Scour Evaluation at the Nile River Bends on Rosetta Branch

Benha University Faculty of Engineering, Shobra Civil Engineering Department

A Thesis Submitted in Partial Fulfillment of the Requirements For the MSc Degree in Civil Engineering

Submitted By Fatma Samir Ahmed Saad B.Sc. in Civil Engineering (2010)

Supervised By

Prof. Dr. Gamal Helmy Mohamed Elsaeed Professor of Water Resources, Civil Engineering Dept. Faculty of Engineering, Shobra, Benha University Dr. Hossam El-Din Mohamed El -Sersawy Associate Prof, Nile Research Institute. National Water Research Center

Dr. Mohammad Mahmoud Mohammed Ibrahim Lecturer, Civil Engineering Dept.

Faculty of Engineering, Shobra, Benha University

Cairo – Egypt March 2015

Benha University Faculty of Engineering, Shobra Civil Engineering Department

APPROVAL SHEET

Scour Evaluation at the Nile River Bends on Rosetta Branch

Examiners Committee

Name and occupation Signature

Prof. Dr. Nahla M. AbdelHamid AboulAtta Professor of Irrigation design, Head of the Irrigation & Hydraulics Dept,

Faculty of Engineering, Ain Shams University

Prof. Dr. Medhat Saad Aziz

Director, Nile Research Institute

National Water Research Center

Prof. Dr. Gamal Helmy Mohamed Elsaeed

Professor of Water Resources, Civil Engineering Dept, Faculty of Engineering, Shobra, Benha University

Cairo – Egypt March 2015

Benha University Faculty of Engineering, Shobra Civil Engineering Department

DECLARATION

I declare that this thesis entitled “Scour Evaluation at the Nile River Bends on Rosetta Branch” is the result of my own research except as cited in the references. It is being submitted to the degree of Master of Science of Philosophy in the Faculty of Engineering at Shoubra, Benha University. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.

Signature : ………………………………. Name : …………………………………… Date : ……………………………………..

Cairo – Egypt March 2015

To My beloved parents, my sister and brother Aalaa & Ahmed

ACKNOWLEDGEMENTS

First of all, I wish to give all my thanks to God for the completion of this work

I wish to express my deepest sense of gratitude and sincerest appreciation to Dr. Gamal Helmy El-Saied, Irrigation and Hydraulics Department, Faculty of Engineering - Shobra, for his excellent advice enthusiastic guidance and continuous encouragement towards the successful completion of this study.

Special thanks to Dr. Hossam El-Din Mohamed El-Sersawy, Associate Professor, Nile Research Institute, National Water Research Center, for his help, effort and support me throughout this study.

Special thanks also to Dr. Mohamed Ibrahim, Researcher, Faculty of Engineering - Shobra, for his outstanding valuable help and supervision.

Special thanks are due to Dr. Medhat Aziz, Director, Nile Research Institute for his continuous support and encouragement through this research and for his help in providing the materials for conducting this research and valuable comments and discussions.

I would like to express my thanks to colleagues in Nile Research Institute who helped me in the preparation of field measurements.

Last but not least I wish to express my deepest thanks, gratitude, and appreciation to my family for their love, warm caring, support, and, great patience throughout the time of this study.

Finally, I want to thank everyone who helped or advised me during my work or even wished me good luck.

TABLE OF CONTENTS LIST OF FIGURES VI LIST OF TABLES XI LIST OF SYMBOLS XII LIST OF ABBREVIATIONS XV ABSTRACT XVI

Chapter 1 Introduction

1-1 General 1 1-2 Problem Definition 2 1-3 Study Objectives 2 1-4 Methodology and Scope of Work 2 1-5 Thesis Layout 3

Chapter 2 Literature Review

2-1 Introduction 5 2-2 The Nile River 5 2-3 Rosetta Branch 6 2-4 Basic Principals and Concepts 7 2-4-1 Channel Types 7 2-5 Meander Characteristics 9 2-6 Scour Holes 12 2-7 Types of Models 19 2-7-1 Physical Models 19 2-7-2 Numerical Models 19 2-8 Previous Works in Morphological Changes in Rivers 20 2-9 Dredging 23 2-10 Sediment Transport 24 2-10-1 Factors Affecting Sediment Transport 24 2-10-1-1 Bed Shear Stress 24 2-10-1-2 Incipient Velocity 26 2-11 Bank Revetment 28

2-11-1 Stone protection 29 2-11-2 Design of Stone 31 2-11-3 Filter Design 32

Chapter 3 Data Collection

3-1 Introduction 34 3-2 Site Description 34 3-3 Hydrographic Survey 35 3-4 Velocity Measurements 37 3-5 Bed Material samples 39 3-6 Hydrological Data 43

Chapter 4 Mathematical Model Preparation

4-1 General 46 4-2 “SMS” 2-D Model Formulation 48 4-2-1 Model Description 48 4-2-2Governing Equations 48 4-2-3 Numerical Techniques and Limitation 52 4-3 Model Preparation 53 4-3-1 Data Assignment 53 4-3-1-1 Roughness estimation (Manning Coefficient) 55 4-3-2 Network Design 57 4-3-3 Calibration Results 62 4-3-4 Verification Results 64 4-4 Sensitivity Analysis 67 4-5 Summary 68

Chapter 5 Morphological Changes

5-1 Introduction 69 5-2 Study Reach General Description 69

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5-3 Bed Elevation Contour Map at Years 1982, 1998, 2003 and 2006 71 5-4 Morphology Comparison of Years 1982, 1998, 2003 and 2006 72 5-4-1 Comparison of Bed Profiles and Thalweg Lines 72 5-5 Scour Holes in the Area of Study 75

Chapter 6 Model Application and Scour Prediction

6-1 Model Application 87 6-1-1 Model Runs for Minimum Discharge 87 6-1-2 Average Discharge 89 6-1-3 Maximum Discharge 91 6-1-4 Emergency Discharge 93 6-2 Scour Prediction 95 6-2-1 The Local Scour at Bridge Piers Prediction 96 6-2-2 Contraction Scour 99 6-2-3 Bend Scour 100 6-2-4 General Scour 101 6-2-5 Evaluation of Total Scour 103

Chapter 7 Alternative Solutions and Testing Results

7-1 Introduction 108 7-2 The Modeled Reach 108 7-3 Simulation of the Proposed Solutions and Results 109 7-3-1 The First Alternative Simulation 109 7-3-1-1 First Alternative Model Run Results 111 7-3-2 The Second Alternative Simulation 117 7-3-2-1 Second Alternative Model Run Results 119 7-3-3 Comparisons of Bed Shear Stress between the Two Alternatives 127 7-4 Riprap Design 133

Chapter 8 Conclusion & Recommendations

9-1 Summary 137 9-2 Conclusions 138 9-3 Recommendations 139

REFERENCES 140 ARABIC SUMMARY

LIST OF FIGURES

Figure (2-1) The River Nile Barrages 6 Figure (2-2) Rosetta Branch 7 Figure (2-3) Major Types of River 9 Figure (2-4) Sinuosity Ranges 9 Figure (2-5) Meander Geometrical Characteristics of Curved River Reach 10 Figure (2-6) Scour Holes Downstream Bridges (Linda, 1993) 12 Figure (2-7) Flow Profile around a Circular Bridge Pier. (HEC18, 2012) 13 Figure (2-8) Contraction Scour 15 Figure (2-9) Live Bed and Clear Water Scour 15 Figure (2-10) General Scour 17 Figure (2-11) Schematic Diagram of Cross Sections Dredging Concepts 23 Figure (2-12) Cross Section at Columbia River 23 Figure (2-13) Stream Load 24 Figure (2-14) Critical Shear Stress as a Function of Grain Size [Lane (1955)] 26 Figure (2-15) Chang’s Approximations to Neill’s Competent Velocity Curves 28 Figure (2-16) Bank Protection Layers 29 Figure (2-17) Typical Stone Revetment at the Nile River in Egypt 30 Figure (2-18) An Example of the Applied Design for Stone Revetment 30 Figure (2-19) Grain Size Distributions of the Protective Layers 33 Figure (3-1) Location of the Study Reach 35 Figure (3-2) Piers of the Bridges 35 Figure (3-3) River Bed Elevation Survey Year 1982 36 Figure (3-4) River Bed Elevation Survey Year 1998 36 Figure (3-5) River Bed Elevation Survey Year 2003 37 Figure (3-6) River Bed Elevation Survey Year 2006 37 Figure (3-7) The Measured Velocity Locations 1998 38 Figure (3-8) The Measured Velocity Locations 2006 38 Figure (3-9) Braystoke Type Current Meter 38 Figure (3-10) Sketch Illustrated the Vertical Positions in Cross Section to Measure Water Velocity 39 Figure (3-11) Computation of the Average Velocity 39 Figure (3-12) The Used Grab Sediment Sampler 40 Figure (3-13) Bed Material Sampling Locations 40 Figure (3-14) Grain Size Distribution Curves at C.S. No. (1) 41 Figure (3-15) Grain Size Distribution Curves at C.S. No. (2) 42

Figure (3-16) Grain Size Distribution Curves at C.S. No. (3) 42 Figure (3-17) River Nile Hydrograph in Years 1982, 1998, 2003 and 2006 43 Figure (3-18) Water Discharge D.S Rositta Barrage at Years 1982, 1998, 2003 and 2006 43 Figure (3-19) Relation Between Water Level at Kafr Al-Zayat and Discharge Down Stream Rosetta Barrage in Years 1990, 1991, 1994, 1995, 1996 and 1997 44 Figure (3-20) Relation Between Water Level at Kafr Al-Zayat and Discharge Down Stream Rosetta Barrage in Years 1998, 2000, 2001, 2002, 2003 and 2004 44 Figure (3-21) Relation Between Water Level at Kafr Al-Zayat and Discharge Down Stream Rosetta Barrage in Years 2009, 2010 and 2011 45 Figure (4-1) Flowchart of Proposed Approaches in this Study 47 Figure (4-2) 3-D Coordinate System 49 Figure (4-3) Depth Average Velocity Definition 50 Figure (4-4) Modeling Steps 53 Figure (4-5) Study Reach Roughness Coefficient Classification 56 Figure (4-6) Study Reach Mesh Element Composition 58 Figure (4-7) Bridge Mesh Element Composition 58 Figure (4-8) Quadrilateral and Triangular Element Aspect Ratios 59 Figure (4-9) Inverse Distance Weighted Average Interpolation Criteria 60 Figure (4-10) Planer and 3D Contouring after Interpolation Process 60 Figure (4-11) Design Mesh Elevation Assignment 61 Figure (4-12) Location of the Calibration Cross Sections 62 Figure (4-13) Flow Velocity Calibration at Cross Section (1) 63 Figure (4-14) Flow Velocity Calibration at Cross Section (2) 63 Figure (4-15) Flow Velocity Calibration at Cross Section (3) 63 Figure (4-16) Comparison between the Measurement and Simulated Water Surface 64 Elevation

Figure (4-17) Location of the Verification Cross Sections 65 Figure (4-18) Flow Velocity Verification at Cross Section (1) 65 Figure (4-19) Flow Velocity Verification at Cross Section (2) 66 Figure (4-20) Flow Velocity Verification at Cross Section (3) 66

Figure (4-21) Comparison between the Measurement and Simulated Water Surface Elevation 66 Figure (4-22) Data Relative Importance to Modeling 67 Figure (5-1) General Plan of the Study Reach 69 Figure (5-2) Meandering Planform Parameters 70 Figure (5-3) River Bed Elevation for Years 1982 and 2003 71

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Figure (5-4) River Bed Elevation for Years 1998 and 2006 72 Figure (5-5) Comparison of Bed Profiles at Cross Sections (1) to (8) 74 Figure (5-6) Variation of the Lowest Bed Levels 74 Figure (5-7) Scour Holes Location in Study Area at Years 1982 75 Figure (5-8) Scour Holes Location in Study Area at Years 2003 75 Figure (5-9) Comparison of Scour Holes in Study Area at Years 1982 and 2003 77 Figure (5-10) Scour Hole Length Change at Years 1982, 1998, 2003 and 2006 82 Figure (5-11) Scour Hole Width Change at Years 1982, 1998, 2003 and 2006 82 Figure (5-12) Scour Hole Depth Change from Years 1982, 1998, 2003 and 2006 83 Figure (5-13) Cross Sections Location for Scour Holes 83 Figure (5-14) Scour Holes Cross Sections for Years 1982, 1998, 2003 and 2006 85 Figure (5-15) Longitudinal Sections Location for Scour Holes 85 Figure (5-16) Scour Holes Longitudinal Sections for Years 1982, 1998, 2003 and 2006 86 Figure (6-1) Comparison between the Cross Sections Velocity Profiles in Case of Minimum Discharge 89 Figure (6-2) Water Surface in Case of Minimum Discharges (6.65 Mm3/day) 89 Figure (6-3) Comparison between the Cross Sections Velocity Profiles in Case of Average Discharge 91 Figure (6-4) Water Surface in Case of Average Discharges (13.92 Mm3/day) 91 Figure (6-5) Comparison between the Cross Sections Velocity Profiles in Case of Maximum Discharge 93 Figure (6-6) Water Surface in Case of Maximum Discharges (69.90 Mm3/day) 93 Figure (6-7) Comparison between the Cross Sections Velocity Profiles in Case of Emergency Discharge 95 Figure (6-8) Water Surface in Case of Emergency Discharges (220 Mm3/day) 95 Figure (6-9) Location of the Bridge Piers 96 Figure (6-10) Cross Sections Location for Contraction Scour 99 Figure (6-11) Cross Sections Location for Bend Scour 100 Figure (6-12) Cross Sections Location for General Scour 101 Figure (6-13) Evaluation of the Total Scour at Kafr El-Zayat 105 Figure (6-14) First Bridge Piers Location 105 Figure (6-15) Second Bridge Piers Location 105 Figure (6-16) Third Bridge Piers Location 105 Figure (7-1) River Bed Elevation in Case of Alternative 1 109 Figure (7-2) The Thalweg Line in Case of the Original and Alternative 1 110 Figure (7-3) Cross Sections Bed Profiles in Case of Original Year and Alternative1 111 Figure (7-4) Velocity along the Reach at Maximum Flow in Case of Alternative1 112

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Figure (7-5) Velocity Profile at the Deepest Points (Outer Curve) along the Reach in Case of the Original & Alternative 1 at Max Flow 112 Figure (7-6) Cross Sections Velocity Profile of the Original & Alternative 1 at Max Flow 114 Figure (7-7) Water Surface Slope at the Deepest Points along the Reach of the Original & Alternative 1 114 Figure (7-8) Velocity along the Reach in Case of Alternative 1 at Emergency Flow 115 Figure (7-9) Velocity Profile at the Deepest Points along the Reach in Case of Alternative 1 at Future Flow 115 Figure (7-10) Cross Sections Velocity Profile of the Original & Alternative 1 at Future flow 117 Figure (7-11) Water Surface Slope at the Deepest Points along the Reach in Future Flow of the Original & Alternative 1 117 Figure (7-12) River Bed Elevation in Case of Alternative 2 118 Figure (7-13) Cross Sections in Case of Original Year and Alternative 2 119 Figure (7-14) Velocity along the Reach in Case of Alternative 2 at Maximum Flow 120 Figure (7-15) Velocity Profile at the Deepest Points along the Reach in Case of Original, 121 Alternative 1 and Alternative 2 at Maximum Flow

Figure (7- 16) Cross Sections Velocity Profile of the Original, Alternative 1 and Alternative 2 at Maximum Flow 122 Figure (7-17) Water Surface Slope at the Deepest Points along the Reach of the Original, Alternative 1 and Alternative 2 at Maximum Flow 123 Figure (7-18) Velocity along the Reach in Case of Alternative 2 at Emergency Flow 124 Figure (7-19) Velocity Profile at the Deepest Points along the Reach in Case of Original, Alternatives 1 and 2 at Emergency Flow 124

Figure (7- 20) Cross Sections Velocity Profile of the Original, Alternatives 1 and 2 at Emergency Flow 126 Figure (7-21) Water Surface Slope at the Deepest Points along the Reach of the Original, Alternatives 1 and 2 at Emergency Flow 126 Figure (7-22) Bed Shear Stress in Max Flow for Original Case 128 Figure (7-23) Bed Shear Stress in Max Flow for Alternative 1 128 Figure (7-24) Bed Shear Stress in Max Flow for Alternative 2 128 Figure (7-25) Cross Sections Shear Stress of the Original, Alternatives 1 and 2 at Maximum Flow 130 Figure (7-26) Bed Shear Stress for Original Case at Emergency Flow 131 Figure (7-27) Shear Stress for Alternative 1 at Emergency Flow 131 Figure (7-28) Shear Stress for Alternative 2 at Emergency Flow 131

Figure (7-29) Cross Sections Shear Stress of the Original, Alternatives 1 and 2 at Emergency Flow 133 Figure (7-30) Grain Size Distributions of the Proposed Filter Layers 136 Figure (7-31) The Designed Filter Layers Thickness 136

LIST OF TABLES

Table (3-1) Hydrograph Survey of Study Area 36 Table (3-2) Characteristics of Bed Samples at C.S. (1,2&3) 41 Table (3-3) Discharge at Rosetta Bridge 45 Table (4-1) Data Needed for Model Validation 54 Table (4-2) Ranges of the Estimated Roughness Coefficients 56 Table (4-3) Boundary Condition of Calibration 62 Table (4-4) Calibration Values for Roughness Coefficients 64 Table (4-5) Boundary Condition of Verification 65 Table (5-1) Meandering Parameters of the Study Reach 71 Table (5-2) Scour Holes Variation from Year 1982 to 1998 78 Table (5-3) Scour Holes Variation from Year 1998 to 2003 79 Table (5-4) Scour Holes Variation from Year 2003 to 2006 80 Table (5-5) Scour Holes Variation from Year 1982 to 2003 81 Table (6-1) Boundary Condition 87 Table (6-2) Location and Diminutions of the Bridge Piers 97 Table (6-3) Boundary Condition 97 Table (6-4) The Used Parameters and The 2D Model Results of Scour Bridge Piers in Case of Maximum Flow 98 Table (6-5) The Used Parameters and The 2D Model Results of Scour Bridge Piers in Case of Emergency Flow 98 Table(6-6) Contraction Scour in Case of Maximum and Emergency Flow 100 Table (6-7) Bend Scour in Case of Maximum and Emergency Flow 101 Table (6-8) General Scour in Case of Maximum and Emergency Flow 102 Table (6-9) General Scour for Maximum and Emergency Flow Conditions 102 Table (6-10) Total Scour 104 Table (6-11) The Expected Increase of the Scour Holes around the Main Piers of Kfer El- Zayat Bridges 106 Table (7-1) Grain Size Distribution of the Proposed Riprap and Filter Layers 135 Table (7-2) Sieve Analysis for the Designed Filters 135

LIST OF SYMBOLS

Description Dimension Symbol a Angle formed by the projection of the channel centerline from the point of curvature to a point which meets a line tangent to the outer bank of the channel. (degrees)

2 Ac Wetted cross section area (L ) 2 Am Mid-ship area (L ) a River bends amplitude (L) B Channel bank full width (L) Bs Ship width (the beam) (L)  Isotropic momentum flux correction coefficient (-) bt Channel width at keel level (L) C Chézy roughness coefficient (L2/T) C Izbach's turbulent coefficient (-) Di Grain size for which i percentage of a material by weight is finer (L) D Mean size of riprap particle (L) z Super elevation between outside and inside bank (L) g Gravitational acceleration. (L/T2) H,h,ho Flow water depth (L) i Longitudinal hydraulic gradient (-) K Roughness height (L) m Roughness correction factor for channel meandering (-) n Manning roughness coefficient (L-0.33 T) Р Meander channel sinuosity (-) Q Flow discharge (L3/T) R* Reynolds No. (-) R Radius of curvature (L) r1 River bend inner radius (L) r2 River bend outer radius (L) rc River bend center radius (L) Sg Specific gravity (-) Sr Transverse water slope (L/L) bx, by Bed shear stresses acting in (x and y) directions respectively (M/LT2) 2 sx, sy Surface shear stresses acting in (x and y) directions respectively (M/LT ) xx , xy, yx, xy shear stress 2 yy acting in x direction on a plane that is perpendicular to the y (M/LT ) direction (L/T) U Flow velocity (L/T) Ū Cross-sectional average velocity (L/T) Beds shear velocity U* (L/T) V Measured point velocity (M)

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Description Dimension Symbol W Weight of the riprap stone in pounds (L/T) ω Fall velocity (L) Z Meander arc length (L) zb Bed elevation (L) zs Water surface elevation (Degree)  Angle of repose (Degree)  Bed slope angle in degrees (L) λ Meander Wavelength (Degree) θ Arc angle (L/T) U Horizontal velocity in the x direction (L/T) 3 V Horizontal velocity in the y direction (M/L )  Water mass density b Pier width. (L)

D50 Particle size in a mixture in which 50% are smaller. (L)

df Scoured depth below design floodwater level. (L)

di Average depth at bankfull discharge in incised reach. (L)

Dm Diameter of the smallest non-transportable particle in the bed material

(1.25xD50) in the contracted section. (L)

Fr1 Froude number directly upstream of the pier

K1 Exponent depending upon the mode of bed material transport.

K1, K2,K3, and K4 Correction factors.

KW Means there would be a 5% reduction in the estimated scour depth approximately 0.95. m Exponent varying from 0.67 for sand to 0.85 for coarse gravel. Q Discharge through the bridge. (L3/T) 3 Q1 Flow in the upstream of bridge transporting sediment. (L /T) 3 Q2 Flow in the contracted section. (L /T) 3 qf Design flood discharge per unit width. (L /T/L) 3 qi Bankfull discharge in incised reach per unit width. (L /T/L)

se Upstream energy slope. (L/L) V Velocity of upstream flow. (L/S)

VC Critical velocity. (L/T)

Vc Critical velocity. (L/T) W Bottom width of the contracted section less pier width. (L)

W1 Bottom width upstream of bridge. (L)

W2 Bottom width in the contracted section. (L)

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Description Dimension Symbol y Maximum depth of upstream flow. (L)

Y0 Average depth of flow in the contracted section before scour. (L)

y0 Average existing depth in the contracted section. (L)

Y1 Depth of flow in the upstream of bridge. (L)

y1 Flow depth. (L)

Y2 Depth of flow in the contracted section. (L)

ya Average depth of flow upstream of the bridge. (L)

ygs General scour depth. (L)

Yh Hydraulic depth of upstream flow. (L)

Ys Average depth of scour. (L)

ys Equilibrium scour depth. (L) Z Multiplying factor (0.5 for straight reach, 0.6 for moderate bend, 0.7 for severe bend).

Zbs Bend scour component of total scour depth. (L)

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LIST OF ABBREVIATIONS

Aswan High Dam AHD Average Avr. Centimeter cm Cross Section C.S Downstream D.S First Bend S1 First Bridge B1 Hydraulic Research Institute HHRI Kfer El-Zayat Station K.St Kilometer Km Kilometer Square Km2 Maximum Max. Mean Sea Level MSL Meter m Meter Cubic m3 Million Cubic Meter Mm3 Minimum Min National Water Research Center NWRC Nile Research Institute NNRI North Direction N Not Available Data N A Old Aswan Dam OAD Second Bend S2 Second Bridge B2 Surface Water Modeling System SMS Third Bridge B3 Two Dimensional Model 2D Upstream U.S Water Level in m WL

ABSTRACT

The objectives of this research are to analyze and evaluate the effect of releasing flow discharges on river meandering and the scour at the bridge piers. This part of river meandering includes 13 piers distributed on 3 bridges. The meandering reach is located on Rosetta branch. It is consisting of two successive bends of length of 9.0 Km from km 145.00 to km 154.00 D.S of El-Roda Gauge at Kfer El-Zayat City. This reach is selected to conduct the current investigation. Several sorts of data were collected including site maps, velocity measurements, bed samples, hydrographic survey data, water levels and discharges at several years and seasons, as well as visual inspection photos. The developing of bed level, thalwege line and scour holes were determined by comparing the surveyed entire reach of years 1982, 1998, 2003 and 2006. Study area was simulated four times by 2D mathematical model “SMS” using a survey reach of years 1982, 1998, 2003 and 2006. This was done to estimate the velocities and the water levels at different discharges on the entire reach. The flow was used as upstream boundary condition and the water level was used as downstream boundary condition. The model was calibrated and verified using the measured velocity data. The model was run for sixteen times at different flow conditions (minimum, average, maximum and emergency). The resulted velocities of these runs were compared. The obtained results showed the local scour in bridge piers. The empirical equations used to predict the general scour, contraction scour and bend scour of the whole reach and around bridge piers.

Two proposed alternatives were suggested and simulated separately by the SMS model. In the first alternative, the outer bends were filled with layers of filter and riprap up to level -5.00 m MSL. In additional to alternative 1, the inner sides of the bends were dredged to level -3.00 m MSL as second alternative. The model was run for the two alternatives at maximum and emergence flows with its corresponding water levels. The results illustrated that the second alternative improved the flow conditions better than the first one. Based on the results, layers of filter and riprap were designed to fill the scour holes.

The empirical equations were used to predict the long term degradation and bend scour of the bed morphological changes along the entire reach of the Rosetta Branch. 2-D model was used to scour at the bridge piers in the study area was predicted using 2-D (SMS) model considering two scenarios of high river discharges. The results showed that in case of

xvi discharges released were maximum (69.90, 220.00m.m3/day), the total scour evaluated at the 3 bridges were, (11.65, 16.93m) for bridge No.1, (9.08, 13.35m) for bridge No.2 and (9.11, 14.07m) for bridge No.3. The expected extend of the scour holes around the main piers of the Bridges were also predicted. It is recommended to follow up the dimension of the scour holes every year or after occurring high floods.

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CHAPTER 1 INTRODUCTION

Chapter 1 Introduction

1-1 General The water release from Aswan Dam is kept as far as possible equal to the water demand, leaving no surplus water to be wasted into the sea except in emergency cases. During high floods, the water managers in the Ministry of Water Resources and Irrigation may release discharges greater than the annual maximum discharge in an average year. These high discharges released from HAD are determined according to the regulation guidelines for operating the High Aswan Dam. These peak discharges may cause damages to the water control structures along the Nile and its branches. Relatively high discharges cause local scour near bridges, harbors and other structures. Also, relatively high discharges may cause inundation to former flood plains that are currently in use. Such inundation may cause damage to agricultural properties, urban areas, roads and may put human lives into danger.

Meandering rivers are classified as either actively or passively meandering. An actively meandering river has sufficient stream power to deform its channel boundaries through active bed scour, bank erosion, and point bar growth. Conversely, while a passively meandering stream is sinuous, it does not migrate or erode its banks.

The Nile River is relatively straight with some sinuous reaches over short distances that are related to steeper slopes. The increase in sinuosity in turn increases the bed slope more than 10cm/km. Steeper portions become more active and bank erosive. Consequently, scouring action was expected to continue in these areas.

The meander wavelengths of the River Nile varied from 2500m to 4500m. The meander pattern was subsequent to the construction of the High Aswan Dam (H.A.D.) as a result of a reduction in discharge and sediment load. These are low amplitude meanders of the river, associated with the growth of alternate point bars and islands, and not meanders that materially change the main riverbank alignment.

A comprehensive analysis of the fluvial characteristics of the River Nile has been accomplished by the RNDP Project (RNDP, 1991a, 1992b). Before the construction of H.A.D., the peak flows were quite constant down the river but after building H.A.D., the peak flows decreases significantly downstream as irrigation water are withdrawn. After 1

Chapter 1 Introduction constructing H.A.D., the Nile is considered as a very low energy river with low water surface gradients.

From the Aswan Dam to the head of the Nile Delta, the river distance is about 950km, and the river bed drops ranging from + 79m to + 11m MSL, giving rise to an average slope of 7.2cm/km. The average bed slope along the Damietta and Rosetta Branches of the Nile Delta (240km from Delta Barrage) was 5.6cm/km. The suspended bed material loads for the Nile downstream Aswan has changed substantially as a result of the creation of Lake Nasser, (HRI, 2005).

1-2 Problem Definition Kfer El-Zayat city is located at the outer curve of a very sharp bend at Km 123 of Rosetta Branch. A field investigation is carried out to the local scour downstream the railway and Highway bridges just after the release of the emergency flood discharge in 1998. The lowest bed level of the local scour increased from -16.0m MSL at year 1996 to level -18.0m MSL at year 1998. This may lead to serious bank instability in front of the city and the local scour at any pier of the railway bridge might affect the stability of the bridge foundation, which consequently affects the stability of the bridge itself.

