spatial variation in the power of mountain streams in the sangre de cristo mountains new mexico the principle indicator of river energy expenditure stream power has a significant influence on many forms and process attributes of the fluvial system yet few basin wide analyses of stream power variations have ever been conducted recent studies hypothesize a peak in the mean stream power distribution in small 10 km2 to intermediate 100 km2 sized basins to test hypothetical stream power profiles in a high mountain setting 129 cross sections of stream networks within the costilla basin of northern new mexico and southern colorado were measured for channel form local sediment conditions and basin characteristics geomorphic and hydrologic analysis of these river sites throughout the costilla basin yielded evidence of abundant local control over fluvial processes and forms within the basin the spatial deviations of stream power from the hypothetical patterns derived from hydraulic geometry in some cases 200 deviation match areas of specific geologic and hydrogeologic control as an alternative to traditional hydraulic descriptions of downstream channel form a probabilistic process response model can incorporate local and basin scale variables and allow more realistic feedback mechanisms than in traditional regime theory the probabilistic nature of this type of model also allows prediction of multiple modes of channel adjustment an ever present challenge to extremal and physically based simulations

a multi scale gis and hydrodynamic modelling approach to fish passage assessment clarence and shoalhaven rivers nsw australia natural barriers such as waterfalls cascades rapids and riffles limit the dispersal and in stream range of migratory fish yet little is known of the interplay between these gradient dependent landforms their hydraulic characteristics and flow rates that facilitate fish passage the resurgence of dam construction in numerous river basins world wide provides impetus to the development of robust techniques for assessment of the effects of downstream flow regime changes on natural fish passage barriers and associated consequences as to the length of rivers available to migratory species this paper outlines a multi scale technique for quantifying the relative magnitude of natural fish passage barriers in river systems and flow rates that facilitate passage by fish first a gis based approach is used to quantify channel gradients for the length of river or reach under investigation from a high resolution dem setting the magnitude of identified passage barriers in a longer context tens to hundreds of km second lidar topographic and bathymetric survey based hydrodynamic modelling is used to assess flow rates that can be regarded as facilitating passage across specific barriers identified by the river to reach scale gradient analysis examples of multi scale approaches to fish passage assessment for flood flow and low flow passage issues are provided from the clarence and shoalhaven rivers nsw australia in these river systems passive acoustic telemetry data on actual movements and migrations by australian bass macquaria novemaculeata provide a means of validating modelled assessments of flow rates associated with successful fish passage across natural barriers analysis of actual fish movements across passage barriers in these river systems indicates that two dimensional hydraulic modelling can usefully quantify flow rates associated with the facilitation of fish passage across natural barriers by a majority of individual fishes for use in management decisions regarding environmental or instream flows

glacially conditioned specific stream powers in low relief river catchments of the southern laurentian great lakes abstract fluvial systems of the southern laurentian great lakes region are carved into a complex glacial landscape shaped by continental ice and meltwater of the late pleistocene these glacially conditioned river catchments are typically small with drainage areas 4 km 2 a 10 m digital elevation model dem is used to map the spatial distribution of stream gradient for 22 major river catchments of peninsular southern ontario which drain to base levels in the lower great lakes huron st clair erie and ontario raw data from the dem show stream gradients that exhibit multiscale variance from real and from artifact sources based on a vertical slice and multiple pass moving window averaging approach slope data are generalised to the river reach scale 1 2 km as a representative spatial scale for fluvial processes operating over holocene timescales models of specific stream power are then compared with glacial landform and surface geology mapping inherited glacial signatures in river slope appear as deviations in a stream length gradient index sl k index where river reaches are frequently oversteepened or understeepened based on a slope area analysis and complementary to theories of channel pattern discrimination constant stream power curves with power law exponent of 0 4 provide a first order approach to stratify river reaches in terms of glacial conditioning and expected planform morphologies however multiple channel planform types are rare and localised in southern ontario indicating that oversteepened reaches with high stream powers may often be moderated by 1 sediment calibre with cobble beds from inherited glacial sediments and or 2 relative bank strength with limited channel widening particularly in gravel and sand bed channels further discrimination of glacially conditioned fluvial process domains will ultimately require consideration of alluvial floodplain characteristics in addition to general observations of river morphology and channel pattern

geomorphic response to flow regulation and channel and floodplain alteration in the gravel bedded cedar river washington usa article i nfo decadal to annual scale analyses of changes to the fluvial form and processes of the cedar river in washington state usa reveal the effects of flow regulation bank stabilization and log jam removal on a gravel bedded river in a temperate climate during the twentieth century revetments were built along 60 of the lower cedar river s length and the 2 year return period flow decreased by 47 following flow regulation beginning in 1914 the formerly wide anastomosing channel narrowed by over 50 from an average of 47 m in 1936 to 23 m in1989and became progressively single threaded subsequent high flows and localized revetment remov al contributed to an increase in mean channel width to about 34 m by 2011 channel migration rates between 1936 and 2011 were up to 8 m year in reaches not confined by revetments or valley walls and less than analysis uncertainty throughout most of the cedar river s length where bank armoring restricted channel movement in unconfined reaches where large wood and sediment can be recruited contemporary high flows though smaller in magnitude than preregulation high flows form and maintain geomorphic features such as pools gravel bars and side channels reaches confined by revetments remain mostly unmodified in the regulated flow regime while high flows are important for maintaining channel dynamics in the cedar river their effectiveness is currently reduced by revetments limited sediment supply the lack of large wood available for recruitment to the channel and decreased magnitude since flow regulation published by elsevier b v

