embedding reach scale fluvial dynamics within the caesar cellular automaton landscape evolution model abstract we introduce a new computational model designed to simulate and investigate reach scale alluvial dynamics within a landscape evolution model the model is based on the cellular automaton concept whereby the continued iteration of a series of local process rules governs the behaviour of the entire system the model is a modified version of the caesar landscape evolution model which applies a suite of physically based rules to simulate the entrainment transport and deposition of sediments the caesar model has been altered to improve the representation of hydraulic and geomorphic processes in an alluvial environment in channel and overbank flow sediment entrainment and deposition suspended load and bed load transport lateral erosion and bank failure have all been represented as local cellular automaton rules although these rules are relatively simple and straightforward their combined and repeatedly iterated effect is such that complex non linear geomorphological response can be simulated within the model examples of such larger scale emergent responses include channel incision and aggradation terrace formation channel migration and river meandering formation of meander cutoffs and transitions between braided and single thread channel patterns in the current study the model is illustrated on a reach of the river teifi near lampeter wales uk

use of airborne lidar and historical aerial photos for characterising the history of braided river floodplain morphology and vegetation responses this paper combines synoptic airborne lidar data with historical aerial photos to reconstruct floodplain formation and relate this with vegetation patch characteristics on three different alpine braided rivers in france displaying a gradient of geomorphic activity bouinenc drome bes lidar data were processed to extract understory topography and vegetation properties once combined with sequential aerial photographs for the dating of floodplain formation they were used to establish the timing of channel incision associated with active channel narrowing it has thus been possible not only to reconstruct the main incision periods following the end of the little ice age but also to show the geomorphic effect of floods on active channel widening which was clearly modulated by sediment supply conditions well developed floodplains with a predominance of mature vegetation units are associated with long term narrowing and incision trajectories whereas rivers maintaining a wide active channel over time show equi diversity of floodplain vegetation units the presence of shrub patches seems to be a good indicator of incision periods a discriminant analysis using lidar derived topographic and vegetation properties of floodplain patches as well as their age provided a validation of the expert based mapping of physiognomic vegetation units shrubland sparse pioneer dense pioneer and post pioneer units this approach also provides insights into identification and interpretation of misclassifications and open new perspectives for exploring landscape ecological trajectories and their controlling factors

gravel bed channel changes upstream of a reservoir the case of the dunajec river upstream of the czorsztyn reservoir southern poland abstract despite a significant increase in the number of dam reservoirs in the world in the last century the effects of these structures on the evolution of river channels above them are poorly understood constructed in 1997 in the polish carpathians the czorsztyn reservoir cr has raised the base level of the single thread gravel bed dunajec river an analysis of five sets of aerial photographs and orthophotos from the period before 1977 1982 1994 and after 2003 2009 the construction of the cr allowed me to investigate the temporal and spatial impact of the raised base level of the river upstream of the reservoir on the evolution of the river channel comparison of channel width changes in the backwater river section with changes observed in the control section unaffected by the presence of the reservoir has shown that in the pre dam period differences in the evolution of the river channel in the backwater section and in the control section were not statistically different in the periods without major floods both channel sections were dominated by channel narrowing or a relative stability of channel width in the post dam period a major flood in 1997 caused more than two times greater channel widening in the backwater section than in the control section the extent of channel widening in the longitudinal channel profile reached farther upstream of the reservoir than the extent of the backwater itself in the later part of the post dam period without major floods channel narrowing were similar in the backwater section and the control section as had been the case in the period before the reservoir construction the comparison of changes in the width of the channel in the backwater and control sections indicates that channel widening in the backwater interpreted as an early stage of backwater channel adjustment was reinforced by the flood of 1997 this study shows that the use of a control section makes it possible to isolate reservoir effects from flood effects in the context of channel dynamics

fluorapatite in the paleoproterozoic thelon basin structural stratigraphic context in situ ion microprobe u pb ages and fluid flow history fluorapatite cements have been documented at more than 18 localities in the thelon basin canada occupying stratigraphic positions from the paleosol below the unconformity to well within the upper parts of depositional sequence of the fluvial siliciclastic thelon formation ion microprobe analyses targeted using cathodoluminescence images to areas of higher uranium content on petrographically characterized cements provide the most precise pin on the timing of mesodiagenesis in the northeastern part of the thelon basin at 1667 5 ma expulsion of phosphate rich basinal brines was associated with development of faults and local breccias in the lower strata where extensive quartz cementation took place before the apatite event the new data do not support previous interpretations for multiple episodes of fluorapatite cementation within the basin despite the wide range of stratigraphic positions and variations in style of occurrence the tectonic cause remains speculative as does the relationship of the fluorapatite cements to the unconformity style uranium mineralization thelon fluorapatite cements are older than those reported in the athabasca basin suggesting distinct fluid flow histories occurred within the two basins the difference in timing indicates that the basinwide events that generated the fluids with the chemistry capable of producing fluorapatite cement took place independently but under similar conditions within the thelon and athabasca basins

effects of lateral confinement in natural and leveed reaches of a gravel bed river snake river wyoming usa this study examined the effects of natural and anthropogenic changes in confining margin width by applying remote sensing techniques fusing lidar topography with image derived bathymetry over a large spatial extent 58 km of the snake river wy fused dem s from 2007 and 2012 were differenced to quantify changes in the volume of stored sediment develop morphological sediment budgets and infer spatial gradients in bed material transport our study spanned two similar reaches that were subject to different controls on confining margin width natural terraces vs artificial levees channel planform in reaches with similar slope and confining margin width differed depending on whether the margins were natural or anthropogenic theeffects of tributaries also differed between the two reaches generally the natural reach featured greater confining margin widths and was depositional whereas artificial lateral constriction in the leveed reach produced a sediment budget that was closer to balanced although our remote sensing methods provided topographic data over a large area net volumetric changes were not statistically significant due to the uncertainty associated with bed elevation estimates we therefore focused on along channel spatial differences in bed material transport rather than absolute volumes of sediment to complement indirect estimates of sediment transport derived by morphological sediment budgeting we collected field data on bed mobility through a tracer study surface and subsurface grain size measurements were combined with bed mobility observations to calculate armoring and dimensionless sediment transport ratios which indicated that sediment supply exceeded transport capacity in the natural reach and vice versa in the leveed reach we hypothesize that constriction by levees induced an initial phase of incision and bed armoring because levees prevented bank erosion the channel excavated sediment by migrating rapidly across therestricted braidplain and eroding bars and islands

cellular modelling of river catchments and reaches advantages limitations and prospects the last decade has witnessed the development of a series of cellular models that simulate the processes operating within river channels and drive their geomorphic evolution their proliferation can be partly attributed to the relative simplicity of cellular models and their ability to address some of the shortcomings of other numerical models by using relaxed interpretations of the equations determining fluid flow cellular models allow rapid solutions of water depths and velocities these can then be used to drive usually conventional sediment transport relations to determine erosion and deposition and alter the channel form the key advance of using these physically based yet simplified approaches is that they allow us to apply models to a range of spatial scales 1 100 km 2 and time periods 1 100 years that are especially relevant to contemporary management and fluvial studies however these approaches are not without their limitations and technical problems this paper reviews the findings of nearly 10 years of research into modelling fluvial systems with cellular techniques principally focusing on improvements in routing water and how fluvial erosion and deposition including lateral erosion are represented these ideas are illustrated using sample simulations of the river teifi wales a detailed case study is then presented demonstrating how cellular models can explore the interactions between vegetation and the morphological dynamics of the braided waitaki river new zealand finally difficulties associated with model validation and the problems prospects and future issues important to the further development and application of these cellular fluvial models are outlined 2007 elsevier b v all rights reserved

a model of channel response in disturbed alluvial channels dredging and straightening of alluvial channels between 1959 and 1978 in west tennessee caused a series of morphologic changes along modified reaches and tributary streams degradation occurred for 10 to 15 years at sites upstream of the area of maximum disturbance and lowered bed levels by as much as 6 1 m following degradation reaches upstream of the area of maximum disturbance experienced a secondary aggradation phase in response to excessive incision and gradient reduction aggradation downstream of the area of maximum disturbance reached 0 12 m per year with the greatest rates occurring near the stream mouths the adjustment of channel geometry and phases of channel evolution are characterized by six process oriented stages of morphologic development premodified constructed degradation threshold aggradation and restabilization down cutting and toe removal during the degradation stage causes bank failure by mass wasting when the critical height and angle of the bank material is exceeded threshold stage channel widening continues through the aggradation stage as the slough line develops as an initial site of lower bank stability the bank profile develops three dynamic elements 1 vertical face 70 to 90 2 upper bank 25 to 50 and 3 slough line 20 to 25 alternate channel bars form during the restabilization stage and represent incipient meandering of the channel

dam induced base level rise effects on the gravel bed channel planform little is known on the planform evolution of gravel bed rivers in base level raised backwater zones upstream from dam reservoirs the general model of river channel response to base level rise predicts a decrease in river sinuosity however the observations of channel adjustments in the reservoir backwater document a narrower and more sinuous channel developed as a result of fine sediment deposition and vegetation expansion here the long term aerial photo based observations 1963 2015 of two gravel bed rivers of different initial channel pattern the dunajec and its tributary the smolnik located in the base level raised zone of the roznow reservoir in the polish carpathians were analyzed the results show that the initially multi thread river in backwater was significantly narrowed and its sinuosity increased phase 1 which was followed by the stabilization of channel planform phase 2 however in the initially single thread river only phase 2 occurred the rate of channel narrowing observed on the initially multi thread river was positively related to the initial channel width r2 0 90 p 0 0001 and bar width r2 0 81 p 0 0001 the increase in sinuosity was higher in the previously wider channel section and did not occur in the valley confined zones of the single thread river the results are conceptualized in a two phase conceptual model which hypothesizes that the trajectories of the long term planform adjustments of gravel bed river in backwater are controlled by the initial river morphology which creates accommodation space for fine sediment deposition and associated vegetation expansion