1-3 Study Objectives The research objectives are summarized as the following: 1) Analyze and evaluate the effect of releasing different discharges including high and emergency flow on the existing structures at Kafr El-Zayat City. 2) Prediction of the morphological changes and the scour holes at the outer curve of the bends. 3) Simulation of the flow conditions to the reach in front of the city of Kfer El-Zayat (including the meander and bridge piers) using the two dimensional model (2D model). Proposed alternative solutions to redistribute the flow in the bend reach to minimize deepening and widening the scour holes of Rosetta Branch at Kfer El-Zayat.

1-4 Methodology and Scope of Work The “SMS” 2-D mathematical model would be employed, at first, to simulate the morphological and hydrological characteristics in the meandering reach of Rosetta branch. The present study would be carried out applying the following: 1. Collecting the available data to the study reach related to hydrographic and hydraulics. 2

Chapter 1 Introduction

2. Reviewing of the available scour hole information in the available literature. 3. Reviewing the previous available studies related to this subject. Determine the different flows at several years passing in the Rosetta Branch from the HAD. 4. To study the development of the morphology on the bends, the reach available bed level data at several years will be compared. This reach includes 2 bends located at Rosseta Branch at Kfer El-Zayat city. 5. The reach will be simulated by 2-D mathematical model, 4 times using the surveyed data at different years. The model will be calibrated and verified. Different runs at several flow conditions will be carried out. 6. Using the convenient empirical formulae for prediction of the morphological changes and the scour holes at the outer curve of the bends and around Bridge piers. 7. Simulating different proposed alternatives using 2-D model SMS to predict the expected scour bed at whole reach including scour around the bridge piers. 8. Analysis of the results. 9. Conclusions and Recommendations.

1-5 Thesis Layout This thesis includes 8 chapters as the following:

Chapter 1: Introduction It describes the problem, the objectives, the procedure and methodology used in this study.

Chapter 2: Literature review This chapter covered the survey of literature concerning river meandering included scour around bridge piers, the outer curve and contraction areas.

Chapter 3: Data collection Several sorts of data were collected including site location, bed level date maps, velocity measurements, bed samples, hydrographic survey data, water level and annual discharges, as well as visual inspection photos.

Chapter 4: Mathematical models formulation and preparation The chapter includes the used mathematical model (SMS) and the collected data for the fulfillment of the study reach model simulation. Also the applied principles and results for model calibration and verification were illustrated.

Chapter 1 Introduction

Chapter 5: Morphological Changes Comparison of study reach morphological plan form development through the last thirty years was illustrated and analyzed. Moreover, Comparison between bed level cross sections and discussions of morphological changes between years 1982, 1998, 2003 and 2006 was achieved.

Chapter 6: Scour Prediction and Model Application This chapter present the model application at different flows. It present also the scour prediction and evaluation which includes general scour, local scour, contraction scour, and bend scour. These scours were analyzed for the whole reach and bridges site.

Chapter 7: Alternative Solutions & Testing Results This chapter provides effects of different scenarios of discharge and test results with respect to differing configurations; velocity measurements, shear stress, expected heading up. It presents a design of expected riprap.

Chapter 8: Conclusion and Recommendations Encompasses the conclusions derived from the present study and suggests some recommendations for future researches.

CHAPTER 2 LITERATURE REVIEW

Chapter 2 Literature Review

2-1 Introduction Flow in curved river reaches is usually under the influence of centrifugal acceleration, which induces transverse velocity component (helical flow currents) and super elevation in water surface. Although, these curved reaches are sometimes stable, there are general tendency of bank failure and bed scour at the outer bend followed by sedimentation at the inner bend. Therefore, lateral migration of the reach planform is occurred, consequently several morphological and navigational problems take place. Due to these dynamic interactions, the transverse velocity profile, shear stress on channel bed, lateral bed slope, sediment size distribution, and energy expenditure will be changed. This revealed that in order to treat and understand the meandering river mechanism, several emerged aspects should be reviewed which will be the intention throughout this chapter.

2-2 The Nile River The Nile River is the main source of water and life to Egypt and the Egyptians. The main flow of the Nile comes through three main rivers in Sudan; the Blue Nile, the White Nile, and Atbara River. These rivers originate from great lakes in the center and east of Africa. Therefore, the River Nile flow income varies from one year to another according to the amount of rain falling at the riverhead. However, the construction of High Aswan Dam gave Egypt the opportunity to control the Nile River flow. Also, there are several control structures (barrages) located along the Nile from Aswan to the Mediterranean Sea to control the flow through the river (Figure (2-1)).

The Nile River is a natural river, thus it has many islands dividing its flow into two branches and also has many bends and meanders along its course from Aswan to the Mediterranean Sea. The Nile River bed from Aswan to Cairo is generally consisted of successive layers of sandy soil. Meanwhile the upper layers of the river banks consisted of clayey silt to silty sand soil layers. On the other hand, some islands on the rivers are consisted of sandy silt soils and the others have the same formation as the river banks.

As mention earlier the discharge flow through the Nile River was controlled after the construction of the High Aswan Dam. The maximum discharge flow was reduced and the

Chapter 2 Literature Review suspended sediment concentration had greatly reduced. Thus, the Nile River subjected to morphological changes in many locations along its course, particularly through the distance between Aswan and Cairo.

Figure (2-1) The Nile River Barrages

2-3 Rosetta Branch Nile River travels along Egypt for about 950 km starting from downstream High Aswan Dam to upstream Delta Barrage, where it divides into two branches, Rosetta and Damietta branches which, each of them runs separately to the Mediterranean Sea, forming the Delta region between both branches, Figure (2-2). Rosetta branch has an average width of 180m and depth from 2 to 4m. It ends at Edfina Barrage, 30km upstream the sea, which releases excess water to the Mediterranean Sea. It is estimated that the aquatic environment of this branch receives more than 3 million cubic meters daily of untreated or partially treated domestic and industrial wastes and in addition to agricultural drainage water.

Chapter 2 Literature Review

Figure (2-2) Rosetta Branch

2-4 Basic Principals and Concepts To study the morphological changes in River, special definitions to identify these phenomena should be illustrated.

2-4-1 Channel types There are three basic types of channels, straight, meandering and braided. Describing the channel by one of the mentioned terms does not mean that the entire channel is straight or otherwise. It simply means that some portion of the channel can be described in such a way. In fact, portions of a stream may be straight, some meandering and others braided.

 Straight channel Different definition of straight channel has been found in the literature for example in 1957 which reported by Leopold, and Wolman, defined that the straight reaches have negligible sinuosity at bank full stage. At low stage the channel develops alternate sandbars and the thalweg meanders around the sandbars in a sinuous fashion. Straight channels are often considered as transitional stage to meandering. If the stream banks are stable, more than a one channel will develop, and the reach will become braided. In 1988, Chang described Straight River that it does not have a distinct meandering pattern; that is its sinuosity is less than about 1.5. Although a river may have a relatively straight alignment, its thalweg moves as Sinuous (Chang, 1988).

Chapter 2 Literature Review

 Braided channel A braided channel is wide and the banks are poorly defined and unstable, and there are two or more main channels. Between sub-channels there are sandbars and islands. The sub-channels and sandbars change position rapidly with time. At low flow the braided river bed starts a braided appearance. At flood stage, the flow straightens, most of the sandbars are inundated or destroyed and the river becomes much wider. Such rivers often have relatively steep slopes and carry large concentrations of sediment (Chang, 1988).

 Meandering channel A meandering river can be described as regular inflections that are sinuous in plan. It consists of a series of bends connected by short straight reaches .In the bends, deep pools are carved to the concave bank by the relatively high velocities because velocities are lower on the inside of the bend, sediments are deposited in this region forming the point bar. Point bar building is enhanced when large transfer’s velocities occur. The heavier concentrations of bed load toward the convex bank and deposited to form the point bar. At low flow, large sandbars are formed in the crossings if the channel is not well confined. Variations in factors such as bed and bank material, width, cross sectional shape, curvature, history and period of development of the bend, as well as gradient, are all likely to influence meander behavior and meander morphology. The scour in the bend causes bend migration downstream and sometimes laterally. Much of the sediment eroded from the outside bank is deposited in the crossing and on the point bar in the next bend downstream. The configuration and geometry of meandering channel are formed by erosion and deposition. Bed slopes are usually relatively flat. Figure (2- 3) shown that in 1988, Chang concluded that a meandering river has a sinuosity greater than about 1.5, and it consists of alternating bends and a distinct sinuous plan form, (Chang, 1988). In 1983 Brice put some classification for river types that is based on four major plan form properties that are most readily observed on aerial photographs: sinuosity, point bars, braiding, and an branching. River meandering consists of three types of sinuous rivers that are classified on the basis of plan form properties: sinuous canal form, sinuous point-bar, and sinuous braided. These are illustrated in Figure (2-4). The canal form tends to have the highest sinuosity, the narrowest widths, the lowest rates of lateral erosion and high silt-clay content for the banks (Brice, 1983).

Sinuous point-bar rivers are steeper and have more rapid rates of lateral migration at bends, river tend to have greater width at bend apexes, and prominent point bars, although straight reaches may remain stable for long period of time. 8

Chapter 2 Literature Review

Figure (2-3) Major Types of River

Sinuous braided rivers are steeper and wider than sinuous point-bar rivers with the same discharge. Point bars are more irregular as the braiding Increases (Chang, 1988).

Figure (2-4) Sinuosity Ranges

2-5 Meander Characteristics Derivations of motion and continuity equations for curved channels were mathematically specified by Rozovskii (1957), Rouse (1959), and Schlichting (1968). Using the sub critical flow restrictions with hydrostatic pressure distribution, the flow in curved channels was deduced in terms of the super-elevation ∆Z between outside bank and inside bank which would be approximated as follows:

2 2 r2 r2 U U B Z  Sr dr  dr  (2-1) r1 r1 gr grc Figure (2-5) illustrates the meander geometrical characteristics of curved river reach which can be described as follows:

Chapter 2 Literature Review

Arc length =Z/2 Apex

Point of inflection r or crossover c Arc angle  

   

Amplitude (a)

Point bar B

Arc length = 0 Arc length = Z Figure (2-4) Geometrical Wave lengthCharacteristics () of Meandering Stream Figure (2-5) Meander Geometrical Characteristics of Curved River Reach

1- Radius of curvature (rc): river forms a series of regular sinusoidal curves with an average radius of 2.3 to 2.7 times the bank-full width. 2- Meander Wavelength (λ): A full meander wavelength is the distance between two similar points along the channel between which waveform is complete. It was found to occur between 6 and 15 times the bank-full width. The bank full width is the width of the channel at water level during an average 1 to 2 year peak discharge event. The bank full discharge is the dominant channel forming discharge. The bank full width can be calculated by either using theoretical relationships or by on the ground measurements using field indicators. 3- Sinuosity (Р): is the ratio of channel length along the center line of the channel to the length of the valley measured along the center of the meander belt or center of the valley. Sinuosity generates resistance to flow and alters the hydraulic slope of the channel. 4- Arc angle (θ): the angle swept out by the radius of curvature between adjacent inflexion points. 5- Meander arc length (Z): the distance measured along the meander path between repeating (inflexion) points. 6- Amplitude (a): width of meander belt measured perpendicular to the valley or straight line axis.

Chapter 2 Literature Review

Additionally, empirical relationships are usually related the wavelength and amplitude of meander bends to the bank-full width of the channel (Inglis, 1949; Leopold and Wolman, 1957, 1960; and Zaller, 1967). Also relation between wave length and radius of curvature were treated by (Leopold and Woleman, 1960). Consequently, the following equations in English units deduce the relations between the radius of curvature and meander wavelength:

λ = 10.77 B1.01 (2-2) a = 3 B1.1 (2-3)

0.98 λ = 4.8 rc (2-4)

Where B is the surface width, from Eq. 2 and 4 one can deduce that:

rc = 2.4 B (2-5)

Equation (2-5) gives a good approximation of the maximum curvature for meander bends. However, Hey (1976) indicated that the above equations are not applicable on bends of sinuosity less than 1.5 where the radius of curvature is very large because the ratio rc/B will be considerably greater than 2.4 or 3.

Furthermore, very relevant applied investigation was conducted in which statistical nature of river bends along Damietta branch was highlighted and consequently some significant geometrical relationships were developed. In this study, three bend types were defined as free, limited and forced which were classified according to the physical and morphological characteristics and degree of freedom to attain the lateral shifting. According to Attia and El-Saied (2004), the three bend types were clarified as follow:

 Free bend: This is usually related with broad flood plains that consist of relatively erodible materials. In this case, the river bends follow the curves of the valley so that each river bend includes a promontory of the parent plateau. It was noticed that this type is not disturbed by the external factors and experienced the highest degree of freedom to form the bend shape.  Limited bend: where the bend cut into solid rock or hard strata in deep gorges and exhibit meandering pattern similar to that of rivers in flood plains. In this case the channel banks are composed of consolidated parent material that limits the lateral erosion. Such rivers are called incised rivers and these bends are called incised bends or entrenched bends.

Chapter 2 Literature Review

 Forced bend: where the channel is highly restricted from external movements and the bank line movements are mainly controlled by either natural or manmade activities. Examples of these constrains are valley walls, protection works, developments of croplands on island, mountains, infrastructures and towns Attia and Abdel-Bary(1998). These constrains forced the river to grab a specific path according to their shape. Sometimes in this type the river impinges onto an almost straight parent bank at large angle (600 to 900).

2-6 Scour Holes Scour is the hole left behind when sediment is washed away from the bottom of a river. Although scour may occur at any time, scour action is especially strong during floods. The different types of scour holes are indicated in Figure (2-6). Swiftly flowing water has more energy than calm water to lift and carry sediment down river.

Figure (2-6) Scour Holes Downstream Bridges (Linda, 1993)

Types of Scour: Scours are classified and defined as the following:  Local scour is removal of sediment from around bridge piers or abutments. Water flowing past a pier or abutment may scoop out holes in the sediment; these holes are known as scour holes.  Contraction scour is the removal of sediment from the bottom and sides of the river. Contraction scour is caused by the increase in the water speed as it moves through bridge opening which is narrower than the natural river channel.  Degradation scour is the general removal of sediment from the river bottom by the flow of the river. This sediment removal is a natural process but may remove large amounts of sediment over time and lowering the River bed.

Chapter 2 Literature Review

Scour is defined also as the erosion or removal of streambed or bank material from bridge foundations due to flowing water, Federal Highway Administration, (2001). It is considered one of the main factors affecting the stability of the highway bridge. Figure (2-7) shows flow profile around a circular bridge pier, (HEC18, 2012).

Figure (2-7) Flow Profile around a Circular Bridge Pier. (HEC18, 2012)

Local Scour is defined as the erosion due to redirected and contracted flow lines around piers or abutments (FCDMC, 2009). The evaluation of local scour was developed by Federal Highway Administration criteria, (2001) and procedure set in (HEC-18). Local scour is caused by flow obstruction and impingement - most local scour caused by man-made structures such as bridge piers, bridge abutment, culverts, grade control, and drop structures. The factor of safety for local scour is basely 1.3 (FCDMC, 2009), but it may be reduced to 1.0 due to excessive calculated local scour. However, the use of 1.0 for the factor of safety should be considered by the (FCDMC, 2007). There are many local scour depth prediction equations considered in the literature as well as a number of review studies that used the comparison techniques between different equations and methodologies involved in scour prediction. Most of these equations are empirical and based primarily on small-scale laboratory data. Melville (1975) measured mean flow directions, magnitude, and turbulent flow fluctuations and computed turbulent power spectra around a circular pile for flatbed, intermediate, and equilibrium scour holes. He found that a strong vertical downward flow developed ahead of the cylinder as the scour hole enlarged. The size and circulation of the horseshoe vortex increased rapidly, and the velocity near the hole bottom decreased as the scour hole was enlarged. As the scour hole develops further, the intensity of the vortex decreases and reaches a constant value at the equilibrium stage. Large

Chapter 2 Literature Review scour holes may also develop downstream from piers under certain circumstances (e.g. Shen et al., 1966). More recently another potential scour mechanism was identified [Sheppard (2004)]. This mechanism resulted from the pressure gradient field generated by the presence of the structure in the flow. Lança et al. (2013), collected new long-duration clear-water scour data for single cylindrical piers with the objective of investigating the effect of sediment coarseness on the equilibrium scour depth and improving the scour depth time evolution modeling by using the exponential function suggested in the literature. Experiments were carried out for the flow intensity close to the threshold condition of initiation of sediment motion, imposing wide changes of sediment coarseness and flow shallowness. The effect of sediment coarseness on the equilibrium scour depth was identified; existing predictors were modified to incorporate this effect. The effect of a single-peaked flood wave on pier scour was investigated theoretically and experimentally by Hager and Unger (2010). The conditions considered involve clear-water scour of a cohesion-less material for a given median sediment size and sediment non- uniformity. An approach flow characterized by a flow depth and velocity, a circular-shaped cylindrical bridge pier, and a flood hydrograph defined by its time to peak discharge. A previously proposed formula for scour advance under a constant discharge was applied to the unsteady approach flow. Sheppard et al. (2014), employed twenty-three of the more recent and commonly used equilibrium local scour equations for cohesion-less sediments which were evaluated using compiled laboratory and field databases. This investigation assembled 569 laboratory and 928 field data. A method for assessing the quality of the data was developed and applied to the data set. This approach reduced the laboratory and field data to 441 and 791 values, respectively. Because the maturity of the scour hole at the time of measurement for the field data was unknown, they were only used to evaluate under prediction by the equations. A preliminary quality control screening of the equilibrium scour methods/equations reduced the number of equations from the initial 23 to 17. The remaining 17 methods/equations were analyzed using laboratory and field data. Contraction scour is located at the flow area of the river at flood stages, Figure (2-8). It is reduced due to the bridge construction. The contraction scour evaluation was developed by Federal Highway Administration criteria. The higher value between the contraction scour equation in this section and Neill’s general scour equation could be used for this component (FCDMC, 2009). If there is a bend, then the higher value between Neill’s equation with a

Chapter 2 Literature Review bend and the contraction scour equation and the bend scour equation could be used. The following equation (for critical velocity) can be used to determine the contraction scour if the flow upstream of the bridge is clear-water or live-bed (FHWA, 2001). The equation has the following form:

1/6 1/3 Vc =11.17 ya D50 (2-6)

Clear-water when Vc> mean velocity, Live-bed when Vc< mean velocity. Live-bed Contraction Scour Determination

6/7 k1 y2/y1 =(Q2/Q1) * (W1/W2) (2-7)

ys = y2 - y0

Clear-water Contraction Scour 2 2/3 2 3/7 Y2 = (0.0077Q /Dm W ) (2-8)

Ys= y2 - y0

Figure (2-9) show Live bed and Clear Water Scour

Figure (2-8) Contraction Scour

Figure (2-9) Live Bed and Clear Water Scour 15

Chapter 2 Literature Review

Bend scour is concentrated near the outside of the bend scour resulting from stream plan form characteristics and scour at confluences (Flood Control District of Maricopa County, 2009). The equation has the form (Simons and Assoc 1989b):

Zbs = (0.0685*Y*V0.8)[2.1*(sin²(a/2)/cos(a))0.2-1]/(Yh0.4*S*exp(0.3)) (2-9)

The general scour component is the scour caused by the passing of one flood, Figure (2-10). The Flood Control District of Maricopa County (FCDMC) uses three general scour equations (FCDMC, 2007): Lacey’s Equation, Neill’s Equation and Blench’s Equation, (Pemberton and Lara, 1984). Neill’s Equation is applicable to streams where there is constriction of the channels due to bridges or other structures. The equation has the form (Pemberton and Lara 1984):

m ygs = Zdf = Zdi (qf/qi) (2-10)

The wide pier problem is considered to be a concern when the relative depth, y/b, is too small to allow the vortices to fully develop where y is the flow depth and b is the pier width. Earlier investigations of the dependence of scour depth on y/b were performed with small piles and very small water depths, Ettema (1980). Melville and Sutherland (1988) established an upper threshold at y/b = 3 beyond which the scour depth is relatively independent of the relative depth. Recent data from J.Sterling Jones and D. Max Sheppard tests, (2000) on large piers indicated that this threshold was closer to 2. HEC-18 is the standard used by most highway agencies for evaluating scour at bridges. The pier scour equation was checked using laboratory data by researchers at Colorado State University and was presented as the CSU equation in an earlier FHWA publication, Highways in the River Environment. All of the data used for the original equation was for circular piers in relatively uniform fine grain sands. Correction factors were added later to account for various pier shapes, angle of attack, bed forms, and coarse bed material fractions to produce the familiar pier scour equation that is currently in HEC-18:

0.65 0.43 yS/y1 = 2 K1K2K3K4 (b/y1) (Fr1) (2-11)

Johnson (1999) defined a wide pier as one situated in shallow, low velocity flows so that y/b

< 0.8 and Fr < 0.8. He isolated the data that met these conditions in the original data set used in the CSU equation and added data from other sources to derive a new equation for wide piers using the same parameters. That equation could be written as:

Chapter 2 Literature Review

0.504 0.639 yS/y1 = 2.08 K1K2K3K4 (b/y1) (Fr1) (2-12)

Then he divided the wide pier equation by the HEC-18 equation to express the difference as another correction factor, KW, for the HEC-18 equation:

-0.15 0.21 KW = 1.04(b/y1) (Fr1) (2-13)

Which can be applied to the HEC-18 equation when y/b < 0.8 and Fr < 0.8 in case both of these conditions were met. But if y/b = 0.5 and Fr =0.5, which could occur, then KW = 0.81 which is a 19% reduction.

Figure (2-10) General Scour

If sediment on which bridge supports rest is scoured by a river, the bridge could become unsafe for travel. In 1987, the Interstate highway bridge over Schoharie Creek in New York State collapsed during a flood. After this accident, the Federal Highway Administration required every State to identify highway bridges over water which are likely to have scour problems and to identify bridges where scour is severe. Knowledge of bridge sites where scour is a potential problem will enable the States to monitor and improve conditions at these bridges ahead of time before they become dangerous (Linda, 1993). The process of bank erosion is much related to the general scour or river-bed-degradation. At river cross sections where the bed level is lowered considerably, the bank height might be higher than a critical value beyond which bank failure might occur. As river-bed-degradation is investigated using numerical morphological modeling approach, therefore, bank scour should be addressed in the context of river morphological modeling (Babaeyan and Valentine, 1999).

Chapter 2 Literature Review

In Egypt, local scour around the hydraulic structures located across the Nile River constitutes a major concern. The two main hydraulic structures on the River Nile are bridges and barrages. Scour downstream barrages seems to be more complex. The RNDP Project (RNDP, 1991a, 1992b) has accomplished a comprehensive analysis of the fluvial characteristics of the River Nile. Before the construction of H.A.D., the peak flows were quite constant down the river but after building H.A.D., the peak flow decreases significantly downstream as irrigation water is withdrawn. During high floods, higher discharges than the annual maximum discharge may be released in an average year. High discharges cause local scour near bridge piers, especially the wide area. When a bridge is built across an alluvial channel, the obstruction of the flow by the bridge piers induces higher velocities and vortices that cause scour of the channel bed around the piers. If this scour reaches the foundation level of bridge piers, the bridge might collapse. Bridge pier scour is the leading cause of bridge failure. In the United States alone, bridge pier scour is the leading cause of failure among more than 487,000 bridges over watercourses (Melville, 1997). In Egypt, concerns about bridge pier scour may limit increasing the current flow releases from Aswan High Dam (AHD) above the current maximum of 270 Mm3/day. In order to release higher flows than the maximum current, knowledge is required about how much scour is expected around bridges built on the Nile River (HRI, 1993). Due to the importance of bridge pier scour, many investigators have worked on this critical subject but most have built their analysis on laboratory data. This empirical approach suffers from its associated simplified conditions and scale effects. When applying the existing empirical equations for predicting bridge pier scour to field cases, the scour depths are over- predicted. Meander migration is a process in which water flow erodes soil on one bank and deposits it on the opposite bank. Therefore, a gradual shift of bank line occurs over the long term. Bank erosion undermines bridge piers and abutments, scours the foundations of parallel highways, and causes loss of useful land, according to Jean-Louis Briaud et al. (2007). Rossell and Ting (2013) used a 2-D depth-averaged river model based on finite element theory (FESWMS) to simulate the hydraulic conditions at a contracted bridge site. The studied area was located at James River bridges near Mitchell, South Dakota. The parallel bridges were located in a crossing between the two bends of a meander. The validated model was used to examine the site characteristics that influence the concentrated flow on the right side of the main channel and the exchange of flow between the main channel and flood plains. The scour analysis was performed using the equations mentioned in Hydraulic Engineering

Chapter 2 Literature Review

Circular No. 18 (HEC-18) and a method that accounts for the soil erodibility using the curve of measured erosion rate versus shear stress. The study demonstrated that the channel meandering, the no-flow boundary condition imposed by the walls of the river valley, skewed roadway embankment, and the dense trees along the left bank were the three main factors creating the unique hydraulic conditions at the bridge site. It was concluded that using the 2-D flow model improved the estimation of contraction scour by providing more accurate information on the hydraulic parameters. The predicted scour depth was highly sensitive to the critical shear stress and curve slope of erosion rate versus shear stress.

2-7 Types of Models Modeling has become a frequently used tool for studies in hydraulic and environmental engineering. In the past many engineers were used physical models or simplified descriptions for the support of engineering studies A model is a physical or mathematical description of a physical system, including the interaction with its outside world, which can be used to simulate the effect of changes in the system itself or the effect of changes in the conditions imposed upon it.

2-7-1 Physical Models Physical model in the laboratory are done primarily in a large flume. Much of the laboratory's recent work has investigated scour at bridge installations. Physical Model Studies are invaluable in designing hydraulic structures, improving the safety of existing hydraulic structures and reducing construction costs. To do this, experimental setups are designed and built on site and installed in the moveable stream bed of the large flume. Flow regimes may be varied to simulate any almost flood event and the resulting scour measured. Physical modeling results may be used directly by the laboratory's clients in the design of a particular structure, or it may be used to develop predictive numerical models with potential for general application in designing structures.

2-7-2 Numerical Models The increasing availability of personal computers and the powerful developments in computer graphics, data bases and on-line control software has brought computer support to the desk of consulting engineers. In-line with these developments we also see a strongly increased availability and use of mathematical molding software tools.

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Numerical (computational) analysis is widely used to solve mathematical expressions that describe the physical phenomena. Numerical models are classified by number of spatial dimensions over which variables are permitted to change. They provide much more detailed results than other methods. Yet they need field data for verification. Numerical models have been extensively and successfully applied to studies on sediment yield, river sedimentation and morphological processes since the 1970s. The accuracy and reliability of a mathematical model in predicting sediment processes depend to a large extent on understanding sediment transport mechanism of effectiveness of numerical solution methods, calibration and verification by field and experimental data as well as the user’s experience and art. There is, obviously, plenty of room for improvement in these aspects. a. One dimensional model One dimensional model is mainly used in assessing long-term and averages in cross-section processes along long distance. b. Two dimensional and Three dimensional numerical-empirical models Two and three dimensional models are mainly used in studying local and detailed phenomena near structures.

2-8 Previous Works in Morphological Changes in Rivers (RNPD) produced a study of the impact of projects on the Nile River (RNPD, 1991a) which included an investigation of water levels, thalweg levels and known navigation bottlenecks.

(Moattassem et al.1990) defined the navigational bottlenecks as the locations where the water depth is less than 1.55m when the discharge from Aswan dam is 75 Mm3/day. They calculated the water depth as the difference between the water surface elevation obtained from rating curves and the thalweg level. They calculated the required depth as 1.55m based on draft 1.3m plus 0.25m as clearance. They defined 14 locations from Aswan to Cairo to have navigational bottlenecks. As their approach was a one-dimensional and the navigational path does not follow the thalweg line exactly, this approach is not accurate enough and there might be more bottlenecks than what they have defined.

(Motiee, et al 2003), reported that the morphological changes in River due to constructed structures (case study of Sephidrood River) caused severe changes in riverbed as well as riverbanks due to different reasons such as economical development, population growth, need for more sand and construction materials and sediment removal from reservoirs. The Sefid- Rud River has reached to its stable condition due to different reasons such as geological and 21

Chapter 2 Literature Review alluvial formations, hydrological characteristics of the basin as well as hydraulic conditions of the river.

(Sarker, et al 2003), studied the morphological changes at the Ganges River distributaries in response to the Declining flow using remote sensing. They used three sets of landsat images supported by hydrologic data. The images were classified with unsupervised classification and knowledge based threshold to produce land, sand and water classes. The time series data used to analyze the characteristics of erosion, accretion and planform changes. The changes of sinuosity, rates of bank erosion and meander migration were derived from the image analysis.

(Fischer-Antze et al 2003), studied the morphological response of the Danube River. The impact of the August 2002 flood on the morphological changes of the Danube River between Vienna and the Austrian-Slovakian border. The river bed elevation changes were determined in turns of volume differences and a number of morphological parameters including cross- sectional shape and asymmetry parameters for both surveys. The results indicate that the overall morphological features - sizes, shapes and locations of the gravel bars, thalweg positions - have not changed. Volume differences indicate no significant overall change and local changes occur of up to 1 meter. Further interpretations of these results will be provided in the context of the long-term evolution of the river bed.

