Pitt River, 30 km inland from. Vancouver, British Columbia at the southern margin of the Coast Mountains, links Fraser River estuary and Pitt Lake. Salt water seldom extends to within 10 km of Fraser - Pitt confluence; nevertheless, tides modulate Fraser flow and cause Pitt River to fluctuate 2 m and Pitt Lake as much as 1.2 m. There is an upstream movement of sediment in Pitt River from Fraser River, evidenced by identical mineralogy of Pitt River and Fraser River sediments, a decrease in grain size from the Fraser to Pitt Lake, and a predominance of flood-oriented bedforms in the river channel. A delta of 12 km2 area has accumulated at the lower (draining) end of the lake. The purposes of the study were to: (1) examine aspects of the hydrodynamics of Pitt River and Pitt Lake as a tidal system; (2) evaluate the effect of bidirectional flow on river and delta morphology; (3) determine processes of sediment movement in the river and of-sediment dispersal on the delta; and (4) estimate present sedimentation rate on the delta. Water Survey of Canada stage data from 3 locations in the system, used in conjunction with velocity measurements (profiles and tethered meter), revealed large seasonal and tidal variations in discharge. Calculations indicate that flood basal shear stress peaks early in the flow, whereas ebb currents have a lower basal, shear stress which peaks late in the flow. Thus, sediment moves farther forward on a flood flow than it moves back on the succeeding ebb. Studies of the river channel using hydrographic charts revealed regular meanders (^M = 6100. m) and evenly spaced riffles and pools which are scaled to the strongest flow (winter flood current, Qe). Meander point bars are accreting on the "upstream" side indicating deposition by the flood-oriented flow. The three dimensional geometry of the large-scale bedforms which cover the sandy thalweg of both river and delta channel was determined by echo sounding and side-scan sonar. Three distinct sizes (height/spacing = 0.8 m/10-15m; 1.5m/25-30 m; 3 m/50-60 m) of large-scale bedforms (sand waves) were found; their linear-relationship of height vs. spacing (XD) on log-log plot suggests a common genesis. The size appears to be related to channel geometry, not to depth of flow. Largest forms are found in reaches which shallow in the direction of water movement and smallest forms occur on relatively flat topography. The following tentative relationship is suggested for sandy meandering rivers: ^M/^B = Qe. Pitt delta morphology was studied with aerial photos and depth soundings. Its shape is considered an excellent example of sediment diffusion and deposition from a simple jet into a low energy lacustrine environment. Analysis of 190 sediment samples from river, delta, and lake bottom shows the sediment to be polymodal. Graphical partitioning of the cumulative probability plots reveals that sediments are composed of up to 4 log-normal distributions. Each distribution is interpreted as a population related to a process of sediment transport. Five subenvironments in the Pitt system are characterized by unique combinations . of these "process" populations. Cores in the delta topsets and lake bottom sediments reveal silt and clay rhythmites, interpreted as varves. The coarse layers are deposited during winter when discharge of Fraser River is low and tidally induced discharge in Pitt system is high. The fine layers are deposited during spring run-off when additional fines are added to the lake from the Pitt basin. 137Cs dating of sediments shows that as much as 1.8 cm/yr are accumulating in the active portions of the delta with an estimated 150 +/- 20 X 103 tonnes deposited annually. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Les travaux présentés dans ce manuscrit portent sur les courants et le transport de matière solide en suspension, au voisinage de grandes structures immergées en eau peu profonde. Nous avons focalisé notre étude sur le cas de cages d'aquaculture installées dans la rade de Cherbourg. Situées dans une zone de fort courant, elles impactent leur environnement en modifiant l'écoulement et la turbidité locale. En dépit de nombreuses études déjà disponibles sur l'impact hydrodynamique de tels obstacles, de nombreuses questions se posent encore concernant l'écoulement sous la cage, la production de turbulence, l'érosion du sol et la remise en suspension de sédiments, ainsi que le devenir des déchets produits par la cage. Nous avons choisi de développer trois approches complémentaires pour apporter des éléments de réponse à ces questions. La thèse débute par une étude purement théorique