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Observation Method To Predict Meander Migration And Vertical Degradation Of Rivers
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Book Synopsis Observation Method to Predict Meander Migration and Vertical Degradation of Rivers by : Axel M. Montalvo Bartolomei
Download or read book Observation Method to Predict Meander Migration and Vertical Degradation of Rivers written by Axel M. Montalvo Bartolomei and published by . This book was released on 2014 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Meander migration and vertical degradation of river bed are processes that have been studied for years. These two erosion controlled processes consist of the gradual change of the geometry of the river due to the flow of water eroding the soil. This erosion may cause a shift that could be a threat to existing bridges, highways, and useful lands. Different methods have been proposed to make predictions of the behavior of rivers with respect to these processes. Many of these methods are used to predict the migration rate and the final position of the bankline or centerline of a river, assuming that the erosion rate is constant for a certain time. However, most of these methods ignore one of the three general processes of meander migration and vertical degradation: geometry, flow, and soil. Therefore, there is need for a method that can accurately predict the amount of erosion that may occur in rivers. Six different sites in Texas were selected for this project. Four of the selected rivers have meander migration problems, and two rivers have vertical degradation problems. Each river has shown erosion problems that have been a threat to the bridges, roads or farm lands. A new method, called the Observation Method, was developed to predict meander migration and vertical degradation by using geometry, water flow, and soil erodibility. Aerial photos and maps from different years were obtained to study the change of the geometry of the rivers. River hydrographs were obtained from the U.S. Geological Survey to estimate the river velocity from daily flow. Soil samples from each site were obtained for laboratory testing, using the Erosion Function Apparatus. A code was written in MATLAB and Excel to estimate the critical velocity by using a model based on the erosion function obtained from the erosion tests. It is important to know where the river was and its history to be able to predict where the river will be. The erosion of each river from the six sites was estimated using the model and predictions were made for 10 years after the last observation for each case. This method proved to be a simple and quick way to obtain results for the movement of one point of the river. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152490
Book Synopsis Prediction of Meander Migration for Four Rivers in Texas at Roadway Crossings by : Fahmidah Ummul Ashraf
Download or read book Prediction of Meander Migration for Four Rivers in Texas at Roadway Crossings written by Fahmidah Ummul Ashraf and published by . This book was released on 2013 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: River meandering can endanger the hydraulic structures by lateral expansion and down-valley translation of meander bends. In this study, the RVR Meander model was used to predict the meander migration for four bridge crossings in the state of Texas, USA. The bridge crossings are SH 105 at the Brazos River, FM 787 at the Trinity River, US 90 at the Nueces River and SH 63 at the Sabine River. A widely used migration coefficient approach developed by Ikeda et al. (1981) was adopted, which relates migration rate linearly to vertically-averaged near bank excess velocity through the use of a coefficient of bank erosion. This study estimates erosion coefficient values for eroded banks from measured long term migration rates and computed near bank excess velocities. The values of erosion coefficients are calibrated using the RVR Meander model with the least prediction error. The predicted planform evolution using the model suggests that the migration coefficient approach used in the model can capture the growth of meander bends if they do not change the migration direction. In general, the model can predict migration well in lateral and downstream direction. This study also attempts to examine the extent to which erosion coefficient depends on resistance of bank material to fluvial erosion. Erosion Function Apparatus (EFA) erodibility values represent the resistance of bank material to fluvial erosion. At the upstream bends adjacent to the road crossings for which both erosion coefficients and EFA erodibility values were obtained, it was found that erodibility values follow the trend of erosion coefficients, unless significant hydraulic or geomorphic changes occurred in the watershed and in the channel due to the human activities. It opens up the possibility that erosion coefficients may be estimated directly from the bank material properties instead of using the historical maps. This suggests that for long term (several decades) meander migration riparian vegetation is not a major controlling factor. This hypothesis requires further testing with data sets from other road crossings over rivers.
