Multiple scales of beach morphodynamic processes ranging from those of wave-breaking induced turbulence, individual wave, storm, seasonal, to inter-annual are examined in this dissertation based on both laboratory and field data. These processes were simulated using process-based numerical models and data-driven models. At a microscale, separating turbulence from orbital motion under breaking waves in the surf zone is essential to understanding wave-energy dissipation. Velocity data under monochromatic and random waves in the large-scale sediment transport facility (LSTF) were analyzed. Moving averaging provides a simple method for extracting turbulence from velocity measurements under random breaking waves collected at a reasonably high frequency. Various moving averaging time intervals were examined. An optimum moving averaging interval of approximately 30° to 42° phase angle (relative to peak wave period) allows a reasonable extraction of turbulence. An adaptive moving averaging with variable averaging time at wave crest and trough are proposed to improve the effect of turbulence extraction. At a mesoscale, hydrodynamic conditions associated with onshore migration of a sandbar and the subsequent equilibrium state of a stable bar were examined in the LSTF. Wave and near bottom velocity across the surf zone were measured during the onshore sandbar migration. The near-bottom velocity skewness indicates that before the sandbar reached equilibrium, the velocity was skewed offshore in the nearshore region, and skewed onshore seaward of the bar. The velocity skewness pattern reversed when the beach profile reached equilibrium and the sandbar became stable. The peak onshore directed acceleration was greater than the peak offshore directed acceleration throughout the surf zone during the periods of both onshore migrating and stable sandbar. The macroscale portion of the study examines the beach processes, particularly the morphodynamics of nearshore bar, at storm and seasonal scales. The bar height and bar position were extracted from bimonthly surveyed beach-profiles spaced at 300 m along the 22-km long Sand Key barrier island, West-Central Florida from October 2010 to August 2015. Seasonal beach cycle in the study area is illustrated by onshore sandbar migration during the summer and offshore sandbar migration during the winter, while subaerial beach remains rather stable. Alongshore variations of onshore and offshore sandbar migration were observed over storm events. The water depth over the pre-storm sandbar crest, or the bar crest elevation, is a major factor controlling the onshore or offshore sandbar movement. The offshore moving sandbar tends to have a shallower pre-storm bar crest, while the onshore moving sandbar tends to have a deeper pre-storm bar crest. A dynamic equilibrium bar height of 0.5 m for the study area was identified. The sandbar tends to evolve toward this equilibrium height during the seasonal cycle. The energetic conditions associated with Tropical Storm Debby caused a deviation from the above dynamic equilibrium conditions. The sandbar at most of the profile locations became higher than the pre-storm bar height regardless of the initial height of being greater or less than 0.5 m. After the storm, the higher and shallower bar experienced substantial erosion, the eroded sand was deposited in the trough landward. This resulted in a lower sandbar height, returning to the dynamic equilibrium height of 0.5 m. The Unibest-TC model (Walstra et al., 2012) is able to capture the measured trend of bar migration. The Modelling results suggest that offshore bar migration is dominated by suspended sediment transport. While onshore bar migration is driven mainly by bedload transport. At megascale, a data-driven model was developed to predict beach-profile evolution at multiple-annual scale. Empirical Orthogonal Function analysis was conducted on a time-series beach profile (R61) to identify temporal and spatial trends. Trends in the temporal EOF are modeled using a simple curve fitting. In this case, logarithmic and linear trends were identified. After the trend in temporal EOF values are identified, the curve fitting can be calibrated with 14-month data. The calibrated temporal EOF curve yielded accurate reproduction of profiles. The close examination of multiple scales of beach processes provides a comprehensive understanding of nearshore morphodynamics.

