a spectral approach for analyzing the rill structure over hillslopes part 1 development of stochastic theory abstract the rill structure over the soil surface plays an important role in determining the runoff and sediment loss from hillslopes the microtopography is often complicated and representation of the hillslope surface on a rill by rill basis is uneconomical and impractical a spectral approach combined with a stochastic theory is proposed for the rill profile the theory develops appropriate probability distribution laws for rill amplitudes and rill periods interrill areas under the assumption that the spectrum of the rill profile is narrow banded this study establishes a foundation for future studies dealing with parameter estimation and determining the global roughness and erodibility for runoff and sediment discharge predictions over hillslopes

an experimental study of rill erosion and morphology abstract rill erosion is recognized as an important process of water erosion on agricultural land the objectives of this study are to examine the effects of rainfall intensity on rill network development and to present some indicators for a quantitative description of rill morphology a soil pan 10 m long 3 m wide and 0 5 m deep and with an adjustable slope gradient from 0 to 30 was subjected to three successive rains under rainfall intensities of 50 and 100 mm h 1 the results showed that rainfall intensity significantly affected rill erosion especially in the active period of rill network development the magnitude of rill erosion was 28 5 and 33 1 kg m 2 and contributed 78 6 and 76 2 to the soil loss under rainfall intensities of 50 and 100 mm h 1 respectively the formation of rill network under the 50 mm h 1 intensity was more complex than that under the 100 mm h 1 intensity for the latter rill networks developed fast and then varied slightly the mean rill inclination angle mean rill density degree of rill dissection and mean rill tortuosity complexity cmean increased with the increase of rains under the same rainfall intensity the value was the optimal derivative morphological indicator to estimate rill erosion and morphology which was followed in descending order by mean cmean and

effects of different spatial distributions of physical soil crusts on runoff and erosion on the loess plateau in china the response of runoff and erosion to soil crusts has been extensively investigated in recent decades however there have been few attempts to look at the effects of spatial configuration of different soil crusts on erosion processes here we investigated the effects of different spatial distributions of physical soil crusts on runoff and erosion in the semi arid loess plateau region soil boxes 1 5 m long 0 2 m wide were set to a slope of 17 6 10 and simulated rainfall of 120 mm h 1 60 minutes the runoff generation and erosion rates were determined for three crust area ratios depositional crust for 20 33 and 50 of the total slope and five spatial distribution patterns depositional crust on the lower lower middle middle mid upper and upper slope of soil crusts the reduction in sediment loss sediment reduction was calculated to evaluate the effects of different spatial distributions of soil crusts on erosion sediment yield was influenced by the area ratio and spatial position of different soil crusts the runoff rate reached a steady state after an initial trend of unsteadily increasing with increasing rainfall duration sediment yield was controlled by detachment limitation and then transport limitation under rainfall the shifting time of erosion from a transport to detachment limiting regime decreased with increasing area of depositional crust no significant differences were observed in the total runoff among treatments while the total sediment yield varied under different spatial distributions at the same area ratio total sediment yield was the largest when the depositional crust was on the upper slope and it was smallest when the crust was deposited on the lower slope the sediment reduction of structural crust 42 5 66 5 was greater than that of depositional crust 16 7 34 3 these results provide a mechanistic understanding of how different spatial distributions of soil crusts affect runoff and sediment production copyright 2017 john wiley sons ltd

wave attenuation and wave drift in the marginal ice zone abstract surface gravity waves in a viscous rotating ocean are studied theoretically when they penetrate an area covered by highly concentrated brashlike ice the motion is described by a lagrangian formulation and the brash is modeled by a viscous newtonian fluid results for wave attenuation and wave drift are obtained in the asymptotic limit of a thin very viscous upper layer the derived damping rate compares favorably with field data from the marginal ice zone miz the drift velocity in the ocean exhibits a marked maximum in the viscous boundary layer near the ice ocean interface at the outer edge of the boundary layer it exceeds the inviscid stokes drift by a factor of 7 4 computed values for the mean viscous drag on the ice induced by the wave motion show that this effect may compete with the frictional effected of the wind in packing the ice finally it is demonstrated that the integrated horizontal mass transports in the open ocean and under the ice do not match which leads to upwelling in

