Reliable estimates of river discharge and sediment transport to the ocean from large tidal rivers are vital for water resources management, efficient river and harbor management, navigational purposes, and climate analyses. Due to the difficulties inherent in measuring tidal-river discharge, hydrological and sedimentological records are typically too short to adequately characterize long-term (decadal) trends. Also, uncertainties associated with observation and calibration of hydrological models suggest a need for more accurate methods based on longer records of hydrodynamic parameters (e.g. tides). Tidal theory indicates that tides and river discharge interact through quadratic bed friction, which diminishes and distorts the tidal wave as discharge increases. In this study, using tidal constituents, astronomical forcing and a model of the frictional interaction of flow and tides, I propose a novel Tidal Discharge Estimate (TDE) to predict freshwater discharge with an approximate averaging interval of 18 days for time periods with tidal data but no river flow records. Next, using continuous wavelet analysis of tidal properties, I develop a method of estimating river discharge using tides measured on multiple gages along tidal rivers to improve the time-resolution and accuracy of TDE. The applicability of the Multiple-gauge Discharge Estimate (MTDE) is first demonstrated in the two largest tidal-fluvial systems of the Pacific Northwest, the Columbia River Estuary (CRE) and Fraser River Estuary (FRE). A numerical model of an idealized estuary with similar forcing as the FRE and CRE is next run under different hydrologic and morphologic scenarios to evaluate the effect of convergence, friction, and river flow variations on the applicability of MTDE. The TDE method was applied to the San Francisco Bay, using the continuous hourly tide record available since 1858. Results show that TDE reproduces known San Francisco (SF) Bay delta inflows from 1930-present with a Nash-Sutcliffe coefficient of 0.81 and is a useful method for hindcasting historical flows from 1858 - 1929, a period that predates direct measurement of delta discharge. I also recover and digitize ~80 years of Sacramento River daily water level data between 1849 and 1946, from which river discharge to SF Bay is estimated on a daily basis, after adjusting for changes to the river channel. This discharge combined with Net Delta Outflow Index estimates (1930 - 2011) and flow estimates from tidal data (1858 - 2011) provides a more accurate version of SF Bay historic daily inflows from 1849 - 2011. Next, the history of sediment transport and discharge into SF Bay from 1849-present is reevaluated using the daily discharge estimates. A non-stationary rating curve between river flow and sediment transport is developed, with net sedimentation observed during five bathymetric surveys that were used to constrain the total integrated sediment discharge. Results show that ~1600±320 million-tons of sediment have been delivered to SF Bay between 1850 and 2011. There has been an approximately 25 - 30% reduction of annual flow since the 19th century, along with decreased sediment supply. This has resulted in a ~60% reduction in annual sediment delivery to SF Bay. The annual hydrograph of inflow to SF Bay and the seasonality of sediment flux have changed considerably over time, due to both human alteration and climate change. Significant historic spring-melt peak floods have disappeared in the modern system and now peak flows mostly occur in winter. My flow estimation methods also confirm that the flood of January 1862 had the largest daily sediment load and the second largest daily discharge since 1849.

