impact of subsurface rock fragments on runoff and interrill soil loss from cultivated soils field and laboratory studies have indicated that rock fragments in the topsoil may have a large impact on soil properties soil quality hydraulic hydrological and erosion processes in most studies the investigated rock fragments still remain visible at the soil surface and only properties of these visible rock fragments are used for predicting runoff and soil loss however there are indications that rock fragments completely incorporated in the topsoil could also significantly influence the percolation and water distribution in stony soils and therefore also infiltration runoff and soil loss rates therefore in this study interrill laboratory experiments with simulated rainfall during 60 min were conducted to assess the influence of subsurface rock fragments incorporated in a disturbed silt loam soil at different depths below the soil surface i e 0 001 0 01 0 05 and 0 10 m on infiltration surface runoff and interrill erosion processes for small and large rock fragment sizes i e mean largest diameter equals 0 04 and 0 20 m respectively although only small differences in infiltration rate and runoff volume are observed between the soil without rock fragments control and the one with subsurface rock fragments considerable differences in total interrill soil loss are observed between the control treatment and both contrasting rock fragments sizes this is explained by a rapid increase in soil moisture in the areas above the rock fragments and

quantitative assessment of the piping erosion susceptibility of loess derived soil horizons using the pinhole test abstract the pinhole test is an empirical test based on the qualitative evaluation of the dispersivity colloidal erodibility of compacted fined grained soils this paper evaluates the pinhole test device for the quantitative assessment of the susceptibility of soil horizons to piping assesses the effects of hydraulic head water quality antecedent soil moisture content and soil disturbance on the hydrological and erosion response during pipeflow and formulates recommendations for the application of the pinhole test to study piping erosion processes in total 255 pinhole test experiments were conducted the results obtained from disturbed soil samples ap horizon indicate i a significant positive linear increase in pipeflow discharge qw and sediment discharge qs with increasing hydraulic head ii no relationship between qw and antecedent soil moisture content asm but significant and negative relationship between qs and asm and iii significantly higher qs for distilled water than for tap water the use of disturbed soil samples resulted in significantly more rapid flow responses and lower sediment discharges than for undisturbed soil samples the pinhole test experiments performed on different loess derived soil horizons show that the plowed topsoil ap and the underlying clay enriched horizon bt are at least two times less susceptible to piping than the decalcified c1 and the calcareous horizons c2 this confirms field observations indicating that loess derived soil horizons are very susceptible for piping erosion especially when the c horizon crops out this study demonstrates that the pinhole test is suitable for assessing the susceptibility of soil horizons to piping in a quantitative way i e qw qs the time to outflow and the cross section of the pipe after the test we recommend the use of i two different hydraulic heads i e 180 and 1020 mm ii distilled water iii contrasting antecedent soil moisture contents of the soil samples to be tested and iv different soil sampling methods to investigate the effect of soil disturbance and particularly to obtain a better understanding of the sediment response during pipeflow

the effect of rock fragment size and position on topsoil moisture on arid and semi arid hillslopes abstract rock fragments on arid hillslopes affect rainwater redistribution and overland flow through various hydrological processes the present study focuses on the evolution of topsoil moisture content under rock fragments following rain events measurement was taken under rock fragments in various sizes large and small and positions on top of the soil surface and partially embedded within the soil surface at north and south facing hillslopes in arid and semi arid areas the main findings 1 the topsoil moisture content under rock fragments was higher over time than that of bare soil areas 2 rock fragments affect the topsoil moisture content for a longer time in semi arid areas than in arid areas and 3 large rock fragments and partially embedded ones are favorable micro environments for accepting and retaining rainwater and overland flowing water this may have eco geomorphic implications regarding the mosaic like patterns of source and sink areas on arid hillslopes

spatial distribution of soil surface coverage on north and south facing hillslopes along a mediterranean to extreme arid climatic gradient four research sites were established along a climatic gradient in israel representing mediterranean xeric mediterranean arid and extreme arid climate conditions the cover percentage of eight soil surface components vegetation annual and perennial forms biogenic crust mosses lichens cyanobacteria and dwarf grass stones and bare soil patches were measured transects along hillslopes on each of two opposite aspects south and north facing slopes were established at each site altogether eight transects dominance and soil surface cover diversity indices and similarity coefficients between the transects were calculated high similarity values in soil surface cover were found between the south facing slopes located in the xeric mediterranean arid and extreme arid areas these hillslopes are dominated by stones and bare soil patches in contrast lower similarity values were found between the northern slope aspects dominated by biotic components vegetation and biogenic crusts the study along a climatic gradient together with the comparison between northern and southern aspects provide useful information that can be utilized for evaluation of changes in soil surface cover characteristics given various scenarios of future climate regimes in that region

