sedimentary processes in the river dominated mvoti estuary south africa abstract the mvoti river enters the indian ocean on the natal coast of south africa in its lower reaches the river comprises a narrow shallow channel that traverses a broad floodplain at the coast an outlet to the sea is maintained through a sandy barrier across an underlying rock outcrop seawater intrusion through the outlet is prevented by the elevation of the rock outcrop and hence reversing currents and tidal salinity variations typical of estuaries are not developed in the lower reaches of the river sedimentary deposits and processes in the back barrier area are predominantly fluvial and the system is best classified as a river dominated estuary a lack of coastal progradation prevents its definition as a delta the greatest geomorphological impacts in the channel and barrier are caused by extreme river floods sedimentary processes revealed by aerial photography and field measurements in the mvoti show changes in response to discharge variation within the normal range of discharge variation the channel varies in dimension and morphology but no major long term buildup of sediment is evident in the floodplain or channel minor floods deposit muddy overbank deposits during such floods the channel gradient is increased by barrier breaching and channel shortening but wave dominated barrier processes act to close the breach rapidly superimposed on these short term changes is a cyclic pattern driven by major floods which cause lateral channel erosion and overbank deposition post flood recovery involves progressive channel confinement and stabilisation as flow reverts to a single or braided channel and the floodplain is re vegetated after major floods the channel assumes a position in the centre of the floodplain but subsequently it shows a tendency to migrate to the edge of the floodplain and elongate its channel current incorrect perceptions of the river mouth area as an estuary degraded by siltation are based on a comparison of present morphology with typical wave dominated estuaries and lack of recognition of the mvoti as one of a suite of river dominated estuaries the study highlights the need for a suite of universally applicable models not only for estuaries but for transitional fluvio marine environments in general

channel erosion along the carmel river monterey county california historic maps photographs and channel cross sections show that the channel of the carmel river underwent massive bank erosion channel migration and aggradation in a major flood in 1911 then narrowed and incised by 1939 the channel was stable until 1978 and 1980 when bank erosion affected some reaches but not others the narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation these events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event the 1911 flood or in a low magnitude event by reducing the resistance to erosion bank devegetation the carmel river is a potentially unstable system its discharge and slope characteristics place it near the threshold between meandering and braided on the lower carmel the presence of bank vegetation can make the difference between a narrow stable meandering channel and a wide shifting channel with braided reaches

river channel adjustment to meander cutoffs on the river bollin and river dane northwest england morphological adjustment of a channel after cutoff should be expected but rarely has the mode and timescale of adjustment in natural channels been measured four natural cutoffs which have occurred since 1980 on two rivers in northwest england have been monitored from pre cutoff stage two of the cutoffs were neck cutoffs of large loops two were chute cutoffs in which significant bend curvature remained all the cutoffs were the terminal result of progressive bank erosion and or scour of the floodplain rather than overflow and all the cutoffs took place in peak flow events though two of these were of relatively low magnitude high frequency rapid widening and sedimentation took place within the straight channels produced by neck cutoffs immediately after breaching adjustment was mainly by formation of multiple riffles and bars producing a variable morphology in the first 2 4 years subsequently the morphology became more regular and in one case had stabilised within about eight years progressive steepening and acceleration of bank erosion appears to have been propagated upstream in one case but in the other cases erosion was very localised rates of vertical accretion at the entrances to the old channel were much higher than most quoted in the literature rates of change in all morphological sedimentary and biotic components exhibit an exponential decline with time but with slightly differing timescales on these active gravel bed streams major adjustment within the new channels may be completed within 6 12 years though lakes persist in the abandoned channels for much longer

application of image cross correlation to the measurement of glacier velocity using satellite image data abstract image to image cross correlation software is applied to pairs of digital satellite images to map the velocity field of moving ice this technique uses small scale glacial surface features such as crevasse scars and snow dunes as markers on the surface of the moving ice displacements of the surface features are mapped by selecting small image areas centered on distinct features or by dividing a large area of densely featured glacial surface into a grid of areas and searching a subsequent image for matching areas using a cross correlation algorithm interpolation of the peak correlation values allows the displacements to be measured to subpixel accuracy resulting in very precise velocity measurements cross correlation is also applied to provide image coregistration in areas devoid of bedrock exposures in such areas subtle large scale topographic undulations in the ice surface related to underlying bedrock structure may be correlated by using large image areas and low pass filtered images both types of applications are demonstrated using ice stream d and ice stream e in west antarctica as test areas a high resolution map of the velocity field of the central portion of ice stream e generated by the displacement measuring technique is presented the use of cross correlation software is a significant improvement over previous manually based photogrammetric methods for velocity measurement and is far more cost effective than in situ methods in remote polar areas

