bluuebunny/crossref_metadata_2025 huggingface dataset:
Coincidence and spatial variability of geology, soils, and vegetation, mill run watershed, Virginia
Authors: Olson C. G. , Hupp C. R.
Published: February 2007

The Mill Run watershed is a structurally‐controlled synclinal basin on the eastern limb of the Massanutten Mountain complex of northwestern Virginia. Bedrock contacts are obscured by coarse sandstone debris from exposures near basin divides. Colluvium blankets more than half the basin, masking geomorphic surfaces, affecting vegetation patterns, and contributing to the convexity of the alluvial, terrace, pediment and erosion surfaces. Examination of the bedrock geology, geomorphology, soils and vegetation shows distinct distributional correspondences. Vegetation is strongly interdependent with geomorphology, bedrock geology, and soils. On convex colluvial slopes, mixed hardwood forests are most common. In concave coves and deep gorges, mixed hardwoods are replaced by conifers. In thin colluvium, in poorly developed soils, and on blockfields, chestnut oak is singularly prevalent. Conifers dominate shaley bedrock areas. Soils and surficial sediments have a major effect on near‐surface hydrology. During wet seasons, cemented horizons in the subsurface cause temporary saturation in the superjacent horizons; lateral movement of soil‐water effectively eliminates a vertical component of ground‐water recharge. Vegetation is strongly dependent on water availability and thus reflects the distribution of subsurface barriers and sediment‐soil fades changes.
The Jakucs CO2 microanalyser—problems and remedies
Authors: Vincent P. , Rose L.
Published: February 2007

This note describes simple procedural changes and corrections to gas pressure calculations for use with the Jakucs CO2 microanalyser.
A rapid method for simulating three‐dimensional fluvial terrain
Authors: Griffin Mark W.
Published: February 2007

A rapid, computer‐based method of simulating ‘geomorphologically‐sensible’ three‐dimensional terrain data by modelling landform morphology is presented. For some engineering applications such an approach, even in a simple form, is preferable to the synthesis of terrain data by purely stochastic methods, and additionally can be useful where real data sets are difficult to obtain.

The approach adopted utilizes a computer program which models landscape evolution by establishing a stream network on a tilted surface, with accompanying fluvial downcutting and slope adjustment. This is achieved by an iterative mechanism that combines deterministic and stochastic processes with geomorphological theory.

The end‐product is a matrix of high‐resolution altitude data that has been used as the terrain model for a vehicle simulation exercise.
Theoretical investigation of the time variation of drainage density
Authors: Kashiwaya Kenji
Published: February 2007

A theoretical equation was developed to express the time variation of drainage density in a basin or geomorphic surface: magnified image Di(t, T) is the drainage density at time T on the i‐th basin or geomorphic surface, which was formed at time t; β(τ) is a factor related to the erosional force causing the development of the rivers of the basin or surface at time τ; δi is the maximum drainage density; and Di is the initial drainage density on the i‐th geomorphic surface or basin. The equation is based on the assumption that the drainage density increases with time until it reaches a specific upper limit δi(t)), the maximum drainage density, which is related to certain physical properties of the basin. The equations for various dated basins or geomorphic surfaces can be combined into one modified equation if the same relative erosional forces have acted on those basins or surfaces (β(t) = β(t) and if the basins or surfaces have the same physical properties δi(t) = δi(t), (Di = D0). The application of this equation to coastal terraces and glacial tills shows that the model is compatible with observed drainage densities on various dated basins or surfaces.
Lake‐ice collapse trenches in Wisconsin, U.S.A.
Authors: Clayton Lee , Attig John W.
Published: February 2007

A series of trenches about a metre deep, 20 to 30 m wide, and as much as 2 km in length occurs in central Wisconsin, along the east shore of proglacial Lake Wisconsin. They are interpreted to be collapse trenches formed when shore ice melted after being buried beneath an expanding outwash plain.
Stability of waste spoils in an area strip mine—geological and geotechnical considerations
Authors: Okagbue C. O.
Published: February 2007

Results of investigations into the stability of coal mine spoil consisting of thick clay, saturated sand, and shale overburden in an areal strip mine are presented. Atterberg limits, particle size distributions, and compaction tests were performed to provide index characteristics of the materials. Unconsolidated undrained and consolidated undrained triaxial compression test results on 10·2 cm diameter samples of compacted shale and shale‐soil mixtures were used to investigate the short‐term and the long‐term conditions respectively of the spoil slope.