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

controls on morphological variability and role of stream power distribution pattern yamuna river western india abstract understanding the controls on the morphological variability of river systems constitutes one of the fundamental questions in geomorphic investigation channel morphology is an important indicator of river processes and is of significance for mapping the hydrology ecologic connectivity in a river system and for predicting the future trajectory of river health in response to external forcings this paper documents the spatial morphological variability and its natural and anthropogenic controls for the yamuna river a major tributary of the ganga river india the yamuna river runs through a major urban centre i e delhi national capital region the yamuna river was divided into eight geomorphically distinct reaches on the basis of the assemblages of geomorphic units and the association of landscape valley and floodplain settings the morphological variability was analysed through stream power distribution and sediment load data at various stations stream power distribution of the yamuna river basin is characterised by a non linear pattern that was used to distinguish a high energy natural upstream reaches b anthropogenically altered low energy middle stream reaches and c rejuvenated downstream reaches again with higher stream power the relationship between stream power and channel morphology in these reaches was integrated with sediment load data to define the maximum flow efficiency mfe as the threshold for geomorphic transition this analysis supports the continuity of river processes and the significance of a holistic basin scale approach rather than isolated local scale analysis in river studies

sea level and turbidity controls on mangrove soil surface elevation change increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees however tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level enabling intertidal habitats to maintain their position relative to mean sea level but there are few tests of these predictions in mangrove forests here we used variation in sea level and the availability of sediments caused by seasonal and inter annual variation in the intensity of la nina el nino to assess the effects of increasing sea level on surface elevation gains and contributing processes accretion on the surface subsidence and root growth in mangrove forests we found that soil surface elevation increased with mean sea level which varied over 250 mm during the study and with turbidity at sites where fine sediment in the water column is abundant in contrast where sediments were sandy rates of surface elevation gain were high but not significantly related to variation in turbidity and were likely to be influenced by other factors that deliver sand to the mangrove forest root growth was not linked to soil surface elevation gains although it was associated with reduced shallow subsidence and therefore may contribute to the capacity of mangroves to keep pace with sea level rise our results indicate both surface sedimentation and subsurface root growth processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine but not coarse sediments are abundant

morphotectonic segmentation and spatial variability of neotectonic activity along the narmada son fault western india remote sensing and gis analysis abstract morphotectonic analysis of landscape using remote sensing and gis is an effective way of deducing the pattern and spatial variation of neotectonic activity along poorly investigated active faults in this paper we evaluate the neotectonic activity along a part of the seismically active but poorly understood narmada son fault nsf a more than 1000 km long ene wsw trending fault transecting through the central part of the indian plate the nsf in the study area is geomorphologically expressed as an ene wsw trending line of north facing scarps that delimit the rugged mountainous topography of the uplands to the south and the alluvial basin to the north which prominently slope away from the scarps the scarps are developed in the south dipping basaltic flows belonging to the deccan trap formation of the late cretaceous eocene and continue westward into tertiary rocks and further as a paleobank of the narmada river field studies have revealed that the nsf in the study area is divisible into four morphotectonic segments i to iv which is attributed to the tilakwada karjan madhumati and rajpardi faults cutting across the nsf we characterize the neotectonic activity of the segments through dem analysis using geomorphic indices which include the mountain front sinuosity hypsometric curves hypsometric integral asymmetry factor stream length gradient index and channel sinuosity interpretations of morphometric data are well supported by field data both the entire length of the nsf and the cross faults are found to be neotectonically active we demonstrate that segment ii has undergone the highest intensity of neotectonic activity followed by segments iii i and iv this is corroborated by the highest elevation of scarps and the alluvial deposits the deepest incision 40 m depth and steep northward slope of the alluvial plain in segment ii we infer that the nsf is characterized by differential uplift in recent past which agrees with the high angle reverse faulting with oblique slip movements along the cross faults

review of methods to measure short time scale sediment accumulation this review paper aims at providing a list of methods available to measure sediment accumulation in underwater or intertidal environments over short term periods in the order of hours to months at the most both in situ and under laboratory conditions methods are classified based on two criteria a whether they measure sediment accumulation or sediment elevation change and b whether they allow continuous or discontinuous measurements the main characteristics of each method are outlined along with its vertical resolution its accuracy its temporal resolution its spatial coverage capacity and an indication of its relative cost typical examples of applications are also provided the purpose of this review is to be a starting point for readers who need an overview of existing techniques that measure short term sediment accumulation in order to guide and facilitate for instance the selection of an appropriate technique for a given application with set requirements

selecting geomorphic variables for automatic river segmentation trade offs between information gained and effort required abstract identifying river segments with apparently distinct geomorphic characteristics but relatively homogeneous internal features may be critically helpful in designing network analysis for characterization environmental assessment and river management automatic segmentation procedures using geographic tools and statistical methods provide objective and replicable results in particular multivariate procedures may be appropriated for different purposes such as coping with the multiple dimensionality of river systems although there is an increasing number of studies dealing with segmentation using different sets of morphological variables the influence that the selected variables have on segmentation results is rarely assessed in this context we defined five combinations of frequently used geomorphic variables i e channel slope active channel width valley bottom width channel confinement and specific stream power and compared the obtained segmentation results we study the upper esla river network covering a total length of 294 km with the largest two rivers regulated by large dams variables were measured at successive river sections 200 m apart five segmentation results were obtained in which we compared the number and characteristics of the segments and the internal variability and the suitability of predicting river dynamics i e occurrence of bare and vegetated gravel bars the number of segments per kilometer of river and their average length were different among segmentations but varied much more across rivers than across segmentations in general segmentations including channel slope and active channel width performed better in predicting the occurrence of bare gravel bars than segmentations based on stream power or valley confinement when splitting the initial data set into regulated and non regulated segments differences in predicting the occurrence of gravel bars were found with better results in the case of non regulated rivers channel slope and active channel width showed a reduced explanatory power for the regulated reaches finally we conclude that primary geomorphic variables such as channel slope and active channel width were more efficient than secondary variables such as stream power which may encompass more information but needed additional data and the use of empirical models with greater effort and much uncertainty in the case of regulated rivers automatic segmentation including the affected variables e g active channel width may help in detecting differences in geomorphic sensitivity to river adjustments across the resulting segments downstream from the dams our results offer valuable insights into the selection of geomorphic variables for river segmentation analysis in which trade offs between the information gained and the effort required must be considered according to the respective research targets

