geomorphological evidence for jokulhlaups from kverkfjoll volcano iceland abstract jokulhlaups glacial outburst floods are known to have drained along the jokulsa a fjollum river in iceland during the holocene however little is known about their number age source and flow characteristics this paper provides detailed geomorphological evidence for jokulhlaups that have routed from the kverkfjoll ice margin and hence into the jokulsa a fjollum erosional evidence of jokulhlaups from kverkfjoll includes gorges cataracts spillways subaerial lava steps and valley wide scoured surfaces depositional evidence includes wash limits boulder bars cataract fill mounds terraces slackwater deposits and outwash fans some of these landforms have been documented previously in association with jokulhlaups however subaerial lava surfaces that have been scoured of the upper clinker gorges within pillow hyaloclastite ridges gorges between pillow hyaloclastite ridges and subaerial lava flows subaerial lava lobe steps cataract fill mounds and boulder run ups are previously undocumented in the literature these landforms may therefore be diagnostic of jokulhlaups within an active volcanic rifting landscape the nature and spatial distribution of these landforms and their stratigraphic association with other landforms suggest that there have been at least two jokulhlaups through kverkfjallarani the biskupsfell eruption occurred between these two jokulhlaups kverkfjallarani jokulhlaups were very strongly influenced by topography geology and interevent processes that together determined the quantity and nature of sediment availability such controls have resulted in jokulhlaups that were probably fluidal turbulent and supercritical over large areas of the anastomosing channel bed kverkfjallarani jokulhlaups would have had highly variable hydraulic properties both spatially and temporally the knowledge of flow characteristics that can be gained from jokulhlaup impacts has implications for recognising jokulhlaups in the rock record and for hazard analysis and mitigation within similar landscapes and upon other glaciated volcanoes

surface based transport model for mixed size sediment we present a transport model for mixed sand gravel sediments fractional transport rates are referenced to the size distribution of the bed surface rather than subsurface making the model completely explicit and capable of predicting transient conditions the model is developed using a new data set of 48 coupled observations of flow transport and bed surface grain size using five different sediments the model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions the model uses the full size distribution of the bed surface including sand and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models the model shares some common elements with two previous surface based transport models but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow transport rate and sediments

flux of debris transported by ice at three alaskan tidewater glaciers the stability of tidewater terminus is controlled by glacial dynamics calving processes and sedimentary processes at the grounding line an investigation of grounding line sediment dynamics and morainal bank sediment budgets in glacier bay alaska u s a has yielded data that enable us to determine the debris fluxes of grand pacific margerie and muir glaciers debris flux ranges from 10 5 to 10 6 m 3 a 1 one to two orders of magnitude lower than the glacifluvial sediment fluxes 10 6 10 7 m 3 a 1 combined these fluxes represent the highest yields known for glacierized basins large debris fluxes reflect the combined effecrs of rapid glacier flow driven by the maritime climate of southeast alaska and highly erodible bedrock englacial debris distribution is affected by valley width and relief both of which control the availability of sediment the number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines at the terminus iceberg rafting removes up to two orders of magnitude more sediment from the ice proximal environment than is deposited by melt out or is dumped during calving events rough estimates of the sediment flux by deforming beds suggests that soft bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice

coarse sediment dynamics in a proglacial fluvial system fagge river tyrol abstract alpine regions are strongly affected by the global climate change alpine glaciers have had a negative net balance since the end of the little ice age lia proglacial areas with freshly exposed subglacial sediments are expanding due to the retreat of glaciers these sediments moraines tills glaciofluvial deposits etc are unconsolidated nearly unvegetated and therefore unstable and highly vulnerable to surface changes triggered by geomorphological processes particularly during heavy rainfall events glacial and glaciofluvial deposits are remobilized and transported within the fluvial system this study is focused on rapidly changing surfaces in the proglacial fluvial system of the fagge river which drains the gepatschferner one of the biggest glaciers in austria and is located in the kaunertal austria the field site covers an area from the snout of the glacier 2206 m a s l to the outlet of the fagge river into the gepatsch reservoir at 1750 m a s l the main goal of this study is to measure surface changes and quantify mass balances of important sediment sources alluvial plains bars in the proglacial area which are directly connected to the fluvial system for this purpose multiple terrestrial laser scans are performed with an optech ilris 36d laser scanner during the field season in 2011 and 2012 several sediment sources were scanned at least twice significant surface changes occurred during the investigation period mainly caused by an extreme flood event after heavy rain on august 26 2012 large amounts of sediment 70 000 m3 were remobilized especially in the upper parts of the proglacial area and were accumulated further downstream during this event

measurement and parameterization of albedo variations at haut glacier d arolla switzerland spatial and temporal variations of surface albedo on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described correlation and regression analyses are used to explain the albedo variations in terms of independent meteorological and surface property variables parameterizations are developed which allow estimation of albedo variation in surface energy balance models snow albedo is best estimated from accumulated daily maximum temperatures since snowfall on deep snow 0 5 cm w e depth a logarithmic function is used while on shallow snow 0 5 cm w e depth an exponential function is used to enable the albedo to decay to the underlying ice or debris albedo the transition from deep to shallow snow is calculated as a function of decreasing snow depth combined r 2 0 65 this new parameterization performs better than earlier schemes because accumulated daily maximum temperatures since snowfall correlate strongly with snow grain size and impurity concentration the main physical controls on snow albedo ice albedo may be parameterized by its relationship to elevation r 2 0 28 but this approach results in only a small improvement over the assumption of a constant mean ice albedo

geometry bed topography and drainage system structure of the haut glacier d arolla switzerland as part of an integrated study of the hydrology meltwater quality and dynamics of the haut glacier d arolla switzerland the glacier s drainage network structure was determined from patterns of dye recovery in 342 injection experiments conducted from 47 moulins distributed widely across the glacier this structure was compared with theoretical predictions based upon reconstructed patterns of water flow governed by a the subglacial hydraulic potential surface and b the subglacial bedrock surface these reconstructions were based on measurements of ice surface and bedrock topography obtained by a combination of ground survey and radio echo sounding techniques the two reconstructions simulate the drainage system structures expected for a closed channels in which water is pressurized by the overlying ice and b gravity driven open channel flow the closed channel model provides the best fit to the observed structure even though theoretical calculations suggest that under summer discharge conditions open channel flow may be widespread beneath the glacier possible reasons for this apparent discrepancy are discussed

