sediment budget analysis of slope channel coupling and in channel sediment storage in an upland catchment southeastern australia abstract slope channel coupling and in channel sediment storage can be important factors that influence sediment delivery through catchments sediment budgets offer an appropriate means to assess the role of these factors by quantifying the various components in the catchment sediment transfer system in this study a fine

sediment budgeting a case study in the katiorin drainage basin kenya the primary objective of this study was to compute a detailed budget for a small semiarid tropical drainage basin in kenya results indicated that transfer of sediments inputs from primary source areas was minor in comparison to changes in storage the major sediment source area within the katiorin drainage basin was the colluvial hillslope zone the net change in storage within this zone was approximately 2100 mg yr 1 surface wash and rilling were the dominant transport processes responsible for the remobilization of colluvial sediments sediment storage within the in channel reservoir increased by 60 mg yr 1 which was minor when compared to the total store of sediment in this reservoir during 1986 the channel network stored only a small fraction 3 per cent of the sediment delivered from the hillslope subsystem therefore the in channel reservoir had limited influence on sediment conveyance to the basin outlet these data indicate that a static equilibrium condition cannot be assumed within the katiorin drainage basin such an assumption would result in erosion estimates of approximately 5 5 mm yr 1 for the entire basin based on a sediment output of 7430 mg km 2 yr 1 and a measured bulk density of 1 35 mg m 3 however this masked the actual rates of 1 2 to 7 1 mm yr 1 in subbasin primary source areas and rates of 0 6 to 17 mm yr 1 for colluvial material in the various subbasins the extreme accelerated erosion rates resulted from minimal ground vegetation steep slopes soil crust formation an erodible substrate and a well integrated drainage network for rapid conveyance of sediments from the hillslope subsystem to the basin outlet

channel erosion along the carmel river monterey county california historic maps photographs and channel cross sections show that the channel of the carmel river underwent massive bank erosion channel migration and aggradation in a major flood in 1911 then narrowed and incised by 1939 the channel was stable until 1978 and 1980 when bank erosion affected some reaches but not others the narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation these events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event the 1911 flood or in a low magnitude event by reducing the resistance to erosion bank devegetation the carmel river is a potentially unstable system its discharge and slope characteristics place it near the threshold between meandering and braided on the lower carmel the presence of bank vegetation can make the difference between a narrow stable meandering channel and a wide shifting channel with braided reaches

climatic controls on holocene lake level changes in europe sensitivity experiments with a simple water balance model were used to constrain the possible climatic causes of distinct holocene patterns of lake level variation in different regions of europe lakes in s sweden were low at 9 ka high around 6 5 ka low again around 4 ka and are high now lakes in estonia show similar but weaker trends lakes in s france were highest around 9 ka lowest around 4 ka intermediate now lakes in greece were also high around 9 ka but continued rising until 7 5 ka then fell gradually from 5 ka with a brief high phase around 3 ka and are low now the model was forced with insolation anomalies deduced from orbital variations temperature anomalies inferred from the pollen record and cloudiness anomalies derived from changes in the position of the subtropical anticyclone inferred from reconstructed changes in the equator to pole temperature gradient in order to evaluate the effects of resultant evaporation changes on catchment water balance the resulting simulated changes in runoff precipitation minus actual evapotranspiration were slight and frequently opposite to the observed trends larger changes in precipitation are plausible and are required to explain the data the required precipitation increase in n europe from 9 ka low to 6 ka high is suggested by gcm experiments to have been a consequence of interacting insolation and residual ice sheet effects on the atmospheric circulation over the north atlantic the explanation of other observed changes including the drying trend during the holocene in s europe has not been provided by gcm experiments to date explanations may lie in changes in mesoscale circulation sea surface temperature patterns and the coupling between these phenomena that may not follow orbital changes in any simple way

changing sediment dynamics due to natural reforestation in the dragonja catchment sw slovenia abstract article history received 18 march 2008received in revised form 20 february 2009accepted 23 february 2009keywords dragonjasloveniahillslope erosionland use changenatural reforestationwatem sedem under the in uence of socio economic changes in many regions in europe a trend of decreasing agriculturalactivity has been observed since the second world war the resulting reforestation profoundly changeswater and sediment supply to river channels deposition rates on the oodplains and erosion rates on thehillslopes we studied these changes in the 91 km 2 dragonja catchment in southwestern slovenia with the spatially distributed erosion and sediment delivery model watem sedem the hillslope sedimentdelivery to the river channel was calculated on the basis of parameters soil and precipitation parameters adem and land use measured in the eld and laboratory in 2002 and land use maps based on aerialphotographs from 1954 1975 1985 and 1994 for two independent calibrations watem sedem modelled asharp decline of 69 in total hillslope sediment delivery from 1954 to 2002 as the sub catchments rokava and upper dragonja did not reforest in the same way the sediment yieldresponse is different as well separate calculations show the same reduction 45 in sediment yield from1954 to 1975 after 1975 the sediment yield was stable in the rokava sub catchment in the upper dragonjathe trend continued to a total reduction of 76 of sediment out ow since 1954 the sources of ne sediment were determined by analysing the hysteresis of the discharge waves and thesuspended sediment texture the sediment that leaves the catchment originates from three sources hillslopes erosional bedrock banks and sedimentary riverbanks the analysis of the suspended sediment texture suggests that during a discharge wave the suspendedsediment originates predominantly from the hillslopes during low stage the sparse sediment in the watercolumn largely originates from large bedrock banks the sedimentary riverbanks are not an important sourceof suspended sediment 2009 elsevier b v all rights reserved

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

effects of check dams on bed load transport and steep slope stream morphodynamics abstract check dams are transversal structures built across morphologically active streams in mountainous regions these structures have been used widely in torrent hazard mitigation for over 150 years thousands of them are regularly maintained by stream managers and torrent control services the stabilization role of these structures is well known i e they durably constrain the stream bed through the creation of vertical and planar fixed points what is not yet clear is to what extent check dams influence bed load transport how do peak solid discharge or flood transported volume change when check dams are added to a reach to address these questions long lasting small scale experiments were conducted in a 4 8 m long flume with either one three or no structures the results show that the addition of structures creates independent compartments in the bed level which have a strong influence on bed surface armouring and stream morphodynamics the consequence is that instantaneous transport intensities are unchanged but peak solid discharge occur more often and for shorter duration this results in the same total transported volume over the long term but reduced volume for a single transport event it reaffirms the observation of pioneering authors of the mid 19th and early 20th century who conceptualized the possible sediment transport regulation function of check dams in addition to stabilizing the stream bed check dams influence bed load transport through a buffering effect releasing frequently and in small doses what in their absence would be transported abruptly en masse during rare extreme events

insights into river bank erosion processes derived from analysis of negative erosion pin recordings observations from three recent uk studies recent studies of river bank erosion in three catchments in the uk have been characterized by the persistent occurrence of negative erosion pin results the cause of these negative recordings is considered with reference to field data from the afon trannon nant tanllwyth and river arrow and to a laboratory study of freeze thaw and desiccation processes it seems that there is potential for and in some cases evidence of a number of different circumstances that generate negative results but none of these alone is sufficient to explain all incidents factors considered include deposition of sediment during high flows soil fall from the upper parts of the bank on to lower erosion pins loosening of the soil surface and expansion contraction of the soil mass with fluctuations in temperature and moisture content movement of the erosion pin within the bank and human interference each has its own implications for the use of erosion pins further issues arise when including negative data in subsequent data analysis and it is demonstrated that attempts to correlate erosion rates with hydro meteorological data in order to ascertain causes of erosion will be influenced by the way in which negative data are handled it is thus suggested that any study of river bank erosion using erosion pins should state whether or not negative data were obtained and if so how they were included in data analysis failure to include this information could lead to comparison of mean erosion rates that reflect bank processes very differently the studies presented here offer a clear example of the value of anomalous field data results which do not appear to fit expected patterns can reveal as much about the processes in operation as those that do

climate change and the episodicity of sediment flux of small california rivers abstract we studied the streamflow and sediment flux characteristics of the 20 largest streams entering the pacific ocean along the central and southern california coast extending for 750 km from monterey bay to just south of the u s mexico border drainage basins ranged in area from 120 to 10 800 km2 with headwater elevations ranging from 460 to 3770 m annual streamflow ranged from 0 to a maximum of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape 1 times 10 9 end document m3 yr for the santa clara river in 1969 with a

fluvial sediment budgets in the north carolina piedmont phillips j d 1991 fluvial sediment budgets in the north carolina piedmont geomorphology 4 231 241 sediment budgets for four large 1000 km 2 drainage basins in the piedmont physiographic province of north carolina were estimated from data compiled during erosion and sedimentation surveys budgets for the upper tar upper neuse haw and deep river basins showed broadly similar trends in allocation of eroded sediment among yield and storage sediment yield as a percentage of mean annual gross erosion within the basins averaged 10 this was less than the rate of alluvial storage which averaged 14 of annual gross erosion about 76 of the mean annual erosion was stored as colluvium on hillslopes there are relatively small differences in sediment delivery and storage ratios among the study basins this suggests that the relative order of magnitude of the allocation of eroded sediment for southern piedmont rivers is colluvial storage alluvial storage and yield of the sediment that does reach the streams more than half is stored as alluvium on an average annual basis aggrading channels and floodplains siltation of benthic habitats and sediment pollution problems are thus likely to persist unless dramatic reductions in upland erosion or in sediment delivery to streams are realized with respect to longer term basin evolution results point to the need for an improved understanding of the temporal scales of colluvial and alluvial sediment storage

