EFFECTS OF TIDES AND SURFACE RUNOFF ON CHANNEL GEOMETRY
ZULKIFLI BIN MUSTAFA
UNIVERSITI TEKNOLOGI MALAYSIA
4
EFFECTS OF TIDES AND SURFACE RUNOFF ON CHANNEL
GEOMETRY
ZULKIFLI BIN MUSTAFA
A project report submitted in partial fulfilment of
the requirements for the award of the degree of
Master of Engineering (Civil – Hydraulics and Hydrology)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
Nov 2007
6
To my beloved family ;
Laila Nazura Nawi,
Muhd Nabel Aiman,
Muhd Luqmanul Hakim,
Aness Natasya,
&
Mak & Ma..
Thanks for your pray, attention and spiritual…….
7
ACKNOWLEDEMENTS
It is great pleasure to address those people who helped me throughout this
project to enhance my knowledge and practical skills especially in research area. My
deepest and most heartfelt gratitude goes to my supervisors, Tn Hj Tarmizi bin
Ismail and En. Abu Bakar bin Fadzil. The continuous guidance and support from
both of them have enabled me to approach work positively.
My gratitude also been extended to all personnel of the Laboratory of
Hydraulics and to all staff especially in the Department of Hydraulics and Hydrology
for their support, cooperation and constructive criticisms during the research period.
Many thanks to Universiti Teknologi Malaysia and generally to Government
of Malaysia for giving me chance to pursue my study. Also thanks to Mohd Kamarul
Huda, Aznan, Azreen, Shah, Amzari, Hood Tendot, Norasman, Hakim, Juwita, Liew
Kuet Fah and other classmates for their helped and support.
Finally, I wish to express my special thanks to my beloved parents and family
especially my wife, Laila Nazura Nawi who gives me spirit, support and
encouragement to me in completion this project. I would also like to thank everyone
who has contributed directly or indirectly to this project. This project would have
been impossible without your guidance, advice and support.
8
ABSTRACT
Hydraulics of the river mouth with a tidal effect intrusion is sometimes quite
different from that of the river without them. Upstream and downstream interactions
of any hydrological and hydraulic system or watershed are complex and elusive. The
type of land use and land cover of the area would largely determine the magnitude
and extent between upstream and downstream interactions and accordingly the
degree of degradation to the environment. Because of these, it is usually difficult to
measure the flow field in the river mouth by using the ordinary methods. In this
study, Sungai Sengkuang is a re-aligned and straightened channel is under tidal
influence. The hydrologic and hydraulic analysis has been carried out for the existing
system to investigate whether it is still able to accommodate the volume of water
comprises the discharge from upstream and high tide from downstream. The actual
data such as rainfall data, velocity, water level, tide level has been collected for the
analysis. HEC-HMS is used to carry out the hydrologic model calibration and
validation. By using HEC-RAS, hydraulic model calibration and validation is carried
out for the channel. The discharge from flow simulation and tide level from
frequency analysis with different ARI are used as the upstream and downstream
boundary condition during the steady flow analysis. The result show that the existing
channel is still able to accommodate the flow from upstream and downstream but the
cross section of channel needs to be improving because of inadequate freeboard.
From the Energy Grade Line of the channel, it can be concluded that the energy from
downstream is more dominant than the energy from upstream.
9
ABSTRAK
Kajian hidraulik di kawasan muara sungai yang mengalami kesan gangguan
air pasang surut kadangkala agak berbeza dengan kawasan yang tidak mengalami
kejadian tersebut. Interaksi di antara hulu sungai dan hiliran dalam konteks sistem
hidrologi dan hidraulik atau titik perubahan adalah kompleks dan elusif. Biasanya,
jenis guna tanah dan litupan tanah di kawasan tersebut yang akan menentukan
magnitud dan takat interaksi antara huluan dan hiliran. Lantaran itu, biasanya adalah
sukar untuk mengukur aliran permukaan yang menuruni ke muara sungai yang
mengalami kesan air pasang dengan menggunakan kaedah-kaedah biasa. Dalam
kajian ini, Sungai Sengkuang telah dijajar dan diluruskan untuk memenuhi kehendak
pembangunan dan disamping itu mengalami kesan pasang surut dari hiliran. Dalam
kajian lepas, didapati kawasan di sekitar Sungai Sengkuang telah mengalami banjir
akibat daripada pembinaan pembentung sementara di CH 600 kesan air balik yang
berpunca daripada air pasang di hiliran. Maka dalam kajian ini, analisis hidrologi dan
hidraulik dengan menggunakan HEC-HMS dan HEC-RAS telah dibina untuk
mengkaji samada Sungai Sengkuang masih dapat menampung kadaralir dari hulu
dan hiliran sungai selepas pembentung sementara dikeluarkan. Data dari kawasan
kajian seperti data hujan, halaju, paras air, aras air pasang surut telah dikutip untuk
dianalisis. Hasil kajian menunjukkan bahawa saluran yang sedia ada masih mampu
untuk menampung kadaralir dari hulu dan hilir sungai. Bagaimanapun untuk
memenuhi piawaian ruang bebas (freeboard) bagi saluran terbuka, keratan rentas
saluran yang baru telah dicadangkan bersama dengan ban untuk menampung aliran
sehingga 100 ARI. Dari analisis Garis Cerun Tenaga saluran pula, ia dapat
disimpulkan bahawa tenaga daripada hiliran adalah lebih berpengaruh daripada
tenaga dari air larian permukaan.
10
TABLE OF CONTENTS
CHAPTER
CONTENT
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF SYMBOLS
xv
LIST OF APPENDICES
xvii
INTRODUCTION
1
1.1
Introduction
1
1.2
Problem Statment
3
1.3
Objectives
5
1.4
Scope of Study
5
LITERATURE REVIEW
6
2.1
Open Channel Flow
6
2.2
Physical of Numerical Hydraulic Modelling
8
2.2.1 Overview of Hydraulic Theory
9
2.2.2 Fundamental Principles
9
1
2
2.2.2.1 Mass and Weight
10
11
2.2.2.2 Mass in Motion
11
2.2.2.3 Velocity
11
2.2.2.4 Acceleration (The Rate of Change
12
Velocity)
2.2.2.5 Momentum
13
2.2.2.6 Mechanical Energy
14
2.2.3 Momentum Equation
15
2.2.4 One Dimension (1-D) Flow Equations
15
2.2.4.1 One Dimension Flow Variables
16
2.2.4.2 One Dimension Continuity Equation
17
2.2.4.3 1D Momentum Equation
17
2.2.4.4 1D Energy Equation
18
2.2.4.5 Energy and Hydraulic Grade Lines
18
2.3
Numerical Hydraulic Modelling Review
19
2.4
Modeling Software
21
2.4.1 The HEC – RAS Model
21
2.4.1.1 Steady Flow Water Surface Profiles
22
2.4.2 The HEC-HMS Model
22
Tides
23
2.5.1 Tidal Datum
23
2.5.2 Tidal Waterways
24
2.5.3 Tide-Generating Forces
27
Estuaries
28
2.6.1 Tidal Mixing And Saline Stratification
30
2.6.2 Highly Stratified Estuary
30
2.6.3 Partially-Mixed Estuary
31
2.6.4 Vertically Well-Mixed Estuary
32
2.6.5 Inverse Estuaries
33
3
STUDY AREA
35
3.1
Site Background
35
3.2
Study Area Location
35
3.3
Topographic Profile
39
2.5
2.6
12
3.4
Types of Soil
39
3.5
Land Use
40
4.0
METHODOLOGY
42
4.1
Introduction
42
4.2
Data Collection
44
4.2.1 Water Level at CH 0 and CH 1040
46
4.2.2 Data Collection at CH 2607.5
49
4.2.2.1 Recorded Rainfall
49
4.2.2.2 Actual Flow
50
4.2.3 Reduced Level, RL
53
4.3
Frequency Analysis of Tide Levels
53
4.4
Hydrologic Model Calibration with HEC-HMS at
54
Catchment 1 (CH 2607.5)
4.4.1 Basin Model
4.5
54
4.4.1.1 Initial Constant Loss
55
4.4.1.2 Clark Unit Hydrograph Transform
55
4.4.1.3 Constant Monthly Baseflow
56
4.4.2 Meteorologic Model
56
4.4.3 Control Specifications
56
4.4.4 Hydrologic Model Calibration
57
4.4.5 Hydrologic Model Validation
58
Hydraulic Model Calibration HEC – RAS (CH 0 - CH
58
2607.5)
4.5.1 Geometry Data
58
4.5.2 Hydraulic Model Calibration
60
4.5.3 Hydraulic Model Validation
60
4.6
Flow Simulation (CH 1350)
60
4.7
Steady Flow Analysis (CH 0 TO CH 1350)
61
13
ANALYSIS AND RESULTS
63
Modelling Procedure
63
5.1.1 Hydrologic Model Calibration
64
5.1.2 Result of Hydrologic Model Calibration
67
5.1.3 Hydrologic Model Validation
68
5.1.4 Hydraulic Model Calibration
69
5.1.5 Result of Hydraulic Model Calibration
70
5.1.6 Hydraulic Model Validation
71
Flow Simulation
72
5.2.1 Result of Flow Simulation
73
Steady Flow Analysis – HEC – RAS
74
5.3.1 Results of Steady Flow Analysis
75
Channel Cross Section Resizing and Bund Introduction
77
DISCUSSION AND CONCLUSION
81
6.1
Discussion
81
6.2
Energy Grade Line Analysis
85
6.2.1 Channel under flow from upstream only
85
6.2.2 Channel under high tide from downstream only
86
6.2.3 Channel under flow from upstream and high tide
87
5
5.1
5.2
5.3
5.4
6
from downstream
Conclusion
88
REFERENCES
89
Appendices
91-95
14
LIST OF TABLES
TITLE
TABLE NO.
4.1
Location, data and equipment used during data
PAGE
45
collection
4.2
Recorded Rainfall from Catchment 1 for Event 1
49
4.3
Recorded Rainfall from Catchment 1 for Event 2
49
4.4
Recorded Rainfall from Catchment 1 for Event 3
50
4.5
Reduced levels at sampling station
53
4.6
Highest Tide Level in LSD
54
4.7
Method selected for hydrologic model calibration
55
4.8
The starting and ending time during data collection
57
5.1
Input data for the basin model
65
5.2
Design rainfall with different return period
73
5.3
Input data for flow simulation in the basin model
73
5.4
Upstream and downstream boundary conditions
75
5.5
Water levels with different ARI
77
5.6
Comparisons between existing and proposed system
78
5.7
Water levels with different ARI
80
15
LIST OF FIGURES
FIGURE NO.
1.1
TITLE
Sungai Damansara overflowing its banks and waters
PAGE
2
flooded 3 000 houses in Shah Alam, Selangor.
1.2
Flood occur due to the creation of back water from tide
2
at Pelabuhan Klang, Selangor
1.3
Flooded area at Shah Alam, Selangor due to high tide
3
2.1
Prismatic channels
7
2.2
Relationship between Mass and Weight
10
2.3
Relationship between Mass and Acceleration
11
2.4
Direction of Velocity Magnitude
12
2.5
Illustration of Momentum
13
2.6
Illustration of Mechanical Energy
14
2.7
One Dimension Flow Variables
16
2.8
One Dimension Energy Equation
18
2.9
Estuary
25
2.10
Bay and Inlet
26
2.11
Passages
26
2.12
Barrier Islands forming complex tidal systems
27
2.13
Schematic of an estuary showing division into different
29
regions
2.14
Schematic vertical section of a salt-wedge estuary
31
2.15
Schematic vertical section of a partially-mixed estuary
32
2.16
Schematic vertical section of a vertically well-mixed
33
estuary
16
2.17
Schematic vertical section of an inverse estuary
34
3.1
Aerial View of Sungai Sengkuang
37
3.2
Aerial View of Sungai Sengkuang and its vicinity
38
3.3
Soil Type within Catchment Area
40
3.4
Land Use and Main Tributaries
41
3.5
Sungai Sengkuang Catchment Area
41
4.1
Hydrologic and Hydraulic Analysis of Sg Sengkuang
43
4.2
Sampling station for model calibrations
45
4.3
Water Level at CH 0
47
4.4
Water Level at CH 1040
48
4.5
Cross section at CH 2607.5
51
4.6
Discharge from Catchment 1 for Event 1
51
4.7
Discharge from Catchment 1 for Event 2
52
4.8
Discharge from Catchment 1 for Event 3
52
4.9
Part of Analysis in Sungai Sengkuang
57
4.10
Schematic Diagram for Sg Sengkuang from CH 0 to
59
CH 2607.5
4.11
Cross-section of Culvert at CH 1350
59
4.12
Procedure to obtain the Peak Flow with different ARI
61
5.1
Actual rainfall data for Event 1
65
5.2
Actual rainfall data for Event 2
66
5.3
Actual rainfall data for Event 3
66
5.4
Result of Hydrologic Model Calibration for Event 1
67
5.5
Result of Hydrologic Model Calibration for Event 2
68
5.6
Actual discharge from catchment 1 ; upstream
69
boundary condition
5.7
Actual tide level at CH 0; downstream boundary
70
condition
5.8
Water level calibration at CH 1040
71
5.9
Water level validation at CH 1040
72
5.10
Discharges with 5 ARI, 20 ARI, 50 ARI and 100 ARI
74
from HEC-HMS flow simulation.