de l'hydrodynamique au voisinage d'un obstacle immergé, assimilé à un milieu poreux, et dans une géométrie simplifiée. Ce modèle bi-dimensionnel, dans le plan vertical, donne de premiers ordres de grandeurs concernant la chute de pression motrice le long du courant, l'accélération du fluide sous la cage, la production de turbulence. Cette étude est suivie d'une analyse numérique de ce même modèle, dans laquelle certaines approximations seront levées. En particulier, le modèle numérique permet de considérer des cages plus imperméables que celles analysées par le modèle théorique. Il est cependant limité en nombre de Reynolds, et a été appliqué avec des échelles réduites. Ce modèle numérique a permis d'analyser le lien direct entre le coefficient de traînée effectif de la cage et diverses quantités-clés : le débit à travers la cage, la chute de pression le long du courant, la production de turbulence et l'apparition d'une zone de recirculation à l'arrière de l'obstacle. Ce dernier effet, visible seulement pour des cages très imperméables, a un impact notable sur le transport de sédiments et d'effluents : lorsque l'arrière de la cage devient une zone morte (zone de recirculation), l'essentiel du débit passe au dessous, ce qui crée de fortes survitesses et produit de la turbulence. Celle-ci peut alors entraîner des particules indésirables dans la zone morte, ce qui augmente notablement la complexité de leurs trajectoires et retarde leur évacuation. Enfin, ces études théoriques ont été complétées par des mesures vélocimétriques et turbidimétriques à l'amont et à l'aval d'une grande cage installée dans la rade de Cherbourg. Celles-ci confirment la présence d'une survitesse en provenance du dessous de la cage, comparable à celle prédite par le modèle théorique. Dans le cas d'une cage très peu perméable, la persistence d'une forte turbidité a été mesurée à l'aval de celle-ci, en accord qualitatif avec les simulations numériques. / This manuscript presents investigations of current and sediment transport in the vicinity of large immersed structures in shallow water flows. It focuses on aquaculture cages installed in the roadstead of Cherbourg. Being located in a high stream zone, these obstacles have a non-negligible effect on currents as well as turbidity. In spite of numerous references on this topic, many questions still arise concerning the environmental impact of such objects. Quantitative information are still needed about the flow below the cage, turbulence production, erosion of the sand bed, sediments resuspension, and evacuation of effluents. To deal with these open questions, we have chosen to develop three complementary approaches. The thesis starts with an analytical study of the flow in a simplified two-dimensional model containing a large rectangular porous structure. Only the motion in the vertical mid-plane of the obstacle is considered. This preliminary model provides estimations of various dynamic quantities, like the velocity increase below the cage, the decay of piezometric pressure along the stream, and turbulence production. Then follows a numerical analysis of the very same flow, based on less stringent approximations. Because of the high cost of computations, simulations have been done at a reduced scale. Nevertheless, they confirm most of the findings of the analytical approach for very permeable cages, and provide crucial information also about weakly permeable cages which were out of reach of the analytical model. In particular, the formation of a recirculation cell behind such cages, together with turbulence production, have been studied with the numerical model. This effect has been observed to affect sediment and effluent transport: when the flow at the rear of the cage takes the form of a cell with closed streamlines, the cage can be thought of as closed and most of the flow passes below. This creates large velocity gradients and produces turbulence which significantly increases the dispersion of sediments and effluents. These particles are then likely to be captured for some time in the cell, instead of being evacuated away. In addition to these theoretical approaches, in-situ current and turbidity measurements have been performed upstream and downstream of a large cage immersed in the roadstead of Cherbourg. They confirm the existence of a fast stream emerging from below the cage. Vertical streamwise velocity profiles have been shown to agree with theoretical ones, in the case of a very permeable cage. Also, large turbidity levels have been recorded at the rear of a weakly permeable cage, in qualitative agreement with simulations.