(Amadi et al 2004), studied the factors influencing morphological changes in an alluvial reach of The Missuri River valley for River sensitivity to climate changes. Distinctions between the meander morphologies are based on differences in their channel width, channel depth, meander wavelength, meander radius, and bar grain size. High sensitively of the river to climate change could have strong influence on ongoing efforts to plan reclamation of the river to accommodate needs of both commerce and habitat because, (1) current river morphology cannot be considered stable over very long time spans, and,(2) foundational substrate materials for habitat are non-uniform in the valley.

Sadek, N., et al. (2006). Studied the impacts of the reduction of the flows downstream High Aswan Dam due to the operation of new national projects for the fourth reach, and unsafe stations are determined for different low flow conditions and the unsafe ranges are also determined for each case.

( Sadek, N. et al, 2000), studied meandering geometry and the regime change of the river for Rossetta Branch before and after the construction of Aswan High Dam by using mathematical 21

Chapter 2 Literature Review model. The analysis of the study shows the effect of hydrological and morphological changes such as meander parameters have changed after AHD, migrated bend occurred from Delta Barrage to Kafr El-Zayat. (Sadek N., et al 2001), studied the morphological changes impact on water surface profile predicted for the River Nile by using Mathematical model to analyzing different hydraulic parameter. By comparing cross sections of year 1982 and year 1997 it found that sedimentation is more frequent than erosion, it found that the difference between the predicted water surface profile for 1982 and 1997 lied within the range of 0.6m and is considered relatively small. (El-Sersawy, 2001), studied the better identification and prediction of the location of the bottlenecks that may affect navigation in the Nile River. In this study he found that using two dimensional hydrodynamic flow and sediment transport model lead to better handling of the input data, and improving the capabilities of the numerical model. The modification gives also the link between hydrodynamic models, and the sediment model increases the ability of the model to simulate long- term behavior of the river reach under study. The proposed approach, is used for navigation studies in the Nile River, to help the decision makers in planning and operation of the navigation system and to evaluate the sedimentation processes and to predict their effects on the morphology of the river reach.

(Enggrob, 2003), studied the morphological forecast simulation of Jamuna River in Bangladesh. Described the set-up and results of a mathematical modeling tool applied in connection with monitoring of the construction of bridge crossing and associated river training works in a highly morphological active river: The Jamuna River in Bangladesh. The objective of the model study was to provide forecasts of the morphological changes over the coming monsoon period with sufficient lead time to enable the contractors to take remedial or preventive actions should critical conditions occur. The model proved to be very useful not only to provide morphological forecasts but also for impact studies. (Kapsimaisi et al 2004), determined the long term morphological changes in a human affected coastal system using GIS. Large-scale patterns of coastline evolution and sea-floor erosion and/or deposition were investigated with the use of a Geographical Information System (GIS). The observed morphological changes have been related to the deltaic processes, local hydrodynamic conditions and human implications. Raslan Y., et al, (2008), studied the implications of dredging in Damietta Branch on river regime and flow water level. Comparing river water level after dredging with that before dredging downstream Delta and Zifta Barrage indicated significant drop in the water level. Drop in water level may increase the capacity of the river.

Chapter 2 Literature Review

However, drop of water level might have impact on flow intake structures inside the reach. The analysis of the results of the numerical models showed that aggradations will be dominant over degradation. Aggradations will likely to happen at few local sites were extensive dredging was carried out. Although navigation in the Nile has its merits, dredging should not be the only solution for maintaining the navigable channel.

2-9 Dredging Dredging is defined as a process by which sediment is removed from the bottom of streams, lakes and rivers as shown in Figure (2-11). Permanent modifications and structures have not succeeded in eliminating the requirement for the dredging of significant quantities of sediment to maintain the desired navigation channel. Figure (2-12) shows the use of the combination of dredging and the training structure in the river to reduce the deposition. Dredging solution of a navigation channel has the advantage of being relatively simple and direct in their application. Dredging operations on the river are closely related to the annual cycle of high and low flow. Comparing river stage, average depth over crossings and dredging requirements shows that, in general, crossings are built up and dredged cuts filled when river stage falls after a period of high flow. Dredging of a channel through a crossing or shoal should be considered successful if the dredged cut meets several criteria.

Figure (2-11) Schematic Diagram of Cross Sections Dredging Concepts

Figure (2-12) Cross section at Columbia River 23

Chapter 2 Literature Review

2-10 Sediment Transport Once material is detached from the channel it can be transported. Transportation is the movement of earth material, in this case, by water. As shown in Figure (2-13) once fine particles are eroded, they can be transported under very low velocities. As particle size increases, the velocity needed to transport it increases, the material transports through the stream load. Stream load is composed of dissolved or solution load, suspended load, and bed load. The dissolved load comes primarily from groundwater seepage into the stream. Ions in solution also come from the solution of materials that line the channel (Demissie et al.,1992).

Suspended load is comprised of sediment suspended and transported through the stream. Turbulent flow suspends clay and silt in the stream. Suspended load comes from material eroded from the surface bordering the channel and deposited in the stream, as well as, erosion of the channel bed itself.

Figure (2-13) Stream Load

Bed load is that which is moved across the bed of the channel. Bed load is transported in two ways, traction, which is a scooting and rolling of particles along the bed. The second is saltation, a bouncing-like movement. Saltation occurs when particles are suspended in the stream for a short distance after which they fall to the bed, dislodging particles from the bed. The dislodged particles move downstream a short distance where they fall to the bed, again dislodging particles upon impact (Krone, 1962).

2-10-1 Factors Affecting Sediment Transport 2-10-1-1 Bed Shear Stress The fluid shear stress depends on several factors such as the flow discharge (Q), water depth, the grain size and the bed forms, the longitudinal hydraulic gradient (i), the ratio between the bend radius (r) and the channel width (B), the cross sectional shape and the hydraulic

Chapter 2 Literature Review roughness which can be represented by the Manning or Chezy roughness coefficients. While river side slope resistance to erosion is mainly concerned with the properties of bank materials. Considering river bed shear stress, the major variables that affect the incipient motion of uniform sediment on a level bed include

c critical shear d water depth

s -  difference in sp.wt. between sol and water  density  kinematic viscosity respectively.

These variables may be grouped into the following dimensionless parameters:

(2-14) Therefore the following relationship may be deduced:

(2-15) 1/2 Where U= (c/ρ) is the critical friction velocity.

This relationship was explicitly solved graphically by Shields (1936). This solution was established based on experimental data on flumes with a flat bed and is generally referred to as the Shields diagram. The Shields diagram may be divided into laminar, transition and turbulent flow regions. In the laminar region where R is less than about 2, the particle size is less than the thickness of the laminar sub-layer and, hence, is enclosed in the thin laminar film. Since the boundary is hydraulically smooth, the movement is mainly caused by viscous action. In turbulent region of Reynolds number ( R*> 400), the laminar sub-layer is interrupted by the grain size and for this hydraulically rough boundary, the critical Shields stress has a constant value of 0.06, independent of the Reynolds number. Additional criteria to quantify critical shear stress in open channel was developed by Lane (1955) as illustrated in Figure (2-14). In this figure, the adopted curve was attached to Shields curve which can be applied to define the critical shear at the case of non-cohesive bed materials and clear water sediment concentration.

Chapter 2 Literature Review

Moreover, the relation between the relative bend curvature and the maximum relative bank erosion was tested by Nanson and Hichin (1986) which revealed that the maximum erosion appear to occur in the range between 2.0 and 4.0. Therefore, the intensity of shear stress near the outer bank would be considered as a function of bank erosion rate, while the shear stress distribution along the bank determines the location of the maximum bank erosion and the bend migration mechanism.

Figure (2-14) Critical Shear Stress as a Function of Grain Size [Lane (1955)]

2-10-1-2 Incipient Velocity Incipient velocity is the velocity at which the bed particles are started to move the erosion occurs only in the zones which subjected to velocity higher than incipient velocity. The incipient velocity is dependent upon water depth and grain size diameter. Figure (2-15) presents the values of the incipient velocity with respect to average water depth and average bed size diameter D50 (Neill’s, 1973). Neill presented a family of curves for estimating critical velocities for no cohesive sediments at varying flow depths and with grain sizes ranging from 0.3 to 300 mm (0.0117 to 11.7 inches). Neill defined the critical velocity as the flow velocity just competent to move the bed material. Neill used a combination of field data and laboratory data to develop his family of curves. Neill used a critical velocity equation very similar to Laursen’s to estimate the critical velocity for grain sizes greater than about 30 mm (1.17 inches). For a grain size of 0.3 mm (0.0117 inch), Neill assumed that a regime theory equation for stable channels in sand would be appropriate for estimating the critical velocity. Regime theory equations are design equations developed from field data collected in the stable, fine sediment canals of Pakistan

Chapter 2 Literature Review

(Mahmood and Shen). Transition curves were hand drawn for grain sizes between 0.3 and 30 mm (0.0117 and 1.17 inches). Chang transformed the plots of Neill’s curves into a set of equations for computing critical velocity based on the flow depth and the median diameter of the particle. This set is given in equations 15 through 18. For D50 greater than 0.03 m (0.1 ft), Neill’s critical velocity, VCN, is given in equation 16.

(2-16) where: y2 is equilibrium scour flow depth (m or ft).

D50 is sediment size (m or ft).

Ku is 0.55217 for SI units, or 1.0 for U.S. customary units.

For D50 less than 0.03 m (0.1 ft) but greater than 0.0003 m (0.001 ft), Neill’s critical velocity is given in equation 17.

(2-17)

The exponent, x, is calculated using equation 18:

(2-18) where: y2 is equilibrium flow depth (m or ft).

D50 is sediment size (m or ft).

KU1 is, for SI units, 0.3048 to the power of 0.65 minus x, or 1.0 for U.S. customary units. X is the exponent as calculated in equation 17.

KU2 is 0.788 for SI units, or 1.0 for U.S. customary units.

For D50 less than 0.0003 m (0.001 ft), Neill’s critical velocity is given in equation 19.

(2-19) where: y2 is equilibrium flow depth (m or ft). 27

Chapter 2 Literature Review

D50 is sediment size (m or ft).

Ku is 0.55217 for SI units, or 1.0 for U.S. customary units.

Chang’s equations are plotted in Figure (2-15). Neill’s competent velocity curves are intended for field conditions with flow depths of 1.5 m (5 ft) or greater. Chang’s equations were extrapolated to flow depths below 0.30 m for these experiments and to curves for flow depths of 0.305 and 0.15 m (1 and 0.5 ft) (Figure 2-15). Note that the sediment sizes used in the experiments fell into the range described by equations 16 and 17.

Figure (2-15) Chang’s Approximations to Neill’s Competent Velocity Curves

2-11 Bank Revetment Bank protection could be applied along river and island to protect its bank against high flow velocity currents which might cause bank erosion. Continuous protection are the most widely applied and successful method on river banks and bends in such a way that to form a smooth bank alignment and least interference with river morphology. Also such rock revetment would be essential to protect water intake structures, different type of bridges, dams, weirs, barrages, shores, wave breaks, and diversion structures. The used materials for bank protection usually consist of cemented layer of lime stones and sand which are economically suitable and widely available in Egypt. This protection type can be successfully applied above the minimum water levels while lower than that level, a freely depend stone is to be used. But in some other cases, a rock protective layer consists of (un-cemented) particles can be applied to allow water to percolate through the revetment.

Chapter 2 Literature Review

In this respect, different design criteria for rock protection can be applied including riprap, rock trench, mattress, gabions, soil cement and concrete blocks (Searcy 1967; Norman, 1975). The main design criteria is that the top elevation of bank protection should be above the highest design water level in straight reaches, while in case of curved reaches the super elevation of water surface should be considered. Furthermore, for any structures built in erodible materials, the toe elevation should be extended below the expected scour by a minimum of about 2 vertical meters in medium to large streams as illustrated in Figure (2-16).

Figure (2-16) Bank Protection Layers

The purpose of the extended toe is only to prevent undermining and not to support the above structure. While, on the concave bank of sharp river bends, severe local scour is expected and the toe protection should be deeper than that in straight reaches. Additionally, and according to practices carried out by many engineers the necessity of using appropriate filters between the protection layers and the underlying permeable soil is recommended. Two types of bank protections would be presented as stone revetment and riprap protection and the design of filter layers would be also illustrated.

2-11-1 Stone protection The river bank may be protected using hand placed particles of different sizes to form a layer thickness of at least 0.5 m. This layer should be carefully arranged to provide river channel bank protection in such a way as to form a smooth bank alignment and least interference with river morphology. In order to fulfill stability of the protective layer board, stone toe should be formed on the original river bed up to the minimum water surface level. While in order to provide such primary stability to the eroded bank materials, a graded gravel filter (traditional aggregate filter) can be applied underneath the rock protective layer. In Egypt after the construction of the High Aswan Dam, many attempts have been made to reduce the adverse impact of bank erosion. Therefore development and updating new techniques for bank protection are representing high priorities to the country. Many aspects 29

Chapter 2 Literature Review were taken into consideration; important amongst them are using local materials and labors, inexpensive and the long life durability of the protection work. Different types of data are collected through hydrographic survey to design the toe structure which would be implemented during the period of the minimum water surface levels as shown in Figure (2- 17).

Figure (2-17) Typical Stone Revetment at the Nile River in Egypt

In addition to the designed filter and protective rock layers which would be applied on the river bank board up to the top level using hand placed dry stones as shown in Figure (2-18) which illustrates an example of the applied stone revetment at the Nile River.

Figure (2-18) An Example of the Applied Design for Stone Revetment

Additionally, complete stability analysis should also be performed. This analysis includes geometry, geotechnical field and laboratory testing programs, surface and ground water levels as well as all other hydrological and morphological data to represent each surveyed cross section. The output of the stability analysis is given in terms of the factor of safety. This factor is compared to the standard specification and when the resulted value does not meet the specified criteria, the design should be improved till reaching the typical required values. So far the presented design for stone revetment has proved to be the most suitable approach for protecting river channel banks against erosion in Egypt which is due to the following reasons:

Chapter 2 Literature Review

 Availability of used materials as local product of Egypt.  Economic accessibility of such materials comparing with other bank protection required materials, which can be disassembled and reused if necessary.  Minor interference with river morphology comparing with other methods such as spur dikes or submerged vanes.  Easy to be monitored and maintained after construction to secure failures.  It can be successfully implemented using unqualified labors.  Long life with minimum maintenance requirements and good appearance.  Grass and vegetation usually grow on the top of the slope adding more stability.

2-11-2 Design of Stone Riprap may be defined as a layer consists of discrete rock particles placed on stream banks, slopes of dams and highway embankments to prevent erosion or scour of structures due to flowing water. Rock material can be successfully employed as riprap, to meet certain requirements such as sufficient weight for stability, porosity for drainage, roughness for energy dissipation, availability in even the most remote areas, and finally low cost compared with manufactured materials such as concrete. A number of design criteria for sizing riprap have been developed by Lane (1955), Stevens and Simons (1971 and 1976), Ruh-Ming et. al.,(1976 and 1979), Samad (1978) and Ahmed (1988). Some of these methods have been derived from the viewpoint of equilibrium of a single particle in flowing water and referred to as deterministic approach. While in the case of the others, which are referred to as the probabilistic approaches, the fluctuating nature of the hydrodynamic forces acting on an individual particle has been considered. The earlier formula to design such riprap protection was adopted by the U.S. Army Corps of Engineers (1970) which was based on the design criteria by Izbach (1936) for the movement of stone in flowing water. The formula can be written as follows:

½ ½ U = C {2g (S3 - 1) } D (2-20)

In which U is the flow velocity (ft/s); S, is the specific gravity of the stone; g is the gravitational acceleration (ft/s2); D is the mean particle diameter (ft); and C is the Izbach's turbulent coefficient which was taken equal to 0.86 for high turbulent level flow and 1.2 for low turbulent level flow. Latter, the ASCE Sedimentation Manual (1972) recommended the formula proposed by Izbash for the construction of dams by depositing rock in running water.

Chapter 2 Literature Review

The formula was modified to take into account the slope of the bank and can be written as follows:

5 6 4.1 x 10 ssU W  3 3 (2-21) (Ss 1) cos 

In which W is the weight of the stone in pounds; and  is the angle of repose. Furthermore based on the experimental studies, the following formula for sizing riprap for river bed was adopted by Stephensen, (1979):

0.25 U 2 D  1 (2-22) 2 2 2 g(Ss 1)cos  (tan   tan )

In which; D is the mean size of riprap particle (m); is the angle of repose; and  is the bed slope angle in degrees. Concerning size distribution of riprap layer, Simons and Senturk (1977) suggested that riprap gradation should follow a smooth size distribution curve. This would be fulfilled by applying the following criterion:

D0 = 0.2 D50

D20 = 0.5 D50

D100 = 2 D50

2-11-3 Filter Design As mentioned in previous section, the appropriate filters between a riprap layers and the underplaying permeable soil is deemed necessary. The filter layer is playing a considerable rule in preventing leaching of the permeable soil through the riprap interstices. Herman (1984) investigated the scour related to improper filter underneath the riprap downstream hydraulic structures. It was proven during this study that piping and leaching were sometimes the main cause for failure reassembly occurring before riprap erosion. Criteria for such filters to prevent leaching as well as piping failure in alluvium have been formulated by Terzaghi, and Peck (1948). On the basis of the tests, the Terzaghi criteria were slightly modified by the U.S. Army Waterways Experiment Station at Vicksburg, Mississippi, for application in dam design as reported by Posey (1969). Those modified formulae can be described in the following subsections:

Chapter 2 Literature Review

A) Piping Criterion To prevent washing of the underlying material through the filter, the smaller particles in the filter should be small enough to trap the underlying materials. Therefore, for uneven shaped riprap particles, the criterion is considered satisfactory if D (Filter ) 15  4 (2-23) D85 (base)

In which Di is the grain size for which i percentage of the material by weight is finer. Where filter refers to the overlying material and base refers to the underlying material. This criterion is applied to any two adjacent layers among the riprap, filter planet, and base material.

B) Segregation Criterion To ensure that the fine particles are not separated from the filter mixture and washed out of one layer into the one beneath, the particle size distribution curve for both layers should be approximately parallel and not too far apart. This criterion could be considered satisfactory if D ( filter ) 50  25 (2-24) D50 (base)

C) Permeability Criterion The permeability of filter should be sufficient for the hydraulic gradient through it to be negligible compared with that of the underlying material. The size D15 was selected to represent the permeability of both filter and base material and the criterion is D ( filter ) 5  15  40 (2-25) D15 (base) As the above mentioned three criteria were satisfied for the conventional filter design the grain size distribution for every layer can be drown as depicted in Figure (2-19).

100

90 80 Filter Layer (2) Filter Layer (1) 70 60 Sand Base 50 40 Riprap Layer 30 20

10 Percentage Finer By Weight By Finer Percentage 0 1000 100 10 1 0.1 0.01 Particle Size (mm) Figure (2-19) Grain Size Distributions of the Protective Layers

CHAPTER 3 DATA COLLECTION

Chapter 3 Data Collection

3-1 Introduction This chapter is devoted to present the site description and to illustrate the comprehensive arrangement of data collection which was achieved to fulfill the study objectives. These data were preferred in such a way as to enable simulation of the three-dimensional bathymetric features of the study reach as well as to highlight the emerged problems and difficulties due to human interventions. The detailed description of the collected data, include the following sub- titles:  Site description  Hydrographic survey  Velocity measurements  Bed material samples  Hydrological data

3-2 Site Description Kafr El-Zayat city is located at the outer curve of a very sharp bend at Km 123 of Rosetta Branch. The study area is approximately 9.0km long which located - as shown in Figure (3-1) downstream of Delta Barrage km 145.00 to km 154.00 downstream of El-Roda Gauge Station. The study area is a meander consisting of two bends and includes two highway bridges and one railway bridge, as shown in Figure (3-2). The bridges are located 145.676, 145.928, 146.391km downstream El-Roda Gauge Station. The first highway bridge (new one) has three rectangle piers with 16m width and 26.5m length, the distance between piers are 134.5m for each, The second highway bridge (old one) has six piers, 5 rectangle piers with 16m width and 26.5m length and one circular pier with diameter 14m, the distance between piers is 70m and the distance between the circular pier and the next is 29m, the railway bridge consists of four piers, 3 rectangle piers with 4m width and 13m length and one circular pier with diameter 11m, the distance between piers is 70m and the distance between the circular pier and the next is 35m.

Chapter 3 Data Collection

Figure (3-2) Location of the Study Reach

Figure (3-2) Piers of the Bridges

3-3 Hydrographic Survey A hydrographic survey of the study reach was carried out by the Nile Research Institute “NRI” and Hydraulic Research Institute “HRI”, the National Water Research Center during years 1982, 1998, 2003 and 2006. The survey in years 1982 & 2003 were along the study reach but the survey in years 1998 & 2006 were in the first 3.5km, as shown in Table (3-1) and Figures (3-3) to (3.6).

Chapter 3 Data Collection

Table (3-1) Hydrographic Survey of Study Area Km From El-Roda Gauge Station Year Up Stream Down Stream Total Length (Km) 1982 145.00 156.11 11.09 1998 145.00 148.29 3.29 2003 145.00 154.93 9.93 2006 145.00 148.09 3.09

Figure (3-3) River Bed Elevation Survey Year 1982

a) Part1 b) Part2 c) Part3

Figure (3-4) River Bed Elevation Survey Year 1998

Chapter 3 Data Collection

Figure (3-5) River Bed Elevation Survey Year 2003

Figure (3-6) River Bed Elevation Survey Year 2006

3-4 Velocity Measurements The measured velocity distribution by HRI in years of 1998 and 2006 are used in the study area. The measured velocity are measured at three cross sections along the entire reach located as shown in Figures (3-7) and (3-8).

Chapter 3 Data Collection

Figure (3-7) The Measured C. S Velocity Figure (3-8) The Measured C. S Velocity Locations 1998 Locations 2006

The velocity measurements were performed using a propeller type Braystoke current-meter Figure (3-9). For each cross section, the velocity was measured at many points along the cross section. At the each point the velocity was measured at three points along the vertical direction and the average velocity for each point was determined, Figure (3-10).

Figure (3-9) Braystoke Type Current Meter

Chapter 3 Data Collection

Western Third Middle Eastern Third

Water surface Water surface .50 Under W.S 25% of Total Depth

50% of Total Depth

75% of Total Depth

.75 above bed

Figure (3-10) Sketch Illustrated the Vertical Positions in Cross Section to Measure Water Velocity

It should be mentioned that the flow velocities were measured on the 30th of Sep 1998 and 11th of Aug. The corresponding recorded discharge downstream Rosetta barrage was 72.58 million m3 /day and 19.25 million m3 /day respectively. For each measurement profile the average velocity was estimated using Equation No. (3-1) and Figure ( 3-11 )

V V  V V  V  V *0.2D   1 2 *0.3D   2 3 *0.3D   3 *0.2D 1 2 2 2 V        …….(3-1) average D

Figure (3-11) Computation of the Average Velocity

3-5 Bed Material samples Manning coefficient (n) of bed roughness is considered an important parameter for calibrating the mathematical models as well as for their verification process. Many factors are interrelated to formulate the exact value of the Manning roughness; important amongst them are the bed grain size distribution and the vegetation process in the channel. Grab Sediment Sampler shown in Figure (3-12) was used to collect 9 bed material samples from three cross 39

Chapter 3 Data Collection sections (sec1 ,sec2 & sec3) as illustrated in Figure (3-10). The location of bed material sampling show in Figure (3-13).

1 10 cm

Figure (3-12) The Used Grab Sediment Sampler

Figure (3-13) Bed Material Sampling Locations

Those locations were selected to cover the entire features of the study reach and to represent the difference in the value of the Manning roughness. The samples were analyzed for grain size distribution in the soil laboratory of Hydraulics Research Institute at Delta Barrages to be dried up and the sieve analysis tests were performed according to the relevant specifications. The obtained results of the grain size distributions for the nine collected samples are depicted in Figures (3-14), (3-15) and (3-16) while the main characteristics of the samples are shown in Table (3-2).

Chapter 3 Data Collection

Table (3-2) Characteristics of Bed Samples at C.S. (1,2&3) Sample No. C.S. (1) C.S. (2) C.S. (3) Sample properties 1 2 3 1 2 3 1 2 3

D84 (mm) 0.448 0.578 0.434 0.858 0.944 0.471 0.957 0.949 0.708

D50 (mm) 0.267 0.33 0.255 0.552 0.721 0.3 0.871 0.847 0.406

D16 (mm) 0.182 0.205 0.174 0.304 0.134 0.182 0.142 0.161 0.133

D84/D50 1.677 1.7515 1.7019 1.554 1.3092 1.57 1.0987 1.1204 1.7438

D50/D16 1.467 1.6097 1.4655 1.815 5.3806 1.6483 6.1338 5.2608 3.0526 Geometric mean 0.267 0.33 0.255 0.552 0.721 0.3 0.871 0.847 0.406 diameter (mm) Geometric standard 1.568 1.681 1.577 1.681 2.657 1.606 2.599 2.426 2.307 deviation Uniformity coefficient 2.198 2.06 2.053 2.41 8.321 2.407 8.221 7.862 4.777 Sorting coefficient 0.741 0.704 0.738 0.696 0.422 0.732 0.449 0.645 0.558 Curvature coefficient 1.096 0.953 1.023 0.991 0.383 1.265 1.055 3.354 1.254 Sample mean diameter 0.307 0.379 0.298 0.571 0.576 0.33 0.649 0.676 0.421 (mm)

Bed Material Samples Grain Size Distribution Curves Cross-Section No. 1 100 90

80 70 60 50 40 30

PercentFiner by Weight 20 10 0 0.001 0.01 0.1 1 10 100 Particle Size (mm) Sample 1 Sample 2 Sample 3

Figure (3-14) Grain Size Distribution Curves at C.S. No. (1)

Chapter 3 Data Collection

Bed Material Samples Grain Size Distribution Curves Cross-Section No. 2 100

80 70 60 50 40

30 PercentFiner by Weight 20 10 0 0.001 0.01 0.1 1 10 100 Particle Size (mm) Sample 1 Sample 2 Sample 3 Figure (3-15) Grain Size Distribution Curves at C.S. No. (2)

Bed Material Samples Grain Size Distribution Curves Cross-Section No. 3 100 90

80 70 60 50 40 30

PercentFiner by Weight 20 10 0 0.001 0.01 0.1 1 10 100 Particle Size (mm) Sample 1 Sample 2 Sample 3

Figure (3-16) Grain Size Distribution Curves at C.S. No. (3)

However, as they obtained samples from the outer curve contain such higher percentage of sand grains than that of the inner curve which mainly consist of muddy grains with fines. This would be an indication to the action of the surface transverse flow velocity components 42

Chapter 3 Data Collection which attack the bank and bed of the outer curve causing fines to travel from outer curve to sediment at the inner curve zone.

3-6 Hydrological Data It is obvious that flow discharges and the corresponding water levels are essential data to simulate the hydrological characteristics of the study reach. For this reason, daily monitoring of passing discharges through the located hydraulic structures (barrages) and the upstream and downstream corresponding water levels of those barrages as well as at different gauge stations is essential. Figure (3-17) show the Nile river hydrograph in years 1982, 1998, 2003 and 2006. The discharges D.S Rosette barrage at years 1982, 1998, 2003 and 2006 are shown in Figure (3-18). Figures (3-19), (3-20) and (3-21) show the relation between water level at Kafr El-Zayat and discharge D.S Rosetta barrage from year 1990 to 2011. The different discharges (min, max, avr and emergency flow) in the reach at last 20 years shown in Table (3-3).

