PERPUSTAKAAN UMP

P I I 1 ^ 0000092726

A STUDY ON THE CHARACTERISTIC AND PERFORMANCE

OF CASCADE DRAIN IN MALAYSIA

SITI NUR AFFIZZA B1NTI MD YUSIJF

AAO8 145

A thesis submitted in fulfilment of the requirements for the award of the degree of

Bachelor of Civil Engineering

Faculty of Civil Engineering & Earth Resources

University Malaysia Pahang

JANUARY 2013

ABSTRACT

Cascade drain is one of the hydraulic structures that are widely used in slope

condition area. The functions of cascade drain are to control and convey flows from

surface runoff at upstream to downstream. The advantages of cascade drain are the

simple, economic and rapid construction procedure plus the aforementioned

economic savings. The aims of this study are to study the characteristic and

performance of cascade drain for the working and the behaviour. There were three

different types of cascade drain which are horizontal step, end sills step and inclined

step. The dimensions of every cascade drain are recorded. The discharge values were

calculated using Rational Method and been compared with the Manning's Equation.

The drop length of water while raining was recorded and the Froude number were

calculated to determine the hydraulic jump. From the comparison among three

different types of cascade drain, the most sufficient cascade drain with the best jump

is the horizontal step cascade drain. Horizontal step cascade drain provided a short

length for each step that influence the distance ofjump;

vi

ABSTRAK

Longkang lata adalah salah satu danpada struktur hidraulik yang digunakan secara

meluas di kawasan berbentuk cerun. Fungsi lonkang lata adalah untuk mengawal

dan memastikan aliran di permukaan hulu mengalir ke hilir dalam aliran yang

terkawal. Kelebihan longkang lata adalah mudah dilaksanakan. Prosedur

pembinaannya yang jimat dan memberikan penjimatan ekonom. Matlamat kajian mi

adalah untuk mengkaji ciri-ciri dan prestasi longkang lata untuk kegunaan dan

sifatnya. Terdapat tiga jenis longkang lata iaitu jenis rata melintang, panjang dan

condong. Dimensi setiap longkang lata direkodkan. Nilai pelepasan telah dikira

menggunakan Kaedah Rasional dan telah dibandingkan dengan Persamaan Manning.

Panjang air yang jatuh antara satu anak mata longkang ketika hujan dicatatkan dan

nombor Froude telah dikira untuk menentukan lompatan hidraulik. Dan

perbandingan diantara ketiga-tiga jenis longkang lata, longkang lata jenis rata

melintang paling mencukupi sifat sebagai longkang lata yang sesuai di Malaysia

dengan lompatan hidraulik yang terbaik. Kepanjangan langkah mendatar longkang

lata adalah pendek untuk setiap langkah dan mi mempengaruhi jarak lompatan.

vii

TABLES OF CONTENTS

CHAPTER TITLE PAGE

TITLE PAGE i

SUPERVISOR'S DECLARATION

STUDENT'S DECLARATION

DEDICATIONS iv

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xiv

LIST OF APPENDICES xv

INTRODUCTION

1.1 Introduction 1

1.2 Problem Statement I

1.3 Objectives 2

1.4 Scope of Study 3

2 LITERATURE REVIEW

2.1 Introduction 5

2.2 Cascade drain 5

2.2.1 Functions 6

2.2.2 Types of Cascade drain 6

2.2.2.1 Horizontal steps 7

vi"