The current period of human history is considered to be the plastics age due to its versatile characteristics, especially the lightweight, durability and low production cost. Plastics can be manufactured to suit multifarious functions, for example, for personal care products, food/drink storage and medical purposes. Thus, the use of plastics is unavoidable now, finally contributing to the severe pollution worldwide. In 2018 alone, the global plastics production amount has exceeded 359 million tons, around 10% of which ultimately become waste persisting in the environment. When plastic wastes exposed to the sun's radiation, climate change and mechanic abrasion, degradation and fragmentation may occur. Once the size of the fragmentation products is less than 5 mm, they are commonly defined as microplastics (MPs) by the National Oceanographic and Atmospheric Administration. Currently, microplastics have been regarded as the most pervasive environmental pollution problems, not only because of their physical hazards but also due to their interactions with other pollutants in the environment. Pollution can be attributed by the release of additives from MPs, as well as the MPs with adsorbed toxic contaminants. Moreover, MPs additives together with adsorbed chemicals can be easily uptaken by animals, which may cause further propagated effects on the ambient ecosystem. Through the bioaccumulation and biomagnification effect, MPs can even be accumulated in the organisms from different trophic levels and cause serious impacts on aquatic ecology and human health. Despite growing number of evidences that have confirmed the presence and consequential effects of microplastics, researches on microplastic pollution are still lacking. Investigations on occurrence, determination and environmental fate of MPs in aquatic systems are clearly needed. Therefore, the major objective of this study is to elucidate the distribution of MPs in natural environment, to develop novel determination methods to characterize the micro-(nano-)plastics (MNPs), and to study the interactions of MPs with other contaminants in different conditions, as well as their consequential fate in different matrices (e.g. freshwater, cold-blooded intestine, and warm-blooded intestine). The spatial-temporal distribution of the MPs along the Maozhou River was investigated for both the surface water and sediments from 17 sites. Results showed that MPs were widely and unevenly distributed along the river. The MP abundances in dry season ranged from 4.0 ± 1.0 to 25.5 ± 3.5 items·L-1 in water and 35 ± 15 to 560 ± 70 item·kg-1 in sediments, which were relatively higher than those observed in wet season (water: 3.5 ± 1.0 to 10.5 ± 2.5 items·L-1; sediments: 25 ± 5 to 360 ± 90 item·kg-1; p value < 0.05). The dominant types of MPs were identified as: polyethylene (PE, water: 45.0%, sediments: 42.0%), polypropylene (PP, water and sediments: 12.5%), polystyrene (PS, water: 34.5%; sediments 14.5%) and polyvinyl chloride (PVC, water: 2.0%; sediments: 15%). Moreover, metals such as Al, Si, Ca were discovered on the rough surface of the MPs, indicating the interactions between the MPs and the aquatic environment. After obtaining the occurrence of the MPs in the aquatic systems, we proposed an accurate method for MNPs identification and quantification with the employment of the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). By optimizing the conditions (e.g. the laser energy, matrix, analyte, cationization agent and their ratio), the peaks of PS and polyethylene terephthalate (PET) were successfully identified. A quantitative correlation was built between the normalized signal intensity and ln[polymer concentration], with a correlation coefficient above 0.96 for low-molecular-weight (LM-) polymers and 0.98 for high-molecular-weight (HM-) polymers. Furthermore, two types of environmental MPs samples were prepared, including the particles of an aviation cup as the fresh plastics and the aged MPs extracted from river sediment. By using MALDI-TOF MS, the PS-related micro-(nano-)plastics (in both aviation cup and sediment) consisted of C8H8 and C16H16O oligomers, while the PET-related MNPs (only found in sediment) were