hydraulic geometry change of a large river a case study of the upper yellow river study on hydraulic geometry can reveal the response of river systems to basin attributes and the trends in channel change based on 35 years of data collected at 10 hydrological stations cross sections the hydraulic geometry relations between cross sectional variables and discharge were established and the derived parameters were analyzed the channel behavior of the mountainous bedrock reach from riverhead to xunhua cross section and the alluvial reach from xunhua to toudaoguai cross sections differed significantly over the past decades in response to dramatic water and sediment changes the hydraulic geometry quasi equilibrium was achieved through equally adjusting water depth and flow velocity in the mountainous bedrock reach while primarily through flow velocity in the alluvial reach the change rate of river width with varying discharge was relatively small in the whole upper yellow river compared with the lower yellow river and other rivers in the world both similarity and differences existed indicating the general adjustment direction of hydraulic quasi equilibrium and also the importance of considering other influencing factors in hydraulic geometry studies in addition dams played an important role in affecting the changes of hydraulic geometry exponents

hydraulic geometry river sediment and the definition of bedrock channels a growing literature deals with bedrock channels erosion processes within them and their role in landscape evolution formal definitions currently in use classify channels as bedrock when alluvial cover is discontinuous or thin this is equated with a physical property of the flow using up to date erosion laws and descriptions of channel dynamics we show that existing definitions are difficult to apply and may lead to conflicting classifications we propose the definition a bedrock channel cannot substantially widen lower or shift its bed without eroding bedrock applied to channels in taiwan this leads to a different classification than previous definitions by analysing at a station hydraulic geometry of these channels we show that the classification exposes different controls of sediment effects on dynamics of channels classified as alluvial and bedrock

stochastic variability of fluvial hydraulic geometry mississippi and red rivers major reasons for uncertainty in engineering predictions of river flows are the spatial variability and measurement error associated with depicting channel geometry this paper develops a descriptive spatial stochastic model of depth based hydraulic geometry in application to four dense data sets from the mississippi and red rivers to represent the irregularity in flow area and hydraulic radius as functions of flow depth at a station cross section geometry is defined using regressed power functions accompanied by random residuals more than 1600 surveyed cross sections are analyzed to describe trends in the spatial variance and gradual large scale and periodic medium scale trends in the spatial mean of cross sectional geometry parameters and channel bed slope also described are the probability distribution and correlation structure of each parameter s random component the relationships between spatial statistics of hydraulic geometry and bankfull width channel sinuosity meander patterns bed elevation and riffle pool spacing and bank composition are explored conclusions and implications are discussed regarding the variable nature of fluvial hydraulic geometry and regarding the incorporation of geometric parameter uncertainty into prescriptive models of river processes

downstream hydraulic geometry relationships gathering reference reach scale width values from lidar abstract this paper examines the ability of lidar topography to provide reach scale width values for the analysis of downstream hydraulic geometry relationships along some streams in the dolomites northern italy multiple reach scale dimensions can provide representative geometries and statistics characterising the longitudinal variability in the channel improving the understanding of geomorphic processes across networks starting from the minimum curvature derived from a lidar dtm the proposed algorithm uses a statistical approach for the identification of the scale of analysis and for the automatic characterisation of reach scale bankfull widths the downstream adjustment in channel morphology is then related to flow parameters drainage area and stream power with the correct planning of a lidar survey uncertainties in the procedure are principally due to the resolution of the dtm the outputs are in general comparable in quality to field survey measurements and the procedure allows the quick comparison among different watersheds the proposed automatic approach could improve knowledge about river systems with highly variable widths and about systems in areas covered by vegetation or inaccessible to field surveys with proven effectiveness this research could offer an interesting starting point for the analysis of differences between watersheds and to improve knowledge about downstream channel adjustment in relation for example to scale and landscape forcing e g sediment transport tectonics lithology climate geomorphology and anthropic pressure

a method for characterising longitudinal irregularity in river channels abstract a method for analysing longitudinal variations in cross sectional shape and channel slope is developed and demonstrated with an application to the wimmera river australia the method involves characterising the geometry and spatial location of individual cross sections using four parameters and then conducting statistical analyses of the parameters from a set of cross sections the method extends the general characterisation of natural channels allows examination of the spatial characteristics of stream channels allows stochastic generation of stream channel cross sections and can provide input into hydraulic and stream habitat analyses the application to the wimmera river identifies longitudinal trends and variability in cross section characteristics including quantification of differences in channel characteristics associated with a quasi periodic switching between two different channel plan forms single thread and anastomosing

downstream hydraulic geometry of rivers in victoria australia abstract downstream variation of hydraulic geometry in rivers characterized by fine textured banks and low width to depth ratios 7 25 is investigated in victoria australia with the aim of developing predictive models of channel geometry for large scale spatial modeling applications a one dimensional hydraulic model is used to determine the mean bank full geometry and discharge q bf for 93 sites which are investigated in relation to discharge of fixed average recurrence interval ari the median bank full ari is estimated at 0 8 years with 75 of sites between 0 5 and 2 5 years exponents in the downstream hydraulic geometry relations for width depth and velocity are respectively 0 43 0 40 and 0 18 q q bf and 0 44 0 38 and 0 03 q q 2 i e 2 year ari falling near the mode of global values q 2 and slope explain 66 of variance in q bf while q 2 explains 73 and 69 of the variance in width and depth relations respectively q 2 provides a reliable substitute for q bf in spatial modeling applications spatial variation in hydraulic geometry relations within and between river basins remains largely unexplained the w d ratio characteristically decreases with increasing distance along the lower reaches of most rivers and this has contributed to the lower than expected value for the width exponent