correction to chronological evolution of the channel functional units in association with palaeo hydrogeomorphological environment in the ancient delta fan of subarnarekha basin india the original article has been published inadvertently with some errors in figures and their caption figs 1 2 3 and errors only in captions of figures figs 4 5 7 8 9 also errors in tables and their caption tables 1 5 6 7 and errors only in captions of tables tables 2 3

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

floodplain river ecosystems lateral connections and the implications of human interference abstract floodplains are ecotones that form a transition between aquatic and terrestrial environments these important ecosystems can be described as dynamic spatial mosaics in which water plays an important role in connecting various patches on the floodplain surface hydrological connections facilitate the exchange of carbon and nutrients between the river channel and the floodplain and therefore influence the productivity of the entire river system this paper examines the influence of hydrological connections on the potential exchange of dissolved organic carbon between a large australian floodplain to a river channel and the effects of land and water developments on these exchanges the paper proposes that an understanding of floodplain ecosystems requires an interdisciplinary approach a recognition of the importance of the three disciplines hydrology geomorphology and ecology large scale water resources and floodplain development has significantly altered the spatial and temporal patterns of hydrological characteristics in the lower balonne floodplain australia the magnitude frequency and duration of flooding events have all been reduced the construction of levees and water storages has also reduced the reactive floodplain surface area the presented data show the impacts of these changes on the potential supply of dissolved organic carbon from the floodplain surface during periods of inundation annual reductions of up to 1293 tonnes of dissolved organic carbon supply were noted and reductions were especially significant for floods with an average recurrence interval of 2 years or less some small flood events no longer facilitate the potential supply of dissolved organic carbon from the floodplain to the river channel because of water resources and floodplain developments

a method of repeat photoclinometry for detecting kilometer scale ice sheet surface evolution small scale glaciological processes can drive large scale ice sheet behavior but remain underreported due to a paucity of surface elevation measurements in remote polar regions satellite images provide a relatively long record of spatially dense surface observations which allow us to investigate changes in ice sheet topography on the spatial scales of 1 10 km inferring surface topography from satellite images is an established technique but in previous efforts strict requirements for illumination conditions and image quality have led to a great quantity of discarded data relaxing quality requirements and fitting linear trends to the time series of image derived surface topography allow inclusion of more total signal and enable blending data from multiple platforms as a proof of concept we combine 121 moderate resolution imaging spectroradiometer images to develop a 250 m resolution map of surface elevation change at totten glacier antarctica achieving a 1 sigma uncertainty of 0 22 textrm m textrm a 1 for a 15 year period our method of repeat photoclinometry agrees with repeat laser altimetry while revealing clear patterns of surface elevation change associated with ice advection channelized ice shelf basal melt subglacial lake activity and possible grounding line migration

geospatial technologies and digital geomorphological mapping concepts issues and research geomorphological mapping plays an essential role in understanding earth surface processes geochronology natural resources natural hazards and landscape evolution it involves the partitioning of the terrain into conceptual spatial entities based upon criteria that include morphology form genetics process composition and structure chronology environmental system associations land cover soils ecology as well as spatial topological relationships of surface features landforms historically the power of human visualization was primarily relied upon for analysis introducing subjectivity and biases with respect to selection of criteria for terrain segmentation and placement of boundaries this paper reviews new spatio temporal data and geocomputational approaches that now permit earth scientists to go far beyond traditional mapping permitting quantitative characterization of landscape morphology and the integration of varied landscape thematic information numerous conceptual theoretical and information technology issues are at the heart of digital geomorphological mapping dgm and scientific progress has not kept pace with new and rapidly evolving geospatial technologies consequently new capabilities exist but numerous issues have not been adequately addressed therefore this paper discusses conceptual foundations and illustrates how geomorphometry and mapping approaches can be used to produce geomorphological information related to the land surface and landforms process rates process form relationships and geomorphic systems