This dissertation addresses hydrodynamics, sediment transport and shoreline erosion within the main pool of Hartwell Lake, a U.S. Army Corps of Engineers reservoir built on the Savannah River, between Anderson, South Carolina, and Hartwell, Georgia, USA. A U.S. Environmental Protection Agency (EPA) Superfund site is located on a tributary of Hartwell Lake because of high concentrations of polychlorinated biphenyls (PCBs) in the lake sediments. PCBs are hydrophobic and typically bond to fine-grained sediments, such as silts and clays. The primary goal of the study was to document, through field measurements, and model, using a 3-D numerical model of flow and sediment transport, the fate of sediments within the main pool of Hartwell Lake. To document forty years of sedimentation within the reservoir, bathymetric survey data were collected in Hartwell Lake during the period, February 10-14, 2003. The bathymetric surveys revealed that deposition was, in places, up to two meters thickness in forty years. During the field campaign, flow velocity measurements were made primarily to provide a check on the magnitude of the velocities predicted by the numerical model used in the study. Shoreline surveys provided data for the modeling procedure for shoreline change. This in turn facilitated specification of the sediment flux into the domain via shoreline erosion. Hartwell Lake is located near the southern terminus of the Appalachian mountain chain in the Piedmont region. Sediments contain high fractions of silt and clay. Hartwell Lake has a shoreline length of 1548 km, and erosion of lake shorelines has been a significant problem for many homeowners. As of September 2002, there were 1123 permitted riprap installations, and 393 permitted retaining walls, for a total of 1516 erosion control structures along the lakeshores (source: USACE Hartwell Office), an indication of the magnitude of the erosion problem. To quantify the erosion rate of the shorelines, an approach that relates erosion rates to wind wave forces was developed. A simplified representation of the shape of beach profiles is employed. Historical shoreline change rates were quantified by comparing available digital aerial photos taken in different years, and the erosion prediction model was calibrated using these computed erosion rates. Sediments derived from shoreline erosion were introduced to the model as an additional source along the model boundary, and the fate of the eroding sediments was investigated via numerical modeling.

Beach profile models predict the changes in bathymetry along a line perpendicular to the shoreline. These models are used to forecast bathymetric changes in response to storms, sea level rise or human activities such as dredging and beach nourishment. Process-based models achieve this by simulating the physical processes that drive the sediment transport as opposed to behavior models which simulate observed profile changes without resolving the underlying processes. Some of these processes are wave shoaling and breaking, boundary layer streaming, and offshore-directed undertow currents. These hydrodynamic processes control the sediment processes such as sediment pick-up from the bottom, diffusion of the sediment across the water column and its advection with waves and currents. For this study, newly developed sediment transport and boundary layer models were coupled with existing models of wave transformation, nearshore circulation and bathymetry update, to predict beach profile changes. The models covered the region from the dry land to a depth of 6-8 meters, spanning up to 500 meters in the cross-shore direction. The modeling system was applied at storm time scales, extending from a couple of hours to several days. Two field experiments were conducted at Myrtle Beach, SC, involving the collection of wave, current and bathymetric data as a part of this study. The results were used to calibrate and test the numerical models along with data from various laboratory studies from the literature. The sediment transport model computes the variation of sediment concentrations over a wave period and over the water column, solving the advection-diffusion equation using the Crank-Nicholson finite-difference numerical scheme. Using a new approach, erosion depth thickness and sediment concentrations within the bed were also predicted. The model could predict sediment transport rates for a range of conditions, within a factor of two. It successfully computed the sediment concentration profile over the water column and within the bed and its variation throughout a wave period. Erosion depth and sheet flow layer thickness were also predicted reasonably well. Wave heights across the profile were predicted within ten percent when the empirical wave breaking parameter was tuned appropriately. Mean cross-shore velocities contain more uncertainty, even after tuning. The importance of capturing the location of the maximum, near-bottom, cross-shore velocity when predicting bar behavior was shown. Bar formation, erosion, accretion, onshore and offshore bar movement were all computed with the model successfully

