calcareous nannofossil zonation of the jurassic cretaceous boundary interval and correlation with the geomagnetic polarity timescale abstract calcareous nannofossil stratigraphy has been investigated in six european land sections and at two deep sea drilling project sites 391c and 534a ranging from the upper kimmeridgian to the lower valanginian most of the sections contain a continuous record of the jurassic cretaceous boundary interval a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval the proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material thirty eight additional biohorizons are proposed based on the stratigraphy of the two dsdp sites these can be accurately established only in moderately well preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time transgressive finally the magnetostratigraphic definitions of two stage boundaries are refined the kimmeridgian tithonian and berriasian valanginian boundaries are placed within chrons cm22n and cm15n respectively two new genera faviconus and umbria and seven new species are described umbria granulosa rhagodiscus nebulosus cretarhabdus octofenestratus faviconus multicolumnatus nannoconus infans nannoconus compressus and nannoconus wintereri eight subspecies and three taxonomic emendations are also described

digital elevation model resolution effects on terrain attribute calculation and quantitative soil landscape modeling the accuracy of digital elevation models dem and dem derived products depends on several factors including the horizontal resolution and vertical precision at which the elevation data are represented and the source of the elevation data this accuracy becomes increasingly important as we extend the use of dem data for spatial prediction of soil attributes our objective was to compare terrain attributes and quantitative soil landscape models derived from grid based dem represented at different horizontal resolutions 10 and 30 m represented at different vertical precisions 0 1 and 1 m and acquired from different sources decreasing the horizontal resolution of the field survey dem produced lower slope gradients on steeper slopes steeper slope gradients on flatter slopes narrower ranges in curvatures larger specific catchment areas in upper landscape positions and lower specific catchment areas values in lower landscape positions overall certain landscape features were less discernible on the 30 m dem than on the 10 m dem decreased vertical precision produced a large proportion of points with zero slope gradient and zero slope curvature and a large number of steeply sloping and more highly curved areas differences among dem from different sources were more significant with less accurate representation of depressions and drainage pathways with the usgs dem as compared to the field survey dem empirical models developed from different dem included similar predictive terrain attributes and were equally successful in predicting a horizon depth ahd in the validation data set

influence of dem resolution on drainage network extraction a multifractal analysis article i nfo drainage network geometry dem resolution d8 algorithm multifractal analysis flow accumulation threshold terrain attributes different hydrological algorithms have been developed to automatically extract drainage networks from digital elevation models dems d8 is the most widely used algorithm to delineate drainage networks and catchments from a dem this algorithm has certain advantages such as simplicity the provision of a reasonable representa tion for convergent flow conditions and consistency among flow patterns calculated contributing areas and the spatial representation of subcatchments however it has limitations in selecting suitable flow accumulation threshold values to determine the pixels that belong to drainage networks although the effects of dem resolu tiononsometerrainattributes streamcharacterisationandwatersheddelineationhavebeenstudied analysesof the influence of dem resolution on flow accumulation threshold values have been limited recently multifractal analyses have been successfully used to find appropriate flow accumulation threshold values the application of thistype of analysisto evaluate therelationship betweendem resolution and flow accumulation threshold value needs to be explored therefore this study tested three dem resolutions for four drainage basins with different levels of drainage network distribution by comparing the renyi spectra of the drainage networks that were ob tained with the d8algorithmagainstthose determined byphotogrammetric restitution according totheresults dem resolution influences the selected flow accumulation threshold value and the simulated network morphol ogy thesuitable flowaccumulationthresholdvalue increasesasthedemresolutionincreasesandshowsgreater variability for basins with lower drainage densities the links between dem resolution and terrain attributes were also examined

effects of dem resolution on the calculation of topographical indices twi and its components summary a variety of landscape properties have been modelled successfully using topographic indices such as the topographic wetness index twi defined as ln a tan where a is the specific upslope area and is the surface slope previous studies have shown the influence of scale on twi values when converting standard resolution dems to coarser resolutions in this study a high resolution digital elevation model dem with a 5 m grid size derived from lidar light detection and ranging data was used to investigate the scale dependency of twi values when converting from high resolution elevation data to standard resolution dems first a set of dems was generated from an initial dem by thinning to resolutions of 10 25 and 50 m grid sizes to study the effects of lower grid size and decreased information content next to investigate the impact of different information content on dems with the same grid size the three lower resolution dems were all interpolated to the original 5 m grid size in addition to comparing index distribution functions a second objective was to evaluate differences in spatial patterns thus the values of twi and its components as computed for the seven different dems were compared in three different ways 1 distribution functions and their statistics 2 cell by cell comparison of four dems with the same resolution but different information content and 3 comparison of blocks of cells within different resolution dems with different information content like previous twi studies the computed specific upstream area decreased on average for higher resolution dems while computed slope values followed a narrower distribution twi variation between neighbouring cells in 50 50 m areas decreased largely with increasing grid size a cell by cell comparison of the twi values of the four 5 m dems with different information content showed a clear decrease in correlation with the twi based on the original dem with decreasing information content the results showed considerable differences between topographic indices computed for dems of different grid resolution interpolating the dems to a higher resolution i e a smaller grid size provided more similar twi distributions but the pixel by pixel comparison showed that different information contents caused clearly different twi maps

the mid valanginian weissert event as recorded by calcareous nannoplankton in the vocontian basin the mid valanginian weissert event represents one of the most significant paleoceanographic events of the early cretaceous and is characterized by a major perturbation of the carbon cycle testified by a positive carbon isotope shift a crisis of both neritic and pelagic carbonate producers and climatic fluctuations here we propose a paleoreconstruction of paleoenvironmental changes that occurred in the reference vergol and la charce sections vocontian basin se france during the weissert event based on the analysis of calcareous nannofossil absolute abundance and assemblages these latter are compared to newly acquired and already published sedimentological and organic geochemical analyses our approach is novel for the time interval considered indeed principal component analysis was applied for the first time to the entire nannofossil assemblage to reconstruct environmental conditions instead of using paleoecological preferences of single species the comparison of calcareous nannofossils and biomarker analyses indicates that a phase of severe sea water stratification occurred prior to the carbon positive excursion of the weissert event in the vocontian basin this was followed by a raise in fertility of surface waters as attested by increased nannofossil abundances in particular of meso eutrophic taxa and biomarkers likely produced by dinoflagellates this increase in fertility was likely triggered by a humid climate and enhanced continental input of clays and nutrients to surface oceanic waters calcareous nannofossils also proved to react to sea level changes that occurred in the valanginian as inferred by previous works species likely inhabiting proximal areas were recorded in higher proportions during a major sea level drop in the peregrinus ammonite zone late valanginian the results of this study also permit to revise previously proposed paleoecological affinities of some nannofossil species we suggest that watznaueria barnesiae one of the most widely used species in the literature should be used cautiously because of its high plasticity with respect to environmental conditions also nannoconids that are usually regrouped in papers with paleoceanographic purposes should be analyzed separately because they show distinct species specific ecological preferences

spatial autocorrelation of topographic index in catchments summary spatial autocorrelation represents the association of a spatial parameter around neighborhoods and it usually distorts the statistics of the distribution of the parameter topographic spatial autocorrelation is rooted with the distribution of land surface elevation using moran s i statistics originating from geographic studies this paper presents a method to quantify the spatial autocorrelation of topographic index ti in catchments derived from digital elevation models dem positive autocorrelation similarity or homogeneity of ti is found over a wide range of spatial extents it declines with the increasing of spatial extents but becomes relatively static beyond a threshold area of approximately 1 km 2 the analysis of the effect of dem grid size resolution on the spatial autocorrelation shows that the effect is characterized by a similar pattern and critical grid size for selected catchments with different terrains based on these analyses further discussions address some issues in catchment hydrology such as the appropriate dem sizes for deriving ti and the causes for the empirical linear or log linear relation between mean ti and dem grid size

evaluation of a distributed catchment scale water balance model the validity of some of the simplifying assumptions in a conceptual water balance model is investigated by comparing simulation results from the conceptual model with simulation results from a three dimensional physically based numerical model and with field observations we examine in particular assumptions and simplifications related to water table dynamics vertical soil moisture and pressure head distributions and subsurface flow contributions to stream discharge the conceptual model relies on a topographic index to predict saturation excess runoff and on philip s infiltration equation to predict infiltration excess runoff the numerical model solves the three dimensional richards equation describing flow in variably saturated porous media and handles seepage face boundaries infiltration excess and saturation excess runoff production and soil driven and atmosphere driven surface fluxes the study catchments a 7 2 km2 catchment and a 0 64 km2 subcatchment are located in the north appalachian ridge and valley region of eastern pennsylvania hydrologic data collected during the machydro 90 field experiment are used to calibrate the models and to evaluate simulation results it is found that water table dynamics as predicted by the conceptual model are close to the observations in a shallow water well and therefore that a linear relationship between a topographic index and the local water table depth is found to be a reasonable assumption for catchment scale modeling however the hydraulic equilibrium assumption is not valid for the upper 100 cm layer of the unsaturated zone and a conceptual model that incorporates a root zone is suggested furthermore theoretical subsurface flow characteristics from the conceptual model are found to be different from field observations numerical simulation results and theoretical baseflow recession characteristics based on boussinesq s groundwater equation

physical interpretation and sensitivity analysis of the topmodel the topmodel is a variable contributing area conceptual model in which the predominant factors determining the formation of runoff are represented by the topography of the basin and a negative exponential law linking the transmissivity of the soil with the distance to the saturated zone below the ground level although conceptual this model is frequently described as a physically based model in the sense that its parameters can be measured directly in situ in line with the analysis of various conceptual rainfall runoff models conducted by franchini and pacciani j hydrol 122 161 219 1991 a detailed analysis of the topmodel is performed to arrive at a closer understanding of the correspondence of the assumptions underpinning the model with the physical reality and in particular the role that topographic information expressed by the topographic index curve and the nature of the soil expressed by saturated hydraulic conductivity and its decay with soil depth have within the model itself also investigated is the extent to which the model parameters actually reflect the physical properties to which they refer and how far their values offset the inevitable schematisation of the model the various applications to real situations include the sieve basin river arno tributary which was used for the comparison of conceptual rainfall runoff models described in the above mentioned study by franchini and paccini this allows that analysis to be extended to the topmodel

evidence for a complex valanginian nannoconid decline in the vocontian basin south east france the early cretaceous is punctuated by widespread biocalcification crises these are characterized by decrease in the carbonate platform growth and in the pelagic realm by a decline in nannoconus relative abundance in the calcareous nannofossil assemblages the valanginian nannoconus decline started before the positive 13c excursion characterizing the weissert event the nannoconid decline is investigated in two sections of the vocontian basin la charce and vergol which are biostratigraphically well constrained and contain wellpreserved calcareous nannofossils absolute and relative abundances of nannoconus show a polyphased decline with a first decrease in the interval from the campylotoxus to the verrucosum ammonite subzones before the positive 13c shift and a second decrease from the end of the peregrinus to the base of the radiatus ammonite zones concomitant with the long term decrease in 13c these two declines are separated by an important increase in the nannoconus abundance from the verrucosum to the peregrinus ammonite subzones concomitant with a slight short term decrease of 13c biometric analysis shows size changes of n steinmannii and n kamptneri along the nannoconid decline the patterns of abundances and size changes seem to be related to paleoenvironmental changes mainly characterized by a temperature decrease and variable nutrient supply the described valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the vocontian basin as well as in the atlantic and tethys oceans these spatial correlations suggest a supra regional character for the valanginian nannoconid recovery event best recorded in the vocontian basin and at low latitudes