mapping spatial patterns of stream power and channel change along a gravel bed river in northern yellowstone abstract stream power represents the rate of energy expenditure along a river and can be calculated using topographic data acquired via remote sensing or field surveys this study sought to quantitatively relate temporal changes in the form of soda butte creek a gravel bed river in northeastern yellowstone national park to stream power gradients along an 8 km reach aerial photographs from 1994 to 2012 and ground based surveys were used to develop a locational probability map and morphologic sediment budget to assess lateral channel mobility and changes in net sediment flux a drainage area to discharge relationship and dem developed from lidar data were used to obtain the discharge and slope values needed to calculate stream power local and lagged relationships between mean stream power gradient at median peak discharge and volumes of erosion deposition and net sediment flux were quantified via spatial cross correlation analyses similarly autocorrelations of locational probabilities and sediment fluxes were used to examine spatial patterns of sediment sources and sinks energy expended above critical stream power was calculated for each time period to relate the magnitude and duration of peak flows to the total volumetric change in each time increment collectively we refer to these methods as the stream power gradient spg framework the results of this study were compromised by methodological limitations of the spg framework and revealed some complications likely to arise when applying this framework to small wandering gravel bed rivers correlations between stream power gradients and sediment flux were generally weak highlighting the inability of relatively simple statistical approaches to link sub budget cell scale sediment dynamics to larger scale driving forces such as stream power gradients improving the moderate spatial resolution techniques used in this study and acquiring very high resolution data from recently developed methods in fluvial remote sensing could help improve understanding of the spatial organization of stream power sediment transport and channel change in dynamic natural rivers

high precision measurements of wetland sediment elevation i recent improvements to the sedimentation erosion table abstract the sedimentation erosion table set developed by boumans and day 1993 is herein renamed the surface elevation table set to better reflect the conceptual view of the processes being measured the set was designed for making high resolution measurements of small scale changes in elevation of loose unconsolidated sediments in shallow water and mudflat habitats the set has undergone three major improvements to increase precision and so that it can be used to measure sediment elevation in vegetated wetlands as well as shallow water habitats the remote release sliding plate mechanism has been replaced with a single plate collars first 2 5 cm then 7 5 cm in length have been attached to the plate to reduce play in the placement of the measuring pins and the brass measuring pins have been replaced with fiberglass pins to reduce bending and consequent loss of precision under ideal laboratory conditions the 95 confidence limit for individual pin measurements averaged about 1 4 mm range 0 7 to 1 9 mm these modifications have resulted in a reduction of error by about 50

where do floodplains begin the role of total stream power and longitudinal profile form on floodplain initiation processes understanding downstream transitions in river character and behavior is a basic concept in fluvial geomorphology downstream patterns of depositional processes can be differentiated between channel and floodplain components in this study a generic set of methods is used to analyze floodplain initiation and continuity in relation to downstream changes in total stream power slope and discharge and longitudinal profile form for river courses in the upper hunter catchment australia absolute values of these controlling factors are shown to be poor indicators of threshold conditions at which floodplains begin to form along river courses catchment scale patterns of stream power and the form of longitudinal profiles provide better predictors of this transitional zone the total stream power plot derived along longitudinal profiles represented by a second order exponential curve has a bimodal pattern in most cases floodplains begin to form in a transition zone characterized by a trough area within the bimodal stream power distribution this bimodal stream power pattern provides a better means to identify this transition in depositional processes along longitudinal profiles than more conventional single peak stream power analyses based on first order exponential longitudinal profiles indirect controls such as basin geology and accommodation space also influence the initiation and pattern of floodplains

a definition for rapid weakening of north atlantic and eastern north pacific tropical cyclones periods of 24 h over water weakening during 1982 2013 for north atlantic nal and eastern north pacific enp tropical cyclones tcs are examined to determine a threshold for rapid weakening rw these periods are defined by consistent weakening while the tc center remained more than 50 km from land weakening thresholds of 25 30 and 35 kt represent the 87th 69th 94th 80th and 97th 89th percentile in the nal enp based on these statistics the 30 kt threshold is chosen to define rw compared to all weakening periods rw events are generally associated with greater 24 h official forecast errors and these errors tend to be overestimates in both basins these events usually occur as the tc crosses a sharp sea surface temperature gradient encounters greater vertical wind shear and entrains drier air these metrics may be useful to forecasters assessing the likelihood of rw

spatial disaggregation and aggregation procedures for characterizing fluvial features at the network scale application to the rhone basin france network scale heterogeneity in fluvial forms and processes has been analyzed for decades through the field based characterization of a reduced number of sites spatially continuous data sets are increasingly available at a national scale e g digital elevation models or aerial orthophotographs and open up new possibilities to investigate spatial structures in stream networks the paper introduces a gis methodological framework to support and automate the large scale characterization of the fluvial system based on spatial disaggregation and aggregation procedures the spatial disaggregation consists in the longitudinal discretisation of geographical objects into relatively high resolution spatial units to characterize fluvial features continuously along stream networks because rivers are heterogeneous and hierarchically organized the spatial aggregation aims to delineate statistically pattern or process based spatial units to answer questions at appropriate scales the paper develops the gis implementation of the disaggregation and aggregation procedures for characterizing stream networks in a geomorphic perspective we illustrate the approach on the rhone network focusing on the characterization of three geographical objects commonly used in classification schemes the streamline the valley bottom and the active channel the latter on a limited area the spatial aggregation is automated using the threshold test of pettitt 1979 to detect change points in univariate data series and delineate homogeneous spatial units throughout the stream network we provide three simple application examples to illustrate the potentialities of the spatial aggregation to investigate spatial heterogeneity in stream networks finally insights limitations and future challenging issues emerging from the application of the methodological framework are discussed

