base level buffers and buttresses a model for upstream versus downstream control on fluvial geometry and architecture within sequences abstract the effects of downstream base level control on fluvial architecture and geometry are well explored in several broadly similar sequence stratigraphic models cretaceous dakota group strata u s western interior have characteristics reflecting combined downstream and upstream base level controls that these models cannot address particularly three layers of amalgamated channel belt sandstone within this group thicken and are continuous for distances 300 km along dip that stretch the reasonable lengths for which these models are intended to apply as well architecture in up dip reaches records repeated valley scale cut and fill cycles this contrasts with equivalent strata down dip which record channel scale lateral migration with no such valley scale cycles apparent we here introduce the concept of buffers and buttresses to address these observations we assume that river longitudinal profiles are each anchored down dip to some physical barrier e g the sea strand etc that we refer to as a buttress buttress shift is considered the primary downstream control on base level profiles extrapolated up dip from the buttress over any modeled duration of buttress shift can range widely because of high frequency variability in upstream base level controls e g discharge etc all these potential profiles however are bounded above by the profile of highest possible aggradation and below by the profile of maximum possible incision these upper and lower profiles are buffers and they envelop the available fluvial preservation space thickness of the buffer zone is determined by variability in upstream controls and should increase up dip to the limit of downstream profile dominance dakota valley scale surfaces record repeated cut and fill cycles driven by up dip controls and are confined between thick stable buffers equivalent strata down dip record lateral reworking within a thinner channel scale buffer zone that was positioned by downstream controls regression exposed slopes similar to the buffer zone thus buffers were stable for long distances and durations this prompted dip extensive lateral reworking of strata into upstream valley scale and downstream channel scale sheets buffers and buttresses provide a broadly applicable model for fluvial preservation that captures upstream vs downstream base level controls on geometry and architecture the model lends general insights into dip oriented variations in fluvial architecture production of sheet vs lens geometry total preservation volumes for fluvial systems and variations in these factors related to contrasting climatic conditions and basin physiography the model can be amended to existing sequence stratigraphic approaches in order to capture dip oriented variations in sequence architecture

temporal buffering of climate driven sediment flux cycles by transient catchment response abstract the marine sedimentary record can exhibit a systematic cyclicity that is consistent with climate variability driven by milankovitch scale forcing milankovitch band cyclicity is widely interpreted in the hemipelagic and pelagic sediments of the marine realm and in terrestrial paleoenvironments has been observed in lacustrine sediments soils and river floodplain successions it remains unclear however if and how mountain catchments as a primary sediment source respond to these high frequency 6 yr climatic cycles and whether particulate sediment flux signals can be expected to be recorded in the clastic sedimentary record of adjacent basin fills recent field and theoretical studies suggest that mountain catchments respond transiently to high frequency forcing and so sediment discharge from the catchment is a non linear function of forcing variables using a catchment basin model we demonstrate that climate driven cyclicity in particulate sediment discharge is strongly damped when the period of climate variability is shorter than the response timescale of the eroding landscape given that the response timescale of landscapes is of the order of 10 6 yr and that milankovitch driven climate cyclicity is of the order of 10 4 10 5 yr it is likely that climate driven perturbation of upland catchments at these periods will be strongly damped by transient landscape behaviour our results therefore suggest that stratigraphy built by particulate fluxes from upland catchments and long term trends in the sediment delivery to the ocean may be relatively insensitive to short term climate variability

routing graded sediments in streams applications a one dimensional numerical model has been tested in simulating the movement of well graded sediments through a stream reach the model is applied to two laboratory flumes and two alluvial channel reaches found in the literature three of these examples are under steady state flow conditions and the other is under unsteady flow conditions in the unsteady flow situation the flow computations are done by using a water routing scheme based on the kinematic wave equations this scheme needs adjustment of one parameter the sediment model also needs adjustment of only one parameter which is the erodibility parameter the model predicts water and sediment discharges coming out of each reach size distributions of these transported materials size distributions of the bed material or the armor coat and changes in bed elevations comparisons of these predictions are made with the measurements available from these examples and are found to be promising

stream profile adjustment to crustal warping nonlinear results from a simple model three numerical experiments have been performed modeling response of a greatly simplified stream system to initiation of crustal tilting and domal uplift model results show signs of nonlinear behavior in varying degrees these signs include river profile adjustments that have forms quite different from the geometries of crustal movements cases of channel erosion following deposition at the same location and spatial transition points between opposing adjustments i e erosion and deposition that fail to coincide with boundaries or axes of crustal movement particular nonlinear effects wax or wane as the system adjusts to a new dynamic equilibrium with the continuing crustal movement the modeled features of stream adjustment are not in so extreme a class as the commonly discussed complex response of fluvial systems but they do serve to suggest some caution in studies that employ stream profile information as an indicator of crustal movement

fluctuations of the svalbard barents sea ice sheet during the last 150 000 years abstract on spitsbergen western svalbard three major glacial advances have been identified during the weichselian all three reached the continental shelf west of the svalbard archipelago radiocarbon luminescence and amino acid dating of interbedded interstadial and interglacial sediments indicate that these glacial advances have early isotope stage 5d middle stage 4 and late weichselian ages stage 2 an additional more local advance has been dated to isotope stage 5b the late weichselian ice sheet expanded across the entire barents sea however in the south western barents sea the late weichselian till is the only till above eemian sediments indicating that the early and middle weichselian ice advances were restricted to the svalbard archipelago and the northern barents sea a major problem with the onshore sites is the dating of events beyond the range of the radiocarbon method to overcome this the onshore record has been correlated with marine cores from the continental slope and the deep sea west of svalbard where a chronology has been established by oxygen isotope stratigraphy ice rafted detritus ird was used as the main monitor of glaciation the ird record closely mirrors the glaciation history as interpreted from the onshore sections during the late weichselian the largest ird peak occurred during deglaciation a pattern also postulated for the earlier events given this the results from the marine cores indicate that the ages for the first glacial advances during the weichselian were a few thousand years older than interpreted from the onshore stratigraphy

incision of alluvial channels in response to a continuous base level fall field characterization modeling and validation along the dead sea abstract the dramatic lake level drop of the dead sea during the twentieth century 30 m provides a field scale experiment in transport limited incision of gravel bed channels in response to quasi continuous base level fall at approximately constant rate we apply a one dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the dead sea the model inputs include the measured twentieth century lake level curve annual shoreline location i e annual channel lengthening following the lake level drop reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces and the current profiles of the active channels the model parameters included the diffusion coefficient and the upstream derived sediment flux both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles the maximum at station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry the model applied predicted degradation rates and the pattern of degradation with high accuracy this suggests that sediment flux in the modeled channels is indeed linearly dependent on slope further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin a proxy for discharge the model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure

mathematical modeling of graded river profiles numerical modeling of the longitudinal profiles of rivers at grade is accomplished using the basic equations of open channel flow sediment transport equations and empirical relations for downstream variation in flow discharge sediment discharge sediment caliber and channel width only in some cases are the computed stream profiles fit exactly by any one of the commonly supported mathematical function analogs to graded profile form exponential logarithmic or power function but in most cases any of these functions can provide a fit with a degree of error smaller than would be noted in treating field data profiles dominated by spatial change in fluid and sediment discharge are distinctly power functions while profiles dominated by sediment size reduction are not necessarily exponential in form other important controls on profile shape are the degree of downstream width change in response to increasing discharge and the general range of sediment size a dynamic model of a river s approach to grade

