SEDIMENT YIELD ACCUMULATION AT RESERVOIR

(BATANG AI DAM)

Sharifah Azmin Binti Wan Hossen

Bachelor of Engineering with Honours

(Civil Engineering)

2009

UNIVERSITI MALAYSIA SARAWAK

R13a

BORANG PENGESAHAN STATUS TESIS

Judul:

SEDIMENT YIELD ACCUMULATION AT RESERVOIR

(BATANG AI DAM)

SESI PENGAJIAN: 2009/2010

Saya SHARIFAH AZMIN BINTI WAN HOSSEN

(HURUF BESAR)

mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak

dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hakmilik Universiti Malaysia Sarawak.

2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk

tujuan pengajian sahaja.

3. Membuat pendigitan untuk membangunkan Pangkalan Data Kandungan Tempatan.

4. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan tesis ini

sebagai bahan pertukaran antara institusi pengajian tinggi.

5. ** Sila tandakan ( ) di kotak yang berkenaan

SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan

Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/

badan di mana penyelidikan dijalankan).

TIDAK TERHAD

Disahkan oleh

(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat tetap: LOT 353, LORONG

CENDERAWASIH 2, KG. SEMERAH PADI, MDM. NORAZLINA BTE BATENI

Nama Penyelia

93050, KUCHING, SARAWAK.

Tarikh: Tarikh:

CATATAN * Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah, Sarjana dan Sarjana Muda.

** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi

berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai

SULIT dan TERHAD.

The following Final Year Project Report:

Title : SEDIMENT YIELD ACCUMULATION AT RESERVOIR (BATANG AI

DAM)

Name : SHARIFAH AZMIN BINTI WAN HOSSEN

Matric No. : 17227

has been read and approved by:

__________________________________ _____________

MDM. NORAZLINA BTE BATENI Date

Project Supervisor

SEDIMENT YIELD ACCUMULATION AT RESERVOIR

(BATANG AI DAM)

SHARIFAH AZMIN BINTI WAN HOSSEN

A report submitted in partial fulfillment of the requirements

for the awards of the degree of Bachelor Degree with Honours

(Civil Engineering)

2010

Faculty of Engineering

UNIVERSITI MALAYSIA SARAWAK

2010

To my beloved parents, family and friends

iii

ACKNOWLEDGEMENT

Alhamdulillah, first and foremost, thanks to Allah, the most gracious, the most

merciful who has enabled me to complete my Final Year Project. Secondly, a special

thanks to my supervisor, Madam Norazlina Bateni, for her kind help and giving a

valuable suggestion, guidance and continuous encouragement throughout the entire

study. Moreover, I would like to express my grateful appreciation with the guidance and

lessons to me by Dr. Onni Suhaiza who share her opinion and knowledge in completing

this project. Without their continuous support and interest, this project report would have

not been the same as presented here.

My sincere appreciation also extends to Mr. Azhari bin Hj Mokhtar, Station

Manager of Batang Ai Hydro Power Station and Mr Chia Chong Kian, Civil Engineer

from Hydro Power Generation Department, Sarawak Energy Berhad (SESCO) for

providing the data and willingness to give information about this project. Further more, a

special thanks to Mr. Frederick Haili Teck and Mr. Ngab Dollah Sallem, Senior

Research Officer of Soil Management Branch for providing the soil map of Batang Ai

which gives very important information for my project.

Last but not least, it is my pleasure to acknowledge my family and all my friends,

who light up my spirit and always give me a support during the completion this Final

Year Project. Their hope and encouragement had inspired me a lot to finish up this

project.

iv

ABSTRAK

Modified Universal Soil Loss (MUSLE) yang merupakan salah satu teknik ramalan

empirikal telah digunakan untuk menganggarkan kehilangan tanah di kawasan tadahan

empangan Batang Ai. Luas kawasan tadahan adalah kira-kira 1200 km² dan data hujan

telah dianalisa untuk tempoh dua puluh tahun bermula dari 1989 sehingga 2008.