the geomorphic evolution and sediment balance of the lower rhone river southern france over the last 130 years hydropower dams versus other control factors article i nfo atthe end of thelittleice age lia agriculturalpractices and successive phasesof channel management involv ing embankments and dams however the respective roles of these various control factors in modifying sedi ment storage and channel stability are often difficult to identify the aim of this paper is to determine the main factors that have driven morphological changes over the past 130 years on the 120 km long downstream reach of the rhone river a gis based analysis of maps and aerial photographs available since 1860 coupled with chrono stratigraphic data on the river s alluvial deposits has enabled quantification of sediment storage and erosion in different morphological units changes measured include riverbed incision narrowing of the main channel in relation with accumulation of fine sediments along the channel margins and reduction of sed iment input at the mouth on the basis of local and reach scale sediment balances we show that these changes are synchronous with engineering works carried out at the end of the nineteenth century and beginning of the twentieth century a period that coincided with a decline in river sediment inputs largely generated by human activities the early stabilisation of mountain slopesresulting from a decline inrural agriculture rural exodus re forestation and engineered torrent control has had a much greater impact in geomorphically transforming the rhone than dams and gravel mining the major identified causes of river destabilisation in the world this calls for caution in the all too common and wholesale attribution of declining sediment budgets of european rivers

stabilizing self organized structures in gravel bed stream channels field and experimental observations stable reticulate structures which we call stone cells have been observed in cobble gravel channel beds with low bed material transport rates experiments show that such structures develop simultaneously with the armor layer during an extended period when flows do not exceed the shields threshold by more than 2 times so that bed material transport is low they are constructed by particles moving from less stable positions into more stable configurations against each other intermediate developments include clusters and stone lines they reduce sediment transport by orders of magnitude and are evidently a major stability promoting mechanism in gravel channels the timescale for their development suggests that the boundaries of many gravel bed channels are not in equilibrium with recent competent flows but reflect the history of recent dominant flows

geomorphic coupling and sediment connectivity in an alpine catchment exploring sediment cascades using graph theory through their relevance for sediment budgets and the sensitivity of geomorphic systems geomorphic coupling and sediment connectivity represent important topics in geomorphology since the introduction of the systems perspective to physical geography by chorley and kennedy 1971 a catchment has been perceived as consisting of landscape elements e g landforms subcatchments that are coupled by geomorphic processes through sediment transport in this study we present a novel application of mathematical graph theory to explore the network structure of coarse sediment pathways in a central alpine catchment numerical simulation models for rockfall debris flows and hillslope and channel fluvial processes are used to establish a spatially explicit graph model of sediment sources pathways and sinks the raster cells of a digital elevation model form the nodes of this graph and simulated sediment trajectories represent the corresponding edges model results are validated by visual comparison with the field situation and aerial photos the interaction of sediment pathways i e where the deposits of a geomorphic process form the sources of another process forms sediment cascades represented by paths a succession of edges in the graph model we show how this graph can be used to explore upslope contributing area and downslope source to sink functional connectivity by analysing its nodes edges and paths the analysis of the spatial distribution composition and frequency of sediment cascades yields information on the relative importance of geomorphic processes and their interaction however regardless of their transport capacity in the study area the analysis stresses the importance of mass movements and their interaction e g the linkage of large rockfall source areas to debris flows that potentially enter the channel network moreover it is shown that only a small percentage of the study area is coupled to the channel network which itself is longitudinally disconnected by natural and anthropogenic barriers besides the case study we discuss the methodological framework and alternatives for node and edge representations of graph models in geomorphology we conclude that graph theory provides an excellent methodological framework for the analysis of geomorphic systems especially for the exploration of quantitative approaches towards sediment connectivity

production storage and output of coarse upland sediments natural and artificial influences as revealed by research catchment studies rates of sediment production in uk river basins are generally low however upland source areas control both runoff and sediment volumes to he routed through larger basins and there are indications that development pressures on land in upland areas have far reaching implications output rates for bedload from semi natural grassland and commercially afforested catchments are now available for a ten year period at the plynlimon catchments mid wales the influence of forestry drainage practice is to increase bedload yields sixfold suspended load yields are doubled in an attempt to predict yields and to investigate the operation of storage and transport processes on bedload a regression analysis was conducted using the weight of bedload trapped as a dependent variable and selected climatic supply and transport factors as independent variables the climatic supply factors chosen are shown to have little influence on yield relative to transport factors despite evidence of supply limited yields tracer studies indicate that channel storage of material exercises a critical control on yield a factor which is not accommodated by the climate based supply indices implications for field measurement techniques are discussed

orbital imprint on holocene palaeohydrological variations in west central europe as reflected by lake level changes at cerin jura mountains eastern france this paper presents a lake level record for the holocene at lake cerin jura mountains eastern france it is based on a range of sedimentological techniques validated in previous studies with a combination of systematic lithostratigraphic investigations of the infillings accumulated in the lacustrine basin and sediment analyses of two selected cores the chronology is based on 10 radiocarbon dates and pollen stratigraphy on a millennial scale the cerin lake level record shows three distinct successive phases characterised by higher lake level conditions until ca 9000 cal a bp followed by a maximal lowering at ca 9000 8500 cal a bp and a progressive rise until the present this rise was punctuated by centennial scale fluctuations with major events around 4000 2800 and after 1500 cal a bp considered on a multimillennial scale the general pattern of palaeohydrological changes reconstructed at cerin reflects the impact of orbitally driven summer insolation this is in agreement with other regional and extra regional palaeoclimatic records although every record shows peculiarities in timing and shape depending on the proxy used for reconstruction in this general context centennial to multicentennial oscillations appear to have been second order events in comparison with the major influence of the orbital factor copyright 2011 john wiley sons ltd

climate and related controls on interglacial fluvial sedimentation in lowland britain lewin john gibbard p l 2002 climate and related controls on interglacial fluvial sedimentation in lowland britain sedimentary geology 151 3 4 pp 187 210 rae2008

lake level and groundwater level changes in the lake gosciąz area poland palaeoclimatic implications lake gosci z is located in the zone of the maximum extent of the last ice sheet distinct lake terraces and deposits related to the lateglacial transgression do not exist detailed examination of annually laminated sediments and landforms revealed three phases of higher water level and storage represented by shore features by littoral deltaic and bog deposits and by higher rates of lacustrine deposition in the pelagic zone holocene lake transgressions at c 8 4 7 7 ka 2 5 2 3 ka and less distinct at 5 4 ka bp coincide with phases of higher flood frequency in poland and glacial advances in the alps because of sedimentation isolation from groundwaters encroachment by peatland and drainage of the lake lake volume during the last 12 ka diminished by as much as 70 and current water level fluctuations of about 1 2 m can change water storage by 20 25

equal mobility bed load transport in a small step pool channel in the ouachita mountains equal mobility transport emt of bed load is more evident than size selective transport during near bankfull flow events in a small step pool channel in the ouachita mountains of central arkansas bed load transport modes were studied by simulating five separate runoff events with peak discharges between 0 25 and 1 34 m3 s 1 0 to 1 6 year recurrence intervals in a natural channel using controlled releases from a storage tank emt occurrence was investigated using four different bed load relationships suggested by previous research with each of these approaches the relationship of a given bed load characteristic dmax distribution percentile displacement distance and skewness to some independent factor c and grain size was assessed to determine which transport mode was evident regression models derived using combinations of these four relationships with different datasets provide seven separate tests five of the seven tests indicate that emt occurred or was predominant several reasons may explain the apparent contradictory results but the confounding effects of changes in the structural arrangements of bed material prior to or during the events seem particularly important

recent channel adjustments in alluvial rivers of tuscany central italy drastic channel adjustments have affected the main alluvial rivers of tuscany central italy during the 20th century bed level adjustments were identified both by comparing available topographic longitudinal profiles of different years and through field observations changes in channel width were investigated by comparing available aerial photographs 1954 and 1993 98 bed incision represents the dominant type of vertical adjustment and is generalized along all the fluvial systems investigated the arno river system is the most affected by bed level lowering up to 9 m whereas lower incision generally less than 2 m is observed along the rivers of the southern part of the region human disturbances appear to be the dominant factors of adjustments the main phase of vertical change occurred during the period 1945 80 in concomitance with the phase of maximum sediment mining activity at the regional scale the second dominant type of adjustment that involved most of the rivers in the region consists of a narrowing of the active channel based on measurements of channel width conducted on aerial photographs 38 of the reaches analysed experienced a narrowing greater than 50 of the initial channel width the largest values of channel narrowing were observed along initially braided or sinuous with alternate bars morphologies in the southern portion of the region a regional scheme of channel adjustments is derived based on initial channel morphology and on the amounts of incision and narrowing different styles of channel adjustments are described rivers that were originally sinuous with alternate bars to braided generally became adjusted by a moderate incision and a moderate to intense narrowing in contrast sinuous meandering channels mainly adjusted vertically with a minor amount of narrowing copyright 2003 john wiley sons ltd

runoff and erosion processes after a forest fire in mount carmel a mediterranean area in the mediterranean forest area of israel fires increase runoff and sediment yield rates relative to undisturbed forested land the september 1989 fire covered an area of 4 km2 in the main recreation area of mount carmel a typical mediterranean forest area the lithology is chalk and limestone and about 40 of the burnt area has steep slopes exceeding 30 three study plots were established in burnt and unburnt areas plots were located on 100 300 m2 areas with different slope exposures runoff and sediments were collected after each storm by a collector system a hydrometric station was established draining an area of 1 km2 in the burnt zone rainfall was measured by two recorders and several rain gauges at the experimental sites in the first rainfall season after the fire runoff and sediment yield were 500 and 100 000 times higher respectively in the burnt areas rainfall intensity is a dominant factor in runoff and sediment yield rates in the measured basin total runoff in the first year was 1 6 revegetation recovery of the area was rapid as shown by the results from the second season runoff decreased by one order of magnitude from an average of 10 mm to 1 5 mm sediment yield decreased by two orders of magnitude from 1200 g m 2 to 10 g m 2 the third season 1991 1992 was an exceptionally rainy year and therefore runoff and sediment yield increased but to less than in the first year runoff and sediment yield are related to vegetation cover rainfall intensity soil properties slope steepness and exposure and fire intensity logging activities after fire increase sediment yields through its effects on vegetation cover and soil fire severity increases the potential for erosion

