the importance of double diffusion to the settling of suspended material the vertical fingering motions which can occur when warm salty water overlies colder fresher water are important to the vertical flux of salt in the ocean an analogous and not uncommon situation is that where turbid water overlies clearer and denser water for the case of an originally sharp horizontal interface between the two water layers associated as an example with an interflow due to a warm muddy river entering a stratified lake the resulting downward sediment flux is compared with that occurring by way of gravitational settling rules are proposed to ascertain when the fingering effect could be important to sedimentation for example it seems that fingering could be of consequence in the situation where the sediment has a diameter of 2 m and the upper layer is about 1 c warmer than the clear lower layer when the upper layer concentration is 1 ppm the effect of fingering on the residence time of a gravitationally stable turbid layer is calculated such layers may be more short lived than commonly thought

shear instability in a highly stratified estuary abstract shear instability is found to be the principal mechanism of vertical exchange within the pycnocline of a salt wedge estuary a field program involving high resolution velocity and density measurements as well as high frequency acoustic imagery allowed direct comparison of instantaneous richardson number distributions to the occurrence of shear instability the theoretical stability threshold of 0 25 is consistent with the measurements based on estimates of gradients that contain the mean as well as fluctuations due to internal waves an effective stability threshold based on mean gradients is found to be approximately one third reflecting a significant contribution of internal wave shear the integral effect of the mixing process is to homogenize the gradients of velocity and density producing linear profiles of these quantities across the pycnocline a turbulent prandtl number of unity is suggested by the vertical distributions of velocity and density during periods of active vertical mixin

the influence of diffusive convection on sedimentation from buoyant plumes abstract diffusive convection driven by the differential diffusion of density altering fluid properties may enhance the scavenging of particles from natural buoyant plumes for single phase fluid solute heat systems this phenomenon has been extensively studied because salt fingering generated at the oceanic thermocline is a major mechanism of salt transport in the oceans however the influence of this process on particle laden plumes for example fluvial plumes in lakes and estuaries volcanic clouds and seafloor hydrothermal plumes is largely unknown in this paper we present direct experimental measurements of the interfacial particle flux at the plume base which can be applied to predict particle scavenging from natural buoyant plumes particle flux is measured using a light attenuation technique employing a chain of photodiodes which average concentration over a large number of fingers the results are in good general agreement with earlier studies based on finger velocity flux measurements cover a wide range of conditions from those where diffusive convection dominates to those where settling and diffusive convection are of a similar magnitude for very small particles double diffusive salt finger theory is applicable to two component particulate systems as suggested by earlier studies green t 1987 the importance of double diffusion to the settling of suspended material sedimentology 34 319 331 two component diffusive convection theory is extended to three components in order to predict particle scavenging from marine fluvial plumes which involve the diffusion of sediment salt and heat for larger particles which settle significantly the flux can be approximated by adding the double diffusive and settling fluxes a theory to predict particle transport through the lower layer and sedimentation at the bed is developed based on the observation of strong convection below the plume application of our theory and experimental results indicates that while double diffusion may significantly influence the longitudinal distribution and vertical sorting of deposits from lacustrine plumes the diffusive convection process is generally insignificant in marine plumes observational evidence for lacustrine double diffusion based on water column measurements is presented

settling driven convection a mechanism of sedimentation from stratified fluids convection driven by sediment particles may play an important role in sedimentation from the base of buoyant hypopycnal plumes for example fluvial plumes in stratified estuaries and lakes black smokers on the ocean floor volcanic clouds and coastal currents in addition to the well known double diffusive convection mechanism another mode of convective instability development is by settling across the density interface we performed laboratory experiments to investigate this fingering convective instability mechanism and its effect on particle distribution in the water column and deposition at the bed a simple theoretical model of finger formation at a fluid density interface is developed based on an analogy with thermal plume formation at a flat heated plate this model which involves a thickening interface layer that becomes gravitationally unstable relative to the ambient fluid is in good agreement with measurements of finger size and instability wavelength from visualization experiments since fingering at the density interface drives larger scale convection in the fluid below a mass balance model of the lower layer assuming strong mixing i e uniform sediment concentration is successfully applied to predict sediment concentration in the water column and deposition at the bed strong mixing can be assumed since convective velocities are usually much greater than the particle fall velocities as convection proceeds the sediment concentrations in the two layers approach each other and convection will die out using the model equations we develop analytical expressions for the time when convection ceases and the portion of sediment remaining in the water column

