disturbances in coarse bedload transport in a high mountain stream channel system western tatras poland abstract bedload transport measurements in the formerly glaciated chocholowski catchment located in the western tatras in poland were performed in the period 1975 to 2018 measurement of bedload displacement allowed to determine the role of bedload transport disturbances in both system connectivity and sediment transfer bedload transport occurred as many as triggered up to several times a year the longest distances were observed during rain on snow events between 12 m in headwaters and over 100 m in the fluvial valley bedload became activated along the entire length of the channel system 10 5 km every 2 to 5 years when the stream discharge exceeded 10 m3 s 1 with an average of 1 25 m3 s 1 in such situations bedload dynamics increased downstream and stream power was sufficient to overcome local barriers i e boulder and log steps downstream increases in bedload dynamics may become disturbed and inverted by sudden snowmelt and locally heavy rainfall these types of events caused the dynamics of bedload transport to be 190 to 320 greater in the upper part of the studied catchment and to decline in the downstream direction over a distance of 7 km to yield an attenuation effect the same pattern was observed in local tributaries where the dynamics of bedload transport were 200 higher in the upper part and attenuation was observed along a distance of 1 5 km in the downstream direction all events of this type cause seasonal disturbances in bedload transport however the greatest effect on bedload dynamics was produced by natural deforestation a 16 decrease in forest cover causes a fluvial system disequilibrium manifested in an intensification of hydro geomorphologic processes and formation of new landforms

distribution of erosion across bedrock channels lateral erosion in bedrock rivers is an important control on the shape of channel crosssections and the coupling of channels and hillslopes recent observations link lateral erosionto the variability of flow we propose two mechanisms to explain this one is based on changing shear stress distributions within the channel with varying flood level the other on the competition between cover and tool effects in fluvial bedrock erosion we assess these processes for the liwu river taiwan and conclude that cover and tool effects dominate the partitioning of lateral and vertical erosion in this case

review of erosion dynamics along the major n s climatic gradient in chile and perspectives abstract chile is an elongated country running in a north south direction for more than 30 along a subduction zone its climate is progressively wetter and colder from north to south this particular geography has been used positively by a growing number of studies to better understand the relationships between erosion processes and climate land use slope tectonics volcanism etc here we review the erosion rates factors and dynamics over millennial to daily periods reported in the literature in addition 21 new catchment mean erosion rates suspended sediment and 10be are provided and previous suspended sediment derived erosion rates are updated a total of 485 local and catchment mean erosion rates are reported erosion rates vary between some of the smallest values on earth 10 5 mm a to moderate values 0 5 mm a compared to other active ranges this review highlights strong limitations concerning the quantification of local erosion factors because of uncertainties in sampling point location slope and rainfall data for the mean erosion rates e for the millennial and decennial catchments a model of the form e s 1 s 0 6 2 r with 0 3 0 8 accounts for 40 to 70 of the erosion variance confirming a primary role of slope s compared to precipitation rate r over this time scale over the long term this review points to the long 5 to 10 ma response time of rivers to surface uplift in north central arid chile over millennia data provide evidence for the progressive contribution of extreme erosion events to millennial averages for drier climates as well as the link between glacier erosion and glacier sliding velocity in this period of time a discrepancy exists between the long term offshore sedimentological record and continental decennial or millennial erosion data for which no single explanation appears still little information is available concerning the magnitude of variation of millennial erosion rates over centuries data show the variable role of groundwater in the dynamics of suspended load and document a decrease in erosion over hundreds of years probably associated with historical harvesting

timescales of fluvial activity and intermittency in milna crater mars milna crater mars 23 4s 12 3w exhibits signs of fluvial modification early in mars history including a large multi lobed fan deposit cut by several sinuous valleys we describe the past hydrologic conditions in milna and the surrounding area including a potential lake with a volume of 50 km 3 we also introduce new methods i to calculate the timescale of sediment deposition by considering fluvial sediment input into the entire crater while accounting for non fluvial input and ii to place improved constraints on the channel dimensions through which sediment was delivered to milna by comparing to the dimensions of inner channels found in valleys in the region surrounding milna by calculating the flux of fluid and sediment into the crater we find that the crater cavity was flooded for at least months and that the time of active fluvial sediment transport without hiatus is on the order of decades to centuries with a preferred timescale of centuries we also calculate the total amount of water required to transport the volume of sediment we measure in milna and conclude that impacts alone are likely insufficient to deliver enough water to milna to allow the sedimentary fill we see combining the timescales of fluvial activity in the adjacent parana valles with estimates for global noachian erosion rates we calculate an intermittency factor for fluvial activity of 0 01 0 1 during 10 5 10 6 yr near the noachian hesperian boundary in the parana valles region these values are comparable to arid climates on earth where the majority of fluvial sedimentary transport takes place during floods with multi year to decadal recurrence intervals our calculations of intermittency help to quantitatively reconcile the divergent estimates of the short and long timescales of fluvial activity on mars reported in the literature

flow pattern and sediment transport in a braided river the torrent de st pierre french alps summary in order to bring some understanding on the mountain stream dynamics we report measurements of flow and sediment transport leveled in a proglacial gravel bed river the torrent de st pierre in the french alps the river exhibits a modest discharge 3 s during most of the glacier melting season a braiding plain developed thanks to the occurrence of a massive landslide providing a small and simplified study area quite similar to recent experimental studies a mass balance was established at the outlet of the braiding plain our measurements indicate that in the range of flows measured the dominating transport mode is suspension though less important bed load transport is far from being negligible dissolved load eventually appears to be very small compared to solid transport analysis of velocity profile measurements shows that in this highly turbulent and shallow stream the use of a logarithmic form fails to recover the velocity profile and to estimate the shear velocity of the flow a uniform chezy like relationship is shown to be valid for the velocity with friction a coefficient considered as constant over the range of our measurements accordingly the only relevant velocity for transport description is the average velocity coupled measurements of bed load and velocity show that bed load transport is related to the average velocity through a power law eventually a correlation between bed load transport and suspended load transport is evidenced and discussed

sediment transport along lower fraser river 1 measurements and hydraulic computations a comprehensive program of sediment transport measurements was conducted along lower fraser river british columbia between 1966 and 1986 the data yield a detailed sediment budget annual total suspended loads at three stations are virtually identical averaging 17 106 tonnes year t yr 1 the suspended sand load is about 5 5 106 t yr 1 about one third of the total in the gravel bed reach of the river the sand behaves as wash load significant transport of gravel begins at agassiz at a discharge of about 5000 m3 s 1 the annual gravel transport was estimated to be about 0 23 106 t yr 1 only 1 of the total load all of this material is deposited in the reach upstream of mission at mission sands finer than 0 177 mm make up more than 50 of the suspended sand load but are virtually absent from the sand bed therefore a portion of the sand load at mission is wash load the total bed material load here was estimated to be 3 0 106 t yr 1 about 18 of the total sediment load virtually all of the bed material load was transported in intermittent suspension near the bed less than 5 occurring as bed load in the long term the suspended sand load upstream is approximately equal to the total sand load at mission however within individual years some of the sand is stored within the reach temporarily and then reentrained later