channel changes due to river regulation the case of the piave river italy this paper deals with the channel changes of the piave river in the eastern alps italy which have occurred during this century in response to human interventions in the fluvial system the flow regime and the sediment supply of the river have been considerably altered by hydroelectric dams flow diversions and gravel mining in addition river dynamics have been affected by the construction of streambank protection structures to document these changes a historical analysis was performed using maps and aerial photographs morphological features that were examined included planform configuration channel width braiding index and bed elevation the results indicate that as a consequence of decreases in the flows and sediment supply remarkable channel changes have occurred in the river during this century especially during recent decades the channel has undergone a general narrowing with a decrease in average width to 35 per cent of its initial value while the braiding index has decreased from about 3 to 1 5 in several reaches the planform pattern has changed from braided to wandering the observed trends of channel change suggest that the river has not yet reached a new equilibrium condition and it may therefore be predicted that reductions in width and braiding intensity are likely to continue in the immediate future copyright 1999 john wiley sons ltd

environmental changes at the younger dryas preboreal transition and during the early holocene some distinctive aspects in central europe data on environmental change at the younger dryas preboreal transition and during the early holocene are reviewed with particular reference to evidence from poland and neighbouring areas of central europe various factors modified the rate of environmental change during the general warming and reforestation the preservation in central europe of coniferous forest at the beginning of the holocene and the relatively late development of deciduous forest were connected with the continuation of a continental climate until 9000 8500 bp this is the main cause for a distinct division of the early holocene into three phases 1 10 300 9500 bp rapid warming 2 preboreal boreal continuous transformation 10 000 8500 bp 3 change to oceanic climate 8700 7700 bp during the eoholocene period the various environmental systems such as biological aeolian fluvial and lacustrine exhibited diachronous evolution with different rates of change the distinctive changes in central europe are contrasted with other re

quantitative determination of the activity of within reach sediment storage in a small gravel bed river using transit time and response time abstract reach scale sediment storage is rarely quantified in sediment budget studies yet it has a considerable effect on the sediment delivery ratio at the basin scale and on the accuracy of morphological methods of bedload estimation at the reach scale deployment of magnetic tracer particles allows accurate characterisation of sediment fluxes in gravel bed rivers and provides the opportunity to quantify storage activity using reservoir theory activity was quantified at reach and sub reach scales in two reaches of a small gravel bed river and the possibility of quantifying the activity of smaller scale sediment stores is explored reach scale transit time functions were derived from the cumulative output of sediment against age or time the shape of the functions in both reaches was determined by flood incidence and magnitude hydraulics sediment tracer availability grain size and local morphology accurate transit time functions were difficult to determine due to reliance upon tracer output and the associated problems of tracer exhaustion over time and imperfect tracer recovery rates in addition if tracers of different ages are allowed to mix for example where upstream input is possible then the resultant transit time distributions age are not comparable with the timing of the hydraulic processes responsible unless the hydraulic conditions are constant these results suggest that transit time is difficult to determine from tracer studies in gravel bed rivers consequently a refinement of transit time the response time is introduced and is defined as the time after the initial input of tracer sediment when cumulative tracer output exceeds the amount of tracer sediment remaining in storage whilst still based upon tracer output the calculation of response time also utilises storage data and is expressed relative to time since the start of the study rather than age it is therefore directly comparable with the incidence of hydraulic conditions this provides a more informative measure of activity which is readily available from tracer data in gravel bed rivers and allows evaluation of the importance of flood incidence and magnitude grain size morphology and reach characteristics stability like transit time response time estimates are hindered by mixing of sediment of different ages at the sub reach scale however it does account for errors from less than 100 recovery and tracer exhaustion more effectively than transit time quantification of absolute and relative size effects in transport is also possible from response time

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

analysis of controls on downstream fining along three gravel bed rivers in the band e golestan drainage basin ne iran abstract in many gravel bed rivers grain size changes exponentially downstream and is mainly related to selective deposition of clasts on the streambed according to size shape and density and abrasion crushing grinding splitting chipping cracking and sandblasting during transport most studies on the cause of downstream fining in rivers emphasize hydraulic sorting or selective transport as the dominant fining mechanism the band e golestan drainage basin with a surface area of about 320 km 2 is located southwest of mashhad in northeast iran this catchment s area consists of three subbasins mayan dehbar and jaghargh that flow toward northeast connecting to the kashafrud river grain size variation and causes for downstream fining were studied at 57 sites compositionally gravels in the study area consist of phyllite slate and a small amount of quartzite consequently these sediments are poorly sorted positively skewed and mainly platykurtic upstream most of the boulders are phyllites while in the downstream part slate makes up the framework of the gravel grain size distributions are weakly bimodality in the upstream and become strongly polymodal downstream based on our study the main factors in downstream fining of grain size in the study area are hydraulic sorting and abrasion

sediment residence time and connectivity in non equilibrium and transient geomorphic systems abstract growing empirical evidence shows that many geomorphic systems are in transient state or out of equilibrium with respect to the external driving forces the transient state is often related to the dis connectivity of the many constituent parts of geomorphic systems as a result of sediment storage along the sediment flow path from its source to the final sink the response time of geomorphic systems to external changes is thus dependent on the residence time of sediment in various storage compartments here i present a mathematical concept based on reservoir theory to model residence time of sediment using millennial scale sediment budgets the framework sheds light on the limitation of the sediment delivery ratio which is often used as a measure of sediment connectivity in geomorphic systems and provides analytical information on process type pace of sediment flux and connectivity of storage compartments along the sediment cascade the application of the reservoir theory to geomorphic systems under agricultural land use shows that sediment delivery ratios are linked to the virtual velocity of the eroded sediment the time since the onset of agricultural land use and the size of the studied basins with respect to the temporal evolution of sediment storages that temporarily remove sediment from the conveyor belt the framework aims to estimate the sediment residence time in storages which is linked to the effective time scale of disconnectivity reanalysis of a long term empirical sediment budget from central europe reveals that the response to agricultural land use which started 5000 years bp is mainly buffered by the long residence time of sediment on hillslopes in the order of 10 3 years which results in a delayed floodplain aggradation furthermore the framework was applied to paraglacial mountain systems that inherit striking evidences of pleistocene glacial erosion and still recover from the change from glacial to interglacial conditions as a consequence of the reduced lateral and longitudinal connectivity i show that paraglacial response times of sediment flux in mountain headwater in the canadian rocky mountains range in the order of 100 400 ka the results indicate that response times at the transition from glacial to interglacial conditions are much longer than the return interval of the major glaciations causing a transient behavior of mountain headwater basins during interglacial periods the presented reanalysis of millennial scale sediment budgets of agricultural and mountain geosystems provides an integrative framework to link paleo environmental reconstructions and the connectivity of transient geomorphic system to external changes

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

downstream variation in grain size along an alpine river analysis of controls and processes downstream variation in bed material size was studied along a 115 km reach of the piave river eastern alps italy this river drains a region producing high sediment yields and has a braided pattern along half of its length during the last century the river system has been affected by several human impacts hydroelectric dams diversions gravel mining which have strongly altered flow regime and sediment dynamics the aim of the study is to analyse the changes of bed material size in the downstream direction and to explain these changes in the light of both natural and anthropogenic factors surface material was sampled at 35 sites using the grid by number method the collected data give a detailed picture of the downstream variation in sediment size which is characterised by a complex pattern rather than by a simple decreasing trend an explanation of this variation was found through identification of discontinuities significant steps in the downstream trend and factors which can determine changes in sediment texture both natural lateral sediment sources and anthropogenic factors e g barrages are significant in this river system and they provide an explanation for most of the observed discontinuities seven out of eight discontinuities few tributaries disrupt downstream fining while as expected the barrages produce important changes in sediment texture fining processes were investigated in the lower part of the study reach where the lateral sediment sources and the barrages have minor effects on the bed material exponential models provide acceptable explanations of the downstream variations and give fining coefficients equal to 0 027 and 0 028 km 1 respectively for d50 and d84 evidence suggests that both abrasion and sorting are important in determining the downstream fining observed but it is likely that sorting is the dominant process

causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern france extensive channel narrowing in southeastern france provides an illustration of geomorphic response to land use changes the study region comprises a range of environments from large piedmont and intramountain gravel bed rivers to small mountain streams field measurements and analysis of historical data demonstrate two distinct periods of channel change from 1850 to 1950 channel narrowing is interpreted to be the result of a recovery process in response to widespread channel destabilization induced by major floods during the second half of the 19th century at the time the largely deforested basins were highly responsive to flooding whereas the recovery process was accelerated by floodplain and basin scale land use changes afforestation and torrential control works which in turn reduced sediment delivery and enabled vegetation development in channels from 1950 to 1970 channel narrowing accelerated in most of the studied rivers this recent phenomenon is considered as a human induced fluvial adjustment directly related to forest development on river margins and human abandonment of intensive floodplain land uses at the same time long profile degradation occurred as a result of long term bedload supply decrease in small mountain streams channel narrowing is mainly explained by channel incision which seems to progress from upstream where sediment sources are progressively stabilized by afforestation copyright 2002 john wiley sons ltd

suspended sediment exchange through the sub tropical richmond river estuary australia a balance approach major sources of suspended sediments and their exchanges with the continental shelf for the richmond river estuary were investigated during two hydrological years of the major sources of suspended sediment inputs into the richmond river estuary fluvial input from the upper catchment area was about 92 99 of the total yearly balance and more than 90 of this fluvial sediment was transported into the estuary during less than 5 time of the year the richmond river estuary received net sediment input of about 1 2 of the total yearly balance from the continental shelf during dry seasons when upper catchment freshwater input was less than 45 106 m3 bank erosion in the richmond river estuary was least 1 during low to moderate floods mainly due to river training works and large mangrove coverage along the banks percentage of sediment export from the richmond river estuary depends on the magnitude of floods which was evident from 47 export during dry year when the estuary experienced a minor flood compared to 88 export during the wet year when the estuary experienced one minor and one moderate flood

