quantifying provenance of reservoir sediment using multiple composite fingerprints in an arid region experiencing both wind and water erosion abstract quantitative information on sediment sources is useful for developing targeted protection measures that effectively control soil erosion in a watershed in this study a multiple composite fingerprints method was tested and used for quantifying the sediment provenance of the danghe river and for providing effective sediment control strategies for the watershed in an arid region experiencing both wind and water erosion surface samples were taken from three geomorphic source areas of dunes gobi and upstream mountains and sediment samples from the watercourses near the reservoir to accommodate the wide range of sediment size distributions resulting from the fluvial and aeolian processes sediment contributions from each source were estimated for each of six particle size groups the results showed that the proportional contributions from each source to the reservoir sediments were 56 73 from upstream mountains 26 36 from gobi and 16 91 from dunes with the relative contributions in each size group following a similar trend the largest fraction of the sediment was from the 0 063 0 1 mm particle size group accounting for about 37 09 of the total in which 4 7 59 and 25 50 were from dunes gobi and upstream mountains our results also indicated that selective erosion existed in both erosion processes especially in wind erosion process and multiple particle size tracking should be used in the cases of severe selective erosion to improve the accuracy of estimation also the sediment contribution rate per unit area was the largest from dunes thus controlling wind blown sand to the river by stabilizing the dunes is recommended to reduce the reservoir siltation

sediment sources and siltation in mountain reservoirs a case study from the central spanish pyrenees abstract based on a 137 cs derived chronology we reconstruct the depositional history of the barasona reservoir in the esera isabena basin central pyrenees spain most of the sediments were delivered to the barasona reservoir during flood events comparative mineralogical studies of the esera and isabena river channels and the barasona reservoir sediments help to identify sediment sources and areas of high sediment yield risk and to establish erosion and sediment transport processes in the watershed changes in the mineralogical composition of the sediments can be used to discriminate the relative contribution of the esera and isabena rivers during flood periods three main periods in the siltation history of the barasona reservoir were distinguished 1 from dam construction 1932 to the early 1950s the reservoir was flushed every year using the lower gates and average sediment accumulation was very low 1 5 cm yr 2 during the 1950s and 1960s the sedimentation rate increased and reached the highest values 15 cm yr 24 6 cm yr and 18 2 cm yr in the esera river mouth the northern and the southern areas of the reservoir respectively both changes in the exploitation regime no annual flushes and climate variability increased flood frequency and river inflow caused this increase in sediment delivery and accumulation 3 the third period was initiated by the enlargement of the dam in 1972 the new sedimentary dynamics in the reservoir caused a general decrease in the sedimentation rate 11 6 cm yr in the southern areas 10 cm yr in the esera mouth that was especially noticeable in the northern areas where the accumulation rate was reduced to 3 7 cm yr an increase in channel erosion processes during this period contributed to the transport of sediments to the inner areas of the reservoir

unravelling changing sediment sources in a mediterranean mountain catchment a bayesian fingerprinting approach to determine the provenance of holocene floodplain deposits of the bugduz catchment in southwest turkey a bayesian fingerprinting approach was used an important requirement for any provenance study is that the potential sediment sources show sufficient spatial and compositional heterogeneity the spatial distribution of potential sources in this case the various lithologies present within the catchment was mapped using field observations and aster and quickbird satellite images to distinguish the source lithologies a set of geochemical tracers was identified using linear discriminant analysis this optimum fingerprint was then used in the mixing model to determine the sediment provenance the bayesian mixing model uses markov chain monte carlo random walks to determine the most probable source composition and mixing proportions the uncertainty associated with the input data can be incorporated into the model through prior probability distributions the spread of the posterior probability distributions represents the uncertainty associated with the mixing proportion calculation the main contrasts in the provenance of the floodplain deposits reflect the spatial distribution of potential sediment sources throughout the catchment there are however also important temporal variations in sediment provenance and lateral differences due to the nature of floodplain build up the observed spatial and temporal variability of sediment provenance gives a first indication that hill slope channel and within channel coupling relations are not uniform through the catchment and that different locations showed a distinct response to disturbances copyright 2012 john wiley sons ltd

an analytical benchmark with combined pressure and shear loading for elastoplastic numerical models we discuss the benchmark strategy to check the accuracy of elastoplastic numerical solutions based on a fully two dimensional analytical solution associated rate independent non hardening plasticity with von mises or tresca criteria is assumed throughout algorithms for integration of the rate equations strategies for stress updating over a time step and tangent operators are discussed the accuracy of a simple incremental algorithm as a function of the time step is discussed

