investigation by multivariate analysis of groundwater composition in a multilayer aquifer system from north africa a multi tracer approach abstract a multi tracer approach has been carried out in the sbeitla multilayer aquifer system central tunisia to investigate the geochemical evolution the origin of groundwaters and their circulation patterns it involves statistical data analysis coupled with the definition of the hydrochemical and isotopic features of the different groundwaters principal components analysis pca of geochemical data used in conjunction with bivariate diagrams of major and trace elements indicate that groundwater mineralization is mainly controlled by water rock interaction and anthropogenic processes in relation to return flow of irrigation waters the pca of isotopic data and bivariate conventional diagrams of stable and radiogenic isotopes i e 18o vs 2h and 18o vs 14c provide valuable information about the origin and the circulation patterns of the different groundwater groups they permit classifying groundwaters into three groups the first group is characterized by low 3h concentrations low 14c activities and depleted stable isotope contents it corresponds to an old end member in relation with palaeoclimatic recharge which occurred during the late pleistocene and the early holocene humid periods the second group is distinguished by high to moderate 3h concentrations high 14c activities and enriched heavy isotope signatures it corresponds to a modern end member originating from a mixture of post nuclear and present day recharge in relation to return flow of irrigation waters the third group is characterized by an average composition of stable and radiogenic isotope signatures it provides evidence for the mixing between the upward moving palaeoclimatic end member and the downward moving present day end member

stream length gradient hotspot and cluster analysis sl hca to fine tune the detection and interpretation of knickzones on longitudinal profiles abstract this work presents a new approach for fine tuning the analysis of stream longitudinal profiles we show that applying hotspot and cluster analysis hca based on the getis ord gi statistic to the stream length gradient sl index improves the visualization of anomalous values assisting in the identification of tectonic structures and large landslides high positive gi values indicate the clustering of sl anomalies hotspots and mirror the occurrence of knickzones on the stream long profiles we applied this methodology to a mountainous sector of the eastern emilia romagna region in northern italy remote sensing and field surveys conducted on hotspot sites indicate that large landslides are the main process associated to over steepened long profile segments along streams connected to the valley slopes along stream changes in bedrock resistance accounts for the main anomalies within sectors where hillslopes and valley floors are disconnected we demonstrate that specific relationships between geometry and intensity of sl hotspots are indicative of the process responsible for the knickzone formation and in particular that tectonic structures generally provide the longest and highest anomalies the results of this work suggest that sl hca maps are more advantageous for detecting and interpreting knickzones compared with traditional sl maps since i they need less input data to be computed thus making them useful to investigate regions poorly covered by detailed geological data and or where field surveys are difficult to be carried out and ii the hotspot geometry can help discriminate the knickzones attributable to gravitational mass movements from litho structural ones

stochastic inversion of seismic pp and ps data for reservoir parameter estimation we have investigated the value of isotropic seismic converted wave i e ps data for reservoir parameter estimation using stochastic approaches based on a floating grain rockphysics model we first performed statistical analysis on a simple two layer model built on actual borehole logs and compared the relative value of ps data versus amplitudevariation with offset avo gradient data for estimating the floating grain fraction we found that ps data were significantly more informative than avo gradient data in terms of likelihood functions and the combination of ps and avo gradient data together with pp data provided the maximal value for the reservoir parameter estimation to evaluate the value of ps data under complex situations we developed a hierarchical bayesian model to combine seismic pp and ps data and their associated time registration we extended a model based bayesian method developed previously for inverting seismic pp data only by including ps responses and time registration as additional data and ps traveltime and reflectivity as additional variables we applied the method to a synthetic six layer model that closely mimics real field scenarios we foundthatpsdataprovidedmoreinformationthan avo gradient data for estimating the floating grain fraction porosity net to gross and layer thicknesses when their corresponding priors were weak

inversion of fluvial channels for paleorock uplift rates in taiwan the transient response of erosion to changes in rock uplift rate leads to the preservation of rock uplift history in the long profiles of rivers however extracting this information is nontrivial as changes in channel steepness are the result of both spatial and temporal changes in rock uplift rate as well as other factors such as climate and rock type we exploit an analytical linear solution for river channel profile evolution in response to erosion and tectonic uplift to investigate the rock uplift history of taiwan the analytical approach allows us to solve the linear inverse problem efficiently extracting rock uplift as a function of space and time from digital elevation data we assess the potential of fluvial topography to resolve rock uplift rates using three approaches 1 a synthetic resolution test 2 analysis of the forward model to demonstrate where in space and time the fluvial topography constrains rock uplift rate and 3 interpretation of the model resolution matrix furthermore the potential to analyze large data sets reduces the influence of stochastic processes such as landslides small scale river network reorganization and also local lithological variability in taiwan our analysis suggests that current rock uplift rates exceed erosion rates across much of the island and that there has been an increase in rock uplift rates since 0 5 ma across the central range

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem 1 fluvial erosion of bedrock occurs during occasional flood events when boundary shear stress exceeds a critical threshold to initiate incision therefore efforts to model the evolution of topography over long timescales should include an erosion threshold and should be driven by a stochastic distribution of erosive events however most bedrock incision models ignore the threshold as a second order detail in addition climate is poorly represented in most landscape evolution models so the quantitative relationship between erosion rate and measurable climatic variables has been elusive here we show that the presence of an erosion threshold when combined with a well constrained probabilistic model of storm and flood occurrence has first order implications for the dynamics of river incision in tectonically active areas first we make a direct calculation of the critical shear stress required to pluck bedrock blocks for a field site in new york second we apply a recently proposed stochastic threshold bedrock incision model to a series of streams in california with known tectonic and climatic forcing previous work in the area has identified a weak relationship between channel gradient or relief and rock uplift rate that is not easily explained by simpler detachment limited models the results with the stochastic threshold model show that even low erosion thresholds which are exceeded in steep channels during high frequency flood events fundamentally affect the predicted relationship between gradient and uplift rate in steady state rivers in a manner consistent with the observed topography this correspondence between theory and data is however nonunique models in which a thin alluvial cover may act to inhibit channel incision in the low uplift rate zone also provide plausible explanations for the observed topography third we explore the broader implications of the stochastic threshold model to the development of fluvial topography in active tectonic settings we suggest that continued field applications of geomorphic models including physically meaningful thresholds and stochastic climate distributions are required to advance our knowledge of interactions among surficial climatic and crustal processes

struggles with stream power connecting theory across scales abstract two empirically consistent explanations exist for the morphology and dynamics of bedrock rivers the stream power law appears to explain rates of rock incision at large scale large drainage basins or landscape scale but appears to be of limited value in predicting reach scale morphology and dynamics the underlying reason why stream power is such an effective tool for understanding landscape evolution is because it is an explicit representation of the inverse power relation between slope and area in rivers incising bedrock this morphometric relation is nearly universal subject to exogenous contingencies independent testing and validation of the stream power incision model is challenging because of the contingencies that exist in almost all landscapes mechanistic models of erosion have been tested and validated at small scales generally below the reach scale and opportunities exist for independent testing and validation by using them to predict reach scale morphologies predicting larger scale bedrock river morphology requires the assumption that flow sediment fluxes and bedrock erosion processes that occur at smaller scale are adequately averaged at larger scales which is not well supported reconciling these two scales of explanation is one of the grand challenges of fluvial geomorphology unless we accept that theory and explanations will be scale delimited

quantifying differential rock uplift rates via stream profile analysis despite intensive research into the coupling between tectonics and surface processes our ability to obtain quantitative information on the rates of tectonic processes from topography remains limited due primarily to a dearth of data with which to test and calibrate process rate laws here we develop a simple theory for the impact of spatially variable rock uplift rate on the concavity of bedrock river profiles application of the analysis to the siwalik hills of central nepal demonstrates that systematic differences in the concavity of channels in this region match the predictions of a stream power incision model and depend on the position and direction of the channel relative to gradients in the vertical component of deformation rate across an active fault bend fold furthermore calibration of model parameters from channel profiles argued to be in steady state with the current climatic and tectonic regime indicates that 1 the ratio of exponents on channel drainage area and slope m n is 0 46 consistent with theoretical predictions 2 the slope exponent is consistent with incision either linearly proportional to shear stress or unit stream power n 0 66 or n 1 respectively and 3 the coefficient of erosion is within the range of previously published estimates mean k 4 3 10 4 m 0 2 yr application of these model parameters to other channels in the siwalik hills yields estimates of spatially variable erosion rates that mimic expected variations in rock uplift rate across a fault bend fold thus the sensitivity of channel gradient to rock uplift rate in this landscape allows us to derive quantitative estimates of spatial variations in erosion rate directly from topographic data

plateau reduction by drainage divide migration in the eastern cordillera of colombia defined by morphometry and 10be terrestrial cosmogenic nuclides catchment wide erosion rates were defined using 10be terrestrial cosmogenic nuclides for the eastern cordillera of the colombian andes to help determine the nature of drainage development and landscape evolution the eastern cordillera characterized by a smooth axial plateau bordered by steep flanks has a mean erosion rate of 11 1 mm ka across the plateau and 70 10 mm ka on its flanks with local high rates of 400 mm ka the erosional contrast between the plateau and its flanks was produced by the increase in the orogen regional slope derived from the progressive shortening and thickening of the eastern cordillera the erosion rates together with digital topographic analysis show that the drainage network is dynamic and confirms the view that drainage divides in the eastern cordillera are migrating towards the interior of the mountain belt resulting in progressive drainage reorganization from longitudinal to transverse dominated rivers and areal reduction of the sabana de bogota plateau this article is protected by copyright all rights reserved