response of reach scale bankfull channel geometry to the altered flow and sediment regime in the lower yellow river abstract the channel geometry in an alluvial river usually varies in response to the altered flow and sediment regime from upstream damming bankfull channel dimensions have significantly adjusted along the lower yellow river lyr because of recent channel degradation caused by the operation of the xiaolangdi reservoir which has led to longitudinal variability in the cross sectional geometry therefore describing the bankfull channel geometry of the lyr is more representative using reach averaged variables in this study an integrated approach is proposed for calculating reach scale bankfull channel dimensions based on the measured section scale bankfull geometry in the lyr and the proposed approach integrates a geometric mean based on the log transformation with a weighted average based on the spacing between two consecutive sections the post flood reach scale bankfull channel dimensions in three different channel pattern reaches of the lyr were then calculated annually during the period from 1999 to 2012 using the proposed approach and the surveyed post flood profiles at 91 sedimentation sections calculated results indicate that the channel geometry changed in the components of bankfull width and depth in the braided reach with an increase of about 400 m in the reach scale bankfull width over the past 13 years and the channel evolution occurred mainly in the component of bankfull depth in the transitional and meandering reaches with the increased reach scale bankfull depths of 2 4 and 1 8 m respectively finally empirical relationships for the three reaches of the lyr were developed between the reach scale bankfull channel dimensions and the previous four year average discharge and incoming sediment coefficient during flood seasons with higher correlations being obtained when calibrated by the measurements from 1999 to 2010 furthermore the developed relations were also verified by the observed data in 2011 and 2012 with encouraging results

depth probability distributions in stream reaches modeling spatial probability distributions of depth in natural stream reaches is of major interest to ecologists analyses of data from a wide range of streams at various stages show that depth probability distributions in reaches tend from exponential to normal with increasing stage this trend is modeled using a simple one parameter density function the model is robust and is a simple tool no topographic sampling nor expensive numerical calculation for predicting the evolution of depth probability distributions as a function of stage

multiple zircon growth within early archaean tonalitic gneiss from the ancient gneiss complex swaziland abstract u pb age determinations by ion microprobe reveal multiple episodes of zircon growth and recrystallization within a single sample of tonalitic gneiss from the ancient gneiss complex the oldest episode at3644 4ma 2 produced the dominant type of zircon characteristically purplish brown and massive in texture this probably constitutes unaltered zircon precipitated from the original magma recrystallization accompanied and obscured by early pb loss took place within the oldest grains at3504 6ma and3433 8ma whole new grains grew at these times also we interpret the post 3644 ma growth as due to episodic deformational and metamorphic events that transformed the tonalite pluton into foliated banded gneiss in addition many grains are visibly overgrown by two layers of younger zircon of different colour and texture dated at2986 20ma and2867 30ma euhedral finely zoned whole grains having the 2986 ma age are present also evidently contributed by very thin felsic veins associated with the nearby lochiel granite the age of3644 4ma combined with precise zircon u pb dating of volcanics from the onverwacht group reported elsewhere demonstrates that at least part of the ancient gneiss complex is older than the barberton greenstone belt

modeling point velocity and depth statistical distributions in steep tropical and alpine stream reaches 1 statistical hydraulic models predict the frequency distributions of point hydraulic variables relative to their reach averaged values in a stream reach based on its average characteristics e g discharge depth width average particle size the models initially developed in europe have not been tested for steeper streams 4 with coarse grain size we recorded water velocities and depths in 44 reaches of steep streams in tropical islands and the alps during 69 surveys we fitted the observed distributions of velocities and depths using a mixture of two distributions one with low variance and the other with a high variance then we predicted the mixing parameter on the basis of the reach averaged characteristics we compared the observed and predicted frequencies for five classes of velocities including a class of negative velocities and four classes of water depths the predictions of class frequencies have a bias of 5 our statistical model of velocity distribution predicts the frequencies of velocity classes with an explained variance between 33 and 72 for four classes of velocity and null for a class of intermediate velocity the statistical model of depth distributions was less efficient with an explained variance between 25 and 38 for three classes of depth and null for large depths the average froude number the total height of large drops relative to the reach length and the average slope are the main explanatory variables of velocity and depth distributions

a 3500 ma plutonic and volcanic calc alkaline province in the archaean east pilbara block variably foliated predominantly granodioritic plutonic rocks from the northern part of the shaw batholith in the east pilbara archaean craton are dated at 3 499 22 ma 2 errors by a whole rock pb pb isochron these rocks intrude the surrounding greenstone sequence and their age is indistinguishable from that sequence high strain grey gneisses which occupy much of the western and southern shaw batholith are chemically and isotopically similar to the north shaw suite and are inferred to have been derived from this suite by tectonic processes felsic volcanics within the greenstones together with a major portion of the granitic batholiths apparently formed in a calc alkaline volcanic and plutonic province at 3 500 ma this volcanic and plutonic suite is similar to modern calc alkaline suites on the basis of major element rare earh element and most other trace element contents the archaean suite contrasts with modern equivalents only in having lower concentrations of hree and higher concentrations of ni and cr

