sensitivity analysis of nonequilibrium adaptation parameters for modeling mining pit migration the nonequilibrium adaptation parameters of a depth averaged two dimensional hydrodynamic and sediment transport model were examined in the study calculated results were compared to data measured in two sets of published laboratory experiments that investigated mining pit migration under well controlled boundary conditions including steady flow and uniform rectangular cross sections along the flume except in the vicinity of the experimental mining area the two sets of experiments were chosen as representatives of bed load dominated and suspended load dominated cases respectively a sensitivity analysis was conducted to estimate the influence of the nonequilibrium adaptation parameters on mining pit migration simulation calculated results indicate that appropriate selection of the adaptation parameters is critical in order to close the nonequilibrium sediment transport formulas when modeling mining pit migration

numerical simulation of downstream fining by selective transport in gravel bed rivers model development and illustration a numerical model has been developed for the routing of gravel sized sediment along a river channel which is free to adjust both its long profile and surface texture hydraulic calculations use a step backwater approach and sediment transport is predicted with the method of parker 1990a which uses a low degree of size selectivity exchange of sediment between the surface and subsurface is described using the modified exner equation of parker and sutherland 1990 the model is applied to an idealized channel based on the highly concave allt dubhaig scotland in which fining by particle wear is minor the rapid downstream fining observed in this river is closely matched by model predictions after a time equivalent to 102 years under the present flow regime of the river the evolution of the fining pattern during the model run and associated changes in sediment transport and bed aggradation are described it is concluded that strong profile concavity can force rapid downstream fining even though bed load transport is only slightly size selective this run of the model serves as a basis for testing of the sensitivity of downstream fining to alternative choices of parameter values and boundary conditions which are summarized here and will be described in a subsequent paper

modeling the evolution of incised streams i model formulation and validation of flow and streambed evolution components a robust computational model for simulating the long term evolution of incised and restored or rehabilitated stream corridors is presented the physically based model simulates the three main processes that shape incised streams hydraulics sediment transport and streambed and bank adjustments a generalized implicit preissmann scheme is used for the spatial and temporal discretization of the flow governing equations to accommodate large time steps and cross sections spaced at irregular intervals the solution method introduces several enhancements that increase its robustness specifically to simulate flashy flows transport of cohesive or cohesionless graded bed material is based on a total load concept and suspended and bed load transport modes are accounted for through nonequilibrium effects the model simulates channel width adjustment by hydraulic erosion and gravitational mass failure of heterogeneous bank material the present paper focuses mainly on the treatment of streamflow hydraulics and evolution of graded streambeds and reports simulations of published experiments on degrading and aggrading channels with graded bed material description and validation of the model s stream bank erosion component and the application of the model to incised stream systems are presented elsewhere

modeling of riverbed evolution for bedload sediment mixtures a new computational methodology for fully coupled simulation of unsteady water and sediment movement in mobile bed alluvial rivers has been developed and tested the one dimensional approach treats bedload transport of nonuniform sediment mixtures with sorting and armoring effects considered spatial lag effects in nonequilibrium bedload transport are taken into account through innovative use of the recently developed notion of a loading law the new system of equations for water and sediment movement is solved in a fully coupled implicit manner using the preissmann finite difference scheme implemented to allow for either upstream or downstream induced mobile bed perturbations formal analysis of the coupled system sheds new light on boundary condition requirements for the multiple size class problem the fully coupled implicit solution has proven to be robust and stable and it respects the underlying volumetric conservation laws remarkably well as demonstrated in continuity analyses of computed bed e

coupled and decoupled numerical modeling of flow and morphological evolution in alluvial rivers existing numerical river models are mostly built upon asynchronous solution of simplified governing equations the strong coupling between water flow sediment transport and morphological evolution is thus ignored to a certain extent an earlier study led to the development of a fully coupled model and identified the impacts of simplifications in the water sediment mixture and global bed material continuity equations as well as of the asynchronous solution procedure for aggradation processes this paper presents the results of an extended study along this line highlighting the impacts on both aggradation and degradation processes simplifications in the continuity equations for the water sediment mixture and bed material are found to have negligible effects on degradation this is however in contrast to aggradation processes in which the errors purely due to simplified continuity equations can be significant transiently the asynchronous solution procedure is found to entail appreciable inaccuracy for both aggradation and degradation processes further the asynchronous solution procedure can render the physical problem mathematically ill posed by invoking an extra upstream boundary condition in the supercritical flow regime finally the impacts of simplified continuity equations and an asynchronous solution procedure are shown to be comparable with those of largely tuned friction factors indicating their significance in calibrating numerical river models it is concluded that the coupled system of complete governing equations needs to be synchronously solved for refined modeling of alluvial rivers