3.5 1982 3.3 1998

3.1

2.9 2003 2.7 2006 2.5 2.3

2.1 WaterLevel (m) 1.9 1.7 1.5 JAN Feb MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Time (month)

Figure (3-17) Nile River Hydrograph in Years 1982, 1998, 2003 and 2006

80 1982

70 1998 /day) ³ 60 2003 50 2006 40 30 20

10 Discharge(million.m 0 JAN Feb MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Time (month)

Figure (3-18) Water Discharge D.S Rosetta Barrage at Years 1982, 1998, 2003 and 2006 43

Chapter 3 Data Collection

1990 R² = 0.7047 1991 R² = 0.1132 Rating Curve 1994 R² = 0.0061 1995 R² = 0.1226 3.5 1996 R² = 0.0615 1997 R² = 0.1107 1990

3 1991 1994 1995 2.5

1996 1997 2 Linear (1990) Linear 1WaterLevel (m) .5 (1991) Linear (1994) Linear (1995) 1 Linear 0 5 10 15 20 25 30 35 (1996) Discharge (m³/sec) Linear (1997) Figure (3-19) Relation Between Water Level at Kafr El-Zayat and Discharge Down Stream Rosetta Barrage in Years 1990, 1991, 1994, 1995, 1996 and 1997 1998 R² = 0.0939 Rating Curve 2000 R² = 0.1156 2001 R² = 0.1249 3.5 2002 R² = 0.3663 2003 R² = 0.0303 3.3 2004 R² = 0.0838 1998 3.1 2000 2.9 2001 2.7 2002 2.5 2003

2.3 2004 WaterLevel (m) 2.1 Linear (1998) Linear 1.9 (2000) Linear 1.7 (2001) Linear 1.5 (2002) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Linear (2003) Discharge (m³/sec) Linear (2004) Figure (3-20) Relation Between Water Level at Kafr El-Zayat and Discharge D.S Rosetta Barrage in Years 1998, 2000, 2001, 2002, 2003 and 2004

Chapter 3 Data Collection

R² = 0.0176 Rating Curve R² = 0.0019 3 R² = 0.2393 2.8 2009 2.6

2.4 2010

2.2 WaterLevel (m) 2 2011 0 2 4 6 8 10 12 14 16 18 20 22 24 Discharge (m³/sec)

Figure (3-21) Relation Between Water Level at Kafr El-Zayat and Discharge D.S Rosetta Barrage in Years 2009, 2010 and 2011

Table (3-3) Discharge at Rosetta Bridge Q(m.m³/month)

Year Min Average Max Emergence 1990 2.89 11.40 33.68 220.00 1991 3.32 11.62 27.46 220.00 1992 - - - 220.00 1993 - - - 220.00 1994 2.62 11.00 23.87 220.00 1995 2.05 7.23 15.05 220.00 1996 1.90 8.31 14.84 220.00 1997 3.51 8.28 17.10 220.00 1998 5.50 24.17 69.90 220.00 1999 11.89 13.01 13.77 220.00 2000 3.75 20.40 39.12 220.00 2001 5.41 22.84 69.09 220.00 2002 2.84 13.71 25.44 220.00 2003 2.81 11.05 20.14 220.00 2004 - - - 220.00 2005 4.75 12.52 21.36 220.00 2006 4.27 12.31 27.25 220.00 2007 - - - 220.00 2008 - - - 220.00 2009 7.23 14.27 21.74 220.00 2010 5.56 12.26 20.45 220.00 2011 4.40 12.42 20.06 220.00

CHAPTER 4 MATHEMATICAL MODEL PREPARATION

Chapter 4 Mathematical Model Preparation

Chapter 4 MATHEMATICAL MODEL PREPARATION

4-1 General Numerical models could be considered as the most widely applied technique to solve mathematical expressions that describe any physical phenomena. Those models are mainly classified by number of spatial dimensions over which variables are permitted to provide much more detailed results than others. However, collection of adequate and reliable field data is highly required to fulfill suitable model calibration and verification leading to successful application. For this respect, in case of large width to depth ratio of the water body, the horizontal distribution of flow quantities might be the main interest and two-dimensional solutions based on the depth-averaged flow approximations will provide an acceptable description of flow motion. For this purpose, the finite element Surface Water Modeling System “SMS” 2-D mathematical model would be used to simulate the water flow along the study reach. Furthermore, model calibration is the process of adjusting the dimensions of simplified geometric elements and empirical hydraulic coefficients so that values computed by a model reproduce as closely as possible the simulated reach. The ability of a model to reproduce and predict measured values depends on the amount and quality of topographic and hydraulic data collected such as velocity distributions, water-surface elevation, flow rates, and bed roughness. Although model parameters can be adjusted to obtain close agreement between computed and measured values, an adjustment may not be extended beyond physically reasonable values. Consequently, the purpose of model calibration is to obtain an accurate mathematical representation of reality, not a forced fit of a poorly constructed model. A detailed description of the mentioned mathematical model and it’s preparation would be provided in this chapter, as well as presenting the main steps of model calibration and verification for the applied 2-D mathematical model under the following sub-titles:  Models Formulation  Model Preparation  Sensitivity analysis A summary of the information needed and the suggested approach as well as the expected outputs from the model is presented in Figure (4-1).

Chapter 4 Mathematical Model Preparation

Proposed Approaches

Data Collection Modeling and Organization

Geometry and Flow Model Topographic Data * FESWMS Model for * Channel Cross Sections Flow Simulation * Channel Morphology

Calibration and Verification Hydraulic Data * Water Level Hydrograph * Discharge Hydrograph Modeling Application * Velocity Measurements * Simulation of flow

Digital Data Sources * Determination the morphological and * Arial Photography hydrological changes * Image Satellite * Digital Terrain Model * Determination the velocity, water surface, water depths, shear stress, changes of bed elevation under the actual flow condition

* Applying of different Scenarios of flow

Prediction of Navigation Problems * Prediction of bed changes in the future. * Prediction of new thalwag line * Determination the future navigation bottlenecks. * Determination the erosion and deposition

Solutions and Alternatives for Navigation *Fill Solution *Fill & Dredging solution

Figure (4-1) Flowchart of Proposed Approaches in this Study 47

Chapter 4 Mathematical Model Preparation

4-2 “SMS” 2-D Model Formulation 4-2-1 Model Description The “SMS” 2-D mathematical model was developed by the Brigham Young University in cooperation with the U.S. Army Corps of Engineers, Engineer Research and Development Center (ERDC), and the U.S. Federal Highway Administration (FHWA). The model consists of family of numerical models that provide multi-dimensional solutions for solving hydraulics behavior, sediment transport problems, reservoirs, wetlands, estuaries and bays.

The model is a pre- and post-processor for surface water modeling, analysis, and design. It includes tools for managing roughness assignment, editing and visualizing geometric and hydraulic data, as well as creating and editing mesh data for use in numerical analysis. The Finite Element Surface Water Modeling System “FESWMS” is a comprehensive environment for two dimensional flows in horizontal plane model running under the SMS Interface. This model simulates either steady or unsteady 2-D surface-water flows, including sub- and super- critical conditions Lee and Froehlich (1986). FESWMS solves the vertically integrated equations of motion and continuity with a finite element scheme.

4-2-2 Governing Equations The SMS 2-D model is used to compute water surface elevation and horizontal velocity components for sub critical, free surface flow in two dimensional flow fields. Friction is calculated with the Manning or Chezy equation, while steady and unsteady state (dynamic) problems can be analyzed. Equations that describe depth averaged surface water flow account for the effects of bed friction, wind induced stress at the water surface, fluid stresses caused by turbulence, and the effect of the earth rotation. With this in mind, the following points may be illustrated:

A) Basic Equations The depth averaged velocity components in horizontal x and y coordinate directions would be respectively defined as follows:

1 U  udz (4-1) H 

1 V  vdz (4-2) H  zs = zb + H (4-3)

Chapter 4 Mathematical Model Preparation

In which: H Flow water depth (m) z vertical direction zb bed elevation (+msl) zs water surface elevation (+msl) U horizontal velocity in the x direction at a point along the vertical coordinate (m/s) V horizontal velocity in the y direction at a point along the vertical coordinate (m/s) The coordinate system and variables are illustrated in Figure (4-2), while the depth averaged velocity definition is shown in Figure (4-3). The depth-averaged surface water flow relationships would be established by integrating the three dimensional mass and momentum transport equations with respect to the vertical coordinate from the bed to the water surface. Considering vertical velocities and accelerations to be negligible, the vertically integrated mass transport equation or continuity equation can be derived as follows: z q q w  1  2  q (4-4) t x y m In which:

q1 = UH = unit flow rate in the x direction

q2 = VH = unit flow rate in the y direction

qm = mass inflow or outflow rate per unit area

Water surface

w v H

u Bed surface Z Y Zb Plane datum

X Figure (4-2) 3-D Coordinate System

Chapter 4 Mathematical Model Preparation

Figure (4-3) Depth Average Velocity Definition

Considering that the water mass density  is constant throughout the modeled reach, description of momentum transport in x and y directions would be respectively as follows:

2 q   q q    q 1 2  z H P 2  ( 1 2 )   1  gH  gH b  a  q     1 t x  H  y  H 2  y  y

1  (H yx) (H yy)   by  sy  -   0 (4-5)   x y 

2 q   q 1 2    q q  z 1   1  gH   1 2  gH b  q     2 t x  H 2  y  H  x

1  (H xx) (H xy)   bx  sx  -   0 (4-6)   x y 

In which = isotropic momentum flux correction coefficient that accounts for the variation of velocity in the vertical direction g = gravitational acceleration  = water mass density

Pa = atmospheric pressure at the water surface = Coriolis parameter

bx and by = bed shear stresses acting in x and y directions, respectively.

sx and sy = surface shear stresses acting in x and y directions, respectively.

xx, xy, yx, and yy = shear stresses caused by turbulence where, for example, xy is the shear stress acting in x direction on a plane that is perpendicular to the y direction.

Chapter 4 Mathematical Model Preparation

B) Momentum Flux Correction Coefficient Vertical velocity profiles can be approximated by the logarithmic function

u*  z  zb  u  log e   (4-7) k  K  In which u*  c f U  bed shear velocity or bed friction velocity cf = bed shear-stress coefficient k = von Karman's constant K = roughness height

When vertical velocities follow the logarithmic profile, the momentum flux correction coefficient is given by

c  1 f (4-8) k 2

Momentum flux correction coefficients in FESWMS are calculated as

  o  c c f (4-9)

where o and c are specified coefficients. Comparing the two expressions for  gives o = 1 2 and c = 1/k . For most open-channel flows, the coefficient k  0.4, which gives C = 6.25. Constant momentum flux correction factors can be specified by setting o to the desired value, and setting c to zero. Default values in Flo2DH are o = 1 and c = 0. Using these default values means that vertical variations in velocity are considered negligible.

C) Bed Shear Stress Directional components of bed shear stress are computed as follows:

q q2  q2    c m 1 1 2 (4-10) bx f b H 2

q q2  q2    c m 2 1 2 (4-11) by f b H 2

Chapter 4 Mathematical Model Preparation

where cf = dimensionless bed-friction coefficient, and

2 2  zb   zb  mb  1      (4-12)  x   y 

Where mb is a factor that accounts for increased shear stress caused by a sloping bed. Bed friction coefficient cf is given by gn2 g c f  2 1/ 3  2 (4-13) n H c

Where n is Manning roughness coefficient, n = 1.486 for U.S. customary units, or 1.0 for SI units, and c is Chézy roughness coefficient. Both Manning and Chézy coefficients can be described by linear functions of water depth in FESWMS. Variations in flow resistance with water depth might occur when short vegetation is submerged and possibly bent by the flow, or where tree branches come into contact with flow at high stages. Appropriate flow resistance coefficients for natural and constructed channels and for floodplains can be estimated using references such as Chow (1959), Barnes (1967), and Arcement and Schneider (1984).

4-2-3 Numerical Techniques and Limitation The partial differential equations that govern two-dimensional surface-water flow in a horizontal plane are derived from equations that govern three-dimensional flow by neglecting fluid velocity in vertical direction. Therefore, pressure within the fluid is considered the same as in a hydrostatic condition. The numerical technique used to solve the governing equations is based on the Galerkin finite element method. This method is a numerical procedure which could be applied to solve various differential equations encountered physics and engineering problems. For this reason, continuous quantities are generally approximated by sets of variables at discrete points that form networks or meshes. Therefore, due to the fact that the finite element method can be modified to problems of great complexity and unusual geometry, it is an extremely powerful tool to solve problems in the field of heat transfer, fluid mechanics, and mechanical systems. In Addition, the availability of fast and reasonably priced computers allows difficult problems using analytical or mathematical methods to be directly solved by the finite element method. Conservation of momentum as described in classical physics is an example of such a process.

Chapter 4 Mathematical Model Preparation

However FESWMS operates under the hydrostatic assumption; meaning accelerations in the vertical direction are negligible. It is two-dimensional in the horizontal plane. It is not intended to be used for near field problems where vortices, vibrations, or vertical accelerations are of primary interest. Vertically stratified flow effects are beyond the capabilities of FESWMS. Additionally FESWMS is a free-surface calculation model for sub critical flow problems.

4-3 Model Preparation The steps generally taken to simulate surface-water flow using Flo2DH are as follows:  Data assessment,  network design,  model calibration,  model testing, and  model application. These five steps, illustrated in Figure (4-4), are common to the operation of almost any type of numerical model and are described in this section. Additionally the direction lines suggest modification or control of the application process is also shown in the figure.

Data Assessment

Network Design

Model Calibration

Model Testing

Model Application

Figure (4-4) Modeling Steps

In order to reach the finest simulation of the model for the study reach, several sequential steps are followed in order to fulfill its need which is the appropriate simulation for the chosen river site and at the same time the model fit to different ideas for the proposed solutions. To reach this goal the following points will be covered:

4-3-1 Data Assignment As the surface-water flow problem has been defined, the first step in model operation is making use of the gathered data mentioned in chapter 3. Needed data are classified as either topographic or hydraulic data. Topographic data describe the geometry of the physical system 53

Chapter 4 Mathematical Model Preparation including the assignment of the bed elevation to the study mesh, and evaluation of surface roughness to be used in estimating bed friction coefficients. Additionally, hydraulic data include measurements of discharges and the corresponding water levels, velocity cross sections, and rating curves are also collected. The hydraulic data are used to establish the model boundary conditions, model calibration, and model testing process. The overall data needed for the different processes of the current study of modeling operation and their use and source are summarized in Table (4-1).

Table (4-1) Data Needed for Model Validation

DATA ITEM USE OF DATA SOURCE(S) OF DATA

Topographic and Ground-surface To define mesh node locations; layout of hydrographic maps, and elevations a finite element network. cross section surveys. Channel and floodplain On site samples, Aerial surface characteristics, Assessment and definition of bed friction photographs, topographic vegetative cover, and coefficients and eddy viscosity. maps, on-site inspection, sediment composition. and field experience. Hydrological data ( water Establishment of boundary conditions, On-site measurements, and surface elevations, and calibration of model coefficients, and historical data base from discharge) testing model accuracy. stream gauge records. Establishment of boundary conditions, On-site measurements and Current velocity calibration of model coefficients, and database records. testing model accuracy.

The type and amount of required data to design a network properly and to apply a model mainly depend on the purpose of the model. The more data that can be obtained the better simulation can be obtained and all of the data can be used to improve the quality of a model's output. Theoretically, any surface-water flow can be simulated as accurately as wanted provided the important physical processes are represented adequately by the governing equations. However, the purpose of a model needs to be considered when deciding what and how much data is needed to provide results of the desired accuracy. For example, a computational resolution of centimeters or less might be needed to provide the desired results for a model of a laboratory flume. On the other hand, a model of a tidal estuary might require a computational resolution of a kilometer or more. Several factors affect the choice of the adequate amount of data required to reach the ideal modeling, these factors may be denoted as study objectives, the available period, required 54

Chapter 4 Mathematical Model Preparation personnel experience, and financial considerations should be considered before model construction. Therefore, decisions need to be made regarding how much detail to be represented by the model and the extent of a calibration and testing to be carried out. If a high level of detail is provided by a network, risk of not representing a physical system properly will be reduced, but difficulty (in time and expense) of obtaining a solution will be increased. On the hand, if a simple wide grid network is designed, the risk of inaccuracy representing the physical system will be increased, but the difficulty of obtaining a solution will be reduced. Knowledge of important physical processes that govern the response of a system under study is needed to evaluate the transaction between risk of inaccuracy and difficulty of obtaining a solution. Sometimes constraints on time, human resources, or funding will predetermine how much detail can be included in a model and the amount of calibration and testing to be carried out. In order to calibrate the applied 2-D numerical model for the selected study reach, some important hydraulic parameters would be prepared as follows:

4-3-1-1 Roughness estimation (Manning Coefficient) Roughness coefficients of bed material and river configurations are empirical parameters that could strongly influence model solution. Therefore, sufficient and accurate topographic data should be collected; the initially predicted roughness coefficient values will not have to be adjusted extensively during the calibration process. Adjusted roughness coefficients would be carefully made according to the type and size of the materials that compose the bed and banks of the channel as well as the channel configuration. With this respect, Cowan (1956) developed a procedure for estimating the effects of these factors to determine a representative Manning value n for a channel which may be computed as follows: n = (nb +n1 +n2 +n3 +n4)m (4-14) Where:

nb = base value of n for a straight, uniform, smooth channel in natural materials n1 = correction factor for the effect of surface irregularities n2 = value for variations in shape and size of the channel cross section, n3 = value for obstructions n4 = value for vegetation and flow conditions m = correction factor for meandering of the channel

Chapter 4 Mathematical Model Preparation

Therefore, by applying the previous formula at different locations along the study reach, the corresponding Manning roughness coefficient ranges could be estimated for each of the banks, natural bed, and vegetative areas. These roughness values were then classified according to their locations as illustrated in Figure (4-5) and listed in Table (4-2) which would be used to calibrate the 2-D model.

Table (4-2) Ranges of the Estimated Roughness Coefficients Region Estimated Manning factor (n) Region Class No. Min. Max. 1 Original bed Profile 0.015 0.020 2 River banks 0.020 0.025 3 Vegetative areas 0.025 0.045

Reach downstream boundary Region (1): Original bed Profile

Region (2): River banks Region (3): Aquatic weed Infestation

Reach upstream boundary

Figure (4-5) Study Reach Roughness Coefficient Classification

In which:  Region (1) is located at the original bed profiles where flow depth is sufficient to convey the mainstream flow discharge. In this case the roughness would be due to bed forms, type and gradation of bed materials.

 Region (2) is located along the river banks where the roughness is mainly due to bank line irregularities such as boulders, trees, and the existence of different types of training works at different locations.

Chapter 4 Mathematical Model Preparation

 Region (3) is located at shallow depths and deposition zones where flow depth is reduced to minimum values which allow for sun rise penetration through the water. In this case, the ability for vegetation and infested plants increased and consequently roughness coefficient is rapidly raised.

4-3-2 Network Design The next step in modeling is to design a finite element network. Network design can be defined simply as the process by which the surface-water body being modeled is subdivided into an assemblage of finite elements. The basic goal of network design is to create a representation of the water body that provides an adequate approximation of the true solution of the governing equations at a reasonable cost. Decisions as to set the number, size, shape, and pattern of elements used is required to provide an adequate representation of the water body that is to be modeled need to be made when designing a finite element network. If the elements obey some basic requirements for a convergent solution, the accuracy of the solution will improve as the size of the elements in a network is reduced. However, increasing the number of elements in a network also increases computational expenses. Elements need to be made small enough to provide a solution of sufficient detail and accuracy, yet large enough to obtain the solution at a reasonable cost. So in the study at hand the number of elements used for simulation was 9389 elements distributed and assigned as subsequently demonstrated. Next, the limits of the area to be modelled are defined. As a rule, model boundaries were placed where water-surface elevations and flows at maximum conditions cannot reach as close as possible so that any errors introduced at the boundaries will have little influence at the points of interest. After defining boundaries the area is divided into regions that have abruptly different topographic and surface cover characteristics, then every region is divided into elements in a criteria at which the size and shape of which will depend on the desired level of detail in that particular area. So referring to the study reach of different mesh density as shown in Figure (4-6) and Figure (4-7) and illustrated as following:

Chapter 4 Mathematical Model Preparation

Downstream boundary

Upstream boundary

Vertex node Midside node Center node

Triangular o o 5 : 120 o o elements 60 : 120 Quadrilateral elements Figure (4-6) Study Reach Mesh Element Composition

Figure (4-7) Bridge Mesh Element Composition 58

Chapter 4 Mathematical Model Preparation

In this case, the elements are defined by a series of node points for nine-node quadrilateral elements at the element vertices, mid-side points, and at their centers, additionally triangular elements joining different sizes of quadrilateral elements are composed of six nodes at the element vertices, mid-side points. Values of dependent variables are approximated within each element using the nodal values and a set of interpolation functions (also called shape functions). Approximations of the dependent variables are substituted into the governing equations, which generally will not be exactly satisfied, thus forming a residual. Because the system of equations is nonlinear, a Newton iterative solution procedure performed, and the resulting system of equations is solved using an efficient frontal solution scheme. Some conditions regarding the shape of an element need to be satisfied so that to eliminate any dimensional errors, it was taken in mind that internal angles of quadrilateral elements be kept between 60o and 120o as shown in Figure (4-6). For triangular elements it was assured to keep interior angles between 5o and 120o, which means avoiding long, thin elements that come to a sharp point. Another characteristic of network design that affects a finite element solution is the aspect ratio of elements used in the network. The aspect ratio of a two-dimensional element is the ratio of the longest element dimension to the shortest element dimension as shown in Figure (4-8). The optimal aspect ratio for a particular element depends on the local gradients of the solution variables, mainly aligning the longest element dimension to the direction of the smallest gradient and the shortest element dimension to the direction of the largest gradient is best. For example, in stream channels where the longitudinal variation of velocity and depth is gradual and the transverse variation is large, elements can be much longer in the longitudinal direction than in the transverse direction. If the interior angles of triangular elements are kept between 5o and 120o, the maximum aspect ratio that can result is about 12.5. So the mesh creation in the study reach was carefully interpolated by elements of aspect ratio between 1:5 and 1:8. b

a a

b Element aspect ratio = a/b Figure (4-8) Quadrilateral and Triangular Element Aspect Ratios

Chapter 4 Mathematical Model Preparation

Till this point the mesh is in the planer form, therefore the bed elevations should be assigned to each element composing nodal point at the same coordinates. Transforming coordinates of each scatter point and mesh node is automatically interpolated by the SMS program as shown below in Figure (4-9). Each mesh node is individually interpolated and a subset of bathymetry scatter points within a user-defined region near that current mesh node is generated. The used algorithm looks for a user-specifiable, minimum number of bathymetry points within successively larger user-specifiable bounding regions. When the minimum number of points is found, the mesh node elevation is calculated using an Inverse Distance Weighted average of the elevations of only the selected bathymetry points.

Node being SMS radial bounding region interpolated

Scatter points

Mesh Elements

Scatter points used for interpolation

Figure (4-9) Inverse Distance Weighted Average Interpolation Criteria

The stage of network design can be said to be finished when a contour of the whole reach can be plotted by the SMS program, but further checks should be made for undefined nodes which may occur from the lack of scatter points near the denoted nodes at the process of interpolation. After that further investigations of the reach topography can easily be carried out by changing the data range in contour options, as shown in the portion in Figure (4-10) it can be deduced that a scour hole exists closer to the center of the channel, and for the whole reach investigation Figure (4-11) shows the transformation process of changing the plan mesh using the scatter data into the contour mapping.

Figure (4-10) Planer and 3D Contouring after Interpolation Process 61

Chapter 4 Mathematical Model Preparation

Created Mesh

Scatter Points

Interpolation

Contour Map

Figure (4-11) Design Mesh Elevation Assignment 61

Chapter 4 Mathematical Model Preparation

4-3-3 Calibration Results Several model runs were made to achieve the best agreement between measured and resulted values from the model. Measured values of water-surface elevation for year 1998, and velocities will be used to calibrate the mode. This was carried out by adjusting roughness coefficients at various locations along the modeled study reach according to the mentioned ranges in Table (4-4) till the best results are achieved. The model was calibrated using the inflow discharges at Delta Barrage and water levels at Kfer El-Zayat station as shown in Table (4-3). Comparison of the measured field velocities and obtained velocity profiles at the three cross sections located as shown in Figure (4-12), and its results are shown in Figures (4- 13 to 4-15). The comparison between the measurements and simulated water surface elevations at Kfer-El Zayat station showed that there is a good agreement as shown in Figure (4-16) for the calibration.

Table (4-3) Boundary Condition of Calibration Calibration Time Q(m³/day) WL(m) 30/09/1998 840 m³/sec 2.7

Figure (4-12) Location of the Calibration Cross Sections

Chapter 4 Mathematical Model Preparation

Cross Section No.(1) 1.50 Model Field

1.25

1.00

0.75

0.50

VELOCITY (m/s) VELOCITY 0.25

0.00 0 50 100 150 200 250 300 350 400

DISTANCE (m)

Figure (4-13) Flow Velocity Calibration at Cross Section (1)

Cross Section No.(2) 1.00 Model Field

0.75

0.50

0.25 VELOCITY (m/s) VELOCITY

0.00 0 50 100 150 200 250 300 350 400

DISTANCE (m)

Figure (4-14) Flow Velocity Calibration at Cross Section (2)

Cross Section No.(3) 1.00 Model Field

0.75

0.50

0.25 VELOCITY (m/s) VELOCITY

0.00 0 50 100 150 200 250 300 350

DISTANCE (m)

Figure (4-15) Flow Velocity Calibration at Cross Section (3)

Chapter 4 Mathematical Model Preparation

Simulated Measurement 4.50 S1 S2 B1 B2 B3 4.00 Flow K.St 3.50

3.00

2.50 (m) 2.00 1.50 1.00

WATER SURFACE ELEVATION ELEVATION SURFACE WATER 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m)

Figure (4-16) Comparison between the Measurement and Simulated Water Surface Elevation

The three figures indicate good agreement between the measured and predicted velocity profiles for the three cross sections which have the same trend and distributions. Moreover. This comparison confirms the close equivalent of the calibration results where most points are comparable with small percentage of less than 10% difference except two points. On the other hand concerning the estimation of real roughness factor for the study reach, several values were estimated within the listed limits which are illustrated in Table (4-4).

Table (4-4) Calibration Values for Roughness Coefficients Region Region Class Calibration values No. 1 Original bed Profile 0.020 2 River banks 0.030 3 Protection bank 0.040 4 Vegetative areas 0.040 5 Dikes 0.050

4-3-4 Verification Results As calibration phase of the 2-D “SMS” mathematical model was considered satisfactory, another testing stage is carried out which is the verification phase. The model was verified

Chapter 4 Mathematical Model Preparation using the inflow discharges at Delta Barrage and water levels at Kfer El-Zayat station as shown in Table (4-5). Measured values of water-surface elevation for year 2006, and velocities will be used in the verification phase. The comparison between measured and simulated cross sections is shown in Figure.(4-18 to 4-20) which located as shown in Figure (4-17). The comparison between the measurements and simulated water surface elevations at Kfer-El Zayat station showed that there is a good agreement as shown in Figure (4-21) for the verification.

Table (4-5) Boundary Condition of Verification Verification Time Q(m³/day) WL (m) 11/08/2006 222.8 m³/sec 2

Figure (4-17) Location of the Verification Cross Sections

Cross Section No.(1)

0.50 Model Field

0.25 VELOCITY (m/s) VELOCITY

0.00 0 50 100 150 200 250 300 350 400

DISTANCE (m)

Figure (4-18) Flow Velocity Verification at Cross Section (1)

Chapter 4 Mathematical Model Preparation

Cross Section No.(2)

0.50 Model Feild

0.25 VELOCITY (m/s) VELOCITY

0.00 0 50 100 150 200 250 300 350 400

DISTANCE (m)

Figure (4-19) Flow Velocity Verification at Cross Section (2)

Cross Section No.(3)

0.50 Model Field

0.25 VELOCITY (m/s) VELOCITY

0.00 0 50 100 150 200 250 300

DISTANCE (m)

Figure (4-20) Flow Velocity Verification at Cross Section (3)

Simulated S1 S2 Measurement 2.40 B1B 2B

2.20 Flow 3 2.00 1.80 K.St 1.60

1.40 ELEVATION (m) ELEVATION

WATER SURFACE SURFACE WATER 1.20 1.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (4-21) Comparison between the Measurement and Simulated Water Surface Elevation 66

Chapter 4 Mathematical Model Preparation

4-4 Sensitivity Analysis Referring to the SMS specifications for the needed input data for calibration and the relative importance of such data, the weight percentages of different parameters would be illustrated as shown in Figure (4-22). This pie chart illustrates the approximate relative importance to the simulation of the different aspects of any study. It can be denoted that the structure of the geometry and overall study design which comprises an assemblage of nodes and elements are the most significant which represents about 60% of the relative importance. Following that by 20% for the boundary condition assignment which makes a total percentage of 80%. While the other 20% of the relative importance is shared between the roughness assignments by 10%, internal fluid viscosity by 6%, and the rest 4% is devoted to the other factors which includes field data issues, amount of time devoted for the effort, and approach chosen to analyze data. (Wail Fahmy 2005 )

Boundary 21% Conditions

Geometry & 61% Study Design 11%

6% Roughnes % s 4 Viscosity

Other

Figure (4-22) Data Relative Importance to Modeling

Bearing in mind the adopted hydraulic parameters to calibrate the 2-D model and the achieved calibration and verification results, such sensitivity test was carried out on the calibrated model. The objective of such test is to justify the reached calibration parameters and the influence of any small variation of the input data on the attainable calibration results. This sensitivity analysis was carried out by increasing the whole reach Manning roughness coefficient values by an increment of 0.005 to assign the corresponding variation on the longitudinal water surface profile as well as the corresponding sectional velocities. Several tests were carried out to justify the application of different values of roughness coefficients. (Wail Fahmy 2005 )

Chapter 4 Mathematical Model Preparation

4-5 Summary It is obvious that satisfactory calibration and verification results are essentially needed to adjust the dimensions of geometric elements and empirical hydraulic coefficients of the study reach so that the produced model parameters represent as closely as possible the simulated reach. In order to calibrate the applied 2-D mathematical model, the required hydraulic parameters of the measured velocity distributions, water-surface elevation, total flow rates, and bed roughness were provided. Those were prepared in the required input forms in such a way as to suit the morphology of the modeled reach during the calibration stage. Several model runs were conducted to achieve the best agreement between measured and resulted parameters during which the roughness coefficients at various locations along the modeled study reach were adjusted.