spatial analysis of soil hydraulic conductivity in a tropical rain forest catchment the topography of first order catchments in a region of western amazonia was found to exhibit distinctive recurrent features a steep straight lower side slope a flat or nearly flat terrace at an intermediate elevation between valley floor and interfluve and an upper side slope connecting interfluve and intermediate terrace a detailed survey of soil saturated hydraulic conductivity ksat depth relationships involving 740 undisturbed soil cores was conducted in a 0 75 ha first order catchment the sampling approach was stratified with respect to the above slope units exploratory data analysis suggested fourth root transformation of batches from the 0 0 1 m depth interval log transformation of batches from the subsequent 0 1 m depth increments and the use of robust estimators of location and scale the ksat of the steep lower side slope decreased from 46 to 0 1 mm h over the overall sampling depth of 0 4 m the corresponding decrease was from 46 to 0 1 mm h on the intermediate terrace from 335 to 0 01 mm h on the upper side slope and from 550 to 0 015 mm h on the interfluve a depthwise comparison of these slope units led to the formulation of several hypotheses concerning the link between ksat and topography

wavelet based regularization of the extracted topographic index from high resolution topography for hydro geomorphic applications high resolution topography e g 1 m digital elevation model dem from light detection and ranging lidar offers opportunity for accurate identification of topographic features of relevance for hydrologic and geomorphologic modelling yet the computation of some derived topographic properties such as the topographic index ti is characterized by daunting challenges that hamper the full exploration of topography based models particular problems for example arise when a distributed or semi distributed rainfall runoff model is applied to high resolution dems indeed the characteristic dependency between landscape resolution and the computed ti distribution results in the formation of un physical unconnected saturated zones which in turn cause unrealistic representations of rainfall runoff dynamics in this study we present a methodology based on a multi resolution wavelet transformation that by means of a soft thresholding scheme on the wavelet coefficients filters the noise of high resolution topography to construct regularized sets of locally smoother topography on which the ti is computed while the methodology needs a somewhat arbitrary definition of the wavelet coefficients threshold our study shows that when the information content entropy of the ti distribution is used as a filtering efficiency metric a critical threshold automatically emerges in the landscape reconstruction the methodology is demonstrated using 1 m lidar data for the elder creek river basin in california while the proposed case study uses a topmodel approach the methodology can be extended to different topography based models and is not limited to hydrological applications copyright 2012 john wiley sons ltd

the magnitude and cause of short term eustatic cretaceous sea level change a synthesis abstract no consensus currently exists regarding the magnitude of cretaceous short term less than 3 ma in duration eustatic sea level change the lack of a consensus limits the ability to predict sedimentary facies and architecture and to assess the potential drivers of eustasy during a period of earth history considered as significantly warmer than today consequently this review documents weighs synthesises and summarises records of short term relative sea level change and evaluates the observed trends in magnitude within the context of potential climatic drivers and their eustatic expression although cretaceous sea level change is addressed in many publications estimates of absolute values are relatively limited often cover short time intervals and use different methods based upon integrated geological and statistical analyses four broad episodes of magnitude change have been identified three of these episodes reflect trends of increasing magnitudes of sea level change from the berriasian to early hauterivian late hauterivian to aptian and santonian to maastrichtian the fourth episode reflects a decreasing magnitude trend from the albian to coniacian in addition the maximum magnitude of sea level change at an approximate stage level has been identified and categorised as slight less than 10 m modest 10 to 40 m or significant 41 to 65 m significant magnitudes are inferred for the valanginian aptian albian and maastrichtian exclusively slight magnitudes are restricted to the berriasian such an assessment casts doubt on the repeated and stratigraphically widespread episodes of very large magnitudes more than 75 m advocated by some workers and instead defines distinct periods and magnitudes of sea level change that should be globally reflected in sedimentary facies patterns for example intervals of sea level fall of significant magnitude are commonly associated with the increased delivery of sediment into basinal settings including the marked progradation of shallow marine sediments whilst up systems tract there can be enhanced development of karst and erosional features because climatically driven eustasy is the likely cause of short term sea level change an assessment of the characteristic maximum magnitude limits of the principal climatic drivers thermo aquifer and glacio eustasy has been made such a comparison argues for glacio eustasy as the driver of significant short term sea level change in addition climate proxy data demonstrates that the valanginian aptian albian and maastrichtian are intervals of cooling within the cretaceous thereby supporting the link between significant magnitudes and glacio eustasy

interhemispheric radio astrochronological calibration of the time scales from the andean and the tethyan areas in the valanginian hauterivian early cretaceous an integrated radio astrochronological framework of the agrio formation in the andean neuquen basin of west central argentina provides new constraints on the age and the duration of the late valanginian through hauterivian stratigraphic interval a ca id tims u pb age of 126 97 0 04 0 07 0 15 ma is presented here from the upper hauterivian agua de la mula member of the agrio formation biostratigraphic data from ammonoids and calcareous nannofossils and this high precision new radioisotopic age together with three former ones from the same agrio formation are combined with new astrochronological data in the andes these are correlated with modern cyclostratigraphic studies in the classical sections of the mediterranean province of the tethys supporting detailed interhemispheric correlations for the early cretaceous we also provide new 13c data from the agrio formation which are compared with records from the classic tethyan sections according to our calibration the minimum in the values in the mid hauterivian appears to be synchronous and thus another important stratigraphic marker for global correlation a new duration of 5 21 0 08 myr is calculated for the hauterivian stage starting at 131 29 0 19 ma and ending at 126 08 0 19 ma the difference between the duration of the hauterivian in gts2016 and in this study is 1 32 myr while the base and top of the gts2016 hauterivian differ respectively by 3 40 and 4 69 myr

demise of the last two spire bearing brachiopod orders spiriferinida and athyridida at the toarcian early jurassic extinction event brachiopods were severely hit by several mass extinctions which fundamentally shaped their long evolutionary history after the devastating end permian extinction the fate of the four surviving orders differed significantly during the triassic and jurassic two orders the rhynchonellids and terebratulids are extant today whereas spiriferinids and athyridids which possess spiral brachidia suffered heavy losses at the end of the triassic and became extinct in the early jurassic toarcian event although the doom of the spire bearing orders has been thought to be related to physiological traits extinction selectivity across the end triassic and toarcian event has not been rigorously assessed previously and the reasons for their demise at the later and lesser toarcian event rather than at the earlier and greater end triassic crisis remained unexplored using primarily the paleobiology database we constructed diversity curves estimated taxonomic rates and assessed the temporal changes in geographic distribution of the two spire bearing and two other orders in the triassic jurassic interval after shared trends and similar origination rates in the post permian recovery leading to a late triassic diversity maximum the end triassic extinction was selective and preferentially eliminated the spire bearers in contrast to the rebound of rhynchonellids and terebratulids spire bearers failed to recover in the early jurassic and their repeated selective extinction at the toarcian event led to their final demise the end triassic event also terminated the worldwide geographic distribution of spire bearers confining them to the western tethys whereas the other groups were able to re establish their cosmopolitan distribution the morphologically diverse spire bearers represent specialized adaptation which further increased their extinction vulnerability compared to the other groups with conservative biconvex shell morphology another key difference is the physiological disadvantage of the fixed lophophore and passive feeding of spire bearers which became critical at times of increased environmental stress the spire bearing spiriferinids and athyridids were dead clades walking in the early jurassic and their disappearance in the early toarcian represents the last major order level extinction event for the brachiopods

hazard assessment of rainfall induced landsliding in mexico abstract rainfall induced landsliding represents a major hazard in mexico about 200 municipalities in the states of puebla veracruz and hidalgo were affected by flooding and mass movement processes that resulted from a tropical depression from the atlantic ocean in october 1999 hundreds of slope failures were triggered by intense precipitation which in some localities reached 420 mm during a 24 h period according to official information 263 people died and 1 475 654 inhabitants were affected by flooding and landsliding rainfall event and cycle coefficient defined and the ratios between event and antecedent rainfalls respectively and the mean annual rainfall are summed to give a total coefficient for landslide triggering rainfalls in the sierra norte values for the total coefficient of 0 8 and 0 4 for beginning and end of the wet season respectively appear to be important in addition a hazard assessment was carried out through the development of a landslide susceptibility indicator this was elaborated by using aerial photographs integrating field observations and the coupling of slope instability analysis within a digital elevation model framework field validation indicated that this approach provides a good representation of shallow translational failures 81 of the observed landslides were satisfactorily predicted as potential unstable zones results suggested that this type of dem based hazard assessment can be extremely valuable not only after but also before any landslide related event so that disaster preparedness and planning could be adequately structured

valanginian weissert oceanic anoxic event biotic changes in nannofossils and radiolarians associated with the valanginian 1 3 c anomaly are documented at ocean drilling program hole 1149b in the pacific ocean they are coeval and similar to those previously documented in the tethys suggesting a global perturbation of marine ecosystems a marked increase in abundance of diazomatolithus absence of nannoconids and a pantanellium peak characterize the valanginian 1 3 c excursion such changes are interpreted as being due to global enhanced fertility and a biocalcification crisis under conditions of excess co 2 the occurrence of organic c rich black shales in the southern alps and in the pacific in the interval corresponding to the 1 3 c excursion suggests a valanginian oceanic anoxic event oae volcanism of the parana etendeka large igneous province ca 132 ma was presumably responsible for an increase of co 2 triggering a climate change and accelerated hydrological cycling possibly causing an indirect fertilization of the oceans widespread nutrification via introduction of biolimiting metals at spreading ridges could have significantly increased during the gondwana breakup and simultaneous tectonic events in three separate oceans there is no paleontological or 1 8 o evidence of warming during the valanginian oae on the contrary both nannofossils and oxygen isotopes record a cooling event at the climax of the 1 3 c excursion weathering of basalts and burial of organic c rich black shales were presumably responsible for co 2 drawdown and establishment of reversed greenhouse conditions

tectonic forcing of longitudinal valleys in the himalaya morphological analysis of the ladakh batholith north india abstract longitudinal valleys form first order topographic features in many mountain belts they are commonly located along faults that separate tectonic zones with varying uplift histories the indus valley of ladakh northern india runs northwestwards following the boundary between the relatively undeformed ladakh batholith to the north east and the folded and thrusted zanskar mountains to the south west in this region the shyok valley on the northern side of the batholith approximately parallels the course of the indus this study investigates geomorphic variations in transverse catchments that drain the ladakh batholith into the indus and shyok rivers the batholith has been divided into three zones based on varying structural characteristics of its northeastern and southwestern boundaries morphometric analysis of 62 catchments that drain into the indus and shyok valleys was carried out using three digital datasets and supported by field observations morphometric asymmetry is evident in the central zone where the shyok valley is considered tectonically inactive but the indus valley is bound by the northeastwardly thrusting indus molasse and the batholith in this zone the catchments that drain into the indus valley are more numerous shorter thinner and have lower hypsometric integrals than those that drain into the shyok by linking these observations with the regional geology and thermochronological data it is proposed that high sediment discharge from the deformed indus molasse indus valley has progressively raised base levels in the indus valley and resulted in sediment blanketing of the opposing tectonically quiescent catchments that drain southwestwards off the batholith the indus molasse thrust front has propagated at least 36 km towards the ladakh batholith over the last 20 ma hence it is proposed that this long term asymmetric structural deformation and exhumation has forced the indus longitudinal valley laterally into the ladakh batholith resulting in the morphometric asymmetry of its transverse catchments

