nri-eg.orgnri-eg.org/download/publications/76_fatma msc.pdfbenha university faculty of engineering,...

Benha University

Faculty of Engineering, Shobra

Civil Engineering Department

Scour Evaluation at the Nile River Bends on Rosetta Branch

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

Cairo – Egypt

March 2015

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.


Benha University



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,


Cairo – Egypt

March 2015

Benha University



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

i

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.

ii

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

LIST OF SYMBOLS

LIST OF ABBREVIATIONS

ABSTRACT

VI

XI

XII

XV

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

iii

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

iv

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

v

9-1 Summary 137

9-2 Conclusions 138

9-3 Recommendations 139

REFERENCES 140

ARABIC SUMMARY

vi

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 (3-7) 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


vii


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


Stream Rosetta Barrage in Years 1998, 2000, 2001, 2002, 2003 and 2004 44


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

Elevation

64

Figure (4-17) Location of the Verification Cross Sections 65

Figure (4-18) Flow Velocity Verification at Cross Section (1) 65




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

viii

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


Maximum Discharge 93

Figure (6-6) Water Surface in Case of Maximum Discharges (69.90 Mm3/day) 93


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

ix

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,

Alternative 1 and Alternative 2 at Maximum Flow

121

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


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


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

x


Emergency Flow 133

Figure (7-30) Grain Size Distributions of the Proposed Filter Layers 136

Figure (7-31) The Designed Filter Layers Thickness 136

xi

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 (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


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

xii

LIST OF SYMBOLS

Symbol Description Dimension

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)

Ac

Am

a

B

Bs

bt

C

C

Di

D

z

g

H,h,ho

i

K

m

n

Р

Q

R*

R

r1

r2

rc

Sg

Sr

bx, by

sx, sy

xx , xy, yx,

yy

U

Ū

U*

V

Wetted cross section area

Mid-ship area

River bends amplitude

Channel bank full width

Ship width (the beam)

Isotropic momentum flux correction coefficient

Channel width at keel level

Chézy roughness coefficient

Izbach's turbulent coefficient

Grain size for which i percentage of a material by weight is finer

Mean size of riprap particle

Super elevation between outside and inside bank

Gravitational acceleration.

Flow water depth

Longitudinal hydraulic gradient

Roughness height

Roughness correction factor for channel meandering

Manning roughness coefficient

Meander channel sinuosity

Flow discharge

Reynolds No.

Radius of curvature

River bend inner radius

River bend outer radius

River bend center radius

Specific gravity

Transverse water slope

Bed shear stresses acting in (x and y) directions respectively

Surface shear stresses acting in (x and y) directions respectively

xy shear stress

acting in x direction on a plane that is perpendicular to the y

direction

Flow velocity

Cross-sectional average velocity

Beds shear velocity

Measured point velocity

(L2)

(L2)

(L)

(L)

(L)

(-)

(L)

(L2/T)

(-)

(L)

(L)

(L)

(L/T2)

(L)

(-)

(L)

(-)

(L-0.33

T)

(-)

(L3/T)

(-)

(L)

(L)

(L)

(L)

(-)

(L/L)

(M/LT2)

(M/LT2)

(M/LT2)

(L/T)

(L/T)

(L/T)

(L/T)

(M)

xiii


W

ω

Z

zb

zs

λ

θ

U

V

Weight of the riprap stone in pounds

Fall velocity

Meander arc length

Bed elevation

Water surface elevation

Angle of repose

Bed slope angle in degrees

Meander Wavelength

Arc angle

Horizontal velocity in the x direction

Horizontal velocity in the y direction

Water mass density

(L/T)

(L)

(L)

(L)

(Degree)

(Degree)

(L)

(Degree)

(L/T)

(L/T)

(M/L3)

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)

Q1 Flow in the upstream of bridge transporting sediment. (L3/T)

Q2 Flow in the contracted section. (L3/T)

qf Design flood discharge per unit width. (L3/T/L)

qi Bankfull discharge in incised reach per unit width. (L3/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)

xiv


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)

xv

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

xvi

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

xvii

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.

CHAPTER 1

INTRODUCTION

Chapter 1 Introduction

1

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


2

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.


3

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.


4

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

5

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


6

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.


7

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).


8

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.


9

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:

c

r

r

r

rr

gr

BUdr

gr

UdrSZ

22

1

22

1 (2-1)

Figure (2-5) illustrates the meander geometrical characteristics of curved river reach which

can be described as follows:


11

Figure (2-4) Geometrical Characteristics 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.

Wave length ()

Point

bar

Arc length = 0 Arc length = Z

Arc length =Z/2

Arc angle

Apex

Point of inflection

or crossover

Am

pli

tud

e (a

)

B

r c


11

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)

λ = 4.8 rc0.98

(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.


12

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 90

0).

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.


13

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


14

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


15

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:

Vc =11.17 ya1/6

D501/3

(2-6)

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

Live-bed Contraction Scour Determination

y2/y1 =(Q2/Q1)6/7

* (W1/W2)k1

(2-7)

ys = y2 - y0

Clear-water Contraction Scour

Y2 = (0.0077Q2/Dm

2/3W

2)3/7

(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


16

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):

ygs = Zdf = Zdi (qf/qi)m (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:

yS/y1 = 2 K1K2K3K4 (b/y1)0.65

(Fr1)0.43

(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:


17

yS/y1 = 2.08 K1K2K3K4 (b/y1)0.504

(Fr1)0.639

(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:

KW = 1.04(b/y1)-0.15

(Fr1)0.21

(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).


18

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


19

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.


21

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

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

mailto:[email protected]


22

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.


23

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


24

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


25

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)

Where U= (c/ρ)1/2

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.


26

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


27

(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).


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).


28


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.


29

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


31

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:


31

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:

U = C {2g (S3 - 1) }½ D

½ (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.


32

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

follows:

33

65

cos)1(

101.4

s

s

S

UsxW (2-21)

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):

2

1

)tan(tancos)1(

25.0

22

2

sSg

UD (2-22)

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:


33

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

4)(

)(

85

15 baseD

FilterD (2-23)

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

25)(

)(

50

50 baseD

filterD (2-24)

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

40)(

)(5

15

15 baseD

filterD (2-25)

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).

Figure (2-19) Grain Size Distributions of the Protective Layers

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100 1000

Perc

enta

ge F

iner

By W

eig

ht

Particle Size (mm)

Riprap

Layer

Filter Layer

(2) Filter Layer (1)

Sand Base

CHAPTER 3

DATA COLLECTION

Chapter 3 Data Collection

34

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.


35

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).


36

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



37



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).


38

Figure (3-7) The Measured C. S Velocity

Locations 1998

Figure (3-8) The Measured C. S Velocity

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


39

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 )

D

DV

DVV

DVV

DV

Vaverage

2.0*2

3.0*2

3.0*2

2.0* 332211

…….(3-1)

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

Middle

Water surface

75% of Total Depth

.75 above bed

50% of Total Depth

25% of Total Depth

.50 Under W.S

Water surface

Eastern Third Western Third


41

sections (sec1 ,sec2 & sec3) as illustrated in Figure (3-10). The location of bed material

sampling show in Figure (3-13).

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).

1 10 cm


41

Table (3-2) Characteristics of Bed Samples at C.S. (1,2&3)

Sample No.

Sample properties

C.S. (1) C.S. (2) C.S. (3)

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

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

Geometric standard

deviation 1.568 1.681 1.577 1.681 2.657 1.606 2.599 2.426 2.307

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

(mm) 0.307 0.379 0.298 0.571 0.576 0.33 0.649 0.676 0.421

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

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10 100

Per

cen

t F

iner

by

Wei

gh

t

Particle Size (mm)

Bed Material Samples

Grain Size Distribution Curves

Cross-Section No. 1

Sample 1 Sample 2 Sample 3


42



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

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10 100

Per

cen

t F

iner

by

Wei

gh

t

Particle Size (mm)



Cross-Section No. 2


0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10 100

Per

cen

t F

iner

by

Wei

gh

t

Particle Size (mm)



Cross-Section No. 3



43

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).

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

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

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

3.5

JAN Feb MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Wa

ter L

evel

(m

)

Time (month)

1982

1998

2003

2006

0

10

20

30

40

50

60

70

80

JAN Feb MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Dis

cha

rge

(mil

lio

n.m

³/d

ay

)

Time (month)

1982

1998

2003

2006


44

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

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

1990 R² = 0.7047 1991 R² = 0.1132 1994 R² = 0.0061 1995 R² = 0.1226 1996 R² = 0.0615

1997 R² = 0.1107

1

1.5

2

2.5

3

3.5

0 5 10 15 20 25 30 35

Wa

ter L

evel

(m

)

Discharge (m³/sec)

Rating Curve

1990

1991

1994

1995

1996

1997

Linear

(1990) Linear

(1991) Linear

(1994) Linear

(1995) Linear

(1996) Linear

(1997)

1998 R² = 0.0939 2000 R² = 0.1156

2001 R² = 0.1249

2002 R² = 0.3663

2003 R² = 0.0303

2004 R² = 0.0838

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

3.5

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Wa

ter L

evel

(m

)

Discharge (m³/sec)

Rating Curve

1998

2000

2001

2002

2003

2004

Linear

(1998) Linear

(2000) Linear

(2001) Linear

(2002) Linear

(2003) Linear

(2004)


45

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

R² = 0.0176

R² = 0.0019

R² = 0.2393

2

2.2

2.4

2.6

2.8

3

0 2 4 6 8 10 12 14 16 18 20 22 24

Wa

ter L

evel

(m

)

Discharge (m³/sec)

Rating Curve

2009

2010

2011

CHAPTER 4

MATHEMATICAL MODEL

PREPARATION

Chapter 4 Mathematical Model Preparation

46

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).


