Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography : leaves 138-142. / Ph.D.

Yes / In the research on environmental hydraulics, its turbulence and sediment transport, constant challenges have been faced. The complexity of hydraulic impacts towards sediment morphology and turbulent flow properties makes research in this area a difficult task. However, due to pressure from climate change and the mounting issue of pollution, environmental flow studies are more crucial than ever. Bedforming within rivers is a complex process that can be influenced by the hydraulics, vegetated field, and various suspended and bedload transports. Changes in flow conditions due to rain and flood can further complicate a hydraulic system. To date, the turbulence, morphologic, and bedforming characteristics of natural environmental flows are still not well understood. This book aims to bring together a collection of state-of-the-art research and technologies to form a useful guide for the related research and engineering communities. It is useful for authorities and researchers interested in environmental and civil engineering studies, as well as for river and water engineers to understand the current state-of-the-art practices in environmental flow modelling, measurement and management. It is also a good resource for research, post-, or undergraduate students who wish to know about the most up-to-date knowledge in this field.

Yes

To quantify sediment contributions due to urban channel enlargement, 50 study sites were selected on 1st- through 3rd-order streams, in watersheds with varying levels of urbanization, in two Physiographic Regions (Coastal Plain and Piedmont), and in the Coastal Zone Management Area of Virginia. At each site, riffle cross-sectional and longitudinal surveys were conducted to measure the channel morphology. Enlargement ratios for bankfull cross-sectional parameters were calculated to quantify channel change relative to stable streams (from regional curves). Relationships between dependent, channel characteristics and watershed-scale, independent variables were assessed. The main objectives were to: 1) test for differences in the morphological features between Coastal Plain and Piedmont streams; 2) develop relationships between watershed-level, urbanization characteristics and stream morphological features; and, 3) determine if relationships exist between watershed urbanization and channel enlargement ratios to estimate sediment loading from urban streams for use in statewide nonpoint source pollution assessment activities. It was determined that: 1) for a given watershed area, streams in the Piedmont tended to be larger than those in the Coastal Plain Region (for regional curve streams and for project streams); 2) among all project sites and sites in the Piedmont, watershed area was the best indicator of channel morphology, but among the Coastal Plain sites, the number of road crossings over streams was the best indicator of channel morphology; and, 3) few significant relationships between enlargement ratios and watershed urbanization variables existed; however, one commonality observed across all sites was an inverse relationship between watershed area and channel enlargement ratios. / Master of Science

Accurately predicting sediment delivery has been a long-standing problem in the field of water resource management. Many different watershed equations and models have been developed such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more, however, these models have not always been able to reliably predict in-stream sediment loads. In this study, two scales, watershed and site level, are used to understand where sediment transported in-stream is being produced. At the watershed scale, USLE was used to estimate sediment yield and then different factors such as connectivity topographic indices were applied as discount factors in an attempt to improve these estimates. The different parameters were then compared to turbidity to determine the level of accuracy of each method. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An implicit assumption of USLE is that runoff is produced on steeper slopes and that sediment production occurs on these hillslopes. However, it was found that flatter-sloped areas were highly correlated with in-stream turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and level of confinement at higher flows were more accurate predictors of in-stream sediment levels. Overall, turbidity and in-stream sediment levels are not well predicted by models that employ USLE. The distribution of runoff source areas, and channel/bank properties appear to be good predictors of sediment production at the watershed scale. These results indicate that sediment production and transport, as conceptualized by common models and equations, often associate sediment source areas with geomorphic and hydrologic processes in ways that are not consistent with the results of this study. Our results show that sediment is most likely being sourced from the channels and in stream areas. / Master of Science / Predicting how sediment moves through a watershed has been a long-standing problem in the field of water resource management. There are many equations and models that have been developed to calculated the amount of sediment that exits a watershed; such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more. However, these models have not always been reliable or accurate in their predictions. In this study, two scales, watershed and site level, are used to understand where sediment transported within streams is being produced. At the watershed scale, USLE was used to estimate sediment leaving a system and then different factors, with different approaches to the understanding of sediment movement, were applied as discount factors in an attempt to improve these estimates. The different values that were calculated were then compared to turbidity to determine the level of accuracy of each parameter. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An assumption of USLE is that runoff is produced on steeper slopes and that sediment erosion occurs on these steeper sloped areas. However, it was found that flatter-sloped areas were highly correlated with turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and the level of confinement at higher flows were more accurate predictors of turbidity. Overall, USLE and models that used USLE were not able to predict turbidity. The distribution of runoff source areas and channel/bank properties appear to be good predictors of turbidity at the watershed scale. These results indicate that sediment movement, as conceptualized by common models and equations, often associate sediment source areas with watershed level morphology and hydrology in ways that are not consistent with the results of this study. Our results show that sediment is most likely being produced from the channels and in stream areas.