There is evidence that the failure envelope of mine spoil made up of shale or shale‐soil mixture is curved. However, stability analyses reveal that the use of strength parameters defined by a linear Mohr‐Coulomb envelope yields results that are comparable with those obtained when the non‐linear failure envelope is used, provided that such strength parameters are defined at the operating normal stress level on the failure surface.

The study illustrates a very good case of spoil instability resulting from very thick overburden soils of low strength and high water content. Results show that the key to achieving stability in such areas lies in an almost total segregation of the soils from the rocks.
A field experiment on the role of small scale wind gustiness in aeolian sand transport
Authors: Lee Jeffrey A.
Published: February 2007

Estimates of aeolian sand transport generally use an average wind speed to assess the wind energy. To determine if variation in small‐scale wind gustiness (on the order of several seconds duration) has a significant effect on sand movement, detailed field measurements were made of wind speed and transport rate. Average wind speed and several gust parameters were derived from the wind data. The results indicate that small‐scale gust information does not improve prediction of transport rates.
The fractal geometry of the soil—covered landscape
Authors: Culling W. E. H. , Datko Mark
Published: February 2007

The soil‐covered landscape surface can be idealized from two viewpoints. The intuitive view is of a smooth, absolutely continuous surface with continuous contour lines and measurable in integral dimensions. The alternative view emphasizes the roughness, a surface of little regularity and at the limit of no contours, the appropriate measure being that of fractional Hausdorff dimension. Regularity is a local property and both idealizations need to stop far short of the limit to avoid awkward consequences.

The dichotomy of viewpoint can be matched in the theory of Gaussian random fields. These, if they are smooth, are very smooth but if they are irregular they are highly irregular (erratic); there is no middle ground. This Belayev dichotomy is defined and both modes applied to the soil‐covered landscape. On the one hand, if the landscape is subject to a general diffusive type degradation or more generally a Davisian downwasting regime then the curvature of the landscape surface is progressively straightened and the distribution of gradient (increments) along a typical traverse will eventually adopt a Gaussian form. Then from the irregular viewpoint the surface is ultimately well represented by a fractional Brownian surface of low Hausdorff dimension (2·0 < dim < 2·3). The Hausdorff dimension is directly related to the entropy of the landscape and as degradation proceeds both quantities decrease in value.

On the other hand, if the surface is regarded as smooth and well represented by an absolutely continuous Gaussian field then the mean value of the number of upcrossings of a level or the extent of an excursion set will also be Gaussian. This analysis is restricted to one dimension; the number of times a profile curve crosses or the amount of time it spends above any given level.

Predictions from both viewpoints are substantially corroborated in a map analysis of 15 sites on varied terrains in Southern England and the map analysis checked against one based upon digital tape data for one of the sites.
Patterns of dissolved organic matter in subarctic peatlands
Authors: Moore T. R.
Published: February 2007

Samples of water from poor to very rich fens in the Schefferville region of subarctic Quebec revealed strong spatial and temporal variations in dissolved organic carbon (DOC), ranging from 2 to 40 mg 1−1. Concentrations of DOC tend to increase during the summer and decrease in the autumn, at most sites, which probably reflects increased plant tissue decomposition and higher rates of evapotranspiration. Principal components analysis revealed that DOC is strongly associated with Fe, NO−3‐N and NO−2‐N, but essentially independent of other chemical properties of the peat water, such as pH, Ca, Mg, K, P, and NH+4‐N. Based on observed concentrations of DOC and estimates of summer runoff (June to September), export of DOC from four peatlands ranges from 1·1 to 4·9 gCm−2, with the lowest values for peatlands underlain by dolomite. Molecular weight fractionation of four samples revealed significant differences in the dissolved organic matter (DOM), with the largest fractions (GF/C to 10 000 nmw) being dominant in the more acid samples. The ratio of absorbance at 400 and 600 nm wavelengths (E4:E6) has been used as a simple indicator of differences in DOM type, ranging from 3 to 15. There is a strong seasonal pattern of increasing E4:E6 ratio during the summer at many sites, though this ratio is essentially independent of other chemical properties of peat waters.
Dust storms and related phenomena measured from meteorological records in Australia
Authors: McTainsh G. H. , Pitblado J. R.
Published: February 2007

