measuring middle pleistocene erosion rates with cosmic ray produced nuclides in buried alluvial sediment fisher valley southeastern utah cosmic ray produced 10 be and 26 al in riverborne quartz sediment are commonly used to estimate average catchment scale erosion rates likewise the concentrations of these nuclides in ancient sediments stored in a depositional basin carry a record of past erosion rates in the sediment source area this is important because such a record could be compared to records of climate change or tectonic events to elucidate relationships between climate tectonics and erosion if the sediments are shielded from the cosmic ray flux after deposition for example in deep water their nuclide concentrations need only be corrected for radioactive decay since deposition in order to determine past erosion rates where sediment is deposited subaerially and buried relatively slowly on the other hand the additional nuclide concentration that builds up during sediment accumulation and storage must be reconstructed and subtracted in order to recover the initial nuclide concentrations in the sediment and thence the past erosion rates we describe an example of this process for an early to middle pleistocene section of alluvial sediment in fisher valley utah we use stratigraphic observations as well as an independently known age model for the sediment section to a subtract post depositional nuclide concentrations and reconstruct past erosion rates between 0 7 and 0 6 ma and b estimate the uncertainty in the results that arises from imperfect dating of the section and the natural variability in accumulation rates the present basinaveraged erosion rate in fisher valley is near 125 m ma 1 and middle pleistocene basinaveraged erosion rates varied between 80 and 220 m ma 1 changes in the erosion rate over time do not appear to be connected to glacial interglacial climate changes but may be related to episodic subsidence of the basin uncertainties are small in the case of low erosion rates and high sediment accumulation rates and large in the opposite situation in this example we could reduce the uncertainties by increasing the sampling density or by better relating our sample locations to the small scale stratigraphy of the sedimentary section in general future attempts to reconstruct past erosion rates from cosmogenic nuclide concentrations in ancient alluvium will be most successful in situations where post depositional nuclide accumulation is minimized for example in lakes or marine basins copyright 2005 john wiley sons ltd

vegetation succession in deglaciated landscapes implications for sediment and landscape stability landscapes exposed by glacial retreat provide an ideal natural laboratory to study the processes involved in transforming a highly disturbed glacially influenced landscape to a stable diverse ecosystem which supports numerous species and communities large scale vegetation development and changes in sediment availability used as a proxy for paraglacial adjustment following rapid deglaciation were assessed using information from remote sensing delineation of broad successional vegetation cover types was undertaken using landsat satellite imagery covering a 22 year period to document the rate and trajectory of terrestrial vegetation development use of a space for time substitution in glacier bay national park alaska allowed back calculation of the age and stage of development of six catchments over 206 years the high accuracy 89 2 of the remotely sensed information used in monitoring successional change allowed detection of a high rate of change in vegetation classes in early successional stages bare sediment and alder in contrast later successional stages spruce and spruce hemlock dominated forest had high vegetation class retention and low turnover modelled rates of vegetation change generally confirmed the estimated rates of successional turnover previously reported these data when combined with the known influence of terrestrial succession on soil development and sediment availability suggest how physical and biological processes interact over time to influence paraglacial adjustment following deglaciation this study highlights the application of remote sensing of successional chronosequence landscapes to assess the temporal dynamics of paraglacial adjustment following rapid deglaciation and shows the importance of incorporating bio physical interactions within landscape evolution models 2014 the authors earth surface processes and landforms published by john wiley sons ltd