size selective entrainment of bed load in gravel bed streams entrainment of mixed size gravel bed material was studied in nine reaches of three high power streams in scotland and norway paired measurements of at a point shear stress estimated from velocity profiles and bed load transport by hand held sampler were made they extended to very high values 400 n m 2 3 5 kg m x s x analyses of maximum bed load diameter mean bed load diameter transport rates of individual size fractions and tracer pebble movements all show some dependence of threshold shear stress for entrainment on absolute particle size despite strong relative size effects precise equal mobility of all sizes was approached in the data set with the highest shear stresses and transport rates size selective transport in the streams studied is also indicated by clear downstream and downbar reductions in surface sediment size over distances too short for abrasion to be significant

change in the frequency of extreme events as the indicator of climatic change in the holocene in fluvial systems abstract the transformation of natural systems of climatic origin in the holocene may be realised by a change in the type of extreme events or by a change in their frequency or by both the rapid warming at the younger dryas preboreal transition exemplifies a parallel drop in frequency and a change in the type of events several wetter phases of the holocene are characterised by rises in frequency of various types of extreme rainfalls the fragmentary records of events in the fluvial and slope systems coincide with smoothed variations in stable ecosystems and shifts of ecotonal zones such as tree line and lake levels

establishing sediment budgets for two small lowland agricultural catchments in the uk sediment budgets have been established for two small 4 km2 lowland agricultural catchments by using 137cs measurements sediment source fingerprinting and more traditional monitoring techniques to quantify the individual components of the budget the gross and net erosion rates for the fields on the catchment slopes were estimated using 137cs measurements within selected fields which encompassed a representative range of slope angles slope lengths and land use these estimates were extrapolated over the entire catchment using a simple topographically driven soil erosion model terrain based gis tbgis superimposed on a dem to derive catchment average gross and net erosion rates suspended sediment yields were measured at the catchment outlets and sediment source fingerprinting techniques were used to establish the relative contributions from the catchment surface subsurface tile drains and eroding channel banks to the sediment yields in channel and wetland storage were quantified using both direct measurements and 137cs measurements the sediment budgets established for the catchments highlighted the importance of subsurface tile drains as a pathway for sediment transfer accounting for ca 60 and 30 of the sediment output from the two catchments erosion from channel banks contributed ca 10 and 6 of the sediment output from the two catchments although the suspended sediment yields from these catchments were considered high by uk standards ca 90 t km 2 year 1 the sediment delivery ratios ranged between 14 and 27 indicating that a major proportion of the mobilised sediment was stored within the catchments in field and field to channel storage were shown to be of similar magnitude but storage of sediment in the channel system and associated wetlands was relatively small representing 5 of the annual suspended sediment yield

late glacial and holocene river development in the teleorman valley on the southern romanian plain this paper reports on a radiocarbon dated sequence of alluvial terraces from the tele orman valley in the southern romanian plain and represents the first late glacial and well constrained holocene alluvial sequence from the lower danube valley of southeast europe the two earliest and most extensive terraces t1 and t2 are dissected by large high amplitude palaeo channels which are dated to ca 12 800 yr bp and are comparable to large meandering palaeochan nels identified from other late glacial contexts across northern and central europe the remaining sequence of alluvial deposits show changes in river activity and accelerated sedimentation around 4900 4800 yr bp 4000 3800 yr bp 3300 2800 yr bp 1000 yr bp and within the past 200 yr a phase of tributary stream alluvial fan deposition is dated to ca 2400 yr bp all these periods of alluvial sedi mentation correlate well with episodes of climatic cooling higher rainfall and enhanced river activ ity both in terms of incision and greater lateral mobility as well as increased flood frequency and magnitude identified elsewhere in central western and northern europe human activity appears to have had little effect on this river environment and significant fine grained sedimentation is not noted until ca 2400 yr bp approximately 5000 yr after the first neolithic farmers settled the area whether this record of river activity truly reflects the impact of prehistoric societies on this catchment will only be elucidated through further ongoing detailed archaeological research copyright 2004 john wiley sons ltd

the role of soil erosion and fluvial processes in the post fallout redistribution of chernobyl derived caesium 137 a case study of the lapki catchment central russia abstract the central area of the russian plain received substantial amounts cs 137 fallout as a result of the chernobyl accident in 1986 with inventories exceeding 40 kbq m 2 in many of the areas close to chernobyl concern over the longer term fate of this contamination has focused attention on the need to predict the post fallout redistribution of the radiocaesium and thus future changes in the spatial distribution of contamination in the landscape since radiocaesium reaching the land surface as fallout is rapidly and strongly adsorbed by soil and sediment particles any attempt to predict its post fallout redistribution must focus on erosion and sediment delivery processes and must rely heavily on a knowledge of the geomorphological processes involved this paper reports a detailed investigation of post fallout cs 137 redistribution in the 2 18 km 2 lapki catchment in the middle russian upland which has required consideration of soil erosion processes sediment delivery pathways sediment delivery ratios and sediment sinks the time elapsed since the chernobyl accident is currently insufficient to result in significant reduction of cs 137 inventories in eroding areas but areas of deposition on both the lower slopes and on the balka sides and bottoms are already marked by significant increases in cs 137 inventories the results obtained emphasise that any attempt to develop meaningful predictions of the longer term redistribution of chernobyl derived cs 137 fallout within the russian plain must be based on a sound and detailed understanding of the linkage between the slopes and the balka systems and the fate of sediment entering the balka systems

a centennial tribute to g k gilbert s hydraulic mining debris in the sierra nevada abstract g k gilbert s 1917 classic monograph hydraulic mining debris in the sierra nevada is described and put into the context of modern geomorphic knowledge the emphasis here is on large scale applied fluvial geomorphology but other key elements e g coastal geomorphology are also briefly covered a brief synopsis outlines key elements of the monograph followed by discussions of highly influential aspects including the integrated watershed perspective the extreme example of anthropogenic sedimentation computation of a quantitative semidistributed sediment budget and advent of sediment wave theory although gilbert did not address concepts of equilibrium and grade in much detail the rivers of the northwestern sierra nevada were highly disrupted and thrown into a condition of nonequilibrium therefore concepts of equilibrium and grade for which gilbert s early work is often cited are discussed gilbert s work is put into the context of complex nonlinear dynamics in geomorphic systems and how these concepts can be used to interpret the nonequilibrium systems described by gilbert broad basin scale studies were common in the period but few were as quantitative and empirically rigorous or employed such a range of methodologies as pp105 none demonstrated such an extreme case of anthropogeomorphic change

reconstruction of hydrological changes between 7000 and 3000 bp in the upper and middle vistula river basin poland rhythmic fluctuations in the hydrological regime are demonstrated based on a review of records sensitive to relative climatic stability between 7000 and 3000 bp in the upper and middle parts of the vistula river basin central europe in the fluvial deposits and landforms these variations are very clear phases of higher flood frequency are dated 6600 6000 5500 4750 4500 4100 and 3250 3000 bp these phases coincide very well with sparse information on landslides data on high lake levels in the early subboreal phases of forest ecosystem transformation and finally the reaction of human cultures to these changes their rhythmicity correlates well with records from the alps and the alpine foreland but poorly with those from scandinavia this may be explained by changes in the zonal pattern of air mass circulation among the causes of the humid phases it is the frequency of volcanic eruptions which should be taken into consideration

effects of check dams reforestation and land use changes on river channel morphology case study of the rogativa catchment murcia spain this work has been financially supported by the project respuesta hidrologica y geomorfologica de los sistemas fluvio torrenciales afectados por proyectos de restauracion hidrologico forestal en cuencas semiaridas del sureste peninsular of the fundacion instituto euromediterraneo de hidrotecnia ce the first author was financially supported by an i3p postdoc contract csic ce and a ramon y cajal contract from the education and science ministry spain gonzalo g barbera also was supported by i3p postdoc contract

channel morphology gradient profiles and bed stresses during flood in a step pool channel abstract the stability of a step pool channel is investigated on the basis of measurements during a median annual flood the study reaches range in gradient from 5 to 10 and the flow was 3 m3 s 1 in an 8 m wide channel the estimated shear stress based on the channel gradient was 102 pa which implies that the channel ought to move half meter class boulders calculations of the shear stress using flow resistance equations yield values of about 30 pa these figures imply that the largest boulders in the channel could be moved in fact the channel is stable the effective stress remains well below the threshold to move the large structure forming boulders the steps are stable structures that result from interlocking of the larger stones they are semi randomly located depending on the location of keystones that are deposited in the channel by debris flows or fall out of the banks the high variation in step pool wavelength step height residual pool depth and pool length is indicative of the random nature of step location and structure along a reach there is no convincing evidence that special conditions govern their formation

vegetation and channel variation a case study of four small streams in southeastern australia abstract channel vegetation of four small streams in southeastern australia varies greatly in detail but it can be broadly categorised and even indexed for quantitative analysis such variations cause the hydraulic geometry of the study streams to differ significantly from each other and from patterns observed in most other geographical regions importantly this study demonstrates that the impact of vegetation on channel form and velocity can be quantified in much the same way that other broadly based hydraulic geometry relations have been developed dense bank vegetation results in narrower channels whereas vegetation growing on the bed greatly increases flow resistance causing channel widening reduced flow velocity but no significant charge in depth the results obtained in this study combined with those from other regions permit an interpretation of the sensitivity of channel width to different forms of channel vegetation information of use for river management