assessing cave internal aerology in understanding carbon dioxide co 2 dynamics implications on calcite mass variation on the wall of lascaux cave france carbon dioxide gas is a key component in dissolution and precipitation of carbonates in karst and cave systems therefore characterizing the internal aerology of a cave is essential to obtain the spatiotemporal distribution of temperature and co2 level in this research lascaux cave france an important adorned cavity was studied first the spatiotemporal distribution of co2 and temperatures were examined using continuous monitoring at a per minute basis high resolution spatial measurements 14 pco2 locations and 27 locations for temperature were carried out for a year in the epikarst and the cave february 2015 to february 2016 the spatiotemporal analysis presents that air and rock temperatures vary for less than a degree celsius 12 4 12 9 c these are controlled by the conduction of the external thermal waves through the overlying calcarenite massif as a consequence two seasonal internal aerologic regimes were identified stratification and convection these regimes govern the spatiotemporal distribution of the co2 levels 1 1 3 7 showing that this parameter is a good natural marker of the internal air movements second a method was proposed to estimate the calcite mass potentially affected by condensation water dissolution process and exfiltration water precipitation process this method based on numerical simulations relies on co2 and air and rock temperature spatiotemporal distributions in the cave third the method was applied using the case of the left wall of the hall of the bulls one of the most adorned part of the cave results showed that the calcite mass possibly dissolved varies from 0 0002 to 0 006 g when the mass potentially precipitated is higher from 0 013 to 0 067 g depending on the aerologic conditions this method allows determining which alteration process e g precipitation or dissolution could eventually lead to the largest variation of calcite on the wall the results can serve as useful data to the cave experts of the french ministry of culture and communication in terms of lascaux cave management policies

transient fluvial incision in the headwaters of the yellow river northeastern tibet china 1 we utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the anyemaqen shan a broad mountainous region in the northeastern tibetan plateau tributary channels to the yellow river display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles steep lower reaches of channels are associated with rapid 1 m ka incision rates along the yellow river while upstream reaches are associated with relatively slow 0 05 0 1 m ka erosion of soil mantled uplands covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long wavelength differential rock uplift across the range geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream the upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed consistent with knickpoint migration as a kinematic rather than diffusional wave tributary channel gradients downstream of knickpoints however display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient k increases during incision our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level

scaling and elevation in river networks the analysis of large river networks obtained from digital elevation models has given insight into the variation of channel slope with scale investigators have recently suggested that channel slopes are self similar with magnitude or area as a scaling parameter our data indicates otherwise in particular the variance of channel slope is larger than that predicted by simple self similarity this suggests multiscaling the scaling exponent for the standard deviation is approximately half the corresponding exponent in the relationship of the slope mean to magnitude or area a model for channel slopes based on a point process of elevation drops along the channel is presented the model reproduces observed multiscaling properties when the density of elevation increments is related to area or magnitude as a

investigating transport properties and turbidity dynamics of a karst aquifer using correlation spectral and wavelet analyses in many places throughout the world drinking water is frequently contaminated by turbidity such turbidity however as representative of particle transport can be used as to trace certain features of particle transport properties in order to investigate the relation between particle and dissolved species transport and hydrodynamics in karst systems correlation and spectral analyses were performed on time series of rainfall input signal and water level specific conductance and turbidity output signals at a karst spring system in the chalk aquifer of the lower seine valley france this system is composed of a spring connected to a sinkhole on the chalk plateau where a small creek enters the subsurface the autocorrelation functions for water level and turbidity showed a short memory effect demonstrating the short duration of the influence of flood events on these two parameters whereas specific conductance representing less mineralized storm derived water had a much longer memory effect these results were interpreted as reflecting the rapid reactivity of the spring to rain events with storage of water in the fissured chalk explaining the longer memory effect for specific conductance than for particles energy spectra computed by fast fourier transform of autocorrelation functions showed a strong structure in the output signals whereas the input signal rainfall was random thus allowing assessment and comparison of system behaviour regarding dissolved and solid transport as well as hydraulics cross correlation functions which allow an assessment of impulse response functions confirmed the low inertia of the system for water level and turbidity and the much higher inertia for specific conductance in addition to the main peak two secondary peaks in the cross correlation functions suggest the existence of additional flowpaths that might involve the contribution of other point source recharge and or delayed infiltration through the clayey surficial formation and solution pipes which could act as epikarst analysis using continuous wavelet spectra allowed a better investigation of the rainfall signal structure and highlighted a strong relationship between turbidity and rainfall which could not be deduced from the energy spectra specific spectral components in water level were isolated and a time domain reconstruction using inverse wavelet transform allowed separation of quick flow and slow flow components

glacial steady state topography controlled by the coupled influence of tectonics and climate glaciers and rivers are the main agents of mountain erosion while in the fluvial realm empirical relationships and their mathematical description such as the stream power law improved the understanding of fundamental controls on landscape evolution simple constraints on glacial topography and governing scaling relations are widely lacking we present a steady state solution for longitudinal profiles along eroding glaciers in a coupled system that includes tectonics and climate we combined the shallow ice approximation and a glacial erosion rule to calculate ice surface and bed topography from prescribed glacier mass balance gradient and rock uplift rate our approach is inspired by the classic application of the stream power law for describing a fluvial steady state but with the striking difference that in the glacial realm glacier mass balance is added as an altitude dependent variable from our analyses we find that ice surface slope and glacial relief scale with uplift rate with scaling exponents indicating that glacial relief is less sensitive to uplift rate than relief in most fluvial landscapes basic scaling relations controlled by either basal sliding or internal deformation follow a power law with the exponent depending on the exponents for the glacial erosion rule and glen s flow law in a mixed scenario of sliding and deformation complicated scaling relations with variable exponents emerge furthermore a cutoff in glacier mass balance or cold ice in high elevations can lead to substantially larger scaling exponents which may provide an explanation for high relief in high latitudes

river incision into bedrock mechanics and relative efficacy of plucking abrasion and cavitation improved formulation of bedrock erosion laws requires knowledge of the actual processes operative at the bed we present qualitative field evidence from a wide range of settings that the relative efficacy of the various processes of fluvial erosion e g plucking abrasion cavitation solution is a strong function of substrate lithology and that joint spacing fractures and bedding planes exert the most direct control the relative importance of the various processes and the nature of the interplay between them are inferred from detailed observations of the morphology of erosional forms on channel bed and banks and their spatial distributions we find that plucking dominates wherever rocks are well jointed on a submeter scale hydraulic wedging of small clasts into cracks bashing and abrasion by bedload and chemical and physical weathering all contribute to the loosening and removal of joint blocks in more massive rocks abrasion by suspended sand appears to be rate limiting in the systems studied here concentration of erosion on downstream sides of obstacles and tight coupling between fluid flow patterns and fine scale morphology of erosion forms testify to the importance of abrasion by suspended load rather than bedload particles mechanical analyses indicate that erosion by suspended load abrasion is considerably more nonlinear in shear stress than erosion by plucking in addition a new analysis indicates that cavitation is more likely to occur in natural systems than previously argued cavitation must be considered a viable process in many actively incising bedrock channels and may contribute to the fluting and potholing of massive unjointed rocks that is otherwise attributed to suspended load abrasion direct field evidence of cavitation erosion is however lacking in terms of the well known shear stress or stream power erosion law erosion by plucking is consistent with a slope exponent n of 2 3 to 1 whereas erosion by suspended load abrasion is more consistent with a slope exponent of 5 3 given that substrate lithology appears to dictate the dominant erosion process this finding has important implications for long term landscape evolution and the models used to study it

differentiated spring behavior under changing hydrological conditions in an alpine karst aquifer abstract limestone massifs with a high density of dolines form important karst aquifers in most of the alps often with groundwater circulating through deep karst conduits and water coming out of closely spaced springs with flow rates of over some cubic meters per second although several hydrogeological studies and tracing experiments were carried out in many of these carbonate mountains in the past the hydrogeology of most of these karst aquifers is still poorly known geological hydrodynamic and hydrochemical investigations have been carried out in one of the most representative of these areas cansiglio monte cavallo ne italy since spring 2015 in order to enhance the knowledge on this important type of aquifer system additionally a cave to spring multitracer test was carried out in late spring 2016 by using three different fluorescent tracers this hydrogeological study allowed 1 gathering new detailed information on the geological and tectonic structure of such alpine karst plateau 2 defining discharge rates of the three main springs gorgazzo santissima and molinetto by constructing rating curves 3 understanding the discharging behavior of the system with respect to different recharge conditions 4 better defining the recharge areas of the three springs the three nearby springs the spring front stretches over 5 km that drain the investigated karst aquifer system show different behaviors with respect to changing discharge conditions demonstrating this aquifer to be divided in partially independent drainage systems under low flow conditions when their chemistry is clearly differentiated under high flow conditions waters discharging at all springs show more similar geochemical characteristics the combination of geochemistry hydrodynamic monitoring and dye tracing tests has shown that the three springs have different recharge areas the study points out that even closely spaced karst springs that apparently drain the same karst mountain can have different behaviors and thus distinctive reactions toward polluting events a characteristic to be taken into account for their management

