evaluating controls on crevasse splay size implications for floodplain basin filling abstract although crevasse splays are often considered important contributors to floodplain basin filling evidence from modern and ancient fluvial deposits indicates that they may not play a significant role in all river systems in order to better understand controls on the abundance and scale of crevasse splays produced in fluvial systems we used aerial photography to observe crevasse splay deposits along three rivers and conducted a targeted numerical modeling study to explore factors which promote widespread crevasse splay deposition on fluvial floodplains results demonstrate that splay size does not always scale directly with channel size or discharge and that hydrodynamic factors primarily sediment size and floodplain drainage conditions play a significant role in determining whether a fluvial system is likely to produce large floodplain filling splays this work suggests that widespread crevasse splays demand both a large supply of relatively coarse suspended sediment and a steep water surface slope away from the channel across the floodplain without both these conditions the role of crevasse splays in flood basin filling is limited

joint isotopic mass balance a novel approach to quantifying channel bed to channel margins sediment transfer during storm events the important role of floodplains and the broader riparian zone in providing temporary storage for a large fraction of the annual sediment load of rivers is well established but this understanding is largely based on observations of the long term average behavior of the catchment here we combine measurements of the fallout radionuclides 7be and 210pb and the stable isotopes of hydrogen in water to quantify fine sediment mobilization and storage in a stream and its channel margins during individual intermediate sized storm events with recurrence intervals of a few months or less we demonstrate this method using five storm events in a small 15 km2 undeveloped gravel bedded tributary of the connecticut river usa we estimate that in each storm the mass of sediment deposited onto the margins accounts for almost 90 of the sediment mobilized from the bed with the remainder of the mobilized bed sediment transported downstream as suspended load the result that the bed is a net source of sediment to the stream and the margins a net sink is robust but estimates of the mass of material eroded from the bed and deposited on the margins are less certain the source of sediment to the bed remains unclear as consistent with earlier studies we observe only limited deposition of sediment to the bed during the storm events the suspended sediment is organic rich and thus its source may be associated with in channel organic decay between storm events understanding the coupled interactions between discharge magnitude and frequency and sediment resupply at the event time scale has important implications for stream restoration efforts seeking to connect the channel and the broader riparian zone and for the development of accurate sediment budgets and predictions of sediment flux from a watershed copyright 2015 john wiley sons ltd

model analyses of the contribution of in channel processes to sediment concentration hysteresis loops summary sediment concentration sc water discharge q relations in rivers are typically governed by multiple and relatively complex processes due to hysteresis effects sediment discharges can differ for similar or equivalent water discharges which causes scatter in empirical datasets and may decrease the predictive power of sc rating curves such hysteresis effects must therefore be understood and accounted for to make dependable predictions for river system management the overall objectives of this study are to develop modelling approaches suitable for reproducing and predicting hysteresis effects at larger scales and to investigate the possible contribution of in channel processes erosion and deposition to sediment concentration hysteresis loops to investigate relevant field scale conditions we develop a one dimensional dynamic sediment transport model of the downstream tuul river northern mongolia investigating in channel processes along a 141 km stretch during a hydrological year the results show that the present modelling approach can reproduce both anti clockwise and clockwise hysteresis effects importantly in channel processes alone can cause considerable anti clockwise hysteresis effects without being reinforced by catchment processes such as hillslope erosion such specific contributions from in channel processes introduced data scatter into the sediment rating curves decreasing their r 2 values from unity to approximately 0 5 to 0 6 more generally possible changes in the number or magnitude of high flow events caused by climatic or other anthropogenic factors could influence total sediment deposition which was primarily found to occur during relatively short high flow events such potential changes also have important implications for the possible spreading of polluted sediments

runoff and soil moisture as driving factors in suspended sediment transport of a small mid mountain mediterranean catchment abstract soil moisture conditions play a key role in runoff and sediment load dynamics in river catchments of contrasting ecosystems however the highly marked seasonality of mediterranean climate affects hydrological processes and sediment transport strongly as evapotranspiration determines a succession of wet transition and dry periods throughout a hydrological year this study examines results of soil moisture water and sediment fluxes during five hydrological years in a representative small mid mountain mediterranean catchment it aims to assess the sediment load contribution and its variability at different temporal scales precipitation runoff and suspended sediment load were calculated at annual seasonal and event scales to assess inter and intra annual variability a database with 45 events was used to identify the main controlling factors over sediment load thought bivariate relationships and an analysis of soil moisture discharge and discharge suspended sediment concentration hysteresis at the annual scale lithology land use and soil conservation structures characteristic of the catchment caused low values of sediment yield although inter annual rates varied by up to three orders of magnitude 0 08 to 11 86 t km 2 y 1 seasonal analysis of accumulated sediment load showed that 80 was generated during the autumn and winter seasons at the event scale streamflow and soil moisture were the controlling factors for the largest sediment load contributions the highest frequency of clockwise discharge suspended sediment concentration hysteresis revealed that most of the sediment was generated from nearby sources although the largest sediment loads were contributed under wet antecedent conditions as depicted by the soil moisture discharge hysteresis assessment

