detection and reconstruction of large scale coherent flow structures in gravel bed rivers large scale flow structures lsfs in the streamwise direction are important features of gravel bed river flows because they may contribute to sediment transport and gas exchange in the present study these structures are detected using huang s empirical mode decomposition and reconstructed with phase averaging techniques based on a hilbert transform of the velocity signal the analysis is based on the fluctuating component of 15 quasi instantaneous velocity profiles measured with a three dimensional 3d acoustic doppler velocity profiler advp in an armoured gravel bed river with a low relative submergence of 2 9 ratio between flow depth and bed grain diameter lsfs were identified in most of the measured profiles and consistently showed similar features we were able to characterize the geometry of these large scale coherent structures the front has a vertical linear shift in the time domain and a vertical profile corresponding to a first quarter moon with the apex situated at z h approximate to 0 4 in the vertical the front scales with flow depth h and in the streamwise direction lsfs scale with three to seven times the mean flow depth on the bed the effect of lsfs is a periodic non linear variation of the friction velocity on average between 0 90 and 1 10 times the mean value a model for the friction velocity cycle resulting from lsfs oscillation is presented copyright c 2014 john wiley sons ltd

simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel topographic interactions generate multidirectional and unsteady air ow that limits the application of velocity pro le approaches for estimating sediment transport over dunes results are presented from a series of wind tunnel simulations using irwin type surface mounted pressure sensors to measure shear stress variability directly at the surface over both isolated and closely spaced sharp crested model dunes findings complement existing theories on secondary air ow effects on stoss transport dynamics and provide new information on the in uence of lee side air ow patterns on dune morphodynamics for all speeds investigated turbulent unsteadiness at the dune toe indicates a greater more variable surface shear despite a signi cant drop in time averaged measurements of streamwise shear stress at this location this effect is believed suf cient to inhibit sediment deposition at the toe and may be responsible for documented intermittency in sand transport in the toe region on the stoss slope streamline compression and ow acceleration cause an increase in ow steadiness and shear stress to a maximum at the crest that is double that at the toe of the isolated dune and 60 70 per cent greater than at ow reattachment on the lower stoss of closely spaced dunes streamwise ow accelerations rather than turbulence have greater in uence on stress generation on the stoss and this effect increases with stoss slope distance and with incident wind speed reversed ow within the separation cell generates signi cant surface shear 30 40 per cent of maximum values for both spacings this supports eld studies that suggest reversed ow is competent enough to return sediment to the dune directly or in a de ected direction high variability in shear at reattachment indicates impact of a turbulent shear layer that despite low values of time averaged streamwise stress in this region would inhibit sediment accumulation downwind of reattachment shear stress and ow steadiness increase within 6 h h dune height of reattachment and approach upwind values by 25 h a distance of at least 30 h is suggested for full boundary layer recovery which is comparable to uvial estimates the irwin sensor used in this study provides a reliable means to measure skin friction force responsible for sand transport and its robust simple and cost effective design shows promise for validating these ndings in natural dune settings copyright 2003 john wiley sons ltd

on the east australian current variability encroachment and upwelling 1 observations from an intensive oceanographic field program which took place in 1998 1999 about the separation point of the east australian current eac show significant spatial and temporal variability of the eac upstream of the separation point southward flowing currents are strong with subinertial velocities of up to 130 cm s 1 in the near surface waters whereas downstream currents are highly variable in both strength 1 70 cm s 1 and direction upwelling is observed to occur through both wind driven and current driven processes with wind effects playing a lesser role by contrast the encroachment of the eac upon the coast has a profound effect on the coastal waters accelerating the southward alongshore currents and decreasing the temperature in the bottom boundary layer bbl by up to 5 degreesc as the axis of the jet moves onshore negative vorticity increases in association with an increase in nonlinear acceleration during this time bottom friction is increased the burger number is reduced and the bbl shut down time lengthens the observed upwelling is attributed to enhanced onshore ekman pumping through the bbl resulting from increased bottom stress as the southerly flow accelerates when the eac encroaches across the continental shelf