buried late holocene luvisols of the oka and moskva river floodplains and their anthropogenic evolution according to soil and pollen data abstract according to radiocarbon dating the ages of the four major soils developed on the floodplains are as follows 1 modern 2 2500 800 cal bp 3 4700 3000 cal bp and 4 7000 5300 cal bp the late holocene soil 2 is usually defined as albeluvisol or luvisol it has a developed profile with clearly expressed argic horizons bt it is markedly different from the underdeveloped soil 1 fluvisol and soil 4 phaeozem or chernozem that have a dark humus mollic chernic horizon soil 2 has a typical light gray color of the humus horizon and is characterized by the accumulation of clay fraction in the bt horizon as compared with the overlying e horizon micromorphological data indicate that the bt horizon has well developed clay films on pore walls and on the surface of aggregates cultural layers belonging to the iron age or early middle ages are sometimes located in soil 2 pollen analysis of this soil attests to its development under forest vegetation which corresponds to the genesis of luvisols and albeluvisols however in some places near ancient settlements characteristic features of the e and bt horizons become weakly pronounced and a well developed dark humus umbric horizon is diagnosed in the soil profiles these soils are marked by the abundance of pollen of herbs including cultivated cereals and weeds this is evidently related to the anthropogenic activity and the propagation of secondary grassy and ruderal vegetation that replaced forests on the floodplains floodplain environments are considered unsuitable for the development of luvisols and albeluvisols within a larger part of the holocene these soils appeared on the floodplains in the late holocene in relation to the propagation of forest vegetation and extremely low floods within a relatively long time

processes facies and architecture of fluvial distributary system deposits abstract there is evidence from the stratigraphic record of examples of fluvial deposits that were the products of deposition from river systems which had decreasing discharge down flow and transitions from proximal channelised to distal unconfined flow these deposits form fan shaped bodies several tens of kilometres in radius and their stratigraphic architecture is aggradational with no evidence of deep incision driven by base level fall the fluvial systems that generated these deposits formed under conditions for which there is no complete analogue today an endorheic basin with a relatively arid climate adjacent to an uplifted area with higher precipitation a conceptual model for fluvial systems of this type has therefore been built on the basis of outcrop examples and a consideration of the controls on sedimentation proximal areas are characterised by amalgamated coarse pebbly and sandy channel deposits with little preservation of overbank facies channel dimensions are generally smaller in the medial areas but sizes are variable deposits are of braided meandering and simple channels which show varying degrees of lateral migration the channel fills may be mud or sand with overbank flow processes playing an important role in filling channels abandoned on the floodplain after avulsion the proportion of overbank deposits increases distally with sheets of sand deposited as lateral and terminal splays by unconfined flow interconnection of sandstone bodies is poor in the distal areas because channel fill bodies are sparse small and are not deeply incised the radial pattern of the sediment body forms by the repeated avulsion of channels active channels build up lobes on the alluvial plain and rivers switch position to follow courses on lower lying areas the term fluvial distributary system is here used to describe a river system which has a downstream decrease in discharge and has a distal zone which is characterised either by terminal splays on to a dry alluvial plain or a lake delta during periods of lake highstand

the formation of an anabranching planform in a sandy floodplain by increased flows and sediment load anabranching rivers evolve in various geomorphic settings and various river planforms are present within these multi channel systems in some cases anabranches develop meandering patterns such river courses existed in europe prior to intensive hydro technical works carried out during the last 250 years proglacial stream valleys inherited from the last glaciation provided a suitable environment for the development of anabranching rivers wide valleys floors with abundant sand deposits the main objective of the present study is to reconstruct the formation of an anabranching river planform characterized by meandering anabranches based on geophysical and geological data obtained from field research and a reconstruction of palaeodischarges a model of the evolution of an anabranching river formed in a sandy floodplain is proposed it is demonstrated that such a river system evolves from a meandering to an anabranching planform in periods of high flows that contribute to the formation of crevasse splays the splay channels evolve then into new meandering flow paths that form second order crevasses avulsions and cutoffs the efficiency of the flow is maintained by the formation of cutoffs and avulsions preventing the development of high sinuosity channels and redirecting the flow to newly formed channels during maximum flow events a comparison with other anabranching systems revealed that increased discharges and sediment loads are capable of forming anabranching planforms both in dryland and temperate climate zones the sediment type available for transport often inherited from older sedimentary environments is an important variable determining whether the channel planform is anabranching with actively migrating channels or anastomosing with stable straight or sinuous branches