simple spatially distributed models for predicting flood inundation a review abstract in this paper we review recent progress in the use of reduced complexity models for predicting floodplain inundation we review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one dimensional shallow water equations we then review how such schemes can be applied in practice and consider issues of space discretization time discretization and model parameterisation before going on to consider model assessment procedures we show that a key advantage of reduced complexity codes is that they force modellers to think about the minimum process representation necessary to predict particular quantities and act as a check on any tendency to reductionism at the same time however the use compared to standard hydraulic codes of strong simplifying assumptions requires us to also address the question how simple can a model be and still be physically realistic we show that by making explicit this debate about acceptable levels of abstraction reduced complexity codes allow progress to be made in addressing a number of long standing debates in hydraulics

hyperpycnal plume formation from riverine outflows with small sediment concentrations a series of laboratory experiments has been conducted in order to elucidate the sediment induced mixing processes accompanying riverine outflows specifically the discharge of a warm fresh particle laden fluid over a relatively dense cool brine in a parameter regime analogous to recently acquired field measurements hypopycnal surface plumes were subject to a convective instability driven by some combination of heat diffusing out of the warm fresh sediment laden plume and particle settling within it convection was robust in the presence or absence of intense turbulence at sediment concentrations as low as 1 kg m 3 and took the form of millimetre scale sediment laden fingers descending from the base of the surface plume a consequence of the convective instability of the original hypopycnal plume is the generation of a hyperpycnal bottom riding flow the experiments presented here indicate that natural river outflows may thus generate hyperpycnal plumes when sediment concentrations are 40 times less than those required to render the outflow heavy relative to the oceanic ambient the resulting hyperpycnal plumes may play an important role in transporting substantial quantities of sediment to the continental slope and beyond

analysis of a detention basin impact on dike failure probabilities and flood risk for a channel dike floodplain system along the river elbe germany highly concentrated asset values are often protected by dikes stretching along the river course during extreme floods dikes may fail due to various breach mechanisms and cause considerable damage therefore detention basins are often additionally installed to reduce the flood risk for downstream communities in such situations however the systemic performance of dikes and spatial redistribution of inundation patterns are often unknown intuitively expected effects such as more probable breaches downstream due to fewer breaches upstream and consequently higher conveyance of upstream reaches lack evidential proof with a coupled probabilistic deterministic 1d channel dike breach 2d inundation flood damage model chain the impact of a detention basin on losses to residential buildings and agricultural crops is investigated we demonstrate the changes in dike performance due to systemic load and relief along the river course on the middle elbe germany considering three breach mechanisms overtopping piping and slope micro instability the reduction of overtopping failures due to the detention basin resulted in the slightly increased breach probabilities due to piping and micro instability farther downstream finally the uncertainty in hazard and damage estimations are analysed using the monte carlo simulation and applying several damage models despite high uncertainties in flood hazard and damage estimations we conclude that the risk reduction to residential buildings downstream of the detention basin exceeds the higher losses to agricultural crops within the filled detention area

convective instability in sedimentation linear stability analysis 1 convective sedimentation in a stably stratified saltwater is studied using the linear stability analysis convective sedimentation is known to occur due to the double diffusive mechanism and the settling driven mechanism in this study a semi empirical closure of sediment diffusivity based on the long range hydrodynamics effect is adopted the sediment phase can act as either the slow or fast diffusing agent in the double diffusive system for the given salt diffusivity moreover the settling driven effect is proportional to the square of the sediment diameter via stoke settling law we consider sediment concentration grain size in the upper freshwater layer to be in the range of 0 1 to 39 4 g l 2 to 60 m which is on top of a saltwater layer with salinity 35 ppt linear stability analysis allows us to identify the dominant mechanism that triggers the instability the growth rate and the resulting characteristic finger width model results suggest that for fine sediment with grain diameter smaller than 10 m settling velocity 0 09 mm s double diffusive mechanism controls the instability and the resulting sediment finger size is of millimeter scale for the given threshold of growth rate of o 0 01 s 1 the minimum sediment concentration is about 8 15 g l for grain size greater than or around 10 m the settling driven mechanism dominates and instabilities occur at sediment concentration as low as o 0 1 g l with centimeter scale fingers our findings may contribute to a better understanding on the observed rapid sediment removal in the plume of small mountainous rivers