5.11
Water surface profile plot at CH 1350
75
17
5.12
Water surface profile plot at CH 1350
76
5.13
Cross section of CH 1350 with different ARI
76
5.14
Water Levels along the channel with different ARI
77
5.15
Proposed cross section of channel
78
5.16
Water surface profile plot of proposed channel
79
5.17
Water surface profile plot of proposed channel
79
5.18
Water Levels along the proposed channel with
80
different ARI
6.1
Water surface profile plot of proposed channel with
83
bund
6.2
Water level at CH 0 after resizing work
84
6.3
Water level at CH 550 after resizing work
84
6.4
Water level at CH 1350 after resizing work
85
6.5
Energy grade line without tide
86
6.6
Energy grade line without flow
87
6.7
Energy grade line with flow from upstream and high
88
tide from downstream
18
LIST OF SYMBOLS
V
-
velocity
t
-
time
m
-
mass
M
-
momentum
F
-
force acting on the mass
A
-
area,
Q
-
Flow rate
P
-
Cross Section “Wetted Perimeter”,
τb
-
Average Bed Shear Stress
B
-
weir base width (m)
H
-
head above weir crest excluding velocity head (m)
RL
-
Reduced level (m)
LSD
-
Land Survey Datum (m)
R
-
Storage Coefficient
yc
-
Critical depth
yo
-
Normal depth
S
-
Slope of stream flow path, m/km
E
-
Specific Energy
V2/2g -
Specific velocity (m)
tc
-
Time of concentration, hr
Qpeak
-
Peak discharge, m3/s
P
-
Rainfall depth, mm
So
-
Slope of channel bed
ARI
-
Average recurrence interval (year)
L
-
Length of flow path catchment divide to outlet (km)
Cd
-
orifice discharge coefficient (0.40 – 0.62)
19
A0
-
area of orifice (m2)
Do
-
orifice diametre (m)
Ho
-
effective head on the orifice measured from the centre of the
opening (m)
g
-
acceleration due to gravity (9.81 m/s2)
Z
-
vertical direction,
Zb
-
bed elevation,
Zw
-
zb + H = water surface elevation
q1
-
UH = unit flow rate in the x direction
q2
-
VH = unit flow rate in the y direction
qm
-
mass inflow rate (positive) or outflow rate (negative) per unit area
β
-
isotropic momentum flux correction coefficient that accounts for the
variation of velocity in the vertical direction
g
-
gravitational acceleration
ρ
-
water mass density
pa
-
Atmospheric pressure at the water surface
Ώ
-
Coriolis parameter
n
-
manning’s
20
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Summary of Data Collection and Calculation
91
B
Summary of Steady Flow Analysis without Flow
94
C
Summary of Steady Flow Analysis with Flow from
95
Upstream and High Tide From Downstream
21
CHAPTER I
INTRODUCTION
1.1
Introduction
Human actions have drastically altered hydro geomorphic processes such as
the volume of tidal exchange, extent of area under tidal influence, speed of tidal
currents, amount of sediment in the main channel, and inputs of freshwater and
sediment from the watershed. As a consequence, the distribution of tidal habitat
types has changed dramatically over the past century.
Floods also become the most severe hazard in Malaysia, a country
that experiencing a wet equatorial climate with heavy seasonal
monsoon rains in the period of November to February. Recently, it
is reported that flood had occur in Sungai Damansara. Two hours of
unusually heavy rainfall since 3:30am on Sunday 26 Feb 2006 has
resulted in Sungai Damansara overflowing its banks and waters
flooded 3,000 houses in Shah Alam. 9,015 people were evacuated.
In many places, flood water hovered around 1m high. It rose to
about 2.3m in a few areas, almost reaching the roof of single storey
houses.
(The Star, 27 Feb 2006)
22
Flood frequently occurred in our country since few years ago. The flood
problem is more serious especially at the downstream part of the channel which
having a low topographic profile. The condition becomes worse if the existing
channel is under influence tide. Flood might occur at upstream part of the channel
due to the creation of back water from tide. Therefore, the impacts of urbanization to
the surrounding area need to be studied in order to avoid any flood problem.
Figure 1.1 : Sungai Damansara overflowing its banks and waters
flooded 3, 000 houses in Shah Alam, Selangor.
Figure 1.2: Flood occur due to the creation of back water from tide
at Pelabuhan Klang, Selangor.
23
Mathematical models have been developed to resolve many problems for
water profile evaluation. A mathematical model consists of a set of differential
equations that are known to govern the flow of surface water. Usually, the
assumptions necessary to solve a mathematical model analytical are fairly restrictive.
To deal with more realistic situations, it is usually necessary to solve the
mathematical model approximately using numerical technique.
Figure 1.3: Flooded area at Shah Alam, Selangor due to high tide.
1.2
Problem Statement
Sungai Sengkuang is situated in the Mukim of Plentong, Johor Bahru District,
Johor Darul Takzim. Surface water runoff flow from the catchment area to Sungai
Sengkuang and it act as the main water channel of the cathment. There was a low
lying, swampy area before it was developed into the housing area today. The Sungai
Sengkuang with the catchment area of 4 km2 is a tributary of the Tebrau River and
drains portions of the heavily populated of Kg Bakar Batu areas. The area affected by
24
flood lies along the downstream portion of the river and also influenced by tide
fluctuation. Due to the development and urbanization process, Sungai Sengkuang
which is under the influence of tide has been straightened up started from CH 0 at the
downstream to CH 1350 at upstream.
After straightening up the channel and reclamation work done, the water level
of the channel becomes drastically higher than before. The condition of the channel
becomes worse when a temporary culvert had been built at CH 600 of Sungai
Sengkuang as a temporary access to the left hand side of the channel. According to
the previous analysis to the channel, the temporary culvert had brought significant
effect to the flow of channel and causes flooding to the nearby residential area. When
the flow of the channel comes across the high tide from the downstream, back water
will be created. From the previous analysis, the backwater reaches 1000 m from the
discharge point. Flood occurred because the channel cannot accommodate the
volume of back water due to the tide and the insufficient design of temporary culvert.
After removing the temporary culvert, the flood problem seems to be reduced. But
the capacity of the existing channel is still have not been determined whether able to
accommodate the flow from upstream and downstream. Therefore, hydraulic and
hydrology model analysis will be carry out in order to determine whether flood will
occur or not.
25
1.3
Objectives
The objectives of the study are as follows:
i.
To investigate the hydraulic characteristic of channel that experiences
flood problem due to heavy rainfall and tide influence. The energy line
along the channel reach shall be evaluated to determine the dominant
energy from either upstream boundary condition or downstream boundary
condition. Therefore, this study is conducted to investigate the optimum
channel geometry.
1.4
Scope of Study
To carry out the hydraulic and hydrology model analysis, the scopes of study
are as stated below:
i.
Delineation of catchment’s boundary and schematization of channel
section of the study area.
ii. Data collection that include rainfall, stream flow, water level and tide
fluctuation in order to evaluate the fundamental understanding of
hydraulic and hydrologic principles.
iii. Hydraulic and hydrologic model calibration.
iv. Evaluate the causes of flood in terms of hydraulic principles.
v. Evaluate and analyze channel hydraulic characteristics for the system
under tidal influence.
26
CHAPTER II
LITERATURE REVIEW
2.1
Open Channel Flow
Open channel hydraulics, deals with flows having a free surface in channels
constructed for water supply, irrigation, drainage, and hydroelectric power
generation; in sewers, culverts, and tunnels flowing partially full; and in natural
streams and rivers. Open channel hydraulics includes steady flows that are
unchanging in time, varied flows that have changes in depth and velocity along the
channel, and transient flows that are time dependent.
Open channel flow is the flow of a single phase liquid with a free surface in a
gravitational field when the effects of surface tension and of the overlying gas can be
neglected. Because laminar open channel flows are seldom encountered in civil
engineering practice, only turbulent flows will be considered. The analysis of open
channel flows is largely based on the approximation that the mean streamlines are
nearly parallel. As shown below, this implies that the piezometric head is nearly
constant on planes normal to the flow, and allows a one-dimensional analysis.
Regions of nonparallel streamlines are considered by using control volume
27
arguments. In some cases, these assumptions are inadequate, and a much more
complicated two- or three-dimensional analysis must be used.
Figure 2.1 : Prismatic channels ; y, depth of stream; d, thickness of stream; z,
bottom elevation;θ, angle between channel bottom and horizontal; E, specific energy;
h, piezometric head and water surface elevation; H, total head; αV2/2g, velocity head.
Special importance attaches to prismatic channels: those that have a constant
cross sectional shape, longitudinal slope, and alignment. The generators of prismatic
channels are parallel straight lines. The most common prismatic channel cross
sections are trapezoids, rectangles, and partially full circles. Constructed channels
often consist of long prismatic reaches connected by short transition sections. Natural
channels are never prismatic, although the assumption that they are is sometimes
tolerable. The direction of flow is indicated by the spatial variable x; the two
coordinates orthogonal to each other and to x are called y’ and z’. For a parallel flow,
the total volume of water flowing per unit time across an orthogonal flow area, is the
flow rate or discharge, Q, is given by
28
Where v (x, y’, z’, t) is the local x -velocity at coordinates x, y’, z’ and time t. The
integral extends across the whole flow area, and V is the mean velocity.
The problems of flood routing and other applications of modeling of unsteady
flow in rivers are represented suitably by means of the complete equations of
continuity and momentum in open channels. In their one-dimensional form, they are
obtained from the three-dimensional fundamental equations of continuity and
momentum, carrying out integration over a cross section of the flow in a channel.
The state of flow as a function of time and distance along the channel is thus
represented by two variables: the flow rate and the area of the cross section. For
subcritical flow two boundary conditions must be imposed at the ends of the channel.
The analytical solution of these partial differential equations is restricted to
problems of very simple geometry, subject to very simple initial and boundary
conditions. Therefore the solution of practical problems requires the application of
efficient and accurate numerical methods. (Liggett and Cunge,1975)
2.2
Physical of Numerical Hydraulic Modelling
Hydraulic is a branch of engineering that studies the mechanical properties of
fluids and deals with practical application of fluids in motion. There are two
subdivisions in this field, hydrostatics and hydrokinetics. Aspects of both
subdivisions will be discussed as they apply to finite elements modelling.
Hydrostatics is the study of liquids at rest, it specially focuses on the problems of
buoyancy and flotation that create pressure on dams, submerged devices and
hydraulic presses. In contrast, hydrokinetics is the study of liquids in motion and is
concerned with such as friction and turbulence generated in pipes by flowing liquids
and the use of hydraulic pressure in machinery.
29
2.2.1 Overview of Hydraulic Theory
A basic understanding of the relationship of fundamental physical principles
to water flow is necessary to recognize the type of analysis needed to solve a
particular problem. If water flows in only one direction and there is no need for
detailed velocity description, a one-dimensional (1D) study of a river will probably
be sufficient. On the other hand, if water flows in both longitudinal and transverse
directions, or detailed velocity description is needed, a two-dimensional (2D)
solution is probably warranted. Both 1D and 2D solutions can be obtained using
several numerical methods.
2.2.2 Fundamental Principles
The interactions of matter and energy in a river system composed of water,
solid surfaces and other external forces are complex. However, there are basic
principles of physics that apply to all matter and energy and can be applied in this
circumstance to enable us to quantify and predict the flow of water and it’s on
surrounding structures and the environment. Mass, velocity, acceleration,
momentum, mechanical energy, the definition of a system and its boundaries all play
a role in developing models of river water flow. The analysis of flow problems is
based on these three main conservation laws, the conservation of mass, momentum,
and energy. For most hydraulic problems, it suffices to formulate these laws in
integral form for one-dimensional flows to which the following is restricted. A
systematic approach is based on the analysis of a control volume, which is an
imaginary volume bounded by control surfaces through which mass, momentum, and
energy may pass.