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

proglacial lakes character behaviour and geological importance proglacial lakes are ubiquitous within the quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information present deglaciation is increasing the number and size of proglacial lakes around the world this study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective we show how ice marginal or ice contact lakes and other distal proglacial lakes can be distinguished from each other by geomorphological sedimentological chemical and biological characteristics the key controls on proglacial lake geomorphology and sedimentology are outlined and discussed proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation proglacial lakes interrupt meltwater flux and are very efficient sediment traps hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the quaternary overall analyses of proglacial lakes can provide a valuable insight into i patterns character and behaviour of mountain glaciers ice sheets and glaciations and ii the impacts of past present and future deglaciation

paraglacial gullying of sediment mantled slopes a case study of colletthogda kongsfjorden area west spitsbergen svalbard this paper evaluates the paraglacial evolution of a sediment mantled slope in a polar maritime environment the intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover the rapid melting of dead ice cores controls gully formation this leads to slope form modifi cation gully profi le gradients are reduced from a mean of 35 to a mean ranging between 10 and 15 profi le evolution results from the collapse of glacier lateral moraine all data mean slope angle of individual gullies frequency distribution of slope angles fractional distance to the apex gullying index volume of debris mobilized vertical erosion rate tend to increase with increasing deglaciation age and the duration of paraglacial activity vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead ice melting the full sequence of paraglacial slope adjustment gully incision stabilization may occur rapidly at the study site i e within two decades finally a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

quantifying sediment storage in a high alpine valley turtmanntal switzerland the determination of sediment storage is a critical parameter in sediment budget analyses but in many sediment budget studies the quantification of magnitude and time scale of sediment storage is still the weakest part and often relies on crude estimations only especially in large drainage basins 100 km2 we present a new approach to storage quantification in a meso scale alpine catchment of the swiss alps turtmann valley 110 km2 the quantification of depositional volumes was performed by combining geophysical surveys and geographic information system gis modelling techniques mean thickness values of each landform type calculated from these data was used to estimate the sediment volume in the hanging valleys and the trough slopes sediment volume of the remaining subsystems was determined by modelling an assumed parabolic bedrock surface using digital elevation model dem data a total sediment volume of 781 3 106 1005 7 106 m3 is deposited in the turtmann valley over 60 of this volume is stored in the 13 hanging valleys moraine landforms contain over 60 of the deposits in the hanging valleys followed by sediment stored on slopes 20 and rock glaciers 15 for the first time a detailed quantification of different storage types was achieved in a catchment of this size sediment volumes have been used to calculate mean denudation rates for the different processes ranging from 0 1 to 2 6 mm a based on a time span of 10 ka as the quantification approach includes a number of assumptions and various sources of error the values given represent the order of magnitude of sediment storage that has to be expected in a catchment of this size copyright 2009 john wiley sons ltd

supra glacial deposition and flux of catastrophic rock slope failure debris south central alaska the ongoing debate over the effects of global environmental change on earth s cryosphere calls for detailed knowledge about process rates and their variability in cold environments in this context appraisals of the coupling between glacier dynamics and para glacial erosion rates in tectonically active mountains remain rare we contribute to filling this knowledge gap and present an unprecedented regional scale inventory of supra glacial sediment flux and hillslope erosion rates inferred from an analysis of 123 large 0 center dot 1km2 catastrophic bedrock landslides that fell onto glaciers in the chugach mountains alaska as documented by satellite images obtained between 1972 to 2008 assuming these supra glacial landslide deposits to be passive strain markers we infer minimum decadal scale sediment yields of 190 to 7400tkm 2yr 1 for a given glacier surface cross section impacted by episodic rock slope failure these rates compare to reported fluvial sediment yields in many mountain rivers but are an order of magnitude below the extreme sediment yields measured at the snouts of alaskan glaciers indicating that the bulk of debris discharged derives from en glacial sub glacial or ice proximal sources we estimate an average minimum para glacial erosion rate by large episodic rock slope failures at 0 center dot 5 0 center dot 7mmyr 1 in the chugach mountains over a 50 yr period with earthquakes likely being responsible for up to 73 of this rate though ranking amongst the highest decadal landslide erosion rates for this size of study area worldwide our inferred rates of hillslope erosion in the chugach mountains remain an order of magnitude below the pace of extremely rapid glacial sediment export and glacio isostatic surface uplift previously reported from the region

the impact of pro glacial lakes on downstream sediment delivery in norway glacier recessions caused by climate change may uncover pro glacial lakes that form important sedimentation basins regulating the downstream sediment delivery the impact of modern pro glacial lakes on fluvial sediment transport from three different norwegian glaciers nigardsbreen engabreen and tunsbergdalsbreen and their long term development has been studied all of these lakes developed in modern times in overdeepened bedrock basins the recession of nigardsbreen uncovered a 1 8 km long and on average 15 m deep pro glacial lake basin during 1937 to 1968 since then the glacier front has been situated entirely on land and the sediment input and output of the lake has been measured the suspended sediment transport into and out of the lake averaged 11 730 t yr 1 and 2340 t yr 1 respectively thus 20 remained in suspension at the outlet the measured mean annual bedload supplied to the lake was 11 800 t yr 1 giving a total transport of 23 530 t yr 1 which corresponds to a specific sediment yield of 561 t km 2 yr 1 a 1 9 km long and up to 90 m deep pro glacial lake basin downstream from engabreen glacier was uncovered during 1890 to 1944 the average suspended sediment load delivered from the glacier during the years 1970 1981 amounted to 12 375 t yr 1and the transport out of the lake was 2021 t yr 1 giving an average of 16 remaining in suspension the mean annual bedload was 8000 t yr 1 thus the total transport was 20 375 t yr 1 giving a specific sediment yield of 566 t km 2 yr 1 for tunsbergdalsbreen glacier measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr 1 from 1987 to 1993 the recession of the glacier uncovered a small pro glacial lake 0 3 km long and around 9 m deep downstream from this the suspended sediment load measured in 2009 was 28 000 t yr 1 indicating that as much as 64 remained in suspension flow velocity grain size of sediment and morphology of the lake are important factors controlling the sedimentation rate in the pro glacial lakes a survey of the sub glacial morphology of tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier the largest is 4 km long and 100 m deep when the glacier melts back they will become lakes and act as sedimentation basins despite an expected increase in sediment yield from the glacier little sediment will pass these lakes and downstream sediment delivery will be reduced markedly beneath nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected 2014 the authors earth surface processes and landforms published by john wiley sons ltd