identified with compositions of C10H8O4 and C12H12O4. The contents of PS and PET MNPs in sediment were quantified as 8.56 ± 0.04 and 28.71 ± 0.20 mg·kg-1, respectively. Also, the interaction between MPs and bisphenols was investigated. PVC was selected as the representative target because it is comparatively easy to decompose into MPs with the release of additives, especially the bisphenols. The released bisphenols may then be readsorbed by the PVC MPs and cause consequential pollution to the ecosystem. To elaborate on the interactions mechanism, a systematic study was carried out to determine the adsorption mechanisms of five bisphenol analogues (BPA, BPS, BPF, BPB, and BPAF) on PVC MPs. The equilibrium adsorption numbers of the bisphenols on PVC MPs are 0.19 ± 0.02 mg/g (BPA), 0.15 ± 0.01 mg/g (BPS), 0.16 ± 0.01 mg/g (BPF), 0.22 ± 0.01 (BPB), 0.24 ± 0.02 mg/g (BPAF), respectively. Intraparticle diffusion modeling (kinetics) divided the adsorption process into three stages: external mass transport, intraparticle diffusion and dynamic equilibrium. The isotherm results showed a better fit of the adsorption to the Freundlich model. Furthermore, the adsorption mechanisms of the five bisphenol analogues were explored intensively, with respect to hydrophobic interaction, electrostatic force and noncovalent bonds. Besides the adsorption process, the transfer and release behaviors of contaminated MPs are of critically importance in the exploration of their role as culprits and/or vectors for the aforementioned toxicity. Therefore, experiments were performed to examine desorption behaviors and cytotoxicity performance of contaminated MPs in aquatic surroundings and intestinal environment after ingestion by organisms (cold-/warm-blooded). The kinetic study showed that the rate of desorption for bisphenols could be enhanced threefold under simulated warm intestinal conditions. The Freundlich isotherms indicated multiple-layer desorption of the bisphenols on the heterogeneous surfaces of PVC MPs. Hysteresis was detected in the adsorption/desorption of bisphenols in a water environment, but no adsorption/desorption hysteresis was observed in the simulated intestinal conditions of warm-blooded organisms. Due to the enhanced bioaccessibility, the desorption results implied that the environmental risk of contaminated PVC MPs might be significantly increased after ingestion at a high bisphenols dosage. Although with different IC50, the five bisphenols released under the intestinal conditions of warm-blooded organisms can cause higher proliferation reduction in fish and human cell lines than the bisphenols released in water. In summary, this study elucidated the spatial-temporal distribution behaviors of MPs, developed effective determination methods for MNPs revealed the interactions mechanisms of MPs with other contaminants, and explored their consequential fate in different environments. The obtained results are helpful of better understanding on the land-based input of MPs from the intensively affected inland waters, realizing the role of microplastics as both source and carrier for emerging organic pollutants, and providing a novel alternative for MPs determination in future studies.

The Upper Souris River was placed on the Environmental Protection Agencies (EPA) impaired waters list for low dissolved oxygen (DO). A Total Maximum Daily Load (TMDL) study was conducted to determine possible causes of DO depletion. From sampling and site visits it was determined nonpoint sources contributed the majority of organic loadings to the Upper Souris River. Through preliminary testing, it was determined that sediment oxygen demand (SOD) played a key role in depleting DO levels during winter months and required further investigation. River profile surveying, water quality sampling, and laboratory testing of SOD were carried out to determine parameters required for water quality modeling. SOD tests were conducted to determine impacts of sediment organic contents and temperature on SOD rate. Sediment oxygen demand rates ranged from 0.37 to 1.22 g O2/m2/d. The QUAL2K model was calibrated to simulate DO variations along the study reach under ice covered conditions.