the partitioning of the total sediment load of a river into suspended load and bedload a review of empirical data the partitioning of the total sediment load of a river into suspended load and bedload is an important problem in fluvial geomorphology sedimentation engineering and sedimentology bedload transport rates are notoriously hard to measure and at many sites only suspended load data are available often the bedload fraction is estimated with rule of thumb methods such as maddock s table which are inadequately field tested here the partitioning of sediment load for the pitzbach is discussed an austrian mountain stream for which high temporal resolution data on both bedload and suspended load are available the available data show large scatter on all scales the fraction of the total load transported in suspension may vary between zero and one at the pitzbach while its average decreases with rising discharge i e bedload transport is more important during floods existing data on short and long term partitioning is reviewed and an empirical equation to estimate bedload transport rates from measured suspended load transport rates is suggested the partitioning averaged over a flood can vary strongly from event to event similar variations may occur in the year to year averages using published simultaneous short term field measurements of bedload and suspended load transport rates maddock s table is reviewed and updated long term average partitioning could be a function of the catchment geology the fraction of the catchment covered by glaciers and the extent of forest but the available data are insufficient to draw final conclusions at a given drainage area scatter is large but the data show a minimal fraction of sediment transported in suspended load which increases with increasing drainage area and with decreasing rock strength for gravel bed rivers whereby in large catchments the bedload fraction is insignificant at 1 for sand bed rivers the bedload fraction may be substantial 30 50 even for large catchments however available data are scarce and of varying quality long term partitioning varies widely among catchments and the available data are currently not sufficient to effectively discriminate control parameters

comparison of sediment load and riverbed scour during floods for gravel bed and sand bed reaches of intermittent rivers case study abstracthydraulic scour is one of the major causes of bridge and embankment failure during typhoon induced or monsoon induced floods in steep intermittent rivers in taiwan in this study field data for sediment load and riverbed scour measured in gravel bed and sand bed reaches between 2003 and 2013 are analyzed to determine their differences under nonequilibrium sediment transport conditions the riverbed scouring potential was extremely high during the fast rising stage of a large flood in the bimodal gravel bed reach by contrast the unimodal sand bed reach with a higher suspended load typically demonstrated a lower scouring rate although it was still higher than that of a perennial river existing bridge scour formulas suitable for intermittent rivers were examined by separating short term general scour and localized scour a maximum general scour depth formula is developed in this study for use as a potential tool for emergency evacuations and bridge closure purposes

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

a comparison of stream bank erosion processes on forested and moorland streams in the balquhidder catchments central scotland stream bank erosion rates measured over a two year period on a moorland and a forested stream in the institute of hydrology s balquhidder paired catchments in central scotland were compared bank erosion rates are generally higher on the mainstream of the moorland catchment and highest in wintger on both streams bank erosion is correlated with the incidence of frost minimum temperatures measured on stream banks of the forested stream were an average of 3 7 c higher than on stream banks both outside the forest and on the moorland stream this makes the incidence of frost on forested stream banks half as frequent volumes of material eroded from the mainstreams were combined with bulk density measurements and it is estimated that erosion of the mainstream banks is contributing 1 5 and 7 3 per cent of the sediment yield of the forested and moorland catchments respectively analysis of the vertical distribution of erosion on the banks of both streams suggests an undercutting mechanism which is more pronounced in the moorland stream the influence of trees on bank erosion and possible implications for the management of forest streams are discussed 1997 by john wiley sons ltd

higher erosion rates in the himalaya geochemical constraints on riverine fluxes the modern erosion rate of continental scale mountains is difficult to estimate and is usually based on measurement of the suspended load flux of rivers combined with assumptions about river bedload transport and sedimentation in flood plains these two parameters are very difficult to measure directly in continental scale basins in this paper we examine the chemical composition of the suspended load bedload and dissolved load of the ganga and brahmaputra rivers and compare them with the average composition of himalayan source rocks a mass balance equation of erosion fluxes shows that a si rich component is needed in addition to suspended and dissolved load fluxes to account for the composition of the source rock it corresponds to bedload sediment and flood plain deposits which are enriched in quartz by mineral sorting during transport the combined budget of si al and fe in the river system allows us to estimate this si rich flux by this method the total himalayan erosion is estimated to be twice the measured flux of suspended load the comparison between the brahmaputra and the ganga shows that the eastern himalaya has a higher erosion rate 2 9 mm yr than the western himalaya 2 1 mm yr this is likely the result of the higher runoff in the brahmaputra basin the intensity of the monsoon acts as a first order control of the erosion rate in the range

a demonstration of the importance of bedload transport for fluvial bedrock erosion and knickpoint propagation we provide field evidence for the role of bedload in driving fluvial incision and knickpoint propagation using aerial photographs field surveys and hydrological data we constrain the incision history of a bedrock gorge 1200 m long and up to 20 m deep cut by da an river in western taiwan this reach of the river experienced 10 m of uplift during the 1999 chi chi earthquake for five years following the earthquake bedload was prevented from entering the uplift zone the knickpoint was static and little incision took place bedload transport across the uplift zone resumed in 2004 initiating extremely rapid incision with 620 m of knickpoint propagation and up to 20 m of downcutting by 2008 this change highlights the relative inefficiency of suspended sediment and the dominant role of bedload as a tool for fluvial erosion and knickpoint propagation once bedload tools became available knickpoint propagation was influenced by geological structure lithology and drainage organization in particular a change in dip of the sandstone beds at the site caused a decrease of knickpoint propagation velocity copyright 2012 john wiley sons ltd

abrasion set limits on himalayan gravel flux rivers sourced in the himalayan mountain range carry some of the largest sediment loads on the planet yet coarse gravel in these rivers vanishes within approximately 10 40 kilometres on entering the ganga plain the part of the north indian river plain containing the ganges river understanding the fate of gravel is important for forecasting the response of rivers to large influxes of sediment triggered by earthquakes or storms rapid increase in gravel flux and subsequent channel bed aggradation that is sediment deposition by a river following the 1999 chi chi and 2008 wenchuan earthquakes reduced channel capacity and increased flood inundation here we present an analysis of fan geometry sediment grain size and lithology in the ganga basin we find that the gravel fluxes from rivers draining the central himalayan mountains with upstream catchment areas ranging from about 350 to 50 000 square kilometres are comparable our results show that abrasion of gravel during fluvial transport can explain this observation most of the gravel sourced more than 100 kilometres upstream is converted into sand by the time it reaches the ganga plain these findings indicate that earthquake induced sediment pulses sourced from the greater himalayas such as that following the 2015 gorkha earthquake are unlikely to drive increased gravel aggradation at the mountain front instead we suggest that the sediment influx should result in an elevated sand flux leading to distinct patterns of aggradation and flood risk in the densely populated low relief ganga plain

focused erosion at the core of the greater caucasus sediment generation and dispersal from mt elbrus to the caspian sea abstract the highest peaks in europe are found in the central greater caucasus an orogenic belt characterized by extremely active tectonic and sedimentary processes in this rugged mountain region we have investigated sand generation and erosion patterns by using high resolution petrographic and heavy mineral data on river sands complemented by detailed morphometric analysis of 9 major mountain branches of the terek river also presented is an extensive review of sediment transport data available in the russian literature on glacial lake outburst floods and rainfall triggered debris flows which owing to global warming and glacier retreat have afflicted the greater caucasus with increasing frequency in the last 50 years the accurate definition of mineralogical signatures characterizing detritus derived from six end member volcanic metamorphic basement and sedimentary metasedimentary rock units allowed us to calculate the relative contribution of each to the sand load with particular precision for the baksan river draining mt elbrus results clearly indicate that volcanic and basement rocks supply a disproportionate amount of sand relatively to their outcrop area testifying to strongly focused erosion in the high relief axial part of the range river channels here display extreme steepness ksn up to 200 300 and low concavity indices 0 15 0 35 typical of thalwegs shaped by debris flows average erosion rates reach as high as 2 4 mm a which is explained by the frequency of catastrophic mass transport events able to mobilize in one single episode between 106 and 107 tons of detritus corresponding to 10 50 mm of erosion distributed across the catchment upstream on 20 september 2002 the kolka glacier disaster mobilized 2 108 tons of debris corresponding to 400 mm of erosion in the upper genaldon valley to quantify the intrinsic capacity of different bedrock types to generate sand isolated from such a strong focused erosion effect we used the normalized steepness index ksn as a proxy of erosion rate and thus redefined the sand generation index as s g i s a s a a a k s n k s n a more realistic values are thus obtained although far more comprehensive data on sediment load than those presently available are required to discriminate robustly between the effect of focused erosion versus lithological control on sand generation