30
2.2.2.1 Mass and Weight
Mass is the measure of body’s resistance to acceleration. Weight is the
product of objects mass and local value of gravitational acceleration. The standard
value for gravitational acceleration is 9.80665 m/s2 on the surface on the earth, but it
varies from a minimum of 9.77 m/s2 to a maximum of 9.83 m/s2. The mass of an
object is constant, but its weight depends on the gravitational pull acting it. Figure
2.2 is showed the relationship between mass and weight.
Figure 2.2 : Relationship between Mass and Weight
31
2.2.2.2 Mass in Motion
In the absence of any resistance, a force applied to a mass will cause the mass
to accelerate at a constant rate in the direction of the applied force. A mass of 1kg
acted on by a force of 1N will accelerate at a rate of 1m/s/s if no other forces are
present. To stop the mass, a force needs to be applied in a direction opposite the
direction of motion. Because the direction in which a force is applied determines the
direction of movement, force and acceleration are vector quantities (that is, they are
defined by both a magnitude and a direction). Figure 2.3 is showed the relationship
between mass and acceleration.
Figure 2.3: Relationship between Mass and Acceleration
2.2.2.3 Velocity
Velocity is the speed of an object in given direction. Velocity is a vector
quantity, since its direction is important as well as its magnitude. The velocity at any
32
instant of a particle travelling in a curved path is the direction of the tangent to the
path at the instant considered (see Figure 2.4).
Figure 2.4: Direction of Velocity Magnitude
2.2.2.4 Acceleration (The Rate of Change Velocity)
Acceleration is the rate of change of velocity with respect to time. According
to Newton’s 2nd Law of Motion, acceleration is a direct result of the action of forces.
If an object increases its velocity from 1 m/s to 3 m/s in the same direction in a
period of 4 seconds, the average rate of acceleration is 0.5 meters per second. The
equation can be write as:
a=
dV
dt
(2.1)
33
where,
V = velocity,
t = time
A change in speed can result in slowing downs as well as speeding up. Many
people call a reduction in speed deceleration.
2.2.2.5 Momentum
Momentum is the product of a body’s mass and linear velocity, that is
M=mxV
(2.2)
where,
m = mass,
V = velocity.
Momentum is a vector value just like velocity because it has both a magnitude and a
direction. A force needs to be applied to the mass to change its velocity (that is, to
accelerate the mass) and thus the momentum of the body (see Figure 2.5).
Figure 2.5: Illustration of Momentum
34
2.2.2.6 Mechanical Energy
Mechanical or usable energy is associated with the motion of a mass and its
potential for creating motion. The kinetic energy of the mass shown above equals
one-half the product of its mass times the square of its speed. The potential energy
equals the height of the mass above some horizontal datum times its weight. The
mechanical energy is the sum of the two.
All the laws of mechanics are written for a system which is defined as an
arbitrary quantity of mass of fixed identity. Everything external to a system is called
the surroundings. The system is separated from its surrounding by its boundaries (see
Figure 2.6).
Figure 2.6: Illustration of Mechanical Energy.
35
2.2.3 Momentum Equation
Issac Newton’s Law of Motion, also called the momentum equation, states
that the resultant force acting on a system equals the rate at which the momentum of
the system changes. The mathematically, can write:
dM/dt = d(mV)/dt = F
(2.3)
where,
M = momentum
m = mass
F = force acting on the mass
If the mass is fixed, then
mdV/dt = ma = F
2.2.4 One Dimension (1-D) Flow Equations
The 1-D flow equations are based on cross-sectional average velocity and a
water surface elevation that is considered constant along a channel transect. Crosssectional area, which is a function of the water surface elevation and cross section
flow rate, which equals the average velocity times the cross section area are usually
the values are calculated.
36
2.2.4.1 One Dimension Flow Variables
The 1D flow variables are found by integrating both vertically and then
laterally across the width of a section (see Figure 2.7).
Figure 2.7: One Dimension Flow Variables
B = ∫ H dy
(2.3a)
B
Q = ∫ U .H dy
B
Where,
Q = Flow rate
B = Cross Section Width
(2.3b)
37
2.2.4.2 One Dimension Continuity Equation
The continuity equation for one-dimensional open channel flow is based on
the continuity principle applied to the “system” contained in length of channel
bounded by two transects or cross sections.
∂A ∂Q
+
=0
∂t ∂x
(2.4)
where,
A = area,
Q = Flow rate.
2.2.4.3 1D Momentum Equation
The one-dimensional momentum equation is found by applying the
momentum principle to the system contained in the channel segment.
∂Q ∂ (VQ)
∂zw τb P
+
+ gA
+
=0
∂t
∂x
∂x
ρ
where,
P = Cross Section “Wetted Perimeter”,
τb = Average Bed Shear Stress.
(2.5)
38
2.2.4.4 1D Energy Equation
When flow is steady, an equation representing the conservation of mechanical
energy of the system is solved to find water surface elevations at channel cross
sections (Hadibah Ismail et. al. 1996).
Figure 2.8: One Dimension Energy Equation
2.2.4.5 Energy and Hydraulic Grade Lines
For the typical steady one-dimensional nearly horizontal flows, hydraulic and
energy grade lines (HGL and EGL, respectively) are useful as graphical
representation of the piezometric and the total head respectively. For flows in which
frictional effects are neglected, the EGL is simply a horizontal line, since the total
head must remain constant. If frictional effects are considered, the EGL slopes
downward in the direction of flow because the total head, H, is reduced by frictional
losses. The slope is termed the friction or energy slope, denoted by Sf = hf /L, where
hf is the continuous head loss over a conduit of length, L, due to boundary friction
along pipe or channel boundaries. In pipe flows, Sf is not related to the pipe slope (in
39
open-channel flows, however, for the special case of uniform flow, Sf is equal to the
slope of the channel). The EGL rises only in the case of energy input. For flows that
are uniform in the stream wise direction, the HGL runs parallel to the EGL because
the velocity head is constant. The HGL excludes the velocity head, and so lay at an
elevation exactly a V2/2g below the EGL; it coincides with the EGL only where the
velocity head is negligible, such as in a reservoir or large tank. Even without energy
input or output, the HGL may rise or fall, due to a decrease or increase in flow area
leading to an increase or decrease in velocity head. The elevation of the HGL above
the pipe centreline is equal to the pressure head; if the HGL crosses or lies below the
centre line, this implies that the pressure head is zero or negative, i.e., the static
pressure is equal to or below atmospheric pressure, which may have implications for
cavitations. Since the pressure at the free surface of an open-channel flow is
necessarily zero, the HGL for an open channel flow coincides with the free surface,
except in flows with highly curved streamlines.
2.3
Numerical Hydraulic Modelling Review
A complete analytical solution of equations governing the flows has not been
possible because of the large number of parameters to be considered. Therefore, a
clear understanding of the hydraulic characteristics will be a useful tool for the
design engineers. A numerical approach was applied, and two basic equations were
used. One accounts for the energy along the channel and the other relates flow rate
over in the main channel. From the study by Yilmaz Mushu (2001), a theoretical
analysis based on the energy principle for discharge was presented and its application
was demonstrated using numerical approach. Equations that were developed were
also used to obtain hydraulic characteristics of storm water overflows as a practical
application.
40
While numerous steady compound channel flow studies have been
conducted, unsteady compound channel flow has received relatively little attention.
From the study by Alex George Mutasingwa (2000) was presented comparison
between 2-dimensional unsteady flow numerical model and experimental results for
flow variables in a compound meandering channel. The numerical method is based
on a finite volume discretization on a staggered grid with upwind scheme in flux, it
handles drying and wetting process for a flood plain, has the ability to handle
complex geometry and discontinuities, which are the main requirements for
modelling compound channel flows. Comparison between the measured and the
simulated water depth hydrographs showed good agreements, this demonstrate how
useful the model can be for flood prediction in channels. This unsteady flow study
shows additional temporal change of those hydraulic variables and parameters need
to be considered during flood flow. The accuracy of upstream and downstream input
data is very important for unsteady flow computations.
Backwater computation is used to model steady flows in non uniform
channels. For a given discharge the method is also suitable to simulate slightly
unsteady flows (e.g. water surface profiles for flood waves or even dam break
waves). For sub-critical flows the solution is straight forward, whereas it become
more complicated for transcritical flows (i.e. flows which change from one stated to
another.). In this case the direction of the calculation has to be changed from
upstream to downstream or depending on the Froude number (Molinas and Yang
(1985)). Such a procedure is suitable for well defined hydraulic jumps (e.g. in abrupt
changes of bed slope) but is difficult to handle if the flow conditions oscillate
between sub and supercritical from one cross section to the other. From the study by
Beffa E. (1995), analysis of the discrete equations for steady open-channel flows
shows that the solution of the upstream backwater computations can be Froude
numbers exceeding one. An iterative method is proposed that allows for solution of
either the momentum equation or the energy equation up to a limiting Froude
number. The value of the limiting Froude number depends mainly on the friction
losses and the size of the calculation interval, i.e. distance between the cross sections.
For the calculation of channel with rough beds and relatively small flow depths a
typical value the limiting Froude number is 1.5. The method is especially useful for
41
transcritical flows in natural river where the flow oscillates sub and supercritical and
changing direction of calculation would be impracticable.
2.4
Modeling Software
2.4.1 The HEC-RAS Model
Numerous software packages have been developed to solve problems of open
channel hydraulics under the approximation of one-dimensional flow. Perhaps the
most powerful program presently available is the U. S. Army Corps of Engineers
Hydrologic engineering Center River Analysis System (HEC-RAS). This Windowsbased program can solve both steady and unsteady flows in single channels, dendritic
systems, or complex networks. It can handle mixed subcritical and supercritical
flows with hydraulic jumps, and can model the effects of obstructions such as bridge
piers, culverts, and weirs. HEC-RAS has superseded the U. S. Army Corps of
Engineers’ HEC-2 (formerly the industry standard) and the Natural Resources
Conservation Service’s WSP-2, both of which are limited to steady state simulations.
HEC-RAS consists of a graphical user interface (GUI), separate hydraulic analysis
components, data storage and management capabilities, graphics and reporting
facilities. The hydraulic analysis components will ultimately contain three onedimensional components for: (1) steady flow water surface profile computations; (2)
unsteady flow simulation; and (3) movable boundary sediment transport
computations. All three of these components will use a common geometric data
representation and common geometric and hydraulic computation routines.
42
2.4.1.1 Steady Flow Water Surface Profiles
This component of the modelling system is intended for calculating water
surface profiles for steady gradually varied flow based on the solution of the onedimensional energy equation. The effects of various obstructions such as bridges,
culverts, weirs, and structures in the floodplain may be considered in the
computations. The steady flow system is also designed for application in floodplain
management to evaluate floodway encroachments. Special features of the steady
flow component include: multiple plans analyses; multiple profile computations;
multiple bridge and/or culvert opening analysis; and split flow optimization.
2.4.2 The HEC-HMS Model
The Hydrologic Modeling System (HEC – HMS) is designed to simulate the
precipitation-runoff of dendritic watershed system developed by the U.S. Army
Corps of Engineers Hydrologic Engineering Center (HEC) that is a “new generation”
software to supercede the HEC-1 Flood Hydrograph Package.. The range of problem
that can be solved includes large river basin water supply and flood hidrology, and
small urban or natural watershed runoff. The hydrograph produced by the program
are used directly or in conjunction with other software. The program features a
completely intergrated work environment including a database, data entry utilities,
computation engine and result reporting tool. All of the programs mentioned in this
section are in the public domain.
HEC-HMS can be used: (1) to estimate unit hydrographs, loss rates, and
streamflow routing parameters from measured data and (2) to simulate streamflow
from historical or design rainfall data. Several new capabilities are available in HECHMS that were not available in HEC-1: (1) continuous hydrograph simulation over
43
long periods of time and (2) distributed runoff computation using a grid cell
depiction of the watershed. HEC-HMS consists of a graphical user interface,
integrated hydrologic analysis components, data storage and management
capabilities, and graphics and reporting facilities. The program features a completely
integrated work environment including a database, data entry utilities, computation
engine, and results reporting tools.
2.5
Tides
Tides, generally known as astronomical tides are caused by the gravitational
attraction of the earth-moon-sun system, local bathymetry and shape of basin. There
are basically three types of tides phenomenon that occur at the beaches. Semi-diurnal
tides are two high water and two low water profile in one day within one tidal cycle.