deriving river networks and catchments at the european scale from medium resolution digital elevation data abstract the extraction of drainage networks and catchment boundaries from digital elevation models dems has received considerable attention in recent years and is recognized as a viable alternative to traditional surveys and the manual evaluation of topographic maps however most studies have covered limited areas due to the lack of detailed information and or the lack of highly efficient algorithms in this paper we present an application that delineates river networks and catchment boundaries across the european continent from a medium resolution 250 m dem we exploit novel algorithms based on the concepts of mathematical morphology and implement a landscape stratification for drainage density a flow direction grid is computed using an efficient algorithm for the removal of spurious pits river networks are then derived by imposing a variable threshold for the minimum contributing area needed to form and maintain a channel this is achieved through a landscape stratification that reflects the ability of the terrain to develop different drainage densities it is shown that the analysis of environmental characteristics coupled with the analysis of local slope versus contributing area enables river network mapping with a spatially varying drainage density the result has been validated by comparing the derived data to digital river and catchment data from other sources and with varying scales of observation

upscaling hydraulic conductivity by means of entropy of terrain curvature representation 1 the effects of topography resolution on upscaling point scale processes and parameters on watershed hydrology numerical routing are investigated parsimonious continuous simulation was applied to two forested catchments with shallow and sloping soils one medium sized 123 km2 and one small sized 4 5 km2 where saturation excess runoff prevails the computed discharge showed highest sensitivity to spatial resolution due to smoothing effects during aggregation of the digital elevation model caused by a coarse grid the loss of information content of terrain curvature as consequence of the averaging procedure was related to the amplification factor required for the soil hydraulic conductivity to compensate the resulting retardation of the runoff hydrograph a scaling relation has been developed that links soil hydraulic conductivity measured at the point scale with that required at the typically much coarser modeling scale the entropy concept for the measurement of information loss could be a good index for parameter rescaling of other basins where the terrain curvature is similarly scale dependent

astrochronology of the valanginian stage from reference sections vocontian basin france and palaeoenvironmental implications for the weissert event abstract high resolution gamma ray measurements performed on five biostratigraphically well dated reference sections from the vocontian basin south eastern france are used to develop a new astrochronology of the valanginian stage and its subdivisions i e ammonite and calcareous nannofossil zones and subzones spectral analyses show a pervasive dominance of 405 kyr eccentricity cycles with the expression of 100 kyr eccentricity obliquity and precession previous rough estimates of valanginian stage duration ranged from 3 9 to 6 5 myr but were generally based on less reliable or indirect methods this study provides a precise duration of 5 08 myr tuning the series to the 405 kyr eccentricity cycle thus further enhancing the accuracy of the geologic time scale new durations of magnetochrons are proposed based on intercalibration between ammonite and calcareous nannofossil biozones cyclostratigraphy and carbon isotope stratigraphy after integrating orbitally calibrated durations and available radio isotopic ages for the berriasian hauterivian interval a link between the weissert event and the emplacement of the parana etendeka traps now appears unlikely strontium carbon and oxygen isotope stratigraphy sedimentological and palaeontological features clay mineralogy and the orbital record during the upper valanginian all suggest that a transient cool arid climate occurred after the carbon isotope event possibly associated with limited polar ice

the upper valanginian early cretaceous positive carbon isotope event recorded in terrestrial plants our understanding of the ancient ocean atmosphere system has focused on oceanic proxies however the study of terrestrial proxies is equally necessary to constrain our understanding of ancient climates and linkages between the terrestrial and oceanic carbon reservoirs we have analyzed carbon isotope ratios from fossil plant material through the valanginian and lower hauterivian from a shallow marine ammonite constrained succession in the crimean peninsula of the southern ukraine in order to determine if the upper valanginian positive carbon isotope excursion is expressed in the atmosphere d 13 cplant values fluctuate around 23x to 22x for the valanginian hauterivian except during the upper valanginian where d 13 cplant values record a positive excursion to 18x based upon ammonite biostratigraphy from crimea and in conjunction with a composite tethyan marine d 13 ccarb curve several conclusions can be drawn 1 the d 13 cplant record indicates that the atmospheric carbon reservoir was affected 2 the defined ammonite correlations between europe and crimea are synchronous and 3 a change in photosynthetic carbon isotope fractionation caused by a decrease in atmospheric pco2 occurred during the upper valanginian positive d 13 c excursion our new data combined with other paleoenvironmental and paleoclimatic information indicate that the upper valanginian was a cool period icehouse and highlights that the cretaceous period was interrupted by periods of cooling and was not an equable climate as previously thought d 2005 elsevier b v all rights reserved

palaeoclimate and palaeoenvironmental changes through the onset of the valanginian carbon isotope excursion evidence from the polish basin abstract the valanginian weissert episode of environmental change is associated with a positive carbon isotope excursion cie in 13ccarb and 13corg records and a crisis in pelagic and neritic carbonate production the cie was interpreted to represent the first oceanic anoxic event oae of the cretaceous linked with the formation of the parana etendeka large igneous province lip recent studies suggest though that the extent of oceanic anoxia was limited to high latitude epicontinental seas and the pacific and that the parana etendeka lip postdates the valanginian cie with these new interpretations the palaeoenvironmental changes behind the observed perturbation of the carbon cycle remain to be elucidated here we present sedimentological and geochemical results from a drill core near w wal central poland the excavated succession is of particular interest due to its near shore depositional setting within the former polish basin and its preservation up to 17 wt of aragonite the core consists of lower to upper valanginian silty to sandy clays deposited under fully marine conditions on top of an upper jurassic karstified limestone a change in weathering mode from very humid and highly hydrolysing towards less humid and seasonally contrasted conditions is indicated by the abrupt change from a kaolinite to a smectite dominated clay mineral association near the boundary between the early and late valanginian moreover two phosphate rich horizons were identified which correlate in time to northern tethyan occurrences in the helvetic alps the lower level is associated with the early valanginian transgression and corresponds to peak humidity recorded in the w wal core the upper layer corresponds to the paroxysmal phase of the valanginian crisis in carbonate production in the w wal core evidence for anoxic conditions during the valanginian cie is lacking the climatic conditions and changes identified in the polish basin are different from those of the northern tethyan area where an increase in humidity is observed near the early late valanginian boundary the contrasting climate conditions are probably an expression of latitudinal shifts in the position of the northern mid latitude humid belt

the valanginian isotope event a complex suite of palaeoenvironmental perturbations abstract the valanginian records a severe crisis of carbonate systems both on platforms and in the pelagic realm this crisis is roughly concomitant with the weissert event characterized by a positive 13c excursion of about 2 in marine carbonates however it is unclear if the response of these two carbonate systems to the global perturbations is contemporaneous or if they react differently for this purpose accumulation rates of pelagic carbonates produced by nannofossils and of platform derived carbonates have been quantified in a hemipelagic environment the vocontian basin se france that has the potential to record the reaction of both shallow water and pelagic carbonate production to a major perturbation of the carbon cycle testified by the isotope excursion also changes through time of clay input have been measured in order to evaluate variations in continental weathering rates and thus in continent derived nutrient input and climatic conditions in terms of humidity aridity accumulation rates of pelagic carbonates of platform derived carbonates and of clays were calculated on the basis of nannofossil absolute abundance and species specific masses of weight percent carbonate content of rocks and a high resolution timescale given by cyclostratigraphy the onset of the positive 13c excursion and the demise of the platforms testify for a synchronous but inverse response of the shallow water and pelagic carbonate systems to an increase in nutrient influx to marine waters as carbonate production by nannofossils decreased during the late valanginian in time of still low platform production the low temperature of marine waters coeval to a still high nutrient input recorded in the latest late valanginian possibly could explain that both platform and pelagic carbonate production contemporaneously decreased

evolution of the last koninckinids athyridida koninckinidae a precursor signal of the early toarcian mass extinction event in the western tethys abstract koninckinids are a suitable group to shed light on the biotic crisis suffered by brachiopod fauna in the early jurassic koninckinid fauna recorded in the late pliensbachian early toarcian from the easternmost subbetic basin is analyzed and identified as a precursor signal for one of the most conspicuous mass extinction events of the phylum brachiopoda a multi phased interval with episodes of changing environmental conditions whose onset can be detected from the elisa mirabile subzones up to the early toarcian extinction boundary in the lowermost serpentinum zone t oae the koninckinid fauna had a previously well established migration pattern from the intra tethyan to the nw european basins but a first phase with a progressive warming episode in the pliensbachian toarcian transition triggered a koninckinid fauna exodus from the eastern central tethys toward the westernmost mediterranean margins a second stage shows an adaptive response to more adverse conditions in the westernmost tethyan margins and finally an escape and extinction phase is detected in the atlantic areas from the mid polymorphum zone onwards up to their global extinction in the lowermost serpentinum zone this migration pattern is independent of the paleogeographic bioprovinciality and is unrelated to a facies controlled pattern the anoxic suboxic environmental conditions should only be considered as a minor factor of partial control since well oxygenated habitats are noted in the intra tethyan basins and this factor is noticeable only in the second westward migratory stage with dwarf taxa and oligotypical assemblages the analysis of cold seep proxies in the subbetic deposits suggests a radiation that is independent of methane releases in the subbetic basin

the use of digital elevation models in the identification and characterization of catchments over different grid scales this study examines the ability of well known hydrological and geomorphological descriptors and statistics to differentiate between catchments with spatially varying geology size and shape subject to the same climate in the northern territory australia the effect of digital elevation model grid resolution on these statistics is also examined results demonstrate that catchment descriptors such as the area slope relationship cumulative area distribution and hypsometric curve can differentiate between catchments with different geology and resultant morphology but catchment network statistics are insensitive to differences in geology examination of the effects of digital elevation model grid scale demonstrates that while considerable catchment information can be gained at digital elevation grids greater than 10 m by 10 m hillslope and hydrological detail can be lost geomorphic descriptors such as the area slope relationship cumulative area distribution width function and strahler statistics were shown to be sensitive to digital elevation model grid scale but the hypsometric curve was not consequently caution is needed when deciding on an appropriate grid resolution as well as the interpretation and analysis of catchment properties at grid scales greater than that for optimal hillslope and area aggregation definition copyright 2005 john wiley sons ltd

a downscaling method of topographic index distribution for matching the scales of model application and parameter identification higher resolution topographic information contained in the topographic index of topmodel is lost when digital elevation models dems with a coarse grid resolution are used thus the topographic index is scale dependent demonstrating identified model parameter values to be dependent on dem resolution this makes it difficult to use model parameter values identified through a different resolution of topmodel the inconsistency is the result of the difference between the scale at which the model parameters are identified and the scale at which the model is applied to overcome this problem scale laws that govern the relationship between the resolution of digital elevation data and geomorphometric parameters of the topographic index were analysed and a method to downscale the topographic index distribution developed to account for the difference in scales between model application and parameter identification the method to downscale the topographic index is composed of two ideas one involves introducing a resolution factor to account for the scale effect in upslope catchment area per unit contour length in the topographic index the other utilizes a fractal method through steepest slope scaling to account for the scale effect on slopes this method successfully derived a topographic index distribution of a fine resolution dem by using only a coarse resolution dem the method has been applied successfully to the kamishiiba catchment 210 km 2 in japan and has demonstrated that the downscaled topographic index distribution derived using a 1000 m grid dem is very similar to the topographic index distribution derived via fine target resolution dems the method is then coupled with a topmodel simulation to match the scales of model application and parameter identification it is shown that the simulated runoff from the downscaled topmodel applied at 1000 m resolution of the kamishiiba catchment with the same set of effective parameter values derived from 50 m resolution dem matched the simulated runoff in the 50 m dem resolution topmodel it was also shown that topmodel coupled with the downscaling method of the topographic index accurately simulated runoff for different rainfall events in the catchment without recalibration copyright 2006 john wiley sons ltd