effectiveness of check dam to control soil erosion in a tropical catchment the ulu kinta basin abstract check dams are commonly used to stabilize sedimentation reduce the through water velocity limit catchment erosion and increase the reservoir storage capacity of a dam in the study area three check dams were constructed before the sultan azlan shah dam by the perak water board lap to control sedimentation this area is an active erosion environment because of the erodible material in the stream and check dams the effectiveness of the check dams cd1 to cd3 was investigated to identify how the construction of such transverse structures can be used to control the soil erosion rates and the reservoir storage capacity of the dam toward this end first geomorphic maps of the channel bed in the upstream and the downstream region were obtained then the distribution of bed material in the study area was determined through sampling at 20 individual locations along the river finally the impact of check dams on settling particles was calculated on the basis of critical velocity cross sections of the river showed a narrow steep channel upstream and a wide shallow channel downstream the median grain size distribution d 50 was between 2 mm before cd1 to 0 082 mm after cd3 with a minimum measured velocity of 0 24 m s the critical velocity showed a significant correlation with measured velocity furthermore the velocity of the river and the dimension of the check dams were suitable for trapping coarse particles especially at the last check dam cd3

regional scale modeling of hillslope sediment delivery a case study in the barasona reservoir watershed spain using watem sedem summary soil erosion and sediment delivery to streams are important environmental problems and major concerns in sustainable development in recent years several tools have been proposed for assessing the delivery of sediment from hillslopes to stream networks but there are still few examples of their application to large basins and studies include a discussion of calibration and validation issues in this study a spatially distributed soil erosion and sediment delivery model watem sedem was applied to the watershed of the barasona reservoir 1504 km 2 central spanish pyrenees which is drained by the esera and isabena rivers model calibration and validation was based on the depositional history of the barasona reservoir and suspended sediment records over 3 years may 2005 may 2008 at the outlet of the isabena river despite interannual differences in precipitation and runoff it was possible to establish an optimum value 7 23 for the ktc parameter this enabled estimation of the long term average annual sediment yield to the reservoir as well as the relative contribution of each river large spatial variability in hillslope sediment delivery was found and the major sediment sources were in the lower part of the watershed agricultural fields and in the badlands developed on eocene marls in the middle part of the watershed pyrenean inner ranges the relative importance of sediment source areas was assessed in relation to land use and the relationship between the sediment delivery ratio and the catchment area was studied as a function of the geomorphological units for the moment watem sedem remains mainly as a researcher s tool until either the problem of the scarcity of soil erosion data or the need for calibration of the transport parameters will be solved

using 137cs technique to quantify soil erosion and deposition rates in an agricultural catchment in the black soil region northeast china article i nfo soil erosion significantly affects the productive black soil region in northeast china quantification of the soil erosion is necessary for designing efficient degradation control strategies 137 cs measurements undertaken on 61 sampling points collected within a 28 5 ha agricultural catchment in the black soil region of northeast china were used to establish the magnitude and spatial pattern of soil redistribution rates as well as sediment budget within the catchment estimated soil redistribution rates using the mass balance model 2 mbm2 ranged from 56 8 to 171 4 t ha 1 yr 1 for the sampling points that were verified by means of both runoff plot data and pedological investigation erosion generally occurred behind the shelterbelts especially in the ephemeral gully susceptibleareas while deposition mainlyoccurred along the shelterbelts and atthe catchment outlet inthestudycatchment 69 oftheerodedsedimentscamefromtheslopes and31 theephemeral gullies sedimentsdepositedalongthe shelterbeltsatarateofca 78 t yr 1 andca 33 t yr 1 atthecatchmentoutlet the gross soil loss rate for the catchment was 4 4 t ha 1 yr 1 with a sediment delivery ratio of 53 the mean rate of 14 5 t ha 1 yr 1 in the erosion areas was much higher than the tolerable value suggesting that effective soilconservationmeasuresare urgentlyrequiredtoreducethesevere black soillossforsustainable management of the soil resource