Erosional issues in the Brahmaputra River in the eastern Himalayas pose increasing pressure on the nearby societies and ecosystems. With a proceeding climate change and increasing anthropogenic disturbance, predictive models are needed to evaluate the effect on sediment transport. Especially in braided rivers, like the Brahmaputra, sediment transport processes imply high demands on numerical models. The objective is therefore to assess the sensitivity of sediment transport on changed river characteristics in the Brahmaputra River, in order to qualitatively evaluate future possible dynamics. Through the one-dimensional steady state model, HEC-RAS 4.1, the braided river was simplified into a single straight channel to enable an extensive reach (700 km) to be modelled. Since little comparative data were at hand, a literature review gathered independent estimates of each parameter. Their natural variability was applied in the sensitivity analysis, and the model produced a suspended sediment load representing approximately 35% of observed data. The sensitivity analysis showed that the channel bathymetry form had a large impact on the model results, whereas the amount of lateral inflow (both surface and subsurface waters) to the main channel flow had a very small impact. Overall, the suspended sediment load were interpreted to be increasing from a future climate change, while further river regulation could counteract such elevation. Further studies are required concerning the river bathymetry in large scale modelling and to address transport of finer cohesive sediments. This methodology proposes a novel approach on how to analyze sediment transport at a large scale that could be used as a tool to interpret future possible changes and ultimately contribute to a better understanding of sediment transport modelling in the area.

Nowadays the sediment becomes one significant problem to reservoir watershed and it is effect and related to reservoir operation system. As the research topic, an integrated sediment approach and impacts of climate change on reservoir sedimentation, there are three main parts demonstrated in this research that all parts are related together with sediment point of view. Annual sediment depositing volume in reservoir was estimated by general soil loss equation but the efficiency was not acceptable. The first part of this study shows that the efficiency is improved by using general soil loss equation with sediment transport model. The second part is about monitoring the sediment inflow to reservoir. The important parameter to operate the reservoir is turbidity concentration of flow into dam, in the second part the suspended sediment concentration was predicted by real time therefore the reservoir operation to release turbid flow will get more efficiency. For last part, in the next future year sediment yield and water resources on the study area were investigated by extrapolated temperature and rainfall data then the results will be useful for long term reservoir operation system. First part, the integrated sedimentation was used to model an annual depositing sediment volume in reservoir. Sediment system in watershed includes not only sediment yield but also sediment transportation along the rivers. In this study, the Geographic Information System (GIS) incorporated with sediment yield model can be assisted to enhance the evaluation estimation of soil erosion. Surface erosion on Managawa river basin is then computed with the Modified Universal Soil Loss Equation (MUSLE) and it is verified to reflect the hydrological processes to which it will be able to estimate soil losses. In the sediment transport routing module, total load equation is applied to carry sediment from soil surface erosion to deposit in Managawa dam. According to annual accumulation sediment volume data in Managawa reservoir during 1981 – 2004, the establish model and simulation results are satisfied. The efficiency of the Modified Universal Equation with sediment routing in rivers is more than the simple Modified Universal Equation. Second part, the real time suspended sediment concentration forecasting was used for monitoring the turbidity flow on the upstream of reservoir. The sediment flow into the reservoir is a factor for decision support in real time reservoir operation therefore the serious area of sediment erosion of Managawa river basin, Japan is monitored by suspended sediment gauge. The hourly suspended sediment concentration at Okumotani station; the upstream of Managawa reservoir, was monitored and estimated by the artificial neural network (ANN) model that the input data were rainfall data and its products. This artificial neural network (ANN) was calibrated and validated by using recently suspended sediment data on heavy rainfall events from December 2006 to January 2008. Choosing an appropriate neural network structure and providing field data to that network for training purpose are address by using a constructive back propagation algorithm. Rainfall and its products; the computed discharge from rainfall runoff model and rainfall intensity, were applied as inputs to neural network. It is demonstrated that the artificial neural network (ANN) is capable of modeling the hourly suspended sediment concentration with good accuracy and