Bedload transport studies are essential in the understanding of river forms, functions and processes. These studies have been done using various methods over the past century. In recent years Radio Frequency Identification Technology (RFID) has become popular with researchers to track bedload particles. However, no standard operating procedures are used in the implementation of this technology. Methods used for tagging, seeding and tracking RFID tracers (RFID transponders inserted into a bedload particle) can introduce variability in their detection. In this study, RFID tracers were used to study four sites in Laurel Creek in Waterloo, Ontario. Two hundred RFID tracers were seeded in each of the four sites. Following three major storm events, the tracers were tracked with an antenna and their locations surveyed. The tracers were able to be detected to a precision of 1 m as a transponder used can be detected at a maximum of this distance. Practical tracking in the field highlighted the need for the understanding of how precisely the tag location can be identified. Laboratory experiments were designed and carried out to determine the effects of factors (tracer orientation, antenna orientation, tracer size, clustering of multiple tracers, burial depth, saturation and submergence of the soil matrix) that possibly confounded detection. Of these factors, tracer orientation, clustering and burial depths were determined to be the ones that affected detection distances the most. A transponder in a vertical orientation was found to have as much as 40% larger range of detection than a transponder in a horizontal orientation (i.e., they could be detected from further away). Additionally, “skip zones” were identified during laboratory and field experiments. These are zones of gaps in the electromagnetic field of the transponder that occur directly over the transponder. These zones were experimentally determined to extend to approximately 10 cm on each side of the transponder. Therefore, by identifying the skip zones, the tracers can be located to a precision of 10 cm; this is an order of magnitude smaller than the published detection limit of the transponder. The precision of detection can also be improved by the reduction of the effects of confounding factors. However, the improvement in the precision of detection is a tradeoff with the ease of detection. A tagging, seeding and tracking protocol is recommended to counter the effects of confounding factors.

Dreissenid mussels alter particle transport dynamics in the near shore environment of the Great Lakes by intercepting, retaining and recycling suspended solids that might otherwise be exported to the offshore environment (Hecky et al., 2004). Particulate materials filtered from the water column by dreissenids are subsequently released as either feces or pseudofeces (Walz, 1978). This bio-transformation process alters the nature (grain size distribution, settling velocity and density) and transport properties (critical shear stress for erosion, erosion rates and bed stability) of particulate matter in surficial sediments. While knowledge of the transport characteristics of this material is required to refine particle transport dynamics and energy flow models in the Great Lakes, few studies have been specifically conducted to directly quantify these processes. An annular flume was used to determine the bed stability, rate of erosion and critical shear stress for erosion of dreissenid biodeposits. Materials studied in the flume consisted of 1) a combination of biodeposits and surface sediments collected from dreissenid beds and 2) biodeposits harvested in a weir box with dreissenids. The results show that erosion characteristics and sediment transport properties were strongly influenced by bed age; however particle sizes did not increase in the presence of mussels as originally speculated. Bed stability increased after 7 days, with a τcrit of 0.26 Pa compared to the 2 and 14 day consolidation periods (τcrit= 0.13 and 0.15 Pa respectively). In 2010, following a 2 day consolidation period, pure biodeposits harvested in the weir box had a critical shear stress for erosion of 0.052 Pa. The decrease in bed stability found in biodeposits from 2010 compared to the 2008 biodeposit mixture, may be a result of a more diffuse biofilm developing on the highly organic substrate. The mixture of biodeposits collected in 2008 were a combination organic and inorganic materials which may be creating a nutrient limited environment, where biofilm structure consists of more tightly organized biofilm cells and as a result enhance stability in the bed sediments. The decrease observed after 14 days is likely a result of the microbes depleting their resources and dying off. Due to the added roughness the mussels created in the flume, τcrit could not be measured and critical revolutions per minute (RPM) for erosion are reported for flume runs with mussels. During experiments conducted in 2009 with pure biodeposits and mussels the critical RPM was 5.83 while in 2010 in the presence of mussels a critical RPM was not observed. Settling experiments found biodeposits from both years (2008 and 2010) had decreased settling velocities when compared to different sediment types from lacustrine environments. I speculate that the added enrichment of the surficial sediments by mussel biodeposits is enhancing the process of biostabilization and increasing the bed stability and that the presence mussels themselves may additionally be enhancing bed stability by inhibiting flow from reaching the surface sediments/biodeposits.

In this thesis, the theory of three dimensional numerical modeling of transport and re-suspension of fine sediments is studied and a computer program is develped for simulation of the three dimensional suspended sediment transport. The computer program solves the three dimensional advection-diffusion equation simultaneously with a computer program prepared earlier for the simulation of three dimensional current systems. This computer program computes the velocity vectors, eddy viscosities and water surface elavations which are used as inputs by the program of fine sediment transport. The model is applied to Bay of Izmir for different wind conditions.