47

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

Proposed Approaches

Data Collection Modeling

and Organization

Geometry and

Topographic DataFlow Model

* Channel Cross Sections* FESWMS Model for

Flow Simulation

* Channel Morphology

Hydraulic Data

* Water Level Hydrograph

* Discharge Hydrograph Modeling Application

* Velocity Measurements

* Simulation of flow

Digital Data Sources

* Arial Photography

* Image Satellite

* Digital Terrain Model

* Applying of different

Scenarios of flow

Prediction of Navigation

Problems

* Prediction of bed

changes in the future.

* Prediction of new

thalwag line

Solutions and

Alternatives for

Navigation

*Fill Solution

*Fill & Dredging solution

* Determination the future

navigation bottlenecks.

* Determination the

erosion and deposition

* Determination the

morphological and

hydrological changes

Calibration and

Verification

* Determination the

velocity, water surface,

water depths, shear stress,

changes of bed elevation

under the actual flow

condition


48

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:

dzuH

U1

(4-1)

dzvH

V1

(4-2)

zs = zb + H (4-3)

mk:@MSITStore:C:/Program%20Files/SMS81/sms81.chm::/Visualization/Post-Processing.htm


49

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:

mw q

y

q

x

q

t

z

21 (4-4)

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

Figure (4-2) 3-D Coordinate System

H

Zb

u

v w

X

Y Z

Water surface

Bed surface

Plane datum


51

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:

0 )(H

- )(H

1

qy

Hz

gH 2

1

y )

qq(

yyyx

1b2

2

1212

yx

P

ygH

H

q

Hxt

q

syby

a

(4-5)

0 )(H

- )(H

1

q x

zgH

qq

y

2

1

x

xyxx

2b212

2

11

yx

HgH

H

q

t

q

sxbx

(4-6)

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.


51

B) Momentum Flux Correction Coefficient

Vertical velocity profiles can be approximated by the logarithmic function

K

zz

k

uu b

elog* (4-7)

In which

Ucu f* 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

21

k

c f (4-8)

Momentum flux correction coefficients in FESWMS are calculated as

fo cc (4-9)

where o and c are specified coefficients. Comparing the two expressions for gives o = 1

and c = 1/k2. 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:

2

2

2

2

11 H

qqqmc bfbx

(4-10)

2

2

2

2

12 H

qqqmc bfby

(4-11)


52

where cf = dimensionless bed-friction coefficient, and

22

1

y

z

x

zm bb

b (4-12)

Where mb is a factor that accounts for increased shear stress caused by a sloping bed. Bed

friction coefficient cf is given by

23/12

2

c

g

H

gnc

n

f

(4-13)

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.


53

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.

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

Data Assessment

Network Design

Model Calibration

Model Testing

Model Application


54

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

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

DATA ITEM USE OF DATA SOURCE(S) OF DATA

Ground-surface

elevations

To define mesh node locations; layout of

a finite element network.

Topographic and

hydrographic maps, and

cross section surveys.

Channel and floodplain

surface characteristics,

vegetative cover, and

sediment composition.

Assessment and definition of bed friction

coefficients and eddy viscosity.

On site samples, Aerial

photographs, topographic

maps, on-site inspection,

and field experience.

Hydrological data ( water

surface elevations, and

discharge)

Establishment of boundary conditions,

calibration of model coefficients, and

testing model accuracy.

On-site measurements, and

historical data base from

stream gauge records.

Current velocity

Establishment of boundary conditions,

calibration of model coefficients, and

testing model accuracy.

On-site measurements and

database records.


55

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


56

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

No. Region Class

Estimated Manning factor (n)

Min. Max.

1

2

3

Original bed Profile

River banks

Vegetative areas

0.015

0.020

0.025

0.020

0.025

0.045

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.

Region (1):

Original bed

Profile

Region (3):

Aquatic weed

Infestation

Region (2):

River banks

Reach

upstream

boundary

Reach

downstream

boundary


57

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:


58

Figure (4-6) Study Reach Mesh Element Composition

Figure (4-7) Bridge Mesh Element Composition

Vertex node

Midside node

Center node

Quadrilateral

elements

Triangular

elements

60o : 120o

5

o : 120o

Upstream

boundary

Downstream

boundary


59

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 120

o as shown in Figure (4-6). For triangular elements it was assured to

keep interior angles between 5o and 120

o, 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 120

o, 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.

Figure (4-8) Quadrilateral and Triangular Element Aspect Ratios

a

b

a

b

Element aspect ratio = a/b


61

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.

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

SMS radial bounding region Node being

interpolated

Scatter points used for

interpolation

Scatter points

Mesh

Elements


61

Figure (4-11) Design Mesh Elevation Assignment

Interp

ola

tion

Created Mesh

Scatter Points

Contour Map


62

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


63

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



0.00

0.25

0.50

0.75

1.00

1.25

1.50

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(1)

Model Field

0.00

0.25

0.50

0.75

1.00

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(2) Model Field

0.00

0.25

0.50

0.75

1.00

0 50 100 150 200 250 300 350

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)



64


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

No. Region Class Calibration values

1

2

3

4

5

Original bed Profile

River banks

Protection bank

Vegetative areas

Dikes

0.020

0.030

0.040

0.040

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

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m)

DISTANCE (m)

Simulated

Measurement

B3

K.St

B1 B2

S2 S1

Flow


65

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

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

0.00

0.25

0.50

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)



66




Elevation

0.00

0.25

0.50

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(2) Model Feild

0.00

0.25

0.50

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1.00

1.20

1.40

1.60

1.80

2.00

2.20

2.40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

Simulated

Measurement

B

3

K.St

B1 B2

S2 S1

Flow


67

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 )

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 )

%61

%21

%11

%6 %

4

Geometry &

Study Design

Boundary

Conditions

Roughnes

s

Viscosity

Other


68

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

69

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


71

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).

Figure (5-2) Meandering Planform Parameters

rc2

2 rc1

θ2

θ1

Z

(λ) is the meander wavelength

(Р) is the sinuosity

(θ) is the arc angle

(Z) is the meander arc length

(a) is the amplitude

(rc) is the radius of curvature

λ1/2

λ2/2

a


71

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) 88 o 112

o

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


72

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


73

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

-14.00 -12.00 -10.00

-8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00

0 50 100 150 200 250 300

EL

EV

AT

ION

(m

)

DISTANCE (m)

Cross Section No.(1) 1982 1998 2003 2006

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 50 100 150 200 250 300 350 400

EL

EV

AT

ION

(m

)

DISTANCE (m)

Cross Section No.(2) 1982 1998 2003 2006


74

Figure (5-5) Comparison of Bed Profiles at Cross Sections (1) to (8)

Figure (5-6) Variation of the Lowest Bed Levels

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200 250 300

EL

EV

AT

ION

(m

)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 20 40 60 80 100 120 140

EL

EV

AT

ION

(m

)

DISTANCE (m)

Cross Section No.(4) 1982 1998 2003 2006

-12.00 -10.00

-8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00

0 25 50 75 100 125 150 175 200 225

EL

EV

AT

ION

(m

)

DISTANCE (m)

Cross Section No.(5) 1982

2003

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 50 100 150 200 250 300 350 400 E

LE

VA

TIO

N (

m))

DISTANCE (m)


2003

-22.00

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 25 50 75 100 125 150 175

EL

EV

AT

ION

(m

)

DISTANCE (m)


2003

-14.00 -12.00 -10.00

-8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00

0 25 50 75 100 125 150 175 200 225

EL

EV

AT

ION

(m

)

DISTANCE (m)


2003

-20.00

-16.00

-12.00

-8.00

-4.00

0.00

4.00

8.00

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

LE

VE

L (

m)

DISTANCE (m)

1982 1998 2003 2006

K.St

Kfr Al zayat Bridges B1 B3 B2

S2 S1

N


75

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


76

1982 2003


77

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


78

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.



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

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


decreased by 32m, width decreased by 11m and the depth decreased by 8.5m comparing with

year 1998.



No.Of

HolesDifferece Differece Differece

Avr

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

8

9

10

Hole Length (m)Hole Width

(m)

Hole Depth

(m)

No Data


79

increased by 172m, width increased by 1m and the depth decreased by 1m comparing with

year 1998.


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.



decreased by 15m, width decreased by 10m and the depth didn’t change comparing with year

2003.



decreased by 159m, width increased by 7m and the depth didn’t change comparing with year

2003.

No.Of


Avr

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

8

9

10


(m)

Hole Depth

(m)

No Data


81


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.



decreased by 97m, width decreased by 10m and the depth decreased by 6m comparing with

year 1982.



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


decreased by 30m, width increased by 9m and the depth decreased by 0.5m comparing with

year 1982.



increased by 29m, width decreased by 2m and the depth didn’t change comparing with year

1982.