the neural network model has efficiency more than the multiple linear regression (MLR) model and the sediment rating curve (SRC) model. Last part, the effects of climate change on water resources and sediment yield were investigated by climate change scenarios which the main meteorological data were rainfall and temperature data. Historic trends of temperature and precipitation on Managawa river basin were detected by parametric and nonparametric tests. The daily mean temperature data from 1981 to 2008 at Ono station, Fukui prefecture was the representative of temperature on the study area. The hourly rainfall data from 1981 to 2008 were obtained by Managawa dam office processed with the reliability of data and weighted data. From monotonic and step trend tests, the temperature trend was found herein to follow a clear and steady trend every month. The average annual temperature exhibited an increasing trend with a magnitude 0.4 ºC per decade. Application of the Mann-Kendall and Mann-Whitney test for rainfall time series on Managawa river basin showed no step change and no monotonic trend in Managawa precipitation. The average annual precipitation exhibited a decreasing trend with a magnitude 52 mm per decade. The weather generating models both temperature and rainfall expressed the high efficiency for validation step. The generated weather series 2009 - 2060; temperature and precipitation height, for future climatic conditions can be inputted into the soil loss equation to investigate the change in sediment sources and extrapolated rainfall can be inputted to rainfall runoff model to investigate the change in runoff for future climate change condition. The sediment yield rate should be reduced because of the decrease in precipitation. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14934号 / 工博第3161号 / 新制||工||1474(附属図書館) / 27372 / UT51-2009-M848 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 角 哲也, 教授 田村 武, 教授 藤田 正治 / 学位規則第4条第1項該当

Malgré les nombreuses études qui ont été effectuées en raison des applications directes au niveau de l’érosion côtière, les processus physiques qui régissent la morphodynamique des plages nécessitent d’être mieux définis. L’objectif de ce travail est d’apporter une contribution à l’étude de ces processus à partir d’une modélisation physique bien contrôlée, menée dans un canal de 10 m de long du LOMC. Le cas particulier des plages intermédiaires selon la classification de Masselink & Short (1993) et mégatidal à marnage relatif faible est considéré. L’évolution temporelle des profils de plage est suivie par méthode acoustique. L’évolution de la surface libre au large et dans la zone de levée de la vague est enregistrée à l’aide de sondes résistives. La surface libre et le fond sableux sont suivis dans la zone de déferlement, la zone de surf et la zone de swash avec une méthode optique. L’effet de la marée sur les profils de plage a été analysé. Une barre intertidale (slip-face bar) est générée et leur processus de formation est analysé mettant en évidence le rôle de la barre subtidale et du déplacement des zones hydrodynamiques d’action au cours du cycle de marée. La dynamique du swash sur une plage mégatidale est étudiée par méthode optique. Une analyse détaillée de la dépendance du runup vis-à-vis des différentes variables est conduite. Celle-ci a permis d’identifier les paramètres les plus appropriés pour prédire le runup. Les résultats montrent qu’il est préférable d’utiliser la pente de la zone de surf et la hauteur de la houle au point de déferlement pour estimer cette grandeur. Une nouvelle formule de calcul du runup adaptée aux plages étudiées est développée. / Numerous studies have been carried out on sandy beach morphology; however, the physical processes which govern beach morphodynamics need to be better defined, despite the significance of this subject in view of the direct applications for coastal erosion. The aim of the present work is to bring a contribution to the study of these processes from well controlled tests carried out in a 10 m long wave flume at LOMC laboratory with a megatidal regime simulation. The tests were performed in the intermediate regime according to the Masselink and Short (1993) classification. The temporal evolution of beach profiles was obtained using an acoustic method. The incident waves and the free surface in the shoaling zone were measured with resistive probes. The free surface and bed level in the breaker, surf and swash zones were recorded with an optical method. The effect of tides on beach profiles was analyzed. Intertidal bar identified as a slip-face bar was generated. Formation processes of this bar were analyzed. The bar is alternately exposed to swash zone processes at low tide and breaker zone processes at high tide. The intertidal bar is fronted by a subtidal bar involved in its formation. Swash hydrodynamics were investigated on a megatidal beach using an optical method. A detailed analysis of the relationship between measured runup elevations and various variables was carried out. This allowed to determine the best parameters to predict runup. The results suggested that the slope of the surf zone and the wave breaking height should be used to estimate runup. A new runup estimation formula adapted to the studied beaches was proposed.