overtopping induced failure of noncohesive homogeneous fluvial dikes accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes laboratory experiments on the breaching of fluvial sand dikes were performed considering a flow parallel to the dike axis the breach was triggered by overtopping the dike crest a detailed monitoring of the transient evolution of the breach geometry was conducted providing key insights into the gradual and complex processes involved in fluvial dike failure the breach develops in two phases 1 the breach becomes gradually wider and deeper eroding on the downstream side along the main channel and 2 breach widening controlled by side slope failures continuing in the downstream direction only increasing the inflow discharge in the main channel the breach formation time decreases significantly and the erosion occurs preferentially on the downstream side the downstream boundary condition has a strong influence on the breach geometry and the resulting outflow hydrograph

a simple raster based model for flood inundation simulation in this paper the development of a new model for simulating flood inundation is outlined the model is designed to operate with high resolution raster digital elevation models which are becoming increasingly available for many lowland floodplain rivers and is based on what we hypothesise to be the simplest possible process representation capable of simulating dynamic flood inundation this consists of a one dimensional kinematic wave approximation for channel flow solved using an explicit finite difference scheme and a two dimensional diffusion wave representation of floodplain flow the model is applied to a 35 km reach of the river meuse in the netherlands using only published data sources and used to simulate a large flood event that occurred in january 1995 this event was chosen as air photo and synthetic aperture radar sar data for flood inundation extent are available to enable rigorous validation of the developed model 100 50 and 25 m resolution models were constructed and compared to two other inundation prediction techniques a planar approximation to the free surface and a relatively coarse resolution two dimensional finite element scheme the model developed in this paper outperforms both the simpler and more complex process representations with the best fit simulation correctly predicting 81 9 of inundated and non inundated areas this compares with 69 5 for the best fit planar surface and 63 8 for the best fit finite element code however when applied solely to the 7 km of river below the upstream gauging station at borgharen the planar model performs almost as well 83 7 correct as the raster model 85 5 correct this is due to the proximity of the gauge which acts as a control point for construction of the planar surface and the fact that here low lying areas of the floodplain are hydraulically connected to the channel importantly though it is impossible to generalise such application rules and thus we cannot specify a priori where the planar approximation will work simulations also indicate that for this event at least dynamic effects are relatively unimportant for prediction of peak inundation lastly consideration of errors in typically available gauging station and inundation extent data shows the raster based model to be close to the current prediction limit for this class of problem q 2000 elsevier science b v all rights reserved

unconformities and porosity development in carbonate strata ideas from a hedberg conference the purpose of this paper is to highlight ideas from a hedberg conference concerning detection of unconformities and associated porosity in carbonate strata many types of information including cores and outcrops seismic data eustatic sea level curves wireline logs biostratigraphic data stable isotope trends cycle stacking patterns and tectonic and basin evolution models can be used to predict and or detect subaerial unconformities all methods of detecting subaerial exposure with these types of information have limits and pitfalls detailed analysis of the stratigraphy sedimentology and diagenetic history of a rock sequence from outcrop or core data is considered the most reliable means of detecting subaerial exposure though an integrated approach using all a ailable information is recommended the relationship between subaerial exposure and subsurface porosity in carbonates is not simple or easily predicted subsurface porosity is the product of many factors operating during deposition subaerial exposure and burial several concepts should be recognized when evaluating porosity associated with subaerial unconformities 1 carbonate diagenesis during subaerial exposure rearranges pore networks but usually does not increase the total porosity near surface dissolution can simply lower a topographic surface without increasing porosity within the host limestone in many cases total porosity in carbonates under unconformities is actually reduced during subaerial exposure 2 permeability is likely to change more than porosity during subaerial exposure increasing in some c ses but decreasing in others 3 pore systems evolve with time during subaerial exposure short periods of subaerial exposure 10 000 400 000 yr are often associated with greater porosity than long intervals of subaerial exposure 1 20 million yr prolonged subaerial exposure may change permeability less than porosity because high permeability karst related conduits can form quickly and persist for millions of years 4 many carbonates subjected to subaerial exposure have little or no porosity in the deep subsurface because compaction cementation and stratal collapse reduce porosity during burial 5 unconformity related diagenesis may enhance reservoir potential by creating pore systems that are resistant to compaction during deeper burial 6 vugs caverns and breccias can fo m in the deep subsurface because of dissolution by basinal fluids independent of subaerial exposure 7 lithologic changes at unconformities like shales overlying carbonates can influence the flow of subsurface fluids during end page 857 deeper burial resulting in deep burial dissolution localized along unconformities if subaerial exposure and exposure surfaces are integrated into a sequence stratigraphic paleogeographic and climatic framework systematic and hopefully predictable patterns will emerge however we do not fully understand the complex interplay between the factors critical to creating and preserving porosity in carbonates additional research is needed to quantify critical processes and products so we can reliably predict porosity associated with subaerial exposure during exploration in frontier basins and on a smaller scale during reservoir analysis