a rational method for estimating erodibility and critical shear stress of an eroding rill abstract soil erodibility and critical shear stress are two of the most important parameters for physically based soil erosion modeling to aid in future soil erosion modeling a rational method for determining the soil erodibility and critical shear stress of rill erosion under concentrated flow is advanced in this paper the method suggests that a well defined rill be used for shear stress estimation while infinite short rill lengths be used for determination of detachment capacity the derivative of the functional relationship between sediment yield and rill length at the inlet of rill flow as opposed to average detachment rate of a long rill was used for the determination of detachment capacity soil erodibility and critical shear stress were then regressively estimated with detachment capacity data under different flow regimes laboratory data of rill erosion under well defined rill channels from a loess soil was used to estimate the soil erodibility and critical shear stress the results showed that no significant change in soil erodibility k r was observed for different slope gradients ranging from 5 to 25 while critical shear stress increased slightly with the slope gradient soil erodibility of the loess soil was 0 3211 0 001 s m 1 the soil erodibility and critical shear stress calculations were then compared with data from other resources to verify the feasibility of the method data comparison showed that the method advanced is a physically logical and feasible method to calculate the soil erodibility and critical shear stress for physically based soil erosion models

the effect of the marginal ice zone on the directional wave spectrum of the ocean abstract during the mizex 84 experiment in the greenland sea in june july 1984 a cooperative program was carried out between the scott polar research institute spri and the institute of oceanographic sciences ios to measure the change in the directional character of the ocean wave spectrum in the immediate vicinity of the ice edge the aim was to extend one dimensional spectral measurements made hitherto so as to study in full the processes of reflection and refraction directional spectrum analysis of these records shows that i significant reflection of wave energy occurs at the ice edge detected using long hasselmann analysis ii within the ice the directional spectrum at high frequencies where attenuation is rapid broadens to become almost isotropic whereas iii the directional spectrum at swell frequencies where the attenuation is slower becomes initially narrower before broadening more slowly than the high frequency energy an explanation of these effects is offered in terms of scatte

morphology and influencing factors of rills in the steep slope in yuanmou dry hot valley sw china abstract it is very important to understand rill morphology in order to understand its dynamics to reveal the morphology and influencing factors of rills in the steep slope rss in the yuanmou dry hot valley the total station photogrammetric technique and microtopographic profiler were used to obtain the parameters of the cross sections and longitudinal profiles of the rss and 12 parameters were used to characterize the rill morphology the results show that the morphology of rills clearly varied between each layer the topography soil properties and ferruginous cemented layer all exerted important influences on the rill morphology the average depth decreased with increasing slope length and the depths dominated by silt and sand were larger than that dominated by clay the average width and average width depth ratio increased with increasing slope length and the width and the width depth ratio that was dominated by clay was larger than that dominated by silt and sand the shape ratio of the rill cross section ranged from 0 50 to 0 58 and the shape of the cross section gradually changed from narrow and deep to wide and shallow with increasing slope length concave convex degree tended to be larger in the segment with ferruginous cement in the longitudinal profile the gradient gradually decreased with decreasing slope gradient and increasing slope length the presence of the ferruginous cemented layer and topsoil crust resulted in abnormal changes in the shape of the rill it is helpful to further understand the mechanisms of rill erosion under different conditions