rapid incision of a small coarse and steep fan delta in response to base level fall the case of nahal qedem the dead sea israel the dead sea has been continuously dropping 0 4 1 0 m yr 1 since the middle of the 20th century and thus provides a unique field laboratory for studying in real time the response of drainage systems to a non tectonic base level fall the aim of this work is to study the short term ongoing erosive response to a rapid base level drop in a small steep fronted erodible fan delta setting the work explores the controls of the steep qedem fan delta guided by its clinoform structure on its incision longitudinal profiles of the fan delta and of its entrenched channel were measured in the field sedimentary facies changes fluviatile shallow lacustrine and beach were followed along exposures the existence of large boulders provided an opportunity to examine the uncertain role of armouring and boulder flux on incision the field study was combined with digital elevation models dems that were extracted from pairs of overlapping aerial photos maps of erosion and deposition were prepared using a change detection algorithm the longitudinal profile of the entrenched channel was found to be steep and linear the outlet temporarily hangs elevated and ungraded above the retreating lake level indicating years without incision flow events which cause lags in response to the rapid lake level drop in spite of the large boulders the small drainage basin and precipitation volume over the basin of the qedem the recorded vertical incision rates in the unconsolidated sediments are as high as 0 8 m yr 1 i e similar to those of the largest wadis draining to the dead sea the steep front of the fan delta is suggested to be a main factor controlling the efficient incision a unique transport mechanism of rolling boulders following undercutting contributed to the entrenchment efficiency copyright 2010 john wiley sons ltd

evidence for late stage fluvial activity in kasei valles mars 1 two inner channels in the southern branch of kasei valles are among the best preserved examples of fluvial erosion on mars attributes of the channels include arcuate alcoves perched boulders and a concave up longitudinal profile all of which are consistent with the interpretation that these channels were carved by a newtonian fluid the sharp concavity of the longitudinal profile is comparable to a terrestrial alluvial system with a minimum work profile the shape of the profile suggests that the system was in a quasi equilibrium state but was not active long enough to achieve grade associated with these channels is a platy meter scale texture identified in high resolution mars orbiter camera images although a lava flow could explain many of the material properties of the platy surface texture we speculate that this texture in the immediate proximity to the southern kasei valles inner channels may be related to waning floodwaters moving through the inner channels and is a mudflow deposit

development and morphometry of drainage network in volcanic terrain central anatolia turkey abstract this paper presents the results of morphotectonic and morphometric research carried out in order to determine the neotectonic development of the volcanic mountains and a drainage network in sw cappadocia the study area extends among the aksaray nigde and nevsehir provinces the study area comprises hasandag melendiz keciboyduran golludag mountains and the adjacent parts of these volcanic mountains data collected exclusively from 1 25 000 digitised topographic maps and 10 m resolution dems were used to define parameters related to the longitudinal profile of streams the study area was divided into 10 volcanic units longitudinal profiles of 20 streams and stream orders were analysed to determine a regional tectonic differentiation pattern in these units the streams in the study area drain into four different tectonic depressions these depressions are aksaray plain controlled by the tuz golu fault tgf ciftlik plain controlled by the keciboyduran melendiz fault kmf misli plain controlled by the derinkuyu fault df and bor plain controlled by the nigde fault zone nfz an analysis of morphometric parameters shows that the development of a drainage network is associated with faults and rock resistance occurrence of morphometric parameters with different values in units reveals that the volcanic mountains were not uplifted in the same period and were subjected to different morphologic processes high total order number in the south of hasandag unit 3 and melendiz mountains unit 7 indicate that the uplift ratio of the southern part is much greater than that of the northern part moreover development of the drainage network in the south is in a more advanced phase than in the north indeed the drainage network in the north is in the youngest erosional phase of all parts of the study area the increased stream length gradient indices sl and stream gradients and an analysis of headward erosion show that the streams displaying the longest and highest reach of the erosional phase are all in the southern part of keciboyduran and melendiz mountains the longitudinal profile lp of the present thalweg of the streams is irregular the irregular lp are associated with four different causes these are geological variations in resistance tectonics and volcanic topography and downcutting in response to stream incision the beginning of the fluvial incision in the northern part is younger than in the south

small profile concavity of a fine bed alluvial channel although most natural streams have concave upward longitudinal profiles there are conflicting perspectives about whether an alluvial channel is less concave than a bedrock channel alluvial channels can be classified as coarse bed and fine bed channels depending on the bed grain size both are transport limited but the threshold of motion differs greatly whereas a coarse bed alluvial channel can be claimed to be as concave as a bedrock channel we claim that a fine bed channel is distinguishably less concave we derive the concavity index of a fine bed alluvial channel using the power law relationships emergent at a steady state river network for known ranges of the scaling parameters our formulation informs a range of concavity index as 0 07 0 09 for a fine bed alluvial channel our analyses of previous laboratory experiments and real fine bed alluvial channels in the midwestern u s and northern europe also support our conclusions i e small profile concavity of steady state fine bed alluvial channels

teaching geomorphology through spreadsheet modelling abstract geomorphology like most scientific disciplines has evolved from a descriptive stage through quantification to modelling of processes and outcomes indeed high resolution modelling has been termed the third branch of science for its ability to generate high quality hypotheses testable in turn through field mapping and laboratory experimentation i teach the principles and basic applications of modelling using microcomputer spreadsheets these serve as transparent boxes in which graphical output is generated in response to numerical input and more importantly in which the modeler student can see the equations and order of steps unlike traditional black box models the technology is widely available and familiarity with it can be assumed required or taught at the undergraduate level modelling can be taught through a series of spreadsheet exercises in which students while learning topical material in a traditional sequence progress from a simple cookbook exercise through more realistic process based exercises to the level of addressing a previously unstudied research question at each step the model can be used to generate testable hypotheses i have worked with scarp evolution stream longitudinal profiles and glacier reconstructions and plan to include eolian soil development mass wasting and coastal processes in additional exercises the first year of use of this technique in a junior level geomorphology course clarified the strengths and weaknesses of the modelling approach the strengths involve students learning the capabilities and flaws of modelling a stronger understanding of causeeffect relationships and the effects of time on landforms the weaknesses involve time commitment supervision in model implementation and limitations to student ability to independently pursue openended research

perturbation of fluvial sediment fluxes following the 2008 wenchuan earthquake quantifying the removal of co seismic landslide material after a large magnitude earthquake is central to our understanding of geomorphic recovery from seismic events and the topographic evolution of tectonically active mountain ranges in order to gain more insight into the fluvial erosion response to co seismic landslides we focus on the sediment fluxes of rivers flowing through the rupture zone of the 2008 m w 7 9 wenchuan earthquake in the longmen shan of the eastern tibetan plateau over the post seismic period of 2008 2013 we annually collected river sediment samples 0 25 1mm at 19 locations and measured the concentration of cosmogenic be 10 in quartz when compared with published pre earthquake data the be 10 concentrations declined dramatically after the earthquake at all sampling sites but with significant spatial differences in the amplitude of this decrease and were starting to increase toward pre earthquake level in several basins over the 5 year survey our analysis shows that the amplitude of be 10 decrease is controlled by the amount of landslides directly connected to the river network calculations based on be 10 mixing budgets indicate that the sediment flux of the 0 25 1mm size fraction increased up to sixfold following the wenchuan earthquake our results also suggest that fluvial erosion became supply limited shortly after the earthquake and predict that it could take a few years to several decades for fluvial sediment fluxes to go back to pre earthquake characteristics depending on catchment properties we also estimate that it will take at least decades and possibly up to thousands of years to remove the co seismic landslide materials from the catchments in the longmen shan copyright c 2017 john wiley sons ltd