Diurnal tides are one high tide and low tide profile in one day within one tidal cycle.
Mixed tide are a tide in which the presence of a diurnal wave is conspicuous due to a
large inequality in either the high or low water heights, with two high waters and two
low waters usually occurring each tidal day. In strictness, all tides are mixed, but the
name is usually applied without definite limits to the tide intermediate to those
predominantly semidiurnal and that diurnal.
2.5.1 Tidal Datum
Tide levels are defined in relation to a selected datum e.g. Admiralty Chart
Datum, ACD. It is the reference datum used by navigators and hydrographic
surveyors. There are also some levels that can be used as the datum for tide levels.
The first one is highest Astronomical Tide, (HAT) and Lowest Astronomical Tide,
44
(LAT). The highest and lowest levels which can be predicted to occur under average
meteorically conditions and under any combination of astronomical conditions, they
will not be reached every year and are not the extreme levels which can be reached.
Storm surges may cause considerably higher and lower levels to occur. Secondly,
Mean High Water Spring, (MHWS) and Mean Low Water Spring, (MLWS). The
height of MHWS is the average spring high water level taken over a long period of
time. The height of MLWS is the average spring low water level obtained during the
same periods. Lastly, Mean High Water Spring, (MHWN) and Mean Low Water
Neap, (MLWN). The height of MHWN is the average neap high water level taken
over a long period of time. The height of MLWN is the average neap low water level
obtained during the same periods.
2.5.2 Tidal Waterways
Tidally affected are characterized by both river flow and tidal fluctuations.
From a hydraulic standpoint, the flow in the river is influenced by tidal fluctuations
which result in a cyclic variation in the downstream control of the tail water in the
river estuary. The degree to which tidal fluctuations influence the discharge at the
river crossing depends on such factors as the relative distance from the ocean to the
crossing, riverbed slope, cross-sectional area, storage volume, and hydraulic
resistance. Although other factors are involved, relative distance of the river crossing
from the ocean can be used as a qualitative indicator of tidal influence. At one
extreme, where the crossing is located far upstream, the flow in the river may only be
affected to a minor degree by changes in tail water control due to tidal fluctuations.
As such, the tidal fluctuation downstream will result in only minor fluctuations in the
depth, velocity, and discharge.
45
As the distance from the crossing to the ocean is reduced, again assuming all
other factors as equal, the influence of the tidal fluctuations increases. Consequently,
the degree of tail water influence on flow hydraulics at the crossing increases. A
limiting case occurs when the magnitude of the tidal fluctuations is large enough to
reduce the discharge to zero at high tide. River crossings located closer to the ocean
than this limiting case have two directional flows, and because of the storage of the
river flow at high tide, the ebb tide will have a larger discharge and velocities than
the flood tide.
Tidal waterways are defined as any waterway either dominated or influenced
by tides and hurricane storm surges. Several types of tidal waterways are depicted in
Figures 2.16 through 2.19. These include estuaries, inlets, bays, and passages. An
estuary (Figure 2.16) is the tidally influenced portion of a river. Estuaries may have a
significant upland flow component or very little upland flow. The size of the channel
often bears little relation to the amount of upland flow. Even for large rivers, the
amount of daily tidal flow often far exceeds upland flows. Similarly, discharges
associated with storm surges often greatly exceed upland flood flows many miles
inland.
Figure 2.9: Estuary
46
Figure 2.10: Bay and Inlet
Figure 2.11: Passages
47
Figure 2.12: Barrier Islands forming complex tidal systems
2.5.3 Tide-Generating Forces.
To understand the effect of tides on an estuarine system, a brief comment
should be made on the tidal-generating forces and rhythms.
Newton’s laws of gravitation state that the force of attraction between two
bodies is proportional to the product of their masses and inversely proportional to the
square of the distance between their centers. Tidal forces, acting on the surface of the
earth, are less than gravitational forces and vary inversely with the cube of the
48
distance between bodies. In our sun-moon-earth system, the sun is the largest body,
but because its distance is so great from the earth, its influence on tides is only 46
percent of the moons.
All forces in the sun-moon-earth system are in equilibrium; however,
individual particles on the earth’s surface are not. In this system of varying distances
from each other and different rotation rhythms (the earth once every 24 hours and the
moon around the earth once every 24 hours and 50 minutes), these tide-generating
forces are never constant. These forces act on land, water, and air. However, the land
mass is not as elastic as liquids, and air, although elastic, has such a low density that
the effects of the tidal forces, although measurable, are small. The media most free to
respond in an observable manner are the earth’s water masses, the oceans.
Tide-generating forces are the residual forces between attraction (earth/moon
and earth/sun) and centrifugal force (due to the rotation of two bodies about a
common axis).
2.6
Estuaries
There are many different definitions of estuaries, often depending on the
legislative context under which the definition is made. Cameron and Pritchard (1963)
define an estuary as "a semi-enclosed body of water which has a free connection with
the open sea water which is measurably diluted with fresh water derived from land
drainage".
49
Fairbridge (1980) defines an estuary as "an inlet of the sea reaching into a
river valley as far as the upper limit of tidal rise, usually being divisible into three
sectors: (a) a marine or lower estuary, in free connection with the open ocean; (b) a
middle estuary, subject to strong salt and fresh water mixing; and (c) an upper or
fluvial estuary, characterized by fresh water but subject to daily tidal action."
From a continental point-of-view, estuaries are the recipients of almost all of
the runoff and groundwater flow yielded by a catchment. Very little surface or
groundwater flow enters the coastal ocean directly via the coast. It is the rivers that
act as the primary drainage system of a catchment, and, as the rivers enter the coastal
zone, they become estuaries. During periods of high rainfall, groundwater systems
are recharged from the rivers or by surface percolation and, during periods of low
river flow, the same groundwater systems discharge to the river. Water that is not
returned to the atmosphere by evaporation or evapo-transpiration by plants flows
downstream to the estuary.
Figure 2.13: Schematic of an estuary showing division into different
regions.
50
2.6.1 Tidal Mixing and Saline Stratification
Estuaries can be described in terms of their salinity structure. The salinity
structure of the estuary is determined by its geometry as well as prevailing and
antecedent climatic conditions which include fresh water inflow, tides, and wind.
Stratification arises because of the differences in density between the fresh and saline
waters that interact within estuaries. Neglecting fjords, four primary classifications of
estuarine saline structure have been identified highly stratified, partially stratified,
well-mixed and inverse estuaries.
2.6.2 Highly Stratified Estuary
Fresh river flow is buoyant compared to sea water. When the fresh water
inflow is high and the estuary relatively deep, the river flow tends to move over the
top of saline waters intruding from the sea, creating a so-called "salt wedge" (see
Figure 2.21). Measured salinity profiles in such system show abrupt increases in
salinity with depth.
Entrainment occurs across the fresh-saline interface that resists the intrusion
by the saline waters at the bed and creates a net circulation of salt water as shown in
Figure 3. Entrainment of salt water across the interface results in an increase in the
surface salinity towards the mouth of the estuary.
51
Figure 2.14: Schematic vertical section of a salt-wedge estuary. Estuary
mouth is at the right.
and
are the tidally-averaged
salinity and velocity profiles at the positions shown along the
estuary.
Flushing of the estuary is dominated by the fresh water flow and flowinduced circulations. The relatively strong fresh water inflows associated with saltwedge estuaries results in strong flushing of the surface waters. However, the poor
exchange between the surface and the bed in the stratified region of such estuaries
which can result in long resident times for the bottom water leading to dissolved
oxygen depletion and anoxia.
2.6.3 Partially-Mixed Estuary
In estuaries where tidal flows are significant, the tidal motion of water in an
estuary will generate turbulence on the bed and banks of the estuary. The turbulence
acts to mix the fresh and saline waters and reduce saline stratification.
52
A partially mixed estuary has a saline structure as shown schematically in
Figure 2.22. Salinity can be observed to increase with depth but without the abrupt
changes observed in highly stratified systems.
It is to be noted that whilst some stratification remains, the inflow of salt
water is favored on the flood tide and outflow of fresh water on the ebb tide. This can
greatly enhance the flushing of such systems beyond that produced by fresh water
flow alone.
Figure 2.15: Schematic vertical section of a partially-mixed estuary.
Estuary mouth is at the right. and are the tidallyaveraged salinity and velocity profiles at the positions shown
along the estuary.
2.6.4 Vertically Well-Mixed Estuary
In estuaries which are relatively shallow with low fresh water inflow and
large tidal currents, flow-induced turbulence can be sufficient to destroy all vertical
stratification and make the estuary vertically homogeneous. Such estuaries are
termed vertically well-mixed. The saline structure of such estuaries is illustrated in
Figure 2.23.
53
Figure 2.16 : Schematic vertical section of a vertically well-mixed estuary.
Estuary mouth is at the right. and are the tidally-averaged
salinity and velocity profiles at the positions shown along
the estuary.
2.6.5 Inverse Estuaries
In wide shallow estuaries and tidal embayment, high evaporation rates in the
presence of very low fresh water inflow can result in hyper salinity. Under such
conditions, the estuarine waters become denser than the ocean waters. This induces a
net circulation in which the dense hyper saline water sinks to the bed of the estuary
and flows towards the ocean and is replaced by inflowing seawater at the surface of
the estuary. The saline structure and net circulation are as shown in Figure 2.24.
This circulation pattern is in the opposite direction to the normal estuarine
behavior and is called negative circulation and the estuary is termed inverse.
54
Figure 2.17 : Schematic vertical section of an inverse estuary. Estuary mouth
is at the right. and are the tidally-averaged salinity and
velocity profiles at the positions shown along the estuary.
55
CHAPTER III
STUDY AREA
3.1
Site Background
The Sungai Sengkuang is situated in the Mukim of Plentong, Johor Bharu
District, Johor Darul Takzim. The Majlis Bandaraya Johor Bharu (MBJB) is the
Local Authority managing this development area. Sungai Sengkuang is situated
approximately 6 km from the Johor Bahru City Center, 20 km from Pasir Gudang
town and 25 km from Sultan Ismail International Airport at Senai.
3.2
Study Area Location
The Sungai Sengkuang estuary is located in between the Sungai Plentong and
Sungai Tebrau. It has a horse-shoe shape of estuary before any development
activities going in to that area. Sungai Sengkuang is located within the latitude
1028’45” to 1030’00” North and from longitude 103045’30” to 103047’30” East. The
main residential areas around are Kampung Bakar Batu and Taman Iskandar. Sungai
56
Sengkuang is the main channel that carrying stormwater runoff from the catchment
area towards the estuary of Sungai Tebrau. The estuary is about 1371.6 meter away
from estuary of Sungai Sengkuang and connected to Selat Johor.
57
Match Point A
Temporary Culvert
CH 1350
CH 1040
CH 0
Downstream Boundary
Match Point A
Match Point B
Match Point B
CH 2607.5
Upstream Boundary
Figure 3.1 : Aerial View of Sungai Sengkuang.
(source : google earth;www.google.com)
58
CH 1350
CH 1040
CH 0
Upstream Boundary
CH 2607.5
Figure 3.2 : Aerial View of Sungai Sengkuang and its vicinity.
(source : google earth;www.google.com)
Downstream Boundary
3.3
Topographic Profile
The topographic profile of the research area is gradually lower towards the
estuary of Sungai Tebrau. The highest point of the contour line is about 44 m and the
lowest point is about 7.7 m from Mean Sea Level. Therefore, the steep catchments area
has created a rapid surface runoff towards the lower land of downstream. Before
straightened up, the surrounding area of Sungai Sengkuang is of low lying, swampy and
Api-api and bakau trees are the main vegetation growth at the site.
3.4
Types of Soil
There are two main types of soil at the Sungai Sengkuang cathment area
which are called KNJ soil (Kranji Association) and HMU UTM (Harimau-Ulu
Tiram Association). The KNJ soil series is from the group of clay which is
distributed around the estuary of Sungai Sengkuang, east part of the research area.
The HMU UTM soil series is distributed at the west part. Probably the content of
the soil is from the group of sand.
60
Figure 3.3: Soil Type within Catchment Area
3.5
Land Use
The surrounding area of Sungai Sengkuang has been developed as residential
area, business and industrial area, main infrastructures like asphalt bituminous roads,
railways and so on. According to figure 3.4, out of 81 % of the study area is impervious
surface.
61
Figure 3.4: Land Use and Main Tributaries
Catchment 2 : 4.03 km2
CH 0
CH 1040
CH 1350
CH 2607.5
Catchment 1 : 2.44 km2
Figure 3.5: Sungai Sengkuang Catchment Area
62
CHAPTER IV
METHODOLOGY
In this section, the numerical model with computer program are described and
discussed. The methodology of this study is designed to achieve the objectives of the
study based on the prescribed on the scope of work. A continuous literature review had
been carried out until report writing stage so that improvement can be made during
research period.
