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.
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.
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
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:
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:
Download or read book Establish Guidance for Soils Properties based Prediction of Meander Migration Rate written by and published by . This book was released on 2007 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several solutions for predicting the movement of meanders have been proposed in the past. This report shows these solutions to be unreliable. The solution outlined in this report considers soil erodibility as an independent parameter influencing meander migration. Other conventional parameters such as flow velocity, meander radius of curvature, river width, and others are part of the proposed solution. Through a combination of well-instrumented large-scale flume tests, quality numerical simulations, and fundamental laboratory erosion tests, a simple and reliable solution is developed.
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.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluvial Processes in River Engineering written by Howard H. Chang and published by Krieger Publishing Company. This book was released on 2008 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Riparian Areas written by National Research Council and published by National Academies Press. This book was released on 2002-10-10 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Clean Water Act (CWA) requires that wetlands be protected from degradation because of their important ecological functions including maintenance of high water quality and provision of fish and wildlife habitat. However, this protection generally does not encompass riparian areasâ€"the lands bordering rivers and lakesâ€"even though they often provide the same functions as wetlands. Growing recognition of the similarities in wetland and riparian area functioning and the differences in their legal protection led the NRC in 1999 to undertake a study of riparian areas, which has culminated in Riparian Areas: Functioning and Strategies for Management. The report is intended to heighten awareness of riparian areas commensurate with their ecological and societal values. The primary conclusion is that, because riparian areas perform a disproportionate number of biological and physical functions on a unit area basis, restoration of riparian functions along America's waterbodies should be a national goal.
Download or read book Texas Riparian Areas written by Nicole A. Davis and published by Texas A&M University Press. This book was released on 2014-01-29 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: Riparian areas—transitional zones between the aquatic environments of streams, rivers, and lakes and the terrestrial environments on and alongside their banks—are special places. They provide almost two hundred thousand miles of connections through which the waters of Texas flow. Keeping the water flowing, in as natural a way as possible, is key to the careful and wise management of the state’s water resources. Texas Riparian Areas evolved from a report commissioned by the Texas Water Development Board as Texas faced the reality of over-allocated water resources and long-term if not permanent drought conditions. Its purpose was to summarize the characteristics of riparian areas and to develop a common vocabulary for discussing, studying, and managing them. To learn more about The Meadows Center for Water and the Environment, sponsors of this book's series, please click here.
Download or read book Preliminary Determination of Epicenters written by and published by . This book was released on 1970 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of urban development on stream ecosystems in nine metropolitan study areas across the United States written by James F. Coles and published by . This book was released on 2012 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mississippi River Water Quality and the Clean Water Act written by National Research Council and published by National Academies Press. This book was released on 2008-02-08 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Mississippi River is, in many ways, the nation's best known and most important river system. Mississippi River water quality is of paramount importance for sustaining the many uses of the river including drinking water, recreational and commercial activities, and support for the river's ecosystems and the environmental goods and services they provide. The Clean Water Act, passed by Congress in 1972, is the cornerstone of surface water quality protection in the United States, employing regulatory and nonregulatory measures designed to reduce direct pollutant discharges into waterways. The Clean Water Act has reduced much pollution in the Mississippi River from "point sources" such as industries and water treatment plants, but problems stemming from urban runoff, agriculture, and other "non-point sources" have proven more difficult to address. This book concludes that too little coordination among the 10 states along the river has left the Mississippi River an "orphan" from a water quality monitoring and assessment perspective. Stronger leadership from the U.S. Environmental Protection Agency (EPA) is needed to address these problems. Specifically, the EPA should establish a water quality data-sharing system for the length of the river, and work with the states to establish and achieve water quality standards. The Mississippi River corridor states also should be more proactive and cooperative in their water quality programs. For this effort, the EPA and the Mississippi River states should draw upon the lengthy experience of federal-interstate cooperation in managing water quality in the Chesapeake Bay.
Download or read book River Meanders written by Luna Bergere Leopold and published by . This book was released on 1964 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Urban Stormwater Management in the United States written by National Research Council and published by National Academies Press. This book was released on 2009-03-17 with total page 611 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rapid conversion of land to urban and suburban areas has profoundly altered how water flows during and following storm events, putting higher volumes of water and more pollutants into the nation's rivers, lakes, and estuaries. These changes have degraded water quality and habitat in virtually every urban stream system. The Clean Water Act regulatory framework for addressing sewage and industrial wastes is not well suited to the more difficult problem of stormwater discharges. This book calls for an entirely new permitting structure that would put authority and accountability for stormwater discharges at the municipal level. A number of additional actions, such as conserving natural areas, reducing hard surface cover (e.g., roads and parking lots), and retrofitting urban areas with features that hold and treat stormwater, are recommended.
Download or read book Federally Coordinated Program of Highway Research and Development written by and published by . This book was released on with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