stream networks and long term surface uplift in the new madrid seismic zone stream networks are sensitive to low rates of surface uplift and can be used to decipher the history of large earthquakes even where faults do not rupture the surface as in intraplate seismic zones statistical analysis of alluvial network data from topographic maps in the new madrid seismic zone in the central united states shows that stream segment gradients deviate the most from an estimated natural stream profile where surface uplift is greatest evidence of cumulative deformation distilled from stream network patterns represents at least several meters of differential surface uplift during holocene time which suggests that more than one cycle of surface deformation occurred

a sand gravel gilbert delta subject to base level change laboratory experiments were conducted on a sand gravel gilbert delta to gain insight on its dynamics under varying base level base level rise results in intensified aggradation over the topset as well as a decrease in topset slope and topset surface coarsening the signals of which migrate in an upstream direction preferential deposition of coarse sediment in the topset results in a finer load at the topset foreset break which creates a fine signature in the foreset deposit base level fall has the opposite effects entrainment of the topset mobile armor causes a coarsening of the load at the topset foreset break and so a coarse signature in the foreset deposit the entrainment of the topset substrate and fine top part of the foreset may follow which causes a fining of the load and a fine signature in the foreset deposit the fact that the upstream sediment supply requires a certain slope and bed surface texture to be transported downstream under quasi equilibrium conditions counteracts the effects of base level change this information travels in the downstream direction in nature base level change is likely so slow that the upstream sediment load maintains the topset slope and bed surface texture and so keeps the topset in a quasi equilibrium state base level change is therefore not expected to leave a clear signal in a mixed sediment gilbert delta other than a change in elevation of the topset foreset interface

spatial and temporal analysis of hillslope channel coupling and implications for the longitudinal profile in a dryland basin author s michaelides katerina hollings rory singer michael bliss nichols mary h nearing mark a

aridity is expressed in river topography globally it has long been suggested that climate shapes land surface topography through interactions between rainfall runoff and erosion in drainage basins1 4 the longitudinal profile of a river elevation versus distance downstream is a key morphological attribute that reflects the history of drainage basin evolution so its form should be diagnostic of the regional expression of climate and its interaction with the land surface5 9 however both detecting climatic signatures in longitudinal profiles and deciphering the climatic mechanisms of their development have been challenging owing to the lack of relevant global data and to the variable effects of tectonics lithology land surface properties and human activities10 11 here we present a global dataset of 333 502 river longitudinal profiles and use it to explore differences in overall profile shape concavity across climate zones we show that river profiles are systematically straighter with increasing aridity through simple numerical modelling we demonstrate that these global patterns in longitudinal profile shape can be explained by hydrological controls that reflect rainfall runoff regimes in different climate zones the most important of these is the downstream rate of change in streamflow independent of the area of the drainage basin our results illustrate that river topography expresses a signature of aridity suggesting that climate is a first order control on the evolution of the drainage basin a global dataset of river longitudinal profiles shows that river profiles become straighter with increasing aridity and numerical modelling suggests that this can be explained by rainfall runoff regimes in different climate zones

flow recession as a driver of the morpho texture of braided streams braiding has been widely studied in humid temperate climates though rarely in arid environments morpho texture of braided streams refers to the morphological textural organization in a braid cell stream section including bars anabranches and chutes that may strongly relate to different processes and hydrological regimes the objective of this study is to compare the morpho texture of braided streams governed by diverse flow recessions in different climates measurements were conducted in the wadis ze elim and rahaf southeast hyper arid israel in the mediterranean barranca de los pinos central spain and in humid temperate braided systems the la bleone river haute provence france and in the saisera and cimoliana torrents northeast italy terrestrial laser scanning was used to produce point clouds and high resolution digital elevation models of the braid cells wet braid cells in humid temperate environments were surveyed by a total station roughness and the upper tail of grain size distributions were derived from the scanned point clouds or from wolman sampling we found that anabranches are commonly finer grained than the bars in dryland systems and in semi arid sandy braided systems contrary to the humid temperate braided systems in both climates chutes are similar or coarser grained than the bars which they dissect in accordance with their steeper gradients due to the considerable bar anabranch relief the saisera s morpho texture is similar to that of the dryland braided channels despite the very humid temperate environment in which it is located due to its short lived ephemeral type hydrograph hydrograph shape specifically the duration of flow recession typical of a climate but not confined to it determines the morpho texture of braided streams and the textural differentiation between a depositional bar and the adjacent anabranches the morpho texture of chutes and bars results also from local erosional processes affected by local topography i e ungraded longitudinal profiles and is not solely determined by flow recession this new morpho textural model enables identifying primary depositional and erosional braiding processes copyright 2015 john wiley sons ltd

river incision and terrace formation in the late cenozoic of europe abstract late cenozoic environmental changes which affected european rivers are reviewed focusing especially on those of mid pleistocene times c 1 2 0 8 ma or around mis 22 and thereafter these involved dominating but fluctuating cold climate periglacial conditions shorter but major episodes of glaciation and brief interglacials there were also related sea level and tectonic responses the known history of european rivers in this period is individually varied but is predominantly marked by multiple stages of episodic incision the form of which changed in style at around the mid pleistocene transition it is suggested that the nature of climatic oscillations the dating of incision episodes and the processes that achieve this incision are as yet insufficiently understood fluvial process studies suggest that the onset of incision may broadly relate to changes in slope discharge sediment load and calibre and bedrock erodibility and these may all have been transformed as the direct or indirect result of mid pleistocene climatic changes common properties of basal sediments on strath terraces suggest that it was during the extended but variable cold stage episodes that both valley deepening and lateral widening occurred and that climatic change was the principal driver of episodic deep valley incision

from grain size to tectonics 1 regional grain size trends in fluvial successions can reveal important information regarding the dynamics of sediment routing systems self similar solutions for down system grain size fining have recently been proposed to explore how key variables such as the spatial distribution of deposition sediment discharge and sediment supply characteristics control spatial distribution of grain size in fluvial successions over time scales of 104 106 years we explore the sensitivity of these solutions to changes in key variables and assess their applicability to ancient fluvial successions several sensitivity analyses are presented to investigate the relative control of the key model variables on the spatial pattern of down system grain size fining in fluvial successions sensitivity analyses demonstrate that 1 an increase in the initial value of sediment discharge to a basin causes a decrease in the rate of grain size fining in fluvial successions an effect that becomes nonlinear for large values of initial sediment discharge 2 a short wavelength high amplitude subsidence regime generates a greater rate of down system grain size fining and a long wavelength lower amplitude subsidence regime generates a lesser rate of down system grain size fining in fluvial successions and 3 an increase in the spread of grain sizes in the sediment supply generates a greater rate of down system grain size fining we apply this modeling technique to grain size data sets collected from two time surfaces within conglomerates of the upper eocene montsor fan succession of the pobla basin spanish pyrenees these data sets exhibit approximately self similar grain size distributions further the observed increase in down system grain size fining associated with smaller depositional system lengths provides support for the application of self similar solutions to fluvial successions by applying these solutions to carefully collected grain size data from fluvial successions we are able to relate explicitly the initial grain size supplied to the system the spatial distribution of subsidence and the sediment discharge into the basin to the rate of grain size fining in fluvial successions this method thus offers a powerful means of elucidating sediment routing system dynamics over time

