stabilization of a gravel channel by large streamside obstructions and bedrock bends jacoby creek northwestern california jacoby creek bed width 12 m bankfull discharge 32 6 m 3 s contains stationary gravel bars that have forms and positions controlled by numerous large streamside obstructions bedrock outcrops large woody debris and rooted bank projections and bedrock bends bank projection width and bar volume measured in 104 channel segments 1 bed width long are significantly cross correlated at lags of 1 3 and 4 indicating the tendency for large obstructions and bends to form bars 3 to 4 bed widths downstream and 1 bed width upstream all of the 18 bars downstream of large obstructions or bends in the study reach were along the obstruction side of the channel or outside bank of the bend most of the pools 85 were next to large obstructions or in bends conversely 92 of large obstructions or bends had pools comparison of the volume of four bars with volumetric bar changes and volume of bedload transported during four high flow events suggests that rates of sediment transport were sufficient to cause major changes in bars during bankfull events the only important channel changes observed in 4 yr however have been associated with the movement of large woody debris and with changes in the angle at which the flow approaches an obstruction a general model is proposed that large obstructions and nonalluvial bends stabilize the form and location of gravel bars bars are stabilized by two related mechanisms 1 large obstructions and bends cause intense quasi steady secondary circulation in scour holes that terminate upstream bars at fixed locations obstruction width channel deflection scour hole width and bed width were measured at 26 obstructions these data show that obstructions wider than approximately one third of the bed form pools spanning the entire channel and thus terminating bars smaller obstructions form scour holes contained within a single bar 2 bars are deposited upstream of large obstructions and sharp bends because of backwater reductions in stream power bars are deposited downstream because flow energy is expended around obstructions and bends and because the flow expands downstream of constrictions that result from large obstructions the formation of bars and pools inherent in many gravel channels can thus be enhanced and fixed in position by flow structures set up around large obstructions and bends formed of resistant materials

changes in lowland floodplain sedimentation processes pre disturbance to post rehabilitation cosumnes river ca during the late holocene sediment deposition on the lowland cosumnes river floodplain ca has depended on factors that varied temporally and spatially such as basin subsidence sea level rise flow and sediment supply from both the sacramento river system and from the cosumnes river system itself and anthropogenic changes through field investigations and analyses of historical maps bridge core logs and sediment size distributions we link hydrogeomorphic processes to three stages of floodplain sedimentation on the lowland cosumnes river stage i 1000 200 ybp combined late holocene pre disturbance flood basin overflow and anastomosing river processes deposited spatially variable sediment consisting of gray blue clay 87 clay interlayered with relatively thin coarser sediment pre disturbance holocene deposition rates of up to f3 0 mm year kept pace with sea level rise and tectonic basin subsidence stage ii 200 to f10 ybp anthropogenic disturbances caused a rapid increase in floodplain sedimentation rates up to 25 mm year between 1849 and f1920 and deposited a relatively coarser reddish brown sandy clay f40 clay layer that overlies the basin deposits between f1920 and 1990 ad sedimentation was greatly limited on the lower cosumnes floodplain because levees inhibited connectivity between both the sacramento and cosumnes river systems and the cosumnes floodplain during this stage the density of channel segments in the anastomosing river floodplain decreased by 30 as agricultural activities filled secondary channels and leveled floodplain topography during stage iii f10 ybp to the present post rehabilitation floodplain sand splay complex sediment deposited after 1998 ad resulted from intentionally breaching levees to promote habitat at the cosumnes river preserve the splay complex is dominated by medium to very coarse sand with finer intervening layers the post rehabilitation splay complex overlies the older basin deposits in a generally upward coarsening sequence that reflects depositional processes and land use changes that continue to affect the lowland cosumnes river floodplain d 2003 elsevier science b v all rights reserved

what s in a name the aurignacian in romania abstract the key position held by romania s territory for the available scenarios regarding the expansion of the upper paleolithic cultural package in europe has been recently reinforced by the finds of the oldest european homo sapiens sapiens remains in the oase cave southwestern romania however in spite of its paradigmatic association to the first anatomically modern humans in europe the aurignacian in romania remained inadequately known and rarely referred to in the european literature the poor descriptions of the aurignacian called lithic industries and their unusually young numerical chronology or geochronological estimations explain this caution a brief evaluation of the available information regarding these issues is proposed based on a comparatively restricted definition of the aurignacian variability as acknowledged in the recent european literature e g numerical chronology large retouched blades bladelet production from carinated forms bone industry the present approach dismisses many postulates widely held in romanian literature the local origin the wide occurrence and the late survival of the aurignacian however given the lack of numerical dates and the fragmentary state of most archaeological collections the precise timing of its emergence and the details of its regional evolution require further research

sources sinks and storage of river sediment in the atlantic drainage of the united states the history of sediment and its movement in the atlantic drainage demonstrate some of the difficulties of modeling sediment on a river basin scale soil erosion was accelerated by a factor of at least 10 when european settlers cleared forests and planted crops although increasing soil conservation practice and decreasing crop farming have since reduced the rates of erosion large quantities of eroded material are still stored on hillslopes and in stream valleys where they continue to augment the sediment loads of the rivers the sediment from this episode of erosion that is largely past can be expected to emerge from storage for many decades and perhaps even several centuries to come the reservoirs that have been built on many of the major rivers trap significant portions of the moving sediment which in some places may be remobilized by large floods essentially all the river sediment that reaches the atlantic coastal zone is trapped in estuaries and coastal marshlands probably less than 5 is deposi

variations in natural levee morphology in anastomosed channel flood plain complexes abstract natural levees are common features of alluvial river systems yet their origin and evolution are poorly understood in this paper we present morphologic and sedimentologic data from two anastomosed rivers and offer a hypothesis of natural levee growth in these systems based on mechanisms of sediment transport in settings where floodbasins fill at the same rate as the channel levees form by turbulent diffusion of suspended sediment away from a high velocity thread into a floodbasin of relatively stagnant water the theory of diffusive transport suggests that these levees should be narrow steep and display abrupt decreases in grain size due to rapid decreases in carrying capacity with distance into the floodbasin in environments where an appreciable water surface slope is maintained between the main channel and the floodbasin levees form by advection of sediment out of the channel and into the floodbasin advective transport theory indicates that these levees should be broad and gently sloped with grain sizes gradually decreasing away from the main channel natural levees occurring in the anastomosed reach of the upper columbia river in se british columbia display significantly different morphology from levees in the cumberland marshes region of the lower saskatchewan river in east central saskatchewan at the upper columbia site the rise in stage of the floodbasin water nearly keeps up with that of the channel water because of good communication between channel and floodbasins through crevasses this inhibits the establishment of a water surface slope and the bulk of the escaping sediment is deposited close to the channel in contrast the cumberland marshes region is characterized by wide and volumetrically large floodbasins these conditions keep floodbasin water surface elevations relatively low and maintain an appreciable elevation head between the channel and its floodbasin fostering levee growth by advective transport

tributary trunk stream relations in a cut and fill landscape a case study from wolumla catchment new south wales australia at the time of european settlement of the south coast of new south wales australia in the mid nineteenth century river courses were discontinuous throughout wolumla catchment within a few decades of settlement intact valley fills had been transformed into incised channels along trunk streams this induced associated patterns of secondary incision into tributary valley fills three of the primary subcatchments in wolumla catchment became fully incised while an upland swamp and a floodout i e sand sheet deposits atop an intact valley floor remain in mid catchment of the fourth subcatchment of the 70 lower order tributaries which join the trunk streams in the four subcatchments 27 have incised 12 of which are discontinuously incised incision of tributary streams in wolumla catchment cannot be explained by subcatchment area and slope relations the position of the trunk stream channel within the valley floor trough is the key determinant of whether or not tributary streams have incised changes to river morphology since european settlement have altered the linkage of tributary streams to the trunk stream impacting directly on the within catchment transfer of water and sediment

dam to delta sediment inputs and storage in the lower trinity river texas livingston dam on the trinity river in se texas usa disrupts the transport of sediment to the lower trinity river and the trinity bay galveston bay estuary however a sediment budget of the lower basin shows that the effects of this disruption are undetectable in the lower river sediment trapped in lake livingston is partly offset by channel erosion downstream of the dam and by inputs from the lower basin most importantly however the lower coastal plain reaches of the trinity are characterized by extensive alluvial storage and are a bottleneck that buffers the bay from effects of upstream changes in sediment flux storage is so extensive that the upper trinity basin and the lowermost river reaches were essentially decoupled in the sense that very little upper basin sediment reached the lower river long before the dam was constructed whereas sediment storage in lake livingston is extensive alluvial storage on the trinity flood plain is even more extensive dam related sediment starvation effects are noted for about 52 km downstream and the sediment budget suggests that a majority of the sediment in this reach is likely derived from channel scour and bank erosion the capacious alluvial storage in the lower trinity not only limits flux to the bay but the large amount of remobilizable alluvium also allows the system to adjust to localized sediment shortages as illustrated in the dam to romayor reach internal adjustments within the lower trinity river valley thus buffer the bay from changes in sediment supply upstream