Beaches and coastal environments are dynamic, constantly shaped and reshaped by natural processes and anthropogenic modifications. The morphodynamics and influence of natural and anthropogenic factors of two different coasts at various temporal and spatial scales are discussed. To quantify the performance of several beach nourishment projects at annual temporal and kilometer spatial scales on three adjacent microtidal low-wave energy barrier islands in west-central Florida, a total of 5,200 beach and nearshore-profiles spaced at 300 m were surveyed monthly to bi-monthly from 2006-2010. Beach nourishment performance is most significantly influenced by the interruption of longshore sediment transport by complex tidal-inlet processes. More specifically, the tidal-inlet processes influencing adjacent beach nourishment performance includes longshore transport interruption resulting from divergence induced by wave refraction over an ebb-tidal shoal, flood-tidal currents along the beach, and total littoral blockage by structured inlets. A morphologic indicator of a large longshore transport gradient within the study area is the absence of a nearshore sandbar. These non-barred beaches are characterized by persistent shoreline erosion and were almost exclusively located in areas with a large longshore transport gradient. The more typical beach state along the three barrier islands was one exhibiting a migratory bar and relatively stable shoreline. The presence of a sandbar indicates the dominance of cross-shore processes, with onshore migration during calm wave conditions and offshore migration during energetic wave conditions. The onshore and offshore migration of the sandbar is closely related to non-stormy summer and stormy winter seasonal beach changes, respectively. The morphodynamics of a mixed sand and gravel beach in Delaware were investigated based on 740 beach profiles surveyed almost monthly from 2009 to 2011, 60 sediment cores, and 550 surface sediment samples collected at various alongshore and cross-shore transects. Inter-seasonal temporal scales of storm-induced beach changes and post-storm recovery were examined based on a hurricane, a typical energetic winter storm, and an extremely energetic storm resulting from the rare collision of a hurricane and winter storm ("Nor'Ida") occurring within a 3-month period in 2009. The mixed sand and gravel beaches in Delaware are characterized by monotonically increasing water depths lacking a sandbar under all wave conditions. A distinctive beach cycle was identified consisting of a built-up berm profile and depleted nearly-planar storm profile, with a time-scale related to the frequency and intensity of storm impact and duration of intra-storm recovery instead of simple seasonality. The sedimentological characteristics of the storm deposit associated with Nor'Ida demonstrated substantial cross-shore variation ranging from sandy-gravel and gravelly-sand within the storm swash zone (near the pre-storm dune edge) to well-sorted medium to coarse sand seaward of the storm swash zone, suggesting that storm deposits along mixed beaches demonstrate a variety of sedimentological characteristics. A new dynamic beach cycle model is proposed for the non-barred mixed sand and gravel beach with temporal variability controlled by storm occurrence and inter-storm duration.

During high flow rates, the acceleration of flow and turbulence around bridge foundations lead to scouring, defined as the removal of bed sediments. Due to the interparticle physico-chemical forces of clay particles, erodibility and transport mechanisms for fine sediments are different from those for coarse sediments, and the capability to predict the erosion resistance of fine sediments is still in question. In this study, silt-clay soil mixtures with different kaolin contents were prepared by mixing ground silica and Georgia kaolin with tap water. Geotechnical tests were carried out to obtain the physical properties of the specimens. The critical shear stress and yield stress of the soil mixtures were determined through hydraulic flume experiments and rheometer tests, respectively. Particle associations of the soil specimens were observed using the technique of scanning electron microscopy (SEM). From the laboratory work and data analysis, relationships among the critical shear stress, yield stress, and the soil physical properties were developed from multiple regression analysis. Specifically, values of the critical shear stress, yield stress, and their dimensionless form can be predicted by the soil properties including bulk density, clay content, and water content. Finally, a single relationship is obtained to predict the Shields parameter as a function of the corresponding dimensionless yield stress in this study. The results can be used to provide a methodology for engineering applications requiring the value of critical shear stress such as estimating fine sediment bed stability and assessing the erosion risk of river beds in proximity to bridge foundations and other flow obstructions.

