case 24 reevaluation of anomalous vertical crustal movement associated with the 1964 niigata japan earthquake it is widely acknowledged that the 1964 niigata japan earthquake is associated with the preseismic anomalous crustal movement detected by repetition of precise levelings while some doubts have been raised on the validity of reported precursory movement validity of the crustal movement is tested by an analysis of tidal data when we are able to deduce crustal movement referring to the determined mean sea level we can discuss the absolute crustal movement tidal data along the japan sea coast of northeast japan are analyzed by the method developed intsumura 1963 1970 for the period from 1955 to 1986

downstream hydraulic geometry and channel adjustment during a flood along an ephemeral arid region drainage in september 1997 a dissipating tropical storm caused a flood with an estimated maximum discharge of 240 m 3 s along yuma wash an ephemeral braided system draining 186 km 2 in southwest arizona older high water marks that record a flood peak of 1280 m 3 s provide a reasonable estimate for the probable maximum flood along the wash detailed channel crosssectional surveys during 1995 and again in 1998 6 months after the 1997 flood facilitated examination of downstream hydraulic geometry and channel adjustment during the flood channel width increased substantially downstream exponent of 0 78 presumably because of low bank resistance whereas hydraulic depth and velocity had modest downstream increases 0 15 and 0 14 respectively channel aggradation generally occurred along wider braided reaches moreover degradation occurred in narrow reaches with fewer channels aggradation and degradation also appeared to be governed by a threshold relationship between flow depth and vegetated bars degradation occurred where flow was confined within a channel or subchannel at discharges sufficiently high to overtop vegetated bars greater roughness facilitated sediment deposition and channels aggraded a discriminant function correctly classified nearly 90 of the cross sections as scoured or filled using a single hydraulic variable maximum depth of flow during the dissipating tropical storm d 2002 elsevier science b v all rights reserved

forms and processes of two highly contrasting rivers in arid central australia and the implications for channel pattern discrimination and prediction tooth s nanson g c 2004 forms and processes of two highly contrasting rivers in arid central australia and the implications for channel pattern discrimination and prediction geological society of america bulletin 116 7 8 802 816 rae2008

channel instability in a braided sand bed river the gila river of central arizona is representative of braided sand bed rivers in alluvial valleys that have inherent unstable behavior and destructive channel migration the 112 year record of channel conditions along a portion of the gila river provides data for the construction of locational probability maps for main flow channels zones of stability and hazardous instability alternate with each other at 3 2 km 2 mi intervals during the past century the overall sinuosity of the main flow channel has remained close to 1 18 despite numerous changes in actual location spatial and temporal variation of sinuosity have occurred in subreaches as a result of sedimentation behind a dam and fluctuations in the density of phreatophyte growth which both affect the hydraulics of flood flows unstable zones of the channel correspond to the surface of the sediment wedge behind the dam and areas dense phreatophyte growth stable zones correspond to areas controlled by bedrock or man made structures as well as locations determined by these external factors plus the requirement to maintain a consistent sinuosity channels such as that of the gila river do not meet most assumptions of equilibrium and are best understood through probabilistic approaches with an assumption of catastrophic adjustment

climatic geomorphic and archaeological implications of a late quaternary alluvial chronology for the lower salt river arizona usa abstract recent archaeological excavations along the lower salt river arizona resulted in the unexpected discovery of buried late pleistocene soils and cultural features dating 5800 7100 cal ybp early archaic the latter representing the earliest evidence of human activity in the lower salt river floodplain thus far identified because the lower salt river floodplain has been heavily impacted by recent agriculture and urbanization and contains few stratigraphic exposures our understanding of the river s geological history is limited here we present a late quaternary alluvial chronology for a segment of the lower salt river based on 19 accelerator mass spectrometry 14 c and four optically stimulated luminescence ages obtained during two previous geoarchaeological investigations deposits are organized into allostratigraphic units and reveal a buried late pleistocene terrace inset into middle to late pleistocene terrace deposits holocene terrace fill deposits unconformably cap the late pleistocene terrace tread in the site area and the lower portion of this fill contains the early archaic archaeological features channel entrenchment and widening 900 cal ybp eroded much of the older terrace deposits leaving only a remnant of fill containing the buried latest pleistocene and middle to late holocene deposits preserved in the site area subsequent overbank deposition and channel filling associated with a braided channel system resulted in the burial of the site by a thin layer of flood sediments our study confirms that the lower salt river is a complex mosaic of late quaternary alluvium formed through vertical and lateral accretion with isolated patches of buried soils preserved through channel avulsion although channel avulsion is linked to changes in sediment load and discharge and may have climatic linkages intrinsic geomorphic and local base level controls limit direct correlations of lower salt river stratigraphy to other large rivers in the north american southwest