Graduation date: 1999

Graduation date: 1982

Samples collected from 5 bridge sites from around the state of Georgia are analyzed to determine their erosion and rheologic behavior. Most sites were subject to large amounts of local scour due to flood events resulting from Tropical Storm Alberto in 1994. According to the Federal Highway Administration's Hydraulic Engineering Circular No. 18 by Richardson and Davis (2001), scouring of bridge foundations is the most common cause of bridge failure resulting from floods. The erosion rates of the soils are measured in a rectangular tilting flume capable of applying up to 21 Pa of shear stress at the bed. Samples from Shelby tubes are extruded into the flow from below the bed using a hydraulic piston. The displacement is measured as a function of time using a cable-pull potentiometer. The soils are also subject to extensive geotechnical analysis. Sieve and hydrometer analyses are performed to obtain the particle size distribution for each sample. Atterberg Limits and other standard geotechnical measures are also found. Additionally, insight into the shear strength and cohesive nature of the fine (<0.75 micrometers) particles is gained using a stress controlled rheometer to measure the rheological characteristics of the slurry. These results are used to improve and extend a relationship for the critical shear stress of soils developed in previous research that can be used in bridge scour prediction formulae as affected by soil parameters. In addition, the rheologic properties of the soil in terms of a dimensionless yield stress are related to the critical value of the Shields parameter for estimating critical shear stress for erosion.

The development and testing of a shear cell for the purpose of measuring swash zone bed shear stress is presented. Direct measurements of bed shear stress were subsequently obtained using the shear plate in small, medium, and large-scale laboratory facilities. Measurements from both dam- break and bore-driven swash experiments are considered, covering a wide range of hydrodynamics and bed roughness. The dam-break problem is of interest here due to the theoretical analogy with the run-up of a solitary bore on a beach. Estimates of the flow velocities through the full swash cycle were obtained through numerical modelling and verified against measured velocity data. In conjunction, these data are used to calculate skin friction coefficients. The measurements indicate strong temporal and spatial variation in bed shear stress throughout the swash cycle, and a clear distinction between the uprush and backwash phase. For a single swash event, the maximum uprush bed shear stresses occur in the lower swash zone, within the range 0<x/Rx<0.3. The maximum backwash bed shear stresses also occur in the lower swash zone, and extend seaward of the initial bore collapse location. For a given cross-shore location the peak uprush bed shear stress is typically greater than the peak backwash bed shear stress by at least a factor two and up to a factor four. Local skin friction coefficients also indicate strong temporal and spatial variation. Furthermore, the behaviour of the local skin friction coefficient (back calculated from the measured bed shear stress using predicted, depth-averaged, flow velocities) over the swash cycle is inconsistent with the classical behaviour that is expected on the basis of the low Reynolds number flow. Smooth bed dam break and swash uprush friction coefficients appear to follow the general behaviour observed for smooth, turbulent open channel flow for an increasing Reynolds number. However, for a decreasing Reynolds number the behaviour of Cf differs from the steady flow relation. This is attributed the unsteady swash flow regime and flow history effects. It is expected that differences in flow history between the uprush and backwash have implications in terms of swash boundary layer growth and the resulting bed shear stress. A Lagrangian model for the swash boundary layer development is presented to consider these flow history effects. The model is based on the momentum integral approach for steady, turbulent, flat-plate boundary layers, with appropriate modifications to account for the unsteady flow regime. Fluid particle trajectories and velocity are computed and the boundary layer growth across the entire swash zone is estimated. Predictions of the bed shear stress agree well with the direct bed shear stress measurements and show a bias toward uprush sediment transport which has consistently been observed in measurements.