channel adjustment of an unstable coarse grained stream opposing trends of boundary and critical shear stress and the applicability of extremal hypotheses channel adjustments in the north fork toutle river and the toutle river main stem were initiated by deposition of a 2 5 km3 debris avalanche and associated lahars that accompanied the catastrophic eruption of mount st helens washington on 18 may 1980 channel widening was the dominant process in combination adjustments caused average boundary shear stress to decrease non linearly with time and critical shear stress to increase non linearly with time at the discharge that is equalled or exceeded 1 per cent of the time these trends converged by 1991 1992 so that excess shear stress approached minimum values extremal hypotheses such as minimization of unit stream power and minimization of the rate of energy dissipation minimum stream power are shown to be applicable to dynamic adjustments of the toutle river system maximization of the darcy weisbach friction factor did not occur but increases in relative bed roughness caused by the concomitant reduction in hydraulic depths and bed material coarsening were documented predictions of stable channel geometries using the minimum stream power approach were unsuccessful when compared to the 1991 1992 geometries and bed material characteristics measured in the field it is concluded that the predictions are not applicable because the study reaches are not truly stable and cannot become so until a new floodplain has been formed by renewed channel incision retreat of stream side hummocks and establishment of riparian vegetation to limit the destabilizing effects of large floods further prediction of energy slope and consequently stream power by the sediment transport equations is inaccurate because of the inability of the equations to account for significant contributions of finer grained sand and gravel bank materials relative to the coarsened channel bed from bank retreat and from upstream terrace erosion

amount and controls of the quaternary denudation in the ardennes massif western europe it is still debated whether the primary control on the middle pleistocene denudation of the uplifted ardennes massif western europe is tectonic or climatic here based on geomorphological observations we calculate the amount of river incision and interfluve denudation in the meuse basin upstream of maastricht since 0 7 ma and we show that the main response to tectonic forcing was incision this allows us to provide first order estimates of the tectonic and climatic contributions to the denudation of the ardennes from a dataset of 71 remnants of a terrace level dated 0 7 ma we first derive a basin scale functional relationship linking incision with distances to the regional base level lc and to the source ls in the ourthe basin pertaining to the ardennian part of the meuse basin expressed as i i0 1 a lcb lsc i0 being the incision measured at the basin outlet this relationship calculates that river incision has removed 84 km3 of rock in the meuse basin upstream of maastricht since 0 7 ma in the same time 292 km3 were eroded from the interfluves a comparison of these volumes shows that the tectonically forced river incision accounts for 22 of the total post 0 7 ma denudation furthermore the mean denudation rate corresponding to our geomorphological estimate of the overall denudation in the meuse basin since 0 7 ma amounts to 27 mm ky a figure significantly lower than the 40 mm ky mean rate derived from 10be studies of terrace deposits of the meuse schaller et al 2004 this suggests that taken as a basin average the 10be derived rate is overestimated probably due to an overrepresentation of the erosion products of the rapidly incising valleys in the alluvial deposits copyright 2009 john wiley sons ltd

geomorphological evolution of longitudinal river profiles in the carpathians abstract the main rivers which drain the east and southeast side of the eastern carpathians and those that drain the southern carpathians have been analysed regarding the sediment transit the change of the riverbeds and the type of channel deposits in this paper attention is focused on the concavity of the stream profile on this basis we tried to determine the evolution of some carpathian rivers and thus estimate their long term evolutionary tendencies the concavity index of the east carpathian rivers shows a trend to increase from north to south from the eastern carpathians to the carpathian bend and the bucegi mountains the explanation of this situation required a review of the evolutionary stages of the eastern carpathians in order to establish the age and the evolutionary tendencies of the river network in our study area the rivers suceava moldova and bistri a have followed the same courses since the sarmathian approximately 13 5 million years ago the trotus river between 10 million and 5 4 million years ago the rivers putna buz u prahova and ialomi a suffered the most important changes so the age of their present course is about 2 5 million years the rivers could be grouped according to the mathematical model which fits best the exponential exponential logarithmic and logarithmic model finally we tried to correlate the age of the river with the form of its longitudinal profile the customary theoretical models require that the older a river is the more its concavity should increase in the headwater area and should asymptotically approach a longitudinal equilibrium profile or grade as davis calls it however the carpathian rivers do not follow this general tendency what we have demonstrated is that age had no influence on the form of the longitudinal profiles for the rivers on the exterior side of the carpathians this is because tectonic uplift was important and this phenomenon is still present today with values of over 6 mm year

the role of sediment in controlling steady state bedrock channel slope implications of the saltation abrasion incision model abstract the saltation abrasion model is a mechanistic model for river incision into bedrock by saltating bedload which we have previously derived and used experimental data to constrain all parameter values here we develop a method for applying the saltation abrasion model at a landscape scale and use the model as a reference for evaluating the behavior of a wide range of alternative incision models in order to consider the implications of the saltation abrasion model as well as other models for predicting topographic steady state channel slope to determine the single valued discharge that best represents the effects of the full discharge distribution in transporting sediment and wearing bedrock we assume all runoff can be partitioned between a low flow and a high flow discharge in which all bedload sediment transport occurs during high flow we then use the gauged discharge record and measurements of channel characteristics at a reference field site and find that the optimum discharge has a moderate magnitude and frequency due to the constraints of the threshold of grain motion and bed alluviation by high relative sediment supply incision models can be classified according to which of the effects of sediment on bedrock incision are accounted for using the predictions of the saltation abrasion model as a reference we find that the threshold of motion is the most important effect that should be represented explicitly followed in order of decreasing importance by the cover effect the tools effect and the threshold of suspension effect models that lack the threshold of motion over predict incision rate for low shear stresses and under predict the steady state channel slope for low to moderate rock uplift rates and rock strengths models that lack the cover effect over predict incision rate for high sediment supply rates and fail to represent the degree of freedom in slope adjustment provided by partial bed coverage models that lack the tools effect over predict incision rate for low sediment supply rates and do not allow for the possibility that incision rate can decline for increases in shear stress above a peak value overall the saltation abrasion model predicts that steady state channel slope is most sensitive to changes in grain size such that the effect of variations in rock uplift rate and rock strength may affect slope indirectly through their possible but as yet poorly understood influence on the size distribution of sediments delivered to channel networks by hillslopes

implications of the saltation abrasion bedrock incision model for steady state river longitudinal profile relief and concavity the saltation abrasion model predicts rates of river incision into bedrock as an explicit function of sediment supply grain size boundary shear stress and rock strength here we use this experimentally calibrated model to explore the controls on river longitudinal profile concavity and relief for the simple but illustrative case of steady state topography over a wide range of rock uplift rates we find a characteristic downstream trend in which upstream reaches are close to the threshold of sediment motion with large extents of bedrock exposure in the channel bed while downstream reaches have higher excess shear stresses and lesser extents of bedrock exposure profile concavity is most sensitive to spatial gradients in runoff and the rate of downstream sediment fining concavity is also sensitive to the supply rate of coarse sediment which varies with rock uplift rate and with the fraction of the total sediment load in the bedload size class variations in rock strength have little influence on profile concavity profile relief is most sensitive to grain size and amount of runoff rock uplift rate and rock strength influence relief most strongly for high rates of rock uplift analysis of potential covariation of grain size with rock uplift rate and rock strength suggests that the influence of these variables on profile form could occur in large part through their influence on grain size similarly covariation between grain size and the fraction of sediment load in the bedload size class provides another indirect avenue for rock uplift and strength to influence profile form copyright 2008 john wiley sons ltd

sediment transport and unit stream power function basic fluid mechanics and turbulence theories are applied to show that suspended sediment concentration at a given depth of an open channel flow is a function of the turbulence energy production rate at that depth depth averaged suspended sediment concentration can be obtained by integrating a function of the turbulence energy production rate over the depth of flow which in turn is a function of unit stream power total sediment concentration can also be expressed as a function of unit stream power following the foresaid and a procedure similar to that proposed by einstein comparisons of seven total load equations indicate that equations derived from the concept that the rate of sediment transport should be related to the rate of energy dissipation of the flow are more accurate than other equations for both laboratory flumes and natural rivers

geomorphic observations of rivers in the oregon coast range from a regional reconnaissance perspective abstract changes in long profile gradient gradient index pseudo hypsometric integral valley incision and sinuosity fractal dimension for rivers in western oregon were studied to determine their usefulness in assessing an hypothesis of differential uplift within the coast range all data were gathered from topographic quadrangles and geologic maps and so the results of this paper are limited to the description of river forms with only limited interpretations rivers were naturally divided into three groups those in the western coast range the eastern coast range and the klamath and cascade ranges and differences in river morphometry were generalized rivers in the western coast range had more divergent characteristics whereas those in the other groups were more similar within each group for example long profiles of western coast range rivers had diverse forms but in the other groups long profiles were similar within the group pseudo hypsometric integrals had a wide scatter in the western coast range but in the other ranges the pseudo hypsometric integral was more narrowly defined valley entrenchment and high sinuosity were common in the western coast range and were less visible in the eastern coast range these regional generalizations do not hold for the central coast range near 44 5 n where the yaquina and marys rivers are located in the eastern coast range the marys river is unique in that it has a convex bulge in its long profile does not have an increasing valley floor width to valley height ratio downstream and has a high sinuosity fractal dimension in the western coast range the yaquina river is unique in that it has a smoothly decreasing long profile has a very low pseudo hypsometric integral and does not have a decreasing valley floor width to valley height ratio downstream there may be many explanations for these observations but these observations are also consistent with tectonic interpretations that the central western coast range is the locus of synclinal tilting and that the entire oregon coast is experiencing landward tilting and uplift

tectonic uplift of the northern qinling mountains central china during the late cenozoic evidence from dem based geomorphological analysis abstract the qinling mountains which stretch from east to west in central china represent an important geological and geographical boundary between north china and south china because of the northeastward growth of the tibetan plateau since the late cenozoic the northern qinling mountains have been strongly reactivated and uplifted to investigate the landscape response to the tectonic uplift the geomorphic indices of the northern qinling mountains including the hypsometry mathematical function of the longitudinal profile channel longitudinal profile and steepness index were analyzed the topographic analysis reveals that the landscape evolution of the heihe river basin is in a transient state the upstream of the heihe river basin has undergone a long period of erosion and represents relict landscape in contrast the downstream represents adjusting landscape which formed by river incision in response to the rapid uplift of the northern qinling mountains this is a result of the extension of the weihe graben which has formed due to the northeastward growth of the tibetan plateau during the late cenozoic the spatial distribution of the geomorphic indices reveals that the ne striking taibai fault has experienced strong tectonic activity since the late cenozoic and is a secondary fault that accelerated the uplift rate of the northern qinling mountains the tectonic stress due to the northeastward growth of the tibetan plateau has been transmitted to the northern qinling mountains along the taibai fault therefore we proposed that the uplift of the northern qinling mountains is due to the combined effects of the weihe graben extension and taibai fault activity forming the highest peak taibai mountain of the northern qinling mountains near the intersection of the qinling piedmont fault and taibai fault

fluvial archives a valuable record of vertical crustal deformation abstract the study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms but also for identifying the nature of crustal deformation and its history in recent decades geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens here we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions the effects of horizontal deformation are not addressed channel long profiles have received considerable attention in the literature and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady state characteristics then we review the literature dealing with the transient response of rivers to tectonic perturbation through the production of knickpoints propagating through the drainage network inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories finally we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes as well as the erosional imprint of tectonic forcing sedimentary deposits such as fluvial terrace staircases are also considered as a classical component of tectonic geomorphology we show that these studies have recently benefited from rapid advances in dating techniques allowing more reliable reconstruction of incision histories and estimation of incision rates the combination of progress in the understanding of transient river profiles and larger more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation i e extrapolation of local data to entire profiles finally planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the dis equilibrium state of drainage systems across regional drainage divides

natural experiments in landscape evolution a natural experiment in landscape evolution is a case study of landform development in which only one element varies significantly and for which the driving forces initial conditions and or boundary conditions are well constrained natural experiments provide a means of testing landscape evolution theory on the large space and time scales to which that theory applies natural experiments can involve either steady or transient conditions cases with steady conditions allow one to test predictions about the relationships among topography erosion rates and various attributes related to climate and material properties transient cases are valuable for distinguishing between models whose predictions might be similar and therefore indistinguishable under steady conditions essential ingredients of a natural experiment include minimal variation in all but one factor good constraints on timing and or rates well characterized processes and high quality topographic data other useful ingredients include information about intermediate topographic states such as a former valley profile revealed by strath terraces and knowledge of the time history of erosion rates in order to deepen our understanding of the physics and chemistry of long term landscape evolution there is a pressing need to identify natural experiments and develop the necessary databases to take advantage of them copyright 2009 john wiley sons ltd

impact of tectonics on drainage network evolution of suru basin kargil n w himalaya jammu and kashmir india the main objective of this paper is to work out quantitative measurement of various geomorphic parameters as well as analysis of geomorphic landforms to study the tectonic character of suru basin morphometric analysis being widely used to assess the drainage characteristics of the river basins has also been found to be a useful tool to delineate tectonically active zones a number of parameters including the mountain front sinuosity asymmetry factor transverse topography symmetry hypsometry longitudinal profile and the shape parameters have been used the low mountain front sinuosity values 1 4 indicate that the tectonic forces dominate over erosive activity also the asymmetry factor 66 98 suggests that the right side of the basin has experienced uplift with the development of unpaired river terraces hypsometric integral 0 96 convex up hypsometric curve and the gps data of year 2011 2013 indicate that the relief of the basin is high relative to mean is in youthful stage and actively uplifting at the rate of 2 18 0 99 mm year the shape parameters further suggest that the suru river basin having lower elongation ratio is indicative of elongate shape of basin with tectonic forces outpacing the erosion power area altitude analysis of the suru river basin indicates that about 72 of the area of the basin is steeply to very steeply sloping and 28 area is moderately to gently sloping the area altitude indicates 72 area of basin could slide when there is slight shift in terms of tectonic disturbance in addition to the geomorphic indices the field investigations reveal tectonically unstable character exhibit a complex topography and varied quaternary sedimentation the major geomorphic landforms viz alluvial terraces alluvial fans debris cone scree and talus cone at the foothills are present throughout the valley with tectonic structures like micro folds back tilted beds deeply incised valleys faults and tectonic deposits ophiolites indicating that the tectonic activity has affected the basin the synergized results of geomorphometry field investigations and gps data indicate that the suru basin is tectonically active and uplifting