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

stress induced seismic azimuthal anisotropy sand shale content and depth trends offshore north west australia abstractseismic azimuthal anisotropy is apparent when p wave velocities vary with source receiver azimuth and downward propagating s waves split into two quasi s waves polarized in orthogonal directions not accounting for these effects can degrade seismic image quality and result in erroneous amplitude analysis and geologic interpretations there are currently no physical models available to describe how azimuthal anisotropy induced by differential horizontal stress varies with sand shale lithology and depth we develop a model that does so in unconsolidated sand shale sequences offshore north west australia our method naturally introduces two new concepts critical anisotropy and anisotropic depth limit critical anisotropy is the maximum amount of azimuthal anisotropy expected to be observed at the shallowest sediment burial depth where the confining pressure and sediment compaction are minimal the anisotropic depth limit is the maximum depth where the stress induced azimuthal anisotropy is ex

structure and water storage capacity of a small karst aquifer based on stream discharge in southwest china summary karst spring stream discharge reflects the global configuration of the aquifer however quantitative description of the aquifer structure such as effective porosity neff and water storage capacity by the discharge analysis is difficult because of the complex conduit fracture system this study attempted to quantify the characteristics of karst aquifer based on discharge recession and time series analysis methods three recession models including modified maillet mangin and boussinesq models were evaluated to choose the most suitable one for analyzing the aquifer structure and auto correlation and cross correlation functions were applied to study the aquifer response in both year and rainfall event time scales the results showed that the modified maillet model was more suitable in the study catchment with mangin model overestimating and boussinesq model underestimating the discharge the neff was 3 73 for the total aquifer and it was 0 07 0 33 and 3 33 for the conduit fracture and matrix respectively based on a case study of a rainfall event with precipitation of 68 mm the water volumes drained by the three media were 25 43 33 40 and 41 17 respectively this indicates that although conduit network is not very developed with lower neff it is still an important water transmissive element draining more than a quarter of water after the rainfall event the memory time of the aquifer was 4 days for the year scale and 8 h for the rainfall event 68 mm scale this demonstrates that the aquifer has a well developed drainage system with a quick response to the rainfall the above results provide further insights for hydrological processes modeling and water resources management for the small catchment in karst regions

dissolved oxygen fluctuations in karst spring flow and implications for endemic species barton springs edwards aquifer texas usa summary karst aquifers and springs provide the dissolved oxygen critical for survival of endemic stygophiles worldwide but little is known about fluctuations of dissolved oxygen concentrations do and factors that control those concentrations we investigated temporal variation in do at barton springs austin texas usa during 2006 2012 do fluctuated by as much as a factor of 2 and at some periods decreased to concentrations that adversely affect the barton springs salamander eurycea sorosum 4 4 mg l a federally listed endangered species endemic to barton springs do was lowest 4 4 mg l when discharge was low 1 m 3 s and spring water temperature was 21 c although not at a maximum the minimum do recorded was 4 0 mg l relatively low do 3 s and maximum t 22 2 c a four segment linear regression model with daily data for discharge and spring water temperature as explanatory variables provided an excellent fit for mean daily do nash sutcliffe coefficient for the validation period of 0 90 do also fluctuated at short term timescales in response to storms and do measured at 15 min intervals could be simulated with a combination of discharge spring temperature and specific conductance as explanatory variables on the basis of the daily data regression model we hypothesize that more frequent low do corresponding to salamander mortality could result from i lower discharge from barton springs resulting from increased groundwater withdrawals or decreased recharge as a result of climate change and or ii higher groundwater temperature as a result of climate change

dissolved organic carbon of infiltration within the autogenic karst hydrosystem this work aims at using the dissolved organic carbon doc as a tracer of infiltration in karstic aquifers with only diffuse recharge regular measurements of doc have been carried out in three karstic systems located in south eastern france during an hydrogeological cycle considering that the doc is mainly located in the soil it might be used as a tracer of the infiltration the behavior of the tracer considerably varies between the high and low flow periods the low concentrations of doc occur when the flow is mainly due to a long residence time of the water in the saturated zone whereas the concentration of doc increases with the contribution of recent waters during the flood period so the doc can be used as a tracer of the infiltration a comparison between the magnesium and the doc allows to demonstrate the ability of using the doc as a tracer of the water residence time

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

rainfall runoff relations for karstic springs part i convolution and spectral analyses karstic basins contain large reserves of subsurface water in this paper three karstic systems located in the pyrenees mountains ariege france are studied long records of rainfall and discharge rates for these karstic springs are available sampled at different rates daily hourly and half hourly this study aims at illustrating and assessing the capabilities and limitations of linear black box methods for analysing rainfall runoff type relationships and reconstructing runoffs from rainfall rate data using such systems in this study precipitation and discharge rates are considered as two autocorrelated and cross correlated stochastic processes a linear and stationary rainfall runoff model is adopted which is used for identification and simulation purposes different versions are analysed including a model based on a convolution integral between the precipitation rate p and a transfer function h t which can be thought of as the unit impulse response of the system it is shown that this linear stochastic model i e the statistical version although accurate in some respects does not represent the hydraulic behaviour of the system very well during low flow episodes and floods it is also shown that the use of fourier analysis alone does not lead to a satisfactory reconstitution of observed runoff sequences for these reasons the use of non linear random process input output models based on volterra integral series is proposed and discussed

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

understanding erosion rates in the himalayan orogen a case study from the arun valley understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution denudation rates derived from terrestrial cosmogenic nuclides tcns are commonly used to quantify erosion and bridge tectonic myr and climatic up to several kiloyears time scales however how the processes of erosion in active orogens are ultimately reflected in 10be tcn samples remains a topic of discussion we investigate this problem in the arun valley of eastern nepal with 34 new 10be derived catchment mean denudation rates the arun valley is characterized by steep north south gradients in topography and climate locally denudation rates increase northward from 0 2 mm yr 1 to 1 5 mm yr 1 in tributary samples while main stem samples appear to increase downstream from 0 2 mm yr 1 at the border with tibet to 0 91 mm yr 1 in the foreland denudation rates most strongly correlate with normalized channel steepness r2 0 67 which has been commonly interpreted to indicate tectonic activity significant downstream decrease of 10be concentration in the main stem arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample this results in 10be concentrations and denudation rates that do not uniformly represent the upstream catchment area we observe strong impacts on 10be concentrations from local nonfluvial geomorphic processes such as glaciation and landsliding coinciding with areas of peak rainfall rates pointing toward climatic modulation of predominantly tectonically driven denudation rates

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

relict landscape resistance to dissection by upstream migrating knickpoints expanses of subdued topographies are common at high elevation in mountain ranges they are often interpreted as relict landscapes and are expected to be replaced by steeper topography as erosion proceeds preservation of such relict fragments can merely reflect the fact that it takes time to remove any preexisting topography however relict fragments could also possess intrinsic characteristics that make them resilient to dissection we document here the propagation of a wave of dissection across an uplifted relict landscape in puerto rico using 10be 26al burial dating on cave sediments we show that uplift started 4 ma and that river knickpoints have since migrated very slowly across the landscape modern detrital 10be erosion rates are consistent with these long term rates of knickpoint retreat analysis of knickpoint distribution combined with visual observations along the streambeds indicates that incision by abrasion and plucking is so slow that bedrock weathering becomes a competing process of knickpoint retreat the studied rivers flow over a massive stock of quartz diorite surrounded by an aureole of metavolcanic rocks earlier studies have shown that vegetation over the relict topography efficiently limits erosion allowing for the formation of a thick saprolite underneath such slow erosion reduces streambed load fluxes delivered to the knickpoints as well as bed load grain size both processes limit abrasion compounding the effect of slow abrasion wide joint spacing in the bedrock makes plucking infrequent thus the characteristics of the relict upstream landscape have a direct effect on stream incision farther downstream reducing the celerity at which the relict subdued landscape is dissected we conclude that similar top down controls on river incision rate may help many relict landscapes to persist amidst highly dissected topographies

relative importance of the saturated and the unsaturated zones in the hydrogeological functioning of karst aquifers the case of alta cadena southern spain summary from analysis of the hydrodynamic and hydrochemical responses of karst springs it is possible to know the behaviour of the aquifers they drain this manuscript aims to contribute to the characterization of infiltration process and to determine the relative importance of the saturated zone and of the unsaturated zone in the hydrogeological functioning of carbonate aquifers using natural hydrochemical tracers thus chemical components together with temperature and electrical conductivity both punctual and continuous records have been monitored in three springs which drain alta cadena carbonate aquifer southern spain an evaluation of the percentage of the electrical conductivity frequency peaks determined for each of the three springs is linked to the chemical parameters that comprise the conductivity signal one of these springs responds rapidly to precipitation conduit flow system due to the existence of a high degree of karstification in the unsaturated zone and in the saturated zone both of which play a similar role in the functioning of the spring another spring responds to precipitation with small increases in water flow somewhat lagged because the aquifer has a low degree of karstification even in the unsaturated zone which seems to influence its functioning more strongly than does the saturated zone the third spring drains a sector of the aquifer with a moderately developed degree of karstification one that is intermediate between the other two in which both the unsaturated zone and the saturated zone participate in the functioning of the spring but with the latter zone having a stronger influence these three springs show different hydrogeological functioning although they are in similar geological and climatic contexts which show the heterogeneity of karst media and the importance of an adequate investigation for groundwater management and protection in karst areas