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

on the kriging of water table elevations using collateral information from a digital elevation model in unconfined aquifers flowing under topographic gradients the water table is a subdued replica of the ground surface above this principle is the basis for using detailed collateral or secondary information from digital elevation models to supplement sparse observations from water wells in the mapping of phreatic surfaces data from dem derived secondary variables are incorporated into the estimation of water table elevations using the geostatistical method known as kriging with an external drift ked two different ked models are proposed based on the choice of secondary variable in the first water table elevation is expressed as the sum of a deterministic trend given by topographic elevation and a residual random component representing depth to water table in the second depth to water table is expressed as a linear function of a deterministic trend given by the topmodel topographic index and a residual random error the relationship between water table depth and topographic index is derived from simplified groundwater dynamics and forms the basis of topmodel type rainfall runoff models the two ked models are applied to the mapping of water table elevations in the oak ridges moraine orm an unconfined aquifer near toronto canada results show that ked with topographic elevation as external drift is the more robust of the two models despite its strong theoretical basis the second model yields kriged water table elevations that are not always physically plausible in part this is because field observations of water table depth do not verify the predicated relationship with topographic index in large parts of the study area however this relationship may be valid in other cases and at other spatial scales in such cases the second model would provide a very powerful approach for mapping water table elevations and for calibrating distributed parameters of the topmodel equations on water well observations

late valanginian extinction and turnover of tethyan brachiopods a signal of the weissert event bakony mountains hungary abstract brachiopods together with ammonoids were collected bed by bed from several lower cretaceous pelagic sections and localities in the bakony mountains transdanubian range hungary dated by detailed ammonoid and nannofossil biostratigraphy these yielded abundant and diverse brachiopod material 1015 specimens 25 species and a possibility to determine the stratigraphic ranges of the brachiopod species two sections including the berriasian to hauterivian interval were studied in detail in the harskut hk 12 section the early late valanginian weissert event was documented previously by stable isotope investigations and it was biostratigraphically correlated with the edesviz key section the lower cretaceous brachiopod record in the bakony was separated into four assemblages the abundant early berriasian brachiopod assemblage 1 diminished and with a stepwise extinction and partial turnover passed to an impoverished assemblage 2 in the early valanginian these species ultimately disappeared at the early late valanginian boundary this extinction is interpreted as the effect of the global weissert event the extinction horizon is marked by an almost monospecific dwarf brachiopod fauna assemblage 3 in the late valanginian an abundant and diverse brachiopod fauna appeared with a complete turnover of species assemblage 4 the development of this assemblage in the late valanginian and hauterivian was probably controlled by environmental changes 1 by a switch in palaeoclimate i e by the late valanginian cooling episode and 2 by the change in the sedimentary environment

jurassic microplate movements and brachiopod migrations in the western part of the tethys abstract the paleobiogeography of the jurassic brachiopods of the alpine carpathian region and adjacent areas is discussed on the basis of the distribution of distinctive taxa the jurassic microplates of the western part of tethys and the present day terranes of the alpine carpathian region are outlined and their relationships are discussed the migration possibilities of the brachiopods in the jurassic tethys were controlled mainly by plate microplate movements and by changes in the oceanic current system the mediterranean microcontinent isolated from the european and african shelves by oceanic deep sea belts was the homeland of the mediterranean brachiopod province in the course of the jurassic the mediterranean microcontinent moved as part of the african plate away from europe the widening alboran ligurian penninic oceanic belt became a barrier preventing migration of brachiopods by the end of the middle jurassic the tisza microplate detached from europe and formed a stepping stone for brachiopod dispersal at about the same time the hesperian strait opened between the basins of the tethys and the central atlantic the opening of this strait resulted in a reorganization of the tethyan current system the westward flowing equatorial currents which made a turn in the western corner of tethys in the first half of the mesozoic now ran to the west through the hesperian strait via the central atlantic to the pacific this change produced a new pattern in brachiopod distribution the mediterranean fauna successfully invaded the european shelf at the same time the mediterranean province became impoverished

effects of digital elevation model accuracy on hydrologic predictions abstract the effect of vertical accuracy of digital elevation models dems on hydrologic prediction accuracy was evaluated by comparing three dems and associated streamflow simulations for the 7 2 km 2 usda ars watershed at mahantango creek pa the dems were the standard 30 m usgs 7 5 dem a 5 m product derived from low altitude aerial photography and a 30 m product derived from interferometric processing of spaceborne imaging radar c sir c statistical analysis of the dems showed that the usgs dem had the typical stipling errors resulting from processing of the source digital contour maps and a vertical error structure related to the topographic attributes of the watershed the sir c dem had a vertical offset of about 50 m from the high resolution and usgs dems as well as error features that were somewhat related to topographic features inaccuracies in both the usgs and sir c dems were apparent in the drainage network as well as in spatial images of elevation slope and contributing area comparisons of runoff predicted using a hydrologic model based on the three dems showed that mean annual predicted runoff volumes were 0 3 and 7 0 larger for the usgs and sir c dems respectively as compared to the reference dem much larger differences were apparent in individual hydrographs and the usgs and sir c dems predicted lower peaks and higher base flows than did the reference

differences in topographic characteristics computed from 100 and 1000 m resolution digital elevation model data topographic characteristics computed from 100 and 1000 m resolution digital elevation model dem data are compared for 50 locations representing varied terrain in the conterminous usa the topographic characteristics are three parameters used extensively in hydrological research and modelling slope s specific catchment area as and a wetness index computed as the logarithm of the specific catchment area divided by slope ln as s slope values computed from 1000 m dems are smaller than those computed from 100 m dems specific catchment area and the wetness index are larger for the 1000 m dems compared with the 100 m dems most of the differences between the 100 and 1000 m resolution dems can be attributed to terrain discretization effects in the computation of the topographic characteristics and are not the result of smoothing or loss of terrain detail in the coarse data in general the terrain discretization effects are greatest on flat terrain with long length scale features and the smoothing effects are greatest on steep terrain with short length scale features for the most part the differences in the average values of the topographic characteristics computed from 100 and 1000 m resolution dems are predictable that is biases in the mean values for the characteristics computed from a 1000 m dem can be corrected with simple linear equations copyright 2000 john wiley sons ltd

early jurassic pliensbachian brachiopod biogeography in the western tethys the euro boreal and mediterranean faunal provinces revised abstract the pliensbachian brachiopod biogeography of the western tethyan region and the euro boreal vs mediterranean faunal provinciality is evaluated the data base was developed from improved and mostly revised taxonomical data of 25 pliensbachian brachiopod localities selected from europe and north africa the revised list and presence absence data of 405 pliensbachian brachiopod species formed the taxonomic units of the numerical analysis based on similarity coefficients cluster analysis hca carried out from the jaccard and raup crick coefficient data showed clear dichotomy between the euro boreal and mediterranean brachiopod biochores principal coordinates pco technique and non metric multi dimensional scaling nmds complemented with the minimal spanning trees resulted in similar grouping of the pliensbachian brachiopod faunas in de trended correspondence analysis dca besides the clearly separated euro boreal and intra mediterranean units the peri mediterranean assemblage formed a discrete scatter between the two major biochores the three algerian faunas ouar trar ksou appear in a somewhat marginal position within the euro boreal province the above pliensbachian brachiopod biochores reveal very high degree of endemicity probably related to the limited dispersal potential of brachiopods from the complete data set distinctive euro boreal and mediterranean species ten from both provinces were selected ribbed spiriferinid morphotypes are frequent among the distinctive euro boreal species whereas besides smooth spiriferinids some rhynchonellid and terebratulid morphotypes with expanded anterior margins are common among the distinctive mediterranean species in the early jurassic tethyan palaeogeography the marked dichotomy between the euro boreal and mediterranean provinces is interpreted in terms of deep sea oceanic barriers which isolated the intra tethyan microcontinent from the european and african shelf regions geographical position and local environmental factors caused the differentiation of the peri mediterranean subprovince along the north western margin of the microcontinent this palaeobiogeographical unit formed an interface between the intra mediterranean and the euro boreal biochores

effects of digital elevation model map scale and data resolution on a topography based watershed model the effects of digital elevation model dem map scale and data resolution on watershed model predictions of hydrologic characteristics were determined for topmodel a topography based watershed model the effects of topography on watershed hydrology are represented in topmodel as the distribution of ln a tan b where ln is the napierian logarithm a is the upslope area per unit contour length and tan b is the gravitational gradient the minimum maximum mean variance and skew values of the ln a tan b distribution were computed from 1 24 000 scale 24k dems at 30 and 90 m resolutions and from 1 250 000 scale 250k dems at 90 m resolution for 71 areas in pennsylvania new york and new jersey an analysis of topmodel showed that model predictions of the depth to the water table the ratio of overland flow to total flow peak flow and variance and skew of predicted streamflow were affected by both the dem map scale and data resolution further topmodel analyses showed that the effects of dem map scale and data resolution on model predictions were due to the sensitivity of the predictions to the mean of the ln a tan b distribution which was affected by both dem map scale and data resolution dem map scale affected the mean of the ln a tan b distribution through its influence on the mean of the ln a distribution which characterizes land surface shape and the mean of ln 1 tan b distribution which characterizes land surface slope dem resolution in contrast affected the mean of the ln a tan b distribution primarily by its influence on the mean of the ln a distribution

the influence of elevation error on the morphometrics of channel networks extracted from dems and the implications for hydrological modelling stream network morphometrics have been used frequently in environmental applications and are embedded in several hydrological models this is because channel network geometry partly controls the runoff response of a basin network indices are often measured from channels that are mapped from digital elevation models dems using automated procedures simulations were used in this paper to study the influence of elevation error on the reliability of estimates of several common morphometrics including stream order the bifurcation length area and slope ratios stream magnitude network diameter the flood magnitude and timing parameters of the geomorphological instantaneous unit hydrograph giuh and the network width function dems of three uk basins ranging from high to low relief were used for the analyses the findings showed that moderate elevation error rmse of 1 8 m can result in significant uncertainty in dem mapped network morphometrics and that this uncertainty can be expressed in complex ways for example estimates of the bifurcation length and area ratios and the flood magnitude and timing parameters of the giuh each displayed multimodal frequency distributions i e two or more estimated values were highly likely furthermore these preferential estimates were wide ranging relative to the ranges typically observed for these indices the wide ranging estimates of the two giuh parameters represented significant uncertainty in the shape of the unit hydrograph stream magnitude network diameter and the network width function were found to be highly sensitive to elevation error because of the difficulty in mapping low magnitude links uncertainties in the width function were found to increase with distance from outlet implying that hydrological models that use network width contain greater uncertainty in the shape of the falling limb of the hydrograph in light of these findings care should be exercised when interpreting the results of analyses based on dem mapped stream networks copyright 2007 john wiley sons ltd