detrital sediment fluxes from continents to oceans abstract detrital sediment is carried from land to the sea by three agents rivers glaciers and winds the shoreline is an arbitrary boundary within the detrital sediment transport system which extends from a site of origin across areas of temporary storage to a site of long term deposition the most important of the agents moving sediment across the land is river transport estimated to be in the order of 20 10 12 kg of sediment annually at present analysis of drainage basins indicates that relief and runoff are the most important factors in determining the sediment load of rivers the competence of rivers to transport sediment is governed by the volume flow gradient and the sediment load itself today most large rivers are fed by snowmelt in highland areas runoff from rainfall in the drainage basin and groundwater inflow along the river course water is lost to evaporation and groundwater infiltration river courses can often be divided into two segments a degradational section in which the gradient is relatively steep and little temporary storage of sediment takes place and an aggradational section where the gradient is sharply reduced through meandering and where large scale temporary sediment storage forms a flood plain lakes trap sediment inland and prevent its transport to the sea today many high and mid latitude rivers are interrupted by lakes of glacial origin there are also some large areas of internal drainage that deliver no sediment to the sea the load carried by rivers has been markedly altered by human activity and may have doubled over the past few thousand years only to be reduced in the past century by the widespread construction of dams the ancient use of fire in hunting and its subsequent use in clearing land has increased erosion extensive deforestation and cultivation processes have also increased the sediment supply dam construction is a relatively new factor and affects the sediment transport system by trapping sediment before it can reach the sea the resulting lower sediment supply from rivers is at least in part compensated by increased coastal erosion glacial erosion is difficult to estimate there is an ongoing controversy whether ice sheets are effective erosive agents or not estimates of the present global flux of glacial detritus range from 0 8 50 10 12 kg annually with the lower value most probable the dust flux is in the order of 0 5 to 0 9 10 12 kg annually but may vary greatly with time

can bed load transport drive varying depositional behaviour in river delta environments abstract understanding the processes and conditions at the time of deposition is key to the development of robust geological models which adequately approximate the heterogeneous delta morphology and stratigraphy they represent we show how the mechanism of sediment transport the proportion of the sediment supply transported as bed load vs suspended load impacts channel kinematics delta morphology and stratigraphy to at least the same extent as the proportion of cohesive sediment supply this finding is derived from 15 synthetic delta analogues generated by processes based simulations in delft3d the model parameter space varies sediment transport mechanism against proportions of cohesive sediment whilst keeping the total sediment mass input constant proximal morphology and kinematics previously associated with sediment cohesivity are also produced by decreasing the proportion of bed load sediment transport however distal depositional patterns are different for changes in sediment transport and sediment load cohesivity changes in sediment transport mechanisms are also shown to impact clinoform geometry as well as the spatiotemporal scale of autogenic reorganisation through channel avulsions we conclude that improving insight into the ratio of bed load to suspended load is crucial to predicting the geometric evolution of a delta

development of channel organization and roughness following sediment pulses in single thread gravel bed rivers large episodic inputs of coarse sediment sediment pulses in forested mountain streams may result in changes in the size and arrangement of bed forms and in channel roughness a conceptual model of channel organization delineates trajectories of response to sediment pulses for many types of gravel bed channels channels exhibited self organizing behavior to various degrees based on channel gradient presence of large in channel wood or other forcing elements the size of the sediment pulse and the number of bed mobilizing flows since disturbance typical channel changes following a sediment pulse were initial decreases in water depth in variability of bed elevations and in the regularity of bed form spacing trajectories of change subsequently showed increased average water depth more variable and complex bed topography and increased uniformity of bed form spacing bed form spacing in streams with abundant forcing elements developed at a shorter spatial scale two to five channel widths than in streams without such forcing mechanisms five to 10 channel widths channel roughness increased as bed forms developed

mass accumulation rates in asia during the cenozoic summary this work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in asia since the beginning of the cenozoic 66 ma the estimates were derived from isopach maps cross sections and drill holes or stratigraphic columns assuming regional similarity of the strata average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods palaeocene 66 58 ma eocene 58 37 ma oligocene 37 30 and 30 24 ma miocene 24 17 17 11 and 11 5 ma pliocene 5 2 ma and quaternary 2 0 ma these rates shed new light on the geological history of asia since the onset of the collision of india with asia 50 ma the overall average accumulation rates curve for asian sedimentary basins since the beginning of the tertiary shows an exponential form with slow accumulation rates less than 0 5 106 km3 myr 1 until the beginning of the oligocene more than 15 myr after the onset of the collision from the oligocene onwards rates increase quickly in an exponential manner reaching their maximum values in the quaternary more than 1 5 106 km3 myr 1 from these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the india eurasia collision history at smaller scales one may distinguish between independent histories at the subcontinental and basin scales this permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of asia during the cenozoic

sediment transport in a large impounded river the lower ebro ne iberian peninsula abstract the sediment transport of the highly regulated lower ebro river is estimated on the basis of a measuring programme carried out between 2002 and 2004 total sediment transport including both suspended load and bedload was measured upstream and downstream from the mequinenza and riba roja reservoirs with special attention to the transport during floods annual total load upstream from the dams is estimated at around 1 64 106 t of which at least 99 is transported in suspension annual total load downstream from the dams is estimated at around 0 45 106 t of which 60 is transported in suspension and the remaining 40 as bedload mean d50 bl in the range of 32 mm total load represents 3 of what was transported at the beginning of the 20th century in the delta plain sediment yield is three to four times lower below the dams a fact that is caused by the trapping of sediment within the reservoirs around 90 in the case of suspended sediment and 100 in the case of bedload as a consequence sediment that is transported downstream from the dams is all entrained from the riverbed and eroded from the banks the sediment deficit causes a mean riverbed incision of 30 mm per year as estimated from bedload measurements and by means of scour chains and painted pebbles located between the lowermost dam and the measuring section 28 km downstream since floods have been reduced on average by 25 but sediment supply from upstream has been reduced to almost nothing the river channel of the lower ebro river will continue exporting sediment both during floods 2000 m3 s mostly bedload and frequent high flows 1000 m3 s to 2000 m3 s making the incision progressive unless restoration steps are taken

extraordinary sediment delivery and rapid geomorphic response following the 2008 2009 eruption of chaiten volcano chile u s geological survey volcano science center sernageomin s programa de riesgos volcanicos conicyt fondecyt grants 1110609 1141064 11130671 conicyt fondap 15090013 vamos research centre

reduced sediment supply in a fast eroding landscape a multi proxy sediment budget of the upper rhone basin central alps alpine water and sediment supply influence the sediment budget of many important european fluvial systems such as the rhine rhone and po rivers in the light of human induced climate change and landscape modification it becomes increasingly important to understand the mechanisms of sediment production and supply in alpine sediment systems this study aims to investigate the modern sediment budget of the upper rhone basin one of the largest alpine intramontane watersheds located in the central alps of southwestern switzerland major areas of sediment generation are fingerprinted by framework petrography heavy mineral concentrations and bulk geochemistry the relative contributions of the three major sources to the sediment of the trunk rhone river are identified by compositional mixing modelling concentrations of the terrestrial cosmogenic nuclide 10be measured in quartz separated from fluvial sediments provide spatially averaged denudation rates for selected tributary basins results from sediment fingerprinting and mixing modelling suggest that tributaries located in the north and the east of the catchment are generating most of the sediment transported by the rhone river to its primary sedimentary sink in lake geneva despite having some of the highest denudation rates within the basin tributaries located in the southern area of the rhone basin are relatively underrepresented in the sediment budget of the rhone river these tributaries are severely affected by human activities for example through sediment mining as well as water and sediment abstraction in large hydropower reservoirs together these processes reduce the basin wide sediment discharge by about 50 thereby explaining most of the observed compositional pattern in addition there is evidence suggesting that large amounts of glaciogenic sediments are currently supplied by retreating glaciers glaciogenic material with its low 10be concentrations can lead to a significant overestimation of denudation rates and thus limit the applicability of cosmogenic nuclide analysis in such glaciated settings

