the measurement and modelling of rill erosion at angle of repose slopes in mine spoil the process of rill erosion causes significant amounts of sediment to be moved in both undisturbed and disturbed environments and can be a significant issue for agriculture as well as mining lands rills also often develop very quickly from a single rainfall event to a season and can develop into gullies if sufficient runoff is available to continue their development this study examines the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogeneous mine spoil on an angle of repose slope it also examines the ability of the siberia erosion model to simulate the rill s spatial and temporal behaviour while there has been considerable work done examining rill erosion on rehabilitated mine sites and agricultural fields little work has been done to examine rill development at angle of repose sites results show that while the overall hillslope morphology was captured by the laser scanner with the morphology of the rills being broadly captured the characteristics of the rills were not well defined the digital elevation model created by the laser scanner failed to capture the rill thalwegs and tops of the banks therefore delineating a series of ill defined longitudinal downslope depressions these results demonstrate that an even greater density of points is needed to capture sufficient rill morphology nevertheless siberia simulations of the hillslope demonstrated that the model was able to capture rill behaviour in both space and time when correct model parameters were used this result provides confidence in the siberia model and its parameterization the results demonstrate the sensitivity of the model to changes in parameters and the importance of the calibration process copyright 2007 john wiley sons ltd

on the nonuniqueness of sediment yield at the catchment scale the effects of soil antecedent conditions and surface shield the understanding of reasons leading to nonuniqueness of soil erosion susceptibility is still inadequate yet indispensable for establishing general relations between runoff volume and sediment yield to obtain relevant insights we performed a series of numerical simulations with a detailed hydrodynamic model using synthetic storms of varying intensity duration and lag time between events as representations of different hydrologic response conditions in a zero order catchment the design targeted to generate surface flow and perturb soil substrate by a first rainfall event creating a set of initial conditions in terms of flow and deposited sediment prior to the onset of a subsequent rainfall event due to the differential effect of re detachment and re entrainment processes on soil particles of varying sizes the deposited sediment mass formed shielding layer one of the essential results is that unless the initial condition of flow and sediment is identical the same volume of runoff can generate different total sediment yields and their variation can reach up to 200 the effect is attributed to two major conflicting effects exerted by the deposited initialization soil antecedent condition sediment mass erosion enhancement because of supply of highly erodible sediment and erosion impediment because of constrain on the availability of lighter particles by heavier sediment consistently with this inference long term simulations with continuous rainfall show that a peculiar feature of sediment yield series is the existence of maximum before the steady state is reached the two characteristic time scales the time to peak and the time to steady state separate three characteristic periods that correspond to flow limited source limited and steady state regimes these time scales are log linearly and negatively related to the spatially averaged shields parameter the smaller the rainfall input and the heavier a given particle is the larger the two scales are the results provide insights on how the existence of shield operates on erosion processes possibly implying that accurate short term predictions of geomorphic events from headwater areas may never become a tractable problem the latter would require a detailed spatial characterization of particle size distribution prior to precipitation events

mapping and quantifying the clay aggregate microporosity in medium to coarse grained sandstones using the 14c pmma method abstract microporous aggregates of kaolin minerals and illite are common products filling the intergranular volume igv of deeply buried sandstones using bsei backscattered electron imaging a full analysis of igv is difficult and time consuming since it necessitates a two step process at the scales of 1 macroporosity between the detrital grains and 2 microporosity within the clay aggregates the 14c pmma method permits the mapping and quantification of the connected porosity in sandstone core samples across scales this method is based on the complete impregnation of the connected porosity by 14c labeled methylmethacrylate mma monomer and its subsequent in situ polymerization imaging the spatial distribution of the radioactive tracer within a section of an impregnated sample allows an integrated analysis of igv from the core scale to the nanometer scale this technique is illustrated through analysis of the clay cement of a medium to coarse grained sandstone from the athabasca basin canada the measured connected porosity distributions of kaolin mineral aggregates average porosity 42 and illite fillings average porosity 70 are in accordance with gaussian distributions this method also permits quantification of the relative volumetric amounts of the both illite and kaolin aggregate

effect of embedded rock fragments on slope soil erosion during rainfall events under simulated laboratory conditions abstract quantifying the role of embedded rock fragments in soil water processes on a slope is crucial for the application of rock fragments in soil and water conservation practice in this study a laboratory runoff and erosion experiment was conducted in the soils embedded with rock fragments including five rock fragment contents rc of 0 0 1 0 2 0 3 and 0 4 kg kg 1 in a metal flume under three slopes 5 10 and 15 results showed that the mean steady infiltration rate in the soil without rock fragment null was lower than that in the soils containing rock fragments low rock fragment contents of 0 1 0 2 kg kg 1 and high rock fragment contents of 0 3 0 4 kg kg 1 labelled as low and high respectively as slope gradient 5 but was higher than the latter two soils as slope gradients 10 and 15 initial infiltration rate significantly increased with rc p

relations between interrill erosion processes and sediment particle size distribution in a semiarid mediterranean area of se of spain abstract erosion and sediment characteristics were measured using simulated rainfall on two cultivated soils of contrasting lithology quaternary calcareous colluvium and tertiary marls in a semiarid mediterranean area of se spain two rainfall intensities high 56 0 2 4 mm h 1 and medium 31 4 1 4 mm h 1 were used in order to know the mechanisms involved in each selected condition for each simulated event runoff and sediment were sampled at 1 min intervals on a 1 m wide by 2 m long erosion plot the erosion rate was calculated as the total amount of soil lost divided by the time period of the test the duration of the test was that needed to reach steady state runoff an average time of 24 5 min for quaternary calcareous colluvium and 17 7 min for tertiary marls the size distribution of the transported sediment in the field effective size distribution was compared with equivalent measurements of the same samples after chemical and mechanical dispersion ultimate size distribution to investigate the detachment and transport mechanisms involved in sediment mobilisation the results showed that the soil type determined the hydrological response regardless of the rainfall intensity the erosional response was however determined by the rainfall and soil surface characteristics in quaternary calcareous colluvial soils the predominant erosion process depended on the rainfall intensity with a prevailing detachment limited condition in high intensity events and prevailing transport limited conditions in those events of medium intensity these differences in the main erosion processes were reflected in the size of the transported material and in the change in sediment size within the storm thus a time dependent size distribution of the eroded material decreasing coarse fractions and increasing fine fractions with runoff time was observed for high intensity events in medium intensity events on the other hand the time independent size distribution of the eroded material indicated transport limited erosion due to the rapid surface crusting on the tertiary marl soil no differences in the main erosion processes or in the sediment size distribution occurred for the different rainfall intensities tested the erosion of marl soils was determined mainly by the limited quantity of available sediment the effective size of material was a more sensitive parameter than the ultimate size of the sediment to study the way in which the sediment was transported

rainfall runoff properties of tephra simulated effects of grain size and antecedent rainfall abstract rain triggered lahars rtls are a significant and often persistent secondary volcanic hazard at many volcanoes around the world rainfall on unconsolidated volcaniclastic material is the primary initiation mechanism of rtls the resultant flows have the potential for large runout distances 100 km and present a substantial hazard to downstream infrastructure and communities rtls are frequently anticipated in the aftermath of eruptions but the pattern timing and scale of lahars varies on an eruption by eruption and even catchment by catchment basis this variability is driven by a set of local factors including the grain size distribution thickness stratigraphy and spatial distribution of source material in addition to topography vegetation coverage and rainfall conditions these factors are often qualitatively discussed in rtl studies based on post eruption lahar observations or instrumental detections conversely this study aims to move towards a quantitative assessment of rtl hazard in order to facilitate rtl predictions and forecasts based on constrained rainfall grain size distribution and isopach data calibrated simulated rainfall and laboratory constructed tephra beds are used within a repeatable experimental set up to isolate the effects of individual parameters and to examine runoff and infiltration processes from analogous rtl source conditions laboratory experiments show that increased antecedent rainfall and finer grained surface tephra individually increase runoff rates and decrease runoff lag times while a combination of these factors produces a compound effect these impacts are driven by increased residual moisture content and decreased permeability due to surface sealing and have previously been inferred from downstream observations of lahars but not identified at source water and sediment transport mechanisms differ based on surface grain size distribution a fine grained surface layer displayed airborne remobilisation accretionary pellet formation rapid surface sealing and infiltration excess overland flow generation whilst a coarse surface layer demonstrated exclusively rainsplash driven particle detachment throughout the rainfall simulations this experimental protocol has the potential to quantitatively examine the effects of a variety of individual parameters in rtl initiation under controlled conditions