channel metamorphosis floodplain disturbance and vegetation development ain river france abstract the purpose of this paper is to describe and explain channel metamorphosis of the ain river in east central france and the effects of this metamorphosis on floodplain disturbance and vegetation development the ain river is a 195 km long stream originating in the jura mountains which flows into the rhone river between lyon france and geneva switzerland the lower 40 km of the ain river beyond the mountain front are situated in a valley of outwash deposits where the floodplain is 0 2 to 1 2 km wide a complex mosaic of floodplain landscape units has developed maps dating back to 1766 and six sets of aerial photographs dated between 1945 and 1991 were used to document changes in channel pattern aerial photos and field surveys were used to compile maps of landscape units based on dominant vegetation life forms species and substrate six maps dated between 1945 and 1991 were digitized in arc info and an overlay was generated to determine the changes in landscape units as related to channel disturbance change from a braided to a single thread meandering channel probably took place in the period 1930 1950 the process of river entrenchment has occurred throughout the holocene but has accelerated in the present century due to shortening of the river course construction of lateral embankments and vegetation encroachment following reservoir construction and cessation of wood cutting and grazing the increase in horizontal channel stability coupled with channel entrenchment have decreased floodplain disturbance and lowered the water table by approximately one meter pioneer and disturbance dependent landscape units have experienced a more terrestrial like succession to an alluvial forest abandoned channels have also been replaced by alluvial forests on poorly drained soils shrub swamp communities of willow and hydrophytic herbaceous plants have been replaced by mixed forests of ash alder black poplar and oak on well drained alluvial soils ash and oak dominated hardwood forests have declined in favor of mesophytic stands of black poplar all types of vegetation but particularly dry grasslands shrublands have been cleared for mines campgrounds agriculture and other types of development using several measures landscape diversity decreased between 1945 and 1991

development of sediment slug upstream from the czorsztyn reservoir southern poland and its interaction with river morphology abstract the effects of base level rising upstream of dam reservoirs on in channel sedimentation and interaction of the stored sediments with the gravel bed channel morphology have received little attention so far previous studies however suggested that the feedback mechanism between in channel sedimentation and bank erosion may affect channel morphology here the pattern of the bar area bank erosion and morphology of the gravel bed dunajec river upstream from the czorsztyn reservoir cr constructed in 1997 in southern poland were analyzed from aerial images 1982 2012 and lidar data 2013 in the part of the post dam period with a large flood the average bar area increased significantly in the backwater section and at some distance upstream and then extended in the upstream direction at an average rate of above 40 m y reaching 2 2 km upstream from the cr in 2012 the bar area variation was 40 and 77 explained by local bank erosion in the periods of large and low to moderate floods respectively the sum of bank erosion from the post dam period explained 80 of the variation in the present width depth ratio significantly increased in the backwater section the results showed that the large floods in 1997 in conjunction with backwater inundation initiated intensive bank erosion and bar growth subsequently in the period with low and moderate floods the localized bar bank interaction connected with the flow divergence around the deposited bar led to localized bank erosion and additional bar growth promoting bend development these processes propagating in the upstream direction were facilitated by the existence of a large amount of easily remobilized sediment stored in the floodplain connected with the sedimentation zone from the end of the nineteenth century bend development was controlled by valley confinement causing downstream bend translation in the narrower valley confined section and its extension in the wider unconfined section of past sediment storage the results obtained from this site specific location imply that the occurrence of similar past sediment storage zones of easily remobilized coarse sediments may favor intensive bank erosion and bar growth during large floods and in the case of low transport competence backwater zones of gravel bed rivers where the remobilized sediments cause localized bar growth it may promote morphologically effective bar bank interaction in the period with low and moderate floods

estimation and propagation of error in measurements of river channel movement from aerial imagery rates of river channel migration or widening are only valid if it can be demonstrated that the amount of change in the measured parameters exceeds the measurement errors however it is still uncommon to see estimates of errors presented alongside rates of river channel change measured from aerial photography here detailed methods are presented for the estimation of errors in quantifying channel migration rates that can be easily applied to gis based analysis of planform change in addition the impact of relaxing assumptions regarding error independence between image dates and systematic registration errors is presented and discussed copyright 2005 john wiley sons ltd

geochemistry and geochronology of the kiggavik uranium deposit nunavut canada the thelon basin nunavut canada is similar in age size and geology to the u producing athabasca basin in saskatchewan the kiggavik project area located immediately south of the aberdeen sub basin of the thelon basin contains u deposits and showings along a 30 km long ne sw structural trend the basement hosted kiggavik deposit comprising three separate mineralized zones main centre and east is located at the northern end of this trend multiple styles of u mineralization and alteration were identified at the kiggavik deposit disseminated euhedral uraninite u1 1284 53 ma has elevated pb contents up to 14 wt pbo and is associated with illite and hematite alteration vein style uraninite u2 284 19 ma forms along fractures contains lower pb contents 3 9 wt pbo and is partly altered to ca si rich 4 5 wt cao and 3 3 wt sio2 uraninite highly altered u2 is associated with galena late u minerals u3 have biogenic textures and are pb free indicating that they formed recently 1 ma based on sims in situ u pb geochronology the minimum age of uraninite at the kiggavik deposit is 1284 53 ma however this is likely a reset age associated with the mackenzie dyke event 1267 ma oxygen and hydrogen stable isotope compositions of illite and muscovite suggest that the kiggavik deposit has been overprinted by high latitude surficial fluids derived from snowmelt

gravel extraction and planform change in a wandering gravel bed river the river wear northern england within channel alluvial gravel extraction is one of the most important forms of anthropogenically induced morphological change in river channels in british rivers commercial gravel extraction was widespread between the 1930s and 1960s and limited gravel extraction operations to reduce flood risk or maintain navigation continue to the present day despite this gravel extraction has received little attention in uk river studies this paper examines the significance of within channel gravel extraction during the period 1945 1960 on the planform of the river wear in northern england the study focuses on two 3 km piedmont reaches at wolsingham and harperley park located at the margin of the upland zone examination of detailed archival accounts of the gravel extraction operations supplemented by the analysis of aerial photographs has enabled the impact of gravel extraction on the channel of the river wear to be determined sediment budget calculations suggest large sediment deficits in both study reaches however assessing potential impacts simply in terms of a sediment deficit may be misleading as channel adjustments depend on local factors and a detailed consideration of the reach scale sediment budget differences in the nature of channel adjustments of both reaches were found to be primarily a function of the method of gravel extraction employed overall patterns of channel change along the extraction reaches over the past 150 years were similar to reaches where gravel extraction was not practiced this highlights the difficulty of trying to establish the significance of different processes where both local gravel extraction and catchment scale factors climate and land use are operating

morphological effects of different channel forming discharges in a gravel bed river the study analyses the morphological response of a gravel bed river to discharges of different magnitude from moderate events that occur several times a year to a 12 year flood and so defines the range of formative discharges for single morphological units channels bars islands and a range of magnitude of morphological activity from the threshold discharges for gravel transport and minor bar modification up to flows causing major morphological changes the study was conducted on the tagliamento river a large gravel bed river in north eastern italy using two different methods analysis of aerial photographs and field observation of painted gravel particles the available photographs five flights from august 1997 to november 2002 and the two commissioned flights june 2006 and april 2007 do not define periods with a single flood event but the intervals are short enough 11 to 22 months to have a limited number of flood events in each case the fieldwork which involved cross section survey grain size analysis and observation of painted sediments complemented the aerial surveys by allowing analysis of channel response to single flood events substantial morphological changes e g bank erosion of several tens of metres up to more than 100 m associated with flood events with a recurrence interval between 1 1 year and 12 years have been documented multiple forming discharges were defined based on the activity of different morphological units discharges equal to 20 50 of the bankfull discharge are formative for the channels whereas the bankfull discharge 1 1 year flood in this case of the tagliamento river is formative for low bars larger floods but still relatively frequent with a recurrence interval less than five years are required for full gravel transport on high bars and significant morphological changes of islands copyright 2009 john wiley sons ltd

sequence stratigraphy and evolution of the paleoproterozoic intracontinental baker lake and thelon basins western churchill province nunavut canada abstract the baker lake and thelon basins lie along the border between the rae and hearne domains of the western churchill province basin fill comprises the dubawnt supergroup a ca 1 85 1 70 ga succession of predominantly continental clastic and intercalated volcanic rocks that nonconformably and unconformably overlies granitic and supracrustal rocks most of late archean age the dubawnt supergroup comprises three second order sedimentary sequences that record deposition within a rift basin a modified rift basin and a thermal sag basin respectively the baker sequence is inferred to represent the principal phase in the development of baker lake basin a series of generally elongate northeast striking half graben and fault bounded troughs filled with continental redbeds and coeval voluminous ultrapotassic volcanic rocks faults parallel to the basin margin exhibit evidence for strike slip ca 1 83 1 81 ga the nature and timing of basin development and associated magmatism allows that it may be a transtensional basin that formed by lateral escape in response to crustal thickening during the trans hudson orogeny similar to the formation of mesozoic and cenozoic strike slip and associated rift basins on the margins of the tibetan plateau the overlying whart sequence was deposited in small basins formed by block faulting and tilting of the baker sequence basin fill comprises eolian and alluvial redbeds with intercalated rhyolite flows and epiclastic rocks distribution of facies and stratigraphy suggest that faulting occurred throughout deposition of the whart sequence but ceased before deposition of the overlying barrens sequence ca 1 72 ga deformation and basin formation can be linked to a regional episode of granite emplacement and associated thermal metamorphism ca 1 76 1 75 ga the barrens sequence represents deposition over a broader area primarily in thelon basin strata generally are thinner and flatter than underlying sequences and display lateral continuity indicating minimal influence from syndepositional faulting the depositional record reflects progressive upward fining and eventually the first record of marine transgression within the dubawnt supergroup these features suggest that the barrens sequence was deposited over a broad region of thermal subsidence likely related to cooling of previously attenuated continental lithosphere the barrens sequence may be a remnant of a huge cratonic sand sheet that included the thelon athabasca amundsen and elu basins a regional subsidence mechanism to account for these basins may be mantle downwelling linked to the late stage amalgamation of laurentia the tripartite sequence evolution of the baker lake and thelon basins represents a framework for future sequence correlation among late paleoproterozoic basins in laurentia and shares characteristics with the evolution of contemporaneous intracontinental basins from north central australia and southeastern brazil