Using meteorological records (1957–1984) in Australia, formal definitions are proposed of four types of dust event: dust storms, blowing dust, dust whirls, and dust haze. Australia‐wide maps of the extent of these four dust event types are presented.
Absolute dating by uranium series disequilibrium of bones from the cave of La Chaise‐de‐Vouthon (Charente), France
Authors: Rae Angela M. , Ivanovich Miro , Schwarcz Henry P.
Published: February 2007

Animal bones, associated with Palaeolithic artefacts and skeletal remains of early hominids from the cave of La Chaise‐de‐Vouthon, have been dated using a new approach to uranium series dating of bone. Speleothem (cave calcite) interstratified with bone‐bearing sediments in the two chambers of Grotte Bourgeois‐Delaunay and Grotte Suard have previously been dated by the 230Th/234 U method. This provides a chronological control for the bone ages, for which the method is still at an experimental stage. A good agreement is shown in most cases between the calcite and the bone ages, showing the cave to have been a stable environment for the deposition of bone and the acquisition of uranium.
An evaluation of the use of size distributions of sediment in runoff as a measure of aggregate breakdown in the surface of a cracking clay soil under rain
Authors: Loch R. J. , Cleary J. L. , Thomas E. C. , Glanville S. F.
Published: February 2007

Two rainfall simulators of different plot sizes were used to test whether sediment in runoff could be used to measure aggregate breakdown in the surface of a cracking clay soil under rain. Plots were prepared with either levelled or furrowed surfaces. Samples of the soil surface under rain were taken from furrow ridges or levelled surfaces, and from areas of deposited sediment. These were compared with samples of sediment in runoff taken at the same times. On both furrowed and levelled plot surfaces and for both simulators, aggregate sizes were significantly finer in sediment in runoff than in samples of the soil surface taken with a spatula. No significant differences in surface aggregate size distributions were found between rainfall simulators, or between furrowed and levelled plot surfaces. Regression lines fitted to the data on size distributions of sediment or of aggregates in the soil surface showed no significant changes through time. The fitted lines showed sediment in runoff to be still significantly finer than aggregates in the soil surface after 50 min rain at 95 mm h−1, except for levelled plots under the rotating disc rainfall simulator, where extreme variability of data meant that even relatively large differences were not statistically significant. Size distributions of deposited sediment were similar to those of the surface of adjacent furrow ridges exposed to raindrop impact. This provides evidence that sampling the soil surface with a spatula gives a representative sample of the material available for rain‐flow transport.
A simulation model of wind erosion and sedimentation as a basis for management of a drift sand area in The Netherlands
Authors: Castel I. I. Y.
Published: February 2007

A simulation model of sand transport by wind is developed to predict the future development of an active aeolian drift sand area in the central part of The Netherlands. The model is based on Bagnolds' sand transport equation, adapted for influence of the vegetation. The results of the simulation indicate that only little sand transport can be expected under present‐day climatic conditions. Consequently the mobility of the dunes can only be guaranteed by special management measures like locally removing all vegetation.
Scale model simulations of the deposition of loess in Hilly Terrain
Authors: Goossens Dirk
Published: February 2007

The sedimentation of loess in a 40 km2 area on the northern border of the Belgian loess belt, is investigated by means of wind tunnel experiments. Loess deposition is simulated on a relief scale model for different wind directions. It appears that simulation with northeast winds produces a loess deposition pattern that coincides closely to the field pattern, which may be an indication that the loess‐bearing winds at the end of the Weichselian came from the northeast.