variations in flood magnitude effect relations and the implications for flood risk assessment and river management abstract in spite of major physical impacts from large floods present river management rarely takes into account the possible dynamics and variation in magnitude impact relations over time in flood risk mapping and assessment nor incorporates feedback effects of changes into modelling using examples from the literature and from field measurements over several decades in two contrasting environments a semi arid region and a humid temperate region temporal variations in channel response to flood events are evaluated the evidence demonstrates how flood physical impacts can vary at a location over time the factors influencing that variation on differing timescales are examined the analysis indicates the importance of morphological changes and trajectory of adjustment in relation to thresholds and that trends in force or resistance can take place over various timescales altering those thresholds sediment supply can also change with altered connectivity upstream and changes in state of hillslope channel coupling it demonstrates that seasonal timing and sequence of events can affect response particularly deposition through sediment supply duration can also have a significant effect and modify the magnitude relation lack of response or deposits in some events can mean that flood frequency using such evidence is underestimated a framework for assessment of both past and possible future changes is provided which emphasises the uncertainty and the inconstancy of the magnitude impact relation and highlights the dynamic factors and nature of variability that should be considered in sustainable management of river channels

morphological impacts of flow events of varying magnitude on ephemeral channels in a semiarid region abstract flows in ephemeral channels in semiarid areas are only occasional and channel changes are episodic but the flash floods can be devastating and have major geomorphological impacts data on morphological impacts of flows in semiarid areas are needed to increase understanding of the dynamics and variability of geomorphic responses in such channels for this purpose nine reaches of river channel in three catchments in se spain the nogalte torrealvilla and salada have been sites for measurement of flows and their effects over the period 1997 2012 the sites encompass a range of channel size channel morphology substrate vegetation and position within the catchments a major difference is between schist and marl bedrock areas peak flow stage has been recorded and topography surveyed at frequent intervals and after major flow events over the 16 year period an average of 0 5 flow events per year has been recorded at the schist sites and an average of one per year at the marl sites but occurrence has been highly variable from year to year threshold daily rainfall for channel flow is mostly 15 20 mm but higher rainfalls do not always produce flow one to two major floods have occurred in each of the catchments in the period including the extreme flood event of september 2012 in the nogalte catchment measured morphological changes have occurred between 2 and 10 times at the monitored sites the same size flow can have differing effects depending on the state of the system low flow can mobilise sediment without producing much morphological change the long term trajectory of the reaches and the sediment substrate has a major influence on response to events channel change is governed by threshold values of hydraulic conditions the measurements provide an indication of the scale of maximum erosion and deposition that occurs within the channels and on the floodplains over a range of flow magnitudes and the flow impacts that need to be considered in management

planform cyclicity in an unstable reach complex fluvial response to environmental change long and short term channel changes are documented and analysed for a historically unstable reach of the river severn at llandinam mid wales long term changes the last 150 years reconstructed from 10 archival sources are characterized by channel planform switching between meandering 1836 1840 and 1948 1963 and braided 1884 1903 and 1975 present phases short term changes monitored by detailed planform surveys over a 2 5 year period showed smaller scale channel adjustments involving channel switching bar accretion and channel expansion phases of braiding at llandinam have been triggered by extrinsic controls primarily flooding but intrinsic controls floodplain sediments planform evolution and channel gradient have been influential in priming the reach prior to destabilization flow regulation on the river severn since 1968 has partly frozen the planform of the contemporary braid zone management of channel planform adjustments where environmental change is phased in over time must be informed by a knowledge of the potential for triggered planform switches in addition the effects of environmental change on fluvial systems are often historically contingent upon the state of the channel at the time of impact 1998 john wiley sons ltd