estimation of error in bankfull width comparisons from temporally sequenced raw and corrected aerial photographs this study investigates the propagation of error through image to image comparison of 285 river bankfull width measurements of the afon trannon mid wales bankfull width is quantified from both aerial photographs analysed as rectified images in erdas imagine orthomax and raw images in paintshop pro a method for the robust estimation of bankfull width measurement error through temporal sequences of scanned aerial photographs is presented and the improvement in accuracy achieved using rectified imagery is quantified results from this study are placed in the context of previously published rates of bankfull width change from a wide range of river scales and the bankfull change rates for robust medium term analysis using approximately 1 10 000 historical aerial photography are identified

channel forms recovery in an ephemeral river after gravel mining palancia river eastern spain abstract during the 1970s the palancia river was intensively affected by gravel mining instream this activity completely destroyed the fluvial forms devastating the original wandering pattern at the end of the 1980s gravel mining ceased and the river started a process of recovery only altered by several clearing operations the aim of this work is to describe these processes of change analyzing the river s morphosedimentary conditions through a gis analysis of aerial photographs previous to simultaneous with and subsequent to the intense gravel mining activity results explain the current difficulties of some ephemeral rivers to recover their original forms because of the sediment and water deficit conditions the critical role of channel incision and inappropriate actions of river clearing and channelization for flood prevention

early paleoproterozoic supracrustal assemblages of the rae domain nunavut canada intracratonic basin development during supercontinent break up and assembly abstract the basal paleoproterozoic supracrustal succession of the churchill province in northern canada comprises sedimentary basins overlying the archean rae and hearne domains the rae domain supracrustal succession e g amer ketyet river chantrey and montresor groups comprises four lithotectonic assemblages which include in ascending stratigraphic position 1 shallow marine fluvial quartzarenite with mainly neoarchean detrital zircons of local provenance 2 shallow marine quartzarenite with mainly local provenance that locally includes carbonates mafic volcanic flows 3 abrupt but conformable transition to basinal dark shales and overlying platformal carbonates that pass upward into siltstones and sandstones that record gradual emergence of the platform sandstones within this assemblage display a substantially different detrital zircon provenance signature dominated by early paleoproterozoic zircons with grains as young as 1 95 ga 4 unconformably to conformably overlying immature marine sandstones including turbidites with a significant component of 2 0 1 9 ga detritus probably derived from a combination of local and distal sources the thickness and relative compositional maturity of the basal lithotectonic assemblage 1 records a protracted period of enhanced weathering on a slowly subsiding but stable supercontinent e g kenorland this was followed by mafic volcanism and marine transgression consistent with partial rifting of the rae domain and crustal extension attending supercontinent break up lithotectonic assemblage 2 strata of lithotectonic assemblage 3 record basin flooding and deepening followed by platformal sedimentation along the margins of extended continental blocks assemblage 4 is interpreted to represent deposition in foreland basins during early amalgamation of laurentia part of nuna at ca 1 9 ga the stratigraphy and detrital zircon geochronology of the hurwitz group which overlies the hearne domain is broadly similar to the supracrustal sequence of the rae domain but differs through the presence of basal diamictites and lack of 2 5 ga detritus a major local source in the rae our data suggest that the rae and hearne domains were assembled together by max 1 91 ga i e max age of deposition of the uppermost hurwitz and amer groups the paleoproterozoic stratigraphic assemblage framework for the churchill province compares well with that of other cratons derived from break up of kenorland and ultimately amalgamated in nuna examples from laurentia include supracrustal rocks that overlie the southern margin of the superior province southern province e g huron supergroup animikie group marquette range supergroup whitewater group and mistassini otish group the paleoproterozoic assemblages of the southern and churchill provinces exhibit first order stratigraphic similarities that indicate a shared history of stable continental sedimentation followed by rifting basin opening and basin closure

recent channel adjustments in alluvial rivers of tuscany central italy drastic channel adjustments have affected the main alluvial rivers of tuscany central italy during the 20th century bed level adjustments were identified both by comparing available topographic longitudinal profiles of different years and through field observations changes in channel width were investigated by comparing available aerial photographs 1954 and 1993 98 bed incision represents the dominant type of vertical adjustment and is generalized along all the fluvial systems investigated the arno river system is the most affected by bed level lowering up to 9 m whereas lower incision generally less than 2 m is observed along the rivers of the southern part of the region human disturbances appear to be the dominant factors of adjustments the main phase of vertical change occurred during the period 1945 80 in concomitance with the phase of maximum sediment mining activity at the regional scale the second dominant type of adjustment that involved most of the rivers in the region consists of a narrowing of the active channel based on measurements of channel width conducted on aerial photographs 38 of the reaches analysed experienced a narrowing greater than 50 of the initial channel width the largest values of channel narrowing were observed along initially braided or sinuous with alternate bars morphologies in the southern portion of the region a regional scheme of channel adjustments is derived based on initial channel morphology and on the amounts of incision and narrowing different styles of channel adjustments are described rivers that were originally sinuous with alternate bars to braided generally became adjusted by a moderate incision and a moderate to intense narrowing in contrast sinuous meandering channels mainly adjusted vertically with a minor amount of narrowing copyright 2003 john wiley sons ltd

mineralogy geochronology and genesis of the andrew lake uranium deposit thelon basin nunavut canada the thelon basin located in nunavut canada shares many similarities with the u producing athabasca basin in saskatchewan the kiggavik project area located near the northeastern edge of the thelon basin contains u deposits and showings along the 30 km long ne sw kiggavik andrew lake structural trend the andrew lake deposit is near the southern end of this trend pre mineralization is characterized by quartz carbonate veins that occupy fault systems later reactivated as conduits for u mineralizing fluids a four phase genetic model is proposed for the andrew lake deposit phase 1 comprises vein style uraninite u1 1031 23 ma that is associated with illite and hematite and contains variable pbo contents 0 2 9 5 wt phase 2 is characterized by altered uraninite u2 530 ma that is associated with coffinite altered uraninite u3 1 ma characterizes phase 3 and occurs as centimetre scale roll fronts in phase 4 all three uraninite stages and coffinite are altered to boltwoodite al

monitoring and modelling morphological change in a braided gravel bed river using high resolution gps based survey recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process and in particular to estimate bedload transport rates and reach scale sediment budgets until recently however this morphometric approach has been limited to comparison of repeatedly surveyed cross sections with the associated problems of low frequency sampling and an emphasis on cross stream as opposed to downstream morphological dynamics recent advances in analytical photogrammetry have however permitted the acquisition of data at sufficient resolutions to represent macroform 101 m and microform 10 m channel geometry in fully three dimensions while inherently spatially distributed the photogrammetric approach to land surveying is however restricted to observable areas of the channel and is thus of limited use in the subaqueous zone especially if flows are turbid or highly coloured this paper presents an alternative approach to the study of three dimensional morphological dynamics of a divided reach of the gravelly river feshie scotland in which topographic survey of both exposed and submerged areas of the reach was undertaken using the global positioning system gps survey results from two field programmes in 1998 and 1999 are presented in which a geotronics geotracer 2000 real time kinematic gps receiving unit was used to survey a 200 80 m reach rapid radial survey methods were employed permitting the collection of 2000 survey points per day giving a mean density over the 13 ha reach of 1 1 points per square metre a detailed assessment of survey errors and dem quality is presented and a limit of detection of c 10 cm proposed as an upper threshold for the identification of significant change between dems preliminary interpretation of channel dynamics in 1998 99 reveals relatively little change to the overall macroscale reach structure dem differencing techniques however highlight important local changes including the progradation of submerged bar fronts bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs copyright 2000 john wiley sons ltd

twentieth century channel change on the dunajec river southern poland patterns causes and controls abstract spatial and temporal patterns of the twentieth century channel changes of the dunajec the second largest river of the polish carpathians are analysed using data from six historical maps hand auger drillings in paleochannels and hydrometric data from 10 gauging stations in its lower course the river was considerably narrowed shortened and embanked between the 1880s and the 1920s here bed degradation commenced in the late 19th century and has so far resulted in 3 1 m of channel incision in the middle river course little change occurred in mountain reaches where the dunajec is confined by valley sides and where bedrock exposures prevent channel incision in the reaches within intramontane basins channelization works carried out in the 1950s 1970s considerably narrowed the river and transformed its multi thread channel into a single thread straight channel rapid bed degradation induced by the works resulted in up to 2 m of channel incision over the second half of the century upstream progression of bed degradation into the adjacent mountain reach was hindered by bedrock exposures at its downstream end in the upper river course reaches with the deeply incised channels up to 3 5 m prevail over a few past decades in response to gravel exploitation river channelization and a reduction in catchment sediment supply more scarce are vertically stable reaches which owe their stability to low unit stream power in wide unmanaged reaches and to fixing of the channel bed by drop structures in channelized reaches this study shows that despite the overall tendency to incision over the 20th century considerable differences in the timing and course of channel changes occurred between particular river reaches due to variable human impact and local geological and geomorphological conditions the main phase of channel incision took place progressively later in the upstream direction however upstream progression of bed degradation from the already incised downstream reaches was precluded by the roznow dam and bedrock controlled reaches where bed material flushed out from an incising upstream reach had been introduced into an artificially narrowed channel of high transport capacity it was easily transferred downstream and could not restore the downstream reach to its pre channelization vertical position

medium and short term channel planform changes on the rivers tay and tummel scotland abstract channel planform change was analysed using a variety of data sources for the medium term 25 years and

bed material transport estimate in large gravel bed rivers using the virtual velocity approach this paper reports on a first attempt of using the virtual velocity approach to assess sediment mobility and transport in two wide and complex gravel bed rivers of northern italy displacement length and virtual velocity of spray painted tracers were measured in the field also the thickness of the sediment active layer during floods was measured using scour chains and post flood morphological changes as documented by repeated survey of channel cross sections the effects of eight and seven floods were studied on the tagliamento and brenta rivers where 259 and 277 spray painted areas were surveyed respectively in the tagliamento river 36 of the spray painted areas experienced partial transport whereas in the brenta river this accounted for 20 whereas full removal gravel deposition was observed on 37 and 26 of these areas on the tagliamento and brenta rivers respectively the mean displacement length of particles the thickness of the active layer and the extent of partial transport are well correlated with the dimensionless shear stress the virtual velocity approach allowed calculation of bed material transport over a wide range of flood magnitudes annual coarse sediment transport was calculated up to 150 for the tagliamento and 30 103 m3 yr 1 for the brenta the outcomes of this work highlight the relevance of partial transport condition as it could represent more than 70 of the total bed material transported during low magnitude floods and up to 40 for near bankfull events results confirm that bed material load tends to be overestimated by traditional formulas copyright 2016 john wiley sons ltd

morphological evolution of the maipo river in central chile influence of instream gravel mining abstract instream gravel mining is one of the most important causes of channel degradation in south america specifically in rivers located near large metropolitan areas with rapidly growing cities where no river management strategies exist in the western region of the continent many of these rivers belong to andean systems in which significant parts of the watersheds are located in mountain areas at high altitude with considerable seasonal rainfall variability and steep channel slopes in these rivers gravel mining has produced significant incision of the channels with serious physical and ecological consequences affecting habitats modifying the supply and transport of sediments and amplifying the risk to infrastructure in and around the channel during floods in spite of the degraded conditions of many channels no quantitative studies of the geomorphic impacts of gravel mining have been carried out in the region mostly because of the insufficient and sparse data available in this investigation we perform an analysis of the morphodynamic evolution in a section of the maipo river in the metropolitan region of santiago chile this river is economically the most important in the country as it provides drinking and irrigation water to urban and rural areas is utilized by the energy generation industry and runs along and below critical infrastructure we have collected and analyzed data from 1954 to 2015 during which the city population increased by more than 5 million inhabitants whose presence accelerated land use changes the analysis shows a rapid morphological evolution of the channel where in 31 years effects such as river sections showing incision of up to 20 m an increase of the area affected by gravel mining from 86 62 to 368 13 ha and a net erosion volume of 39 4 million m3 can be observed this work yields quantitative information on the consequences of gravel mining in the maipo river providing the necessary data to develop an integrated strategy to define management and restoration actions for this and other similar andean rivers

observations on sediment mobility in a large gravel bed river article this study investigates sediment mobility in a large gravel bed river tagliamento river northeastern italy field data were used to identify the morphological effectiveness of a range of flows floods with recurrence interval b1 to 3 5 year and for a detailed analysis of the partial transport condition the analyses were carried out on three cross sections where a number of areas representative of different morphological units main and secondary channels low and high bars islands were painted grain size of the painted area was measured using a photographic method monitoring of bed mobility during the study period supplied new photographs of the painted areas measurements of size and travel distance of the mobilized particles and estimate of flow depth after each flood event our analyses have shown that with dimensionless shear stress around 0 073 17 n m 2 the morphological effect over the painted areas was primarily partial transport while with stresses n0 1 25 n m 2 the bed experienced full mobility i e all the painted particles were transported or totally buried full sediment mobility was observed on lower morphological units i e main and secondary channels under floods with very high frequency rib1 y whereas on the low bars full mobility occurred under floods with a recurrence interval slightly n1 year instead fine deposition and partial transport conditions were observed on the higher bars even after the largest of the monitored floods ri 3 5 y the analysis of the partial transport condition relies on more than 3500 measurements of particle travel distance travel distances range from a few centimetres up to 22 m the transported particles were generally finer than the painted sediments and the analysis of the sediment transport ratio revealed that partial transport occurred under equal mobility conditions for particles finer than 32 mm and under size selective mobility for coarser fractions this appears to be corroborated for db32 mm by the insensitiveness of particle transport distance to particle sizes even if the exponent 1 of the relationship between the dimensionless shear stress and the maximum transported diameter would suggest that all fractions are transported under equal mobility conditions

energy time and channel evolution in catastrophically disturbed fluvial systems abstract two diverse fluvial systems show that with time channels adjust such that the rate of energy dissipation is minimized one fluvial system characterized by high relief and coarse grained sediment was subjected to an explosive volcanic eruption the other system characterized by low relief and fine grained sediment was subjected to dredging and straightening study of the expenditure of kinetic and potential energy components of total mechanical energy provide an energy based rationale of the interdependency between processes and forms during channel evolution spatial and temporal trends of aggradation and degradation are similar although relative amounts of aggradation in the high energy system are greatly enhanced by the deposition of large amounts of eroded bank material from upstream reaches degradation accompanied by widening is the most efficient means of energy dissipation because all components of total mechanical energy decrease with time widening dominates energy dissipation in the coarse grained system to offset increases in hydraulic depth caused by incision in the low energy fine grained system channel adjustment and energy dissipation are dominated by vertical processes because of low relative values of kinetic energy and because eroded bank sediment is transported out of the drainage basin and does not aid in downstream aggradation energy dissipation or channel recovery specific energy is shown to decrease nonlinearly with time during channel evolution and provides a measure of reductions in available energy at the channel bed data from two sites show convergence towards a minimum specific energy with time time dependent reductions in specific energy at a point act in concert with minimization of the rate of energy dissipation over a reach during channel evolution as the fluvial systems adjust to a new equilibrium

channel adjustments in a mediterranean river over the last 150 years in the context of anthropic and natural controls abstract evolutionary trajectories and related control factors of the fortore river southern italy are analyzed over a 150 year period as to assess channel modifications a multitemporal gis analysis of topographic maps and aerial photographs together with topographic and geomorphological field surveys were performed attention was focused on the impact caused by human disturbance above all the presence of the occhito dam at only 40 km upstream of the fortore mouth central adriatic coast results show that channel adjustments occurred in three distinct phases and were primarily driven by human disturbance that diversely affected reaches located upstream and downstream of the dam from the last decades of the nineteenth century to the 1950s phase 1 channel widening prevailed along upstream reaches whilst narrowing along downstream reaches major channel adjustments occurred from the 1950s until the end of the 1990s phase 2 especially channel narrowing of up to 81 in upstream reaches and 98 in downstream reaches narrowing was accompanied by channel bed lowering of 1 to 5 m and by pattern changes in prevalence from multithread to largely prevailing single thread channel configurations in channel mining channel works and hydraulic interventions are considered key driving factors of observed channel adjustments the closure of the occhito dam in 1966 had significant and permanent effects on downstream reaches through overall discharge regulation and permanent sediment trapping as also proved by the progressive retreat of the fortore river mouth area from 2000 to 2015 phase 3 a substantial trend inversion was observed with overall channel widening and partial aggradation of upstream reaches and total stabilization of downstream reaches as highlighted by an integrated multitemporal analysis of recent channel changes and flood events the latter have played an important role in channel recovery of upstream reaches comparison between the fortore river and other rivers in southern italy has allowed us to ascertain that the reconstructed evolutionary trajectories are quite similar and that control factors are essentially the same in particular it confirms the role of major hydraulic structures as to the amount of channel adjustments of downstream reaches and the ensuing scarce to nil potential to channel recovery of regulated reaches

spatial variability in the timing nature and extent of channel response to typical human disturbance along the upper hunter river new south wales australia prior to european settlement the upper hunter river near muswellbrook new south wales was a passively meandering gravel bed river of moderate sinuosity and relatively uniform channel width analyses of floodplain sedimentology archival records parish maps and aerial photographs document marked spatial variability in the pattern of channel change since european settlement in the 1820s different types rates and extents of change are reported for seven zones of adjustment along an 8 km study reach this variable adjustment reflects imposed antecedent controls buried terrace material and bedrock which have significantly influenced local variability in river sensitivity to change as well as contemporary morphodynamics and geomorphic complexity local variability in system responses to disturbance has important implications for future river management and rehabilitation

spatio temporal patterns of channel changes in response to a major flood event the case of the magra river central northern italy on october 25th 2011 the magra river central northern italy was affected by a significant flood event with an estimated return interval ranging from 30 to 200 years this study investigates the morphological responses of the magra river to this major flood event with the aims of i documenting the channel changes which occurred in response to the flood ii analysing this response within the context of the historical trend of width changes iii investigating the possible factors controlling the spatial pattern and the intensity of the observed changes significant channel widening was documented along the entire length studied about 34 km ranging from 3 to 90 of the pre flood channel width braided reaches were characterized by the most severe planimetric changes although characterized by high rates of change these variations are however amply included in the historical range of channel width variability over approximately the last 150 years from 1877 to present day and are comparable with though generally lower than the channel width of the 1950s statistical analyses simple and multiple regressions between the observed changes in channel width and a series of selected morphological and hydraulic controlling factors showed no robust correlations to explain the spatial pattern and the variability of channel adjustments instead major adjustments occurred along reaches characterized by the confluence of those streams draining the sub catchments where the storm was concentrated copyright 2014 john wiley sons ltd