ix

2.2.2.2 Inclined steps 8

2.2.2.3 Steps with End Sills 8

2.2.3 Design Considerations 9

2.2.4 The Advantages of Cascade drain 10

2.3 Flows in Cascade drain 12

2.4 The Hydraulic Jump 13

2.4.1 Types of Hydraulic Jump 14

2.4.2 The Analysis of Hydraulic jump 18

2.4.3 Equations for hydraulic jump 19

2.4.4 The Depth of Jump 20

2.5 Calculation for Discharge 20

2.5.1 Coefficient of Runoff 21

2.5.2 Time of Concentration 22

2.5.2.1 Kerby-Kirpich Method 23

2.5.3 Intensity of Rainfall 24

2.5.3.1 Polynomial Approximation of IDF 24

Curves

2.5.3.2 Design storms - average 24

Recurrence interval

2.5.4 Adequacy of Drains 26

3 METHODOLOGY

3.1 Introduction 27

3.2 Flows Chart of the Study 27

3.3 Study Area 29

3.4 Labelling 35

3.5 Data Collection 35

4 RESULTS AND ANALYSIS

4.1 Introduction 37

4.2 Analysis of Data 37

4.2.1 Dimensional Analysis 37

4.2.1.1 Cascade drain type A: Horizontal 37

Step

4.2.1.2 Cascade drain type B: End sills 40

Step

4.2.1.3 Cascade drain type C: Inclined 43

Step

4.2.2 Discharge of runoff 45

4.2.3 Hydraulic Jump 50

5 CONCLUSION & RECOMMENDATIONS

5.1 Introduction 54

5.2 Conclusions 54

5.3 Recommendations 56

REFERENCES

57

APPENDICES 63

x

LIST OF TABLES

TABLE NO. TITLE PAGE

Table 2.1: The Types of Hydraulic Jump 15

Table 2.2: Rational Method Runoff Coefficients 22

Table 2.3: Recommended design average recurrence intervals 25

Table 4.1 : Value of actual discharge, Q using the rational method 48

Table 4.2: Value of theoretical discharge, Q using Manning's 49

equation

Table 4.3: Comparison between actual and theoretical discharge, Q 49

Table 4.4: The values of upstream and downstream depth for each 50

cascade drain.

Table 4.5: The Froude number for every cascade drain 52

Table 4.6: The description of Froude number 52

xi

LIST OF FIGURES

xli

PAGE

7

7

8

6

10

FIGURES NO. TITLE

Figure 2.1: The types of cascade drain (a) Horizontal Steps, (b)

Inclined Steps and (c) End Sills steps

Figure 2.2: The horizontal steps

Figure 2.3: The inclined steps

Figure 2.4: The End Sill steps

Figure 2.5: Standard design of cascade drain. (Public Work

Department, 2000)

Figure 2.6: Sketch of hydraulic jump

Figure 2.7: The Figure of Hydraulic Jump

Figure, 2.8: Nomograph for Estimating Overland Sheet Flow

Times

Figure 3.1: The Flow Chart of project

Figure 3.2: Case Study 1 - Kuantan RC 0.0 km Lebuhraya Pantai

Timur (LPT) Kuantan-Gambang

Figure 3.3: Location of Case Study 1

Figure 3.4: Case Study 2- 1.2 Km from roundabout Taman Desa

Aspa (FR 14)

Figure 3.5: Location of Case Study 1

Figure 3.6: Case Study 3 - Km 232.4 Lebuhraya Pantai Timur

(LPT) Kuantan-Gambang

Figure 3.7: Location of Case Study 3

Figure 3.8: Case Study 4— I3atu 12, Kuantan-Gambang Road in

front of Binaan Desjaya Sdn. Bhd

Figure 3.9: Location of Case Study 4

Figure 3.10: Case Study 5 - 9 Km from . Kuantan-Kemaman

Bypass Junction Gambang-Kuantan Road (FR03)

14

16

23

28

29

30

30

31

32

32

33

33

34

xl"