a new methodology for flood hazard assessment considering dike breaches 1 this study focuses on development and application of a new modeling approach for a comprehensive flood hazard assessment along protected river reaches considering dike failures the proposed inundation hazard assessment model iham represents a hybrid probabilistic deterministic model it comprises three models that are coupled in a dynamic way 1 1d unsteady hydrodynamic model for river channel and floodplain between dikes 2 probabilistic dike breach model which determines possible dike breach locations breach widths and breach outflow discharges and 3 2d raster based inundation model for the dike protected floodplain areas due to the unsteady nature of the 1d and 2d models and runtime coupling the interdependence between the hydraulic loads on dikes at various locations along the reach is explicitly considered this ensures a more realistic representation of the fluvial system dynamics under extreme conditions compared to the steady approaches the probabilistic dike breach model describes dike failures due to three failure mechanisms overtopping piping and slope instability caused by seepage flow through the dike core micro instability the 2d storage cell model computes various flood intensity indicators such as water depth flow velocity and inundation duration iham is embedded in a monte carlo simulation in order to account for the natural variability of the input hydrograph form and the randomness of dike failures besides binary wet dry inundation patterns iham generates new probabilistic flood hazard maps for each intensity indicator and the associated uncertainty bounds furthermore the novel probabilistic dike hazard maps indicate the failure probability of dikes for each considered breach mechanism

building the 3 d jigsaw puzzle applications of sequence stratigraphy to 3 d reservoir characterization permian basin reservoir characterization involves the quantification integration reduction and analysis of geological petrophysical seismic and engineering data this is no small task a principal goal of reservoir characterization is to derive a spatial understanding of interwell heterogeneity traditionally geologic attempts to characterize interwell heterogeneity have been done using hand drawn or computer generated two dimensional 2 d maps and cross sections results can be improved dramatically using three dimensional 3 d interpretation and analysis techniques three dimensional reservoir characterization requires the same input data used in 2 d approaches and the cost is equal to and commonly lower than traditional 2 d methods the product of 3 d reservoir characterization is a 3 d reservoir model the language used to communicate the results of a 3 d reservoir model is visualization i e visual images of numerical data all of the available log and core data in a model area are incorporated in a 3 d model but the data are depicted as colored cells rather than as log traces the integrity of the 3 d reservoir model is largely a function of the stratigraphic framework interpreting the correct stratigraphic framework for a subsurface reservoir is the most difficult and creative part of the 3 d modeling process sequence and seismic str tigraphic interpretation provide the best stratigraphic framework for 3 d reservoir modeling the purpose of this paper is to discuss the process of 3 d deterministic reservoir modeling and to illustrate the advantages of using a sequence stratigraphic framework in 3 d modeling mixed carbonate and siliciclastic sediment outcrop and subsurface examples from the permian basin of west texas and new mexico will be used as examples but the concepts and techniques can be applied to reservoirs of any age three dimensional reservoir modeling results in an improved geologic interpretation provides a means of integrating geological petrophysical geophysical and engineering data and allows for immediate model updates as new data are acquired as a result of 3 d reservoir characterization reservoir management decisions data quality control volumetric calculations numerical sim lation input and communication between disciplines are improved

modelling floodplain flows using a two dimensional finite element model a prototype two dimensional finite element flow model for depth averaged free surface flows was developed for floodplain environments limited refinement of the model s physical representation was undertaken and the enhanced scheme applied to an 11 km river channel floodplain reach in the u k preliminary model results indicate that this modelling approach can be used to identify dynamic variations in the flow field parameters over length scales of the order of 10 100 m potentially such data have the ability to permit detailed analysis of short term floodplain sedimentary dynamics