Loess deposition occurs preferably on windward slopes and not on leeward ones. The wind‐shadow concept, which is important in the case of sand deposition, may therefore not necessarily apply to fine materials such as fine silt and clay.
The use of ‘rock hard’‐sodium sulphate tablets for quickly determining preferential water flow routes in soils
Authors: Renshaw C. E.
Published: February 2007

Subsurface water flow routes have been inferred from gypsum sphere weight loss with minimal disturbance to soil structure or flow nets (Crabtree and Trudgill, 1984). This technique is limited by the relatively slow, fixed dissolution of gypsum. A solution is to use tablets consisting of Durham's ‘Rock Hard Water Putty’ and sodium sulphate. Laboratory tests indicate that tablet dissolution is controlled by the ratio of Rock Hard to sodium sulphate and is proportional to net throughflow yet independent of throughflow pH (between 3·0 and 9·0) and throughflow rate (at rates < 0·04 1 hr−1). The tablets are also mechanically stable, economical, and environmentally safe. Field study results using the Rock Hard‐sodium sulphate tablets are consistent with both the laboratory findings and the results of previous investigators.
Hydraulics of sediment‐laden sheetflow and the influence of simulated rainfall
Authors: Gut B. T. , Dickinson W. T. , Rudra R. P. , Wall G. J.
Published: February 2007

Laminar sheetflows, transporting sediment at their capacity rates, both with and without rainfall disturbance, were investigated. Values of flow depth and relative submergence were very small. In the flows without rainfall, measured velocities exceeded the predictions of the smooth‐surface, clear‐water laminar model by an average of 12 per cent. Reduced flow resistance due to high sediment concentrations may explain this result. Velocities in the rainfall‐disturbed flows were not significantly different from the predictions of the smooth‐surface, clear‐water model, and the velocity reduction due to rainfall was about 12 per cent. Although the uniformity of rainfall intensity under the single‐nozzle rainfall simulator is high, variation of momentum and kinetic energy fluxes along the 1‐5 m long flume was significant. The rainfall angle of incidence was highly correlated with deviations from expected flow velocities in the upper and lower sections of the flume.
Flood hydrology and geomorphic effectiveness in the central Appalachians
Authors: Miller Andrew J.
Published: February 2007

This paper compares hydrologic records and geomorphic effects of several historic floods in the central Appalachian region of the eastern United States. The most recent of these, occurring in November 1985, was the largest ever recorded in West Virginia, with peak discharges exceeding the estimated 500‐year discharge at eight of eleven stations in the South Branch Potomac River and Cheat River basins. Geomorphic effects on valley floors included some of the most severe and widespread floodplain erosion ever documented and exceeded anything seen in previous floods, even though comparable or greater rainfall and unit discharge have been observed several times in the region over the past 50 years. Comparison of discharge‐drainage area plots suggests that the intensity and spatial scale of the November 1985 flood were optimal for erosion of valley floors along the three forks of the South Branch Potomac River. However, when a larger geographic area is considered, rainfall totals and discharge‐drainage area relationships are insufficient predictors of geomorphic effectiveness for valley floors at drainage areas of 250 to 2500 km2.

Unit stream power was calculated for the largest recorded flood discharge at 46 stations in the central Appalachians. Maximum values of unit stream power are developed in bedrock canyons, where the boundaries are resistant to erosion and the flow cross‐section cannot adjust its width to accommodate extreme discharges. The largest value was 2570 W m−2; record discharge at most stations was associated with unit stream power values less than 300 W m−2, but more stations exceeded this value in the November 1985 flood than in the other floods that were analysed. Unit stream power at indirect discharge measurement sites near areas experiencing severe erosion in this and other central Appalachian floods generally exceeded 300 W m−2; reach‐average values of 200‐500 W m−2 were calculated for valleys where erosion damage was most widespread. Despite these general trends, unit stream power is not a reliable predictor of geomorphic change for individual sites. Improved understanding of flood impacts will require more detailed investigation of interactions between local site characteristics and patterns of flood flow over the valley floor.
Erosion processes and rates for gullies in granitic soils bathurst, new south wales, australia
Authors: Crouch R. J.
Published: February 2007

Soil movement rates from fluted gully sides in New South Wales were measured over three years by erosion pins and survey. Erosion rates varied considerably over short distances from 0 to 53 mm yr−1 with an average removal rate of 19‐8 mm yr−1.
Rates and mechanisms of discontinuous gully erosion in a red‐brown earth catchment, new south wales, australia
Authors: Crouch R. J.
Published: February 2007