rapid onset of late paleozoic glaciation on gondwana evidence from upper mississippian strata of the midcontinent united states direct evidence of the late paleozoic glaciation of gondwana from glacial deposits suggests that geographically extensive continental glaciation began some time in the namurian late mississippian however the timing and characteristics of the onset of glaciation are poorly understood because of a lack of reliable paleontological control and reworking of initial glacial deposits by subsequent glacial advances indirect evidence of glaciation preserved in unconformity bounded low latitude ramp sequences in the illinois basin united states suggests that geographically extensive continental glaciation of gondwana actually began in the late visean an abrupt change from carbonate dominated sequences bounded by disconformities with little evidence of erosion to mixed carbonate siliciclastic sequences bounded by unconformities with deep incised valleys was likely produced by a three fold increase in the magnitude of eustatic sea level fluctuations the increase in the magnitude of sea level fluctuations was likely driven by an equally abrupt increase in ice volume and marks the onset of the geographically extensive late paleozoic glaciation of gondwana a possible explanation for the rapid onset of glaciation is the closing of the equatorial seaway between laurussia and gondwana closing of this seaway would have led to an abrupt change in oceanic and atmospheric circulation patterns that could have initiated major continental glaciation in the southern hemisphere

response of sedimentary organic matter source to rainfall events using stable carbon and nitrogen isotopes in a typical loess hilly gully catchment of china abstract understanding the information on sedimentary organic matter som source is of great importance for better understanding biogeochemical cycling and terrestrial carbon sequestration on the earth s surface such information especially during field rainfall process however is unavailable or difficult to assemble in order to further study the dynamic variation of sedimentary organic matter source during rainfall process suspended sediment were sampled manually at the outlet of two paired typical hilly gully watersheds of loess plateau in china qiaozi east watershed qew and qiaozi west watershed qww and source materials included subsoil i e soils from channel bank and gully bank and topsoil i e surface soils from different slope positions in land uses along with c 3 and c 4 plants in this study reported natural stable isotopes 13 c and 15 n and elemental compositions toc and tn combined with a isotope mixing model stable isotope analysis in r siar were successfully used to assemble this information the results showed that the response of source contributions to som displayed difference significantly during different rainfall processes showing fluctuation with flow subsoil was the main source of som pool for two similar small watersheds accounting for 38 50 for qww and 35 63 for qew minor contribution was sourced from the c 3 and c 4 plants 4 plants indicating that the c 3 plants dominated the input of organic matter in superficial soils of this study region the source of sedimentary organic matter transported by erosion showed different contribution proportions from potential sources in two similar small watersheds with different management practices indicating that management practice could decrease the soil organic matter loss by reducing the sediment transportation and flow during rainfall process in the loess plateau of china

sediment yield estimation in a small watershed on the northern loess plateau china abstract soil erosion is a major form of land degradation throughout the world and the key environmental problem that threatens the ecosystem of the chinese loess plateau in this study we determined the sediment yield from a small dam controlled watershed in the huangfuchuan watershed northern loess plateau with a drainage area of 0 64 km2 the dam infill sediment provided evidence of at least 31 flood couplets which corresponded to rain storms during 1958 1972 in total 1 65 105 t sediment was accumulated within the whole check dams in this period the annual sediment yield ranged from null in 1965 to 59 990 t in 1959 we used the modified watem sedem model to simulate soil erosion and the sediment yield in the watershed and the sedimentation records were used for model verification the model produced satisfactory results the total soil erosion and sediment delivery ratio were estimated to be 1 97 105 t and 83 6 respectively bare weathered stone in the steep gullies contributed 90 of the sediment yield while the remainder was derived mainly from bare loess slopes and the alluvial plain this study suggests that analyzing sedimentation behind check dams and applying the watem sedem model are useful for the quantitative analysis of sediment dynamics in ungauged basins on the loess plateau