the entrainment of bubbles by drop impacts various processes are described by which a drop of water impacting on a water surface may entrain a bubble there are i irregular entrainment in which the complex details of a splash entrain bubbles ii regular entrainment in which the crater formed by the drop impact develops in a predictable way to form a single bubble iii entrainment of large bubbles in which most of the volume of the crater is trapped as a bubble and iv mesler entrainment in which many very small bubbles are trapped in the very early stages of the impact process possibly between wave crests of capillary waves which develop on the drop and on the water surface this last process is different from the preceding three in that it produces very little sound all of the processes except the third one have been described individually in the literature here we present them together for comparison the regular entrainment process is discussed in the greatest detail and some new experimental results are presented which concern the size and nature of the entrained bubbles the significance of the regular and irregular entrainment processes to the generation of underwater sound by rain is discussed

experimental investigation of morphological characteristics of rill evolution on loess slope abstract the development of rill is the result of a complex interaction of soil properties with high spatial and temporal variability the rill morphology may act as a determinant as well as a stochastically driven process the description of their complex morphology requires geostatistics and nonlinear theories a study of the morphological characteristics of rill evolution was performed via indoor soil pan rainfall simulations experiments were run with loessial soil bulk density of 1 25 g cm 3 under a rainfall intensity of 90 mm h with a 20 slope gradient a detailed scan of the slope topographic analysis and statistical analyses were the main methods utilized in the study statistical analyses showed that characteristic parameters exhibited differences in the expression of the dynamic change of soil loss according to the comparison of quantitative methods we found that the fractal dimension can reflect the complexity of rill network but it is not able to reflect the dynamic changes of the erosion process perfectly in contrast geomorphologic comentropy is sensitive to the dynamic changes of soil erosion intensity and its variation can reflect the dynamic changes of erosion perfectly the topological parameters can reflect the degree of stability in the rill network structure but it is not suitable for reflecting the dynamic changes of erosion intensity the geomorphologic comentropy was evaluated as the most appropriate characterization parameter for the rill morphology description

modeling overland flow and soil erosion on nonuniform hillslopes a finite volume scheme 1 this paper presents a finite volume scheme for coupling the saint venant equations with the multiparticle size class hairsine rose soil erosion model a well balanced monotone upstream centered schemes for conservation laws hancock muscl hancock method is proposed to minimize spurious waves in the solution arising from an imbalance between the flux gradient and the source terms in the momentum equation additional criteria for numerical stability when dealing with very shallow flows and wet dry fronts are highlighted numerical tests show that the scheme performs well in terms of accuracy and robustness for both the water and sediment transport equations the proposed scheme facilitates the application of the hairsine rose model to complex scenarios of soil erosion with concurrent interacting erosion processes over a nonuniform topography

prediction of engineering properties of a selected litharenite sandstone from its petrographic characteristics using correlation and multivariate statistical techniques abstract the determination of rock strength and elastic parameters in laboratory tests requires high quality core samples which are not always available from fractured and or weathered strata the purpose of this study is to apply a correlation analysis in conjunction with multivariate statistical techniques to petrographical and laboratory geomechanical data for the investigation of correlations that exist between these properties of a selected sandstone and to suggest inexpensive predictive models in a preliminary investigation sandstone samples from a borehole drilled for a preliminary investigation of a shaft location at a hard coal region black sea turkey were tested to determine uniaxial compressive strength elastic parameters unit weight porosity point load index and quality index secondly fifteen selected samples were subjected to petrographic examination which included fifteen parameters and modal analysis based on the statistical analysis results polynomial prediction equations were developed for estimating mechanical properties from petrographic characteristics and index properties the study revealed that the influence of textural characteristics appear to be more important than mineralogy for predicting engineering properties it is also noted that type of contacts grain shape and size rock fragments with packing density and proximity are the petrographic characteristics which have significant influence upon engineering properties of the sandstones results of this study were presented in the form of correlation coefficient models and predictive models

sandstone reservoir quality prediction the state of the art joanna ajdukiewicz joined exxon production research company in 1980 she was reservoir quality assessment and prediction team lead there from 1991 to 1995 and at imperial oil research centre in calgary from 1995 to 1997 subsequently she has worked a variety of exploration company assignments in the north sea gulf of mexico and middle east her current interests are in predicting the distribution of early diagenetic controls on deep reservoir quality rob lander develops diagenetic models for geocosm llc he obtained his ph d in geology from the university of illinois in 1991 was a research geologist at exxon production research from 1991 to 1993 and worked for rogaland research and geologica as from 1993 to 2000 he is also a research fellow at the bureau of economic geology to guess is cheap to guess wrongly is expensive chinese proverb reservoir quality predictive models will be a useful element of risk analysis until remote sensing tools are invented that accurately measure effective porosity and permeability ahead of the bit this issue of the aapg bulletin highlights recent advances in a new generation of reservoir quality models that have successfully predicted porosity and permeability in diverse siliclastic reservoirs under many different burial conditions most previous attempts at predrill reservoir quality prediction have relied on empirical correlations or on first principle geochemical simulations that incorporate laboratory derived input parameters wood and byrnes 1994 the new reservoir quality models differ from previous approaches in that although incorporating theory inspired algorithms they include terms with values that are explicitly designed to be calibrated by and tested against data sets of high quality petrographic analyses that are linked to thermal and effective stress histories petrographic observations therefore provide essential constraints in these models on the types timing and rates of key geologic processes affecting sandstone pore systems this approach avoids the pitfalls inherent

reservoir quality and rock properties modeling triassic and jurassic sandstones greater shearwater area uk central north sea abstract the complex burial and diagenetic histories of the jurassic fulmar and triassic skagerrak sandstones in the uk central north sea present significant challenges with regard to reservoir quality and rock property prediction commercial reservoir quality is retained despite deep burial and associated high temperatures and pressures shallow marine fulmar sands are normally compacted mean igv 26 3 yet have porosities of 21 33 porosity was preserved through inhibition of quartz cementation by clay and microquartz coatings and enhanced by dissolution of framework grains 5 skagerrak fluvial sands are more compacted mean igv 23 2 exhibit minor feldspar dissolution we modeled reservoir quality evolution using the forward diagenetic model touchstone which simulates porosity loss due to compaction and quartz cementation quantitative petrographic analyses and burial history data were used to calibrate touchstone model parameters the results were applied to deeper prospects for pre drill prediction of porosity and permeability in parallel petrophysical data were used to characterize the elastic properties of the sandstones to provide a basis for quantitative seismic forward modeling experimental data and core calibrated petrophysical results reflecting variable in situ fluids and saturations were used to build an elastic properties model the model is robust and was used to generate fluid filled sandstone properties incorporating touchstone results for prospect specific seismic attribute modeling well results from exploration wells are in good agreement with pre drill touchstone and elastic properties model predictions