field investigation of rill and ephemeral gully erosion in the sparacia experimental area south italy abstract this paper reports the results of a field investigation aiming at characterizing the morphology and hydraulics of both rills and ephemeral gullies egs monitored at sparacia experimental area sicily italy the comparison between rill and interrill erosion measurements showed that sediment delivery processes occurred in some erosive events and that the rill erosion rate was dominant in many cases the measurements were used for testing both the empirical relationships between the channel rill egs and gully length and its eroded volume and among the morphological variables length width depth and volume describing the channelized process finally the rill and egs hydraulic geometry was modelled by three well known power equations relating the discharge with the mean flow velocity with the flow depth and with the width of each channel segment respectively the rill measurements also showed that the flow velocity was affected by the rill segment slope while the flow depth and width were controlled by the plot slope therefore three equations taking into account these slope effects were proposed to estimate the hydraulic characteristics of the rills monitored at the sparacia area

geoarchaeological prospection for roman waterworks near the late holocene rhine waal delta bifurcation the netherlands abstract romans who settled in the low countries at the northern margin of their empire were practicing diverse systems of water management to maintain economic and above all strategic stability in the early roman period 12 bc ad 70 they created a shipping route from the rhine towards the north by digging canals and constructing dams such as the dam of drusus accompanied by the adjacent roman fortress of carvium herwen this dam was situated at the bifurcation point of the rhine and waal river branches and was designed to channel more water into the rhine all these engineering feats were undertaken in order to control the northern part of germania via the wadden sea and the german rivers ems weser and elbe by the middle roman period ad 70 270 the romans had cancelled their efforts to subdue germania and this is a period when the rhine is known as the limes roman state border the research area described in this paper is situated near herwen in the eastern part of the rhine meuse delta system the area has a dynamic late holocene erosional and depositional history close to the river system s equilibrium point in order to reconstruct the former landscape and to investigate whether evidence of roman waterworks could be detected geoarchaeological coring campaigns were carried out to gain insight into the sedimentology chronology stratigraphy and geoarchaeology of the region results indicate that pleistocene sediments are only preserved in the western part of the research area but further east then previously known dating of gullies and levees has confirmed roman and potentially pre roman fluvial activity closer to the roman fortress of carvium then was previously known four newly discovered residual gullies provide a greater insight into the character of the roman landscape than hitherto known the largest of the newly identified gullies may be instrumental in finding the location of the dam of drusus however much depends on the question as to whether the gully represents an actual former stream channel or simply a crevasse and this cannot be ascertained on the current evidence nevertheless the results of this study reinforce the assumption that the roman castellum was situated on the apex of the insula batavorum and close to the dam of drusus at the bifurcation of the rhine and waal

the role of vegetation on gully erosion stabilization at a severely degraded landscape a case study from calhoun experimental critical zone observatory abstract gully erosion was evidence of land degradation in the southern piedmont site of the calhoun critical zone observatory cczo during the cotton farming era understanding of the underlying gully erosion processes is essential to develop gully erosion models that could be useful in assessing the effectiveness of remedial and soil erosion control measures such as gully backfilling revegetation and terracing development and validation of process based gully erosion models is difficult because observations of the formation and progression of gullies are limited in this study analytic formulations of the two dominant gullying processes namely plunge pool erosion and slab failure are utilized to simulate the gullying processes in the 4 km2 holcombe s branch watershed in order to calibrate parameters of the gully erosion model gully features e g depth and area extracted from a high resolution lidar map are used after the calibration the gully model is able to delineate the spatial extent of gullies whose statistics are in close agreement with the gullies extracted from the lidar dem several simulations with the calibrated model are explored to evaluate the effectiveness of various gully remedial measures such as backfilling and revegetation the results show that in the short term the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies e g backfilling decreased the spatial extent of gullies by 21 46 and decreased the average depth of gullies by up to 9 revegetation however is a more effective approach to stabilizing gullies that would otherwise expand if no gully remedial measures are implemented analyses of our simulations show that the gully stabilization effect of revegetation varies over a wide range i e leading to 23 69 reduction of the spatial extent of gullies and up to 45 reduction in the depth of gullies depending on the selection of plant species and management practices