No.Of


Avr

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

8

9

10


(m)

Hole Depth

(m)

No Data


81


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.


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.



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.


No.Of

HolesDifference Differece Differece

Avr

Rate/YearStates

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

Hole Length

(m)

Hole Width

(m)

Hole Depth

(m)


82

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.

Figure (5-10) Scour Hole Length Change at Years 1982, 1998, 2003 and 2006

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

-200.00

-100.00

0.00

100.00

200.00

1 2 3

Len

gth

(m

)

Scour Hole No.

Different Length L1998 - L 1982

L2003 - L1998

L2006 - L2003

Dcc

rease

In

crea

se

-20.00

-10.00

0.00

10.00

20.00

1 2 3

Wid

th (

m)

Scour Hole No.

Different Width W1998 - W1982

W2003 - W1998

W2006 - W2003

Incr

ease

D

ccre

ase


83

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

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

1 2 3

Dep

th (

m)

Scour Hole No.

Different Depth D1998 - D1982

D2003 - D1998

D2006 - D2003

Ero

sion

D

eposi

tion


84

deposition was existed along the section in year 2003 comparing with other years. This was

because filling work in the reach after 1998 flood.

-14.00

-10.00

-6.00

-2.00

2.00

0 40 80 120 160 200 240 280

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(1) 1982 1998 2003 2006

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 40 80 120 160 200 240 280

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(2) 1982 1998 2003 2006

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 20 40 60 80 100 120 140

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

-12.00

-8.00

-4.00

0.00

4.00

0 40 80 120 160 200 240 280

LE

VE

L

(m)

DISTANCE (m)


2003

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)


2003

-12.00

-8.00

-4.00

0.00

4.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)


2003

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 40 80 120 160 200

LE

VE

L

(m)

DISTANCE (m)


2003

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)


2003


85

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

-20.00

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 40 80 120 160

LE

VE

L

(m)

DISTANCE (m)


2003

-14.00

-10.00

-6.00

-2.00

2.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)


2003

-14.00

-10.00

-6.00

-2.00

2.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(1) 1982 1998 2003 2006

-16.00

-12.00

-8.00

-4.00

0.00

0 50 100 150 200 250 300

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(2) 1982 1998 2003 2006


86

Figure (5-16) Scour Holes Longitudinal Sections for Years 1982, 1998, 2003 and 2006

-16.00

-12.00

-8.00

-4.00

0.00

0 400 800 1200

LE

VE

L

(m)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

-14.00 -12.00 -10.00

-8.00 -6.00 -4.00 -2.00 0.00 2.00

0 40 80 120 160 200 240

LE

VE

L

(m)

DISTANCE (m)


2003

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

0 60 120 180 240 300 360

LE

VE

L

(m)

DISTANCE (m)


2003

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

0 60 120 180 240 300 360

LE

VE

L

(m)

DISTANCE (m)


2003

-8.00

-6.00

-4.00

-2.00

0.00

0 40 80 120 160 200 240 280

LE

VE

L

(m)

DISTANCE (m)


2003

-8.00

-6.00

-4.00

-2.00

0.00

0 100 200 300 400 500 600

LE

VE

L

(m)

DISTANCE (m)


2003

-20.00

-16.00

-12.00

-8.00

-4.00

0.00

0 200 400 600 800

LE

VE

L

(m)

DISTANCE (m)


2003

-16.00

-12.00

-8.00

-4.00

0.00

0 200 400 600 800 1000

LE

VE

L

(m)

DISTANCE (m)


2003

CHAPTER 6

MODEL APPLICATION AND SCOUR

CALCULATION

Chapter 6 Model Application and Scour Prediction

87

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

WL

(m)

U.S

145 km

Kfer El-Zayat

Station

146 km

D.S

154 km Discharge

Q

(million.m³/day)

Q

(m³/sec)

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

Emergency 6.01 5.90 5.06 QEmergancy 220.00 2546.30

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


88

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).

0.00

0.15

0.30

0.45

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.05

0.10

0.15

0.20

0.25

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.10

0.20

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.05

0.10

0 20 40 60 80 100 120 140

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006


89

Figure (6-1) Comparison between the C. S Velocity Profiles in Case of Min Discharge

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.

0.00

0.05

0.10

0 25 50 75 100 125 150 175 200 225

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0.15

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0 25 50 75 100 125 150 175

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0 25 50 75 100 125 150 175 200 225

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

1.45

1.50

1.55

1.60

1.65

1.70

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

1982 1998 2003 2006

K.St

Kfer El Zayat Bridges B1 B3 B2

S2 S1

Flow


91

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).

0.00

0.25

0.50

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.10

0.20

0.30

0 50 100 150 200 250 300 350

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.10

0.20

0.30

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

0.00

0.05

0.10

0.15

0 20 40 60 80 100 120 140

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006


91

Figure (6-3) Comparison between the C. S Velocity Profiles in Case of Ave. Discharge

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-


0.00

0.05

0.10

0.15

0.20

0 30 60 90 120 150 180 210

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0.15

0.20

0.25

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0.15

0 25 50 75 100 125 150 175

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.05

0.10

0.15

0.20

0 30 60 90 120 150 180 210 V

EL

OC

ITY

(m

/s)

DISTANCE (m)


2003

2.00

2.05

2.10

2.15

2.20

2.25

2.30

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

1982 1998 2003 2006

Kfer El Zayat Bridges

K.St

B1 B3 B2

S2 S1

Flow


92

The model was runs 4 times at maximum flow for years of 1982, 1998, 2003 and 2006. The


are shown in Figure (6-5). The results show that:



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



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).

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(1) 1982 1998 2003 2006

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 50 100 150 200 250 300 350

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

0.00

0.20

0.40

0.60

0.80

0 20 40 60 80 100 120 140

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006


93

Figure (6-5) Comparison between the C. S Velocity Profiles in Case of Max. Discharge

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-


0.00

0.20

0.40

0.60

0.80

1.00

0 25 50 75 100 125 150 175 200 225

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.20

0.40

0.60

0 25 50 75 100 125 150 175

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.20

0.40

0.60

0.80

0 25 50 75 100 125 150 175 200 225 V

EL

OC

ITY

(m

/s)

DISTANCE (m)


2003

2.20

2.30

2.40

2.50

2.60

2.70

2.80

2.90

3.00

3.10

3.20

3.30

3.40

3.50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

1982 1998 2003 2006


K.St

B1 B3 B2

S2 S1

Flow


94

The model was runs 4 times at emergency flow for years of 1982, 1998, 2003 and 2006. The


are shown in Figure (6-7). The results show that:



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



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).

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(1) 1982 1998 2003 2006

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300 350

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(2) 1982 1998 2003 2006

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(3) 1982 1998 2003 2006

0.00

0.40

0.80

1.20

1.60

2.00

0 20 40 60 80 100 120 140

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


1998

2003

2006


95

Figure (6-7) Comparison between the C. S Velocity Profiles in Case of Emer. Discharge

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

0.00

0.40

0.80

1.20

1.60

2.00

0 25 50 75 100 125 150 175 200 225

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

0 50 100 150 200 250 300 350 400

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.40

0.80

1.20

1.60

0 25 50 75 100 125 150 175

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

0.00

0.40

0.80

1.20

1.60

2.00

0 25 50 75 100 125 150 175 200 225

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2003

5.00

5.10

5.20

5.30

5.40

5.50

5.60

5.70

5.80

5.90

6.00

6.10

6.20

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

1982

1998

2003

2006


B3

K.St

B1 B2

S2 S1

Flow


96

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).

Figure (6-9) Location of the Bridge Piers

Highway Bridge 1

Highway Bridge 2

Railway Bridge 3


97

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

Bridge

No. Bridge 1 Bridge 2 Bridge 3

Location

(km) 146.00 146.239 149.682

Pier No. Pier

1 Pier

2 Pier

3 Pier

4 Pier

5 Pier

6 Pier

7 Pier

8 Pier

9 Pier

10 Pier

11 Pier

12 Pier

13

Pier Shape Rec Rec Rec Rec Rec Cir Rec Rec Rec Rec Rec Cir Rec

Diameter

(m) ------ ------ ------ ------ ------ 14.00 ------ ------ ------ ------ ------ 11.00 ------

Width

(m) 16.00 16.00 16.00 4.00 4.00 ------ 4.00 4.00 4.00 4.00 4.00 ------ 4.00

Length

(m) 26.50 26.50 26.50 15.00 15.00 ------ 15.00 15.00 13.00 13.00 13.00 ------ 13.00

Dist.