numerical simulation of contraction scour in an open laboratory channel a finite volume computer code developed at the institute for hydromechanics university of karlsruhe has been used to calculate the flow and sediment transport in a laboratory channel with constriction and movable bed the flow is calculated by solving the fully three dimensional reynolds averaged navier stokes equations with k e turbulence model the bed deformation is obtained from an overall mass balance equation for sediment transport and the bed load transport is simulated with a nonequilibrium model the calculated results for flow and scour development in the laboratory channel are compared with experimental measurements the sensitivity of the simulated results to the nonequilibrian adaptation length parameter in the nonequilibrium bed load transport model is investigated systematically which represents the main contribution of this paper

fully coupled unsteady mobile boundary flow model a fully coupled one dimensional river model capable of predicting sediment transport and bed level changes under unsteady flow conditions is described the governing equations for mass and momentum balance of sediment water mixture under unsteady flow conditions in natural rivers with irregular geometries are solved simultaneously using the preissmann four point linear implicit scheme with weighting factors for space and time coordinates the resulting system of algebraic equations is solved using a solution procedure that bridges upstream and downstream boundary nodal values by successive substitutions the friction slope is expressed in a consistent form that allows the consideration of the changing alluvial roughness effect the system of governing equations is explicitly coupled by introducing the term representing the rate of change of bed level the fully coupled unsteady mobile boundary flow model fcm is applied to the classical problem of sediment deposition upstream of a dam with an arbitrar

morphodynamic responses to the deep water harbor development in the caofeidian sea area china s bohai bay vast bay type tidal inlets can be found along the coastal zones of china they are generally suitable for deep water channels and large harbors because of the presence of large water depth and good mooring conditions the deep channel in front of the head of caofeidian island in bohai bay china is a typical bay type tidal inlet system the tidal current a type of reverse flow makes the key contribution to maintain the deep water depth the co action of waves and tidal currents is the main dynamic force for sediment motion waves have significant influence on the sediment concentration based on the characteristics of waves tidal currents sediment and seabed evolution in caofeidian sea area a 2d mathematical model for sediment transport under influence of waves and tidal currents is developed to study the development schemes of the caofeidian harbor the model has been verified for spring and neap tides in winter as well as in summer of 2006 the calculated tidal stages flow velocities flow directions and sediment concentrations at 15 stations are in good agreement with the observations furthermore the calculated data on pattern and magnitude of sedimentation and erosion in the related area agree well with the observations this model has been used to study the effects of the reclamation scheme for caofeidian harbor on the hydrodynamic environment sediment transport and morphological changes attentions are paid to the project inducing changes of flow velocities and morphology in the deep channel at the south side of caofeidian foreland in the laolonggou channel and in various harbor basins the conclusions can provide the important foundation for the protection and use of bay type tidal inlets and the development of harbor industry

bed scouring downstream of hydraulic structures under steady flow conditions experimental analysis of space and time scales and implications for mathematical modeling abstract sediment transport and bed deformation in alluvial rivers are space and time dependent the knowledge of the space and time scales can be helpful for the definition of predictive procedures of an alluvial reach response to changing boundary conditions in this work attention is paid to scouring process occurring downstream of the rigid basement of a hydraulic structure the analysis is focused on transient bed profiles which are determined under steady flow conditions by a decrease of the upstream sediment transport rate in particular the paper is aimed at improving understanding of the space and time scales required by the alluvial system to reach the equilibrium conditions for this purpose movable bed runs are carried out in a straight laboratory channel for two values of the water discharge during each run the longitudinal bed profiles are measured at different times based on experimental data spatial scale factors of the bed scouring and of the bed load transport to reach the equilibrium conditions are defined particularly it is found that the scour length varies especially during the first evolution phase and then it oscillates around of a mean value that is about 40 of the channel reach interested by the phenomenon under consideration an expression is found for the adaptation coefficient which allows the estimation of the spatial delay of the bed load transport rate using both the collected data and literature data an expression defining the time scale of scouring is deducted according to this expression the non dimensional time scale is related to shields parameter through an exponential law then by the help of a 1 d numerical model previously developed by the writer the implications for choosing the spatial and temporal resolutions on which numerical results depend significantly are shortly discussed the results show that the time and space scales which represent physical constraints of the spatial and temporal resolutions need to be properly defined in order to simulate the scouring process evolution

