large scale dam removal on the elwha river washington usa river channel and floodplain geomorphic change abstract a substantial increase in fluvial sediment supply relative to transport capacity causes complex large magnitude changes in river and floodplain morphology downstream although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution few opportunities exist to quantify those processes over field scales we investigated the downstream effects of sediment released during the largest dam removal in history on the elwha river washington usa by measuring changes in riverbed elevation and topography bed sediment grain size and channel planform as two dams were removed in stages over two years as 10 5 million t 7 1 million m3 of sediment was released from two former reservoirs downstream dispersion of a sediment wave caused widespread bed aggradation of 1 m greater where pools filled changed the river from pool riffle to braided morphology and decreased the slope of the lowermost river the newly deposited sediment which was finer than most of the pre dam removal bed formed new bars largely pebble granule and sand material prompting aggradational channel avulsion that increased the channel braiding index by almost 50 as a result of mainstem bed aggradation floodplain channels received flow and accumulated new sediment even during low to moderate flow conditions the river system showed a two to tenfold greater geomorphic response to dam removal in terms of bed elevation change magnitude than it had to a 40 year flood event four years before dam removal two years after dam removal began as the river had started to incise through deposits of the initial sediment wave 1 2 million t of new sediment 10 of the amount released from the two reservoirs was stored along 18 river km of the mainstem channel and 25 km of floodplain channels the elwha river thus was able to transport most of the released sediment to the river mouth the geomorphic alterations and changing bed sediment grain size along the elwha river have important ecological implications affecting aquatic habitat structure benthic fauna salmonid fish spawning and rearing potential and riparian vegetation the response of the river to dam removal represents a unique opportunity to observe and quantify fundamental geomorphic processes associated with a massive sediment influx and also provides important lessons for future river restoration endeavors

mapping the interactions between rivers and sand dunes implications for fluvial and aeolian geomorphology article i nfo the interaction between fluvial and aeolian processes can significantly change earth surface morphology when riversandsanddunes meet theinteractionofsedimenttransportbetweenthetwosystemscanleadtochangein eitherorboth systems however these two systemsare usuallystudied independently which leavesmanyques tions unresolved in terms of how they interact this paper carries out a global inventory using satellite imagery to identify 230 sites where there are significant fluvial aeolian interactions at each location key attributes such as wind river direction net sand transport direction fluvial aeolian meeting angle dune type and river channel pattern were identifiedand relationshipsbetween each factorwere analysed from thesedata six different types of interaction were classified that reflect a shift in dominance between the fluvial and aeolian systems results from this classification confirm that only certain types of interaction were significant the meeting angle and dunetype themeeting angle and interaction type and finally thechannel pattern andinteraction type however the findings also indicate the difficulties of classifying dynamic geomorphic systems from snapshot satellite images

climate and lake level history of the northern altiplano bolivia as recorded in holocene sediments of the rio desaguadero abstract strata exposed in terraces and modern cutbanks along the rio desaguadero contain a variety of lithofacies that were deposited in four distinct facies associations these facies associations document a history of aggradation and downcutting that is linked to holocene climate change on the altiplano braided stream meandering stream deltaic and shoreline and lacustrine sediments preserved in multi level terraces in the northern rio desaguadero valley record two high water intervals one between 4500 and 3900 yr bp and another between 2000 and 2200 yr bp these wet periods were interrupted by three periods of fluvial downcutting centered at approximately 4000 yr bp 3600 yr bp and after 2000 yr bp braided river sediments preserved in a single terrace level in the southern rio desaguadero valley record a history of nearly continuous fluvial sedimentation from at least 7000 yr bp until approximately 3200 yr bp that was followed by a single episode post 3210 yr bp of downcutting and lateral migration the deposition and subsequent fluvial downcutting of the northern strata was controlled by changes in effective moisture that can be correlated to holocene water level fluctuations of lake titicaca the deposition and dissection of braided stream sediments to the south are more likely controlled by a combination of base level change and sediment input from the rio mauri