(m) 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

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


98

Table (6-4) The Used Parameters and the 2D Model Results of Scour Bridge Piers in

Case of Maximum Flow

Pier

1

Pier

2

Pier

3

Pier

4

Pier

5

Pier

6

Pier

7

Pier

8

Pier

9

Pier

10

Pier

11

Pier

12

Pier

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

[a/Y1]0.65

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


Case of Emergency Flow

Pier

1

Pier

2

Pier

3

Pier

4

Pier

5

Pier

6

Pier

7

Pier

8

Pier

9

Pier

10

Pier

11

Pier

12

Pier

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

[a/Y1]0.65

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

K2 : Correction angle of attack YS/Y1 = 2*K1*K2*K3*K4*(a/Y1)0.65

(Fr1)0.43

K3 : Correction bed forms YS : Scour depth

K4 : Correction armoring


99

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


111

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

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

Bend Scour (m)


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


112

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

General Scour by Neil Incised Equation (m)


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

C.S No. Discharge

(m.m3/day)

General Scour

by Neil’s

Equation (m)

Bend scour

(m)

Contraction

Scour

(m)

Bend + Contraction

Scour (m)

Considered

General

Scour (m)

Bridge 1 69.90 2.70 3.86 0.48 4.34 4.34

220.00 4.50 4.10 0.87 4.97 4.97

Bridge 2 69.90 2.58 2.60 0.25 2.85 2.85

220.00 3.90 2.90 0.41 3.31 3.90

Bridge 3 69.90 3.30 4.35 0.34 4.69 4.69

220.00 5.10 6.22 0.57 6.79 6.79

C.S1 69.90 4.50 - - - 4.50

220.00 6.00 - - - 6.00

C.S2 69.90 4.20 - - - 4.20

220.00 8.89 - - - 8.89

C.S3 69.90 6.60 5.70 - 5.70 6.60

220.00 8.11 7.04 - 7.04 8.11

C.S4 69.90 3.90 - - - 3.90

220.00 6.00 - - - 6.00


113

C.S No. Discharge

(m.m3/day)

General Scour

by Neil’s

Equation (m)

Bend scour

(m)

Contraction

Scour

(m)

Bend + Contraction

Scour (m)

Considered

General

Scour (m)

C.S5 69.90 4.80 - - - 4.80

220.00 6.90 - - - 6.90

C.S6 69.90 4.50 - - - 4.50

220.00 6.00 - - - 6.00

C.S7 69.90 3.60 - - - 3.60

220.00 5.10 - - - 5.10

C.S8 69.90 4.80 - - - 4.80

220.00 5.10 - - - 5.10

C.S9 69.90 6.60 7.79 - 7.79 7.79

220.00 8.11 8.58 - 8.58 8.58

C.S10 69.90 5.10 - - - 5.10

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.


114

Table (6-10) Total Scour

Bridge No. Pier No. Discharge

(m.m3/day)

General Scour

(m)

Local Scour

(m)

Total Scour

(m)

Bridge 1 Pier 2 69.90 4.34 9.64 13.98

220.00 4.97 12.77 17.74

Bridge 2 Pier 6 69.90 2.85 7.48 10.33

220.00 3.90 10.03 13.93

Bridge 3 Pier 12 69.90 4.69 6.95 11.64

220.00 6.79 9.60 16.39

C.S1 69.90 4.34 - 4.50

220.00 4.97 - 6.00

C.S2 69.90 2.85 - 4.20

220.00 3.90 - 8.89

C.S3 69.90 5.69 - 6.60

220.00 5.74 - 8.11

C.S4 69.90 4.34 - 3.90

220.00 4.97 - 6.00

C.S5 69.90 2.85 - 4.80

220.00 3.90 - 6.90

C.S6 69.90 5.69 - 4.50

220.00 5.74 - 6.00

C.S7 69.90 5.69 - 3.60

220.00 5.74 - 5.10

C.S8 69.90 4.34 - 4.80

220.00 4.97 - 5.10

C.S9 69.90 7.79 - 7.79

220.00 8.58 - 8.58

C.S10 69.90 5.69 - 5.10

220.00 5.74 - 5.10


115

Water Level (5.90)m for Q = 220m.m^3/day

Max. Water Level(2.60)mMin. Water Level(1.57)m

Nourth South

Kfer El-Zayat Bridge

Q = 220m.m^3/day

Original Bed (-4.00)

General Scour = 4.97m

Local Scour = 12.77m

Total Scour = 17.74m

Bridge

Pier

(-21.74)m

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

Figure (6-14) First Bridge Piers Location

Figure (6-15) Second Bridge Piers Location

Figure (6-16) Third Bridge Piers Location

-5

-3

-1

1

3

5

0 50 100 150 200 250 300 350

Ele

vati

on

(m

)

Distance from Left Bank (m)

Pier 1 Pier 2 Pier 3

-5

-3

-1

1

3

5

0 100 200 300 400

Ele

vati

on

(m

)




-7

-5

-3

-1

1

3

5

0 50 100 150 200 250 300

Ele

vati

on

(m

)


Pier10 Pier11 Pier12

Pier13


116

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

El-Zayat Bridges

Pier

No.

Discharge

(m.m3/day)

Water

Surface

Elevation

(m)

Water

Depth

(m)

Total

Scour

(m)

Expected

River

Bed

Elevation

(m)

Actual

River

Bed

Elevation

(m)

Magnitude

of Scour

Holes Depth

Enlargement

(m)

Pier 2 69.90 2.99 7.20 13.98 14.19 -4.00 -18.19

220.00 5.90 10.00 17.74 17.84 -4.00 -21.84

Pier 6 69.90 2.98 5.90 10.33 10.25 -3.00 -13.25

220.00 5.86 8.90 13.93 13.97 -3.00 -16.97

Pier

12

69.90 2.88 9.00 11.64 11.76 -6.00 -17.76

220.00 5.72 11.90 16.39 16.57 -6.00 -22.57

C.S1 69.90 2.96 14.00 4.50 4.54 -11.00 -15.54

220.00 5.99 17.00 6.00 6.01 -11.00 -17.01

C.S2 69.90 2.80 12.00 4.20 4.90 -8.50 -13.40

220.00 5.73 15.00 8.89 9.66 -8.50 -18.16

C.S3 69.90 2.76 17.00 6.60 6.34 -14.50 -20.84

220.00 5.62 19.50 8.11 7.49 -14.50 -21.99

C.S4 69.90 2.71 13.00 3.90 4.19 -10.00 -14.19

220.00 5.52 15.50 6.00 5.98 -10.00 -15.98

C.S5 69.90 2.71 16.50 4.80 5.09 -13.50 -18.59

220.00 5.52 19.50 6.90 7.38 -13.50 -20.88

C.S6 69.90 2.67 13.50 4.50 4.83 -10.50 -15.33

220.00 5.43 16.50 6.00 6.57 -10.50 -17.07

C.S7 69.90 2.66 10.00 3.60 3.64 -7.30 -10.94

220.00 5.40 12.90 5.10 5.30 -7.30 -12.60

C.S8 69.90 2.60 9.80 4.80 5.00 -7.00 -12.00

220.00 5.80 12.80 5.10 5.10 -7.00 -12.10

C.S9 69.90 2.56 20.00 7.79 8.23 -17.00 -25.23

220.00 5.18 22.50 8.58 8.90 -17.00 -25.90

C.S10 69.90 2.52 14.50 5.10 4.58 -12.50 -17.08

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.


117

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.

CHAPTER 7

ALTERNATIVE SOLUTIONS AND

RESULT ANALYSIS

Chapter 7 Alternative Solutions and Result Analysis

118

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).


119

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, 2546.30m

3/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


111

Figure (7-2) The Thalweg Line in Case of the Original and Alternative 1

-20.00

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

2006

Fill

K.St Kfer El Zayat Bridges

B1 B3 B2

S2 S1

Flow

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250 300

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 20 40 60 80 100 120 140 Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200 250

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill


111

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

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200 250

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-8.00

-4.00

0.00

4.00

0 50 100 150 200

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-8.00

-4.00

0.00

4.00

0 50 100 150 200 Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-20.00

-14.00

-8.00

-2.00

4.00

0 50 100 150

Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250 Bed

Lev

els

(m)

MS

L

DISTANCE (m)


Fill


112

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

Figure (7-5) Velocity Profile at the Deepest Points (Outer Curve) along the Reach in

Case of the Original & Alternative 1 at Max Flow

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

VE

LO

CIT

Y (

m/s

ec)

DISTANCE (m)

2006

Fill

B1 B2 Kfer El -Zayat Bridges

K.St B3

S2 S1

Flow


113

0.00

0.25

0.50

0.75

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

Cross Section No.(1) Fill

2006

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006


114

Figure (7- 6) Cross Sections Velocity Profile of the Original & Alternative 1 at Max Flow

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

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 25 50 75 100 125 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

2.20

2.30

2.40

2.50

2.60

2.70

2.80

2.90

3.00

3.10

3.20

3.30

3.40

3.50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

2006

Fill


K.St B1 B3 B2

S2 S1

Flow


115

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

Figure (7-9) Velocity Profile at the Deepest Points along the Reach in Case of Alternative

1 at Emergence Flow

0.50

0.70

0.90

1.10

1.30

1.50

1.70

1.90

2.10

2.30

2.50

2.70

2.90

3.10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

VE

LO

CIT

Y (

m/s

ec)

DISTANCE (m)

2006

Fill Kfr Al Zayat Bridges

K.St

B1 B3 B2

S2 S1

Flow


116

0.00

0.25

0.50

0.75

1.00

1.25

1.50

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.50

1.00

1.50

2.00

2.50

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006


117

Figure (7- 10) Cross Sections Velocity Profile of the Original & Alternative 1 at

Emergence Flow

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,

0.00

0.50

1.00

1.50

2.00

2.50

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


2006

5.00

5.20

5.40

5.60

5.80

6.00

6.20

6.40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)

2006

Fill


B3

S2

K.St

B1 B2

S1

Flow


118

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

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250 300

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-18.00

-14.00

-10.00

-6.00

-2.00

2.00

0 20 40 60 80 100 120 140

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200 250 Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging


119

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

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200 250

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150 200

Bed

Lev

el (

m)

MS

L

DISTANCE (m)

Cross Section No.(6) 2003 Fill& Dredging

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 50 100 150 200

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

0 50 100 150 200

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-20.00

-16.00

-12.00

-8.00

-4.00

0.00

4.00

0 50 100 150

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging

-14.00

-10.00

-6.00

-2.00

2.00

0 50 100 150 200 250

Bed

Lev

el (

m)

MS

L

DISTANCE (m)


Fill& Dredging


121

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


121



0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

VE

LO

CIT

Y (

m/s

ec)

DISTANCE (m)

2006 Fill Fill&Dredge

B1 B2 Kfer El Zayat Bridges

K.St B3

S2 S1

Flow

0.00

0.25

0.50

0.75

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

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

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


Fill

Fill&Dredging

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)



122

Figure (7- 16) Cross Sections Velocity Profile of the Original, Alternative 1 and

Alternative 2 at Maximum Flow

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 25 50 75 100 125 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


Fill

Fill&Dredging

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)



123



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.