As our global community grapples with the ongoing challenges of climate change mitigation and adaptation, records of past climate changes provide important benchmarks for climate models and insights into the interactions between climate changes, human societies, and the landscape. In this dissertation, I reconstruct past changes in climate and redefine the human settlement history of the North Atlantic region. Understanding the human and climate history of the North Atlantic is particularly important because the region is especially sensitive to changes in climate, and climate and oceanographic changes in the region have global ramifications. I focus on the Faroe Islands and Iceland. These islands are close to oceanographic and atmospheric fronts and are sensitive to small changes in the climate system. Furthermore, the Faroes and Iceland were not settled by humans until the the first millennium CE, and as such, provide climate records that are unaltered by human land use activities for most of the Holocene, and are important test cases for understanding human-climate-landscape interactions after human settlement. In this work, I use lake sediment cores to reconstruct continuous climate records for the Holocene period, and in some cases, snapshots of previous interglacials. Lipid biomarkers are a group of molecules that accumulate in lake sediment and can be traced back to organisms in the lake or its watershed. I use these molecules and their isotopic compositions to quantify past changes in temperature and precipitation isotopes, which provide constraints on past climate and atmospheric circulation. I use fecal biomarkers, which are produced by the gut bacteria of humans and livestock, to determine when humans first settled in a lake’s watershed, and the impact they had on the environment. Ancient DNA stored in lake sediment can also be used to trace past changes in vegetation and to determine if livestock were present in the watershed, enhancing our understanding of agricultural impacts on the landscape. By combining these molecular tools, in Chapter 2, I reconstruct the Holocene and Last Interglacial climate in the Faroe Islands using the hydrogen and carbon isotopes of leaf waxes. In this case, I found that the Faroe Islands slowly transitioned over the Holocene from a climate that was warmer and wetter than present conditions, to a climate that is cooler and drier. In the Faroes, the Last Interglacial climate was similar to the early Holocene. In Chapter 3, I use fecal biomarkers and sedimentary ancient DNA to determine that humans arrived 300 years prior than previously thought. Human settlement caused erosion in the catchment and a shift in the vegetation community. In Chapter 4, I use the hydrogen isotopic composition of leaf waxes in conjunction with a biomarker-based temperature reconstruction from a lake in Iceland to determine past shifts in regional atmospheric circulation. I found that a shift towards more northerly-sourced precipitation, consistent with conditions similar to a positive NAO, occurred at the same time as regional neoglaciation and expansion of sea ice. All together, these records advance our understanding of Holocene and Last Interglacial climate change, the human settlement history

Bibliography: p. 420-430. / In this thesis the processes that produced diamond placer deposits within closed endoreic basins along the west coast of Namibia are addressed. These deposits, first discovered in 1908, and documented by Kaiser in 1926, occur in an area of wind deflation between latitudes 26 and 28 degrees South. Salt rock weathering and aeolian abrasion has eroded elongated depressions that are up to 120 m deep, that happen to be parallel with the dominant wind flow from the south and south-southeast, which governs aeolian processes in the coastal tract. The velocity of winds from the south and south-southeast frequently averages 50 to 60 km/hour between October and March, and gusts at 80 to 90 km/hour. At these velocities, grains exceeding -1 phi (2 mm) in diameter are commonly entrained into the saltation load above stone pavement surfaces, making this an extremely active aeolian environment.

The current period of human history is considered to be the plastics age due to its versatile characteristics, especially the lightweight, durability and low production cost. Plastics can be manufactured to suit multifarious functions, for example, for personal care products, food/drink storage and medical purposes. Thus, the use of plastics is unavoidable now, finally contributing to the severe pollution worldwide. In 2018 alone, the global plastics production amount has exceeded 359 million tons, around 10% of which ultimately become waste persisting in the environment. When plastic wastes exposed to the sun's radiation, climate change and mechanic abrasion, degradation and fragmentation may occur. Once the size of the fragmentation products is less than 5 mm, they are commonly defined as microplastics (MPs) by the National Oceanographic and Atmospheric Administration. Currently, microplastics