The Chilliwack River flows through the Cascade Mountains until reaching a narrow gorge near Vedder Crossing where it flows onto the Fraser Lowlands and eventually meets the Fraser River. Below Vedder Crossing, the river is actively building an alluvial fan by depositing its sediment load of gravel and sand. This deposition has resulted in frequent channel shifts over the fan surface with the most recent migration occurring around 1894 when the river shifted down Vedder Creek. Over the last century the Vedder River has been undergoing very complex changes in response to changes in the incidence of severe floods, changes in sediment supply and interference from river training. Extensive channelization works carried out in the 1960's induced temporary degradation over part of the channel which was accompanied by rapid aggradation in the reach immediately downstream. This rapid channel adjustment ceased in less than 10 years. In 1975 a flood having a return period of about 10 years deposited 260,000 cubic yards of sediment onto the fan which increased the mean bedlevel by nearly 1 foot. By comparison, the average annual deposition rate was estimated to be 72,000 cubic yards per year. Based on bedload transport calculations, approximately 700,000 cubic yards of sediment could be deposited by a 50 year rainstorm flood. In order to provide long term flood control, either the upstream sediment supply will have to be reduced or dredging will have to be carried out on the lower river. It is not feasible to eliminate aggradation by transporting the incoming bedload through the system and into the Fraser River. Some strategies are considered which, by controlled dredging and training would maintain the channel permanently in its present position. More severe floods would be contained by set-back dikes. It is thought that, with care, these measures could be consistent with salmon habitat requirements. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Orientador: Erick de Moraes Franklin / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T21:46:41Z (GMT). No. of bitstreams: 1 Penteado_MarcosRobertoMendes_M.pdf: 9443939 bytes, checksum: ee4e74d0df7e1ec320410dcc330c86e3 (MD5) Previous issue date: 2015 / Resumo: O transporte de sedimentos por um fluido é frequentemente encontrado em rios, oceanos, escoamentos periglaciais e outros processos naturais. É também encontrado na indústria, tal como em linhas de petróleo que arrastam sedimentos, em sistemas de esgotos e em processos de dragagem, por exemplo. Nessa dissertação, o transporte de grãos em um leito granular cisalhado pelo escoamento de um líquido será investigado experimentalmente. Nos experimentos, um escoamento de água turbulento totalmente desenvolvido foi imposto sobre o leito granular de geometria conhecida. Sob as condições testadas, os grãos foram transportados como leito móvel (\textit{bed load}, em inglês), i.e., sedimentos são transportados rolando ou deslizando sobre o leito. Para diferentes vazões de água, os deslocamentos dos grãos são filmados por uma câmera rápida. Os deslocamentos e campos de velocidade dos grãos foram determinados através do tratamento das imagens. A taxa de transporte dos grãos foi então estimada e correlacionada com o escoamento do fluido / Abstract: Sediment transport by a fluid flow is frequently found in rivers, oceans, periglacial flows and other natural processes. It is also commonly found in industry, such as in petroleum pipelines conveying grains, in sewer systems and in dredging lines, for example. In this thesis, the transport of grains of a granular bed sheared by a liquid flow was experimentally investigated. In the experiments, fully-developed turbulent water flows were imposed over a granular bed of known granulometry. Under the tested conditions, the grains were transported as bed load, i.e., sediment was carried by rolling and sliding over the bed. For different water flow rates, the displacements of grains were filmed by a high-speed camera. The grains displacement and velocity fields were determined by post-processing the images. The bed-load transport rate was estimated and correlated to the water flow conditions / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Une rivière alluviale s'écoule sur une épaisse couche de sédiments. Lorsqu'elle construit son lit, elle entraîne, transporte et dépose des sédiments, façonnant ainsi sa propre forme. Ainsi, le couplage entre l'écoulement et le transport sédimentaire régit la taille et la forme de la rivière. Dans cette thèse, nous étudions l'influence du transport sédimentaire sur la forme et la stabilité d'une rivière alluviale. Pour ce faire, nous reproduisons des rivières en laboratoire en laissant s'écouler un liquide visqueux sur un lit granulaire. L'aspect du chenal ainsi formé dépend des débits de liquide et de sédiment injectés en entrée. A l'aide de ces expériences, nous mettons en évidence les deux mécanismes qui contrôlent l'équilibre d'une rivière. D'abord, la gravité entraîne les grains vers le centre du chenal. Ce mécanisme érode continuellement les berges de la rivière, et tend donc à l'élargir. Cependant, les collisions d'un grain avec le lit dévient sa trajectoire dans la direction transverse à l'écoulement. Les grains se comportent ainsi comme des marcheurs aléatoires, qui, collectivement, diffusent vers les berges de la rivière. A l'équilibre, cette diffusion compense la gravité, et fixe ainsi la forme de la rivière. Lorsque la diffusion prend le dessus sur la gravité, elle peut induire une instabilité. En effet, si on perturbe un lit sédimentaire avec des stries longitudinales, le cisaillement fluide est plus faible là où l'écoulement est moins profond. Par conséquent, les grains diffusent depuis les creux de la perturbation vers ses crêtes. Cette rétroaction déstabilisante pourrait générer de nouveaux chenaux, et expliquer la formation des rivières en tresses. / An alluvial river builds its own bed with the sediment it transports. The channel bounds the flow, which in turns deforms the channel through erosion and deposition. This coupling between flow and sediment transport selects the shape and the size of the river. In this manuscript, we investigate it using laboratory experiments. The first ingredient of this coupling is gravity, which pulls the moving grains towards the center of the channel, thus continually eroding the banks. However, due to the roughness of the bed, the trajectory of a moving grain fluctuates across the stream. The bedload layer is therefore a collection of random walkers which diffuse towards the less active areas of the bed. In a river at equilibrium, this diffusion counteracts gravity to maintain the banks. When gravity and diffusion are out of balance, their interaction causes an instability. Indeed, if an initially flat bed of sediment is perturbed with longitudinal streaks, the flow-induced shear stress is weaker where the flow is shallower. Therefore, bedload diffusion induces a sediment flux towards the crests of the perturbation. This positive feedback induces an instability which can generate new channels. We suggest that this mechanism could initiate the braiding of alluvial rivers.