note on lag in bedload discharge it is postulated that movable sediment beds comprise of two types of grains termed undisturbed and disturbed grains the probability of entrainment by flow of the latter is higher than that of the former the lag in bedload transport is due to the difference in the entrainment probabilities of the two types of grains a model is developed to predict lag in bedload transport the spatial and temporal lag coefficients are functions of both the inner and outer variables the 50 of the equilibrium bedload discharge is attained within about 26 of the total lag distance or lag time the lag model was verified by conducting laboratory experiments and using experimental data of bagnold the proposed model agrees with the experimental data both the lag distance and lag time decrease with increasing equilibrium bedload discharge the findings of the model can be used to improve the einstein formula for the equilibrium bedload discharge

routing graded sediments in streams formulations a one dimensional numerical model is developed for simulating the movement of well graded sediments through a stream network the model is based on the physical processes governing the mechanics of sediment movement in alluvial channels it incorporates the effect of sediment gradation on the stream s potential transport capacity it also accounts for the effect of particle exchange between the sediment load and the bed while simulating aggradation degradation and armoring of the bed the applicability of the model is restricted to noncohesive materials and relatively stable channel geometries any valid water routing algorithm can be used in simulating the movement of water

the lower jurassic hanson formation of the transantarctic mountains implications for the antarctic sector of the gondwana plate margin the hanson formation antarctica consists of interbedded sandstones and tuffaceous rocks of early jurassic age the sandstones pebbly to medium grained range between quartzo feldspathic and volcaniclastic with some of the former being coarse grained arkoses that imply proximal sources geochronology of detrital zircons provides evidence for source rock ages whereas sandstone petrology demonstrates a mixed provenance tuffaceous strata are reworked fine to very fine grained tuffs resulting from distal plinian eruptions dated tuffs provide time constraints on the duration of volcanism the sandstones and tuffs accumulated in a rift environment geochemically the tuffs are rhyolitic in composition and the sr and nd isotope data together with the patterns on multi element diagrams suggest they were derived from a volcanic arc which is interpreted to have been located along the west antarctic gondwana margin the silicic volcanism extends the distribution and timing of magmatism in the early jurassic along that margin the early jurassic extensional regime was delimited by the plate margin region and the east antarctic craton the rift valley system along the east antarctic craton margin in which the hanson strata accumulated was the focus for subsequent emplacement of the intrusive and extrusive rocks of the lower jurassic ferrar large igneous province the early jurassic extensional rifts may have been reactivated during cretaceous cenozoic development of the west antarctic rift system

1d finite volume model of unsteady flow over mobile bed summary a one dimensional 1d finite volume method fvm model was developed for simulating unsteady flow such as dam break flow and flood routing over mobile alluvium the governing equation is the modified 1d shallow water equation and the exner equation that take both bed load and suspended load transport into account the non equilibrium sediment transport algorithm was adopted in the model and the van rijn method was employed to calculate the bed load transport rate and the concentration of suspended sediment at the reference level flux terms in the governing equations were discretised using the upwind flux scheme harten et al 1983 hll and hllc schemes roe s scheme and the weighted average flux waf schemes with the double minmod and minmod flux limiters the model was tested under a fixed bed condition to evaluate the performance of several different numerical schemes and then applied to an experimental case of dam break flow over a mobile bed and a flood event in the rillito river tucson arizona for dam break flow over movable bed all tested schemes were proved to be capable of reasonably simulating water surface profiles but failed to accurately capture the hydraulic jump the waf schemes produced slight spurious oscillations at the water surface and bed profiles and over estimated the scour depth when applying the model to the rillito river the simulated results generally agreed well with the field measurements of flow discharges and bed elevation changes modeling results of bed elevation changes were sensitive to the suspended load recovery coefficient and the bed load adaptation length which require further theoretical and experimental investigations