have been regarded as the most pervasive environmental pollution problems, not only because of their physical hazards but also due to their interactions with other pollutants in the environment. Pollution can be attributed by the release of additives from MPs, as well as the MPs with adsorbed toxic contaminants. Moreover, MPs additives together with adsorbed chemicals can be easily uptaken by animals, which may cause further propagated effects on the ambient ecosystem. Through the bioaccumulation and biomagnification effect, MPs can even be accumulated in the organisms from different trophic levels and cause serious impacts on aquatic ecology and human health. Despite growing number of evidences that have confirmed the presence and consequential effects of microplastics, researches on microplastic pollution are still lacking. Investigations on occurrence, determination and environmental fate of MPs in aquatic systems are clearly needed. Therefore, the major objective of this study is to elucidate the distribution of MPs in natural environment, to develop novel determination methods to characterize the micro-(nano-)plastics (MNPs), and to study the interactions of MPs with other contaminants in different conditions, as well as their consequential fate in different matrices (e.g. freshwater, cold-blooded intestine, and warm-blooded intestine). The spatial-temporal distribution of the MPs along the Maozhou River was investigated for both the surface water and sediments from 17 sites. Results showed that MPs were widely and unevenly distributed along the river. The MP abundances in dry season ranged from 4.0 ± 1.0 to 25.5 ± 3.5 items·L-1 in water and 35 ± 15 to 560 ± 70 item·kg-1 in sediments, which were relatively higher than those observed in wet season (water: 3.5 ± 1.0 to 10.5 ± 2.5 items·L-1; sediments: 25 ± 5 to 360 ± 90 item·kg-1; p value < 0.05). The dominant types of MPs were identified as: polyethylene (PE, water: 45.0%, sediments: 42.0%), polypropylene (PP, water and sediments: 12.5%), polystyrene (PS, water: 34.5%; sediments 14.5%) and polyvinyl chloride (PVC, water: 2.0%; sediments: 15%). Moreover, metals such as Al, Si, Ca were discovered on the rough surface of the MPs, indicating the interactions between the MPs and the aquatic environment. After obtaining the occurrence of the MPs in the aquatic systems, we proposed an accurate method for MNPs identification and quantification with the employment of the matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). By optimizing the conditions (e.g. the laser energy, matrix, analyte, cationization agent and their ratio), the peaks of PS and polyethylene terephthalate (PET) were successfully identified. A quantitative correlation was built between the normalized signal intensity and ln[polymer concentration], with a correlation coefficient above 0.96 for low-molecular-weight (LM-) polymers and 0.98 for high-molecular-weight (HM-) polymers. Furthermore, two types of environmental MPs samples were prepared, including the particles of an aviation cup as the fresh plastics and the aged MPs extracted from river sediment. By using MALDI-TOF MS, the PS-related micro-(nano-)plastics (in both aviation cup and sediment) consisted of C8H8 and C16H16O oligomers, while the PET-related MNPs (only found in sediment) were identified with compositions of C10H8O4 and C12H12O4. The contents of PS and PET MNPs in sediment were quantified as 8.56 ± 0.04 and 28.71 ± 0.20 mg·kg-1, respectively. Also, the interaction between MPs and bisphenols was investigated. PVC was selected as the representative target because it is comparatively easy to decompose into MPs with the release of additives, especially the bisphenols. The released bisphenols may then be readsorbed by the PVC MPs and cause consequential pollution to the ecosystem. To elaborate on the interactions mechanism, a systematic study was carried out to determine the adsorption mechanisms of five bisphenol analogues (BPA, BPS, BPF, BPB, and BPAF) on PVC MPs. The equilibrium adsorption numbers of the bisphenols on PVC MPs are 0.19 ± 0.02 mg/g (BPA), 0.15 ± 0.01 mg/g (BPS), 0.16 ± 0.01 mg/g (BPF), 0.22 ± 0.01 (BPB), 0.24 ± 0.02 mg/g (BPAF), respectively. Intraparticle diffusion modeling (kinetics) divided the adsorption process into three stages: external mass transport, intraparticle diffusion and dynamic equilibrium. The isotherm results showed a better fit of the adsorption to the Freundlich model. Furthermore, the adsorption mechanisms of the five bisphenol analogues were explored intensively, with respect to hydrophobic interaction, electrostatic force and noncovalent bonds. Besides the adsorption process, the transfer and release behaviors of contaminated MPs are of critically importance in the exploration of their role as culprits and/or vectors for the aforementioned toxicity. Therefore, experiments were performed to examine desorption behaviors and cytotoxicity performance of contaminated MPs in aquatic surroundings and intestinal environment after ingestion by organisms (cold-/warm-blooded). The kinetic