influence of subglacial drainage conditions on the velocity distribution within a glacier cross section substrate properties and hydrological conditions at the base of haut glacier d arolla switzerland are nonuniform the thickness and grain size of subglacial sediment vary on length scales less than one ice thickness whereas hydrological conditions vary seasonally and on length scales of about one ice thickness transverse to ice motion there is a close relationship between the annually averaged velocity field and this nonuniformity of bed conditions basal motion dominates in an area with large water level variations in boreholes whereas ice deformation contributes significantly to total movement elsewhere localized enhanced basal motion occurs primarily in summer especially during a july spring event but this motion is barely discernible in annually averaged surface velocity measurements because transverse coupling suppresses surface expression of the basal motion discontinuity these results highlight the need to include representations of bed nonuniformity in models of glacier flow and to consider ice deformation and basal motion as interdependent processes

structure composition and bulk properties of upland stream gravels upland gravel bedded streams in the u k have received only scant attention from both hydrologists and sedimentologists but are worthy of further investigation the sedimentology of three small streams in teesdale in the pennines has been examined in detail grain size characteristics bedforms structure composition and packing characteristics of these deposits are described and compared where appropriate with published information it is argued that a fuller appreciation of gravel bed composition and morphology should eventually contribute to an improved understanding of sediment transport and deposition mechanisms and hence to improved accuracy in sediment transport and deposition estimates

the influence of ground ice distribution on geomorphic dynamics since the little ice age in proglacial areas of two cirque glacier systems holocene glaciers have contributed to an abundance of unstable sediments in mountainous environments in permafrost environments these sediments can contain ground ice and are subject to rapid geomorphic activity and evolution under condition of a warming climate to understand the influence of ground ice distribution on this activity since the little ice age lia we have investigated the pierre ronde and rognes proglacial areas two cirque glacier systems located in the periglacial belt of the mont blanc massif for the first time electrical resistivity tomography temperature data loggers and differential global positioning systems dgps are combined with historical documents and glaciological data analysis to produce a complete study of evolution in time and space of these small landsystems since the lia this approach allows to explain spatial heterogeneity of current internal structure and dynamics the studied sites are a complex assemblage of debris covered glacier ice rich frozen debris and unfrozen debris ground ice distribution is related to former glacier thermal regime isolating effect of debris cover water supply to specific zones and topography in relation with this internal structure present dynamics are dominated by rapid ice melt in the debriscovered upper slopes slow creep processes in marginal glacigenic rock glaciers and weak superficial reworking in deglaciated moraines since the lia geomorphic activity is mainly spatially restricted within the proglacial areas sediment exportation has occurred in a limited part of the former rognes glacier and through water pocket outburst flood and debris flows in pierre ronde both sites contributed little sediment supply to the downslope geomorphic system rather by episodic events than by constant supply in that way during holocene and even in a paraglacial context as the recent deglaciation proglacial areas of cirque glaciers act mostly as sediment sinks when active geomorphic processes are unable to evacuate sediment downslope especially because of the slope angle weakness

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

modelling ice bed coupling during a glacier speed up event haut glacier d arolla switzerland fischer u h mair d kavanaugh j l willis i nienow p hubbard b 2011 modelling ice bed coupling during a glacier speed up event haut glacier d arolla switzerland hydrological processes 2599 1361 1372

alpine subglacial hydrology abstract the size and shape of subglacial flow pathways exert a strong influence over the pressure and speed at which meltwaters are routed through glaciers these characteristics in turn influence glacier sliding velocity and the quantity and quality of bulk meltwaters discharging from glaciers in this paper we summarise four empirical research approaches that have been developed to improve our understanding of the subglacial hydrology of predominantly temperate based alpine glaciers investigations of bulk meltwater discharge and chemistry tracer studies proglacial bedrock investigations and borehole investigations as a result of linking these studies to conceptual or numerical models three arborescent and four non arborescent or distributed subglacial drainage configurations are described these drainage networks may be neither spatially nor temporally persistent but may compete with and replace each other on a seasonal basis a qualitative model of the temporal and spatial evolution of a typical alpine subglacial drainage system is advanced on the basis of research conducted at haut glacier d arolla switzerland

paraglacial response of steep sediment mantled slopes to post little ice age glacier recession in the central swiss alps this research assesses the morphological consequences of recent post little ice age paraglacial reworking of valley side sediment mantles in the european alps it aims to identify the extent and conditioning factors of slope adjustment at sites in the swiss alps model the temporal pattern and assess the rates of sediment reworking involved gully systems have cut into steep high level lateral moraines and debris cones have accumulated downslope debris flow is the dominant agent of sediment transfer factors controlling the extent of this activity include moraine slope gradient relief and moisture availability gullies appear to have reached their maximum dimensions within ca 50 yr of deglaciation after which gully relief is reduced by removal of inter gully slopes and gully infilling within 80 140 yr on the most recently deglaciated terrain minimum erosion rates average ca 95 mm yr 1 since gully initiation greatly exceeding normal erosion rates in other environments mean annual accumulation of a single debris cone since ice retreat was calculated to be ca 30 mm yr 1 implications of these findings are applied to patterns of paraglacial sediment mantled slope adjustment conceptualising paraglacial landscape response in terms of a sediment release exhaustion model and paraglacial landform succession copyright 2005 john wiley sons ltd

a multi dimensional analysis of pro glacial landscape change at solheimajokull southern iceland proglacial landscapes are some of the most active on earth previous studies of proglacial landscape change have often been restricted to considering either sedimentological geomorphological or topographic parameters in isolation and are often mono dimensional this study utilised field surveys and digital elevation model analyses to quantify planform elevation and volumetric proglacial landscape change at solheimajokull in southern iceland for multiple time periods spanning from 1960 to 2010 as expected the most intense geomorphological changes persistently occurred in the ice proximal area during 1960 to 1996 the proglacial river was relatively stable however after 2001 braiding intensity was higher channel slope shallower and there was a shift from overall incision to aggradation attributing these proglacial river channel changes to the 1999 jokulhlaup is ambiguous because it coincided with a switch from a period of glacier advance to that of glacier retreat furthermore glacier retreat of 40 m yr 1 coincided with ice marginal lake development and these two factors have both altered the proglacial river channel head elevation from 2001 to 2010 progressive increase in channel braiding and progressive downstream incision occurred these together probably reflecting stream power due to increased glacier ablation and reduced sediment supply due to trapping of sediment by the developing ice marginal lake overall this study highlights rapid spatiotemporal proglacial landscape reactions to changes in glacial meltwater runoff regimes glacier terminus position sediment supply and episodic events such as jokuhlaups recognising the interplay of these controlling factors on proglacial landscapes will be important for understanding the geological record and for landscape stability assessments

