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A Hydrograph-Based Prediction of Meander Migration

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A Hydrograph-Based Prediction of Meander Migration A HYDROGRAPH-BASED PREDICTION OF MEANDER MIGRATION A Dissertation by WEI WANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2006 Major Subject: Civil Engineering A HYDROGRAPH-BASED PREDICTION OF MEANDER MIGRATION A Dissertation by WEI WANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Jean-Louis Briaud Committee Members, Hamn-Ching Chen Kuang-An Chang Hongbin Zhan Head of Department, David Rosowsky May 2006 Major Subject: Civil Engineering iii ABSTRACT A Hydrograph-based Prediction of Meander Migration. (May 2006) Wei Wang, B.S., Tongji University, Shanghai, China; M.S., Tongji University, Shanghai, China Chair of Advisory Committee: Dr. Jean-Louis Briaud 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 iv 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. v ACKNOWLEDGMENTS I am beholden to my advisor, Dr. Jean-Louis Briaud, for the guidance and wonderful working environment he has provided. Dr. Briaud is a forerunner in many fields of Geotechnical Engineering and scour related subjects and has made significant contributions in adding to the greatness of the Department of Civil Engineering at Texas A&M University. I want to express my respect and admiration to Dr. Briaud for his achievements as a professional and for his success as a family man. Dr. Briaud belongs to the category of people who are smart and nice. I want to thank Dr. Hamn-Ching Chen and Dr. Kuang-An Zhang, who are team members of the research project, for their guidance in my work and their insights about the project. I also want to thank Dr. Hongbin Zhan for his consistent support and critical review of my dissertation. Many thanks go to Johnnie Reed of Hydraulic Engineering Lab, Matt Potter and Jeff Perry of the High-Bay Lab. They have graciously provided help in the setting up and running of flume test. I applied to Texas A&M University because a certain person was here. He has been impressive for his exemplary work ethic and outstanding achievements. I have been enjoying discussions with him on many issues for years. My deep appreciation goes to this good friend of mine and my college classmate, Yiwen Cao. I wish to express special appreciation to my friends and fellow students: Yuanyuan Ding, Diqing Lou, Dr. Ya Li, Dr. Xiong Zhang, Juanyu Liu, Dr. Yanfeng Li, Dr. Jun Wang, Zhigang Yao, Namgyu Park, Po-Hung Yeh, Xiaoyan Long, Junying Pan, Dr. Wentao Dai, Dr. Han Shi, Hongrui Hu, Xingnian Chen, Jinquan Zhong. It has been a wonderful experience to work and study with them. Ya Li has been a great help to my flume test. The discussions with Xiong Zhang helped me better understand unsaturated soil mechanics. I also wish to thank Jinming Xu from the Department of Mechanical Engineering, Guobin He and Guangtong Cao from the Department of Computer Science, and Shanfeng Chen and Xiang Lu from the Department of Electrical Engineering for their help in Visual C++ programming. vi I want to acknowledge with deep appreciation the efforts in proofreading this dissertation provided by my friends: Stanley Mathew, Juanyu Liu, Jinquan Zhong, Li Liu and Ermilo Richer. Stan and Juanyu proofread several chapters and their work was very impressive. Jinquan’s advice on both the probabilistic background about Chapter VII and my English language is appreciated. vii TABLE OF CONTENTS Page ABSTRACT ..................................................................................................................... iii ACKNOWLEDGMENTS..................................................................................................v TABLE OF CONTENTS.................................................................................................vii LIST OF FIGURES............................................................................................................x LIST OF TABLES ..........................................................................................................xvi CHAPTER I INTRODUCTION TO AND FUNDAMENTAL CONCEPTS OF MEANDER MIGRATION...........................................................................................................1 1.1 Introduction ...........................................................................................1 1.2 Fundamental Concept about Meander Migration...................................4 1.3 Factors Affecting Meander Migration..................................................13 II EXISTING KNOWLEDGE OF MEANDER MIGRATION ................................15 2.1 General Approaches .............................................................................15 2.2 Selected Empirical Methods.................................................................16 2.3 Selected Numerical Methods ...............................................................30 2.4 SRICOS-EFA Method..........................................................................39 III RESEARCH OBJECTIVES AND METHODOLOGY.........................................49 3.1 Research Objectives .............................................................................49 3.2 Methodology ........................................................................................49 IV FLUME TEST.......................................................................................................54 4.1 Experimental Setup..............................................................................54 4.2 Measurement of Velocity and Geometry Change................................58 4.3 Calibration of the Flow Meter..............................................................63 4.4 Test Procedure......................................................................................67 4.5 Sample Test Output..............................................................................69 V THE APPLICATION OF SRICOS-EFA METHOD IN THE PREDICTION OF MEANDER MIGRATION ...................................................................................71 viii CHAPTER Page 5.1 The Existence of Maximum Migration Mmax .......................................71 5.2 Developing Equations for Mmax ...........................................................74 5.3 Developing Equations for τmax .............................................................75 5.4 Application of the SRICOS-EFA Method ...........................................84 VI GEOMETRY STUDY ..........................................................................................87 6.1 Fit a Circle for a Given Group of Points ..............................................87 6.2 Calculate Radius of Curvature of Each Point on a Curve ....................92 6.3 Identify Bends for Which Circles Will be Fitted ...............................100 6.4 At a Certain Bend Find the Best Fit Circle ........................................104 6.5 Calculate Bend Angle.........................................................................111
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