contribution of glacial isostatic adjustment to the geocenter motion abstract the geocenter motion describes the surface net displacement of the entire solid earth with respect to the center of mass of the entire earth including surface masses therefore it resembles an integrative quantity of surface displacement and mass redistribution inside the earth as well as at its surface seasonal variations of this quantity are understood to originate mainly from mass redistribution in the water cycle in contrast a secular trend of the geocenter motion is possible to result also from the dynamics of the earth s interior one mechanism inducing a secular geocenter motion is the glacial isostatic adjustment describing the deformation and mass redistribution in the earth s interior due to glaciations during the pleistocene focusing on this contribution we compute the geocenter motion from the displacement and gravity potential fields calculated for a spherical self gravitating incompressible and viscoelastic earth model loaded by the last pleistocene glacial cycle we discuss the fluid core approximation usually adopted and assess the influence of a list of modelling parameters which are the upper and lower mantle viscosity lithosphere thickness and glaciation history we find a rather robust geocenter motion with respect to parameter variations which is directed towards northeast canada and shows velocities that vary between 0 1 and 1 mm yr depending on the adopted earth model and glaciation history parameterizations

a numerical study of sediment transport and event bed genesis during tropical storm delia some event beds tempestites are thought to be emplaced on shallow marine shelves by the combined action of strong coastal currents and high waves during fairly short lived storms to test this hypothesis a storm sedimentation system has been constructed from six numerical models describing a cyclonic wind field three dimensional coastal circulation wind waves generated over the continental shelf the combined effect of steady and oscillatory currents within the benthic boundary layer suspended and bed load transport of sediment and conservation of the seafloor this model system is used to hindcast winds currents waves and resulting sedimentation during tropical storm delia which passed over the texas louisiana shelf on september 3 4 1973 sensitivity to the initial substrate is investigated in four experiments using uniform silt uniform sand a mud line at the 20 m isobath and a simplified modern sediment distribution modeled coastal currents are vertically uniform and do not reveal the structure predicted by the mid latitude geostrophic storm circulation model because the predicted depth of the wind mixed layer is greater than the water depth over the shelf shelf currents in excess of 2 m s flow predominantly along the coast to the southwest during most of the storm driven by the wind stress and the trapped coastal wave which peaks at 180 cm near galveston significant wave heights reach 8 m on the outer shelf but are less than 4 m over the inner shelf these waves combine with steady currents to produce bed shear velocities which locally exceed 20 cm s the region of highest stresses always lies to the right of the storm track viewed down the path and moves across the shelf with the eye of the storm three general sediment transport paths are evident 1 onshore transport of finer sediment over the outer shelf to the right of the storm track 2 westward directed along shelf transport of predominantly fine sediment between approximately 40 m and 20 m water depths and 3 minor offshore transport of sand from the shoreface to depths less than 30m the resulting event bed has a ragged appearance with a maximum thickness of about 20 cm in region 1 and covers an area of approximately 3 104 km2 to the right of the storm track aside from local transport associated with finer sediments these results are relatively insensitive to initial sediment type comparison of model results to observed data from buccaneer platform shows that the different models performed adequately during the peak of the storm except for a significant underprediction of the significant wave height by the wind sea model the estimated uncertainty in the calculated combined shear stresses u based on errors produced by the individual model components is most dependent on the wave bottom orbital amplitude the total uncertainty in u is estimated to be approximately 7

simulation of missouri river bed degradation the future course of bed degradation in the middle missouri river has been predicted using numerical simulation techniques the simulation required development of the new total load transport model tltm which incorporates the interdependence of friction factor and sediment transport through data based empirical relations tltm was implemented in a mathematical simulation model called ialluvial which computes quasi steady water and sediment flow in natural rivers having nonuniform bed sediments ialluvial also incorporates bed sediment sorting and armoring which are processes of fundamental importance to the future course of missouri river degradation ialluvial was first validated through simulation of the 1960 1980 severe degradation in the missouri river between sioux city iowa and omaha nebraska subsequently ialluvial was used to predict 1980 2000 degradation for several river management scenarios the simulations suggest that the worst of the degradation is now over and that it is the channelization rather than upstream regulation which is primarily responsible for the degradation a companion paper describes the details of ialluvial s armoring and sorting simulation procedures