Thesis advisor: Noah P. Snyder / Though previous studies have shown saltmarsh adaptability to some degree of sea-level rise (SLR), sediment supply is critical to sustaining saltmarshes as SLR accelerates. Land-use activities, such as dams, often influence watershed sediment transport and delivery to the coast. Previous studies have suggested that, even in small watersheds, dams can significantly impact coastal sediment budgets. The Parker River watershed (PRW) in northeastern Massachusetts hosts 20 dams and several natural lakes, and drains into the Plum Island Sound Estuary (PIE). This research aims to evaluate the impact of dams and sediment transport in the PRW. Three approaches were used: theoretical modeling of sediment transport patterns using digital elevation models; spatial analysis of suspended sediment concentration (SSC) and remote sensing data; and empirical calculations of reservoir trap efficiency. Geomorphic modeling indicates that bankfull discharge can transport 20 μm grains (silt) as wash load throughout the PRW. Sediment deposition might happen at Crane Pond and in reservoirs, but removing dams would not change this pattern. Both SSC data and observations of satellite images during high-flow events indicate low supply and transport of sediment throughout the PRW. The estimates of sediment yield (Y) are low for the PRW. An empirical calculation indicates little-to-no trap efficiencies for all dams. Therefore, fluvial contribution to the sediment budget of the PIS estuary is limited and dam removals in the PRW are unlikely to change the rate of sediment delivery to the PIE. The proposed method of this study provides an additional scope to assess the ecological benefits of removing a dam and could be easily replicated for other locations for similar assessment. Future studies should assess sediment dynamics and management practices from a more thorough perspective incorporating the riverine, estuarine and shelf system. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

The Bîc River in the Republic of Moldova is a heavily polluted water body. Along the river stretch, from a small creek in Sipoteni close to the river mouth at Gura Bîcului, sediment samples were taken using a very cost-effective method and analyzed for a number of pollutants. The results showed very high levels of petroleum products in and downstream of the city of Chişinău, situated in the middle of the river basin, ex-ceeding even the guideline value for cleanup of industrial land. Concentrations of heavy metals were detected at all sample points, exceeding the Lowest Effect Level (LEL) in 37 out of 48 samples and the Probable Effect Level (PEL) in four of them. High concentrations of nutrients (N and P) were detected, especially outside of the city, where concentrations exceeded even the Severe Effect Level (SEL) for both N and P at one site. DDT concentrations were highest at the beginning of the river, the concentrations becoming lower and lower when getting closer to the river mouth. At three of the six sampling sites, DDT concentrations exceeded the LEL. PCB levels were lower than the LEL. This was attributed to unsuitable handling of the samples before analysis and therefore the PCB concentration levels requires further investiga-tion. The continued monitoring of the sediments is of great need, therefore a proposal for a monitoring program was written. It was estimated that Bîc contributes 118000 tons of suspended particles to Dniester each year, almost 60 % more per km2 than Dniester contributes to the Black Sea.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23479号 / 工博第4891号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 准教授 市川 温, 教授 角 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM