sediment contributions from floodplains and legacy sediments to piedmont streams of baltimore county maryland abstract disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades with the role of floodplains in sediment storage as a common focus in the piedmont province of the eastern usa upland deforestation and agricultural land use following european settlement led to accumulation of thick packages of overbank sediment in valley bottoms commonly referred to as legacy deposits previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening this paper seeks to quantify 1 rates of sediment remobilization from baltimore county floodplains by channel migration and bank erosion 2 proportions of streambank sediment derived from legacy deposits and 3 potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the mid atlantic piedmont we calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0 18 and 155 km2 in baltimore county maryland we compared stream channel and floodplain morphology from lidar based digital elevation data collected in 2005 with channel positions recorded on 1 2400 scale topographic maps from 1959 1961 in order to quantify 44 46 years of channel change sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources average annual lateral migration rates ranged from 0 04 to 0 19 m y which represented an annual migration of 2 5 0 9 4 4 channel width across all study segments suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates gross bank erosion rates varied from 43 to 310 mg km y median 114 and were positively correlated with drainage area measured deposition within channels accounted for an average of 46 28 75 of gross erosion with deposition increasingly important in larger drainages legacy sediments accounted for 6 90 of bank erosion at individual study segments represented about 60 of bank height at most exposures and accounted for 57 16 of the measured gross erosion extrapolated results indicated that first and second order streams accounted for 62 38 of total streambank erosion from 1005 km2 of northern baltimore county after accounting for estimated redeposition extrapolated net streambank sediment yields 72 mg km2 y constituted 70 of estimated average piedmont watershed yields 104 mg km2 y the results suggest that streambank sediments are a relatively large source of sediment from piedmont tributaries to the chesapeake bay

degradation of the mitchell river fluvial megafan by alluvial gully erosion increased by post european land use change queensland australia along low gradient rivers in northern australia there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains on the mitchell river fluvial megafan in northern queensland river incision and fan head trenching into pleistocene and holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion in this study rates of alluvial gully erosion into incipiently unstable channel banks and or pre existing floodplain features were quantified to assess the influence of land use change following european settlement alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent gps surveys and historic air photos demonstrating rapid increases in gully area of 1 2 to 10 times their 1949 values extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950 which is post european settlement this is supported by young optically stimulated luminescence osl dates of gully inset floodplain deposits lidar terrain analysis historic explorer accounts of earlier gully types and archival records of cattle numbers and land management it is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks adjacent floodplain hollows and precursor gullies this is a result of reduced native grass cover increased physical disturbance of soils and the concentration of water runoff along cattle tracks in addition to fire regime modifications episodic drought and the establishment of exotic weed and grass species geomorphic processes operating over geologic time across the fluvial megafan predisposed the landscape to being pushed by land used change across an intrinsically close geomorphic threshold towards instability the evolution of these alluvial gullies is discussed in terms of their initiation development future growth and stabilisation and the numerous natural and anthropogenic factors influencing their erosion

remote measurement of river morphology via fusion of lidar topography and spectrally based bathymetry this study developed and evaluated a hybrid approach to remote measurement of river morphology that combines lidar topography with spectrally based bathymetry comparison of filtered lidar point clouds with surveyed cross sections indicated that subtle features on low relief floodplains were accurately resolved by lidar but that submerged areas could not be detected due to strong absorption of near infrared laser pulses by water the reduced number of returns made the active channel evident in a lidar point density map a second dataset suggested that pulse intensity also could be used to discriminate land from water via a threshold based masking procedure fusion of lidar and optical data required accurate co registration of images to the lidar and we developed an object oriented procedure for achieving this alignment information on flow depths was derived by correlating pixel values with field measurements of depth highly turbid conditions dictated a positive relation between green band radiance and flow depth and contributed to under prediction of pool depths water surface elevations extracted from the lidar along the water s edge were used to produce a continuous water surface that preserved along channel variations in slope subtracting local flow depths from this surface yielded estimates of the bed elevation that were then combined with lidar topography for exposed areas to create a composite representation of the riverine terrain the accuracy of this terrain model was assessed via comparison with detailed field surveys a map of elevation residuals showed that the greatest errors were associated with underestimation of pool depths and failure to capture cross stream differences in water surface elevation nevertheless fusion of lidar and passive optical image data provided an efficient means of characterizing river morphology that would not have been possible if either dataset had been used in isolation copyright 2011 john wiley sons ltd