gradation effects in sediment transport to determine the effects of grain size and density gradation in oscillatory sheet flow experiments are conducted in an oscillating water tunnel a formal derivation of a schematised transport model shows that the transport rates per sediment fraction can be determined with and without the assumption of an active layer a technique that measures sediment composition from natural occurring radionuclides is used to determine the transport rates without that assumption of an active layer the measurements on total sediment transport rates and suspended sediment concentrations show that effects of gradation are present the effects of size gradation are mainly in the increased transport rates of the coarse fraction with respect to the uniform coarse material and the availability at the bed under similar conditions the experiments on density graded sediments indicate that total mass transport rates are larger than the mass transport rates of quartz material whilst the transport rates of the quartz fraction show that this fraction is not hindered by the availability at the bed

one dimensional numerical modeling of sediment transport and bed deformation in open channels 1 a one dimensional numerical model for simulating unsteady flow and sediment transport in open channels is presented and tested the flow hydrodynamics is represented by the shallow water equations and the bed morphodynamics is represented by the exner equation and an additional equation describing the nonequilibrium sediment transport sediment size distribution is represented by the median grain diameter and the standard deviation instead of the usual modeling with multiple particle size classes various methods for computing bed elevation changes at a cross section due to erosion or deposition of sediment are proposed and tested including an innovative approach that relates the spatial pattern of erosion and deposition rates to boundary shear stress distribution which is calculated by the merged perpendicular method an explicit finite difference scheme is employed for solving the water and sediment governing equations the pertinence of the model is examined for two hypothetical cases the model is then tested on one set of laboratory experiments on bed degradation under steady flow showing excellent model data fit and indicating that incorporating a nonequilibrium sediment transport equation into the model structure is an important element in reproducing the bed degradation process finally the model is applied to simulate the morphological changes taking place in the ha ha river quebec after the failure of the ha ha dyke on july 1996 relevant results can be obtained in terms of changes in longitudinal bed profile and cross sectional geometry as well as water levels although some discrepancies are obtained between the simulated and surveyed cross sectional geometries mainly because bank failure and channel widening are not modeled

numerical modeling of gravel bed river response to meander straightening the coupling between the evolution of bed pavement and long profile 1 artificial meander straightening rectification was conducted in the early 1960s along the sainte marguerite river canada in order to facilitate highway construction along the valley previous studies talbot and lapointe 2002 confirm that vertical reprofiling coupled with pavement coarsening in the degrading reach were the main responses counteracting the disequilibrium in gravel transport rates triggered at rectification of this system numerical simulations using sedrout2 0 a one dimensional hydraulic and sediment transport model and validated against the observed channel response show the important role played by an advancing wave of pavement coarsening down the rectified reach in modulating the bed degradation response simulations extending into the future reveal an asymptotically slowing approach to equilibrium in the middle of the 21st century with a response half time of the order of 10 years in near threshold gravel bed systems like the sainte marguerite river pavement coarsening after rectification buffers the system against extreme degradation most significantly for watershed management this also appears to severely limit the extent of propagation of degradation upstream of the rectification

numerical simulation of widening and bed deformation of straight sand bed rivers ii model evaluation in this paper the numerical model presented in the companion paper is tested and applied assessment of model accuracy was based on two approaches first predictions of evolution of a 13 5 km reach of the south fork of the forked deer river in west tennessee were compared to observations over a 24 yr period results suggest that although the model was able to qualitatively predict trends of widening and deepening quantitative predictions were not reliable simulated widths and depths were within 15 of the corresponding observed values but observed change in these parameters at the study sites were also close to these values simulated rates of depth adjustment were within 15 of observed rates but observed rates of channel widening at the study sites were approximately three times those simulated by the model in the second approach the model was used to generate relationships between stable channel width and bank full discharge the model was able to successfully replicate the form of empirically