Details are given herein of the development, refinement and application of a higher-order accurate 3-D finite difference model for non-cohesive suspended sediment transport processes, in non-stratified estuarine and coastal waters. The velocity fields are computed using a 2-D horizontal depth-integrated model, in combination with either an assumed logarithmic velocity profile or a velocity profile obtained from field data. Also, for convenience in handling variable bed topographies and for better vertical resolution, a δ-stretching co-ordinate system has been used. In order to gain insight into the relative merits of various numerical schemes for modelling the convection of high concentration gradients, in terms of both accuracy and efficiency, thirty six existing finite difference schemes and two splitting techniques have been reviewed and compared by applying them to the following cases: i) 1-D and 2-D pure convection, ii) 1-D and 2-D convection and diffusion, and iii) 1-D non-linear Burger's equation. Modifications to some of the considered schemes have also been proposed, together with two new higher-order accurate finite difference schemes for modelling the convection of high concentration gradients. The schemes were derived using a piecewise cubic interpolation and an universal limiter (proposed scheme 1) or a modified form of the TVD filter (proposed scheme 2). The schemes have been tested for: i) 1-D and 2-D pure convection, and ii) 2-D convection and diffusion problems. The schemes have produced accurate, oscillation-free and non-clipped solutions, comparable with the ULTIMATE fifth- and sixth-order schemes. However, the proposed schemes need only three (proposed scheme 1) or five cell stencils. Hence, they are very attractive and can be easily implemented to solve convection dominated problems for complex bathymetries with flooding and drying. The 3-D sediment transport equation was solved using a splitting technique, with two different techniques being considered. With this technique the 3-D convective-diffusion equation for suspended sediment fluxes was split into consecutive 1-D convection, diffusion and convective-diffusion equations. The modified and proposed higher-order accurate finite difference schemes mentioned above were then used to solve the consecutive 1-D equations. The model has been calibrated and verified by applying it to predict the development of suspended sediment concentration profiles under non-equilibrium conditions in three test flumes. The results of numerical predictions were compared with existing analytical solutions and experimental data. The numerical results were in excellent agreement with the analytical solutions and were in reasonable agreement with the experimental data. Finally, the model has also been applied to predict sediment concentration and velocity profiles in the Humber Estuary, UK. Reasonable agreement was obtained between the model predictions and the corresponding field measurements, particularly when considered in the light of usual sediment transport predictions. The model is therefore thought to be a potentially useful tool for hydraulic engineers involved in practical case studies

In glacierised regions, suspended sediment fluxes are highly responsive to climate-driven environmental change and can provide important information regarding the relationships between glacier variations, climate and geomorphic change. As a result, understanding patterns of suspended sediment transport and their relationship with meltwater delivery is of critical importance. However, studies of glacial suspended sediment transport are often limited by interpreting patterns of suspended sediment transfer based on whole-season data, allowing precise patterns to become masked. This thesis aims to contribute to the understanding of suspended sediment transfer in glacierised basins through the investigation of patterns of suspended sediment delivery to the proglacial area of Storglaciären, a small polythermal valley glacier located in the Tarfala valley, Arctic Sweden. High temporal resolution discharge and suspended sediment concentration data were collected during two summer field campaigns at Storglaciären. Interpretations of suspended sediment transport data were made using diurnal hysteresis and sediment availability data, combined with suspended sediment shape and magnitude data classified by applying principal component and hierarchical cluster analyses. Analysis of the dominant discharge generating processes at Storglaciären was also conducted using principal component analysis, allowing patterns of discharge to be better understood. This was complemented by analysis of the structure and evolution of the glacier drainage system by linear reservoir modelling and flow recession analysis. The results suggest that patterns of discharge and suspended sediment transport at Storglaciären are complex, with distinct processes and magnitudes of transport evident at both proglacial outlet streams, Nordjåkk and Sydjåkk. These processes are intrinsically linked to meteorological variables, with both ablation-driven and precipitation-driven discharge exerting influence over patterns of suspended sediment transport in the proglacial area of Storglaciären.