an evaluation of surface flow types as a rapid measure of channel morphology for the geomorphic component of river condition assessments abstract riverine assessments of channel morphology and fluvial processes typically involve a time consuming survey of channel cross sections and longitudinal profiles expensive aerial imagery and or require specialised knowledge as a result geomorphic input is not widely included in multiparameter river condition assessments we were interested in determining if surface flow type observations can be used as a rapid measure of channel morphology and then subsequently be used in river condition assessments to monitor channel change over time we examined the relationship between flow types e g rippled flow no perceptible flow and channel morphology two aspects of channel morphology were assessed i within reach depth variability and ii cross section geometry e g width area froude number in a two part study each of these was correlated with flow type diversity for a range of study sites from upland and lowland environments in victoria australia we found that an increased diversity of flow types correlated with greater depth diversity based on the coefficient of variation of depth along a reach flow types also correlated well with the cross sectional froude number but less so with other geometric parameters the proportion of flow types present was also notably sensitive to discharge within the low flow range examined 70 99 flow exceedance three geo topes cross section units of a dominant flow type were found to be the most physically distinct units at this cross section scale no perceptible flow deadwater smooth boundary turbulent glide and rippled flow run riffle rippled flow is a revision to previous run riffle classifications and is identified by the presence of unbroken waves of any size with crests moving in a general downstream direction our findings indicate that flow types can provide indicative information on channel morphology along a reach when assessed at low flow levels the diversity of flow types reflects the variability of cross sectional geometry and also the diversity of the channel bed depth on this basis the inclusion of flow type observations in river condition assessments can provide meaningful information on channel morphology in a rapid and repeatable way with repeat surveys flow types could be used as a geomorphic metric to track changes in morphologic diversity over time including changes associated with processes of sediment transport scour and deposition at a reach

a variable parameter bidirectional stage routing model for tidal rivers with lateral inflow abstract water stage variations are complicated in tidal rivers due to the combination of upstream flood and downstream tide this study proposed a bidirectional stage routing model bsr for tidal rivers by considering the stage hydrograph as the overlay of bidirectional propagation of upstream flood wave and downstream tidal wave the basic stage routing equations derived from the storage equation and water balance equation are used to calculate the upstream flood wave routing and the downstream tidal wave propagation respectively the lateral inflow can be directly specified as an additive term in the basic equation of bsr model or indirectly estimated by a lateral flow rate reflecting the proportion of lateral inflow to the upstream water parts of the model parameters are time variable to account for the effect of water surface slope on water stage the model inputs include stage hydrographs at the upstream and downstream boundaries the channel geometric characteristics data are not required when the average channel width is estimated as a parameter the case study results in the tidal reaches of the caoe river and qiantang river in china demonstrate that the bsr model performs well in water stage simulation with relatively simple structure modest data requirement and stable performance the physically based bsr model has the potential for water stage routing in tidal rivers when channel geometry data are not available

regional bankfull geometry relationships for southern california mountain streams and hydrologic applications abstract this study develops and intercompares regional relationships for bankfull channel width hydraulic depth and cross sectional area for southern california mountain streams based on several data sources surveyed streams us geological survey stream survey reports and existing literature although considerable uncertainty exists in estimating bankfull conditions the relationships developed from the varying data sources show significant agreement for small watersheds with drainage area ranging from 15 to 2000 km 2 the estimates of bankfull top width ranged from 7 2 to 44 5 m and hydraulic depth estimates ranged from 0 35 to 1 15 m the utility of the developed bankfull geometry regional curves is demonstrated for southern california catchments through a the computation of the bankfull discharge and b the estimation of the surface runoff response necessary to produce bankfull conditions in the streams at the outlet of these catchments for selected locations with instantaneous flow records the occurrence frequency of events exceeding bankfull flow was examined for the available 10 15 year span of observational records bankfull discharge estimates for all small watersheds in the region ranged from 1 3 to 74 m 3 s while the range at the selected gauged stream locations was from 2 6 to 16 4 m 3 s stream locations along the transverse mountains of southern california showed an average occurrence frequency of less than 1 year whereas along the peninsular mountains the average return period tended to be greater than 1 year the application of the regional curves to the estimation of the surface runoff response necessary to produce bankfull conditions at the channel outlets of small catchments may be used as an index for conditions of minor flooding with saturated soils this surface runoff response index ranges from 2 0 to 5 5 mm for a 3 hour rainfall duration for southern california watersheds greater than 15 km 2 in area differences between the values for the peninsular and transverse mountain ranges are linked to geological climatic and geomorphologic differences the developed regional geometry relationships are suitable for use in various hydrologic modeling applications including distributed modeling with high resolution pertinent to flash flood forecasting

a stochastic model of hydraulic variations within stream channels 1 this paper presents a stochastic model of the joint depth and velocity probability distribution in stream channels model input is restricted to simple measures of channel geometry hydraulic distributions are quantified using two independent hydraulic variables each a function of velocity and depth and varying either longitudinally or laterally within a stream channel the stochastic model provides a useful tool for exploring relations between fine scale hydraulic variations and channel geometry one application is modeling fine scale hydraulic habitat conditions in stream channels

on the use of srtm and altimetry data for flood modeling in data sparse regions the growing availability of remotely sensed data has fostered the implementation of hydraulic modeling in poorly gauged regions however these applications suffer the lack of knowledge of river bathymetry which cannot be directly inferred from satellite instruments this study explores the possibility to set up calibrate and validate a hydrodynamic model which geometry is based on global and freely available satellite data first the study tests two different procedures for inferring the river bathymetry under the water surface level second focusing on a po river stretch of 140 km northern italy the study further assesses the suitability of spaceborne topographic and remotely sensed altimetry data i e ers 2 and envisat for implementing and calibrating hydrodynamic models referring to 90 m srtm shuttle radar topography mission digital elevation model for the representation of the riverbed morphology the work analyzes the performances of different 1 d numerical models which cross sections are modified according to two approaches 1 channel bankfull depth cb and 2 slope break sb approach the calibration and validation processes are performed by referring to extended altimetry time series 16 years of data while the accuracy and trustworthiness of 1 d models are tested with reference to a quasi 2 d model based on detailed geometry data results show that both cb and sb approaches enhance the performance of srtm based models in particular the sb approach is completely based on satelliteborne data and shows nash sutcliffe efficiency mae and rmse values similar to those obtained with the benchmark model