turbidity and suspended sediment dynamics in small catchments in the nepal middle hills the himalayan environment has until recently been perceived to be in a critical state of environmental decline resulting from rapid population growth and associated land use change recent research however has emphasized the di culty of developing an objective appraisal of the state of the environment in a region where empirical data are scarce and unstructured and where an understanding of the spatial and temporal dynamics of natural environmental processes remains highly uncertain this paper presents results from an intensive three year project designed to help address the regional empirical de cit establish detailed baseline environmental data and to gain an insight into storm period and seasonal suspended sediment dynamics the instrumentation calibration and analysis of high frequency infrared turbidimetric records from a number of small subcatchments in the nepal middle hills are reported storm period and seasonal variation in turbidity and suspended sediment are examined and hysteresis patterns explored and explained a variety of methods to estimate seasonal suspended sediment yield in a mixed land use catchment are examined and found to vary by up to a factor of ve despite the inherent uncertainty all estimates of catchment sediment yield are found to be high with respect to erosion plot studies from the local area and this suggests the importance of riparian and channel erosion as major sediment sources a nding consistent with other regional studies copyright 1999 john wiley sons ltd

hysteresis in suspended sediment to turbidity relations due to changing particle size distributions 1 turbidity t is the most ubiquitous of surrogate technologies used to estimate suspended sediment concentration ssc the effects of sediment size on turbidity are well documented however effects from changes in particle size distributions psd are rarely evaluated hysteresis in relations of ssc to turbidity ssc t for single stormflow events was observed and quantified for a dataset of 195 concurrent measurements of ssc turbidity discharge velocity and volumetric psd collected during five stormflows in 2009 2010 on yellow river at gees mill road in metropolitan atlanta georgia regressions of ssc normalized turbidity t ssc on concurrently measured psd percentiles show an inverse exponential influence of particle size on turbidity that is not constant across the size range of the psd the majority of the influence of psd on t ssc is from particles of fine silt and smaller sizes finer than 16 m this study shows that small changes in the often assumed stability of the psd are significant to ssc t relations changes of only 5 m in the fine silt and smaller size fractions of suspended sediment psd can produce hysteresis in the ssc t rating that can increase error and produce bias observed ssc t hysteresis may be an indicator of changes in sediment properties during stormflows and of potential changes in sediment sources trends in the psd time series indicate that sediment transport is capacity limited for sand sized sediment in the channel and supply limited for fine silt and smaller sediment from the hillslope

mineralogical and geochemical features of sulfide chimneys from the meso zone central indian ridge hydrothermal activity is fairly well documented from most mid ocean ridges however despite various efforts there is only one hydrothermal field recognized so far in the indian ocean products of former hydrothermal activity were sampled in the fourth segment of the central indian ridge cir north of the rodriguez triple junction rtj near 23 s the mineralized area referred to as meso zone covers an area of about 0 6 km2 and is located at a water depth of 2850 m close to the height of a neovolcanic intrarift ridge hydrothermal mineralization is structurally controlled by fissures and cracks running both parallel and orthogonal to the general strike direction of the cir axis 152 n sulfides of the meso zone formed over a period of at least 30 000 years hydrothermal activity ceased 10 000 years ago detailed mineralogical and geochemical studies of sulfides establish the growth and decay of chimney structures which are mainly composed of pyrite marcasite and chalcopyrite chimneys show high concentrations of base metals particularly cu and fe more than 40 wt as well as high trace element contents like co up to 0 24 wt and as 1 wt in contrast sphalerite is rarely observed which is attributed to replacement and refining processes during the weathering and physical disintegration of the hydrothermal products the zn content is generally low 1 wt only selected samples show higher zn concentrations up to 7 9 wt remnants of chimney structures are characterized by the absence of sulfates but they contain minor amounts of amorphous silica

temporal distribution of suspended sediment transport in a mediterranean basin the lower tordera ne spain abstract suspended sediment dynamics are still imperfectly understood especially in areas of mediterranean climate with strong seasonal contrasts where few studies have been conducted the aim of this study is to analyze the variability in the suspended sediment load at different temporal scales within flood variability monthly seasonal and annual in the tordera river 894 km 2 located in northeastern spain suspended sediment samples were obtained during base flows q 3 5 m 3 s 1 and flood events q 3 5 m 3 s 1 the analysis of the variability in the suspended sediment is structured in two consecutive steps i the construction of statistical relations between suspended sediment concentrations c and discharge q and ii the application of those relations to assess the suspended sediment yield the results show that in a single event the sediment peak generally precedes the peak discharge following a clockwise hysteretic loop furthermore it was observed that the reduction in the suspended sediment concentrations in a sequence of events can be mainly associated with a phenomenon of sediment exhaustion the total amount of suspended sediment transported during a single flood is thus related to its duration and time during the year as well as to its magnitude at a seasonal scale the export of suspended sediment takes place in two phases i sediment preparation and ii sediment transfer and exhaustion during the latter phase the exhaustion of the sediment load is primarily related to the sequence of flood events at the annual scale the results show high inter annual variability according to the number of floods recorded yearly since almost all the suspended load is transported during those events