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The primary aim of the research was to determine the optimum diversion location in a curved channel to minimise the abstraction of sediment. The secondary aim was to determine the optimum diversion angle for a diversion channel located on the outside of a bend at the optimum diversion location. The velocity distribution in the curved channel was investigated to try obtain a better understanding of curvilinear flow. The scour patterns in the channel were monitored in order to compare them with the measured velocity distributions. Simulations were carried out with the DELFT 3D (hydrodynamics) and Mike21C (sediment dynamics) modelling programmes and compared with the results obtained from laboratory experiments and with existing empirical formulas. The optimum diversion location was found to be located on the outside of the bend in the downstream section of the bend. Three main scour zones were identified with the third scour zone at the location of the maximum velocity. The location of the maximum velocity was found to be relatively constant with varying Froude numbers, but moving in the downstream direction with increasing radius of curvature-to-width ratio. The velocity distributions in the horizontal and vertical planes are well defined and correspond to descriptions in the literature. It is evident that the diverted discharge ratio increases with an increase in the diversion angle while it decreases with an increase in Froude number. Higher Froude numbers in the curved channel lead to more favourable conditions for the diversion of water. The diversion does not influence the secondary flow patterns (for the range of Diversion Discharge Ratio’s tested) and that the maximum velocity zone stayed in the same location as in the tests without a diversion. The hydrodynamics of the laboratory experiments were well simulated with the DELFT 3D hydrodynamic model, using three-dimensional and two-dimensional formulations. Mike21C was used to simulate the sediment dynamics of some of thelaboratory experiments that gave relatively good agreement with experimental data. A two-dimensional depth averaged model could therefore be used with reliability to simulate field conditions in relatively shallow rivers, and is preferred to empirical methods to predict maximum scour that were calibrated under very specific hydraulic conditions. / AFRIKAANSE OPSOMMING: Die primêre doel van navorsing was om die optimum uitkeer-posisie in ‘n draai te bepaal om sodoende sediment onttrekking te minimiseer. Die sekondêre doel was om die optimum uitkeringshoek vir ‘n uitkeerkanaal te bepaal wat geleë is aan die buitekant van ‘n draai by die voorgestelde optimum uitkeer-posisie. Die snelheidsverspreiding in die draai was ook ondersoek om te probeer om spiraalvloei beter te verstaan. Die uitskuurpatrone in die kanaal is ook gemonitor om dit te kon vergelyk met die gemete snelheidsverspreiding. Numeriese simulasies is gedoen met DELFT 3D (hidrodinamika) en Mike21C (sediment dinamika) modelleringsprogrammatuur en is vergelyk met die resultate van die laboratorium eksperimente asook met die van bestaande empiriese vergelykings. Daar is gevind dat die optimum uitkeer-posisie aan die buitekant van ‘n draai aan die stroomaf-kant van die draai geleë is. Drie hoof uitskurings-areas is gevind terwyl die derde area ooreenstem met die posisie van maksimum snelheid. Die posisie waar die maksimum snelheid voorkom is relatief konstant met ‘n verandering in Froude-getal, maar beweeg in die stroomaf-rigting met ‘n styging in die radius-tot-wydte verhouding. Die vertikale en horisontale snelheidsverspreiding is goed gedefinieer en stem ooreen met soortgelyke beskrywings in die literatuur. Die uitkeer-vloei verhouding styg met ‘n stygende uitkeerhoek terwyl dit daal met ‘n styging in Froude-getal. Daar is ook gevind dat groter Froude-getalle meer gunstige omstandighede skep vir die uitkeer van water. Die uitkeer-kanaal beïnvloed nie die sekondêre vloei-patrone nie (vir die reeks van uitkeer vloei-verhoudings wat getoetsis) en die sone van maksimum snelheid bly in dieselfde omgewing vir hierdie toetse as vir die toetse sonder ‘n uitkeer kanaal. Die hidrodinamika van die laboratorium eksperimente is goed gesimuleer m.b.v die DELFT 3D numeriese program, terwyl Mike21C gebruik is om die sedimentdinamika te simuleer. Die resultate van die Mike21C simulasies vergelyk relatief goed met die eksperimentele data en kan met ‘n redelike graad van vertroue aangewend word om veldkondisies te simuleer in relatiewe vlak riviere. Dit word aanbeveel bo die empiriese vergelykings om maksimum uitskuring te voorspel aangesien die empiriese vergelykings gekalibreer is vir baie spesifieke hidroulise kondisies.