Book Synopsis Predicting Meander Migration of the Sacramento River, CA by : Jessica Louise Thomas
Download or read book Predicting Meander Migration of the Sacramento River, CA written by Jessica Louise Thomas and published by . This book was released on 2001 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mechanics and Modeling of River Meander Migration by : Eric Walsh Larsen
Download or read book Mechanics and Modeling of River Meander Migration written by Eric Walsh Larsen and published by . This book was released on 1995 with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Evaluating River Restoration Design Using a Meander Migration Model on the Trinity River, California by : Alex Jeremiah Young
Download or read book Evaluating River Restoration Design Using a Meander Migration Model on the Trinity River, California written by Alex Jeremiah Young and published by . This book was released on 2006 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Meander Migration written by J.-L. Briaud and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Hydrograph-based Prediction of Meander Migration by : Wei Wang
Download or read book A Hydrograph-based Prediction of Meander Migration written by Wei Wang and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 M[subscript]max equation and [tau][subscript]max equation are developed. Uncertainties in theparameters 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 [tau] [subscript]max 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.
Book Synopsis A Prediction of Meander Migration Based on Large-scale Flume Tests in Clay by : Namgyu Park
Download or read book A Prediction of Meander Migration Based on Large-scale Flume Tests in Clay written by Namgyu Park and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Meander migration is a complex and dynamic process of the lateral movement of a river due to erosion on one bank and deposition on the opposite bank. As a result, the channel migrates in a lateral direction, which might be a major concern for the safety of bridges during their life span of 75 years. Although there are several existing models for predicting meander migration of a river, none of them are based on the physical model tests on a specific type of soil. A total of eight flume tests are conducted to develop a prediction equation of meander migration in clay. The test results of migration rate follow a hyperbolic function, and spatial distribution of the maximum migration distance is fitted with the Pearson IV function. The proposed equations of the initial migration rate and the maximum migration distance, obtained by a multiple regression technique, are validated with the laboratory data. A new methodology for risk analysis is developed to process a number of predicted channel locations based on each future hydrograph generated in such a way that all the hydrographs have the same probability of occurrence. As the output from risk analysis, a CDF map is created for a whole river representing a general trend of migration movement along with the probability associated with new location of the river. In addition, a separate screen is generated with a CDF plot for a given bridge direction so that bridge engineers can read a specific migration distance along the bridge corresponding to the target risk level (e.g. 1 %). The newly developed components through this research are incorporated with the other components in the MEANDER program which is a stand-alone program and the final outcome of the research team. Verification study of the MEANDER program is conducted with full-scale field data at the Brazos River at SH 105, Texas. The prediction results matched quite well with the measured field data. However, a more extensive verification study for other sites is highly recommended.
Book Synopsis Predicting Meander Migration by : Jean-Louis Briaud
Download or read book Predicting Meander Migration written by Jean-Louis Briaud and published by . This book was released on 2001 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis River Meandering by : Syunsuke Ikeda
Download or read book River Meandering written by Syunsuke Ikeda and published by . This book was released on 1989 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis River Meanders--theory of Minimum Variance by : Walter Basil Langbein
Download or read book River Meanders--theory of Minimum Variance written by Walter Basil Langbein and published by . This book was released on 1966 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The geometry of a meander is that of a random walk whose most frequent form minimizes the sum of the squares of the changes in direction in each unit length. Changes in direction closely approximate a sine function of channel distance. Depth, velocity, and slope are adjusted so as to decrease the variance of shear and the friction factor in a meander over that in an otherwise comparable straight reach of the same river.
Book Synopsis Meandering Valleys and Underfit Rivers by : William Morris Davis
Download or read book Meandering Valleys and Underfit Rivers written by William Morris Davis and published by . This book was released on 1914 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis River Meandering by : Charles Morelle Elliott
Download or read book River Meandering written by Charles Morelle Elliott and published by . This book was released on 1984 with total page 1062 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection contains 91 papers on river behavior presented at Rivers '83, held in New Orleans, Louisiana, October 24-26, 1983.