morphometric and hydraulic geometry assessment of a gully in sw spain abstract gully erosion represents one of the most significant types of land degradation in the mediterranean areas giving place to important on and off site effects in this paper a second order gully located in sw spain is analyzed along the gully 28 cross sections were established and measured with a leica tcrm1102 laser total station approximately every 6 months from 2001 to 2007 the sections were located at variable distance placing them in areas where active erosion was evident in total 13 field measurements were carried out and the geometric characteristics of 28 cross sections were obtained morphometric analyses were carried out in both the main gully and a tributary reach by applying an empirical relationship between channel length and eroded volume morphometric variables of the gully sections were combined into two dimensionless groups and a morphological similarity between different linear erosion landforms rills ephemeral and permanent gullies was obtained then the coefficient of variation of the calculated volumes was used to compare the instability between the main gully and the tributary reach finally the hydraulic geometry of the gully was assessed by calibrating three empirical power equations which relate bankfull discharge with mean flow velocity cross sectional depth and width the hydraulic characterization of the main gully and the tributary reach was investigated for each field survey and a different behavior was detected the hydraulic analysis also demonstrated that higher values of discharge provide better predictions of flow velocity the size of the main and tributary gullies affects the discharge width relationship and that gully depth is the variable which can be predicted with the highest accuracy

geomorphic response of the jingjiang reach to the three gorges project operation upstream damming often causes significant downstream geomorphic adjustments remarkable channel changes have occurred in the jingjiang reach of the middle yangtze river since the onset of the three gorges project tgp therefore it is important to investigate the variations in different fluvial variables for better understanding of the channel evolution characteristics as an example of the jingjiang reach recent geomorphic adjustments in the study reach have been investigated quantitatively including variations in sediment rating curve fluvial erosion intensity channel deformation volume and bankfull channel geometry these fluvial variables adjusted in varying degrees in response to the altered flow and sediment regime caused by the tgp operation a focus of this study has been especially paid on the variation in the bankfull channel geometry calculated bankfull dimensions at section and reach scale indicate that i there were significant bank erosion processes in local regions without bank protection engineering with empirical relations being developed to reproduce the variation in bankfull widths at four typical sections ii the variation in the reach scale channel geometry occurred mainly in the component of bankfull depth owing to the construction of large scale bank revetment works with the depth increasing from 13 7 m in 2002 to 15 0 m in 2014 and with an increase in the corresponding bankfull area of about 11 and iii the reach scale bankfull channel dimensions responded to the previous five year average fluvial erosion intensity during flood seasons at zhicheng with higher correlations for the depth and area being obtained when calibrated by the measurements in 2002 2012 furthermore these developed relations for the section and reach scale bankfull channel geometry were also verified by the observed data in 2013 2014 with encouraging results being obtained this article is protected by copyright all rights reserved

correlation between environment and late mesozoic ray finned fish evolution in order to better understand the parameters that drove evolution of actinopterygian fishes from the late jurassic to the late cretaceous this being the time of diversification of crown group teleosts by far the dominant fish group today we define three environmental indicators which are detectable as concordant patterns in the geological and fossil records these are 1 freshwater radiations 2 vicariant events and 3 sea temperature we mapped the indicators onto a phylogeny of the late jurassic palaeocene actinopterygian taxa and plotted the variations against time for each of the indicators our results show that for several of the marine clades diversity is positively correlated with sea temperature and for one clade negatively correlated with sea temperature the marine radiation is very important in the mid cretaceous especially in the tethys which may have been a centre of origin for some clades vicariant events occurred in both marine and freshwater groups and are abundant during the opening of the south atlantic in the early cretaceous freshwater radiations forming in some cases species flocks are especially evident in the basal cretaceous in asia although these results are affected by biases related to the fossil record and to its study we propose that these global patterns are genuine and reflect the strong impact of the earth system on the evolution of fishes in the late mesozoic

modeling energy dissipation and hydraulic jump regime responses to channel nonuniformity at river steps 1 the river step is an important driver for geomorphic evolution in bedrock rivers but the effect that variations in channel geometry upstream and downstream of a river step have on hydraulic jump regime and energy dissipation has not previously been investigated the associated hydraulic jump is inherent to a river step and its regime is a primary control on step morphodynamics in turn the hydraulic jump regime is controlled by several variables as detailed in a new conceptual framework herein also in this study a parsimonious semianalytical numerical model of step hydraulics is developed to quantify energy dissipation and delineate hydraulic jump regimes accounting for discharge jump submergence and nonuniform channel geometry through a step despite remaining limitations in step theory the model simulates how natural steps respond to a wide range of conditions the model shows that hydraulic jump regime and energy dissipation exhibit greater sensitivity to channel nonuniformity as discharge increases and or step height decreases also channel conditions that create greater jump submergence lead to decreased energy dissipation regardless of the discharge regime the model also reinforces the common observation about gully erosion that downstream channel widening enhances upstream knickpoint migration the new algorithm may be used to aid river engineering involving steps and could be useful for landscape evolution modeling

an unconventional approach to modeling spatial and temporal variability of local shear stress in stream segments measuring and especially modeling the spatial and temporal variability of local bottom shear stress in streams are major issues in concepts of hydraulic engineering and cotic ecology and becomes very complicated with increasing channel complexity and or decreasing channel size using fliesswasserstammtisch fst hemispheres an unconventional method for near bottom flow measurements we determined the parameters of shear stress frequency distributions of german mountainous streams by a maximum likelihood procedure the resulting model is robust and generates information on the spatial and temporal variability of local shear stress in stream segments from easily obtained input variables discharge mean stream width and depth