squeezing river catchments through tectonics shortening and erosion across the indus valley nw himalaya tectonic displacement of drainage divides and the consequent deformation of river networks during crustal shortening have been proposed for a number of mountain ranges but never tested in order to preserve crustal strain in surface topography surface displacements across thrust faults must be retained without being recovered by consequent erosion quantification of these competing processes and the implications for catchment topography have not previously been demonstrated here we use structural mapping combined with dating of terrace sediments to measure quaternary shortening across the indus river valley in ladakh nw himalaya we demonstrate 0 21 m k y 1 of horizontal displacement since ca 45 ka on the stok thrust in ladakh which defines the southwestern margin of the indus valley catchment and is the major back thrust to the tethyan himalaya in this region we use normalized river channel gradients of the tributaries that drain into the indus river to show that the lateral continuation of the stok thrust was active for at least 70 km along strike shortening rates combined with fault geometries yield vertical displacement rates that are compared to time equivalent erosion rates in the hanging wall derived from published detrital 10be analyses the results demonstrate that vertical displacement rates across the stok thrust were approximately twice that of the time equivalent erosion rates implying a net horizontal displacement of the surface topography and hence narrowing of the indus valley at 0 1 m k y 1 a fill terrace records debris flow emplacement linked to thrust activity resulting in damming of the valley and extensive lake development conglomerates beneath some of the modern alluvial fans indicate a northeastward shift of the indus river channel since ca 45 ka to its present course against the opposite side of the valley from the stok thrust the integration of structural topographic erosional and sedimentological data provides the first demonstration of the tectonic convergence of drainage divides in a mountain range and yields a model of the surface processes involved

role of karstification and rainfall in the behavior of a heterogeneous karst system the complex functioning of karst systems depends on several factors e g geology karstification status climate which influence flow conditions understanding a system requires monitoring that includes a sampling interval well adapted to the system s size and the use of hydrodynamic and geochemical approaches from our own observations the general physical and geochemical characteristics of the aquifers are perennial and representative of karst evolution at a given moment the notre dame des anges karst system which is situated in france on the rim of the vaucluse karst region was studied during 2 water years this study demonstrates that several parameters are not definitive and that they do not provide information about the actual status of the karst evolution of the system we were able to observe that hydrological parameters in particular are dependent on the configuration of the outlets which can dramatically change for example a heavy storm 300 mm of rain in 4 h which occurred in the intake area on 22 september 1992 produced a piston effect in the aquifer which was expressed by extensive unclogging of the whole aquifer the appearance of a new gryphon at the outlet induced a change in the flow rate and added to the unclogging

use of total organic carbon toc as tracer of diffuse infiltration in a dolomitic karstic system the nerja cave andalusia southern spain 1 recent studies in several karstic systems in france have highlighted that total organic carbon toc was a relevant parameter in order to characterise the behaviour of aquifers to differentiate the water types that participate in karstic flow fast infiltration unsaturated zone saturated zone and to evaluate their vulnerability this study on toc dynamics at the experimental site of the nerja cave has been performed to test the potential of this tracer in a particular climatic mediterranean climate lithologic dolomitic marbles and hydrodynamic diffuse flow behaviour context toc evolution compared to those of classical tracers used in hydrogeology permits the understanding of the hydrodynamical behaviour of the unsaturated zone of this dolomitic aquifer whose response to precipitation is slower than that commonly obtained in karstic aquifers of calcareous nature

abrupt changes in the rate of andean plateau uplift from reversible jump markov chain monte carlo inversion of river profiles abstract knowledge of the rate of surface uplift of the central andean plateau provides important boundary conditions for regional geodynamic models and paleoclimate reconstructions here we present a fully nonlinear inverse method to extract the rock uplift history of the central andean plateau from the cotahuasi river and its tributaries our approach is based on an analytical solution to the stream power model that relates elevation to rock uplift history under the assumptions of constant climatic conditions in space and time and spatially invariant rock uplift we use a bayesian framework that allows us to quantify the full state of knowledge of model parameters i e uncertainties trade offs the erosional efficiency defines the landscape response time and this must be determined using independent data therefore using thermochronometric data from the cotahuasi ocona canyon which record rapid fluvial incision at 13 10 ma we calibrate our results to infer a rock uplift history for the north central andean plateau we infer a pulse of rock uplift between 25 and 10 ma at rates as high as 0 25 km my however the rock uplift rate inferred during this pulse is not as high as is predicted if the central andean plateau grew as a result of loss of unstable lithospheric mantle therefore our results are more consistent with models requiring gradual uplift of the central andean plateau

paleogene initiation of the western branch of the east african rift the uplift history of the rwenzori mountains western uganda abstract the two branches of the east african rift system ears are believed to have initiated diachronously however a growing body of work continues to suggest the onset of rifting in the western branch occurred in the paleogene coeval to the eastern branch due to a lack of pre miocene stratigraphy attempts to resolve the geological history of the western branch must study the uplift and erosional histories of the modern rift topography in this study the rock uplift history of the rwenzori mountains western uganda is resolved to better our understanding of the tectonic history of the western branch of the ear through the application of low temperature thermochronology mapping and the modelling of river profiles we show that rock uplift of the rwenzori dates back to the oligocene with thermal history models suggesting uplift induced exhumation may date back as far as the eocene this provides tangible evidence that extension began in the region in the paleogene coeval with the eastern branch and not the late neogene these results have broad implications for the tectonic evolution of the entire east african rift system and suggest our current understanding of the region s rift history remains incomplete

lithological control on the post orogenic topography and erosion history of the pyrenees abstract numerous studies on active mountain ranges have demonstrated the interaction between tectonics and climate in shaping topography here we explore how variations in rock types have affected the topographic development of the pyrenees since cessation of orogenesis ca 20 ma our study is based on a multidisciplinary approach and integrates topographic analyses rock strength measurements and thermal modelling of low temperature thermochronological data published across the central pyrenees results indicate a strong influence of rock strength in determining the post orogenic morphology of the pyrenees we observe a correlation between rock strength and the normalized channel steepness index k s n of the different lithologies moreover the highest topography is dominated by the variscan plutonic massifs which have highest rock strength consequently the drainage divide appears to track the position of these massifs abrupt deceleration of exhumation recorded in inverse modelling of low temperature thermochronologic data suggests that the exhumation of the variscan massifs also played role in lowering in erosion rates over the massifs during orogenesis

field measurements of incision rates following bedrock exposure implications for process controls on the long profiles of valleys cut by rivers and debris flows until recently published rates of incision of bedrock valleys came from indirect dating of incised surfaces a small but growing literature based on direct measurement reports short term bedrock lowering at geologically unsustainable rates we report observations of bedrock lowering from erosion pins monitored over 1 7 yr in 10 valleys that cut indurated volcanic and sedimentary rocks in washington oregon california and taiwan most of these channels have historically been stripped of sediment their bedrock is exposed to bed load abrasion plucking and seasonal wetting and drying that comminutes hard intact rock into plates or equant fragments that are removed by higher fl ows consequent incision rates are proportional to the square of rock tensile strength in agreement with experimental results of others measured rates up to centimeters per year far exceed regional long term erosionrate estimates even for apparently minor sediment transport rates cultural artifacts on adjoining strath terraces in washington and taiwan indicate at least several decades of lowering at these extreme rates lacking sediment cover lithologies at these sites lower at rates that far exceed long term rock uplift rates this rate disparity makes it unlikely that the long profi les of these rivers are directly adjusted to either bedrock hardness or rock uplift rate in the manner predicted by the stream power law despite the observation that their profi les are well fi t by power law plots of drainage area vs slope we hypothesize that the threshold of motion of a thin sediment mantle rather than bedrock hardness or rock uplift rate controls channel slope in weak bedrock lithologies with tensile strengths below 3 5 mpa to illustrate this hypothesis and to provide an alternative interpretation for power law plots of area vs slope we combine shields threshold transport concept with measured hydraulic relationships and downstream fi ning rates in contrast to fl uvial reaches none of the hundreds of erosion pins we installed in steep valleys recently scoured to bedrock by debris fl ows indicate any postevent fl uvial lowering these results are consistent with episodic debris fl ows as the primary agent of bedrock lowering in the steepest parts of the channel network above 0 03 0 10 slope

hypogene sulfuric acid speleogenesis and rare sulfate minerals in baume galiniere cave alpes de haute provence france record of uplift correlative cover retreat and valley dissection the oxidation of hydrocarbons and sulfide sources h2s pyrite produces sulfuric acid that strongly reacts with bedrock causing limestone dissolution and complex interactions with other minerals from the bedrock or from cave fillings mainly clays this type of cave development known as sulfuric acid speleogenesis sas is a subcategory of hypogene speleogenesis where aggressive water rises from depth it also produces uncommon minerals mainly sulfates the typical byproducts of sas baume galiniere is located in southern france in the vaucluse spring watershed this small maze cave displays characteristic sas features such as corrosion notches calcite geodes iron crusts and various sulfate minerals sulfur isotopes of sas byproducts jarosite and gypsum clearly show they derive from pyrite oxidation using xrd and micro raman spectroscopy thirteen minerals were identified including elemental sulfur calcite quartz pyrite goethite gypsum and fibroferrite plus all of the six members of the jarosite subgroup jarosite argentojarosite ammoniojarosite hydroniumjarosite natrojarosite plumbojarosite the baume galiniere deposits are the first documented cave occurrence of argentojarosite and the second known occurrence of plumbojarosite hydronium jarosite ammoniojarosite and fibroferrite in the vaucluse watershed there were numerous upwellings of deep water along major faults located at the contact of the karstic aquifer and the overlying impervious covers the mixing of deep and meteoric waters at shallow depths caused pyrite depositions in numerous caves including baume galiniere sulfuric acid speleogenesis occurred later after base level drop when the cave was under shallow phreatic conditions then in the vadose zone with oxidation of pyrites generating sulfuric acid attenuated oxidation is still occurring through condensation of moisture from incoming air baume galiniere cave records the position of the semi impervious paleo cover and documents its retreat in relationship to valley incision caused by uplift and tilting of the vaucluse block during the neogene