the effects of survey frequency on estimates of scour and fill in a braided river model an erratum has been published for this article in earth surface processes and landforms 27 7 2002 795 estimates of scour and fill in rivers that are derived by differencing topographic surfaces are known to be negatively biased by local compensation of scour and fill between surveys but the magnitude of bias is not well known this study examines the effect of survey frequency on volumes of scour and fill over a period of active channel braiding in a small scale river model a 100 min high temporal resolution time series of digital elevation models is artificially coarsened by selectively removing models the resulting four overlapping time series have survey intervals of 10 min 20 min 50 min and 100 min cumulative scour and fill volumes for the 100 min period are compared between the four series it is concluded that the decay in measured volumes of scour and fill with increased survey interval can be described using inverse functions cumulative scour fill volumes are approximately 420 per cent greater over the study period for 10 min survey intervals than for a 100 min interval after the 100 min period of competent flow nearly 65 per cent of the channel area experienced significant compensation of scour and fill several compensation mechanisms were identified in association with braided channel kinetics including lateral channel migration the migration of bed forms and channel avulsion it is demonstrated that by negatively biasing scour fill and net estimates this error significantly affects morphological approaches to the estimation of bed load sediment transport copyright 2002 john wiley sons ltd

terrestrial sediment yield and the lifetimes of reservoirs lakes and larger basins water reservoirs lakes and larger basins including their drainage areas represent sedimentologically closed to semi closed denudation accumulation systems the mean rates of mechanical denudation drme and clastic sedimentation srme are related by the ratio of the drainage lake area ad al if the latter is known drme or the specific sediment yield sy in t per km2 a can be calculated from srme or vice versa the best data for modern sy mainly come from the sediment fills of artificial reservoirs small drainage areas of mountainous regions show sy values up to two orders of magnitude higher than lowlands and approximately one order higher than larger regions of mixed relief this is also true of arid to semi arid zones which often provide approximately as much sediment sy as humid temperate and even tropical zones of comparable relief lithology and climate river runoff also may play some role for sy from catchments of limited size the importance of these factors is exemplified by perialpine lakes and two east african lakes sediment yields gained from some large reservoirs compare well with long term denudation rates derived from geological studies e g the tarbela dam reservoir along the indus river in many other cases human activities have raised sy by factors of 2 10 locally up to 100 artificial reservoirs in mountainous regions with sy in the range of 300 2000 t per km2 a tend to become filled within several tens to hundreds of years some have even shorter lifetimes perialpine lakes of the alps and british columbia are strongly affected by delta prograding and have lifetimes mostly between 15 and 40 ka closed lake systems in deep morphological depressions lake bonneville aral sea northern caspian sea have a high potential for sediment storage up to the level of spillover and therefore can persist over long time periods basins with markedly subsiding basin floors lakes of the east african rift zone the southern caspian sea and the black sea both on oceanic crust can survive for many ma in the future despite relatively high terrigenous input

changes in morphometric meander parameters identified on the karoon river iran using remote sensing data abstract river meander dynamics and mobility are important indicators of environmental change related to climate changes and anthropogenic activities at local and river basin scales the aim of the present study is to identify morphological changes of the karoon river in iran using high accuracy maps and landsat satellite images by analyses during the time period 1989 2008 in this study 20 meandering reaches were analyzed over a 128 km long river reach located in the middle part of the karoon river iran morphometric indicators such as river width w meander neck length l axis length a radius of curvature r water flow length s and sinuosity of meander c were extracted for the identified meanders the results of a paired t test showed that river width w and meander neck length l have significantly changed during the study period 1989 2008 with an increase of 3 5 m for w and a decrease of 274 m for l spearman correlation analysis has shown that meander parameter changes are highly correlated to each other the parameters that do not have significant correlation together are c with w and l w and l and l with s and a during the period of the study the flow length and river sinuosity decreased for the whole river reach by 4 77 km and 0 11 respectively analysis of land use land cover categories 1989 and 2008 using the support vector machine svm and kernel function method served as one of the tools for interpretation of the meander parameter changes these changes can be attributed not only to lu lc riparian vegetation to agriculture area ratio but also to dam construction in the upstream part of the river that leads to major hydrological regime and sediment transfer alteration sediment extraction may also be an important factor

the missing dimension effects of lateral variation on 1 d calculations of fluvial bedload transport most calculations of bedload transport in rivers including those in numerical models of aggradation and degradation are 1 d all hydraulic and transport rate calculations are averaged over the channel width because bedload transport laws are nonlinear width averaged calculations will underestimate the true bedload flux if there is any local spatial variation in either the bed or the flow this paper analyses the effects on bedload transport capacity of spatial variation in applied and critical c shear stress separately and in combination a simple but versatile statistical model is used to represent variability in with allowance for differences between sand and gravel bed rivers and for below bankfull flow bedload flux is shown to increase greatly with the variance of especially in gravel bed rivers variability in c through bed patchiness may increase reduce or make little difference to bedload flux depending on the correlation between and c simple width averaging leads to severe underestimation of bedload transport in most conditions some alternatives are considered the findings have implications for sediment routing models srms but further research is needed to explore the issue fully

assessment of channel changes due to long term bedload supply decrease roubion river france this paper presents the observations made in the watershed of the upper roubion river which drains a submediterranean mountainous environment and in two of its main tributaries the soubrion and bine creeks our aim was to analyze contemporary morphological and sedimentary changes in response to a progressive decrease in bedload supply this decrease is linked to an increase of forest cover in the watershed during the 20th century following rural depopulation and to a correlated decrease in peak flows several variables were systematically measured width slope bed level change sediment size along 23 km of river whereas dendrochronological data floodplain cross sections and estimated recurrence intervals of sediment entrainment based on critical shear stress calculations were also produced for specific sites to complete our analysis evidence of three major phenomena was obtained on both the roubion and its tributaries i bed degradation ii development of stable pavement in incised reaches and iii channel narrowing associated with the development of alluvial forest on recently abandoned portions of the pre existing active channel forest development began in the 1950s these three phenomena show positively covariant relationships that lead us to propose a descriptive model of mountain fluvial system adjustments to progressive decrease of bedload

identifying the controls over downstream fining of river gravels abstract a wide range of rates of downstream fining in gravel bed rivers has been reported as a consequence explanations of the phenomenon range from those that consider only abrasion to others that consider only selective sediment transport this apparent confusion results in part from inconsistent definitions of downstream fining analysis of results from a small gravel bed stream is used to show how the method of sediment sampling and the percentile used to characterize fining rates can affect the results when fining is adequately defined a theoretical relationship between fining rate and drainage basin area is derived from established alluvial fan relations this relationship is remarkably consistent with a range of studies by numerous authors using often different methods such results suggest that fining is achieved through the mechanism of selective transport but that the overall control on fining patterns is the volume of sediment supplied from within the drainage basin as such the rate of size decline in sedimentary deposits such as river terraces has the potential to be used to infer past changes in climate tectonics and or relative base level models of this are presented and these are shown to be broadly consistent with observations made in an ancient sandstone body full use of changing rates of fining as paleo environmental indicators requires further work on the rate of adjustment of fining profiles with respect to the rates of change in the forcing environmental conditions

post last glacial maximum fluvial incision and sediment generation in the unglaciated waipaoa catchment north island new zealand abstract small river systems contribute a significant component of sediment delivered to oceans but the temporal evolution of fluvially eroded landscapes is needed a sequence of postglacial terraces in the unglaciated waipaoa river catchment provides the opportunity to document fluvial incision and sediment flux on an 2000 year timescale since the last glacial maximum lgm which has previously only been undertaken for the entire post lgm period this study also calculates sediment mass where previously sediment volume was calculated using a 15 m dem field mapping and surveying and tephrochronology we calculate rates of fluvial incision and sediment volumes excavated during successive age constrained postglacial incision events and correlate these with a framework of inferred climatic events established for new zealand we identify seven periods of terrace formation each succeeded by a period of fluvial incision six in total although the magnitude of the response during each incision event and thus the sediment volumes generated varied through time and across subcatchments draining two contrasting lithological terrains we conclude that incision events were essentially synchronous at least within the timeframe constrained by the ca 2000 year interval between successive eruptive airfall events slope relaxation processes were simultaneous with incision thereby indicating that both processes were likely climate driven we identify a period of accelerated fluvial incision 7 mm y 1 commencing before ca 14 0 cal ka bp during the early postglacial period and ceasing ca 7 9 cal ka bp toward the end of the early holocene warming period the magnitude of this incision response was significantly higher in subcatchments draining highly erodible lithologies in the higher uplifting parts of the catchment when river bedload was at over capacity in contrast within the remainder of subcatchments draining the more resistant lithologies and in areas of lower uplift and in parts subsiding incision and sediment generation was moderated by the presence of knickpoints overall since abandonment of the lgm to present day fluvial incision in the waipaoa and the adjacent waimata catchments generated 16 7 km3 of sediment of which 10 km3 90 of the estimated 35 mt of glacial postglacial slope and shelf sediment mass was potentially available for transport offshore of this 14 08 km3 7 4 km3 derived from upper and 6 7 km3 from remainder of subcatchments was excavated from waipaoa catchment at an average of 0 6 km3 ka 1 of which 80 was generated by ca 7 9 cal ka bp this potentially validates previous accounts of high rates of offshore sediment flux before 8000 14c ybp ca 8877 cal ybp thereafter for the period mid holocene cooling and variability mhcv ca 6 5 cal ka bp until the present day the rate of incision across all subcatchments slowed to 2 mm y 1 and generated just 20 of the total sediment volume in part this reflected a depletion of available sediment as rivers in the upper subcatchments returned to a steady state and coincidental with an increase in accommodation space in the rapidly growing coastal floodplain sediment flux to the marine depocentres was thereby limited