frequency wavenumber velocity spectra taylor s hypothesis and length scales in a natural gravel bed river 1 macroscale turbulent coherent flow structures in a natural fast flowing river were examined with a combination of a novel 2 mhz acoustic doppler beam adb and a maximum likelihood estimator mle to characterize the streamwise horizontal length scales and persistence of coherent flow structures by measuring the frequency f streamwise wavenumber ks energy density velocity spectrum e f ks for the first time in natural rivers the adb was deployed under a range of froude numbers 0 1 0 6 at high reynolds numbers 106 based on depth and velocity conditions within a gravel bed reach of the kootenai river idaho the mle employed on the adb data increased our ability to describe river motions with relatively long 10 m length scales in 1 m water depths the e f ks spectra fell along a ridge described by v f ks where vis the mean velocity over depth consistent with taylor s hypothesis new consistent length scale measures are defined based on averaged wavelengths of the low frequencye f ks and coherence spectra energetic 50 of the total spectral energy low frequency f 1 m s lmwere found to be significantly longer than their corresponding coherence lengths suggesting that the turbulent structures evolve rapidly under these conditions this is attributed to the stretching and concomitant deformation of preexisting macroturbulent motions by the ubiquitous bathymetry induced spatial flow accelerations present in a natural gravel bed river

effects of turbulence on the transport of individual particles as bedload in a gravel bed river this study investigates the association between mean and turbulent flow variables and the movement of individual particles in a gravel bed river the experimental design implemented in the eaton north river quebec canada is based on the simultaneous observations at a high temporal resolution of both particle movements as bedload using an underwater video camera and of the streamwise and vertical flow velocity components using a vertical array of three electromagnetic current meters ecms the frequency and distance of displacement of particles larger than 20 mm that were sliding or rolling on the bed were measured from a 10 minutes long film mean and turbulent flow properties obtained for periods without sediment transport are compared to those when particles were sliding and rolling when particles are sliding weak differences are present for the mean streamwise velocity and normal vertical stresses instantaneous reynolds shear stresses are significantly lower for sliding events which was not expected but could be explained by the important dominance of quadrant 3 events inward interactions when particles are rolling only the vertical normal stresses show a weak difference from those observed in the absence of transport but they tend to occur when quadrant 2 ejections dominate the flow field for both sliding and rolling particles vertical and or streamwise fluid accelerations show high magnitude values when compared to periods without transport for sliding particles streamwise acceleration is mostly negative and combines most of the time with a positive vertical acceleration for rolling particles streamwise and vertical acceleration are predominantly of opposite sign these results suggest that fluid acceleration or deceleration in the streamwise and vertical directions is affecting the pressure field around particles in this study fluid acceleration seems to play a more important role than reynolds shear stress or normal stresses for bedload movements copyright 2010 john wiley sons ltd

correlative velocity fluctuations over a gravel river bed velocity fluctuations in a steep coarse bedded river were measured in flow depths ranging from 0 8 to 2 2 m with mean velocities at middepth from 1 1 to 3 1 m s 1 analyses of synchronous velocity records for two and three points in the vertical showed a broad range of high coherence for wave periods from 10 to 100 s centering around 10 30 s streamwise correlations over distances of 9 and 14 m showed convection velocities near mean velocity for the same wave periods the range of coherent wave periods was a small multiple of predicted boil periods correlative fluctuations in synchronous velocity records in the vertical direction suggested the blending of short pulses into longer wave periods the highest spectral densities were measured beyond the range of coherent wave periods and were probably induced by migration of low relief bed forms

dune migration in a steep coarse bedded stream during 1986 and 1987 migrating bed forms composed of coarse sand and fine gravel d50 1 8 to 9 1 mm were documented in the north fork toutle river at kid valley washington at flow velocities ranging from 1 6 to 3 4 m s 1 and depths of 0 8 to 2 2 m the bed forms predominantly lower regime dunes were studied with a sonic depth sounder transducer suspended in the river at a stationary point twelve temporal depth sounding records were collected during storm runoff and nearly steady average streamflow with record durations ranging from 37 to 261 min waveform height was defined by dune front heights which ranged from 12 to 70 cm a weak correlation between flow depth and the standard deviation of bed elevation was noted dune front counts and spectral analyses of the temporal records showed that dune crests passed the observation point every 2 to 5 min dunes were often superposed on larger bed forms with wave periods between 10 and 30 min gradual changes in waveform height and periodicity occurred over several hours during storm runoff the processes of dune growth and decay were both time dependent and affected by changes in streamflow rates of migration for typical dunes were estimated to be 3 cm s 1 and dune wavelengths were estimated to be 6 to 7 m