The Louisiana Gulf Coast is a dynamic system of heavy influence on the cultures that live and prosper around it. Land in this area is in jeopardy of being lost. In 2017, the Coastal Protection and Restoration agency will issue a new State Master and this thesis provides a more intricate way of numerically predicting the behaviors of associated sediments. A model for the estimation of resuspension and deposition is proposed and prepared for integration into the existing model. The silt and clay fractions of the bed sediment and the sediment inflow were modeled by the widely used hydrodynamic models of Delft3D and ECOMSED, using the Young and Verhagen wave properties to obtain orbital velocities and bed shear stress. The critical shear stress for erosion was based on empirical formulas developed by van Rijn.

An alongshore sediment transport and shoreline change analysis on Galveston Island in the period of 1990-2001 is conducted in this study using the Generalized Model for Simulating Shoreline Change (GENESIS). The study is divided into three main parts: 1. Assessment of the numerical accuracy of GENESIS, 2. Assessment of the alongshore sediment transport and shoreline change on the Galveston coast in the period of 1990-2001, and 3. Assessment of several erosion control practices on the Galveston coast for the period of 2001-2011. The first assessment shows that GENESIS has a numerical error which tends to be large for low energy wave (small breaking wave height) and large breaking wave angle. This numerical inaccuracy cannot be neglected and needs to be compensated for. This can be done, for instance, by adjusting the transport parameter K1. In the second assessment, good agreement between the calculated and measured transport/shoreline is achieved, particularly on the West Beach. Comparison between the potential alongshore sediment transport and sediment budget-inferred alongshore transport provides a systematic way of selecting the proper wave data set for the alongshore and shoreline change calculation. The third assessment proves that beach nourishment is the best alternative to overcome/reduce the erosion problem on the Galveston coast. Constructing coastal structure (groins, offshore breakwater) on the West Beach does not resolve the problem of erosion, but instead shifts it further west.

Elevated concentrations of mercury (Hg) in aquatic systems can be a threat to ecosystems and human health. Mercury-bearing sediment particles from eroding riverbanks can be an ongoing source of bioavailable Hg to aquatic ecosystems. Hyporheic zones in particular can be important sources of both inorganic and organic-complexed Hg, which can be rapidly transported to adjacent surface waters. The objective of this study was to investigate the release and treatment of dissolved and particle-bound Hg in water derived from the riverbank sediments of the South River, Virginia. The solid-phase forms of Hg in riverbank sediment samples were characterized by sequential extraction and synchrotron based techniques. The analyses suggest that 79-93% of Hg in the sediment samples is in the form of insoluble sulfides (βHgS metacinnabar); however significant masses of more-soluble Hg phases (0.4-33 μg/g) are also present. Simulated erosion events resulted in elevated concentrations of Hg in the river water up to 80 μg/L. There was no correlation between the mass of water-soluble Hg in the sediment and the concentrations of Hg released in the river water following sediment suspension. Column transport experiments were conducted to assess Hg release from the sediment under water:sediment ratios typical of those that might occur at the bottom or in the banks of the river. Concentrations of Hg in the 0.45 μm-filtered fraction of the effluent varied from 0.15 μg/L for samples collected from the base of the riverbank to 8 μg/L for samples collected from the top of the riverbank. Filter size-fractionation of water column effluent suggested approximately 50% of the leached Hg was present in the dissolved phase, with the remainder in particulate form. Riverbank sediments were amended with various types of reactive material including complexing agents, reductants and charcoals. Batch experiments indicate that the mass of Hg released from the sediment could be lessened by 64-99% with the addition of reactive media, and that aerating and re-wetting the sediment amendments resulted in equal or greater removal of Hg from the water. The greatest removal of Hg was observed when more amendment was added to the sediment, however the greatest Hg uptake capacity (Hg captured per mass of material) was observed for the lowest doses of reactive media. The Hg uptake capacities ranged from 35-500 ng/g and were greatest for treatment of water with elevated concentrations of Hg. The Hg uptake capacities were a function of the Hg concentrations in the untreated water, and were generally lower relative to values reported in the literature. Column studies were used to simulate the flow of river water containing elevated concentrations of Hg through a reactive zone containing a charred hardwood material. The concentration of filtered Hg was < 120 ng/L for treated effluent from columns, resulting in > 98% removal of Hg from the water. Assuming that the majority of removal occurred within the initial 2-3 cm along the length of the column, the calculated uptake of Hg2+ ranged from 1.2-7.7 μg/g. The uptake capacity for charred hardwood material was much greater for the column experiments relative to the batch experiments, suggesting that the uptake capacity is limited by Hg loading. The chemical composition of the treated column effluent was similar to the South River water, and suggests the material did not add or remove significant constituents during the course of these experiments.