2.20

2.30

2.40

2.50

2.60

2.70

2.80

2.90

3.00

3.10

3.20

3.30

3.40

3.50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)


Kfer El -Zayat Bridges

K.St B1 B3 B2

S2 S1

Flow


124

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


Alternatives 1 and 2 at Emergency Flow

0.50

0.70

0.90

1.10

1.30

1.50

1.70

1.90

2.10

2.30

2.50

2.70

2.90

3.10

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

VE

LO

CIT

Y (

m/s

ec)

DISTANCE (m)

2006

Fill

Fill&Dredge

Kfr Al zayat Bridges

K.St

B1 B3 B2

S2 S1

Flow


125

0.00

0.25

0.50

0.75

1.00

1.25

1.50

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)

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

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.50

1.00

1.50

2.00

2.50

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250 300

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)



126

Figure (7- 20) Cross Sections Velocity Profile of the Original, Alternatives 1 and 2 at

Emergency Flow


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.

0.00

0.50

1.00

1.50

2.00

2.50

0 50 100 150

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250

VE

LO

CIT

Y (

m/s

)

DISTANCE (m)


Fill

Fill&Dredge

5.00

5.20

5.40

5.60

5.80

6.00

6.20

6.40

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

WA

TE

R S

UR

FA

CE

EL

EV

AT

ION

(m

)

DISTANCE (m)


Kfr Al zayat Bridges B3

K.St

B1 B2

S2 S1

Flow


127

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/m

2. 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.


128

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


129

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

2.00

2.40

0 50 100 150 200 250 300 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

2.00

0 50 100 150 200 250 300 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

2.00

2.40

0 50 100 150 200 250

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 200 250

SH

EA

R S

TR

ES

S (

N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.40

0.80

1.20

1.60

0 50 100 150 200 250 SH

EA

R S

TR

ES

S (

N/m

2)

DISTANCE (m)



131


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/m

2. 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.

0.00

1.00

2.00

3.00

4.00

0 25 50 75 100 125 150 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 200 250

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge


131

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


132

0.00

4.00

8.00

12.00

16.00

20.00

0 50 100 150 200 250 300

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

4.00

8.00

12.00

16.00

0 50 100 150 200 250 300

SH

EA

R S

TR

ES

S

(N/m

2

DISTANCE (m)


0.00

4.00

8.00

12.00

16.00

0 50 100 150 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

2.00

4.00

6.00

0 50 100 150 200 250 300

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

4.00

8.00

0 50 100 150 200 250 300

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

2.00

4.00

6.00

8.00

10.00

0 50 100 150 200 250 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

4.00

8.00

12.00

16.00

0 50 100 150 200 250 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

2.00

4.00

6.00

8.00

0 50 100 150 200 250

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)



133


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.

33

65

cos)1(

101.4

s

s

S

USXW

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

3

1

))(

6(

ws

wD

(7-2)

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

2

1

22

2

)tan(tancos)1(

25.0

sSg

UD

(7-3)

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

0.00

4.00

8.00

12.00

16.00

0 50 100 150

SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge

0.00

4.00

8.00

12.00

0 50 100 150 200 250 SH

EA

R S

TR

ES

S

(N/m

2)

DISTANCE (m)


Fill

Fill&Dredge


134

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



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


135

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)

4)(

)(

85

15 baseD

FilterD

25)(

)(

50

50 baseD

filterD

40)(

)(5

15

15 baseD

filterD

65.0/20.0 = 3.3

105.0/15.0 = 7.0

65.0/10.0 = 6.5

10.0/3.0 = 3.3

15.0/1.5 = 10.0

10.0/1.0 = 10.0

1.0/0.65 = 1.54

1.5/.33 = 4.55

1.0/0.18 = 5.56

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


136

Figure (7-30) Grain Size Distributions of the Proposed Filter Layers

0.30 m

0.20 m

0.50 m

Base Layer

Filter Layer (2)

Riprap Layer

D50 = 0.33 mm

D50 = 1.50 mm

Stone D50 = 105 mm

Filter Layer (1)

D50 = 15.00 mm

Figure (7-31) The Designed Filter Layers Thickness

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100 1000

Pe

rce

nt

Fin

er

by

We

igh

t

Particle Size (mm)

Base Filter 1 Filter 2 Riprap

CHAPTER 8

CONCLUSIONS AND

RECOMMENDATIONS

Chapter 8 Conclusions and Recommendations

137

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.


138

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.


139

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.

REFERENCES

References

141

REFERENCES

Ahmed, A. F.,(1988), “Stability of Riprap Side Slope in Open Channels,” Thesis

presented for University of Southampton, U.K., for the Fulfillment of the Requirements for

the Degree of Doctor of Philosophy in Civil Engineering.

Amadi, Faith Onyinye, Holbrook John, Pagan Steve, Macklin Larry, and Dolde John,

(2004): "Factors influencing Morphological changes in an Alluvial reach of the

Missouri River valley" Research Report.

Arcement, G. J., and Schneider, V. R., (1984). “Guide for Selecting Manning's

Roughness Coefficients for Natural Channels and Flood Plains.” Report No. FHWA-

TS-84-204, Federal Highway Administration, McLean, Virginia.

ASCE Task Committee on Preparation of Sedimentation Manual, (1972), “Sediment

Control Methods: B. Stream Channels,” Journal of the Hydraulics Division, ASCE, Vol.

98, No. HY7, Proc. Paper 9071, July, pp. 1295-1326.

Attia, K. M. and Abdel-Bary, M. R., (1998), ”Bank Line Movements along the River

Nile,” International Conference on Coping with Water Scarcity, Hurgada City, Red Sea,

Egypt, 26-28 August.

Attia, K. M. and El-Saied, N.,(2004), “Plan Form Geometry of River Meander at

Damietta Branch” Scientific Bulletin, Faculty of Engineering, Ain Shams University,

ISSN 1110-1385, Vol. 39, No. 1, pp.359-379, March 31, 2004.

Babaeyan-Koopaei K., and Valentine, E.M. (1999), “Bridge Pier Scour in Self-Formed

Laboratory Channels,” The XXVIII IA HR congress 22-27 August 1999.

Barnes, H. H., (1967),”Roughness Characteristics in Natural Channels,” U.S.

Geological Survey Water Supply Paper 1849.

Brice, J.C., (1983), "Planform properties of Meandering Rivers", River Meandering,

Proceedings of the October 24-26, 1983 Rivers,83 Conference, ASCE, New Orleans,

Louisiana, pp. 1-15.

Chang, Howard H., (1988), " Fluvial Processes in River Engineering", A book published

by Wiley- Interscience publication, Jonhn Wiley & Sons, Inc. ISBN 0-471-63139-6.

Chow, V. T., (1959), “Open Channel Hydraulics,” McGraw-Hill Book Co., Inc., New

York, N.Y.

Demissie, M., L. Keefer, and R. Xia. (1992), “Erosion and Sedimentation in the Illinois

River Basin”. ILENR/RE-WR- 92/04. Illinois Department of Energy and Natural

Resources, Springfield, IL.

El Sersawy, H., (2001), “Modeling of the Morphological Processes in the Navigation

uses”. Thesis submitted to a PH. D., Cairo University, Faculty of Engineering.

mailto:[email protected]

References

141

Enggrob, H., G., (2003), "Morphological forecast simulation of Jamuna River in

Bangladesh". River Meandering Book.

Ettema, R. (1980), “Scour at Bridge Piers”, Dissertation, Department of Civil

Engineering, University of Auckland, New Zealand.

Federal Highway Administration (FHWA), (1991), "Scour ability of Rock Formations",

U.S. Department of Transportation Memorandum, HNG-31, Washington, D.C. R5.

Federal Highway Administration (FHWA), (2001), “Evaluating Scour at Bridges”,

Hydraulic Engineering Circular Number 18, HEC-18.

Fischer-Antze D., Gutknecht, W. Bors and C. Kolbl (2003), "Morphological response of

the Danube River”, European Geophysical Society 2003, Vol. 5, 11873, 2003.