dem resolution effects on shallow landslide hazard and soil redistribution modelling in this paper we analyse the effects of digital elevation model dem resolution on the results of a model that simulates spatially explicit relative shallow landslide hazard and soil redistribution patterns and quantities we analyse distributions of slope specific catchment area and relative hazard for shallow landsliding for four different dem resolutions grid sizes of 10 25 50 and 100 m of a 12 km2 study area in northern new zealand the effect of dem resolution is especially pronounced for the boundary conditions determining a valid hazard calculation for coarse resolutions the smoothing effect results in a larger area becoming classified as unconditionally stable or unstable we apply simple empirical soil redistribution algorithms for scenarios in which all sites with a certain landslide hazard fail and generate debris flow the lower initial number of failing cells but also the inclusion of slope limit in those algorithms becomes apparent with coarser resolutions for finer resolutions much larger amounts of soil redistribution are found which is attributed to the more detailed landscape representation looking at spatial patterns of landslide erosion and sedimentation the size of the area affected by these processes also increases with finer resolutions in general landslide erosion occupies larger parts of the area than deposition although the total amounts of soil material eroded and deposited are the same analysis of feedback mechanisms between soil failures over time shows that finer resolutions show higher percentages of the area with an increased or decreased landslide hazard when the extent of sites with lower and higher hazards are compared finer grid sizes and higher landslide hazard threshold scenarios tend to increase the total extent of areas becoming more stable relative to the less stable ones extreme care should be taken when quantifying landslide basin sediment yield by applying simple soil redistribution formulas to dems with different resolutions rather quantities should be interpreted as relative amounts for studying shallow landsliding over a longer timeframe the perfect dem resolution may not exist because no resolution can possibly represent the dimensions of all different slope failures scattered in space and time we assert that the choice of dem resolution possibly restricted by data availability in the first place should always be adapted to the context of a particular type of analysis copyright 2005 john wiley sons ltd

on the effect of digital elevation model accuracy on hydrology and geomorphology this study compares published cartometric and photogrammetric digital elevation models dems of various grid spacings with a ground truth data set obtained by ground survey and studies the implications of these differences on key hydrologic statistics inferred catchment sizes and stream networks from published dems were found to be significantly different than those from the ground truth in most instances furthermore the width functions and cumulative area relationships determined from the published dems were found to fall consistently outside the 90 confidence limits determined from the ground truth for more than 60 of the relationship suggesting that these hydrologic properties are poorly estimated from published dems however the slope area relationships determined from published dems were found to be less sensitive to catchment shape size and stream network with the relationship falling outside the 90 confidence limits for less than 40 of the relationship for all catchments identified from the published dems a published relationship linking the horizontal resolution with the vertical accuracy of the dem was tested predicting a horizontal resolution of about 10 m for the published dems tested

applications of hydrologic information automatically extracted from digital elevation models digital elevation models dems can be used to derive a wealth of information about the morphology of a land surface traditional raster analysis methods can be used to derive slope aspect and shaded relief information recently developed computer programs can be used to delineate depressions overland flow paths and watershed boundaries these methods were used to delineate watershed boundaries for a geochemical stream sediment survey to compare the results of extracting slope and flow paths from dems of varying resolutions and to examine the geomorphology of a martian dem

conceptualization of runoff processes using a geographical information system and tracers in a nested mesoscale catchment tracer investigations were combined with a geographical information system gis analysis of the 31 km2 girnock catchment cairngorm mountains scotland in order to understand hydrological functioning by identifying dominant runoff sources and estimating mean residence times the catchment has a complex geology soil cover and topography gran alkalinity was used to demonstrate that catchment geology has a dominant influence on baseflow chemistry but flow paths originating in acidic horizons in the upper soil profiles controlled stormflow alkalinity chemically based hydrograph separations at the catchment scale indicated that 30 of annual runoff was derived from groundwater sources similar contributions 23 36 were estimated for virtually all major sub basins 18o of precipitation mean 9 4 range 16 1 to 5 0 and stream waters mean 9 1 range 11 6 to 7 4 were used to assess mean catchment and sub basin residence times which were in the order 4 6 months gis analysis showed that these tracer based diagnostic features of catchment functioning were consistent with the landscape organization of the catchment soil and host hydrology of soil type maps indicated that the catchment and individual sub basins were dominated by hydrologically responsive soils such as peats histosol peaty gleys histic gleysols and rankers umbric leptosols and histosols soil cover in combination with a topographic index predicted extensive areas of saturation that probably expand during hydrological events thus providing a high degree of hydrological connectivity between catchment hillslopes and stream channel network this was validated by aerial photographic interpretation and groundtruthing these characteristics of hydrological functioning i e dominance of responsive hydrological pathways and short residence times dictate that the catchment is sensitive to land use change impacts on the quality and quantity of streamflows it is suggested that such conceptualization of hydrological functioning using tracer validated gis analysis can play an important role in the sustainable management of river basins copyright 2006 john wiley sons ltd

saturation regions in catchments and their relations to soil and topographic properties abstract criteria are derived for the existence of saturated areas on draining hillslopes in natural catchments these are given in terms of soil transmissivity the hillslope gradient and its wetness state characterised by the baseflow discharge from the catchment analyses are made for idealised hillslopes with uniform soils to obtain expression for the width of the saturated zone the size of saturated zones on undulating hillslopes with gradiational soils is shown to depend strongly on topographic convergence or divergence the effects of soil transmissivity hillslope geometry and drainage flux density are lumped into a dimensionless parameter whose value determines the location of seepage boundaries on slopes of specified geometry scaling relations for seepage area in catchments of different size are shown to be generally nonlinear and depend primarily on local hillslope gradients relative predictions of seepage zone size are confirmed by observed hydrographs from three catchments with different physical characteristics

mesozoic plate tectonic reconstruction of the carpathian region abstract palaeomagnetic palaeobiogeographic and structural comparisons of different parts of the alpine carpathian region suggest that four terranes comprise this area the alcapa tisza dacia and adria terranes these terranes are composed of different mesozoic continental and oceanic fragments that were each assembled during a complex late jurassic cretaceous palaeogene history palaeomagnetic and tectonic data suggest that the carpathians are built up by two major oroclinal bends the alcapa bend has the meliata oceanic unit correlated with the dinaric vardar ophiolite in its core it is composed of the western carpathians eastern alps and southern alcapa units transdanubian range bukk this terrane finds its continuation in the high karst margin of the dinarides further elements of the alcapa terrane are thought to be derived from collided microcontinents czorsztyn in the n and a carbonate unit tisza in the se the tisza dacia bend has the vardar oceanic unit in its core it is composed of the bihor and getic microcontinents this terrane finds its continuation in the serbo macedonian massif of the balkans the bihor getic microcontinent originally laid east of the western carpathians and filled the present carpathian embayment in the late palaeozoic early mesozoic the vardar ocean occupied an intermediate position between the western carpathian austroalpine transdanubian high karst margin and the bihor getic serbo macedonian microcontinent the vardar and pindos oceans were opened in the heart of the mediterranean adriatic microcontinent in the late permian middle triassic vardar subducted by the end of jurassic causing the bihor getic serbo macedonian microcontinent to collide with the internal dinaric western carpathian margin an external penninic vahic ocean tract began opening in the early jurassic separating the austroalpine western carpathian microcontinent and its fauna from the european shelf further east the severin ceahlau magura also began opening in the early jurassic but final separation of the bihor getic ribbon and its fauna from the european shelf did not take place until the late middle jurassic the alcapa and the tisza dacia were bending during the albian maastrichtian the two oroclinal bends were finally opposed and pushed into the gates of the carpathian embayment during the palaeogene and neogene at that time the main n s shortening in distant alpine and hellenic sectors was linked by a broader right lateral shear zone along the former vardar suture

assessment of the effects of dem gridding on the predictions of basin runoff using mike she and a modelling resolution of 600 m summary a 586 km 2 catchment was modelled with the distributed hydrologic model mike she coarse digital elevation models dems having a 600 m resolution and gridded from a set of elevation points geographically distributed with a much finer resolution were used in the modelling with the purpose of investigating potential effects of the dem generation methods on i model parameter values ii adequacy of model global predictions and iii the evaluation of internal state predictions to address these aspects this paper describes the dem gridding methods assesses the accuracy of the dems and examines systematically the sensitivities of parameter values and predictions of the distributed model with respect to the dems three types of gridding methods were applied methods type i were based on the use of the mike she interpolation tool bilinear algorithm for processing input elevation data distributed about the periphery of the gridded dem cells input elevation data distributed about the centre of the gridded dem cells were processed in gridding methods type ii the third type was based on the use of the topogrid algorithm that considers landscape features such as digitised streams to improve the drainage structure of the gridded dems a multi criteria protocol was applied for assessing the elevation quality of dems and their suitability for hydrologic purposes it was found that the quality of the dem products of the mike she interpolation tool were poorer the independent calibration of the assembled hydrologic models revealed i important variations of model predictions and ii from average to important variations of effective parameter values as a function of the different dems a multi criteria protocol analysing discharge time series peak flows and piezometric levels showed that model performance is in broad terms in agreement with the elevation and slope quality of the dems

effects of dem horizontal resolution and methods on calculating the slope length factor in gently rolling landscapes abstract the usle is used world wide to predict soil loss on the field scale from sheet and rill erosion the slope length l factor is derived as its topographical factor the accuracy of l factor determines the precision of soil loss estimation with usle uncertainties on l factor are caused by dem resolution and the choice of the processing algorithm in the present study we made two comparisons to evaluate the effects of dem horizontal resolution and processing algorithm on the accuracy of the l factor in gently sloped landscapes one is between the grid cumulating method gc and the contributing area method ca using d8 flow routing algorithm the other is among single d8 rho8 and multiple fd8 frho8 and demon flow routing algorithms for processing the contributing area method in two comparisons 5 m 10 m 25 m 50 m and 100 m dem of a 0 88 km2 catchment in the lowland of northern germany were applied the results indicate that l factor calculated with any of the six methods is sensitive to horizontal resolution which strongly affects the accuracy with decreasing resolution correlations of lca rho8 and lca d8 lca fd8 and lca d8 lca fd8 and lca rho8 increase while those between demon and the other flow routing algorithms do not change significantly with decreasing resolution the difference between lgc d8 and lca d8 is enlarged while differences between any two flow algorithms using ca did not change significantly the l factor variation between any two methods is larger on the upslope than the flat valley for the 5 m and 10 m dem while terrain characteristics are not visible on the 25 m 50 m and 100 m dem the l factor also depends on the computation method lgc d8 is approximately half of lca it is concluded that dem horizontal resolution is very important for l factor calculation the most suitable calculation method is lgc d8 for gently rolling landscapes this study can be used for selecting a suitable method and dem resolution for accurate calculation of l factor and soil loss in gently rolling landscapes

