some observations on suspended sediment dynamics in storbregrova jotunheimen observations are reported of the dynamics of suspended sediment transport in the meltstream of storbreen in the jotunheimen fine sediment is transferred from the subglacial to the proglacial environment during low flow meltdominated periods and then removed from the catchment during high flow rainfall controlled events both diurnal and storm period sediment load discharge relationships involve clockwise hysteresis but separate multivariate rating curves define variations of load with streamflow according to 1 the relative importance of meltwater and rainfall runoff and 2 changes in the sediment source areas contributing to the stream at different times particle size variations in the suspended sediment also reflect varying source area influences

a conceptual model for alpine proglacial river channel evolution under changing climatic conditions this paper integrates concepts derived from the literature to focus upon interactions between riparian vegetation and river channel dynamics in alpine glacier basins discussion of the nature and variability of discharge and sediment regimes of alpine glacier fed rivers downstream variations in the physical character of the river channel and corridor consequent downstream variations in lateral processes and regional variations in alpine glacier dynamics lead to the proposal of a conceptual model of proglacial river channel riparian vegetation interactions under changing climatic conditions

the evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of small river glacier canada abstract spatially sampled suspended sediment data from extra channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to little ice age lia deglacierization at small river glacier canada surface ages were determined by aerial photograph interpretation turbidimeters were installed in three ephemeral channels on young mature and old surfaces and their response to rainfall events of different magnitudes recorded results showed young ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events a suspended sediment response from old surfaces exposed since 1910 was recorded for only three events with 5 and 30 year return periods the intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude the rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the lia maximum ca 1910 at small river glacier however further perturbation for example by glacial advance or extreme climatic events would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores we therefore suggest that it is difficult to determine when paraglacial sedimentation ceases to influence suspended sediment yields and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization

archaeological and sedimentological data indicate lapita settlement on a newly formed coastal plain tavua island mamanuca group fiji the timing and choice of initial settlement location are examined on the small island of tavua in fiji s mamanuca group the mid to late holocene sea level retreat influenced the island s coastal landforms through the acceleration of coastal progradation and the production of habitable land archaeological sedimentological and chronological data are integrated to better understand the island s settlement and geomorphological history these datasets are then compared with regional and modeled sea level curves for fiji in order to constrain the time period for the onset of coastal regression the results indicate that tavua was initially settled around 3000 years ago within a few centuries of the formation of the coastal plain integrating archaeological sedimentological and sea level datasets helps produce a more precise understanding of the relationship between sea level change and the timing of settlement on small islands in oceania

particle size analysis of the sediment suspended in a proglacial stream glacier de tsidjiore nouve switzerland hourly at a point samples of suspended sediment taken from the outflow stream of glacier de tsidjiore nouve switzerland over a 60 day sampling period n 1440 are shown to be dominantly composed of silt sized particles particle size sem and xrd analyses indicate a subglacial provenance for the suspended sediment temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge being dominated by erratic hour to hour fluctuations and clockwise hysteresis over diurnal flow events examination of grain size and sorting dynamics over snowmelt and icemelt related ablation events during precipitation events and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes we conclude that although the bulk of the suspended sediment in the proglacial stream of glacier de tsidjiore nouve is derived directly from subglacial sources with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods a portion of the suspended load undergoes intermittent flush fall transfer through the proglacial zone which acts as a sediment source during rising flows and as a sink during periods of waning flow

determining sediment source areas in a tropical river basin costa rica abstract four hydrologic events were studied at three gauging stations in the pejibaye river basin costa rica the sediment sources were determined by comparing the timing of the sedigraph at the gauging station and the timing of rainfall in the catchment with addition of time for the new water to flow from different land use districts along the main rivers to the gauging stations the rainfall was recorded in the basin upstream of pejibaye gauging station which was therefore the only station where the sedigraph rainfall method could be properly used for determining sediment sources on three occasions the sediment discharges at the pejibaye station were of about equal height the sedigraph rainfall method indicated that on two of these occasions the sediment came mainly from the pasture and sugar districts and in one case from the forested middle basin on the fourth occasion rainfall amounts and intensities were locally high in the forested upper basin but water and sediment discharges were small re erosion of material deposited in the channel increased the width of clockwise sediment concentration discharge loops in one storm the concentration discharge loop changed from an eight shaped loop at the upper station to a counter clockwise loop at the downstream station explained by the lagging of the sediment after the water