variation in suspended sediment concentration during storm discharges in three small streams in upper osun basin central western nigeria the suspended sediment concentration response of three small streams draining quartzites and quartz schists in south western nigeria to storms of varying magnitude are presented a total of 1468 water samples from 62 storm responses with peak stream discharge values ranging from 80 to 120 l s 2 were analysed and storm and suspended sediment concentration hydrographs and hysteresis loops were used to depict the response patterns the six different types of responses identified include the single and multiple discharge peak rises with sediment lead and lag and also the mixed response patterns both valley slope and channel erosion constituted important sources of suspended sediment however sediment availability exhaustion and flushing effects determined the variation in the different response types

suspended sediment transport in a highly erodible catchment the river isabena southern pyrenees abstract understanding and quantifying sediment load is important in catchments draining highly erodible materials that eventually contribute to siltation of downstream reservoirs within this context the suspended sediment transport and its temporal dynamics have been studied in the river isabena 445 km 2 south central pyrenees ebro basin by means of direct sampling and turbidity recording during a 3 year dry period the average flood suspended sediment concentration was 8 g l 1 with maximum instantaneous values above 350 g l 1 the high scatter between discharge and suspended sediment concentrations up to five orders of magnitude has not permitted the use of rating curve methods to estimate the total load interpolation techniques yielded a mean annual sediment load of 184 253 t y 1 for the study period with a specific yield of 414 t km 2 y 1 this value resembles those reported for small torrents in nearby mountainous environments and is the result of the high connectivity between the badland source areas and stream courses a fact that maximises sediment conveyance through the catchment floods dominated the sediment transport and yield however sediment transport was more constant through time than that observed in mediterranean counterparts this can be attributed to the role of base flows that entrain fine sediment temporarily stored in the channel and force the river to carry high sediment concentrations i e generally in the order of 0 5 g l 1 even under minimum flow conditions

event based suspended sediment dynamics in a central new york watershed abstract using discharge and sediment data collected from 23 events between 2008 and 2010 in a 311 km2 watershed of central new york we investigated event sediment dynamics of the studied watershed after showing the statistical difference of the data in different seasons we examined the detailed hysteresis patterns of all events spring events had figure eight with anticlockwise figure 8 ac clockwise c anticlockwise ac and complicated patterns summer events had c ac figure 8 ac figure 8 c and complicated patterns fall and winter events had the same patterns as those in summer as well as a weak loop pattern the diversity of patterns within and between seasons suggests that detailed processes of sediment transport were not only complicated during one event but also varied from season to season although hysteresis analysis failed to identify these detailed processes and the associated sediment sources in such a relatively large watershed it successfully revealed a common feature dominating the transport processes event sediment transport was generally supply limited further analysis on the correlation between event sediment yield ssye and event peak discharge qpeak indicated that i events with clockwise patterns tended to have more ssye than those with other patterns for the same qpeak and ii data from all events may be statistically well described by a single ssye qpeak equation regardless of hysteresis patterns this equation i reveals that complicated event transport processes may be lumped into a simple process over events and ii reflects the general supply limited nature identified by hysteresis analysis using this equation and the magnitude frequency analysis we further discovered that in the past 21 years sediment was mainly transported by more frequent but relatively small discharges with the recurrence interval no more than 0 5 year

altered regional sediment transport regime after a large typhoon southern taiwan analyses of river suspended sediment response to record breaking regional rainfall in southern taiwan during typhoon morakot 7 9 august 2009 reveal systematic changes in the regional sediment transport regime as characterized by rating curve parameters with decreasing b typically considered to be a constant for a given gauging station and increasing intercept k values in concentration discharge c q relations c kq b these changes result in much greater sediment concentration and thus sediment transport in subsequent low flow events after the typhoon an effect that amplifies and extends the influence of such extreme events through increased low flow sediment transport our finding that the exponent b is not constant contrasts with the conventional assumption that large events influence sediment yields through increased intercept k values thereby supporting the interpretation that basin sediment delivery influences both rating parameters and increases post event low flow sediment transport surveys of landslide density and riverbed grain sizes before and after typhoon morakot support the interpretation that the observed decrease in b values and the synchronous shift from an inverse correlation between k and mean catchment slope before the typhoon to a positive correlation afterward reflect an altered sediment transport regime and a change from channel migration and bank erosion to reworking of landslide debris and enhanced bed mobility as the dominant processes supplying fluvial sediment

relationships between suspended sediment concentrations and discharge in two small research basins in a mountainous mediterranean area vallcebre eastern pyrenees abstract the relationships between suspended sediment concentrations and discharge were studied at the can vila 0 56 km2 and ca l isard 1 32 km2 sub basins of the vallcebre research area eastern pyrenees during a period of 5 years that included 67 events of diverse magnitude abandoned agricultural fields and forests are the main land use in the can vila basin whereas the ca l isard basin is mainly forested though there are also some heavily eroded landscapes badlands the most frequent events were of a single discharge peak although double and multiple peaked events were also recorded clockwise positive hysteretic loops occurred in both catchments mainly during the wet seasons when precipitation was of moderate intensity average of 18 mm h 1 and baseflow before the event was rather high average for ca l isard 8 1 l s 1 km 2 and for can vila 11 76 l s 1 km 2 the bulk of stream discharge came from saturated areas whereas sediments came mainly from the stream channels counter clockwise negative hysteretic loops were much more frequent in the ca l isard basin mainly in summer when rainfall intensity was high average of 32 5 mm h 1 and baseflow was low average for ca l isard 0 94 l s 1 km 2 and for can vila 0 73 l s 1 km 2 most of the water and sediment came from the badlands eight shaped loops occurred in transition periods mainly in the ca l isard basin