Thesis (PhD)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The process of sand being moved parallel to the coast by wave and current action is called longshore (sediment) transport. Knowledge oflongshore transport is essential for the design of breakwaters at harbour entrances, for navigation channels and for calculating the amount of dredging they require, for beach improvement schemes and for the determination of the stability of inlets and estuaries. Different aspects oflongshore transport have been investigated, namely, (1) analysis offield data, (2) evaluation oflongshore transport formulae and (3) the development of the wave power approach as an alternative method to calculate longshore transport. In the development of a better understanding oflongshore sediment transport, the following has been done for the first time: (1) a comprehensive data set has been compiled covering almost a full range of conditions occurring on natural beaches; and (2) virtually all longshore transport formulae have been evaluated against this extensive data set. A new improved method, the applied wave power approach, has been developed and extensively calibrated against the same data set. Based on this evaluation, guidelines are now available for design engineers as to which are the best bulk and detailed predictors oflongshore sediment transport. These are respectively, the recalibrated Kamphuis formula and the applied wave power approach. Another useful first, is the derivation of confidence intervals for a longshore transport formula, showing what accuracy can be obtained and that accurate predictions are now possible. In addition, it has now been determined what the minimum required measurement period should be and what the most cost-effective way is for obtaining the true long-term mean net longshore transport rate at a particular site. / AFRIKAANSE OPSOMMING: Die proses waarvolgens sand ewewydig aan die kus deur golf- en stroomwerking vervoer word, word langsstrandse (sediment-) vervoer oflangsvervoer genoem. Kennis van langsvervoer is noodsaaklik vir die ontwerp van golfbrekers by hawe-ingange, navigasiekanale en vir die berekening van die hoeveelheid baggerwerk daarvoor benodig, strandverbeteringskemas en vir die bepaling van die stabiliteit van inlate en getyriviere. Verskillende aspekte van langsvervoer is ondersoek, naarnlik, (1) die ontleding van velddata, (2) die beoordeling van langsvervoerformules en (3) die ontwikkeling van die golfdrywingsbenadering as 'n altematiewe metode om langsvervoer mee te bereken .. Tydens die ontwikkeling van 'n beter begrip van langsstrandse sedimentvervoer is die volgende vir die eerste keer gedoen: (1) 'n omvattende datastel is versamel wat bykans aIle toestande wat aan natuurlike strande voorkom, dek; en (2) feitlik aile langsvervoerformules is teen hierdie uitgebreide datastel beoordeel. 'n Nuwe verbeterde metode, die aangewende golfdrywingsbenadering, is ontwikkel en omvattend teen dieselfde datastel geyk. Gebaseer op hierdie beoordeling, is riglyne nou vir ontwerp-ingenieurs beskikbaar rakende watter totaal- en detail-iangsvervoervoorspellers die beste is. Dit is onderskeidelik die hergeykte Kamphuisformule en die aangewende golfdrywingsbenadering. Nog 'n nuttige eerste is die afleiding van betroubaarheidsgrense vir 'n langsvervoerformule, wat wys watter akkuraatheid nou haalbaar is en dat noukeurige voorspellings nou moontlik is. Verder is dit nou vasgestel wat die vereiste meettydperk behoort te wees en wat die mees koste-effektiewe manier is waarop die ware langtermyn-gemiddelde netto langsvervoertempo by 'n spesifieke terrein verkry kan word.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The floodplain of a river forms a close relationship with the stream that created it. Not only does the river influence the characteristics of the floodplain, the floodplain can also very easily influence its river, as is evidenced by examples such as the Huang He River in China and the Columbia River in Canada. These two cases clearly indicate that suspended sediment has a pronounced influence on the floodplain. This thesis investigates the processes which cause sediment to move onto the floodplain. As observed in many rivers worldwide suspended sediment on the floodplain has a tendency to settle near but not directly next to the main river channel. This gap between the river channel and the location of highest sedimentation rate stems from the fact that there is a zone of relatively higher turbulence at the boundaries of the floodplain. Close to this zone flow on the floodplain is increased in velocity whilst the flow velocity in the main channel is decreased as can be seen in the figure below: ...