similarity between morphological characteristics of rills and ephemeral gullies in sicily italy this paper reports the results of a field investigation aimed to establish morphological similarity between rills and ephemeral gullies rill measurements were made on 14 plots having a surface area of 22 352 m2 located on a 14 9 slope and on a plot 6 0 m wide and 22 0 m long having a uniform 22 0 slope the plots are located on the experimental station for soil erosion measurements sparacia of the agricultural faculty of palermo university in sicily italy all plots are subjected to natural rainfall the measurements were made immediately following five events between november 2004 and december 2005 the ephemeral gully measurements were made on a cultivated area of about 120 ha located in central sicily which is representative of many soil crop conditions in the mediterranean basin the morphological similarity between rill and ephemeral gully was first tested then a power relationship between rill or gully volume and length theoretically deduced by dimensional analysis and self similarity theory was applied this power relationship needs a different scale factor for rill and gully measurements finally using two dimensionless groups representative of the channel morphology variables the analysis showed that a single relationship can be applied to rill and gully measurements copyright 2009 john wiley sons ltd

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

a theoretical laboratory and field study of ice coupled waves field and laboratory data of ice coupled waves propagating beneath shore fast ice are presented and compared with a theoretical model for sea ice which allows temperature variation although the laboratory data set is essentially qualitative because of scaling problems the measured wave characteristics compare favorably with those seen in the field the theory fits the field data set well both for the dispersive behavior and for the energy decay as the ice coupled waves penetrate the ice sheet moreover a maximum displacement suggested by theory is seen in field data for the first time it is proposed that this peak may be associated with the breakup of shore fast ice in exposed regions the theoretical treatment presented assumes sea ice to be thermorheologically simple an untested hypothesis which will require later experimental verification however the theory is quite general and can be used to solve a variety of sea ice mechanical problems where creep is considered important but where the loads and displacements are small enough that linearity prevails

observations of wind generated waves in antarctic fast ice abstract observations of naturally induced propagating waves in the fast ice cover of mcmurdo sound antarctica were made during the austral winter of 1986 with a rosette of three wire strainmeters the data collected over a seven month period and including a wide range of ice conditions and wind velocities constitute a winter wave climatology and show for the first time the nature and magnitude of flexural gravity waves induced by the direct action of turbulent air flow over the ice surface it is observed that below a threshold wind velocity corresponding roughly to the minimum group velocity for wave propagation in the ice 10 m s 1 no resolveable waves are produced at wind speeds above the threshold wave energy increases significantly with increasing wind velocity analyses of the wave energy density spectra show the observed wave characteristics to be in general agreement with existing theory although considerable scatter in the data prevents detailed comparisons the absolute magnitudes of

reflection and transmission characteristics at the edge of shore fast sea ice the reflection and transmission of ocean waves at a sea ice boundary is reconsidered the sea ice is modelled as a continuous thin elastic plate of uniform thickness floating on water of arbitrary constant depth unlike earlier solutions matching of potentials between the free surface domain and the ice covered domain is done at all depths previous solutions were incompletely matched as the potentials in each domain were deficient in the present solution a number of the infinity of evanescent modes which were hitherto ignored are included in the solution and allow matching to be carried out by minimization of an integrated error term from surface to seafloor reflection and transmission are found to be markedly influenced by the inclusion of these modes suggesting that conclusions based on the incomplete potentials may be substantially in error

the attenuation rates of ocean waves in the marginal ice zone during field operations in the greenland and bering seas in 1978 1979 and 1983 a number of experiments were carried out in which wave energy was measured along a line of stations running from the open sea deep into an icefield wave buoys in the water and accelerometer packages on floes were the instruments employed with airborne vertical photography to supply information on floe size distribution it was found that the decay of waves is exponential with a decay coefficient which generally increases with frequency except for a roll over at the highest frequencies the observations can be fitted reasonably well to a theory of one dimensional scattering

