionless material and situated in temperate, humid climates. The morphologic changes may be understood in terms of an analytical model which assumes that the rate of change in elevation at a point on a hillslope profile is proportional to the profile curvature at that point.
Channel morphology and sediment movement in a tidal river, pitt river, British Columbia
Authors: Ashley Gail M.
Published: February 2007

The Pitt River is a meandering river channel linking the Fraser River estuary and Pitt Lake. The lake acts as a temporary reservoir for tidally diverted Fraser River flow. Stage level can fluctuate 2 m in Pitt River and as much as 1.2 m in Pitt Lake on a tidal cycle. Stage data from three locations in the system, used in conjunction with velocity measurements (profiles and tethered meter), revealed large tidal and seasonal variations in discharge. Calculations indicate that during the flood, basal shear stress peaks earlier in the cycle and reaches higher values than during the ebb. Thus, sediment moves farther forward on a flood flow than it moves back on the succeeding ebb. An upstream movement of sediment in Pitt River from the Fraser River is indicated by: (1) the identical mineralogy of the two rivers, (2) a decrease in median grain size from the Fraser to Pitt Lake, and (3) a predominance of flood‐oriented bedforms in the river channel. A delta, 12 km2 area, has accumulated at the lower (draining) end of the lake.

Studies of the river channel using hydrographic charts revealed regular meanders (λM = 6100 m) and evenly spaced riffles and pools which appear to be scaled to the strongest flow, winter flood current (2400 m3/s). The winter flood is thus considered to be the effective discharge. Meander point bars are accreting on the ‘upstream’ side indicating deposition by the flood‐oriented flow. The three dimensional geometry of the large‐scale bedforms which cover the sandy thalweg of both river and delta channel was determined by echo sounding and side‐scan sonar. Three distinct sizes (height/spacing = 0.8 m/10–15 m; 1.5 m/25–30m; 3m/50–60 m) of large‐scale bedforms (sand waves) were found; their linear relationship of height vs. spacing on a log‐log plot suggests a common genesis. Their occurrence by size does not appear to be related to depth of flow but rather to their position in the channel with respect to large scale features which alter flow.