tectono geomorphic indices of the erin basin ne kashmir valley india abstract the present study aims to assess the tectonic activity in the erin basin ne kashmir on the basis of several relevant geomorphic indices and field observations we use digital elevation model srtm and survey of india soi topographic maps in gis environment to compute the geomorphic indices the indices i e convex hypsometric curve high hypsometric integral value h i 0 5 low basin elongation ratio eb 0 17 low mountain front sinuosity values s mf 1 08 average low valley floor width ratios vf 4 suggest that the area is tectonically active moreover prominent irregularities knickpoints knickzones along longitudinal profile of the erin river even in homogenous resistant lithology panjal trap and anomalous stream gradient index sl values reflect that the erin basin is dissected by two faults ef 1 and ef 2 with nnw sse and ssw nne trends respectively the results of this preliminary study further substantiate the recent gps studies which argue that the maximum strain is accumulating in the ne part of the kashmir himalaya

longitudinal profiles in simple alluvial systems theoretical considerations suggest that exponential or quadratic functions are apt for describing the longitudinal profiles of aggrading alluvial systems that are unaffected by significant lateral inputs of water or sediment a new set of field data confirms this for individual sedimentary links along a wandering gravel bed river in british columbia canada each link is viewed as a simple alluvial system without major water or sediment inputs within which grain size typically fines downstream in a relatively systematic manner such homogeneous reaches are suitable for the investigation of simple profile form it is found that quadratic approximations are the most flexible descriptor for link longitudinal profiles overall the river forms an irregularly cuspate long profile structured by these fundamental length scale units both link gradients and link fining rate reflect size selective aggradation associated with the bounding lateral inputs

subduction of decadal north pacific temperature anomalies observations and dynamics abstract observations of oceanic temperature in the upper 400 m reveal decadal signals that propagate in the thermocline along lines of constant potential vorticity from the ventilation region in the central north pacific to approximately 18 n in the western pacific the propagation path and speed are well described by the geostrophic mean circulation and by a model of the ventilated thermocline the approximate southward speed of the thermal signal of 7 mm s 1 yields a transit time of approximately eight years the thermal anomalies appear to be forced by perturbations of the mixed layer heat budget in the subduction region of the central north pacific east of the date line a warm pulse was generated in the central north pacific by a series of mild winters from 1973 to 1976 and reached 18 n around 1982 after 1978 a succession of colder winters initiated a cold anomaly in the central north pacific that propagated along a similar path and with a similar speed as the warm anomaly then arrived in the west

integrating channel form and processes in the gangetic plains rivers implications for geomorphic diversity abstract geomorphic diversity at a variety of spatial and temporal scales has been studied in the western ganga plains wgp india to isolate the dominating factors at each scale that have the potential to cause major geomorphic change the ganga river and its major tributaries draining the wgp have been investigated in terms of longitudinal cross sectional and planform morphology to assess the influence of potential controls such as climate geology topography land use hydrology and sediment transport these data were then compared with those from the rivers draining the eastern ganga plains egp to understand the geomorphic diversity across the ganga plains and the causal factors our investigations suggest that in channel geomorphic diversity over decadal scale in rivers with low width to depth w d ratio is caused by periodic incision aggradation but it is driven by channel avulsion in rivers characterized by high w d ratio similarly planform reach scale parameters such as sinuosity and braid channel ratio are influenced by intrinsic factors such as changes in hydrological conditions and morphodynamics cutoffs small scale avulsion that are in turn impacted by natural and human induced factors finally we have isolated the climatic and hydrologic effects on the longitudinal profile concavity of alluvial trunk channels in tectonically stable and unstable landscapes we demonstrate that the rivers flowing through a tectonically stable landscape are graded in nature where higher discharge tends to create more concave longitudinal profiles compared to those in tectonically unstable landscape at 103 year scale

longitudinal profile development into bedrock an analysis of hawaiian channels analysis of topographic maps of rivers incised into dated hawaiian lava flows shows that the long term average bedrock erosion rate along certain reaches is linearly related to stream power field observations suggest that two processes may control hawaiian channel downcutting 1 stream power dependent erosion including abrasion of the channel bed by transported particles and 2 step wise lowering caused by knickpoint propagation modeling results indicate that a simple stream power dependent erosion law predicts the straight to weakly convex longitudinal profiles characteristic of kauai channels but is insufficient to predict two other characteristic features the upslope propagation of knickpoints and the straight 5 8 channel slopes below the knickpoints thus more than this single transport law is apparently required to model bedrock channel incision field surveys also indicate that significant portions of the channel lengths below the knickpoints are mantled with large boulders we propose that

fluvial response to rapid episodic erosion by earthquake and typhoons tachia river central taiwan abstract analysis of typhoon and earthquake triggered landsliding and fluvial response in the tachia river central taiwan documents highly episodic sediment supply over decade to century timescales landslide data from the chi chi earthquake 1999 and subsequent typhoons 2001 2004 and 2005 quantify the sediment supply from these events fluvial response was investigated by decadal scale and century scale longitudinal river profile data spanning 1904 to 2008 and by sediment delivery recorded in suspended sediment load and reservoir sedimentation data our results show that the different time periods of satellite images and aerial photographs used in previous studies make it difficult to unambiguously identify the causes of landslides previously attributed by some studies to the effects of the chi chi earthquake rather than subsequent high intensity precipitation in response to significant variability in sediment delivery from hillslopes century scale profile variation data indicate substantial bed surface elevation change of 2 6 6 7 m and decade scale bed surface elevation change of 1 1 3 3 m since 1993 the downstream reaches incised in response to bedload sediment trapping by reservoirs while headwater reaches aggraded in response to increased sediment delivery from uplands a tremendous increase in reservoir sedimentation after 2000 likely reflects the effects of the highest decade average daily rainfall since 1900 suspended sediment load data indicate a post chi chi earthquake increase in sediment concentration in low flow events but do not exhibit the clear influence on sediment yields at higher flows as e g typhoons reported by others for fluvial response in the epicentral region

onlap offlap and the origin of unconformity bounded depositional sequences christie blick n 1991 onlap ofttap and the origin of unconformity bounded depositional sequences mar geol 97 35 56 unconformity bounded depositional sequences represent the fundamental building blocks of sedimentary successions they are typically characterized by onlap at the base and by offlap at the top and they tend to be markedly asymmetrical with onlap accounting for a larger part of any cycle of sedimentation than offlap offlap cannot be attributed solely to erosional truncation but instead implies that sequence boundaries develop over a finite interval of time depositional sequences are commonly associated with a cyclic arrangement of facies but transgressive regressive cycles are out of phase with respect to sequence boundaries which in down dip locations are both overlain and underlain by progradational deposits and hence form during times of regression of the shoreline these observations are used to develop some ideas about the origin of unconformity bounded sequences with reference to the inter related roles of changes in depositional base level and sediment supply in particular it is shown than onlap and offlap are due to lateral migration of a line of critical bypassing defined so as to incorporate the effects of sediment loading and compaction as well as the rate of change of elevation with respect to sea level downward shifts in onlap may be achieved by either an increase in the rate of eustatic fall or a decrease in the rate of tectonic subsidence and it is premature to assume that eustatic and tectonic controls on sea level may be distinguished solely on the basis of the frequency of depositional cyclicity small shifts in the position of onlap can also be produced by changes in sediment supply and more attention needs to be paid to the influence of sediment supply in the development of minor boundaries unconformities related to eustatic fluctuations are thought to correspond approximately to times of relatively rapid sea level fall inflection points but questions remain about the existence of possible leads and lags of up to cycle and hence about the degree to which sequence boundaries of eustatic origin may vary in age both within a given basin and from one basin to another

global river slope a new geospatial dataset and global scale analysis abstract a rivers longitudinal gradient i e slope is a key parameter in fluvial hydrology hydraulics and geomorphology it affects a multitude of fluvial variables such as flow velocity and sediment transport limitations in river slope data both its availability and accuracy constrain the fidelity of fluvial modeling particularly at larger or global scales traditional slope calculation algorithms cannot accurately predict river slopes as these are based on cell by cell calculation which is only suitable for hillslopes and small mountainous streams this paper presents a methodology for calculating global river slope and a procedure to upscale it for relatively coarse resolution suitable for global scale modeling the methodology is based on a simple principle of calculating slope from elevation depression over the length of a river segment which is automated to allow global scale calculations version 1 0 of the global river slope glors geospatial dataset is introduced and shown to be a step improvement over a previous product nhdplus for the contiguous united states and compares favorably to observed slope data collected from the literature statistical analysis of earth s continents and large basins highlights interesting spatial trends a semi empirical regression analysis between basin average river slope and other basin scale parameters show that terrain slope accounts for 67 of the variability in basin average river slope with average discharge sediment load and basin temperature contributing additional improvements to global predictions of 3 4 and 3 respectively