interactions between soil properties and moisture content in crust formation runoff and interrill erosion from tilled loess soils soil surface seals and crusts resulting from aggregate breakdown reduce the soil infiltration rate and may induce erosion by increasing runoff the cultivated loess areas of northwestern europe are particularly prone to these processes surface samples of ten tilled silty loamy loess soils ranging in clay content from 120 to 350 g kg 1 and in organic carbon from 10 to 20 g kg 1 were packed into 0 5 m2 plots with 5 slopes and subjected to simulated rainfall applied at 30 mm h 1 the 120 minutes rainfall events were applied to initially field moist soil air dried soil and rewetted soil to investigate the effect of soil moisture content prior to rainfall runoff and eroded sediments were collected at 5 minutes intervals aggregate stability of the soils was assessed by measuring particle size distribution after different treatments all soils formed seals runoff rates were between 70 and 90 by the end of the rainfall event for field moist plots there were large differences between soil runoff rates for the air dried and rewetted plots interrill erosion was associated with runoff and sediment concentration in runoff readily reached a steady state value measurements of aggregate stability for various treatments were in good agreement with sealing runoff and erosion responses to rainfall runoff and erosion were lower for air dried plots than for field moist plots and were either intermediate or lowest for rewetted plots depending on soil characteristics soils with a high clay content had the lowest erosion rate when they were rewetted whereas the soil with a high organic carbon content had the lowest erosion rate in air dry conditions the results indicate the complexity of the effect of initial moisture content and the interactions between soil properties and climate

quantifying anthropogenic modification of the shallow geosphere in central london uk abstract the veneer of artificial anthropogenic deposits present beneath contemporary cities is commonly markedly heterogeneous particularly in cities such as london with a history of two millennia of development to what extent can the analysis of borehole data historical land use maps and digital terrain models provide adequate assessment of such heterogeneity two adjacent london boroughs city of london and tower hamlets are selected because of their contrasting historical development and current land use statistical comparison of the variations in deposit thickness is related to the natural holocene topography underlying geological deposits non anthropogenic deposits and heights of overlying buildings estimates of the volume 67 million m3 and mass 100 million tonnes of the deposits and additional volume 359 million m3 and mass 25 million tonnes of buildings provides indication of additional loading that may cause local compaction or regional subsidence a concern during a time of rising global sea level extrapolated across greater london the mass of anthropogenic deposits is estimated at 6 billion tonnes assessment of the compositional variations within the artificial deposits provides an approximation of accumulation rates post world war ii a potential event horizon coincident with the early 1940s blitz could not be demonstrated as an extensive marker but distinct lithological compositions for post world war ii strata are broadly coincident with the globally resolved signals marking the start of the anthropocene epoch

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

lidar derived high resolution palaeo dem construction workflow and application to the early medieval lower rhine valley and upper delta abstract reconstruction of past topography in palaeo dems serves various geomorphological analyses constructing a palaeo dem by stripping young elements from a lidar dem can provide results for large study areas at high resolution however such a top down approach is more suited to recent periods and geomorphologically static parts of the landscape than to geomorphologically dynamic areas and periods farther back in time here we explore this approach by reconstructing the early medieval circa 800 ce topography of the lower rhine river valley and upper delta in germany and the netherlands the large 4500 km2 study area contains abundant anthropogenic terrain modification and stretches across geomorphologically active as well as inactive zones we first removed all anthropogenic relief elements from the lidar dem using separate procedures for linear and non linear elements these steps were sufficient to obtain the palaeotopography of the inactive zone characterized by inherited natural relief then we reconstructed the topography and bathymetry in the fluvially reworked active zone by incorporating geological and historical geographical information we present and evaluate zonal averages of elevation differences between the modern and past valley floor topography in this densely populated area with complex land use history which allows us to approximate total anthropogenic volumetric change further comparisons with the modern lidar dem elucidate changes in floodplain negative relief connectivity showing the potential importance of investing in palaeo dems when assessing past river flooding our palaeo dem construction workflow is deployable at diverse spatial scales and widely applicable to other lowland areas because of its top down and generic nature the relative importance of different workflow aspects depends on the time period that is targeted beyond a target age of 10 15 ka valley floors that are too large in area are to be considered geomorphologically dynamic and the top down approach to palaeo dem construction is no longer advisable