estimation of snow and glacial melt contribution through stable isotopes and assessment of its impact on river morphology through stream power approach in two himalayan river basins the impact of increased temperature on the third pole as the himalayas is referred to and the likely cascading impacts on the general downstream hydrology have been widely noted however the impact on fluvial geomorphology has not received specific attention change in the glacial domain in terms of melt increase will change discharge and sediment flux into fluvial system which will induce changes in fluvial processes and forms the present work attempts to study this process based glacio fluvial coupling in the two neighbouring glaciated river basins in the northwest himalaya viz the sutlej and the yamuna river basins till the mountain front a total of 194 samples of river tributary and groundwater of pre and post monsoon seasons in the two river basins were analysed for stable isotopes the trend of 18o and electrical conductivity along the mainstream gives qualitative idea on the influence of headwaters in the downstream of the catchment thereby allowing inference on melt contribution further two component mixing model using stable oxygen isotope of two seasons water samples showed that melt contributes about 41 1 66 8 and 6 6 10 6 at different points to the total river discharge in the sutlej and the tons river the glaciated major tributary of the yamuna river basins respectively for different scenarios of increase in melt stream power increase in the sutlej river basin is significant as opposed to the tons river river channel in the sutlej river basin will be significantly more impacted in comparison with the yamuna river system

temporal profiling of uplift rate along an active fault using river long profile in the kuchchh region western india abstract river long profiles are widely used as tectonic event markers incision uplift rate estimations based on the dating of river terrace or exposed scarp sediment give long term averaged uplift rate values with the limitation of not giving the intermediate phases of highs and lows on the other hand gps based estimates provide only decadal scale uplift rate estimates in our study we adopted the long profile inversion methodology to obtain a temporal profile of uplift rate history over the late pleistocene holocene time period along an active fault the kuchchh mainland fault in kuchchh region western india which has experienced several large magnitude earthquakes in recent past we also used long profiles analysis to quantify the transient response of kuchchh landscape to uplift activity along the kuchchh mainland fault steepness index and chi profiles were estimated to display the spatial variability in landscape disequilibrium integral method based chi profiles were used to obtain the optimum value of basin area exponent of the stream power incision model spim our estimates provide a mean uplift rate value of 1 1 1 4 mm yr along the kuchchh mainland fault during the late pleistocene holocene period which matches with the average uplift rate derived from other independent observations in this region further a chronology of major tectonic phases from the estimated uplift rate time series also corroborates with field based estimates of major incision events in kuchchh region we also tested the robustness and sensitivity of our uplift rate estimates to model parameters such data can be complementary to the existing sparsely both spatially and temporally distributed uplift rate database which is imperative to seismic hazard assessment

a method for measuring vertical accretion elevation and compaction of soft shallow water sediments high resolution measures of vertical accretion elevation and compaction of shallow water sediments are fundamental to understanding the processes that control elevation change and the mechanisms of progradation e g development of mudflats and intertidal wetlands in coastal systems yet measurements of elevation by traditional survey methods often are of low accuracy because of the compressible nature of the substrates nor do they provide measures of vertical accretion or sediment compaction this paper evaluates the use in shallow water systems of an approach designed to measure these variables in vegetated wetlands the approach employs simultaneous measures of elevation from temporary benchmarks using a sedimentation erosion table set and vertical accretion from marker horizons with sediment cores collected with a cryogenic coring apparatus the measures are made with a level of resolution sufficient to distinguish between the influence of surface and subsurface processes on elevation thus providing quantitative estimates of shallow subsidence the set marker horizon approach was evaluated on a developing splay created by an artificial crevasse of a distributary in the mississippi river delta the approach provided high resolution measures of vertical accretion 48 3 2 0 cm and elevation 36 7 1 6 cm over a 4 year period with the difference between the two indicating the amount of shallow subsidence in addition by laying new marker horizons in later years the approach provided rates not only of shallow subsidence 3 9 0 5 cm y 1 but also compaction of newly deposited sediments 2 1 0 6 cm y 1 and compaction of underlying sediments 1 8 0 20 cm y 1 over a two year period hence the set marker horizon approach has widespread applicability in both emergent wetland and shallow water environments for providing high resolution measures of the processes controlling elevation change

geomorphic effectiveness of a long profile shape and the role of inherent geological controls in the himalayan hinterland area of the ganga river basin india abstract long profiles of rivers provide a platform to analyse interaction between geological and geomorphic processes operating at different time scales identification of an appropriate model for river long profile becomes important in order to establish a quantitative relationship between the profile shape its geomorphic effectiveness and inherent geological characteristics this work highlights the variability in the long profile shape of the ganga river and its major tributaries its impact on stream power distribution pattern and role of the geological controls on it long profile shapes are represented by the sum of two exponential functions through the curve fitting method we have shown that coefficients of river long profile equations are governed by the geological characteristics of subbasins these equations further define the spatial distribution pattern of stream power and help to understand stream power variability in different geological terrains spatial distribution of stream power in different geological terrains successfully explains spatial variability in geomorphic processes within the himalayan hinterland area in general the stream power peaks of larger rivers lie in the higher himalaya and rivers in the eastern hinterland area are characterised by the highest magnitude of stream power

assessment of downstream trends in channel gradient total and specific stream power a gis approach geographic information systems gis analyses of digital elevation models dems coupled with catchment area based discharge estimation techniques provide a relatively simple means of modelling contiguous downstream trends in channel gradient total stream power and in riverscapes conducive to regime analysis also specific stream power for a small high relief coastal catchment in se australia good agreement was obtained between channel gradients derived from a 25 m cell size dem and field survey equivalents over distances of several kilometres indicating that channel gradients derived from dems can have a reasonable degree of absolute as well as relative accuracy over multi kilometre reach scales assessment of downstream rates of change in channel gradient and specific stream power across four river systems suggests that some of the river reaches most responsive to high magnitude floods occur in zones where these variables rapidly decrease downstream modelling of downstream trends in channel gradient total and specific stream power from catchment wide dems has potential to provide a framework with which to investigate conceptual and empirical models between channel gradient stream power and the form and dynamics of river systems