alterations of channel parameters in response to river regulation works since 1840 on the lower tisza river hungary abstract in the last few years an increase in the frequency and magnitude of floods was detected on the tisza river endangering large areas of hungary the causes of these record floods were complex including both natural and human induced factors this paper focuses on river management works and their effect on planimetric and cross sectional parameters with special attention to the flood conductivity changes to the river channel during 19th century river regulation works half of the total length of the tisza river was altered by cut offs while in the 20th century mostly revetments and groynes were constructed subsequently horizontal and vertical channel parameters have changed considerably due to semi natural bed processes in order to reveal changes hydrological map series 1842 1890 1929 1957 1976 and 1999 and cross sectional surveys from the same dates were analysed prior to the intensive human interventions before 1890s the river s course was highly sinuous with some very sharp bends due to cut offs both the length and sinuosity of the tisza river decreased by 35 while the lengths of straight sections and the river s slope doubled as a consequence the river incised by up to 3 8 m until the 1929 survey resulting better flood conductivity which improved flood safety in the 1920s river management favoured bank stabilisation in order to stop the lateral migration of the channel despite these measures meander development has continued however in a distorted manner this is reflected by the opposing processes of lengthening centre line on the one hand and gradually decreasing radius of curvature on the other these processes can be explained by the continuous development of natural point bars on the convex bank and the lack of lateral retreat on the concave stabilised bank the width of the river decreased by 17 45 while its mean and maximum depth increased by 5 48 the area of cross sections influenced by revetments decreased by 6 19 resulting in a 6 15 decline in flood conductivity the non stabilised sections were influenced by upstream revetments therefore their parameters show similar changes but with a smaller rate at present the flood conductivity of the channel is worse than it was in its natural state in all it was found that the ongoing process of cross sectional distortion is a significant factor in increasing flood stage and hazard and high floods can be expected more frequently in the future partly due to this factor

assessing channel response of a long river influenced by human disturbance article i nfo this paper describes an approach to assess channel changes of a long anthropogenised river the middle loire river over decadal timescales channel changes are evaluated along geomorphically homogeneous river reaches the classic geomorphic parameters active channel width bed slope grain size are complemented with parameters extracted from a 1d hydraulic model width depth ratio effective bed shear stress and specific stream power calculated for the biennial discharge assimilated to bankfull flow conditions the delineation of reaches is undertaken by combining visual inspection with the implementation of simple statistical tests to corroborate discontinuities in flow and sediment transport the 450 km long study area has been divided into 167 homogeneous reaches the general trends observed over the last fiftyyearsarenarrowingoftheactivechannel width and incision of the river bed however changes in bed level and active channel width are not consistently correlated channel changes at the reach scale are mainly controlled by the presence of former sediment extraction sites significant incision is observed at the peak of the in stream sediment mining period this was followed by channel recovery when extractions stopped the 1d numerical model provides a more rigorous manner to derive hydraulic parameters the effective bed shear stress made dimensionless by its critical value and the width depth ratio helps to explain observed channel responses more effectively by relating patterns to geological units along the middle loire

river channel adjustments in southern italy over the past 150 years and implications for channel recovery abstract multi temporal gis analysis of topographic maps and aerial photographs along with topographic and geomorphological surveys are used to assess evolutionary trends and key control factors of channel adjustments for five major rivers in southern italy the trigno biferno volturno sinni and crati rivers to support assessment of channel recovery and river restoration three distinct phases of channel adjustment are identified over the past 150 years primarily driven by human disturbances firstly slight channel widening dominated from the last decades of the nineteenth century to the 1950s secondly from the 1950s to the end of the 1990s altered sediment fluxes induced by in channel mining and channel works brought about moderate to very intense incision up to 6 7 m accompanied by strong channel narrowing up to 96 and changes in channel configuration from multi threaded to single threaded patterns thirdly the period from around 2000 to 2015 has been characterized by channel stabilization and local widening evolutionary trajectories of the rivers studied are quite similar to those reconstructed for other italian rivers particularly regarding the second phase of channel adjustments and ongoing transitions towards channel recovery in some reaches analyses of river dynamics recovery potential and connectivity with sediment sources of the study reaches framed in their catchment context can be used as part of a wider interdisciplinary approach that views effective river restoration alongside sustainable and risk reduced river management

comparison of diagenetic fluids in the proterozoic thelon and athabasca basins canada implications for protracted fluid histories in stable intracratonic basins the paleoproterozoic thelon basin located on the border between nunavut and the northwest territories of canada is a contemporaneous analog of the uranium rich paleoproterozoic athabasca basin in canada early diagenesis resulted in precipitation of extensive hematite on the surfaces of detrital quartz grains throughout the thelon formation and minor hydroxy phosphate in veins locally continued diagenesis then resulted in syntaxial quartz cementation of detrital quartz at 130 c from fluids having ca 17 wt equivalent nacl similar to the athabasca basin cementation of this type is most pronounced in fine grained sequences in the thelon basin a period of extensive desilicification during continued burial was followed by formation at ca 200 c of peak diagenetic illite having ar ar ages of ca 1400 1690 ma in the thelon formation this illite was associated with fluids with 18 oa nd d values of ca 6 and 50 respectively similar to those during peak diagenesis of the athabasca basin although the timing salinity and isotopic composition of the peak diagenetic fluids in the thelon and athabasca basins are similar the peak diagenetic mineral assemblage in the athabasca formation is dickite and illite with minor dravite and goyasite rather than simply illite consequently the fluids at peak diagenesis which in the athabasca basin are synchronous with formation of world class unconformity type uranium deposits had different compositions in each basin post peak diagenesis in the thelon basin was quite distinct from that in the athabasca basin in that illite was replaced in the central portion of the basin by k feld spar and then sudoite which crystallized from saline brines at ca 1000 ma and 100 c evidence for later infiltration of these brines is absent in the athabasca basin although uranium mobilization at ca 900 ma from fluids having the same characteristics as those at peak diagenesis was pronounced in the athabasca basin recent incursion of meteoric waters along reactivated structures into the athabasca basin has variably affected hydrous and uraniferous minerals but evidence for this is lacking in the thelon basin the thelon basin reflects less intensive fluid rock interaction in its early history than that recorded in the basal units of the athabasca basin 132

framework geophysical modelling of granitoid versus supracrustal basement to the northeast thelon basin around the kiggavik uranium camp nunavut the northeast thelon basin in the kivalliq region of nunavut is prospective for uranium deposits recently discovered basement hosted unconformity associated prospects west of kiggavik are restric

detailed chronology of mid altitude fluvial system response to changing climate and societies at the end of the little ice age southwestern alps and cevennes france abstract over a historical timescale landscapes have been strongly affected by fluctuations in climate and by the impact of human societies this study examines the historical evolution of mid altitude fluvial systems in the western alps and cevennes se massif central in the context of marked climate and anthropogenic change at the end of the little ice age late 19th century this work contributes to the reconstruction of river paleodynamics by investigating the nature and chronology of geomorphological changes in upper river basins in order to produce a detailed reconstruction of hydromorphological changes we combined two approaches the study of historical archives and the use of bioindicators the dating of terraces using dendrochronology and of silt benches using lichenometry in order to reconstruct the evolution of the river channels the 19th century is a particularly propitious period for the study of surface dynamics because archives have preserved a wealth of qualitative and quantitative data concerning rivers economic statistics meteorological and hydrological observations illustrative documents descriptions by contemporary observers it is also a period for which reliable dating methods are available for detrital deposits in rivers the period provides new information on how the transition between the little ice age and current climate conditions affected the evolution of drainage basins and stream channels by highlighting a succession of phases in the erosive process e g the preparatory role of the drought of 1830 1838 in the erosion crisis of 1855 1870 and refining the chronology of events very early onset of riverbed incision the results highlight the effect of climate small hydroclimatic fluctuations amplified by strong anthropization on the rhythm of landscape change and on the relative stabilization of the landscape at the end of the 19th century in addition the synchronization of phenomena on the two sides of the rhone valley shows that these changes took place on a regional scale

changes in morphometric meander parameters identified on the karoon river iran using remote sensing data abstract river meander dynamics and mobility are important indicators of environmental change related to climate changes and anthropogenic activities at local and river basin scales the aim of the present study is to identify morphological changes of the karoon river in iran using high accuracy maps and landsat satellite images by analyses during the time period 1989 2008 in this study 20 meandering reaches were analyzed over a 128 km long river reach located in the middle part of the karoon river iran morphometric indicators such as river width w meander neck length l axis length a radius of curvature r water flow length s and sinuosity of meander c were extracted for the identified meanders the results of a paired t test showed that river width w and meander neck length l have significantly changed during the study period 1989 2008 with an increase of 3 5 m for w and a decrease of 274 m for l spearman correlation analysis has shown that meander parameter changes are highly correlated to each other the parameters that do not have significant correlation together are c with w and l w and l and l with s and a during the period of the study the flow length and river sinuosity decreased for the whole river reach by 4 77 km and 0 11 respectively analysis of land use land cover categories 1989 and 2008 using the support vector machine svm and kernel function method served as one of the tools for interpretation of the meander parameter changes these changes can be attributed not only to lu lc riparian vegetation to agriculture area ratio but also to dam construction in the upstream part of the river that leads to major hydrological regime and sediment transfer alteration sediment extraction may also be an important factor

channel degradation and restoration of an alpine river and related morphological changes abstract river degradation and thus necessity for restoration are major issues worldwide however adequate methodologies to assess morphological variations linked to these actions and the morphological success of restoration interventions are still to be determined the ahr river south tyrol italian alps was characterized until the mid twentieth century by an anabranching and meandering pattern but starting from the 1960s it underwent intense channel degradation in terms of narrowing incision and floodplain disconnection in the period 2003 2011 several reaches of the ahr river were restored by widening and raising the channel bed the planimetric changes that occurred historically in the ahr river were determined by the interpretation of 10 maps and aerial photos covering the period 1820 2011 the estimation of the incision that occurred during the degradation phase was assessed by the difference in elevation between gravel surfaces whereas the changes introduced by restoration interventions in two reaches were evaluated through the comparison of topographic cross sections surveyed in year 2000 and a high resolution bathymetric lidar survey flown in late 2012 the mqi morphological quality index was applied to different reaches in order to test how assessment methodologies respond to degradation and restoration actions the combined analysis of planform and vertical changes indicates that gravel mining has been the largest pressure for the river but a change in sediment flow regimes probably led to the channel adjustments that occurred during the early twentieth century the restoration measures have locally increased channel width elevation and morphometrical diversity compared to the unrestored reaches as well as the morphological quality assessed by mqi however the extent of the modifications brought about by restoration works differs between the two restored reaches pointing out the need for a quantitative analysis of the historical evolution of each river reach before designing and implementing restoration actions and to the necessity to monitor the subsequent morphological adjustments