discontinuous ephemeral streams abstract many ephemeral streams in western north america flowed over smooth valley floors before transformation from shallow discontinuous channels into deep arroyos these inherently unstable streams of semiarid regions are sensitive to short term climatic changes and to human impacts because hillslopes supply abundant sediment to infrequent large streamflow events discontinuous ephemeral streams appear to be constantly changing as they alternate between two primary modes of operation either aggradation or degradation may become dominant attainment of equilibrium conditions is brief disequilibrium is promoted by channel entrenchment that causes the fall of local base level and by deposition of channel fans that causes the rise of local base level these opposing base level processes in adjacent reaches are maintained by self enhancing feedback mechanisms the threshold between erosion and deposition is crossed when aggradational or degradational reaches shift upstream or downstream extension of entrenched reaches into channel fans tends to create continuous arroyos upvalley migration of fan apexes tends to create depositional valley floors with few stream channels less than 100 years is required for arroyo cutting but more than 500 years is required for complete aggradation of entrenched stream channels and valley floors discontinuous ephemeral streams have a repetitive sequence of streamflow characteristics that is as distinctive as sequences of meander bends or braided gravel bars in perennial rivers the sequence changes from degradation to aggradation headcuts concentrate sheetflow a single trunk channel conveys flow to the apex of a channel fan braided distributary channels end in an area of diverging sheetflow and converging sheetflow drains to headcuts the sequence is repeated at intervals ranging from 15 m for small streams to more than 10 km for large streams lithologic controls on the response of discontinuous ephemeral streams include 1 amount and size of sediment yielded from hillslopes 2 infiltration capacity of valley floor alluvium that influences both the unit stream power available for upstream headcut migration and the attenuation of flashy streamflow events by riparian vegetation in sheetflow reaches and 3 cohesiveness of alluvium which affects headcut and streambank morphology and rates of arroyo extension downcutting and widening initiation of arroyo cutting may be too complex to be attributed to a single cause such as change in mean annual precipitation or grazing by livestock but is most likely associated with a decrease in density of protective plant cover on hillsides and along valley floors relatively larger unit stream power makes downstream reaches more susceptible to initial entrenchment during floods than headwaters reaches and favors persistent arroyos entrenchment continues until an equilibrium longitudinal profile is briefly attained then channel widening occurs streambanks are undercut and aggradation begins

palaeoflood hydrology of the salt river arizona geomorphic evidence along bedrock confined reaches of the salt river in east central arizona provides a record of the river s largest flood events fine grained flood slackwater deposits accumulated at channel margin irregularities several metres above the low flow channel discharges associated with flow events responsible for the deposits were estimated by computer flow modelling these estimates document flood magnitudes in excess of gauged historic streamflows relative and radiocarbon dating suggest that a flood record in excess of 600 y is preserved in the slackwater sequences a prominent flood scar cut into grussy hillslope soils allows the extension of the prehistoric flood record to several thousand years a maximum discharge estimate of 4600 m3s 1 affixed to the flood scar represents the largest flood event in the record and is given a minimum recurrence interval of 1000 2000 y the 1952 flood is the largest historic flow event experienced along the study reach and is estimated at 2900 m3s 1 two palaeoflood events preserved in the slackwater stratigraphy exceed the 1952 event and are given recurrence intervals of 300 and 600 y the latter flood event had an estimated discharge of 3200 m3s 1 it is apparent that discharge estimates affixed to these infrequent large magnitude flood events approach a maximum with decreased probabilities large recurrence intervals this suggests that a physical limit on discharge may exist within the salt river drainage basin and is perhaps directly related to drainage basin size

typology of segregated armoured paved surfaces some comments a review of the characteristics of segregated surfaces and consideration of the origins of the terms armoured and paved suggests that the two terms are interchangeable and that neither term is specifically associated with a particular segregation process the dichotomy between segregated surfaces which are formed in channels in which the entire range of bed material is mobile under the prevailing hydrologic regime and segregated surfaces which are intrinsically stable forms the basis of an elementary distinction between different types of segregated surface it is suggested that the term stable armour or stable pavement be applied to those cases where the segregated surface is considered to be inactive under the prevailing hydrologic regime and that the term unstable armour or unstable pavement be applied to cases where the segregated surface experiences periodic mobilization