surface expression of eastern mediterranean slab dynamics neogene topographic and structural evolution of the southwest margin of the central anatolian plateau turkey 1 the southwest margin of the central anatolian plateau has experienced multiple phases of topographic growth including the formation of localized highs prior to the late miocene that were later affected by wholesale uplift of the plateau margin our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1 5 km elevation to 7 17 ma and regional lithostratigraphic correlations imply that the age is 6 7 ma single grain ca tims u pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10 6 ma indicating a maximum age that is consistent with the biostratigraphy our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions with early contraction followed by strike slip and extensional deformation during uplift focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present broad similarities in the change in the tectonic stress regime after 8 ma and the onset of surface uplift after 7 ma imply that deep seated process es caused post 7 ma uplift the geometry of lithospheric slabs beneath the plateau margin pliocene to recent alkaline volcanism and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post 7 ma uplift of the southwest margin considering previous work in the region there appears to be an important link between slab dynamics and surface uplift throughout the anatolian plateau s southern margin

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

relation between infiltration and stone cover on a semiarid hillslope southern arizona abstract a knowledge of the spatial distribution of infiltration rates is essential to the application of realistic distributed rainfall runoff models in semiarid areas one method of determining this distribution is to develop a predictive equation based on a readily observable surface property such as stone cover previous studies of the relation between infiltration and stone cover on shrub covered semiarid hillslopes have yielded both positive and negative correlations it is suggested that positive correlations result where infiltration measurements are confined to areas between large shrubs negative correlations on the other hand reflect pronounced shrub intershrub differences in infiltration and stone cover and are found where both shrub and intershrub areas are sampled in this study of a semiarid hillslope in southern arizona both shrub and intershrub areas are sampled and a negative correlation is obtained between infiltration and stone cover this correlation arises from the fact that under shrubs fine sediments have accumulated primarily as a result of differential splash whereas between shrubs such sediments have been selectively removed by a combination of rainsplash and overland flow leaving behind a gravel lag consequently infiltration rates are higher under shrubs than between them owing to the higher percentage of sand in the surface soil the larger quantity of organic matter both within the soil and on its surface and the greater digging and burrowing by animals in addition simulated rainfall experiments imply that shrubs with moderately dense canopies are more effective than adjacent surface gravels in dissipating the kinetic energy of raindrops and thereby reducing surface sealing and promoting infiltration inasmuch as the field site is typical of gentle shrub covered piedmont hillslopes over much of the sonoran desert inverse relations between infiltration rate and stone cover are probably characteristic of such hillslopes and may be used to predict the spatial distribution of infiltration rates for inclusion in rainfall runoff models

significance of preferential flow at the rock soil interface in a semi arid karst environment abstract in many semi arid environments the surface materials are frequently characterized by thin soils and large proportions of bare rock both of which are expected to considerably influence infiltration and groundwater recharge processes in this study small plot scale irrigation experiments in combination with dye tracer application as well as real time and subsequent soil moisture measurements and soil particle size analysis were conducted to investigate the significance of preferential flow at the rock soil interface large scale assessments of soil depth and surface type distribution were used to upscale the findings of the irrigation experiments to the scale of a complete hillslope and further to estimate percolation properties of a hypothetical rainfall event the two experimental plots were each located in the west bank mountains close to ramallah each irrigation experiment was designed with 50 mm of precipitation applied on an area of 1 m 2 during the course of ca 2 5 h each irrigation plot had a surface share of approximately 50 rock outcrop and 50 soil surface percolation properties were investigated by subsequent soil moisture measurements at high spatial resolution on vertical soil profiles on the irrigated plot dye tracer application on the rock outcrop during the sprinkling allowed for tracking of resulting outcrop runoff in the subsurface the soil depth survey included 2100 measurement points on 7 transects which allowed the estimation of local soil depth distribution results of the irrigation experiments showed that precipitation induced runoff from rock outcrops continued below ground as preferential flow along the rock soil interface while water from the soil surface percolated mainly vertically and much more homogeneously this was evident from the high density soil moisture measurements as well as from the dye tracer patterns outcrop runoff percolated faster and to greater depths than water infiltrating directly from the soil surface thus possessing a greater potential for groundwater recharge