alluvial and colluvial sediment storage in the geul river catchment the netherlands combining field and modelling data to construct a late holocene sediment budget abstract we used a combined approach of a two dimensional erosion and hillslope sediment delivery model watem sedem and detailed geomorphological reconstructions to quantify the different components in a sediment budget for the geul river catchment southern netherlands since the high middle ages hillslope erosion and colluvium deposition were calculated using the model while floodplain storage was estimated using field data our results show that more than 80 of the total sediment production in the catchment has been stored as colluvium mostly generated by hillslope erosion while almost 13 is stored in the floodplain since the high middle ages this situation resembles a capacity limited system model results for the period prior to the high middle ages with a nearly completely forested catchment show that far less sediment was generated and that most of the sediments were directly transported to the main river valleys or out of the catchment a supply limited system geomorphological analysis of a large alluvial fan shows the sensitivity of the study area to changes in the percentage of arable land our combined field data modeling study presents an elegant method to calculate a catchment sediment budget for a longer period and is able to identify and quantify the most important sediment storage elements furthermore it provides a valuable tool to calculate a sediment budget while only limited dated fluvial sediment sequences are available

stable channels with mobile gravel beds regime type equations for mobile gravel bed rivers are presented based on data obtained from 62 stable gravel bed river reaches in the united kingdom multiple regression techniques are applied to derive equations relating reach average and riffle values of width mean and maximum depth slope velocity sinuosity and riffle spacing to bankfull discharge bed and bank material characteristics valley slope bank vegetation type and an independent estimate of bankfull bed load transport rates although discharge has a dominant control on channel geometry these equations indicate that bed load discharge also has a significant influence particularly with regard to channel slope bank vegetation has a major control on width and velocity while depth velocity and slope are storngly affected by bed material size reasons for these results are considered in terms of the physical processes controlling channel adjustment the application of these regime equations is discussed and particular consideration is given to the design of sinuous channels with a pool riffle bed topograph

landscape history since the saalian drenthe stadial in the widawa catchment area in silesia poland a case study on long term landscape changes abstract with the pre roman iron age approximately in the 2nd century bce a cluster of iron smelting sites began to develop in the catchment area of the widawa river located in the old drift landscape of northeastern silesia poland before this area became an important local center for early iron smelting during the late pre roman iron age to the roman period its landscape had undergone distinct changes since it was covered for the last time by ice sheets during the saalian drenthe stadial besides climate driven environmental and landscape changes during the late pleistocene and holocene the area is influenced by a settlement history since the mesolithic in order to understand the holistic development of this pre roman iron age iron smelting cluster this paper investigates the late pleistocene landscape history of the southeastern part of the widawa catchment with a focus on study sites in the context of early human impacts therefore a multi proxy approach was applied integrating geomorphological mappings and sedimentological analyses lithology particle grain size bulk parameters total inorganic and organic carbon of selected drilling transects dated by ams radiocarbon with archaeological records geological and topographical data the study area developed its present shape in six main phases subsequently to the last ice coverage a which extensively accumulated saalian glacial till the widawa valley initially developed its present directionality b the subsequent valley formation is characterized by a succession of accumulation phases of glaciofluvial deposits of the drenthe c and warthe stadial d and fluvial deposits of the weichselian glacial period e and the holocene f which each were followed by a subsequent incision of the widawa valley first human impacts on the sediment budget are represented by alluvial fan deposits which accumulated at the end of the 4th millennium bp this alluvial fan situated in the context of three prehistoric slag sites shows a complex sedimentological succession of charcoal dated fan sediments that indicate a human impact on the landscape development during the pre roman iron age and the roman period pointing to a temporal and spatial context of early iron smelting

the causes of bedload pulses in a gravel channel the implications of bedload grain size distributions unsteady bedload transport was measured in two c 5 m wide anabranches of a gravel bed braided stream draining the haut glacier d arolla switzerland during the 1998 and 1999 melt seasons bedload was directly sampled using 152 mm square helley smith type samplers deployed from a portable measuring bridge and independent transport rate estimates for the coarser size fractions were obtained from the dispersion of magnetically tagged tracer pebbles bedload transport time series show pulsing behaviour under both marginal 1998 and partial 1999 transport regimes there are generally weak correlations between transport rates and shear stresses determined from velocity data recorded at the measuring bridge characteristic parameters of the bedload grain size distributions d50 d84 are weakly correlated with transport rates analysis of full bedload grain size distributions reveals greater structure with a tendency for transport to become less size selective at higher transport rates the bedload time series show autoregressive behaviour but are dif cult to distinguish by this method state space plots and associated measures of time series separation reveal the structure of the time series more clearly the measured pulses have distinctly different time series characteristics from those modelled using a one dimensional sediment routing model in which bed shear stress and grain size are varied randomly these results suggest a mechanism of pulse generation based on irregular low amplitude bedforms that may be generated in channel or may represent the advection of material supplied by bank erosion events copyright 2003 john wiley sons ltd

residence time of alluvium in an aggrading fluvial system relationships between the surface area and age of alluvial deposits were used to estimate the residence time of alluvium in the 2205 km2 waipaoa river basin new zealand the contemporary waipaoa river is an efficient transporter of sediment to the continental shelf but the basin has been characterized by rapid channel and valley aggradation in the historic period and by extensive mid to late holocene alluvial storage in the lower reaches the area weighted mean age of alluvial deposits in the lower part of the river basin is 4400 yr these deposits comprise terrace remnants isolated by downcutting and holocene to recent sediments that are potentially remobilizable by the modern river even though the amount of storage is small relative to downstream transport the majority of the potentially remobilizable alluvium is likely to remain in storage for 100 yr and its half life time for 50 per cent removal is 2000 yr within the confines of the flfloodplain the apparent loss of older deposits is due primarily to burial but losses of the most recent deposits are due almost entirely to remobilization 30 40 per cent with the remainder preserved in the alluvial record for at least 104 yr most of this sediment is likely to remain in storage until there is a shift to a degradational state copyright 2006 john wiley sons ltd

selective sorting and abrasion of river gravel i theory most gravel rivers show a tendency for characteristic grain size to decrease in the downstream direction over scales of tens or hundreds of kilometers it has been surmised that this downstream fining is due to some combination of selective sorting by which finer grains are preferentially transported downstream and abrasion by which individual particles are reduced in size here a framework for the simultaneous treatment of both phenomena is developed the analysis is restricted to bed load transport of gravel only abrasion due to binary collisions between moving bed load and stationary bed particles is considered the formulation includes the possibility of differential basin uplift and subsidence due to tectonism and mixtures of rock types with differing coefficients of abrasion the formulation of selective sorting is based on the concept of hiding as applied to a surface based bed load transport relation abrasion is first treated in terms of a lagrangian formulation for individual grains and t

evolution of the morphology of the river dragonja sw slovenia due to land use changes the effects of increasing agricultural land use on fluvial morphology have received much attention in fluvial research however in several regions in europe a reversing trend of decreasing agricultural activity and land abandonment followed by reforestation is observed the response of fluvial morphology deserves attention because of its large impacts on landscape and riverine habitats with the help of geomorphological mapping multi date aerial photography and a range of dating techniques we reconstructed the evolution of the morphology of the riverbed and the floodplain of the dragonja river in southwestern slovenia the results of this study show that the fluvial morphology in this mediterranean catchment has changed considerably as a result of shifts in agricultural land use in particular large scale land abandonment in the second half of the 20th century until the first half of the 19th century floodplain aggradation prevailed probably around 1870 a large erosion event occurred from which the floodplain did not fully recover a terrace standing 2 5 m above the present floodplain was formed natural reforestation due to depopulation since world war ii caused a reduction in discharge and sediment supply to the river the decreased intensity and frequency of floods allowed invasion of the riverbed by vegetation causing narrowing and incision of the riverbed this resulted in the formation of a terrace which now stands 1 5 m above the present day river this terrace is about 60 years old however the largest increase in forest area occurred since 1975 which intensified this process of riverbed narrowing and incision creating a local terrace at 0 5 m at 0 5 m above the presently meandering river

present day events and the evaluation of holocene palaeoclimatic proxy data abstract reconstruction of holocene climatic changes should be based on correlation of proxy data representing various sediment facies and ecosystem characteristics in addition to long term fluctuations in such data various extreme events such as downpours floods and slope failures whose type and frequency fluctuate in time have also been recorded events may reflect global regional or local changes examples from poland are used to illustrate general principles the observation of present day processes and their erosional or deposition effects linked with proxy indicators from the past should help in interpretation of environmental changes in the holocene and to inferences about the causative mechanisms

early holocene fluvial activity from the sedimentology and palaeohydrology of gravel terrace in the semi arid mahi river basin india abstract palaeocompetence analysis and palaeodischarge estimation techniques are applied to a late pleistocene early holocene gravel terrace in the mahi river basin western india terrace sedimentology comprising gravels overlain by sand lithofacies suggests a gradual change in palaeohydrological conditions marking a switch from braided to meandering fluvial styles the discharge values for the gravel bedforms based on the clast size and the cross bed set thickness are estimated between 150 180 m 3 s 1 comparable with the present day observed values albeit with a much higher competence results indicate that fluvial aggradation occurred under low discharge conditions with intermittent high discharge events depositing longitudinal gravel bars the incision of these gravel bars and the formation of terraces can be attributed to the higher discharge regime post 9 2 ka the study further indicates that whereas the aggradation of the gravel terrace during the early holocene was controlled by the large sediment influx the incision that followed was in response to the increase in the discharge and competence of the river flow