Flood Control District of Maricopa County (FCDMC), (2007), “Drainage Design Manual

for Maricopa County”, Draft: chapter 11.

Flood Control District of Maricopa County (FCDMC), (2009), “River Mechanics Manual

for DDMSW”, Draft.

Hager, W. and Unger, J., (2010), “Bridge Pier Scour under Flood Waves”, ASCE,

Journal of the Hydraulic Division, Vol. 136, Issue 10.

Herman, J. K., (1984), “Scour Due to Riprap and Improper Filters”, j. Hydraulic. Div.

ASCE, 110(HY10), October, pp.1315-1324.

Hydraulic Engineering Circular 18, Fifth Edition, (2012), “Evaluating Scour at Bridges”,

FHWA HIF 12 003 HEC-18, Federal Highway Administration, U.S. Department of

Transportation, Washington, D.C.

Hydraulic Research Institute (HRI), (1993), “Monitoring Local Scour in the River Nile

at Imbaba Bridge”, in Arabic, Cairo, Egypt.

Hydraulic Research Institute (HRI), (2005), “Protection of Bank against Erosion along

the River Nile”, report no 3, Cairo, Egypt.

Inglis, C. C., (1949), “The Behavior and Control of Rivers and Canals,” Central Water

and Power Research Station, Poona, India, Research Publication No. 13.

Izbash, S. V., (1936), “Construction of Dams by Depositing Rocks in Running Water”,

Proceedings of Second Congress on Large Dams, Washington D.C., Vol. 5, pp. 123-136.

Jean-Louis Briaud, Hamn-Ching Chen, Kuang-An Chang, Young-An Chung, Namgyu

Park, Wei Wang, and Po-Hung Yeh, (2007), ”Establish Guidance for Soils Properties

Based-Prediction of Meander Migration Rate”, Zachry Department of Civil

Engineering, Texas A&M University.

References

142

Jones, J. Sterling and D. Max Sheppard, (2000), “Scour at Wide Piers”, Proceedings for

the 2000 Joint Conference on Water Resources Engineering and Water Resources

Planning and Management Conference, Minneapolis, MN, July 30-August 2, 2000.

Johnson, Peggy A.(1999), “Scour at Wide Piers Relative to Flow Depth”, “Stream

Stability and Scour at Highway Bridges, Compendium of ASCE conference papers edited

by E. V. Richardson and P. F. Lagasse, pp280 . 287”.

Kapsimaisi, V., Karagorgisi, A.P., Poulos, S. (2004), "Morphological changes in a

human affected coastal system using GIS", Jour. Hydr. Eng. Vol. 117, No.12.

Krone, R. B. (l962), " Flume Studies of the Transport of Sediment in Estuarial

Shoaling Processes", Final Report, Hydraulic Engineering Laboratory and Sanitary

Engineering Research Laboratory, University of California, Berkeley.

Lança, R., Fael, C., Maia, R., Pêgo, J., and Cardoso, A., (2013), “Clear-Water Scour at

Comparatively Large Cylindrical Piers”, ASCE, Journal of the Hydraulic Division, Vol.

139, Issue 11.

Lane, E. W., (1955), “Design of Stable Channels”, Trans. ASCE, Vol. 120, pp. 1234-

1260.

Lee, J. K. and Froehlich, D. C., (1986), “Review of Literature on the Finite-Element

Solution of the Equations of Two-Dimensional Surface-Water Flow in the Horizontal

Plane”, U.S. Geological Survey Circular 1009, Washington, D. C.

Leopold, L. B. and Wolman, M. G., (1957), “River Channel Patterns: Braided,

Meandering and Straight,” USGS Professional Paper 282-B, pp. 45-62.

Leopold, L. B. and Wolman, M. G., (1960), “River Meanders,” Geolo. Soc. Bull., 71, pp.

769-794.

Linda P. Warren, (1993), "The mission of the Water Resources Division of the U.S.

Geological Survey (USGS)", Open-File Report 93-W0487.

Melville, B.W. (1975),“Local Scour at Bridge Sites”, Report no. 117, University of

Auckland, School of Engineering, Auckland, New Zealand.

Melville, B.W. (1997), “Pier and abutment scour, integrated approach”, Journal of

Hydr. Eng., ASCE, 118(4): pp615-630.

Melville, B.W. and Sutherland, A.J.,( 1988), “Design Method for Local Scour at Bridge

Piers”, American Society of Civil Engineers, Journal of the Hydraulic Division, Vol

114,No. 10, Oct. 1988.

Motiee, H. and Darakhani, J., (2003), "Morphological changes of River due to

constructed structures (case study Sephidrood River)", European Geophysical Society,

Journal of Hydr. Eng., Vol. 121, No.10, pp 845-851.

References

143

Moattassem, M., Makary, A., and Ayoud, S. (1990), “An Approach to Detect River Nile

Navigation Bottlenecks”, National Seminar on Physical Response of the River Nile to

Interventions, Cairo, November 12-13, 1990, (First Edition Of The Proceedings Only).

Nanson, G. C. and Hickin, E. J., (1986), “Channel Migration and Incision on the

Beatton River”, Journal of Hydraulic Engineering, ASCE, 109(3), pp. 327-337, March.

Neill C.R. (1973), "Guide to Bridge Hydraulics", University of Toronto Press, Toronto,

Canada.

Norman, J. M., (1975), “Design of Stable Channel with Flexible Lining,” Hydraulic

Engineering Circular No. 15, Federal High way Administration, U.S. Department of

Transportation, 136 pp.

Pemberton, E.L. and Lara, J.M., (1984), “Computing Degradation and Local Scour”, U.

S. Bureau of Reclamation, Sedimentation section, Denver CO.

Posey, C. J., (1969), “Erosion Prevention Experiments”, Proc. Of the 13th

Congress of

IAHR, Vol. 2, Aug. 31 Sep. pp. 211-219.

Raslan, Y., Sadek N., and Attia k., “Impact of Navigation Development on Damietta

Branch”, Water Research Center Journal, March, 2008, Cairo, Egypt.

River Nile Development Project, RNDP, (1991a, 1992b), Ministry of Public Works and

Water Resources, Egypt.

River Nile Protection and Development Project (RNPD) (1991a), “Water levels in the

Nile with Low Flow Projects”, Working Paper No. 320-1, Nile Research Institute (NRI),

Egypt.

Rossell, R. and Ting, F. (2013), ”Hydraulic and Contraction Scour Analysis of a

Meandering Channel: James River Bridges near Mitchell, South Dakota”, J. Hydraul.

Eng., 139(12), 1286–1296.

Rouse, H., ed., (1959), “Advanced Mechanics of Fluids,” John Wiley & Sons, New York.

Rozovskii, I. L., (1957), “Flow of Water in Bends of Open Channels,” The Academy of

Sciences of the Ukrainian SSR, Translated from Russian by the Israel Program for

Scientific Translation, Jerusalem, Israel, 1961 (available from Office of Technical

Services, U.S. Department of Commerce, Washington, D. C., PST Catalog No. 363, OTS

60-51133).

Ruh-Ming, L. et al., (1976), “Probabilistic Approach to Design of Riprap for River

Bank Protection”, Symposium on Inland Water-Ways for Navigation, Flood Control and

Water Diversions, Vol.2, pp. 1572-1591.

Ruh-Ming, L. and Simons, D. B., (1979), “Failure Probability of Riprap Structures”,

ASCE Convention and Exposition, Atlanta, pp. 1-21.

References

144

Sadek N., Aziz M. and Attia K., (2000), "High Aswan Dam Impacts on Wadi

Morphology", International Conference on Wadi Hydrology, Sharm, Nov., 21-23.

Sadek N., Mohamed A. Talaat, Ahmed Aly, Mohamed R. Abdel Bary and M.Aziz, (2001),

"High Floods Impacts on Nile River", Sixth International Water Technology

Conference, Alexandria, Egypt.

Sadek, N. and Aziz, M. (2006), “Analysis of Different Floods on River Nile Fourth

Reach", Third Regional Conference on Perspectives of Arab Water Co-operation

Challenges, Constraints and Opportunities, Cairo, Egypt, 9 -11 Dec., 2006.

Samad, M. A., (1978), “Analysis of Riprap for Channel Stabilization”, Ph.D.

Dissertation, Colorado State Univ., Fort Collins, Colorado.

Sarker, M. Haque, Kamal M. and Hassan, Kh., (2003), "Morphological Changes of

Distributaries of the Ganges River", Journal of Hydr. Eng., ASCE, 116(3): pp561-570.

Schlichting, H., (1968), “Boundary Layer Theory,” 6th

edition, Mc Graw-Hill, New York.

Searcy, J. K., (1967),”Use of Riprap for Bank Protection,” Hydraulic Engineering

Circular No. 11, Bureau of Public Roads, (Federal High way Administration), U.S.

Department of Transportation, June.

Shen, H.W., Schneider, V.R. and Karaki, S.S. (1966),“Mechanics of Local Scour”,

Colorado State University, Civil Engineering Dept., Fort Collins, Colorado, Pub. No.

CER66-HWS22.