variability in sediment delivery and storage along river courses in bega catchment nsw australia implications for geomorphic river recovery in many catchments in southeastern australia alluvial stores have been the dominant source of sediments mobilised in the period since european settlement in bega catchment on the south coast of new south wales nsw this has been reflected by dramatic changes to river morphology extensive volumes of material have been released and efficiently flushed to the lowland plain with a sediment delivery ratio of almost 70 however only 16 of these alluvial sediments have been flushed through to the estuary as antecedent controls on valley width have resulted in the lowland plain acting as a large sediment sink the changing nature of sediment source transfer and accumulation zones has varied markedly from subcatchment to subcatchment the volume of material supplied to the lowland plain from differing subcatchments is not related to subcatchment area rather the pattern of river types dictates the spatial variability in storage and transfer over 67 of sediment released has been sourced from just 25 of the catchment from subcatchments characterised by large valley fills cut and fill river style that previously stored extensive volumes of material at the base of the escarpment these parts of bega catchment were especially sensitive to disturbance sediment exhaustion from these parts of the catchment and from river courses elsewhere has major implications for the geomorphic recovery potential of rivers constraining what can be realistically achieved in terms of river rehabilitation

luminescence chronology of pleistocene loess deposits from romania testing methods of age correction for anomalous fading in alkali feldspars the irsl dating method is applied to silt sized alkali feldspar grains 40 60mm from upper and middle pleistocene loess deposits of southeastern romania sites of tuzla and giurgiu malu rosu using both the multiple aliquot g dose technique and the sar method all samples show evidence of anomalous fading the measured irsl ages are in correct stratigraphic order but systematically underestimate the expected geological age up to 40 three protocols of age correction for the observed fading have been tested the correction of huntley and lamothe can j earth sci 38 2001 1093 the correction of mejdahl quat sci rev 7 1988 357 and the correction model suggested by wintle quat sci rev 9 1990 385 the three protocols yield corrected irsl ages that are in better agreement with the expected ages this study demonstrates the potential of the irsl dating method to provide chronological information on upper and middle pleistocene loess deposits of romania r 2003 elsevier science ltd all rights reserved

the aurignacian way of life contextualizing early modern human adaptation in the carpathian basin abstract the culture and dispersal of early modern humans are top priorities of many research agendas while the debate primarily centers on genetics dispersal trajectories and points of earliest presence the context climate landscape demography culture of the colonizing process is usually considered in a coarse grained manner or even ignored to understand the context of human dispersal and to decipher relevant push and pull factors requires the consideration of multiple environmental proxies and the research on different geographic scales in this paper we present the late quaternary carpathian basin as a specific context area of early modern human dispersal into europe the multitude of early upper paleolithic sites in this region suggests that it was part of a major dispersal corridor along the danube and its catchment area some 40 000 years ago the aurignacian land use model describes the interaction of early modern humans with their environment one important parameter is the specific distribution of archaeological sites that exemplifies their boundedness to specific eco zones to reconstruct the latter paleo environmental proxies and archaeological data are examined together in regional vector models and in a gis based landscape archaeology approach in the final section we present the carpathian basin as an idiosyncratic habitat that mirrors the dynamics and complexity of early modern human adaptation

the distribution and residence time of suspended sediment stored within the channel margins of a gravel bed bedrock river previously undocumented deposits are described that store suspended sediment in gravel bedded rivers termed fine grained channel margin fgcm deposits fgcm deposits consist of sand silt clay and organic matter that accumulate behind large woody debris lwd along the margins of the wetted perimeter of the single thread gravel bed south river in virginia these deposits store a total mass equivalent to 17 to 43 of the annual suspended sediment load radiocarbon 210pb and 137c dating indicate that sediment in fgcm deposits ranges in age from 1 to more than 60 years reservoir theory suggests an average turnover time of 1 75 years and an annual exchange with the water column of a mass of sediment equivalent to 10 to 25 of the annual sediment load the distribution of ages in the deposits can be fitted by a power function suggesting that sediment stored in the deposits has a wide variety of transit times most sediment in storage is reworked quickly but a small portion may remain in place for many decades the presence of fgcm deposits indicates that suspended sediment is not simply transported downstream in gravel bed rivers in agricultural watersheds significant storage can occur over decadal timescales south river has a history of mercury contamination and identifying sediment sources and sinks is critical for documenting the extent of contamination and for developing remediation plans fgcm deposits should be considered in future sediment budget and sediment transport modeling studies of gravel bed rivers in agricultural watersheds copyright 2010 john wiley sons ltd

reconstructing palaeoenvironments on desert margins new perspectives from eurasian loess and australian dry lake shorelines abstract desert margins preserve evidence of more extensive arid conditions in the past and represent global hot spots with respect to climate change the balance of scientific evidence now suggests that dryland landscape reactivation did not correspond simply to ice age aridity peaks as previously assumed this paper provides a new perspective on and more nuanced understanding of desert marginal landscapes as palaeoenvironmental archives the two case studies represent ends of a sediment availability spectrum both environments experience substantial spatial and temporal variability in deposition with implications for reconstructing past environments at individual sites recently generated chronostratigraphic data from the dry subhumid dobrogea loess romania are synthesised to provide quantitative insights into the spatial and temporal organisation of loess plateaux loess accumulation peaks during the lgm and mis4 but not at all sites accumulation rates vary substantially between sites comparison of geographical context yields no clear driving mechanism for this variability secondly two transverse lunette dunes in semi arid willandra lakes australia yield comparable chronostratigraphies and distribution of stratigraphic units a first attempt is made to identify changes in wind regime through time on the australian desert margins and suggests that high latitude climate forcing may have acted upon semi arid australia over millennial scales the novel perspectives generated from the new datasets provide unprecedented insights into past climate circulation and land surface processes along desert margins these new perspectives coupled with the new geochronological and quantitative palaeoclimate proxy tools now available represent the next frontier for palaeoenvironmental research on desert margins

human impact on land ocean sediment transfer by the world s rivers abstract land ocean transfer of sediment by rivers is a key pathway for material transfer on earth contemporary data on the sediment loads of rivers provide clear evidence of significant recent changes in the sediment fluxes of several rivers in response to human impact the key drivers of increased sediment loads include land clearance for agriculture and other facets of land surface disturbance including logging activity and mining although programmes for soil conservation and sediment control can result in reduced sediment loads the trapping of sediment by dams represents the dominant cause of reduced loads this influence is currently assuming increasing importance at the global scale any attempt to link these drivers to changes in the global land ocean sediment flux must take account of the aggregation and buffering effects that operate in larger basins which can cause damping and even removal of signals of increasing flux within the upstream basin and complicate the link between upstream and downstream response to human impact further work is required to provide a precise quantitative assessment of the human impact on global land ocean sediment fluxes and the net effect of increasing and decreasing fluxes particular attention must be paid to the temporal perspective and the variation of impact trajectories in different areas of the globe and for river basins of different sizes

assessing grain size correspondence between flow and deposits of controlled floods in the colorado river u s a abstract flood deposited sediment has been used to decipher environmental parameters such as variability in watershed sediment supply paleoflood hydrology and channel morphology it is not well known however how accurately the deposits reflect sedimentary processes within the flow and hence what sampling intensity is needed to decipher records of recent or long past conditions we examine these problems using deposits from dam regulated floods in the colorado river corridor through marble canyon grand canyon arizona u s a in which steady peaked floods represent a simple end member case for these simple floods most deposits show inverse grading that reflects coarsening suspended sediment a result of fine sediment supply limitation but there is enough eddy scale variability that some profiles show normal grading that did not reflect grain size evolution in the flow as a whole to infer systemwide grain size evolution in modern or ancient depositional systems requires sampling enough deposit profiles that the standard error of the mean of grain size change measurements becomes small relative to the magnitude of observed changes for simple steady peaked floods 5 10 profiles or fewer may suffice to characterize grain size trends robustly but many more samples may be needed from deposits with greater variability in their grain size evolution

on the calculation of suspended load for noncohesive sediments calculation of suspended sediment transport rates requires integration of the product of sediment concentration times velocity over the depth of the flow hence accurate profiles of these quantities are required especially near the sediment bed although this would appear to be a straightforward task many effects can cause significant deviation of these quantities from those values expected from simple known relationships for example density stratification by suspended particulates can dampen turbulence fluctuations and significantly reduce the effective viscosity and diffusivity of the flow the momentum and suspended sediment equations are solved herein including the effects of stratification by suspended sediment and the effects due to size distribution and bedforms the results show that stratification and bedforms generally reduce the transport capacity of the flow whereas treating the sediment as an assemblage of different sizes rather than a single size d50 increases the expected transport

early upper paleolithic surface collections from loess like sediments in the northern carpathian basin abstract the way in which modern humans first entered europe has been a recent focus of upper paleolithic research a leading theory posits that the danube served as a conduit for migration from southeastern into central and western europe however a challenge to this has been the scarcity of early upper paleolithic sites along the middle danube carpathian basin though several sites with early upper paleolithic features szeletian aurignacian are known from surface prospections few have been archeologically investigated in detail here our aim is to elucidate this long standing deficiency by evaluating two unknown and three known sites from the northern carpathian basin in hungary and slovakia through a series of keyhole excavations the objectives were to see if in situ stratified material still existed and to characterize the sites archeological assemblages and sedimentological contexts to do this field observations supplemented by granulometry were employed to determine if the surrounding sedimentary matrix was eolian loess and or if it had been mixed with underlying older deposits the results indicate that the lithics represent early upper paleolithic assemblages that experienced post depositional mixing however two sites se a i nagyrede 1 showed more nuanced site formation processes and may contain in situ artifacts warranting further exploration these studies highlight the importance of including sedimentological research into archeological investigations because the paucity of sites may not simply mean a lack of human occupation but can indicate a dynamic geomorphological evolution of the pleistocene landscape that may have erased past traces of human settlements through insufficient sedimentation the results provide new insights into the early upper paleolithic settlement and the sedimentary dynamics of the carpathian basin ultimately leading to a greater understanding of the early modern human settlement patterns in europe

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

the character and age structure of valley fills in upper wolumla creek catchment south coast new south wales australia extensive valley fills at the base of the escarpment in upper wolumla creek on the south coast of new south wales australia have formed from a combination of cut and fill processes the valley fills comprise series of alternating horizontally bedded sand and mud units reflecting reworking of detritus from deeply weathered granites of the bega batholith sand units are deposited as sand sheets or splays on floodplain surfaces or in floodouts that form atop intact valley fill surfaces downstream of discontinuous gullies alternatively sands are deposited from bedload and form bars or part of the valley floor within channel fills organic rich mud units are deposited from suspension in swamps or in seepage zones at the distal margin of floodouts within 5 km of the escarpment valley deposits grade downstream from sand sheet and splay deposition in floodouts to mud deposition in swamp and seepage zones radiocarbon dates indicate that virtually the entire valley fill of upper wolumla creek was excavated prior to 6000 years bp remnant terraces are evident at valley margins the valley subsequently filled between 6000 years bp and 1000 years bp producing valley fills around 12 m deep but no greater than 300 m wide reincision into the valley fill on a scale smaller than the present incision phase is indicated at around 1000 years bp following which the channel refilled portion plans dated from 1865 refer to the study area as wolumla big flat and show large areas of swampy terrain suggesting that the valley fill had re established by this time within a few decades of european settlement the valley fill incised once more upper wolumla creek now has a channel over 10 m deep and 100 m wide in places draining a catchment area of less than 20 km2 1998 john wiley sons ltd

a preliminary investigation of the integration of modelled floodplain hydraulics with estimates of overbank floodplain sedimentation derived from pb 210 and cs 137 measurements this paper investigates the possibility of linking finite element modelled two dimensional hydraulics with floodplain sedimentation rates derived from radionuclide dating techniques the telemac 2d system is used to simulate the full dynamic velocity vector and water depth distributions for a 1 in 12 year flood event for the river culm devon these are compared to patterns of medium term 30 100 years sedimentation rates and a degree of correlation is found to exist this information is used to comment on the complexity of flow and sediment deposition interactions in floodplain environments and to provide a research design for the development of a more fully integrated floodplain morphodynamic model copyright 1999 john wiley sons ltd

the bearded vulture gypaetus barbatus as an accumulator of archaeological bones late glacial assemblages and present day reference data in corsica western mediterranean assemblages of 751 bone remains of an endemic corsican deer megaloceros cazioti from late glacial layers at luri gritulu cave northern corsica show an uncommon taphonomic pattern mainly characterized by high dominance of third phalanxes and high rate of digestion marks the authors demonstrate that this pattern cannot result from accumulation by human beings or by large mammal carnivores the bearded vulture which is able to accumulate large mammal bones in its nest and the presence of which is attested in the faunal remains at gritulu is the principal putative accumulator in order to test this hypothesis bone contents from 11 nests of modern corsican bearded vultures 871 bone remains i e more than 105 individual carcasses are analysed from a taphonomic point of view they are mainly characterized by overwhelming quantities of third phalanxes from middle size ruminants abundance and location of digestion marks around proximal articulations and few bone flakes a comparison of the gritulu cave assemblages with these new present day reference data leads to the conclusion that they have actually been accumulated by late glacial bearded vultures small discrepancies can however be explained by differences in food availability between the late glacial and modern times

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

floodplain processes in the bengal basin and the storage of ganges brahmaputra river sediment an accretion study using 137cs and 210pb geochronology floodplain deposits are recognized as potentially large sinks for fluvial sediments yet spatial and temporal patterns of accumulation are not known for many river systems in the tectonically active bengal basin the ganges and brahmaputra rivers coalesce and have formed a large floodplain delta complex where widespread overbank flooding may deposit a significant portion of the river s estimated sediment discharge to investigate the magnitude and distribution of this process accumulation rates were determined by 137cs and 210pb radioisotope geochronology at 60 sites located in three regions of the bengal basin differing in age physiography and river influence these geochronological methods have been applied to floodplain environments in only a few recent studies and the present research offers a revised approach for heterogeneous systems patterns of sediment deposition in the bengal basin reveal three dominant controls on floodplain accretion channel processes overbank flooding and surface runoff accretion is most rapid in the river braidbelt and adjacent floodplain decreasing rapidly with distance from the main channel accumulation rates increase again in low lying distal basins where several meters of annual precipitation and associated runoff rework surrounding floodplain surfaces and transport remobilized sediments to local catchments the extent and magnitude of this process indicate its comparable importance with overbank deposition for floodplain accumulation a sediment budget for the study area reveals that at least 15 of the estimated 1 billion tonnes of fluvial sediment discharge is stored annually and not reaching the oceans as previously assumed extrapolated to the remaining 60 000 km2 of floodplain not covered in this project the sequestered load could rise to 30 of annual sediment discharge

the recent history of erosion and sedimentation on the southern tablelands of southeastern australia sediment flux dominated by channel incision abstract as in other regions colonised from europe within the last few centuries australia s vegetation and soils have been dramatically changed by clearing cropping and grazing in southeastern australia particularly on the southern tablelands the impacts of european settlement are clearly manifested by channel incision by using stratigraphic and documentary evidence in conjunction with aerial photographs sediment budgets for the post settlement period have been constructed to define the fluxes and stores of sediment for each of the major geomorphic components of the 136 km2 catchment of jerrabomberra creek near canberra using these budgets and some plausible assumptions it has been possible to approximate the history of both the sediment delivery ratio and sediment yield for this catchment while the quantities estimated in this analysis are approximations the trends through time are credible sediment yield increased rapidly to a peak after european settlement and has returned to a level between the peak and the pre european value the delivery ratio has followed a similar trend the most general conclusion to emerge is that in this landscape both the total sediment flux and the sediment yield of the catchment have been dominated by channel erosion this result is contrary to the findings in many parts of the world where sheet and rill erosion dominates the fluxes the soil conservation implication of these results is clear to control off site effects of erosion the focus must be on the channels

river width adjustment i processes and mechanisms in 1993 a task committee tc of the asce was established to study the hydraulics bank mechanics and modeling of width adjustment in alluvial channels the work of the tc in reviewing width adjustment processes and mechanisms is reported in this paper a companion paper presents the findings of the tc with regard to width adjustment modeling this paper first establishes the geomorphic context within which width adjustments occur and it demonstrates that width adjustment may take place over a wide range of scales in time and space in the past engineering analyses of channel width have tended to concentrate on prediction of the equilibrium width for stable channels most commonly the regime extremal hypothesis and rational mechanistic approaches are used and these are reviewed herein more recently attention has switched to channels that are adjusting their morphology either due to natural instability or in response to changes in watershed land use river regulation or channel engineering chara

probable evidences of bone accumulation by pleistocene bearded vulture at the archaeological site of el miron cave spain the bearded vulture gypaetus barbatus a bird or prey that mainly feeds on bones of large mammal carcasses has been recently evidenced as an accumulating agent with significant contributions to palaeontological assemblages in caves and shelters but extremely rare at archaeological sites the results of the taphonomic analyses carried out in the upper palaeolithic layers of el miron cave cantabrian spain which are presented here evidence the existence of special digestive marks and a typical skeletal pattern in a noticeable amount of small and medium sized ungulates bones this fact suggest that a representative part of the bone assemblage has been caused by bearded vultures and strengthens the idea that this bird has to be definitely included among other potential non human accumulators in archaeological sites

fluvial sediment delivery to a coastal plain estuary in the atlantic drainage of the united states abstract drastic changes in sediment production in drainage basins can have significant impacts on sediment yield to estuaries however significant but less spectacular changes in fluvial sediment regimes have not greatly influenced sediment output of some rivers in the united states atlantic drainage the limited influence of moderate or incremental changes in fluvial sediment systems on estuarine sediment delivery may be attributable to the large proportion of eroded sediment which is stored within the basins and the transport limited nature of long term sediment yields a sediment budget for the pee dee river basin and waccamaw river winyah bay estuary of the carolinas shows that only a small proportion of gross eroded sediment within the basin about 4 reaches the estuary on an average annual basis because the system appears to be transport limited it is estimated that an 88 reduction in the quantity of eroded sediment reaching streams would be necessary to produce significant change in sediment yield to the estuary any increase in sediment production would not be reflected at all in the estuary unless it was accompanied by a corresponding increase in fluvial sediment conveyance capacity estuarine sedimentary records thus may not reflect some significant changes in fluvial sediment systems

the role of vegetation and bed level fluctuations in the process of channel narrowing abstract a catastrophic flood ire 1965 on plum creek a perennial sandbed stream in the western great plains removed most of the bottomland vegetation and transformed the single thalweg stream into a wider braided channel following eight years of further widening associated with minor high flows a process of channel narrowing began in 1973 narrowing continues today the history of channel narrowing was reconstructed by counting the annual rings of 129 trees and shrubs along a 5 km reach of plum creek near louviers colorado sixty three of these plants were excavated in order to determine the age and elevation of the germination point the reconstructed record of channel change was verified from historical aerial photographs and then compared to sediment stratigraphy and records of discharge and bed elevation from a streamflow gaging station in the study reach channel narrowing at plum creel occurs in two ways first during periods of high flow sand and fine gravel are delivered to the channel temporarily raising the general bed level subsequently several years of uninterrupted low flows incise a narrower channel second during years of low flow vegetation becomes established on the subaerial part of the present channel bed in both cases surfaces stabilize as a result of vegetation growth and vertical accretion of sediment