suspended sediment dynamics in a southeast asian mountainous catchment combining river monitoring and fallout radionuclide tracers summary soil erosion is intense in mountainous tropical regions where heavy storms result in the supply of large quantities of sediment to rivers the origin and dynamics of suspended sediment were analysed in a catchment located in northern laos during the first erosive flood of the rainy season in may 2012 the catchment was equipped with 4 successive gauging stations draining areas ranging 0 2 11 6 km2 fallout radionuclides beryllium 7 7be unsupported pb 210 210pbxs and cesium 137 137cs were determined on rainfall overland flow stream water suspended sediment soil surface and subsurface samples with n 3 19 75 75 65 and 14 respectively assumptions underpinning the 7be labelling method were validated by implementing experiments in the laboratory i e rainwater 7be sorption to soil particles and in the field i e 7be 210pbxs activity ratio evolution in rainwater and related overland flow during a natural storm event radionuclide analyses provided a way to quantify variations in sediment dynamics and origin throughout the flood 1 a proportion of recently eroded sediment labelled by 7be and referred to as fresh sediment ranging between ca 8 35 in suspended loads 2 higher contributions of fresh sediment at the beginning of the flood rising stage 3 a progressive dilution of fresh sediment by particles remobilised from the riverbed channel 4 the dominance of particles originating from the soil surface ca 70 80 of total sediment load in upper parts and a much larger contribution of subsurface material ca 64 at the downstream station the original contribution of 7be labelled particles derived from collapsed riverbanks to sediment export was also demonstrated this pilot study supports the use of fallout 7be and 210pbxs in tropical catchments to constrain sediment dynamics it also puts forward the need to better characterize the sources of sediment in order to avoid possible misinterpretations

the effect of rock mass gradual deterioration on the mechanism of post mining subsidence over shallow abandoned coal mines in this study the effect of gradual deterioration on the long term stability of shallow abandoned room and pillar coal mines is investigated the conventional tributary area method is adopted and modified to take into account the rate of deterioration on the lifetime of pillars moreover a simple quantitative approach is proposed to incorporate the effects of deterioration in numerical modelling the suggested methods are then used to assess the stability of the shallow abandoned room and pillar coal mines around dolphingstone village uk results of this study indicate that the gradual deterioration plays a significant role in the long term stability of shallow abandoned coal mines the stand up time of a room and pillar mining panel is also estimated based on the modified q system a good agreement is observed between the results of numerical modelling and the rock mass classification system

turbidity observations in sediment flux studies examples from russian rivers in cold environments turbidity is commonly used as a proxy to estimate suspended sediment content in streams and for hydroecological purposes the scope of this paper is to give an outlook to wider applications of nephelometric turbidimetry as a method uncalibrated turbidity records in conjunction with water chemistry data prove useful in detecting watershed reaction to single hydrological events during the spring flood in arctic russia the turbidimetric survey technique was applied to study the spatial variability of sediment yield features on small rivers of the south eastern part of sakhalin island suspended sediment concentration ssc vs turbidity relation follows the geological features of the terrain and reflects the land use intensity within the watersheds for our igarka key site a logarithmic regression model was developed as an instrument of ssc calculation with turbidity data for each of the four studied watersheds a regional regression model was developed for this site and supplementary water optics data filtered sample turbidity was employed to increase the reliability of ssc calculations our results show that factors influencing turbidity namely water colour and sediment grain size have to be considered in multivariate models to minimize errors and acquire an understanding of what kind of physical response is actually measured by nephelometry based instruments

drivers of erosion and suspended sediment transport in three headwater catchments of the mexican central highlands quantifying suspended sediment exports from catchments and understanding suspended sediment dynamics within river networks is important especially in areas draining erodible material that contributes to the siltation of downstream reservoirs and to the degradation of water quality a one year continuous monitoring study of water and sediment fluxes was conducted in three upland subcatchments 3 0 9 3 and 12 0 km2 located within the cointzio basin in the central volcanic highlands of mexico michoacan state two subcatchments generated high sediment exports i e huertitas 900 1500 t km 2 y 1 and potrerillos 600 800 t km 2 y 1 whereas the third subcatchment was characterized by a much lower sediment yield i e la cortina 30 t km 2 y 1 such disparities in subcatchment behaviours were associated with the presence of severely gullied areas in huertitas and potrerillos rather than with rainfall erosivity indices an adapted classification of hysteretic patterns between suspended sediment concentration ssc and discharge was proposed because 42 of flood events contributing to 70 of sediment export were not discriminated by the classical clockwise anticlockwise typology this new classification allowed the identification of relationships in the hydrosedimentary responses of successive floods a stream transport capacity limit was also detected during hydrograph recession phases overall hydrosedimentary processes proved to be seasonally dependent sediment export was repeatedly limited by the stream transport capacity during the first part of the rainy season whereas a channel minimum erosivity threshold was frequently reached at the end of the season