measurement and parameterization of aerodynamic roughness length variations at haut glacier d arolla switzerland spatial and temporal variations in aerodynamic roughness length z0 on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described based on measure ments of surface microtopography the validity of the microtopographic z0 measurements is established through comparison with independent vertical wind profile z0 measurements over melting snow slush and ice the z0 variations are explained through correlation and regression analyses using independent measurements of meteorological and surface variables and parameterizations are developed to calculate z0 variations for use in surface energy balance melt models several independent variables successfully explain snow z0 variation through their correlation with increasing surface roughness caused by ablation hollow formation during snow melt non linear parameterizations based on either accumulated melt or accumulated daily maximum temperatures since the most recent snowfall explain over 80 of snow z0 variation the z0 following a fresh snowfall on an ice surface is parameterized based on relationships with the underlying ice z0 snow depth and accumulated daily maximum temperatures none of the independent variables were able to successfully explain ice z0 variation although further comparative studies are needed the results lend strong support to the microtopo graphic technique of measuring z0 over melting glacier surfaces

hyperconcentrated flow and sediment transport at steep slopes in order to simulate a fine material slurry of a debris flow a clay suspension of various concentrations was recirculated in a steep flume the effect of an increasing fluid density and viscosity on the flow behavior and the bed load transport capacity of the flow was examined viscous effects were found to become important below a limiting particle reynolds number of about 10 above this limiting value density effects cause an increase in the bed load transport rates as compared to similar conditions with clear water as transporting fluid the experimental data in this range can be described with conventional newtonian formulas and is analyzed together with other bed load transport data two different calculation schemes are proposed for the steep slope range is n n 10 where the bed load concentration is significant with respect to the total flow depth below the critical particle reynolds number of 10 the bed load transport rates decreased strongly

reconstructing morphometric change in a proglacial landscape using historical aerial photography and automated dem generation this paper explores the feasibility of using historical aerial photographs and digital photogrammetric procedures to reconstruct morphometric landscape changes in a proglacial setting of the southern coast mountains british columbia canada the photographic record includes 12 sets of vertical photography obtained at a range of large to medium nominal scales for the period 1947 to 1997 an automated procedure of digital elevation model dem extraction was employed and details of morphometric change were assessed by differencing the dem surfaces obtained for different dates of photography results are used to describe terrain surface changes associated with glacier recession moraine gully erosion and forest growth in the glacial forefield methods are reviewed for the estimation and handling of systematic and random vertical errors in the dems that are suitable for this type of environment where there are no historical surveys or monuments to use as a common benchmark and only natural features are available for establishing ground control digital photogrammetry applied to scanned archived photography can be used to generate high resolution sub meter dem surfaces of proglacial terrain suitable for quantifying decadal scale morphometric changes that have occurred since the mid 20th century to recent times potential applications of these techniques and the associated historical data are discussed

channel pattern of proglacial rivers topographic forcing due to glacier retreat this is the peer reviewed version of the following article marren p m toomath s c 2014 channel pattern of proglacial rivers topographic forcing due to glacier retreat earth surface processes and landforms 39 7 943 951 doi 10 1002 esp 3545 which has been published in final form at http onlinelibrary wiley com doi 10 1002 esp 3545 abstract this article may be used for non commercial purposes in accordance with wiley terms and conditions for self archiving

surface texture analysis of a high resolution dtm interpreting an alpine basin abstract this study focuses on a geomorphometric analysis of a small headwater basin of the dolomites eastern italian alps the analysis of the fine scale surface morphology was performed on a high resolution digital elevation model cell size 2 m derived from an airborne lidar survey the topography was synthesized by a set of spatial statistical indexes representing a signature of the local surface morphology and the relationships between the geomorphometric indexes and morphological features were evaluated the studied basin was then segmented by means of a fuzzy k means classification algorithm into different spatial subdomains characterized by specific local geomorphic signatures this method allows us to objectively choose the optimal combination of the number of classes and degree of fuzziness characterizing the studied basin accordingly the analysis can be adopted to the characteristics of the studied area improving the interpretation of surface morphology and offering a valuable tool for comparative analysis between different geomorphological contexts the results of the classification were compared with the actual surface morphology based on high resolution orthophotos aerial photos and field surveys

discharge and sediment supply controls on erosion and deposition in a dynamic alluvial channel research on dynamic alluvial channels has recognised the influence on river channel change of both discharge and sediment supply although it has proved difficult to measure the latter this paper presents the first accurate data from a dynamic alluvial channel that describe the interrelated effect on channel morphological change of both discharge and sediment supply variations over different timescales reliable information on the spatial patterns of erosion and deposition were obtained using combined photogrammetry and tacheometric survey of the meltwater stream of a glacierised catchment over a 5 week period over the full time period the morphological evidence suggested the passage of a wave of sediment counter intuitively the period of aggradation was associated with increasing diurnal peak and base flow discharge magnitude while degradation occurred during a period of steady peak diurnal discharge this suggests that the channel change was controlled by variation in upstream sediment supply over a shorter timescale information on diurnal changes in morphology reveals that although discharge was responsible for some aspects of channel change this was modified by the effects of upstream sediment supply consideration of the spatial patterns of erosion and deposition at the within reach scale reinforces this point with spatial aspects of morphological change being driven by discharge and sediment supply fluctuations but modified by spatial feedbacks associated with internal channel morphology the implications of these findings for fluvial geomorphology in general are considered

seasonal changes in the morphology of the subglacial drainage system haut glacier d arolla switzerland dye tracing techniques were used to investigate the glacier wide pattern of change in the englacial subglacial drainage system of haut glacier d arolla during the ablation seasons of 1990 and 1991 analysis of breakthrough curve characteristics indicate that over the course of a melt season a system of major channels developed by headward growth at the expense of a hydraulically inefficient distributed system by the end of the melt season this channel system extended at least 3 3 km from the snout of the 4 km long glacier and drained the bulk of supraglacially derived meltwater passing through the glacier the upper limit of the channel system closely followed the retreating snowline up glacier rates of headward channel growth reached c 65 m d 1 although these rates decreased in the upper 1 km of the glacier where snowline retreat exposed a patchy firn aquifer it appears that the removal of snow with its high albedo and significant water storage capacity from the glacier surface resulted in a dramatic increase in the volume of runoff into moulins and in the peakedness of daily runoff cycles this induced transient high water pressures within the distributed drainage system which caused it to evolve rapidly into a channelised system it is therefore likely that at a local scale channel growth occurred down glacier from moulins and that the overall up glacier directed pattern of channel formation was caused by the retreating snowline exposing new moulins and crevasses to inputs of ice derived meltwater damping of diurnal melt inputs by storage in the firm aquifer accounts for the slowing of channel growth in the upper glacier 1998 john wiley sons ltd