soil landscape modeling across a physiographic region topographic patterns and model transportability abstract soil landscape modeling techniques have been developed as a quantitative method to predict patterns of soil properties from observed patterns in soil forming factors however transportability of these models to unsampled landscapes is unknown our objective was to develop quantitative soil landscape models for multiple study sites and examine the similarity of these quantitative models and therefore the similarity of soil landscape relationships among areas with similar soils we collected high resolution digital elevation models dem for six study sites across the pennyroyal physiographic region of kentucky and for each study site used terrain attributes derived from the dem to collect discrete soil samples using a stratified random sampling design for morphological physical and chemical characterization for three of these sites we examined the inherent differences in terrain attributes among sites and developed quantitative soil landscape models that predict the spatial patterns in a horizon depth surface soil organic carbon content and surface sand and silt content the other three sites were used to test the transportability of these models terrain attribute distributions differ significantly among study sites with regional terrain attributes upslope contributing area topographic wetness index being more similar among fields than local terrain attributes slope gradient slope curvature predictive models explained from 28 to 67 of the variation in soil properties the terrain attributes that best predicted soil variability were similar across all three fields used for model development with slope gradient elevation slope curvature and upslope contributing area appearing in most of the models however applying models from one field to other fields within the same physiographic region produced inconsistent results in general prediction quality decreased with distance from the site of model development further sampling modeling and validation at additional field sites are required to properly establish model transportability

berriasian and early valanginian environmental change along a transect from the jura platform to the vocontian basin valanginian sedimentary archives display a positive anomaly in the carbon isotope record which is associated with a crisis in neritic and pelagic carbonate production this study aims to reconstruct the evolution of palaeoenvironments in the jura area and the vocontian basin during late berriasian and early valanginian times in order to better understand the controlling factors leading to the valanginian episode of major environmental change three sections along a transect through the jura platform switzerland and france and the vocontian basin france have been studied stratigraphic correlations have been established by combining biostratigra phy benthic foraminifera ammonites and calpionellids with geochemistry 13c trends and sequence stratigraphy a change from a rimmed ramp to a swell dominated ramp morphology is observed through the berriasian valanginian boundary the disappearance of the barrier appears to have been controlled by large sea level variations in combination with the arrival of significantly more humid climate conditions this barrier played a major role in the distribution of geochemical mineralogical and palynological fluxes towards the basin during the berriasian continental fluxes detrital particles nutrients pollen and spores were buffered by the platform morphology whereas in the early valanginian they were more readily transported towards the basin the initiation of a major transgression onto lateritic soils leading to their intense reworking instigated a fertilization of ocean waters during the earliest valanginian and with that a change towards heterozoan carbonate production and subsequently to the demise of the already weakened carbonate platform

re scaling the topographic index to improve the representation of physical processes in catchment models abstract the assignment of hydrological model parameters from physically measurable catchment attributes remains an unsolved problem several authors have shown that for the hydrological model topmodel there is a relationship between the scale of the digital elevation model dem and the saturated hydraulic conductivity parameter used to calculate water table position and baseflow for models that use dem data from pixels measured in tens of metres the value of the corresponding saturated hydraulic conductivities for satisfactory flow reproduction are often much larger than measured values and this causes most surface flow to be generated by the saturation excess mechanism this is undesirable in environments where infiltration excess runoff can also occur this paper presents a way to objectively compensate for the distorting effect of dem scale on the value of the saturated hydraulic conductivity so that its measured value can be used in topmodel simulations the method described links the distribution of topographic index ln a tan to a spatial variability measure svm based on the shannon and weaver information content equation for a digital signal by maximising the svm an optimum adjustment to the mean of the distribution of topographic index can be made so that the distribution represents what would have been calculated had a dem been available at the spatial resolution at which the saturated hydraulic conductivity was measured the method is applied to a topmodel of the mahurangi basin in new zealand and it is shown that physically reasonable simulations are achieved with the adjusted distribution of topographic index

estimating transmissivity fields and their influence on flow and transport the case of champagne mounts 1 this paper presents a flexible and general methodology that combines hydrogeological and geostatistical modeling techniques to estimate a set of transmissivity fields and their influence on flow and transport the methodology may be applied to any case with only hydraulic head observations even if most of them are concentrated inside a small part of the entire domain of interest it is applied here to the case of the champagne chalk aquifer france where it is shown to be very efficient the methodology is decomposed in three independent parts first a reference head distribution is constructed by kriging in order to constrain the inverse problem as hydraulic heads and elevations are correlated a smoothed digital elevation model is used as external drift the inverse problem is then solved by using a simplified pilot point method with an efficient and easy to use minimization algorithm finally geostatistical simulations combined with flow simulations lead to a set of acceptable transmissivity fields the induced uncertainty is evaluated by calculating tracer concentrations pointing out areas where flow behavior is uncertain and where new borings would be advantageously drilled

analysis and characterization of the vertical accuracy of digital elevation models from the shuttle radar topography mission 1 the first near global high resolution digital elevation model dem of the earth has recently been released following the successful shuttle radar topography mission srtm of 2000 this data set will have applications in a wide range of fields and will be especially valuable in the earth sciences prior to widespread dissemination and use it is important to acquire knowledge regarding the accuracy characteristics in this work a comprehensive analysis of the vertical errors present in the data set and the assessment of their effects on different hydrogeomorphic products is performed in particular the work consisted of 1 measuring the vertical accuracy of the data set in two areas with different topographic characteristics 2 characterizing the error structure by comparing elevation residuals with terrain attributes 3 assessing a wavelet based filter for removing speckle and 4 assessing the effects of vertical errors on hydrogeomorphic products and on slope stability modeling the results indicate that in the two sites relief has a strong effect on the vertical accuracy of the srtm dem in the high relief terrain large errors and data voids are frequent and their location is strongly influenced by topography while in the low to medium relief site errors are smaller although the hilly terrain still produces an effect on the sign of the errors speckling generates deviations in the drainage network in one of the investigated areas but the application of a wavelet filter proved to be an effective tool for removing vertical noise although further fine tuning is necessary vertical errors cause differences in automatically extracted hydrogeomorphic products that range between 4 and 1090

the effects of dem resolution and neighborhood size on digital soil survey terrain characteristics such as slope gradient slope aspect profile curvature contour curvature computed from digital elevation model dem are among the key inputs to digital soil surveys based on geographic information systems gis these terrain attributes are computed over a neighborhood spatial extent the objective of this research was to investigate the combined effect of dem resolution and neighborhood size on digital soil surveys using the soil landscape inference model solim approach the effect of neighborhood size and dem resolution on digital soil survey was examined through computing the required terrain attributes using different neighborhood sizes from 3 to 54 m for 3 6 9 12 18 and 27 m resolution dem these attributes were then compiled and used to digitally map soils using the solim approach field work completed on a hillslope in dane county wi in the summer of 2003 was used to validate each of the solim derived soil surveys for accuracy the results of the soil survey validations suggest that there is a range of neighborhood sizes that produces the most accurate results for a given resolution dem this range of neighborhood sizes however varies from landscape to landscape when the soils on a gently rolling landscape were mapped the neighborhood sizes that produced the most accurate results ranged from about 33 48 m when soils on short steep backslope positions were mapped the neighborhood size values that produced the most accurate results range from about 24 36 m this paper also shows that it is not always the highest resolution dem that produces the highest accuracy knowing which dem resolution and neighborhood size combinations produce the most accurate digital soil surveys for a particular landscape will be extremely useful to users of gis based soil mapping applications

constraining saturated hydraulic transmissivity values by means of maximum saturated area mapping and maximum subsurface discharge long term simulation in the amazon basin although saturated hydraulic conductivity k0 and saturated hydraulic transmissivity t0 are physically based parameters quite often their calibrated values lie out of the physically based range driving modellers to increased k0 values in some orders of magnitude from field measured values in order to fit observed discharge data therefore calibration is a necessary process in hydrological modelling within a hydrological model k0 or t0 plays an important role they allow the model to represent the hydrograph separation through estimates of subsurface discharges simulating different flow components in hydrological modelling is an increasing need for basin management and water quality predictions the present study has the objective to develop two criteria to constrain t0 values using a topmodel multi velocity approach in order to represent the hydrograph separation in a more realistic way the method was i applied to three sub basins in the amazon basin the obidos the humaita and santo antonio basins ii evaluated by means of a combined objective function and uncertainty bounds and iii validated in a long term simulation because the constraint criteria were applied it has verified a significant reduction in subsurface uncertainty for all the basins the constraint criteria reduced the number of simulations to 11 42 and 23 for the obidos basin the humaita basin and the santo antonio basin respectively this means that a large number of simulations were rejected in the sense they represented unrealistic hydrograph separation copyright 2012 john wiley sons ltd

relations between topography and water table depth in a shallow forest soil the relations between water table depth in a shallow forest soil and topographic characteristics derived from a raster digital elevation model dem were studied water table depths at times of observation and peak levels between times of observation were measured weekly during an autumn winter rainy season at 59 wells in a catchment ca 0 04 km 2 drained by an ephemeral stream located 80 km east of vancouver canada digital elevation models with grid spacings of 4 8 and 16 m were derived from a ground survey and values of a upslope contributing area per unit contour length tan surface slope and x a measure of surface curvature were computed from the dems to avoid problems with data censoring when the water table dropped below the bottom of some wells the depths were discretized into classes and discriminant analysis was used to relate water table depth classes to the topographic indices the relations were derived using data from 30 wells and were tested on data from the other 29 wells to provide an independent test of predictive capability the index in a tan provided more reliable classifications than a multiple discriminant analysis using in a tan and x as separate predictor variables water table depths at some wells were consistently misclassified e g 0 3 correct classifications whereas at others they were classified correctly in up to 100 of cases consistent misclassification at individual wells could reflect either the effects of errors in the derived topographic indices through errors in the dem or the algorithms used to calculate the indices or phenomena not related to surface topography such as variability in soil properties or differences between the surface topography and the topography of the base of the soil profile the predictive accuracy and statistical significance of derived relations decreased as the dem grid size increased from 4 to 8 to 16 m these results are valid only for predictions of water table depths at points further research should explore the effect of grid scale on relations between grid averaged water table depths and topographic indices and on methods to parameterize subgrid scale variability

comparison of single and multiple flow direction algorithms for computing topographic parameters in topmodel single flow direction sfd and multiple flow direction mfd algorithms were used to compute the spatial and statistical distributions of the topographic index used in the watershed model topmodel an sfd algorithm assumes that subsurface flow occurs only in the steepest downslope direction from any given point an mfd algorithm assumes that subsurface flow occurs in all downslope directions from any given point the topographic index in topmodel is in a tan 3 where in is the napierian logarithm a is the upslope area per unit contour length and tan 3 is the slope gradient the in a tan 3 distributions were computed from digital elevation model dem data for locations with diverse topography in arizona colorado louisiana nebraska north carolina oregon pennsylvania tennessee vermont and virginia the means of the in a tan 3 distributions were higher when the mfd algorithm was used for computation compared to when the sfd algorithm was used the variances and skews of the distributions were lower for the mfd algorithm compared to the sfd algorithm the differences between the mfd and sfd algorithms in the mean variance and skew of the in a tan 3 distribution were almost identical for the various dems and were not affected by dem resolution or watershed size topmodel model efficiency and simulated flow paths were affected only slightly when the in a tan 3 distribution was computed with the sfd algorithm instead of the mfd algorithm any difference in the model efficiency and simulated flow paths between the sfd and mfd algorithms essentially disappeared when the model was calibrated by adjusting subsurface hydraulic parameters