sediment concentration versus water discharge during single hydrologic events in rivers relations between sediment concentration c and water discharge q for a hydrologic event such as a flood are studied qualitatively by analyzing smoothed temporal graphs discharge and concentration vs time in terms of mode spread and skewness comparing cq ratios at a given discharge on the rising and falling limbs of the discharge hydrograph provides a consistent reliable method for categorizing c q relations five common classes of such relations are single valued straight or curved clockwise loop counterclockwise loop single valued plus a loop and figure eight temporal graph mode and skewness influence the type of relation whereas temporal graph spread affects the details of the particular c q relation its graphical breadth shape orientation and plotted location field examples of the various types of relations are given including varieties that heretofore have received little attention such as the figure eight explanations for each type of c q relation are discussed

coupling fine particle and bedload transport in gravel bedded streams abstract fine particles in the silt and clay size range are important determinants of surface water quality since fine particle loading rates are not unique functions of stream discharge this limits the utility of the available models for water quality assessment data from 38 minimally developed watersheds within the united states geological survey stream gauging network in california usa reveal three lines of evidence that fine particle release is coupled with bedload transport first there is a transition in fine particle loading rate as a function of discharge for gravel bedded sediments that does not appear when the sediment bed is composed of sand cobbles boulders or bedrock second the discharge at the transition in the loading rate is correlated with the initiation of gravel mobilization third high frequency particle concentration and discharge data are dominated by clockwise hysteresis where rising limb discharges generally have higher concentrations than falling limb discharges these three observations across multiple watersheds lead to a conceptual model that fine particles accumulate within the sediment bed at discharges less than the transition and then the gravel bed fluidizes with fine particle release at discharges above the transition discharge while these observations were individually recognized in the literature this analysis provides a consistent conceptual model based on the coupling of fine particle dynamics with filtration at low discharges and gravel bed fluidization at higher discharges

hydrologic controls on wash load sediment concentrations within a low ordered ephemeral watershed summary this study explores the influence of rainfall and runoff production on wash load sediment transport in a low order ephemeral watershed in southeast arizona wash load concentrations measured at the watershed outlet generally decreased throughout a runoff event and were better correlated with the rainfall intensity and the rainfall volume that fell within the 6 min the watershed s time of concentration before the sediment concentration was measured than with the runoff discharge the difference between the rainfall volume per unit time and the runoff discharge was primarily due to infiltration and transmission losses processes that reduce runoff volume but do not appear to affect the wash load concentration within the runoff infiltration and transmission losses are significant in this watershed and vary considerably in space and time but are generally described by an inverse relationship between the runoff coefficient and drainage area runoff coefficients vary amongst runoff events and are correlated to the peak rainfall intensity during each event results indicate that wash load concentrations are set by the sediment entrainment processes occurring on the hillslopes e g rainsplash hortonian overland flow and do not greatly fluctuate as water is routed through the watershed this suggests that wash load concentration may be better predicted by metrics of rainfall than flow discharge in certain environments using rainfall as a predictor of wash load could be useful for estimating sediment fluxes in semiarid regions where flow discharge is often difficult to monitor and sediment transport concentrations can be high i e 10 000 mg l 1

interpreting sediment delivery processes using suspended sediment discharge hysteresis patterns from nested upland catchments south eastern australia in this study suspended sediment concentration ssc and discharge q hysteresis patterns recorded at the outlets of two nested upland catchments in south eastern australia were examined detailed monitoring of sediment flux was undertaken in a 1 64 km2 sub catchment located within a 53 5 km2 catchment for which sediment yield was measured and the extent of incised channels mapped the analysis of ssc q hysteresis patterns was supplemented by these additional datasets to contribute to the explanation of observed patterns clockwise ssc q hysteresis loops with the suspended sediment peak leading the discharge peak were recorded most frequently at both sites this was attributed to initial rapid delivery of sediment from channel banks the dominant sediment source in the sub catchment and probably also for the catchment in conjunction with remobilization of in channel fine sediment deposits sediment exhaustion effects were considered to enhance clockwise hysteresis with reduced ssc on the falling limb of event hydrographs pronounced exhaustion effects were observed on some multi rise events with subsequent flow peaks associated with much reduced sediment peaks to compare ssc q hysteresis patterns between the two catchments a dimensionless similarity function sf was derived to differentiate paired event hysteresis patterns according to the extent of pattern similarity this analysis coupled with the other datasets provided insight into the function of erosion and sediment delivery processes across the spatial scales examined and indicated the dependency of between scale suspended sediment transfer on defined flow event scenarios quantitative measures of event ssc q hysteresis pattern similarity may provide a mechanism for linking the timing and magnitude of process response across spatial scales this may offer useful insights into the between scale linkage of dominant processes and the extent of downstream suspended sediment delivery copyright 2009 john wiley sons ltd