dating reservoir deposits to reconstruct sediment yields from a small limestone catchment in the yimeng mountain region china abstract in this study we use reservoir deposits to reconstruct sediment yields over the past 50 years from the quananzi catchment a small limestone catchment in the yimeng mountain region china three sediment cores were collected from the reservoir and the chronology of each core was established using 137cs and 210pbex dating the area specific sediment yields ssy for different time periods since dam construction were estimated from each core by referring to the original capacity curves of the reservoir the estimated ssy from the quananzi catchment in each core for each period ranged between 0 9 0 3 and 2 6 0 9 t ha 1 y 1 with a mean value of 1 8 0 6 t ha 1 y 1 which is low compared with reported ssy from catchments worldwide the mean value was only about 1 7 of the equivalent value reported from the jiangzhang catchment in the granite area of the yimeng mountain region this low ssy reflects the shortage of erodible luvisols resistance to erosion and the limited effect of human disturbance in this small limestone catchment the decrease in ssy from 1959 to1972 suggests that the effect of the deforestation that occurred in 1958 on soil erosion decreased with time the continual increase of ssy through the two subsequent periods after 1972 reflects the expansion and intensification of cultivation during this time however the decreased ssy over the latest period of 1998 2012 can be related to the limitations imposed by the karst landscape on cultivation and to the impact of increasing numbers of residents leaving the area since the end of the 1990s to become temporary migrant workers elsewhere resulting in a decrease in human activity in the area overall the trend in ssy reflects the general history of changing human disturbance in this small limestone catchment over the past 50 years the results indicate that reservoir deposits provide a means of estimating the historical sediment yields from a karstic environment

modelling the impact of land use change and farm dam construction on hillslope sediment delivery to rivers at the regional scale abstract landscapes in southeastern australia have changed dramatically since the spread of european colonisation in the 19th century due to widespread forest clearance for cultivation and grazing erosion and sediment yields have increased by a factor of more than 150 in the 20th century erosion and sediment yield were reduced again due to an increasing vegetative cover furthermore during the last decades thousands of small farm dams were constructed to provide drinking water for cattle these dams trap a lot of sediment thereby further reducing sediment delivery from hillslopes to river channels changes in sediment delivery since european colonisation are documented in sediment archives within this study these changing rates in hillslope erosion and sediment delivery were modelled using a spatially distributed erosion and sediment delivery model watem sedem that was calibrated for australian ecosystems using sediment yield data derived from sedimentation rates in 26 small farm dams the model was applied to the murrumbidgee river basin 30 000 km 2 under different land use scenarios first the erosion and sediment yield under pre european land use was modelled secondly recent land use patterns were used in the model finally recent land use including the impact of farm dams and large reservoirs was simulated the results show that the watem sedem model is capable of predicting the intensity of the geomorphic response to changes in land use through time changes in hillslope erosion and hillslope sediment delivery rates are not equal illustrating the non linear response of the catchment current hillslope sediment supply to the river channel network is predicted to be 370 higher compared to the pre european settlement period yet farm dams have reduced this back to 2 5 times the pre 19th century values the role of larger reservoirs is even more important as they have reduced the current sediment supply downstream to their pre european values thus completely masking the increased hillslope erosion rates from land use change however the model does so far not include valley widening and sediment storage in river systems therefore modelled rates of sediment delivery are lower than observed values

determinants of extinction in the fossil record the causes of mass extinctions and the nature of biological selectivity at extinction events are central questions in palaeobiology it has long been recognized however that the amount of sedimentary rock available for sampling may bias perceptions of biodiversity1 2 3 4 5 6 7 and estimates of taxonomic rates of evolution5 6 7 8 this problem has been particularly noted with respect to the principal mass extinctions5 6 7 8 9 10 11 12 here we use a new compilation of the amount of exposed marine sedimentary rock to predict how the observed fossil record of extinction would appear if the time series of true extinction rates were in fact smooth many features of the highly variable record of apparent extinction rates within marine animals can be predicted on the basis of temporal variation in the amount of exposed rock although this result is consistent with the possibility that a common geological cause determines both true extinction rates and the amount of exposed rock it also supports the hypothesis that much of the observed short term volatility in extinction rates is an artefact of variability in the stratigraphic record

sources of fine sediment recovered from the channel bed of lowland groundwater fed catchments in the uk abstract groundwater fed lowland permeable catchments in the uk are particularly susceptible to fine sediment accumulation on the bed of their main channel systems appropriate catchment management solutions are therefore required accurate targeting of sediment abatement strategies is however hampered by the dearth of reliable information on the principal sediment sources involved in view of this a composite fingerprinting technique incorporating uncertainty analysis has been used to investigate the primary sources of fine sediment samples recovered from a total of 18 individual sampling sites on the channel bed of the rivers frome 437 km 2 and piddle 183 km 2 dorset uk in the frome study catchment mean relative contributions from areas of woodland pasture and cultivation and from channel banks subsurface sources ranged between 1 1 6 2 10 2 42 2 44 4 81 2 and 7 2 19 4 respectively the corresponding mean relative contributions in the piddle study area were 1 1 11 4 woodland 10 2 28 4 pasture 44 2 80 2 cultivated and 7 2 21 2 channel banks and subsurface sources these findings have important implications for establishing a scientific basis for assisting the targeting of sediment management and control policies