longitudinal distribution and parameters of large wood in a mediterranean ephemeral stream abstract although large wood lw has been intensively studied in forested basins of humid temperate climates data on lw patterns in different fluvial environments are rather scarce therefore we investigated the dimensions characteristics longitudinal distribution and dynamics of lw along a 4 05 km long reach of an ephemeral channel typical of european mediterranean mountainous landscape sfakiano gorge crete greece we analysed a total of 795 lw pieces and the mean observed abundance of lw was generally lower 14 3 m3 ha of active valley floor or 19 6 lw pieces 100 m of stream length than is usually documented for more humid environments the number of lw pieces was primarily controlled by trees growing on the valley floor these living trees acted as important lw supply agents by tree throws or the supply of individual branches with sufficient lw dimensions and flow obstructions during large flood events causing storage of transported lw pieces in jams however the downstream transport of lw is probably episodic and large jams are likely formed only during major floods after 15 years we still observed significant imprints of the last major flood event on the present distribution of lw the geomorphic function of lw in the studied stream can only be perceived to be a spatially limited stabilising element for sediments which was documented by a few accumulations of coarse clastic material by lw steps and jams

instantaneous geodetic positioning with 10 50 hz gps measurements noise characteristics and implications for monitoring networks 1 recent earthquake recordings from high rate 1 hz continuous gps stations in california indicate that even higher temporal resolution provided by modern gps receivers is desirable we measured seven baselines during time intervals devoid of detectable transient signals at sampling rates of 1 50 hz with geodetic receivers from four manufacturers to investigate the noise characteristics of these data our tests over short distances meters to typical station spacing tens of kilometers of regional gps networks show no loss of spatial resolution compared to 1 hz samples measurement noise is red with the typical ramp profile of log log spectra below about 0 5 hz above this frequency noise is essentially white low pass filtering of high rate positions achieves improved spatial resolution compared to decimated raw samples averaging 20 hz measurements to 2 hz samples on a 40 km baseline for example yields about 0 5 mm horizontal and about 3 4 mm vertical accuracy at high frequencies these estimates are a factor of 2 2 5 better than for 2 hz raw samples the improvements in spatial resolution due to averaging at high frequencies are substantial and approach the theoretical square root of n expectation for independent samples however since noise spectral densities rise rapidly below about 0 5 hz low pass filtering is only effective above this frequency these results have important implications for the design of continuous gps networks for crustal deformation and structural monitoring and for positioning and attitude determination of dynamic platforms

sedimentology geochemistry and osl dating of the alluvial succession in the northern gujarat alluvial plain western india a record to evaluate the sensitivity of a semiarid fluvial system to the climatic and tectonic forcing since the late marine isotopic stage 3 abstract the alluvial successions in the northern gujarat alluvial plain western india have been investigated for reconstructing the climatic fluctuations during the last 40 ka alluvial architecture and geochemical proxies indicate prevalence of a strengthened indian summer monsoon ism with fluctuations between the late marine isotopic stage 3 mis 3 37 ka to the early mis 2 27 ka a gradual onset of aridity declining ism after 27 ka with peak aridity at 22 ka is observed a gradual strengthening of ism at around 18 and 12 ka followed by a short reversal in ism intensity between 12 and 11 ka is attributed to the younger dryas yd cooling event the aeolian sand sheet dated to 6 and 3 5 ka represents the onset of regional aridity following this a short lived humid phase was observed after 2 ka which includes the medieval warm period mwp the study suggests that the variability in the ism to the latitudinal migration of the inter tropical convergence zone was caused by insolation driven cooling and warming events in the north atlantic the incision of the valley fill alluvium occurred in two distinct phases the older incision phase occurred after 11 ka and before 6 ka whereas the younger incision phase that led to the development of present day topography is bracketed between 3 5 ka and before 1 ka the older incision phase is ascribed to the early to mid holocene enhanced ism climatically driven whereas the younger incision seems to be modulated by the activation of basement faults tectonically driven