fluvial clastic sediment yield in canada scaled analysis this report presents a set of maps of regional fluvial sediment yield in canada based mainly on the water survey of canada archive of riverine suspended sediment observations regional scaling rel

paraglacial redistribution of glacial sediments in the vestfold hills east antarctica abstract the vestfold hills landscape is dominated by bare rock slopes and unconsolidated deposits form a minor component of the surficial geology the principal objectives of the study were to explain the distribution of unconsolidated deposits determine the nature and timing of sedimentary processes during and after deglaciation and the impact of these processes on landscape development observations of late quaternary glaciation and deglaciation of the area and contemporary depositional processes are reported and a conceptual model of geomorphological change since deglaciation is presented the model attempts to reconcile the types and rates of contemporary depositional processes with the distribution of deposits and landforms and to explain why unconsolidated deposits cover less than 20 of the hills despite the effects of recent glaciation the lack of unconsolidated deposit in the landscape can be attributed to the combined effects of low debris volumes in the ice and the redistribution of debris during and after deglaciation redistribution of debris can be explained by paraglacial processes which are non glacial sedimentary processes that are directly conditioned by glaciation paraglacial sedimentation is a response to rapid adjustment of the debris system after the dominance of glacial conditions and is characterized by disequilibrium between sediment supply and transportation of sediment by nonglacial processes evidence from the vestfold hills suggests paraglacial sedimentary processes are dominated by mass movement of glacial debris from slopes and the formation of stable valley fills and that the main sediment transfers occur within a few thousand years of deglaciation

suspended sediment load during floods in a small stream of the dolomites northeastern italy abstract suspended sediment load was analyzed in a small high gradient stream of the eastern italian alps which was instrumented to measure discharge and sediment transport the ratio of suspended to total sediment yield and the relations between sediment concentration and water discharge were analyzed for seven floods which occurred from 1991 to 1996 in summer and autumn from june to october different patterns of hysteresis in the relation between suspended sediment and discharge were related to types and locations of active sediment sources the within storm variation of particle size of suspended sediment during a major flood indicates a coarsening of transported material for increasing discharge an analysis of grain size has shown that erosion areas on hillslopes were the main sources of suspended load

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

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

field testing of three bedload samplers efficiency in a gravel bed river spitsbergen abstract a comparative study of the three bedload traps was accomplished to determine the effectiveness differences between the devices the research was carried out in two transverse sections of the proglacial gravel bedded scott river sw svalbard using three devices to perform direct measurements of bedload transport in the river channels several samplers are used for field measurements but none of them has gained widespread acceptance as a standard so far the paper compares transport rates collected in three bedload samplers that differ in structure and functionality i a portable helley smith pressure difference bedload sampler h s ii an anchored river bedload trap rbt and iii the portable sampler used by the polish hydrological services pihm type c all three samplers are constructed using the same components a frame made of thin stainless steel sheet and a nylon bag with the same 2 mm mesh size except pihm measurements were conducted within three consecutive days in two cross sections in the same vertical profiles and at the same time at intervals of 30 and 60 min measurements of bedload transport and water velocity were performed simultaneously in order to determine the effectiveness and representativeness of short term measurements using particular devices the masses of the samples were converted into a specific rate of bedload transport and compared to the results of long term continuous measurement 24 h measurement cycle the results confirm that both specific transport indicators and the mass of the samples collected by the tested devices show a significant variation generally the highest mass and specific transport indicators were obtained using the h s sampler the rbt produced moderate transport rates while the pihm sampler gave the lowest rates the bedload transport rate in a profile estimated on the short term measurements was compared to results of the continuous measurements conducted in the same cross sections in the 7 cases we obtained underestimation to max 10 times and in the next 7 cases overestimation to max 114 times only in four cases were the results of short term measurements similar to the continuous ones the results obtained from the rbt sampler show the smallest variability among all tested devices