hydrological controls on diurnal ice flow variability in valley glaciers 1 this paper uses a combination of field data and three dimensional modeling to investigate the spatial variability in basal conditions required to induce observed fluctuations in diurnal ice velocity at haut glacier d arolla switzerland a network of surface velocity markers was observed at intervals of as little as four hours over diurnal cycles in both winter and late summer winter motion showed limited diurnal variability presumably due to the absence of supraglacial meltwater inputs by contrast diurnal fluctuations in ice motion were recorded in summer across the lower and upper glacier in the lower glacier surface velocities were intimately linked to hydrological forcing in the vicinity of a subglacial channel previously observed diurnal excursions of meltwater away from the channel should reduce areas of basal drag adjacent to the channel thereby impacting on ice dynamics using a first order ice flow approximation we investigated the distribution of basal shear traction adjacent to the channel necessary to replicate the observed surface velocity field during periods of rapid ice motion the modeling suggests that the observed variations in diurnal velocity will only occur with extensive reductions in basal drag across a transverse zone of up to 560 m across well beyond the immediate vicinity and previously observed extent of diurnal excursions of meltwater away from the subglacial channel

measurements in a braided river chute and lobe 2 sorting of bed load during entrainment transport and deposition grain size distributions of bed material bed load and bar head deposition were sampled during the evolution of a chute and lobe in the braided gravel bed sunwapta river alberta although bed shear stress and total bed load transport rate varied substantially within the reach and from day to day ferguson et al this issue the median diameter d50 of bed load was remarkably constant the bed initially fined from chute to bar head but became more uniform sediment deposited on the bar head also had a near constant d50 similar to that of the bed load truncated at the same lower size limit both load and deposition were finer on average than the bed suggesting overall selective transport despite little sign of local sorting in contrast to median diameters maximum sizes dmax of sediment in motion and deposited on the bar head varied substantially and showed a weak but significant dependence on shear stress inferring selective entrainment from this evidence alone would be dubious because dmax was also found to increase systematically with the mass of sediment sampled however two different methods of analysis of fractional transport rates throughout the size range also showed size selective entrainment and transport in the marginal transport conditions of this study size sorting appears to occur but only weakly and mainly in the coarser fractions

proglacial sediment trapping in recently formed silt lake upper lillooet valley coast mountains british columbia the sedimentology of proglacial silt lake was assessed by lake sediment coring and monitoring of lacustrine processes during a late summer period of high glacier melt to characterize sediment delivery from the heavily glacierized catchment and investigate the sediment trapping dynamics of this upland lake a complete varve chronology was established for a distal basin of the lake which was exposed by lillooet glacier retreat between 1947 and 1962 the varve record showed decreasing sedimentation rates in the basin while the glacier retreated and as the lake became free of ice contact in the early 1970s although recession has continued over recent decades and glacier proximity to the lake has therefore continued decreasing lacustrine sedimentation rates are now accelerating due to changing basin morphometry caused by delta progradation over shorter time scales lake sedimentation patterns respond to changing runoff conditions including late summer glacier melt intensity intra annual flooding events diumal runoff fluctuations and within lake turbidity currents turbidity currents included quasi regular flows during high diurnal discharges and an episodic flushing of temporarily stored sediment from the sandur or delta at a time of low stage suspended sediment yield to silt lake is estimated to exceed 103 mg km 2 a 1 a magnitude that surpasses previous local and regional yield estimates for the glacierized headwaters of the lillooet river valley since silt lake currently traps a significant prooportion of that upland sediment supply and the trapping efficiency of the basin has been variable at decadal time scales the formation and continued development of lilt lake has likely had a significant influence on downstream sediment delivery lacustrine sediment based proxies of long term hydroclimatic variability being developed in glacially distal settings should include provisions for dynamic sediment trapping effects in upstream water bodies that often form in the active proglacial environment copyright 2008 john wiley sons ltd

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

fission track age 400 000 yr of the rockland tephra based on inclusion of zirco grains lacking fossil fission tracks abstract a zircon fission track age of about 400 000 yr b p has been determined for the rockland tephra a widespread pyroclastic layer in northern california and western nevada new ages of zircon separates from both proximal and distal exposures of this layer range from 370 000 to 460 000 yr ages of the best material provide a narrower range from 370 000 yr for unwelded ash flow tuff to 420 000 yr for distal air fall ash that appears to be uncontaminated by clastic detritus or xenocrysts detrital or xenocrystic grains in the ash flow tuff may have been annealed during emplacement and cooling of the tuff detrital and xenocrystic zircons are identified on the basis of their physical characteristics and distinctly older ages independent stratigraphic and magnetostratigraphic data constrain the age of the rockland tephra between 300 000 and 600 000 yr a range that is compatible with the fission track age zircon grains containing no spontaneous fossil tracks are regarded as part of the normal population of comagmatic grains because maximum ages calculated for these grains form a population that mimics the distribution of ages of individual zircon grains that contain fossil tracks modal ages of both groups fall between 250 000 and 500 000 yr induced fission tracks from grains that lack fossil tracks are included in the age calculations resulting in significantly younger and more coherent dates than would result if these tracks had been omitted especially those of the finer grained distal samples

temporal patterns of suspended sediment yield following moderate to extreme hydrological events recorded in varved lacustrine sediments a 487 year annually laminated varved sediment record from nicolay lake cornwall island in the canadian high arctic was evaluated to determine the impact that years with high sediment yields had on sediment yields in subsequent years all of the 40 largest years showed evidence for increased sediment yield in the subsequent 10 30 years the positive anomalies in lagging years were approximately scaled according to the size of the initiating year although many intermediate years 25 to 100 year recurrence showed weak or variable responses the smallest events considered 10 to 25 year recurrence showed a consistent but low amplitude response additionally the 10 year events revealed frequent negative sediment yield anomalies in the preceding decade this behaviour was interpreted as a frequent sediment activation cycle initiated by the modest year and leading to sediment yield hysteresis lasting 15 25 years the largest years greater than 50 year recurrence showed consistently above average sediment yields in the preceding decade in part due to the frequent occurrence of moderate q10 years it is hypothesized that temporary storage of sediment and previous initiation of erosion sites resulted in extraordinary sediment yields during intense summer rainfall events this study demonstrates the potential use of varved lake sediment records to improve our understanding of long term sediment dynamics these records present an opportunity to further develop and test sediment dynamic and routing models to gain insight into the interaction of time and space in fluvial and sediment delivery processes copyright 2002 john wiley sons ltd