high resolution interpretative geomorphological mapping of river valley environments using airborne lidar data the availability of airborne lidar data provides a new opportunity to overcome some of the problems associated with traditional field based geomorphological mapping such as restrictions on access and constraints of time or cost the combination of airborne lidar data and gis technology facilitates the rapid production of geomorphological maps of floodplain environments however unfiltered lidar data which include vegetation and buildings are currently more suitable for geomorphological mapping than data that have been filtered to remove these features classification of lidar data according to elevation in a gis enables the user to identify and delineate geomorphological features in a manner similar to field mapping but it is necessary to use a range of classification intervals in order to map the various types of feature that occur within a single reach comparison of a lidar derived geomorphological map with an independently produced field geomorphological map showed a high degree of similarity between the results of the two methods although ground truthing is essential in cases where a high degree of accuracy is required ground truthing of a lidar derived geomorphological map showed that around 80 of features mapped using both methods were identified from the lidar data suggesting that the method is suitable for applications such as production of base maps for use in field mapping and selection of sites for detailed investigation copyright 2007 john wiley sons ltd

a millennium of variable ice flow recorded by the ross ice shelf antarctica an enhanced composite advanced very high resolution radiometer avhrr image is used to map flow stripes and rifts across the ross ice shelf antarctica the patterns of these flow related features reveal a history of discharge variations from the ice streams feeding the eastern part of the shelf the most profound variations are visible in the track of rifts downstream of crary ice rise flow stripe bends to the west of this ice rise and adjacent to steershead ice rise and changes in the northern margin of ice stream b the track of rifts downstream of crary ice rise indicates that the ice rise has existed for at least 700 years the character of this track changes about 350 km downstream indicating a rearrangement of flow patterns about 550 years ago the large bulge in the flow stripes to the west of crary ice rise is shown in detail with bent flow stripes extending for several hundred kilometers along flow this feature formed from the south possibly due to a change in the discharge of ice stream a the avhrr image documents a complex history associated with the shutdown of ice stream c with changes in the margins of ice stream c and the northern margin of ice stream b and the grounding of steershead ice rise with an associated bending and truncation of flow stripes landsat imagery shows a region that appears to be actively extending just downstream of the ice rise as the shelf continues to respond to recent changes in ice stream discharge we present a four stage flow history which accounts for the features preserved in the ice shelf

including strain data in balanced cross sections abstract almost all published balanced cross sections include cleaved and or strained rocks and may therefore violate the requirement that bed lengths and formation areas are preserved between undeformed and deformed states knowledge of distortions presence and type of cleavage and overprinting relations in poly deformed segments are necessary to define area changes related to volume loss strike elongation and poly deformation work in the southern and central appalachians has shown variation in structural complexity and changing deformation styles both along and across the thrust belt this necessitates separate treatment of individual sheets during balancing regions of little or no interstratal slip pinning points should be chosen for each thrust sheet and each fold strain in the sheet in external sheets where deformation intensity increases towards thrusts pin points should be back limb inflection points in intermediate and internal sheets where cleavage is approximately coeval with folding pin points should be at fold hinges where cleavage and strain are heterogeneously developed throughout a stratigraphic sequence a line length balance using massive relatively uncleaved beds e g knox group southern appalachians can be used as a basis for restoring the section unstraining of deformed layers given strain data and cleavage trajectories for individual thrust sheets provides line lengths and formation areas which can be fitted to the key bed of the undeformed section cleavages which partially or fully postdate folding indicate continued shortening in the thrust wedge and modify earlier pinning points in upper sheets these cleavages and poly deformed segments are difficult to restore as strain data are generally scarce in the metamorphosed internal thrust sheets