Elevated concentrations of mercury (Hg) in aquatic systems can be a threat to ecosystems and human health. Mercury-bearing sediment particles from eroding riverbanks can be an ongoing source of bioavailable Hg to aquatic ecosystems. Hyporheic zones in particular can be important sources of both inorganic and organic-complexed Hg, which can be rapidly transported to adjacent surface waters. The objective of this study was to investigate the release and treatment of dissolved and particle-bound Hg in water derived from the riverbank sediments of the South River, Virginia. The solid-phase forms of Hg in riverbank sediment samples were characterized by sequential extraction and synchrotron based techniques. The analyses suggest that 79-93% of Hg in the sediment samples is in the form of insoluble sulfides (βHgS metacinnabar); however significant masses of more-soluble Hg phases (0.4-33 μg/g) are also present. Simulated erosion events resulted in elevated concentrations of Hg in the river water up to 80 μg/L. There was no correlation between the mass of water-soluble Hg in the sediment and the concentrations of Hg released in the river water following sediment suspension. Column transport experiments were conducted to assess Hg release from the sediment under water:sediment ratios typical of those that might occur at the bottom or in the banks of the river. Concentrations of Hg in the 0.45 μm-filtered fraction of the effluent varied from 0.15 μg/L for samples collected from the base of the riverbank to 8 μg/L for samples collected from the top of the riverbank. Filter size-fractionation of water column effluent suggested approximately 50% of the leached Hg was present in the dissolved phase, with the remainder in particulate form. Riverbank sediments were amended with various types of reactive material including complexing agents, reductants and charcoals. Batch experiments indicate that the mass of Hg released from the sediment could be lessened by 64-99% with the addition of reactive media, and that aerating and re-wetting the sediment amendments resulted in equal or greater removal of Hg from the water. The greatest removal of Hg was observed when more amendment was added to the sediment, however the greatest Hg uptake capacity (Hg captured per mass of material) was observed for the lowest doses of reactive media. The Hg uptake capacities ranged from 35-500 ng/g and were greatest for treatment of water with elevated concentrations of Hg. The Hg uptake capacities were a function of the Hg concentrations in the untreated water, and were generally lower relative to values reported in the literature. Column studies were used to simulate the flow of river water containing elevated concentrations of Hg through a reactive zone containing a charred hardwood material. The concentration of filtered Hg was < 120 ng/L for treated effluent from columns, resulting in > 98% removal of Hg from the water. Assuming that the majority of removal occurred within the initial 2-3 cm along the length of the column, the calculated uptake of Hg2+ ranged from 1.2-7.7 μg/g. The uptake capacity for charred hardwood material was much greater for the column experiments relative to the batch experiments, suggesting that the uptake capacity is limited by Hg loading. The chemical composition of the treated column effluent was similar to the South River water, and suggests the material did not add or remove significant constituents during the course of these experiments.

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