Figure 3.11: Location of Case Study 5 34

Figure 3.12: Measuring the length of end sills cascade drain 35

Figure 3.13: Mesuring a depth of water at horizontal step cascade 36

dram

Figure 3.14: Upstream and downstream depth of horizontal step 36

cascade drain

Figure 4.1: The actual cascade drain A 1 38

Figure 4.2: The 3-Dimension of cascade drain A, 38

Figure 4.3: The actual cascade drain A 2 39

Figure 4.4: The 3-Dimension of cascade drain A2 39

Figure 4.5: The actual cascade drain B 1 40

Figure 4.6: The 3-dimensional view of actual cascade drain B, 41

Figure 4.7: The 2-dimensional right view of actual cascade drain 41

B,

Figure 4.8: The actual cascade drain B 2 42

Figure 4.9: The 3-dimensional view of actual cascade drain B2 42

Figure 4.10: The 2-dimensional right view of actual cascade drain 43

B,

Figure 4.11: The actual cascade drain C, 44

Figure 4.12: The 3-Dimension of cascade drain C 1 44

LIST OF SYMBOLS

SYMBOLS TITLE

LPT: Lebuhraya Pantai Timur

FR: Federal Road

FRL: Finished road level

MSMA: Urban Stormwater Management Manual for Malaysia

RCC: Roller compacted concrete

Fr: Froude number

Time of concentration

m3/s: Meter cube per second

m: Meter

cm: Centimetre

SWD: Storm Water Drainage

mm/br: Millimetre per hour M2: Meter square

xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

Appendix A Plan of horizontal step cascade drain 63

Appendix B Plan of end sills step cascade drain 64

Appendix C Plan of inclined step cascade drain 65

xv

CHAPTER 1

INTRODUCTION

1.1 Introduction

Generally, the cascade drain is formerly used in the dam structure as the

stepped spillway. Then, the cascade drain design is developed and widely used in

other hydraulic design. The cascade drain consists of a series of steps or drops that

built into the spillway. The cascade drain is widely used at the slope areas which

have the different level and height of soil. This situation allows the water flow from

upstream to downstream. This is especially true at road constructed in sloping area in

order to manage and divert the natural flow of water.

Basically, cascade drain can be classified as the spillway type because it has

similar function. The main function of the cascade drain is to manage and control the

flow of water on the earth surface from upstream to the downstream area. It

effectiveness can be visualised during rainy day. The water from the precipitation

process will flow in the cascading drain at a specific flow rate. This depends on the

precipitation rate which is the rainfall and the area of cascade drain. In addition, the

flow in the cascade drain allows the hydraulic jump, an abrupt change in depthfrom

supercritical to subcritical flow.

1.2 Problems Statement

1

The cascade drain is used to manage the flow of water approximately from

upstream to downstream area. The cascade drain is fully function at when the

FA

precipitation process occurs which is during the raining day. The main problems

usually happen when the cascade drain cannot handle the high volume and flow rate

of the water from the heavy rain. The heavy rain increase the flow rate of water in

the cascade drain and thus, creating uncontrolled flow. Theoretically, the flow must

follow the steps without surpasses. This high flow rate will eventually affect the

hydraulic jump performance and increase the distance of the hydraulic jump in the

cascade drain. The uncontrolled distance of hydraulic jump can surpass the flow over

the steps.

In addition, the flood will occur when the flow is not contained within the

cascade drain structure. The uncontrolled flow will decrease the ability of cascade

drain to flow the water smoothly and decrease the storm water management system

function. The storm water management is constructed beyond the structure in order

to convey the flow downstream to the river. This over flow can disturb the road user.

The water will splash to the finished road level (FRL) near the road side and creates

water ponding. This water ponding is a non cohesive area that will reduce the friction

of tyres on the road and make the vehicle becomes difficult to handle. These

phenomena can cause accident to road user when driving in a high speed.

Hence, it is essential to ensure the design of cascade drain in Malaysia is

follow the specification to avoid the cascade drain become uncontrolled and over

flow that can make a flood. This study will identify the problems that occur at the

cascading drain structure. It will also increase the road ability and road user safety.

1.3 Objectives

The objectives of this study are:

i. To determine the existing design and characteristics of cascade drain

in Malaysia.

3

ii. To determine the suitable types of cascade drain to be used in

Malaysia.