erosion rates obtained from check dam sedimentation se spain a multi method comparison abstract the main aims of this article are to calculate the erosion rates from sediments accumulated in the check dams and to compare the results with those of other methodologies the study was carried out in a semi arid area in the south east of spain in the basin of the river segura where 425 check dams have been built in order to prevent silting up of a reservoir built in the estuary from the records of sediments deposited in the different dikes since their construction various erosion rates have been calculated variations in the rates obtained are very high and explanations have been proffered based on physical parameters like the surface areas of the drainage basins to the dikes the slope of the channel the lithology or the year in which the dikes were constructed the results show that in general terms the larger the area and the steeper the incline the lower the erosion rates highest rates were found in lithologies of marls and in dikes which have been operational for only a few years the erosion rates for the whole set as well as by sub basins have been compared with those obtained through other methods usle fournier and bathymetric the bathymetric rates are similar to those obtained from the dikes 3 95 t ha year but the usle values are 4 5 fold higher and contrary to those of the dikes

low erosion rates measured for steep sparsely vegetated catchments in southeast spain abstract in order to reduce widespread degradation in desertification prone areas there is an urgent need to understand the mechanisms controlling human induced degradation processes in semi arid ecosystems southeast spain is known as one of the most arid regions of europe and its landscape is marked by sparsely vegetated degraded hillsides large areas of dry cultivation have been abandoned since the early part of the twentieth century and irrigated cultivation is now expanding rapidly in this study modern erosion rates for two mountain ranges belonging to the betic cordillera were assessed by direct measurements of the accumulated sediment volumes behind 20 checkdams the volume of sediment deposited behind the checkdams ranges between 4 and 920 m 3 for catchments with a drainage area varying between 1 5 and 317 ha our measurements indicate that mean annual catchment wide erosion rates in these mountain ranges are generally low the observed erosion rates are well below maximum tolerable annual soil loss rates for the mediterranean region as 90 of the catchments have mean annual erosion rates below 2 t ha 1 y 1 our erosion data from 20 small catchments in the betic range are lower than the results of previous erosion studies in southeast spain that were conducted in the neogene intramontane basins this study deals with erosion rates on thin soils developed on metamorphic rocks which are not often the subject of study in the mediterranean region in the ephemeral stream systems in the betic range the spatial pattern of the vegetation cover within the catchment in relation to the concentrated flow lines appears to be crucial our data question the direct association of steep sparsely vegetated hillsides with enhanced soil erosion rates and suggest that the main erosion problems are currently not located in these steep sparsely vegetated environments of the betic mountain ranges

depressed rates of origination and extinction during the late paleozoic ice age a new state for the global marine ecosystem rates of origination and extinction for marine animal genera dropped to low levels in latest mississippian time immediately after massive glaciers formed in the southern hemisphere and a second order mass extinction occurred evolutionary turnover and diversity remained low for 50 m y shifting markedly upward precisely when extensive glaciation ended in early permian time all diverse taxa with good fossil records experienced low rates of origination and extinction during this major ice age such sluggish rates would be predicted for faunas of shallow seas on or adjacent to a heavily glaciated supercontinent such as pangea where cool and highly seasonal thermal regimes should dictate that species have broad ecological niches widespread geographic distributions and large and relatively stable populations

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

assessing the sources of sediment transported in gully systems using a fingerprinting approach an example from south east china abstract eroded sediment is an important feature of permanent gully s development however obtaining the specific characteristics of the sediment transport in the gully can be difficult thus a composite fingerprinting technique incorporating uncertainty analysis has been employed to investigate the mean relative contribution of sediment sources in permanent gullies in this study 31 tracers were measured at 62 different sampling sites from three layers of a gully wall surface layer sl sandy soil layer ssl and semi weathering rock layer swl and 36 sediment samples from the slumping deposit and alluvial fan of the gullies the sediment source tracing procedure was therefore used to assess the relative contribution of each source the mean relative contribution from the sl to the sediment of the slumping deposit is higher in the active gully g1 and is relatively lower in the potentially stable g2 and stable gullies g3 thus there was no obvious gully bank retreat in g2 and g3 in different places of the g1 alluvial fan the mean relative contribution of the sl ssl and swl ranged from 9 11 36 43 and 46 55 respectively however the sediment contribution of the sl increased in g2 and g3 due to the changes in the erosion type the mean relative contributions of the sl were 33 5 g2 and 30 3 g3 these findings have important implications for the establishment of a scientific basis for permanent gully sediment transport management and control policies