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

the mendocino triple junction active faults episodic coastal emergence and rapid uplift a complex zone of rapid holocene surface uplift and deformation occurs at the mendocino triple junction the juncture of three plate bounding faults the cascadia subduction zone san andreas fault and mendocino fault within this mountainous structural knot up to 1 4 m of coastal emergence occurred during the 1992 cape mendocino m s 7 1 earthquake surveying and radiometric dating of ancient marine strandlines 7 5 along the cascadia subduction zone megathrust however another plausible interpretation of the data is that multiple earthquakes resulting in smaller amounts of net surface uplift per event similar to the 1992 earthquake occurred closely spaced in time giving the appearance in the geologic record of less frequent and larger events regardless of the number and timing of paleoearthquakes the number of platforms is a minimum of the number of events that resulted in sudden rapid uplift because platform preservation is also a function of rising holocene sea level at present rates and patterns of net surface uplift are better constrained than the timing and magnitude of paleoearthquakes periods of rapid holocene emergence also are identified as far south of the area of 1992 uplift and the mendocino fault as 30 km along the unlocated san andreas fault these also might be associated with coseismic uplift based on new mapping of active faults in the region it is proposed here that this uplift is the result of multiple discontinuous thrust and strike slip fault segments which distribute plate boundary deformation along a restraining bend at the termination of the san andreas fault this interpretation is consistent with the fact that a single prominent strike slip fault has not been identified in the mendocino triple junction region while several small reverse faults crossing holocene deposits and geomorphic surfaces have been mapped and dated

landslides control the spatial and temporal variation of channel width in southern taiwan implications for landscape evolution and cascading hazards in steep tectonically active landscapes

investigating topographic metrics to decipher structural model and morphotectonic evolution of the frontal siwalik ranges central himalaya nepal abstract the fold and thrust belt in the himalayan front is marked by the upliftment of the frontal outermost siwalik hills along the main frontal thrust mft these frontal ranges display distinct morphology with prominent curved stair stepped and overlapping segments in the central himalaya in this study we analyse the structural framework morphology growth and relative uplift rates of the frontal ranges in the central himalaya using various topographic metrics the results suggest that the frontal ranges are folds developed along six mft segments that have interacted to form the present day topography these segments are also overlapping in some areas thus resulting in stress partitioning we also identify a nw se trending pre existing tear fault in the region that forms barrier to the growth and propagation of the mft segments and the frontal ranges along it the uplift rates are generally lower on relatively older fault segments due to initiation of the younger overlapping faults it is supported by the results of the morphometric indices as the older and less active mft segments yield high mountain front sinuosity ratio 1 3 2 2 and valley floor width to height ratio 3 3 14 6 and low values of steepness index 0 2 0 8 and hypsometric integral 0 4 0 5 growing folds along the mft segments have resulted in the deflection of the narayani and the east rapti rivers we establish a model for the initiation and growth of various structural segments in the study area and the resultant drainage reorganisation

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

diagenetic variation in the oregon coast range implications for rock strength soil production hillslope form and landscape evolution the mechanisms by which lithology modulates geomorphic processes are poorly known in the oregon coast range ocr rhythmically bedded sandstones of the eocene tyee formation underlie steep soil mantled hillslopes with relatively uniform ridge valley spacing these characteristic landforms are perturbed where diagenetic variations manifest as resistant cliffs here we use petrology rock mechanics and lidar to characterize grain scale variations in rock properties and their influence on rock strength hillslope processes and landscape morphology in two adjacent watersheds petrographic analyses suggest that a suite of diagenetic products in the resistant bedrock account for a 2 5 times increase in tensile strength relative to typical tyee bedrock our reference catchment exhibits negligible resistant outcrops and consistent hillslope gradients and longitudinal valley profiles by contrast the adjacent catchment teems with resistant 1 to 10 m thick noncontiguous sandstone beds that form hanging valleys with gentle upstream hillslopes and anomalously narrow valleys mechanical and topographic analyses suggest that the low fracture density characteristic of these resistant beds may render them relatively impervious to comminution by tree root activity the dominant ocr soil production mechanism based on both hillslope gradient and hilltop curvature erosion models we estimate that hillslopes perched above resistant beds erode at approximately half the pace of hillslopes unencumbered by downstream knickpoints the diagenetic variations likely influence relief at the watershed scale depositional position and diagenetic processes appear to control the occurrence of resistant beds providing a framework to quantify how seemingly subtle variations in rock properties can impose first order controls on landscape form and evolution

a deterministic approach to the coupled analysis of karst springs hydrographs and chemographs abstract during the chemically based recession flow phase of karstic springs the carbonate dissolved limestone concentration can be expressed as negative power of the flow rate the empirically determined conc q relationship allows two parameters and a to be defined of which one depends on the geometric dimensions of the saturated submerged karstic network in this paper we present a deterministic model which simulates the concentration of carbonate at the outlet of a network of circular rectilinear conduits as a function of flow rate this model based on hydraulic principles and the calcite dissolution kinetics allows the sensitivity of the and a parameters to be studied under different chemical physical and geometric scenarios simulation results show that a is a function of the calcite saturation concentration whereas depends on the spatial dimensions of the karstic network void length and aperture the deterministic model results were applied to real karstic systems to evaluate the geometric dimensions of submerged karstic networks

the signature of shear wave splitting theory and observations on heavy oil data the use of shear wave splitting analysis as a tool for fracture analysis is well established in this article we discuss the analysis of shear wave splitting in a relatively new context shallow heavy oil plays where we believe stress is the dominant cause of the shear wave splitting rather than macroscale fracturing there is clear laboratory evidence in the literature for shear wave splitting caused by differential stress which we believe supports this viewpoint we are particularly interested in the use of shear wave splitting technology for monitoring reservoir stress changes which correlate with thermal production for heavy oil reservoirs this article also takes a fresh look at some well established characteristics of split shear waves as they appear in wide azimuth multicomponent data and in particular the relative merits of the radial and transverse amplitude signatures we describe a recently developed method which combines both radial and transverse analysis to improve the effective azimutha

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

interpreting quaternary uplift rates at the mendocino triple junction northern california from uplifted marine terraces analysis of the altitudinal spacing of 14 flights of marine terraces indicates a spatial pattern of varying uplift rates that agrees with that determined from previously dated terraces for the past 3 81 ka and temporal changes in uplift rates from 1 m ka to 3 5 m ka that may reflect response to changes in tectonic regime during passage of the mendocino triple junction mtj a possible mechanism for regional uplift is growth of a slab window south of the mtj the region of most rapid uplift is 25 43 km south of the mtj immediately south of the northern boundary of the slab window the coastline is tilted upward to the south in the region directly above the southern edge of the subducted gorda plate at point delgada 55 km south of the present mtj where the northern edge of the slab window passes approximately 300 ka uplift rates have been 1 2 m ka for at least 330 ka more than 1 4 m y after passage of the southern edge of the subducted slab at the mendocino coast uplift rates have been less than 0 4 m ka for at least 330 ka

temperature as a marker for karstic waters hydrodynamics inferences from 1 year recording at la peyrere cave ariege france abstract we present temperature measurements recorded at a 15 min time step between october 2002 and april 2003 inside the la peyrere cave baget karstic system central pyrenees on six 0 01 c sensitivity sensors distributed on the whole recognized cave down to a depth of 57 m rainy events are associated to a steep signal of a few hundredth to a few tenth of degrees in amplitude starting 1 h to one day after rain and with a sign depending mostly of the outside temperature the temperature signal does not correlate well with the rainfall while the water level does with a maximum water rising rate 2 5 h after rain the spectral density of the temperature signal displays one peak at a period of 3 days which is also present in the rain signal and which is likely to be related to climatic parameters and a broad smooth zone of spectral energy close to a 1 day period by comparing a superficial and a deepest group of sensors we note that the flood signal is more pronounced on the deepest sensor group whatever the outside temperature and that the annual temperature variation is also larger on this sensor group this could indicate that rain water flows in the cave through its base and explain the development in depth of the cave due to the arrival of water with different temperatures and mineralizations at different levels double diffusive convection is likely to be triggered in the cave we suggest that the onset of convection could be associated to the oscillations observed on the temperature signal at the onset of the flood