late pleistocene braided rivers of the atlantic coastal plain usa abstract infrared landsat imagery band 4 clearly reveals braided river patterns on late pleistocene terraces of unglaciated rivers in the atlantic coastal plain of the southeastern united states a region that presently exhibits meandering patterns that have existed throughout the holocene these pleistocene braided patterns provide a unique global example of river responses to late quaternary climate changes in an unglaciated humid subtropical region at 30 35 north latitude detailed morphological and chronological results are given for the oconee altamaha river valley in georgia and for the pee dee river valley in south carolina including 15 optically stimulated luminescence osl dates and four radiocarbon dates correlative examples are drawn from additional small to large rivers in south and north carolina osl and radiocarbon 14 c dates indicate distinct braiding at 17 30 ka within oxygen isotope stage 2 ois 2 and braiding probably existed at least during parts of ois 3 and possibly ois 4 back to ca 70 ka the chronology suggests that braiding is the more common pattern for the late quaternary in the southeastern united states braided terraces appear to have been graded to lower sea levels and are onlapped by holocene floodplain deposits up to 10 60 km from the coast the braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates which may have had a pronounced runoff season sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late pleistocene our chronological data contribute to a body of literature indicating that reliable osl age estimates can be obtained from quartz rich bed load sand from braided rivers based on good correlations with both radiocarbon dates from braided fluvial sediment and osl dates from stratigraphically correlative eolian sand

the geometry and organization of fluviodeltaic channel sandstones in the jurassic saltwick formation yorkshire england within the middle jurassic saltwick formation of yorkshire england 65 of the fluvial channel sandstones n 22 have width to thickness ratios in the range 17 30 more than 90 lie in the range 17 67 and are classified as narrow sheet channel sandstones a broad sheet channel sandstone c 15 m thick 3 km wide width to thickness ratio of 200 occurs at the base of the formation in the proximal part of the studied depositional system the thicknesses of the channel sandstones are in the range 4 m to more than 22 m with 90 in the range 4 12 m the widths of the channel sandstone sections are in the range 100 800 m with 80 between 100 and 400 m in plan view the channel sandstones display relatively constant thicknesses across the main part 80 of the channel body channel sandstones are usually multistorey the storeys are separated by major scour surfaces with depths of scour ranging from 2 m to 8 10 m the individual storeys are 4 13 m thick and transverse and oblique storey sections have lateral extents of 60 480 m vertical stacking of storeys is accompanied by a decrease in the width to thickness ratio of the channel sandstones whereas lateral stacking of storeys is accompanied by an increase mudstones and siltstones within channel sandstone bodies occur at the top of storeys and were in most cases deposited during channel abandonment the saltwick formation was deposited during increasing accommodation forming a transgressive systems tract the channel sandstone to interchannel sediment ratio is highest in the lower parts of the transgressive systems tract the quantitative geometry and architecture data from the saltwick formation may be useful for describing and modelling humid delta plain hydrocarbon reservoirs of transgressive systems tracts

depositional architecture of a maar pitted playa sedimentation in the hopi buttes volcanic field northeastern arizona u s a abstract primary and reworked tephra in the mio pliocene bidahochi formation of northeastern arizona was produced by and partly preserved in maar volcanoes and related hydrovolcanic structures the temporal and geometric relationships among lithofacies of the bidahochi formation illustrate the dynamic interplay between volcanism and sedimentation in an essentially closed sedimentary system maar volcanism in the low relief basinal environments of the bidahochi appears to have resulted in little net aggradation both because the total amount of magma erupted was relatively modest and because the large maar volcano craters produced areas of lowered base level within the basin that formed sediment sinks for much of the newly erupted tephra the volcanically eroded maar craters commonly contain deposits of lakes multiple stream channels and eolian dunes they formed an integral part of the basin s overall depositional environment and affected sedimentation in the playa lake stream systems beyond the vents both during and following the major eruptive period

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

fluvial dynamics of an anabranching river system in himalayan foreland basin baghmati river north bihar plains india abstract anabranching river systems are now regarded as a separate class in river classifications owing to their distinctive morphological hydrological characteristics and fluvial processes a better understanding of anabranching rivers still needs detailed data from different environmental and geographical settings this paper presents a detailed account of an anabranching river system from the himalayan foreland basin the baghmati river system from north bihar plains eastern india provides a typical example of an anabranching river system located in the interfan area between the kosi and the gandak megafans the river system is braided in upstream reaches and meandering in downstream reaches but the midstream anabranching reach is characterized by low width depth ratio 11 16 gentle gradient 0 00018 0 00015 variable peak discharge frequent flooding and high sediment load the anabranching in the midstream reaches is a response to its inability to transport high sediment load due to gentle channel slope and dominance of aggradation process the development of anabranches is related to rapid and frequent avulsions of the river channels with eight major avulsions observed in the 30 km wide floodplain in the last 230 years the decadal scale avulsion history of the baghmati river system makes it hyperavulsive and the major causative factors for such channel instability are sedimentological readjustments and active tectonics in the basin area