Book Synopsis Quantifying the Connections Between Flow, Bar Deposition, and Meander Migration in Large Gravel-bed Rivers by : Candice R. Constantine
Download or read book Quantifying the Connections Between Flow, Bar Deposition, and Meander Migration in Large Gravel-bed Rivers written by Candice R. Constantine and published by . This book was released on 2006 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Predicting channel migration is a key component of designing plans for river management and restoration. Fundamentally, the lateral migration rate depends on the rate of excavation of the outer bank toe. This rate is a function of bank resistance to erosion, flow velocity, bend geometry, and sediment transport and storage. Although it is certain that all these variables play some role in determining migration rates in gravel-bed rivers, the importance of sediment storage in particular has not been thoroughly investigated. Currently employed meander migration models are driven by curvature effects on near-bank flow and account for differences in bank erodibility through use of a calibrated bank erosion coefficient. Despite increasing application of such models to sensitive management problems, it remains unclear how the coefficient varies with properties of the channel and to what extent it incorporates the effects of changes in bed-material storage on migration rate.
Book Synopsis Analysis and Modelling of River Meandering by : Alessandra Crosato
Download or read book Analysis and Modelling of River Meandering written by Alessandra Crosato and published by IOS Press. This book was released on 2008 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines the morphological changes of non-tidal meandering rivers at the spatial scale of several meanders. With this purpose, a physics-based mathematical model, MIANDRAS, has been developed for the simulation of the medium-term to long-term evolution of meandering rivers. Application to several real rivers shows that MIANDRAS can properly simulate both equilibrium river bed topography and planimetric changes. Three models of different complexity can be obtained by applying different degrees of simplification to the equations. These models, along with experimental tests and field data, constitute the tools for several analyses. At conditions of initiation of meandering, it is found that river bends can migrate upstream and downstream. This depends on meander wave length and width-to-depth ratio, irrespective of whether the parameters are in the subresonant or the superresonant range.
Book Synopsis Curvature-Migration Relations and Planform Dynamics of Meandering Rivers by :
Download or read book Curvature-Migration Relations and Planform Dynamics of Meandering Rivers written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Valley Evolution by Meandering Rivers by : Ajay Brian Sanjay Limaye
Download or read book Valley Evolution by Meandering Rivers written by Ajay Brian Sanjay Limaye and published by . This book was released on 2015 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluvial systems form landscapes and sedimentary deposits with a rich hierarchy of structures that extend from grain- to valley scale. Large-scale pattern formation in fluvial systems is commonly attributed to forcing by external factors, including climate change, tectonic uplift, and sea-level change. Yet over geologic timescales, rivers may also develop large-scale erosional and depositional patterns that do not bear on environmental history. This dissertation uses a combination of numerical modeling and topographic analysis to identify and quantify patterns in river valleys that form as a consequence of river meandering alone, under constant external forcing. Chapter 2 identifies a numerical artifact in existing, grid-based models that represent the co-evolution of river channel migration and bank strength over geologic timescales. A new, vector-based technique for bank-material tracking is shown to improve predictions for the evolution of meander belts, floodplains, sedimentary deposits formed by aggrading channels, and bedrock river valleys, particularly when spatial contrasts in bank strength are strong. Chapters 3 and 4 apply this numerical technique to establishing valley topography formed by a vertically incising, meandering river subject to constant external forcing -- which should serve as the null hypothesis for valley evolution. In Chapter 3, this scenario is shown to explain a variety of common bedrock river valley types and smaller-scale features within them -- including entrenched channels, long-wavelength, arcuate scars in valley walls, and bedrock-cored river terraces. Chapter 4 describes the age and geometric statistics of river terraces formed by meandering with constant external forcing, and compares them to terraces in natural river valleys. The frequency of intrinsic terrace formation by meandering is shown to reflect a characteristic relief-generation timescale, and terrace length is identified as a key criterion for distinguishing these terraces from terraces formed by externally forced pulses of vertical incision. In a separate study, Chapter 5 utilizes image and topographic data from the Mars Reconnaissance Orbiter to quantitatively identify spatial structures in the polar layered deposits of Mars, and identifies sequences of beds, consistently 1-2 meters thick, that have accumulated hundreds of kilometers apart in the north polar layered deposits.