cover effect in bedrock abrasion a new derivation and its implications for the modeling of bedrock channel morphology the sediment load of a bedrock river plays an important role in the fluvial incision process by providing tools for abrasion the tools effect and by covering and thereby protecting the bed the cover effect we derive a new formulation for the cover effect in which the fraction of exposed bed area falls exponentially with increasing sediment flux or decreasing transport capacity and explore its consequences for the model of bedrock abrasion by saltating bed load erosion rates predicted by the model are higher than those predicted by earlier models in a closed system the maximum erosion rate is predicted to occur when sediment supply is equal to transport capacity for a flat bed by optimizing the channel geometry to minimize the potential energy of the stream and using representative values for both discharge and grain size we derive equations for the geometry of a bedrock river and explore how predictions for width slope and bed cover vary as functions of drainage area rock uplift rate and rock strength the equations predict a dependence of channel width on drainage area similar to the relations using a simple shear stress incision law the slope area relationship is predicted to be concave up in a log log regime with a curvature dependent on uplift rate however this curvature does not deviate sufficiently from a straight line to allow discrimination between models using empirical data dependence of channel width and slope on rock uplift rate can be separated into two domains for low uplift rates channel geometry is largely insensitive to uplift rate due to a threshold effect at high uplift rates there is a power law dependence bed cover is predicted to increase progressively downstream and to increase with increasing uplift rate in our model the width to depth ratio is a function of both tectonic and climatic forcing this indicates that the scaling between channel width and bed slope is neither a unique indicator of tectonic forcing at steady state nor a signature of transience or steady state we conclude that sediment effects need to be taken into account when modeling bedrock channel morphology

cenozoic river profile development in the upper lachlan catchment se australia as a test of quantitative fluvial incision models 1 we have used early miocene valley filling basalts to reconstruct fluvial long profiles in the upper lachlan catchment se australia in order to use these as well constrained initial conditions in a forward model of fluvial incision many different fluvial incision algorithms have been proposed and it is not clear at present which one of these best captures the behavior of bedrock rivers we test five different formulations the ability of these models to reproduce the observed present day stream profiles and amounts of incision is assessed using a weighted mean misfit criterion as well as the structure of the misfit function the results show that for all models parameter combinations can be found that reproduce the amounts of incision reasonably well however for some models these best fit parameter combinations do not seem to have a physical significance whereas for some others best fit parameter combinations are such that the models tend to mimic the behavior of other models overall best fit model predictions are obtained for a detachment limited stream power model or an undercapacity model that includes a river width term that varies as a function of drainage area the uncertainty in initial conditions does not have a strong impact on model outcomes the model results suggest however that lithological variation may be responsible for variations in parameter values of a factor of 3 5

criteria and tools for determining drainage divide stability abstract watersheds are the fundamental organizing units in landscapes and thus the controls on drainage divide location and mobility are an essential facet of landscape evolution additionally many common topographic analyses fundamentally assume that river network topology and divide locations are largely static allowing channel profile form to be interpreted in terms of spatio temporal patterns of rock uplift rate relative to base level climate or rock properties recently however it has been suggested that drainage divides are more mobile than previously thought and that divide mobility and resulting changes in drainage area could potentially confound interpretations of river profiles ultimately reliable metrics are needed to diagnose the mobility of divides as part of routine landscape analyses one such recently proposed metric is cross divide contrasts in a proxy for steady state channel elevation but cross divide contrasts in a number of topographic metrics show promise here we use a series of landscape evolution simulations in which we induce divide mobility under different conditions to test the utility of a suite of topographic metrics of divide mobility and for comparison with natural examples in the eastern greater caucasus mountains the kars volcanic plateau and the western san bernadino mountains specifically we test cross divide contrasts in mean gradient mean local relief channel bed elevation and all measured at or averaged upstream of a reference drainage area our results highlight that cross divide contrasts in only faithfully reflect current divide mobility when uplift rock erodibility climate and catchment outlet elevation are uniform across both river networks on either side of the divide otherwise a anomaly only indicates a possible future divide instability the other metrics appear to be more reliable representations of current divide motion but in natural landscapes only cross divide contrasts in mean gradient and local relief appear to consistently provide useful information multiple divide metrics should be considered simultaneously and across divide values of all metrics examined quantitatively as visual assessment is not sufficiently reliable in many cases we provide a series of matlab tools built using topotoolbox to facilitate routine analysis

discharge discharge variability and the bedrock channel profile long term bedrock incision is driven by daily discharge events of variable magnitude and frequency with ineffective events below an incision threshold we explore theoretically how this short term stochastic behavior controls long term steady state incision rates and bedrock channel profiles combining a realistic frequency magnitude distribution of discharge with a deterministic detachment limited incision model in which incision rate is a power function of basal shear stress above a critical shear stress our model predicts a power law relationship between steady state slope and drainage area consistent with observations the exponent of this power law is independent of discharge mean and variability while the amplitude factor which controls mountain belt relief is a power law function of mean runoff with an exponent of 0 5 and a complex function of runoff variability in accordance with evidence that incision occurs between 6 and 20 of time in rapidly incising rivers 1 mm yr our model predicts that channel steepness is virtually insensitive to runoff variability runoff variability can only decrease channel steepness for very slow incision rates and or weak lithologies the relationship between channel steepness and incision rate is always a power law whose exponent depends on the channel cross sectional geometry and runoff variability this contradicts models neglecting discharge stochasticity in which the steepness incision scaling is set by the incision law exponent our results suggest that changes in climate variability cannot explain an increase in bedrock incision rates during the late cenozoic within the context of a detachment limited model

lithological control on the geomorphic evolution of the shillong plateau in northeast india abstract the shillong plateau in northeast india is a block of raised topography in the himalayan foreland which consists of crystalline basement rocks partially covered by a cretaceous to miocene sedimentary succession it is dominated by a mature low relief landscape surrounded by high relief fluvially dissected margins particularly along its southern flank which is bounded by the dauki thrust fault we use river profiles and geological relationships to show that the low relief plateau is a topographic expression of a re exposed basement palaeosurface following the stripping of sedimentary cover by scarp retreat we show that initiation of the wave of incision does not require surface rupture on the dauki fault or an increase in fault slip rate at the end of the miocene as suggested by previous studies we propose that incision has been spatially controlled by the slope of the basement palaeosurface likely moderated by an incision threshold river profiles in the shillong plateau cannot be interpreted as simple records of surface uplift the observed heterogeneous spatial pattern of steepness is a function of a dynamic landscape response to the erosion of layered lithology with contrasting erodibility such dynamics have implications for fluvial geomorphology highlighting that near horizontal lithological contacts can strongly influence river profiles and topography even when no longer physically preserved the topography of the northern shillong plateau is controlled by the structure of basement rocks and is reminiscent of stable cratonic interior landscapes consistent with its surface exposure during late cretaceous times

the influence of sandstone caprock material on bedrock channel steepness within a tectonically passive setting buffalo national river basin arkansas usa bedrock channel profile analysis typically assumes that channels evolve toward a condition of topographic steady state where channel morphology is adjusted to rock erodibility uplift rates and stream power here we use the integral method of channel profile analysis to quantify channel steepness within a large set of tributary channels that incise through layered rocks in the buffalo national river basin in northern arkansas statistical analysis of these channels demonstrates that normalized channel steepness is not a function of local bedrock lithology but is influenced by coarse sediment supply specifically normalized steepness is greatest in reaches of the basin where an interval of pennsylvanian sandstone forms a caprock on the ridges block detachment of the sandstone causes large boulders to be stranded in the upper tributaries where stream power is too low to mobilize or effectively erode the boulders within these channels normalized steepness is correlated with sandstone boulder size and percent boulder coverage rather than local lithology despite strong contrasts in the mechanical strength of the lithologies incised this analysis suggests that removal of caprock material is rate limiting within the landscape and may be responsible for the long term persistence of topography within this tectonically passive setting

the topographic state of fluvially conditioned mountain ranges abstract the topography of mountain ranges reflects the competition of constructive and destructive processes driven by tectonics and climate respectively there is a vital debate whether the topography of individual orogens reflects stages of growth steady state or decay that is fueled by the million year time scales hampering direct observations on landscape evolution the superposition of various process patterns and the complex interactions among different processes hence there is a demand for sophisticated analysis tools to extract constraints on the long term evolution of orogens from their topography we review the field of orogen scale landscape evolution from a numerical perspective summarize the most prominent modelling concepts and their implications for the fluvially driven development of mountain topography and finally evaluate their applicability for understanding real world orogens following the concept of equilibrium a state where uplift rates are balanced by erosion rates and topography remains steady over time the erosional long term response of rivers and hillslopes can be mathematically formalised by the stream power and mass diffusion equations respectively based on a simple 1 dimensional model consisting of two rivers separated by a watershed we explain the influence of uplift rate and rock erodibility on steady state channel profiles and show the time dependent development of the channel drainage divide system dynamic drainage network reorganisation adds additional complexity and its effect on topography is explored on a two dimensional model river capture events and drainage divide migrations as expression of the ongoing drainage network reorganisation cause changes in topography until a stable network topology and hence full topographic steady state is achieved the long time spans needed for this drainage network optimization suggest that orogens on earth may never reach full topographic steady state in real world orogens we find evidence for premature mature and decaying topography as well as relief rejuvenation by analysing slope elevation distributions and trace the expression of crustal strain distorting drainage networks by applying the transform we conclude that modern concepts of landscape evolution allow sophisticated analyses of real world orogens but emphasize that unambiguous results are mostly derived from regions dominated by a limited number of interacting processes such as mountain ranges with limited or no glacial imprint this results in a high demand for techniques to disentangle the complex topography of real world orogens into the signals resulting from the individual land shaping processes