4.1
Introduction
Sungai Sengkuang is one of the main tributary of Sg Tebrau in which its
tributary is situated very near to the river mouth. The river is straightened due to the
increasing housing demand within prime development area of MBJB. The
improvement work has resulted in a series of flood in the Sungai Sengkuang flood
63
plain that requires channel analysis, taking the effect of surface runoff and tidal
flow.
The evaluation process requires the following analysis in order to provide a
better understanding of the behavior and basic characteristics of the channel.
a. To study the relationship of the rainfall and runoff to be used as the
upstream input boundary data. This involves the actual event measurement
of stream flow in respond to the recorded rainfall. Further analysis will be
done based on these basic relationships. A better understanding of the
hydrologic process will be emphasized.
b. The energy line along the channel reach are determined to evaluate the
dominant energy from either upstream boundary condition of stream flow or
downstream boundary condition of tide fluctuation using different analytical
methods and calibrated by hydraulic models.
A few scenarios are carried out to provide a better scope of analyses to
understand the basic hydrologic and hydraulic principles. The overall components of
analysis are schematized in Figure 4.1.
64
Figure 4.1: Hydrologic and Hydraulic Analysis of Sg Sengkuang.
4.2 Data Collection
The data have been collected at site from 1:30 pm to 9:00 pm 26 January 2007.
Figure 4.2 and Table 4.1 is the brief explanation for the data and the sampling station.
65
Catchment 1 – 2.44 km2
Hydrologic Model
- HEC – HMS
- model parameter
Catchment 2 – 4.03 km2
H
+
v
t
=
t
Q
t
Q
CH 2607.5
t
H
CH 1350
t
Hydraulic Model
- HEC – RAS
- boundary condition
- Q @ U/S
- WL @ D/S
- Calibration model parameter
WL for calibration
CH 1040
Tide Level
- monitoring Station
WL
CH 0
Q
t
Figure 4.2: Sampling station for model calibrations.
Table 4.1: Location, data and equipment used during data collection.
Location
Data
Equipment
Downstream (CH 0)
Water Level (Tide Level)
Global Water
Jetty (CH 1040)
Water Level
Global Water
Actual Rainfall,
Rain Gauge
Cathment 1
Velocity,
Current Meter
(CH 2607.1)
Water Level,
Measuring Stick Gauge
Channel Cross Section.
Measuring Tape
Reduced Level
Leveling Equipment
Along Sungai Sengkuang
66
4.2.1 Water Level at CH 0 and CH 1040
The actual tide level time series at CH 0 and water level time series at CH 1040
are recorded using water level recorder (Global Water). Then, the raw data has been
converted into the Land Survey Datum by carrying out the reduced level in the
leveling work along Sungai Sengkuang. Figure 4.3 and Figure 4.4 had show the water
level time series for CH 0 and CH 1040 respectively.
67
Figure 4.3 : Water Level at CH 0.
68
Figure 4.4 : Water Level at CH 1040.
69
4.2.2 Data Collection at CH 2607.5
4.2.2.1 Recorded Rainfall
The actual rainfall has been recorded from catchment 1 on 26 January 2007
which started from 1:30 pm to 9:00 pm for three events as shown in Table 4.2,
Table 4.3 and Table 4.4.
Table 4.2: Recorded Rainfall from Catchment 1 for Event 1.
Time
1:45
1:50
1:55
2:00
2:05
2:10
2:15
2:20
2:25
2:30
2:35
2:40
2:45
2:50
Incremental Rainfall, mm
0.3
4.7
3.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Table 4.3: Recorded Rainfall from Catchment 1 for Event 2.
Time
3:45
3:50
3:55
4:00
4:05
4:10
4:15
4:20
Incremental Rainfall, mm
0.3
1.2
1.3
0.4
0.2
0.2
0.2
0.1
70
Table 4.4 : Recorded Rainfall from Catchment 1 for Event 3.
Time
6:40
6:45
6:50
6:55
7:00
7:05
7:10
7:15
7:20
7:25
7:30
7:35
7:40
7:45
7:50
7:55
8:00
8:05
8:10
8:15
8:20
8:25
8:30
Incremental Rainfall, mm
0.1
0.1
0.1
0.1
0.1
0.1
1.1
1.2
0.7
0.6
1.3
1.1
0.3
0.3
0.3
0.1
0.1
0.1
0.1
0.1
0.4
0.4
0.1
4.2.2.2 Actual Flow
The Current Meter has been used for the measurement of velocity at 5
minutes time interval from 1:30 pm to 9:00 pm. The water level of Sungai
Sengkuang is recorded manually in order to calculate the rate discharge in each
second (m3/s). The cross section at CH 2607.5 as described in Figure 4.5 and the
discharge from catchment 1 for event 1, event 2 and event 3 are shown in Figure
4.6, Figure 4.7 and Figure 4.8 respectively.
71
9.5 m
4.875 m LSD
1:4
2.875 m LSD
0.2 m
3.0 m
8.5 m
Figure 4.5: Cross section at CH 2607.5
Figure 4.6: Discharge from Catchment 1 for Event 1.
72
Figure 4.7: Discharge from Catchment 1 for Event 2.
Figure 4.8: Discharge from Catchment 1 for Event 3.
73
4.2.3 Reduced Level, RL
The reduced levels, RL along Sungai Sengkuang have been worked out in
order to convert the measurement of water level at sampling stations into Land
Survey Datum, LSD. The reduced level at sampling station is shown in Table 4.5
below.
Table 4.5: Reduced levels at sampling station.
Sampling Station
CH 0
CH 1040
CH 1350
CH 2607.5
4.3
Reduced Level
0.095 m
- 0.230 m
- 0.210 m
2. 875 m
Frequency Analysis of Tide Levels.
The highest tide level for the passed 24 years (1984 – 2004), at station Johor
Bahru have been used in the steady flow analysis. To determine the Return Period
of the highest tide level, a frequency analysis of tide data with statistical methods
need to be carried out. From the previous study with Weibull Method, the highest
tide levels with Average Recurrence Interval, 5 ARI, 20 ARI, 50 ARI and 100 ARI
are determined and there are used as the input data at the downstream boundary
condition in the steady flow analysis as shown in Table 4.6.
74
Table 4.6: Highest Tide Level in LSD (Foo Kar Lai, 2006).
4.4
Return Period
(year)
Highest Tide Level,
Chart Datum (m)
Highest Tide Level,
LSD (m)
5
4.693
2.893
20
4.795
2.995
50
4.860
3.060
100
4.906
3.106
Hydrologic Model Calibration with HEC-HMS at Catchment 1
(CH 2607.5)
Basin Model, Meteorologic Model and Control Specifications are the three
major components that require in the calibration of HEC-HMS modeling. The
Hydrologic Modeling System (HEC-HMS) is design to simulate the precipitationrunoff processes of dendritic watershed systems
4.4.1 Basin Model
Basin models are one of the main components in a project. Their principal
purpose is to convert atmospheric conditions into streamflow at specific locations
in the watershed. Hydrologic elements are used to break the watershed into
manageable pieces and they are connected together in a dendritic network to form a
representation of the stream system. In this study, the data need to be entered into
the basin model for calibrations are shown in Table 4.7.
75
Table 4.7: Method selected for hydrologic model calibration.
Loss Rate
Initial/Constant
Transform
Clark
Baseflow
Constant Monthly
Initial Loss
Constant Loss Rate
Imperviousness
Time of Concentration
Storage Coefficient
Constant Baseflow
4.4.1.1 Initial Constant Loss
The initial constant loss method is relatively simple but still appropriate for
watersheds that lack of detailed soil information. It is also suitable for certain types
or flow-frequency studies. The initial loss specifies the amount of incoming
precipitation that will be infiltrated or stored in the watershed before surface runoff
begins. There is no recovery of the initial loss during periods without precipitation.
The constant rate determines the rate of infiltration that will occur after the initial
loss is satisfied. The same rate is applied regardless of the length of the simulation.
4.4.1.2 Clark Unit Hydrograph Transform
The Clark unit hydrograph is a synthetic hydrograph method. The time of
concentration defines the maximum travel time in the subbasin. It is used in the
development of the translation hydrograph. The storage coefficient is used in the
linear reservoir that accounts for storage affects. Many studies have found that the
76
storage coefficient, devided by the sum of time of concentration and storage
coefficient, is constant over the region.
4.4.1.3 Constant Monthly Baseflow
The constant monthly baseflow allows the specification of a constant
baseflow for each month of the year. It does not converse mass within the subbasin.
It is intended primarily for continuous simulation in subbasins where the baseflow
is nicely approximated by a constant flow for each month.
4.4.2 Meteorological Model
Meteorological models purpose is to prepare meteorologic boundary
condition for subbasins and it can be used with many different basin models. The
precipitation data which necessary to simulate the catchment area processes is
stored in this component, the flow simulation will be done for 5 ARI, 20 ARI, 50
ARI and 100 ARI.
4.4.3 Control Specifications
The starting date and time of a run and the ending date and time are set in
the control specifications. For calibration of outflow at CH 2607.5, the starting time
is as shown below on 26 January 2007.
77
Table 4.8: The starting and ending time during data collection.
Event
Event 1
Event 2
Event 3
Starting Time
1:30 pm
3:45 pm
6:30 pm
Ending Time
3:15 pm
5:00 pm
8:45 pm
Time Interval
5 min
5 min
5 min
4.4.4 Hydrologic Model Calibration
The purpose of calibration is to obtain the affecting parameter of the
channel by entering a different value of Storage Coefficient, R until the Model
Hydrograph similar to the Observed Hydrograph. From Figure 4.9, Part A is the
hydrologic model calibration. It is carried out at catchment 1, upstream of Sungai
Sengkuang. Recorded rainfall in Table 4.2, 4.3 and 4.4 and the data stated in Table
4.7 have been entered to the software HEC – HMS. In Fact, the model parameter
that obtained from calibration is used in the flow simulation in Part C.
Catchment 1
Catchment 2
PART A
CH 2607.5
PART C
CH1350
CH 1040
PART B
PART D
CH 0
Figure 4.9 : Part of Analysis in Sungai Sengkuang.
78
4.4.5 Hydrologic Model Validation
Validation is one of the requirements for modelling. For this study, the
validations are involved 2 event data. All the data are showed on Table 4.3 and Table
4.4 have been used for model validation.
4.5
Hydraulic Model Calibration HEC – RAS (CH 0 - CH 2607.5)
Part B is the Hydraulic Model Calibration using HEC – RAS. There are
three hydraulic analysis components that can be computed by this software which
are steady flow water surface profile computations, unsteady flow simulation and
moveable boundary sediment transport computations. The computation that has
been used in the hydraulic model calibration is unsteady flow analysis.
4.5.1 Geometry Data
The geometry data consists of connectivity information for the stream
system and cross section data, it show how the channel is connected. The cross
section data is required to show the locations throughout the channel and locations
where the changes occur in the discharge, slope and roughness. The detail about
culvert exists along the channel also need to be entered into the bridge culvert data.
In this channel, the culvert located at CH 1350 as shown below.
79
2607.5
2232.5
2107.5
Straighten
1832.5
Su ng a i
S e ng k ua
ng
1457.5
1350
1040
950
750
550
350
167
0
Some schematic data outside default extents (see View/Set Schematic Plot Extents...)
Partial GIS data
Figure 4.10: Schematic Diagram for Sg Sengkuang from CH 0 to CH 2607.5
Figure 4.11: Cross-section of Culvert at CH 1350.
80
4.5.2 Hydraulic Model Calibration
A hydraulic model calibration has been carried out in Part B, the discharge
from CH 2607.5 is used as the upstream boundary condition and the water level at
CH 0 is used as the downstream boundary condition. The reference point of the
actual water level and model’s water level from HEC – RAS is at CH 1040. The
measured water level is compared until it similar with model’s water level by
adjusting the Manning’s n value of the channel. The Manning’s n value with least
deviation between simulated water level and actual water level is used in the Part D
of analysis.
4.5.3 Hydraulic Model Validation
Validation for hydraulic model calibration has been done with data from
event 2 and event 3 as shown in Figure 4.3 as reference point at CH 1040, Figure 4.4
as downstream boundary condition, Figure 4.7 and Figure 4.8 as upstream boundary
condition.