modeling large scale fluvial erosion in geographic information systems variants of the stream power model have become standard for large scale erosion modeling in geographic information systems gis because they can be applied over broad areas without the need for detailed knowledge of stream characteristics gis based implementations of the shear stress stream power per unit length and stream power per unit area models are closely related to one another and related also to empirical sediment yield models derived from continental scale factor analyses based on a detailed examination of the implementation of stream power analyses at the scale of continental mountain ranges we demonstrate that 1 the careful selection of a digital elevation model dem projection can minimize length and area distortion when analyzing large portions of the earth such as the himalaya or andes in the two dimensional plane of a dem 2 the area discharge proxy frequently employed in gis based stream power studies may not be appropriate for rivers that flow through significant rain shadows or climatic zones 3 decreasing the resolution of a dem from 30 to the 900 m typical for studies of large extent decreased the mean slopes of 15 rivers in the olympic mountains by 65 increased the mean drainage basin size by 14 and caused a 17 reduction in median main stem channel length 4 the coefficients k m and n common to different versions of the stream power law are themselves sensitive to grid resolution when determined from an analysis of area slope plots 5 stream power per unit area decreased in the olympics mountains as grid resolution decreased d 2002 elsevier science b v all rights reserved

characterizing structural and lithologic controls on deep seated landsliding implications for topographic relief and landscape evolution in the oregon coast range usa in mountainous areas landslides regulate temporal variations in sediment production and may suppress simple linkages between topographic development and tectonic forcing rates and mechanisms of mass wasting depend on lithology bedrock structure and climatic and tectonic setting these factors tend to vary signifi cantly in active tectonic regions thus clouding our ability to predict how landsliding modulates topographic development over human and geological time scales here we use a novel dem based technique to document the distribution of large landslides in the oregon coast range ocr and quantify how they affect topographic relief we developed an automated algorithm that exploits the distinctive topographic signature specifi cally the relationship between curvature and gradient of large landslides to map their distribution within the gently folded tyee formation eocene deltaicsubmarine ramp sediments in contrast to steep and highly dissected terrain frequently identifi ed as characteristic of the ocr which exhibits steep planar sideslopes and highly curved low gradient ridgetops and valleys terrain prone to large landslides tends to have low values of both drainage density and curvature and gradient values that cluster between 0 16 and 0 44 the distribution of failure dominated terrain in our 10 000 km2 study area is infl uenced by systematic variations in sedimentary facies and bedrock structure the fraction of terrain altered by large landslides 0 1 km2 varies from 5 in the sand rich delta slope and proximal ramp facies southern section of our study area to 25 in the north distal ramp facies coincident with an increase in the thickness of siltstone beds and a decrease in the sandstone siltstone ratio local relief declines progressively northward suggesting that deep seated landsliding is sensitive to the thickness and frequency of low shearstrength siltstone beds and may serve to limit topographic development in the ocr structural controls are superimposed on facies related variations as deep seated landslides are frequently found on slopes whose downslope aspect corresponds to the bedrock dip direction for 1516 strike and dip measurements in our study area we calculated the fraction of proximal terrain 2 5 km altered by deep seated landsliding in the sand rich southern region the proportion of proximal slide dominated terrain increases modestly with bedrock dip in the silt rich northern region terrain altered by deep seated landsliding is pervasive and an increase in dip from 0 to 16 corresponds to a change in the fraction of slide prone terrain from 10 to 28 our technique for mapping large landslides has utility for hazard analysis and land management over million year time scales the progradational character of the tyee formation suggests that continued uplift and exhumation of the ocr should result in a southward propagation of slide prone silt rich distal facies as a result deep seated landsliding will become increasingly prominent and topographic relief in the central and southern ocr will progressively decline whereas spatial variability in climatic or tectonic forcing is often invoked to explain systematic variations in topographic development our results emphasize the importance of structural and intraformation lithologic controls on landsliding as such analyses linking surface processes climate tectonics and landscapes should be couched in the context of diverse geologic and topographic data

air photo based change in channel width in the minnesota river basin modes of adjustment and implications for sediment budget abstract the minnesota river and major tributaries have experienced large increases in discharge over the past century aerial photograph based measurements of channel width were made for the 1938 2015 period at 16 multibend subreaches by digitizing the area between vegetation lines and dividing by centerline length results show considerable increases in width for the main stem 0 62 0 10 y and major tributaries 0 31 0 08 y but are inconclusive for smaller channels width