secular and earthquake related vertical crustal movements in japan as deduced from tidal records 1951 1981 abstract monthly tidal records for the last 31 years from about 100 tidal stations are used to delineate vertical crustal movements in japan a new computer aided processing system was created for this purpose its principle is differential use of tidal records in a region so that the oceanographic disturbances of common causes may be eliminated from the sea level data this method enables us to observe nearly absolute vertical land movement at tidal stations with a precision of a few centimeters the japanese islands are divided into nine regions taking oceanographic conditions into account general discussion on recent vertical movements has yielded several notable features and trends as follows 1 1 rapid and stationary subsidence in the northeastern part of japan presumably of tectonic origin 2 2 a complex pattern of uplift and subsidence in the southwestern part of japan which seems to reflect subduction of the philippine sea plate against the honshu block 3 3 relatively stable land on the japan sea side of honshu movements related to the earthquakes during the period 1951 1981 are also discussed although few of the cases show clear cut premonitory movements if abnormal movements in a coastal area appeared with an amplitude exceeding 2 or 3 cm we could detect them by the present system

meander hydromorphology of ephemeral streams similarities and differences with perennial rivers abstract the geomorphology hydrology and processes of ephemeral streams are poorly known and studies on the geomorphic characteristics of ephemeral meandering streams ems are even less investigated we collected geomorphic data namely channel width sinuosity wavelength and curvature radius from 107 ems reaches in different drylands of the world from googleearth pro satellite images geomorphology features processes such as neck cutoffs point scrolls and chute cutoffs were also assessed the main aim of this paper is to investigate similarities and differences between ems and perennial counterparts of more humid areas on which almost all hydrogeomorphic models are based for the purpose of explaining why meandering rivers form in environments where the lack of vegetation sporadic flows and a high sediment supply should favour the development of braided rivers ems showed both geomorphological similarities and differences with perennial rivers point bar chute cutoffs and point bar scrolls are the most common geomorphic features of ems suggesting a certain stability of meander behaviour though within a continuous process of changes towards the most probable form similarly to perennial streams the bimodal distribution of curvature ratio values departs substantially from that of perennial rivers that are commonly in the 2 3 range data from the rivers in this study indicate that their channel pattern is well described by the same sine generated function used for perennial rivers wavelength to channel width ratio and bankfull discharge to streambed gradient of ems unexpectedly plot in different areas of classical diagrams developed for perennial rivers we interpret such differences in terms of excess energy expenditure for high sediment load transport we also propose a new function to discriminate the meandering from the braided pattern of ephemeral streams and present a conceptual model of meander formation in ephemerals streams based on an autogenic process of bank collapse and bar deposition

flood related channel change in an arid region river a review of 112 years of change in the channel of the salt river central arizona u s a shows that this arid region river has a main flow channel that has migrated laterally up to 1 6 km 1 mi in response to floor events maps showing locational probabilities indicate that along the channel zones of relative locational stability alternate with zones of relative instability at a 3 2 km 2 mi interval construction of upstream reservoirs has reduced sediment input into the main river but has not controlled floods the channel width has not changed except for moderate fluctuations around mean values the main flow channel has incised approximately 6 m 20 ft over most of the 48 km 30 mi study reach during six recent floods gradient has remained unchanged during floods bed material was mobilized to a depth below the original bed level that was greater than the height of the water surface above the original bed calculations based on tractive force indicate a threshold discharge of instability that is equal to the flow with a five year return interval the river exhibits remarkable stability with respect to gradient and sinuosity irrespective of water and sediment discharges but horizontal channel location exhibited selective instability over the record period of more than a century the channel appears not to have been in equilibrium considering geometry discharge and sediment

impact of flow variability on the morphology of a low energy meandering river few studies have precisely documented the response of stream channels to short term flow variability this paper examines the impact of sequential flows of various magnitudes on the morphology of a low energy river in northeastern illinois u s a between june 1986 and november 1988 channel cross sections were surveyed on a semiannual basis at 26 locations along a 7 2 km stretch of the des plaines river during this period an estimated 100 year flood several bankfull flows and an extreme low flow associated with a severe drought occurred the response of the river channel to each of these events was relatively minor mean changes for the reach were generally less than 3 per cent for mean depth and less than 1 per cent for width statistical analysis indicates that net changes in width and depth over the entire period were not significantly different from zero this lack of geomorphic response is attributable to low stream power low hydrologic variability fine bed materials and cohesive banks along this stretch of river although dramatic changes in channel morphology did not occur subtleties in geomorphic response were observed that reflect the temporal ordering of hydrologic events