a field investigation into the effects of progressive rainfall induced soil seal and crust development on runoff and erosion rates the impact of surface cover abstract surface crusts and seals can form from a variety of processes both physical and biological and have the potential to alter runoff and erosion especially in regions with low vegetation covers despite the obvious links between seals and crusts these features have rarely been considered together this study uses rainfall simulation experiments to investigate interrill soil crust and seal development in response to structural or raindrop impact induced and depositional or runoff induced processes on a semiarid piedmont in southern new mexico usa which has undergone substantive vegetation change replacement of grasses by shrubs over the last 100 years the study design incorporates six double paired runoff plots divided into four subplots each of which was exposed to three rainfall simulation events crust development on these plots was assessed using penetration resistance measurements while seal development was assessed using runoff coefficients the penetration resistance data indicate that subplots directly exposed to raindrop impacts uncovered plots have crusts that are 40 stronger than those positioned beneath a mesh cover covered plots that intercepts the kinetic energy of the rainfall the crusts exposed to raindrop impacts increased in strength following each simulation whereas the crusts on the covered surfaces reached a plateau after two events runoff data indicate that seal development does not directly mirror crust formation runoff coefficients increased after each rainfall simulation event but were not significantly different between the covered and uncovered plots rather the presence of stone lags or litter on the soil surface influenced the relation between runoff and seal development sediment yields from uncovered surfaces exceeded those from covered surfaces indicating that raindrop impacts contribute to the delivery of sediment into flows the results of this study indicate that the loss of vegetation cover on the piedmont has increased the extent of surface crust and seal development but that those crusts may be playing an important role in mitigating erosion

effect of raindrop splash and transversal width on soil erosion laboratory flume experiments and analysis with the hairsine rose model the parameter consistency of the one dimensional hairsine rose h r erosion model under conditions of significant rainfall splash was examined to account for the splash characteristic length scale and its interaction with the transverse erosion width experiments were carried out using erosion flumes of the same length 6 m but different widths with sediment concentrations measured at the flume exits total sediment concentration and the concentration of seven size fractions 1000 m were measured at high rainfall intensity 60 mm h and with a gentle slope 2 2 the conditions employed ensured that erosion was predominantly precipitation driven the experimental results showed that raindrop splash affected particularly the sediment breakthrough from the wider flumes flumes 1 and 2 1 and 0 5 m wide respectively however the raindrop splash effect was less significant in observed sediment concentrations from the narrower flumes flumes 3 and 4 both 0 25 m wide for these flumes the detached sediment was affected by the transversal width of the flume in that an amount of detached sediment adhered to the barriers instead of being removed in the overland flow the one dimensional h r model was fitted to the experimental results and good agreement was found in particular for the finer size classes the data for the coarser grain sizes were more scattered suggesting sediment motion by mechanisms other than as a suspension in the overland flow e g rolling along the soil surface the optimized parameters indicated that the shield layers where the shield consists of redeposited eroded sediment of the wider flumes 1 and 2 developed within 5 10 min from the start of the experiment whereas in the narrower flumes 3 and 4 they never fully developed the optimized detachment rates were consistent with previous findings but the estimated thickness of the deposited layer was too small to provide complete protection of the original soil against raindrop detachment indicating that the shield was not uniform the experimental design allowed us to investigate directly the effect of flow non uniformity on soil erosion by inclusion of an offset drainage point in flume 4 the observations taken during and after the experiment as well as surface elevation data confirmed the noticeable impact of non uniform flow on the erosion process

effects of rock fragments incorporated in the soil matrix on concentrated flow hydraulics and erosion rock fragments can act as a controlling factor for erosional rates and patterns in the landscape thus the objective of this study is to better understand the role that rock fragments incorporated into the soil matrix play in concentrated flow hydraulics and erosion laboratory flume experiments were conducted with soil material that was mixed with rock fragments rock fragment content ranged from 0 to 40 per cent by volume other treatments were slope 7 and 14 and flow discharge 5 7 and 11 4 l min 1 an increase in rock fragment content resulted in lower sediment yield and broader width of flow rock fragment cover at the soil surface i e surface armour increased with time in experiments with rock fragments flow energy was largely dissipated by rock fragment cover for more turbulent flow conditions when roughness elements were submerged in the flow hydraulic roughness was similar for different rock fragment contents in experiments with few or no rock fragments a narrow rill incised flow energy was dissipated by headcuts total sediment yield was much larger than for experiments with rock fragments in the soil adding just a small number of rock fragments in the soil matrix resulted in a significant reduction of sediment yield copyright 2007 john wiley sons ltd

laboratory experimental study of soil crusting relation between aggregate breakdown mechanisms and crust stucture abstract crusts formation on cores of air dry and prewetted aggregates was studied using a laboratory rainfall simulator samples were taken out during the experiment in order to study changes in water content and aggregates size distribution inside the crust and under the crust pore space geometry of the crusts is described using light optical microscopy and mercury porosimetry in the case of air dry aggregates aggregates become micro cracked macropores at the surface are quickly closed and ponding occurs rapidly with prewetted aggregates microcracking does not occur and only a very slow abrasion of the aggregates is observed porosity remains high and no ponding excess occurs the discussion of these results shows that it is the way of the wetting and the initial water content which determine the breakdown mechanism and therefore the behaviour of the aggregates submitted to rainfall

tracing sediment movement in interrill overland flow on a semi arid grassland hillslope using magnetic susceptibility experiments were undertaken to determine the feasibility of tracing sediment movement in interrill overland flow crushed magnetite was introduced as a source line 10 cm wide by 8 m long on a runoff plot 18 m wide by 29 m long located in southern arizona initial magnetic susceptibilities along this source line and along three transects located 0 25 2 95 and 5 m downslope of the source line were measured movement of the magnetite in response to three rainfall simulation experiments was monitored during the first two experiments overland flow discharge was sampled at miniature flumes located along two cross sections on the plot downslope of the source line and at a supercritical flume at the plot outlet magnetic susceptibilities along the source line and transects were measured after all three experiments results show that the magnetite moves very early in the experiments and that it reaches one of the flumes 2 m downslope of the source line in 3 min most of the tracer moves a very short distance 29 7 per cent is deposited within 25 cm of the source line and only 2 2 per cent is deposited 2 95 m away the deposition rate appears to decrease exponentially away from the source line very little magnetite is recorded in the flow through the miniature flumes in general it makes up less than 1 per cent of the total sediment load no temporal pattern in these percentages is observed magnetite appears to be an effective tracer of sediment movement in interrill overland flow though its higher density than natural soil may affect its detachment and transport

soil erodibility and processes of water erosion on hillslope abstract the importance of the inherent resistance of soil to erosional processes or soil erodibility is generally recognized in hillslope and fluvial geomorphology but the full implications of the dynamic soil properties that affect erodibility are seldom considered in canada a wide spectrum of soils and erosional processes has stimulated much research related to soil erodibility this paper aims to place this work in an international framework of research on water erosion processes and to identify critical emerging research questions it focuses particularly on experimental research on rill and interrill erosion using simulated rainfall and recently developed techniques that provide data at appropriate temporal and spatial scales essential for event based soil erosion prediction results show that many components of erosional response such as partitioning between rill and interrill or surface and subsurface processes threshold hydraulic conditions for rill incision rill network configuration and hillslope sediment delivery are strongly affected by spatially variable and temporally dynamic soil properties this agrees with other recent studies but contrasts markedly with long held concepts of soil credibility as an essentially constant property for any soil type properties that determine erodibility such as soil aggregation and shear strength are strongly affected by climatic factors such as rainfall distribution and frost action and show systematic seasonal variation they can also change significantly over much shorter time scales with subtle variations in soil water conditions organic composition microbiological activity age hardening and the structural effect of applied stresses property changes between and during rainstorms can dramatically affect the incidence and intensity of rill and interrill erosion and therefore both short and long term hillslope erosional response similar property changes linked to climatic conditions may also significantly influence the stability and resilience of plant species and vegetation systems full understanding of such changes is essential if current event based soil erosion models such as wepp and eurosem are to attain their full potential predictive precision the complexity of the interacting processes involved may however ultimately make stochastic modelling more effective than physically based modelling in predicting hillslope response to erodibility dynamics

