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Meander migration is a process in which water flow erodes soil on one bank and deposits it on the opposite bank creating a gradual shift of the bank line over time. For bridges crossing such a river, the soil foundation of the abutments may be eroded away before the designed lifetime is reached. For highways parallel to and close to such a river, the whole road may be eaten away. This problem is costing millions of dollars to TxDOT in protection of affected bridges and highway embankments. This research is aimed at developing a methodology which will predict the possible migration of a meander considering the design life of bridges crossing it and highways parallel to it. The approaches we use are experimental tests, numerical simulation, modeling of migration, risk analysis, and development of a computer program. Experimental tests can simulate river flow in a controlled environment. Influential parameters can be chosen, adjusted, and varied systematically to quantify their influence on the problem. The role of numerical simulation is to model the flow field and the stress field at the soil-water interface. Migration modeling is intended to integrate the results of experimental tests and numerical simulations and to develop a model which can make predictions. The Hyperbolic Model is used and its two major components Mmax equation and τmax equation are developed. Uncertainties in the parameters used for prediction make deterministic prediction less meaningful. Risk analysis is used to make the prediction based on a probabilistic approach. Hand calculation is too laborious to apply these procedures. Thus the development of a user friendly computer program is needed to automate the calculations. Experiments performed show that the Hyperbolic Model matches the test data well and is suitable for the prediction of meander migration. Based on analysis of shear stress data from numerical simulation, the τmax equation was derived for the Hyperbolic Model. Extensive work on the simplification of river geometry produced a working solution. The geometry of river channels can be automatically simplified into arcs and straight lines. Future hydrograph is critical to risk analysis. Tens of thousands of hydrographs bearing the same statistical characteristics as in history can be generated. The final product that can be directly used, the MEANDER program, consists of 11,600 lines of code in C++ and 2,500 lines of code in Matlab, not including the part of risk analysis. The computer program is ready for practice engineers to make predictions based on the findings of this research.

Doctor of Philosophy / Environmental Design and Planning Program / Timothy D. Keane / The original purpose of this investigation was to develop streambank erosion prediction curves for Northeast Kansas streams. Rosgen's (2001, 2006) methods were employed and eighteen study banks were measured and monitored over a four-year period, summer 2007 through summer 2010. At each study bank, a toe pin and two to three bank pins were set at a recorded longitudinal profile station of the stream. Vertical and horizontal measures from the toe pin to the bank face were taken each summer, 2007 as the baseline measure and 2008 - 2010 as bank change years. Bank profiles were overlaid to gain insight into bank area lost or gained due to erosional or depositional processes. A Bank Erosion Hazard Index (BEHI) and Near Bank Stress (NBS) combination rating was assessed and calculated for each study bank during the initial survey of 2007. The streambanks experienced varied erosion rates for similar BEHI/NBS combinations producing R2 values from 0.43 as the High/Very High BEHI rating and 0.80 as the Moderate BEHI rating. In addition, Moderate BEHI ratings provided higher erosion rates than the High/Very High BEHI rating and curves intersected at lower NBS ratings, suggesting a discrepancy in the fit of the model used in the Northeast Kansas region and conditions. In this light, modification of the BEHI model was evaluated and variables were assessed in the model for additional influence exerted in the Northeast Kansas region. Vegetation seemed to provide the most influence to bank resistance and was more closely evaluated. Banks with and without woody riparian vegetation were then plotted against BEHI and NBS values, as banks lacking woody vegetation eroded at higher rates. This study's findings can allow us to calibrate the BEHI model according to woody vegetation occurrence levels along streambanks in the Black Vermillion watershed. Modifications regarding vegetation occurrence of the BEHI model was completed and the results of these modifications generated R2 values of 0.78 for High/Very High BEHI and 0.82 for Moderate BEHI ratings. High/Very High ratings provided higher predicted erosion rates than Moderate ratings, while the curve slopes did not intersect at lower NBS ratings.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18560号 / 工博第3921号 / 新制||工||1602(附属図書館) / 31460 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 中川 一, 教授 藤田 正治, 准教授 川池 健司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Increased sediment loads within river catchments have well-documented detrimental effects on water quality and catchment management plans are required to address reduction and mitigation of these problems. In order to do this it is essential that tools are available that deliver reliable sediment generation data at appropriate temporal and spatial scales. Currently, most sediment generation models do not include bank erosion individually as a sediment source. Therefore, to enable improved accuracy in predictions of future sediment pressures under environmental change, explicit modelling of the rates of sediment production by the bank erosion is required to provide a more complete representation of the catchment sediment budget. In this study, an existing prototype national bank erosion index has been refined. Using Geographical Information Systems (GIS) digitised overlays, channel migration rates were calculated for several UK catchments. Relationships between the rate of channel bank erosion and factors controlling the rates of channel migration were investigated, including channel sinuosity, slope, upstream catchment area, and restriction of migration due to valley width. Significant correlations between bank erosion and sinuosity, upstream area and channel confinement were observed. The non-linear influence of channel planform geometry (curvature and sinuosity) on migration rates was further investigated using an existing meander migration model. A new bank erosion model was developed to incorporate the influence of both channel confinement and sinuosity. As the model incorporates the key physical controls on bank erosion, hence it is expected that it will have wide applicability in catchment- to national-scale bank erosion assessment. A computationally efficient catchment routing model was developed. Data output from a newly developed catchment overland sediment and runoff estimation model (ADAS APT) was used as input to the routing model. The newly developed bank erosion model and an existing floodplain sedimentation model were incorporated within the routing methodology to provide a catchment sediment budget model. The model was applied to the Exe catchment, Devon, UK and validated against observational data. Model estimations of annual sediment generation through bank erosion, sediment deposition on floodplains, and sediment load at the catchment outlet were within the range of observed values. The catchment sediment budget model developed in this thesis provides a more comprehensive representation of catchment sediment processes than existing alternative methodologies.

Fluvial erosion incites significant bridge scour and large-scale bank erosion causing estimated $1.1 billion damage in the Midwest. Conventional, manual, field monitoring methods, typically erosion pins, cross-section resurveys or terrestrial photogrammetry, used to monitor fluvial erosion rates merely provide a net change in bank surface retreat since the previous measurement. If mass wasting has occurred, the ongoing fluvial erosion would be masked. Erosion event timing, and the precise bank response to individual flow or flow hydrograph changes, is generally uncertain. Thus, a technique that automatically quantifies bank erosion on a continuous basis is needed. This study will monitor the bank response to individual flow (i.e., fluvial erosion) using the Photo-Electronic Erosion Pin (PEEP) sensors in Clear Creek Iowa. It attends to monitor a full episode of bank change, including event timings and magnitude information for specific erosion and deposition events, which can be compared to flow discharges and hydrographs. If exploited, this method can lead to more detailed analysis of bank erosion related to temporal fluctuations in the suspected hydraulic forces.

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