rill network development and sediment budgets threshold conditions for rill incision are well known but few studies have examined the effect of network geometry on water and sediment fluxes within an evolving rill system this paper reports the first in a series of studies designed to identify the influence of soil properties on rill network and confluence geometry and on water and sediment fluxes in rill systems the object of this study was to prepare detailed rill network water and sediment budgets identifying important sources and sinks simulated rainfall experiments were carried out on a canadian silt loam soil in a 7 1 m 2 4 m flume on a 5 slope rill networks of varying complexity developed which were ultimately constrained by flume boundaries sediment and water fluxes and hydraulic conditions were measured within networks and at a terminal weir networks evolved by initial knickpoint incision in the lower flume as flow shear velocities reached critical levels of 4 5 5 cm s 1 followed by headward migration and tributary development microtopography determined tributary location but the timing and intensity of development were controlled by the incision and migration rate of the main channel which changed local thalwegs and base levels raising shear velocities on side slopes above critical levels sediment discharge at the weir broadly reflected rill incision intensity and transport limited conditions but as active incision moved headward the linkage became attenuated and identification of discrete erosional incidents e g local bank collapse in the signal of the weir record became very difficult detailed water and sediment budgets showed much more complex patterns of localized incision and deposition within networks strongly influenced by local changes in thalweg and in water discharge due to seepage or return flow and by the effect of confluences on hydraulic conditions results indicate the value of detailed sediment budgets in interpreting weir water and sediment flux records and the necessity of linking such measurements for erosion plots and hillslope segments to rill network characterization experimental results are consistent with a simple model of rill system evolution based on channel incision headward migration and the critical shear velocities for rill initiation copyright 2000 john wiley sons ltd

rill erosion and morphological evolution a simulation model a mathematical model is advanced to simulate dynamically and spatially varied shallow water flow and soil detachment transport and deposition in rills the model mimics the dynamic process of rill evolution including variable rates of sediment redistribution along the bed and changes in local bed morphology the sediment source term in the model uses a point scale probabilistic relationship based on turbulent flow mechanics and a recently developed sediment transport relationship for rills based on stream power the interdependent feedback loops between channel bed morphology local flow hydraulics and local scour and deposition within the framework of the full hydrodynamic equations with inertial terms constitute a mathematical model with the capacity to represent spatial variability and temporal evolution of the rill finite elements were applied to numerically solve the hydrodynamic and sediment continuity equations a series of laboratory flume experiments were performed to evaluate the model initial bed slopes were 3 5 and 7 with step increases of water inflow rates of 7 6 11 4 and 15 2 l min 1 the soil material used in the flume was a kaolinitic sandy clay loam the rill model equations were solved for increasingly complex cases of spatial and temporal variabilities the model followed measured patterns of morphological changes as the rill evolved which suggests that the feedback loops in the model between erosion bed morphological changes and hydraulics were adequate to capture the essence of rill evolution

a mechanism for the formation of ice edge bands we propose a mechanism for the formation of multiple bands at an ice edge that is subjected to an off ice wind the wind moves the outermost floes seaward faster than the interior ice dilating the marginal ice zone and opening up random polynyas in the largest of the polynyas the off ice wind generates a significant fetch limited wave spectrum which produces a wave radiation pressure on floes at the downwind end of the polynya increasing their velocity they are herded against their downwind neighbors creating a band of high ice concentration the band is stabilized by an internal compacting stress due to the exponential decay of the wind wave spectrum across the band and to a slower decay of swell incident from seaward the band s growth terminates when it encounters a second downwind polynya of sufficiently large size we show how an array of immature bands generated in this way matures by selective mergers into larger regularly spaced bands of approximately equal width