assessment of channel changes due to long term bedload supply decrease roubion river france this paper presents the observations made in the watershed of the upper roubion river which drains a submediterranean mountainous environment and in two of its main tributaries the soubrion and bine creeks our aim was to analyze contemporary morphological and sedimentary changes in response to a progressive decrease in bedload supply this decrease is linked to an increase of forest cover in the watershed during the 20th century following rural depopulation and to a correlated decrease in peak flows several variables were systematically measured width slope bed level change sediment size along 23 km of river whereas dendrochronological data floodplain cross sections and estimated recurrence intervals of sediment entrainment based on critical shear stress calculations were also produced for specific sites to complete our analysis evidence of three major phenomena was obtained on both the roubion and its tributaries i bed degradation ii development of stable pavement in incised reaches and iii channel narrowing associated with the development of alluvial forest on recently abandoned portions of the pre existing active channel forest development began in the 1950s these three phenomena show positively covariant relationships that lead us to propose a descriptive model of mountain fluvial system adjustments to progressive decrease of bedload

the contact uranium prospect kiggavik project nunavut canada tectonic history structural constraints and timing of mineralization uranium mineralization in the kiggavik area on the eastern border of the thelon basin nunavut canada hosts significant uranium resources within the basement and its understanding is critical to comprehending the genesis of unconformity related deposits structural controls and therefore exploration of these types of deposits in this prospective district this article deciphers the complex multiphase fracture network associated with uranium mineralization of the most recently discovered basement hosted prospect in the kiggavik area named contact the contact prospect is located along the andrew lake fault alf a major ne sw fault corridor in the area this study combines field work drillcore logging sampling and macro to micro petro structural analyses key results from this study highlight that the ne trending alf along with the ene trending thelon tf and judge sissons jsf faults formed early during intracratonic rifting and deposition of the baker lake and wharton groups ca 1850 1750 ma in response to the thelon and trans hudsonian orogeny the alf was affected by a strong silicification brecciation event that likely developed at ca 1750 ma and partitioned later deformation and fluid circulation in the contact prospect the alf was reactivated multiple times and mineralized in three stages with distinctive secondary fracture patterns alteration and mineralization types ten fracture stages have been identified at the contact prospect f1 to f10 the first stage of mineralization coeval with f5 is related to fluids of unconstrained origin that circulated through e w faults in the area that locally reactivated quartz veins of the brecciation event at the intersection with the alf mineralization at this stage is polymetallic and associated with weak clay alteration the second stage of uranium mineralization occurred coeval with transtensional reactivation of the ne sw trending alf f6c and in relation to circulation of oxidizing basinal brines within the fault zone mineralization at this stage is monometallic and associated with illite and sudoite alteration later reactivation of the inherited fracture network f8 led to strong illitization and bleaching of the host rock with local reworking of the ore body finally reactivation of the fracture network during f9 and 10 lead to circulation of meteoric fluids that remobilized mineralization in a third stage of uranium re concentration along redox fronts with strong illitization and bleaching of the host rock unlike the classic unconformity related uranium deposits in the athabasca basin where clay alteration halos occur around the ore bodies related to mineralizing processes in the contact prospect the strongest clay alteration event f8 postdates both main stages of mineralization along with uranium remobilization the basement hosted contact prospect is likely a relict of what was once a larger deposit

channel adjustments in response to the operation of large dams the upper reach of the lower yellow river the yellow river in china carries an extremely large sediment load river channel form and lateral shifting in a dynamic partly meandering and partly braided reach of the lower yellow river have been significantly influenced by construction of sanmenxia dam in 1960 liujiaxia dam in 1968 longyangxia dam in 1985 and xiaolangdi dam in 1997 using observations from huayuankou station 128 km downstream of xiaolangdi dam this study examines changes in the river before and after construction of the dams the temporal changes in the mean annual flow discharge and mean annual suspended sediment concentration have been strongly influenced by operation of theses dams observations of sediment transport coefficient ratio of sediment concentration to flow discharge at a station hydraulic geometry and bankfull channel form observed from 1951 to 2006 have shown that although variations in flow and sediment load correspond to different periods of dam operation changes in channel form are not entirely synchronous with these the channel has been subject to substantial deposition due to the flushing of sediment from sanmenxia dam resulting in a marked reduction in bankfull cross sectional area flows below bankfull had a greater impact on channel form than higher flows because of very high sediment load at a station hydraulic geometry shows that the variation of channel cross sectional area below bankfull in this wide and relatively shallow system largely depends on changes in width such at a station changes are significantly influenced by 1 events below bankfull and 2 overbank floods bankfull depth is the main component of channel adjustment in that depth adjusts synchronously with channel area the channel adjusts its size by relatively uniform changes in depth and width since 1981 channel morphology is not the product of single channel forming flow frequency it is determined by the combination of relatively low flows that play an important role in fine sediment transport and bed configuration as with relatively high flows that are effective at modifying the channel s morphology the sediment transport coefficient is a useful index for efficiently guiding the operation of the dams in a way that would minimize channel changes downstream sedimentation over the nearly 60 years of study period caused the lower yellow river to aggrade progressively the only significant exception being the two years following completion of sanmenxia dam

channel changes in the jarama and tagus rivers central spain over the past 500 years abstract long term channel changes of the tagus and the jarama rivers in central spain were studied in relation to variations in hydroclimatic factors such as rainfall and flooding and also with respect to human activities undertaken in their valleys data were taken from historical 1580 1823 and topographical 1877 1988 maps as well as aerial photographs 1945 1999 the available hydroclimatic data consists of a series of monthly rainfall totals 1859 1994 and mean river flow values recorded at gauging stations 1911 1985 in addition a historical flood record 1550 1947 was produced from documentary sources some of the data was incorporated into a geographical information system gis to quantify the changes in the course of the rivers the results show there have been two distinct periods before and after human intervention in the river system which took place around 1950 during the earlier period 1550 1950 a correlation exists between climate frequency and magnitude of flooding and changes in fluvial geomorphology between 1860 and 1892 an increase in flood frequency and magnitude occurred which produced half of the cut offs recorded in the study area between 1823 and 1877 the meanders length l width w and radius of curvature rc of the tagus river have decreased since 1750 however those of the jarama reached their maximum values during flood periods both rivers have different geomorphological responses during flood events which can explain these different trends floods in the jarama not only led to the cut offs but also enlarged the channel size l w and rc in the second period 1956 present flow regulation via dams and gravel mining modified the system completely and impeded the natural development of these rivers

the topographic signature of vegetation development along a braided river results of a combined analysis of airborne lidar color air photographs and ground measurements 1 this paper combines archived remotely sensed data airborne lidar and digital color air photographs with nonsynchronous ground observations including observations of topographic form and vegetation cover and growth to test the hypothesis that colonization of exposed river sediments by riparian trees has an impact on channel form and to quantify any impact that is identified this is achieved along a 21 km reach of the braided gravel bed tagliamento river in northeast italy where the width of the braided corridor typically exceeds 800 m lidar data are analyzed to extract a 2 m resolution digital evolution model dem and determine riparian vegetation extent height and structure within the active corridor aerial photographs are used to map the topography of the submerged parts of the corridor these data are divided into 1 km length subreaches which possess strong contrasts in vegetation height and extent joint analysis of vegetation and morphological properties of these subreaches reveals significant associations between vegetation properties and reach morphology residuals from a gamma function fitted to the topographic data for each subreach show a good fit with poorly vegetated reaches but a weakening fit with increasing vegetation cover largely as a result of the appearance of secondary peaks in the elevation frequency distribution associated with the heavily vegetated areas furthermore the overall skewness and kurtosis of the elevation frequency distribution within each of the subreaches are both significantly correlated with vegetation extent height median elevation and growth rate indicating a clear topographic signature of vegetation development along this braided river that reflects sediment accumulation within and around the vegetated patches

channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years article i nfo the timing and extent of the morphological changes that occurred in the last 200 years in a large gravel bed river the piave river eastern italian alps that was heavily impacted by human activities training structures hydropower schemes and gravel mining have been analyzed by historical maps aerial photos repeated topographic measurements and geomorphological surveys results show that the channel underwent a strong narrowing during the twentieth century but with a faster pace during the 1970s 1990s and with an associated shift from a dominant braided pattern to a wandering morphology bed incision up to 2 m mostly from gravel mining has been documented for this period large areas of the former active channel were colonized by riparian forests both as islands and as marginal woodlands the ceasing of gravel extraction in the late 1990s seems to have determined a reversal in the evolutionary trend with evidence of vegetation erosion channel widening even though a significant aggradation phase is not present we conclude that alteration of sediment regime has played a major role on the long term channel evolution however only relevant flood events rin10 15 years appear to determine substantial island erosion and therefore the proportion of island vs channel area fluctuates depending on flood history

basement geology beneath the northeast thelon basin nunavut insights from integrating new gravity magnetic and geological data current models for unconformity associated uranium deposits predict fluid flow and ore deposition along reactivated faults in 1 76 ga basement beneath mesoproterozoic siliciclastic basins in frontier regions such as the thelon basin in the kivalliq region of nunavut little is known about the sub basin distribution of units and structures making exploration targeting very tenuous we constructed a geological map of the basement beneath the unconformity by extrapolating exposed features into the subsurface the new map is constrained by detailed geological geophysical and rock property observations of outcrops adjacent to the basin and by aeromagnetic and gravity data over the geophysically transparent sedimentary basin from rock property measurements it is clear that the diverse magnetic and density characteristics of major rock packages provide quantitative three dimensional constraints gravity profiles forward modelled in four cross sections define broad synforms of the amer belt and archean volcanic rocks that are consistent with the structural style outside the basin major lithotectonic entities beneath the unconformity include supracrustal rocks of the archean woodburn lake group and marjorie hills meta sedimentary gneiss and associated mixed granitoid and amphibolitic gneiss the amer mylonite zone and inferred mafic intrusions oriented parallel and sub parallel other igneous intrusions of 2 6 ga 1 83 ga and 1 75 ga vintage and the 1 84 ga amer group four main brittle regional fault arrays 040 060 075 90 120 and 150 controlled development and preservation of the basin the reactivated intersections of such faults along fertile basement units such as the rumble assemblage marjorie hills assemblage nueltin igneous rocks and pitz formation are the best targets for uranium exploration