a multi parametric climatological approach to study the 2016 amatrice norcia central italy earthquake preparatory phase based on observations prior to earthquakes recent theoretical considerations suggest that some geophysical quantities reveal abnormal changes that anticipate moderate and strong earthquakes within a defined spatial area the so called dobrovolsky area according to a lithosphere atmosphere ionosphere coupling model one of the possible pre earthquake effects could be the appearance of some climatological anomalies in the epicentral region weeks months before the major earthquakes in this paper the period of 2 months preceding the amatrice norcia central italy earthquake sequence that started on 24 august 2016 with an m6 earthquake and a few months later produced other two major shocks i e an m5 9 on 26 october and then an m6 5 on 30 october was analyzed in terms of skin temperature total column water vapour and total column of ozone compared with the past 37 year trend the novelty of the method stands in the way the complete time series is reduced where also the possible effect of global warming is properly removed the simultaneous analysis showed the presence of persistent contemporary anomalies in all of the analysed parameters to validate the technique a confutation confirmation analysis was undertaken where these parameters were successfully analyzed in the same months but considering a seismically calm year when significant seismicity was not present we also extended the analysis to all available years to construct a confusion matrix comparing the occurrence of climatological data anomalies with real seismicity this work confirms the potentiality of multi parameters in anticipating the occurrence of large earthquakes in central italy thus reinforcing the idea of considering such behaviour an effective tool for an integrated system of future earthquake prediction

the contribution of aeolian processes to fluvial sediment yield from a desert watershed in the ordos plateau china in arid zones many active aeolian dunes terminate at ephemeral and perennial desert rivers the desert rivers show very high rates of sediment transport that cause deleterious downstream effects on the river system and ecology high sediment loading has been attributed to severe water erosion of sparsely covered watersheds during infrequent but heavy rainfall although aeolian erosion is known to lead to high rates of wind blown sand transport direct confirmation of whether the aeolian processes accelerate or inhibit fluvial sediment loss is lacking here we show that an aeolian fluvial cycling process is responsible for the high rate of suspended sediment transport in a sudalaer ephemeral desert channel in the ordos plateau of china frequent aeolian processes but low frequency once every 3 years on average flooding occur in this region wind blown saltating grains appeared to be unable to cross the desert channel because of interruption of channel induced recirculating air flow and therefore tended to settle in the channel during the windy seasons leading to channel narrowing during flooding this narrowed channel was found to yield a threefold increase in suspended sediment loading and a 3 4 fold increase in the weight percentage of the 0 08 0 2 mm sediment fraction on 18 july 2012 loss of stored aeolian sand due to channel erosion accounted for about half of the total sediment yield in this watershed these findings show that aeolian processes play an essential role in accelerating the sediment yield from a watershed characterized by aeolian fluvial interplay and also suggest that the drier the region and the greater the aeolian process the more the aeolian process contributes to fluvial sediment yield copyright 2013 john wiley sons ltd

sedimentology of the lower huronian supergroup early proterozoic elliot lake area ontario canada abstract the early proterozoic huronian supergroup is a slightly metamorphosed sedimentary succession locally 10 km thick exposed to the north of lake huron ontario canada the lower part of the supergroup comprising the matinenda mckim ramsay lake and pecors formations was studied in the quirke syncline area elliot lake and regions immediately to the west and south thirteen lithofacies are present trough and planar cross stratified sandstone quartz pebble conglomerate clay rich sandstone lenticular bedded sandstone siltstone mudstone laminated sandstone siltstone mudstone massive sandstone massive pebbly sandstone massive diamictite stratified matrix supported diamictite stratified clast supported diamictite graded diamictite and massive siltstone the lithofacies may be grouped into associations which correspond approximately to the mapped formations the crossbedded sandstones and conglomerates comprise a fluvial association matinenda formation which was formed mainly in shallow braided channels clay rich sandstone and the lenticular and laminated lithofacies constituting portions of the mckim and pecors formations were deposited on the strand and offshore areas of braid deltas interfingering laterally and vertically with the matinenda fluvial deposits four glacigenic subassociations are present in the ramsay lake formation an ice proximal subassociation i consists of massive pebbly sandstone and diamictite which progressively truncates the matinenda and mckim formations to the north the massive sandstone may be an ice override deposit formed by erosion and reworking of the underlying matinenda formation or a sub ice shelf rain out accumulation of locally eroded glacial debris subassociations ii and iii consist mainly of subaqueous sediment gravity flow and ice rain out deposits subassociation iv is interpreted as an ice proximal fluvial outwash deposit containing resedimented blocks of moraine material stratigraphic and paleocurrent data indicate a south dipping paleoslope that tilted southeast during the deposition of the fluvial and deltaic units a trough of relatively deep water extended nw se across the region transverse to the e w divergent continental margin hinge line that is assumed to have existed to the south of the project area analogies are suggested to mesozoic recent basins on the atlantic margin of canada where transverse paleogeographic trends reflect either landward extension of active oceanic fracture zones or reactivation of earlier structural lineaments