coupled dynamics of the co evolution of gravel bed topography flow turbulence and sediment transport in an experimental channel a series of flume experiments were conducted in a large experimental channel at the st anthony falls laboratory to understand the coupled dynamics of flow and bed forms above the sediment water interface simultaneous high resolution measurements of velocity fluctuations bed elevations and sediment flux at the downstream end of the channel were made for a range of discharges the probability density functions pdfs of bed elevation increments and instantaneous reynolds stress reveal a power law tail behavior and a wavelet cross correlation analysis depicts a strong dependence of these series across a range of scales indicating a feedback between bed form dynamics and near bed turbulence these results complement our previous findings in which the signature of bed form evolution on the near bed velocity fluctuations was confirmed via the presence of a spectral gap and two distinct power law scaling regimes in the spectral density of velocity fluctuations we report herein a strong asymmetry in the probability distribution of bed elevation increments and instantaneous reynolds stresses the latter being further analyzed and interpreted via a quadrant analysis of velocity fluctuations in the longitudinal and vertical directions we also report the presence of intermittency multifractality in bed elevation increments and interpret it in view of the asymmetric nature of the pdfs as the result of scale coupling in other words the geometric asymmetry at the bed form scale gets transferred down to a probabilistic asymmetry at all smaller scales indicating a local anisotropy in the energy transfer finally we propose a predictive relationship between bed form averaged sediment transport rates and bed form averaged instantaneous reynolds stress and validate it using our experimental data

bridging the gap between turbulence and larger scales of flow motions in rivers although flow turbulence in rivers is of critical importance to earth scientists ecologists and engineers its relations with larger flow scales are not well understood thus leaving a fundamental gap in our knowledge from an analysis of a long time series of the streamwise and vertical flow velocity fluctuations measured in a gravel bed river we show that the signature of the fundamental turbulent flow structures e g ejections and sweeps is embedded within increasingly larger flow scales in a self similar manner the imbrication of turbulent structures into large flow pulsations of flow acceleration and deceleration covers more than two orders of magnitude from a few seconds to nearly 10 minutes this property is explained by the clustering of turbulent events creating an emergent pattern at larger scales the size of the larger flow pulsations scales with the spacing of the pools and riffles in the river this implies a mutual adjustment between turbulence generation mechanisms and long pulsations of flow acceleration and deceleration controlled by the bed morphology these results bridge a gap in our understanding of flows in rivers and offer a new perspective on the interactions between the turbulent flow with larger scales of flow motion that are critical for sediment transport habitat selection and fish behaviour copyright 2011 john wiley sons ltd

time and the rivers flowing fluvial geomorphology since 1960 fluvial geomorphology has been the largest single subdiscipline within geomorphology for many decades fluvial geomorphic expertise is integral to understanding and managing rivers and to developing strategies for sustainable development this paper provides an overview of some of the significant advances in fluvial geomorphology between 1960 and 2010 with respect to conceptual models fluvial features and environments being studied tools used by fluvial geomorphologists geomorphic specialty groups within professional societies journals in which fluvial geomorphic research is published and textbooks of fluvial geomorphology during this half century fluvial geomorphology broadened considerably in scope from a focus primarily on physical principles underlying process and form in lower gradient channels with limited grain size range to a more integrative view of rivers as ecosystems with nonlinear behavior and great diversity of gradient substrate composition and grain size the array of tools for making basic observations analyzing data and disseminating research results also expanded considerably during this period as did the diversity of the fluvial geomorphic community