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

slope and climate variability control of erosion in the andes of central chile climate and topography control millennial scale mountain erosion but their relative impacts remain matters of debate confl icting results may be explained by the infl uence of the erosion threshold and daily variability of runoff on long term erosion however there is a lack of data documenting these erosion factors here we report suspended load measurements derived decennial erosion rates and 10 be derived millennial erosion rates along an exceptional climatic gradient in the andes of central chile both erosion rates decennial and millenial follow the same latitudinal trend and peak where the climate is temperate mean runoff 500 mm yr 1 both decennial and millennial erosion rates increase nonlinearly with slope toward a threshold of 0 55 m m the comparison of these erosion rates shows that the contribution of rare and strong erosive events to millennial erosion increases from 0 in the humid zone to more than 90 in the arid zone our data confi rm the primary role of slope as erosion control even under contrasting climates and support the view that the infl uence of runoff variability on millennial erosion rates increases with aridity

lithological controls on hillslope sediment supply insights from landslide activity and grain size distributions the volumes rates and grain size distributions of sediment supplied from hillslopes represent the initial input of sediment delivered from upland areas and propagated through sediment routing systems moreover hillslope sediment supply has a significant impact on landscape response time to tectonic and climatic perturbations however there are very few detailed field studies characterising hillslope sediment supply as a function of lithology and delivery process here we present new empirical data from tectonically active areas in southern italy that quantifies how lithology and rock strength control the landslide fluxes and grain size distributions supplied from hillslopes landslides are the major source of hillslope sediment supply in this area and our inventory of 2800 landslides reveals that landslide sediment flux is dominated by small shallow landslides we find that lithology and rock strength modulate the abundance of steep slopes and landslides and the distribution of landslide sizes outcrop scale rock strength also controls the grain sizes supplied by bedrock weathering and influences the degree of coarsening of landslide supply with respect to weathering supply finally we show that hillslope sediment supply largely determines the grain sizes of fluvial export from catchments and that catchments with greater long term landslide rates deliver coarser material therefore our results demonstrate a dual control of lithology on hillslope sediment supply by modulating both the sediment fluxes from landslides and the grain sizes supplied by hillslopes to the fluvial system

sediment supply controls equilibrium channel geometry in gravel rivers in many gravel bedded rivers floods that fill the channel banks create just enough shear stress to move the median sized gravel particles on the bed surface d50 because this observation is common and is supported by theory the coincidence of bankfull flow and the incipient motion of d50 has become a commonly used assumption however not all natural gravel channels actually conform to this simple relationship some channels maintain bankfull stresses far in excess of the critical stress required to initiate sediment transport we use a database of 300 gravel bedded rivers and 600 10be derived erosion rates from across north america to explore the hypothesis that sediment supply drives the magnitude of bankfull shear stress relative to the critical stress required to mobilize the median bed surface grain size formula see text we find that formula see text is significantly higher in west coast river reaches 2 35 n 96 than in river reaches elsewhere on the continent 1 03 n 245 this pattern parallels patterns in erosion rates and hence sediment supplies supporting our hypothesis we find a significant correlation between upstream erosion rate and local formula see text at sites where this comparison is possible our analysis reveals a decrease in bed surface armoring with increasing formula see text suggesting channels accommodate changes in sediment supply through adjustments in bed surface grain size as also shown through numerical modeling our findings demonstrate that sediment supply is encoded in the bankfull hydraulic geometry of gravel bedded channels through its control on bed surface grain size

historic and contemporary sediment transfer in an upland pennine catchment uk a sediment budget for an upland catchment reservoir system at burnhope reservoir north pennines uk has been developed this provides a framework for quantifying historic and contemporary sediment yields and drainage basin response to disturbance from climate change and human activities in the recent past bathymetric survey core sampling 137cs dating and aerial photographs have been used to assess sediment accumulation in the reservoir the average reservoir sedimentation rate is 1 24 cm yr 1 annual sediment yield 33 3 t km 2 yr 1 10 trap efficiency 92 mean annual reservoir sedimentation over the 67 year period has been estimated at 592 t 10 inputs of suspended sediment from direct catchwater streams account for 54 of sediment supply to the budget best estimate yield of 318 t yr 1 129 while those from actively eroding reservoir shorelines contribute 328 t yr 1 92 sediment yield estimates from stream monitoring and reservoir sedimentation are an order of magnitude lower than those reported from south pennine reservoirs of comparable drainage basin area analysis of historical rainfall series for the catchment shows fluctuations in winter and summer rainfall patterns over the past 62 years from 1976 to 1998 there has been a diverging trend between winter and summer rainfall with a large increase in winter and a gradual decrease in summer totals periods of maximum variation occur during the summer drought events of the late 1970s early 1980s and mid 1990s analysis of the particle size of core sediments highlights abrupt increases in sand sized particles in the top 20 cm of the core based on the 137cs chronology these layers were deposited from the late 1970s onwards and relate to these diverging rainfall records and rapidly fluctuating reservoir levels this provides evidence of potential sediment reworking within the reservoir by rapid water level rise after drought copyright 2008 john wiley sons ltd

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

frequency and magnitude of bedload transport in a mountain river magnitude and frequency of bedload transport was examined in the lainbach river bavaria using magnetically tagged particles during the study 18 small to moderate events and one major event occurred about 1 per cent of the flow period exceeded the entrainment threshold and at least once every year about 50 per cent of the tagged particles were mobile themajor event which occurred during the study period resulted in the deposition of a thick layer of sediment in parts of the channel and passive burial of most of the recovered particles the step pool pattern which characterized the study site prior to the large event was obliterated however the channel recovered quickly and has returned to a new step pool pattern the event changed the boundary conditions by increasing the availability of loose sediment and creating higher river bed slopes in reaches between breached check dams as a result movement of individual particles measured for events of both the same magnitude and duration occurring before and after the large event yielded different values for events which occurred after the large event the range and the mean distance of movement were about ten times higher