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

numerical modeling of fluvial strath terrace formation in response to oscillating climate many river systems in western north america retain a fluvial strath terrace rec ord of discontinuous downcutting into bedrock through the quaternary their importance lies in their use to interpret climatic events in the headwaters and to determine long term incision rates terrace formation has been ascribed to changes in sediment supply and or water discharge produced by late quaternary climatic fluctuations we use a one dimensional channel evolution model to explore whether temporal variations in sediment and water discharge can generate terrace sequences the model includes sediment transport vertical bedrock erosion limited by alluvial cover and lateral valley wall erosion we set limits on our modeling by using data collected from the terraced wind river basin two types of experiments were performed constant period sinusoidal input histories and variable period inputs scaled by the marine 18 o rec ord our simulations indicate that strath terrace formation requires input variability that produces a changing ratio of vertical to lateral erosion rates straths are cut when the channel floor is protected from erosion by sediment and are abandoned and terraces formed when incision can resume following sediment cover thinning high sediment supply promotes wide valley floors that are abandoned as sediment supply decreases in contrast wide valleys are promoted by low effective water discharge and are abandoned as discharge increases widening of the valley floors that become terraces occurs over many thousands of years the transition from valley widening to downcutting and terrace creation occurs in response to subtle input changes affecting local divergence of sediment transport capacity formation of terraces lags by several thousand years the input changes that cause their formation our results suggest that use of terrace ages to set limits on the timing of a specific event must be done with the knowledge that the system can take thousands of years to respond to a perturbation the incision rate calculated in the field from the lowest terrace in these systems will likely be higher than the rate calculated by using older terraces because the most recent fluvial response in the field is commonly downcutting associated with declining sediment input since the last glacial maximum this apparent increase in incision rates is observed in many river systems and should not necessarily be interpreted as a response to an increase in rock uplift rate

geological setting of the lower pleistocene fossil deposits of chilhac haute loire france the chilhac deposits ch2 and ch3 have long been known to contain exceptionally well preserved late pliocene now lower pleistocene fossils as well as alleged pebble culture artifacts found in ch3 attesting to the presence of hominins the geological complexity of the deposits in the small valley previously prevented ascertaining their stratigraphic position recent farm extension upstream the deposits provided a continuous profile and revealed previously unknown geological structures additional trenches dug at the margins of the chilhac deposits confirm the superposition of a lava flow ca 1 8 ma on the ch2 sediments after a major phase of erosion and allowed correlation of these deposits with those of ch3 another lava flow topographically inverted provides an upper limit of 2 5 ma for the age of the deposits these new observations also reveal that the valley underwent several cycles of erosion the structural complexity of the ch3 deposits suggests a landslide event affecting surface deposits volcanic tuffs and the upper part of ch2 sediments this landslide probably occurred shortly after the deposition of the ch2 sediments and the volcanic eruption these observations are compatible with the age of 2 2 ma inferred from the ch2 and ch3 fauna mnq17 biozone

sediment translation waves in braided gravel bed rivers bed load transport capacity in braided gravel bed rivers varies as hydraulic geometry changes downstream differences in capacity lead to variations in bed material storage as a consequence of bed load transport during floods in turn storage changes produce irregular fluctuations in bed level or sediment translation waves in the bed material these waves are the mechanism by which bed load is transported in braided and in fact all alluvial rivers with variable downstream hydraulic geometry an approximate expression for wave velocity indicates that annual wave travel distance can be hundreds of meters or more per year for waves up to 0 5 m high although sediment waves cause shifts in bed load rating at a cross section bed load yield may still be estimated using bed load ratings based on depth discharge relations defined for periods between rating changes a procedure is given for stable channel design in the presence of sediment waves based on equivalence of yield for some period in the design reach