4.6
Flow Simulation (CH 1350)
In Part C, simulated flows with 5 ARI, 20 ARI, 50 ARI and 100 ARI
discharged from catchment 2 has been determined by HEC – HMS based on the
calibrated parameter, Storage Coefficient, R obtained from Part A. In this case,
catchment 2 is assumed having the same characteristics and hydrologic response
81
with catchment 1. Figure 4.12 show the procedure to obtain the Peak Flow for the
different ARI.
Time of Concentration, tc
Storm Duration
Rainfall Intensity, RIt
Rainfall Pattern
Storm Distribution
Hydrograph with Different ARI – HEC - HMS
Qpeak from Different ARI
Figure 4.12: Procedure to obtain the Peak Flow with different ARI
4.7
Steady Flow Analysis
The channel which included in steady flow analysis is from CH 1350 to CH
0. The Manning’s n value which obtained from PART B is used as the geometry
data, where it is representing the actual condition or the roughness of the channel
bed.
In the analysis, the peak flows with different ARI from flow simulation in
PART C is used as the input data at CH 1350 for upstream boundary condition. The
82
downstream boundary condition at CH 0 is the highest tide level with different ARI
that obtain from the frequency analysis.
As a result, the analysis showed the hydraulic characteristic of channel and
the dominant energy either from the upstream or downstream boundary condition.
83
CHAPTER V
ANALYSIS AND RESULTS
As stated previously, this study involves observation site data and model
simulation. For every test case, results from both sources are presented together for
comparison purpose. Input parameters for each simulation are provided and results
from both sources were analysed.
In additional, the simulation was involved several rainfall events. The data
simulation at site gathered on 26 January 2006 (Friday), from 1:30pm to 9:00pm at
different stations.
5.1
Modelling Procedure
Analysis has been carried out to the channel by using software HEC – HMS
and HEC – RAS. Several data that have been collected are rainfall data, streamflow
and water level and has been used as the input data in the hydrologic and hydraulic
model calibration. Data collection is an important stage for the study. For this study,
84
all information and data required such size of channel, slope and topography are
provided by the relevant authority, whilst water surface depth are taken from
observation on site. The storage coefficient, R obtained from hydrologic model
calibration has been used as the input data for the flow simulation. Then, design
rainfall for different ARI has been calculated for catchment 2 in order to obtain the
simulated discharge from the flow simulation process.
The tide levels with different ARI are used as the downstream boundary
condition in the hydraulic model analysis. The peak discharges with different ARI
obtained from flow simulations are used as upstream boundary condition. The
analysis is to determine whether the existing system is still able to accommodate the
flow from upstream and downstream.
5.1.1 Hydrologic Model Calibration
An important of any computer model is the verification of results. Surface
water modelling is no exception. Before using a surface water model to predict
results, the model should be tested for accuracy. Calibration is the process of altering
model parameters until the computed solution matches observed field within an
acceptable tolerance. Calibration is an important step before simulation model in the
channel for different flow rate and level. Calibration has been carried out to obtain
the affecting parameter of the catchment area. The input data for the basin model in
HEC – HMS as shown in Table 5.1.
85
Table 5.1: Input data for the Basin Model.
Initial Loss
Constant Loss Rate
Imperviousness
Time of Concentration
Transform Clark
Storage Coefficient
Baseflow
Constant Monthly Constant Baseflow
* Storage Coefficient, R is obtained from the calibration.
Loss Rate
Initial/Constant
1.5 mm
0 mm/hr
90%
0.42 hr
0.535 hr*
0.5 cms
In the basin model, precipitation data that has been collected from catchment
1 and the discharge data for event 1 and event 2 and event 3 are also need to be
entered which as shown in Figure 5.1, Figure 5.2 and Figure 5.3. The data for event 2
and event 3 have been used for model validation.
Figure 5.1: Actual rainfall data for Event 1.
86
Figure 5.2: Actual rainfall data for Event 2.
Figure 5.3: Actual rainfall data for Event 3.
87
5.1.2 Result of Hydrologic Model Calibration
The purpose of hydrologic model calibration is to adjust the model’s
hydrograph until it is similar to the observed hydrograph (actual discharge). The
result of calibration is shown in Figure 5.4, the red line representing the actual
discharge; blue line representing the model’s discharge and the brown line is
representing the base flow from the upstream channel. According to the Figure 5.4,
the peak discharges are similar for both observed and model hydrograph. The
Storage Coefficient, R obtained from the calibration is 0.535 hours.
Figure 5.4: Result of Hydrologic Model Calibration for Event 1.
88
5.1.3 Hydrologic Model Validation
Validation is one of the requirements for modelling. For this study, the
validations are involved 2 event data; event 2 and event 3. All the data are showed on
Figure 5.2 and Figure 5.3. Figure 5.5 show the result of validation with the Storage
Coefficient, R is 0.535 hours. According to the Figure 5.5 and Figure 5.6, the peak
discharges are similar for both observed and model hydrograph. According to the
MAPE method the analysis will be consider accurate when the error between range
of 5% to 10 %. Average different at position B is 2.12% and at position C is 1.72%
which are both are less than 10%. So, the model is accepted.
Figure 5.5: Result of Hydrologic Model Validation for Event 2.
89
5.1.4 Hydraulic Model Calibration.
The value need to be determined for calibration purpose is the bottom
roughness, n (Manning). After determining the value of bottom roughness, n the
simulation prediction of the flow for different depth can be estimated. As mention
before, the water level time series at CH 1040 is used as calibration station to
calibrate the channel. The upstream boundary condition is the actual discharge from
catchment 1 at CH 2607.5 and the actual tide level has been used as the downstream
boundary condition. By adjusting the model water level until similar to the actual
water level, different value of Manning’s n has been entered into the software.
Figure 5.6: Actual discharge from catchment 1; upstream boundary condition.
90
Figure 5.7: Actual tide level at CH 0; downstream boundary condition.
5.1.5 Result of Hydraulic Model Calibration.
From the results of calibration, the Manning’s n is 0.03 for CH 1350 to CH
2607.5 and 0.02 for CH 0 to CH 1350. It is adequate because the limitation of
Manning’s n for lined or build-up channel is within 0.023 – 0.030. The maximum
simulation water level is 0.55 m and 0.61 m for the observed water level. The
91
different between model water level and actual water level is about 0.06m. The peak
stage is occurred at 3:00pm, the peak flow is 4.99 m3/s and the volume of water is
about 1000 m3. Figure 5.7 shows the calibrated water level time series at CH 1040.
Consequently, the Manning’s n value will be used in the flow analysis.
Flood Analysis of Sungai Sengkuang
Plan: Plan 04zul#2
9/30/2007
CH490 of Sg. Sengkuang
.02
.02
.02
4
Legend
WS Max WS
Ground
Bank Sta
OWS Max WS
3
2
Elevation (m)
WS MAX = 0.55m
OWS MAX = 0.61m
1
0
-1
0
10
20
30
40
50
Station (m)
Figure 5.8: Water level calibration at CH 1040.
5.1.6 Hydraulic Model Validation
In Hydraulic Model Validation, the validation is involved event 2 data. Figure
5.9 show the result of model validation. According to the Figure 5.9, the water levels
are similar for both observed and model water level. According to the MAPE method
the analysis will be consider accurate when the error between range of 5% to 10 %.
Average different between model and actual water level is 5.2 % which are both are
less than 10%. So, the model is accepted.
92
Flood A nalysis of Sungai Sengkuang
Plan: Plan 04zul#2
9/29/2007
CH490 of Sg. Sengkuang
.02
.02
. 02
4
Legend
EG Max WS
WS Max WS
Ground
Bank Sta
3
OWS Max WS
WS MAX = 1.02m
Elevat ion (m)
2
OWS MAX = 0.97m
1
0
-1
0
10
20
30
40
50
St ation (m)
Figure 5.9: Water level validation at CH 1040.
5.2
Flow Simulation
The Storage Coefficient, R that obtained from hidrologic calibration in
catchment 1 have been used in the flow simulation for Catchment 2 which is
representing the actual catchment of Sungai Sengkuang. The catchment area is about
4.031 km2. According to the existing data, the time of concentration, tc for the real
catchment is about 120 minutes.
The design rainfalls for 5 ARI, 20 ARI, 50 ARI and 100 ARI have been
calculated by using the procedures which stated in MASMA (JPS, 2000). Four sets
of design rainfall with different return period are entered into the Precipitation Data
in HEC – HMS. It is used to simulate the peak flows from catchment 2 with the
Storage Coefficient, R 0.535 hours which obtain from the calibration. The output of
the flow simulation is the hydrograph with different return period.
93
5.2.1 Result of Flow Simulation
Flow simulation is carried out to determine the discharge from catchment 2
with different ARI which is representing the actual catchment of Sungai Sengkuang.
Design rainfall with different ARI and the relevant data are entered in the software as
shown in Table 5.2 and Table 5.3.
Table 5.2: Design rainfall with different return period.
ARI (year)
5
20
50
100
Design Rainfall
94.03 mm
124.39 mm
136.67 mm
152.70 mm
Table 5.3: Input data for flow simulation in the Basin Model.
Initial Loss
Constant Loss Rate
Imperviousness
Time of Concentration
Transform Clark
Storage Coefficient
Baseflow
Constant Monthly Constant Baseflow
* Storage Coefficient, R is obtained from the calibration.
Loss Rate
Initial/Constant
1.5 mm
0 mm/hr
90%
2 hr
0.535 hr
0.5 cms
The discharge of 5 ARI, 20 ARI, 50 ARI and 100 ARI are shown in Figure 5.10.
94
Discharge from Catchment 2
90
80
70
60
Flow (m3/s)
ARI 5
50
ARI 20
ARI 50
40
ARI 100
30
20
10
2100
2045
2030
2015
2000
1945
1930
1915
1900
1845
1830
1815
1800
1745
1730
1715
1700
1645
1630
1615
1600
1545
1530
1515
1500
1445
1430
1415
1400
1345
1330
0
Time
Figure 5.10: Discharges with 5 ARI, 20 ARI, 50 ARI and 100 ARI from HECHMS flow simulation.
5.3
Steady Flow Analysis – HEC – RAS
The analysis is done by using software HEC – RAS. The Manning’s n value
that obtained from the hydraulic calibration is used in the analysis. The input data for
upstream boundary condition are the peak discharge with different ARI which
obtained from the flow simulations. The tide levels with different ARI which
obtained from frequency analysis are used as the downstream boundary conditions,
the flow regime of the channel is subcritical where the yo is larger than the yc for all
the ARI as shown in Table 5.4.
95
Table 5.4: Upstream and downstream boundary conditions.
Upstream, Peak
Flow (m3/s)
60.10
68.69
75.48
84.34
ARI (year)
5
20
50
100
Downstream, Tide
Level (m)
2.893
2.995
3.060
3.106
Normal Depth,
yo (m)
0.526
0.618
0.652
0.696
Critical Depth,
yc (m)
0.245
0.294
0.312
0.335
5.3.1 Results of Steady Flow Analysis
From the result, the water level at Sungai Sengkuang for different ARI can be
obtained. As shown in Figure 5.11 and Figure 5.12, the blue line which representing
the height of water level is lower than the channel bank (dotted line). In other words,
the existing channel is still able to accommodate the flow from upstream and
downstream.
Steady Flow Analysis of Sg. Sengkuang
Plan: Plan 01
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 Year ARI
WS 50 Year AR I
WS 20 Year AR I
WS 5 Y ear AR I
3
Ground
LOB
ROB
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
Main Channel Distance (m)
Figure 5.11: Water surface profile plot at CH 1350.
1600
96
Bank Level
100 ARI
20 ARI
50 ARI
5 ARI
Figure 5.12: Water surface profile plot at CH 1350.
Steady Flow Analysis of Sg. Sengkuang
Plan: Plan 01
9/30/2007
CH 00 of Sg. Sengkuang
.02
.02
.02
4
Legend
WS 50 Year ARI
WS 100 Year ARI
WS 20 Year ARI
WS 5 Year ARI
3
Ground
Bank Sta
Elevation (m)
2
1
0
-1
0
10
20
30
40
50
Station (m)
Figure 5.13: Cross section of CH 1350 with different ARI.
The height of the left bank and right bank is 3.2 m LSD from CH 0 to CH
1150 whereas the left bank and right bank at CH 1350 is 3.3 LSD. According to
Chapter II, Section 28.5 in MASMA (JPS, 2000), the standard freeboard of channel
is less than 300mm for 20 ARI, 50 ARI and overflow for 100 ARI. It is not adequate
to the standard freeboard. Therefore, some cross-section resizing works are needed to
be done in order to avoid the occurrence of flood.