Rainfall, runoff, sediment discharge, and gully expansion were measured for five years in a small (45 ha) catchment in central N.S.W. Sixty per cent of the sediment produced from this catchment originated from gully erosion. Gully head erosion was episodic depending on pipe development, cracking, and soil detachment during small runoff events which prepared the heads for rapid soil movement by the infrequent large event.
The flank margin model for dissolution cave development in carbonate platforms
Authors: Mylroie John E. , Carew James L.
Published: February 2007

The Bahama Islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level. The development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens. Lens position is controlled by sea level, which in stable carbonate platforms like the Bahamas is a function of glacioeustatic sea level still stands. Caves in the Bahamas that are currently subaerial must have developed during past higher sea levels. During the Late Quaternary, sea levels higher than present have been relatively short‐lived, and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation. The Bahama Islands are low‐lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level. Past high sea level events greatly reduced the exposed land area of the Bahama Islands, thus also limiting both the catchment for and size of freshwater lenses. Caves must be younger than the rock in which they are developed; most subaerial Bahamian caves are found in limestones that are less than 150000 years old. Development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism. The mixing of discharging freshwater with tide‐pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary. Bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes. Their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands.
A comment on ‘enhanced boulder weathering under late‐lying snow patches’ by ballantyne, C. K., Black, N. M., and Finlay, D. P.
Authors: McCarroll Danny
Published: February 2007

Ballantyne et al. (1989) compare Schmidt hammer results from late‐lying snowpatches with adjacent snow‐free control sites and claim that their results lend ‘strong and unequivocal support to the concept of enhanced weathering under late‐lying snowpatches’. However, the data presented from sites of different age but in the same area suggest that the difference in results between snowpatch and control sites is unlikely to reflect differences in degree of boulder surface weathering. Their statistical treatment of the data also lends exaggerated significance to rather small absolute differences and obscures between‐boulder variability within sites.
Palaeovelocity: A parsimonious proposal
Authors: Church Michael , Wolcott John , Maizels Judith
Published: February 2007

Using data collected in her field studies, Maizels (1983) compared five methods of calculating palaeovelocity from coarse gravel deposits. Her paper indicated that the five methods provide estimates which differ by up to 2 x. There are several errors in the published equations, however. Upon correction, the smallest estimate is within 3% per cent of the largest. Other published data sets suggest that the distinction among a variety of palaeovelocity equations is not worth pursuing in light of the amount of scatter in typical data. This paper recommends use of the Thompson and Campbell (1979) modification of the basic Keulegan flow resistance equation because it fits the data as well as any other, whilst covering a more comprehensive range of flow conditions. Problems of appropriate roughness length and entrainmnet function remain.
Observations of desert flood bores
Authors: Hassan Marwan A.
Published: February 2007

Flood bores have been measured in desert stream floods. The bores were steep and small pebbles were observed to be pushed ahead. Bore velocity changed downstream and was controlled by local channel geometry. In narrow reaches, the bore advanced at rates twice those of wide reaches. Mean bore velocity was about 50 per cent of that of mean flow at peak flood discharge. The surfaces of shallow bores were covered by air foams. This was not the case in deeper, faster examples.
Flood dynamics of a concrete‐lined, urban stream in Kansas City, Missouri
Authors: Vaughn D. M.
Published: February 2007

Brush Creek drains a 76·1 km2 watershed within urban Kansas City, Missouri and eastern Kansas. A concrete‐lined reach trending 6·1 km through the Plaza District of Kansas City, Missouri has been the focus for several major floods over the past ten years. Channel geometry, slope, and floodwater elevations were determined in the field for segments of the concrete‐lined section of Brush Creek for a flood event that occurred on September 18, 1986. Discharge was computed by indirect methods and compared to a value determined from a rating curve established by the Water Resources Division of the U.S.G.S. Boundary shear stress, unit stream power, and average velocity were also computed in order to establish a quantitative relationship between sediment distribution, volume, and size fractions; and flow dynamics operating throughout the channel during this event. Boundary shear stress ranged from 91‐96 Nm−2, stream power was 528‐557 Wm−2, while average velocity was 5‐8 ms−1. These values were sufficient to displace concrete slabs as large as 5 m long by 4·6 m wide by 0·23 m thick weighing an estimated 12 245 kg. As the channel was sediment free and unsecured prior to the flood, the distribution of deposits and subsequent channel scour provide valuable evidence for potentially hazardous sections of this urban stream.
The effect of hydrochemical factors on the dissolution rate of gypsiferous rocks in flowing water
Authors: Navas Ana
Published: February 2007