a systematic compilation of earthquake precursors article a survey of published scientific literature was undertaken to identify and catalog observed earthquake pre cursors the earthquake precursors selected for analysis included electric and magnetic fields gas emissions groundwater level changes temperature changes surface deformations and seismicity for each of these precursors the published scientific literature was searched to document the statistics of each reported earth quake precursor spatial extent time duration amplitude signal noise ratio to analyze dependence of the observable for each precursor on earthquake magnitude and to explore proposed physical models to explain eachearthquakeprecursor somegeneralcharacteristics wereobservedfortheseprecursoryphenomena first the largest amplitude precursory anomalies tend to occur before the largest magnitude earthquakes also the number of precursory anomalies tends to increase the closer in time to the occurrence of the earthquake finally theprecursoryanomaliestendtooccurclosetotheeventualepicenterof theearthquake ingeneral the physical models indicate that all of the precursory phenomena are related to deformation that occurs near the fault prior to the main earthquake while the models provide plausible physical explanations for the pre cursors there are many free parameters in the models that are poorly resolved

the natural and human structuring of rivers and other geomorphological systems a tribute to william l graf this special issue honors the contributions of william l graf to geomorphology and river science a hallmark of will s work over the course of his career has been a focus on the natural and human structuring of river systems more broadly will has been an innovator and leader who has shaped the way in which geomorphologists conduct research through his work he has made fundamental contributions to basic fluvial theory to the understanding of human impacts on river systems and to policy relevant science he has demonstrated by example how to pursue policy relevant science and to participate in science based policy formulation his contributions to river science can be classified into several themes 1 the hydrology and geomorphology of suburban drainage systems 2 riparian vegetation and river systems 3 the spatial structure and dynamics of incised channels 4 the dynamics of dryland river systems 5 heavy metals in river systems 6 dams and dam removal and 7 water and public policy the papers in this special issue reflect many aspects of these themes and address topics related to 1 the understanding of rivers and other geomorphic systems in the midst of dynamic physical change 2 human influences on geomorphic processes 3 the intersection of geomorphology and public policy and 4 the fusion of geomorphic analysis and giscience

downstream trends in sediment size and composition of channel bed bar and bank deposits related to hydrologic and lithologic controls in the llano river watershed central texas usa abstract the downstream fining of fluvial sediments is a fundamental tenet of drainage systems and for decades has been the subject of considerable research most of this research has focused on variability in channel bed material other sedimentological components such as channel bars and banks however represent distinctively different processes occurring at various flow magnitudes and durations and thus provide an opportunity to examine a more comprehensive set of controls on the larger fluvial system this study analyses downstream patterns of sediment size and composition for channel bed material bars and banks in the llano river watershed 11 568 km2 in central texas usa fluvial deposits in the study area were characterized through field laboratory and statistical analyses and standard sedimentary indices d16 d50 d84 sorting were computed two hundred thirty eight sediment samples were collected at 15 sites along the main stem channel with sampling occurring at the low flow channel thalweg lateral bars banks and overbank locations channel bar deposits are characterized by a downstream reduction in particle size but low flow channel deposits have a substantially weaker trend a discrepancy possibly attributed to uniformity and continuity of hydraulic sorting mechanisms during moderate and high flows channel bar deposits reveal an abrupt downstream reduction in gravel size in the upper watershed which is attributed to an increase in drainage area further an abrupt gravel to sand transition occurs immediately downstream of a distinct lithologic change from mostly carbonate rocks to igneous and metamorphic rocks the downstream decrease in channel bar particle size occurs despite an increasingly constricted alluvial valley commonly associated with greater unit stream power and relatively coarse sediment contrasting with channel bed material particle size of channel banks increases downstream which is attributed to the addition of sand sized sediment from igneous and metamorphic rocks the consideration of distinctive sedimentological components of a dynamic fluvial system represents a more comprehensive and nuanced study of the topic of downstream sediment trends than prior studies which is important to a range of engineering biological and planning issues at the watershed scale