fine gravel controls hydrologic and erodibility responses to trampling disturbance for coarse textured soils with weak cyanobacterial crusts article i nfo we compared short term effects of lug soled boot trampling disturbance on water infiltration and soil erodibility on coarse textured soils covered by a mixture of fine gravel and coarse sand over weak cyanobacterially dominated biological soil crusts trampling significantly reduced final infiltration rate and total infiltration and increased sediment generation from small 0 5 m 2 rainfall simulation plots pb0 01 trampling had no effect on time to runoff or time to peak runoff trampling had similar effects at sites with both low and very low levels of cyanobacterial biomass as indicated by chlorophyll a concentrations we concluded that trampling effects are relatively independent of differences in the relatively low levels of cyanobacterial biomass in this environment instead trampling appears to reduce infiltration by significantly reducing the cover of gravel and coarse sand on the soil surface facilitating the development of a physical crust during rainfall events the results of this study underscore the importance of carefully characterizing both soil physical and biological properties to understand how disturbance affects ecosystem processes published by elsevier b v

volcanic materials as mulches for water conservation abstract arid regions are characterised by a limited rainfall a circumstance that acts as a barrier to dryland farming lanzarote in the canary islands spain is one of the most arid regions in europe with less than 150 mm annual rainfall and potential evapotranspiration in excess of 2000 mm a traditional farming system developed on the island has led to a diversified and productive form of agriculture that uses no irrigation the system utilizes a layer of 10 20 cm of tephra covering the natural soil the tephra acts as mulch and is highly effective for soil water conservation in this work we present the results of a 3 year monitoring of soil moisture content in three plots covered with two types of basaltic tephra with different grain sizes the results are compared to those obtained on adjacent plots that were not covered with the mulch sampling was conducted once a month every 10 cm up to a depth of 1 m compared to the noncovered soils the tephra covered soils managed to retain eight times more water in the surface layer during the driest months at a depth of 1 m twice the amount of water was retained in the tephra covered plots this positive effect was explained by the tephra s physical properties particularly its low water retention capacity and high porosity enhancing water infiltration and reducing evaporation rates differences observed in the water conservation depending on the mulch type was explained largely by grain size the pyroclastic materials proved to be very effective for soil water conservation under arid conditions

deformation of laminated silt loam due to repeated freezing and thawing cycles the effect of repeated freezing and thawing cycles on an experimentally produced laminated silt loam was studied with the purpose of obtaining more insight into the genesis of macro and microstructures observed in the loessic formations of northwestern europe the laminated silt loam was subsequently subjected to 18 cycles of alternate freezing and thawing the minimum temperature recorded after 11 days of frost was 7 c at a depth of 5 cm and 4 c at 29 cm the underlying sediments compact loam except its upper part and sand always remained unfrozen the experiment reproduced a seasonal superficially frozen ground new structures and microfabrics in the form of vesicles platy structures shear planes and micro undulations were created by ice segregation and thawing mechanical stress and subsequent frost creep the impact of the freezing and thawing cycles is very strong all the laminae being deformed or broken judging by the abundance and the diversity of the structures created freezing is a more important process than simple drying without frost as is evidenced by the range in temperature chosen for the experiment and the low number of cycles these structures do not necessarily require severe climatic conditions to develop unlike frost cracks or ice wedge casts they could develop in winter conditions similar to those present today in the french southern alps

surface sealing as influenced by slope angle and position of simulated stones in the top layer of loose sediments the influence of five different slope angles and two different positions of simulated stones in the top layer of a sandy and a silty sediment on surface sealing intensity is examined in the laboratory sealing intensity is assessed by studying changes of percolation rate through a sediment layer with simulated rainfall duration and by measuring cohesion of the 5 mm thick upper sediment layer a measure of seal strength by means of a torvane slope has a negative influence on sealing intensity for a constant per cent of simulated stone cover sealing intensity is lowest in the case of stones placed on the sediment surface compared to the case of stones pushed into the surface layer explanations for these findings are given and some implications are further discussed