1.4 Scope of Study

The case studies of the project were selected from five different locations at

the Kuantan district in Pahang state due to its convenience and easy access. The

comparisons among the three different types of cascading drain at these six locations

were taken in order to study their different performances.

The five locations of case study are:

. Cascade drain type A: Horizontal Step

Case Study 1- Kuantan RC 0.0 km Lebuhraya Pantai Timur (LPT) Kuantan-

Gambang

Case Study 2- 1.2 Km from roundabout Tainan Desa Aspa (FR 14)

• Cascade drain type B: End sills Step'

Case Study 3—Km 232.4 Lebuhraya Pantai Timur (LPT) Kuantan-Gambang

Case Study 4— Batu 12, Kuantan-Gambang Road in front of Binaan

Desjaya Sdn. Bhd

. Cascade drain type C: Inclined Step

Case Study 5-9 Km from Kuantan-Kemaman Bypass junction at Gambang-

Kuantan Road (FR03)

The surface runoff discharge were determine using the rational method while

the drop length of cascading drain were calculated using drop length function that

stated in Urban Stormwater Management Manual for Malaysia (MSMA, 2000).

The implementation of the study is to ensure that the jump is within the

allowable distance in order to avoid surpassed. The allowable distance of jump

4

reduced the water flow rate and work as the energy dissipater for the cascade drain.

Moreover, it will control and manage the flow within the cascading area from

upstream to downstream.

Besides that, the allowable distance will help to control the flood phenomena

at the road side. The uncontrolled flow of water on the road is very dangerous and

can cause an accident. Thus the cascade drains were built to control the flow and

reduce the accident on the road downstream.

This study will enhance the development of the cascade drain structure in

highway and other hydraulic design in the construction field.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Cascade dram is one of the hydraulic structures that commonly used to

control the flow from upstream to downstream in a drainage system. Cascade drain is

a drainage that consists of series of steps and can be in any shape. The existing of

steps can contribute to a substantial flow resistance and the place where energy

dissipation happen form drag process. The flow acceleration and boundary layer on

the stepped also can affect the flow properties significantly (Peruginelli , 2000)

Open channel flow occurs when there is a free surface that exposed to

atmospheric pressure (Larry, 2005). Open channel flow assumes that the pressure at

the surface is constant and the hydraulic grade line is at the surface of the fluid.

Examples of open channel flow include streams, rivers and culverts not flowing full.

It is difficult to solve the problem from open channel because the flow conditions are

complicated by the position of the free surface which will change with time and

surface. Open channel can be in any shape (Blair, 1990).

2.2 Cascade drain

The cascade drain was formerly introduced as the stepped spillway that

commonly use at the dam structure. Then, the stepped concept has been developed

and widely use in many hydraulic design because it can function to discharge the

5

water flow and works as the energy dissipater. An interesting feature of the

6

cascading dram is a series of steps or drops system which is flexibility by allowing

differential settlements of the embankment (Chanson, 2002).

2.2.1 Functions

Generally, the function of the cascade dram is to control and manage the flow

of water from the precipitation process. The cascade drain is fully functioning during

the precipitation process where any form of water such as rain that falls from the sky

to the earth surface. The water that fall to the ground surface will be channeled and

controlled by the cascade drain from the upstream to downstream. This phenomenon

usually occurs at the slope conditions where the different heights of soils are

observed.

The other function of cascade drain is to discharge the water flow over dams

or steep slopes and works as the energy dissipater. The steps produce considerable

energy dissipation along the chute and reduce the size of the required downstream

energy dissipation basin The main influencing factors for the energy dissipation

ratio in stepped spillways are unit discharge, slope condition and height of step. The

energy dissipation ratio decreases with the increase in the unit discharge and

increases as the slope becomes gentle.

2.2.2 Types of Cascade drain

Basically, the cascade drain was constructed with series of steps into the

drain. The area on to which the water falls from each step is built to resist the force

of the falling water. Cascade drains are practical if the slope exceeds 30%, but

otherwise they become too expensive. There are various types of stepped chutes

which were horizontal steps, inclined steps, and steps with end sills and were show in

Figure 2.1.