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

stream channel convexity induced by continuous base level lowering the dead sea israel abstract the dead sea level has dropped from 388 4 m in 1896 to 417 2 m in 2004 and continues to fall rapidly reaching a record of 1 m y drop such a dramatic base level fall on time scales of several tens of years makes the dead sea area a unique field laboratory the aim of this study is to examine the effect of the lowering dead sea as a base level on the longitudinal profiles of channels on the formation of knick points and on the sinuosity field studies were made along the lower courses of creeks which drain lakeward precise longitudinal profile measurements and their fitting to linear and logarithmic curves show they are planar to slightly convex the short convexity the absence of hydrological or lithological control and former experimental results of profile response to base level fall suggest that the convexity results from the recent continuous rapid drop of the dead sea the convexity is also an inheritance of the paleo morphology i e the original convex front of the fan deltas and coastal scarps following channel incision slope displacement and diffusion the erodible substrate and the high stream power prevented preservation of nickpoints along the main channels sinuosity of the meandering thalwegs remained low 1 1 1 2 indicating no response to the base level lowering along the steep slopes although the stream channels are incised in soft sediments the base level induced entrenchment dies out within 1000 m or less from the receding shoreline the channel profiles demonstrate different phases of adjustment to the lowering base level the uniqueness of the dead sea case is that contrary to former field and experimental studies the system is in a continuous relaxation period without reaching a final adjustment the channels are trapped in their convex form following a rapid on going base level fall upon exposed paleo fan deltas

inverting topography for landscape evolution model process representation 3 determining parameter ranges for select mature geomorphic transport laws and connecting changes in fluvial erodibility to changes in climate

predictions of steady state and transient landscape morphology using sediment flux dependent river incision models 1 recent experimental and theoretical studies support the notion that bed load in mountain rivers can both enhance incision rates through wear and inhibit incision rates by covering the bed these effects may play an important role in landscape evolution and in particular the response of river channels to tectonic or climatic perturbation we use the channel hillslope integrated landscape development child numerical model with two different bedrock incision models that include the dual role of the sediment flux to explore the transient behavior of fluvial landscapes both models predict that steady state channel slopes increase in landscapes with higher rock uplift rates however the incision models predict different transient responses to an increase in uplift rate and the behavior of each incision model depends on both the magnitude of change in uplift rate and the local drainage area in some cases the transient channel behavior is indistinguishable from that predicted for transport limited alluvial rivers in other cases knickpoints form in some or all of the drainage network as predicted by the detachment limited stream power model in all cases the response in the lower parts of the network is highly dependent on the response in the upper parts of the network as well as the hillslopes as the upper parts of the network send more sediment downstream channel incision rates may rise or fall and slopes in the lower parts of the channel may in fact decrease at times during the transient adjustment to an increase in rock uplift rate in some cases channel incision in the upper parts of the network ceases during the transient while the hillslopes adjust to the new uplift rate drainage density may also change as a function of uplift rate our results suggest that if the sediment flux strongly controls bedrock incision rates then 1 the transient fluvial response will take longer than predicted by the detachment limited stream power model 2 changes in channel slope may be much more complex than predicted by the detachment limited stream power model and 3 changes in the fluvial system will be closely tied to sediment delivery from the hillslopes importantly our results outline quantitative differences in system behavior produced by competing models and provide a framework for identifying locations in natural systems where differences in channel morphology can be used to discern between competing fluvial erosion models

emergence and pseudo equilibrium in geomorphology abstract many geomorphic system states and behaviors often interpreted as tendencies toward establishment and maintenance of steady state equilibrium are actually emergent outcomes of two simple principles gradient selection and threshold mediated modulation the principle of gradient selection is simply that geomorphic features associated with gradient driven flows persist and grow relative to other features and pathways the principle of threshold mediated modulation reflects the inherent limits on system development along any particular pathway thresholds not only define a restricted state space for any given geomorphic system but may also result in oscillatory behavior around an intermediate condition that resembles fluctuations around a steady state equilibrium together these principles often produce outcomes that mimic steady state equilibria examples are given involving several aspects of fluvial systems channel profiles alluvial channel changes and drainage density hillslope gradients and barchan dunes steady states indeed occur in earth surface systems and are a useful simplification in some models however the assumption that such states are somehow normative or the only natural condition is incorrect and can lead to problems in geomorphic interpretations environmental restoration and management and conceptions of how earth systems work

crossing the divide representation of channels and processes in reduced complexity river models at reach and landscape scales abstract reduced complexity models have considerable potential as tools for elucidating river behaviour over periods of 10 0 10 4 years and consequently for addressing fundamental questions concerning the scale dependent nature of explanation in geomorphology this paper proposes a simple subdivision of reduced complexity models of river behaviour into two categories that mirror methodological developments in fluvial geomorphology over the past 50 years first high resolution cellular approaches that are implemented within a framework that resolves process form feedbacks at small time and space scales second models that incorporate section averaged representations of channel geometry and processes and that are typically underpinned by regime theory and equilibrium concepts examples of both model types are presented here in the form of a cellular representation of stream braiding and a combined lattice network model of alluvial fan evolution simulations conducted using these models demonstrate how small scale process form interactions determine the emergence of larger scale channel and fan morphology and in so doing regulate system response to external forcing in this sense both models demonstrate that internal feedbacks play a critical role in controlling river responses to environmental change over historic and holocene timescales however both classes of model are characterised by uncertainty in their parameterisation of geomorphic processes such that internal feedbacks and thresholds for channel response to external forcing may vary substantially between competing models methods of refining both approaches are considered and hybrid models based on lattice network structures and mechanistic representations of channel process form interactions are identified as a means of addressing the shortcomings of existing strategies

drainage organization on the newly emerged dead sea bed israel abstract the organization of distributary drainage systems on the emerging coastal areas of the dead sea was studied following a rapid base level fall of 24 m during the period 1945 2002 which made the emerging pristine coastal zone a natural field laboratory photogrammetric digital elevation models were extracted to identify different emerged areas and to quantify erosion and deposition processes visual interpretation of orthophotos was used in order to recognize different drainage networks and to delineate the receding shoreline the remotely sensed data were backed by field surveys including measurement of longitudinal profiles the study demonstrates the spatial variability of runoff allocation from prograding fans to the emerging areas and the variable drainage responses three distinct environments were revealed on the emerged areas from the coast to the land deeply incised channels which are the main transmitters of the base level effect headward dendritic coalescing systems that are the reversal of the diverging channel system on alluvial fans and areas with unconfined sheet flowouts which are detached from base level control the threshold gradient of erosion on the emerged areas is 3 headward erosion was uncoupled with the lake level drop i e the rate of headward entrenchment increased with time despite an almost constant base level fall