overbank sand deposition in relation to transport volumes during large magnitude floods in the dutch sand bed rhine river system using aerial photographs and field measurements sandy overbank deposits formed by the large magnitude floods of 1993 94 and 1995 were quantified along two branches of the dutch rhine river system the waal 1993 94 and 1995 and the ijssel 1995 these deposits were laid down intermittently all along the length of these rivers on the top and landward slope of the natural levees and covered about 4 per cent of the embanked floodplain on the waal and about 1 per cent on the ijssel the overbanks and transport mechanism is basically convective by nature the spatial variability of overbank sedimentation points to the important role played by helicoidal currents in determining overbank deposition the presence of embankments and training works appears to influence the sand transport to and morphological development of the floodplains along the dutch rhine river system overbank deposition volumes about equal present estimates of sand transport during a large magnitude flood it appears that studies on sand transport in the dutch rhine carried out so far underestimate sand transport during floods 1998 john wiley sons ltd

re development of fluvial islands along the lower mississippi river over five decades 1965 2015 abstract the development and evolution of islands along the lower mississippi river were examined over a 50 year period between 1965 and 2015 fluvial islands were historically a fundamental component of the riparian corridor serving as important ecological habitat for aquatic and terrestrial species their degradation was associated with channel engineering leading to a pronounced single thread channel continued channel engineering in the latter twentieth century however is associated with a rapid increase in channel islands along the lower mississippi river the study utilizes a gis framework to examine and analyze a range of geospatial data sets including i lidar dems ii historic aerial photos iii historic and recent satellite imagery iv historic topographic maps and vi hydrologic data from gauging stations along the lower mississippi river islands were digitized in google earth pro and arcgis by identification of vegetation lines spatial data polygons were used to extract clip the lidar dem data for subsequent analysis the island data was statistically analyzed using a manova and two way t test to examine the association of dikes with the morphologic characteristics of islands the number of islands 1 ha significantly increased over the five decade study period from 105 in 1965 206 in 1995 to 295 in 2015 the average size of islands decreased from 101 ha hectare to 63 ha because so many new small islands formed within the dike fields the total area of islands within the river channel increased from 103 km2 in 1965 169 km2 in 1995 to 206 km2 in 2015 the total sediment storage within fluvial islands above the average low water surface is 1 81 billion m3 the lower mississippi has sufficient coarse sediment to construct new riparian lands despite the large historic decline in sediment load and overall channel bed degradation that occurred in response to large scale engineering projects over much of the twentieth century the new rapid growth and development of fluvial lands within the riparian corridor of the lower mississippi is a positive outcome of an unintended geomorphic consequence but one that requires additional management considerations

restoration of floodplain topography by sand splay complex formation in response to intentional levee breaches lower cosumnes river california restoration of sustainable geomorphic processes that create floodplain topography through development of sand splay complexes at intentional breaches is one method to promote variability in physical structure needed for habitat restoration the topography of splay complexes provides a range of floodplain elevations that creates local variability in i inundation duration and frequency and depth to ground water that influence riparian vegetation establishment and ii flow depth and velocity that create refuge for fish two intentional levee breaches along the lowland cosumnes river central valley ca were evaluated during water years 1999 and 2000 in order to document changes in morphology and relief associated with deposition of sandsplay complexes during the study period annual peak flow recurrence intervals ranged from 1 to 3 years and water flowed through the breaches for a minimum of 55 days during water year 1999 and 53 days during water year 2000 at the two study sites rapid vertical accretion and scour occurred within the first several years after intentionally breaching the levee at the accidental forest floodplain constructed in 1995 and at the corps breach floodplain constructed in 1997 splay complexes are organized into a variety of landforms including lateral levees and lobes separated by new floodplain channels maximum deposition measured on the splay surface is 0 36 m year while maximum scour in channels is 0 27 m year juxtaposition of floodplain splay deposition and adjacent channel scour creates relief ranging from 1 6 to 0 25 m that decreases with distance from the breach and that becomes more pronounced over time as higher magnitude floods scour channels in the old floodplain sediment and deposit new sand and silt onto the surface of the splay the ratio of splay complex height to depth of formative flow is estimated as 0 4 progradation of main and secondary splay channels takes place by down floodplain sand transport 25 m year maximum large wood recruited onto the floodplain through the breach promotes local scour and deposition that enhances topographic variability at one of the study sites initial grading of a low setback berm prior to opening the breach forced a change in floodplain flow direction and the geometry of the splay complex additionally progradation of the complex is arrested by an excavated pond that creates a sediment trap we present a conceptual model that describes the importance of floods in constructing and modifying sand splay complexes that create floodplain topography the potential habitat variability created as floodplain topography evolves is the linkage between physical and ecological processes that are critical for restoration d 2002 elsevier science b v all rights reserved

an isotopic record of mercury in san francisco bay sediment article i nfo we analyzed eight sediment cores from wetland and subtidal locations around san francisco sf bay terrace sediment from the yuba river ca and precipitation from the sf bay region we defined the hg isotopic com position of uncontaminated sf bay sediment two contributing endmember sediments contaminated by dis tinct hg sources and regional precipitation deep subtidal sediments with pre mining thg concentrations less than 60 ng g have 202

variation in flow and suspended sediment transport in a montane river affected by hydropeaking and instream mining abstract the temporal and spatial variability of water and sediment loads of rivers is controlled by a suite of factors whose individual effects are often difficult to disentangle while land use changes and localised human activities such as instream mining and hydropeaking alter water and sediment transfer tributaries naturally contribute to discharge and sediment load of mainstem rivers and so may help compensate upstream anthropogenic factors the work presented here aimed to assess water and the sediment transfer in a river reach affected by gravel extraction and hydropeaking set against a backdrop of changes to the supply of water and sediment from tributaries discharge and suspended sediment transport were monitored during two average hydrological years at three cross sections along a 10 km reach of the upper river cinca in the southern pyrenees water and sediment loads differed substantially between the reaches the upper reach showed a largely torrential discharge regime controlled mainly by floods and had high but variable water and sediment loads the middle reach was influenced markedly by hydropeaking and tributary inflows which increased its annual water yield four fold suspended sediment load in this reach increased by only 25 compared to upstream indicating that dilution predominated in the lowermost section while discharge remained largely unaltered sediment load increased appreciably as a result of changes to sediment availability from instream mining and inputs from tributaries at the reach scale snowmelt and summer and autumn thunderstorms were responsible for most of the water yield while flood flows determined the magnitude and transport of the sediment load the study highlights that a combination of natural and human factors control the spatial and temporal transfer of water and sediment in river channels and that depending on their geographic location and effect size can result in marked variability even over short downstream distances

crustal structure of the ancestral northwestern california forearc region from seismic reflection imaging implications for convergent margin tectonics abstract analysis of a suite of 2 d seismic reflection profiles reveals that the northwestern sacramento valley and eastern coast range foothills northern california are underlain by a system of blind west dipping thrust faults homoclinally east dipping and folded mesozoic marine forearc strata exposed along the western valley margin define the forelimbs of northeast vergent fault propagation folds developed in the hanging walls of the thrusts exhumed coherent blueschists of the accretionary complex and attenuated remnants of the ophiolitic forearc basement presently exposed in the eastern coast ranges are in the hanging wall of the blind thrust system and have been displaced from their roots in the footwall deep east dipping magnetic reflectors in the footwall of the thrust system may be fragments of sheared serpentinized and attenuated ophiolitic basement restoration of slip on the thrusts suggests that the coast range fault which is the exposed structural contact between the coherent blueschists and attenuated ophiolite originally dipped east and is associated with the east dipping magnetic reflectors in the footwall this interpretation of the reflection data is consistent with previous inferences about the deep structure in this region and supports a two stage model for blueschist exposure in the eastern coast ranges 1 blueschist exhumation relative to the forearc basin by attenuation of the ophiolitic basement along the east dipping coast range fault system in late cretaceous 2 blueschists attenuated ophiolite and forearc strata all were subsequently uplifted and folded in the hanging wall of the blind thrust system beginning in latest cretaceous early tertiary the blind thrust system probably rooted in and was antithetic to the east dipping subduction zone beneath the forearc region active transpressional plate motion in western california is locally accommodated in part by reactivation of blind thrust faults that originally developed during the convergent regime

slope channel decoupling in wolumla catchment new south wales australia the changing nature of sediment sources following european settlement within a few decades of european settlement channel incision transformed discontinuous river courses throughout wolumla catchment on the south coast of new south wales australia the development of continuous channels greatly increased sediment delivery from the catchment this paper documents the character timing and proportion of sediment sourced from upland valley fills channel expansion sites and gully networks volumes of material transferred from these sources are compared with estimates of sediment eroded from hillslopes and the movement of sediment off the slopes to the valley floor is assessed although disturbance of slopes resulted in significant movement of materials most of this material has been stored on slope in trapped tributary fills and along lower order drainage lines the slopes are effectively decoupled from the channel sediment accumulation in farm dams over the past few decades has been negligible around 75 of the total volume of material released from creeks in wolumla catchment since 1865 i e 5500 103 m3 has been derived from channel incision into valley fills at the base of the escarpment sediment flushing occurred within a few decades of catchment disturbance bedrock confinement in the middle and lower catchment resulted in very efficient downstream transfer of materials although gully networks and channel expansion sites have released a relatively small volume of material these sources are the greatest contemporary source of sediment in wolumla catchment