characterizing physical habitats in rivers using map derived drivers of fluvial geomorphic processes abstract new understanding of fluvial geomorphological processes has successfully informed flood mitigation strategies and rehabilitation schemes in recent years however well established geomorphological assessments are location specific and demanding in terms of resource and expertise required and their routine application for regional or national river characterization although desirable is unlikely at present this paper proposes a framework based on gis procedures empirical relationships and the self organized map for the analysis and classification of map derived drivers of fluvial morphological processes the geomorphic controls analysed are channel gradient and hydrology specific stream power river order and floodplain extent the case study is a gravel bed river in england using the self organized map we analyse patterns of these controls along the river longitudinal profile and identify clusters of similar configuration the reciprocal relationships that emerge amongst the geomorphic controls reflect the hierarchical nature of fluvial systems and are consistent with the current theoretical understanding of fluvial processes field observations from the river habitat survey are used to prove the influence of geomorphic drivers on reach scale morphological forms six clusters are identified which describe six distinctive channel types these proved to be characterized by distinctive configurations of geomorphic drivers and specific sets of physical habitat features the method successfully characterizes the notable transitions in channel character along the river course the framework is suitable for regional or national scale assessments through automatic gis and statistical procedures with moderate effort

estimating shallow subsidence in microtidal salt marshes of the southeastern united states kaye and barghoorn revisited abstract simultaneous measurements of vertical accretion and change in surface elevation relative to a shallow 3 5 m subsurface datum were made in selected coastal salt marshes of louisiana florida and north carolina to quantitatively test kaye and barghoorn s contention that vertical accretion is not a good surrogate for surface elevation change because of autocompaction of the substrate rates of subsidence of the upper 3 5 m of marsh substrate were calculated for each marsh as the difference between vertical accretion and elevation change measured with feldspar marker horizons and a sedimentation erosion table surface elevation change was significantly lower than vertical accretion at each site after 2 years indicating a significant amount of shallow subsidence had occurred ranging from 0 45 to 4 90 cm the highest rate of shallow subsidence occurred in the mississippi delta results confirm kaye and barghoorn s contention that vertical accretion is not generally a good surrogate for elevation change because of processes occurring in the upper few meters of the substrate including not only compaction but also apparently shrink swell from water storage and or plant production decomposition at some sites indeed surface elevation change was completely decoupled from vertical accretion at the florida site the assumption of a 1 1 relationship between vertical accretion and surface elevation change is too simplistic a generalization of the complex interactions between accretionary and substrate processes consequently the potential for coastal marsh submergence should be expressed as an elevation deficit based on direct measures of surface elevation change rather than accretion deficits these findings also indicate the need for greater understanding of the influence of subsurface and small scale hydrologic processes on marsh surface elevation

antecedent controls on river character and behaviour in partly confined valley settings upper hunter catchment nsw australia abstract a partly confined river is one along which the contemporary channel abuts the valley margin along 10 90 of its length they occur along sections of longitudinal profiles that are transitional from fully bedrock confined to fully alluvial rivers at this position in the landscape there is sufficient accommodation space for discontinuous floodplain pockets to form segregation of the river s load and dissipation of flow energy result in sediments being stored outside the channel bedrock and planform controlled variants of these rivers and associated floodplains are differentiated terraces fans and piedmont zones act as secondary confining features on channel planform and floodplain formation in these valleys the influence of these antecedent features on contemporary river character and behaviour in partly confined valleys of the upper hunter catchment new south wales australia is appraised the balance of formative and reworking processes and associated capacity for geomorphic adjustment is influenced by the site specific configuration of antecedent controls at any floodplain pocket downstream patterns of these river types are analysed along all major tributaries of the upper hunter catchment to highlight the extent of antecedent control on contemporary river forms and processes in this landscape setting

biophysical controls on accretion and elevation change in caribbean mangrove ecosystems abstract habitat stability of coastal ecosystems such as marshes and mangroves depends on maintenance of soil elevations relative to sea level many such systems are characterized by limited mineral sedimentation and or rapid subsidence and are consequently dependent upon accumulation of organic matter to maintain elevations however little field information exists regarding the contribution of specific biological processes to vertical accretion and elevation change this study used biogenic mangrove systems in carbonate settings in belize bz and southwest florida fl to examine biophysical controls on elevation change rates of elevation change vertical accretion benthic mat formation and belowground root accumulation were measured in fringe basin scrub and dwarf forest types plus a restored forest elevation change rates mm yr 1 measured with surface elevation tables varied widely bz dwarf 3 7 bz scrub 1 1 fl fringe 0 6 fl basin 2 1 bz fringe 4 1 and fl restored 9 9 root mass accumulation varied across sites 82 739 g m 2 yr 1 and was positively correlated with elevation change root volumetric contribution to vertical change mm yr 1 was lowest in bz dwarf 1 2 and fl fringe 2 4 intermediate in fl basin 4 1 and bz scrub 4 3 and highest in bz fringe 8 8 and fl restored 11 8 sites surface growth of turf forming algae microbial mats or accumulation of leaf litter and detritus also made significant contributions to vertical accretion turf algal mats in fringe and scrub forests accreted faster 2 7 mm yr 1 than leaf litter mats in basin forests 1 9 mm yr 1 but similarly to microbial mats in dwarf forests 2 1 mm yr 1 surface accretion of mineral material accounted for only 0 2 3 3 of total vertical change those sites with high root contributions and or rapid growth of living mats exhibited an elevation surplus 2 to 8 mm yr 1 whereas those with low root inputs and low or non living mat accumulation showed an elevation deficit 1 to 5 7 mm yr 1 this study indicates that biotic processes of root production and benthic mat formation are important controls on accretion and elevation change in mangrove ecosystems common to the caribbean region quantification of specific biological controls on elevation provides better insight into how sustainability of such systems might be influenced by global e g climate atmospheric co2 and local e g nutrients disturbance factors affecting organic matter accumulation in addition to relative sea level rise

downstream trends in discharge slope and stream power in a lower coastal plain river conceptual models of river estuary interaction are typically based on a notion of systematic downstream change in the intensity of fluvial processes low slopes backwater effects and effects of antecedent topography and landforms may complicate downstream tends in water and sediment flux in coastal plain rivers an analysis of the lower trinity river texas shows no consistent downstream pattern of increases or decreases in the discharge stream power or water surface slope flows may decrease downstream due to coastal backwater effects in the lowermost reaches and due to diversion of flow into valley bottom depressions during high flows in both the fluvial and fluvial estuarine transition reaches in general however stream power and slope decrease in the lower reaches consistent with earlier findings of limited fluvial sediment delivery to the coastal zone some tributaries may become distributaries at high but sub bankfull flows as backwater effects reverse flows into depressions associated with paleomeanders the paleomeanders and possibly the locations of these reversible channels are related to antecedent topography associated with aggradation degradation cycles over the past 100 ka low gradient coastal plain rivers may not function as simple conduits from land to sea further the transition from fluvial to coastal dominance may be variable along the river with the variability controlled not just by the relative magnitude of river and tidal or backwater forcing but also by valley topography controlled in part by antecedent landforms