monitoring alluvial sand suspension by eddy correlation eddy correlation techniques are standard tools in micrometeorology and oceanography to measure momentum and contaminant transport across turbulent boundary layers they can in theory be used to estimate the net vertical suspended sediment flux directly over different areas of an alluvial channel boundary and thus disclose ongoing erosion deposition patterns the basic principles and main problems in applying the technique to alluvial suspension are first introduced results from a trial application of the method in a large sand bed river are then presented the focus of the analysis is on the substantial and surprising contributions of multi minute flow fluctuations to suspension work in the study environment the data were collected in a 10 m deep channel of the fraser river near mission british columbia canada turbulent fluctuations of flow components streamwise and normal to the bed along with the output of an optical suspended sediment sensor were monitored over 7 h 1 m above the bed flow velocities averaged 0 9 ms 1 and mean suspended sediment concentrations 500 mgl 1 at sensor level above 1 5 dm high dunes spectral analysis of the records reveals that approximately 30 per cent of the vertical suspended sand mixing across the sensor level and roughly as much of the momentum exchange was linked to gradual flow oscillations with periods between 1 and 13 6 min underlying briefer turbulent fluctuations extended periods of sediment rich slightly upward directed but slower mean flow alternated with periods of sediment poor slightly downward and faster mean flow these slow fluctuations involved 10 20 cms 1 changes in 5 min average flow speed 2 4 changes in vertical flow angle and 100 mgl 1 changes in mean sand concentration to obtain accurate eddy correlation estimates of the vertical suspension flux in the study conditions hour scale flow and turbidity records that include many of these multi minute cycles appear to be necessary the spectra of the fraser river near bed signals do not conspicuously differ in overall shape in terms of low frequency content and location of peak from turbulent spectra encountered in some atmospheric boundary layers nonetheless the long period fluctuations observed on the fraser river may not be turbulent rather they may reflect slowly evolving perturbations in the near bed streamlines caused by bedform translation or gradual fluctuation within the large scale streamwise cells of the secondary flow

the pattern of surface waves in a shallow free surface flow 1 this work presents new water surface elevation data including evidence of the spatial correlation of water surface waves generated in shallow water flows over a gravel bed without appreciable bed forms careful laboratory experiments have shown that these water surface waves are not well known gravity or capillary waves but are caused by a different physical phenomenon in the flow conditions studied the shear present in shallow flows generates flow structures which rise and impact on the water air interface it is shown that the spatial correlation function observed for these water surface waves can be approximated by the following analytical expression w e 2 2 w2cos 2 l0 1 the proposed approximation depends on the spatial correlation radius w characteristic spatial period l0 and spatial lag this approximation holds for all the hydraulic conditions examined in this study it is shown that l0 relates to the depth averaged flow velocity and carries information on the shape of the vertical velocity profile and bed roughness it is also shown that w is related to the hydraulic roughness and the flow reynolds number

statistics of bedload transport over steep slopes separation of time scales and collective motion steep slope streams show large fluctuations of sediment discharge across several time scales these fluctuations may be inherent to the internal dynamics of the sediment transport process a probabilistic framework thus seems appropriate to analyze such a process in this paper we present an experimental study of bedload transport over a steep slope flume for small to moderate shields numbers the sampling technique allows the acquisition of high resolution time series of the solid discharge the resolved time scales range from 10 1 s up to 105 s we show that two distinct time scales can be observed in the probability density function for the waiting time between moving particles we make the point that the separation of time scales is related to collective dynamics proper statistics of a markov process including collective entrainment are derived the separation of time scales is recovered theoretically for low entrainment rates

evolution of coarse gravel bed forms field measurements at flood stage field measurements to investigate the origin and growth of mesoscale gravel bed forms in deep flows were made in the north fork toutle river washington sonar observations of the gravel streambed at a stationary point were recorded during two storm flows in december 1989 and january 1990 with concurrent bed load sampling and continuous velocity measurements mean diameter of bed load was about 3 cm flow depths were 1 4 2 4 m and bed shear stresses were 2 5 times the critical stress of mean bed load diameter as computed from the depth slope product these records document the hydrodynamic conditions under which dunelike coarse gravel bed forms were observed coarse gravel dunes height 20 cm length 6 15 m evolved more than 24 hours after peak stage primarily by accretion as inferred from bed form changes revealed in dual sonar records dune heights increased to 40 cm as mean trough elevation rose about 50 cm over several hours smaller dunes wavelength 1 3 m transitional from bed load sheets migrated on the backs of the large dunes the superposed dunes finally became indistinguishable from the large dunes which diminished in height by increasing the mean level of troughs gravel deposition occurred at the observation point in conjunction with migration of gravel dunes the direct comparison of known bed form regimes and gravel bar facies provides alternative interpretations of gravelly deposits