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

paleoclimatic implications of late pleistocene sediment yield rates for the bonneville basin northern utah abstract climate factors such as precipitation and temperature as well as climate driven geomorphic processes such as glaciation affect rates of erosion and the amount of sediment supplied from a drainage basin sediment yield thus sediment yield rates provide paleoclimatic implications although very little work has been published on ancient sediment yield rates late pleistocene lake bonneville utah idaho and nevada with its well documented lake level history and well preserved deltaic sequences provides a unique opportunity to estimate ancient sediment yield rates two end member delta systems coarse grained gravel classic gilbert type deltas and fine grained sand silt and clay deltas are exposed along the eastern margin of paleolake bonneville one example of each end member delta is examined in this study american fork and weber river deltas the established bonneville hydrograph can be used to determine time of deposition for a given package of sediments because these shoreline deltaic sediments were deposited in shallow water the geomorphic expressions of these deltas are well preserved and their sediment volumes can be determined river drainage basin area can be combined with time constraints and delta volumes to estimate sediment yield rates sediment yield rate estimates for the coarse grained american fork and fine grained weber river deltas are 478 m 3 km 2 yr 1 34 and 705 m 3 km 2 yr 1 15 respectively the similarity of these values is somewhat surprising due to the large difference in drainage basin sizes american fork 160 km 2 and weber river 3328 km 2 however this similarity suggests that precipitation may be the dominant control on sediment yield using sediment yield precipitation regression equations developed for similar modern basins in the southern alps of new zealand a first order approximation of paleoprecipitation is 1 6 m yr 14 for american fork delta and 1 9 m yr 7 for weber river delta these paleoprecipitation value are comparable to modern precipitation values of 0 4 1 5 m yr range of mean values over both drainage basins a maximum late pleistocene precipitation increase of 33 over the modern day value is suggested this is determined by the difference between the highest paleoprecipitation rate 1 9 m yr 7 of the weber river delta and the modern value 1 5 m yr previous climate models and this 33 paleoprecipitation increase suggest a maximum decrease in basin floor paleotemperature of approximately 13 c this paleotemperature decrease is consistent with previous estimates of late pleistocene temperatures using amino acid epimerization rates and periglacial wedges in the bonneville basin and adjacent areas these estimates suggest that although late pleistocene precipitation rates may have been slightly higher than present up to 33 higher late pleistocene temperature and evaporation rates were more important in the development of lake bonneville and associated glaciers

simplified process modeling of river avulsion and alluvial architecture connecting models and field data abstract modeling is an invaluable tool for studying sedimentary basin filling and for understanding depositional processes with long recurrence intervals including channel avulsion simplified modeling approaches such as cellular models and process analogue experiments are particularly useful for efficiently exploring alternative hypotheses and evaluating first order controls on river avulsion and alluvial architecture here we review the history and current state of the art in simplified avulsion and alluvial architecture models with a particular focus on how results and insights from these models can be incorporated into field and subsurface studies and vice versa simplified avulsion and alluvial architecture models have proliferated in the past decade providing a wide variety of models to serve as a basis for future coupled field modeling studies we compare features of leading models and discuss avenues for effectively pairing model capabilities with hypotheses and field data outstanding questions highlighted by recent modeling efforts include 1 what thresholds control avulsion initiation in different systems 2 how do floodplain processes and topography influence avulsion dynamics and alluvial architecture 3 what factors determine where avulsion channels stabilize answering these questions will require targeted modeling efforts coupled to data from ancient systems hence our model comparison emphasizes features that can be used to choose or design fit for purpose models and we outline how quantitative data useful for model selection and validation can be obtained from modern systems and ancient deposits matching model goals with targeted questions and model parameters and predictions with quantitative field data will help tighten communication between field and model oriented sedimentary geologists facilitating advances in our understanding of river avulsion and alluvial architecture

a new experimental material for modeling relief dynamics and interactions between tectonics and surface processes abstract we developed a new granular material mativ to study experimentally landscape evolution in active mountain belt piedmonts its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation erosion transport and sedimentation natural processes mativ is a water saturated composite material made up with 4 granular components silica powder glass microbeads plastic powder and graphite whose physical mechanical and erosion related properties were measured with different laboratory tests mechanical measurements were made on a modified hubbert type direct shear apparatus erosion related properties were determined using an experimental set up that allows quantifying the erosion sedimentation budget from tilted relaxation topographies for mativ we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1d as a function of slope our results indicate that mativ satisfies most of the defined criteria it deforms brittlely according to the linear mohr coulomb failure criterion and localizes deformation along discrete faults its erosion pattern is characterized by realistic hillslope and channelized processes slope diffusion mass wasting channel incision during transport eroded particles are sorted depending on their density and shape which results in stratified alluvial deposits displaying lateral facies variations to evaluate the degree of similitude between model and nature we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes results indicate that mativ succeeded in producing detailed morphological and sedimentological features drainage basin channel network terrace syntectonic alluvial fan geometric kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature although scaling is incomplete it yields particularly informative orders of magnitude with all these characteristics mativ appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics erosion and sedimentation processes