rainwash experiments on the erodibility of loose sediments laboratory experiments using simulated rainfall splash boards and trays were conducted in order to obtain information on the erodibility of loose sediments as a time dependent phenomenon in all ten different sediments ranging from silt d50 24 m to coarse sand d50 593 m were studied the effect of three different initial states of the sediments namely the air dry state t1 the field capacity state t2 and the desiccated state t3 on the erodibility was also assessed variations in detachability during a rain erosion experiment can be explained by change in water content including liquefaction and the development of a water layer on the surface cohesion and granulometric composition of the top layer the coarsest sandy sediments almost always yielded the highest detachability when starting from an initial field capacity state t2 for the finer sediments the highest detachability was found for the homogeneous and not yet compacted initial air dry state t1 the effect of the initial desiccated state t3 on the detachability of the finer sediments was also a function of the rainfall duration the relationship between detachability and median grain size of the sediments was very similar to the relation between grain size and the susceptibility to runoff and wind erosion established by other investigators the highest detachability was found for a fine very well sorted sand with a median grain size of 96 m

effects of rock fragments on soil erosion by water at different spatial scales a review this paper reviews the various effects of rock fragments on soil erosion by water since these effects are scale dependent they are investigated at three different nested spatial scales the microplot 4 10 6 100m2 the mesoplot 10 2 102 m2 and the macroplot 101 104 m2 for each scale the corresponding process mechanisms are discussed particular attention is paid to the effects of rock fragment cover on the intensity of soil erosion processes at the mesoplot scale i e on interrill areas rock fragments at the soil surface can have negative as well as positive effects on sediment yield these ambivalent effects are conditioned by the type of fine earth porosity soil surface slope vertical position and size of rock fragments and by the occurrence of horseshoe vortex erosion at the microplot scale i e the soil surface area which is covered by a single rock fragment and at the macroplot scale i e upland areas where both interrill and rill erosion takes place rock fragments at the soil surface have a negative effect on sediment yield in these two scales rock fragments can thus be considered as natural soil surface stabilizers at the macroplot scale the mean decrease of relative interrill and rill sediment yield with rock fragment cover can be expressed by an exponential decay function the scatter of the data indicates that a given rock fragment cover can have different efficiencies in reducing interrill and rill sediment yield depending on the varying intensities of the hydrological and erosion subprocesses these findings have implications for erosion modelling and soil conservation

use of palm mat geotextiles for rainsplash erosion control abstract soil detachment by raindrop action rainsplash erosion is a very important subprocess of erosion by water it is a particular problem in the uk as most soils are sandy or loamy sand in texture and lands have gentle to medium slope however few studies report potential rainsplash erosion control options under field conditions hence the utilization of palm mat geotextiles as a rainsplash erosion control technique was investigated at hilton east shropshire u k 52 33 5 7 n 2 19 18 3 w geotextile mats constructed from borassus aethiopum borassus palm of west africa and mauritia flexuosa buriti palm of south america leaves are termed borassus mats and buriti mats respectively two year field experiments were conducted at hilton to study the effects of emplacing borassus and buriti mats on rainsplash erosion of a loamy sand soil two sets 12 plots each of experiments were established to study the effects of these mats on splash height and splash erosion splash height needs to be known to assess the transport mechanism of major soil fraction and its constituents on sloping land by rainsplash in both sets six randomly selected plots were covered with mats and the rest were bare results during 22 01 2007 23 01 2009 total precipitation 1731 5 mm show that borassus mat covered plots had 89 p 2 than bare plots 27 02 kg m 2 comparatively mean splash height from borassus mat covered plots 0 12 m was significantly p p 0 05 effect in rainsplash erosion control during that period although plots with buriti mats significantly p 2 and thickness 10 mm respectively compared with borassus mats were not effective in rainsplash erosion control both mats did not significantly p 0 05 improve selected soil properties i e soil organic matter particle size distribution aggregate stability and total soil carbon as soil organic matter som input from mat decomposition was much less than total som content however the changes in fine and medium sand contents after 2 years in the borassus covered plots were significantly p n 6 related to the total rainsplash erosion during 2007 2009 emplacement of borassus and buriti mats on bare soils did not decrease som contents after 2 years indicating that improvements in some soil properties might occur over longer durations after 10 months buriti mats lost 70 of their initial weight p c decreased drastically p c to the initial condition although mass per unit area decreased by 20 p

size fractions resulting from an aggregate stability test interrill detachment and transport aggregate stability is a soil characteristic often linked with soil erodibility but this relationship is generally empirical the aggregate size distribution is a recognized factor in uencing crust characteristics and transport during interrill erosion events this parameter was used in this work in order to improve the understanding of the relationship between aggregate stability and erodibility a second aspect of this study was to investigate the size selectivity of interrill erosion processes i e breakdown detachment by splash and transport by overland ow this experimental work was based on rainfall simulations and aggregate stability tests which were performed using two different soils a clay loam slightly sensitive to erosion and a more susceptible silt loam size distributions of soil fragments either produced by aggregate stability tests or detached by splash or transported by runoff were measured by both wet sieving and laser diffraction sizer analysis the clay loam is particularly stable and has coarse breakdown products with mean weight diameters larger than 1400 m aggregate breakdown is more ef cient for the silt loam and leads to ner soil fragments with mean weight diameters between 229 and 380 mm for the more stable soil the clay loam splash rate and sediment concentration are respectively two and six times lower and less time variable than for the silt loam for the two soils detachment by splash and short distance transport are size selective interrill erosion processes this selectivity leads to the enrichment of silt and clay fractions of the eroded aggregates in comparison with the breakdown products the low erodibility of the more stable soil is in accordance with results of aggregate stability tests copyright 2004 john wiley sons ltd

underwater noise due to rain open ocean measurements measurements of underwater noise produced by rain over the open ocean were made at a site some 1 km off ucluelet on the west coast of vancouver island british columbia canada a hydrophone was placed near the bottom in 55 m of water in the path of the prevailing eastward moving pacific storm systems the spectral noise level dependence on rain rate between zero and 20 mm h was determined for various frequencies and sea states a straight line least squares fit to the sample values of spectral level plotted against the log of rain rate was found to best represent the relationship representative rain noise spectra for various rain rates and sea states were derived

critical shear stress for erosion of cohesive soils subjected to temperatures typical of wildfires received 26 february 2004 revised 15 september 2004 accepted 5 november 2004 published 22 january 2005 1 increased erosion is a well known response after wildfire to predict and to model erosion on a landscape scale requires knowledge of the critical shear stress for the initiation of motion of soil particles as this soil property is temperature dependent a quantitative relation between critical shear stress and the temperatures to which the soils have been subjected during a wildfire is required in this study the critical shear stress was measured in a recirculating flume using samples of forest soil exposed to different temperatures 40 550 c for 1 hour results were obtained for four replicates of soils derived from three different types of parent material granitic bedrock sandstone and volcanic tuffs in general the relation between critical shear stress and temperature can be separated into three different temperature ranges 275 c which are similar to those for water repellency and temperature the critical shear stress was most variable 1 0 2 0 n m 2 for temperatures 2 0 n m 2 between 175 and 275 c and was essentially constant 0 5 0 8 n m 2 f or temperatures 275 c the changes in critical shear stress with temperature were found to be essentially independent of soil type and suggest that erosion processes in burned watersheds can be modeled more simply than erosion processes in unburned watersheds wildfire reduces the spatial variability of soil erodibility associated with unburned watersheds by eliminating the complex effects of vegetation in protecting soils and by reducing the range of cohesion associated with different types of unburned soils our results indicate that modeling the erosional response after a wildfire depends primarily on determining the spatial distribution of the maximum soil temperatures that were reached during the wildfire

work done by splash laboratory experiments 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