landslide area probability density function statistics to assess historical landslide magnitude and frequency in coastal california abstract landslide area probability density function pdf statistics elucidate the landslide magnitude frequency distribution in a small coastal watershed in central california detailed mapping into a gis and compilation of two slide inventories in walker creek marin county reflect erosional effects of storms occurring in 1941 and 1998 respectively we focus on the spatial distribution and area of slides to illustrate that during both periods slides originate mainly from hillslopes underlain by franciscan complex units with slopes ranging from 10 to 40 the majority of slides 70 have areas ranging between 100 and 1000 m 2 the magnitude frequency distribution of slides represented by the pdf produces a curve that has a linear portion representing the relatively large slides the power functions of the linear portion of these curves have exponents of about 2 0 for both inventories results suggest that the storm event based pdf of landslide area developed using historical aerial images is a viable means of quantifying the landslide magnitude frequency relationship at the scale of a small watershed

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

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

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

the camera and the geomorphologist abstract the methods we use to produce geomorphic data are deeply interwoven with the geomorphic questions we choose to ask and with the geomorphic theories we construct authors have described major changes in the history of geomorphology in terms of theoretical shifts and or social cultural changes but it seems clear that shifts in methodological practices also can produce deep changes in geomorphology as a whole the camera has had a long illustrious and complex history as a geomorphic tool and as such is useful for assessing larger geomorphological concerns and themes the camera is also a symbol of the ongoing revolution in geomorphology from a data poor to a data rich subject this revolution is built upon many methodological changes and it has had many side effects the interrelated history of cameras and fluvial geomorphology provides an illuminating case study in past and present changes in the geomorphic sciences some past geomorphic practices such as using photos as descriptive evidence for verifying geomorphic theory remain as important approaches today other camera based practices have dwindled to some degree such as the production of large area topographic maps through traditional aerial photogrammetry which have been overtaken by alternative methods such as lidar and interferometric radar and newer camera based techniques such as structure from motion photogrammetry are at the heart of the recent democratization of geomorphic data as the modern data revolution progresses it is important to ask questions such as who has been part of the data revolution and what have been their motivations and have winners and losers been produced as part of the data revolution not all effects of the data revolution have been completely positive many geomorphologists feel overwhelmed by big data expectations and methodological concerns from a philosophy of science perspective the moves toward population like geomorphic data have strained normal inductive inference procedures and recent research has brought to light inferential alternatives such as advanced data mining and the hypothetico deductive approach even so most current analytical techniques appear to be lagging behind the newly introduced big data producing new wine in old bottles new data for old analyses beyond pure geomorphic research the camera and its derivatives are also part of profound shifts in educational and outreach expectations and practices clearly the data revolution in geomorphology is still in its infancy and much of that revolution has been wrought by the humble camera

airborne and ground based data sources for characterizing the morpho structure of a coastal landslide abstract landslide analysis is increasingly based on the combination of multiple information sources at different spatial and temporal resolutions spatial coverage accuracy and acquired using various airborne and terrestrial platforms and geomorphological geophysical and geotechnical methods morphological mapping and morpho structure characterization are preliminary steps to analyze the observed and future landslide distributions the objective of this work is to propose a morpho structural model of an active landslide complex on the normandy coast north west france by combining different data sources the methodology associates field investigation with interpretation of high resolution topographic and geophysical images the proposed morpho structural model highlights the division of the landslide into several morphological features this division may explain the spatial variability and temporal variability of the slope dynamics

a 184 year record of river meander migration from tree rings aerial imagery and cross sections abstract channel migration is the primary mechanism of floodplain turnover in meandering rivers and is essential to the persistence of riparian ecosystems channel migration is driven by river flows but short term records cannot disentangle the effects of land use flow diversion past floods and climate change we used three data sets to quantify nearly two centuries of channel migration on the powder river in montana the most precise data set came from channel cross sections measured an average of 21 times from 1975 to 2014 we then extended spatial and temporal scales of analysis using aerial photographs 1939 2013 and by aging plains cottonwoods along transects 1830 2014 migration rates calculated from overlapping periods across data sets mostly revealed cross method consistency data set integration revealed that migration rates have declined since peaking at 5 m year in the two decades after the extreme 1923 flood 3000 m 3 s averaged over the duration of each data set cross section channel migration occurred at 0 81 m year compared to 1 52 m year for the medium length air photo record and 1 62 m year for the lengthy cottonwood record powder river peak annual flows decreased by 48 201 vs 104 m 3 s after the largest flood of the post 1930 gaged record 930 m 3 s in 1978 declining peak discharges led to a 53 reduction in channel width and a 29 increase in sinuosity over the 1939 2013 air photo record changes in planform geometry and reductions in channel migration make calculations of floodplain turnover rates dependent on the period of analysis we found that the intensively studied last four decades do not represent the past two centuries