sediment delivery to the three gorges 1 catchment controls abstract the paper examines sediment yield and its response to catchment disturbance and environmental variables in the upper yangtze basin where the attention of environmentalists has been drawn to the three gorges project tgp information about the source and conveyance of sediment from the catchment area to the three gorges reservoir has implications for management strategies methodologies for establishing the relationships between land cover climatic and topographic variables with sediment yield are introduced the analysis uses a sediment load data set containing 250 stations with up to 30 years of measurement a 1 1 km resolution land cover database and variables extracted from various geodatabases the mean sediment load delivered from the yangtze upstream of chongqing is 318 mt a 1 but the contribution from the jialing tributary is higher in terms of specific sediment yield at 928 t km 2 a 1 long term sediment yield at yichang has not exhibited an upward trend despite the evidence for increased soil erosion within the basin examination of sediment response to catchment disturbance and spatial variability in relation to controlling variables has been undertaken in an attempt to predict future sedimentation impacts time series analysis illustrates that significant increases in sediment yield have occurred over about 8 of the catchment area while about 3 have experienced decreasing sediment yields the latter are associated with major reservoir schemes on the tributaries of the yangtze when the spatial pattern of sediment yields within the basin is analysed natural climatic and topographic factors explain most of the variability in the relatively sparsely populated western part of the upper yangtze basin but do not afford very good prediction in the more populated eastern part incorporation of land cover information does not provide additional explanation of spatial variability examination of the response of sediment delivery to catchment disturbance and environmental variables provides an illustration which may have some lessons for the management of the sedimentation problem in the three gorges reservoir and a basis for modelling future changes in sediment delivery

a descriptive and quantitative approach regarding erosion and development of landforms on abandoned mine tailings new insights and environmental implications from se spain abstract the san cristobal perules mining site in mazarron in southeast spain was subjected to about a hundred years of intense mining activity for lead silver and zinc metallurgical operations smelting calcination gravity concentration carried out during the late nineteenth century early twentieth century induced significant land transformation and the most conspicuous wastes of this period consist of a chaotic piling of old tailing deposits later on during the mid twentieth century modern tailings resulting from froth flotation were accumulated filling small valleys these latter valley fill tailings rose sequentially according to the upstream construction method progressively raising the level of the dam during the process once abandoned both types of tailing deposits underwent severe erosion resulting in a mosaic of erosional and sedimentary landforms developed upon e g gully formation and within them e g piping we made an inventory and classification of these landforms our study shows the geomorphic work to reestablish a new steady state between the tailings deposits and the local erosive conditions this scenario implies several hazards related to the extremely high heavy metal contents of these tailings and the geomorphic instability of the deposits we also quantified the tailings tonnage and erosion that occurred at one of the tailings dams el roble as shown by an oblique aerial photograph taken in 1968 this dam had a terraced topography whereas in 2013 this morphology had evolved into a badland type relief with deep parallel gullies by recognizing and surveying specific remnant points along the benches and outslopes of the older terraced topography we were able to build up a first digital elevation model dem 1 reflecting the initial topography a second dem this time showing the present topography allowed quantification of erosion via material loss dem 1 dem 2 this yields an erosion rate 1968 2009 of 151 8 mg mt ha 1 y 1 which matches well typical values for erosion of mined areas commonly above 100 mg mt ha 1 y 1 abandoned mine tailing deposits are extremely common in the semiarid scenarios of the sw usa australia chile and peru given the similarities of these scenarios with se spain the example from mazarron may provide useful new insights regarding the erosion and geomorphic evolution of such tailing deposits these matters should be addressed in key environmental actions such as mine closure plans and land reclamation projects a solution may come via restoration of these deposits through landform design involving the building up of stable mature landscapes which in turn can withstand erosion much more easily