use of landslide dammed lake deposits and pollen tracing techniques to investigate the erosional response of a small drainage basin in the loess plateau china to land use change during the late 16th century a major landslide that occurred in 1569 in the huangtuwa gully catchment within the rolling loess plateau region of china resulted in the creation of a landslide dammed lake at the outlet of the small 0 1 km2 tributary valley of the houxiaotan gully all the sediment transported to the outlet of this catchment was deposited in the lake after about 30 years the dam failed and the lake deposits were dissected as the stream cut down to its former base level substantial remnants of the sediment deposits that accumulated over the ca 30 year period are however preserved as terraces near the outlet of the catchment and a vertical section through these sediment deposits was investigated using stratigraphic and pollen tracing techniques individual flood couplets could be clearly distinguished and these permitted the establishment of a chronology for the sediment deposits and the estimation of the sediment yields associated with individual events and individual years pollen analysis undertaken on samples collected from the individual flood couplets also provided information on the variation of the pollen content of the sediment and the proportion of artemisia pollen during the period represented by the deposits interpretation of the information assembled from the sediment section has made it possible to reconstruct the erosional history of the houxiaotan catchment during the 31 year period following the landslide the average sediment yield of the catchment in the late 16th century was very similar to its present day sediment yield the sediment yield from the catchment and the relative contribution of the inter gully areas as compared to the gully system declined immediately after the landslide as a result of abandonment of the cultivated land within the catchment the restoration of cultivation in the catchment after about 17 years resulted in an increase in sediment yield from ca 9000 t km 2 yr 1 to ca 30 000 t km 2 yr 1 and a substantial increase in the proportion of sediment contributed by the cultivated inter gully areas scope exists to apply a similar approach to the sediment deposits that accumulated in other former landslide dammed lakes within the rolling loess plateau region of china in order to develop an improved understanding of the erosion history of the region

consequences of hyperconcentrated flow for process based soil erosion modelling on the chinese loess plateau high sediment concentrations in runoff are a characteristic feature of the chinese loess plateau and are probably caused by factors such as the occurrence of erodible materials on steep slopes the characteristics of the loess and the harsh climate that results in low plant cover when sediment concentration increases fluid density increases viscosity increases and settling velocity decreases these effects become increasingly important with increasing concentration and can result in flow behaviour that is quite different from that of clear water flow although the net effect of these changes on the flow is not always apparent erosion models that deal with high sediment concentrations should consider such effects and could include corrections for some of these effects a case study in a small catchment on the loess plateau indicated that sediment concentrations were considerable and literature data suggested that for such sediment concentrations corrections for settling velocity fluid density and viscosity are needed furthermore a number of corrections are necessary to be able to compare field measurements with results of soil erosion models sediment volume should be subtracted from runoff volume and a density correction is needed to use data from a pressure transducer for flumes that were used to measure discharge from smaller areas inside the catchment the measured water level should be corrected by subtracting the sediment level in the flume from the water level while the sediment volume should also be subtracted from the discharge finally measured concentration should be corrected to give concentration expressed as grams per litre of clear water since soil erosion models express sediment concentration in this way

soil and water losses from new citrus orchards growing on sloped soils in the western mediterranean basin ten representative research sites were selected in eastern spain to assess soil erosion rates and processes in new citrus orchards on sloping soils the experimental plots were located at representatives sites on limestone in areas with 498 to 715 mm year 1 mean annual rainfall north facing slopes herbicide treated and new less than 3 years old plantations ten rainfall simulation experiments 1 h at 55 mm h 1 on 0 25 m2 plots were carried out at each of the 10 selected study sites to determine the interill soil erosion and runoff rates the 100 rainfall simulation tests 10 10 m showed that ponding and runoff occurred in all the plots and quickly 121 and 195 s respectively following rainfall initiation runoff discharge was one third of the rainfall and sediment concentration reached 10 4 g l 1 the soil erosion rates were 2 4 mg ha 1 h 1 under 5 year return period rainfall thunderstorms these are among the highest soil erosion rates measured in the western mediterranean basin similar to badland mine spoil and road embankment land surfaces the positive relationship between runoff discharge and sediment concentration r2 0 83 shows that the sediment availability is very high soil erosion rates on new citrus orchards growing on sloped soils are neither tolerable nor sustainable copyright 2009 john wiley sons ltd