seasonal variations in ice deformation and basal motion across the tongue of haut glacier d arolla switzerland records of surface motion englacial tilt and repeat inclinometry are used to determine patterns of surface internal and basal motion across the tongue of haut glacier d arolla switzerland over temporal scales ranging from days to months findings are interpreted with reference to contemporaneous measurements of subglacial water pressures and prior knowledge of the glacier s subglacial drainage system structure long term inclinometry results show pronounced extrusion flow over a subglacial drainage axis with basal velocities up to twice those measured at the glacier surface deformation profiles are more conventional away from the drainage axis with basal velocities 60 70 of surface velocities comparison of long term tilt rates from repeat inclinometry and englacial tilt meters shows close correspondence englacial tiltmeter data are used to reconstruct internal velocity profiles and to split surface velocities into internal deformation and basal motion contributions over spring summer and autumn winter periods although spatial patterns of surface movement are similar between periods patterns of internal and basal motion are not results are interpreted in terms of the location of sticky and slippery spots with temporally changing patterns of basal drag reflecting changing distributions of water pressure

the effects of kinetic sorting on sediment mobility on steep slopes in poorly mobile static armour sorting is usually considered the result of hiding exposure effects we called this effect static sorting in opposition to very efficient grain to grain mechanisms produced by a mobile mixture called kinetic sorting we hypothesized that kinetic sorting can be an important contributor to the morphodynamics of mountain streams and attempted to demonstrate this with new flume experiments two long runs were produced with natural poorly sorted sediments and with transport stages of the coarse fraction defined by the ratio between the shear stress and the critical shear stress for transport smaller and higher than 1 respectively both runs produced an efficient transfer downstream of the injected material but with a major difference the first run no kinetic sorting produced permanent armour figuring clusters akin to what has already been observed in similar experiments the second run with kinetic sorting also produced bed armouring but this armour was periodically totally destroyed leading to substantial bed erosion this phenomenon was explained by kinetic sorting the effects of which are to produce an efficient downward migration of fine materials and bed surface armouring the consequence is that fine materials are hidden to the flow during aggradation allowing the slope to attain values much steeper than would have been expected at equilibrium for the mixture however whereas the surface armouring tends to stabilize the bed construction of a layer of fine sediments at the subsurface also contributes to making it very unstable these two contradictory effects explain the complex bed behaviours and the existence of very large bedload and slope fluctuations copyright 2014 john wiley sons ltd

continuous measurements of bedload transport rates in a small glacial river catchment in the summer season spitsbergen abstract the study on bedload transport was conducted on the gravel bed scott river catchment with a glacial alimentation regime located in the nw part of the wedel jarlsberg land spitsbergen with subpolar climatic conditions in the melt season of 2010 bedload transport rate was continuously monitored at 24 hour intervals by means of four river bedload trap devices aligned across the width of the channel the maximum bedload transport rate varied strongly at portions of the cross section from 16 to 152 kg m 1 d 1 in cross profile i c p i and 4 to 125 kg m 1 d 1 in cross profile ii c p ii the maximum channel mean bedload transport rate qa amounted to 54 kg m 1 d 1 c p i and 35 kg m 1 d 1 c p ii mean daily bedload discharge qb was estimated at a level of 97 kg day 1 c p i and 35 kg m 1 d 1 c p ii and the total bedload yield was determined at approx 4345 kg in the measurement period 2086 kg c p i 2203 kg c p ii from 13 07 to 10 08 the analysis of the relationship between channel mean bedload transport rate and water velocity or shear stress revealed a significant value of the correlation coefficient r2 0 6 discharge and rate of bedload transport were dependent on the weather and number of days with flood discharge approx 58 of the entire discharged bedload was transported during 3 violent ablation precipitation floods bedload grain size distribution was right skewed and showed moderate sorting

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

geomorphic implications of subglacial drainage configuration rates of basal sediment evacuation controlled by seasonal drainage system evolution abstract although basal sediment evacuation by subglacial meltwater is widely assumed to dominate the sediment budget of most temperate glaciers and ice caps its potential influence for glacial geomorphic processes and landforms has largely been overlooked in the glacial literature data collected at haut glacier d arolla switzerland during the 1998 ablation season are used to test theoretical predictions that subglacial drainage configuration should exert a primary control on rates of basal sediment evacuation by subglacial meltwater seasonal evolution of the subglacial drainage system enables observation of sediment evacuation from both distributed and channelised drainage systems daily suspended sediment load exhibits an extreme nonlinear increase with respect to discharge between winter and summer periods which correspond to periods of predominantly distributed and channelised subglacial drainage respectively these results suggest that subglacial drainage configuration should significantly impact upon a rates of subglacial erosion and debris production b the nature of debris transport and the proportion of sediment in glacial versus fluvioglacial transport pathways and c rates and styles of ice marginal sedimentation in contrast to their distributed counterparts channelised drainage configurations are predicted to encourage subglacial erosion through the removal of basal sediment from the ice bedrock interface and with the exception of supraglacial transport will discourage sediment transport by alternative glacial mechanisms direct sedimentation at the glacier margin may therefore be reduced resulting in smaller moraines despite an overall increase in sediment production an appreciation of the coupling between glacier hydrology and geomorphic processes suggests new frameworks for the understanding of rates and styles of glacial erosion sediment transfer and deposition and the complex geomorphology of ice marginal environments

basal sediment evacuation by subglacial meltwater suspended sediment transport from haut glacier d arolla switzerland proglacial suspended sediment transport was monitored at haut glacier d arolla switzerland during the 1998 melt season to investigate the mechanisms of basal sediment evacuation by subglacial meltwater sub seasonal changes in relationships between suspended sediment transport and discharge demonstrate that the structure and hydraulics of the subglacial drainage system critically influenced how basal sediment was accessed and entrained under hydraulically inefficient subglacial drainage at the start of the melt season sediment availability was generally high but sediment transport increased relatively slowly with discharge later in the melt season sediment transport increased more rapidly with discharge as subglacial meltwater became confined to a spatially limited network of channels following removal of the seasonal snowpack from the ablation area flow capacity is inferred to have increased more rapidly with discharge within subglacial channels because rapid changes in discharge during highly peaked diurnal runoff cycles are likely to have been accommodated largely by changes in flow velocity basal sediment availability declined during channelization but increased throughout the remainder of the monitored period resulting in very efficient basal sediment evacuation over the peak of the melt season increased basal sediment availability during the summer appears to have been linked to high diurnal water pressure variation within subglacial channels inferred from the strong increase in flow velocity with discharge basal sediment availability therefore appears likely to have been increased by 1 enhanced local ice bed separation leading to extra channel flow excursions and sol or 2 the deformation of basal sediment towards low pressure channels due to a strong diurnally reversing hydraulic gradient between channels and areas of hydraulically less efficient drainage copyright 2005 john wiley sons ltd