Shields, I. A., (1936), “Application of Similarity Principles and Turbulence Research

to Bed-Load Movement”, A Translation from the German by W. P. Ott and J. C. van

Vchelin, U.S. Soil Conserv, Service Coop. Lap., California Inst. Technology, Pasadena, 21

p.

Sheppard, D. M. (2004), "An Overlooked Local Sediment Scour Mechanism",

Proceedings of the 83rd Meeting of the Transportation Research Board, Washington, D.C.,

January 11-15, 2004 and published in the J. of the Transportation Research Board,

Transportation Research Record, No. 1890, pp107-111.

Sheppard, D., Melville, B., and Demir, H., 2014, “Evaluation of Existing Equations for

Local Scour at Bridge Piers”, ASCE, Journal of the Hydraulic Division, Vol. 140, Issue

1.

Simons, D. B., and Senturk, F., (1977), “Sediment Transport Technology”, Water

Resources Publications, Fort Collins, Colorado, USA.

Simons, Li & Assoc. (SLA), 1989b (revised July, 1998), “Standards Manual for

Drainage Design and Floodplain Management in Tucson”, Arizona, Prepared for City

of Tucson, Department of Transportation, Engineering Division.

http://ascelibrary.org/toc/jhend8/140/1

http://ascelibrary.org/toc/jhend8/140/1

References

145

SMS,(2002), Surface Water Modeling System, "Reference Manual", version 8.0.

Brigham,Young University, Engineering Computer Graphics Laboratory, Provo, Utah.

Stephenson, D., (1979), “Rock fill in Hydraulic Engineering”, Elsevier Scientific

Polishing Company, The Netherlands.

Stevens, M. A., and Simons, D. B., (1971), “Stability Analysis for Coarse Granular

Material on Slopes”, Chapter No.17 in SHEN, H.W. (Ed.), “River Mechanics, Vol. 1”,

Fort Collins, Colorado, pp. 17.1-17.17.

Stevens, M. A. and Simons, D. B., (1976), “Safety Factors for Riprap Protection,”

Proceeding of the ASCE, Vol. 102, No. HY5, May.

Terzaghi, K., and Peck, R., (1948), “Soil Mechanics in Engineering Practice”, John

Wiley and Sons, New York, Inc., 13th

Print.

U.S. Army Corps of Engineers (1970), “Little Rock District”, The Arkansas –

Renaissance of a River.

Zaller, J., (1967), “Meandering Channels in Switzerland,” International Symposium on

River Morphology, IASH, Hydraulic. 75, pp. 174-186.

ARABIC SUMMARY

ملخص البحث

1

عنوان الرساله

تقييم النحر لمنحنيات نهر النيل علي فرع رشيد

:مقدمة ( 1

حفاظا علي مياه النهر تسمح وزاره الاشغال العامه والموارد المايه بمرور تصرفات المياه علي حسب الاحتياجات الفعليه

د العالي ولا تسمح بمرور تصرفات اكبر من الاحتياجات الا في حالات الفيضانات حتي لا يصل منسوب المياه خلال الس

. الي حد الخطوره علي منشات السد العالي

وهذه التصرفات العاليه وكذلك التصرفات خلال اقصي الاحتياجات يمكن ان تسبب مشاكل للمنشأت المقامه علي نهر النيل

ويمكن ايضا للفيضان . ثل النحر الموضعي حول دعامات الكباري والمواني والقناطر والمنشأت الاخريوفروعه وذلك م

تسبب النشط منها , تصنف الانهار نوعين نشطه وخامله. ان يسبب غرق لبعض الاراضي والطرق والقري حول نهر النيل

. جوانب النهر بها نحر بقاع النهر او تأكل الجسر بينما الخامله لا يتغير شكل القاع او

تم اجراء رفع . وتتعرض لكثير من مشاكل النحر 123تقع مدينه كفر الزيات علي المنحني الخارجي لفرع رشيد عند كم

وكان من نتائج هذا الرفع ان 1998مساحي للنحر خلف كوبري السكه الحديد وكوبري الطريق السريع بعد فيضان عام

والذي تم تسجيله عام -16.11رب من المنحني الخارجي للمنحنيات تغير من منسوب منسوب النحر لبعض البيارات بالق

وهذا سبب مشكله كبيره لاتزان الجسر امام المدينه وللنحر حول . متر من منسوب سطح البحر -18.11الي منسوب 1996

. دعامات الكباري في المنطقه مما سبب عدم امان للمدينه والكباري

ملخص البحث( 2

كيلومتر والذي يتميز بوجود 9.1يبلغ طوله حوالي رشيدإستخدام جزء منحني من مجري نهر النيل بمجري فرع تم

لنفس لرفع المساحي السابقالرفع المساحي الهيدروجرافي الحديث للمنطقه المذكورة ومقارنتها با وضح .منحنيان منعكسان

لإجراء هذه ناسبلهيدروليكية المختلفة أنه يمكن اعتبار هذا الحبس مالحبس علاوة علي البيانات الهيدرولوجية والقياسات ا

هذه القياسات . الدراسه لوضوح تأثير ظاهرتي النحر والترسيب علي كل من المنحني الخارجي والداخلي علي الترتيب

جانبيه بينما يحدث لنهر مما يهدد استقرار الميول اللالخارجي للمنحنيأوضحت حدوث نحر موضعي وإنتقال لمواد القاع

للنهر مما ادي الي عدم إنتظام سرعة التيار المائي وإزاجة المجري في إتجاه للمنحني الداخليترسيب ملحوظ في الجانبين

.المنحني الخارجي

حيث تم عمل مقارانات لقاع . 2116و 2113و 1998و 1982جي النهر في هذه المنطقه لعام وقد تم دراسه مورفولو

وتم ايضا امرار تصرفات مختلفه علي . ماكن النحر الموجوه في منطقه الدراسهالنهر في هذه السنين ودراستها ودراسه ا

وتم دراسه السرعات الناتجه علي القطاعات العرضيه علي طول ( منخفضه و متوسطه وعاليه و حاله الطواريء)النهر

.الحبس في الاعوام المختلفه

النحر الناتج من )نحر المحتمل علي كامل الحبس النحر المحتمل حول دعامات الكباري و حساب ال وتم حساب ايضا

وبناءا عليه تم حساب النحر الكامل لكل القطاعات (. المنحنيات والنحر الناتج عن ضيق عروض القطاعات و النحر العام

.الموجوده بطول الحبس والنحر المحتمل في حاله التصرفات العاليه وحاله الطواريء

ملخص البحث

2

حلول المقترحه لمنطقه الدراسه لتجنب النحر إختبار بدائل الفي (SMS) ضي ثنائي الأبعادتلي ذلك إستخدام النموذج الريا

متر فوق سطح البحر و البديل الاخر ردم البيارت 5-ردم البيارات الموجوده حتي مستوي , علي جوانب و قاع النهر ومنها

متر فوق سطح البحر وتم 3-رات حتي مستوي من سطح البحر مع تكريك للناحيه الاخري للقطاع من البيا 5-حتي مستوي

وتبين من خلال هذه . 2116محاكاه كل بديل علي حده علي البرنامج الرياضي ومقارنه نتائجهم بالرفع المساحي لعام

وبناءا عليه تم تصميم طبقات الحمايه .الاول ومن الحاله الاصليه للنهر عطي نتائج أفضل مني المقارنات ان الحل الثاني

.مستخدمه لردم البياراتال

محتويات الرسالة( 3

الباب الأول

المقدمة

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

.الاهداف الرئيسية للبحث وخطة الدراسة ومكونات البحث

الباب الثاني

مراجعة الأبحاث المتعلقة بالدراسه

علي نبذة تاريخية للدراسات والبحوث التي أجريت في مجال البحث وما يتعلق بها من خصائص وتكوٍن هذا الباب يحتوي

علاوة علي حنيهالأنهار و مراحل تطورها وما يتعلق بالأنهار ذات الأجزاء المن المجاري المائية الطبيعية وتصنيف

وتم عرض . لتوصيف العناصر الهيدروليكية الخاصة بمنحنيات الأنهار مناسبهالعلاقات والمعادلات الرياضية المختلفة ال

.مجالال هذا خلاصة البحوث والدراسات والخبرات السابقة في

وتم عرض ايضا انواع النماذج المختلفه . النحر وخواصه وانواعه المختلفه والنتائج المترتبه عليه تلي ذلك عرض لتعريف

كما عرض في هذا الباب ايضا تعريف التكريك والترسيب وتجميع . من نماذج رياضيه و نماذج طبيعيه وخواص كل منهما

علي حبيبات التربه المكونه لقاع ( Shear Stress) اهم العلاقات التي تستخدم في حساب القوه المؤثره من سريان المياه

. المجري

الباب الثالث

البيانات المطلوبه للبحث

للتعرف علي علي مدار السنين السابقه التي تم تجميعها المتاحه يعرض هذا الباب مختلف القياسات الحقلية والبيانات

دامها في تشغيل النموذج الرياضي ثنائي الأبعاد علاوة علي التغيرات المورفولوجية بالحبس موضوع البحث والتي تم استخ

شمل ذلك القياسات الهيدروجرافية التي تمت حديثا للحبس والأجهزة . تصميم الحماية اللازمة للمنحني الخارجي لهذا الحبس

ي ونتائج هذه القياسات الباب مواقع قياس توزيع سرعه التيار المائفي هذا كما عرض . المستخدمة وطريقة القياس ونتائجها