channel changes due to river regulation the case of the piave river italy this paper deals with the channel changes of the piave river in the eastern alps italy which have occurred during this century in response to human interventions in the fluvial system the flow regime and the sediment supply of the river have been considerably altered by hydroelectric dams flow diversions and gravel mining in addition river dynamics have been affected by the construction of streambank protection structures to document these changes a historical analysis was performed using maps and aerial photographs morphological features that were examined included planform configuration channel width braiding index and bed elevation the results indicate that as a consequence of decreases in the flows and sediment supply remarkable channel changes have occurred in the river during this century especially during recent decades the channel has undergone a general narrowing with a decrease in average width to 35 per cent of its initial value while the braiding index has decreased from about 3 to 1 5 in several reaches the planform pattern has changed from braided to wandering the observed trends of channel change suggest that the river has not yet reached a new equilibrium condition and it may therefore be predicted that reductions in width and braiding intensity are likely to continue in the immediate future copyright 1999 john wiley sons ltd

floodplain sediments of the 2002 catastrophic flood at the vltava moldau river and its tributaries mineralogy chemical composition and post sedimentary evolution fine grained floodplain sediments of the catastrophic 2002 flood deposited along the lower reaches of the berounka and vltava rivers czech republic were not highly contaminated with heavy metals and other toxic elements this is due to the dominantly mineral character of the sediments ctot in the range 3 97 5 01 relatively low content of clay minerals and due to the very high degree of contamination dilution by eroded pre industrial non contaminated floodplain sediments despite this high degree of dilution the influence of the small litavka river draining the historical pb zn ag p ibram ore region is well visible the litavka river is one of important sources of pb and zn contamination in the whole berounka vltava labe river system the 2002 flood sediments deposited in the floodplain of the berounka and vltava rivers show poor vertical chemical zoning except for some components enriched in the uppermost layer by precipitation from evaporated pore water contained in the mud i e secondary carbonate the content of ccarb of the sediments 0 05 0 15 is partly represented by this secondary carbonate which is later leached by rainwater and partly by fragments of river mollusk shells a majority of the heavy metals contained in sediments can be readily leached by diluted acids and to a much smaller degree by rainwater

geomorphic diversity in the braided wandering bela river slovak carpathians as a response to flood variability and environmental changes abstract changes in the morphological pattern of the gravel bed bela river slovak carpathians were investigated to infer about the impact of flood events and environmental changes on the evolutionary trend of the river since the mid twentieth century the post flood period serial geomorphic analysis popsega approach coupled with gis analysis was used to identify morphological changes that occurred during particular flood periods the study focused on assessing how six flood periods fp with differing flood characteristics have influenced the evolutionary trend of the river several sets of aerial photos 1949 1961 1973 1986 1992 2003 2009 taken after the periods with the occurrence or lack of major floods provided data about channel landform changes in 227 river segments of 100 m length a decreasing trend of the area of the river s active zone from 2 5 km2 in 1949 to 1 4 km2 in 2009 was identified the first fp 1949 1961 with a very high magnitude flood in 1958 ri50 was characterized by increasing total channel length island number area and the number density of confluence diffluence pairs nodes and by decreasing bar area during this fp the frequency of cores of channel dynamics as well as the shannon s index of landforms diversity reached the highest values the following fp 1962 1973 with four 5 to 10 year floods exhibited the inverse pattern of changes in channel form parameters although the core frequency of channel dynamics and shannon s diversity index were still high the river system seems to have been relatively stable between 1974 and 1986 third fp with some decrease in the area of channel forms and in pattern metrics values during the fourth fp 1987 1992 several 1 5 to 3 year floods occurred and were associated with a decrease in some channel forms and a further decrease of the pattern metrics values an increase in all analysed channel parameters especially bar area and pattern metrics values occurred in the years 1993 2002 fifth fp as a consequence of two floods of moderate magnitude in 1997 ri7 and 2001 ri3 5 the lowest values of bar area and pattern metrics during the whole study period were recorded during the last fp 2002 2008 whereas island area increased at that time the study shows that the occurrence of floods during the last six decades has not returned the bela to its former state because of the overall decrease in flood magnitudes changes in catchment sediment supply induced by the increasing forest cover in the catchment from 22 7 in 1957 to 34 8 in 2008 and changes in channel boundary conditions channelization channel incision small hydropower plant constructions