evolution of the quaternary alluvial fan system in the himalayan foreland basin implications for tectonic and climatic decoupling abstract the quaternary evolution of an alluvial fan system in the himalayan foothills reveals two distinct phases the early quaternary siwalik system i and the late quaternary intramontane piggy back system ii have been studied in detail in the subathu sub basin of nw himalaya with system i followed by system ii sedimentary architecture and facies analysis from chronologically constrained sections using magnetostratigraphy and tl osl indicate that systems i and ii although developed in similar hinterland basin settings indicate contrasting aggradation and entrenchment system i is characterised by predominant fan aggradation in contrast to the variable aggradation entrenchment response in time and space for system ii system i is time transgressive laterally from east to west with the central part remaining as the uplifted inter fan domain further confinement of system i along the basin margin indicates its syn orogenic evolution linked to the intra foreland thrusting this continued with the formation of the piggy back basin of system ii glacial interglacial cycles influenced the evolution of both alluvial fan systems however greater sediment yield and larger accommodation space favored aggradation during system i in contrast in system ii insufficient accommodation space relative to sediment yield and ongoing upliftment and reduced subsidence resulted in aggradation at the fan head during incessant precipitation followed by entrenchment during low precipitation the latest phase late quaternary to recent is characterised by two level terraces at ca 16 and 5 ka within the entrenched streams due to variation in water budget and sediment load governed by glacial interglacial cycles this study thus demonstrate the variable importance of accommodation space base level change and magnitude of tectonic and climatic forcing as controlling factors on aggradation and entrenchment in quaternary alluvial fan systems of the himalayan foreland basin

experimental modelling of orogenic wedges a review abstract experimental modelling applied to the study of orogenic wedge dynamics has been a subject of fruitful research for more than 30 years although the technique dates back as far as the early xix th century on one hand several first order parameters controlling the structural evolution of mountain belts have been intensively investigated using the classic tectonic sandbox models the main parameters are the properties of the basal decollement the deforming material the backstop and fluxes kinematics and surface processes on the other hand the morphological evolution of a mountain relief subjected to changing tectonic or climatic forcing has been addressed using another kind of approach called geomorphic models nowadays the literature is extremely rich particularly for the sandbox technique so that it becomes difficult to have an exhaustive view of the effects of the above parameters on mountain evolution in this article we propose a detailed review of the main results obtained using both tectonic and geomorphic approaches our goal is to provide an almost complete state of the art in the experimental study of relief dynamics to guide present and future researchers in their understanding of mountain belt evolution

management responses to pulses of bedload sediment in rivers abstract rivers can experience sudden pulses of sediment from human and natural erosion processes that can accumulate in the bed abundant studies have examined the sources and dynamics of sediment pulses and problems caused by these pulses particularly flooding avulsions and habitat simplification much less has been written about what managers can do about sediment pulses and that is the purpose of this review the first option for managers is to do nothing and this decision can be informed by many case studies and by theory on the propagation and character of sediment pulses their diffusion translation and celerity doing nothing should be informed by the secondary effects of sediment pulses on channels including widening avulsions and tributary interactions if managers decide that something needs to be done about the sediment they have four options 1 reducing the sediment supply at source 2 trapping sediment in the channel 3 accelerating sediment transport through a reach and 4 directly extracting sediment the most common of these actions is undoubtedly to reduce the supply at source but there are few examples of the consequences of this for sediment pulses there are even fewer examples of trapping accelerating and extracting sediment all of these options have great potential for managing sediment pulses however they also have the potential to trigger incision of tributaries and of the channel behind the passing sediment wave overall the literature equips managers to understand the dynamics of sediment pulses but it does not yet equip them to confidently manage these geomorphic events

drainage network expansion of the salagou drainage basin s france an example of relief response to recent climate change continental erosion is known to be strongly controlled by climate but the way by which geomorphological systems respond to climate change still remains poorly understood recent numerical modelling suggests that drainage networks are subjected to strong spatial fluctuations but few studies of natural systems have addressed this phenomenon because of the difficulty of documenting the evolution of erosional landscapes a detailed field analysis has allowed reconstruction of the past topography of a drainage basin located in southern france where remnants of a past landscape are well preserved a change from a smooth to a present day dissected landscape is observed and related to a change in the dominant processes of erosion this evolution is interpreted in terms of fluctuations in drainage network extent in response to a holocene increase in precipitation