Since good were achieved, verification testing stage was carried out during which the corresponding longitudinal water surface profiles to different flow conditions were used. This test was carried out applying the same values that representing the minimum, average, and maximum passing discharges through the study reach during the past ten years.

A third stage was carried out on the calibrated 2-D mathematical model, such sensitivity test was carried out to justify the reached calibration parameters and the influence of any small variation of the input data on the attainable results. In this study, the Manning roughness coefficient increased by increment of 0.005 to assign the corresponding variation on the longitudinal water surface profiles. Several tests were carried out to justify the application of different values of roughness coefficients. This showed that, the minimum attainable difference in the water surface profiles is achieved with the previously reached calibration parameters. This revealed that the adopted calibration parameters of roughness coefficients are the most suitable values which satisfy the best results. At this stage of the study the model can be used to study the proposed training works on the study reach.

CHAPTER 5 MORPHOLOGICAL CHANGES

Chapter 5 Morphological Changes

5-1 Introduction It is obvious that Nile River downstream the Old Aswan Dam (OAD) can be considered as a very low energy river with low water surface gradient. Moreover, the average bed slope along each of the Damietta and Rosetta branches of the Nile Delta of about 240 km long is about 5.6 cm/km. Bearing in mind the tremendous reduction which took place in suspended sediment and flow discharges through the river after the construction of High Aswan Dam (HAD), this leads to conclude that morphological changes took place and extended towards the downstream direction where the study reach is located along Rosetta branch.

5-2 Study Reach General Description The chosen reach for conducting the present study is approximately 9.000 km long of Rosetta Branch with main features as shown in Figure (5-1). The reach is located in Kfer El-Zayat City downstream of Delta Barrages Rosetta Branch which is corresponding to the distance from km 145.00 to km 154.00 downstream of El-Roda Gauge Station. The selected reach consists of two successive meandering curves where bed forms composed of a relatively homogeneous combination of sand. The study area also consists of two highway bridges and one railway bridge.

Figure (5-1) General Plan of the Study Reach

Chapter 5 Morphological Changes

Considering the meandering features of the selected study reach, the following two successive sharp curved zones would be distinguished:

 The upstream curved reach which is about 3.000km long located between km 145.00 and km 148.00 downstream of El-Roda Gauge Station. The curved reach is following anti clock wise direction where the inner curve is situated on the west side and the outer curve is located along the east side of the river.  The downstream curved reach which is about 2.455km long located between km 150.50 and km 153.00 downstream of El-Roda Gauge Station. The curved reach is following clock wise direction where the inner curve is situated on the east side and the outer curve is located along the west side of the river. Therefore, using the geometrical definitions shown in Figure (5-2), parameters of the meandering planform relevant to the study reach were deduced as illustrated in Table (5-1).

(λ) is the meander wavelength

(Р) is the sinuosity a (θ) is the arc angle (Z) is the meander arc length (a) is the amplitude (rc) is the radius of curvature

θ2 rc2

2 rc1 θ1 λ1/2 λ2/2

Figure (5-2) Meandering Planform Parameters

Chapter 5 Morphological Changes

Table (5-1) Meandering Parameters of the Study Reach No. Curvature characteristics U.S. curve D.S. curve 1 Radius of curvature (rc) (km) 2.679 2.678 2 Meander Wavelength (λ) (km) 5.653 (average) 3 Sinuosity (Р) (-) 1.26 2.43 4 Arc angle (θ) (degree) 88o 112o 5 Meander arc length (Z) (km) 7.782 6 Amplitude (a) (km) 4.697

5-3 Bed Elevation Contour Map at Years 1982, 1998, 2003 and 2006 In order to understand the main character of the Nile River after the construction of HAD, comparison of cross section profiles along the study reach during years 1982, 1998, 2003 and 2006 would be illustrated. The survey in years 1982 & 2003 were done along the study reach but the survey in years 1998 & 2006 were done in the first 3.5km. as shown in Figure (5-3) and Figure (5-4).

Figure (5-3) River Bed Elevation for Years 1982 and 2003

Chapter 5 Morphological Changes

Figure (5-4) River Bed Elevation for Years 1998 and 2006

5-4 Morphology Comparison of Years 1982, 1998, 2003 and 2006 The total number of 8 cross sections- as shown in Figure (5-1) was utilized in order to understand the hydrological and morphological change along the study reach. Cross sections 1, 2 and 3 are located just upstream, downstream high way bridge 1 and downstream the railway bridge respectively. Cross section 4 is located at the middle of curve one and cross section 5 is located at transition zone between the two curves. Cross sections 6, 7 and 8 are located at upstream, middle and downstream the second curve.

5-4-1 Comparison of Bed Profiles and Thalweg lines Comparison between the deduced cross section profiles corresponding to the previous and recent hydrographic measurements of years 1982, 1998, 2003 and 2006 are shown in Figure (5-5). This description would be presented as follows:  Cross Section (1) It can be noticed that the section in different years have the same profile. It’s clear also that the deepest point located in the same place and have a level of - 10.65 m MSL at survey 1982 and 1998 but it have a level of -6.15m MSL and -5.93 MSL at survey of years 2003 and 2006 respectively. This mean that deposition was occurred by the time. Also clear that the bank at the right side was filled.  Cross Section (2) It is clear that for all studied years, the deepest points are located in the same place, at right side which consider unsafe to the bank. These deepest points were at level of -1.86, -2.64, -4.82 and -1.78m MSL at years 1982, 1998, 2003 and 2006 respectively. This mean that scour was done until year 2003 and deposited again at year 2006.  Cross Section (3) It can be noticed that the deepest point of the scour hole at right side (outer curve) was filled from level -14.5m MSL at years 1982 and 1998 until reached to

Chapter 5 Morphological Changes

about -7.8m MSL at years 2003 and 2006. It is also noticed that the deviation to the scour hole of about 30m was done towards the inner curve in year 1998.  Cross Section (4) It is clear that the deepest point at year 1982 was -15.15m MSL which is almost the same of year 1998, only deviation to the scour hole of about 40m to the inner curve was done. The bed was deposited to level -12.82m MSL for year 2003 and still stable until year 2006.  Cross Section (5) A little deposition was occurred in a year 2003 compared with a surveyed of a year 1982. The deepest point almost in the same place and have a level of -9.8m and -10.8m MSL in survey of years 1982 and 2003 respectively.  Cross Section (6) Scour at the whole section was occurred in survey of year 2003 compared with 1982. The deepest point didn’t move at a survey of years 2003 and 1982 and they have levels of -6.5 m and -6.0 m MSL respectively.  Cross Section (7) Scour was occurred of 30m distance towards the outer curve from a survey of year 1982 to 2003 while deposition was done to the other side of the section. The deepest point didn’t move at a survey of years 2003 and 1982 and they have levels of -14.6 m and -18.1 m MSL respectively.  Cross Section (8) Comparing a survey of year 1982 to 2003, deposition was occurred to the whole section except a distance of 60m at right hand side where scour was occurred. The deepest point moved 20m to the right hand side from year 1982 to 2003 and have levels -12.9m and -12.7m MSL respectively. Figure (5-6) shows the variation of the lowest bed levels

1982 1982 Cross Section No.(1) 1998 Cross Section No.(2) 1998 2003 4.00 2003

4.00 2006 2006 2.00 2.00 0.00 -2.00 0.00 -4.00 -6.00 -2.00 -8.00 -10.00 -4.00

- ELEVATION (m) 12.00 -14.00 ELEVATION (m) -6.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m)

Chapter 5 Morphological Changes

1982 Cross Section No.(4) 1982

Cross Section No.(3) 1998 1998

4.00 2003 2.00 2003 2006 2006 0.00 -2.00 -4.00 -6.00 -8.00 -10.00

-12.00 -14.00 ELEVATION ELEVATION (m) -16.00 - ELEVATION (m) 18.00 0 50 100 150 200 250 300 0 20 40 60 80 100 120 140 DISTANCE (m) DISTANCE (m)

Cross Section No.(5) 1982 Cross Section No.(6) 1982 4.00 2003 2003

4.00 2.00 0.00 2.00 -2.00 0.00 -4.00 -2.00 -6.00 -8.00 -4.00

-10.00 -6.00 ELEVATION ELEVATION (m) -12.00 ELEVATION (m)) -8.00 0 25 50 75 100 125 150 175 200 225 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m) 1982 Cross Section No.(7) Cross Section No.(8) 1982 2003

2.00 4.00 2003

2.00 -2.00 0.00 -6.00 -2.00 -4.00 -10.00 -6.00 -14.00 -8.00 -18.00 -10.00

-12.00 ELEVATION ELEVATION (m) -22.00 ELEVATION (m) -14.00 0 25 50 75 100 125 150 175 0 25 50 75 100 125 150 175 200 225 DISTANCE (m) DISTANCE (m) Figure (5-5) Comparison of Bed Profiles at Cross Sections (1) to (8)

1982 1998 2003 8.00 S1 S2 Kfr Al zayat Bridges 2006 4.00 B1 B2 B3 N K.St

0.00

-4.00

-8.00

LEVEL (m) LEVEL -12.00

-16.00

-20.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (5-6) Variation of the Lowest Bed Levels 74

Chapter 5 Morphological Changes

It can be concluded that the scour and thalweg line always locate at the outer bend while in transition zone the scour locate approximately near the middle of the section. It is noticed that in some places the recent survey recorded deepest point among the others surveys. The reason of that was the human interfering by filling the critical scour holes after big floods.

5-5 Scour Holes in the Area of Study Figure (5-7) shows the location of the scour holes in the study area. In the outer curve, the velocity is higher than inner curve so, the scour holes are located in the outer curve of the meander where, bank failure can occurring. Figures (5-7) and (5-8) show also the top width, length and depth of the scour holes from year 1982 to 2003. Figure (5-9) show that the area of scour holes no.1 and no.7 were wider in year 2003 than year 1982, but the scour holes no.2 &3 &4 &6 &9 &10 were deposited from year 1982 to year 2003, and scour hole no.5, 8 almost stable.

Figure (5-7) Scour Holes Location in Study Area at Year 1982

Figure (5-8) Scour Holes Location in Study Area at Year 2003

Chapter 5 Morphological Changes

1982 2003

Chapter 5 Morphological Changes

Figure (5-9) Comparison of Scour Holes in Study Area at Years 1982 and 2003

Table(5-2) shows the different variation in characteristics of scour holes no.1&2&3 from year 1982 to year 1998. The scour hole no.1 have length, width and depth of 122, 44 and -11m in 77

Chapter 5 Morphological Changes year 1982 while it reached to 80, 44 and -13m in year 1998 respectively. It means that in year 1982, the length decreased by 42m, width didn’t change and the depth increased by 2m comparing with year 1998. The scour hole no.2 have length, width and depth of 195, 70 and -15m in year 1982 while it reached to 145, 81 and -17m in year 1998 respectively. It means that in year 1982, the length decreased by 50m, width increased by 11m and the depth increased by 2.5m comparing with year 1998. The scour hole no.3 have length, width and depth of 903, 58 and -16m in year 1982 while it reached to 837, 76 and -15m in year 1998 respectively. It means that in year 1982, the length decreased by 66m, width increased by 18m and the depth decreased by 1m comparing with year 1998. Table (5-2) Scour Holes Variation from Year 1982 to 1998

No.Of Hole Width Hole Depth Avr Hole Length (m) Differece Differece Differece Holes (m) (m) Rate/Year

1982 1998 1982 1998 1982 1998 1 122.00 80.00 -42.00 44.00 44.00 - -11.00 -13.00 -2.00 -0.13 2 195.00 145.00 -50.00 70.00 81.00 11.00 -15.00 -17.50 -2.50 -0.16 3 903.00 837.00 -66.00 58.00 76.00 18.00 -16.00 -15.00 1.00 0.06 4 5 6 7 No Data 8 9 10

Table (5-3) shows the different variation in characteristics of scour holes no.1&2&3 from year 1998 to year 2003. The scour hole no.1 have length, width and depth of 80, 44 and -13m in year 1982 while it reached to 148, 53 and -11m in year 1998 respectively. It means that in year 1998, the length decreased by 68m, width increased by 9m and the depth decreased by 2m comparing with year 1982. The scour hole no.2 have length, width and depth of 145, 81 and -17.5m in year 1998 while it reached to 113, 70 and -9m in year 2003 respectively. It means that in year 2003, the length decreased by 32m, width decreased by 11m and the depth decreased by 8.5m comparing with year 1998. The scour hole no.3 have length, width and depth of 837, 76 and -15m in year 1998 while it reached to 1009, 77 and -14m in year 2003 respectively. It means that in year 2003, the length 78

Chapter 5 Morphological Changes increased by 172m, width increased by 1m and the depth decreased by 1m comparing with year 1998.

Table (5-3) Scour Holes Variation from Year 1998 to 2003 No.Of Hole Width Hole Depth Avr Hole Length (m) Differece Differece Differece Holes (m) (m) Rate/Year 1998 2003 1998 2003 1998 2003 1 80.00 148.00 68.00 44.00 53.00 9.00 -13.00 -11.00 2.00 0.40 2 145.00 113.00 -32.00 81.00 70.00 -11.00 -17.50 -9.00 8.50 1.70 3 837.00 1009.00 172.00 76.00 77.00 1.00 -15.00 -14.00 1.00 0.20 4 5 6 7 No Data 8 9 10

Table(5-4) shows the different variation in characteristics of scour holes no.1&2&3 from year 2003 to year 2006. The scour hole no.1 have length, width and depth of 148, 53 and -11m in year 2003 while it reached to 147, 63 and -11.5m in year 2006 respectively. It means that in year 2006, the length decreased by 1m, width increased by 10m and the depth increased by 0.5m comparing with year 2003.

The scour hole no.2 have length, width and depth of 113, 70 and -9m in year 2003 while it reached to 98, 60 and -9m in year 2006 respectively. It means that in year 2006, the length decreased by 15m, width decreased by 10m and the depth didn’t change comparing with year 2003.

The scour hole no.3 have length, width and depth of 1009, 77 and -14m in year 2003 while it reached to 850, 84 and -14m in year 2006 respectively. It means that in year 2006, the length decreased by 159m, width increased by 7m and the depth didn’t change comparing with year 2003.

Chapter 5 Morphological Changes

Table (5-4) Scour Holes Variation from Year 2003 to 2006 No.Of Hole Width Hole Depth Avr Hole Length (m) Differece Differece Differece Holes (m) (m) Rate/Year 2003 2006 2003 2006 2003 2006 1 148.00 147.00 -1.00 53.00 63.00 10.00 -11.00 -11.50 -0.50 -0.17 2 113.00 98.00 -15.00 70.00 60.00 -10.00 -9.00 -9.00 - - 3 1009.00 850.00 -159.00 77.00 84.00 7.00 -14.00 -14.00 - - 4 5 6 7 No Data 8 9 10

Table (5-5) shows the different variation in characteristics of all scours holes no.1 to 3 from year 1982 to year 2006 and scour holes no.4 to 10 from year 1982 to 2003. The scour hole no.1 have length, width and depth of 122, 44 and -11m in year 1982 while it reached to 147, 63 and -11.5m in year 2006 respectively. It means that in year 2006, the length increased by 25.5m, width increased by 19m and the depth increased by 0.5m comparing with year 1982. The scour hole no.2 have length, width and depth of 195, 70 and -15m in year 1982 while it reached to 98, 60 and -9m in year 2006 respectively. It means that in year 2006, the length decreased by 97m, width decreased by 10m and the depth decreased by 6m comparing with year 1982. The scour hole no.3 have length, width and depth of 903, 58 and -16m in year 1982 while it reached to 850, 84 and -14m in year 2006 respectively. It means that in year 2006, the length decreased by 53m, width increased by 26m and the depth decreased by 2m comparing with year 1982. The scour hole no.4 have length, width and depth of 162, 44 and -10.5m in year 1982 while it reached to 132, 53 and -10m in year 2003 respectively. It means that in year 2003, the length decreased by 30m, width increased by 9m and the depth decreased by 0.5m comparing with year 1982. The scour hole no.5 have length, width and depth of 238, 67 and -14m in year 1982 while it reached to 267, 65 and -14m in year 2003 respectively. It means that in year 2003, the length increased by 29m, width decreased by 2m and the depth didn’t change comparing with year 1982.

Chapter 5 Morphological Changes

The scour hole no.6 have length, width and depth of 275, 55 and -11m in year 1982 while it reached to 197, 46 and -10.8m in year 2003 respectively. It means that in year 2003, the length decreased by 78m, width decreased by 9m and the depth increased by 0.2m comparing with year 1982. The scour hole no.7 have length, width and depth of 74, 35 and -7m in year 1982 while it reached to 74, 26 and -7.5m in year 2003 respectively. It means that in year 2003, the length didn’t change, width decreased by 9m and the depth increased by 0.5m comparing with year 1982. The scour hole no.8 have length, width and depth of 572, 73 and -7m in year 1982 while it reached to 615, 40 and -7m in year 2003 respectively. It means that in year 2003, the length increased by 43m, width decreased by 33m and the depth didn’t change comparing with year 1982. The scour hole no.9 have length, width and depth of 837, 108 and -19.2m in year 1982 while it reached to 793, 87 and -17m in year 2003 respectively. It means that in year 2003, the length decreased by 44m, width decreased by 21m and the depth decreased by 2.2m comparing with year 1982. The scour hole no.10 have length, width and depth of 846, 109 and -13.5m in year 1982 while it reached to 840, 62 and -12.7m in year 2003 respectively. It means that in year 2003, the length decreased by 6m, width decreased by 47m and the depth decreased by 0.8m comparing with year 1982. Table (5-5) Scour Holes Variation from Year 1982 to 2003

No.Of Hole Length Hole Width Hole Depth Avr Difference Differece Differece States Holes (m) (m) (m) Rate/Year

1982 2006 1982 2006 1982 2006 1 122.00 147.50 25.50 44.00 63.00 19.00 -11.00 -11.50 -0.50 - Erosion 2 195.00 98.00 -97.00 70.00 60.00 -10.00 -15.00 -9.00 6.00 0.29 Deposition 3 903.00 850.00 -53.00 58.00 84.00 26.00 -16.00 -14.00 2.00 0.10 Deposition 1982 2003 1982 2003 1982 2003 4 162.00 132.00 -30.00 44.00 53.00 9.00 -10.50 -10.00 0.50 0.02 Deposition 5 238.00 267.00 29.00 67.00 65.00 -2.00 -14.00 -14.00 - - - 6 275.00 197.00 -78.00 55.00 46.00 -9.00 -11.00 -10.80 0.20 0.01 Deposition 7 74.00 74.00 - 35.00 26.00 -9.00 -7.00 -7.50 -0.50 -0.02 Erosion 8 572.00 615.00 43.00 73.00 40.00 -33.00 -7.00 -7.00 - - - 9 837.00 793.00 -44.00 108.00 87.00 -21.00 -19.20 -17.00 2.20 0.10 Deposition 10 846.00 840.00 -6.00 109.00 62.00 -47.00 -13.50 -12.70 0.80 0.04 Deposition

Chapter 5 Morphological Changes

Figures (5-10 ), (5-11 ) and (5-12 ) illustrate the development of length, width and depth for each of the scour holes in the surveys of 1982, 1998, 2003 and 2006.

It is clear that the scours length decreased from year 1982 to 1998, while the scour’s width for no2&3 increased and there is no change in scour no1, and it show also that the depth of no 1&2 increased but no.1 almost didn’t change.

The scours length and width for no.1&3 increased from year 1998 to 2003 opposite of no.2, and also the depth of no 1&2&3 decreased. The scours length decreased from year 2003 to 2006,while the scour’s width for no1&3 increased opposite of scour no2, and also the depth of no.1 increased but no.2&3 didn’t change.

Different Length L1998 - L 1982 200.00 L2003 - L1998 L2006 - L2003

Increase 100.00

0.00

1 2 3

Length (m) Length -100.00

Dccrease -200.00 Scour Hole No. Figure (5-10) Scour Hole Length Change at Years 1982, 1998, 2003 and 2006

Different Width W1998 - W1982 20.00 W2003 - W1998 W2006 - W2003

10.00

Increase

0.00

1 2 3

-(m) Width 10.00

Dccrease -20.00 Scour Hole No.

Figure (5-11) Scour Hole Width Change at Years 1982, 1998, 2003 and 2006

Chapter 5 Morphological Changes

Different Depth D1998 - D1982 10.00 D2003 - D1998 D2006 - D2003 8.00

6.00

4.00 Deposition

2.00

Depth (m) Depth 0.00 1 2 3 -2.00 Erosion -4.00 Scour Hole No. Figure (5-12) Scour Hole Depth Change from Years 1982, 1998, 2003 and 2006

 Comparison Between Scour Hole Cross Sections for Years 1982, 1998, 2003 and 2006 Figure (5-13) and (5-15) show the location of cross and longitudinal sections from 1 to 10 which are chosen by such way to describe the scour hole development along the whole reach.

Figure (5-13) Cross Sections Location for Scour Holes

Figure (5-14) and (5-16) illustrated the comparison of cross and longitudinal sections on the scour holes for years of 1982, 1998, 2003 and 2006. It is noticed that for cross section 1&2&3 the scour hole became the deepest and shifted to left hand side in year of 1998 with a comparison with the other years. This was happened due to big flood in year 1998. For the cross section of scour hole no.3 was shifted to the left hand side and the irregular longitudinal section was existed at 1998 if it compared by the other years. This was done due to the big flood in a year 1998 and the location of this scour hole which is just downstream the bridge piers and narrow width. For cross and longitudinal sections no.4 to no.10, it is found that slide 83

Chapter 5 Morphological Changes deposition was existed along the section in year 2003 comparing with other years. This was because filling work in the reach after 1998 flood.

Cross Section No.(1) 1982 Cross Section No.(2) 1982 1998 1998 2003 2.00 2003 2.00 2006 2006 -2.00 -2.00 -6.00 -6.00 -10.00

-10.00 LEVEL (m)

LEVEL LEVEL (m) -14.00 -14.00 -18.00 0 40 80 120 160 200 240 280 0 40 80 120 160 200 240 280 DISTANCE (m) DISTANCE (m)

Cross Section No.(3) 1982 Cross Section No.(4) 1982 1998 4.00

2.00 2003 2003

2006 -2.00 0.00 -6.00 -4.00 -10.00

LEVEL LEVEL (m) -8.00 LEVEL LEVEL (m) -14.00 -18.00 -12.00 0 20 40 60 80 100 120 140 0 40 80 120 160 200 240 280 DISTANCE (m) DISTANCE (m) Cross Section No.(5) 1982 Cross Section No.(6) 1982 4.00 2003 4.00 2003

0.00 0.00 -4.00 -4.00 -8.00

LEVEL LEVEL (m) -8.00

-12.00 LEVEL (m)

-16.00 -12.00 0 40 80 120 160 200 240 0 40 80 120 160 200 240 DISTANCE (m) DISTANCE (m)

Cross Section No.(7) 1982 Cross Section No.(8) 1982 4.00 4.00

2003 2003

2.00 2.00 0.00 0.00 -2.00 -2.00

-4.00 -4.00 LEVEL LEVEL (m) LEVEL LEVEL (m) -6.00 -6.00 -8.00 -8.00 0 40 80 120 160 200 0 40 80 120 160 200 240 DISTANCE (m) DISTANCE (m)

Chapter 5 Morphological Changes

Cross Section No.(9) 1982 Cross Section No.(10) 1982 4.00 2003 2003 2.00

0.00

-4.00 -2.00 -8.00 -6.00 -12.00

LEVEL LEVEL (m) -10.00

LEVEL LEVEL (m) -16.00 -20.00 -14.00 0 40 80 120 160 0 40 80 120 160 200 240 DISTANCE (m) DISTANCE (m)

Figure (5-14) Scour Holes Cross Sections for Years 1982, 1998, 2003 and 2006

 longitudinal Sections Combination Between Scour Holes

Figure (5-15) Longitudinal Sections Location for Scour Holes

Cross Section No.(1) 1982 Cross Section No.(2) 1982 1998 0.00 1998 2003 2003

2.00

2006 2006 -4.00 -2.00

-6.00 -8.00 LEVEL LEVEL (m) -10.00 LEVEL (m) -12.00

-14.00 -16.00 0 40 80 120 160 200 240 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m)

Chapter 5 Morphological Changes

1982 Cross Section No.(3) Cross Section No.(4) 1982 0.00 1998 2.00

2003 0.00 2003

-4.00 2006 -2.00 -4.00 -8.00 -6.00 -8.00

-12.00 -10.00 LEVEL LEVEL (m) LEVEL LEVEL (m) -12.00 -16.00 -14.00 0 400 800 1200 0 40 80 120 160 200 240 DISTANCE (m) DISTANCE (m)

Cross Section No.(5) 1982 Cross Section No.(6) 1982 0.00 0.00

-2.00 2003 -2.00 2003

-4.00 -4.00 -6.00 -6.00 -8.00 -8.00

-10.00 -10.00 LEVEL LEVEL (m) -12.00 LEVEL (m) -12.00 -14.00 -14.00 0 60 120 180 240 300 360 0 60 120 180 240 300 360 DISTANCE (m) DISTANCE (m) Cross Section No.(7) 1982 Cross Section No.(8) 1982 0.00 0.00

2003 2003

-2.00 -2.00

-4.00 -4.00

-6.00 -6.00

LEVEL LEVEL (m) LEVEL LEVEL (m) -8.00 -8.00 0 40 80 120 160 200 240 280 0 100 200 300 400 500 600 DISTANCE (m) DISTANCE (m) Cross Section No.(9) 1982 Cross Section No.(10) 1982 0.00 0.00

2003 2003

-4.00 -4.00 -8.00 -12.00 -8.00

-16.00 -12.00

LEVEL LEVEL (m) LEVEL LEVEL (m) -20.00 0 200 400 600 800 -16.00 DISTANCE (m) 0 200 400 600 800 1000 DISTANCE (m) Figure (5-16) Scour Holes Longitudinal Sections for Years 1982, 1998, 2003 and 2006

CHAPTER 6 MODEL APPLICATION AND SCOUR CALCULATION

Chapter 6 Model Application and Scour Prediction

Chapter 6 Model Application and Scour Calculation

6-1 Model Application After the calibration process the model can be used to run several cases of different flow conditions such as minimum, average, maximum and emergency flow to predict the flow pattern.

The reach was simulated 4 times using surveys of 1982, 1998, 2003 and 2006. The calibration and verification were done as shown in chapter four. The model was run 4 times at minimum, average, maximum and emergency flow for each of years 1982, 1998, 2003 and 2006. The discharge and their corresponding water level were taken as upstream and downstream boundary conditions respectively. The collected data indicated in Table (6-1) for the different discharge and water level as follows:-  Minimum discharge 6.65 Mm3/day  Average discharge 13.92 Mm3/day  Maximum discharge 69.90 Mm3/day  Emergency discharge (future release) 220 Mm3/day

Table (6-1) Boundary Condition Kfer El-Zayat WL U.S D.S Q Q Station Discharge (m) 145 km 154 km (million.m³/day) (m³/sec) 146 km

WL min 1.57 1.57 1.54 Qmin 6.65 76.97

WL avr 2.09 2.08 2.04 Qavr 13.92 161.11

WL max 2.62 2.60 2.48 Qmax 69.90 809.03 WL 6.01 5.90 5.06 Q 220.00 2546.30 Emergency Emergancy

For each run the water surface along the reach following the thalwege line and velocity profiles at 8 cross sections were estimated. The location of these cross sections are shown in Figure (5-1).