revisiting the drivers of at a station hydraulic geometry in stream reaches abstract knowledge of temporal variations in river hydraulic characteristics i e width depth velocity across stream networks is a key element for catchment management because hydraulics influence physical habitats and biodiversity water temperature nutrient fluxes sediment transport and associated ecosystem services reach scale at a station hydraulic geometry describes the variation of mean water depth and width with discharge within a stream reach the ability to understand and predict the form of these hydraulic geometry relationships across river networks therefore represents a powerful tool for river managers although variations of these relationships between rivers have been widely documented they are still largely unexplained this study provides an analysis of a unique data set of hydraulic geometry collected in 492 stream reaches in france relationships between the hydraulic geometry parameters and many variables describing catchment and reach scale characteristics of reaches were analyzed using stepwise linear regression and discriminant analysis results show that width discharge relationships across reaches are well predicted by longitudinal and lateral descriptors of reaches the ratio of median to bankfull width the median froude number the width to depth ratio the active channel relative to the catchment area and the fluvial pattern braided or not fluvial pattern reach averaged active channel width and bankfull width can be accurately estimated using aerial imagery making application of our models over river networks possible fewer relationships significantly explained depth discharge relationships despite a weak influence of reach froude number flow resistance i e relative grain size relative bedform submergence and width to depth ratio unavailable descriptors of channel resistance would probably improve these models e g describing bank stability spill and form resistance despite the uncertainties of hydraulic geometry relationships this study shows that predictions of hydraulic geometry exponents across river networks are possible offering a large range of potential applications

a two stage model for the formation of the granite greenstone terrains of the kalgoorlie norseman area western australia abstract accurate dating of granites and greenstones from the kalgoorlie norseman area shows that there is considerable overlap in time between the formation of granites and greenstones however within any given area the oldest granites are always younger than the oldest greenstones it is suggested that the long lived 100 ma thermal anomaly in the uppermost asthenosphere that gave rise to the greenstones is also responsible for regional metamorphism and widespread crustal melting leading to the production of granites the time lag between greenstone and granite formation reflects the time taken to conduct heat from the mantle to the lower crust anatexis of the lower crust produces a layer of light granitic magma that may temporarily stop the ascent of basaltic magma where this happens the basaltic magma ponds at the base of the crust supplying additional heat and accelerating the melting process eventually the granitic melt layer becomes unstable and rises within the crust areas intruded by granite become topographic highs with topographic lows forming above areas where light melt has been withdrawn from the lower crust when the topographic highs protrude above sea level they are eroded to shed sediments into the topographic lows which contain the basaltic greenstones thus the change from a basalt dominated lower greenstone succession to a sediment and felsic volcanic dominated upper whitestone sequence seen in many granite greenstone terrains results from the intrusion of granitic magma into the upper crust the crust of the kalgoorlie norseman area formed in two distinct stages separated by a time break of up to 700 ma the first stage involved the formation of primitive crust probably above subduction zones this primitive crust was characterized by low rb sr and high sm nd ratios the second stage resulted from a major change in mantle convection that produced thermal upwellings in the mantle below the continents this led to the eruption of basaltic magmas and to metamorphism and anatexis of the lower crust to produce granitic magmas melting reset the rb sr sm nd and u pb systems giving the impression that the second event which occurred at 2 7 ga was a major crust forming event it was in fact a crustal reworking process although some basalt was added to the crust at this time although the two stage history of the kalgoorlie norseman area is clearly seen in the lead isotopes and in zircons it is not readily discernible from the rb sr and sm nd systematics due to mantle like ratios of those elements in the primitive crust

hydraulic characterization of river networks based on flow patterns simulated by 2 d shallow water modeling scaling properties multifractal interpretation and perspectives for channel heads detection

integrating hydraulic equivalent sections into a hydraulic geometry study abstract hydraulic geometry hg is an important geomorphic concept that has played an indispensable role in hydrological analyses physical studies of streams ecosystem and aquatic habitat studies and sedimentology research more than 60 years after leopold and maddock 1953 first introduced the concept of hg researchers have still not uncovered the physical principles underlying hg behavior one impediment is the complexity of the natural river cross section the current study presents a new way to simplify the cross section namely the hydraulic equivalent section which is generalized from the cross section in the gradually varied flow of an alluvial river gvfar and features hydrodynamic properties and bed building laws similar to those of the gvfar energy balance was used to derive the stage z discharge q relationship in the gvfar the gvfar in the songhua river and the yangtze river were selected as examples the data including measured discharge river width water stage water depth wet area and cross section were collected from the hydrological yearbooks of typical hydrological stations on the songhua river and the yangtze river from 1955 to 1987 the relationships between stage z discharge q and cross sectional area a stage z at various stations were analyzed and at a station hydraulic geometry ahg relationships were obtained in power law forms based on derived results and observational data analysis the z q and z a relationships of ahg were similar to rectangular weir flows thus the cross section of the gvfar was generalized as a compound rectangular hydraulic equivalent cross section as to bed building characteristics the bankfull discharge method and the stage discharge relation method were used to calculate the dominant variables of the alluvial river this hydraulic equivalent section has the same z q relation z a relation dominant discharge dominant river width and dominant water depth as the cross section in the gvfar with the hydraulic equivalent section the relationships between the discharge and river width river depth and width to depth ratio are easier to depict in dhg analysis replacement of the cross section in the gvfar with the hydraulic equivalent section is expected to promote further development of hg

non linearity of reach hydraulic geometry relations summary reach average hydraulic geometry rhg defines the relations between the average hydraulic variables estimated at river reach water depth velocity channel width and the discharge single log linear models are classically used by fluvial geomorphologists hydrologists and ecologists to represent these relations in this paper we show that these single log linear models are not relevant in most of cases and so can lead to significant errors rhg estimated on 15 alluvial river reaches the catchment sizes vary from 10 km 2 to 1700 km 2 were found non linear for two thirds of the river reaches when considering discharges ranging from low to bankfull flows so we propose using two power functions or log linear to model these relations i e the log piecewise linear model this model can detect a discharge qbreak i e a physical transition or break point between both relations from very low flows about 30 of the median discharge to qbreak a first relation is comparable to the rhg found in the literature for aquatic habitat analysis the second relation is relevant for flows ranging from qbreak to bankfull discharge and therefore may be more useful for sediment transport and flood routing analysis averaging along a reach including several pool riffle units makes it difficult to clearly ascribe the form of rhg to particular physical processes the non linearity of rhg may have multiple origins the presence of lateral gravel bars the hydraulic conditions of riffle cross sections a change in the resistance to flow with water depth vegetation sediment influences further research is needed to focus on the physical processes that govern the rhg non linearity