genesis of loess like sediments and soils at the foothills of the banat mountains romania examples from the paleolithic sites românesti and cosava abstract the paleolithic sites rom nesti and cosava situated at the foothills of the banat mountains in romania provide an important testament of life of the first european modern humans homo sapiens sapiens during middle pleniglacial even though these sites have been extensively excavated little is known about the site formation of related loess like sediments and soils first luminescence data at the two investigated sections confirm sediments from the penultimate glacial period to the holocene assigning the levels of findings is difficult because the sediments are close to the surface and are overprinted by recent soil development albeluvisols influenced by stagnic features are the typical surface soils in the study area and on comparable morphological positions in the region laboratory analysis has revealed that this soil has a complex genesis from hydrolysis weathering which is connected with the development of a fragic soil horizon overprinting the major find horizons at both sites by using sedimentological and geochemical methods in combination this study aims to reconstruct sedimentary evolution and soil processes at the sites as well as to evaluate the state of preservation and the actual content of the archeological contexts initial results indicate hints for a forest step and higher vegetation during mis 3 at the foothills of the carpathian mountains in the western plain of romania these natural factors offer a local attractiveness of the region which could be the most important reason for the occurrence of first anatomically modern humans our investigations lend a better understanding of the paleoenvironment as well as a first age control of paleolithic levels for the region

floodplain sedimentation and sensitivity summer 1993 flood upper mississippi river valley patterns of overbank sedimentation in the vicinity of and far removed from levee breaks that occurred in response to the 100 year summer 1993 flood in the upper mississippi river valley are elucidated two suites of overbank deposits were associated with the failure of artificial levees within a 70 km long study reach circumjacent sand deposits are a component of the levee break complex that develops in the immediate vicinity of a break site as epitomized by the levee break complex at sny island these features consist of an erosional scoured and or stripped zone together with a horseshoe shaped depositional zone at locales farther removed from the break site the impact of flooding was exclusively depositional and was attributed to the settling of suspended sediment from the water column the overall picture was one of modest scour at break sites and minimal suspended deposition 4 mm at locales farther removed from the breach downriver from the confluence with the missouri river suspended sediment deposition was of a similar magnitude to that observed within the study reach and levee break complexes exhibited a similar morphology but scour at break sites was greatly enhanced and the excavated sand formed extensive deposits on the floodplain surface the different erosional response was probably engendered by the higher sand content and reduced aggregate cohesion of the floodplain soils downriver from the confluence with the missouri river a qualitative comparison serves to highlight the influence that the resistance threshold may have on the sensitivity of floodplains bordering large low gradient rivers to high magnitude floods 1997 john wiley sons ltd

sediment load and floodplain deposition rates comparison of the fly and strickland rivers papua new guinea 1 rates of aggradation and infilling of accommodation space along lowland channels in response to postglacial sea level rise should depend on sediment supply the strickland and fly rivers join at just 6 m above sea level and have experienced the same holocene sea level rise historically the strickland has carried about 7 times the sediment load and 1 4 times the water discharge as the fly therefore we hypothesize that the lowland strickland floodplain should be more developed and consequently should presently be capturing proportionately less sediment than the floodplain of the lowland fly river we use mine derived elevated pb and ag concentrations in 111 shallow 1 m floodplain cores collected in 2003 to determine deposition rates across the lower strickland floodplain sediment deposition rates decrease across the floodplain with distance from the channel bank and the average rate of deposition is 1 4 cm a over the first 1 km overbank deposition along the lowland sandbedded strickland results in 13 loss of the total load 0 05 km of channel length of the main stem deposition rates over the first 1 km from the channel bank on the strickland are about 10 times those on the fly for estimated natural sediment loads however the proportional loss per channel length on the strickland is less than that on the fly 0 09 km of main stem channel length because of an extensive network of tributary and tie channels that convey sediment to the floodplain on the fly furthermore the lateral migration of the strickland channel is 5 times that on the fly such that most overbank deposits on the strickland are returned to the channel causing the net loss of sediment to the floodplain to be small we conclude that the strickland river which has a much higher overbank deposition rate than the fly river as a function of distance from channel bank nonetheless has significantly less net accumulation than the fly because 1 a large proportion of the sediment load is conveyed up tributaries and tie channels on the fly and 2 lateral migration which presumably results from the higher load on the strickland sweeps sediment back into the channel hence our field observations support our initial hypothesis though the primary reason for this is because of active lateral migration rather than low overbank deposition rates

quantitative model of the growth of floodplains by vertical accretion a simple one dimensional model is developed to quantitatively predict the change in elevation over a period of decades for vertically accreting floodplains this unsteady model approximates the monotonic growth of a floodplain as an incremental but constant increase of net sediment deposition per flood for those floods of a partial duration series that exceed a threshold discharge corresponding to the elevation of the floodplain sediment deposition from each flood increases the elevation of the floodplain and consequently the magnitude of the threshold discharge resulting in a decrease in the number of floods and growth rate of the floodplain floodplain growth curves predicted by this model are compared to empirical growth curves based on dendrochronology and to direct field measurements at five floodplain sites the model was used to predict the value of net sediment deposition per flood which best fits in a least squares sense the empirical and field measurements these values fall within the range of independent estimates of the net sediment deposition per flood based on empirical equations these empirical equations permit the application of the model to estimate of floodplain growth for other floodplains throughout the world which do not have detailed data of sediment deposition during individual floods copyright 2000 john wiley sons ltd

three dimensional numerical modelling of levee depositions in a scandinavian freshwater delta abstract a three dimensional numerical model was used to compute the water flow and the sediment deposition for a 100 year flood in the delta of lake oyeren in norway the model solved the reynolds averaged navier stokes rans equations with the k e turbulence model on a three dimensional unstructured grid the sediment transport was computed solving the convection diffusion equation for sediment concentration using an empirical formula for the bed pickup rate the results were tested against sedimentation data obtained from field measurements in a qualitative way both the mapped sedimentation patterns on the delta islands and the computed ones showed the typical levee like structures along the deltaic channels a series of sensitivity tests showed the important role of uncertainties in the bed roughness parameter the incoming sediment concentration the grain size distribution on the channel bed and the vegetation parameters the presence of vegetation strongly affected the position and intensity of the sediment depositions and its proper parameterization plays a key role for the modelling according to the computations the levee deposition during the 1995 flood appeared as a process where fine sand mainly originating from the channel bed was brought into suspension and deposited on the floodplain where the flow velocity was lower and the flow became overloaded with sediment an inspection of the simulated flow patterns and velocity vectors suggested that advective sediment transfer out of the channel and into the floodplain probably was the dominating process for the levee depositions

holocene paleoclimate records from a large california estuarine system and its watershed region linking watershed climate and bay conditions abstract the san francisco bay delta system includes a watershed that covers a large area of california and provides water to two thirds of the state s population climate over the estuary and its watershed in the dry summer months is controlled by the subtropical high which dominates and deflects storms from california the subtropical high weakens and migrates south as the aleutian low strengthens bringing wet winter storms to the region paleoclimatic records from the bay and its greater watershed spanning the holocene are reviewed here in order to better understand natural variations of precipitation and runoff and the linkages between those variations and the salinity and ecosystems of the estuary to better understand regional scale climate patterns paleoclimate records from coastal california and the great basin are also considered large fluctuations in climate have occurred during the period of interest and there is generally good agreement between the paleoclimate records from different regions early holocene climate throughout california was marked by rising temperatures and reduced moisture as seen in fire records from the watershed this warmth and aridity peaked about 5000 7000 years ago and was followed by a cooling trend with variable moisture conditions the estuary formed relatively rapidly in response to a high rate of sea level rise that dominated the holocene until about 6000 years ago and the subsequent reduced rate of inundation allowed vast tidal marshes to form along the edges of the estuary which have since been recording changes in environmental conditions the impacts of changing regional climate patterns are experienced in the san francisco bay delta system as altered fresh water flows result in altered estuary salinity for example approximately 3800 cal yr b p records from throughout the state indicate a cool moist period and bay salinity was reduced this period was followed by a general drying trend throughout california over the last two millennia punctuated by decades to centuries long droughts and brief extremely wet events in particular during the period ca 1000 800 cal yr b p a d 950 1150 conditions seem to have been unusually dry in many parts of the watershed reducing the fresh water flows to the estuary and shifting tidal marsh plant assemblages toward less diverse but more salt tolerant plants in contrast the little ice age ca 550 200 cal yr b p brought unusually cool and wet conditions to much of the watershed and lowered salinity in the bay many reconstructions suggest that notably stable conditions have prevailed over the instrumental period i e after ca a d 1850 even including the severe short term anomalies experienced during this period interdecadal variability is common in many of the records with timescales of ca 55 70 90 100 150 and 200 years

a sediment fingerprinting approach to understand the geomorphic coupling in an eastern mediterranean mountainous river catchment article i nfo article history to understand the response of a river to anthropogenic disturbance knowledge of the links between erosion sed iment deposition and sediment export iscrucial therefore starting from field observations and connectivity prox ies a sediment fingerprinting approach using geochemical tracers was used to elucidate the subrecent sediment dynamics in the 264 km 2 bugduz river catchment in sw turkey a topography based connectivity index was used as a proxy for hillslope channel coupling and stream power estimations as a proxy for the within channel connectivity quantitative provenance information providesa link between potential sediment sources and the de rived sediment currently stored within the fluvial system provenance signals from both contemporary river bed sediments n 144 and subrecent floodplain deposits n 2 8 provide more insight into the coupling of the hillslopes to the river channel and the coupling within the river channel itself furthermore comparing the prov enance signal with the areal extent of potential sediment sources upstream in the form of enrichment ratios sheds light upon the variation of the erodibility of the sources andthe connectivity within the catchment results indicate that the valleygradient exerts an important control on the spatial variability of geomorphic coupling in the bugduz catchment furthermore different sediment sources lithologies show distinct sediment production rates in ad dition to the observed spatial variability coupling relations are characterized by an important seasonal variation indicated by variable contributions of local and more distant sediment sources