effect of wind on continental shelf carbon fluxes off southeast australia a numerical model 1 a coupled physical biological chemical model is used to study the effect of upwelling favorable and downwelling favorable winds on carbon biogeochemistry on the continental shelf off the southeast australian mainland along the continental shelf from 30 s to 34 s upwelling favorable winds with the aid of bottom ekman transport bring dissolved inorganic carbon dic rich slope waters onto the shelf increasing the carbon held in shelf waters for downwelling favorable winds bottom ekman transport still lifts slope waters onto the shelf but the slope water transport and therefore carbon held is reduced compared with the upwelling scenario under upwelling favorable winds filaments of dic and dissolved inorganic nitrogen din rich water reaching the surface produce an outgassing near the site of upwelling and absorption downstream due to primary productivity in a region of the ocean that is generally absorbing the net effect of upwelling is a reduced absorption of atmospheric co2 as a result of the ratio of deep dic and din 12 2 1 mol c mol n being greater than the redfield ratio 6 625 carbon fluxes in the waters off the southeast australian mainland are variable in space with the transport of continental shelf waters to deep waters occurring mainly where alongshore currents separate from the coast and flow over the 200 m isobath

mean flow and turbulence structure over fixed two dimensional dunes implications for sediment transport and bedform stability detailed measurements of flow velocity and its turbulent fluctuation were obtained over fixed two dimensional dunes in a laboratory channel laser doppler anemometry was used to measure the downstream and vertical components of velocity at more than 1800 points over one dune wavelength the density of the sampling grid allowed construction of a unique set of contour maps for all mean flow and turbulence parameters which are assessed using higher moment measures and quadrant analysis these flow field maps illustrate that 1 the time averaged downstream and vertical velocities agree well with previous studies of quasi equilibrium flow over fixed and mobile bedforms and show a remarkable symmetry from crest to crest 2 the maximum root mean square rms of the downstream velocity values occur at and just downstream of flow reattachment and within the flow separation cell 3 the maximum vertical rms values occur within and above the zone of flow separation along the shear layer and this zone advects and diffuses downstream extending almost to the next crest 4 positive downstream skewness values occur within the separation cell whereas positive vertical skewness values are restricted to the shear layer 5 the highest reynolds stresses are located within the zone of flow separation and along the shear layer 6 high magnitude high frequency quadrant 2 events ejections are concentrated along the shear layer kelvin helmholtz instabilities and dominate the contribution to the local reynolds stress and 7 high magnitude high frequency quadrant 4 events occur bounding the separation zone near reattachment and close to the dune crest and are significant contributors to the local reynolds stress at each location these data demonstrate that the turbulence structure associated with dunes is controlled intrinsically by the formation magnitude and downstream extent of the flow separation zone and resultant shear layer furthermore the origin of dune related macroturbulence lies in the dynamics of the shear layer rather than classical turbulent boundary layer bursting the fluid dynamic distinction between dunes and ripples is reasoned to be linked to the velocity differential across the shear layer and hence the magnitude of the kelvin helmholtz instabilities which are both greater for dunes than ripples these instabilities control the local flow and turbulence structure and dictate the modes of sediment entrainment and their transport rates