97
Table 5.5: Water Levels with different ARI.
Water Level (m)
LSD
2.91
3.04
3.20
3.24
ARI (year)
5
20
50
100
Steady Flow Analysis of Sg. Sengkuang
Freeboard (m)
0.29
0.16
0.00
-0.04
Plan: Plan 01 9/30/2007
Legend
WS 5 Year ARI
1350
WS 20 Year ARI
WS 50 Year ARI
1150
WS 100 Year ARI
Ground
Bank Sta
1040
950
750
550
350
167
0
Figure 5.14: Water Levels along the channel with different ARI.
5.4
Channel Cross Section Resizing and Bund Introduction
Due to the inadequate freeboard of Sungai Sengkuang, the cross section of
channel needs to be improved. By using HEC – RAS, the steady flow analysis of
existing cross section of Sungai Sengkuang with purposed bund has been carried out.
98
The input and output data for upstream and downstream boundary condition are
same with the previous steady flow analysis.
Table 5.6: Comparisons between existing and proposed system.
Items
Bank Level
(m)
Existing Details
Proposed Details
3.2
3.5
Invert Level
(m)
-0.5 (CH 1350)
-1.5 (CH 0)
-0.5 (CH 1350)
-1.5 (CH 0)
Channel
Length (m)
1350
1350
Cross
Section
Figure 5.12
Figure 5.14
Recommendationzull
Plan: Plan 02
Explanation
A 0.3 m height of
bund will be added.
It is limited by the
existing invert level
at u/stream and
d/stream
New cross section
and bund has been
added to the existing
channel
9/30/2007
CH490 of Sg. Sengkuang
.02
.02
.02
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
WS 5 Year ARI
3
2m
Ground
Bank Sta
Elevation (m)
2
2m
1
The side slopes, slope of
channel cross section size
are remained.
0
-1
0
10
20
30
40
50
Station (m)
Figure 5.15: Proposed cross section of channel.
60
99
Recommendationzull
Plan: Plan 02
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
WS 5 Year ARI
3
Ground
LOB
ROB
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
Main Channel Distance (m)
Figure 5.16: Water surface profile plot of proposed channel.
Bank Level
100 ARI
50 ARI
20 ARI
5 ARI
Figure 5.17: Water surface profile plot of proposed channel.
1600
100
Table 5.7: Water Levels with Different ARI.
Water Level (m)
LSD
2.91
3.04
3.13
3.20
ARI (year)
5
20
50
100
Recommendationzull
Plan: Plan 02
Freeboard (m)
0.59
0.46
0.37
0.30
9/30/2007
Legend
WS 5 Year ARI
1350
WS 20 Year ARI
WS 50 Year ARI
1150
WS 100 Y ear ARI
Ground
Bank Sta
1040
950
750
550
350
167
Figure 5.18: Water Levels along the proposed channel with different ARI.
101
CHAPTER VI
DISCUSSION AND CONCLUSION
6.1
Discussion
The objective of this study is to determine the dominant energy from either
upstream boundary condition or downstream boundary condition. Therefore,
hydrologic and hydraulic model analysis has been carried out in order to investigate
the hydraulic characteristic of channel that experiences flood problem due to heavy
rainfall and tide influence.
The hydrologic model calibration for catchment 1 has been carried out to
determine the storage coefficient, R for the actual catchment of Sungai Sengkuang.
In this case, catchment 1 assumed having the same characteristics or hydrologic
response with catchment 2. Calibration has been carried out using HEC – HMS by
entering different values of R until the model hydrograph similar to the observed
hydrograph. The Storage Coefficient, R obtained from the calibration is 0.535 hours.
Storage Coefficient represent the duration of surface runoff which can be stored or
detained at the catchment area before flow into the channel. The surface runoff at the
catchment area of Sungai Sengkuang takes about 32 minutes to drain the runoff to
the channel.
102
The Storage Coefficient, R that obtained from hydrologic model calibration
from catchment 1 is used in the flow simulations for the whole catchment area of
Sungai Sengkuang. The flow simulations computed the simulated discharges with
different ARI using HEC – HMS software by entering the design rainfall with
different ARI. The peak flow of simulated discharges with different ARI is used in
flow analysis as upstream boundary condition.
In the hydraulic model calibration using HEC – RAS, the actual discharge
from catchment 1 and actual tide level has been entered as the upstream and
downstream boundary condition. From the result, the Manning’s value that
representing the roughness of channel bed is 0.03 for CH 0 to CH 1350. The value
still within the limitation for the channel with gravel bottom with sides of dry rubber
or riprap (Design Chart 26.1 – MASMA). The Manning’s value, n obtained from the
calibration is used in the flow analysis of Sungai Sengkuang.
Steady flow analysis has been carried out from CH 0 to CH 1350. It has been
done by considering the peak flow from upstream obtained in the flow simulation
and high tide from downstream obtained in the frequency analysis with 5 ARI, 20
ARI, 50 ARI and 100 ARI. From the result, overflow does not occur at Sungai
Sengkuang. The water levels with different ARI are still below the left and right bank
of the channel from CH 0 to CH 1350. According to the previous analysis, the flood
problem occurred previously has been proved that is caused by the back water
created by the improper hydraulic design of culvert at CH 600. From the flow
analysis, it shows that the flood problem was neither caused by the improper channel
size nor the high tide from downstream.
Although the channel is still capable to accommodate the flow from upstream
and downstream, the freeboard of channel is less than 300 mm for 20 ARI, 50 ARI
and 100 ARI. It is not adequate to the standard freeboard. Therefore, some cross
section resizing work are needed to be done in order to avoid the occurrence of flood.
Some of the cross section has been resized and widen and bund has been introduced
103
to build at the both side of the channel bank and the analysis has been done for the
existing channel with the additional of bund.
Figure 6.1 show the water surface profile plot of the proposed channel. It
shown that the freeboards of the channel with different ARI are more than 300 mm
height at the left and right banks of the channel. Figure 6.2, Figure 6.3 and Figure 6.4
shows the new cross section of proposed channel of Sungai Sengkuang. It is safe to
drain the water surface runoff from the catchment to downstream and the standard of
freeboard height states in MASMA.
Recommendationzull
Plan: Plan 02
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 Year AR I
WS 50 Year AR I
WS 20 Year AR I
WS 5 Year ARI
3
Ground
LOB
ROB
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
1600
Main Channel Distance (m)
Figure 6.1: Water surface profile plot of proposed channel with bund.
104
Recommendationzull
Plan: Plan 02
9/30/2007
Downstream of Sg. Sengkuang CH1350
.02
.02
.02
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
3
WS 5 Year ARI
Ground
Bank Sta
Elevat ion (m)
2
1
0
-1
-2
0
10
20
30
40
50
60
Station (m)
Figure 6.2: Water level at CH 0 after resizing work.
Recommendationzull
Plan: Plan 02
9/30/2007
CH600 of Sg. Sengkuang
.02
.02
.02
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
WS 5 Year ARI
3
Ground
Bank Sta
Elevation (m)
2
1
0
-1
0
10
20
30
40
50
Station (m)
Figure 6.3: Water level at CH 550 after resizing work.
60
105
Recommendationzull
Plan: Plan 02
9/30/2007
CH00 of Sg. Sengkuang
.02
.02
.02
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
WS 5 Year ARI
3
Ground
Bank Sta
Elevat ion (m)
2
1
0
-1
0
10
20
30
40
50
60
Station (m)
Figure 6.4: Water level at CH 1350 after resizing work.
6.2
Energy Grade Line Analysis.
In order to determine the dominant energy whether from upstream or
downstream, the analysis of energy grade line has been carried out.
6.2.1 Channel under flow from upstream only.
The energy grade line of channel is carried out by only considering the flow
from upstream without influence of tide from downstream. The water level at the
downstream boundary condition is set to zero. From the result as shown in Figure
6.5, the energy grade line along the channel is constant until CH 167. The specific
106
energy changes along a channel because of changes of the bottom elevation and
energy losses such as friction loss. It is believed that the changes of energy grade line
is not caused by the changes of the bottom elevation but caused by the friction loss
because the slope along the channel is considered gentle and constant which is
1:1350. Friction has been created by the gravel at the bottom of Sungai Sengkuang.
Therefore, the energy is gradually reduced when the water flows from upstream to
downstream.
EG Line Analysiszul#2
Plan: Plan 01
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 ARI
WS 50 ARI
WS 20 ARI
WS 5 ARI
3
Ground
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
1600
Main Channel Distance (m)
Figure 6.5: Energy grade line without tide.
6.2.2 Channel under high tide from downstream only.
In the second analysis as shown in Figure 6.6, the high tide from downstream
has been entered as downstream boundary condition and the flow from upstream is
set to zero. From the result, the energy from downstream is obviously higher than the
energy grade line from upstream which has been shown in the first analysis. The
107
energy grade line is constant and flat from CH 0 to CH 1350. In this case, the
changes of bottom elevation of the channel and friction loss do not bring many
effects to the energy grade line. It is because of the energy of high tide from
downstream is much higher than the energy of flow from upstream.
EG Line w ithout f low
Plan: Plan 01
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 ARI
WS 50 ARI
WS 20 ARI
WS 5 ARI
3
Ground
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
1600
Main Channel Dist ance (m)
Figure 6.6: Energy grade line without flow.
6.2.3 Channel under flow from upstream and high tide from downstream.
In the third analysis, the result of the energy grade line analysis considering
both flows from upstream and high tide from downstream gave the same result as
second analysis. In Figure 6.7, the water surface profile shows that the energy of high
tide from downstream is more dominant than the flow from upstream. The flat and
constant energy grade line shows that the changes of energy grade line do not occur
between CH 0 to CH 1350. It might occur at upstream above CH 1350 which
possesses the weakest energy from downstream.
108
Steady Flow Analysis of Sg. Sengkuang
Plan: Plan 01
9/30/2007
Sungai Sengkuang Straighten
4
Legend
WS 100 Year ARI
WS 50 Year ARI
WS 20 Year ARI
3
WS 5 Y ear ARI
Ground
LOB
ROB
Elevation (m)
2
1
0
-1
-2
0
200
400
600
800
1000
1200
1400
1600
Main Channel Distance (m)
Figure 6.7: Energy grade line with flow from upstream and high tide from
downstream.
6.3 Conclusion
The result of hydrologic and hydraulic model analysis shows that there is no
overflow occurs along the channel. It means that the existing channel is still able to
accommodate the flow from upstream and downstream. But, the freeboard of the
channel is less than 300 mm and inadequate the standard freeboard for open channel
for 20 ARI, 50 ARI and 100 ARI. Therefore, a resizing cross section of the channel
and a new bund has been proposed to build at the both side of the channel.
The comparison between energy grade line analyses with high tide from
downstream and both flow from upstream and downstream shows no different in the
water level (Appendix B and C). It means, the energy grade line analysis shows that
the changes of energy grade line do not occur between CH 0 to CH 1350. It also
proved that the dominant energy is from downstream of the channel which means
that the tidal influence is more significant than the discharge from upstream.