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

muddled or mixed inferring palaeoclimate from size distributions of deep sea clastics abstract one of the outstanding problems of palaeoclimate reconstruction from physico chemical properties of terrigenous deep sea sediments stems from the fact that most basin fills are mixtures of sediment populations derived from different sources and transported to the site of deposition by different mechanisms conventional approaches to palaeoclimate reconstruction from deep sea sediments do not distinguish between provenance and dispersal related variations and therefore often fail to recognise the true significance of variations in sediment properties we formulate a set of requirements that each proposed palaeo environmental indicator should fulfil and focus on the intrinsic coupling between grain size and chemical composition a critical review of past achievements in grain size analysis serves to introduce a conceptual model of spatio temporal grain size variation based on dynamic populations each dynamic population results from a characteristic combination of production and transport mechanisms that corresponds to a distinct subpopulation in the data analysed the mathematical statistical representation of the conceptual model can be obtained by means of the end member modelling algorithm emma applications of the model to several ocean basins are discussed as well as methods to examine the validity of grain size based palaeoclimate reconstructions palaeoclimate reconstructions of a high and low latitude basin illustrate the common degree of complexity of deep sea grain size records

importance of surface sealing in the erosion of some soils from a mediterranean climate abstract poor aggregate stability and high erodibility of soils found in mediterranean climates are often due to low organic matter content the low organic matter content is sometimes compensated for by iron oxides that stabilize soil structure low water stability of aggregates often determines the propensity for soils to form surface crusts and seals wet crusts seals reduce soil infiltration rate and may increase erosion by increasing runoff we conducted rainfall simulation experiments on 30 cm 30 cm plots inclined at 9 slope in which we measured soil splash and wash erosion runoff and splash volume for seventeen california soils the soils ranged in clay content from 8 to 36 esp from

rill erosion processes on a steep colluvial deposit slope under heavy rainfall in flume experiments with artificial rain abstract understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss however limited information is available concerning the impacts of rainfall on rill erosion on steep slopes colluvial deposits with steep slopes make up the packed material underlying the collapsing walls in benggang which collapse due to hydraulic pressure and gravity they contain loose materials and large amounts of coarse particles the objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process rill development and rill flow dynamic mechanisms on the steep slopes of colluvial deposits the colluvial soils were subjected to simulated rainfall in a 5 m2 5 m by 1 m flume at heavy rainfall intensities 100 120 and 140 mm h 1 and on five steep slopes 20 25 30 35 and 40 rill erosion contributed significantly to colluvial slope erosion on average rills accounted for 61 of the soil loss and the effects of slope gradient were greater than those of the rainfall intensity after rill development rill density rill length width and depth all significantly increased correspondingly the soil loss rate sharply raised and irregularly fluctuated moreover the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development the rill flow was characterized by transitional and subcritical flow regimes the rill flow velocity was the most sensitive hydraulic parameter and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on colluvial deposits the collapse of rill heads or sidewalls could result in negative values for critical shear stress critical stream power and critical unit stream power of rill erosion which were 19 pa 5 3 n m 1 s 1 and 0 09 m s 1 respectively these results provide a better understanding of the mechanism of rill erosion on steep slopes