channel response to tectonic forcing field analysis of stream morphology and hydrology in the mendocino triple junction region northern california abstract an empirical calibration of the shear stress model for bedrock incision is presented using field and hydrologic data from a series of small coastal drainage basins near the mendocino triple junction in northern california previous work comparing basins from the high uplift zone huz uplift rates around 4 mm year to ones in the low uplift zone luz 0 5 mm year indicates that the huz channels are about twice as steep for a given drainage area this observation suggests that incision processes are more effective in the huz it motivates a detailed field study of channel morphology in the differing tectonic settings to test whether various factors that are hypothesized to influence incision rates discharge channel width lithology sediment load change in response to uplift or otherwise differ between the huz and luz analysis of regional stream gaging data for mean annual discharge and individual floods yields a linear relationship between discharge and drainage area increased orographic precipitation in the huz accounts for about a twofold increase in discharge in this area corresponding to an assumed increase in the erosional efficiency of the streams field measurements of channel width indicate a power law relationship between width and drainage area with an exponent of 0 4 and no significant change in width between the uplift rate zones although interpretation is hampered by a difference in land use between the zones the huz channel width dataset reveals a scaling break interpreted to be the transition between colluvial and fluvial dominated incision processes assessments of lithologic resistance using a schmidt hammer and joint surveys show that the rocks of the study area should be fairly similar in their susceptibility to erosion the huz channels generally have more exposed bedrock than those in the luz which is consistent with protection by sediment cover inhibiting incision in the luz however this difference is likely the result of a recent pulse of sediment due to land use in the luz therefore the role of sediment flux in setting incision rates cannot be constrained with any certainty to summarize of the four response mechanisms analyzed the only factor that demonstrably varies between uplift rate zones is discharge although this change is likely insufficient to explain the relationship between channel slope and uplift rate the calibrated model allows us to make a prediction of channel concavity that is consistent with a previous estimate from slope drainage area data we show that the inclusion of nonzero values of critical shear stress in the model has important implications for the theoretical relationship between steady state slope and uplift rate and might provide an explanation for the observations this analysis underscores the importance of further work to constrain quantitatively threshold shear stress for bedrock incision

groundwater flow characterization in a multilayered karst aquifer on the edge of a sedimentary basin in western france abstract on the edge of sedimentary basins burial of geological layers can involve the formation of confined karst aquifers in some cases relationships between confined and unconfined karst aquifers can exist and imply an increased difficulty in delineating contributive areas of karst system outlets with accuracy this work aims to develop a multi disciplinary approach to highlight groundwater exchanges between multilayered karst aquifers feeding a single spring toulon springs located in western france provides the opportunity to study relationships between two multilayered karst aquifers hydrograph and chemograph analysis coupled with principal component analysis pca are used to evaluate groundwater flow origins on the northern edge of a sedimentary basin natural hydrodynamic responses baseflow recession analysis auto cross correlation function show an important volume of water located in a saturated zone of the toulon karst system significant contrasts in water quality as a function of the hydrological regime flood recession and baseflow regime and comparison with shallow and deep water show the participation of a deep aquifer supporting the flow of toulon springs

effects of a tectonically triggered wave of incision on riverine exports and soil mineralogy in the luquillo mountains of puerto rico we document the long term response of a tropical mountain stream to tectonics and show how this response exerts a first order spatial control on the delivery of weatherable minerals to forest soils in its catchment these minerals in turn affect nutrient availability and biogeochemical cycles the luquillo mountains is a rainforest covered isolated massif on puerto rico island instead of displaying typical concave up long profiles of most mountain streams the rivers draining the southern flank of these mountains display a systematic downstream increase in gradient using concentrations of in situ produced cosmogenic 10be in quartz from river sediments we find that the downstream steepening is due to the propagation of an erosion wave along the rivers from the coastal plain upstream toward the headwaters decreased 10be concentration along the steepened reaches knickpoint faces or knickzones results from faster denudation of the valley sides around the steepened reaches the upper portions of the steepened reaches knickpoint lips cluster in elevation around the altitude of a flat lying dissected surface traceable around the luquillo mountains inspection of similar platforms over other parts of puerto rico and in the surrounding seas suggests that the dissected surface is an uplifted shore platform formed in the early pliocene 4 my ago upstream of the knickpoints rivers possess alluvial reaches still graded to this uplifted platform they represent relict profiles of the rivers that once drained an island that was surrounded by the now uplifted platform we conclude that the knickpoints initiated when the platform started to rise above the caribbean sea the knickpoints then started propagating upstream defining the front of a slow moving wave of erosion 10be derived catchment scale denudation rates measured above and below the knickpoints indicate a 30 210 increase in denudation associated to the passage of the knickpoints mineralogical analysis of the soils show that soils upstream of the knickpoints overlie deeply depleted saprolite and only contain recalcitrant minerals whereas soils downstream of the knickpoints experience an input of fresh weatherable minerals this influx considerably increases nutrient availability porder et al 2015 in a forest where atmospheric inputs are otherwise the main source of nutrients mcdowell et al 1990 zarin and johnson 1995 pett ridge 2009

shear wave splitting in compliant rocks shear wave splitting is a phenomenon that has received a lot of attention primarily because of its connection with vertically aligned cracks or fractures within reservoirs however in most cases the largest amount of shear wave splitting is observed to occur in the near surface layers where the rocks are the least consolidated and so are least likely to be stiff enough to support cracks ironically we have observed during the processing of many multicomponent data sets in western canada that the largest amounts of shear wave splitting occur in an area where we least expect to see it in the highly unconsolidated sediments that comprise the heavy oil plays in the northwestern part of alberta at first we thought that the rocks in this area were surely too soft to support cracks and therefore that shear wave splitting would be smaller than observed elsewhere the data have taught us that the opposite is true

geologic constraints on bedrock river incision using the stream power law denudation rate in unextended terranes is limited by the rate of bedrock channel incision often modeled as work rate on the channel bed by water and sediment or stream power the latter can be generalized as ka m s n where k represents the channel bed s resistance to lowenng whose variation with lithology is unknown a is drainage area a surrogate for discharge s is local slope and m and n are exponents whose values are debated we address these uncertainties by simulating the lowering of ancient river profiles using the finite difference method we vary m n and k to match the evolved profile as closely as possible to the corresponding modern river profile over a time period constrained by the age of the mapped paleoprofiles we find at least two end member incision laws ka 0 3 0 5 s for australian rivers with stable base levels and k f a 0 1 0 2 s n for rivers in kauai subject to abrupt base level change the long term lowering rate on the latter expression is a function of the frequency and magnitude of knickpoint erosion characterized by k f incision patterns from japan and california could follow either expression if they follow the first expression with m 0 4 k varies from 10 7 10 6 m 0 2 yr for granite and metamorphic rocks to 10 5 10 4 m 0 2 yr for volcaniclastic rocks and 10 4 10 2 m 0 2 yr for mudstones this potentially large variation in k with lithology could drive strong variability in the rate of long term landscape change including denudation rate and sediment yield

a statistical framework to quantify spatial variation in channel gradients using the integral method of channel profile analysis 1 we present a statistical technique for analyzing longitudinal channel profiles our technique is based on the integral approach to channel analysis drainage area is integrated over flow distance to produce a transformed coordinate which has dimensions of length assuming that profile geometry is conditioned by the stream power law defined as e kamsn where e is erosion rate k is erodibility a is drainage area s is channel gradient and m and n are constants the slope of a transformed profile in elevation space should reflect the ratio of erosion rate to channel erodibility raised to a power 1 n this quantity is often referred to as the channel steepness and represents channel slope normalized for drainage area our technique tests all possible contiguous segments in the channel network to identify the most likely locations where channel steepness changes and also identifies the most likely m n ratio the technique identifies locations where either erodibility or erosion rates are most likely to be changing tests on a simulated landscape demonstrate that the technique can accurately retrieve both the m n ratio and the correct number and location of segments eroding at different rates where model assumptions apply tests on natural landscapes illustrate how the method can distinguish between spurious channel convexities due to incorrect selection of the m n ratio from those which are candidates for changing erodibility or erosion rates we also show how given erosion or uplift rate constraints the method can be used to constrain the slope exponent n

objective extraction of channel heads from high resolution topographic data fluvial landscapes are dissected by channels and at their upstream termini are channel heads accurate reconstruction of the fluvial domain is fundamental to understanding runoff generation storm hydrology sediment transport biogeochemical cycling and landscape evolution many methods have been proposed for predicting channel head locations using topographic data yet none have been tested against a robust field data set of mapped channel heads across multiple landscapes in this study four methods of channel head prediction were tested against field data from four sites with high resolution dems slope area scaling relationships two techniques based on landscape tangential curvature and a new method presented here which identifies the change from channel to hillslope topography along a profile using a transformed longitudinal coordinate system our method requires only two user defined parameters determined via independent statistical analysis slope area plots are traditionally used to identify the fluvial hillslope transition but we observe no clear relationship between this transition and field mapped channel heads of the four methods assessed one of the tangential curvature methods and our new method most accurately reproduce the measured channel heads in all four field sites feather river ca mid bailey run oh indian creek oh piedmont va with mean errors of 11 7 5 and 24 m and 34 3 12 and 58 m respectively negative values indicate channel heads located upslope of those mapped in the field importantly these two independent methods produce mutually consistent estimates providing two tests of channel head locations based on independent topographic signatures