In order to investigate the rate of dissolution of gypsiferous rocks under natural conditions in streams of the Ebro river basin, 55 dissolution trials were carried out with spheres of alabastrine gypsum placed in flowing water. Experimental conditions involved flow velocities between 0·3 and 1·2 m s−1, electrical conductivities between 0·3 and 1·9 dS m−1, and the saturation indices of gypsum between −2·1 and −0·33. Mean values of dissolution rate obtained vary from 104 to 226 gm−2 h−1. This loss of mass corresponded to a volume of gypsum of between 393 and 853mmm−2 year−1. The factors most affecting the dissolution of gypsum are in descending order of importance: flow velocity > electrical conductivity > gypsum saturation.
A study of river channel pattern information recorded by grain size parameters of fluvial sediment
Authors: Jiongxin Xu
Published: February 2007

River channel pattern may be regarded as the outcome of streamflow, sediment load, and channel boundary conditions, as can the grain size distribution of bed material. It may therefore be expected that connections should exist between river channel pattern characteristics and the corresponding river bed material grain size parameters. Using data from some Chinese rivers, an attempt has been made to express these connections quantitatively by using statistical methods. The work demonstrates that the river's bed load can be related to the percentage of the traction subpopulation of the bed material shown by the probabilistic plot of grain size cumulative‐frequency curve. The study has also revealed some correlations between the bed material grain size parameters of rivers and their channel geometry such as channel width‐depth ratio and channel sinuosity. For instance, the higher the ratio of the traction to suspension subpopulation in bed material, the more sinuous, more shallow, and wider the river channel would be. Furthermore, a discrimination function has been given to distinguish between meandering and wandering braided rivers. If the existence of these relationships can be supported by data from more rivers in other regions, then by using them we can postdict palaeoriver channel geometry and its channel pattern character from fluvial sediment grain size parameters of the palaeoriver. This would open a new way to reconstruct the physicogeographical environment in which palaeorivers developed.
A stochastic distributed model of soil erosion by overland flow
Authors: Wright A. C. , Webster R.
Published: February 2007

A model has been built to simulate runoff and erosion on slopes of varying form with soil of varying hydraulic conductivity, porosity, storage capacity, and particle size distribution. The model is based on known physical laws and takes into account spatially dependent random variation in the initial conditions of the soil. The rainfall is similarly both random and autocorrelated in space.

Detailed results show how runoff is generated as a result of slow conductivity and high water table, how this leads to erosion, the degradation of the land surface, the capture of flow lines, and the development of networks of rills. The last accords well with results from laboratory experiments. Changing the initial conditions produces results that accord with intuition and reality.
Sediment yield and delivery in the blanket peat moorlands of the southern Pennines
Authors: Labadz J. C. , Burt T. P. , Potter A. W. R.
Published: February 2007

In contrast to much previous research on blanket peat moorland, which has concentrated upon studies of the form and causes of gully erosion, this paper attempts to investigate sediment transport and to estimate both short‐term and long‐term sediment yields in such terrain. The research was conducted on Wessenden Head Moor to the west of Huddersfield, Yorkshire, where automatic stream sampling continued over a period of two years. Use of corrected rating curves (Ferguson, 1988) provided a mean estimate of sediment yield over this period of 55 t km−2 yr−1.

In addition an estimate of longer‐term sediment yield was derived from four reservoir sediment surveys in the Wessenden Valley. Total yield was 203.69 t km−2 yr−1, including an organic fraction of 38.82 t km −2 yr−1. Stream sampling at three sites on Shiny Brook, including headwaters and the outflow to the reservoir, suggested that there is great temporal and spatial variability in mineral and organic inputs to the reservoirs. Although not excessive in gravimetric terms, the low density of peat means that there is a serious erosion problem. Estimates of erosion rates for the peat gully network at Shiny Brook appear to confirm earlier evidence concerning the relatively recent occurrence of this erosion, within the last two centuries.
Spatial and seasonal aspects of shoreline changes at Forcados Beach, Nigeria
Authors: Oyegun C. U.
Published: February 2007

The influence of the seasons of the year on beach changes is well documented in the literature. One generalization which has emerged is that beaches are ‘combed down’ in winter and ‘built up’ in summer. Some workers have disagreed with this dictum because field evidence does not necessarily support the assertion.