Figure 2.1 : The types of cascade drain. (a) Horizontal Steps, (b) Inclined

Steps and (c) End Sills steps

7

(a) (c)

h= height

2.2.2.1 Horizontal steps

The horizontal steps drain were used to slow down the flow of water from the

upstream before the flow reach the downstream area. This type of drain was built at

the steep slope with the specific degree. The advantages of this drain are very easy to

construct and economical. The cross section of horizontal cascade drain was depicted

in Figure 2.2 where h is the height of step (Barani, et. a!, 2000).

Figure 2.2 : The horizontal steps

8

2.21.2 Inclined steps

The structures of step are all the same but the additional structure in shape of

triangular was placed • on top of the steps. The water flow from upstream will

experience the inclined situation on the first step before flow to the next step and

continuous flowing to the downstream area. This extra structure provided an extra

height of step and will influence the discharge of water (Chinnarasri, et. al, 2004).

Figure 2.3 shows the examples of inclined, h is height of step.

Figure 2.3 The inclined steps

2.2.2.3 Steps with End Sills

The characteristic of steps with end sills is the additional of rectangular

structure on top of each step provided. Those rectangular were function as the weir

for the cascade drain by reducing the flow of water. The advantage of this step is it

can prevent scouring of the channel bottom. The example of end sill step drain was

shown in Figure 2.4 (Chaturabul, et. al, 2000).

Figure 2.4: The End Sill steps

.s.

9

The steps with end sills seem to be the most efficient configuration in terms

of relative energy dissipation. The effect of number of steps is evident since the

relative energy loss increases with the number of steps. In addition, new correlations

showing the relation between relative energy loss and relative critical flow depth are

proposed for practical applications.

2.2.3 Design Considerations

There are several considerations that should be included in designing

cascading drain and stilling basins.

i. Surface Runoff

The high precipitation will cause a rise in the upstream water surface. The

available of surface runoff will depend on the topography and rainfall at the

area. The runoff will flow to the cascade drain which utilize all of the

available runoff and create the design discharge, since the discharge increase

with the value of intensity from the rainfall and surface runoff.

ii. The Hydraulic jump

There are three positions or alternative patterns that allow a hydraulic jump to

form downstream of the transition in the channel. These positions are

controlled by tail water (MSMA, 2000).

70 235

ROA IDE 1RAfI/ IDE DR.PIN

LZI

10

For design purposes in roadside channels, hydraulic conditions are usually

assumed to be uniform and steady. This means that the energy slope is approximately

equal to average ditch slope, and that the flow rate changes gradually over time. This

allows the flow conditions to be estimated using a flow resistance equation to

determine the so-called normal flow depth.

The standard design of cascade drain in Malaysia with the dimension was

shown in Figure 2.5.

Figure 2.5: Standard design of cascade drain. (Public Work Department, 2000)

IN1RCPTOR MAiN

URS O 7 S0iJR 150

11SH A142 - '-

_Gtr?FALL DRAN 50 i. coc.—'

TYPE 0D2BLNG

S0ARE MESH A142

2.2.4 The Advantages of Cascade drain

In hydraulic engineering the energy dissipation capacity of spillways and

energy dissipaters is a key element to minimize the erosion potential of the flow

downstream of a dam and thus to ensure its stability against failure during floods.

11

Stepped spillways allow to continuously dissipating a considerable amount of

the kinetic energy such that the downstream stilling basin where the residual energy

is dissipated by hydraulic jump can be largely reduced in dimension compared to a

basin at the toe of a conventional smooth chute.

Also, the cavitations risk along the spillway decreases significantly due to

smaller flow velocities and the large air entrainment rate. Stepped spillways or

cascades are thus a combination of spillway chute and energy dissipater.