distinction between epigenic and hypogenic maze caves abstract certain caves formed by dissolution of bedrock have maze patterns composed of closed loops in which many intersecting fractures or pores have enlarged simultaneously their origin can be epigenic by shallow circulation of meteoric groundwater or hypogenic by rising groundwater or production of deep seated solutional aggressiveness epigenic mazes form by diffuse infiltration through a permeable insoluble caprock or by floodwater supplied by sinking streams most hypogenic caves involve deep sources of aggressiveness transverse hypogenic cave origin is a recently proposed concept in which groundwater of mainly meteoric origin rises across strata in the distal portions of large flow systems to form mazes in soluble rock sandwiched between permeable but insoluble strata the distinction between maze types is debated and is usually based on examination of diagnostic cave features and relation of caves to their regional setting in this paper the principles of mass transfer are applied to clarify the limits of each model to show how cave origin is related to groundwater discharge dissolution rate and time the results show that diffuse infiltration and floodwater can each form maze caves at geologically feasible rates typically within 500 ka transverse hypogenic mazes in limestone to enlarge significantly within 1 ma require an unusually high permeability of the non carbonate beds generally 10 4 cm s large discharge and calcite saturation no greater than 90 which is rare in deep diffuse flow in sedimentary rocks deep sources of aggressiveness are usually required the origin of caves by transverse hypogenic flow is much more favorable in evaporite rocks than in carbonate rocks

the contribution of time series analysis to the study of the hydrodynamic characteristics of the karst systems application on two typical karst aquifers of greece trifilia almyros crete time series analysis was applied to the precipitation spring discharge and piezometric head data of two representative karst systems of greece in order to study the function hydrodynamic behaviour and hydraulic properties of the aquifers results obtained through autocorrelation spectral density cross correlation cross amplitude gain coherence and phase functions showed that the trifilia karst system is slightly karstified and has a large storage capacity baseflow dominates while quickflow is absent due to the lack of a well organized karst network suggesting that probably darcian conditions exist on the other hand unlike the trifilia karst system the karstification processes in the almyros karst system are more enhanced producing a better developed karst network but contrary to the typical karst systems baseflow and quickflow coexist this system can be classified as an intermediate case between the two extreme karst types

single event time series analysis in a binary karst catchment evaluated using a groundwater model lurbach system austria the lurbach karst system styria austria is drained by two major springs and replenished by both autogenic recharge from the karst massif itself and a sinking stream that originates in low permeable schists allogenic recharge detailed data from two events recorded during a tracer experiment in 2008 demonstrate that an overflow from one of the sub catchments to the other is activated if the discharge of the main spring exceeds a certain threshold time series analysis autocorrelation and cross correlation was applied to examine to what extent the various available methods support the identification of the transient inter catchment flow observed in this binary karst system as inter catchment flow is found to be intermittent the evaluation was focused on single events in order to support the interpretation of the results from the time series analysis a simplified groundwater flow model was built using modflow the groundwater model is based on the current conceptual understanding of the karst system and represents a synthetic karst aquifer for which the same methods were applied using the wetting capability package of modflow the model simulated an overflow similar to what has been observed during the tracer experiment various intensities of allogenic recharge were employed to generate synthetic discharge data for the time series analysis in addition geometric and hydraulic properties of the karst system were varied in several model scenarios this approach helps to identify effects of allogenic recharge and aquifer properties in the results from the time series analysis comparing the results from the time series analysis of the observed data with those of the synthetic data a good agreement was found for instance the cross correlograms show similar patterns with respect to time lags and maximum cross correlation coefficients if appropriate hydraulic parameters are assigned to the groundwater model the comparable behaviors of the real and the synthetic system allow to deduce that similar aquifer properties are relevant in both systems in particular the heterogeneity of aquifer parameters appears to be a controlling factor moreover the location of the overflow connecting the sub catchments of the two springs is found to be of primary importance regarding the occurrence of inter catchment flow this further supports our current understanding of an overflow zone located in the upper part of the lurbach karst aquifer thus time series analysis of single events can potentially be used to characterize transient inter catchment flow behavior of karst systems

geochemical evolution of groundwater in the unsaturated zone of a karstic massif using the pco2 sic relationship summary in karstic environments groundwater is strongly influenced by co 2 partial pressure variations of air present in the infiltration zone of these aquifers in order to characterize the geochemical changes in groundwater as it moves through the infiltration zone we monitored various rising springs in the perched karstic aquifer of cussac dordogne france and measured the co 2 partial pressure in air of a nearby cavity the cussac cave for 24 months our method is based on the relationship between the saturation index with respect to calcite sic and the co 2 partial pressure at atmospheric equilibrium with water we distinguished a value for this last parameter when water is at equilibrium with respect to calcite sic 0 called saturation co 2 partial pressure the use of this parameter can provide information on flow conditions and relationships between water air and rock cussac aquifer is a suitable area to apply these methods because of its small size numerous springs and a cave that provides data for co 2 partial pressure condition inside the massif results show that most of the calcium carbonate mineralization is acquired in the epikarst followed by a precipitation phase in the upper part of the infiltration zone groundwater reaches the saturated zone with some degree of saturation depending on co 2 partial pressure variations in air inside the massif

contribution a l etude des courbes de recession des sources karstiques exemples du pays hellenique abstract a study of the recession curves of the major springs of some systems of karstic aquifers in greece shows that each of these aquifers is unique in respect of its boundary conditions its internal organization and its hydrodynamics differences which result in different forms of recession curves these case studies can therefore form the basis for the prediction of the recession curves of karstic springs and hence for the classification of the systems of aquifers

significance and origin of very large regulating power of some karst aquifers in the middle east implication on karst aquifer classification summary karst aquifers are the main groundwater resource in lebanon as well as in most mediterranean countries most of them are not exploited in a sustainable way partly because their characteristics remain unknown karst aquifers are so complex that the assessment of their resource and their exploitable storage requires an analysis of their whole functioning particularly by analysing the spring hydrograph among all various methods the method proposed by mangin aims to characterize at the same time the recharge conditions and the storage and recession of the saturated zone by analyzing the spring hydrograph this method defines two parameters the infiltration delay i and the regulating power k which are the roots of a classification of karst systems this classification makes the distinction between karst and porous aquifers considering the value of the regulating power k is assumed to be lower than 0 5 in karst and between 0 5 and 1 for all other aquifers 1 being the upper limit the study of karst aquifers in lebanon shows values of k 0 5 and even 1 former data from the literature show that other karst springs in middle east have comparable characteristics in fact what is not considered by mangin and others k is equivalent to a mean residence time in years of water in the saturated zone so long residence times are normally observed in poorly karstified aquifers or containing abandoned not functioning karstification the geological framework in which the studied springs are located in fact shows that these aquifers have been subject to a long complex evolution as a consequence of the base level rising this rising produced the flooding of the successive karst drainage network which does not really function anymore and provides a large storage capacity to the aquifer the very interesting properties of these aquifers make them prime targets for fulfilling the increasing needs of water

time series analyses for karst river interactions assessment case of the coulazou river southern france summary in many karst systems throughout the world numerous karst features facilitate the exchange of water between the surface the vadose zone and the saturated zone of the aquifer these interactions play actually a prominent role in the ground and surface waters circulation this study aims at assessing karst river interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research as in many others binary karst system the captured waters of the coulazou river travel through conduits and preferential flow paths in the vadose zone and join the saturated zone of the aquifer this river is an ephemeral river in a mediterranean context where rapid and intense floods occur each year this hydrologic behaviour is appropriate to study the transfer of a flood through a karst area the water level in caves the rainfall all over the karst aquifer catchment area the piezometric level within the karst aquifer and the discharge in the river upstream and downstream of the karst aquifer are measured in order to understand the karst river exchanges during a flood the modification of the surface flows in the river is treated as a linear time invariant system lti system correlation and spectral analyses are used to understand how the lti system dissipates or enhances the flood wave energy for several floods the frequency response function estimations are interpreted in term of flood wave modification through the karst area in this way according to the initial state of the karst river system the autogenic and or allogenic recharge of the aquifer may induce surge flows and a significant karst contribution to surface flows

geomorphic response of coastal streams to low intermediate and high rates of uplift medocino triple junction region northern california analysis of three dimensional morphological properties of 24 coastal drainage basins that have evolved in areas of low 3 m 1 000 yr rates of uplift near the mendocino triple junction mtj coastal northern california identified channel gradients as the best indicator of tectonism in the landscape lower order tributaries best reflect tectonically controlled differences the largest streams examined of third order are able to adjust to most base level change and maintain their profile form whereas lower order streams farther upstream tend to accumulate the effects of net base level fall and have steepest profiles in the areas of highest uplift rates variations in steepness of first order channel gradients indicate that 1 high uplift rates in the wake of the mtj have existed for at least 73 000 yr and 2 differential tilt of the region to the north and south of the current locus of highest uplift rate is occurring in association with regional uplift although first order streams are excellent indicators of areas of both high uplift rates and regional differential tilting they are less useful in distinguishing between areas of low and intermediate uplift rate analysis of the longitudinal profile of the main trunk stream of ten of the 24 drainage basins using the stream gradient index was more useful to categorize broadly the uplift rates and to distinguish between streams in low and intermediate uplift rate areas although the hypotheses tested herein do not identify the exact mechanism off uplift in the mtj region they do indicate that the nature of deformation is most likely regional tilt rather than crustal shortening with localized compressional folding and thrust faulting they also indicate that geomorphic responses trail in the wake of the uplift rate response caused by development of a slab window beneath the north american plate 1 maximum uplift rates occur 9 km south of the northern boundary of the slab window 2 maximum mean first order channel gradient occurs 16 km south of the northern edge of the slab window and 3 maximum drainage basin relief occurs 20 km south of the northern edge of the slab window associated lag times between passage of the southern edge of the subducted gorda plate slab and geomorphic responses are 160 000 yr for maximum uplift rates 290 000 yr for maximum channel gradients and 370 000 yr for maximum relief