nested temporal suspended sediment yields green lake basin british columbia canada suspended sediment yield was determined for a mountain watershed by calculating the volume of sediment stored in the watershed s outlet lake basin and monitoring sediment transport for the lake s primary inflow lake based yields for the 1931 2001 period 0 21 0 03 mg km 2 day 1 are 10 higher than estimates for the last 3000 years 0 19 0 05 mg km 2 day 1 fluvial 0 24 0 08 mg km 2 day 1 and lake based yields ca 0 21 0 07 mg km 2 day 1 are comparable over the period of overlap 1999 2001 persistence in the long term yield record is dominated by low frequency century to decadal periodicity this periodicity is shown to inflate the standard error of the sediment yield estimate for the basin elevated transport of suspended sediments following years of extreme yield is uncommon in the green lake record and indicates a sediment transport regime that is supply limited for this watershed approximately 50 years of suspended sediment monitoring would be required to reduce the uncertainty of the yield estimate to 37 of its average value a summer rainstorm in 1991 delivered more suspended sediment to the green lake basin than any other event in the last 3000 years

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

modelling suspended sediment concentration and load in a transport limited alluvial gully in northern queensland australia alluvial gullies are often formed in dispersible sodic soils along steep banks of incised river channels field data collected by shellberg et al earth surface processes and landforms 38 1765 1778 2013 from a gully outlet in northern australia showed little hysteresis between water discharge and fine 63 m suspended sediment indicating transport limited rather than source limited conditions the major source of the fine silt clay component was the sodic soils of upstream gully scarps and the coarser sand component was sourced locally from channel bed material in this companion paper at the same study site a new method was developed for combining the settling velocity characteristics of these two sediment source components to estimate the average settling velocity of the total suspended sediment this was compared to the analysis of limited sediment samples collected during flood conditions these settling velocity data were used in the steady state transport limit theory of hairsine and rose water resources research 28 237 243 245 250 1992 that successfully predicted field data of concentrations and loads at a cross section regardless of the complexity of transport limited upstream sources sheet erosion scalds rills gullies mass failure bank and bed erosion other disturbed areas the analysis required calibration of a key model parameter the fraction of total stream power f 0 025 that is effective in re entraining sediment practical recommendations are provided for the prediction of sediment loads from other alluvial gullies in the region with similar hydrogeomorphic conditions using average stream power efficiency factors for suspended silt clay fw 0 016 and sand fs 0 038 respectively but with no requirement for field data on sediment concentrations only basic field data on settling velocity characteristics from soil samples channel geometry measurements estimates of water velocity and discharge and associated error margins are needed for transport limit theory predictions of concentration and load this theory is simpler than that required in source limited situations copyright 2015 john wiley sons ltd

the spatio temporal invariability of sediment concentration and the flow sediment relationship for hilly areas of the chinese loess plateau abstract the spatio temporal variation underlies and complicates studies related to earth surface processes subsequent to our previous studies reporting the temporal invariability of sediment concentration this study further reports the spatial invariability of sediment concentration or the flow sediment relationship in the hilly part of the chinese loess plateau the dense channel network dissects this area into numerous sub watersheds which are composed of entire slopes a combination of the hill slope and the valley side slope our data mainly involves ten experimental sites of entire slope and sub watershed and 580 flood events at three locations our analysis at the intra event time scale shows that the instantaneous sediment concentrations in runoff can generally approach the detach limited maximum sediment concentration since the active massing wasting ensures an abundant sediment supply consequently the event mean sediment concentration does not only remain fairly constant among flow events but also among the experimental sites despite the possible differences in topography soil management or land cover water source soil surface properties etc this observation also holds at the annual time scale our result implies that a single proportional function is adequate to fit the flow sediment relationship for any entire slope or sub watershed where eroded sediments are primarily sourced over a considerable areal extent unless soil property has changed or check dams are installed moreover the proportionality coefficient which is indicative of the maximum detachment capacity can be approximated through flume experiments rather than necessarily through long term field observations our finding can facilitate the obtainment of spatially distributed information on soil loss in the chinese loess plateau and is also indicative of other locations where sediment supply is sufficiently available

temporal dynamics of suspended sediment transport in a glacierized andean basin abstract suspended sediment transport can affect water quality and aquatic ecosystems and its quantification is of the highest importance for river and watershed management suspended sediment concentration ssc and discharge were measured at two locations in the estero morales a chilean andean stream draining a small basin 27 km2 hosting glacierized areas of about 1 8 km2 approximately half of the suspended sediment yield 470 t year 1 km 2 was transported during the snowmelt period and half during glacier melting the hysteresis patterns between discharge and ssc were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale during snowmelt an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in ssc precede the peak of discharge in daily hydrographs instead during glacier melting the source of fine sediments is the proglacial area producing counterclockwise hysteresis it is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale

the suspended sediment dynamics in the inner mongolia reaches of the upper yellow river article i nfo suspended sediment dynamics are still imperfectly understood especially in the upper yellow river where few studies on this issue have been conducted this study analyzed the variability in suspended sediment concentration at different temporal scales within flood monthly seasonal and annual using a dataset up to 49 years long 1954 2002 at toudaoguai station this paper provided insight into the characteristics of suspended sediment transport in the ningxia inner mongolia reaches of the upper yellow river the results show that in a single flood event changes in ssc are not simultaneous with changes in discharge resulting in counterclockwise hysteretic loops clockwise loops or figure eight loops the c q loops and sediment rating curves for different seasons had different characters the diversiform c q loops in the inner mongolia reaches of the upper yellow river may be mainly caused by the sediment inputs from tributaries the differ ent propagation velocity of sediment and water discharge spatial and temporal storage depletion processes of available sediment at annual scale the variations of annual mean discharge and ssc displayed a similar gradually deceasing trend and the relation between water discharge and ssc during 1954 2002 could be de scribed by a cubic polynomial function since the joint operation of liujiaxia and longyangxia reservoirs after 1986 the transport capacity of the upper yellow river has been much reduced

temporal changes in suspended sediment transport in a gullied loess basin the lower chabagou creek on the loess plateau in china suspended sediment dynamics are still imperfectly understood especially in the loess hilly region on the loess plateau with strong temporal variability where few studies heretofore have been conducted using a dataset up to eight years long in the lower chabagou creek the variability in suspended sediment load at different temporal scales within flood variability monthly seasonal and annual is analyzed in this paper the results show that on the within flood scale most of the sediment peaks lag behind peak discharges implying that slope zones are the main sediment source area independent of the occurring sequences of the peaks of sediment and discharge all the events could present an anti clock wise hysteresis loop resulting from the abundant material and the influence of hyperconcentrated flows on suspended sediment concentration at monthly and seasonal scales there is a store release process i e sediment is prepared in winter spring and late autumn and exported in summer and early autumn at the annual scale the high variability in concentration and sediment yield are highly correlated with water yield resulting from the number and magnitude of floods recorded yearly and almost all the suspended load is transported during these events copyright c 2008 john wiley sons ltd

temporal changes in suspended sediment transport in an atlantic catchment nw spain catchment scale suspended sediment ss transport studies in northwest spain are of special interest as little research at this scale has been done in this region however the role of sediments in the transfer of nutrients and contaminants to coastal areas in this region has been highlighted data were collected from the corbeira catchment during a 3 year period and the variability in ss load at different temporal scales within events variability monthly seasonal and annual was analyzed the statistical relationship between discharge and suspended sediment concentration ssc from samples obtained every 15 days as well as during runoff events in october 2004 to september 2007 showed a marked scatter of points hence the rating curve method does not seem appropriate to estimate ssc in this catchment the results also demonstrated that at the within events scale most of the ss peaks preceded the discharge peaks 70 of runoff events implying that zones nearby or well connected to the stream are the dominant sediment source areas in some cases rills and ephemeral gullies developed in cropland were the main source of sediment delivered to the stream furthermore a reduction in ssc was observed in sequences of events which can be mainly linked to a phenomenon of sediment exhaustion at the seasonal scale most of the total annual ss load was transported during the autumn months the period in which generally the largest number of events occurred while in the summer total annual ss load was very low 1 at the annual scale specific ss yield ssy ranged from 5 4 to 11 2 mg km 2 y 1 the variability in ssy was correlated with the number and magnitude of runoff events recorded yearly since runoff events dominated ss transport and yield for instance in the last hydrological year 2006 07 more than 80 of the ss load was exported in runoff events involving 10 of the time

suspended sediment transport in a semiarid watershed wadi abd algeria 1973 1995 summary a quantification of the fine sediment budget of a wadi dryland river in nw algeria is presented for a period of 22 hydrological years 1973 1995 the climate is mediterranean over the wadi abd basin 2480 km 2 the mean annual precipitation is 250 mm and the mean annual discharge is 1 0 m 3 s 1 at the gauging station regression relationships between water discharge q and suspended sediment concentration c are calculated from 1432 paired measurements in the wadi abd leading to power law equations of the type c aq b the variability of coefficients a and b calculated for 138 floods and flood stages is analyzed the median value of b is 0 757 indicating that c is almost proportional to q 3 4 given that the a b pairs are correctly aligned r 2 0 578 the coefficients a and b are not independent regression relationships between daily q and daily suspended sediment concentration and discharge qs are calculated from 702 input data the performances of these regression relationships are shown to be equivalent leading to over estimations of 20 25 of the suspended sediment flux the non biased c q sediment rating curve is used to extrapolate a time series of c measurements and thus to analyze the long term patterns in suspended sediment transport average sediment wash down 136 t km 2 yr 1 is similar to the mean global value the ratio of sediment wash down to the river water discharge is 10 7 10 6 tk m 3 20 times greater than the average ratio in the earth s eastern hemisphere and illustrates the highly erosive power of wadis variability is shown to be significant at the seasonal scale cv 89 and higher at the interannual scale cv 139 the fine sediment flux mainly occurs in autumn 48 4 and spring 32 7 although precipitation decreased it was more irregular from one year to another over the period 1985 1995 than during the period 1973 1985 and the wadi abd which was a perennial river became intermittent in the late 1980s this increasing irregularity is accompanied by an amplification of the variations of discharge an increase in the average discharge of approximately 20 during the second period and a higher and more irregular suspended particulate flux the mean annual suspended