6-1-1 Model Runs for Minimum Discharge Minimum discharge of 6.65Mm3/day and their corresponding water level of 1.57m at Kfer El- Zayat station are considered as up and down stream boundary conditions. The model was runs 4 times at minimum flow for years of 1982, 1998, 2003 and 2006. The average velocity 87

Chapter 6 Model Application and Scour Prediction profile at 8 cross sections for the above mentioned 4 runs in a comparison are shown in Figure (6-1). The results show that:  The velocity average magnitudes at the study area where ranges from (0.02m/s to 0.4m/s) at left hand side, while the velocity at right hand side ranges from ( 0.04m/s to 0.16m/s).  Big difference in magnitude was appeared at a distance of 65m from left hand side of the velocity in cross section no.1 at flood of year 1998 compared with other years. The reason of this high velocity is that, the concerned area is shallow while the rest of the section have big depths.  It is noticed that the velocity profile along some cross sections in year 2003 almost bigger than the corresponding one in year 1982 such as cross sections no.4, 5, 7 and 8. This means that the cross section area of those sections were bigger in year 1982 than in year 2003.

Water surface level at the study area (above the thalwege line) in case of minimum discharge is the highest in year 1998 from the beginning up to first bridge while the water surface in year 1982 is the highest at the rest of the reach as shown in Figure (6-2).

Cross Section No.(1) 1982 Cross Section No.(2) 1982 1998 1998 0.25 2003 0.45 2003

2006

2006 0.20

0.30 0.15

0.10

0.15 VELOCITY (m/s) VELOCITY VELOCITY (m/s) VELOCITY 0.05

0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m) Cross Section No.(3) 1982 Cross Section No.(4) 1982 1998 1998 0.10 2003 2003 2006

0.20 2006

0.05

0.10

VELOCITY (m/s) VELOCITY VELOCITY (m/s) VELOCITY 0.00 0.00 0 50 100 150 200 250 300 0 20 40 60 80 100 120 140 DISTANCE (m) DISTANCE (m)

Chapter 6 Model Application and Scour Prediction

Cross Section No.(5) 1982 Cross Section No.(6) 1982 0.10 0.15

2003 2003

0.10

0.05

VELOCITY (m/s) VELOCITY VELOCITY (m/s) VELOCITY

0.00 0.00 0 25 50 75 100 125 150 175 200 225 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m)

Cross Section No.(7) 1982 Cross Section No.(8) 1982 0.10 0.10

2003 2003

0.05 0.05

VELOCITY (m/s) VELOCITY VELOCITY (m/s) VELOCITY

0.00 0.00 0 25 50 75 100 125 150 175 0 25 50 75 100 125 150 175 200 225 DISTANCE (m) DISTANCE (m) Figure (6-1) Comparison between the C. S Velocity Profiles in Case of Min Discharge

S1 S2 1.70 1982 Kfer El Zayat Bridges 1998 Flow 2003 1.65 B1B 2 B3 2006

1.60

1.55 K.St

1.50

1.45 WATER SURFACE ELEVATION SURFACE WATER ELEVATION (m) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (6-2) Water Surface in Case of Minimum Discharges (6.65 Mm3/day)

6-1-2 Average Discharge Average discharge is 13.92Mm3/day and the corresponding water level is 2.08m at Kfer El- Zayat station are considered as up and down stream boundary conditions.

Chapter 6 Model Application and Scour Prediction

The model was run 4 times at average flow for years of 1982, 1998, 2003 and 2006. The average velocity profile at 8 cross sections for the above mentioned 4 runs in a comparison are shown in Figure (6-3). The results shows that:  The velocity average magnitudes at the study area ranges from (0.05m/s to 0.6m/s) at left hand side, while the velocity at right hand side ranges from (0.03m/s to 0.28m/s).  Big difference in magnitude appeared at a distance of 65m from left hand side of the velocity in cross section no.1 at flood of year 1998 compared with other years. The reason of this high velocity is that concerned area is shallow while the rest of the section has big depths.  It is noticed that the velocity profile along some cross sections in year 2003 are bigger than the corresponding one in year 1982 such as cross sections no.4, 5, 7 and 8. This means that the cross section area of those sections were bigger in year 1982 than in year 2003.

Water surface level at the study area (above the thalweg line) in case of average discharge is the highest in year 1982 as shown in Figure (6-4).

Cross Section No.(1) 1982 Cross Section No.(2) 1982 1998 0.30 1998

2003 2003 0.50 2006 2006 0.20

0.25 0.10 VELOCITY VELOCITY (m/s) 0.00 VELOCITY (m/s) 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 DISTANCE (m) DISTANCE (m) Cross Section No.(3) 1982 Cross Section No.(4) 1982 1998 1998 0.30 2003 0.15 2003

2006 2006 0.20 0.10

0.10 0.05

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 20 40 60 80 100 120 140 DISTANCE (m) DISTANCE (m)

Chapter 6 Model Application and Scour Prediction

Cross Section No.(5) 1982 Cross Section No.(6) 1982

0.20 0.25

2003 2003 0.15 0.20 0.15 0.10 0.10 0.05 0.05

0.00 VELOCITY VELOCITY (m/s)

VELOCITY VELOCITY (m/s) 0.00 0 30 60 90 120 150 180 210 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m)

Cross Section No.(7) 1982 Cross Section No.(8) 1982 0.15 0.20

2003 2003 0.15 0.10 0.10 0.05

0.05 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 175 0 30 60 90 120 150 180 210 DISTANCE (m) DISTANCE (m) Figure (6-3) Comparison between the C. S Velocity Profiles in Case of Ave. Discharge

S1 S2

2.30 1982 Kfer El Zayat Bridges 1998 B3 2.25 B1 B2 2003 Flow 2006 2.20 K.St

2.15

2.10

2.05 WATER WATER SURFACE ELEVATION (m) 2.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (6-4) Water Surface in Case of Average Discharges (13.92 Mm3/day)

6-1-3 Maximum Discharge Maximum discharge is 69.90Mm3/day and the corresponding water level is 2.60m at Kfer El- Zayat station are considered as up and down stream boundary conditions.

Chapter 6 Model Application and Scour Prediction

The model was runs 4 times at maximum flow for years of 1982, 1998, 2003 and 2006. The average velocity profile at 8 cross sections for the above mentioned 4 runs in a comparison are shown in Figure (6-5). The results show that:  The velocity average magnitudes at the study area ranges from (0.4m/s to 1.6m/s) at left hand side, while the velocity at right hand side ranges from (0.3m/s to 1.1m/s).  Big difference in magnitude was appeared at a distance of 65m from left hand side of the velocity in cross section no.1 at flood of year 1998 compared with other years. The reason of this high velocity is that concerned area is shallow while the rest of the section have big depths.  It is noticed that the velocity profile along some cross sections in year 2003 are bigger than the corresponding one in year 1982 such as cross sections no.4, 5, 7 and 8. This means that the cross section area of those sections were bigger in year 1982 than in year 2003.

Water surface level at the study area (above the thalwege line) in case of maximum discharge is the highest in year 1982 as shown in Figure (6-6).

Cross Section No.(1) 1982 Cross Section No.(2) 1982 2.00 1998 1998 2003 1.40 1.75 2003

2006 1.20 1.50 2006 1.25 1.00 1.00 0.80 0.75 0.60 0.50 0.40 0.25 0.20 VELOCITY VELOCITY (m/s) 0.00 VELOCITY VELOCITY (m/s) 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 DISTANCE (m) DISTANCE (m) Cross Section No.(3) 1982 Cross Section No.(4) 1982 1998 1998 1.20 0.80 2003 2003

1.00 2006 2006 0.80 0.60 0.60 0.40 0.40 0.20 0.20

0.00 0.00 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0 50 100 150 200 250 300 0 20 40 60 80 100 120 140 DISTANCE (m) DISTANCE (m)

Chapter 6 Model Application and Scour Prediction

Cross Section No.(5) 1982 Cross Section No.(6) 1982

1.00 1.00

2003 2003 0.80 0.80 0.60 0.60 0.40 0.40

0.20 0.20 VELOCITY VELOCITY (m/s)

0.00 VELOCITY (m/s) 0.00 0 25 50 75 100 125 150 175 200 225 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m)

1982 Cross Section No.(8) 1982 Cross Section No.(7) 0.80 0.60

2003 2003

0.60 0.40 0.40 0.20

0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 175 0 25 50 75 100 125 150 175 200 225 DISTANCE (m) DISTANCE (m) Figure (6-5) Comparison between the C. S Velocity Profiles in Case of Max. Discharge

3.50 S1 S2

3.40 Kfer El Zayat Bridges 1982 3.30 Flow 1998 B2 B3 2003 3.20 B1 2006 3.10 3.00 2.90 2.80K.St 2.70 2.60 2.50 2.40

2.30 WATER WATER SURFACE ELEVATION (m) 2.20 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (6-6) Water Surface in Case of Maximum Discharges (69.90 Mm3/day)

6-1-4 Emergency Discharge Emergency discharge is 220Mm3/day and the corresponding water level is 5.09m at Kfer El- Zayat station are considered as up and down stream boundary conditions.

Chapter 6 Model Application and Scour Prediction

The model was runs 4 times at emergency flow for years of 1982, 1998, 2003 and 2006. The average velocity profile at 8 cross sections for the above mentioned 4 runs in a comparison are shown in Figure (6-7). The results show that:  The velocity average magnitudes at the study area ranges from (0.77m/s to 1.84m/s) at left hand side, while the velocity at right hand side ranges from (0.64m/s to 1.7m/s).  Big difference in magnitude appeared at a distance of 65m from left hand side of the velocity in cross section no.1 at flood of year 1998 compared with other years. The reason of this high velocity is that concerned area is shallow while the rest of the section have big depths.  It is noticed that the velocity profile along some cross sections in year 2003 almost bigger than the corresponding one in year 1982 such as cross sections no.4, 5, 7 and 8. This means that the cross section area of those sections were bigger in year 1982 than in year 2003. Water surface level at the study area (above the thalwege line) in case of emergency discharge is the highest in year 1998 from the beginning up to first bridge while the water surface in year 1982 is the highest at the rest of the reach as shown in Figure (6-8).

Cross Section No.(1) 1982 Cross Section No.(2) 1982 2.00 1998 1998 2003 2.00 2003 1.75

2006 2006 1.50 1.60 1.25 1.20 1.00 0.75 0.80 0.50

0.25 0.40 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 350 DISTANCE (m) DISTANCE (m) Cross Section No.(3) 1982 Cross Section No.(4) 1982 1998 2.00 1998 2.00 2003

2003 2006 1.60 1.60 2006 1.20 1.20 0.80 0.80

0.40 0.40 VELOCITY VELOCITY (m/s)

0.00 VELOCITY (m/s) 0.00 0 50 100 150 200 250 300 0 20 40 60 80 100 120 140 DISTANCE (m) DISTANCE (m)

Chapter 6 Model Application and Scour Prediction

Cross Section No.(5) 1982 Cross Section No.(6) 1982 2.00 1.80 1.60 2003 2003 1.60 1.40 1.20 1.20 1.00 0.80 0.80 0.60 0.40 0.40

0.20 VELOCITY VELOCITY (m/s)

VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 175 200 225 0 50 100 150 200 250 300 350 400 DISTANCE (m) DISTANCE (m)

Cross Section No.(7) 1982 Cross Section No.(8) 1982 2.00

1.60 2003 2003

1.60

1.20 1.20

0.80 0.80

0.40 0.40 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 175 0 25 50 75 100 125 150 175 200 225 DISTANCE (m) DISTANCE (m) Figure (6-7) Comparison between the C. S Velocity Profiles in Case of Emer. Discharge

S2 6.20 S1 6.10 Kfer El Zayat Bridges 1982 B1B 2 B3 1998 6.00 2003 5.90 Flow 2006 5.80 5.70 5.60 K.St 5.50 5.40 5.30 5.20 5.10 5.00 WATER WATER SURFACE ELEVATION (m) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (6-8) Water Surface in Case of Emergency Discharges (220 Mm3/day)

6-2 Scour Prediction The effect of releasing high and emergency discharges in the study reach were analysed. The scour at the three bridge piers and the meander in Rosetta Branch in front of Kfer El-Zayat city were evaluated. The potential magnitude and extent of scour that may occur at bridge

Chapter 6 Model Application and Scour Prediction sites during flood events in response to rapid changes in flow discharges in the river was considered. The following sections show the scour prediction and evaluation which includes general scour, local scour, contraction scour, and bend scour were analyzed for the whole reach and bridges site.

6-2-1 The Local Scour at Bridge Piers Prediction The study area consists of a meander includes two successive bends, two highway bridges and one railway bridge. The location of the bridges is shown in Figure (6-9). The bridges are located at 145.676, 145.928, 146.391km downstream of El-Roda Gauge Station. The first highway bridge has three rectangle piers with 16m width and 26.5m length, the distance between each two piers are 134.5m. The second highway bridge has six piers, five rectangle piers with 16m width and 26.5m length and in the middle of them one circular pier with diameter of 14m, the distance between each two piers is 70m and the distance between the circular pier and the next one is 29m. The railway bridge consists of four piers, three rectangle piers with 4m width and 13m length and one circular pier with diameter of 11m, the distance between piers is 70m and the distance between the circular pier and the next one is 35m, Table (6-2).

Railway Bridge 3

Highway Bridge 2

Highway Bridge 1

Figure (6-9) Location of the Bridge Piers

Chapter 6 Model Application and Scour Prediction

Table (6-2) Location and Diminutions of the Bridge Piers

Bridge Bridge 1 Bridge 2 Bridge 3 No. Location (km) 146.00 146.239 149.682 Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Pier Shape Rec Rec Rec Rec Rec Cir Rec Rec Rec Rec Rec Cir Rec Diameter ------14.00 ------11.00 ------(m) Width 16.00 16.00 16.00 4.00 4.00 ------4.00 4.00 4.00 4.00 4.00 ------4.00 (m)

Length 26.50 26.50 26.50 15.00 15.00 ------15.00 15.00 13.00 13.00 13.00 ------13.00 (m) Dist. 41.25 182.1 300.9 77.64 147.3 170.0 206.1 276.8 347.7 58.11 132.04 157.61 195.90 (m)

Where: Location: downstream of El-Roda Gauge Station, Rec: rectangular, Cir: circular, Dist. : distance from left bank.

The local piers' scour was calculated using the hydraulic parameters based on the water velocities' magnitudes and water depths obtained from applying the 2D model in case of maximum and emergency flow at Rosetta Branch, Table (6-3). The model results showed that in case of maximum flow piers numbers 2, 6 and 12 had a maximum local scour depth for each bridge. The interpretation of that is at piers no.2, 6 and 12, the point velocities were 0.7, 0.61 and 0.71m/sec and the depths were 6.53, 4.82 and 5.47m, which means that, it has maximum point discharges (q) along the bridge piers no.1, 2 and 3 respectively. The same interpretation was considered in case of emergency flow. Tables (6-4) and (6-5) show the parameters which are used in calculation of the local scour at each bridge piers. It shows also the local scour results.

Table (6-3) Boundary Condition

Flow Case Discharge (m.m3/day) Water Level (m)

Maximum 69.90 2.60 Emergency 220.00 5.90

Chapter 6 Model Application and Scour Prediction

Table (6-4) The Used Parameters and the 2D Model Results of Scour Bridge Piers in Case of Maximum Flow Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier 1 2 3 4 5 6 7 8 9 10 11 12 13 a (m) 16.00 16.00 16.00 4.00 4.00 14.00 4.00 4.00 4.00 4.00 4.00 11.00 4.00 L (m) 26.50 26.50 26.50 15.00 15.00 14.00 15.00 15.00 13.00 13.00 13.00 11.00 13.00 L/a 0.60 0.60 0.60 3.75 3.75 0.00 3.75 3.75 3.25 3.25 3.25 0.00 3.25 K1 1.10 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 K2 1.02 1.07 1.07 1.29 1.39 1.00 1.67 1.75 1.58 1.55 1.49 1.00 1.12 K3 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 K4 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 V1 (m/s) 0.60 0.70 0.00 0.65 0.67 0.61 0.57 0.56 0.33 0.58 0.72 0.71 0.71 Y1 (m) 2.66 6.53 0.00 3.09 4.51 4.78 4.82 4.82 5.00 2.31 4.20 5.47 6.75 Fr1 0.12 0.09 0.00 0.12 0.10 0.09 0.08 0.08 0.05 0.12 0.11 0.10 0.09 0.65 [a/Y1] 3.21 1.79 0.00 1.18 0.92 2.01 0.89 0.89 0.86 1.43 0.97 1.57 0.71 YS/Y1 3.16 1.48 0.00 1.34 1.06 1.56 1.12 1.16 0.81 1.97 1.24 1.27 0.61 YS (m) 8.40 9.64 0.00 4.15 4.77 7.48 5.38 5.60 4.04 4.56 5.22 6.95 4.15

Table (6-5) The Used Parameters and The 2D Model Results of Scour Bridge Piers in Case of Emergency Flow Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier Pier 1 2 3 4 5 6 7 8 9 10 11 12 13 a (m) 16.00 16.00 16.00 4.00 4.00 14.00 4.00 4.00 4.00 4.00 4.00 11.00 4.00 L (m) 26.50 26.50 26.50 15.00 15.00 0.00 15.00 15.00 13.00 13.00 13.00 0.00 13.00 L/a 0.60 0.60 0.60 3.75 3.75 0.00 3.75 3.75 3.25 3.25 3.25 0.00 3.25

K1 1.10 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

K2 1.02 1.07 1.07 1.25 1.32 1.00 1.51 1.62 1.59 1.36 1.32 1.00 1.11

K3 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10

K4 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 V1 (m/s) 0.98 1.20 0.64 1.09 1.13 1.04 0.97 0.96 0.66 1.36 1.34 1.32 1.28

Y1 (m) 5.57 9.45 4.10 6.01 7.43 7.70 7.75 7.76 7.94 5.19 7.09 8.36 9.65

Fr1 0.13 0.12 0.10 0.14 0.13 0.12 0.11 0.11 0.07 0.19 0.16 0.15 0.13 0.65 [a/Y1] 1.99 1.41 2.42 0.77 0.67 1.47 0.65 0.65 0.64 0.84 0.69 1.20 0.56

YS/Y1 2.05 1.35 2.13 0.91 0.81 1.30 0.84 0.90 0.73 1.23 0.91 1.15 0.58

YS (m) 11.39 12.77 8.75 5.49 6.04 10.03 6.52 6.96 5.81 6.40 6.45 9.60 5.56

Where:

a : Pier width 'V1 : Approach velocity, upstream L : Pier length 'Y1 : Approach depth, upstream K1 : Correction Pier nose shape Fr1 : Froude number 0.65 0.43 K2 : Correction angle of attack YS/Y1 = 2*K1*K2*K3*K4*(a/Y1) (Fr1) K3 : Correction bed forms YS : Scour depth K4 : Correction armoring

Chapter 6 Model Application and Scour Prediction

6-2-2 Contraction Scour To predict the contraction scour, first the mean velocities for the maximum and emergency flow at the studied area were estimated using the numerical model. Secondly, the critical velocities at the locations of the expected contraction scour at the studied reach were calculated using empirical equations 2-6 and 2-7, (HEC-18). Figure (6-10) shows the five cross sections location for expected contraction scour. Three of these cross sections located at the three bridge piers respectively. Based on the results of the above mentioned methods, it is noticed that the estimated velocities by the empirical equations (critical velocity) were less than the estimated velocities using the numerical model (mean velocity). Hence the live bed contraction scour technique was used in order to estimate the contraction scour at the bridges. While the clear water contraction scour technique was used in order to estimate the contraction scour at the other cross sections. The contraction scour was estimated in Table (6- 6). The results showed that cross section no.1, 2 and 3 have contraction scour. This is expected because the bridge piers widths reduced the whole section widths by ratio of 15, 8.5 and 9% at bridges no.1, 2 and 3 respectively. The results showed also that cross sections no.4 and 5 have no contraction scour because they have enough cross section area to path the maximum flow. It compensate the eroded area of the bank at the outer bend by deposition in the inner side.

Figure (6-10) Cross Sections Location for Contraction Scour

Chapter 6 Model Application and Scour Prediction

Table(6-6) Contraction Scour in Case of Maximum and Emergency Flow Contraction Scour (m)

C.S Maximum Flow Emergency Flow

C.S 1 0.48 0.87 C.s 2 0.25 0.41 C.S 3 0.34 0.57 C.S 4 0 0 C.S 5 0 0

6-2-3 Bend Scour The bend scour was calculated at the studied area using empirical Equation (2-9), (Simons et al. 1989b). Figure (6-11) shows five cross sections location for expected bend scour. The results are shown in Table (6-7). Expected results were shown where cross section no.4 and 5 which located at head of the bend had maximum bend scour.

Figure (6-11) Cross Sections Location for Bend Scour

111

Chapter 6 Model Application and Scour Prediction

Table (6-7) Bend Scour in Case of Maximum and Emergency Flow Bend Scour (m)

C.S Maximum Flow Emergency Flow

C.S 1 3.86 4.10 C.S 2 2.60 2.90 C.S 3 4.35 6.22 C.S 4 5.70 7.04 C.S 5 7.79 8.58

6-2-4 General Scour To define the general and bend scour at the study area, the Neil’s incised Equation (2-10) (Pemberton and Lara 1984) was applied to the two considered high discharges, aiming at predicting the general river bed scour. Figure (6-12) shows the cross sections location for general scour. The general scour was estimated and presented in Table (6-8).

The higher value between Neill’s equation with a bend and the contraction scour equation plus the bend scour equation was considered as the general scour (Pemberton and Lara 1984) and the results shows in Table (6-9). The results showed that contraction scour results gave the lowest scour values when compared to the other types of scours, while the general scour by Neil’s equation is higher than bend and contraction scours.

Figure (6-12) Cross Sections Location for General Scour 111

Chapter 6 Model Application and Scour Prediction

Table (6-8) General Scour in Case of Maximum and Emergency Flow

General Scour by Neil Incised Equation (m)

C.S Maximum Flow Emergency Flow

C.S 1 4.50 6.00 C.S 2 4.20 8.89 C.S 3 6.60 8.11 C.S 4 3.90 6.00 C.S 5 4.80 6.90 C.S 6 4.50 6.00 C.S 7 3.60 5.10 C.S 8 4.80 5.10 C.S 9 6.60 8.11 C.S 10 5.10 5.10 C.S B1 2.70 4.50 C.S B2 2.58 3.90 C.S B3 3.30 5.10

Table (6-9) General Scour for Maximum and Emergency Flow Conditions General Scour Contraction Considered Discharge Bend scour Bend + Contraction C.S No. by Neil’s Scour General (m.m3/day) (m) Scour (m) Equation (m) (m) Scour (m) 69.90 2.70 3.86 0.48 4.34 4.34 Bridge 1 220.00 4.50 4.10 0.87 4.97 4.97 69.90 2.58 2.60 0.25 2.85 2.85 Bridge 2 220.00 3.90 2.90 0.41 3.31 3.90 69.90 3.30 4.35 0.34 4.69 4.69 Bridge 3 220.00 5.10 6.22 0.57 6.79 6.79 69.90 4.50 - - - 4.50 C.S1 220.00 6.00 - - - 6.00 69.90 4.20 - - - 4.20 C.S2 220.00 8.89 - - - 8.89 69.90 6.60 5.70 - 5.70 6.60 C.S3 220.00 8.11 7.04 - 7.04 8.11 69.90 3.90 - - - 3.90 C.S4 220.00 6.00 - - - 6.00 112

Chapter 6 Model Application and Scour Prediction

General Scour Contraction Considered Discharge Bend scour Bend + Contraction C.S No. by Neil’s Scour General (m.m3/day) (m) Scour (m) Equation (m) (m) Scour (m) 69.90 4.80 - - - 4.80 C.S5 220.00 6.90 - - - 6.90 69.90 4.50 - - - 4.50 C.S6 220.00 6.00 - - - 6.00 69.90 3.60 - - - 3.60 C.S7 220.00 5.10 - - - 5.10 69.90 4.80 - - - 4.80 C.S8 220.00 5.10 - - - 5.10 69.90 6.60 7.79 - 7.79 7.79 C.S9 220.00 8.11 8.58 - 8.58 8.58 69.90 5.10 - - - 5.10 C.S10 220.00 5.10 - - - 5.10

6-2-5 Evaluation of Total Scour The total scour can be expressed as the summation of the general, local, contraction and bend scours. The total scour was evaluated by the following Equation: Total Scour = General Scour + Pier Scour + Contraction Scour + Bend Scour The predicted flow pattern at the studied area indicated that the values of bend scour were significant due to the meandering pattern in this area of river reach. The magnitudes of total scour are presented in Table (6-10). Figure (6-13) shows the evaluation of the total scour at Kafr El-Zayat bridge piers. The maximum expected scour for all piers and cross sections from 1 to 10 were estimated. It was found that Piers 2, 6 and 12 had a maximum scour depth. The expected enlargement of the scour holes around Piers 2, 6 and 12 and the other cross sections were computed as follows:

The expected enlargement of the scour holes around the bridge piers = Actual River Bed Elevation - (Water Surface Elevation – Water Depth – Total Scour).

The results are presented in Table (6-11). Figures (6-14) to (6-16) show the location of the bridge piers.

113

Chapter 6 Model Application and Scour Prediction

Table (6-10) Total Scour

Discharge General Scour Local Scour Total Scour Bridge No. Pier No. (m.m3/day) (m) (m) (m) 69.90 4.34 9.64 13.98 Bridge 1 Pier 2 220.00 4.97 12.77 17.74 69.90 2.85 7.48 10.33 Bridge 2 Pier 6 220.00 3.90 10.03 13.93 69.90 4.69 6.95 11.64 Bridge 3 Pier 12 220.00 6.79 9.60 16.39 69.90 4.34 - 4.50 C.S1 220.00 4.97 - 6.00 69.90 2.85 - 4.20 C.S2 220.00 3.90 - 8.89 69.90 5.69 - 6.60 C.S3 220.00 5.74 - 8.11 69.90 4.34 - 3.90 C.S4 220.00 4.97 - 6.00 69.90 2.85 - 4.80 C.S5 220.00 3.90 - 6.90 69.90 5.69 - 4.50 C.S6 220.00 5.74 - 6.00 69.90 5.69 - 3.60 C.S7 220.00 5.74 - 5.10 69.90 4.34 - 4.80 C.S8 220.00 4.97 - 5.10 69.90 7.79 - 7.79 C.S9 220.00 8.58 - 8.58 69.90 5.69 - 5.10 C.S10 220.00 5.74 - 5.10

114

Chapter 6 Model Application and Scour Prediction

Kfer El-Zayat Bridge Q = 220m.m^3/day

Nourth South Bridge Pier Water Level (5.90)m for Q = 220m.m^3/day Max. Water Level(2.60)m Min. Water Level(1.57)m

Original Bed (-4.00)

(-21.74)m General Scour = 4.97m

Local Scour = 12.77m Total Scour = 17.74m

Figure (6-13) Evaluation of the Total Scour at Kafr El-Zayat

Pier 1 Pier 2 Pier 3 Pier 4 Pier 6 Pier 8 Pier 5 Pier 9

5 5 Pier 7

3 3 1 1 -1 -1 -3 -3 -5 (m) Elevation Elevation (m) Elevation -5 0 50 100 150 200 250 300 350 0 100 200 300 400 Distance from Left Bank (m) Distance from Left Bank (m) Figure (6-14) First Bridge Piers Location Figure (6-15) Second Bridge Piers Location

Pier12 Pier10 Pier11 Pier13

5 3 1 -1 -3 Elevation (m) Elevation -5 -7 0 50 100 150 200 250 300 Distance from Left Bank (m) Figure (6-16) Third Bridge Piers Location

115

Chapter 6 Model Application and Scour Prediction

Table (6-11) The Expected Increase of the Scour Holes around the Main Piers of Kafr El-Zayat Bridges

Expected Actual Magnitude Water Water Total River River of Scour Pier Discharge Surface Depth Scour Bed Bed Holes Depth No. (m.m3/day) Elevation (m) (m) Elevation Elevation Enlargement (m) (m) (m) (m) 69.90 2.99 7.20 13.98 14.19 -4.00 -18.19 Pier 2 220.00 5.90 10.00 17.74 17.84 -4.00 -21.84 69.90 2.98 5.90 10.33 10.25 -3.00 -13.25 Pier 6 220.00 5.86 8.90 13.93 13.97 -3.00 -16.97 Pier 69.90 2.88 9.00 11.64 11.76 -6.00 -17.76 12 220.00 5.72 11.90 16.39 16.57 -6.00 -22.57 69.90 2.96 14.00 4.50 4.54 -11.00 -15.54 C.S1 220.00 5.99 17.00 6.00 6.01 -11.00 -17.01 69.90 2.80 12.00 4.20 4.90 -8.50 -13.40 C.S2 220.00 5.73 15.00 8.89 9.66 -8.50 -18.16 69.90 2.76 17.00 6.60 6.34 -14.50 -20.84 C.S3 220.00 5.62 19.50 8.11 7.49 -14.50 -21.99 69.90 2.71 13.00 3.90 4.19 -10.00 -14.19 C.S4 220.00 5.52 15.50 6.00 5.98 -10.00 -15.98 69.90 2.71 16.50 4.80 5.09 -13.50 -18.59 C.S5 220.00 5.52 19.50 6.90 7.38 -13.50 -20.88 69.90 2.67 13.50 4.50 4.83 -10.50 -15.33 C.S6 220.00 5.43 16.50 6.00 6.57 -10.50 -17.07 69.90 2.66 10.00 3.60 3.64 -7.30 -10.94 C.S7 220.00 5.40 12.90 5.10 5.30 -7.30 -12.60 69.90 2.60 9.80 4.80 5.00 -7.00 -12.00 C.S8 220.00 5.80 12.80 5.10 5.10 -7.00 -12.10 69.90 2.56 20.00 7.79 8.23 -17.00 -25.23 C.S9 220.00 5.18 22.50 8.58 8.90 -17.00 -25.90 69.90 2.52 14.50 5.10 4.58 -12.50 -17.08 C.S10 220.00 5.12 17.50 5.10 4.98 -12.50 -17.48

The general scour, local scour, contraction scour and bend scour were computed at the bridges area. The following main conclusions may be drawn: 1. Unexpected velocity profiles resulted in complex flow, and the human interference affects the geometry. 2. Maximum scour depth was located at the upstream piers. 3. The maximum scour depth was directly proportional to discharge.