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

hydrological controls on patterns of surface internal and basal motion during three spring events haut glacier d arolla switzerland three early melt season high velocity events or spring events occurred on haut glacier d arolla switzerland during the melt seasons of 1998 and 1999 the events involve enhanced glacier velocity during periods of rapidly increasing bulk discharge in the proglacial stream and high subglacial water pressures however differences in spatial patterns of surface velocity internal ice deformation rates the spatial extent of high subglacial water pressures and in rates of subglacial sediment deformation suggest different hydrological and mechanical controls the data from two of the events suggest widespread ice bed decoupling particularly along a subglacial drainage axis creating the highest rates of basal motion and plug flow in the overlying ice the other event showed evidence of less extensive ice bed decoupling and sliding along the drainage axis with more mechanical support for ice overburden transferred to areas adjacent to decoupled areas we suggest that 1 plug flow may be a common feature on glaciers experiencing locally induced reductions in basal drag 2 under certain circumstances enhanced surface motion may be due in part to non locally forced enhanced bed deformation and 3 subglacial sediment deformation is confined to a depth of the order of centimetres to decimetres

hydrodynamics and geomorphic work of jokulhlaups glacial outburst floods from kverkfjoll volcano iceland jokulhlaups glacial outburst floods occur frequently within most glaciated regions of the world and cause rapid landscape change infrastructure damage and human disturbance the largest jokulhlaups known to have occurred during the holocene within iceland drained from the northern margin of vatnajokull and along the jokulsa a fjollum some of these jokulhlaups originated from kverkfjoll volcano and were routed through anastomosing high gradient and hydraulically rough channels landforms and sediments preserved within these channels permit palaeoflow reconstructions kverkfjoll jokulhlaups were reconstructed using palaeocompetence point measurements slope area one dimensional and depth averaged two dimensional 2d hydrodynamic modelling techniques the increasing complexity of 2d modelling required a range of assumptions but produced information on both spatial and temporal variations in jokulhlaup characteristics the jokulhlaups were volcanically triggered had a linear rise hydrograph and a peak discharge of 50 000 100 000 m3 s 1 which attenuated by 50 75 within 25 km frontal flow velocities were 2 m s 1 but as stage increased velocities reached 5 15m s 1 peak instantaneous shear stress and stream power reached 1 104 n m 2 and 1 105 w m 2 respectively hydraulic parameters can be related to landform groups a hierarchy of landforms is proposed ranging from the highest energy zones erosional gorges scoured bedrock cataracts and spillways to the lowest energy zones of valley fills bars and slackwater deposits fluvial erosion of bedrock occurred in kverkfjallarani above 3 m flow depth 7m s 1 flow velocity 1 102 n m 2 shear stress and 3 102 w m 2 stream power fluvial deposition occurred in kverkfjallarani below 8 m flow depth 11 m s 1 flow velocity 5 102 n m 2 shear stress and 3 103 w m 2 stream power hence erosional and depositional envelopes have considerable overlap probably due to transitional flow phenomena and the influence of upstream effects such as hydraulic ponding and topographic constrictions for example holocene kverkfjoll jokulhlaups achieved geomorphic work comparable to that of other late pleistocene megafloods this work was a result of steep channel gradients topographic channel constrictions and high hydraulic roughness rather than to extreme peak discharges the kverkfjoll jokulhlaups have implications for landscape evolution in north central iceland for water sediment inputs into the north atlantic and for recognizing jokulhlaups in the rock record 2d hydrodynamic modelling is likely to be important for hazard mitigation in similar landscapes and upon other glaciated volcanoes because it only requires an input hydrograph and a digital elevation model to run a model rather than suites of geomorphological evidence and field surveyed valley cross sections for example copyright 2006 john wiley sons ltd

sediment connectivity in the high alpine valley of val muschauns swiss national park linking geomorphic field mapping with geomorphometric modelling abstract the efficiency of sediment routing through mountain sediment cascades is controlled by the connectivity of hillslopes to the main river system a lack of connectivity may cause long term sediment storage and exclude large fractions of a basin from the sediment routing for several thousand years here we studied sediment dynamics in a small formerly glaciated valley in the swiss alps to characterise the sediment connectivity to the stream we calculated a morphometric index using a gis algorithm the modelling results were tested against a field based geomorphic mapping of sediment storages which were evaluated with respect to their state of de coupling in accordance to the field diagnostics the modelling results indicate very well that the present day sediment flux is conditioned by the glacial valley morphometry inherited through pleistocene glaciation especially in the upper hanging valleys the connectivity index is reduced noticeably due to the glacial cirque morphology based on the field mapping 30 of the hillslope sediment cascades are interrupted and 20 of the storage boundaries are currently affected by a lack of material transfer as a consequence 29 of the basin surface is currently disconnected from the main river nevertheless the gis algorithm overestimates the connectivity within the basin because it fails to calculate decoupling between neighbouring pixels in digital terrain models dtms around 35 of the basin surface which has been mapped in the field as being decoupled is related to relative high connectivity our study highlights the potential of morphometric gis modelling for studying sediment connectivity but additionally emphasises the indispensability of geomorphic field mapping for a holistic understanding of mountain cascading systems