the age of water and ventilation timescales in a global ocean model abstract the age of water in the world ocean is studied using a passive age tracer introduced into a global ocean model additional information is derived from a transient dye tracer that tracks the time dependent spreading of surface waters into the model ocean interior of particular interest is the nature of ocean ventilation over the 10 100 yr timescale as well as the simulated age of deep and bottom water masses in the upper model levels young water is found to correspond with regions of convergence and downwelling in the surface ekman layer upwelling and convection are both shown to age the upper ocean by entraining older waters into the surface mixed layer in the deep model levels water age varies greatly between oceans with young water found in convectively active regions in the north atlantic and in the ross and weddell seas and old water found in the deep north pacific the oldest water mass mixture located at 2228 m depth in the western pacific ocean is dated at 1494 years made

on ocean transport diagnostics the idealized age tracer and the age spectrum abstract the idealized age tracer is commonly used to diagnose transport in ocean models and to help interpret ocean measurements in most studies only the steady state distribution the result of many centuries of model integration has been presented and analyzed however in principle the transient solution provides more information about the transport here it is shown that this information can be readily interpreted in terms of the ventilation histories of water masses a simple relationship is derived valid for stationary transport between the transient evolution id r t of the idealized age tracer and the age spectrum g r t the distribution of times t since a water mass was last ventilated namely g r t tt id r t implications of the relationship are discussed and the relationship is illustrated with an idealized model

reach scale variability of turbulent flow characteristics in a gravel bed river in gravel bed rivers bed roughness is often controlled by the spatial distribution of pebble clusters and large protuberant clasts the turbulent flow structure around these roughness elements has been studied extensively as opposed to the effects of the spatial variability of the bed roughness on the structure of the flow at the reach scale in this paper we examine the effects of roughness elements on the spatial variability of the mean flow velocity profiles and of the properties of turbulent flow structures at the reach scale the experiment was carried out in two reaches of 25 m long in the eaton north river quebec we produced detailed topographic maps of the river reaches to obtain the spatial distribution of the main roughness elements the flow is characterized with velocity time series measured using electromagnetic current meters mounted on a vertical wading rod we collected 65 velocity profiles from which we derived turbulent flow characteristics results showed that in spite of the complex configuration of the bed velocity profiles are predominantly log linear mean and turbulent flow characteristics are only affected at a local scale and over short distances by the presence of roughness elements at the reach scale the distribution of individual roughness elements does not greatly control the spatial variability of turbulent flow properties

burst like sediment suspension events in a sand bed river in a much quoted paper jackson 1976 hypothesized that turbulent bursting motions such as those documented in laboratory boundary layers play a major role in alluvial sediment suspension to date the hypothesis remained largely untested due to difficulties in monitoring turbulent suspension in rivers this study provides field data documenting burst like turbulent motions over a sandy bed channel and quantifying the role of these motions in sand suspension the data were collected in a 10 m deep channel of the fraser river near mission british columbia canada turbulent fluctuations of both flow components downstream and normal to the bed along with the output of an optical suspended sediment sensor were monitored 1 m above the river bed typical flow velocities averaged 0 9 ms 1 at the sensors where mean suspended sediment concentrations were 500 mgl 1 decimetre height small dunes on the backs of larger half metre amplitude dunes covered the channel bed in the area brief but intense burst like ejection and inrush events were identified in the flow records where they are responsible for a high degree of intermittency in shear stress over the dunes 80 per cent of the turbulent momentum exchange across the 1 m level can be ascribed to such brief 3 8 s duration events active under 12 per cent of the time in addition the record of fluctuating sediment concentrations reveals these burst like motions to be highly effective in vertically mixing suspended sediment and thus ultimately in maintaining suspended sediment transport above the dune bed the bulk 60 and 90 per cent in two deployments of the vertical sediment mixing was accomplished by intense events active some 10 per cent of the time no discrete recurrence timescale for these burst like mixing events is evident however rather a continuous variation of return periods was observed as a function of the magnitude of vertical mixing event considered to that extent conceptual models of sediment transport in terms of burst events with a predictable recurrence such as proposed by jackson 1976 may be misleading