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4. The increase of the scour hole around the piers of the first bridge was higher than the increase of the scour hole around the piers of the second and third bridges. 5. The local scour around the bridge piers estimated by the 2-D numerical model gave higher scour values than the general scour (Neil’s equation) under the same conditions. 6. The scour around the bridge piers calculated by the scour bend equation (Simons et al. 1989b) gave higher scour values than both general scour equation (Neil’s equation) and contraction scour. 7. Contraction scour results gave the lowest scour values when compared to the other types of scours. 8. The general scour by Neil’s equation is higher than bend and contraction scours.

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CHAPTER 7 ALTERNATIVE SOLUTIONS AND RESULT ANALYSIS

Chapter 7 Alternative Solutions and Result Analysis

7-1 Introduction A comparison of the previous and recent profiles of the study reach revealed that the ultimate effect of river meandering is reached at outer bend where fully developed spiral and transverse flow components are attain.

The measured hydraulic parameters and relevant collected data for the study reach would be worked out to design different proposed solutions. It is obvious that due to economic reasons, the proposed dredging and filling of the bed should be limited to specific selected locations to maintain the required flow improvements near the inner bank as well as the outer bank. Therefore, different alternatives of river bed dredging and filling would be designed to redistribute the velocity profiles along the cross sections for protecting the outer curve along the vulnerable locations of the upstream and downstream curved reaches. Using 2-D numerical model, filling and dredging of the river bed would be tested.

Such higher velocities associated with the release of emergency discharges downstream High Aswan Dam may cause degradation and scour to the entire bed of the reach particularly in the outer curve of the reach where the city of Kfer El-Zayat is located. Consequently, a severe damage to the bridges, agricultural properties, urban areas and roads is expected. So, it is required to improve the velocities at the outer curve. To achieve that, two proposed alternatives were suggested and simulated separately by the 2-D model.

7-2 The Modeled Reach The total length of 9.00 km of the entire reach at Kfer El-Zayat are simulated using 2-D mathematical model. The survey of year 2006 is used in the simulation as the original one. Within this reach, the railway bridge and the two highway bridges are simulated; also, the river bank in front of Kfer El-Zayat is included. The calibration of the hydrodynamic model is carried out by comparing the velocity data produced by the model and velocity obtained from field measurement at three cross sections as shown at chapter 4. The results of water surface slope to the simulated reach is adjusted to be close to survey of year 2006, as shown in Figure (4-19).

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7-3 Simulation of the Proposed Solutions and Results Two proposed alternatives to improve the morphology of the study bend are suggested and simulated separately by the SMS model. In the first alternative, the scour hole of the outer curves is filled with layers of filter and riprap up to level -5.00m MSL. In additional to alternative 1, dredging the inner sides to level -3.00m MSL is proposed as second alternative. The model was run for the two alternatives at maximum and emergence flow with its corresponding water levels which are 809.03m3/s, 2546.30m3/sec, +2.60m MSL and +5.90m MSL respectively. The flow was used as upstream boundary condition and the water level was used as downstream boundary condition.

7-3-1 The First Alternative Simulation The bed levels of the reach are filled to level -5.00 MSL to represent the first alternative. The first alternative is simulated as the above mentioned description. Figure (7-1) shows the entire reach bed elevation in case of alternative 1. Figure (7-2) shows the thalweg line before and after the filling as a comparison between the bed level of the first alternative and the original one. It is clear from Figure (7-1) that the most of the filling areas are concentrated at the outer curves. These also are shown at Figure (7-3), which represents ten cross sections distributed along the reach. The location of these sections is shown in Figure (7-1). The level of deepest point of the scour holes at cross sections from 1 to 10 are -11, -9, -14, -10, -13, 8, -10.7, -7, -7, -17 and -12.5 MSL, respectively. This means that the filling layers of some holes are more than 12m.

Figure (7-1) River Bed Elevation in Case of Alternative 1

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Chapter 7 Alternative Solutions and Result Analysis

2006 Fill

S1 S2 4.00 Kfer El Zayat Bridges K.St B1B 2 B3 Flow 0.00

-4.00

-8.00

-12.00

-16.00

WATER SURFACE ELEVATION SURFACE WATER ELEVATION (m) -20.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-2) The Thalweg Line in Case of the Original and Alternative 1

Cross Section No.(1) 2006 Cross Section No.(2) 2006

Fill Fill 2.00 2.00 -2.00 -2.00 -6.00 -6.00 -10.00 -10.00 -14.00 -14.00

Bed Levels (m) LevelsBed(m) MSL -18.00 0 50 100 150 200 250 MSL (m) Levels Bed 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 Cross Section No.(3) Cross Section No.(4) 2003

Fill 4.00 Fill

2.00 0.00 -2.00 -6.00 -4.00 -10.00 -14.00 -8.00 -18.00

Bed Levels (m) LevelsBed(m) MSL -12.00

Bed Levels (m) LevelsBed(m) MSL 0 20 40 60 80 100 120 140 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

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Cross Section No.(5) 2003 Cross Section No.(6) 2003 Fill 4.00 Fill

4.00

0.00 0.00 -4.00 -4.00 -8.00 -12.00 -8.00 -16.00

Bed Levels (m) LevelsBed(m) MSL -12.00 0 50 100 150 200 250 LevelsBed(m) MSL 0 50 100 150 200 DISTANCE (m) DISTANCE (m) Cross Section No.(7) 2003 Cross Section No.(8) 2003

4.00 Fill 4.00 Fill

0.00 0.00

-4.00 -4.00

-8.00 -8.00 Bed Levels (m) LevelsBed(m) MSL 0 50 100 150 200 LevelsBed(m) MSL 0 50 100 150 200 DISTANCE (m) DISTANCE (m) Cross Section No.(9) 2003 Cross Section No.(10) 2003

4.00 Fill

Fill 2.00 -2.00 -2.00 -8.00 -6.00 -14.00 -10.00

Bed Levels (m) LevelsBed(m) MSL -20.00 -14.00 0 50 100 150 MSL (m) Levels Bed 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7-3) Cross Sections Bed Profiles in Case of Original Year and Alternative 1

7-3-1-1 First Alternative Model Run Results  Maximum Flow Run In case of Maximum flow, the discharge is 809.03m3/s and its corresponding water level is +2.60m MSL. The flow velocities along the reach are shown in Figure (7-4), which shows that the maximum value of velocities were occurred at the outer curves. The resulted velocity recorded by the figures are ranged from 0.45 and 1.05m/sec in the outer curve at sections no 1 to10. While the normal velocity of the reach is about 0.70m/s, as appeared in Figure (7-5). Figure No (7-6) shows the velocity profiles of alternative 1 comparing to the original results at cross sections No 1 to 10. The figure shows that the results of velocity profiles in case of alternative 1 were similar to the profiles as the original case. It is clear that the values of the 111

Chapter 7 Alternative Solutions and Result Analysis velocities at cross sections 1, 3, 5, 6, 9 and 10 increased than its corresponding in case of original case because of considerable part of those sections were filled, Figure (7-3). The results of water surface slope at the location of the deepest points in case of alternative 1 became steeper than its corresponding of the original one. This is expected because of filling the scour holes. Figure (7-7) shows the water surface slope at the deepest points along the reach of the original and alternative 1.

Figure (7-4) Velocity along the Reach at Maximum Flow in Case of Alternative 1

2006 Fill 1.40 S1 S2 Kfer El -Zayat Bridges B1B 2 B3 Flow 1.20 K.St 1.00

0.80

0.60

0.40 VELOCITY VELOCITY (m/sec) 0.20

0.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-5) Velocity Profile at the Deepest Points (Outer Curve) along the Reach in Case of the Original & Alternative 1 at Max Flow

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Cross Section No.(1) Fill Cross Section No.(2) Fill 1.00 1.00

2006 2006

0.80 0.75 0.60 0.50 0.40

0.25 0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

Cross Section No.(3) Fill Cross Section No.(4) Fill 0.80 1.40 2006 0.70 2006 1.20 0.60 1.00 0.50 0.80 0.40 0.60 0.30 0.40 0.20 0.20

VELOCITY VELOCITY (m/s) 0.10 VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) Cross Section No.(5) Fill Cross Section No.(6) Fill

1.00 2006 1.00 2006

0.80 0.80 0.60 0.60 0.40 0.40 0.20 0.20

0.00 VELOCITY (m/s) 0.00 VELOCITY VELOCITY (m/s) 0 50 100 150 200 250 300 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Cross Section No.(7) Fill Cross Section No.(8) Fill 1.00 1.00 2006 2006 0.80 0.80 0.60 0.60 0.40 0.40

0.20 0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

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Chapter 7 Alternative Solutions and Result Analysis

Cross Section No.(9) Fill Cross Section No.(10) Fill 1.20 1.20 2006 2006 1.00 1.00 0.80 0.80 0.60 0.60 0.40 0.40

0.20 0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7- 6) Cross Sections Velocity Profile of the Original & Alternative 1 at Max Flow

2006 S1 S2 Fill 3.50 Kfer El Zayat Bridges 3.40 Flow 3.30 K.St B1B 2 B3 3.20 3.10 3.00 2.90 2.80 2.70 2.60 2.50 2.40 2.30

WATER WATER SURFACE ELEVATION (m) 2.20 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-7) Water Surface Slope at the Deepest Points along the Reach of the Original & Alternative 1 at Max Flow

 Emergency Flow Run The model was run at emergency discharge with its corresponding water levels. The discharge was 2546.30m3/s and its corresponding water level was +5.90m MSL. The flow velocities along the reach are shown in Figure (7-8), which shows the maximum value of velocities are occurred at the outer curves. The resulted velocity recorded by the figure are ranged between 1.00 and 2.20m/sec in the outer curve. While the normal velocity of the reach is about 1.50m/s, as appeared in Figure (7-9). Figure No (7-10) shows the velocity profiles of alternative 1 in case of emergency flow comparing to corresponding original results at cross sections No 1 to 10, The figure shows that the results of velocity profiles in case of alternate 1 are similar to the profiles as the original case. It is clear that the values of the velocities at cross sections 1, 3, 5, 6, 9 and 10 114

Chapter 7 Alternative Solutions and Result Analysis increased than in case of original case because of considerable part of those sections were filled, Figure (7-3). The results of water surface slope at the location of the deepest points in case of alternative 1 became steeper than its corresponding of the original one. This is expected because of filling the scour holes. Figure (7-11) shows the water surface slope at the location of deepest points along the reach of the original and alternative 1 in case of emergency flow.

Figure (7-8) Velocity along the Reach in Case of Alternative 1 at Emergency Flow

S2 3.10 S1 2.90 2006 Kfr Al Zayat Bridges 2.70 B1B 2 B3 Flow Fill 2.50 K.St

2.30 2.10 1.90 1.70 1.50 1.30 1.10 VELOCITY VELOCITY (m/sec) 0.90 0.70 0.50 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-9) Velocity Profile at the Deepest Points along the Reach in Case of Alternative 1 at Emergence Flow

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Chapter 7 Alternative Solutions and Result Analysis

Cross Section No.(1) Fill Cross Section No.(2) Fill 2.00

1.50 2006 2006

1.60 1.25 1.00 1.20 0.75 0.80 0.50 0.40

0.25 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) Cross Section No.(3) Fill Cross Section No.(4) Fill

2.50 2006 1.80 2006

1.60 2.00 1.40 1.50 1.20 1.00 1.00 0.80 0.60 0.50 0.40

0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m)

Cross Section No.(5) Fill Cross Section No.(6) Fill 1.80 2006

1.60 1.60 2006

1.40 1.20 1.20 1.00 0.80 0.80 0.60 0.40 0.40

0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Cross Section No.(7) Fill Cross Section No.(8) Fill 2006 1.80 2006

1.60 1.60 1.40 1.20 1.20 1.00 0.80 0.80 0.60 0.40 0.40

0.20 VELOCITY VELOCITY (m/s) 0.00 VELOCITY (m/s) 0.00 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

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Chapter 7 Alternative Solutions and Result Analysis

Cross Section No.(9) Fill Cross Section No.(10) Fill 2.50 2006 2006

2.00

2.00 1.60 1.50 1.20 1.00 0.80

0.50 0.40 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7- 10) Cross Sections Velocity Profile of the Original & Alternative 1 at Emergence Flow

2006 S1 S2 Fill

6.40 Kfer El Zayat Bridges Flow 6.20 B1 B2 B3

6.00 K.St 5.80

5.60

5.40

5.20

WATER WATER SURFACE ELEVATION (m) 5.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-11) Water Surface Slope at the Deepest Points along the Reach in Emergence Flow of the Original & Alternative 1 at Emergence Flow

7-3-2 The Second Alternative Simulation The bed levels of the reach are filled to level -5.00 MSL and the other part are dredged to level -3.00 MSL to represent the second alternative. Figure (7-12) shows the entire reach bed elevation in case of alternative 2. It is clear from Figure (7-12) that the most of the filling areas are concentrated at the outer curves and the dredging area in the inner curve. These also are shown at Figure (7-13), which represents ten cross sections distributed along the reach. The location of these sections is shown in Figure (7-12). The deepest point of the scour holes at cross sections from 1 to 10 are 2, 2, 2, 1.5, 1.5, 1.5, 1.01, 0.6, 0.9 and 1.5 above MSL,

117

Chapter 7 Alternative Solutions and Result Analysis respectively. This means that the filling layers of some holes are more than 12m and the dredging layers of some area within 5m.

Figure (7-12) River Bed Elevation in Case of Alternative 2

2006 Cross Section No.(1) Cross Section No.(2) 2006

Fill& Dredging Fill& Dredging

2.00 2.00 -2.00 -2.00 -6.00 -6.00 -10.00 -10.00 -14.00

-14.00 LevelBed (m) MSL -18.00 Bed Level (m) LevelBed (m) MSL 0 50 100 150 200 250 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m)

Cross Section No.(3) 2006 Cross Section No.(4) 2003 Fill& Dredging 4.00 Fill& Dredging

2.00

-2.00 0.00 -6.00 -4.00 -10.00 -8.00 -14.00

-18.00 -12.00 Bed Level (m) LevelBed (m) MSL

0 20 40 60 80 100 120 140 LevelBed (m) MSL 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

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Chapter 7 Alternative Solutions and Result Analysis

Cross Section No.(5) 2003 Cross Section No.(6) 2003

4.00 Fill& Dredging 4.00 Fill& Dredging

0.00 0.00 -4.00 -4.00 -8.00 -8.00 -12.00 -12.00

-16.00 LevelBed (m) MSL Bed Level (m) LevelBed (m) MSL 0 50 100 150 200 250 0 50 100 150 200 DISTANCE (m) DISTANCE (m) Cross Section No.(7) 2003 Cross Section No.(8) 2003

4.00 Fill& Dredging Fill& Dredging

4.00 2.00 2.00 0.00 0.00 -2.00 -2.00 -4.00 -4.00

-6.00 -6.00 Bed Level (m) LevelBed (m) MSL Bed Level (m) LevelBed (m) MSL -8.00 -8.00 0 50 100 150 200 0 50 100 150 200 DISTANCE (m) DISTANCE (m) Cross Section No.(9) 2003 Cross Section No.(10) 2003 Fill& Dredging

4.00 Fill& Dredging

2.00 0.00 -4.00 -2.00 -8.00 -6.00 -12.00 -10.00

-16.00 Bed Level (m) LevelBed (m) MSL -20.00 LevelBed (m) MSL -14.00 0 50 100 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7-13) Cross Sections in Case of Original Year and Alternative 2

7-3-2-1 Second Alternative Model Run Results  Maximum Flow Run In case of Maximum flow, the discharge was 809.03m3/s and its corresponding water level was +2.60m MSL. The flow velocities along the reach are shown in Figure (7-14), which shows that the maximum value of velocities are occurred at the outer curves. The resulted velocity recorded by the figure are ranged between 0.28 and 0.93m/sec at the concerned section. While the normal velocity of the reach is about 0.55m/s, as appeared in Figure (7-15).

Figure No (7-16) shows the velocity profiles of alternative 2 comparing to the original results at cross sections No 1 to 10. The figure shows that the results of velocity profiles in case of

119

Chapter 7 Alternative Solutions and Result Analysis alternative 2 were redistributed along the sections to be more regular than in case of the original at cross sections no 1, 3, 4, 7, 8 and 10. It is clear that the values of the velocities increased at cross sections 3 and 9 and decreased at cross sections no 2, 4, 7 and 8 comparing with the original case because of considerable part of those sections were filled and dredged respectively, Figure (7-13). The results of water surface slope at the deepest points in case of alternative 2 became almost the same as the original one. This is expected because of filling the scour holes and dredging in other places. Figure (7-17) shows the water surface slope at the location of the deepest points along the reach of the original and alternative 2 in case of maximum flow.

Figure (7-14) Velocity along the Reach in Case of Alternative 2 at Maximum Flow

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Chapter 7 Alternative Solutions and Result Analysis

2006 Fill S1 S2 Fill&Dredge 1.40 Kfer El Zayat Bridges B1B 2 B3 1.20 K.St Flow

1.00

0.80

0.60

0.40 VELOCITY VELOCITY (m/sec) 0.20

0.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-15) Velocity Profile at the Deepest Points along the Reach in Case of Original, Alternative 1 and Alternative 2 at Maximum Flow

2006 2006 Cross Section No.(1) Fill Cross Section No.(2) Fill Fill&Dredging Fill&Dredging

1.00 1.00

0.75 0.80 0.60 0.50 0.40 0.25

0.20 VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(3) Fill Cross Section No.(4) Fill

Fill&Dredging 0.80 Fill&Dredging

1.40 0.70 1.20 0.60 1.00 0.50 0.80 0.40 0.60 0.30 0.40 0.20

VELOCITY VELOCITY (m/s) 0.10

VELOCITY VELOCITY (m/s) 0.20 0.00 0.00 0 50 100 150 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m)

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Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(5) Fill Cross Section No.(6) Fill Fill&Dredging

1.00 Fill&Dredging 1.00

0.80 0.80

0.60 0.60

0.40 0.40

0.20 0.20

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) 2003 2006 Cross Section No.(7) Fill Cross Section No.(8) Fill

1.00 Fill&Dredging 1.00 Fill&Dredging

0.80 0.80

0.60 0.60

0.40 0.40

0.20 0.20

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(9) Fill Cross Section No.(10) Fill Fill&Dredging

1.20 Fill&Dredging 1.20

1.00 1.00

0.80 0.80

0.60 0.60

0.40 0.40

VELOCITY VELOCITY (m/s) 0.20 0.20 VELOCITY VELOCITY (m/s) 0.00 0.00 0 25 50 75 100 125 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7- 16) Cross Sections Velocity Profile of the Original, Alternative 1 and Alternative 2 at Maximum Flow

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Chapter 7 Alternative Solutions and Result Analysis

2006 Fill S1 Fill&Dredge

S2 3.50 Kfer El -Zayat Bridges 3.40 B1B 2 B3 Flow 3.30 K.St 3.20 3.10 3.00 2.90 2.80 2.70 2.60 2.50 2.40

2.30 WATER WATER SURFACE ELEVATION (m) 2.20 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-17) Water Surface Slope at the Deepest Points along the Reach of the Original, Alternative 1 and Alternative 2 at Maximum Flow

 Emergency Flow Run The model is run at emergency discharge with its corresponding water levels. The discharge is 2546.30m3/s and its corresponding water level is +5.90m MSL. The resulted velocity recorded in this case are ranged between 0.80 and 2.00m/sec in the outer curve. While the normal velocity along the reach is about 1.40m/s. Figure (7-18) shows velocity along the reach at emergency flow in case of alternative 2. Figure (7-19) show the velocity profile at the deepest points along the reach in case of original, alternatives 1 and 2 at emergency flow.

Figure (7-20) shows the velocity profiles at ten cross sections along the reach of alternative 2 in case of emergency flow comparing to the original results. The figure shows that the results of velocity profiles in case of alternative 2 are redistributed along the cross sections to be more regular than in case of the original at cross sections no 1, 4, 5, 6, 7 and 9. It is clear that the values of the velocities increased at cross sections 3 and 9 and decreased at cross sections no 2, 4, 7 and 8 comparing with the original case because of considerable part of those sections were filled and dredged respectively, Figure (7-13). The results of water surface slope at the deepest points in case of alternative 2 became almost the same as the original one. This is expected because of filling the scour holes and dredging in other places. Figure (7-21) shows the water surface slope at the location of the deepest points along the reach of the original and alternative 2 in case of emergency flow.

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Chapter 7 Alternative Solutions and Result Analysis

Figure (7-18) Velocity along the Reach in Case of Alternative 2 at Emergency Flow

2006 Fill S1 S2 Fill&Dredge 3.10 Kfr Al zayat Bridges 2.90 B1 B2 B3 2.70 K.St Flow 2.50 2.30 2.10 1.90 1.70 1.50 1.30 VELOCITY VELOCITY (m/sec) 1.10 0.90 0.70 0.50 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-19) Velocity Profile at the Deepest Points along the Reach in Case of Original, Alternatives 1 and 2 at Emergency Flow

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Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(1) Fill Cross Section No.(2) Fill Fill&Dredge 2.00 Fill&Dredge

1.50

1.25 1.60

1.00 1.20 0.75 0.80 0.50 0.40

0.25

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(3) Fill Cross Section No.(4) Fill Fill&Dredge Fill&Dredge

2.50 1.60 2.00 1.20 1.50

1.00 0.80

VELOCITY VELOCITY (m/s) 0.50 0.40

0.00 VELOCITY (m/s) 0.00 0 50 100 150 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(5) Fill Cross Section No.(6) Fill

Fill&Dredge Fill&Dredge

1.60 1.60

1.20 1.20

0.80 0.80

0.40 0.40

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(7) Fill Cross Section No.(8) Fill

Fill&Dredge Fill&Dredge

1.60 1.60

1.20 1.20

0.80 0.80

0.40 0.40

VELOCITY VELOCITY (m/s) VELOCITY VELOCITY (m/s) 0.00 0.00 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

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Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(9) Fill Cross Section No.(10) Fill Fill&Dredge 2.50 Fill&Dredge

2.00

2.00 1.60 1.50 1.20

1.00 0.80

0.50 0.40

VELOCITY VELOCITY (m/s) VELOCITY (m/s) 0.00 0.00 0 50 100 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7- 20) Cross Sections Velocity Profile of the Original, Alternatives 1 and 2 at Emergency Flow

2006 Fill

Fill&Dredge 6.40 S1 S2 Kfr Al zayat Bridges 6.20 B1 B2 B3 Flow

6.00

5.80 K.St

5.60

5.40

5.20

WATER WATER SURFACE ELEVATION (m) 5.00 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 DISTANCE (m) Figure (7-21) Water Surface Slope at the Deepest Points along the Reach of the Original, Alternatives 1 and 2 at Emergency Flow

The original, alternatives 1 and 2 were simulated separately by SMS model. For each case the model was run two times, during maximum and emergency flow. Based on the results and analysis of those runs, the following can be concluded:

 Big difference in velocities between outer and inner curve of the bend is appeared as a result of the original case in the maximum and emergency flow.  When the scour holes (at the outer curve) are filled up to level of -5 MSL (Alternative 1), the water surface slope increased, consequently the velocity profile along the cross sections are increased.

126

Chapter 7 Alternative Solutions and Result Analysis

 When the scour holes were filled up to level of -5 MSL and the other side dredged to -3 MSL (Alternative 2), slightly difference is appeared of water surface slope compared with the original case.  In case of alternative 2 the results velocity profiles along the cross sections redistributed and became more regular comparing to the alternative 1and original cases.  The results appeared in cases of maximum and emergency flow that the velocity take similar profile, only the difference on values.

7-3-3 Comparisons of Bed Shear Stress between the Two Alternatives

 Maximum Flow Bed shear stress is estimated at the whole reach in the cases of original, alternatives 1 and 2. For the original case, Figure (7-22) shows the locations of bed shear stress more than 2N/m2 and ranges between 2 and 15N/m2 and concentrated on the outer curves of the bend. For alternative 1, Figure (7-23) shows the locations of bed shear stress more than 2N/m2 and ranges between 2 and 6N/m2. For alternative 2, Figure (7-24) shows the locations of bed shear stress more than 2N/m2 which ranges between 2 and 4N/m2. It is noticed also that the value of shear stress reduced in the case of alternative 2 compared with cases of alternative 1 and the original. The bed shear stress is disappeared in some areas at the outer curve in case of alternative 2 compared with alternative 1 and the original. Figure (7-25) shows comparison of the bed shear stress along ten cross sections in the cases of original, alternative 1 and 2. After reviewing the shear stress distribution along the ten cross section the following can be concluded:

 The bed shear stress in case of alternative 2 became regular in cross sections 1, 3, 4, 5, 6, 7, 8 and 10 compared with alternative 1 and original. Also the shear stress beside the banks reduced at section 2 comparing with the original and alternative 1. The shear stress of cross section no 9 in case of alternative 2 increased than the original because this section have big filling consequently the velocity is increased.  In general, in the case of alternative 2 the bed shear stress reduced beside the banks compared with the other cases. This means that the bank failures become more safe than the other cases.

127

Chapter 7 Alternative Solutions and Result Analysis

Figure (7-22) Bed Shear Stress in Max Flow for Original Case

Figure (7-23) Bed Shear Stress in Max Flow for Alternative 1

Figure (7-24) Bed Shear Stress in Max Flow for Alternative 2

128

Chapter 7 Alternative Solutions and Result Analysis

Cross Section No.(1) 2006 Cross Section No.(2) 2006 Fill Fill

Fill&Dredge Fill&Dredge

2.40

)

) 2 2 2.00 2.00 1.60 1.60 1.20 1.20 0.80 0.80

0.40 0.40

0.00 0.00 SHEAR STRESS SHEAR STRESS (N/m SHEAR STRESS SHEAR STRESS (N/m 0 50 100 150 200 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(3) Fill Cross Section No.(4) Fill Fill&Dredge Fill&Dredge

4.00 2.00

) ) 2 2 3.50 1.60 3.00 2.50 1.20 2.00 1.50 0.80 1.00 0.40 0.50

0.00 0.00 SHEAR STRESS STRESS (N/m SHEAR 0 50 100 150 SHEAR STRESS (N/m 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(5) Fill Cross Section No.(6) Fill Fill&Dredge

Fill&Dredge

2.00 ) )

2 2.40 2 1.60 2.00 1.60 1.20 1.20 0.80 0.80 0.40 0.40

0.00 0.00 0 50 100 150 200 250

0 50 100 150 200 250 300 SHEAR STRESS (N/m SHEAR STRESS SHEAR STRESS (N/m DISTANCE (m) DISTANCE (m) 2003 2006

Cross Section No.(7) Fill Cross Section No.(8) Fill

Fill&Dredge ) Fill&Dredge )

4.00 2 2 3.50 1.60 3.00 1.20 2.50 2.00 0.80 1.50 1.00 0.40 0.50 0.00 0.00

0 50 100 150 200 250 0 50 100 150 200 250

SHEAR STRESS SHEAR STRESS (N/m SHEAR STRESS SHEAR STRESS (N/m DISTANCE (m) DISTANCE (m)

129

Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(9) Fill Cross Section No.(10) Fill

Fill&Dredge Fill&Dredge

) 4.00

4.00 2

)

2 3.50 3.00 3.00 2.50 2.00 2.00 1.50 1.00 1.00 0.50

0.00 0.00 SHEAR STRESS SHEAR STRESS (N/m

SHEAR STRESS SHEAR STRESS (N/m 0 25 50 75 100 125 150 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7-25) Cross Sections Shear Stress of the Original, Alternatives 1 and 2 at Maximum Flow  Emergency Flow Bed shear stress is estimated at the whole reach in the cases of original, alternatives 1 and 2. For the original case, Figure (7-26) shows the locations of bed shear stress more than 2N/m2 and ranges between 2 and 30N/m2 and concentrated on the outer curves of the bend. For alternative 1, Figure (7-27) shows the locations of bed shear stress more than 2N/m2 and ranges between 2 and 18N/m2. For alternative 2, Figure (7-28) shows the locations of bed shear stress more than 2N/m2 which ranges between 2 and 15N/m2. It is noticed also that the value of shear stress reduced in the case of alternative 2 compared with cases of alternative 1 and the original. The bed shear stress is disappeared in some areas at the outer curve in case of alternative 2 compared with alternative 1 and the original. Figure (7-29) shows comparison of the bed shear stress along ten cross sections in the cases of original, alternative 1 and 2. After reviewing the shear stress distribution along the ten cross section the following can be concluded:  The bed shear stress in case of alternative 2 became regular in cross sections 1, 2, 3, 4, 5, 6 and 7 comparing with alternative 1 and original. Also the shear stress beside the banks reduced at sections 1, 2, 5, 6 and 7 comparing with the original.  In general, in the case of alternative 2 the bed shear stress reduced beside the banks compared with the other cases. This means that the bank failures become more safe than the other cases.  The results of the runs at emergency flow condition for the original and the two alternatives show that, a huge values at the whole reach were appeared. This means that bed scours and bank instability will be occurred along the whole reach so failure of the bridge piers and the road of Kfer El-Zayat city may expected.