change in the mathematical function type describing the longitudinal profile of a river through an evolutionary process japanese rivers where a large amount of sediment accumulates along the middle reaches are today not at grade nevertheless most of their longitudinal profiles can be described by one of the mathematical functions proposed for graded rivers for these rivers the mathematical function should show an aspect of fluvial processes different from the explanations of grade theories the geomorphological significance of differences in the mathematical functions describing the longitudinal profiles of rivers is discussed here a dynamic change in the shape of longitudinal profile of a river accompanying the change in mathematical function type is proposed in relation to changes in fluvial processes and stage of evolution of a river most japanese rivers can be described by either exponential or power functions the fluvial processes of the rivers described by exponential functions are in the depositional state the front of depositional area of gravels increases in altitude and migrates downstream the rivers exp

synthetic river valleys creating prescribed topography for form process inquiry and river rehabilitation design abstract the synthesis of artificial landforms is complementary to geomorphic analysis because it affords a reflection on both the characteristics and intrinsic formative processes of real world conditions moreover the applied terminus of geomorphic theory is commonly manifested in the engineering and rehabilitation of riverine landforms where the goal is to create specific processes associated with specific morphology to date the synthesis of river topography has been explored outside of geomorphology through artistic renderings computer science applications and river rehabilitation design while within geomorphology it has been explored using morphodynamic modeling such as one dimensional simulation of river reach profiles two dimensional simulation of river networks and three dimensional simulation of subreach scale river morphology to date no approach allows geomorphologists engineers or river rehabilitation practitioners to create landforms of prescribed conditions in this paper a method for creating topography of synthetic river valleys is introduced that utilizes a theoretical framework that draws from fluvial geomorphology computer science and geometric modeling such a method would be valuable to geomorphologists in understanding form process linkages as well as to engineers and river rehabilitation practitioners in developing design surfaces that can be rapidly iterated the method introduced herein relies on the discretization of river valley topography into geometric elements associated with overlapping and orthogonal two dimensional planes such as the planform profile and cross section that are represented by mathematical functions termed geometric element equations topographic surfaces can be parameterized independently or dependently using a geomorphic covariance structure between the spatial series of geometric element equations to illustrate the approach and overall model flexibility examples are provided that are associated with mountain lowland and hybrid synthetic river valleys to conclude recommended advances such as multithread channels are discussed along with potential applications

dem based identification of fluvial knickzones and its application to japanese mountain rivers stream gradients of mountain bedrock rivers in central japan were examined using gis and 50 m digital elevation models to discuss the distribution of knickzones the gradients are classified into local and trend types based on the measurement lengths the transition rate from the local to trend gradients i e the decreasing rate of gradient with increasing measurement length is then obtained as the indicator of relative steepness of a river segment which permits the objective identification of fluvial knickzones the identified knickzones occur widely in the study area and indicate that the knickzone is one of the common landforms in japanese mountain rivers the knickzones are more abundant in steep upstream reaches of the rivers subjected to active erosion and rapid rock uplift this suggests a hydraulic origin of the knickzones which is similar to step pool morphology but on a much larger scale some knickzones in piedmont areas can be on the other hand consistent with tectonic faulting at the mountain foot although some influences of volcanic activities on the formation of knickzones are observed regional lithology seems to exert a relatively weak influence on the abundance of knickzones knickzones are more consistent with other local mechanisms of fluvial erosion including reach scale processes

headwater channel dynamics in semiarid rangelands colorado high plains usa incised ephemeral channels provide a window into the fluvial processes that help sculpt rangeland landscapes this paper presents observations of ephemeral channels and valley networks in the high plains of colorado usa with an eye toward painting a picture of the ingredients that must be included in mathematical models of landscape evolution in such environments channel incision in the study area is driven by summer thunderstorms which can with reasonable frequency 3 5 yr generate boundary shear stresses high enough to penetrate the highly resistant vegetation armor but only within erosional hot spots where hydraulic forces are amplified by channel constriction and locally steep gradients focusing of erosion at these hot spots which correspond to knickpoints and channel heads is amplified by the small areal footprint and short erosional reach of most convective storms upstream migration of knickpoints creates a pattern of short active channel reaches separated by unchanneled or weakly channeled fully vegetated stable reaches based on our observations we interpret the necessary and sufficient conditions leading to the observed channel forms and dynamics as 1 a resistant vegetation layer overlying an erodible substrate which sets up a conditional instability through which erosional perturbations can grow by positive feedback 2 high flow variability 3 moderate to high substrate cohesion and 4 a high volume fraction of fine grained erodible material concave upward valley long profiles are interpreted as a trade off between downstream increasing flood frequency and downstream decreasing flood effectiveness the observed process dynamics imply that long term rates of valley incision should be especially sensitive to climatic oscillations between episodes of drought and warm season convective rainfall

kinematics of arc continent collision in the eastern central range of taiwan inferred from geomorphic analysis active arc continent collision in taiwan is an example of a typical collisional orogen with a deformed continental margin foothills belt hsueshan range and central range separated from an accreted island arc coastal range by a collapsed forearc basin longitudinal valley the geomorphology of the eastern central range reflects spatial and temporal variations in uplift rate and pattern along the orogen during late quaternary time digitized drainage basin perimeters stream channels and the mountain piedmont junction of a 200 km long segment of the eastern central range provide data for calculating quantitative geomorphic parameters statistical analyses of these parameters define four domains of distinct landscape character the northern domain extends northward along the coast from the northern end of the longitudinal valley lv and has landscape characteristics suggesting uplift near the mountain front the central two domains are adjacent to the lv and show evidence of uplift concentrated in the interior of the range away from the front the boundary between the two central domains occurs near the middle of the lv the southern domain extends southward along the coast from the southern end of the lv and has characteristics suggesting a transient response to increased uplift rate analysis of fluvial terrace profiles in the central range adjacent to the southern half of the lv indicates a change in uplift pattern through time with migration of maximum uplift rate from the mountain front to the interior of the range this change probably occurred just prior to late pleistocene time

colorado river long profile metrics knickzones and their meaning abstract the numerical analysis of river long profiles has a rich history and is experiencing a rejuvenation with the advent of improved terrain models and computational tools the highly variable profile and the unusual hydrology of the green colorado river system crossing the colorado plateau provide an example that is germane to debates about transient versus equilibrium knickzone features about the controls of baselevel change due to drainage integration or differential uplift and the role of adjustments to climate hydrology and changing bedrock in order to explore these controls in more detail we define objective geologic study reaches along the green colorado river calculate unit stream power and develop a discharge adjusted steepness index kqsn that avoids the scaling assumptions in substituting contributing area for discharge which are erroneous in this dryland setting determining the nature of knickzones is key and the colorado plateau is a prime setting for study because of the legacy of previous work and a burst of new research and debate the four canyon knickzones along the green colorado are characterized by energy expenditure an order of magnitude greater than in intervening reaches and our kqsn proxy tracks stream power well the strong coincidence of the grand canyon cataract canyon and eastern uinta knickzones with stronger bedrock and mass movement inputs suggests they are pinned equilibrium adjustments to greater bed resistance with the possible exception of desolation canyon as a transient feature marked by anomalous profile convexity along the trunk drainage the knickzone anomalies become greater downstream this and patterns of kqsn in headwater tributaries correspond to some proposed sources of broad mantle driven uplift but they do not match other proposed uplift patterns thus a poorly understood decoupling of topography and proposed uplift exists in some regions