deciphering magmatic processes in calc alkaline plutons using trace element zoning in hornblende hornblende in the kuna crest lobe kcl of the tuolumne intrusive complex tic and the upper zone of the wooley creek batholith wcb precipitated over a temperature range of 835 to 700 c and thus has the potential to record magmatic processes we measured trace element concentrations in hornblende from the wcb from the kcl of the tic and from one sample from an adjacent interior unit of the tic to compare and contrast magmatic processes in these two mid crustal intrusions in both systems the magmatic amphibole is magnesiohornblende in which ti zr hf nb sr ba and rare earth elements ree typically decrease from crystal interiors to rims an indication of compatible behavior of these elements and the size of the negative eu anomaly decreases in the kuna crest lobe hornblende from individual mapped units differs in trace element abundances and zoning trends some samples contain at least two distinct hornblende populations which is particularly evident in the shapes of ree patterns in contrast compositions of hornblende from all structural levels of the upper wcb and related dacitic roof zone dikes form a single broad array and the ree patterns are essentially indistinguishable regardless of rock type from quartz diorite to granite in the wcb zr hf ratios in hornblende are consistent with crystallization from a melt with chondritic zr hf values in contrast most hornblende in the kcl has zr hf values lower than expected from crystallization from a melt with chondritic values suggesting that zircon fractionation occurred before and during crystallization of the hornblende simple fractional crystallization models indicate that ree high field strength elements sr and ba were compatible in kcl and wcb magmas as hornblende grew these trends require removal of hornblende plagioclase zircon ilmenite biotite the uniform variations of trace element concentrations and patterns in the upper wcb and roof zone dikes indicates crystallization from a large magma body that was compositionally uniform probably stirred by convection caused by influx of mafic magmas at the base of the zone coint et al 2013a 2013b cf burgisser and bergantz 2011 in contrast in the kcl each analyzed sample displays distinct hornblende compositions and zoning patterns some of which are bimodal these features indicate that each analyzed sample represents a distinct magma and that individual magmas were variably modified by fractionation and mixing hornblende trace element contents and zoning patterns prove to be powerful tools for identification of magma batches and for assessing magmatic processes and thereby relating plutonic rocks to hypabyssal and volcanic equivalents

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

river loads and modern denudation of the alps a review this paper presents the first comprehensive analysis of sediment and dissolved load across an entire mountain range we investigate patterns and rates of modern denudation of the european alps based on a compilation of data about river loads and reservoir sedimentation from 202 drainage basins that are between ca 1 to 10 000 km2 large the study basins cover about 50 of the total area of the alps modern glaciated basins have the highest sediment yields of up to 7000 t km 2 a 1 which are on average 5 to 10 times higher than in non glaciated basins likewise sediment yield and glacial cover are positively correlated instead relief is a relatively weak predictor of sediment yield the strong glacial impact in the correlations is due to glacier recession since the 19th century as well as due to glacial conditioning during repeated quaternary glaciations which have produced the strong transient state of the alpine landscape we suggest that this is the major cause for ca 3 fold enhanced denudation of the western compared to the eastern alps chemical denudation rates are highest in the external alps dominated by carbonate sedimentary rocks where they make up about one third of total denudation the high rates cannot be explained without anhydrite dissolution we estimated that only 45 of the sediments mobilized in headwaters are exported out off the alps most sediments being trapped in artificial reservoirs the total amount of sediment annually trapped within the alps equates to 43 mt when corrected for sediment storage we obtain an area weighted mean total denudation rate for the alps of about 0 32 mm a 1 the pre dam rate might be as high as 0 42 mm a 1 in total ca 35 plus 23 mt of mass are exported each year out of the alps as solids and solutes respectively these rates are not enough to out pace modern rock uplift nevertheless pattern of sediment yield across the alps coincides roughly with the intensity of glacial conditioning and modern rock uplift supporting the hypothesis of an erosion driven uplift of the alps

partial transport of a sand gravel sediment grains of a single size within a mixed size bed are entrained over a range of flows within this range some grains exposed on the bed surface are active entrained at least once over the duration of a transport event while the remaining surface grains are immobile a condition we define as partial transport we demonstrate the existence and domain of partial transport using observations of grain entrainment on time series of bed photographs of flume experiments with a widely sorted sand gravel mixture the active proportion of the bed surface increases with bed shear stress 0 at a given 0 90 of the active grains are entrained when the cumulative mass transported exceeds approximately 4 times the active mass on the bed mobilization of grains in a size fraction increases from 10 to 90 over a range of 0 of a factor of 2 the bounds of this range increase with grain size di so that at a given 0 sizes over a range of a factor of 4 are in a state of partial transport fractional transport rates are independent of di for fully mobilized fractions and decrease rapidly with di for partially mobile fractions partial transport is associated with substantial transport rates of finer fully mobile sizes limits both the rate and size distribution of grain exchange with the bed subsurface and may be the dominant transport condition in many gravel bed rivers

quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery images from specially commissioned aeroplane sorties manned aerial vehicle mav repeat unmanned aerial vehicle uav surveys and planet cubesat satellites are used to quantify dune and bar dynamics in the sandy braided south saskatchewan river canada structure from motion sfm techniques and application of a depth brightness model are used to produce a series of digital surface models dsms at low and near bankfull flows a number of technical and image processing challenges are described that arise from the application of sfm in dry and submerged environments a model for best practice is presented and analysis suggests a depth brightness model approach can represent the different scales of bedforms present in sandy braided rivers with low turbidity and shallow 2 m deep water the aerial imagery is used to quantify the spatial distribution of unit bar and dune migration rate in an 18 km reach and three 1 km long reaches respectively dune and unit bar migration rates are highly variable in response to local variations in planform morphology sediment transport rates for dunes and unit bars obtained by integrating migration rates from uav with the volume of sediment moved from dsms using mav imagery show near equivalence in sediment flux hence reach based sediment transport rate estimates can be derived from unit bar data alone moreover it is shown that reasonable estimates of sediment transport rate can be made using just unit bar migration rates as measured from 2d imagery including from satellite images so long as informed assumptions are made regarding average bar shape and height with recent availability of frequent repeat satellite imagery and the ease of undertaking repeat mav and uav surveys for the first time it may be possible to provide global estimates of bedload sediment flux for large or inaccessible low turbidity rivers that currently have sparse information on bedload sediment transport rates

the effects of low magnitude flow conditions on bedload mobility in a steep mountain stream abstract the transport of coarse material strongly controls the stability and evolution of mountain fluvial systems but despite this bedload dynamics are not yet fully understood especially in mountain streams in this sense particular attention was paid on the bedload magnitude volume expressed at event scale and on the long term while few studies were focused on when and how the transport of the coarse material occurs the aim of this work was to investigate the bedload mobility in the rio cordon a mountain stream characterized by cascade and step pool morphologies with a rough streambed here the critical conditions for initiation of motion transport distance and virtual velocity expressed by the coarse streambed material were assessed and their relationships with hydraulic forcing conditions and grain size were analyzed to this end a monitoring program based on bedload tracing was maintained over 7 years allowing to analyze the bedload mobility during persistent high frequency low magnitude flow conditions to investigate the bedload mobility 250 tracers were released between 2011 and 2012 and their propagation along study site was monitored until 2018 overall 14 tracer inventories were realized determining 1697 tracer localizations during the study period the bedload dispersion resulted well described by the peak discharge magnitude qp qp and p c while no significant relationships were observed with duration of competent flow tover and effective runoff volume er transport distance and tracer grain size were negatively correlated whereas virtual velocity increased with increasing particle size in this sense the propagation velocity seems to be affected by the high frequency flows that on the one hand triggered mobilization of the coarser tracers only through limited and impulsive events and on the other hand favored a slowdown on the finer particles due to bedforms disturbance compared to other study sites the rio cordon exhibited accentuated threshold conditions with lower transport distance and virtual velocity confirming that steep mountain streams are generally influenced by a reduced transport efficiency due to protruding bedforms and macro roughness that cause a pronounced energy dissipation interestingly such condition seems to have progressively reduced from under to near bankfull flows the results were compared to the bedload mobility observed in the rio cordon during 1993 1998 enabling to quantitatively assess how the bedload dispersion varied between a setting of stable armouring layer with protruding bedforms 2012 2018 and a partial alteration of these 1993 1998 an evident difference was observed in terms of transport distance while critical conditions did not significantly change lastly the long term bedload tracing investigation highlighted that a certain legacy on the transport efficiency was produced by the persistent high frequency flow conditions over the study period a general decrease of transport distance was observed that could be explained by a progressive stabilization of streambed material previous studies suggested that such condition can be interrupted by high magnitude low frequency floods