assessment of river bank erosion in southern minnesota rivers post european settlement article i nfo river bank erosion is one of the major sources of sediment for many rivers around the world with the cur rent emphasis on developing total maximum daily loads tmdls for impaired waters in the united states there is heightened interest in quantifying background sediment levels in rivers in this study we assessed variations in river bank erosion over time using a combination of 1855 public land survey system plats aerial photographs from 1938 to 2009 and light detection and ranging lidar data from 2005 to 2009 for sediment impaired rivers in southern minnesota results showed that bank erosion was episodic making comparisons of erosion rates from dissimilar time intervals unreliable for comparable time intervals average river bank retreat rates 0 51 m yr 1 from 1855 to 1938 vs 0 37 m yr 1 from 1938 to 2009 were statistically similar t 2 13 p 0 14 suggesting that bank erosion rates have remained stable since european settlement comparisons over shorter time intervals of 1938 1971 and 1971 2009 also showed similar statistical trends t 0 76 p 0 45 with average river bank retreat rates of 0 57 and 0 50 m yr 1 respectively however additional 145 observations of bank retreat were found in the period 1971 2009 relative to 1938 1971 in dicating that the number of actively eroding river banks may have increased over time contrary to assump tions made in the literature bank erosion measurements using lidar data showed a poor relationship r 2

remote sensing of stream depths with hydraulically assisted bathymetry hab models this article introduces a technique for using a combination of remote sensing imagery and open channel flow principles to estimate depths for each pixel in an imaged river this technique which we term hydraulically assisted bathymetry hab uses a combination of local stream gage information on discharge image brightness data and manning based estimates of stream resistance to calculate water depth the hab technique does not require ground truth depth information at the time of flight hab can be accomplished with multispectral or hyperspectral data and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images hab also has the potential to be applied retroactively to historic imagery allowing researchers to map temporal changes in depth we present two versions of the technique hab 1 and hab 2 hab 1 is based primarily on the geometry discharge and velocity relationships of river channels manning s equation assuming average depth approximates the hydraulic radius the discharge equation and the assumption that the frequency distribution of depths within a cross section approximates that of a triangle are combined with discharge data from a local station width measurements from imagery and slope measurements from maps to estimate minimum average and maximum depths at a multiple cross sections these depths are assigned to pixels of maximum average and minimum brightness within the cross sections to develop a brightness depth relation to estimate depths throughout the remainder of the river hab 2 is similar to hab 1 in operation but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical beer lambert law of light absorbance in this case the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage r 2 values for measured depths versus depths estimated by hab 1 and hab 2 are 0 51 and 0 77 respectively in the relatively simple brazos river texas r 2 values for hab 1 and hab 2 are 0 46 and 0 26 respectively in the lamar river a complex mountain river system in yellowstone national park although the r 2 values are moderate depth maps and crosssections derived from the hab techniques are consistent with typical stream geomorphology patterns and provide far greater

statistical analysis of the evolution of a semialluvial stream channel upstream from an inversion type reservoir the case of the matawin river quebec canada abstract built in 1930 on the matawin river 5770 km to supply hydroelectric plants located downstream on the saint maurice river the taureau reservoir caused an inversion of the natural hydrological cycle maximum flows occur in winter and minimum flows occur in spring during snowmelt this inversion induces a very rapid rise of the reservoir level base level for the channel upstream from the reservoir in april may during the filling up process the goal of the study is to analyze the effect of the rapid rise of the base level on the morphological evolution of the 7 km long sandy section of the matawin river located immediately upstream from the reservoir and to compare it with jiongxin s general model comparison of aerial photos taken before 1928 and after 1937 1950 1965 1975 1983 and 1995 reservoir construction reveals no significant change in the bankfull mean width sinuosity and bankfull depth of the studied section it follows that the morphological evolution of the matawin river channel upstream from the dam is not consistent with the jiongxin model the effect of the inverted hydrological regime in fact produces high channel stability this stability will probably contribute to a slow but progressive reduction of the channel width and an increase of the sinuosity this morphological evolution seems typical of the semialluvial streams found upstream from the inverted type reservoir of the canadian shield