mineral soil surface crusts and wind and water erosion the rst few millimetres of soil largely control the soil s response to the eroding forces of wind and water the tendency of soils to form surface seals and crusts in uences the processes of wind and water erosion differently for wind dry particle size distribution and particle organization determine the shear strength and threshold wind velocity necessary to initiate particle movement in loams and clay loams seals and crusts decrease roughness but increase surface soil strength generally decreasing wind erosion conversely in sand and sandy loams loose erodible sandy material may either deposit on the crust and is subject to erosion or it may disrupt the crust accelerating the erosion process for water erosion particle size distribution and structure determine in ltration rate time to ponding and energy required for soil particle detachment seals and crusts tend to decrease in ltration rate and time to ponding thus increasing overland ow and soil erosion this paper brie y reviews how permanent and time dependent soil properties in uence surface seals and crusts and how these affect soil erosion by wind and water the tendency of a soil to form a seal and crust depends to some degree on the time dependent property of soil structural stability which tends to increase with increasing clay content and smectitic mineralogy which are permanent properties these permanent properties and their effect on structure are variable depending on dynamic properties of exchangeable sodium percentage and soil solution electrical conductivity antecedent water content prior to irrigation or rainfall rate of wetting before an erosive event and aging the time between wetting and an erosive event greatly in uence the response of soil structure to raindrop impact the effect of these dynamic processes is further in uenced by the static and dynamic properties of the soil weak structure will be less in uenced by wetting rate than will a soil with strong structure process based models of wind and water erosion need to consider the details of the interactions between soil static and dynamic properties and the dynamic processes that occur prior to erosive events copyright 2004 john wiley sons ltd

sand detachment under rains with varying angle of incidence abstract in the case of wind driven rain as the angle of rain incidence increases greater force components act parallel to the surface and lower force components act perpendicular to the surface therefore raindrop impact angle could influence the detachment process in the existence of substantial lateral jet development this could be particularly significant for a cohesionless sand surface that has a weaker resistance to the dislodgement by a raindrop impact than a soil surface experiments of simulated wind driven rain were conducted to evaluate sand detachment rates under increased lateral jetting induced by wind velocities of 6 4 10 0 and 12 0 m s 1 at nozzle operating pressures of 75 100 and 150 kpa and incident on windward and leeward slopes of 4 and 9 with these set ups it was possible to have varying angles of incidence and to determine the effect of the compressive stress and shear stress evaluated by the horizontal and vertical kinetic energy fluxes e tx and e tz respectively on the detachment rates from the sand surface at the same vectorwise sum of e tz and e tx the results showed that there was for similar values of e tz and e tx in windward slopes more sand detachment rate however for dissimilar values of e tz and e tx in leeward slopes where e tx was significantly higher than e tz there was less sand detachment rate consequently with certain values of the compressive stress and shear stress the sand detachment rates under wind driven rains peaked and e tz was the limiting component since the rates significantly decreased as e tz particularly decreased in spite of very large values of e tx

echolocation signals of free ranging killer whales orcinus orca and modeling of foraging for chinook salmon oncorhynchus tshawytscha fish eating resident type killer whales orcinus orca that frequent the coastal waters off northeastern vancouver island canada have a strong preference for chinook salmon oncorhynchus tshawytscha the whales in this region often forage along steep cliffs that extend into the water echolocating their prey echolocation signals of resident killer whales were measured with a four hydrophone symmetrical star array and the signals were simultaneously digitized at a sample rate of 500 khz using a lunch box pc a portable vcr recorded the images from an underwater camera located adjacent to the array center only signals emanating from close to the beam axis 1185 total were chosen for a detailed analysis killer whales project very broadband echolocation signals q equal 0 9 to 1 4 that tend to have bimodal frequency structure ninety seven percent of the signals had center frequencies between 45 and 80 khz with bandwidths between 35 and 50 khz the peak to peak source level of the echolocation signal

evaluating a multiclass net deposition equation in overland flow conditions 1 the movement of sediment and related pollutants in overland flow from the point of erosion to a stream normally occurs through a series of deposition zones here we present the evaluation of a new multiclass model of sediment transport through these zones this model simulates size selective net deposition as a result of simultaneous deposition by settling and nonselective reentrainment of previously deposited sediment hairsine et al 2002 sander et al 2002 multiclass sediment deposition models provide a useful basis for simulating off site effects of soil erosion but information on the grain size composition of deposited and exported sediment is crucial for calibrating and evaluating such models therefore the multiclass sediment deposition model was tested using detailed experimental data information on the amount of sediment deposition on the grain size distribution of the deposited and exported sediment and on the spatial pattern of the deposits was collected during sediment deposition experiments calibration of the multiclass model using one part of these data was performed by adjusting the fraction of stream power available for sediment reentrainment by minimizing errors between both simulated and observed total outflow sediment concentration and grain size distribution of the exported sediment evaluation was conducted using the other part of the data over a wide range of conditions the evaluation shows that the deposition equation is capable of reasonably simulating the observed size selectivity of the deposition process however the model is not capable of simulating correctly the spatial pattern of the deposited sediment because of simplifications used in the hydraulic model

settling velocity of sediments at high concentrations new data on the settling velocity of artificial sediments and natural sands at high concentrations are presented the data are compared with a widely used semiempirical richardson and zaki equation trans inst chem eng 32 1954 35 which gives an accurate measure of the reduction in velocity as a function of concentration and an experimentally determined empirical power n here a simple method of determining n is presented using standard equations for the clear water settling velocity and the seepage flow within fixed sediment beds the resulting values for n are compared against values derived from new and existing laboratory data for beach and filter sands for sands the appropriate values of n are found to differ significantly from those suggested by richardson and zaki for spheres and are typically larger corresponding to a greater reduction in settling velocity at high concentrations for fine and medium sands at concentrations of order 0 4 the hindered settling velocity reduces to about 70 of that expected using values of n derived for spheres at concentrations of order 0 15 the hindered settling velocity reduces to less than half of the settling velocity in clear water these reduced settling velocities have important implications for sediment transport modelling close to and within sheet flow layers and in the swash zone

the seismic signature of rain abstractrain has long been a problem for land seismic surveys in terms of its effect on the condition of the surface and near surface and also due to the seismic noise it creates when raindrops hit the ground i measured the seismic signature of rainfall using water dripped from height using a pipette and natural rain in winchester england over a three month period my results indicated that rain noise is concentrated at frequencies of greater than 80 hz with a detectable range of less than 1 m drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone items placed on the surface of the ground such as cables absorb the energy of the impact and reduce the level of the resulting seismic noise burying geophones results in attenuation of rain noise by between 7 7 and 8 6 db 0 1 m but given the effort required to bury geophones it is likely that data processing algorithms or the placement of vibration absorbent ma

runoff characteristics and soil erosion dynamic processes on four typical engineered landforms of coalfields an in situ simulated rainfall experimental study abstract large engineered landform tracts formed during coalfield development and construction cause serious soil erosion and threaten the ecological security of the coalfield area a series of in situ simulated rainfall experiments with rainfall intensities ranging from 1 0 to 3 0 mm min 1 were conducted to explore the runoff characteristics and erosion dynamic processes of four engineered landforms namely waste slag heap with more gravel wsg waste slag with more sand wss waste soil heap wsh and disturbed land dl with undisturbed land ul as the control ck compared with ul the wss wsg and wsh runoff rates rrs increased by 38 83 71 39 and 63 16 respectively but decreased by 9 25 for dl the slope flow of ul was in the subcritical laminar and subcritical transition flow regimes while the four engineered landform flow regimes were mainly subcritical transition and subcritical turbulent flow regimes the ul and dl soil loss rates slrs followed a declining fluctuating levelling off trend while the wss wsg and wsh slrs followed a trend of multiple early stage peaks and valleys before levelled off the mean wss wsg wsh and dl slrs were 11 19 times 138 67 times 73 47 times and 2 82 times that of ul respectively ul disturbance significantly increased the runoff ability to detach sediments by 2 48 94 90 times based on the relationships between runoff rate and soil loss rate the shear stress stream power and unit stream power up critical values initiating dl soil erosion were 58 86 37 06 and 56 67 lower than those of ul respectively while higher critical hydrodynamic values were required to detach wsg wss and wsh particles the rainfall intensity ri slope gradient median particle size d50 fractal dimension fd and up were employed to develop an empirical model for predicting engineered landform slrs