the evolution of the great hungarian plain fluvial system fluvial processes in a subsiding area from the beginning of the weichselian abstract in the great hungarian plain ghp one of the most complex fluvial systems of europe developed through tectonic and climatic factors and vegetation change the aim of the present study is to summarise these controlling factors and to describe the evolution of the ghp special attention is paid to the latest results on late weichselian and holocene development in the tisza river and their effects on the river s largest tributary the maros river several tectonically active subsiding basins existing in the ghp have determined the direction of river courses and erosional accumulational fluvial processes as a result of uneven subsidence the river s flow routes have shifted frequently for example the danube and the tisza shifted 80 100 km abandoning their alluvial fans where extensive aeolian processes started upstream from the subsiding areas incision propagated headward which resulted in the development of floodplain levels and terraces though climate and vegetation changes also simultaneously influenced the rivers hydro morphology channel pattern changes were found just along the margin of the plain and only meandering paleo channels remained in the center of the ghp during dry and cold periods braided patterns appeared in the alluvial fans most likely the result of abundant sediment supply and due to the inability of sparse riparian vegetation to stabilise the banks effectively based on paleo discharge calculations by the end of the pleistocene the rivers of the ghp produced three to eight times more discharge than they do currently and discharge levels continuously decreased during the holocene however due to the long length of the rivers there is a considerable time lag between the response rates of the different river sections which makes creating paleo hydrological reconstructions even more difficult

from deposition to erosion spatial and temporal variability of sediment sources storage and transport in a small agricultural watershed article i nfo article history the spatial and temporal variability of sediment sources storage and transport were investigated in a small agricultural watershed draining the coast ranges and sacramento valley in central california results of field laboratory and historical data analysis in the willow slough fluvial system document changes that transformed a transport limited depositional system to an effective erosion and transport system despite a large sediment supply these changes were caused by a combination of factors i an increase in transport capacity and ii hydrologic alteration alteration of the riparian zone and drainage network pattern during the past 150 years included a twofold increase in straightened channel segments along with a baselevel change from excavation that increased slope and increased sediment transport capacity by 7 hydrologic alteration from irrigation water contributions also increased transport capacity by extending the period with potential for sediment transport and erosion by 6 months year field measurements document quaternary alluvium as a modern source of fine sediment with grain size distributions characterized by 5 to 40 fine material about 60 of an upland and 30 of a lowland study reach incised into this deposit exhibit bank erosion during this study the wet 2006 and relatively dry 2007 water years exhibited a range of total annual suspended sediment load spanning two orders of magnitude 108 500 kg km

three climatic cycles recorded in a loess palaeosol sequence at semlac romania implications for dust accumulation in south eastern europe recent inve stigations of the semlac loess section in the south eastern carpathian basin which is situated at an undercut slope position on the right bank of the mures river in its lower reaches banat region western romanian are presented and discussed dating back to marine isotope stage mis 10 the more than 10 m thick loess sequence includes four fossil soil complexes developed in homogenous and relatively fine silty loess because of the good preservation of the sediment semlac is regarded as a key section for the carpathian basin which offers possibilities to a improve the understanding of the type and composition loess homogeneity and pedogenic alteration of the lowland loess sequences in the carpathian basin also beyond the last interglacial palaoesol complex b to reconstruct the temporal evolution of the local loess palaoesol successions c gain better insight into the regional paleoenvironments of the last 300ka and d to compare the loess of the region to loess sequences in adjacent areas and to dust proxy data in the northern hemisphere an integrated age model based on correlation to reference records and luminescence dating is compiled applying this age model we compare climate proxy data from semlac to both global data and to data from the very southeast of the carpathian basin vojvodina serbia the obtained results provide new insight into the dust accumulation regime for the eastern carpathian basin and offer new palaeoenvironmental information for the region and are an important step towards establishing a catena from the thin loess like sediments of the banat foothills in the east towards the thicker and seemingly more complete loess sections of the south eastern and central carpathian basin disentangling grain size data from soil formation proxies is used to investigate patterns of non local dust patterns of non pedogenetic fine material are similar to grain size proxies from china and other parts of the northern hemisphere suggesting western and eastern eurasian loess to have at least partly similar mechanistic climatic origins c 2016 elsevier ltd all rights reserved

floodplain sedimentation quantities patterns and processes this paper presents the result of measurements of floodplain sedimentation using sediment traps the study was carried out on two embanked floodplains along the rivers rhine and meuse in the netherlands during a 3 day flood in january 1993 raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging the sediment maps show clear patterns in sediment accumulation together with the estimated interpolation errors average sediment accumulation ranges between 0 57 and 1 0 kg m 2 high sediment accumulation is found on the levees 4 kg m 2 or more and on low lying areas 1 6 kg m 2 sediment accumulation decreases with distance from the main channel the sedimentation patterns are related to floodplain topography and sediment transporting mechanisms sediment transport by turbulent diffusion as well as by convection can be recognized also flood duration and the process of sediment settling out in ponding water in closed depressions are important the applied method allows comparison of the results with raster based sedimentation models

the impact of the streamflow hydrograph on sediment supply from terrace erosion abstract sediment supply from banks and terraces has important implications for grain size distributions in alluvial rivers and by extension for aquatic habitat as well as for the delivery of floodplain stored nutrients and contaminants to the aquatic environment the interactions between streamflow hydrographs and lateral channel boundary failure control the sediment supply from banks and terraces however the relationships between variable flow and discrete sediment supply from catastrophic erosion of lateral boundaries and subsequent mass sediment flux in rivers are not well characterised by existing methods and models that focus only on one of several relevant interrelated processes in order to improve predictive capability of catastrophic sediment supply from lateral boundaries we adopt a new approach to modelling the process interactions between stream hydrology erosion of banks terraces and the corresponding discrete supply of sediment to channels we develop a modelling framework for terrace channel coupling that combines existing theories of flow through porous media bank stability and fractional sediment flux we demonstrate the utility of this modelling approach by assessing hydrologically driven erosion evolution of grain size in the channel and fine sediment flux from a study site along the yuba river in california over individual flood hydrographs and over decadal historical flow series we quantify the supply of sediment eroded from a contaminated nineteenth century fan terrace of hydraulic gold mining tailings intersecting the yuba and find that a threshold for erosion exists at a stage in the channel in excess of 8 m producing episodic sediment concentrations in excess of 300 mg l 1 the modelling produced erosion and fine sediment pulses from each of three major floods in the past several decades until the flow drops below 500 m3 s 1 and a bed armor layer forms while no sediment was generated from the terrace during smaller floods we further assess the impact on terrace erosion of various river management scenarios with distinct hydrograph shapes and find increased erosion potential when the terrace contains antecedent moisture or the flood time series is run over an extended duration sensitivity analysis demonstrated that elevated antecedent moisture within the lateral boundary and increased hydrograph rising time each reduce bank stability and thus increase volumes of failed material we also show that fluctuations in the hydrograph typically associated with hydroelectricity generation result in a more stable terrace than those of a longer duration because there is less time for hyporheic stream water to infiltrate the lateral boundary this study demonstrates that changes in hydrograph shape as a consequence of climatic forcing or anthropogenic dam releases may have considerable impacts upon sediment delivery and associated contaminants from banks and terraces to the downstream environment

new data on the avifauna from the middle stone age layers of sibudu cave south africa taphonomic and palaeoenvironmental implications abstract the results of a detailed taxonomic and taphonomic study of the bird assemblage from all excavated middle stone age msa layers from sibudu cave wadley s excavations a rock shelter in kwazulu natal south africa are presented here throughout the sequence the assemblage is characterised by the richest taxonomic diversity observed in msa deposits from southern africa while pigeons and doves clearly dominate the bird assemblage the presence of several previously unidentified taxa associated with evergreen and deciduous forest such as woodpeckers turacos hornbills and parrots picidae musophagidae bucerotidae and psittacidae in the pre still bay still bay and howiesons poort layers are useful to document the habitats surrounding sibudu cave from 75 000 to 60 000 years ka ago birds associated with fresh water namely waders charadriidae and scolopacidae and kingfishers alcedinidae are present throughout the layers and are consistent with the proximity of the uthongathi river a study of the general bone preservation implies a shift in the modes of introduction of the birds into the archaeological sediments from a predominantly natural origin accumulation by a bird of prey most likely a falcon in the pre still bay layers to a greater anthropogenic contribution in the still bay and howiesons poort layers

human topographic signatures and derived geomorphic processes across landscapes abstract the earth s surface morphology in an abiotic context is a consequence of major forcings such as tectonic uplift erosion sediment transport and climate recently however it has become essential for the geomorphological community to also take into account biota as a geomorphological agent that has a role in shaping the landscape even if at a different scale and magnitude from that of geology although the modern literature is flourishing on the impacts of vegetation on geomorphic processes the study of anthropogenic pressures on geomorphology is still in its early stages topography emerges as a result of natural driving forces but some human activities such as mining agricultural practices and the construction of road networks directly or indirectly move large quantities of soil which leave clear topographic signatures embedded on the earth s morphology these signatures can cause drastic changes to the geomorphological organization of the landscape with direct consequences on earth surface processes this review provides an overview of the recent literature on the role of humans as a geological agent in shaping the morphology of the landscape we explore different contexts that are significantly characterized by anthropogenic topographic signatures landscapes affected by mining activities road networks and agricultural practices we underline the main characteristics of those landscapes and the implications of human impacts on earth surface processes the final section considers future challenges wherein we explore recent novelties and trials in the concept of anthropogenic geomorphology herein we focus on the role of high resolution topographic and remote sensing technologies the reconstruction or identification of artificial or anthropogenic topographies provides a mechanism for quantifying anthropogenic changes to landscape systems this study may allow an improved understanding and targeted mitigation of the processes driving geomorphic changes during anthropogenic development and help guide future research directions for development based watershed studies human society is deeply affecting the environment with consequences on the landscape therefore establishing improved management measures that consider the earth s rapidly changing systems is fundamental