Parameter-parameter untuk persamaan MUSLE seperti faktor kebolehakisan tanah,K

telah dikenalpasti dengan menggunakan peta tanah yang mengandungi penerangan

mengenai klasifikasi kebolehakisan tanah berdasarkan simbol siri yang terdapat pada

peta tersebut. Lagipun, nilai bagi faktor panjang dan kecuraman cerun, LS telah dikira

dari satu titik ke titik yang lain sepanjang takungan Batang Ai. Pekali air larian,C dan

faktor penanaman dan pengurusan, CP diperolehi berdasarkan rujukan dan pemerhatian

di kawasan kajian. Nilai K yang diperolehi adalah 0.438, manakala nilai LS ialah 0.782.

Tambahan lagi, nilai bagi C dan CP masing-masing ialah 0.015 dan 0.010. Nilai

maksimum dan minimum hasil mendapan tahunan yang diperolehi menggunakan kaedah

ini adalah 70, 224 ton setahun dan 42,620 ton setahun. Selain itu, hubungan di antara

hujan dan hasil mendapan yang diperolehi pula adalah y = 17.12x – 320.3 dengan r² =

0.950. Kajian ini adalah penting untuk menggambarkan keadaan hakisan tanah di

kawasan kajian dan memberi idea bahawa hakisan tanah dan hasil mendapan adalah

masalah yang serius dan memerlukan perhatian dari pihak yang bertanggungjawab.

Hasil daripada kajian ini juga boleh digunakan untuk meningkatkan perlaksanaan sistem

pengurusan tanah di kawasan kajian.

v

ABSTRACT

Modified Universal Soil Loss (MUSLE) which is one of the empirical prediction

techniques was used to estimate the annual soil loss at catchment area of Batang Ai dam.

The catchment area is about 1200km² and the rainfall data was analyzed for 20 years

duration which from 1989 until 2008. The MUSLE parameters such as the soil

erodibility factor, K was obtained from the soil map which contains the description of

soil erodibility classification based on the symbol of series on the map. Moreover, the

values of slope length and steepness factor, LS are taken from one point to another point

of Batang Ai reservoir. The runoff coefficient, C and crop management factor, CP based

on the references and determined by visual observation of the study area. The obtained

K value is 0.438 whereas LS value is 0.782. In addition, the value of C and CP is 0.015

and 0.010 respectively. Maximum and minimum annual values of sediment yield

obtained using the method is 70,224 tons per year and 42,620 tons per year. Besides, the

relationship between rainfall and sediment yield obtained was y = 17.12x – 320.3 with r²

= 0.950. This study is important to describe the soil erosion condition of the study area

and give an idea about erosion and sediment yield which is a serious problem that needs

more attention from the responsible party. The result of this study can be used in order to

improve the implementation of the land management system at the study area.

vi

TABLE OF CONTENT

CONTENTS

Acknowledgement

Abstrak

Abstract

Table of Contents

List of Tables

List of Figures

List of Abbreviations

List of Symbols

List of Appendix

PAGES

iii

iv

v

vi

x

xi

xii

xiii

xiv

Chapter 1 INTRODUCTION

1.1 General 1

1.2 Problem of Statement 5

1.3 Objective 7

1.4 Study Area 8

1.5 Scope of Study 10

Chapter 2 LITERATURE REVIEW 12

2.1 Introduction 12

2.2 Soil Erosion 14

2.3 Water Erosion 16

vii

2.3.1 Splash Erosion 16

2.3.2 Sheet Erosion 17

2.3.3 Rill Erosion 18

2.3.4 Gully Erosion 20

2.3.5 Stream Channel Erosion 21

2.3.6 Tunnel Erosion 21

2.4 Wind Erosion 22

2.5 Mass Movement 24

2.6 Factors of Erosion 25

2.6.1 Climate 26

2.6.2 Vegetation Cover 27

2.6.3 Characteristic of Soil 29

2.6.4 Slope Steepness and Slope Length 32

2.7 Effects of Sediment 33

2.8 Modified Universal Soil Loss Equation (MUSLE) 35

2.9 Sediment 36

2.10 Sediment Transportation 39

2.11 Sediment Yield 40

2.12 Reducing Sediment Inflow Method 42

2.13 Previous Research 44

2.13.1 Application of MUSLE in Prediction of Sediment

Yield in Iranian Conditions, 2004

44

2.13.2 Sediment Yield Estimation from a Hydrographic 48

viii

survey: A case study for the Kremasta Reservoir

Basin, Greece, 2001.