109
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111
APPENDIX A
Summary of Data Collection and Calculation
Date : 26 January2007
Time
Rain
mm
Water Level
(CH2607.5)
RL
LSD
Flow
m/s
3
m /s
cm
1:20 PM
0
0
1:25 PM
0
0
1:30 PM
0
0
1:35 PM
0
0
m
1:40 PM
0
1:45 PM
0.3
0.986
0.59
0
0
2.875
1:50 PM
4.7
1.145
1.66
10
2.975
1:55 PM
3.1
1.238
2.65
18
3.055
2:00 PM
0.1
1.355
4.89
35
3.225
2:05 PM
0.1
1.451
6.49
45
3.325
2:10 PM
0.1
1.473
7.24
50
3.375
2:15 PM
0.1
1.364
7.30
55
3.425
2:20 PM
0.1
1.246
4.17
32
3.195
2:25 PM
0.1
1.012
2.34
20
3.075
2:30 PM
0.1
1.016
1.65
12
2.995
2:35 PM
0.1
0.905
1.24
9
2.965
2:40 PM
0.1
0.937
1.12
7
2.945
2:45 PM
0.1
0.956
0.98
5
2.925
2:50 PM
0.1
0.942
0.73
2
2.895
2:55 PM
0
0.972
0.75
2
2.895
3:00 PM
0
0.941
0.64
1
2.885
3:05 PM
0
0.961
0.58
0
2.875
3:10 PM
0
0.843
0.51
0
2.875
3:15 PM
0
0.878
0.53
0
2.875
3:20 PM
0
0.775
0.47
0
2.875
3:25 PM
0
0.764
0.46
0
2.875
3:30 PM
0
0.890
0.53
0
2.875
3:35 PM
0
0.775
0.47
0
2.875
3:40 PM
0
0.764
0.46
0
2.875
3:45 PM
0.3
0.890
0.53
0
2.875
3:50 PM
1.2
0.851
0.58
1
2.885
3:55 PM
1.3
0.833
0.64
2
2.895
4:00 PM
0.4
0.964
1.07
6
2.935
Water Level (CH0)
Water Level (CH1040)
RL
LSD
RL
cm
m
cm
LSD
m
1.04
-0.0666
13.17
-0.28
2.09
-0.0561
19.62
-0.22
2.61
-0.0509
29.03
-0.13
2.61
-0.0509
37.37
-0.04
3.65
-0.0405
44.89
0.03
1.56
-0.0614
47.58
0.06
4.17
-0.0353
67.74
0.26
2.09
-0.0561
76.34
0.35
3.65
-0.0405
81.18
0.40
5.21
-0.0249
83.06
0.41
2.61
-0.0509
85.48
0.44
4.69
-0.0301
92.20
0.51
4.17
-0.0353
97.31
0.56
4.69
-0.0301
102.15
0.61
4.30
-0.0340
116.13
0.75
3.65
-0.0405
121.24
0.80
4.69
-0.0301
123.92
0.82
112
Time
Rain
Water Level
(CH2607.5)
RL
LSD
Flow
3
mm
m/s
m /s
cm
m
4:05 PM
0.2
1.446
2.35
12
2.995
4:10 PM
0.2
1.477
2.78
15
3.025
4:15 PM
0.2
1.426
3.17
19
3.065
4:20 PM
0.1
1.398
3.11
19
3.065
4:25 PM
0
1.379
2.59
15
3.025
4:30 PM
0
1.235
2.01
12
2.995
4:35 PM
0
1.171
1.70
10
2.975
4:40 PM
0
1.146
1.47
8
2.955
4:45 PM
0
1.053
1.17
6
2.935
4:50 PM
0
1.051
0.90
3
2.905
4:55 PM
0
1.008
0.86
3
2.905
5:00 PM
0
1.148
0.79
1
2.885
5:05 PM
0
1.075
0.65
0
2.875
5:10 PM
0
0.984
0.59
0
2.875
5:15 PM
0
0.968
0.58
0
2.875
5:20 PM
0
0.966
0.58
0
2.875
5:25 PM
0
0.802
0.41
-1
2.865
5:30 PM
0
0.833
0.36
-2
2.855
5:35 PM
0
0.841
0.36
-2
2.855
5:40 PM
0
0.808
0.35
-2
2.855
5:45 PM
0
0.776
0.27
-3
2.845
5:50 PM
0
0.763
0.13
-5
2.825
5:55 PM
0
0.787
0.14
-5
2.825
6:00 PM
0
0.821
0.14
-5
2.825
6:05 PM
0
0.832
0.15
-5
2.825
6:10 PM
0
0.776
0.14
-5
2.825
6:15 PM
0
0.763
0.00
-7
2.805
6:20 PM
0
0.774
0.00
-7
2.805
6:25 PM
0
0.777
0.00
-7
2.805
6:30 PM
0
0.776
-0.19
-7
2.805
Water Level (CH0)
Water Level
(CH1040)
RL
LSD
RL
LSD
cm
m
cm
m
0.52
-0.0718
125.81
0.84
0.52
-0.0718
129.57
0.88
1.04
-0.0666
133.87
0.92
1.56
-0.0614
134.68
0.93
2.09
-0.0561
134.14
0.93
2.61
-0.0509
136.56
0.95
3.65
-0.0405
138.17
0.97
3.65
-0.0405
138.44
0.97
4.69
-0.0301
138.71
0.97
4.17
-0.0353
137.90
0.96
3.65
-0.0405
136.02
0.94
1.56
-0.0614
134.41
0.93
1.56
-0.0614
132.26
0.91
1.56
-0.0614
129.84
0.88
1.56
-0.0614
125.81
0.84
113
Time
Rain
Water Level
(CH2607.5)
RL
LSD
Flow
3
mm
m/s
m /s
cm
m
6:35 PM
0
0.763
0.01
0
2.875
6:40 PM
0.1
0.779
0.01
1
2.885
6:45 PM
0.1
0.798
0.01
1
2.885
6:50 PM
0.1
0.787
0.01
1
2.885
6:55 PM
0.1
0.821
0.56
1
2.885
7:00 PM
0.1
0.832
0.64
2
2.895
7:05 PM
0.1
0.824
0.70
3
2.905
7:10 PM
1.1
0.977
1.00
5
2.925
7:15 PM
1.2
1.055
1.17
6
2.935
7:20 PM
0.7
1.176
2.11
14
3.015
7:25 PM
0.6
1.342
2.98
19
3.065
7:30 PM
1.3
1.320
3.96
28
3.155
7:35 PM
1.1
1.215
3.23
24
3.115
7:40 PM
0.3
1.181
2.53
18
3.055
7:45 PM
0.3
1.329
2.50
15
3.025
7:50 PM
0.3
1.327
2.27
13
3.005
7:55 PM
0.1
1.333
1.94
10
2.975
8:00 PM
0.1
1.161
1.19
5
2.925
8:05 PM
0.1
1.186
1.01
3
2.905
8:10 PM
0.1
1.052
0.81
2
2.895
8:15 PM
0.1
1.059
0.82
2
2.895
8:20 PM
0.4
0.912
0.62
1
2.885
8:25 PM
0.4
0.866
0.59
1
2.885
8:30 PM
0.1
0.808
0.55
1
2.885
8:35 PM
0
0.833
0.57
1
2.885
8:40 PM
0
0.887
0.53
0
2.875
8:45 PM
0
0.796
0.48
0
2.875
8:50 PM
0
0.773
0.46
0
2.875
8:55 PM
0
0.771
0.27
-3
2.845
9:00 PM
0
0.796
0.14
-5
2.825
Water Level (CH0)
Water Level
(CH1040)
RL
LSD
RL
LSD
cm
m
cm
m
1.56
-0.0614
120.16
0.79
1.56
-0.0614
113.44
0.72
1.56
-0.0614
105.91
0.64
6.78
-0.0092
98.39
0.57
7.30
-0.0040
92.74
0.51
2.09
-0.0561
86.02
0.44
2.09
-0.0561
83.33
0.42
2.09
-0.0561
81.18
0.40
2.09
-0.0561
76.88
0.35
1.56
-0.0614
70.97
0.29
3.13
-0.0457
64.78
0.23
1.56
-0.0614
58.33
0.17
1.56
-0.0614
52.69
0.11
1.56
-0.0614
0.00
-0.42
2.09
-0.0561
0.00
-0.42
114
APPENDIX B
Summary of Steady Flow Analysis without Flow.
HEC-RAS Plan: Plan 01 River: Sungai Sengkuang
River
Q
Min
Reach
Sta
Profile
Total
Ch El
(m3/s)
(m)
Straighten 1350 5 ARI
0.01
-0.5
Straighten 1350 20 ARI
0.01
-0.5
Straighten 1350 50 ARI
0.01
-0.5
Straighten 1350 100 ARI
0.01
-0.5
W.S.
Elev
(m)
2.89
2.99
3.06
3.11
E.G.
Elev
(m)
2.89
2.99
3.06
3.11
E.G.
Slope
(m/m)
0
0
0
0
Flow
Area
(m2)
66.5
69.55
71.52
72.94
Top
Width
(m)
29.6
30.2
30.58
30.86
Straighten
1349
Culvert
Straighten
Straighten
Straighten
Straighten
1150
1150
1150
1150
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-0.65
-0.65
-0.65
-0.65
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
70.95
74.09
76.12
77.57
30.47
31.07
31.46
31.73
Straighten
Straighten
Straighten
Straighten
1040
1040
1040
1040
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-0.73
-0.73
-0.73
-0.73
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
73.46
76.66
78.72
80.5
30.96
31.56
31.94
41.11
Straighten
Straighten
Straighten
Straighten
950
950
950
950
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-0.8
-0.8
-0.8
-0.8
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
75.52
78.75
81.31
83.22
31.34
31.95
41.14
42.08
Straighten
Straighten
Straighten
Straighten
750
750
750
750
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-0.94
-0.94
-0.94
-0.94
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
80.52
84.71
87.44
89.4
40.43
41.62
42.37
42.91
Straighten
Straighten
Straighten
Straighten
550
550
550
550
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-1.09
-1.09
-1.09
-1.09
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
86.62
90.9
93.66
95.64
41.51
42.34
42.86
43.24
Straighten
Straighten
Straighten
Straighten
350
350
350
350
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-1.24
-1.24
-1.24
-1.24
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
92.74
97.07
99.86
101.85
42.08
42.72
43.13
43.41
Straighten
Straighten
Straighten
Straighten
167
167
167
167
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-1.39
-1.39
-1.39
-1.39
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
98.9
103.26
106.06
108.06
42.44
42.96
43.29
43.52
Straighten
Straighten
Straighten
Straighten
0
0
0
0
5 ARI
20 ARI
50 ARI
100 ARI
0.01
0.01
0.01
0.01
-1.5
-1.5
-1.5
-1.5
2.89
2.99
3.06
3.11
2.89
2.99
3.06
3.11
0
0
0
0
103.53
107.91
110.72
112.72
42.63
43.09
43.38
43.58
115
APPENDIX C
Summary of Steady Flow Analysis with Flow from Upstream and High Tide From
Downstream.
HEC-RAS Plan: SteadyFlow River: Sungai Sengkuang
River
Q
Min
Reach
Sta
Profile
Total
Ch El
(m3/s)
(m)
Straighten
1350 5 Year ARI
3.79
-0.5
Straighten
1350 20 Year ARI
5.02
-0.5
Straighten
1350 50 Year ARI
5.51
-0.5
Straighten
1350 100 Year ARI
6.16
-0.5
W.S.
Elev
(m)
2.89
3
3.06
3.11
E.G.
Elev
(m)
2.89
3
3.06
3.11
E.G.
Slope
(m/m)
0.000001
0.000001
0.000001
0.000001
Flow
Area
(m2)
66.54
69.62
71.61
73.05
Top
Width
(m)
29.61
30.22
30.6
30.88
Straighten
1349
Culvert
Straighten
Straighten
Straighten
Straighten
1150
1150
1150
1150
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-0.65
-0.65
-0.65
-0.65
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0.000001
0.000001
0.000001
0.000001
70.96
74.11
76.15
77.61
30.48
31.08
31.46
31.74
Straighten
Straighten
Straighten
Straighten
1040
1040
1040
1040
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-0.73
-0.73
-0.73
-0.73
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0.000001
0.000001
0.000001
0.000002
73.48
76.68
78.74
80.53
30.96
31.56
31.95
41.13
Straighten
Straighten
Straighten
Straighten
950
950
950
950
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-0.8
-0.8
-0.8
-0.8
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0.000001
0.000001
0.000001
0.000001
75.53
78.77
81.33
83.26
31.35
31.95
41.15
42.09
Straighten
Straighten
Straighten
Straighten
750
750
750
750
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-0.94
-0.94
-0.94
-0.94
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0.000001
0.000001
0.000001
0.000001
80.53
84.73
87.46
89.42
40.43
41.62
42.38
42.91
Straighten
Straighten
Straighten
Straighten
550
550
550
550
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-1.09
-1.09
-1.09
-1.09
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0
0.000001
0.000001
0.000001
86.62
90.91
93.68
95.66
41.51
42.34
42.87
43.24
Straighten
Straighten
Straighten
Straighten
350
350
350
350
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-1.24
-1.24
-1.24
-1.24
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0
0.000001
0.000001
0.000001
92.75
97.08
99.87
101.86
42.08
42.72
43.13
43.41
Straighten
Straighten
Straighten
Straighten
167
167
167
167
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-1.39
-1.39
-1.39
-1.39
2.89
3
3.06
3.11
2.89
3
3.06
3.11
0
0
0.000001
0.000001
98.9
103.27
106.07
108.06
42.44
42.96
43.29
43.52
Straighten
Straighten
Straighten
Straighten
0
0
0
0
5 Year ARI
20 Year ARI
50 Year ARI
100 Year ARI
3.79
5.02
5.51
6.16
-1.5
-1.5
-1.5
-1.5
2.89
2.99
3.06
3.11
2.89
3
3.06
3.11
0
0
0
0.000001
103.53
107.91
110.72
112.72
42.63
43.09
43.38
43.58