mountain erosion over 10 yr 10 k y and 10 m y time scales we used cosmogenic 10 be to measure erosion rates over 10 k y time scales at 32 idaho mountain catchments ranging from small experimental watersheds 0 2 km 2 t o large river basins 35 000 km 2 these long term sediment yields are on average 17 times higher than stream sediment fluxes measured over 10 84 yr but are consistent with 10 m y erosion rates measured by apatite fission tracks our results imply that conventional sediment yield measurements even those made over decades can greatly underestimate long term average rates of sediment delivery and thus overestimate the life spans of engineered reservoirs our observations also suggest that sediment delivery from mountainous terrain is extremely episodic sporadically subjecting mountain stream ecosystems to extensive disturbance

fluvial and slope wash erosion of soil mantled landscapes detachment or transport limited many numerical landform evolution models assume that soil erosion by flowing water is either purely detachment limited i e erosion rate is related to the shear stress power or velocity of the flow or purely transport limited i e erosion deposition rate is related to the divergence of shear stress power or velocity this paper reviews available data on the relative importance of detachment limited versus transport limited erosion by flowing water on soil mantled hillslopes and low order valleys field measurements indicate that fluvial and slope wash modification of soil mantled landscapes is best represented by a combination of transport limited and detachment limited conditions with the relative importance of each approximately equal to the ratio of sand and rock fragments to silt and clay in the eroding soil available data also indicate that detachment entrainment thresholds are highly variable in space and time in many landscapes with local threshold values dependent on vegetation cover rock fragment armoring surface roughness soil texture and cohesion this heterogeneity is significant for determining the form of the fluvial slope wash erosion or transport law because spatial and or temporal variations in detachment entrainment thresholds can effectively increase the nonlinearity of the relationship between sediment transport and stream power results from landform evolution modeling also suggest that aside from the presence of distributary channel networks and autogenic cut and fill cycles in non steady state transport limited landscapes it is difficult to infer the relative importance of transport limited versus detachment limited conditions using topography alone copyright 2011 john wiley sons ltd

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

cover effect in bedrock abrasion a new derivation and its implications for the modeling of bedrock channel morphology the sediment load of a bedrock river plays an important role in the fluvial incision process by providing tools for abrasion the tools effect and by covering and thereby protecting the bed the cover effect we derive a new formulation for the cover effect in which the fraction of exposed bed area falls exponentially with increasing sediment flux or decreasing transport capacity and explore its consequences for the model of bedrock abrasion by saltating bed load erosion rates predicted by the model are higher than those predicted by earlier models in a closed system the maximum erosion rate is predicted to occur when sediment supply is equal to transport capacity for a flat bed by optimizing the channel geometry to minimize the potential energy of the stream and using representative values for both discharge and grain size we derive equations for the geometry of a bedrock river and explore how predictions for width slope and bed cover vary as functions of drainage area rock uplift rate and rock strength the equations predict a dependence of channel width on drainage area similar to the relations using a simple shear stress incision law the slope area relationship is predicted to be concave up in a log log regime with a curvature dependent on uplift rate however this curvature does not deviate sufficiently from a straight line to allow discrimination between models using empirical data dependence of channel width and slope on rock uplift rate can be separated into two domains for low uplift rates channel geometry is largely insensitive to uplift rate due to a threshold effect at high uplift rates there is a power law dependence bed cover is predicted to increase progressively downstream and to increase with increasing uplift rate in our model the width to depth ratio is a function of both tectonic and climatic forcing this indicates that the scaling between channel width and bed slope is neither a unique indicator of tectonic forcing at steady state nor a signature of transience or steady state we conclude that sediment effects need to be taken into account when modeling bedrock channel morphology

formation of waterfalls by intermittent burial of active faults waterfalls commonly exist near bounding faults of mountain ranges where erosional bedrock catchments transition to depositional alluvial fans we hypothesize that aggradation on alluvial fans can bury active faults and that the faults accumulate slip in the subsurface to produce a bedrock scarp following entrenchment of the alluvial fan the scarp can be exposed as a waterfall to explore this hypothesis we derived a geometric model for waterfall height that depends on alluvial fan length and the relative time scales of 1 tectonic uplift 2 a forcing mechanism for cycles of fan aggradation and incision and 3 a response of fan aggradation to changes in sediment flux we find that the model is consistent with observations at gower gulch death valley california where a man made drainage capture event in 1941 caused rapid fan incision and exposed a waterfall at the canyon fan transition we also compared the model to 62 waterfalls in 18 catchments of the death valley area and found that at least 15 of the waterfalls are best explained by the fault burial mechanism using field measurements of grain size and channel geometries we show that the fault burial mechanism can produce the observed waterfall heights measuring 4 19 m under a uniform climatic forcing scenario requiring variations of 20 in precipitation during the late pleistocene the fault burial mechanism through the creation of upstream propagating waterfalls may allow catchment fan systems to experience frequent cycles of enhanced erosion in catchments and deposition on fans that likely convolve tectonic and climatic signals

pleistocene holocene climate change re establishment of fluvial drainage network and increase in relief in the swiss alps abstract data are presented about modern sediment discharge of the swiss rivers and related to the size of catchments the information reveals that the central alps have experienced denudation rates of 0 15 mm yr 1 in the foreland and 0 5 mm yr 1 in the alpine core mapping however indicates that modern erosion only affects 30 50 of the alpine surface and that fluvial and associated hillslope processes have focused erosion in 50 200 m deep valleys these valleys are incised into the glacial surface if this limited spatial extent of erosion is considered then effective erosion rates are significantly higher than average denudation rates these effective rates equal or locally exceed modern rates of rock uplift this implies that the modification of erosional processes related to the pleistocene holocene climate change has resulted in an increase in the relief at a local scale at a drainage basin scale however the relief appears not to change at present

denudation rate changes along a fast eroding mountainous river with slate headwaters in taiwan from 10 be meteoric 9 be ratios

erosion in the western alps dora baltea basin 2 quantifying sediment yield abstract the present work shows how sediment composition can be used to constrain bed load sediment budgets in mountain catchments a database of high resolution petrographic and dense mineral analyses of detritus carried by the dora baltea river and its tributaries allowed us to partition bed load sediment budgets obtained from data available from a public authority between two different sets of sediment sources major tributaries and major geological units relative and absolute budgets of sediment bed load thus obtained are more robust than those derived from traditional empirical methods alone total detrital flux in the dora baltea drainage basin is 1 000 000 ton year bed load 590 000 ton year suspended load 410 000 ton year with denudation rates of 0 12 mm year data from italian public authority progetto di piano stralcio per l assetto idrogeologico pai parma supplemento straordinario della gazzetta ufficiale 166 more than 75 of the dora baltea total bed load 453 000 9000 ton year is derived from tributaries dora di ferret dora di veny savara grand eyvia buthier lys sourced from the highest granitoid peaks 4000 m a s l m bianco m rosa m cervino gran paradiso massifs which drain 36 of the whole catchment the m bianco massif with its granitoid lithology extreme relief and heavily glaciated drainage basins occupies only 3 of total basin area but it produces 294 000 6000 tons of arkosic sands per year which represents 50 of total dora baltea bed load the dora di veny 2 of total dora baltea mountain catchment exhibits the highest denudation rate of the whole dora baltea mountain basin 0 73 mm year the values calculated in this study compare well with measured modern river loads of partly glaciated mid latitude mountain regions