They are preferably applied for dam spillways or combined sewer systems for

the safe discharge of water , over large drops. Basically, the cascade drain is often

combined with the spillway of the dam. They are also used in parks and are suitable

to the type of river course design improving natural surroundings.

The cascade drain will flow the water from level to level and the optimal

dissipation is expected if a hydraulic jump occur. The skimming flow occurs for

steeper stepped chutes and large discharges in which the step acts as roughness

element and causes a strong mixing of the water with air.

Stepped spillways have regained popularity over the last two decades thanks

to financial benefits resulting mainly from:

1. The simple, economic and rapid construction procedure, especially with the

roller compacted concrete (RCC) construction method.

2. The aforementioned economic savings with the downstream energy dissipater

due to the high amount of energy dissipation along the chute.

The roller compacted concrete (RCC) placement in layers enables a

simultaneous and thus economic construction of the spillway steps on the

downstream dam face. Mother common application is the use of stepped overlays on

the downstream face of hydraulically unsafe embankment dams as emergency

spillways to safely pass a flood over the crest of the dam (Michael et. a!, 2005).

12

The macro-roughness of the steps significantly reduces flow velocities and

leads to flow aeration along the spillway. In contrast to conventional smooth

spillways the cavitations risk is therefore markedly reduced.

2.3 Flows in Cascade drain

For design purposes in roadside channels, hydraulic conditions are usually

assumed to be uniform and steady. This means that the energy slope is approximately

equal to average ditch slope, and that the flow rate changes gradually over time. This

allows the flow conditions to be estimated using a flow resistance equation to

determine the so-called normal flow depth (Mays, 2005)..

Flow conditions can be either mild (subcritical) or steep (supercritical).

Supercritical flow may create surface waves whose height approaches the depth of

flow. For very steep channel gradients, the flow may splash and surge in a violent

manner and special considerations for freeboard are required.

More technically, open-channel flow can be classified according to three

general conditions:

• Uniform or non-uniform flow

• Steady or unsteady flow

Subcritical or supercritical flow

In uniform flow, the depth and discharge remain constant along the channel.

In steady flow, no change in discharge occurs over time. Most natural flows are

unsteady and are described by runoff hydrographs. It can be assumed in most cases

that the flow will vary gradually and can be described as steady, uniform flow for

short periods of time.

Subcritical flow is distinguished from supercritical flow by a dimensionless

number called the Froude number (Fr), which is defined as the ratio of inertial forces

to gravitational forces in the system. Subcritical flow (Fr < 1.0) is characterized as

13

tranquil and has deeper, slower velocity flow. In a small channel, subcritical flow can

be observed when a shallow wave moves in both the upstream and downstream

direction.

Supercritical flow (Fr> 1.0) is characterized as rapid and has shallow, high

velocity flow. At critical and supercritical flow, a shallow wave only moves in the

downstream direction (Morris, 2009).

2.4 The Hydraulic Jump

Generally, the hydraulic jump can be defined as an abrupt change in depth

from supercritical to sub-critical flow and accompanied by a significant energy loss.

Usually, a hydraulic jump primarily serves as an energy dissipater to dissipate the

excess energy of flowing water downstream of hydraulic structures such as spillway,

cascading drain and sluice gate.

The rapidly flowing liquid expands which in an open channel appears as an

increase in elevation that converting some of the initial kinetic energy of flow into a

lower kinetic energy and an increasing of potential energy and the remainder to

irreversible losses. Moreover, this phenomenon dependent on the initial fluid speed

and if the initial fluid speed is below the critical speed then no jump is possible.

For relatively low initial flow speed which is above the critical speed an

undulating wave appears. When the flow speed increases further the transition grows

more abrupt and at high enough speeds the front will break and curl back upon itself.

This rise can be accompanied by violent turbulence, eddying, air entrainment and

surface undulations.

The Figure 2.6 below shows how the hydraulic jump occurs. The existing of

hydraulic jump will decrease the flow rate of the water. Next, hydraulic jump can

works to recover head or raise the water level on the downstream side of a measuring