high spatial resolution hyperspectral mapping of in stream habitats depths and woody debris in mountain streams this article evaluates the potential of 1 m resolution 128 band hyperspectral imagery for mapping in stream habitats depths and woody debris in third to fifth order streams in the northern yellowstone region maximum likelihood supervised classification using principal component images provided overall classification accuracies for in stream habitats glides riffles pools and eddy drop zones ranging from 69 for third order streams to 86 for fifth order streams this scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams multiple regressions of measured depths y versus principal component scores x1 x2 xn generated r 2 values ranging from 67 for high gradient riffles to 99 for glides in a fifth order reach r 2 values were lower in third order reaches ranging from 28 for runs and glides to 94 for pools the less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels where a wide range of depths and surface turbulence occurred within a single pixel matched filter mf mapping of woody debris generated overall accuracies of 83 in the fifth order lamar river accuracy figures for the in stream habitat and wood mapping may have been misleadingly low because the fine resolution imagery captured fine scale variations not mapped by field teams which in turn generated false misclassifications when the image and field maps were compared the use of high spatial resolution hyperspectral hsrh imagery for stream mapping is limited by the need for clear water to measure depth by any tree cover obscuring the stream and by the limited availability of airborne hyperspectral sensors nonetheless the high accuracies achieved in northern yellowstone streams indicate that hsrh imagery can be a powerful tool for watershed wide mapping monitoring and modeling of streams d 2003 elsevier science b v all rights reserved

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

river channel planform change software for historical analysis abstract er mapper an image processing system was used to manipulate scanned maps plans and aerial photographs to enable detailed analysis of historical river channel planform change the er mapper package offers the opportunity to spatially reference each item of planform data into the same scale and co ordinate space as a base map using a warping algorithm and operator selected ground control points once all the data are in the same co ordinate space and at the same scale a given point can be returned to over time and a number of indices can be easily calculated to examine past channel behaviour here lateral shift channel width sinuosity and area of sedimentation within the reach were used as the maps and aerial photographs themselves are used the errors associated with digitising vectors are avoided and a more flexible approach towards analysis and the identification of important indices can be adopted at the outset results obtained for the cleekhimin burn a site in southern scotland are briefly presented and discussed and the advantages of the package and the limitations of the historical database are also outlined

error in a usgs 30 meter digital elevation model and its impact on terrain modeling calculations based on us geological survey usgs digital elevation models dems inherit any errors associated with that particular representation of topography we investigated the potential impact of error in a usgs 30 m dem on terrain analysis over 27 km 2 the difference in elevation between 2652 differential global positioning systems measurements and usgs 30 m dem derived elevations provided the comparative error dataset analysis of this comparative error data suggested that although the global average error is small local error values can be large and also spatially correlated stochastic conditional simulation was used to generate multiple realizations of the dem error surface that reproduce the error measurements at their original locations and sample statistics such as the histogram and semivariogram model the differences between these alternative error surfaces provide a model of uncertainty for the unknown dem error spatial distribution these dem errors had a significant impact on terrain attributes which compound elevation values of many grid cells e g slope wetness index etc a case study using terrain modeling demonstrates that the result of error propagation is most dramatic in valley bottoms and along streamlines q 2000 elsevier science b v all rights reserved

the ebro river in the 20th century or the ecomorphological transformation of a large and dynamic mediterranean channel in the first decades of the 20th century the ebro river was the iberian channel with the most active fluvial dynamics and the most remarkable spatial temporal evolution its meandering typology the dimensions of its floodplain and the singularities of its flow regime produced an especially interesting set of river functions the largest dynamics of the ebro river are concentrated along the meandering profile of the central sector during the 20th century this sector experienced a large alteration of its geomorphological structure we present here an analysis of this evolution through the cartographic study of a long segment of the river 250 km in 1927 1956 and 2003 the results show a large reduction in bank sinuosity a progressive loss of fluvial territory and a large decrease in channel width these changes are especially clear in the areas previously most ecologically connected with the active channel the fluvial territory of the river in 2003 was approximately half that found during the first decades of the 20th century forest plantations which were non existent in 1927 occupied more than 1500 ha of the study area in the last decade this intense geomorphological transformation becomes ecologically visible in i a 35 reduction of the area occupied by riparian vegetation ii a loss of the heterogeneity of riparian forest spots which were formerly structured in an irregular mosaic far from the river thalweg and iii a modification of the riparian forest structure which is currently linear uniform thin and very close to the river axis the ecomorphological alteration was intensified by the remarkable reduction in bank length 13 and the reduced dynamism of the present river system indicated by an increase in the percentage of fluvial territory occupied by riparian forests and a reduction in the area occupied by the active channel copyright 2002 john wiley sons ltd