enhanced sediment scavenging due to double diffusive convection abstract river water intruding into a lake or ocean typically results in a surface layer of warm sediment laden water overriding relatively dense cold fluid though this system is stable with respect to density instability may arise as a result of the different diffusivities of sediment and heat a series of experiments were conducted which indicated that double diffusive convection ddc was responsible for rapid sedimentation of slowly settling particles a simple theory based upon relevant physical processes is developed that describes this behavior it also incorporates the previously neglected effects of ambient stratification on the strength of the ddc application of the theory and our results to field data taken from oceanic river plumes demonstrates that the flux due to double diffusive sedimentation dds can be at least as strong as flocculation enhanced gravitational settling

a numerical investigation of convective sedimentation 1 understanding the fate of riverine sediment in the coastal environment is critical to the health of the coastal ecosystem and the changing morphology one of the least understood mechanisms of initial deposition is the convective sedimentation of hypopycnal plumes this study aims at investigating convective sedimentation by means of a numerical model for fine sediment transport solving the non hydrostatic reynolds averaged navier stokes equations for stratified turbulent flow model validation is sought by comparison to laboratory results for turbidity and saline currents over a changing slope the model is shown to be capable of predicting both the upstream supercritical and the downstream subcritical flows the numerical model is then utilized to study convective sedimentation and its depositional and mixing characteristics by analyzing model results of more than 40 runs for different inlet sediment concentration density ratio settling velocity particle reynolds number rep and inlet velocity height inlet reynolds number re four distinct flow regimes are revealed for large we observe divergent plumes with significant deposits near the inlet for intermediate and large rep intense convective fingers are predicted which are only marginally affected by ambient shear flow further reducing the density ratio or rep gives weak convective fingers that are significantly affected by the ambient shear flow eventually no convective fingers are observed during the computation for very small or rep sediment deposits in the divergent plume and intense convective finger regimes are relatively insensitive to re deposit increases with re in the weak convective finger regime

high resolution numerical modeling of wave supported gravity driven mudflows 1 wave supported gravity driven mudflow has been identified as a major offshore fine sediment transport mechanism of terrestrial sediment into the coastal ocean this transport process essentially occurs within the wave boundary layer in this study wave supported gravity driven mudflow is investigated via a wave phase resolving high resolution numerical model for fluid mud transport the model results are verified with field observation of sediment concentration and near bed flow velocities at po prodelta the characteristics of wave supported gravity driven mudflows are diagnosed by varying the bed erodibility floc properties fractal dimension and rheological stresses in the numerical simulations model results for moderate concentration suggest that using an appropriately specified fractal dimension the dynamics of wave supported gravity driven mudflow can be predicted without explicitly incorporating rheological stress however incorporating rheological stress makes the results less sensitive to prescribed fractal dimension for high concentration conditions it is necessary to incorporate rheological stress in order to match observed intensity of downslope gravity driven current model results are further analyzed to evaluate and calibrate simple parameterizations analysis suggests that when neglecting rheological stress the drag coefficient decreases with increasing wave intensity and seems to follow a power law however when rheological stress is incorporated the resulting drag coefficient is more or less constant around 0 0013 for different wave intensities model results further suggest the bulk richardson number has a magnitude smaller than 0 25 and is essentially determined by the amount of available soft mud i e the erodibility suggesting a supply limited condition for unconsolidated mud

inundation of a dutch river polder sensitivity analysis of a physically based inundation model using historic data 1 the inundation model delft flooding system delft fls was applied to simulating the historical flood of 1805 in the polder land van maas en waal netherlands delft fls is a two dimensional 2 d hydrodynamic model that simulates overland flow sensitivity analyses show a large influence of floodplain topography and hydraulic friction on the propagation of the inundation because of the typical topography of dutch polders a virtually flat floodplain bordered by high dikes the extent of the inundated area alone cannot be used for evaluating the model performance therefore the inundation time and water levels within the inundated area were used to test the model capabilities this study shows that using historic data has a potential advantage over using contemporary data historic data allow evaluation of a model for real flood disasters that have long return periods and fortunately have not occurred in modern times

hydraulic jumps in sediment driven bottom currents laboratory experiments were conducted to observe the behavior of turbidity currents in the vicinity of a slope transition both sediment laden and saline hydraulic jumps were produced the vertical structure of the currents was found to depend on flow regime the saline and turbid hydraulic jumps showed similar characteristics the amount of water entrained by the flows through a jump was small the change in flow regime caused a marked reduction of the bed shear stress downstream of the jump in nature a turbidity current experiencing a hydraulic jump will drop most of its bedload immediately downstream from the jump while the suspended load will respond more gradually to the change in flow regime and will deposit sediment over a distance far exceeding 1 000 times the jump height