spatial analysis of stream power using gis slk anomaly maps the stream length gradient index sl shows the variation in stream power along river reaches this index is very sensitive to changes in channel slope thus allowing the evaluation of recent tectonic activity and or rock resistance nevertheless the comparison of sl values from rivers of different length is biased due to the manner in which the index is formulated thus making correlations of sl anomalies along different rivers difficult therefore when undertaking a comparison of sl values of rivers of different lengths a normalization factor must be used the graded river gradient k has already been used in some studies to normalize the sl index in this work we explore the relationships between the graded river gradient k the sl index and the stream power proposing the use of a re named slk index which enables the comparison of variable length rivers as well as the drawing of slk anomaly maps we present here a gis based procedure to generate slk maps and to identify slk anomalies in order to verify the advantages of this methodology we compared an slk map of the ne border of the granada basin with both simple river profile knickpoint identification and with an sl map the results show that the slk map supplies good results with defined anomalies and suitably reflects the main tectonic and lithological features of the study area copyright 2008 john wiley sons ltd

thresholds and the spatial variability of flood power during extreme floods abstract analysis of the effects of extreme events on overall landscape form has shifted geomorphic attention away from a focus on the magnitude and frequency relationship of discharge to a focus on flood power this paper analyzes the variation in flood power both at a station and downstream in a basin of differing lithologies and discusses the geologic and geomorphic controls on flood power design floods ranging from the 2 year discharge tothe 500 year discharge are routed trough a drainage basin and channel boundary shear stress and unit stream power are calculated using hec 2 along 21 cross valley transects because of the strong lithologic control on valley width and channel slope an irregular downstream pattern of flood power emerges which reflects primarily the pattern in valley width narrow valleys correspond to a greater percent of channel conveyance during large magnitude floods and increasing rates of depth increases thus maximizing flood power in these zones the opposite occurs in anomalously wide valleys where flood power is minimized a downstream spatial pattern emerges reflecting both local and general controls for a given probability event flood power varies at least threefold within the basin with a maximum occuring in a specific downstream section holding flood power constant produces an extremely wide range in flow probabilities in order to establish a link between critical flood power magnitude and flow frequency minimum flood powers are developed from an analysis of previous work on catastrophic flooding for humid alluvial channels these minimum thresholds tentatively correspond to 100 n m2 or 300 w m2 for shear stress and unit stream power respectively discharges required to attain these critical flood powers vary from events roughly twice the 100 year flood to a maximum of roughly 18 times the discharge of the 100 year flood

tectonic constraints on watershed development on frontal ridges mohand ridge nw himalaya india abstract uplifting frontal ridges are one of the most conspicuous geomorphic features that mark the frontal parts of actively converging mountain belts growth of these ridges can lead to the simultaneous development of a drainage system that is defined by watersheds stream network and long profiles of channels in the present study shape parameters of watersheds stream network characteristics and pattern of network growth shape of long profiles and the sl index have been investigated in a part of nw himalaya to understand the relationship between endogenic tectonic processes and exogenic fluvial processes this explains the tectonic control on drainage systems in the uplifting frontal ridge this watershed analysis was carried out using a digital elevation model dem and a number of anomalies have been identified and analysed the most striking is the asymmetric development of watersheds on either side of an almost straight ridge crest watershed asymmetry along the ridge crest is characterized by larger area and less elongated watersheds in the southern flank forelimb in comparison to the northern flank backlimb drainage network and long profile analysis establishes that the larger watershed area in the forelimb is due to dominance of headward erosion and its impact on drainage network growth dominance of headward erosion is due to slope variation in response to forelimb development along a fault related fold even through headward erosion has shifted the ridge crest it is parallel with the trace of the himalayan frontal thrust hft the parallel ridge crest with reference to the hft is indicative of the tectonic control of the hft on the development of the watersheds hence a well developed linkage between tectonic processes fold development and surface processes headward erosion is responsible for variation in watershed and drainage network pattern across the ridge crest the study also investigates the role of planform ridge curvature on watershed development the effect is more pronounced on an asymmetric ridge such as the mohand ridge than on a symmetric ridge

a catchment scale model of mountain stream channel morphologies in southeast australia the position of mountain streams high in the channel network and their proportional dominance mean that channel modifications and adjustments within these systems will have important implications for downstream processes and linkages this study develops an analysis framework for examining the catchment scale distribution of reach morphologies and the relationship among reach type catchment lithology and flow competence in southeast australian mountain streams the analysis framework is applied to three catchments which have contrasting proportions of the two dominant lithologies of the region devonian granites and ordovician metasediments the model successfully delineated 68 of reach types and the resultant spatial maps allowed the effects of stream network position and catchment specific controls on channel morphology to be evaluated maximum lengths of the majority of reach morphology types were in second order streams and the maximum number of morphology types six was present in third order streams with dramatic reductions in reach type variability as the network expands the position of catchment lithology within the channel network structure was recognized as more important than the aerial extent of a particular lithology on the distribution and abundance of reach morphologies the model provides an important tool in the management of channel networks for the protection or restoration of ecological diversity by identifying river segments and tributaries with high morphological diversity

dem and gis analysis of the stream gradient index to evaluate effects of tectonics the normandy intraplate area nw france computer based geomorphometry using a dem digital elevation model allows the analysis of the three dimensional properties of landscape this methodology is particularly useful in an intraplate region like western europe where the simple visual inspection of the topography cannot resolve the evolutionary trends of landforms in these domains the morphologies of the topographic surface may be controlled mainly by climate under a low rate of tectonic deformation among the geomorphometric parameters the stream length index sl has been used to characterize fluvial systems in relation to tectonics movements this work develops an algorithm to derive and map the sl index using a dem and gis to investigate its spatial variations in a broad area the algorithm is applied to a zone of weak intraplate deformation the coastal lowlands of normandy france the obtained spatial distributions of sl point to anomalous zones with high sl values these zones are adjacent to mapped fault scarps and characterized by changes in flow direction a kruskal wallis test shows that the bedrock lithology has no impact on the sl value therefore the sl variations can be related mainly to a differential uplift due to quaternary tectonic forcing quaternary sea level fluctuations may also be responsible for high sl values in a part of the coastal lowland

comparative assessment of three approaches for deriving stream power plots along long profiles in the upper hunter river catchment new south wales australia abstract the downstream distribution of stream power is derived and analysed for 11 different streams in the upper hunter river catchment australia stream long profiles were produced in a gis environment using dem data and catchment area discharge analysis these profiles were analysed using three approaches namely long profile smoothing curve fitting and a theoretical model the methodology for deriving stream power profiles using these three approaches is discussed the long profile smoothing method provides a good approximation of the subcatchment variability in stream power trends the curve fitting method shows that higher order exponential curves provide a better fit for long profile data for the streams of the upper hunter river catchment second order exponential curves fit well with significantly less error the curve fitting method predicts a bimodal upstream and midstream distribution of stream power which is a deviation from our earlier understanding of a single midstream peak the theoretical approach provides a mathematical expression of the observed bimodal stream power distribution the bimodal distribution emphasises the erosion potential of headwater reaches the resultant stream power distribution provides a catchment scale characterisation of the distribution of available energy in any given system using these approaches the variability of stream power in headwater reaches is explained by discharge variability while variability in midstream and downstream reaches is related to high variability in channel gradient

an approach for measuring confinement and assessing the influence of valley setting on river forms and processes valley setting and confinement or lack thereof are primary controls on river character and behaviour although there are various proxies for valley confinement direct measures that quantify the nature and extent of confinement are generally lacking and or inconsistently described as such they do not lend themselves to consistent analysis over large spatial scales here we clearly define forms of confinement to aid in quantification of degrees of confinement types of margin that can induce confinement are differentiated as a valley margin valley bottom margin and or anthropogenic margin such margins sometimes overlap and share the same location and in other situations are separated giving immediate clues as to the valley setting we apply this framework to examples from australia united states and new zealand showing how this framework can be applied across the spectrum of river diversity this method can help to inform interpretations of reach scale river behaviour highlighting the role of antecedent controls on contemporary forms and processes clear definitions of confinement are shown to support catchment scale analysis of river patterns along longitudinal profiles and appraisals of the geomorphic effectiveness of floods and sediment flux in catchments e g process zone distribution lateral sediment inputs and dis connectivity copyright 2015 john wiley sons ltd

downstream variation in stream power abstract stream power has a significant influence on many form and process attributes of the fluvial system using a similar approach to that suggested by d m lawler in 1992 and 1995 a model is developed to explore how stream power might vary in the downstream direction based on the assumption that the longitudinal profile of the river has an exponential form no particular discharge is necessarily specified but near bankfull flows are regarded as significant morphologically and one such discharge is the focus here total stream power per unit channel length qs is predicted to peak at an intermediate location the position of which depends on the ratio b where b and are the downstream rates of change of discharge and slope respectively if b is a relatively conservative quantity then the form of the longitudinal profile and in particular its degree of concavity will have the major influence on the position of maximum stream power specific stream power w is even more sensitive to and is expected to peak closer to the headwaters about half way between source and the location of the stream power maximum although this will depend on how channel width w varies with distance from source the model is tested along three connected streams of different size in the catchment of the river trent taking advantage of a relationship between mean annual flood and link magnitude which enables this near bankfull discharge to be estimated at any point within the network the model is verified in so far as stream power does attain a mid basin maximum but the observed and predicted locations of the maxima do not always correspond largely because of the distinctive variation in discharge and especially slope along individual pathways for example maximum power lies far downstream along the trent because of the large increase in mid basin discharge associated with a series of large closely spaced tributaries the importance of slope is borne out by the near headwater locations for specific power maxima which tend to be further upstream than predicted along all three rivers as a result of the steepness of upper reaches the variety of geomorphic settings produces deviations from expectation which has implications for the movement and storage of material in the fluvial system

alluvial terrace preservation in the wet tropics northeast queensland australia alluvial terraces provide a record of aggradation and incision and are studied to understand river response to changes in climate tectonic activity sea level and factors internal to the river system terraces form in all climatic regions and in a range of geomorphic settings however relatively few studies have been undertaken in tectonically stable settings in the tropics the preservation of alluvial terraces in a valley is driven by lateral channel adjustments vertical incision aggradation and channel stability processes that can be further understood through examining catchment force resistance frameworks this study maps and classifies terraces using soil type surface elevation sedimentology and optically stimulated luminescence dating across five tropical catchments in northeast queensland australia this allowed for the identification of two terraces across the study catchments t1 t2 the t1 terrace was abandoned 13 9 ka with its subsequent removal occurring until 7 4 ka abandonment of the t2 terrace occurred 4 9 ka with removal occurring until 1 2 ka differences in the spatial preservation of these terraces were described using an index of terrace preservation tpi assessments of terrace remnant configuration highlighted three main types of terraces paired unpaired and disconnected indicating the importance of different processes driving preservation regional scale variability in tpi was not strongly correlated with catchment scale surrogate variables for drivers of terrace erosion and resistance however catchment specific relationships between tpi and erosion resistance variables were evident and are used here to explain the dominant processes driving preservation in these tropical settings this study provides an important insight into terrace preservation in the tectonically stable humid tropics and provides a framework for future research linking the timing of fluvial response to palaeoclimate change