stratigraphic architecture of the proterozoic succession in the eastern chattisgarth basin india tectonic implications abstract the basin fill succession of the proterozoic eastern chattisgarth basin comprises a sandstone shale conglomerate dominated shallow marine assemblage and an assemblage of limestone shale pyroclastics deposited in off shelf slope base of slope environments the proximal and distal lithologic assemblages developed as lateral equivalents and show signatures of sea level fluctuations amenable to chronostratigraphic correlation the stratigraphic architecture of the proximal assemblage is characterized by cyclic deposition on different scales the largest order cyclicity is represented by alternating sandstone sequences and mudstone dominated sequences of the order of several tens of metres the smallest order cyclicity is represented by metre scale units punctuated aggradation cycles pac bounded by isochronous surfaces the lowermost large scale sandstone sequence the lohardih sandstone unconformably overlies the highly deformed rocks of the gneissic basement complex the sequence was deposited as alluvial fan fan delta complexes controlled by basin margin faulting the upper two sandstones the daihan sandstone and the kansapathar sandstone represent two different phases of major sand accumulation in fan or river deltas their rapid emplacement over muddy shelf deposits along erosional surfaces signaled abrupt sea level fall and basinward migration of facies belts generation and accumulation of very large volumes of sand and their rapid influx into the basin accompanied by major changes in depositional motif and in the circulation system in the basin collectively indicate that larger order sand depositing cycles were caused by tectonic uplift of the cratonic basement the smallest order cycles the pacs on the other hand may be attributed to glacioeustacy though tectonic control cannot be ruled out the sand deficient mud dominated large scale sequences are attributed to major transgression during periods of relative tectonic quiescence and subsidence of the cratonic hinterland episodic tectonic uplift and derivation of sands from similar quartzo feldspathic sources suggest repeated rifting of the cratonic basement and expansion of the rift into a major marine basin

a model to study the grain size components of the sediment deposited in aeolian fluvial interplay erosion watershed abstract aeolian fluvial interplay erosion areas with complex dynamics and physical sources are the main suppliers of coarse sediment in the yellow river understanding the composition distribution and sources of deposited sediments in such areas is of great importance for the control of sediment transport in rivers in this paper a typical aeolian fluvial interplay erosion watershed the dongliu gully was studied and the frequency distribution curves of sediments deposited in the stream channel were fitted using the weibull function sources of deposited sediment in the stream channel were analyzed based on the law of the conservation of matter results showed that the hilly zone accounted for 78 of deposited sediments which were dominated by material with a median grain size d 50 of 0 093 mm and the desert zone accounted for 22 of deposited sediments which were dominated by material with a d 50 of 0 01 mm wind erosion dynamics accounted for 72 of deposited sediments while water erosion dynamics accounted for only 28 this research provides a theoretical basis for the control and management of rivers with high sediment content

late quaternary palaeolakes rivers and wetlands on the bolivian altiplano and their palaeoclimatic implications drill cores of sediments from the rio desaguadero valley bolivia provide new information about the climate of tropical south america over the past 50 000 years the modern rio desaguadero is fed by lake titicaca overflow and by local tributaries in the wetter northern altiplano and discharges into lake poopo in the more arid central altiplano during the late quaternary the rio desaguadero valley was the site of several generations of palaeolakes and wetlands that formed during periods of increased precipitation and local runoff augmented by increased overflow from lake titicaca sediments recovered by drilling in eight localities along the 390 km long valley of the rio desaguadero yield a regional history of lacustrine sedimentation and effective precipitation lacustrine strata in the drill cores record 12 distinct wet periods in the past 50 000 years four of these wet periods resulted in the formation of major palaeolakes in the rio desaguadero valley during the last glacial maximum from before 20 000 to 16 000 cal yr bp during the late glacial from about 14 000 to 12 000 cal yr bp in the early holocene from about 10 000 to 7900 cal yr bp and in the late holocene from 4500 cal yr bp to present the period that appears to have been most arid was between 7900 and 4500 cal yr bp the altiplano wet periods were generally synchronous with north atlantic cold events respectively the last glacial maximum the younger dryas the 8200 cal yr bp event and the neoglacial implying a relationship between past precipitation variability in tropical south america and north atlantic sea surface temperature copyright 2005 john wiley sons ltd

william river an outstanding example of channel widening and braiding caused by bed load addition the lower william river in northwestern saskatchewan canada presents an excellent and unambiguous example of rapid channel adjustment to abrupt additions of sandy bed load a relatively narrow and deep single channel stream as it flows northward to lake athabasca the river picks up a 40 fold increase of bed load over a 27 km reach as it encounters a large dune field just south of the lake as a result of the large infusion of eolian sand the channel develops a thoroughly braided pattern while undergoing a 5 fold increase in width and a 10 fold increase in width depth ratio