the effects of flocculation and bed erodibility on modeling cohesive sediment resuspension 1 flocculation and bed erodibility are two main processes causing the transport of cohesive sediments to be more complicated than typical noncohesive sediments earlier flocculation models assume a constant fractal dimension and or a constant floc yield strength however recent studies have shown that considering both the fractal dimension and the floc yield strength to be variable is critical to the prediction of temporal evolution of floc size due to consolidation it is also well established that critical bed shear stress of a mud bed cannot be parameterized as a constant this study further investigates how flocculation models with different degrees of complexity and bed erodibility can affect the resulting cohesive sediment resuspension driven by tidal flows a one dimensional vertical numerical model for sediment transport is revised to incorporate modules for flocculation and bed erodibility model results are compared with data measured in the ems dollard estuary model study suggests that it is important to incorporate variable critical shear stress in order to properly model the supply of sediment from the bed when flocculation is neglected or incorporated incompletely numerical model predicts nearly zero sediment concentration during slack water and very steep concentration gradient which are inconsistent with the observed data when the fractal dimension and the floc yield strength are both considered to be variable the numerical model predicts much smaller settling velocity and hence captures the more well mixed condition consistent with field observations

gravity driven sediment transport on the continental shelf implications for equilibrium profiles near river mouths an analytical model is developed for equilibrium bathymetric profiles off river mouths associated with the shoreward convex upward portion of subaqueous deltas and clinoforms the model builds on recent field results demonstrating that gravity driven flux of suspended mud is important on shelves provided that wave induced suspension of sediment supports the requisite turbid hyperpycnal layer because the maximum sediment load is determined by the critical richardson number the results are independent of the properties of the suspended mud or the bed the model assumes the equilibrium state to represent a balance between the supply of sediment by a river at the coast and the downslope bypassing of sediment to deep water within wave supported turbid near bed layers progressive seaward increases in bed slope across the convex shelf profile allow the attenuation of wave agitation with depth to be compensated for by a downslope increase in the contribution of gravity the model is consistent with shelf profiles off the mouths of the eel california ganges brahmaputra bangladesh waiapu new zealand po italy and rhone france rivers the equilibrium profile is predicted to be a function of wave climate and riverine sediment supply only with deeper and broader profiles associated with decreasing sediment supply increasing wave height and or increasing wave period

toward modeling turbulent suspension of sand in the nearshore 1 we present two depth and phase resolving models based on single and two phase approaches for suspended sediment transport under water waves both models are the extension of a wave hydrodynamic model cornell breaking wave and structure cobras in the two phase approach dilute two phase mass and momentum equations are calculated along with a fluid turbulence closure based on balance equations for the fluid turbulence kinetic energy k f and its dissipation rate f in the single phase approach the fluid flow is described by the reynolds averaged navier stokes equations while the sediment concentration is calculated by an advection diffusion equation for the conservation of sediment mass the fluid turbulence is calculated by k f f equations that incorporate the essential influence of sediment which can also be consistently deduced from the two phase theory by adopting a commonly used sediment flux boundary condition near the bed the proposed models are tested against laboratory measurements of suspended sediment under nonbreaking skewed water waves and shoaling broken waves although the models predict wave averaged sediment concentrations reasonably well the corresponding time histories of instantaneous sediment concentration are less accurate we demonstrate that this is due to the uncertainties in the near bed sediment boundary conditions in addition we show that under breaking waves the near bed sediment pickup cannot be solely parameterized by the bottom friction suggesting that other effects may also influence the near bed sediment boundary conditions

extreme storm events landscape denudation and carbon sequestration typhoon mindulle choshui river taiwan we have performed the first known semicontinuous monitoring of particulate organic carbon poc fluxes and dissolved si concentrations delivered to the ocean during a typhoon sampling of the choshui river in taiwan during typhoon mindulle in 2004 revealed a poc flux of 5 00 105 t associated with a sediment flux of 61 mt during a 96 h period the linkage of high amounts of poc with sediment concentrations capable of generating a hyperpycnal plume upon reaching the ocean provides the first known evidence for the rapid delivery and burial of poc from the terrestrial system these fluxes when combined with storm derived co2 consumption of 1 65 108 mol from silicate weathering elucidate the important role of these tropical cyclone events on small mountainous rivers as a global sink of co2