This study, located in the humid tropics, shows, with the aid of graduated pegs emplaced perpendicularly to the shoreline, that the magnitude and frequency of beach changes are greater in the wet, than in the dry season. Furthermore, there is a net loss of beach materials in the wet season and a net gain in the dry season, even though erosion and accretion occur throughout the year with no statistically significant difference in their magnitudes.

Erosion prevails at the northern half of the beach while accretion is dominant to the south. The upper and lower foreshore zones are more prone to changes than the mid‐tide level.
Comments on Allison's (1990) developments in a non‐destructive method of determining rock strength
Authors: Campbell Ian A.
Published: February 2007

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

The effect of peat on crust strength was investigated using ten soils with organic matter levels ranging from 1‐50 to 18‐23 per cent. As peat content increased, the crust strength reduced. This occurred in spite of the inability of peat to increase the stability of soil aggregates. Peat reduced crust strength by acting as a mulch on the soil surface, thereby reducing breakdown of soil aggregates. Peat also formed a source of weakness on the soil, reducing crust formation.

Using a factorial experiment involving a further seven soils with different levels of peat treatment, exposed to four rainfall durations and with two aggregate sizes, crust strength was described in terms of the direct effects and the interactions of these factors. Most of the crust strength values reduced with increasing peat content. For each soil, crust strength increased significantly with increasing rainfall duration. Crust strength was greater for the smaller aggregate size.

The most significant interactions affecting crust strength were between soil and aggregate size, rainfall duration and aggregate size, and soil and rainfall duration in that order. These interactions were used to describe the effect of organic matter in form of peat on crust strength. For each soil and aggregate size, polynomial relationships were established to relate crust strength to total kinetic energy of rainfall.
Time‐dependency of runoff velocity and erosion the effect of the initial soil moisture profile
Authors: Govers Gerard
Published: February 2007

The paper reports on experiments carried out to evaluate the effect of the initial soil moisture profile on temporal variations in runoff erosion rate. The moisture profile was varied by applying infrared heating to the soil sample surface over various time periods, while runoff erosivity was varied by varying the slope of the flume. The experiment confirms that dry loamy soils are very erodible: on a slope length of only 4.3 m long sediment concentrations are near transporting capacity in case of a dry soil sample. It appears that temporal variations in sediment concentrations can be well simulated using a simple relationship between runoff erosion resistance and initial soil moisture content, thereby implicitly assuming that the effect of initial moisture content is persistent over the whole duration of the experiment. The implications of these findings with respect to the modelling of sediment output from larger catchments and the design of experiments on rill erodibility are discussed.

The experiments also show that, under the present circumstances, mean velocities in the rills appear to be independent of slope. This finding may be of importance with respect to overland flow routing and deterministic erosion modelling.
A reappraisal of the significance of obstacle clasts in cluster bedform dispersal
Authors: De Jong Carmen
Published: February 2007

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

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

The seventy‐kilometre‐long Herbert Gorge of northeastern Australia preserves a record of past floods in slackwater deposits and palaeostage indicators. Step‐backwater modelling of water‐surface profiles indicates that discharges ranging from 11000 to 17000 m3s−1 have occurred six times in the gorge during the last 900 years. These flood reconstructions provide insight into the role of extreme flows in shaping bedrock channel morphology. In particular, the hydraulics of extreme flows can be related to boulder transport, and to the location of large boulder bars.