impact of natural reforestation on floodplain sedimentation in the dragonja basin sw slovenia changes in floodplain sediment dynamics have profound effects on riverine habitats and riparian biodiversity depopulation due to socio economic changes in the dragonja catchment 91 km2 in southwestern slovenia resulted in the abandonment of agricultural fields followed by natural reforestation since 1945 this profoundly changed the water and sediment supply to the streams as well as floodplain sediment deposition this paper presents a reconstruction of the development of the dragonja floodplain due to these land use changes during the last 60 years the reconstruction is based on dating of floodplain sediments using 137cs profiles measurement of actual sedimentation rates using artificial grass sedimentation mats and linking this information to the present day hydrological behaviour of the river the sedimentation mats showed that floodplain sedimentation was restricted to peak flows of considerable magnitude due to the reforestation the return period of such high flows increased from 0 31 year in the period 1960 1985 to 0 81 year between 1986 and 2003 with commensurate changes in sedimentation rates at the 1 5 m river terrace formed about 60 years ago 137cs based sedimentation rates 1960 1986 were roughly twice the rates inferred from the artificial grass mats 2001 2003 this finding matches the increase in the return period for larger peak events during the 1986 2003 period which caused fewer major inundations at this level conversely sedimentation rates determined for the lowest terrace at 0 5 m were similar for both techniques and periods because the return periods of the peak events responsible for sediment deposition at this lower level did not change much over the period 1986 2003

the importance of high resolution monitoring in erosion and deposition dynamics studies examples from estuarine and fluvial systems abstract erosion and deposition processes lie at the centre of geomorphological explanation but progress in understanding has been limited by a lack of appropriate high resolution monitoring methodologies which permit detection of erosion and deposition dynamics this paper presents a case for monitoring erosion and deposition at high temporal resolutions and uses hypothetical approaches supported by example erosion and deposition events and analyses drawn from estuarine and fluvial systems the paper first presents testable hypotheses to demonstrate the complexity of possible event combinations sequences and juxtapositions for the erosion driving forces which underpin the need for high resolution monitoring second it summarises recent improvements to the photo electronic erosion pin peep automatic erosion and deposition monitoring system including the novel concept of thermal consonance timing tct which is particularly promising because it helps to define the timing of nocturnal events and through the entire hydrograph third example results are discussed from high resolution monitoring of bank erosion at a tidal site at burringham on the river trent in northern england tidal banks are revealed to be much more dynamic than previous conventional monitoring has indicated a key result is that because the high resolution approach allows erosional and depositional activity to be assigned to specific periods of tidal inundation it becomes possible for the first time routinely to produce event based erosion 36 mm h 1 and deposition rates 4 5 and 8 4 mm h 1 such rate determinations are potentially very useful in the field validation of sedimentological and geomorphological models including grain settling and resuspension theory fourth through a longer term of aggregated daily data a striking 2 week cycle of deposition and erosion emerges which correlates most strongly with spring neap tidal cycling but is moderated by wind stress effects sediment was deposited on the bank relatively quickly over 4 5 days but then removed by erosion rather slowly over 9 10 days fifth the dangers of low resolution monitoring are illustrated by comparing the daily peep data set with a series resampled at a lower 14 day frequency to simulate the information generated by conventional resurvey methodologies the low frequency series failed adequately to represent the cyclicity mean range variability and trend of bank elevation changes and without this dynamics information rate and process definition is very difficult largely because of self concealing activity sixth a useful advance is illustrated by the fluvial erosion sequence for the river wharfe n england this shows how tct can generate rare and important results with the definition of the precise time of an erosion event within the hydrograph bank retreat here occurred very quickly after initial inundation and within 4 h of the flow peak information which can be used to define thresholds for entrainment e g critical shear stresses such high resolution monitoring helps to unravel some of the erosional effects of complex sequences combinations and juxtapositions of similar or different forcing events finally high resolution approaches have been adopted worldwide for fluvial estuarine mudflat and canal systems but considerable potential exists for their development and use in these and other contexts e g gully hillslope beach and dune environments to improve understanding and modelling of geomorphological processes more widely

nonlinear dynamical systems in geomorphology revolution or evolution abstract geomorphic systems typically exhibit complex apparently random behaviors and patterns in both spatial and temporal domains this complexity can arise from the cumulative impacts of individual process response mechanisms which are far too numerous to be accounted for in individual detail or due to multiple controls over process response relationships which operate over a range of spatial and temporal scales stochastic complexity nonlinear dynamical systems nds theory which includes specific techniques and concepts such as chaos dissipative structures bifurcation and catastrophe theory and fractals shows that extreme complexity can also arise due to the nonlinear dynamics and couplings of relatively simple systems represented by relatively small equation systems deterministic complexity while emphasis in earth science has been largely on stochastic complexity geomorphologists have long recognized the presence of deterministic complexity as well recent developments in the study of nonlinear dynamical systems have implications for the ability to make reliable long term predictions and therefore applications of nds in geomorphology may be revolutionary to some extent however virtually all the basic conceptual underpinnings of nds theory can be mapped onto existing and even traditional theoretical concepts in geomorphology in this sense the use of nds concepts in understanding earth surface processes and landforms is evolutionary the link between traditional and nds based concepts is illustrated by analyzing a generalized geomorphic mass flux system it is shown that the system is in most cases unstable consistent with chaos or deterministic complexity however the three attractor states of the system correspond exactly to the states of aggradation degradation and steady state

the nature and controls on downstream fining within sedimentary links abstract at scales of 100 to 102 km grain size change in gravelly alluvial systems is characterized by punctuated downstream fining significant lateral sediment inputs define a sequence of sedimentary links within which fluvial processes produce fining trends using a new set of surface grain size data eighteen such links along two canadian gravel bed rivers are examined negative exponential functions are found to be most appropriate for describing within link grain size changes development of a pragmatic means of predicting grain size is then pursued by searching for a means to relate model diminution coefficients to link attributes consideration of lithologically differentiated fining trends indicates that lithology plays an insignificant role in controlling fining rate examination of within link longitudinal profiles indicates a reasonable relation between fining rate and the rate of change of channel slope the predictive value of this relation is limited by the regional nature of the data upon which it is based and the relative difficulty of obtaining accurate gradient information however as previously noted for alluvial fans although for different reasons channel gradient is correlated with link length and a reasonable predictive tool is apparent in a relation between link length and diminution rate the validity of the derived relation cannot be tested for want of a suitable data set several lines of evidence indicate that abrasion is unimportant as a fining mechanism on these rivers and it is argued that this may be typical of sedimentary links fining rate must then be a function of the efficiency with which sorting processes operate and it is suggested that this efficiency is dependent on aggradation rates associated with the lateral sediment influxes at the head and terminus of individual links

fluvial sediment budget of a mediterranean river the lower tordera catalan coastal ranges ne spain abstract the lower tordera river is a representative case of water and sediment dynamics and uses in a large river in the western mediterranean region along the study reach the fluvial regime of the river changes shifting from a perennial water and sediment circulation in the upper parts to an ephemeral flow pattern in the lower sections the fluvial sediment budget of the lower tordera was estimated based on field measurements of suspended and bedload and a survey of cross sections field data were obtained between january 1997 and june 1999 a period that was dryer than the average most sediment is transported as bedload more than 3 4 of the total load both at the entrance section of the river reach and at the outlet section close to the mediterranean sea a total of 156 700 tonnes of sediment 62 680 tonnes year entered the system mostly during discharges below bankfull while 107 000 tonnes 42 800 tonnes year were exported to the sea almost exclusively during floods the net accumulation of sediment was 14 600 tonnes per year as bedload especially during the dry years of 1998 and 1999 when small floods circulated through the upper sections but did not reach the lowermost part of the river as a consequence a mean aggradation of the riverbed of around 6 8 mm year has occurred a figure that has been corroborated after the analysis of a series of cross sections residence time of sediment in the perennial reach calculated at a long term ranges from 6 years for sediments in the active base flow channel to 164 years for sediment placed above bankfull level which is only entrained during high flows residence time of sediment in the ephemeral reach calculated for the period 1997 1999 is only slightly higher than that of the perennial part of the river this fact can be related to the current adjustment of the river system to historical mining the riverbed is slowly adjusting to the new conditions and important sedimentation is taking place in many upstream sections while erosion still occurs in the lowermost reaches thus causing the relatively low residence time of sediment

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

human induced soil erosion and the implications on crop yield in a small mountainous mediterranean catchment sw turkey abstract many hillslopes in the limestone dominated taurus mountain range sw turkey are characterized by severely depleted soils while a significant amount of sediment is being stored in the valley bottoms the same holds true for the 11 4 km2 endorheic gravgaz basin in the vicinity of the hellenistic roman city of sagalassos in sw turkey previous palaeo environmental research in this basin already yielded both detailed sedimentological and palynological information on sedimentation in the valley bottom and vegetation changes that took place during the last several millennia an adapted watem sedem geomorphic model version was used to simulate the impact of the observed changes in vegetation cover climate and hillslope soil properties on hillslope soil erosion and valley bottom sediment deposition over the last 4000 years the calibrated watem sedem model is able to reconstruct the temporal changes of sedimentation in the valley bottom reasonably well to simulate the impact of historic soil erosion on crop productivity a simple crop yield model was coupled to the reconstructed soil thickness maps the main outcomes are that soil erosion was mainly driven by deforestation and hence anthropogenic activity but the resulting soil erosion did not cause a complete collapse of crop yields on the contrary we were able to quantify that the sediment accumulation in the lower lying valley bottoms compensated at least a part of the loss in crop yield from the hillslopes potential crop yield value changed from 2 80 t ha 1 a 1 before widespread deforestation to 2 58 t ha 1 a 1 during roman imperial times and 2 19 t ha 1 a 1 at present these model approaches are tools that allow us to quantify human impact in the past going beyond traditional qualitative descriptions which will ultimately lead to a better understanding of human environment interactions in the past