spatial resolution sensitivity of catchment geomorphologic properties and the effect on hydrological simulation the geomorphologic area function and width function that characterize the forms of hillslope and river networks are two key parameters employed in the gbhm geomorphology based hydrological model for representing the hydrological processes together with other spatial information one fundamental issue on the use of the geomorphologic properties is the spatial resolution sensitivity in both the threshold area for river network generation and digital elevation model dem resolution the threshold area is the minimum drainage area required to initiate the river the dem resolution depends on the available elevation data in the present study multifractal analysis was used to investigate the sensitivity of width functions extracted by different threshold areas and the sensitivity of area functions extracted from various resolutions of dems fifteen japanese catchments were selected for the sensitivity analysis based on 250 m mesh dem data it was found that the river networks generated with larger threshold areas tend to lose the detailed scaling information when the dem mesh size increases the river networks extracted with the same threshold area become sparser and the topography tends to be flat and scaling structures of the area functions become simpler the runoff generations of the gbhm were influenced by the dem resolution the effect of the dem resolution on the hydrological response is related to the temporal resolution with more influence on the hourly response compared with the daily response from the relation between the scaling structure expressed by the multifractal spectrum and the hydrological response of a catchment it was found that the detailed scaling information had more effect on the hydrological response of higher temporal resolution copyright 2001 john wiley sons ltd

effects of catchment discretization on topographic index distributions summary digital elevation models dems are widely used in topographically based hydrology models most researchers dealing with dems have worked exclusively with either grid or contour based techniques intercomparisons of these techniques are empirical in nature few in number and limited to a small number of catchments we examine the relative effects of these techniques on the distribution of the topographic index ti for nine idealised hillslope types and eight natural catchments 4 4 83 km 2 in southeast australia in particular we investigate the underlying causes for the frequently observed increase in the ti with grid size a simple analytical model for a parallel planar hillslope indicates that median ti is asymptotic with respect to the number of grid cells and a linear function of grid size we demonstrate that the latter result holds for hillslopes with more complex geometry using a multiple flow direction algorithm we find that hillslope geometry and flow partitioning affect the spatial pattern of the ti and the rate of change m of median ti with grid size this makes it impractical to recommend general guidelines for the value of the directional parameter in flow partitioning algorithms for the natural catchments we show that median ti is also a linear function of grid size and that there is some evidence for a linear relationship between m and the inverse of the median topographic slope throughout the investigation we find that contour dems are less sensitive to changes in resolution than grid dems

channel head location and characteristics using digital elevation models the drainage network is the conduit through which much surface water and sediment are routed within a catchment in a catchment the position of where hillslopes begin and channels end has long been considered the position of transition between diffusive processes upslope and the more incisive fluvial processes downslope consequently understanding channel head location is an important issue in understanding catchment hydrology and geomorphology this study examines channel head position and characteristics in a catchment in arnhem land northern territory australia in this study the position of channel heads was mapped within the catchment and plotted on a reliable digital elevation model of the catchment it was found that the majority of channel heads have relatively small source areas and that graphical catchment descriptors such as the area slope relationship and cumulative area distribution can provide reliable measures of the field position of the heads of first order streams and the transition from hillslope to channel the area slope relationship and cumulative area distribution are also shown to be good tools for determining digital elevation model grid size which can capture hillslope detail and the transition from hillslope to channel copyright 2005 john wiley sons ltd

clausius clapeyron scaling of peak cape in continental convective storm environments abstracta thermodynamic constraint on convective available potential energy cape in continental environments is established using an idealized one dimensional model this theoretical model simplifies the synoptic scale preconditioning framework for continental severe convection by considering a dry adiabatic column that comes into contact with a moist land surface a system of equations is derived to describe the evolution of the ensuing surface boundary layer from these the maximum value of transient cape in the column can be found for any particular combination of surface temperature and moisture it is demonstrated that for a given range of surface temperatures the value of peak cape scales with the clausius clapeyron relation

nannofossil carbonate fluxes during the early cretaceous phytoplankton response to nutrification episodes atmospheric co2 and anoxia 1 greenhouse episodes during the valanginian and aptian correlate with major perturbations in the c cycle and in marine ecosystems carbonate crises and widespread deposition of corg rich black shales quantitative analyses of nannofossil micrite were conducted on continuous pelagic sections from the southern alps northern italy where high resolution integrated stratigraphy allows precise dating of early cretaceous geological events rock forming calcareous nannofloras were quantified in smear slides and thin sections to obtain relative and absolute abundances and paleofluxes that are interpreted as the response of calcareous phytoplankton to global changes in the ocean atmosphere system increased rates of volcanism during the formation of ontong java and manihiki plateaus and the parana etendeka large igneous province lip are proposed to have caused the geological responses associated with early aptian oceanic anoxic event oae 1a and the valanginian event respectively calcareous nannofloras reacted to the new conditions of higher pco2 and fertility by drastically reducing calcification the valanginian event is marked by a 65 reduction in nannofossil paleofluxes that would correspond to a 2 3 times increase in pco2 during formation of the parana endenteka lip a 90 reduction in nannofossil paleofluxes which occurred in a 1 5 myr long interval leading into oae1a is interpreted as the result of a 3 6 times increase in pco2 produced by emplacement of the giant ontong java and manihiki plateaus high pco2 was balanced back by an accelerated biological pump during the valanginian episode but not during oae1a suggesting persisting high levels of pco2 in the late aptian and or the inability of calcareous phytoplankton to absorb excess pco2 above threshold values

effects of digital elevation model resolution on derived stream network positions 1 this study examines the effect of digital elevation model dem resolution on the positional accuracy of derived hydrologic networks and quantitatively confirms that dem resolution should be greater than the average hillslope length when used for hydrologic modeling seven hundred kilometers of mapped stream networks are compared to stream networks derived from 17 dems with resolutions ranging from 30 m to 3 km comparison between predicted and mapped streams reveals that accuracy of predicted stream locations decays quickly beyond a dem resolution of 180 m a new application of gyasi agyei et al s 1995 dem resolution suitability test based on average slope and vertical resolution indicates an average hillslope length of between 150 and 180 m tarboton et al s 1991 method of determining average hillslope length based on slope and accumulation areas reconfirms the length to be 150 m and verifies the link between network accuracy and hillslope scale two algorithms are used to derive stream networks the d algorithm tarboton 1997 which allows for flow dispersion and the d8 algorithm o callaghan and mark 1984 which does not a comparison between the d8 and d algorithms shows that modeling flow dispersion is not necessary in steep terrain as both algorithms performed equally well however the d algorithm is found to be less susceptible to modeling erroneous hillside flow convergence making it preferable to the d8 algorithm when used by tarboton et al s 1991 method of determining the average hillslope lengths finally field observation indicates that predicted first and second order streams tend to exist when predicted however mapped streams have a higher positional accuracy

the effect of dem resolution on the computation of the factor of safety using an infinite slope model abstract the quality of digital elevation models dems is essential for reliable landslide susceptibility assessments in this paper two dems derived from aster aster gdem v 2 with 30 m horizontal resolution and terrasar x geoelevation10 with 10 m horizontal resolution data are compared to study the effects of resolution on the derived slope and wetness index parameters in the application of the infinite slope model for the computation of the factor of safety several slope stability scenarios representing different wetness conditions with 5 10 and 100 mm d 1 of steady state recharge were calculated for the eastern flank of mount rinjani volcano on lombok island indonesia each scenario was conducted by computing the static factor of safety with mean values of the bulk density angle of internal friction cohesion and failure depth parameters as well as for their normally distributed values by monte carlo simulation all scenarios were applied to both dems the scenarios were evaluated by calculating the success prediction rate using the respective area under the curve auc and an existing landslide inventory additionally uncertainties in the estimated positions of landslides were taken into account depending on the particular scenario the success rate of the geoelevation10 model shows differences up to 3 compared to the aster gdem model this apparent improvement is mainly caused by the higher ground resolution in geoelevation10 however the success rate increases for the 10 mm d 1 and decreases for the 100 mm d 1 steady state recharge conditions consequently the more detailed flow direction in the geoelevation10 dem has the highest impact under conditions with lower water saturation the slight improvement in the total model quality shows that the higher resolution of the dem has a small impact on poorly parameterized models in which the material properties are described by roughly estimated parameters therefore the application of a high resolution dem to areas with a lack of data on the soil s physical properties is inefficient due to its low cost benefit ratio for quick analysis the aster gdem is of a suitable quality to fully benefit from the high resolution of the dems other parameters should be available in appropriate detail

digital elevation analysis for distributed hydrological modeling reducing scale dependence in effective hydraulic conductivity values the recent widespread availability of digital terrain data has made automatic procedures for topographic analyses popular previous studies have shown that hydrological models and their effective parameter values are dependent on the resolution of the elevation grid this paper examines the analysis of raster elevation data within the topography based model topmodel framework it is demonstrated that the algorithm used in processing channel pixels in calculating the topographic index k ln a tan can have a dramatic effect on the sensitivity of effective parameter values to the grid size suggestions are made for calculating the topographic index of channel pixels consistent with the topmodel assumptions that strongly decrease the sensitivity of the calibrated effective hydraulic conductivity values to grid size

is the drainage network a fractal sierpinski space the most common approach to extract the channel network from digital elevation models is to specify a threshold area s which is the minimum area required to drain to a point within which a channel forms this threshold area is usually specified arbitrarily although it is recognized that different threshold areas will result in substantially different channel networks for the same basin this paper studies the effects of s which is also the scale of observation on scaling and morphometric properties such as the number of sources and the areas of source basins and lateral basins the gardon basin located in southern france was extensively studied the results indicate that morphometric properties vary considerably with s and that the spatial distribution of source basins can be considered as a fractal sierpinski space a simple model based on the procedure similar to the sierpinski carpet construction is proposed to explain empirical relations between the number of source areas and the threshold s the model presents a new approach to estimate basin fractal properties and defines new indices to characterize the spatial distribution of first order basins this methodology is useful for hydrologists and geomorphologists dealing with river networks and spatial patterns of various basin properties such as vegetation soil soil moisture and human activities

a network index based version of topmodel for use with high resolution digital topographic data this paper describes the preliminary development of a network index approach to modify and to extend the classic topmodel application of the basic beven and kirkby 1979 form of topmodel to high resolution 2 0 m laser altimetric data based upon the u k environment agency s light detection and ranging lidar system to a 13 8 km 2 catchment in an upland environment identified large areas of saturated areas that remained unconnected from the drainage network even during an extreme flood event this is shown to be a particular problem with using high resolution topographic data especially over large spatial scales to deal with the hydrological consequences of disconnected areas we present a simple network index modification in which saturated areas only connect when the topographic index is sufficient for there to be zero or negative saturation deficits along a complete flow path this is combined with an enhanced method for dealing with the problem of pits and hollows which is shown to become more acute with higher resolution topographic data the paper concludes by noting the implications of the research as presented for both methodological and substantive research that is currently under way