Large boulder bars occur throughout the Herbert Gorge, being best developed at loci of stream power minima along the inside of bends, at tributary junctions, and at obstructions in the channel caused by bedrock highs. Only the flows exceeding approximately 8000 m3 s−1 are competent to transport the boulders which constitute the bars. In the straight channel reaches, the boulder accumulations and bedrock highs have a fairly regular spacing which appears to be independent of lithologic or structural controls. The bars provide an efficient means of energy dissipation, and they are interpreted as a result of the inherent high turbulence of flow in a steep channel. The regular spacing of the bars, and their correspondence with the hydraulics of large flows, suggest that the bars and associated bedrock highs may represent a self‐regulating mechanism akin to the pool‐riffle sequence of alluvial channels. It may therefore be appropriate to view bedrock channels as deformable on the timescale of extreme discharges.
The relations between modulus of elasticity and temperature in the context of the experimental simulation of rock weathering by fire
Authors: Goudie A. S. , Allison R. J. , McLaren S. J.
Published: February 2007

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

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

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

The geomorphology of the central Coastal Range, a north‐south trending horst along the west coast of northern Calabria, is governed largely by major faults, fault scarps and the distribution of principal rock types, as well as by a variety of slope processes operative in a Mediterranean climate. Segments of the major rivers and streams have three principal orientations parallel to major faults in the study area: northwest right‐oblique slip faults (oldest); E‐W oblique slip faults; NE left‐oblique slip faults; and north‐south right oblique normal faults (youngest), all of which cut pre‐Tertiary metamorphic rocks, Mesozoic limestone, Miocene molasse and calcarenite. Small, underfit alluvial fans, composed chiefly of locally derived debris flow detritus, are present at the mouths of large, west‐flowing canyons, some of which reach eastward to the crest of the mountain range. Not only do the north‐south normal faults displace rocks and structures of all orientations, but they also make steep scarps in the small alluvial fans and in sediments of the coastal plain. Locally, some of the scarps are buried by recent debris flow deposits.

Incipient young rivers utilized the weaknesses along the major faults and cracks as avenues of erosion. Smaller streams and gullies generally flowed westward downflank of the north‐trending horst and incised, thereby, deep, V‐shaped canyons; some of them have captured older, SW‐flowing canyons. Locally, they were guided in other directions where they encountered faults or tectonic fractures.

The rocks present a varied resistance to erosion, depending upon the degree of cementation by groundwater salts, upon the orientation of the foliation, and upon the rocks themselves. Thus, mica schist with a relatively flat foliation forms nearly vertical sea cliffs, but the sea cliffs are more gentle where the foliation is steep or dips towards the sea. Therefore, downslope movements are facilitated by seaward slip on foliation, schistosity, bedding and fault surfaces, and are evinced especially by large and deep pre‐Holocene landslides (Sackung) in phyllite having areal dimensions up to 2 Km2. Other downslope processes include surficial creep and soil slip, particularly of highly fractured phyllite and schist, block sliding and rock falls.
Spatial variability of infiltration and related properties of tropical soils
Authors: Jetten V. G. , Th. Riezebos H. , Hoefsloot F. , Van Rossum J.
Published: February 2007

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

Runoff generated from large storm events, such as hurricanes, is expected to transport large quantities of suspended sediment. Observations of suspended‐sediment loads transported during Hurricane Hugo in the Lago Loìza (Lake Loiza) basin, Puerto Rico, indicate that loads were lower than expected. In the two main tributaries that enter Lago Loìza, Rio Grande de Loìza and Rio Gurabo, 99 600 tonnes of suspended sediment was transported by 58·2 × 106 m3 of runoff in a 48 h period.

The storm‐average suspended‐sediment concentration in the Río Grande de Loìza for Hurricane Hugo was 2290 mgl−1, the second lowest for the 12 storms that have been monitored at this site. In Río Gurabo the storm‐average suspended‐sediment concentration was 1420 mgl−1, the sixth lowest recorded out of 15 monitored storms. In Quebrada Salvatierra, a small tributary to Río Grande de Loìza, suspended‐sediment concentrations were as low as 33 mgl−1 during the peak runoff of 20 m3 s−1. Normally the suspended‐sediment concentrations at this discharge are 3000 mgl−1.

Hurricane force winds seem to be the most important factor contributing to the lower than expected suspended‐sediment loads in the Lago Loìza basin. The high winds caused vegetation and debris to be dislodged and displaced. Debris accumulated on hillslopes and in small channels, blocked bridges and formed debris dams. These dams caused local backwater effects that reduced stream velocities and decreased suspended‐sediment loads.