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

revisiting lake sediment budgets how the calculation of lake lifetime is strongly data and method dependent lake sedimentation has a fundamental impact on lake lifetime in this paper we show how sensitive calculation of the latter is to the quality of data available and assumptions made during analysis based on the collection of a large new dataset we quantify the sediment masses 1 mobilized on the hillslopes draining towards lake tana ethiopia 2 stored in the floodplains 3 transported into the lake 4 deposited in the lake and 5 delivered out from the lake so as to establish a sediment budget in 2012 2013 suspended sediment concentration ssc and discharge measurements were made at 13 monitoring stations including two lake outlets 4635 ssc samples were collected and sediment rating curves that account for land cover conditions and rainfall seasonality were established for the 11 river stations and mean monthly ssc was calculated for the outlets effects of the floodplain on rivers sediment yield sy were investigated using measurements at both sides of the floodplains sy from ungauged rivers was assessed using a model that includes catchment area and rainfall whereas bedload and direct sediment input from lake shores were estimated as a result the gross annual sy was ca 39 55 0 15 mt dominantly from gilgel abay and gumara rivers the 2 57 0 17 mt sediment deposited in floodplains indicate that the floodplains serve as an important sediment sink moreover annually ca 1 09 mt of sediment leaves the lake through the two outlets annual sediment deposition in the lake was ca 36 97 0 22 mt and organic matter accumulation was 2 15 mt with a mean sediment trapping efficiency of 97 furthermore ssc and sy are generally higher at the beginning of the rainy season because soils in cultivated fields are bare and loose due to frequent ploughing and seedbed preparation later on in the season increased crop and vegetation cover lead to a decrease in sediment production based on the established sediment budget with average rainfall the lifetime of lake tana was estimated as 764 to 1032 years which is shorter than what was anticipated in earlier studies the sedimentation rate of lake tana 11 7 0 1 kg m 2 y 1 is in line with the sedimentation rates of larger lakes in the world like lake dongting and lake kivu

glacial sediment production and development of hydro electric power in glacierized areas by jim bogen glaciology section norwegian water resources and energy administration p o box 5091 majorstua n 0301 oslo 3 norway abstract this paper discusses the results of a sediment monitoring programme carried out in connection with hydro electric power development plans in the river basins surrounding the jostedalsbreen ice cap in norway whereas the highest suspended sediment transport rates occur during years with several flash flood events the bed load is more dependent upon the duration of large magnitude flood events bed load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers during the years 1968 86 the mean ratio of bed load to total load amounted to 0 30 0 50 of the total load but in years with large magnitude floods this ratio decreased the mean annual suspended sediment yield of norwegian glaciers ranges from 100 tonnes km2 a i to 1300 tonnes km2 a i valley glaciers cause the highest erosion rates with the exception of the small cirque glacier trollbergdalsbreen which is thought to be a soft bed glacier the investigation programme undertaken involved monitoring the volume of suspended sediments together with the size distribution mineralogy and shape of grains in general the valley glaciers supply more sand than the smaller cirque glaciers whereas particles in the fine sand and silt size ranges in almost all of the glaciers are angular in shape methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed long term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier fed lakes introduction during the last few years several glacier areas in norway have been developed for hydro electric power in this paper the results of a sediment monitoring programme carried out in connection with hydro electric power plans in the river basins surrounding the jostedalsbreen ice cap are discussed the hydro electric power plans on the western side the breheimen stryn project involve diversions of water at 32 intakes fig

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

bedload transport in se asian streams uncertainties and implications for reservoir management article this paper reviews the current state of knowledge regarding bedload transport in se asian streams and presents the results from a case study on bedload transport in a mountain stream in northern thailand together the review and new data help contextualize the paucity of work done in the region in the face of a rapid increase in development and reservoir building throughout se asia data from both the reviewed studies and the case study indicate that bedload transport in many se asian streams e g catchment areas b 100 km 2 i s often much higherthan iscommonly assumed for tropicalstreams i e about 10 of the totalsediment load estimat ed annual bedload proportion was 18 of the total annual sediment load in the 74 km

the impact of exceptional events on erosion bedload transport and channel stability in a step pool channel sediment transport in the erlenbach a small stream with step pool morphology in the canton of schwyz switzerland has been monitored for more than 20 years during this time three exceptional events events with high sediment yield and long return times that have a large effect on channel morphology have impacted the stream and partly or completely rearranged the existing step pool morphology in the aftermath of the events sediment transport rates at a given discharge and total sediment yield remained elevated for about a year or longer for the last event dated on the 20 june 2007 observations of boulder mobility and step destruction were used to interpret channel stability boulders with median diameters of up to 135 cm and estimated weights of more than 2 5 tons have moved during the 2007 event using hydraulic observations and shear stress calculations boulders up to 65 cm in diameter were predicted to have been fully mobile in peak conditions even if form resistance and increased critical stresses needed for the initiation of motion in steep streams were taken into account for two of the events estimated peak shear stresses at the bed exceeded 1000 pa calculated both from observations of the flow hydraulics and from boulder mobility this suggests that highly energetic flows occur relatively frequently in small steep streams and that large boulders can be transported by fluvial processes in such streams the observations have potential significance for hazard risk mitigation stream engineering and restoration copyright 2009 john wiley sons ltd

detrital cosmogenic 21ne records decoupling of source to sink signals by sediment storage and recycling in miocene to present rivers of the great plains nebraska usa the preservation of conglomerates far from mountainous sources is commonly interpreted in terms of tectonic or climatic forcing to relate a depositional signal to changing conditions in source areas the process and duration of sediment routing from source to sink need to be determined for the first time we quantified sediment transport histories using cosmogenic 21ne in quartzite pebbles from modern river gravels and neogene conglomerates from the modern and ancient north platte river of the great plains of nebraska united states we demonstrate that at 400 km distance from the front ranges of the rocky mountains the majority of pebbles were stored in older channel deposits for up to several millions of years before being recycled this was enabled by very slow to zero basin subsidence rates this implies that upstream tectonic or climatic controls on surface processes were decoupled from the downstream depositional record a result supported by the similarities in cosmogenic 21ne values among miocene pliocene and modern river channel pebbles despite known changes in tectonic and climatic forcing

combining impact sensor field and laboratory flume measurements with other techniques for studying fluvial bedload transport in steep mountain streams the timing and rate of fluvial bedload transport are of central importance within sediment budget studies and in many applications in river science and engineering during the years 2010 2011 and 2012 detailed field measurements with portable impact sensors as a non invasive technique for indirectly determining fluvial bedload transport intensity were conducted in two instrumented and supply limited drainage basin systems erdalen and bodalen in the fjord landscape in western norway additional field measurements with portable impact sensors were carried out in 2010 and 2011 in selected transport limited fluvial systems in the coast mountains of western canada the collected impact sensor field data were calibrated with laboratory flume experiments the data from the impact sensor field measurements in western norway and the flume experiments were combined with field data from continuous discharge monitoring repeated surveys of channel morphometry and sediment texture particle tracer measurements helley smith samplings underwater video filming and biofilm analyses the combination of methods and techniques applied provides insights into the temporal variability and intensity of fluvial bedload transport in the selected mountain streams i in the transport limited systems with generally high bedload transport rates during high discharge and with bedload material moving in clusters over the impact sensor plates impact sensor data based on a 1 s measuring interval provide the opportunity to detect the start and end of bedload transport thus to identify discharge thresholds for sediment entrainment and to roughly estimate the intensity and relative intensity of change of bedload transport during the measuring period ii in the supply limited systems with low bedload transport rates and bedload components moving separately as single particles over the impact sensor plates impact sensor data with a 1 s measuring interval allow the detection of the start and end of transport of bedload components 11 3 mm thus the identification of discharge thresholds for possible entrainment of particles the quantification of the number of particles 11 3 mm moving over the impact sensor plates during the measuring period the rough estimation of grain sizes of the particles moving separately over the impact sensor plates and the calculation of the total mass of the bedload material 11 3 mm moving over the impact sensor plates during the measuring period iii when combined with other methods and techniques helley smith sampling particle tracer measurements biofilm analyses underwater video filming which provide information on the active bedload transport channel width on discharge thresholds for possible entrainment of particles of different grain sizes and on transport rates of bedload material 11 3 mm total rates of fluvial bedload transport covering all given grain sizes of the bedload material can be calculated for the supply limited mountain streams with generally low bedload transport the higher measured annual bedload yield in bodalen 13 6 t km 2 yr 1 compared to erdalen 2 6 t km 2 yr 1 reflects a higher level of slope channel coupling in bodalen than in erdalen