بالحبس موضوع البحث ونتائج تحليل هذه العينات وعلاقة نتائج كل منها بتغير ومواقعهاقاع ال من مواد علاوة علي عينات

ملخص البحث

3

تبع ذلك عرض الخصائص الهيدرولوجية الخاصة . في هذا الحبس النهر منحني شكل القطاع المائي علي إمتداد مسافة

. رشيدسيب المقابلة علي إمتداد الحبس الواقع من خلف قناطر الدلتا فرع بالتصرفات المارة والمنا

الباب الرابع

و معايرتهالمستخدم ج الرياضى ذالنمو

والذي تم إستخدامه لمحاكاة ( SMS)يتضمن هذا الباب شرح موجز للمعادلات المستخدمة في النموذج الرياضي ثنائي الأبعاد

لباب شرح تطبيقات النموذج الرياضي ومميزاته وأسباب إختياره علاوة علي كيفية إعداد كما شمل ا. الحبس موضوع البحث

شبكة العناصر التي تمثل الحبس موضوع البحث مع عرض كيفية تغذيته بالعناصر الهندسية والهيدروليكية الممثلة لطبيعة

الباب متطلبات معايرة النموذج وتحقيق بناءا عليه عرض . المجري وتشغيله والمخرجات التي تنتج عن تطبيق النموذج

. النموذج بحيث يحاكي الحبس المذكور لإجراء الدراسات المطلوبة

كما شمل هذا الباب ايضا عرض اسلوب معايرة وتحقيق وتجهيز النموذج الرياضي ثنائي الأبعاد للإستخدام في بحث أفضل

بناء عليه تم عرض البيانات الخاصة بكل . بس موضوع البحثتصميم لتحسين خواص التدفق المائي بالمنحني الداخلي بالح

من تقدير معاملات الإحتكاك المناسبة لطبيعة التربة والتغيرات المورفولوجية بالحبس موضوع البحث وكذلك القيم المتوسطة

عند الحدين الأمامي والخلفي لتوزيع سرعة التيار المائي بالقطاعات المختلفة علاوة علي بيانات التصرفات والمناسيب المقابلة

والتي يتم خلالها تغيير قيم ( SMS)تلي ذلك عرض نتائج معايرة النموذج الرياضي ثناءي الأبعاد . للحبس موضوع البحث

معاملات الإحتكاك بالمواقع المختلفة في حدود معينة بحيث تكون مخرجات النموذج بالنسبة لتوزيع سرعة التيار بالقطاعات

بناءا عليه تم إستخدام البيانات الخاصة بمختلف التصرفات المارة بالحبس . قرب ما يمكن من القياسات الحقليةالمختلفة أ

. موضوع الدراسة والمناسيب المقابلة لكل منها في تحقيق النموذج بعد نجاح مرحلة معايرته والتي أوضحت أفضل النتائج

إختبار مدي دقة إختيار قيم معامل الإحتكاك التي تم إستخدامها في تلي ذلك عرض نتيجة إستخدام النموذج الرياضي في

. معايرة النموذج

الباب الخامس

التغيرات المورفولوجيه لمنطقه الدراسه

عند رشيدكيلومتر من فرع 9.1يعرض هذا الباب خواص الحبس الذي تم إختيارة للبحث والذي يشكل جزء طوله حوالي

إختيار هذا الحبس لاجراء الدراسه وذلك لما يحتويه من منحنيين معكوسي الإتجاه وما يتطلبة من وأسباب مدينه كفر الزيات

تلي ذلك عرض الخصائص المورفولوجية والمميزات والأبعاد . تحسين خواص التدفق المائي بالمنحني الداخلي لكل منهما

عرض . وتأثير ذلك علي تغيرات مناسيب القاعالهندسية لكل من المنحنيين الأمامي والخلفي للحبس موضوع الدراسة

التي الكنتوريهأيضا هذا الباب التطور الزمني للتغيرات التي توضح شكل الحبس موضوع البحث وذلك من واقع الخرائط

تم تحديد . وعلاقة ذلك بالتغيرات التي طرأت علي مجري نهر النيل 2116 و 2113و 1998و 1981تمت خلال الأعوام

موزعة بصوره منتظمه علي كامل طول الحبس موضوع البحث وإستنتاج تغيرات مناسيب هعرضي اتقطاع 8دد مواقع ع

ثم تم تحديد مواقع البيارات الناتجه من نحر .المشار أليها عاليه الهيدروجرافي خلال الأعوام ام الرفع \باستخالقاع بكل منها

ملخص البحث

4

وتم مقارنه هذه البيانات علي مدار السنين المختلفه وتحليل كامل . جيحول دعامات الكباري و نتيجه النحر للمنحني الخار

.لها

السادسالباب

تشغيل النموزج الرياضي ودراسه الانواع المختلفه للنحر

( منخفضه و متوسطه و عاليه و حاله طواريء)تشغيل للنموزج ثنائي الابعاد لاربع تصرفات مختلفه يتضمن هذا الباب

وتم دراسه السرعات الناتجه ومقارنتها , (2116 و 2113و 1998و 1981)كونتوريه لاعوام مختلفه وذلك لاربع خرائط

. ببعضها وتحليل نتائجها

وتم حساب النحر المحتمل علي . وتم ايضا حساب النحر المحتمل حول دعامات الكباري عن طريق النموذج ثنائي الابعاد

وبناءا عليه تم حساب (. لنحر الناتج عن ضيق عروض القطاعات و النحر العامالنحر الناتج من المنحنيات وا)كامل الحبس

.أجمالى النحر لكل القطاعات الموجوده بطول الحبس والنحر المحتمل في حاله التصرفات العاليه وحاله الطواريء

الباب السابع

الحلول المقترحه وتحليل النتائج

حلول المقترحه لمنطقه الدراسه لتجنب النحر ثنائي الأبعاد في إختبار بدائل الإستخدام النموذج الرياضي في هذا الباب تم

متر أعلى سطح البحر ودراسه 5-وتم دراسه البديل الاول بملاء البيارات الموجوده حتي منسوب . علي جوانب و قاع النهر

راسه البديل الثاني المقترح بمليء البيارت وتم ايضا د. تأثير ذلك علي مجري النهر ومقارنه النتائج بالحاله الاصليه للنهر

متر أوطى سطح 3-متر أعلى سطح البحر مع تكريك للناحيه الاخري للقطاع من البيارات حتي منسوب 5-حتي منسوب

ن تم ايضا حساب تأثير القوه الناتجه من سريا. ج هذا المقترح مع البديل الاول والحاله الاصليه للنهرتم مقارنة نتائالبحر و

الاول ومن الحاله عطي نتائج أفضل مني وتبين من خلال هذه المقارنات ان الحل الثاني. المياه علي حبيبات التربه في القاع

. وبناءا عليه تم تصميم طبقات الحماية الازمة للبيارات .الاصليه للنهر

اثامنالباب

الخلاصه و التوصيات

صة النتائج التي توصل اليها البحث وتوصيات الأعمال المقترحة لحماية خلا ملخص ما سبق تقديمة و يتضمن هذا الباب

إزاحة تقليل معدل المنحنيين الخارجيين للحبس موضوع البحث والتي تحقق توزيع أفضل لسرعة التيار المائي بما يضمن

. لها باحثين التعرضكما يعرض الباب مقترحات لبعض الدراسات المستقبليه التي يمكن لل. نحو جوانب النهر المجري

جامعة بنها

كلية الهندسة بشبرا

المدنيهقسم الهندسة


المدنيهرسالة مقدمة كجزء من متطلبات الحصول علي درجة الماجستير في الهندسة

(هيدروليكا)

مقدمة من

فاطمه سمير أحمد سعد

(2111) هندسه المدنيهال بكالوريوس في

إشراف

جمهورية مصر العربية –القاهرة

2115مارس

السعيد محمد جمال حلمي /د.أ

الهندسة المدنيةقسم - الموارد المائية هندسة ستاذأ

جامعه بنها -كليه الهندسه بشبرا

السرساويالدين محمد حسام / د.م.أ

بمعهد بحوث النيل ستاذ مساعد أ

مي لبحوث المياهالمركز القو

محمد ابراهيم محمد محمود/ د

الهندسة المدنيةبقسم مدرس


جامعة ينها

كلية الهندسة بشبرا

قسم الهندسة المدنيه

القبول النهائي للرسالة


لجنة الحكم والمناقشة

جمهورية مصر العربية –القاهرة

2115مارس

الاسم الأمضاء

(مقررا –ممتحن خارجي ) نهله محمد عبدالحميد ابو العطا .د.أ رئيس قسم الري والهيدروليكا -عمال الري أأستاذ تصميم

جامعة عين شمس -كلية الهندسة

(عضوا –ممتحن خارجي ) مدحت سعدعزيز . د.أ

النيل حوث مدير معهد ب -أستاذ

هالمركز القومى لبحوث الميـا

( عضوا –عن لجنه الاشراف ) محمد السعيد جمال حلمي .د.أ الهندسة المدنية قسم - الموارد المائية هندسة ستاذأ


nri-eg.orgnri-eg.org/download/publications/76_fatma msc.pdfbenha university faculty of engineering,...

Documents