linking bed morphology changes of two sediment mixtures to sediment transport predictions in unsteady flows flume experiments were conducted to measure bed morphology adjustments in sand gravel and sand silt sediment mixtures during repeated hydrographs and to link these changes to sediment transport patterns over multiple time scales sediment composition and hydrograph flow magnitude greatly influenced channel morphology which impacted sediment yield hysteresis and transport predictions bed load yields were larger and more variable for the sand silt mixture as gravel in the sand gravel sediment inhibited grain entrainment limited bed form growth and acted to stabilize the bed hysteresis patterns varied due to bed form and surface structure adjustments as well as the stabilizing effect of antecedent low flows using half the data set a dimensionless fractional transport equation was derived based on excess shear stress dimensionless reference shear stresses were estimated in two ways as bulk values from all transport measurements and by applying a separate limb approach in which values were estimated for each limb of each hydrograph for the other half of the data set transport predictions with the separate limb approach were more accurate than those from six existing transport equations and the fractional relationship applied with bulk reference shear stresses thus hydrograph limb dependent dimensionless reference shear stress links changing bed morphology and sediment transport providing a parameter to improve transport predictions during individual flood events and in unsteady flow regimes this approach represents a framework with which to develop site specific transport relationships for varying flow regimes particularly in cases where detailed bed morphology measurements are not feasible and heterogeneous sediment complicates bed structure over time

bedload hysteresis in a glacier fed mountain river sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before counterclockwise hysteresis or after clockwise hysteresis the peak of bedload hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions respectively hysteresis has been mainly explored for the case of suspended sediment transport but it was rarely reported for bedload transport in mountain streams this work focuses on the temporal variability of bedload transport in an alpine catchment saldur basin 18 6 km2 italian alps where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0 5m long steel pipe runoff dynamics are dominated by snowmelt in late spring early summer mostly by glacier melt in late summer early autumn and by a combination of the snow and glacier melt in mid summer the results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin on the contrary counterclockwise hysteresis tend to be more frequent during late glacier melting period possibly due to the time lag needed for sediment provided by the glacial and peri glacial area to be transported to the monitoring section however intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis thus indicating the activation of different sediment sources these results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams

influence of declining mean annual rainfall on the behavior and yield of sediment and particulate organic carbon from tropical watersheds abstract the capacity to forecast climate and land use driven changes to runoff soil erosion and sediment transport in the tropics is hindered by a lack of long term data sets and model study systems to address these issues we utilized three watersheds characterized by similar shape geology soils vegetation cover and land use arranged across a 900 mm gradient in mean annual rainfall mar using this space for time design we quantified suspended sediment ss and particulate organic carbon poc export over 18 months to examine how large scale climate trends mar affect sediment supply and delivery patterns hysteresis in tropical watersheds average daily ss yield ranged from 0 128 to 0 618 t km 2 while average daily poc ranged from 0 002 to 0 018 t km 2 for the largest storm events we found that sediment delivery exhibited similar clockwise hysteresis patterns among the watersheds with no significant differences in the similarity function between watershed pairs indicating that 1 in stream and near stream sediment sources drive sediment flux and 2 the shape and timing of hysteresis is not affected by mar with declining mar the ratio of runoff to baseflow and inter storm length between pulse events both increased despite increases in daily rainfall and the number of days with large rainfall events increasing with mar there was a decline in daily ss yield possibly due to the exhaustion of sediment supply by frequent runoff events in high mar watersheds by contrast mean daily poc yield increased with increasing mar possibly as a result of increased soil organic matter decomposition greater biomass or increased carbon availability in higher mar watersheds we compared results to modeled values using the load estimator loadest fortran model confirming the negative relationship between mar and sediment yield however because of its dependency on mean daily flow loadest tended to under predict sediment yield a result of its poor ability to capture the high variability in tropical streamflow taken together results indicate that declines in mar can have contrasting effects on hydrological processes in tropical watersheds with consequences for instream ecology downstream water users and nearshore habitat

effects of watershed management practices on the relationships among rainfall runoff and sediment delivery in the hilly gully region of the loess plateau in china abstract the relationships among rainfall runoff and sediment delivery are significant in predicting soil erosion and in evaluating the benefits of watershed management practices wmp on the hilly gully regions of the loess plateau hydrologic data 1987 to 2010 were analyzed for variations in precipitation runoff and sediment delivery at annual and event scale these data were obtained from the qiaozi east watershed qe and the qiaozi west watershed qw with and without wmp respectively results indicated that the runoff coefficients of the watersheds decreased significantly although the runoff coefficient of qe was less than half of that of qw sediment delivery decreased more in qe than in qw mainly because of the increase in vegetation cover in both watersheds in qe the relationship between runoff and sediment delivery did not change significantly from 1987 to 2006 although the variation was significant from 2007 to 2010 in qw the relationship between runoff and sediment delivery was not notably altered from 1987 to 2010 this finding suggested that vegetation practices and engineering measures on the hillslope did not strongly affect the relationship between runoff and sediment delivery in the watersheds but the construction of check dams reduced gully erosion and the suspended sediment concentration hence control practices for gully erosion significantly influenced the relationship between runoff and sediment delivery this study suggests that a combination of hillslope and gully erosion control practices effectively reduces erosion and sediment delivery in the hilly gully regions of the loess plateau