experimental study on soil erosion prediction model of loess slope based on rill morphology abstract rill erosion frequently occurs in agriculturally disturbed dry areas despite many research efforts over recent decades the characteristics of rill erosion and its intrinsic mechanisms remain unclear the objectives of this study were to investigate the impacts of rill morphology evolution on rill erosion processes a soil pan 5 m long 1 m wide and 0 6 m deep and with an adjustable slope gradient of 0 30 was subjected to rainfall simulation experiments under three intensities of representative erosive rainfall 66 94 and 127 mm h 1 the rill morphology evolution exhibited significant nonlinear change regulation and the stronger the rainfall intensity the clearer the nonlinear feature the equation between rill morphological characteristics with geomorphological comentropy and bifurcation ratio was generated which indicated that the contribution rate of geomorphological comentropy to sediment yield was 80 and the contribution rate of bifurcation ratio was 20 for the experimental treatments a soil erosion model was constructed with and without rill development and the coefficient to describe the influence of rill development on slope erosion was obtained the rill erosion coefficient was embedded into an existing soil erosion model for steep slopes as a result when rill erosion occurred on the slope the contribution of the rill morphology to the rill erosion was fully realized by the model verification indicated that the accuracy of the model was significantly improved in previous studies the accuracy of slope water erosion prediction model was low because the evolution process of slope topography was not considered our results solve the spatial variability problem in the slope erosion prediction model and improve the simulation accuracy of the soil erosion prediction model on a loess slope

the natural oscillations of an ice covered channel les modes d oscillations naturelles d un chenal infiniment long recouvert de glace sont envisages en utilisant l approximation hydrostatique et en supposant que la glace ait un comportement elastique la relation de dispersion le mode de forme et les forces associees sur les bords du chenal sont obtenus pour les trois modes inferieurs une attention particuliere est portee aux limitations dues aux approximations hydrostatiques et elastiques

distribution morphology and influencing factors of rills under extreme rainfall conditions in main land uses on the loess plateau of china abstract rill erosion is one of the main forms of soil erosion of the hillslopes on the loess plateau of china few studies have evaluated the effects of land use on the distribution and morphology of rills under extreme rainstorms a total of 50 rill survey sites were selected in a typical watershed of the loess plateau of china to investigate the rill distribution and morphology of three land uses fallow land fl slope farmland sf and annual grassland ag under extreme rainstorm conditions called 7 26 rainstorm seven parameters rill width rill depth width depth ratio cross section area rill density degree of rill dissection and rill erosion modulus were used to characterize rill morphology and the basic soil and vegetation properties bulk density particle size distribution and vegetation coverage and topographic factors slope length gradient direction were measured it was found that rills developed on three land uses and those with widths ranging from 5 to 20 cm accounted for 80 rills developed on fl were deeper than those on sf and ag almost all rills on fl had a depth of 5 20 cm 90 3 while the depth of rills on sf and ag were mainly smaller than 15 cm 91 5 and 91 9 respectively in addition to width rill depth and cross section area of sf and ag were also significantly less than those of fl sf and fl had a relatively high width depth ratio and dissection degree however land use had no significant effect on rill density crop plantations sf and grass restoration ag significantly reduced rill erosion modulus 28 70 and 45 07 reduction respectively land use topography soil and vegetation factors significantly affected rill morphology p 0 001 based on redundancy analysis rda and can explain 48 0 of the total variability of rill morphology with slope length vegetation coverage and slope gradient having the greatest influences most of the rill morphological parameters significantly decreased as the vegetation coverage increased but they significantly increased with increasing slope length and slope gradient this study clearly illustrates the severe rill erosion caused by this rainstorm and indirectly indicates that crop harvesting fl aggravates rill erosion and that revegetation ag can effectively contain rill erosion therefore rehabilitation efforts should be focused on revegetation grassland and or woodland on steep slopes to control soil erosion

measurements of rill and gully erosion in sicily this article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at sparacia experimental area and two ephemeral gullies egs located in the tremamargi basin sicily italy at first the available literature data together with the measurements carried out in this investigation were used to show that the eg length is a key parameter for the estimation of the eroded volume then the comparison among the pairs length and volume corresponding to measured rills egs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type rill eg and gully while a different scale factor has to be used for each erosion process finally a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self similarity theory copyright 2011 john wiley sons ltd