environmental impact of the 1 8 ka taupo eruption new zealand landscape responses to a large scale explosive rhyolite eruption abstract large scale ignimbrite eruptions from rhyolitic caldera volcanoes can trigger geologically instantaneous changes in sedimentary systems over huge areas by either burying existing environments or overloading them with vast quantities of unconsolidated particulate material the post eruption readjustment of the landscape to such perturbations is one of the most dramatic processes in physical sedimentology exemplified here by the 1 8 ka taupo eruption in the central north island of new zealand this eruption generated voluminous fall deposits then climaxed with emplacement of a c 30 km 3 non welded ignimbrite over a near circular area of c 20 000 km 2 approximately 90 of the area but the headwaters of many of the north island s largest rivers were impacted by both the primary pyroclastic fall and flow material large scale post eruption remobilisation of this material coupled with the re establishment of fluvial systems occurred in a distinct sequence as recorded by the evolution of sedimentary facies in different sub environments following an initial period dominated by mass flows re establishment of fluvial systems began with the headward erosion of box canyons through the ponded ignimbrite deposits a process often associated with the break out of temporary lakes aggradational streams developed in these channels rapidly evolved from shallow ephemeral sediment laden outbursts associated with flash flood events to deeper permanent braided rivers before declining sediment yields led to retrenchment of single thread rivers and a return to pre eruption gradients and bedloads years to decades later typically the modern profile of many streams and rivers follow closely their pre eruption profiles and incision and erosion is overwhelmingly confined to the deposits of the eruption itself although the general remobilisation pattern is similar for all impacted river systems detailed studies of the waikato rangitaiki mohaka ngaruroro and whanganui catchments show that the relative timing and scale of each eruption response phase differs between each catchment these reflect differences in catchment physiography and hydrology and the volume and type of pyroclastic material deposited in each ultimately the landscape response reflects the relative spatial distributions of and the volumetric ratios between the volumes of pyroclastic debris water and accommodation space in the basin cf kataoka and manville this volume

late cenozoic fluvial successions in northern and western india an overview and synthesis abstract late cenozoic fluvial successions are widespread in india they include the deposits of the siwalik basin which represent the accumulations of the ancient river systems of the himalayan foreland basin palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by himalayan tectonics as well as by major climatic fluctuations during the long 13 ma span of formation the indo gangetic plains form the world s most extensive quaternary alluvial plains and display spatially variable controls on sedimentation himalayan tectonics in the frontal parts climate in the middle reaches and eustasy in the lower reaches close to the ganga brahmaputra delta climatic effects were mediated by strong fluctuations in the sw indian monsoon and himalayan rivers occupy deep valleys in the western ganga plains where stream power is high cut in part during early holocene monsoon intensification the broad interfluves record the simultaneous aggradation of plains fed rivers since 100 ka the eastward increase in precipitation across the ganga plains results in rivers with low stream power and a very high sediment flux resulting in an aggradational mode and little incision the river deposits of semi arid to arid western india form important archives of quaternary climate change through their intercalation with the eolian deposits of the thar desert although the synthesis documents strong variability both spatial and temporal in fluvial stratigraphy climatic events such as the decline in precipitation during the last glacial maximum and monsoon intensification in the early holocene have influenced fluvial dynamics throughout the region

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

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

sediment yield from disturbed earth systems changes of sediment yield rates through time reflect evolutionary changes within a landscape when a drainage basin is perturbed significantly by base level climatic or tectonic change sediment yields increase dramatically but with no further disturbance they decline rapidly these sediment yield changes have been documented at all scales from small experimental studies to incised channels to the colorado river basin and to the himalaya mountains thus the shape of the sediment yield curve can be used to estimate future sediment yields and to interpret past tectonic events