sediment connectivity a framework for understanding sediment transfer at multiple scales a major challenge for geomorphologists is to scale up small magnitude processes to produce landscape form yet existing approaches have been found to be severely limited new ways to scale erosion and transfer of sediment are thus needed this paper evaluates the concept of sediment connectivity as a framework for understanding processes involved in sediment transfer across multiple scales we propose that the concept of sediment connectivity can be used to explain the connected transfer of sediment from a source to a sink in a catchment and movement of sediment between different zones within a catchment over hillslopes between hillslopes and channels and within channels using fluvial systems as an example we explore four scenarios of sediment connectivity which represent end members of behaviour from fully linked to fully unlinked hydrological and sediment connectivity sediment travel distance when combined with an entrainment parameter reflecting the frequency magnitude response of the system maps onto these end members providing a coherent conceptual model for the upscaling of erosion predictions this conceptual model could be readily expanded to other process domains to provide a more comprehensive underpinning of landscape evolution models thus further research on the controls and dynamics of travel distances under different modes of transport is fundamental copyright 2014 john wiley sons ltd

holocene paleofloods of the ross river central australia abstract the rivers of central australia rise in the macdonnell ranges and flow out across broad low relief plains into the surrounding desert the stratigraphy of the ross river plain records the areal extent and frequency of holocene floods this floodout plain is underlain by deeply weathered alluvial deposits characterized by red earth soils dated by thermoluminesence at 59 000 yr this old alluvium is covered by a sheet like deposit of very silty sand of probable eolian origin dated by thermoluminesence at 9200 900 yr the oldest holocene alluvium occurs as broad low relief bars and levee deposits flanking the modem channel and as low relief long wavelength bedforms that fan out across the plain this deposit resulted from a flood flow up to 10 km wide that covered the entire plain evidence for several large floods between 1500 and 700 yr b p is also preserved in a 500 to 1500 m wide paleochannel thus the surface features on the floodout plains are the product of a few rare large flood events this paleohydrologic record is additional evidence of the dynamic nature of the hydrometerological regime of central australia

sediment transport and bed morphology at river channel confluences river channel confluences form important morphological elements of every river system being points at which rapid changes in flow sediment discharge and hydraulic geometry must be accommodated this article presents results of a quantitative investigation of sediment transport at channel confluences accomplished through both scaled laboratory flume simulation and complementary monitoring of a natural channel confluence bed morphology at channel confluences is characterized by three distinct elements avalanche faces at the mouth of each confluent channel a deep central scour and a bar within the separation zone formed at the downstream junction corner these elements are controlled predominantly by the confluence angle and the ratio of discharges between the tributary and mainstream channels as confluence angle and discharge ratio increase the sediment contributions from the confluent channels are progressively segregated in their paths through the junction with sediment being transported around rather than through the centre of the confluence this segregation of sediment loads is accompanied by the retreat of the main channel avalanche face from the confluence an increase in the scour depth a change in the orientation of the scour and an increase in the size of the separation zone bar field measurements closely replicate the flume simulation a model of sediment transport and bed morphology links these features to the fluid dynamics of these sites an understanding of confluence dynamics is important not only in considerations of channel morphology and design criteria but must form the basis for the interpretation of confluence sediments in the ancient record

landsat imagery based visualization of the geomorphological development at the terminus of a dryland river system abstract in this remote sensing based study we present the analysis of the geomorphological development at the low gradient terminus of the modern rio colorado dryland river system in the endorheic altiplano basin bolivia changes in the river morphology occur after short periods of catastrophic peak discharge which result in the expansion of existing crevasse splays formation of new crevasse splays and in river path avulsion episodic peak discharge events in the study area were pinpointed and quantified by combining daily precipitation records from gauging stations in the vicinity with catchment area analysis from aster global dem gdem remote sensing data a time series of landsat imagery for the period 1975 2001 was then used to analyze the river morphology changes after major peak discharge events compensational stacking of crevasse splays in combination with river avulsion produced a thin but aerially extensive connected sand sheet at the terminus of the fluvial system