on morphometric properties of basins scale effects and hydrological response one of the important problems in hydrology is the quantitative description of river system structure and the identification of relationships between geomorphological properties and hydrological response digital elevation models dems generally are used to delineate the basin s limits and to extract the channel network considering pixels draining an area greater than a threshold area s in this paper new catchment shape descriptors the geometric characteristics of an equivalent ellipse that has the same centre of gravity the same principal inertia axes the same area and the same ratio of minimal inertia moment to maximal inertia moment as the basin are proposed they are applied in order to compare and classify the structure of seven basins located in southern france these descriptors were correlated to hydrological properties of the basins responses such as the lag time and the maximum amplitude of a geomorphological unit hydrograph calculated at the basin outlet by routing an impulse function through the channel network using the diffusive wave model then we analysed the effects of the threshold area s on the topological structure of the channel network and on the evolution of the source catchment s shape simple models based on empirical relationships between the threshold s and the morphometric properties were established and new catchment shape indexes independent of the observation scale s were defined this methodology is useful for geomorphologists dealing with the shape of source basins and for hydrologists dealing with the problem of scale effects on basin topology and on relationships between the basin morphometric properties and the hydrological response copyright 2002 john wiley sons ltd

fertilization of the northwestern tethys vocontian basin se france during the valanginian carbon isotope perturbation evidence from calcareous nannofossils and trace element data a high resolution calcareous nannofossil study associated with a geochemical analysis major trace elements and carbon and oxygen isotope stratigraphies was carried out in the angles section hemipelagic setting of the vocontian basin se france during the valanginian positive carbon isotope excursion the behaviour of calcareous nannofossil taxa in relation to fertility conditions was studied to elaborate new nutrient indices in this environment a high nutrient index based on biscutum spp discorhabdus rotatorius zeugrhabdotus fissus high fertility indicators and watznaueria barnesae low fertility indicator and a medium nutrient index based on lithraphidites carniolensis medium fertility indicator and w barnesae low fertility indicator these two indices show a major fertilization from the stephanophorus ammonite zone to the trinodosum ammonite zone with a maximum during the positive carbon isotope excursion since high values of the nutrient indices are in phase with high values of chemical elements related to terrigenous material and low values of the coccolith total abundance it is proposed that pulses of detrital inputs into the basin triggered the nutrification which in turn caused a biocalcification crisis of the calcareous nannofossils nutrification is also responsible for the reef demise in the surrounded platforms as indicated by the increased sr ca seawater ratio at that time the intensification of the parana etendeka volcanic activity triggering co2 excess in the atmosphere is probably responsible for an acceleration of the hydrological cycle the increased weathering and the subsequent higher terrigenous and nutrient transfer from continents to the vocontian basin in such a scenario nutrification is a dominant factor controlling neritic and hemipelagic biocalcification however one cannot exclude that the global increase of atmospheric co2 could generate chemical changes of the sea surface waters acting with the nutrification to modify the biocalcification of the carbonate producers

integration of remote sensing and gis for modelling flash floods in wadi hudain catchment egypt this paper presents a new approach to modelling flash floods in dryland catchments by integrating remote sensing and digital elevation model dem data in a geographical information system gis the spectral reflectance of channels affected by recent flash floods exhibit a marked increase due to the deposition of fine sediments in these channels as the flood recedes this allows the parts of a catchment that have been affected by a recent flood event to be discriminated from unaffected parts using a time series of landsat images using images of the wadi hudain catchment in southern egypt the hillslope areas contributing flow were inferred for different flood events the srtm3 dem was used to derive flow direction flow length active channel cross sectional areas and slope the manning equation was used to estimate the channel flow velocities and hence the time area zones of the catchment a channel reach that was active during a 1985 runoff event that does not receive any tributary flow was used to estimate a transmission loss rate of 7 5 mm h 1 given the maximum peak discharge estimate runoff patterns resulting from different flood events are quite variable however the southern part of the catchment appears to have experienced more floods during the period of study 1984 2000 perhaps because the bedrock hillslopes in this area are more effective at runoff production than other parts of the catchment which are underlain by unconsolidated quaternary sands and gravels due to high transmission loss runoff generated within the upper reaches is rarely delivered to the alluvial fan and shalateen city situated at the catchment outlet the synthetic gis based time area zones on their own cannot be relied on to model the hydrographs reliably physical parameters such as rainfall intensity distribution and transmission loss must also be considered copyright 2009 john wiley sons ltd

comparison of grid based algorithms for computing upslope contributing area 1 terrain attributes based on upslope contributing area a are used widely in distributed hydrologic models several grid based algorithms are available for estimating a in this study five algorithms d8 8 mfd demon and d were compared quantitatively on two undulating agricultural fields 63 and 109 ha in northeastern colorado global positioning system gps data 0 02 m accuracy were used to generate grid digital elevation models dems at 5 10 and 30 m cell sizes relative differences between a values estimated using single and multiple direction algorithms increased with decreasing grid cell size relative differences were greatest along ridges and side slopes and differences decreased where the terrain became more convergent multiple direction algorithms mfd demon and d allowing for flow divergence are recommended on these undulating terrains for 5 and 10 m grids where a is most sensitive to the algorithm selection

how does modifying a dem to reflect known hydrology affect subsequent terrain analysis summary many digital elevation models dems have difficulty replicating hydrological patterns in flat landscapes efforts to improve dem performance in replicating known hydrology have included a variety of soft i e algorithm based approaches and hard techniques such as stream burning or surface reconditioning e g agree or anudem using a representation of the known stream network these methods trench or mathematically warp the original dem to improve how accurately stream position stream length and catchment boundaries replicate known hydrological conditions however these techniques permanently alter the dem and may affect further analyses e g slope this paper explores the impact that commonly used hydrological correction methods stream burning agree aml and anudem v4 6 3 and anudem v5 1 have on the overall nature of a dem finding that different methods produce non convergent outcomes for catchment parameters such as catchment boundaries stream position and length and differentially compromise secondary terrain analysis all hydrological correction methods successfully improved calculation of catchment area stream position and length as compared to using the dem without any modification but they all increased catchment slope no single method performing best across all categories different hydrological correction methods changed elevation and slope in different spatial patterns and magnitudes compromising the ability to derive catchment parameters and conduct secondary terrain analysis from a single dem modification of a dem to better reflect known hydrology can be useful however knowledge of the magnitude and spatial pattern of the changes are required before using a dem for subsequent analyses

the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

a global palaeoclimatic reconstruction for the valanginian based on clay mineralogical and geochemical data abstract high resolution clay mineral and 18ocarb analyses have been performed on three sections of valanginian age early cretaceous from northwestern 20 30 n and southern 53 s tethyan realms the data have been integrated in a large set of published mineralogical clays and geochemical 18ocarb 18obivalve 18olenticulina 18obelemnite and tex86 data from 17 sections situated between 45 n and 53 s based on this data set we provide new insights into valanginian climate conditions from a wide range of palaeolatitudes we highlight climate trends within specific areas and identify main climate belts in the proto north atlantic realm 15 17 n large amounts of smectite together with the occurrence of palygorskite testify for a semi arid climate belt throughout the valanginian significant variations in kaolinite content in the northwestern tethyan realm 20 to 30 n suggest that this realm has been more sensitive to changes in hydrological cycling and subsequent erosion and runoff processes during the early to early late valanginian transition interval this time interval that is coincident with the pronounced positive and globally recognized carbon isotope excursion cie the weissert episode documents the wet conditions of a humid subtropical climate belt temperature ranges derived from 18o records suggest climate warming by about 3 5 0 9 c in the northern hemisphere during the weissert episode this is followed by a global cooling of about ca 1 5 0 9 c in both hemispheres during the late valanginian we postulate that these patterns were due to interplays between tectonic and orbital factors which have controlled the distribution of regional palaeoclimate belts during the valanginian the semi arid belt expressed in the proto north atlantic realm has probably been induced by its specific palaeogeographic configuration and the existence of isolated basins which were each characterized by strong and continuous thermohaline circulation an eccentricity paced monsoon like system might have played a significant role in maintaining the subtropical belt around the northwestern tethyan realm up to the mid latitudes 35 45 n superimposed on these regional processes a widespread magmatic pulse in parana etendeka volcanic activity might have stimulated greenhouse conditions impacting marine biota and favouring the development of a dense vegetation cover on the continent an increase in sedimentary burial of 13c depleted organic carbon on the continents may have contributed to the progressive global positive carbon isotope excursion in the medium term it has also probably led to a significant decrease in atmospheric co2 as testified by the global cooling recorded during the late valanginian in both hemispheres and the probable concomitant extension of polar ice caps

a theory for buoyancy and velocity scales in deep moist convection buoyancy and velocity scales for dry convection in statistical equilibrium were derived in the early twentieth century by prandtl but the scaling of convective velocity and buoyancy as well as the fractional area coverage of convective clouds is still unresolved for moist convection in this paper high resolution simulations of an atmosphere in radiative convective equilibrium are performed using the weather research and forecasting wrf model a three dimensional nonhydrostatic convection resolving limited area model the velocity and buoyancy scales for moist convection in statistical equilibrium are characterized by prescribing different constant cooling rates to the system it is shown that the spatiotemporal properties of deep moist convection and buoyancy and velocity scales at equilibriumdependontheterminalvelocityofraindrops andahypothesisisdevelopedtoexplainthisbehavior this hypothesis is evaluated and discussed in the context of the numerical results provided by the wrf model the influence of domain size on radiative convective equilibrium statistics is also assessed the dependence of finescale spatiotemporal properties of convective structures on numerical and physical details is investigated

160 m y record of marine sedimentary phosphorus burial coupling of climate and continental weathering under greenhouse and icehouse conditions a compilation of all meaningful phosphate data published in the proceedings of the deep sea drilling project and the ocean drilling program is used here for the extraction of a 160 m y marine burial record of bulk phosphorus all sediment types 5648 measurements and a 100 m y marine burial record of biogenic phosphorus pelagic biogenic sediment types 1754 data these records serve as estimates for total and dissolved bioavailable phosphorus flux rates which in turn are highly dependent on total and chemical continental weathering rates respectively the similarity of both records indicates that in the past 100 m y changes in total weathering rates may have been tracked by changes in chemical weathering rates prior to 32 ma phosphorus burial and long term sea level change are positively correlated from 32 ma to the present this correlation is inverse this points to a fundamental change in feedback mechanisms between continental weathering phosphorus and climate which was probably linked to the onset of major glaciation

on the relative role of upslope and downslope topography for describing water flow path and storage dynamics a theoretical analysis many current conceptual rainfall runoff and shallow landslide stability models are based on the topographic index concept derived from the steady state assumption for subsurface water flow dynamics and the hypothesis that the surface gradient is a good approximation for the gradient of the total hydraulic head however increasing field evidence from sites around the world has shown poor correlations between the topographic index and the patterns of soil water storage here we present a new smoothed dynamic topographic index and test the ability of this index to reproduce spatial patterns of wetness areas and storage as provided by a distributed physically based boussinesq equation beq solver our results show that the new smoothed dynamic topographic index outperforms previous locally computed indices in the estimation of storage dynamics resulting in less fragmented and disconnected spatial patterns of storage our new dynamic index is able to capture both the upslope and downslope controls on water flow and approximates storage dynamics across scales the new index is compatible with high resolution topographic data we encourage the use of our smoothed dynamic topographic index to describe the lateral subsurface flow component in landslide generation models and conceptual rainfall runoff models especially when high resolution digital elevation models are available copyright 2011 john wiley sons ltd