meso scale catchment sediment budgets combining field surveys and modeling in the dragonja catchment southwest slovenia in this paper we present a methodology to construct a sediment budget for meso scale catchments we combine extensive field surveys and expert knowledge of the catchment with a sediment delivery model the meso scale mediterranean drainage basin of the dragonja 91 km2 southwest slovenia was chosen as case study area during the field surveys sheet wash was observed on sloping agricultural fields during numerous rainfall events which was found to be the main source of sediment with the sediment yield model watem sedem the estimated net erosion on the hillslopes 4 1 t ha 1 y 1 91 of inputs the second source bank erosion 4 2 0 25 t ha 1 y 1 was monitored during several years with erosion pins and photogrammetric techniques the last source channel incision was derived from geomorphological mapping and lichenomery and provided 3 8 0 17 t ha 1 y 1 of the sediment input the river transports its suspended sediment mainly during high flow events sampled with automated water samplers about 27 1 2 t ha 1 y 1 of the sediment delivered to the channel is deposited on floodplains and low terraces downstream estimated with geomorphological mapping coring and cesium 137 measurements the sediment transported as bedload disintegrates during transport to the outlet due to the softness of the bedrock material as a result the river carries no bedload when it reaches the sea the results imply a build up of sediment in the valleys catchment however extreme flood events may flush large amounts of sediment stored in the lower parts of the system geomorphological evidence exists in the catchment that such high magnitude low frequency events have happened in the past

what were the primary forcing mechanisms of high frequency holocene climate and glacier variations a compilation of holocene glacial advances throughout the world is compared with summer solar insolation integrated over the northern hemisphere and the magnitudes of global acid fallout from volcanic eruptions north of 20 s estimated from the acidity signal of annual ice layers in the crete and camp century ice cores in greenland correlation analysis between glacial advances versus volcanic eruptions yielded a correlation coefficient of r 0 71 a climatic forcing curve solar insolation and volcanic eruptions weighted 1 1 versus glacial advances increased the correlation coefficient to r 0 90 this suggests that the combined effect of volcanic aerosols and orbital related northern hemisphere summer insolation may have been the primary forcing mechanism of worldwide climate and glacier fluctuations throughout the holocene

rules of the road a qualitative and quantitative synthesis of large wood transport through drainage networks abstract to effectively manage wood in rivers we need a better understanding of wood mobility within river networks here we review primarily field based and some numerical studies of wood transport we distinguish small medium large and great rivers based on wood piece dimensions relative to channel and flow dimensions and dominant controls on wood transport we suggest further identification and designation of wood transport regimes as a useful way to characterize spatial temporal network heterogeneity and to conceptualize the primary controls on wood mobility in diverse river segments we draw analogies between wood and bedload transport including distinguishing eulerian and lagrangian approaches exploring transport capacity and quantifying thresholds of wood mobility we identify mobility envelopes for remobilization of wood with relation to increasing peak discharges stream size and dimensionless log lengths wood transport in natural channels exhibits high spatial and temporal variability with discontinuities along the channel network at bankfull flow and when log lengths equal channel widths although median mobilization rates increase with increasing channel size maximum mobilization rates are greatest in medium sized channels most wood is transported during relatively infrequent high flows but flows under bankfull can transport up to 30 of stored wood we use conceptual models of dynamic equilibrium of wood in storage and of spiralling wood transport paths through drainage networks as well as a metaphor of traffic on a road to explore discontinuous wood movement through a river network the primary limitations to describing wood transport are inappropriate time scales of observation and lack of sufficient data on mobility from diverse rivers improving models of wood flux requires better characterization of average step lengths within the lifetime travel path of a piece of wood we suggest that future studies focus on i continuous or high frequency monitoring of wood mobility ii monitoring changes in wood storage iii using wood characteristics to fingerprint wood sources iv quantifying volumes of wood buried within river corridors v obtaining existing or new data from unconventional sources such as citizen science initiatives and vi creating online interactive data platforms to facilitate data synthesis

stream channel erosion and change resulting from riparian forests forested stream banks compared to grassed ones can destabilize stream channels by promoting erosion four reaches of coon creek wisconsin each with long term grassed and forested subreaches were examined grassed reaches were narrower and had smaller channels bankfull cross sections than forested reaches suggesting that grassed channel reaches stored about 2100 to 8800 m 3 more sediment per kilometre than forested reaches available evidence suggests that conversion of riparian forests to grass would allow storage of sediment along channels possibly decreasing downstream sediment yields these findings are important as many grassed riparian corridors are rapidly reverting to forest because of economic conditions and governmental policies

modeling sediment yields in italian catchments abstract sediment yield observations derived from 40 long term sedimentation records in italian reservoirs were used to calibrate and validate the spatially distributed sediment delivery model watem sedem using the best data available at national scale the sediment yield data set includes records from semi natural catchments in northern italy as well as agricultural and semi natural basins in central and southern italy the average size of the catchments is 150 km2 with mean annual sediment yields ranging from 0 20 to 20 t ha 1 year 1 watem sedem estimates mean annual sediment fluxes to permanent river channels depending on the local transport capacity the sediment flux is detachment limited or transport limited the optimal transport capacity parameters for italian conditions were derived via automatic calibration procedures a global model calibration procedure taking into account all catchments in the dataset led to an overestimation of the sediment yield for the mountain catchments and an underestimation for the non mountain catchments sediment yield estimates are more reliable when calibration procedures are applied separately for mountain and non mountain catchments the model performance of watem sedem is rather poor in the mountain catchments r 0 25 which suggests that the model structure is too simplified to come to an adequate description of the sediment fluxes the model performance for the non mountain catchments which are more important from a management point of view is significantly better r 0 51 considering the fact that data layers with a 75 75 m resolution were used the results are encouraging the further development and application of spatially distributed sediment yield models at regional and national scale levels

holocene fluctuations of lake levels in the french jura and sub alpine ranges and their implications for past general circulation patterns temperature and precipitation variations reflected in lake level fluctuations in the french jura and pre alps during the last nine millennia are qualitatively assessed by reference to 1 climatic oscillations reconstructed in the alps and 2 modern processes behind alpine tree limit variations the summer season and mainly the late summer appears to have a deterministic impact on the holocene environment correlations between palaeoclimatic proxy data recorded in the north atlantic area from high and middle latitudes and climatic dynamics illustrated by the little ice age and the recent warming suggest 1 the existence of climatic oscillations due to varying solar activity superimposed on larger plurimillennial climatic trends and 2 that these minor climatic phases correspond with two main types of general circulation pattern alternating over western europe during the last six millennia the climatic deteriorations correspond with cooling at high latitudes inducing a stronger thermal grad

a neolithic yew bow in the polish carpathians evidence of the impact of human activity on mountainous palaeoenvironment from the kamiennik landslide peat bog abstract a unique artefact the fragment of a bow made of yew wood indicating the hunting activity of prehistoric man was found within the sediments of the landslide peat bog at the depth of 330 cm formed on the mt kamiennik polish flysch carpathians the datings of this artefact using 14 c method at ca 3790 3380 cal bc indicate its connection with the activity of the neolithic man related to the funnel beaker culture in the sequence of the peat bog deposits formed since the atlantic phase the palaeoclimatic changes of the middle and late holocene as well as traces of human impact in these and subsequent periods were recorded and analysed using palynological macrofossils lithological methods and dated with radiocarbon palaeoenvironmental changes identified in the peat horizon bearing the artefact were marked by the delivery of minerogenic high energy deposits with charcoal to the peat bog as well as distinct changes of plant communities these phenomena confirm a significant human impact caused by the prehistoric man on landslide areas on the other hand the study confirms significant importance of climatic condition for human activity and proves that landslide peat bog deposits are very sensitive records of palaeoenvironmental changes the archaeological artefact essentially supplements the results of our interdisciplinary palaeoenvironmental study it is one of the rare neolithic bows found in the area of europe till now

selective sorting and abrasion of river gravel ii applications most gravel rivers show a tendency for characteristic grain size to decrease in the downstream direction over scales of tens or hundreds of kilometers it has been surmised that this downstream fin

predicting fine sediment dynamics along a pool riffle mountain channel abstract fine sediment dynamics in mountain rivers are of concern because of implications for aquatic habitat channel stability and downstream sediment yields many mountain river systems have episodic fine sediment transport because of infrequent point source sediment inputs from landslides basin instability triggered by land uses such as logging or infrequent mobilization of the coarse surface layer in channels dam removal which is now more likely along mountain rivers may also provide a substantial fine sediment input to downstream channel reaches fine sediment storage in the interstices of spawning gravels and within pools along mountain rivers is of particular interest because of impacts to aquatic organisms in this study we focus on sediment dynamics within pools of the north fork poudre river in colorado as an example of the processes controlling fine sediment deposition storage and transport within laterally constricted pools the 1996 release of 7000 m3 of silt to gravel sized sediment from a reservoir on the north fork provided an opportunity to develop a field data set of fine sediment dynamics and to test the predictions of three different one or two dimensional sediment transport and hydraulic models against the field observations the models were calibrated against quantitative measurements of pool scour and fill one dimensional hec 6 results indicate that robust simulations yield the greatest agreement between predicted and measured pool bed elevation change model calibration on two pools and validation on one pool indicate that at least 58 of observed bed changes after the sediment release were predicted by hec 6 modeling accuracy using quasi two dimensional gstars 2 0 was considerably more variable and no pool wide trends were obtained the two dimensional model rma2 substantially improved the representation of eddy pool hydraulics within a compound pool of the north fork results from the hydraulic modeling coupled with bed load and total load computations delineate areas of scour and deposition which are consistent with observations in the field a conceptual model of sediment delivery and storage for laterally confined pools suggests that persistent deposition of fine sediment within eddies distal from the sediment source may result from sediment releases the original loss of channel capacity facilitated additional deposition within eddies as sediment within upstream proximal pools became mobilized at high discharges the development of a strong shear zone prevents degradation of sediment deposits within the eddy central portions of these proximal pools may clear according to existing models whereas deposition within recirculating zones may be long term water managers could use these models to estimate minimum pool volume for overwinter habitat and residence time of pool sediment