accuracy assessment of georectified aerial photographs implications for measuring lateral channel movement in a gis aerial photographs are commonly used to measure planform river channel change we investigated the sources and implications of georectification error in the measurement of lateral channel movement by testing how the number 6 30 and type human versus natural landscape features of ground control points gcps and the order of the transformation polynomial first second and third order affected the spatial accuracy of a typical georectified aerial photograph error was assessed using the root mean square error rmse of the gcps as well as error in 31 independent test points the rmse and the mean and median values of test point errors were relatively insensitive to the number of gcps above eight but the upper range of test point errors showed marked improvement i e the number of extreme errors was reduced as more gcps were used for georectification using more gcps thus improved overall georectification accuracy but this improvement was not indicated by the rmse suggesting that independent test points located in key areas of interest should be used in addition to rsme to evaluate georectification error the order of the transformation polynomial also influenced test point accuracy the second order polynomial function yielded the best result for the terrain of the study area gcp type exerted a less consistent influence on test point accuracy suggesting that although hard edged points e g roof corners are favored as gcps some soft edged points e g trees may be used without adding significant error based upon these results we believe that aerial photos of a floodplain landscape similar to that of our study can be consistently georectified to an accuracy of approximately f5 m with 10 chance of greater error the implications of georectification error for measuring lateral channel movement are demonstrated with a multiple buffer analysis which documents the inverse relationship between the size of the buffers applied to two channel centerlines and the magnitude of change detected between them this study demonstrates the importance of using an independent test point analysis in addition to the rsme to evaluate and treat locational error in channel change studies d 2005 published by elsevier b v

petrology and geochronology of paleoproterozoic intrusive rocks kiggavik uranium camp nunavut we investigated the age and petrology of paleoproterozoic granitic intrusions in the area of the kiggavik uranium exploration camp near the southeast margin of the aberdeen subbasin of the thelon basin a subset of these intrusions e g the lone gull stock is spatially associated with and mineralized by basement hosted unconformity related uranium deposits surface outcrop samples have field relations textures and compositions consistent with hudson suite granitoids and mixtures of monzogranite with minette we obtained u pb zircon ages ranging from ca 1818 to 1840 ma within the known range of the hudson suite and cogenetic minettes of the baker lake group 1 80 1 84 ga core samples of granitic rocks adjacent to mineralized zones are more complex and indicate an influence from the younger nueltin granite kivalliq igneous suite ca 1 77 1 73 ga one sample from the lone gull stock contains two zircon populations in texturally distinctive domains one at 1806 41 ma and the other at 1748

three dimensional gravity modelling applied to the exploration of uranium unconformity related basement hosted deposits the contact prospect case study kiggavik northeast thelon region nunavut canada in unconformity related uranium deposits mineralization is associated with hydrothermal clay rich alteration haloes that decrease the density of the host rock in the kiggavik uranium project located in the eastern thelon basin nunavut canada basement hosted shallow deposits were discovered by drilling geophysical anomalies in the 1970s in 2014 gravity data were inverted for the first time using the geosoft voxi earth modellingtm system to generate three dimensional 3d models to assist exploration in the contact prospect the most recent discovery at kiggavik a 3d unconstrained inversion model was calculated before drilling and a model constrained by petrophysical data was computed after drilling the unconstrained inversion provided a first approximation of the geometry and depth of a low density body and helped to collar the discovery holes of the contact mineralization the constrained inversion was computed using density values measured on 315 core samples collected from 21 drill holes com

spatial and temporal controls on historical channel responses study of an atypical case somesu mic river romania in this paper the spatial and temporal responses of the somesu mic river romania to natural and anthropogenic controls over the past 150 years are analysed based on a series of morphometric parameters extracted from five successive sets of topographic maps and one set of orthophotos prior to the intensive hydrotechnical interventions of the last four decades the river was characterized by a complex alternation of different channel types resulting in a mixture of alluvial and mixed sinuous meandering sinuous anabranched meandering anabranched reaches each a few hundred metres to a few kilometres long the main cause for this spatial behaviour was the local geology its effects were intensified by a larger scale slope slightly higher than along a longitudinal profile with normal concavity as a consequence of the presence of a 400 m elevation knick point located in the catchment area a generalized maintenance of river in the floodplain perimeter during the entire interval of study centennial scale with local planform adjustments and lack of median scale avulsion in lateral tilting areas and along the anabranched reaches channel lengthening and meander development during hydrological stable periods and channel shortening and increasing of natural cutoffs during periods with higher incidence of floods decadal scale and the incapacity of local morphologic changes resulted from human interventions to completely counterbalance general trends decadal scale supports the idea of decreasing the amplitude and frequency of important floods after the end of the little ice age channel metamorphosis by canalization diminishing elimination of overflows and medium scale avulsions by changes in flow regimes dams and the presence of dykes in the floodplain perimeter channel narrowing 43 and incision at least after 1945 downstream from dams and probably because of in channel gravel mining are the main anthropically induced changes along the somesu mic river even if human impact is important both at the drainage basin scale and along the somesu mic river it has only local impacts subordinated to climate the low level of human impact on this river could be the consequence of the higher general slope downstream from 400 m elevation knick point which probably forces the positioning of its effects under an important internal threshold of the fluvial system this boundary condition defines somesu mic river as an atypical river this study supports the idea that climate has a more important role in the post little ice age lia rivers behaviour than currently accepted copyright 2011 john wiley sons ltd

morphological changes in alpine rivers following the end of the little ice age abstract this work investigates the channel changes of alpine rivers from the end of the little ice age 1850s to the 1950s with the aim to determine the possible role of climatic variations occurred in this period before the onset of anthropic pressures i e dams check dams bank protections and gravel mining the research was conducted on 17 river catchments of south tyrol northern italy glaciated and unglaciated a multitemporal gis analysis approach was adopted to assess the morphological changes in terms of channel width and pattern from three different sources i austrian cadastral map 1858 ii maps from the italian institute of military geography 1917 1925 and iii two aerial photo sets taken in 1945 and 1954 the analysed river network a total of 480 km was subdivided into 162 morphologically homogeneous reaches 76 confined 81 partly confined and 5 unconfined with lengths ranging from 630 to 5500 m slope from 0 3 to 24 and drained area from 20 to 4000 km 2 the statistical relationships among morphological changes and reach and basin scale factors were analysed by univariate and multivariate methods and the relationships between width changes and 36 controlling factors were explored using principal component analysis the variability in width and morphological pattern changes were very pronounced between and within single rivers highlighting the value of such a large data set overall the analysed rivers varied their morphological pattern mostly exhibiting a shift from multithread transitional to single thread patterns but unchanged planform types were also common variations in channel width varied substantially among the analysed rivers which featured narrowing slightly prevailing and widening the least common as well as many cases of very limited changes channel width variations appear statistically although weakly related to some morphometric variables and significant differences emerge comparing glaciated vs unglaciated basins climate related variations glacier dynamics and channel disturbance frequency are argued to be the dominant factors that affected channel variations

planform dynamics of braided streams the high dynamism and complexity of braided networks poses a series of open questions significant for river restoration and management the present work is aimed at the characterization of the morphology of braided streams in order to assess whether the system reaches a steady state under constant flow conditions and in that case to determine how it can be described and on which parameters it depends a series of 14 experimental runs were performed in a laboratory physical model with uniform sand varying the discharge and the longitudinal slope planimetric and altimetric configurations were monitored in order to assess the occurrence of a steady state a set of parameters was considered such as the braid plain width and the number and typology of branches and nodes results point out that a relationship exists between braiding morphology and two dimensionless parameters related to total water discharge and stream power we found that network complexity increases at higher values of water discharge and a larger portion of branches exhibits morphological activity results are then compared to the outputs of a simple one dimensional model that allows to easily predict the average network complexity once the bed topography is known model computations permit also the investigation of the effect of water discharge variations and to compare different width definitions the at a station variability of planimetric parameters shows a peculiar behaviour both regarding number of branches and wetted width in particular the analysis of the relationship between width and discharge highlighted relevant differences in comparison to single thread channel copyright 2009 john wiley sons ltd

impacts of flow regulation on geomorphic adjustment and riparian vegetation succession along an anabranching reach of the upper yellow river abstract closure of longyangxia dam in 1986 the uppermost large dam along the trunk stream of the upper yellow river in western china permanently altered the flow regime in guide reach an anabranching section of river located 41 km downstream of the dam two smaller hydropower structures nina and laxiwa dams were constructed between longyangxia dam and guide in 2003 and 2009 respectively but they had a minor influence on the flow regime this study uses the indicators of hydrologic alteration model satellite imagery and field analyses to assess how the magnitude and duration of changes to the flow regime impacted upon geomorphic adjustments and riparian vegetation succession from 1987 to 2015 flow impoundment resulted in near instantaneous reduction in the width of the active channel zone human activities have manipulated the additional floodplain areas created by these changes aggregation of mid channel bars into larger compound features decreased channel multiplicity negligible bed incision likely reflects local supply of sediment from tributary sources downstream of the dam significant correlations are shown between changes to the balance between channel depositional and erosional processes induced by flow regulation and the functional composition of vegetation succession patterns maintenance of a higher water table for longer periods of time is inferred to have altered mutual interactions between hydrogeomorphic processes and riparian vegetation in this semi arid setting