estimating the contribution of tributary sand inputs to controlled flood deposits for sandbar restoration using elemental tracers colorado river grand canyon national park arizona

sediment yield and sources in dam controlled watersheds on the northern loess plateau abstract an improved understanding of the temporal variations in soil erosion rates and sediment sources is necessary to identify the main areas prone to soil erosion and to effectively implement soil and water conservation measures in this study we selected two dam controlled watersheds xiaoshilata and yangjiagou on the northern loess plateau china and determined the temporal variations in the sediment yield the sedimentation upstream of the dams showed that there were 31 and 9 flood couplets in the xiaoshilata 1958 1972 and yangjiagou watersheds 2007 2011 respectively which have trapped 16 5 104 t and 3 38 104 t of sediment respectively the estimated specific sediment yield was approximately 173 6 t ha a and 106 1 t ha a in the xiaoshilata and yangjiagou watersheds respectively a multivariate mixed model was applied to identify the different sediment sources the results indicated that weathered sandstone contributed approximately 61 52 of the total sediment and the remaining sediment loss was from bare loess soil 32 54 and grassland 5 94 in the xiaoshilata watershed in the yangjiagou watershed approximately 66 8 of the sediment originated from weathered sandstone whereas bare loess and grassland accounted for 17 5 and 15 7 of the sediment yield respectively based on these findings we recommend that comprehensive soil conservation measures are needed to soil erosion control for the permanent steep gullies due to high sediment contribution the sedimentation behind the check dams provides an indirect method for estimating the sediment yield in ungauged basins

use of bathymetry and clay mineralogy of reservoir sediment to reconstruct the recent changes in sediment yields from a mountain catchment in the western high atlas region morocco abstract the dam of takerkoust located at the outlet side of n fis basin western high atlas of morocco is one of the strategic reservoirs in morocco facing a serious problem of siltation due to soil erosion a paleo hydrology approach combining chronological and sedimentological analyses is conducted to understand the evolution of the depositional sediment history of the takerkoust reservoir between 1988 and 2016 first a series of 8 bathymetric surveys in the takerkoust reservoir was used to determine the chronology of flood event deposits second grain size distribution clay mineralogy xrd and organic matter content were analyzed in 2 cores drilled in the takerkoust reservoir and the newly build ouirgane reservoir in upstream from which 46 samples were taken third soils samples collected from the uppermost soil horizons first 5 cm of different localities of the n fis watershed were also analyzed to identify sediments origins eleven couplets with different textures and thickness are identified in the takerkoust reservoir corresponding to the period 1988 2016 the highest correlation is observed between instantaneous maximum flow and thickness of the sandy component of the couplets the variation of the siltation rate allows highlighting two distinct periods the oldest period 1988 1999 characterized by a high sediment yield sy 908 6 t km 2 yr 1 and a youngest one 1999 2016 characterized by a low sy 203 9 t km 2 yr 1 the newly built ouirgane dam seems to be responsible for the decreasing siltation rate and change of the clay assemblages of the sedimentary series in takerkoust reservoir

investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers rare earth element oxides reos have excellent potential for use as tracers in erosion studies using laboratory and field experiments we aimed to develop and test a simple application method for spreading reos and to use reos to determine the source of sediment to concentrated overland flow paths tracks left by farm machinery tramlines in fields act as concentrated flow paths delivering a large amount of surface runoff and entrained sediment to the field boundary however little is known regarding where this sediment is sourced from two field experiments were conducted to investigate this one looking at whether sediment is entrained from different points along the length of the tramline and one looking at the area over which sediment is entrained from either side of a tramline results from leaching tests and rainfall simulations clearly demonstrated the potential of this method for tracing sediment there was very little movement of reos through the soil profile and they were transported with sediment in overland flow in the field experiment a large proportion of the sediment transported in the tramline originated within the first metre either side of it however the total area over which eroded sediment collects and flows into the tramline is potentially large with small amounts of sediment eroded from the between 4 and 6 m being transported in the tramline reos have an excellent potential for use as a tracer of soil erosion they provide a quick and cheap method of identifying sources of eroded sediments and have good potential for use in determining erosion rates