the influence of slope angle on final infiltration rate for interrill conditions abstract despite numerous studies the relationship between slope angle and infiltration rate remains unclear under different experimental conditions new processes may be introduced which influence the relationship the presence of rills for example may significantly affect the relationship between slope angle and infiltration rate so distinct relationships may exist for rill and interrill areas the objective of this study was to investigate the influence of slope angle on infiltration rate for an interrill area with a surface crust the experiment was carried out in a laboratory using simulated rainfall and soil trays designed to limit the processes to those found in interrill areas slope angles ranged from 1 5 to 21 5 infiltration was calculated from the overland flow rate and microtensiometers and micromorphological analysis were used to characterise the seals infiltration rate decreased with increasing slope angle image analysis of pore characteristics in the affected layer and subseal pressure head measurements indicated there were no differences in seal characteristics between slope angles the results showed that sealing intensity did not vary with slope angle and the dominant influence of slope angle on infiltration rate resulted from changes in overland flow depth and surface storage the results also suggest that small changes in seal hydraulic conductivity with microrelief play an important role in the infiltration process

spatial patterns of soil water balance on intensively cultivated hillslopes in a semi arid environment the impact of rock fragments and soil thickness during past decades a diverse system of subsistence agriculture in south east spain annual rainfall of less than 300 mm has been overturned in favour of large scale plantations of almond trees without consideration for topography and related spatial patterns in soil hydrological properties the objective of this paper is to investigate the spatial pattern in soil physical properties induced by this cultivation system and to highlight its impacts on the water balance soil properties were recorded along hillslopes with shallow soils developed on slates and greywackes in the upper part of the guadalentin drainage basin murcia region frequent tillage of these almond plantations covering entire hillslopes has resulted in denudation by tillage erosion on the topographic convexities as well as transport of rock fragments and fine earth along the slopes these processes have created a systematic spatial pattern of soil thickness and rock fragment content shallow and stony soils on the topographic convexities and deep soils with a rock fragment mulch in the concavities at the foot of the slopes at the same time a negative relationship between rock fragment content and fine earth bulk density was observed the impact of this spatial pattern in soil properties on the water balance was evaluated using the pattern one dimensional hydrological and plant growth model the model simulates the water balance of soil profiles covering the observed variation in soil thickness stoniness and bulk density the model results indicate that the highest rates of infiltration evaporation and drainage as well as the lowest rates of overland flow are restricted to shallow soils on the hilltops in contrast the deeper soils in the valley bottoms produce a more stable moisture regime than shallower soils which tend to saturate and dry out quickly these model results are in agreement with the spatial patterns of almond productivity an asymptotic increase with soil thickness copyright c 2000 john wiley sons ltd

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

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

hydric properties of some spanish soils in relation to their rock fragment content implications for runoff and vegetation abstract physical and hydric characteristics of the upper three horizons average depth of sampling 0 0 25 0 25 0 60 and 0 60 1 20 m of 92 soil profiles of spain grouped according to the geological nature of the rock fragments on the soil surface or in the soil profile were studied mathematical relations were developed to separate the contributions of the fine earth fraction and of the fraction above 2 mm indexes were obtained that relate gravitational water and available water in the fine earth fraction with the values from total soil a multiple comparison statistical study was performed for the mean values of 1 rock fragment content 2 organic matter content 3 silt plus clay content 4 gravimetric water content at different suction values the linear correlations of the gravitational and available water indexes with the rock fragment content by volume as independent variable were studied they showed positive or negative effects of the increase of rock fragment content on both indexes depending on their petrographical composition finally conclusions related tothe development of vegetation and to the production of runoff have been drawn when rock fragment content increases the results show positive effects for the development of vegetation and for the production of saturation overland flow

effects of drainage ditches and stone bunds on topographical thresholds for gully head development in north ethiopia abstract gully erosion is an extreme process of land degradation operating in different regions of the world a common way to quantify the susceptibility of land to gully incision is the use of topographical thresholds for different land use types however the impact of various management practices in cropland on these thresholds has not been studied to date although land management may significantly affect runoff production erosion processes and rates here the impact of different land management practices on gully head development in cropland is studied based on a standardized procedure for topographical threshold analysis s ka b where s represents the slope gradient of the soil surface a the drainage area at the gully head b an exponent and k a coefficient reflecting the resistance of the land to gully head development a case study area was chosen around wanzaye north ethiopia where three different cropland management practices were studied in 75 catchments i the catchment wide use of stone bunds on the contour ii the use of slightly sloping drainage ditches feses and iii the combined use of stone bunds and feses the lowest k values 0 078 0 090 are found for catchments treated with feses the highest k values 0 198 0 205 are observed for stone bund catchments and medium k values 0 092 0 099 are found for mixed catchments this finding implies that catchments with the exclusive use of drainage ditches are the most vulnerable to gully head development compared with mixed catchments and stone bund catchments however on site sheet and rill erosion rates are reduced by feses as they lower the gradient of the overland flow lines three trends in cropland management around wanzaye and the wider region are observed i feses are exclusively made on rather steep slopes where small drainage areas lead to the rapid development of gully heads ii stone bunds are constructed on both steeper and gentle sloping cropland and iii larger and gently sloping catchments seem to be most suitable for the combined use of drainage ditches and stone bunds