Thesis (PhD)--Macquarie University, School of Earth Sciences, 1981. / Bibliography: leaves 218-233. / Introduction -- Methods -- Boulder size -- Boulder morphology -- Boulder roundness -- Beach form -- Boulder movement -- Process inference from studies of coastal protection structures -- Summary and conculsion. / Five boulder beaches along the central New South Wales coast were selected for the study of their sedimentary properties, form, and sediment transport. Each beach is aligned obliquely to the approaching waves and is composed of local sediment. One beach, which appears to have little or no recent sediment input, is considered to be a closed sediment system and the other four beaches, which appear to have recent sediment supply, are considered to be open sediment systems. -- On the open system beaches, boulder size fines towards the embayment in the direction of transport, and on all beaches size fines up-beach (contrasting with the up-beach coarsening of pebble and cobble beaches). During transport, breakage and chipping diminish boulder size, and the products of these forms of abrasion constitute a subordinate fine population causing the distribution of size to be positively skewed, contrasting with most fine-sediment beaches which exhibit negative size skewness. -- More boulders are oblate than prolate, but this may reflect geology rather than coastal weathering processes. In contrast to pebble beaches, no longshore or up-beach shape zoning exists, and boulder shapes are believed to be largely determined by geology. Boulder shape is not related to boulder size. Sphericity varies little within each beach and nowhere does it increase seaward as is common for pebble and cobble beaches. -- Boulder roundness tends to increase longshore towards the embayment, and decrease up-beach. The relationships between boulder roundness and size may be influenced by sediment supply. Roundness and shape of boulders do not appear to be related. -- Overall beach form is consistent and no rhythmic features could be identified. Surface packing or armouring occurs on all beaches and may contribute to beach stability. Foreshore slopes tend to be concave upward and range between 7° and 12°, significantly lower than the slopes of >= 24° predicted in the literature for boulder-sized sediment. This anomaly may be explained by the fact that only very high-energy waves, which produce low beach slopes, are competent to transport boulders. -- Boulder mobility is evident on all beaches and was monitored on one beach. Wave competency appears to determine the maximum size of transported boulders, and a competency model is proposed in which it is predicted that there exists a power relationship between transported particle diameter and significant wave height. Since boulder beaches and rubble coastal protection structures have environmental and compositional similarities, beach-boulder movement is examined in the light of engineering studies of protection-structure stability. Two no-damage design formulae were found to over-predict the movement of the smaller-sized beach sediment and underpredict the movement of the larger-sized sediment. This effect may be due to the packing of beach boulders. -- Up-beach fining, positive size skewness, the absence of shape zoning, much particle breakage, the absence of sphericity grading, and low foreshore slope are all characteristics of the five studied boulder beaches which contrast markedly with the characteristics of pebble and cobble beaches. These findings, combined with the development of a reasonable predictive transport model, suggest that the studied boulder assemblages are organized and distinct coastal deposits, which may properly be termed beaches. / Mode of access: World Wide Web. / 309 leaves ill. (some col.), maps

The adverse impacts on vegetation and soils due to livestock grazing have been extensively studied for many years. The extent to which native wildlife may also be causing change to their environment, as a result of local increases in population density, has been the subject of debate in a number of countries. In Australia there has been a growing awareness in recent years that native herbivores, particularly kangaroos and wallabies, may also be causing changes to ecosystem dynamics. Environmmental changes, produced firstly by the aboriginal people and then by Europeans, have favoured the larger macropods, resulting in increased population levels. These impacts can also be seen in areas around cities, where pressure from urbanisation has restricted populations to smaller and smaller patches of remnant vegetation and reserves, increasing the pressure on diminishing food resources within these patches. This study focuses on one of the areas that supplies drinking water to Melbourne, the Yan Yean Reservoir catchment, which is situated 37 km north east of Melbourne. This study adds to our understanding of the impacts of native wildlife populations by investigating the extent of some of these possible changes to ecosystem dynamics.

New laboratory data are presented on the influence of long waves on sediment transport in the surf zone. Due to the very significant difficulties in isolating the morphodynamic processes induced by long waves in field conditions, the laboratory study was designed practically to measure the net sediment transport rates, and gradients in sediment transport, arising from the interaction between long waves and short waves in the surf zone. The bathymetric evolution of model sand beaches, with dB50B = 0.2 mm, was observed under monochromatic short waves, long-wave short-wave combinations (free long waves), and bichromatic wave groups (forced long waves). The beach profile change and net cross-shore transport rates, Q(x), were extracted and compared for conditions with and without long waves. The experiments include a range of wave conditions, e.g. high-energy, moderate-energy, low-energy waves, and the beaches evolve to form accretionary, erosive, and intermediate beach states. Hydrodynamic measurements were made to identify the influence of long waves on short waves and to determine the correlation between surf zone bars and standing long waves. A shallow water wave model was modified for this application to surf zone morphodynamics and compared to both hydrodynamics and measured sediment transport. This data clearly demonstrate that free large-amplitude long waves influence surf zone morphodynamics not only under accretive conditions, by promoting onshore sediment transport, but also under erosive conditions, by decreasing offshore transport. For the dominant berm-bar feature, the strong surf beat induces offshore transport in the inner surf zone and onshore transport around the outer surf zone and throughout the shoaling zone. In contrast, forced (bound) long waves and wave groups correlated with bichromatic short wave groups play a pronounced role under erosive conditions, increasing offshore sediment transport across the whole beach profile. For accretionary conditions, only a very narrowbanded wave group promotes onshore sediment transport across the whole beach profile, while broader banded wave groups again promote offshore transport. The modified numerical model of Li et al. (2002) provides good predictions of the standing long wave pattern for the long-wave short-wave combinations, but generally poor agreement for the bichromatic wave groups. Similarly, this model performs poorly in terms of predicting the net sediment transport for all waves, even after optimising the sediment transport coefficients. This is because the model cannot predict the correct hydrodynamics around the breakpoint position and does not correctly represent net sediment transport mechanics. Overall, the model does not correctly predict the trends in beach profile evolution induced by the long waves and wave groups. Further, there is little evidence that the long wave nodal structure plays a dominant role. The influence of the free long waves and wave groups is consistent with the concept of the Gourlay parameter, H/wBsBT, as a dominant parameter controlling net erosion or accretion. Free long waves tend to reduce H/wBsBT, promoting accretion, while wave groups tend to increase H/wBsBT, promoting erosion.