the impact of atmospheric sodium on erodibility of clay in a coastal mediterranean region heavy rainfalls between 25 and 100 mm h 1 were simulated on pliocene quaternary sediments to reproduce the heterogeneity of natural environments 231 small plots of various sizes between 2 5 and 3 5 m2 mean about 3 m2 were used the duration of all simulations was 1 h we used water that had been collected during natural rainfall the concentration of clay particles in the sheet wash depended upon the concentration of dissolved sodium in the wash for about 42 and of the sheet wash quantity for about 37 under natural water conditions colloidal matter like clay minerals is charged negatively and therefore is destabilized by metal cations such as in the case of na results suggest that relatively higher concentrations of montmorrillonite were related to higher concentrations of sodium as opposed to illite and kaolinite microflakes of up to 25 were observed to vary between face to edge and face to face modes competition between protons and other cations the concentration of dissolved sodium na in the runoff water depends on water and sodium balances such as atmospheric input infiltration evaporation and surface water runoff the reduction of vegetation cover increases the amount of salt and amorphous matter in on the topsoil between heavy rainfall generations the best predictor to explain montmorillonite illite and kaolinite in of mineral clay sized matter in the surface water runoff sheet wash is the percentage of each clay mineral in the topsoil as opposed to illite and kaolinite more sheet wash indicate for montmorillonite relatively higher concentrations in the wash the results of model simulations were confirmed on different field plots of about 1 ha and small catchments during natural heavy rainfall events models can also be used to understand and to better simulate sheet rill and gully erosion micropedimentation and pedimentation

influence of rock fragment coverage on soil erosion and hydrological response laboratory flume experiments and modeling two laboratory flume experiments on the effect of surface rock fragments on precipitation driven soil erosion yields were carried out the total sediment concentration the concentration of seven individual size classes and the flow discharge were measured digital terrain models dtms were generated before and after one of the experiments the results revealed that the rock fragments protected the soils from raindrop detachment and retarded the overland flow therefore decreasing its sediment transport capacity rock fragments were found to affect selectively the different size classes in a manner that changed according to the time scale for short times the rock fragment coverage reduced erosion of the finer particles 100 m was unaffected at long times the rock fragment cover decreased the concentration of the individual size classes in proportion to effective rainfall intensity and the area exposed to raindrops an area based modification of the hairsine and rose h r soil erosion model was employed to analyze the experimental data the h r model predictions agreed well with the measured sediment concentrations when high rainfall intensity and low rock fragment cover were used predictions were instead less accurate with low rainfall intensity and high rock fragment cover the dtm results showed that the presence of rock fragments on the soil surface led to increased soil compaction perhaps due to higher soil moisture content from greater infiltration within the rock fragment covered flumes

influence of sediment settling velocity on mechanistic soil erosion modeling we report on a series of soil erosion experiments performed on the 2 m x 6 m epfl erosion flume total sediment concentrations and the concentrations of seven size fractions 1000 mm were measured during 14 high intensity 47 5 52 5 mm h rainfall experiments on three different slopes 2 2 12 4 the short time and long time analytical solutions for the hairsine rose erosion model were rewritten to account for infiltration the newly collected data were used to test the model under conditions that had not been explored before steeper slopes infiltration more realistic soil composition the analytical solutions could predict the observed total sediment concentration well however the observed sediment concentrations for the individual size classes could be predicted only when adjusted settling velocities were used the adjusted settling velocities were estimated through manual optimization the optimized settling velocities for the smallest and midsize particles 315 mm were smaller than measured the effective settling velocities could also be calculated from the calculated amount of material in the shield of each size class at the end of the experiments this calculated settling velocity distribution agreed very well with the optimized settling velocities this study moves the hairsine rose model another step closer to an operational soil erosion model for field applications

interrill erosion of carbon and phosphorus from conventionally and organically farmed devon silt soils abstract globally between 0 57 and 1 33 pg of soil organic carbon soc may be affected by interrill processes also a significant amount of phosphorus p is contained in the surface soil layer transformed by raindrop impact runoff and crust formation in the eu the p content of a crusted 2 mm surface layer corresponds to 4 to 40 kg ha 1 of p on arable land 1 094 mil km2 therefore the role of interrill processes for nutrient cycling and the global carbon cycle requires close attention interrill erosion is a complex phenomenon involving the detachment transport and deposition of soil particles by raindrop impacted flow resistance to interrill erosion varies between soils depending on their physical chemical and mineralogical properties in addition significant changes in soil resistance to interrill erosion occur during storms as a result of changes in surface roughness cohesion and particle size as a consequence erosion on interrill areas is selective moving the most easily detached small and or light soil particles this leads to the enrichment of clay phosphorous p and carbon c such enrichment in interrill sediment is well documented however the role of interrill erosion processes on the enrichment remains unclear enrichment of p and c in interrill sediment is attributed to the preferential erosion of the smaller lighter soil particles in this study the p and organic c content of sediment generated from two devon silts under conventional cs and organic os soil management were examined artificial rainfall was applied to the soils using two rainfall scenarios of differing intensity and kinetic energy to determine the effects on the p and c enrichment in interrill sediment interrill soil erodibility was lower on the os irrespective of rainfall intensity sediment from both soils showed a significant enrichment in p and c compared to the bulk soil however sediment from the os displayed a much greater degree of p enrichment this shows that the net p export from organically farmed soils is not reduced by a similar degree than soil erosion compared to conventional soil management the enrichment of p and c in the interrill sediment was not directly related to soc p content of the soil and soil interrill erodibility a comparison of soil and sediment properties indicates that crusting p and c content as well as density and size of eroded aggregate fragments control p and c enrichment due to complex and dynamic interactions between p soc and interrill erosional processes the nutrient and c status of sediments cannot be predicted based on soil p content soc or interrill erodibility alone clearly further research on crust formation and the composition of fragments generated by aggregate breakdown and their transport in raindrop impacted flow under different rainfall conditions is required attaining this critical missing knowledge would enable a comprehensive assessment of the benefits of organic farming on nutrient budgets off site effects of interrill erosion and its role in the global c cycle

splash detachment runoff depth and soil cohesion summary a set of laboratory experiments has been carried out in order to investigate the importance of soil cohesion and the interference due to the depth of the surface runoff on the detachment rate of soil particles and aggregates experimental data show that the soil detachment rate decreases as the runoff depth increases this indicates that the detachment power of the raindrops is partially dispersed by the water layer an inverse relationship between soil detachment and soil cohesion has been confirmed nevertheless the grain size distribution must also be used in order to define soil detachability

exact solutions of the hairsine rose precipitation driven erosion model for a uniform grain sized soil hairsine and rose developed a mechanistic one dimensional precipitation driven erosion model that since its appearance has been validated by several sets of experimental results the model allows any sediment particle to be present in one of three zones viz the flow zone the deposited layer or the original soil the model has the general form of a two region model in which advection is the only transport process for the special case of a soil composed of a single particle size and for overland flow that occurs at a steady rate and with a uniform depth it is possible to derive fully explicit analytical solutions to the model details of the solutions for a slightly generalized mathematical form of the model are provided the goldstein j function which appears commonly in two region model solutions was modified to accommodate some of the solutions presented the form of the model analyzed indicated that based only on sediment concentrations in runoff water it is not possible to distinguish one mechanistic feature of the hairsine rose model i e that raindrop induced detachment of the undisturbed soil moves directly into the flowing water from the point of view of the model it is equally plausible for raindrop impact to move sediment directly into the deposited layer