bedload to suspended load ratio and rapid bedrock incision from himalayan landslide dam lake record about 5400 cal yr bp a large landslide formed a n400 m tall dam in the upper marsyandi river central nepal the resulting lacustrine and deltaic deposits stretched n7 km upstream reaching a thickness of 120 m 14 c dating of 7 wood fragments reveals that the aggradation and subsequent incision occurred remarkably quickly 500 yr reconstructed volumes of lacustrine 0 16 km 3 and deltaic 0 09 km 3 deposits indicate a bedload to suspended load ratio of 1 2 considerably higher than the 1 10 that is commonly assumed at the downstream end of the landslide dam the river incised a new channel through 70 m of greater himalayan gneiss requiring a minimum bedrock incision rate of 13 mm yr over last 5400 yr the majority of incision presumably occurred over a fraction of this time suggesting much higher rates the high bedload ratio from such an energetic mountain river is a particularly significant addition to our knowledge of sediment flux in orogenic environments 2007 university of washington all rights reserved

contrasting mountain and piedmont dynamics of sediment discharge associated with groundwater storage variation in the biobio river supply and transport of sediment in catchments involve processes with fundamental consequences for river management land use and the prediction of climate driven sediment fluxes in the present study we addressed spatial variability in the water routes through the surface and subsurface of a catchment and the suspended sediment discharge qs over a mountain piedmont system we analyzed daily suspended sediment concentration cs and water discharge q measurements at stations located in different topographic settings mountain and piedmont in the biobio river basin southern central andes 37 39 s in steep catchments the q versus qs relationship has a marked seasonal hysteresis in the piedmont qs is proportional to q with no seasonal hysteresis the contrast in the hysteresis pattern between catchments with different topographies is explained by differences in the routing of rainfall derived water in the piedmont most of the rainfall is converted into surface runoff because the water table is near the surface in the mountains groundwater storage results in large seasonal variations in the proportion of q that flows at the surface and transports sediment from the hillslopes producing hysteresis by separating the total q into two components direct discharge qd and base flow qb we observed the response of qs to the fraction of water that quickly leaves the catchment after a rainfall event qd similar results between the mountain and piedmont and the absence of hysteresis simplify the behavior of qs into a linear relationship with qd over the entire catchment and lead us to propose that sediment mobilization to the river along the biobio catchment is primarily controlled by overland flow our findings highlight the importance of an adequate hydrological model for understanding the erosion and transport processes of a catchment and which can be applied to other natural and modeled mountain piedmont systems

near channel versus watershed controls on sediment rating curves predicting riverine suspended sediment flux is a fundamental problem in geomorphology with important implications for water quality land and water resource management and aquatic ecosystem health to advance understanding we evaluated environmental and landscape factors that influence sediment rating curves srcs we generated srcs with recent total suspended solids tsss and discharge data from 45 gages on 36 rivers throughout the state of minnesota usa watersheds range from 32 to 14 600 km2 and represent distinct settings regarding topography land cover and geologic history rivers exhibited three distinct src shapes simple power functions threshold power functions and peaked or negative slope functions we computed src exponents and coefficients describing the steepness of the relation and the tss concentration at median flows respectively in addition to quantifying watershed topography climate hydrology geology soil type and land cover we used lidar topography to characterize the near channel environment upstream of gages we used random forest models to analyze relations between src parameters and attributes of the watershed and the near channel environment the models correctly classify 78 of src shapes and explain 37 60 of variance in src parameters we find that src steepness exponent is strongly related to near channel morphological characteristics including near channel relief channel gradient and presence of lakes along the local channel network but not to land use in contrast land use influences tss concentrations at moderate and low flow these findings suggest that the near channel environment controls changes in tss as flows increase whereas land use drives median and low flow tss conditions

partitioning sediment flux by provenance and tracing erosion patterns in taiwan we critically evaluate the potential and limitations of an alternative way to calculate erosion rates based on petrographic and mineralogical fingerprints of fluvial sediments coupled with gauged sediment fluxes our approach allows us to apportion sediment loads to different lithological units and consequently to discriminate erosion rates in different tectonic domains within each catchment our provenance data on modern taiwanese sands indicate focused erosion in the backbone range and tananao complex of the retrowedge lower rates are inferred for the northern part of the island characterized by tectonic extension and for the western foothills in the prowedge the principal factor of uncertainty affecting our estimates is the inevitably inaccurate evaluation of total sediment load because only the suspended flux was measured another is the assumption that suspended load and bed load are derived from the same sources in fixed proportions additional errors are caused by the insufficiently precise definition of lithologically similar compositional end members and by the temporal variability of sediment composition at the outlet of each catchment related to the spatial variability of erosional processes and triggering agents such as earthquakes typhoons and landslides to evaluate the robustness of our findings we applied a morphometric technique based on the stream power model the results obtained are broadly consistent with local discrepancies ascribed to poorly constrained assumptions and choices of scaling parameters our local erosion estimates are consistent with gps uplift rates measured on a decadal timescale and generally higher than basin wide results inferred from cosmogenic nuclide and thermochronology data

erosion in the western alps dora baltea basin 1 quantifying sediment provenance abstract sourced in the m bianco the highest mountain of the alps the dora baltea river cuts across the arc of the western alps drains all major alpine tectonic units from the helvetic domain to the south alpine domain and finally joins the po river petrographic composition of clastic detritus carried by the dora baltea river and its tributaries faithfully mirrors the complex geology of the western alps high resolution modal analysis of dora baltea sands allowed us to distinguish seven end member metamorphoclastic provenances river sands from the m bianco external massif are dominated by quartz feldspars and hornblende detritus from basement and cover rocks of the brianconnais zone includes low grade metasedimentary lithic fragments epidote chloritoid and garnet sands from the internal penninic massifs include quartz and subordinate feldspars garnet and epidote abundant metabasite and serpentine schist lithic grains along with epidote actinolite and few pyroxenes characterize detritus from the calcschists and meta ophiolites of the oceanic piemonte zone sands from the austroalpine zone include quartz abundant metamorphic lithic fragments garnet and locally significant sillimanite dent blanche kinzigites the relative contribution of each end member to the dora baltea sediment flux was assessed with forward modelling of end member mixing our estimates calculated from the entire petrographic and mineralogical data set indicate that the main sources of bed load in the dora baltea mountain basin are the granitoid to gneissic rocks exposed in the m bianco massif and in the austroalpine zone in order to make allowance for the contribution of a particular bedrock constituent in a compound source area to the derivative sand the original concept of sand generation index sgi was modified to assess the relative contribution of the seven end member sources of detritus the highest total basin sgi indices are calculated for the m bianco massif sgi 16 4 and austroalpine domain sgi 1 4 the m bianco massif which represents only 3 of the whole catchment has the highest capacity of sand sized bed load production owing to its granitoid lithology and extreme relief this actualistic provenance study demonstrates that sediment composition can be markedly influenced by source rocks that occupy only a minor portion of the drainage area