131

Chapter 7 Alternative Solutions and Result Analysis

Figure (7-26) Bed Shear Stress for Original Case at Emergency Flow

Figure (7-27) Shear Stress for Alternative 1 at Emergency Flow

Figure (7-28) Shear Stress for Alternative 2 at Emergency Flow

131

Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(1) Fill Cross Section No.(2) Fill Fill&Dredge Fill&Dredge ) 20.00

2 16.00

16.00 2 12.00 12.00 8.00 8.00

4.00 4.00

SHEAR STRESS SHEAR STRESS (N/m 0.00 0.00 0 50 100 150 200 250 300 0 50 100 150 200 250 300 DISTANCE (m) SHEAR STRESS (N/m DISTANCE (m) 2006 2006 Cross Section No.(3) Fill Cross Section No.(4) Fill Fill&Dredge Fill&Dredge

16.00

) 6.00

)

2 2

12.00 4.00 8.00

2.00 4.00

0.00 0.00 SHEAR STRESS SHEAR STRESS (N/m SHEAR STRESS SHEAR STRESS (N/m 0 50 100 150 0 50 100 150 200 250 300 DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(5) Fill Cross Section No.(6) Fill

Fill&Dredge

Fill&Dredge )

) 8.00 10.00

2 2 8.00

6.00 4.00 4.00

2.00

0.00 0.00

0 50 100 150 200 250 300 0 50 100 150 200 250 SHEAR STRESS SHEAR STRESS (N/m SHEAR STRESS STRESS (N/m SHEAR DISTANCE (m) DISTANCE (m) 2006 2006 Cross Section No.(7) Fill Cross Section No.(8) Fill

Fill&Dredge Fill&Dredge

16.00 ) 8.00

)

2 2

12.00 6.00

8.00 4.00

4.00 2.00

0.00 0.00 SHEAR STRESS SHEAR STRESS (N/m SHEAR STRESS SHEAR STRESS (N/m 0 50 100 150 200 250 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m)

132

Chapter 7 Alternative Solutions and Result Analysis

2006 2006 Cross Section No.(9) Fill Cross Section No.(10) Fill Fill&Dredge Fill&Dredge

16.00

)

) 2 2 12.00 12.00

8.00 8.00

4.00 4.00

0.00 0.00 SHEAR STRESS SHEAR STRESS (N/m 0 50 100 150 SHEAR STRESS (N/m 0 50 100 150 200 250 DISTANCE (m) DISTANCE (m) Figure (7-29) Cross Sections Shear Stress of the Original, Alternatives 1 and 2 at Emergency Flow

7-4 Riprap Design In order to determine the suitable mean particle diameter for the riprap protective layer, the mentioned three design methods for sizing riprap would be applied U = C [ 2g (Ss - 1) ]1/2 D 1/2 (7-1)

In which U is the flow velocity (ft/s); Ss is the specific gravity of the stone; g is the gravitational acceleration (ft/s2); D is the mean particle diameter (ft); and C is the Izbach’s turbulent coefficient which was taken equal to 0.86 for high turbulent level flow and 1.2 for low turbulent level flow.

4.1 X 105 S U 6 W  s (S 1)3 cos3  s

In which W is the weight of the stone in pounds; and Φ is the angle of repose. Assume that the particle is round; the average diameter can be defined as 6 w 1 D ( )3  (   ) s w (7-2)

In which γs and γw are the specific weight of the particle and water respectively

0.25 U 2 D  1 g (S 1) cos (tan2 tan2 ) 2 s (7-3)

In order to determine the suitable mean particle diameter for the riprap protective layer, the 133

Chapter 7 Alternative Solutions and Result Analysis above design methods for sizing riprap will be applied with the following data:  Maximum flow velocity (U) = 1.32 m/s = 4.33 ft/s  Specific gravity of the stone (Ss) = 2.65  Gravitational acceleration (g) = 9.81 m/s2 = 32.4 ft/s2  Izbach turbulent coefficient (C) = 0.86  Angle of repose (Φ) = 36.5 degree  Angle of bed slope (θ) = 0.0  Specific weight of the water (γw) = 62.4 lb/ft3  Specific weight of the rock (γs) = 165.4 lb/ft3

Apply the various empirical methods for sizing riprap for the previously mentioned bed protection methods, the following mean particle sizes was obtained as follows: Apply method No. (1) D = 0.24 ft = 7.3 cm Apply method No. (2) D = 0.18 ft = 5.5 cm Apply method No. (3) D = 0.15 ft = 4.6 cm

Application of the available formula revealed a mean particle size of D= 0.073m. Therefore, as the calculated mean particle size is rather small, a certain safety factor can be applied and the average particle size of 0.15m was adopted for bank protection. On the other hand, concerning size distribution of riprap layer, Simons and Senturk (1977) suggested that riprap gradation should follow a smooth size distribution curve. This would be fulfilled by applying the following criterion:

D0 = 0.2 D50 = 0.03 m

D20 = 0.5 D50 = 0.075 m

D100 = 2 D50 = 0.3 m

Where D0 and D100 are the minimum and maximum particle sizes respectively within the riprap mixture. This grain size distribution would be utilized to design the under layer protective layers of the conventional filter. On the other hand, according to the provided analysis for the design of under layer filter, the conventional (inverted) granular type would be applied. While for the case of riprap protective layer with mean particle diameter of 0.15m the following values were adopted:

D85 = 113 mm

D50 = 105 mm

134

Chapter 7 Alternative Solutions and Result Analysis

D15 = 65 mm In case of large stone size and fine diameter of bed materials, multiple filter layers with gradual size variations would be required. Therefore, it was suggested during the present study to apply the provided filter design criteria which would be applied to any two adjacent layers that comprising the riprap, filter planet and base material. Consequently, the mentioned design criteria of protective layers were applied as depicted in Table (7-1) which were used to prepare the grain size distribution of the filter layers (1) and (2) as shown in Figure (7-30). Table (7-2) shows the sieve analysis for the designed filters. Figure (7-31) shows the designed filter layers thickness.

Table (7-1) Grain Size Distribution of the Proposed Riprap and Filter Layers Criterion Riprap Layer Filter Layer (2) Filter Layer (1)

D (Filter ) 65.0/20.0 = 3.3 10.0/3.0 = 3.3 1.0/0.65 = 1.54 15  4 D (base) 85

D ( filter ) 105.0/15.0 = 7.0 15.0/1.5 = 10.0 1.5/.33 = 4.55 50  25 D (base) 50

D ( filter ) 65.0/10.0 = 6.5 10.0/1.0 = 10.0 1.0/0.18 = 5.56 5  15  40 D (base) 15

Table (7-2) Sieve Analysis for the Designed Filters D Sand Base Filter Layer (1) Filter Layer (2) Riprap Layer

D0 (mm) 0.11 0.60 6.00 30.00 D15 (mm) 0.18 1.00 10.00 65.00 D20 (mm) 0.24 1.20 11.00 75.00 D50 (mm) 0.33 1.50 15.00 105.00 D85 (mm) 0.65 3.00 20.00 113.00 D100 (mm) 0.80 4.00 33.00 300.00

135

Chapter 7 Alternative Solutions and Result Analysis

100 90 80

70 60 Base Filter 1 Filter 2 Riprap 50 40 30

Percent FinerPercentby Weight 20 10 0 0.1 1 10 100 1000 Particle Size (mm) Figure (7-30) Grain Size Distributions of the Proposed Filter Layers

0.50 m Stone D50 = 105 mm Riprap Layer

0.30 m D50 = 15.00 mm Filter Layer (2) 0.20 m D50 = 1.50 mm Filter Layer (1) D50 = 0.33 mm Base Layer

Figure (7-31) The Designed Filter Layers Thickness

136

CHAPTER 8 CONCLUSIONS AND RECOMMENDATIONS

Chapter 8 Conclusions and Recommendations

8-1 Summary To understand and improve the behavior of flow, morphology and hydraulically to the meandering of the Nile River in Egypt, two dimensional mathematical model “SMS” was used to simulate meandering reach of 9.0km long on Rosetta branch at Kfer El- Zayat city. This was achieved by studying the meandering river reach of Rosetta branch including two successive bends located from km 145.00 to km 154.00 downstream El-Roda Gauge Station. The surveyed reach of years 1982, 1998, 2003 and 2006 were compared. The developing of bed level, thalwege line and scour holes were determined.

The study area was simulated four times by the model using the survey reach of years 1982, 1998, 2003 and 2006. The flow and the water level were used as upstream and downstream boundary conditions, respectively. The model was calibrated to actual field water velocity measurements at different locations along the study area. The model was run for sixteen times at different (minimum, average, maximum and emergency) flow conditions. The resulted velocities were compared.

The model was run at maximum and emergency (69.90, 220.00m.m3/day) flow conditions using survey of year 2006. The obtained results showed the variation of the local scour at bridge piers. The empirical equations used to predict the general scour, contraction scour and bend scour of the whole reach and around bridge piers.

Two proposed alternatives were suggested and simulated separately by the SMS model. In the first alternative, the scour hole of the outer bends was filled with layers of filter and riprap up to level -5.00m MSL. In additional to alternative 1, dredging the inner sides to level -3.00m MSL was proposed as second alternative. The model was run for the two alternatives at maximum and emergence flows with its corresponding water levels. The results illustrated that the second alternative improved the flow conditions better than the first one. The filling layers of filter and riprap were designed.

137

Chapter 8 Conclusions and Recommendations

8-2 Conclusions In this research, the following conclusions were obtained: a) As a result of comparing different surveys reach and the results of the model runs at different flow conditions, the following was concluded:

1. Unexpected velocity profiles resulted in some cross sections was appeared due to the human interference. 2. Maximum scour depth was found at the piers located in the middle of the cross section. 3. The maximum scour depth was directly proportional to discharge. 4. The increase of the scour hole around the piers of the first bridge (upstream) was higher than the increase of the scour hole around the piers of the second and third bridges (downstream).

b) As a result of studding the scours along the reach, the following was concluded:

5. The local scour around the bridge piers estimated by the 2-D numerical model gave higher scour values than the general scour (Neil’s equation) under the same conditions. 6. The scour around the bridge piers calculated by the scour bend equation (Simons et al. 1989b) gave higher scour values than both general scour equation (Neil’s equation) and contraction scour. 7. Contraction scour results gave the lowest scour values when compared to the other types of scour. 8. The general scour by Neil’s equation was considered because it gave general scour higher than bend and contraction scours.

c) Based on the results of comparing the two proposed solutions by surveying of year 2006, the following was obtained:

9. When the scour holes (at the outer curve) were filled up to level of -5 MSL (Alternative 1), the water surface slope increased, consequently the velocity along the cross sections was increased. This means that the probability of the expected scour was increased.

138

Chapter 8 Conclusions and Recommendations

10. When the scour holes were filled up to level of -5m MSL and the other side dredged to -3m MSL (Alternative 2), slightly difference was appeared of water surface slope compared with the original case. This means that the probability of the expected scour was reduced. 11. In case of alternative 2 the resulting velocity profiles along the cross sections were redistributed and became more regular comparing to the alternative 1and original case. 12. The results appeared that in case of maximum and emergency flows, the obtained velocity had similar profile, only the difference on values.

8-3 Recommendations Based on the results and conclusions of this study, the following are recommended:

 Studying the impact of any construction on the river or on its banks and the impact of the expected scour at the structure location is necessary.  The foundation level of Kfer El-Zayat bridges should be checked by designer taking at consideration the expected total scour depth. Regular monitoring of the study reach is recommended specially after each high flood.  The critical scour holes should be filled by filter and riprap until to the average bed level.  Future studies are needed to apply three dimensional model or physical model to give accurate and reliable estimations for the morphological changes.  Hydraulic structures to reduce the velocity such as weirs, vans and dikes should be studied.

139

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145

ARABIC SUMMARY

ملخص البحث

عنوان الرساله تقييم النحر لمنحنيات نهر النيل علي فرع رشيد

1( مقدمة : حفاظا علي مياه النهر تسمح وزاره االشغال العامه والموارد المايه بمرور تصرفات المياه علي حسب االحتياجات الفعليه خالل السد العالي وال تسمح بمرور تصرفات اكبر من االحتياجات اال في حاالت الفيضانات حتي ال يصل منسوب المياه الي حد الخطوره علي منشات السد العالي. وهذه التصرفات العاليه وكذلك التصرفات خالل اقصي االحتياجات يمكن ان تسبب مشاكل للمنشأت المقامه علي نهر النيل وفروعه وذلك مثل النحر الموضعي حول دعامات الكباري والمواني والقناطر والمنشأت االخري. ويمكن ايضا للفيضان ان يسبب غرق لبعض االراضي والطرق والقري حول نهر النيل. تصنف االنهار نوعين نشطه وخامله, تسبب النشط منها نحر بقاع النهر او تأكل الجسر بينما الخامله ال يتغير شكل القاع او جوانب النهر بها.

تقع مدينه كفر الزيات علي المنحني الخارجي لفرع رشيد عند كم 123 وتتعرض لكثير من مشاكل النحر. تم اجراء رفع مساحي للنحر خلف كوبري السكه الحديد وكوبري الطريق السريع بعد فيضان عام 1998 وكان من نتائج هذا الرفع ان منسوب النحر لبعض البيارات بالقرب من المنحني الخارجي للمنحنيات تغير من منسوب 16.11- والذي تم تسجيله عام 1996 الي منسوب 18.11- متر من منسوب سطح البحر. وهذا سبب مشكله كبيره التزان الجسر امام المدينه وللنحر حول دعامات الكباري في المنطقه مما سبب عدم امان للمدينه والكباري.

2( ملخص البحث تم إستخدام جزء منحني من مجري نهر النيل بمجري فرع رشيد يبلغ طوله حوالي 9.1 كيلومتر والذي يتميز بوجود منحنيان منعكسان. وضح الرفع المساحي الهيدروجرافي الحديث للمنطقه المذكورة ومقارنتها بالرفع المساحي السابق لنفس الحبس عالوة علي البيانات الهيدرولوجية والقياسات الهيدروليكية المختلفة أنه يمكن اعتبار هذا الحبس مناسب إلجراء هذه الدراسه لوضوح تأثير ظاهرتي النحر والترسيب علي كل من المنحني الخارجي والداخلي علي الترتيب. هذه القياسات أوضحت حدوث نحر موضعي وإنتقال لمواد القاع للمنحني الخارجي للنهر مما يهدد استقرار الميول الجانبيه بينما يحدث ترسيب ملحوظ في الجانبين للمنحني الداخلي للنهر مما ادي الي عدم إنتظام سرعة التيار المائي وإزاجة المجري في إتجاه المنحني الخارجي.

وقد تم دراسه مورفولوجي النهر في هذه المنطقه لعام 1982 و 1998 و 2113 و 2116. حيث تم عمل مقارانات لقاع النهر في هذه السنين ودراستها ودراسه اماكن النحر الموجوه في منطقه الدراسه. وتم ايضا امرار تصرفات مختلفه علي النهر )منخفضه و متوسطه وعاليه و حاله الطواريء( وتم دراسه السرعات الناتجه علي القطاعات العرضيه علي طول الحبس في االعوام المختلفه. وتم حساب ايضا النحر المحتمل حول دعامات الكباري و حساب النحر المحتمل علي كامل الحبس )النحر الناتج من المنحنيات والنحر الناتج عن ضيق عروض القطاعات و النحر العام(. وبناءا عليه تم حساب النحر الكامل لكل القطاعات الموجوده بطول الحبس والنحر المحتمل في حاله التصرفات العاليه وحاله الطواريء.

ملخص البحث

تلي ذلك إستخدام النموذج الرياضي ثنائي األبعاد )SMS( في إختبار بدائل الحلول المقترحه لمنطقه الدراسه لتجنب النحر علي جوانب و قاع النهر ومنها, ردم البيارات الموجوده حتي مستوي -5 متر فوق سطح البحر و البديل االخر ردم البيارت حتي مستوي -5 من سطح البحر مع تكريك للناحيه االخري للقطاع من البيارات حتي مستوي -3 متر فوق سطح البحر وتم محاكاه كل بديل علي حده علي البرنامج الرياضي ومقارنه نتائجهم بالرفع المساحي لعام 2116. وتبين من خالل هذه المقارنات ان الحل الثاني يعطي نتائج أفضل من االول ومن الحاله االصليه للنهر. وبناءا عليه تم تصميم طبقات الحمايه المستخدمه لردم البيارات.

3( محتويات الرسالة الباب األول المقدمة

يحتوى هذا الباب على المقدمة واسباب إختيارجزء من نهر النيل علي فرع رشيد عند منطقة كفر الزيات لهذه الدراسة وفكرة عامة عن المشاكل المترتبة نتيجة للتغيرات المورفولوجية و الهيدروليكية الحادثة بمنطقة كفر الزيات كما يوضح االهداف الرئيسية للبحث وخطة الدراسة ومكونات البحث.

الباب الثاني مراجعة األبحاث المتعلقة بالدراسه

يحتوي هذا الباب علي نبذة تاريخية للدراسات والبحوث التي أجريت في مجال البحث وما يتعلق بها من خصائص وتك ٍون المجاري المائية الطبيعية وتصنيف األنهار و مراحل تطورها وما يتعلق باألنهار ذات األجزاء المنحنيه عالوة علي العالقات والمعادالت الرياضية المختلفة المناسبه لتوصيف العناصر الهيدروليكية الخاصة بمنحنيات األنهار. وتم عرض خالصة البحوث والدراسات والخبرات السابقة في هذا المجال.

تلي ذلك عرض لتعريف النحر وخواصه وانواعه المختلفه والنتائج المترتبه عليه. وتم عرض ايضا انواع النماذج المختلفه من نماذج رياضيه و نماذج طبيعيه وخواص كل منهما. كما عرض في هذا الباب ايضا تعريف التكريك والترسيب وتجميع اهم العالقات التي تستخدم في حساب القوه المؤثره من سريان المياه )Shear Stress( علي حبيبات التربه المكونه لقاع المجري.

الباب الثالث البيانات المطلوبه للبحث

يعرض هذا الباب مختلف القياسات الحقلية والبيانات المتاحه التي تم تجميعها علي مدار السنين السابقه للتعرف علي التغيرات المورفولوجية بالحبس موضوع البحث والتي تم استخدامها في تشغيل النموذج الرياضي ثنائي األبعاد عالوة علي تصميم الحماية الالزمة للمنحني الخارجي لهذا الحبس. شمل ذلك القياسات الهيدروجرافية التي تمت حديثا للحبس واألجهزة المستخدمة وطريقة القياس ونتائجها. كما عرض في هذا الباب مواقع قياس توزيع سرعه التيار المائي ونتائج هذه القياسات عالوة علي عينات من مواد القاع ومواقعها بالحبس موضوع البحث ونتائج تحليل هذه العينات وعالقة نتائج كل منها بتغير

ملخص البحث

شكل القطاع المائي علي إمتداد مسافة منحني النهر في هذا الحبس. تبع ذلك عرض الخصائص الهيدرولوجية الخاصة بالتصرفات المارة والمناسيب المقابلة علي إمتداد الحبس الواقع من خلف قناطر الدلتا فرع رشيد.

الباب الرابع النموذج الرياضى المستخدم و معايرته

يتضمن هذا الباب شرح موجز للمعادالت المستخدمة في النموذج الرياضي ثنائي األبعاد )SMS( والذي تم إستخدامه لمحاكاة الحبس موضوع البحث. كما شمل الباب شرح تطبيقات النموذج الرياضي ومميزاته وأسباب إختياره عالوة علي كيفية إعداد شبكة العناصر التي تمثل الحبس موضوع البحث مع عرض كيفية تغذيته بالعناصر الهندسية والهيدروليكية الممثلة لطبيعة المجري وتشغيله والمخرجات التي تنتج عن تطبيق النموذج. بناءا عليه عرض الباب متطلبات معايرة النموذج وتحقيق النموذج بحيث يحاكي الحبس المذكور إلجراء الدراسات المطلوبة.

كما شمل هذا الباب ايضا عرض اسلوب معايرة وتحقيق وتجهيز النموذج الرياضي ثنائي األبعاد لإلستخدام في بحث أفضل تصميم لتحسين خواص التدفق المائي بالمنحني الداخلي بالحبس موضوع البحث. بناء عليه تم عرض البيانات الخاصة بكل من تقدير معامالت اإلحتكاك المناسبة لطبيعة التربة والتغيرات المورفولوجية بالحبس موضوع البحث وكذلك القيم المتوسطة لتوزيع سرعة التيار المائي بالقطاعات المختلفة عالوة علي بيانات التصرفات والمناسيب المقابلة عند الحدين األمامي والخلفي للحبس موضوع البحث. تلي ذلك عرض نتائج معايرة النموذج الرياضي ثناءي األبعاد )SMS( والتي يتم خاللها تغيير قيم معامالت اإلحتكاك بالمواقع المختلفة في حدود معينة بحيث تكون مخرجات النموذج بالنسبة لتوزيع سرعة التيار بالقطاعات المختلفة أقرب ما يمكن من القياسات الحقلية. بناءا عليه تم إستخدام البيانات الخاصة بمختلف التصرفات المارة بالحبس موضوع الدراسة والمناسيب المقابلة لكل منها في تحقيق النموذج بعد نجاح مرحلة معايرته والتي أوضحت أفضل النتائج. تلي ذلك عرض نتيجة إستخدام النموذج الرياضي في إختبار مدي دقة إختيار قيم معامل اإلحتكاك التي تم إستخدامها في معايرة النموذج.

الباب الخامس التغيرات المورفولوجيه لمنطقه الدراسه

يعرض هذا الباب خواص الحبس الذي تم إختيارة للبحث والذي يشكل جزء طوله حوالي 9.1 كيلومتر من فرع رشيد عند مدينه كفر الزيات وأسباب إختيار هذا الحبس الجراء الدراسه وذلك لما يحتويه من منحنيين معكوسي اإلتجاه وما يتطلبة من تحسين خواص التدفق المائي بالمنحني الداخلي لكل منهما. تلي ذلك عرض الخصائص المورفولوجية والمميزات واألبعاد الهندسية لكل من المنحنيين األمامي والخلفي للحبس موضوع الدراسة وتأثير ذلك علي تغيرات مناسيب القاع. عرض أيضا هذا الباب التطور الزمني للتغيرات التي توضح شكل الحبس موضوع البحث وذلك من واقع الخرائط الكنتوريه التي تمت خالل األعوام 1981 و1998 و2113 و 2116 وعالقة ذلك بالتغيرات التي طرأت علي مجري نهر النيل. تم تحديد مواقع عدد 8 قطاعات عرضيه موزعة بصوره منتظمه علي كامل طول الحبس موضوع البحث وإستنتاج تغيرات مناسيب القاع بكل منها باستخ\ام الرفع الهيدروجرافي خالل األعوام المشار أليها عاليه. ثم تم تحديد مواقع البيارات الناتجه من نحر

ملخص البحث

حول دعامات الكباري و نتيجه النحر للمنحني الخارجي. وتم مقارنه هذه البيانات علي مدار السنين المختلفه وتحليل كامل لها.

الباب السادس تشغيل النموزج الرياضي ودراسه االنواع المختلفه للنحر

يتضمن هذا الباب تشغيل للنموزج ثنائي االبعاد الربع تصرفات مختلفه )منخفضه و متوسطه و عاليه و حاله طواريء( وذلك الربع خرائط كونتوريه العوام مختلفه )1981 و1998 و2113 و 2116(, وتم دراسه السرعات الناتجه ومقارنتها ببعضها وتحليل نتائجها. وتم ايضا حساب النحر المحتمل حول دعامات الكباري عن طريق النموذج ثنائي االبعاد. وتم حساب النحر المحتمل علي كامل الحبس )النحر الناتج من المنحنيات والنحر الناتج عن ضيق عروض القطاعات و النحر العام(. وبناءا عليه تم حساب أجمالى النحر لكل القطاعات الموجوده بطول الحبس والنحر المحتمل في حاله التصرفات العاليه وحاله الطواريء.

الباب السابع الحلول المقترحه وتحليل النتائج

في هذا الباب تم إستخدام النموذج الرياضي ثنائي األبعاد في إختبار بدائل الحلول المقترحه لمنطقه الدراسه لتجنب النحر علي جوانب و قاع النهر. وتم دراسه البديل االول بمالء البيارات الموجوده حتي منسوب -5 متر أعلى سطح البحر ودراسه تأثير ذلك علي مجري النهر ومقارنه النتائج بالحاله االصليه للنهر. وتم ايضا دراسه البديل الثاني المقترح بمليء البيارت حتي منسوب -5 متر أعلى سطح البحر مع تكريك للناحيه االخري للقطاع من البيارات حتي منسوب -3 متر أوطى سطح البحر وتم مقارنة نتائج هذا المقترح مع البديل االول والحاله االصليه للنهر. تم ايضا حساب تأثير القوه الناتجه من سريان المياه علي حبيبات التربه في القاع. وتبين من خالل هذه المقارنات ان الحل الثاني يعطي نتائج أفضل من االول ومن الحاله االصليه للنهر. وبناءا عليه تم تصميم طبقات الحماية االزمة للبيارات.

الباب اثامن الخالصه و التوصيات

يتضمن هذا الباب ملخص ما سبق تقديمة و خالصة النتائج التي توصل اليها البحث وتوصيات األعمال المقترحة لحماية المنحنيين الخارجيين للحبس موضوع البحث والتي تحقق توزيع أفضل لسرعة التيار المائي بما يضمن تقليل معدل إزاحة المجري نحو جوانب النهر. كما يعرض الباب مقترحات لبعض الدراسات المستقبليه التي يمكن للباحثين التعرض لها.

جامعة بنها كلية الهندسة بشبرا قسم الهندسة المدنيه

تقييم النحر لمنحنيات نهر النيل علي فرع رشيد

رسالة مقدمة كجزء من متطلبات الحصول علي درجة الماجستير في الهندسة المدنيه )هيدروليكا(

مقدمة من فاطمه سمير أحمد سعد بكالوريوس في الهندسه المدنيه )2111(

إشراف

أ.د/ جمال حلمي محمد السعيد أستاذ هندسة الموارد المائية - قسم الهندسة المدنية كليه الهندسه بشبرا - جامعه بنها

أ.م.د/ حسام الدين محمد السرساوي أستاذ مساعد بمعهد بحوث النيل المركز القومي لبحوث المياه

د/ محمد محمود محمد ابراهيم مدرس بقسم الهندسة المدنية

كليه الهندسه بشبرا - جامعه بنها

القاهرة – جمهورية مصر العربية مارس 2115

جامعة ينها كلية الهندسة بشبرا قسم الهندسة المدنيه

القبول النهائي للرسالة

تقييم النحر لمنحنيات نهر النيل علي فرع رشيد

لجنة الحكم والمناقشة

االسم األمضاء

أ.د. نهله محمد عبدالحميد ابو العطا )ممتحن خارجي – مقررا( أستاذ تصميم أعمال الري - رئيس قسم الري والهيدروليكا كلية الهندسة - جامعة عين شمس

أ.د. مدحت سعدعزيز )ممتحن خارجي – عضوا( أستاذ - مدير معهد بحوث النيل المركز القومى لبحوث الميـاه

أ.د. جمال حلمي محمد السعيد )عن لجنه االشراف – عضوا( أستاذ هندسة الموارد المائية - قسم الهندسة المدنية كليه الهندسه بشبرا - جامعه بنها

القاهرة – جمهورية مصر العربية مارس 2115