mesoscale structure of the mean east australian current system and its relationship with topography abstract we document the mean circulation of the east australian current eac system which is the major western boundary current in the southwest pacific ocean a new high resolution climatology of the region csiro atlas of regional seas cars is used to produce regional fields of steric height and sections of geostrophic velocity the realism of these fields has been enhanced by the high spatial resolution allowance for bathymetric control and the influence of land barriers the increased detail in the maps and sections reveal the major influence that the complex regional topography has on the circulation the results also provide the appropriate resolution for comparison with recent model studies of the region we have been able to both resolve well known features with greater detail and identify previously unrecognized aspects of the circulation important results include 1 the zonal inflow north of 30 s breaks into a series of individual jets after flowing through the island chains as suggested by recent model results 2 the interaction of the zonal inflow with the local topography as it undergoes bifurcation is documented 3 a detailed picture of the evolution of the eac at the western boundary is presented including surface currents and transports 4 separation and recirculation of the eac within the tasman abyssal basin are shown to occur as a double cell structure constrained by bathymetry 5 the eac outflow is resolved as a series of eastward and northeastward currents 6 the path of the tasman front is defined as it interacts with the tasman ridge systems 7 a quasi permanent eddy is identified for the first time adjacent to the norfolk ridge northwest of new zealand

basin evaluation using burial history calculations an overview burial history calculations available to the petroleum geologist include plots of burial history and geohistory porosity and conductivity as a function of depth and lithology as well as the results obtained from algorithms to handle unconformities and backstripped crustal subsidence calculations that predict the breakdown of kerogen to hydrocarbons in terms of time and temperature and methods for determining heat flow from geologic models and vitrinite reflectance data inputs required for these calculations include depths of formation tops ages of formation tops lithologies of formations depths of water at deposition of the different formations porosities of the formations as a function of depth bottom hole temperatures and or formation temperatures and any ke ogen content and vitrinite reflectance values as functions of depth sources of many of these data may be well logs well reports geologic papers and or seismic sections the paper considers how parameters can be extracted from burial history calculations to construct maps that can be compared to the current locations of oil and gas fields and so used to locate and rank prospective acreage these parameters include the potential source rock maturity of a formation plotted as a function of time and depth the thermal history of any hydrocarbons associated with the potential source rock the rate of sediment accumulation of a formation as a function of time and subsidence rate of a formation as a function of time subsidence rate includes total subsidence compaction induced subsidence isostatic response to sediment load and backstripped crustal subsidence total subsidence minus the effects of compaction and isostatic response

the cold core eddy and strong upwelling off the coast of new south wales in early 2007 abstract during the austral summer of 2006 07 a series of extreme oceanic events occurred in the tasman sea following a series of strong wind driven upwelling events an intense cold core eddy developed off sydney australia a data assimilating eddy resolving ocean model is used to create a three dimensional time varying reanalysis of these events the reanalysis indicates that the cold anomalies associated with the upwellings were in excess of 5 c near the coast where sea level decreased by as much as 0 2 m the reanalysed three dimensional structure of the cold core eddy shows the eddy leaning to the west north west in towards the continental shelf the diameter of the eddy is about 100 km and the sea level anomaly at the eddy centre peaks at around 1 m with an associated sub surface temperature anomaly in excess of 8 c at 200 m depth corresponding to an upward isotherm excursion of 600 m the circulation around the cyclonic eddy is ageostrophic with upwelling in the southern sector of the eddy where flow is onshore and climbing the continental slope and downwelling in the northern sector where flow is descending off the slope three dimensional trajectories of water parcels around the eddy involve 50 100 m vertical excursions based on the reanalysed circulation and composite satellite images of chlorophyll a we hypothesise that the circulation around the eddy led to significant nutrient enrichment in the euphotic zone around the perimeter of the eddy

1 min in the life of a river selecting the optimal record length for the measurement of turbulence in fluvial boundary layers in the analysis of instantaneous velocity measurements it is important to consider carefully the properties of the instruments as well as the sampling frequency and the record length although several studies have examined the influence of instrument settings on velocity measurements in rivers little information is available on the effects of the record length on these measurements and on the turbulence parameters that can be extracted from the time series decisions on the record length are often made ad hoc here we quantify the effects of the sampling period on the precision of turbulence statistics e g mean standard deviation skewness reynolds stress quadrant analysis obtained from velocity measurements in fluvial turbulent boundary layers a bootstrapping method is used to determine the standard errors s e of turbulence statistics from 19 time series the time series were sampled in three gravel bed rivers using both electromagnetic current meters ecm and acoustic doppler velocimeters adv the record lengths ranged between 20 and 60 min the sampling frequencies were 20 and 25 hz for the ecms and advs respectively we show that for most turbulence statistics the optimal record length minimum sampling effort to achieve low standard errors ranges between 60 and 90 s we discuss the implication of these record lengths for standard errors estimates and variance losses