the dynamics of ice sheet outlets a comparison of data from aircraft altimetry landsat imagery and radia echo sounding has shown characteristic surface topographies associated with sheet and stream flow the transition between the two is abrupt and occurs at a step in the subglacial topography this marks the onset of basal sliding and high velocities caused by subglacial water it results in crevassed amphitheatre like basins round the head of outlet glaciers it is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase this abrupt transition appears to be topographically controlled since basal temperatures are at the pressure melting point well inland of the change in regime the marie byrd land ice streams exhibit qualitative differences from other ice sheet outlets however the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice the repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion this is concentrated towards the heads of outlet glaciers up stream of the region where significant basal decoupling occurs this may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls

human topographic signatures and derived geomorphic processes across landscapes abstract the earth s surface morphology in an abiotic context is a consequence of major forcings such as tectonic uplift erosion sediment transport and climate recently however it has become essential for the geomorphological community to also take into account biota as a geomorphological agent that has a role in shaping the landscape even if at a different scale and magnitude from that of geology although the modern literature is flourishing on the impacts of vegetation on geomorphic processes the study of anthropogenic pressures on geomorphology is still in its early stages topography emerges as a result of natural driving forces but some human activities such as mining agricultural practices and the construction of road networks directly or indirectly move large quantities of soil which leave clear topographic signatures embedded on the earth s morphology these signatures can cause drastic changes to the geomorphological organization of the landscape with direct consequences on earth surface processes this review provides an overview of the recent literature on the role of humans as a geological agent in shaping the morphology of the landscape we explore different contexts that are significantly characterized by anthropogenic topographic signatures landscapes affected by mining activities road networks and agricultural practices we underline the main characteristics of those landscapes and the implications of human impacts on earth surface processes the final section considers future challenges wherein we explore recent novelties and trials in the concept of anthropogenic geomorphology herein we focus on the role of high resolution topographic and remote sensing technologies the reconstruction or identification of artificial or anthropogenic topographies provides a mechanism for quantifying anthropogenic changes to landscape systems this study may allow an improved understanding and targeted mitigation of the processes driving geomorphic changes during anthropogenic development and help guide future research directions for development based watershed studies human society is deeply affecting the environment with consequences on the landscape therefore establishing improved management measures that consider the earth s rapidly changing systems is fundamental

digital mapping in polar regions from landsat photographic products a case study landsat photographic products on the space oblique mercator som projection are used to construct a map of nordaustlandet svalbard of known accuracy the map includes ice divides accurately enlarged landsat images were digitized combined digitizer and operator errors were 64 m at the enlargement scale fifteen ground control points fixed the two scenes rms errors in control point identification were 123 m geographical coordinates were extracted by i converting digitizer coordinates to som cartesian coordinates and 2 transforming these coordinates to latitude and longitude this map production method is applicable to any imagery of known projection the digitally stored map may be plotted on a variety of map projections and scales two problems in image interpretation were i shadows obscuring detail on nne facing coasts and 2 summer snow cover obscuring parts of the terrestrial ice cap margins the map is similar to an east coast map produced from landsat computer compatible tapes differences between the landsat map and a 1 50 000 scale

subdividing the holocene series epoch formalization of stages ages and subseries subepochs and designation of gssps and auxiliary stratotypes the holocene which currently spans 11 700 years is the shortest series epoch within the geological time scale gts yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution on 14 june 2018 the executive committee of the international union of geological sciences formally ratified a proposal to subdivide the holocene into three stages ages along with their equivalent subseries subepochs each anchored by a global boundary stratotype section and point gssp the new stages are the greenlandian lower early holocene subseries subepoch with its gssp in the greenland ngrip2 ice core and dated at 11 700 a b2k before 2000 ce the northgrippian middle holocene subseries subepoch with its gssp in the greenland ngrip1 ice core and dated at 8236 a b2k and the meghalayan upper late holocene subseries subepoch with its gssp in a speleothem from mawmluh cave north eastern india with a date of 4250 a b2k we explain the nomenclature of the new divisions describe the procedures involved in the ratification process designate auxiliary stratotypes to support the gssps and consider the implications of the subdivision for defining the anthropocene as a new unit within the gts less

the surface topography of large ice masses from landsat imagery les images de landsat mss de l antarctique et du svalbard ont ete comparees a des mesures altimetriques effectuees a partir d avion