aerodynamic stability and turbulent sensible heat flux over a melting ice surface the greenland ice sheet the turbulent sensible heat flux to a melting ice surface is calculated from wind speed and air temperature at 2 m over the ice surface assuming a certain wind profile with the appropriate surface roughness the aerodynamic stability of the boundary layer over melting ice is examined by comparing sensible heat fluxes for logarithmic and log linear wind profiles where the logarithmic profile is strictly valid only for neutral conditions increasing stability reduces the sensible heat flux to the glacier surface and introduces a non linear relation between heat flux and air temperature the stability effect is greatest at low wind speeds and fairly small at the high wind speeds that are common over the ice sheet earlier estimates of ablation by energy balance modelling may be too large due to neglect of stability but this was almost offset by using a surface roughness that was too small the log linear wind profile should be used in future energy balance models to take account of stability but more research is needed on the parameters of the profile as well as on the surface roughness

reconnaissance sediment budgets for lynn valley british columbia holocene and contemporary time scales volumes of erosional and depositional landforms were estimated by reconnaissance methods in a steep forested drainage basin in the coast mountains british columbia to examine what insight might be gained into the sediment budget in the absence of direct measurements of sediment transfer processes sediment transfers in postglacial and contemporary time were inferred on hillslopes from hillslopes to stream channels and within stream channels data were collected by aerial photographic analysis and field observation postglacial sediment sources are major gullies created by debris slides and flows failures in glaciolacustrine terraces and stream channel degradation depositional landforms consist of talus slopes and colluvial and alluvial fans contemporary sediment sources include debris slides and flows in established gullies and minor processes on hillslopes debris slide and debris flow volumes were calculated and other processes were estimated from regional values erosion rate averaged over postglacial time is 276 t km 2 a 1 0 15 mm a 1 surface lowering with gullies and stream channel degradation contributing 170 and 82 t km 2 a 1 respectively a terminal alluvial fan provides an independent check of the results in contemporary time erosion rates are calculated to be 350 t km 2 a 1 with debris flows and slides contributing nearly all of this sediment the contemporary rate is probably perturbed by recent land use history mass movement processes appear to be the dominant mechanism of sediment transfer and contributions from pleistocene valley deposits have declined significantly during holocene time resume les volumes de terrain erodes et deposes ont ete estimes par des methodes de reconnaissance dans un bassin de drainage boise a pentes abruptes des montagnes cotieres de la colombie britannique afin d etudier quelles connaissances sur le budget sedimentaire pourraient etre acquises en l absence de mesures directes du processus de transfert de sediments les transferts de sediments a l epoque post glaciaire et contemporaine ont ete inferes sur les flancs des cotes des flancs des cotes vers les chenaux des rivieres et dans les chenaux des rivieres les donnees proviennent de l analyse de photographies aeriennes et d observations sur le terrain les sources de sediments post glaciaires sont des ravines creees par des glissements et des coulees de debris des effondrements de terrasses glacio lacustres et la degradation de chenaux les formes de terrain creees par deposition comprennent des tabliers d eboulis et des deltas colluviaux et alluvionnaires les sources contemporaines de sediments comprennent des glissements et des coulees de debris dans des ravines etablies et des processus mineurs sur des pentes les volumes des glissements et des coulees de debris ont ete calcules et d autres processus ont ete evalues a partir de valeurs regionales la moyenne du taux d erosion pour la periode post glaciaire est de 276 tonnes km 2 a 1 abaissement de la surface de 0 15 mm a les ravines et la degradation des chenaux des ruisseaux contribuant respectivement 170 et 82 tonnes km 2 a 1 un delta alluvionnaire terminal permet une verification independante des resultats a l epoque contemporaine les taux d erosion sont calcules comme etant 350 tonnes km 2 a 1 et les glissements et des coulees de debris y contribueraient pour la presque totalite le taux contemporain est probablement perturbe par l utilisation recente du terrain les processus de mouvements de masse semblent etre le mecanisme dominant de transfert de sediments et les contributions provenant des depositions dans les vallees au pleistocene ont diminue de facon significative durant l holocene traduit par la redaction campbell and church 713