an inexpensive turbidimeter for monitoring suspended sediment abstract temporal and spatial variability of suspended sediment in proglacial streams means that discrete monitoring is unlikely to characterize suspended sediment patterns accurately continuously recording turbidimeters provide a solution to the temporal problem of sampling however the problem of spatially limited sampling is constrained largely by the cost of establishing networks of commercially available turbidimeters in this paper we present the design and testing of an inexpensive custom built datalogger compatible and rugged infrared nephelometric turbidimeter the hobs laboratory testing showed that the hobs was most sensitive to coarse clay and fine silt fractions the dominant particle sizes transported in proglacial streams further testing showed that the hobs had a non linear but regular response to bulk sediment concentrations from 0 to 3500 mg l 1 with explained variances of 99 2 to 99 8 in the field the hobs showed a linear response up to 2000 mg l 1 and a non linear response up to 10 000 mg l 1 with explained variances between 75 and 83 this variability emphasizes the necessity of individual site specific field calibrations the hobs s sensitivity to a wide range of suspended sediment concentrations is particularly suited for use in proglacial streams where large fluctuations in concentration are likely the generic design low cost and good performance of the hobs suggests potential for application in other environments where distributed monitoring of suspended sediment is of interest

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

spatial scale dependence of sediment dynamics in a semi arid badland drainage basin abstract problems of spatial scale transference are of key interest in drainage basin research the objective of this study was to investigate the spatial scale dependence of sediment dynamics in semi arid badland drainage basins simulated rainfall experiments indicated that on microscale plots runoff generation and sediment entrainment occurred when total rainfall exceeded 0 5 to 6 mm on pediment surfaces 1 5 to 4 mm on sandstone surfaces and 8 to 25 mm on shale surfaces the sediment concentration discharge relationship for two mesoscale basins displayed a change from clockwise to counterclockwise hysteresis when total rainfall exceeded the threshold rainfall for the initiation of flow in deep tunnel systems the initiation of tunnel flow causes counterclockwise hysteresis due to a delayed increase in sediment concentrations during a runoff event this contrasts with the clockwise hysteresis caused by flushing in the early stages of runoff for smaller rainstorms comparison of micro and mesoscale sediment dynamics indicates that microscale thresholds are not by necessity in evidence at the mesoscale in addition at the mesoscale elements exist which are non existent at the microscale e g a deep tunnel system the behaviour of the mesoscale basin is dominated by these elements rather than by the microscale components it contains

paraglacial debris cone formation on recently deglaciated terrain western norway five debris cones have formed on terrain deglaciated since ad 1750 75 in bergsetdalen western norway three were surveyed and studied in detail two accumulated over 108 215 years and the third over 57 108 years accumulation on all three appears to have effectively ceased around or slightly before ad 1965 through exhaustion of readily entrainable sediment in source areas upslope the volumes of the three cones range from c 9500 m3 to 403 600 m3 and imply average sediment accumulation rates of 8 44 mm yr 1 sediment erosion at one site was calculated to be 37 93 mm yr 1 averaged over the entire sediment source area paraglacial reworking of glacial drift by debris flows appears to have been the main agent of cone development at two sites but snow avalanches are thought to represent the main process of sediment transport at the largest cone these findings indicate that substantial debris cones may form and become inactive within 100 200 years of deglaciation implying that many late pleistocene parag

age and nature of paraglacial debris cones along the margins of the san rafael glacier chilean patagonia this study employs sedimentological indices and lichenometric dating on the lichen species plac opsis patagonica to investigate the nature and age of debris cones which have accumulated at the margins of the downwasting san rafael glacier in chilean patagonia these cones appear to have accumulated by the resedimentation of glacigenic deposits by debris flows with debris movement starting in the early 1980s cone activity follows a pattern of intense initial activity and sediment mobilisation followed by increased stability and colonization by vegetation three of the four cones had stabilized within 15 years of sediment movement initiation these features may be seen as being conditioned by glacial activity with second order controls provided by the local climate and sediment supply the cones have accumulated in a paraglacial environment

small scale cyclicity in alpine proglacial fluvial sedimentation abstract this paper compares contemporary sedimentation in an alpine proglacial braided river with deposits from inactive areas of the braidplain this approach allows confidence in determining the key characteristics of alpine proglacial braided river deposits the diagnostic features are 1 repeated coarse fine couplets in fine grained sediment