study showed that the rate of desorption for bisphenols could be enhanced threefold under simulated warm intestinal conditions. The Freundlich isotherms indicated multiple-layer desorption of the bisphenols on the heterogeneous surfaces of PVC MPs. Hysteresis was detected in the adsorption/desorption of bisphenols in a water environment, but no adsorption/desorption hysteresis was observed in the simulated intestinal conditions of warm-blooded organisms. Due to the enhanced bioaccessibility, the desorption results implied that the environmental risk of contaminated PVC MPs might be significantly increased after ingestion at a high bisphenols dosage. Although with different IC50, the five bisphenols released under the intestinal conditions of warm-blooded organisms can cause higher proliferation reduction in fish and human cell lines than the bisphenols released in water. In summary, this study elucidated the spatial-temporal distribution behaviors of MPs, developed effective determination methods for MNPs revealed the interactions mechanisms of MPs with other contaminants, and explored their consequential fate in different environments. The obtained results are helpful of better understanding on the land-based input of MPs from the intensively affected inland waters, realizing the role of microplastics as both source and carrier for emerging organic pollutants, and providing a novel alternative for MPs determination in future studies.

Bibliography: pages 131-139. / The construction of bridge embankments and other physical obstacles in estuaries has often resulted in the redistribution of sediments, which ultimately leads to detrimental impacts in these environments. The aim of this study is to investigate how the sediment distribution and dynamics within a specific estuary, the Uilkraals estuary, have been affected by human disturbance; focusing on the impacts arising from construction of two temporary embankments and a permanent bridge and embankment. The Uilkraals estuary is situated in the south-western Cape, approximately 60 kilometres north-west of Cape Agulhas. Human impact has been extensive and engineering projects of various sizes and permanence have marked the recent history of this estuary. A bridge and embankment which cross the estuary 800 m from the mouth were built in 1973. In 1978 an embankment was built between the bridge and the estuary mouth. A second embankment which replaced the first in 1980, was removed before the end of that year. Extensive dune reclamation occurred on the left bank between 1938 and 1973. The techniques used in the study include: (i) a quantitative analysis of all available aerial photographs from 1938 to 1987 (ii) a ground survey and (iii) core and surface sediment sampling. The quantitative analysis reveals that the major changes in estuarine characteristics have been in response to human disturbance. The contour map and cross-sections drawn from the ground survey indicate a build-up of sediment downstream of the bridge and scouring of the channel upstream. The latter suggests the dominance of the flood-tidal current in the estuary. The core sediment analyses are unable to distinguish any real difference in the modes of sediment deposition on either side of the bridge embankment. The embankment has, however, affected deposition by acting as a "hydraulic shelter" to sediment accumulated downstream of the bridge during high run-off events and by initiating deposition of sediment upstream of the embankment. The surface sample analyses indicate that there has been an increase in flow velocities in the vicinity of the bridge since its construction and that the major agents which bring marine sediment into the estuary are flood-tidal currents and wind. It is concluded that the sediment distribution and dynamics of the Uilkraals estuary have been affected by human disturbance. Recommendations for future management of the estuary are that no further embankments should be constructed in the estuary and that the construction of a culvert or culverts under the existing bridge embankment would alleviate a number of problems presently experienced in the estuary.

The author has sampled the recent bottom sediments in Tillamook Bay, Oregon. Sediment distribution is assessed in relation to sediment source areas and related to sedimentary environments. Particular attention was directed to the precision with which granulometric data can be stated. It was found that variance is quite high for granulometric parameters of the bay sediments. Sediment distribution using different measures are displayed on charts of the bay. Size distributions of sediments at any given location are examined for geologic significance. Plotting of size distribution on graph paper using probability ordinate is shown to increase the ease of geologic interpretation. Total heavy minerals were X-rayed and provenance determinations from this and other data show a marine sediment source for a small area of the bay near the mouth and terrestrial source for the remainder of the bay.

No description available.