relationship between magdalenian subsistence and environmental change the mammalian evidence from el miron spain abstract during the magdalenian roughly 20 13 ka cal bp intensive human occupation of the el miron cave coincided with oldest dryas and the climate amelioration of bolling allerod pleniglacial gs 2a interstadials gi 1e 1d 1c 1b 1a the evolution of small mammal assemblages throughout the stratigraphic sequence displays a pattern similar to those of pollen geological and other studies elsewhere in the cantabrian region during the magdalenian there was a climatic recovery indicated by the first record in the stratigraphic sequence of small mammals living in forested habitats such as dormice at the end of the magdalenian there was an important diminishment of species of small mammal especially those living in meadow habitats at the beginning of the younger dryas cold period surprisingly the small mammals living in forest habitats maintained or even further increased in numbers tardiglacial use of el miron cave coincided with several climate oscillations whose impact on hunting decisions is still debated this environmental variability during the late glacial has been indicated by different proxy records palynological geological etc throughout the cantabrian region however the exact timing and intensity of these changes is unclear due to the lack of continuous rich archaeological sequences with many radiometric determinations el miron cave sequence fills this gap in the record and this paper presents a detailed reconstruction of the development of biotopes around the site based on its micromammal assemblages it shows an interesting trend of increasing forest related species notably dormice during the pleistocene holocene transition that was preceded by a significant peak of wooded biotopes towards the end of the pleniglacial during heinrich event 1 this pattern can be correlated with the strategy of subsistence that was developed as shown by the macromammalian faunas in the search for any relationship that can shed light on the type of economy adopted by magdalenian populations in terms of their reaction to resource availability

colorado river sediment transport 1 natural sediment supply limitation and the influence of glen canyon dam analyses of flow sediment transport bed topographic and sedimentologic data suggest that before the closure of glen canyon dam in 1963 the colorado river in marble and grand canyons was annually supply limited with respect to fine sediment i e sand and finer material furthermore these analyses suggest that the predam river in glen canyon was not supply limited to the same degree and that the degree of annual supply limitation increased near the head of marble canyon the predam colorado river in grand canyon displays evidence of four effects of supply limitation 1 seasonal hysteresis in sediment concentration 2 seasonal hysteresis in sediment grain size coupled to the seasonal hysteresis in sediment concentration 3 production of inversely graded flood deposits and 4 development or modification of a lag between the time of a flood peak and the time of either maximum or minimum depending on reach geometry bed elevation analyses of sediment budgets provide additional support for the interpretation that the predam river was annually supply limited with respect to fine sediment but it was not supply limited with respect to fine sediment during all seasons in the average predam year sand would accumulate and be stored in marble canyon and upper grand canyon for 9 months of the year from july through march when flows were dominantly below 200 300 m3 s this stored sand was then eroded during april through june when flows were typically higher after closure of glen canyon dam because of the large magnitudes of the uncertainties in the sediment budget no season of substantial sand accumulation is evident because most flows in the postdam river exceed 200 300 m3 s substantial sand accumulation in the postdam river is unlikely

preliminary reassessment of the aurignacian in banat south western romania abstract despite its richness the romanian paleolithic record has remained for decades relatively poorly known to the broader scientific community the situation swiftly changed after the find at oase cave which brought the romanian paleoanthropological and archeological record into intensive focus spurring several international research projects devoted to the regional early upper paleolithic the present paper provides the first summary of recent research undertaken in the neighboring area of oase the romanian banat particularly focused on the aurignacian open air occupation at cosava a detailed attribute analysis of both old and recently excavated aurignacian collections from cosava supplemented by a comparative overview of the allegedly similar industry at rom nesti dumbr vi a is presented an initial chronological assessment of the banat aurignacian by means of several osl samples from rom nesti is also proposed the results of the lithic analysis much like the new chronological estimations in excess of 30 ka bp confirm the early assignment of the banat assemblages to the krems type aurignacian but also dismiss the unusually young chronology initially attributed to these settlements while several features including the constant presence of krems dufour tools point strongly to an archaic stage of the aurignacian technocomplex protoaurignacian aurignacian 0 other elements carinated forms twisted bladelets and aurignacian blades recall more classical features conventionally associated to the aurignacian i no coherent chrono stadial trend or functional requirements can explain these mixed features in the banat industries with the data at hand their presence nevertheless points to the internal variability of these early aurignacian occurrences

spatial and temporal dynamics of sediment accumulation and exchange along strickland river floodplains papua new guinea over decadal to centennial timescales 1 we investigated the processes of sediment exchange between the strickland river and its lowland floodplain documenting 1 the rates textures and distributions of sediment accumulation 2 temporal variations in these rates 3 the remobilization of sediment by erosive processes and 4 whether net storage is significant over century timescales we used 210pb geochronology of floodplain cores from 11 transects to measure deposition rates over the past 65 years finding a decline from 5 5 cm a 0 10 m distance from the channel to 0 9 cm a 400 m to 0 1 cm a 1 km rates are elevated along curved sections of channel and are stable over time and episodic accumulation is prevalent and may be correlated to floods integrated temporally and spatially the average rate is 1 6 cm a integrating along both sides of 318 river km we studied for the lowland strickland we calculate 12 19 mt of annual sediment accumulation 0 05 mt km or 0 07 of the annual load per km of river length representing 17 27 of the total annual sediment flux we used georeferenced landsat images 1972 2001 to quantify channel migration and the resulting return of sediment to the channel mean lateral migration was 5 1 0 8 m a given the floodplain width of 10 km this implies a waiting time of 1 ka between floodplain formation and subsequent reentrainment of the bank as the channel migrates laterally this raises the possibility that the net return of material from the floodplain due to channel migration could balance the overbank deposition we observed the exchange flux between cut bank erosion and point bar deposition is 20 40 mt highlighting the significance of sediment recycling 50 of the total load such sediment trapping and recycling affects the transport storage and evolution of biogeochemically reactive particles the evolution of the floodplain and the morphodynamics of basin infilling

210pb geochronology of flood events in large tropical river systems floodplain sedimentation removes particles from fluvial transport and constructs stratigraphic records of flooding biogeochemical sequestration and other aspects of the environmental history of ri

interactions between upland catchment and lowland rivers an applied australian case study abstract persistent allegations have been made mainly by victorian farmers that channel and floodplain aggradation are occuring on the floodplain of the snowy river in victoris as a consequence of a accelaerated erosion of degraded agricultural land in parts of the new south wales upland catchment these claims prompted the victorian department of water resources to initiate geomorphological investigations involving reviews of historical evidence including the squential aerial photographs and a study of sediment sources based on environmental tracers a qualitative approach set within a sediment budget framework was adopted for data integration a detailed quantitative analysis being precluded by financial temporal and practical constrainsts no compelling evidence was found to support claims of recent channel aggradation in the downstream snowy river transfer of sediment eroded from catchment slopes in nsw to the lowland floodplain in victoria is indirect with some sediments stored temporarily in fans and floodplains within tributary catchments and in the snowy valley for long delay times storage and interbasin transfer of water as part of the snowy mountains scheme have affected sediment delivery the catchment upstream of lake jindabyne is effectively isolated by this large impoundment and sediment transport rates as far downstream as the delegate river junction appear to have significantly decreased as the result of the considerable reduction in discharge

deposition and storage of fine grained sediment within the main channel system of the river tweed scotland thispaperassessestheimportanceofdepositionandstorageoffine grained c 150m sedimentonthefloodplainsand bedsofthemain non tidal channelsoftherivertweed 4390km 2 scotland andtwoofitstributaries riverteviotand ettrick water caesium 137 analysis of floodplain sediment cores has been used to estimate average rates of overbank sedimentation during the last 30 to 40 years average values for individual transects ranged from 016 to 218 kg m 2 a 1 013to2 2m ma 1 themeanforthe10transectsinvestigatedwas129kgm 2 a 1 1 3m ma 1 thetotalamountoffine sediment deposited was estimated to be about 44 000 t a 1 the fine grained sediment stored in the channel bed was quantifiedusingresuspensiontechniques averagevaluesforindividualsitesrangedfrom012to096kgm 2 themeanfor the10sitesinvestigatedwas056kgm 2 thetotalamountofsedimentstoredonthechannelbedofthemainchannelsystem at the time of sampling was estimated to be about 4300 t comparison of these estimates of floodplain and channel storage with the estimated suspended sediment loadfor the river tweed at the downstream gauging site atnorham indicates that floodplainsedimentationandchannelbedstoragerepresentabout40and4percent respectively oftheannualloadoffine sedimentdeliveredtothemainchannelsystem erosionofchannelbankswillreintroducetheequivalentofabout30percent of the floodplain deposited sediment back into the channel the residence time of the fine grained sediment stored on the channel bed is probably less than one year but that of sediment deposited on the floodplain is likely to be considerably longer conveyance losses associated with overbank deposition have important implications for the routing of sediment throughfluvialsystemsandtheinterpretationofdownstreamsedimentyields copyright 1999johnwiley sons ltd