sediment export transient landscape response and catchment scale connectivity following rapid climate warming and alpine glacier recession abstract in the face of rapid climate warming rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins the extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export there is good reason to expect that glacier recession could increase basin scale sediment connectivity as sediment becomes less dependent on glacier surface transport proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity by using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment sand and gravel export from a basin with a rapidly retreating valley glacier the haut glacier d arolla from 1977 to 2014 modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity indeed there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area more recently we were able to show possible temperature control on sediment export which may only have become apparent because of the progressive development of better sediment connectivity however whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached we identified two possible examples of why first gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream maintaining disconnection of the upper basins second the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates thus the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export

a general model of paraglacial landscape response a unifying attribute of all forms of paraglacial response is that deglaciation results in the exposure of unstable or metastable sediment sources that are subsequently tapped by a wide variety of processes over a wide range of timescales the paraglacial period in different geomorphological contexts is therefore con ditioned by two variables glacially conditioned sediment release and rate of sediment reworking under steady state conditions the latter may be approximated by an exhaustion model in which sediment yield is related to the amount of remaining available sediment by a negative exponential function this model offers an approximation for the behaviour of primary paraglacial systems in which glacigenic sediment sources are not replenished the long term behaviour of secondary primarily uvial paraglacial systems in which sediment inputs include both in situ and reworked glacigenic sediment appears intrinsically more complex but consistent with an exhaustion model if initial sediment avai

inner gorge slot canyon system produced by repeated stream incision eastern alps significance for development of bedrock canyons abstract many inner bedrock gorges of the alps show abrupt downstream changes in gorge width as well as channel type and gradient as a result of epigenetic incision of slot canyons many slot canyons also are associated with older gorge reaches filled with quaternary deposits the age of slot canyons and inner bedrock gorges however commonly is difficult to constrain for the inner bedrock gorge system of the steinberger ache catchment eastern alps active slot canyons as well as older abandoned gorge reaches filled with upper wurmian proglacial deposits record three phases of gorge development and slot canyon incision a 234u 230th age of cement of 29 7 1 8 ka in fluvial conglomerates onlapping the flank of an inner gorge fits with late wurmian valley bottom aggradation shortly before pleniglacial conditions in addition the age indicates that at least the corresponding canyon reach must be older during advance of ice streams in the buildup of the last glacial maximum lgm the catchment was blocked and a proglacial lake formed bedrock gorges submerged in that lake were filled with fluviolacustrine deposits during the lgm the entire catchment was overridden by ice during post glacial reincision streams largely found again their preexisting inner bedrock canyons in some areas however the former stream course was missed and a slot canyon formed the distribution of pleistocene deposits the patterns of canyon incision and the mentioned u th cementation age however together record a further discrete phase of base level rise and stream incision well before the lgm the present course of steinberger ache and its tributaries is a patchwork of 1 slot canyons incised during post glacial incision 2 vestiges of slot canyons cut upon an earlier middle to late wurmian cycle of base level rise and fall 3 reactivated reaches up to 200 m in width of inner bedrock gorge that are watershed at present and more than at least 30 ka in age and 4 abandoned sediment filled reaches of bedrock canyons that also must be older than 30 ka and that are exposed alongside the active streams multi cyclic bedrock canyon systems composed of reaches of markedly different ages may be common in mountain ranges subject to glaciations and or mass wasting

recent glacier advances in the premier range british columbia aerial photography 1948 1985 and field investigations are used to reconstruct recent ice front fluctuations for 27 glaciers size range 0 63 17 9 km2 in the premier range british columbia rapid rates of frontal recession between ca 1930 and the mid fifties were followed by glacier readvance at many sites culminating in the 1973 1976 period when 90 of the monitored ice fronts were either advancing 68 or stable maximum downvalley advance was about 0 5 km median 90 m and 14 glaciers formed new terminal or lateral moraine ridges between 1970 and 1985 nine of these postdate 1976 one is dated to the 1980 1981 winter using tree rings the glacial advance is attributed to significant mass balance changes inferred from periods of increased winter precipitation ca 1951 1976 and low summer temperatures 1954 1968 measured at valemount warmer summers and reduced winter precipitation after 1976 account for the slight recession of ice fronts from maximum downvalley positions in the last few years