low flow hydraulic geometry of small steep mountain streams in southwest british columbia abstract this investigation explores the at a station hydraulic geometry ahg of small steep mountain streams at low discharge thirteen reaches in five tributaries of chilliwack river british columbia ranging in size from 12 to 77 km 2 are examined the resulting data set is composed of eight to twelve measurements of water surface width mean depth and mean velocity at each of 61 cross sections or 625 unique combinations of the three variables mean velocity in a given cross section responds most rapidly to changing discharge and 31 of the 61 cross sections have velocity exponents that are greater than the water surface width and mean depth exponents combined the velocity exponent m averages 0 51 while the mean water surface width exponent b and mean depth exponent f average 0 20 and 0 29 respectively somewhat surprisingly the ahg of steep mountain streams can be reasonably predicted from just a few measurements of the primary flow variables and stream discharge while conditions at the cross section appear predictable from a few measurements extrapolating the results from one cross section to another in the same reach involves large errors the section to section variability of the exponents and coefficients even when they are located in similar channel units such as riffles prevents accurate extrapolation to unmeasured cross sections

stable channels with mobile gravel beds regime type equations for mobile gravel bed rivers are presented based on data obtained from 62 stable gravel bed river reaches in the united kingdom multiple regression techniques are applied to derive equations relating reach average and riffle values of width mean and maximum depth slope velocity sinuosity and riffle spacing to bankfull discharge bed and bank material characteristics valley slope bank vegetation type and an independent estimate of bankfull bed load transport rates although discharge has a dominant control on channel geometry these equations indicate that bed load discharge also has a significant influence particularly with regard to channel slope bank vegetation has a major control on width and velocity while depth velocity and slope are storngly affected by bed material size reasons for these results are considered in terms of the physical processes controlling channel adjustment the application of these regime equations is discussed and particular consideration is given to the design of sinuous channels with a pool riffle bed topograph

the varasichthyid and other crossognathiform fishes and the break up of pangaea crossognathiforms have been traditionally considered typical marine cretaceous forms widely represented in the northern hemisphere and by a few members in brazil during the last 30 years they have been interpreted as teleostei incertae sedis clupeocephalans or a non monophyletic group new evidence indicates that the oxfordian taxon chongichthys previously considered a teleostei incertae sedis or a clupeocephalan the late jurassic family varasichthyidae interpreted as basal teleosts and the crossognathoids and pachyrhizodontoids form a clade here recognized as the crossognathiformes varasichthyids are the sister group of a clade including chongichthys at the base and crossognathoids pachyrhizodontoids the crossognathiformes including varasichthyidae and chongichthys are basal teleosts placed between the late jurassic basal genera tharsis and ascalabos in one tree or between ascalabos and the ichthyodectiforms in the second tree the position of elopomorphs as the most basal extant teleosts is confirmed a new interpretation of the phylogenetic position of the clade humbertia erichalcis leptolepides orthogonikleithrum at the base of clupeocephalans is suggested the presence of the late jurassic varasichthyids e g domeykos in south america chile and central america cuba luisichthys and chongichthys chile and of the late jurassic genera ascalabos and tharsis and the ichthyodectiforms e g allothrissops in europe e g germany allows the proposal of a sister area relationship between chile and cuba which was the sister area of germany during the late jurassic the late jurassic connection between the palaeopacific chilean region and the tethys sea southern germany was through the newly formed central atlantic ocean cuban region as a result of the break up of pangaea and separation of north america south america and africa

hydraulic geometry of stream reaches abstract variation in river hydraulic geometry throughout stream networks is central to the problems of catchment management because of its influence on flow and sediment routing physical habitats and channel floodplain interactions in its simplest form at a station hydraulic geometry is described by power functions relating the surface width water depth and mean velocity at a channel cross section to discharge this paper extends hydraulic geometry analysis to represent the mean and variation of hydraulic characteristics along a river reach as power functions of discharge using 54 surveys of 17 river reaches mostly in south east australia it is shown that five reach hydraulic variables are sufficient to characterise the gross hydraulic conditions along a river reach the means and coefficients of variation of surface width and hydraulic depth plus the coefficient of variation of cross sectional velocity exponents for the mean width and mean depth hydraulic geometry relations are sensitive to measurement and cross section location and may best be treated as constant for regional studies coefficients for the mean width and mean depth hydraulic geometry relations are correlated positively with mean discharge and negatively with reach gradient respectively further analysis of variations in reach hydraulic geometry parameters particularly the power function coefficients in relation to river type flow parameters sediment load bank material and bank vegetation is warranted reach hydraulic geometry relations show considerable potential for improving analyses of fluvial processes and physical habitats across catchments

jurassic and cretaceous marine connections between the southeast pacific and tethys abstract the affinities of the ammonoid faunas from central west and southern south america are used to analyze the evolution of seaways and oceanic connections with tethys during the jurassic and cretaceous during the early and middle jurassic marine connection with eastern tethys was around the australian margin of gondwana from the pliensbachian onwards connection with western tethys occurred through the sporadically opened hispanic corridor in central america in late jurassic time the break up of gondwanaland was initiated and a seaway began to open between south america africa and antarctica connection of the eastern pacific with tethyan waters through southern africa was sporadic and was still mainly around australia and along the now open central american seaway throughout the early cretaceous the opening of the south atlantic proceeded from south to north and the first marine connection between the southern and northern atlantic took place in albian time a definite marine connection between the opened south atlantic and eastern tethys with faunal migration routes was established in late hauterivian barremian time and became fully open in the aptian albian successive stages in the opening of a south african seaway between tethys and the southeast pacific show an asymmetric development to the west and east of south africa during late cretaceous time oceanic circulation continued between the south atlantic and eastern tethys and true oceanic conditions developed between the southern and northern atlantic the antarctic peninsula was still located in a position adjacent to south america preventing open circulation between the south atlantic and pacific oceans