dynamical role of mode water ventilation in decadal variability in the central subtropical gyre of the north pacific abstract decadal variability in the interior subtropical north pacific is examined in the geophysical fluid dynamics laboratory coupled model cm2 1 superimposed on a broad classical subtropical gyre is a narrow jet called the subtropical countercurrent stcc that flows northeastward against the northeast trade winds consistent with observations the stcc is anchored by mode water characterized by its low potential vorticity pv mode water forms in the deep winter mixed layer of the kuroshio oyashio extension koe east of japan and flows southward riding on the subtropical gyre and preserving its low pv characteristic as a thick layer of uniform properties the mode water forces the upper pycnocline to shoal and the associated eastward shear results in the surface intensified stcc on decadal time scales in the central subtropical gyre 15 35 n 170 e 130 w the dominant mode of sea surface height variability is characterized by the strengthening and weakening of the stcc because of variations

the measurement of river bank erosion and lateral channel change a review a detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change the techniques are classified according to the time scales involved long intermediate and short and each is discussed with respect to accuracy and repeatability the methods covered include sedimentological evidence botanical evidence historical sources planimetric resurvey repeated cross profiling erosion pins and terrestrial photogrammetry prospects for future developments are also discussed

geomorphic change detection using historic maps and dem differencing the temporal dimension of geospatial analysis abstract the ability to develop spatially distributed models of topographic change is presenting new capabilities in geomorphic research high resolution maps of elevation change indicate locations processes and rates of geomorphic change and provide a means of calibrating temporal simulation models methods of geomorphic change detection gcd based on gridded models may be applied to a wide range of time periods by utilizing cartometric remote sensing or ground based topographic survey data to measure volumetric change advantages and limitations of historical dem reconstruction methods are reviewed with a focus on coupling them with subsequent dems to construct dems of difference dod which can be created by subtracting one elevation model from another to map erosion deposition and volumetric change the period of dod analysis can be extended to several decades if accurate historical dems can be generated by extracting topographic data from historical data and selecting areas where geomorphic change has been substantial the challenge is to recognize and minimize uncertainties in data that are particularly elusive with early topographic data this paper reviews potential sources of error in digitized topographic maps and dems although the paper is primarily a review of methods three brief examples are presented at the end to demonstrate gcd using dods constructed from data extending over periods ranging from 70 to 90 years

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

investigating decadal scale geomorphic dynamics in an alpine mountain setting we know little about the effect of recent climate variability upon landscapes at the timescale of decades because of 1 the complex nonlinear and path dependent nature of the response of a landscape to climate forcing and 2 the difficulty of quantifying spatially distributed impacts at the timescale of decades to centuries despite this being the timescale over which significant hypotheses have been raised over human impacts upon climate change and hence geomorphic systems a unique resource to investigate the linkages between climatic variability and geomorphic response is provided by the extensive coverage of aerial imagery commonly available since the 1950s here we use archival digital photogrammetry to produce high precision digital elevation models over large spatial scales and so to reconstruct the quantitative history of surface downwasting and sediment flux in a high mountain alpine system over the timescales of decades propagation of error methods is used to identify locations of significant landscape response and to compute volumes of significant surface change orthorectified aerial images are used in an image correlation framework to detect horizontal and vertical displacements of components of the landscape results are coupled to extant climate data and modeled snow cover to show how the landscape responds to climate forcing and to geomorphological maps to understand how this response varies between landscape elements the results show distinct landscape response to both warming and cooling periods and a tendency for the acceleration of surface displacement under warming conditions precipitation and snow cover are critical in controlling glacier dynamics and rock glacier displacement velocities however while some landforms might lead to locally high sediment flux landscape heritage can disconnect zones of high change rates from the valley bottom hence the landscape response to climate forcing is not necessarily reflected in valley system processes or sediment deposits