small mammal taphonomy of gran dolina atapuerca burgos spain abstract the middle pleistocene sequence at the atapuerca burgos complex of caves is most completely represented at gran dolina eleven stratigraphic units are distinguished seven of which contain abundant small mammal fossils these seven units are analysed in order to determine the taphonomic processes present during the accumulation of their faunal remains the fossil bones are extensively broken both before and after burial fossils from six of the units show evidence of localized pre depositional acid corrosion which occurred both before and after breakage in the upper levels there is also evidence of post depositional corrosion both from alkaline and from acid environments of deposition and in the top level some fossil bones also show evidence of weathering and root marks images of these modifications by means of the scanning electron microscope and their comparison with a large comparative data base of recent modifications from known causal agents permits the identification of the agents responsible for many of the modifications and consequently the reconstruction of the sequence of events leading to the accumulation and preservation of the fossil assemblages predators are implicated for some of the breakage and all of the pre depositional corrosion which is the result of digestion in the predators stomachs in all cases the category of predator can be identified and at three stratigraphic levels the actual species can be identified with moderate degrees of reliability post depositional corrosion is linked with observations on local acidity alkalinity of different levels and the incidence of weathering is linked with evidence for roof collapse over parts of the cave taking account of the effects of these processes particularly the selectivity resulting from predator hunting methods allows estimates to be made of the degree of bias in the faunal composition and the palaeoecology thereby indicated

european impacts on downstream sediment transfer and bank erosion in cobargo catchment new south wales australia abstract upland valley fills in cobargo catchment on the south coast of new south wales represent substantial sediment source zones contemporary channels within these fills are up to 8 m deep and 50 m wide for catchment areas 2 virtually all banks are eroding downstream of this sediment source zone sediment transfer zones are characterised by sinuous channels that are partially choked by sands released from upland valley fills coarse sands stored in point bars deflect flow to outer banks where colluvial footslopes are eroded approximately 50 of banks are eroding in this section of the catchment other than the 10 km river reach upstream of the river mouth the remainder of the catchment is a bedrock confined sediment throughput zone characterised by fluctuations in channel bed elevation the downstream 10 km of the catchment is a sediment accumulation zone in which erosion is restricted to occasional concave banks prior to european settlement of cobargo catchment upland valley fills were largely unincised and middle transfer reaches of the catchment comprised swamps vegetation clearance along with disturbance and drainage of swamps transformed discontinuous water courses into continuous channels working from a base point of intact upland valley fills almost 50 of available material has been removed from the upper catchment sediment source zone contributing 2 9 10 6 m 3 of material to the lower catchment of this roughly 65 has been stored along the channel bed and floodplain this gives a total sediment contribution to the delta of 1 0 10 6 m 3 sufficient materials are stored in transient storage units along transfer zones to maintain current rates of sediment throughput to the delta for several decades cobargo catchment experienced dramatic acceleration of channel incision and bank erosion processes within a few decades following european settlement of the catchment i e around 1830 transition in landscape form and associated sediment delivery were rapid with a negligible lag interval i e within a few decades of disturbance however given the extensive volume of sediment released from upland valley fills landscape recovery i e refilling of upland valleys will likely take thousands of years

use of fallout pb 210 measurements to investigate longer term rates and patterns of overbank sediment deposition on the floodplains of lowland rivers the potential for using fallout unsupported pb 210 210pb measurements to estimate rates of overbank sediment deposition on the floodplains of lowland rivers is explored a model which distinguishes the contribution from direct atmospheric fallout and the catchment derived input associated with the deposition of suspended sediment has been developed to interpret the fallout pb 210 inventories at floodplain sampling sites and to estimate average sediment accumulation rates over the past 100 years the approach has been successfully used to estimate rates of overbank sedimentation on the floodplains of the rivers culm and exe in devon u k a detailed investigation of the pattern of longer term sedimentation rates within a small reach of the floodplain of the river culm indicated a range of deposition rates between 0 07 and 0 59 g cm 2 a 1 which was in close agreement with estimates of current sedimentation rates obtained using sedimentation traps

floodplain development in an engineered setting engineered flood bypasses or simplified conveyance floodplains are natural laboratories in which to observe floodplain development and therefore present an opportunity to assess delivery to and sedimentation within a specific class of floodplain the effects of floods in the sacramento river basin were investigated by analyzing hydrograph characteristics estimating event based sediment discharges and reach erosion deposition through its bypass system and observing sedimentation patterns with field data sediment routing for a large iconic flood suggests high rates of sedimentation in major bypasses which is corroborated by data for one bypass area from sedimentation pads floodplain cores and sediment removal reporting from a government agency these indicate a consistent spatial pattern of high sediment accumulation both upstream and downstream of lateral flow diversions and negligible sedimentation in a hydraulic shadow directly downstream of a diversion weir the pads located downstream of the shadow recorded several centimeters of deposition during a moderate flood in 2006 increasing downstream to a peak of 10 cm thick and thinning rapidly thereafter flood deposits in the sediment cores agree with this spatial pattern containing discrete sedimentation layers from preceding floods that increase in thickness with distance downstream of the bypass entrance to several decimeters thick at the peak and then thin downstream these patterns suggest that a quasi natural physical process of levee construction by advective overbank transport and deposition of sediment is operating the results improve understanding of the evolution of bypass flood control structures the transport and deposition of sediment within these environments and the evolution of one class of natural levee systems copyright 2008 john wiley sons ltd

first chronometric dates tl and osl for the aurignacian open air site of românesti dumbrăviţa i romania abstract currently absolute dates for the emergence of the early upper paleolithic and the timing of the earliest dispersal of anatomically modern humans amh into europe are sparse this is especially true for regions adjoining the eastern mediterranean and central europe with its dense clusters of sites along the austrian and german danube valley this article makes a first step toward filling this gap and for the first time presents absolute ages for the open air site of rom nesti dumbr vi a i banat sw romania located close to the oase cave where some of the oldest amh fossils were found a set of heated artefacts recently excavated from the aurignacian layer gh3 was dated by thermoluminescence tl and gives early chronometric dates for this technocomplex in romania the luminescence behavior of artefact samples required the use of different multiple and single aliquot measurement protocols to obtain reliable age information in addition analyses of glow curves and the performance during regenerative dose measurements allowed us to distinguish two types of samples since one group is characterized by poor dose reproducibility only samples showing reliable luminescence behavior were considered for final age interpretations as a result we could determine that the last heating of artefacts from gh3 happened most likely between 39 ka single aliquot age estimate and 45 ka multiple aliquot age estimate ago with a weighted average age of the gh3 finds of 40 6 1 5 ka including all data these dates were confirmed by osl dating of sediments of the find layer such an early age fits well to technological and typological features which place the dated lithic assemblage at the very beginning of the development of the aurignacian technocomplex usually seen as a proxy for the earliest wide spread presence of amh in europe

episodic sediment accumulation on amazonian flood plains influenced by el nino southern oscillation continental scale rivers with a sandy bed sequester a significant proportion of their sediment load in flood plains the spatial extent and depths of such deposits have been described and flood plain accumulation has been determined at decadal timescales but it has not been possible to identify discrete events or to resolve deposition on near annual timescales here we analyse 210 pb activity profiles from sediment cores taken in the pristine beni and mamore river basins which together comprise 720 000 km2 of the amazon basin to investigate sediment accumulation patterns in the andean amazonian foreland we find that in most locations sediment stratigraphy is dominated by discrete packages of sediments of uniform age which are typically 20 80 cm thick with system wide recurrence intervals of about 8 yr indicating relatively rare episodic deposition events ocean temperature and stream flow records link these episodic events to rapidly rising floods associated with la nina events which debouch extraordinary volumes of sediments from the andes we conclude that transient processes driven by the el nino southern oscillation cycle control the formation of the bolivian flood plains and modulate downstream delivery of sediments as well as associated carbon nutrients and pollutants to the amazon main stem

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion

new chronological constraints for middle palaeolithic mis 6 5 3 cave sequences in eastern transylvania romania abstract the middle to upper palaeolithic transition is one of the crucial periods of change in the prehistory of europe due to the full emergence continent wide of modern human lithic technologies and detrimental of neanderthal survival knowledge about the transition is growing however the evidence for cultural and technological developments for the middle palaeolithic in the carpathian lower danube basin is still rather sparse here we discuss latest findings arising from a chronological investigation of middle palaeolithic assemblages within the varghis karst eastern transylvania romania combining our first chronological results with information from previous excavations we can distinguish two main stages of habitation albeit middle palaeolithic lithics and faunal remains appear scattered throughout the investigated profile within the abri 122 rock shelter in order to augment the typological cultural considerations we applied direct radiocarbon dating on bones and charcoal from within the occupation layers radiocarbon dating of bones suggests that the middle palaeolithic sequence is older than the upper dating limit of the method whereas direct luminescence ages on the lowermost productive horizon and immediately above it indicate surprisingly old ages of ca 106 141 ka osl optically stimulated or 99 174 ka irsl infrared stimulated multiple protocol dating of charcoal found within the two habitation layers produced ages 38 14 c ka bp also suggesting that the lowermost lithic rich horizon pertains to the middle palaeolithic industries overall the recovered lithics currently forming one of the most significant collections for romania are fully consistent with two main habitation phases connected to middle palaeolithic cultural affinities the occurrence of a volcanic ash layer within ursului cave and originating from the ciomadul volcanic complex carpathians is first reported here recently dated to 43 50 ka it might represent an important marker horizon providing that it is identified within other palaeolithic cave assemblages