estimation of river discharge propagation speed and hydraulic geometry from space lena river siberia 1 moderate resolution imaging spectroradiometer modis derived measurements of lena river effective width we display a high predictive capacity r2 0 81 mean absolute error 60 90 km 2 3 time valley width satellite derived we q rating curves and hydraulic geometry b exponents converge upon stable values b 0 48 indicating transferability of the discharge retrieval method between different locations put another way at length scales exceeding 60 90 km all subreaches display similar behavior everywhere at finer reach length scales e g 0 25 1 km longitudinal extraction of b exponents represents the first continuous mapping of a classical hydraulic geometry parameter from space while at least one gauging station is required for calibration results suggest that multitemporal satellite data can powerfully enhance our understanding of water discharge and flow conveyance in remote river systems

age and origin of granitic rocks in the kalgoorlie norseman region of western australia implications for the origin of archaean crust three granites from the norseman area at stennet rocks buldania rocks and east of lake johnston have u pb zircon ages of 2691 8 95 c l 2689 22 and 2661 8 ma respectively one stennet rocks contains 3100 3200 ma cores providing support for oversby s 1975 argument that all three plutons were derived by anatexis of much older basement common leads within the zircons show evidence of having been derived from within the rock and represent mixtures of initial rock leads and radiogenic leads the unusually 208pb rich compositions of the common leads suggest the breakdown of a th rich phase perhaps uranothorite as a major contributor to the radiogenic component available zircon geochemical and isotopic data are used to develop a two stage model for archaean crustal development in this region with formation of primitive crust of broadly andesitic composition from depleted mantle or basalt beginning at 3400 ma followed by extensive thermal reworking and possibly continued growth over the period 3000 3300 ma in the second stage at 2700 ma anatexis resulted in large scale intra crustal differentiation giving a thick upper granitic layer and a lower crust residual from anatexis it is this second major thermal event that is recorded by most geochronometers implicit in the andesitic crustal growth model is that because the sm nd and rb sr ratios of newly formed archaean crust are close to mantle values this process is transparent to the sm nd and rb sr isotope systems until recycling of incompatible element rich sediment becomes important following the late archaean production of a wide spread differentiated upper crust

statistical models of fluvial systems abstract statistical methods have dominated quantitative analyses of fluvial systems over the last 40 years this paper assesses the utility of statistical models by examining methodological issues associated with empirical analysis of hydraulic and channel geometry relationships it also describes and presents examples of advanced statistical models that promise to enhance our understanding of the structure and dynamics of fluvial systems bivariate and multivariate power function models of fluvial systems provide objective numerical descriptions of the relationship between channel geometry and hydrologic hydraulic sedimentologic and biotic controls traditional regression models are limited in that they only describe simple input output relations between the states of dependent and independent variables advanced statistical models transcend these limitations simultaneous equation models continuously varying parameter models and distributed lag models are statistical tools for explicitly analyzing 1 mutual adjustments among fluvial variables 2 the factors controlling the spatial structure of channel geometry flow relations and 3 the equilibrium or disequilibrium dynamics of fluvial systems respectively these advanced statistical techniques can be used to empirically test conceptual models of fluvial systems at a variety of spatial and temporal scales

early and mid jurassic molluscan biogeography and the establishment of the central atlantic seaway abstract a new analysis of lower and middle jurassic bivalve faunas of western north america and the southern andes in comparison to europe supported by evidence from other molluscs throws further light on the establishment of a central atlantic epicontinental seaway prior to the formation of a true oceanic strait between eastern north america and africa south america some restriction to free communication persisted until the early callovian but there was an episode of relatively free intermigration in the toarcian to early bajocian time interval which is associated with major rise of sea level one of the most significant consequences of this event was a spread into northwest europe of taxa which were previously confined to the pacific margins to occupy niches vacated as a result of an early toarcian extinction event

prediction of discharge from water surface width in a braided river with implications for at a station hydraulic geometry 1 the total discharge of small braided rivers can be monitored nearly continuously using ground based orthorectified oblique images and a locally derived relationship between mean water surface width in a reach and total discharge with accuracy of the order of 10 the width discharge relationship is nearly linear over the normal range of summer flows measured in this proglacial stream the width discharge relation for a given location and channel configuration is transferable to adjacent reaches with different morphology with little loss in accuracy however the prospect of a more universal relation for braided rivers is remote because of differences in channel geometry and hydraulics between rivers the classical at a station hydraulic geometry exponent for width in this case is approximately 1 05 which is unique well above that observed in the few other braided rivers for which this has been derived and implies almost no change in mean velocity and depth with changing stage