the relation between surface rock fragment cover and semiarid hillslope profile morphology abstract rock fragment covers veneer hillslopes in many parts of the world and influence the operation of hydrologic and geomorphic processes on those surfaces the purpose of this investigation was the examine the spatial variability of rock fragment cover on morphological units of hillslopes in southeastern arizona u s a simple statistical models based upon hillslope gradient as well as a soil slope factor ssf were developed and validated for the estimation of percent rock fragment covers rfc on these units although reasonably accurate estimates were made using either hillslope gradient or the ssf it appears more efficient to utilize hillslope gradient alone likewise reasonably accurate estimates of rfc can be made using either a composite model for the entire hillslope or unit specific models however it appears more efficient to utilize the gradient composite model

orographic wave drag over the southern ocean a linear theory perspective abstractrecent studies suggest that stratospheric wind biases in global and climate models in the southern hemisphere may result from insufficient orographic wave drag particularly over the southern ocean in the latitude belt centered near 60 s in this study contributions to the stratospheric wave drag along 60 s from three neighboring orographic wave sources are evaluated using a multiple layer linear wave model with large scale wind and stratification profiles derived from the interim ecmwf re analysis era interim between the years 1991 and 2010 the orographic wave sources include the patagonian peaks in the southern andes the antarctic peninsula and the island of south georgia the climatological and dynamical aspects of the wave drag and its dependence on tropospheric winds are investigated the results suggest that these orographic wave sources may have significant contributions to the stratospheric drag over the southern ocean through meridional spreading of the wave momentum flux aloft assoc

can ash control infiltration rate after burning an example in burned calcareous and gypseous soils in the ebro basin ne spain abstract fire is a long established ecological factor that has shaped the life history hydrogeomorphological processes soil formation and landforms of mediterranean environments soil infiltration is one of the properties affected by fire as a consequence of litter and vegetation removal and heating of and changes to the biological chemical and physical soil properties in this context ash can play an important role in soil infiltration behavior and therefore affect sediment and runoff yield the aim of this work is to determine the effect of ash cover on infiltration rates a single ring infiltrometer was used immediately after a wildfire and before the first storm events to determine the soil infiltration rate a total of 24 infiltrations were made 2 soil types 2 treatments 6 replicates in each infiltration experiment the soil wetting front the bulk density and stoniness were also measured the results show that the final infiltration rate fc values are higher in calcareous soils than in gypseous soils the ash cover in calcareous burned soils only temporarily decreases the bulk density of topsoil and enhances infiltration

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

development of badlands and gullies in the sneeuberg great karoo south africa abstract the study aims to examine the origin and development of land degradation with particular emphasis on badland and gully systems in the sneeuberg uplands of the great karoo this is an area of semiarid extensive stock farming where land degradation in the form of rill and gully erosion has accompanied the replacement of grassland by shrub vegetation species diversity has declined and ground cover has been reduced leading to a positive feedback loop which exacerbates the degradation many foot slopes developed in shales clays and colluvium have extensive incipient badland development with closely spaced gullying up to 1 5 m deep in valley bottom and valley side depression locations gullies up to 8 m deep have developed usually cut to bedrock through valley fills of mainly holocene colluvium both badlands and gullies appear to have developed since european settlement and to be part of the same hydrological system with extensive areas of bare ground badlands feeding water to incising gullies experiments using simulated rainfall throw some light on current processes badland areas are active under high frequency low magnitude rainfall events major gullies are likely to be the result of occasional high magnitude events but these have not been observed overgrazing in the past is the most likely cause of the degradation