calendar dated early little ice age glacier advance at robson glacier british columbia canada dendrochronological studies at robson and bennington glaciers have provided the first calendar dating of an early little ice age glacier advance in north america dates derived from in situ stumps indicate that robson glacier began over riding forest between c ad 1142 and 1150 and continued until at least ad 1350 the highest rates of glacier advance c 3 8 m yr 1 occurred between ad 1214 and 1261 based on a series of kill dates from in situ stumps between c ad 1142 1214 and 1261 1350 rates were somewhat lower at c 2 2 5 m yr 1 this glacier advance terminated upvalley of the little ice age maximum position of robson glacier and there is no evidence at this site for glacial events between ad 1350 and 1783 however two smaller glaciers in the robson area and the main tongue of small river glacier have outermost little ice age moraines that date from the first decades of the ad 1700s all glaciers examined in the mount robson area have several well developed moraines dating from the period c

paraglacial modification of slope form the morphological consequences of paraglacial modification of valley side drift slopes are investigated at six sites in norway here paraglacial slope adjustment operates primarily through the development of gully systems whereby glacigenic sediment is stripped from the upper drift slope and redeposited in debris cones downslope this results in an overall lowering of average gradient by up to 4 5 along gully axes in general slope profile adjustment appears to be characterized by a convergence of slope profiles towards an equilibrium form with an upper rectilinear slope gradient at 29 4 and a range of concavities of approximately 0 0 to 0 4 after initial rapid incision further gully deepening is limited but gullies become progressively wider as sidewall gradients decline to c 25 after which parallel retreat appears to predominate the final form of mature paraglacial gully systems consists of an upper bedrock floored source area a mid slope area of broad gullies whose sidewalls rest at stable moderate gradients and a lower slope zone where gullies discharge onto the surfaces of debris cones and fans some gullies appear to have attained this final form and have stabilized following exhaustion of readily entrainable sediment within decades of gully initiation at most sites paraglacial activity has transformed steep drift mantled valley sides into gullied slopes where an average of c 2 3 m of surface lowering has taken place at the most active sites these average amounts imply minimum erosion rates averaging c 90 mm a 1 since gully initiation which highlights the extreme rapidity of paraglacial erosion of deglaciated drift mantled slopes copyright 1999 john wiley sons ltd

physical and chemical characterization of a spring flood event bench glacier alaska u s a evidence for water storage previous studies of alpine glaciers have demonstrated that as water discharge increases through the summer the predominant mode of subglacial drainage shifts from a distributed system to a more efficient conduit drainage system we observed an early melt season speed up and flood event lasting roughly 2 days in a small uncomplicated alaskan glacier that appears to have resulted from a sudden shift of the subglacial system in response to a significant accumulation of meltwater within the glacier calculated melt water inputs exceeded discharge before the event the implied change in storage over this 10 day period was equivalent to roughly 0 13 m averaged over the entire glacier bed the pattern of discharge and suspended sediment variations and the appearance of large ice chunks in the stream suggest that the speed up occurred during a period of establishment of new subglacial conduits a culminating flood and associated suspended sediment pulse appear to have marked the final establishment of the new section of subglacial conduit the flood ended the episode of high sliding velocity but released water with high solute concentrations that reflect relatively long contact time with sediments discharge of stored water inferred from high solute concentrations and lack of diurnal variation in discharge continued for at least 3 days while events such as this must recur through the melt season as the conduit system extends up glacier and the locus of meltwater inputs shifts their manifestations in the outlet stream will likely be more subdued later in the season

links between proglacial stream suspended sediment dynamics glacier hydrology and glacier motion at midtdalsbreen norway two hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining midtdalsbreen norway are modelled using multiple regression and time series techniques suspended sediment fluctuations are influenced by stream discharge variations diurnal hysteresis effects medium term sediment supply and transport variations and the recent suspended sediment concentration history of the stream they do not appear to be influenced by seasonal exhaustion or rainfall variations possible reasons for this are discussed large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations these sediment flushes correlate with periods of enhanced glacier motion they cannot be explained by enhanced sediment production by subglacial erosion but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and or configuration of the subglacial hydrological system seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration

radiocarbon chronology of depositional regimes in the western arctic ocean abstract the foraminiferal abundance and percentage of coarse ice rafted detritus ird define glacial deglacial and interglacial depositional regimes in ams radiocarbon dated box cores from the western arctic ocean sediment deposition rates are generally less than 0 5 cm ka for glacial regimes greater than this for deglacial regimes and greater than 1 2 cm ka for interglacial regimes these differences in deposition rates might account for the much lower average sedimentation rates for the last 780 ka of 1 3 mm ka in cores from the central arctic ocean if glacial regimes dominated this interval foraminiferal abundances are less than 500 g during glacial maxima and mostly higher than 2000 g during deglacial and interglacial regimes slightly higher coarse ird percentages occur in deglacial intervals 5 10 up to 30 compared with interglacial intervals mostly 5 which characterize the last 10 12 ka in the western arctic ocean glacial regimes occurred from about 40 to 11 ka except for a brief interglacial or deglacial interval around 24 28 ka in the central arctic ocean the coarsest deglacial events occurred prior to 45 ka the late wisconsin deglaciation sediments approximately 9 16 ka are difficult to detect in the central arctic ocean sediments because they are only slightly coarser than the holocene and in some box cores less coarse than the holocene a previously unrecognized coarse ird event occurred near the core tops 0 3 cm between 1500 and 3500 radiocarbon years ago in the western arctic ocean only sediment older than 40 ka is coarser than this recent ird event which might correspond to a neoglaciation recognized in the north atlantic and elsewhere

controls on slope to channel fine sediment connectivity in a largely ice free valley hoophorn stream southern alps new zealand there has been little work to date into the controls on slope to channel fine sediment connectivity in alpine environments largely ice free for most of the holocene characterization of these controls can be expected to result in better understanding of how landscapes relax from such perturbations as climate shock we monitored fine sediment mobilization on a slope segment hydrologically connected to a stream in the largely ice free 8 3 km2 hoophorn valley new zealand gerlach traps were installed in ephemeral slope channels to trap surficial material mobilized during rainfall events channel sediment flux was measured using turbidimeters above and below the connected slope and hysteresis patterns in discharge suspended sediment concentrations were used to determine sediment sources over the 96 day measurement period sediment mobilization from the slope segment was limited to rainfall events with increasingly larger particles trapped as event magnitude increased less than 1 of the mass of particles collected during these events was fine sediment during this period 714 t of suspended sediment was transported through the lower gauging station 60 of it during rainfall events channel sediment transfer patterns during these events were dominated by clockwise hysteresis interpreted as remobilization of nearby in channel sources further suggesting limited input of fine sediment from slopes in the lower valley strong counterclockwise hysteresis representing input of fine sediment from slope segments was restricted to the largest storm event jd2 2009 when surfaces in the upper basin were activated the results indicate that the slopes of the lower hoophorn catchment are no longer functioning as sources of fine sediment but rather as sources of coarse material with flux rates controlled by the intensity and duration of rainfall events although speculative these findings suggest a shift to a coarse sediment dominated slope to channel transfer system as the influence of pre holocene glacial erosion declines copyright 2011 john wiley sons ltd

the quaternary stratigraphic record of british columbia evidence for episodic sedimentation and erosion controlled by glaciation the terrestrial quaternary stratigraphic record of british columbia is largely a product of brief depositional events separated by long periods of nondeposition and erosion thick stratified quaternary sediments are present mainly in valleys and coastal lowlands and accumulated during periods of growth and decay of the cordilleran ice sheet at glacial maxima till was deposited over large areas of low and moderate relief however at the same time much of the landscape was eroded by glaciers sedimentation has been more restricted and has occurred at lower rates during nonglacial periods than during glaciations on land the only important sediment accumulation sites during nonglacials have been lakes floodplains and fans however large amounts of sediment have accumulated offshore especially in fjords and basins such as the strait of georgia because of the restricted aspect of sedimentation during nonglacials the stratigraphic record of these periods is meagre in most places true nonglacial uni

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