alluvial sedimentation rates from southeastern australia indicate post european settlement landscape recovery increased catchment sediment yields are common following the introduction of european style agriculture to relatively undisturbed landscapes catchment erosion rates generally increase immediately after disturbance and then decline over time consequently where a catchment currently sits along this disturbance recovery sequence will strongly influence future catchment sediment yields and river morphology in this study field stratigraphy optical dating and hydraulic modelling are used to investigate changes in catchment sediment yield and storage in the lake burragorang catchment in australia with emphasis placed upon changes occurring since european settlement in a d 1820 on the southern tablelands and the upper cox s river subcatchment a large volume of sediment was liberated by gully erosion early in the post settlement period much of which was deposited at break of slope positions below the catchment s headwaters or stored in alluvial benches adjacent to the channel but within the confines of older holocene alluvium a lack of substantial sediment deposition over the last 20 to 40 years is evidence that catchment sediment yields have strongly declined this is consistent with both reduced erosion rates and re aggradation of the incised gullies that in their erosive phase dominated the catchment s post settlement sediment flux collectively these characteristics indicate the catchment is undergoing a phase of landscape recovery

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

weathering flux and co2 consumption determined from palaeosol sequences across the eocene oligocene transition abstract rates of base cation depletion are determined for late eocene and early oligocene alluvial palaeosols pacific northwest of north america from pedogenic mass balance geochemistry and time estimates of palaeosol sequences pedogenic strain volume change and mass transfer of base cations silica and other pertinent elements are calculated from the geochemical differences between palaeosol horizons and parent material parent material compositions are determined by identification of the least altered alluvial strata in the sequence time spans of sequences of palaeosols are estimated from 40ar 39ar age dates of interbedded tuff beds and from time of formation estimates of palaeosols based on their degree of development palaeosol sequences from the mid latitude setting of central oregon document a significant decrease in the degree of weathering of individual palaeosols across the eocene oligocene transition as the climate became cooler and drier this decrease in the degree of weathering is accompanied by an increase in the accumulation rate of alluvial soils as indicated by sedimentation rates of stratigraphic packages according to these calculations and estimates the weathering flux of base cations in the john day basin measured in grams per 1000 years per square centimetre increased across the eocene oligocene transition these results when attributed to climate change indicate that weathering flux at this local increased as climate changed from warm humid late eocene conditions to cooler drier oligocene conditions furthermore the extrapolation of these weathering flux results to other mid latitude settings with similar climate change history may help to explain the severe climate change of the eocene oligocene boundary it is proposed that in some mid latitude settings greater quantities of less weathered silicate material were exposed during the early oligocene than during the late eocene thus causing an increase in flux of weathered product increased weathering flux during this time in certain regions of the mid latitudes may have increased both co2 consumption and bicarbonate transport to the ocean and contributed to atmospheric pco2 drawdown and global cooling

restoring earth surface processes through landform design a 13 year monitoring of a geomorphic reclamation model for quarries on slopes the application of geomorphic principles to land reclamation after surface mining has been reported in the literature since the mid 1990s mostly from australia canada and the usa this paper discusses the reclamation problems of contour mining and quarries on slopes where steep gradients are prone to both mass movement and water erosion to address these problems simultaneously a geomorphic model for reclaiming surface mined slopes is described called the highwall trench concave slope model it was first applied in the 1995 reclamation of a quarry on a slope la revilla in central spain the geomorphic model does not reproduce the original topography but has two very different sectors and objectives i the highwall trench sector allows the former quarry face to evolve naturally by erosion accommodating fallen debris by means of a trench constructed at the toe of the highwall ii the concave slope base sector mimicking the landforms of the surrounding undisturbed landscape promotes soil formation and the establishment of self sustaining functional ecosystems in the area protected from sedimentation by the trench the model improves upon simple topographic reconstruction because it rebuilds the surficial geology architecture and facilitates re establishment of equilibrium slopes through the management and control of geomorphic processes thirteen years of monitoring of the geomorphic and edaphic evolution of la revilla reclaimed quarry confirms that the area is functioning as intended the highwall is backwasting and material is accumulating at the trench permitting the recovery of soils and vegetation on the concave slope however the trench is filling faster than planned which may lead to run off and sedimentation on the concave slope once the trench is full the lesson learned for other scenarios is that the model works well in a two dimensional scheme but requires a three dimensional drainage management breaking the reclaimed area into several watersheds with stream channels copyright 2010 john wiley sons ltd