a device for measuring downwearing rates on cohesive shore platforms the device described in this paper known as the traversing erosion beam is believed to be the first to be designed specifically for measuring rates of downwearing of cohesive foreshores such as clay shore platforms under high energy wave conditions it is primarily constructed of flexlink aluminium structural system components and consists of a horizontal beam with a main leg and two further support legs a sliding dolly module is moved along the beam at precise intervals using a longitudinal scale as a reference the topographic profile of the measurement surface is transferred to the dolly by a vertical sliding steel alloy rod from which the relative height differences are measured by a separate engineer s digital height gauge placed on the dolly the main leg of the device fits into a marine grade stainless steel box which is deeply embedded into the foreshore or shore platform to act a permanent datum the box is robust and can be expected to have a lifetime of at least a year and possibly even five years or more sample data are provided from a clay shore platform at warden point in the isle of sheppey kent uk which demonstrate that the teb can provide information on seasonal as well as annual rates of downwearing the device has also been tested successfully on a peat and clay foreshore at pett level in sussex and on a shore platform cut in glacial till at easington yorkshire

spatial coincidence of rapid inferred erosion with young metamorphic massifs in the himalayas a spatially distributed rate of erosion index ei based on models of bedrock river incision documents a strong spatial correspondence between areas of high erosion potential and young metamorphic massifs as well as structural highs throughout the himalayas the ei is derived from slopes and drainage areas calculated from a hydrologically cor rected digital elevation model gtopo30 combined with precipitation data iiasa to generate synthetic annual stream discharges these variables drive three generalized pro cess models to produce ei maps that while differing in detail provide an internally con sistent spatially continuous index of large scale erosion rates the large spatial variation in potential erosion rates in the himalayas suggested by the ei patterns contrasts with the uniform convergence of the indian subcontinent if these ei gradients persist through time they support the emerging view of a positive feedback between localized rapid ero sion and upward advection of lower crust

spatio temporal variability in stream power distribution in the upper kosi river basin central himalaya controls and geomorphic implications abstract river processes in a drainage basin are strongly governed by the spatio temporal variability in stream power recently various approaches have been developed to derive the spatial variability of stream power in a river basin however the temporal variability in stream power due to hydrological changes remains poorly understood an assessment of the temporal variability of stream power is critical for river studies in monsoonal regimes because significant geomorphic work is performed during this period particularly in the himalayan rivers this paper presents a novel methodology to derive the stream power distribution at a basin scale using a physically based hydrological model the soil and water assessment tool swat hydrological changes in the upper kosi also called koshi basin in the central himalaya were analysed and integrated with slope variability and channel width to obtain the basin scale distribution of total stream power and specific stream power most of the tributaries of the kosi river are characterized by a multi peak distribution of stream power stream power distribution in the basin shows no systematic downstream increase or decrease of either total stream power or specific stream power total and specific stream power peaks during the monsoon period are 100 1500 times higher compared to the non monsoon period and exceed the threshold for erosion and sediment transport processes the swat model also helped to assess controls on the stream power distribution in the basin the downstream distribution of stream power between confluence points is influenced by slope variability while major increases at confluence points are due to discharge variability geological characteristics control the spatial distribution of stream power while the annual rainfall distribution influences the seasonal variability of stream power

sediment dynamics and morphological stability of estuarine mangrove swamps in sherbro bay west africa abstract the relationship between the circulation of fine suspensions in a mangrove colonised estuarine complex short term mangrove substrate accretion and medium term mangrove swamp geomorphic evolution was studied in sherbro bay an infilling microtidal to mesotidal embayment in southern sierra leone formed behind holocene sandy beach ridge barriers the estuarine reaches of streams debouching into the bay have relatively high suspension concentrations sc of silts and clays that ranged during the survey period in 1991 from 0 8 to 40 g l 1 in association with the constitution of turbidity maxima 5 50 g l 1 at the interface between freshwater drainage and the saltwater intrusion however the surveyed mangrove swamp plots showed much lower suspension concentrations 0 09 0 6 g l 1 and low albeit minimum rates of accretion 1 1 3 mm a 1 monitored between 1980 and 1989 these low rates are attributed mainly to the short duration of tidal flooding due to a high substrate elevation within the tidal range and to the low settling potential of the very fine grained suspensions circulating over the swamps a comparison of two sets of aerial photographs 1954 1960 and 1976 showed that these swamps and their channel networks are also characterised by a remarkable medium term morphodynamic stability this stability and the low accretion suggest that the swamps and their channel networks are largely in equilibrium with the hydrology notably flooding duration and sediment loads settling out of mud from the turbidity zones contributes to higher accretion rates up to 12 mm a 1 not taking into account the effects of shallow subsidence on parts of the mudflats fronting the mangroves which are flooded for longer periods some of the mud is deposited over sandy channel bars in the main bay channel and the rest exported seaward it is tentatively suggested that an increase in the duration of tidal flooding generated by global sea level rise at the presently predicted rates could lead to higher sedimentation in the mangrove swamps thus enhancing accretion and the chances of mangrove survival

sedimentation elevation and marsh evolution in a southeastern australian estuary during changing climatic conditions mangrove and salt marsh vertical accretion and surface elevation change was measured at kooragang island within the ramsar listed lower hunter estuarine wetlands in new south wales australia using surface elevation tables and marker horizons over a ten year period we surveyed mangrove salt marsh and a zone of mangrove encroachment into salt marsh the period of analysis was dominated by el nino drought climatic conditions though included a series of east coast low pressure systems and associated storms over the central coast of nsw in june 2007 the storms may have initially caused scouring of sediments in the mangrove zone followed by significant accretion within both the mangrove and salt marsh during the six months following the storms with most of this accretion corresponding to spring tides several months after the storms these accretion events were not accompanied by an equivalent elevation change and robust elevation trends over the study period in mangrove and salt marsh indicate that the storms may have had little impact on the longer term elevation dynamics within both the mangrove and salt marsh at kooragang island elevation dynamics in these zones appear to be regulated by vertical accretion over longer time periods and modulated by hydrology at shorter temporal scales elevation declined in the mangrove encroachment zone despite continued vertical accretion and we propose that this discrepancy may be associated with expansion of tidal creeks near the zone of mangrove encroachment or loss of salt marsh vegetation this pattern of encroachment is consistent with observations from sites throughout the region and may be related to climatic perturbations el nino southern oscillation rather than directly attributed to the storms