holographic measurements of surface topography in laboratory models of mantle hotspots summary the evolution of surface topography produced by the rise of a buoyant droplet or diapir towards the free surface of a very viscous fluid in laboratory experiments is monitored using holographic interferometry such experiments enable us to investigate implications for surface topography of one possible unsteady model for intraplate hotspots the arrival of mantle thermals or diapirs near the base of the earth s lithosphere our model is possibly of most direct relevance to the interaction with the earth s surface and lithosphere of large spherical caps that are expected to rise at the head of new mantle plumes to previous experimental results for the axial height of topography olson nam we add further information on the height shape and width of the surface swell and on the evolution of the diapir itself when the ambient fluid has uniform density and viscosity no lithosphere surface topography is determined by the diameter density anomaly and depth of the droplet as the diapir approaches the surface a broad axisymmetric surface swell appears and initially increases in height while decreasing in width when the leading edge of the diapir is 0 2 diapir diameters below the surface the height passes through a maximum and the width through a minimum the swell then proceeds to subside and increase in width as the diapir spreads beneath the surface in separate experiments the lithosphere is modelled by a discrete surface layer of more viscous fluid whose thickness and viscosity contrast with the mantle are treated as independent parameters effects of lithosphere buoyancy relative to the mantle a property which may influence continental hotspot swells are also studied within the parameter range used the maximum swell height is independent of the lithosphere viscosity contrast but decreases with increasing lithosphere thickness and with decreasing lithosphere density surface uplift produced by the rise of two consecutive diapirs is shown to be more complex comparison of results with the characteristics of hotspot swells is attempted and should assist in determining the nature of hotspot plumes

implications of melting for stabilisation of the lithosphere and heat loss in the archaean abstract the increased depth and volume of melting induced in a higher temperature archaean mantle controls the stability of the lithosphere heat loss rates and the thickness of the oceanic crust the relationship between density distributions in oceanic lithosphere and the depth of melting at spreading centres is investigated by calculating the mineral proportions and densities of residual mantle depleted by extraction of melt fractions the density changes related to compositional gradients are comparable to those produced by thermal effects for lithosphere formed from a mantle which is 200 c or more hotter than modern upper mantle if archaean continental crust formed initially above oceanic lithosphere the compositional density gradients may be sufficient to preserve a thick archaean continental lithosphere within which the archaean age diamonds are preserved the amount of heat advected by melts at mid ocean ridges today is small but heat advected by melting becomes proportionally more important as higher mantle temperatures lead to a greater volume of melt and as the rate of production of oceanic plates increases archaean tectonics could have been dominated by spreading rates 2 3 times greater than now and with mantle temperatures between ca 1600 c and 1800 c at the depth of the solidus mid ocean ridge melting would produce a relatively thick but light refractory lithosphere on which continents could form protected from copious volcanism and high mantle temperatures

controls on at a station hydraulic geometry in steep headwater streams colorado usa detailed hydraulic measurements were made in nine step pool five cascade and one plane bed reach in fraser experimental forest colorado to better understand at a station hydraulic geometry ahg relations in these channel types average values for ahg exponents m 0 49 f 0 39 and b 0 16 were well within the range found by other researchers working in steep gradient channels a principal component analysis pca was used to compare the combined variations in all three exponents against five potential control variables wood d84 grain size distribution coefficient of variation of pool volume average roughness area projected wetted area and bed gradient the gradient and average roughness area were found to be significantly related to the pca axis scores indicating that both driving and resisting forces influence the rates of change of velocity depth and width with discharge further analysis of the exponents showed that reaches with m b f are most likely dominated by grain resistance and reaches below this value m b f are dominated by form resistance copyright 2010 john wiley sons ltd

european hydraulic geometries for continental scale environmental modelling summary this paper presents a geo exploratory analysis carried out using publicly accessible data to estimate river channel width and mean lake depth these two parameters combined with other more readily available information are key in many environmental assessment applications such as sedimentological and ecological studies and the prediction of surface water residence times for river width runoff estimates have been used to produce a european map of mean annual discharge based on the flow accumulation computed for the gtopo30 digital elevation model dem a regression equation is fitted to predict river width as a function of river discharge for lake depth a landscape roughness index has been calculated on the gtopo30 dem based on this index a regression equation predicts lake depth allowing to populate the existing geographic databases with information on estimated depth using these models for river width and lake depth it is possible to compute representative values of velocity and depth in rivers as well as residence time in lakes at a pan european level these parameters define the hydraulic geometry of european inland waters for typical conditions with errors on the predictions generally within a factor of 2 errors are generally unbiased and geographic patterns such as macroscopic differentiation of catchments and physiographic environments are reproduced in a qualitatively correct way so that overall representativeness of the values for continental scale modelling is further corroborated

dimensionless morphological ratios versus stream power variations at bankfull stage in an ephemeral channel abstract dimensionless morphological ratios dmr generally are used in systemic proposals for stream classification and river restoration projects often such morphometric parameters including field data from channel cross sections develop into a template for a given geomorphic reference site in this study high resolution digital terrain models hrdtms combined with orthophotographs from 2018 and ground based surveys were used to analyze the spatial variability of dmr in a semi arid ephemeral stream subject to changes in stream power under bankfull conditions in particular a channel reach of 2 7 km in length along the upper mula stream in southeastern spain was chosen to test the relationships between the two types of variables rosgen s dmr width to depth ratio entrenchment ratio bank height ratio and hydraulic data at bankfull stage flow velocity froude number shear stress mean stream power and energy gradient among others were calculated by 1d hydrodynamic modeling and hrdtms prior entry of field information the resulting maps allowed comparison of stream power with dmr in relation to the channel stretch class and bed stability the results showed similar spatial patterns for the width to depth ratio and the bank height ratio the average values estimated in bend stretches were lower than along straight and slightly sinuous stretches and very similar to those of sub reaches from the inflection point to the meander bend apex however the entrenchment ratio followed a different pattern according to which the straight and slightly sinuous stretches were the most entrenched and the bend stretches presented a more moderate average entrenchment ratio in addition the energy balance and power gradient also experienced spatial variations in relation to the bed stability and dmr only in highly incised sub reaches were such relationships not significant the lack of a significant correlation between excess energy and bank height ratio or width to depth ratio over short lag distances was also verified regardless of the affected bedforms an anova showed important differences between the straight and slightly sinuous stretches and bend stretches which were strongly influenced by the incision and entrenchment ratios and the maximum bankfull depth