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

surface roughness evolution of soils containing rock fragments soil surface roughness is a dynamic property which determines to a large extent erosion and infiltration rates although soils containing rock fragments are widespread in the mediterranean region the effect of the latter on surface roughness evolution is yet poorly understood therefore laboratory experiments were conducted in order to investigate the effect of rock fragment content rock fragment size and initial moisture content of the fine earth on the evolution of interrill surface roughness during simulated rainfall surface elevations of simulated plough layers along transects of 50 cm length were measured before and after simulated rainfall totalling 192 5mm z 70mm h with a laser microreliefmeter the results were used to investigate whether systematic variations in interrill surface roughness along stony hillslopes in southeastern spain could be attributed to rock fragment cover and rock fragment size soil surface elevations were measured along the contour lines 50 cm long transects with a contact microreliefmeter roughness was expressed by two parameters related to the height and frequency of roughness elements respectively standard deviation of de trended surface elevations random roughness rr and correlation length l derived from exponential fits of the autocorrelation functions the frequently used assumption that surface roughness rr of cultivated topsoils decreases exponentially with cumulative rain is not valid for soil surfaces covered by rock fragments the rr of soils containing small rock fragments 1 72 7 cm increased with cumulative rainfall after an initial decrease during the first 17 5 mm of rainfall for soils containing large rock fragments 7 7 cm rr increased with rainfall above a threshold rock fragment content by mass of 52 per cent for a given rainfall application rr increased non linearly with rock fragment content the correlation length for soils containing small rock fragments decreases with rock fragment content and is significantly lower than for soils with large rock fragments soils covered with small rock fragments large rr and small l are thus well protected against raindrop impact by a water film in the depressions between the rock fragments on abandoned agricultural fields along hillslopes in southeastern spain rock fragments cover increases non linearly with slope owing to selective erosion of finer particles on steep slopes the increase of surface cover by large rock fragments 25 mm is even more pronounced the simultaneous increase of rock fragment cover and rock fragment size with slope explains the non linear increase of rr with slope these relationships differ for soils covered by platy misaschists and those covered with cubic andesites the variations in correlation length along the hillslopes are not clear probably owing to a simultaneous increase in rock fragment cover and rock fragment size these findings may provide a better prediction of soil surface roughness of interrill areas covered by rock fragments using slope angle and lithology

assessing the impact of soil surface characteristics on vineyard erosion from very high spatial resolution aerial images cote de beaune france we describe a new method to map intra plot soil surface heterogeneities at a 5 cm spatial resolution our approach unites aerial image classification acquired at very high spatial resolution vhsr with local soil sampling vhsr aerial image processing based on image classification allows precise mapping of the spatial distribution of soil surfaces soil sampling defines soil typology by physical and chemical characteristics this method has been applied to a plot area located on the hillslopes of burgundy vineyards monthelie france where decennial erosion data were already available in order to assess the effect of soil surface characteristics and slope angle on erosion intensity and localisation from this method four classes of radiance were distinguished and interpreted as four soil surface state classes ssc defining specific areas within the studied plot these sscs have been characterised by their grain size distribution their organic carbon calcium carbonate and total nitrogen contents by allowing soil surface states to be mapped at five centimetre resolution this approach provides novel insights into the characterisation of soil patterns and into erosion analysis on cultivated hillslopes our work shows that the spatial distribution of soil erosion is related to the local slope steepness but also to the spatial distribution of stoniness that results from water and tillage erosion processes

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

effects of interrill erosion soil crusting and soil aggregate breakdown on in situ co2 effluxes soil and carbon redistribution on arable land and the associated impacts on carbon sequestration and mineralisation may play an important role in the global carbon cycle while our insight in the process chain of erosion transport and deposition has significantly grown over recent years there are still major gaps in understanding making it difficult to make an overall assessment of erosion processes on carbon exchange between the soil and the atmosphere one issue is the potential effect soil degradation and erosion processes may have on co2 effluxes at eroding sites the major goal of this study was therefore to analyse and understand the effects of interrill erosion soil crusting and soil aggregate breakdown on in situ co2 effluxes therefore a set of rainfall simulations were carried out on bare loess burden soil with different antecedent soil moisture content all treatments were compared with controls protected from rain drop impact using a fine meshed geotextile as expected runoff and sediment delivery was significantly larger on bare compared to covered soils while surface runoff and sediment delivery increased in most cases with rising antecedent soil moisture as well as rainfall duration crust thickness increased with antecedent soil moisture and rainfall intensity and was in general smaller for the controls however variations in crust thickness did not result in significant differences in in situ measured co2 effluxes also the destruction of the soil crust after six to seven days of measurements did not have a significant effect this leads to the conclusion that crusting and interrill erosion has no or only a minor effect on in situ co2 effluxes nevertheless it should be recognised that topsoil carbon is preferentially removed due to interrill erosion which may result in additional co2 release at depositional sites or in stream and or standing water bodies