catchment scale cumulative impact of human activities on river channels in the late anthropocene implications limitations prospect abstract evidence for the proposed anthropocene epoch in fluvial geomorphology hinges on the influence of human activities relative to natural forcing however research on cause effect understanding in river channel evolution has rarely focused on the cumulative impact of multiple drivers for change limiting insights systematic review of 25 recent studies professing to explain reach scale channel responses to cumulative impacts of human activities and natural forcing over the recent past ca 1880 2005 reveals some consistencies in spatio temporal response across various catchment sizes median 3000 km2 in mostly industrialized nations common drivers for change include changing flood and flow regimes dam construction changing land uses and forest cover bank protection and instream aggregate mining recent channel evolution has predominantly involved narrowing incision and terrace development reduced bed sediment storage lower activity rates and simplified channel geometries rates of channel change frequently peaked 1955 1990 providing some support for the anthropocene great acceleration evidence here suggests that many river systems are now in morphologically novel configurations coinciding temporally with dramatic recent declines in global freshwater aquatic biodiversity sustainable approaches to freshwater management must acknowledge these configurations placing emphasis on process based approaches to river ecosystem health in which sediment cascades are reconceived to reflect altered longitudinal and lateral connectivity however the reviewed studies are driven largely by expert judgment depicting cause effect associations through summary conceptual models based on spatial proximity and temporal synchronicity providing insufficient scientific proof for the anthropocene based on the overwhelming impact of human factors more conclusive cause effect statements will require hypothetic deductive approaches explicit functional criteria and best practice environmental model building geomorphologists should now move beyond the phase of discovery and develop rigorous proofs for cause effect relationships of cumulative impact this may be enhanced by developing an avowedly anthropocene perspective in which rivers are viewed critically as socio biophysical systems co evolving with human activity

evolutionary trajectory of channel morphology and controlling factors in a large gravel bed river abstract interpretation of channel changes is not always straightforward since it requires a detailed reconstruction of the evolutionary trajectory of channel morphology a quantitative analysis of controlling factors and finally identification of links between evolutionary trajectories and controlling factors the aim of this paper is to explain channel adjustments and controlling factors in the tagliamento river a large gravel bed river in northeastern italy traditional methods for studying historical channel changes i e use of aerial photos topographic data were employed but numerical modelling turned out to be very useful for the quantification of bedload transport and for supporting interpretation of past changes and likely future channel evolution river channel underwent three main phases of adjustment over the last 200 years the first two phases from the end of the nineteenth century to the early 1990s were characterized by narrowing channel width decreased from 1250 to 540 m and incision about 1 m and the third phase from the 1990s to present day by widening from 540 to 600 m and slight aggradation about 0 2 m combining evolutionary trajectories of channel morphology and analysis of controlling factors we argue that the long term channel evolution of the tagliamento river was driven mainly by human intervention at the reach scale i e sediment mining and channelization changes in sediment supply in the catchment area had no or minor effects in the study reach the most recent changes i e widening and slight aggradation are explained as a response to past disturbances that have produced a remarkable change of channel geometry and an increase of unit stream power in the reach magnitude and frequency of formative discharges are a key driving factor of the intensity of recent changes while this was not the case during the previous phases of adjustment

flood plain and channel dynamics of the quinault and queets rivers washington usa abstract comparison of historic channel migration rates modern planform conditions and overall sediment wood and flow conditions and interactions for the quinault river and queets river in the western olympic peninsula washington reveals decadal to century scale interactions between gravel bed channels and forested flood plains in temperate maritime environments the downstream alluvial portions of these two rivers can be divided into three reaches of different slope flow sediment and wood regimes i the upper quinault river is aggrading behind lake quinault a natural lake that traps most sediment and wood transported from the olympic mountain headwaters ii the lower quinault river downstream of lake quinault transports only sediment and wood derived from reworking of flood plain deposits and contributed from valley margins iii the queets river has unimpeded movement of sediment and water from the mountainous headwaters to the pacific ocean measurements of channel planform characteristics and historic migration rates and patterns show that these three reaches have correspondingly distinct channel and flood plain morphologies and dynamics the aggrading and sediment rich upper quinault river has the widest flood plain widest active channel greatest number of low flow channels and flanking gravel bars and an average channel migration rate of 12 7 3 3 m year between 1900 and 1994 the comparatively sediment poor lower quinault river has the narrowest flood plain narrowest active channel and lowest channel migration rate 4 0 1 2 m year and most flow is through a single channel with few adjacent gravel bars the queets river has attributes intermediate between the lower and upper quinault rivers including an average channel migration rate of 7 5 2 9 m year flood plain turnover rates are similar for all three reaches with channels eroding the flood plain at the rate of about 0 2 of the flood plain area per year and with corresponding flood plain half lives of 300 to 500 years observations from this study and previous studies on the queets river show that channel and flood plain dynamics and morphology are affected by interactions between flow sediment and standing and entrained wood some of which likely involve time frames similar to 200 500 year flood plain half lives on the upper quinault river and queets river log jams promote bar growth and consequent channel shifting short distance avulsions and meander cutoffs resulting in mobile and wide active channels on the lower quinault river large portions of the channel are stable and flow within vegetated flood plains however locally channel spanning log jams have caused channel avulsions within reaches that have been subsequently mobile for several decades in all three reaches log jams appear to be areas of conifer germination and growth that may later further influence channel and flood plain conditions on long time scales by forming flood plain areas resistant to channel migration and by providing key members of future log jams appreciation of these processes and dynamics and associated temporal and spatial scales is necessary to formulate effective long term approaches to managing fluvial ecosystems in forested environments

a methodological framework for hydromorphological assessment analysis and monitoring idraim aimed at promoting integrated river management a methodological framework for hydromorphological assessment analysis and monitoring named idraim has been developed with the specific aim of supporting the management of river processes by integrating the objectives of ecological quality and flood risk mitigation the framework builds on existing and up to date geomorphological concepts and approaches and has been tested on several italian streams the framework includes the following four phases 1 catchment wide characterization of the fluvial system 2 evolutionary trajectory reconstruction and assessment of current river conditions 3 description of future trends of channel evolution and 4 identification of management options the framework provides specific consideration of the temporal context in terms of reconstructing the trajectory of past channel evolution as a basis for interpreting present river conditions and future trends a series of specific tools has been developed for the assessment of river conditions in terms of morphological quality and channel dynamics these include the morphological quality index mqi the morphological dynamics index mdi the event dynamics classification edc and the river morphodynamic corridors mc and emc the monitoring of morphological parameters and indicators alongside the assessment of future scenarios of channel evolution provides knowledge for the identification planning and prioritization of actions for enhancing morphological quality and risk mitigation

contemporary channel changes in the eygues basin southern french prealps the relationship of subbasin variability to watershed characteristics the southern french prealps are sub mediterranean mountains in which forest cover has increased since the end of the 19th century forest development linked with agricultural decline and planned reafforestation has induced a decrease of bedload supply from hillslopes in response to this evolution several channel changes are observed in mountain streams channel narrowing channel degradation and pavement development the intensity of these adjustments differs from one stream to another twenty catchments 10 100 km2 located in the eygues river basin 1150 km2 a tributary of the rhone river are studied to highlight the subbasin variability of channel changes and to give causal interpretations we conducted field surveys and analyzed aerial photographs to characterize present channel morphology and contemporary channel changes and gis was used to quantify morphometry relief land use and geology of the watersheds multivariate statistical analysis determined relations between channel changes and watershed characteristics the potential bedload supply of these mountain streams is controlled largely by watershed morphometry and land use the most active tributaries of the eygues river are characterized mainly by high drainage density and poor vegetation cover linked to agricultural land use

channel response to increased and decreased bedload supply from land use change contrasts between two catchments abstract the catchments of pine creek idaho usa 200 km 2 and the drome river in the drome department france 1640 km 2 illustrate contrasting changes in land use bedload sediment production and channel response hard rock mining began in the catchment of pine creek near the end of the 19th century and together with road construction timber harvest and historically heavy grazing of uplands resulted in increased tributary bedload yield increased bedload migrating to the channel combined with removal of large cedar trees on the floodplain resulted in channel instability which propagated downstream over a period of decades on many reaches of pine creek active channel width has increased by over 50 since 1933 over roughly the same time period the drome river catchment was extensively reforested after at least one century of denudation and heavy grazing and numerous check dams were constructed on torrents to reduce erosion as a result the drome river has experienced a reduction in bedload sediment supply since the late 19th century in addition gravel has been extracted from some reaches consequently the channel has degraded and gravel bars have been colonized with woody riparian vegetation channel widths in wide braided reaches decreased from 1947 to 1970 by 60 on pine creek channel instability has resulted in bank erosion exposing contaminated mine tailings and increased flood hazard on the drome river degradation has undermined bridges and embankments and lowered the water table in areas dependent on groundwater for irrigation resulting in loss of 6 million m 3 of groundwater storage since 1960 though they differ in drainage area by nearly an order of magnitude pine creek and the drome river provide an excellent contrast in that they represent two sides of an epicycle of alluvial sedimentation set off in each case by land disturbance in both cases the most recent channel changes though in opposite directions were viewed as negative by river managers on pine creek managers have removed or protected from erosion mine tailings and have attempted to train the stream into a more stable channel and most rock waste piles the principal sediment sources have recently been controlled on the drome river managers have prohibited gravel mining and adopted new policies to permit coarse sediment to migrate through the river system

evolutionary trajectory of channel planforms in the middle garonne river toulouse sw france over a 130 year period contribution of mixed multiple factor analysis mfamix the purpose of this study is to propose a methodological essay for defining evolutionary trajectories of channel planforms and to examine the channel change in the middle garonne river southwest france over a 130 year period the study focuses on a reach of 90 km situated downstream from the city of toulouse a set of four historical maps 1868 1940s 1970s and 2000s is used to build a geomorphometric diachronic database data processing through mixed multiple factor analysis mfamix and hierarchical cluster analysis hca allows distinction between four homogeneous zones within the study reach depending on their evolutionary trajectories channel behavior in the upstream and median zones evolved as of the beginning of the study period narrowing of the fluvial area colonization by vegetation and removal of alluvial bars likely owing to punctual anthropogenic actions the downstream zone is characterized by stabilization of the channel and alluvial bar removal over the second half of the twentieth century coinciding with the campaign undertaken by french local authorities between 1960 and 1984 to protect river banks the role of accepted manuscript climate transition between the little ice age lia and the onset of the global warming period gw is also discussed results generally are consistent with the chronology established for most european rivers