a year of internal poincare waves in southern lake michigan 1 a unique set of full year deep water observations from the middle of lake michigan s southern basin are analyzed to quantify the seasonal variability of the dominant near inertial internal poincare wave at this mid lake location the poincare wave is seen to describe more than 80 of the observed surface current variability for much of the year with characteristic near inertial frequency and clockwise rotating velocities the dominance of the near inertial seiche on the flow decreases with depth the wave persists during the stratified period roughly may through late december and is supported by as few as 1 2 degrees of thermal stratification over 150 m only after complete water column mixing does the wave go dormant for january through april the strongest poincare wave activity is seen to correspond to the period of strongest summer thermal stratification august in spite of the relatively weak winds at this time a simple inertial slab model optimized with linear friction is shown to capture the seasonal variability of the near inertial energy at this location reasonably well the vertical structure of the wave shows good agreement with that calculated with a standard normal modes formulation which is in turn used to characterize the potential shear and mixing caused by the wave late spring and summer events of elevated poincare wave activity are shown to generate sufficiently strong shear with persistent periods of sub 1 richardson numbers within the thermocline suggesting that the near inertial seiche is likely generating thermocline instabilities in the lake s interior

an enhanced temperature index glacier melt model including the shortwave radiation balance development and testing for haut glacier d arolla switzerland an enhanced temperature index glacier melt model incorporating incoming shortwave radiation and albedo is presented the model is an attempt to combine the high temporal resolution and accuracy of physically based melt models with the lower data requirements and computational simplicity of empirical melt models represented by the degree day method and its variants the model is run with both measured and modelled radiation data to test its applicability to glaciers with differing data availability five automatic weather stations were established on haut glacier d arolla switzerland between may and september 2001 reference surface melt rates were calculated using a physically based energy balance melt model the performance of the enhanced temperature index model was tested at each of the four validation stations by comparing predicted hourly melt rates with reference melt rates predictions made with three other temperature index models were evaluated in the same way for comparison the enhanced temperature index model offers significant improvements over the other temperature index models and accounts for 90 95 of the variation in the reference melt rate the improvement is lower but still significant when the model is forced by modelled shortwave radiation data thus offering a better alternative to existing models that require only temperature data input

high sensitivity of subglacial hydrological pathways in antarctica to small ice sheet changes 1 the flow of water beneath the antarctic ice sheet has recently been shown to involve drainage from and exchange between subglacial lakes with flow routing over distances of 100km as subglacial water is known to be important to ice sheet dynamics changes to the flow routing of basal water may yield an ice sheet response here we show that the directions of subglacial hydrological flowpaths are highly sensitive to the ice sheet surface topography at certain sites in antarctica surface elevation changes of between 5 and 15 m are found to be sufficient to produce significant changes to the subglacial water flowpaths which affect the potential drainage routes of large subglacial lakes we identify the reasons for this high sensitivity and recognise several locations in east antarctica where changes to the drainage regime could have important effects on large scale basal water distribution

hydro meteorological drivers and sources of suspended sediment flux in the pro glacial zone of the retreating castle creek glacier cariboo mountains british columbia canada glaciers are major agents of erosion that increase sediment load to the downstream fluvial system the castle creek glacier british columbia canada has retreated 1 0 km in the past 70 years suspended sediment concentration ssc and streamflow q were monitored independently at five sites within its pro glacial zone over a 60 day period from july to september 2011 representing part of the ablation season meteorological data were collected from two automatic weather stations proximal to the glacier the time series were divided into hydrologic days and the shape and magnitude of the ssc response to hydro meteorological conditions cold and wet hot and dry warm and damp and storm were categorized using principal component analysis pca and cluster analysis ca suspended sediment load ssl was computed and summarized for the categories the distribution of monitoring sites and results of the multivariate statistical analyses describe the temporal and spatial variability of suspended sediment flux and the relative importance of glacial and para glacial sediment sources in the pro glacial zone during the 2011 study period 60 of the total ssl was derived from the glacial stream and sediment deposits proximal to the terminus of the glacier during storm events that contribution dropped to 40 as the contribution from diffuse and point sources of sediment throughout the pro glacial zone and within the meltwater channels increased while storm events accounted for just 3 of the study period ssl was 600 higher than the average over the monitoring period and 20 of the total ssl was generated in that time determining how hydro meteorological conditions and sediment sources control sediment fluxes will assist attempts to predict how pro glacial zones respond to future climate changes copyright 2015 john wiley sons ltd

wind influence on snow depth distribution and accumulation over glaciers 1 in mountain regions wind is known to cause snow redistribution while physically based models of snow redistribution have been developed for flat to gently rolling terrain extension of these findings to steep terrain has been limited by the complexity of wind fields in such areas in this study we applied a nonhydrostatic and compressible atmospheric prediction model to steep alpine topography and compared the results to a fully distributed data set of snow depth estimations the results show reduced horizontal wind velocity as well as an increasing downward vertical wind velocity over areas with the largest winter accumulation which are mostly glacierized we show that the wind velocity normal to the local surface which should be zero in a nondivergent flow field and is a direct measure of increased or decreased local deposition is a function of small scale features of local topography the correlation between wind fields snow accumulation and glacierization suggests that accurate modeling of wind fields over glacierized areas in complex terrain is a key factor for understanding the mass balance distribution of glaciers

retreating ice research in pro glacial areas matters glacier forefields are landscapes in transition from glacial to non glacial conditions this implies intense geomorphic hydrological and ecological dynamics with important on and off site effects this special issue collects 13 papers covering recent research in both sub polar and alpine proglacial environments that focus on i proglacial sediment sources ii proglacial rivers iii proglacial lakes iv ground water and ice and v the development of soil and vegetation in its interplay with morphodynamics advances in mapping surveying and geophysical techniques form the basis for research perspectives related to the historical evolution of proglacial areas the understanding of complex interactions of multiple processes and the effects of continued glacier recession

changes in geometry and subglacial drainage of midre lovenbreen svalbard determined from digital elevation models digital elevation models dems of the bed and surface of the polythermal midre lovenbreen svalbard are used to identify changes in glacier geometry between 1977 and 1995 the calculated mean annual mass balance 0 61 m water equivalent w e a 1 is more negative than that derived from field measurements 0 35 m w e a 1 although the error associated with this value 0 7 m a 1 suggests that the difference may be accounted for by errors however similar discrepancies between dem based and field based measurements of mass balance have been reported elsewhere in svalbard although errors may be responsible patterns of surface elevation change may also be explained in terms of patterns of ablation accumulation and dynamics the theoretical structure of the subglacial drainage system is modelled using different assumptions about subglacial water pressure in 1977 and 1995 these reconstructions are compared with the observed positions of proglacial outlet streams decreasing subglacial water pressure results in a decrease in the influence of surface morphology and an increase in the role of the bed topography on drainage routing which generally leads to more dispersed drainage long term changes in the position of proglacial outlet streams occur as a result of changes in glacier geometry but short term changes may also occur in response to early season water pressures controlled by meteorological and hydrological conditions copyright 2003 john wiley sons ltd