scalings for large turbulent flow structures in gravel bed rivers 1 the relations between frequency and duration of large scale turbulent flow structures in gravel bed rivers and the distributions of the time intervals between turbulent events are investigated using flow visualisation and velocity measurements the time of occurrence and the duration and amplitude of large bursting motions were estimated independently from a five minute underwater video and from high resolution velocity time series sampled at 20 hz during 38 minutes at three heights above the bed results from both experiments show that the frequency duration relations of the large scale turbulent flow structures follow a power function with exponents ranging between 1 4 and 1 95 values that are typical of bursting systems e g solar flares the frequency distributions of time intervals between two successive ejections display an exponential tail these findings provide models for simulating sequences of large scale turbulent events in a gravel bed river an important step in linking flow turbulence and sediment transport

seasonality of sporadic physical processes driving temperature and nutrient high frequency variability in the coastal ocean off southeast australia physical processes forced by alongshore winds and currents are known to strongly influence the biogeochemistry of coastal waters combining in situ observations moored platforms hydrographic surveys and satellite data sea surface wind and sea surface height we investigate the transient occurrence of wind driven upwelling downwelling and current driven upwelling events off southeast australia remote sensed indices are developed and calibrated with multiannual time series of in situ temperature and current measurements at two shelf locations based on archives up to 10 years long climatological analyses of these indices reveal various latitudinal regimes with respect to seasonality magnitude duration of events and their driving mechanisms wind or current generally downwelling favorable winds prevail in this region however we demonstrate that up to 10 wind driven upwelling days per month occur during spring summer at 28 33 5 degrees s and up to 5 days in summer further south current driven upwelling upstream of the east australian current separation zone approximate to 32 degrees s occurs twice as often as downstream using independent in situ data sets we show that the response of the coastal ocean is consistent with our climatology of shelf processes upwelling leads to a large range of temperatures and elevated nutrient concentrations on the shelf maximized in the wind driven case while downwelling results in destratified nutrient poor waters the combination of these sporadic wind and current driven processes may drive an important part of the high frequency variability of coastal temperature and nutrient content our results suggest that localized nutrient enrichment events of variable magnitude are favored at specific latitudes and seasons potentially impacting coastal ecosystems key points multisensor analysis of shelf processes combining in situ and satellite data spatio temporal variability of transient wind and current driven up downwelling cold nutrient rich water intrusions favoured at specific locations seasons

a consideration of the dune antidune transition in fine gravel hydraulic data defining the dune antidune transition in fine gravel are compared with potential flow theory and information is drawn from published experiments and field based studies attention is given to both transitional bedforms and the development of downstream migrating antidunes in the latter case most data pertain to sand beds and not to gravel empirical data provide some weak support for the theoretical notion that the transition occurs at progressively lower froude numbers at greater relative depths although a critical froude number of 0 84 may reasonably be applied for the beginning of the dune to antidune transformation lag effects and a possible depth limitation ensure that transitional bedforms may persist across a broad range of froude numbers from 0 5 to 1 8 this latter observation has great relevance for palaeohydraulic estimates derived from outcrop data whereas the application of theoretical bedform existence fields based upon potential flow theory to fine gravel was previously purely speculative the addition of experimental and field data to these plots provides a degree of confidence in applying stability theory to practical geological problems for the first time laboratory data pertaining to downstream migrating gravel antidunes are compared with theory these bedforms have been reported from certain experimental near critical flows above sand or gravel beds but have been observed infrequently in natural streams however there are no detailed studies from natural rivers and only a few contentious identifications from outcrops nevertheless the limited hydraulic data conform to theoretical expectations