can rock fragment cover maintain soil and water for saline sodic soil slopes under coastal reclamation abstract seeking a potential erosion control method for saline sodic soil slopes under coastal reclamation is essential we investigated the effect of rock fragment covers rc on the rainfall partitioning infiltration and runoff processes and the erosion processes for saline sodic slopes of 15 and 30 subjected to a 50 min simulated rainstorm with an intensity of 92 mm h 1 six rock fragment covers 0 10 20 40 60 and 80 were investigated soil was packed in 200 cm 100 cm 30 cm flumes divided into two to create two replicates for each treatment two sequential soil erosion events e1 followed by e2 were induced under two rainstorms that were 24 h apart results showed that in general rc had a positive effect on the runoff rate for both slopes a logarithmic relationship existed between the steady state infiltration rate and the rc for the gentler slopes an rc between 40 and 60 could protect the soil from erosion for e2 and e1 e2 events but did not do so for the e1 events alone for the steeper slopes the rc had no effect on soil losses for the e2 and e1 e2 events but increased the soil losses for the e1 events as the situation of rock fragment changed from situation 1 well embedded into the soil surface to situation 4 submerged in water the relationship between rc and soil loss became more complex and might change over time from a positive to a negative one the results suggested that the effect of rc on runoff and soil losses was influenced by the change of rock fragment situations over time during individual rainstorms the benefits of rc might be augmented by using them in combination with another protective measure

rock fragments and soil hydrological processes significance and progress abstract in this review we explore the significance of rock fragments in studies of soil hydrological processes because according to research the effects of rock fragments on soil hydrological processes are inconsistent positive negative rock fragments play a critical role in the biosphere as the primary filter for water and solutions containing contaminants and heavy metals rock fragments have a complex influence on soil hydrological processes e g soil erosion runoff generation water infiltration solute transport and water flow and are highly relevant in a typical system in the soil plant atmosphere continuum cracks related to rock fragments provide preferential flow paths through which pollutants are transported into groundwater in this paper the published literature is reviewed concentrating on rock fragments and their effects on soil hydrological processes systematic studies and examples illustrate the effects of rock fragments architecture i e coverage content size position spatial heterogeneity morphology weathering and topography on soil hydrological processes methods and models applied to evaluate the effects of rock fragments on soil hydrological processes are examined in detail we conclude that the relationship between rock fragments and soil hydrological processes is complicated and requires more international research efforts this review concludes with a discussion of perspectives on areas of research that can improve understanding of the effects of rock fragments on soil hydrological processes with insights and suggestions also being provided regarding potential research trends requirements and solutions

application of back scattered electron microscopy to the quantification of clay mineral microporosity in sandstones abstract computer assisted image analysis of back scattered electron bse micrographs of petrographic sections is useful for the quantification of clay mineral microporosity in sandstones authigenic clay minerals from north sea clastic reservoirs generally have higher microporosities than detrital clay minerals diagenetic kaolinite has microporosities varying from 25 to 50 diagenetic chlorite has a generally uniform grain coating texture and microporosities of about 50 dispersed diagenetic illitic clays are difficult to characterize using this method because their delicate morphology is susceptible to damage during sample preparation despite this limitation the analytical data indicate a minimum microporosity of 63 for dispersed illitic clays analytical data for clay rich detrital lasts have much lower microporosity values of about 10 interpretation of images from detrital clasts is complicated by the effects of sample preparation

hysteretic sediment fluxes in rainfall driven soil erosion particle size effects a detailed laboratory study was conducted to examine the effects of particle size on hysteretic sediment transport under time varying rainfall a rainfall pattern composed of seven sequential stepwise varying rainfall intensities 30 37 5 45 60 45 37 5 and 30 mm h 1 each of 20 mins duration was applied to a 5 m 2 m soil erosion flume the soil in the flume was initially dried ploughed to a depth of 20 cm and had a mechanically smoothed surface flow rates and sediment concentration data for seven particle size classes 1000 m were measured in the flume effluent clockwise hysteresis loops in the sediment concentration versus discharge curves were measured for the total eroded soil and the finer particle sizes 1000 m overall it is found that hysteresis varies amongst particle sizes and that the predictions of the hr model are consistent with hysteretic behavior of different sediment size classes this article is protected by copyright all rights reserved

laboratory investigations of rill dynamics on soils of the loess plateau of china abstract we conducted a laboratory study on rill network evolution with detailed measurements under controlled experimental conditions the concepts of fractal geometry entropy and topology were used to quantify rill erosion intensity and morphology the objectives of this study are to reveal rill erosion processes and rill network development under different rainfall intensities and to present some indicators to provide a quantitative description of rill morphology a soil pan 5 m long 1 m wide and 0 6 m deep with slope gradient of 20 was subjected to three successive rainfall events under rainfall intensities of 66 94 and 127 mm h 1 the results showed that rainfall intensity played a major role in rill erosion the development of a rill network is most rapid under medium intensity rainfall rainfall intensity that is too weak or too strong is not conducive to rill development as rainfall duration increased under the same rainfall intensity the values of soil loss rill density geomorphologic comentropy and nodes increased rill network development was slow at the early stage but became more rapid at a later stage the results also indicated that the geomorphologic comentropy was the best basic morphological indicator of rill erosion and the number of rill nodes was the best derived morphological indicator of rill morphology which was followed in descending order by the fractal dimension rill density and bifurcation ratio

the significance of rainsplash in the surficial debris cascade of the colorado front range foothills the surficial characteristics and precipitation regime of sparsely vegetated hillslopes in the montane zone of the colorado front range suggest that rainsplash may be an important component of the surficial debris cascade site sediment flux data from two study periods reveal marked spatial and temporal variability comparison of these date with sediment movement data from splashcups suggests the following conclusions 1 detachment rates of the rainsplash process appear great enough to account for the sediment flux in the open gerlach type traps 2 areal extrapolation of rainsplash transport suggest that 88 per cent of the fine sediment flux in 1982 can be attributed to rainsplash 3 estimates of rainfall energy and changes in the potential energy of hillslopes by mass transport suggests a process efficiency of 0 05 per cent for rainsplash if this procedure is applied to sediment flux values from open traps the low precipitation energy cascade of 1982 appears to be largely rainsplash transported sediment extrapolation with the 1981 data suggests more aggressive overland flow erosion and transport

effect of antecedent conditions and fixed rock fragment coverage on soil erosion dynamics through multiple rainfall events the effect of antecedent conditions and specific rock fragment coverage on precipitation driven soil erosion dynamics through multiple rainfall events was investigated using a pair of 6 m 1 m flumes with 2 2 slope four sequential experiments denoted e1 e2 e3 and e4 involved 2 h precipitation rates of 28 74 74 and 28 mm h 1 respectively and 22 h without rainfall were conducted in each experiment one flume was bare while the other had 40 rock fragment coverage the soil was hand cultivated and smoothed before the first event e1 only and left untouched subsequently sediment yields at the flume exit reached steady state conditions over time scales that increased with sediment size experiments were designed such that both steady and non steady effluent sediment yields were reached at the conclusion of e1 results from subsequent experiments showed that short time soil erosion was dependent on whether steady state erosion was achieved during the preceding event although consistent steady state effluent sediment yields were reached for each sediment size class steady state erosion rates were however dependent on the rainfall intensity and its duration if steady state sediment yields were reached for a particular size class that class s effluent sediment yield peaked rapidly in the next rainfall event the early peak was followed by a gradual decline to the steady state condition on the other hand for size classes in which steady state was not reached at the end of the rainfall event i e e1 in the following event e2 the sediment yields for those classes increased gradually to steady state i e the sharp peak was not observed the effect of rock fragment cover 40 on the soil surface was also found to be significant in terms of the time to reach steady state i e their presence reduced the time for steady conditions to be attained effluent sediment yields for the bare and rock fragment covered flumes e1 showed steady conditions were reached for the latter in contrast to the former we used the hairsine rose h r model to simulate the experimental data as it explicitly models soil particle size classes experiments e1 and e2 involved soil compaction by raindrops and in this case the model predictions were found to be unsatisfactory however compaction was effectively completed by the end of experiment e2 and the model provided reasonable predictions for experiments e3 and e4

the hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments in the top layer rainfall experiments have been conducted in the laboratory in order to assess the hydrological response of top soils very susceptible to surface sealing and containing rock fragments in different positions with respect to the soil surface for a given cover level rock fragment position in the top soil has an ambivalent effect on water intake and runoff generation compared to a bare soil surface rock fragments increase water intake rates as well as time of runoff concentration and decrease runoff volume if they rest on the soil surface for the same cover level rock fragments reduce infiltration rate and enhance runoff generation if they are well embedded in the top layer the effects of rock fragment position on infiltration rate and runoff generation are proportional to cover percentage micromorphological analysis and measurements of the saturated hydraulic conductivity of bare top soils and of the top layer underneath rock fragments resting on the soil surface reveal significant differences supporting the mechanism proposed by poesen 1986 i e runoff generated as rock flow or as horton overland flow can partly infiltrate into the unsealed soil surface under the rock fragments provided that they are not completely embedded in the top layer hence rock fragment position beside other rock fragment properties should be taken into account when assessing the hydrological response of soils susceptible to surface sealing and containing rock fragments in their surface layers a simple model based on the proportions of bare soil surface soil surface occupied by embedded rock fragments and soil surface covered with rock fragments resting on the soil surface describes the runoff coefficient data relatively well

stochastic sediment transport in soil erosion a stochastic model governing the downslope transport of a sediment particle during an erosion event is described particles alternate between resting on the soil bed and being transported by the overland flow probability densities and moments are constructed for the distribution of a particle s position at a given time and also for time of passage to a given location we show that a suitable averaging of the stochastic particle motions in our model gives rise to the deterministic erosion differential of hairsine and rose hairsine p rose c 1991 soil sci soc am j 55 2 320 324 the model generalized h einstein s stochastic model der geschiebebetrieb als wahrscheinlichkeitsproblem verlag rascher zurich 1937 for bedload transport in streams

diagenetic modeling to assess the relative timing of quartz cementation and brittle grain processes during compaction this study describes porosity reduction by brittle deformation and the application of touchstone sandstone diagenesis modeling software to assess the relative timing and interactions between grain fracturing and cement formation during burial compaction two examples from a previous study of compactional fracturing are used the oligocene frio formation gulf of mexico basin and the cambrian mount simon formation illinois basin united states grain fracturing during compaction creates intragranular fracture surfaces that are favorable sites for quartz nucleation compared to external grain surfaces that may bear coatings that inhibit the nucleation and growth of quartz cement thus the progress of brittle fracture processes during diagenesis affects quartz cementation in turn modeling of the quartz cementation process can serve to place fracturing into its proper context in burial history in the mount simon formation the extent of brittle deformation of quartz grains correlates with reconstructed effective stress at the onset of quartz cementation for frio formation samples however the extent of brittle deformation does not correlate well with reconstructed effective stress obtained using a one dimensional basin model that uses compaction disequilibrium as the dominant mechanism for overpressure generation judging from the observed degree of grain fracturing significant fluid overpressures in the frio may not have developed at the shallow depths indicated by our basin models the degree of compactional fracturing in sandstones constitutes observable evidence that can be used to decipher the complexities of pressure history

effects of rock fragment covers on erosion and transport of noncohesive sediment by shallow overland flow rock fragments on soil surfaces can have a variety of contrasting effects on the hydraulics of overland flow and soil erosion this makes modeling soil erosion difficult systematic studies are needed to assess the effects of rock fragments on the hydraulics of overland flow and to specifically relate these hydraulics to sediment yield therefore flume experiments were conducted in which overland flow was applied to a highly erodible sediment surface covered by various percentages of rock fragments high local turbulence was caused by horseshoe vortex erosion around individual rock fragments for a given discharge and slope the dimension of the scour was affected by the space between the rock fragments for low cover percentages the scour can develop undisturbed and sediment yield increases with percent of rock fragment cover up to about 20 sediment yield then declines as percent cover increases above 20 beyond a cover threshold value of 20 the larger opportunity for scour hole development is counteracted by limited inter rock fragment space that does not allow scour holes to develop to their full extent as sediment yield varies nonmonotonically with rock fragment cover percent sediment yield cannot be predicted by spatially averaged flow hydraulics

drying soil surface condition and interrill erosion on two ontario soils abstract interrill erodibility summarizes the resistance of soil to rainsplash sheetwash and rainflow erosion and incorporates changes in infiltration roughness and resistance to detachment and transportation resistance to interrill erosion varies during storms reflecting the effect of wetting sealing crusting and erosion on surface conditions significant changes in soil conditions also occur as a result of progressive drying between storms producing considerable uncertainty in event based erosion prediction however a clear link between drying primary soil properties and soil condition as well as interrill erosion during subsequent storms has not been established in this study soil condition and interrill erosion of soils from southern ontario were examined in detail during a sequence of simulated rainstorms and linkages between primary soil properties drying surface soil structure and interrill erosion were established interrill erosion after drying differed depending on the persistence of the changes in soil structure caused by drying pronounced stabilization of aggregates on drying led to an increase of erodibility indicating a transition from a coherent to granular structure requiring lower stresses for particle detachment the sensitivity of soil erodibility to drying appears to be determined by the tendency of a soil to form aggregates the results show that a better understanding of the linkages between primary soil properties rainfall and drying history soil condition and interrill erosion is required for effective event based erodibility assessment however the wide range of possible initial soil conditions and the complex nature of soil climate interaction are likely to limit the effectiveness of erodibility assessment

detachment and transportation of loose sediments by raindrop splash summary laboratory experiments on sediments ejected by splash consisted of two parts quantities ejected and mean projected distances were measured since the splash tray was 100 cm long and 20 cm wide and since both measurements were made on a receiving screen of one square metre it was obvious that only part of the translocated sediment was caught it was subject to serious doubt that the measured distances were representative for all sediment translocated if it is stated that the ejected sediment is distributed according to an exponential function around any point of impact located on the tray and if by definition tray and rainfall are perfectly homogeneous the ratio of the true to the measured distance and the ratio of the caught to the translocated sediment are only a function of the exponent of the real function the apparent distance being also a function of this exponent is thus the only factor needed to solve the two questions hence all empirical data were transformed into true data

relationships between the petrographical physical and mechanical properties of some italian sandstones abstract sandstones quarried in the firenzuola district florence italy have been investigated in order to evaluate their outdoor durability we have studied the relationships between mineralogical petrographical physical and mechanical properties the sandstones from firenzuola are characterized by a heterogeneity of mineralogical petrographical characteristics that strongly affected the physical and mechanical properties simulation of different environmental conditions has been performed using accelerating ageing tests freeze thaw salt crystallization acid rains and a comparison with the real cases of use of this stone in the urban marine and mountain environments is proposed this paper highlights how the mineralogical and petrographical characteristics affect the physical and mechanical properties the presence of a high amount of carbonatic cement determines a low effective porosity a prevalence of small pores and a high value of uniaxial compressive strength while a high amount of clay matrix determines high effective porosity a prevalence of larger pores and a low uniaxial compressive strength these parameters in turn determine a different proneness of this material to decay the most relevant cause of decay for these sandstones is salt crystallization which determines a decrease in mechanical properties this paper also stresses the need for new standard methodologies for evaluating the tendency to decay of superficial portions of material such as the analyzed pavements