2.13.3 Sediment Yield Modelling of an Agricultural

Watershed using MUSLE, Remote Sensing and

GIS,2009

53

Chapter 3

METHODOLOGY

57

3.1 Introduction 57

3.2 Modified Universal Soil Loss Equation (MUSLE) 58

3.3 Storm Runoff Volume, Q 59

3.3.1 Runoff Coefficient, C 59

3.3.2 Watershed Area, A 60

3.4 Peak Runoff Rate,qp 60

3.5 Soil Erodibility Factor, K 61

3.6 Slope Length and Steepness or Gradient Factor, LS 66

3.7 Assumption of Cover and Management Factor, CP 67

Chapter 4

3.8 Procedure of Implementation of MUSLE Flowchart

RESULTS, ANALYSIS AND DISCUSSIONS

69

70

4.1 Input Data (Data Collection) 70

4.1.1 Annual Rainfall data and Catchment Area value 71

4.1.2 Runoff Coefficient, Cover and Management Factor 71

4.1.3 Soil Erodibility factor and Soil Map 72

ix

4.1.4 Slope Length and Steepness Factor 73

4.2 Output Data 75

4.2.1 Rainfall 75

4.2.2 Peak Runoff Rate 77

4.3 MUSLE Output data 85

Chapter 5 CONCLUSION 90

5.1 Introduction 90

5.3 Recommendation 92

REFERENCES

93

APPENDIX

96

x

LIST OF TABLES

TABLE DESCRIPTIONS PAGE

2.1 Major Impacts of Soil Erosion Failures 34

2.2 Types of Sediments 37

2.3 Some of the Geometric Factors of the

Amameh Catchment

45

3.1 Soil Structure 63

3.2 Soil Permeability 63

3.3 Soil Erodibility Classification 65

3.4 Exdponential m-value Associated with Slope

Gradient

66

3.5 Value of CP 67

4.1 MUSLE Parameters 74

4.2

4.3

Annual Rainfall

Peak Runoff Rate

78

80

4.4 Mean Rainfall (1989-2008) 82

xi

LIST OF FIGURES

FIGURE DESCRIPTIONS PAGE

1.1 Typical Reservoir 5

1.2 Batang Ai Dam 10

2.1 Fluvial Systems with Dam and Reservoir 41

3.1 Soil Erodibility Nomograph 62

3.2 Procedure of the Implementation of MUSLE 69

4.1 Monthly Rainfall (1989-2008) 76

4.2 Peak Runoff Rate (1989-2008) 77

4.3 Annual Rainfall 79

4.4 Annual Peak Runoff Rate 81

4.5 Mean Rainfall 83

4.6 Sediment Yield (tons per event) 1989-2008 85

4.7 Sediment Yield (1989-2008) 86

4.8 Relative Frequency for Sediment (tons per

event)

88

4.6 Rainfall against Sediment Yield 89

xii

LIST OF ABBREAVIATIONS

cm centimeters

CP Crop and Management Factor

GIS Geographic Information System

ha hacters

km kilometers

km² square kilometers

km³ cubic kilometers

m meters

mg milligram

mm millimeters

m³/s meter cube per second

MOL Minimum Operating Level

SESCO Sarawak Electricity Supply Corporation

RS Remote Sensing

ton tones

xiii

LIST OF SYMBOLS

ºC Celcius

C Runoff of Coefficient

E East

N North

S South

xiv

LIST OF APPENDIX

APPENDIX DESCRIPTIONS PAGE

A Catchment Area Map of Batang Ai dam 96

B Analysis of Sediment Yield Accumulation at

Batang Ai dam

98

C Soil Map of Ulu Ai 108

D Description of Soil Map 110

1

CHAPTER 1

INTRODUCTION

1.1 General

Reservoir storage is necessary to use the highly variable water resources of a

river basin for beneficial purpose such as municipal and industrial water supply,

irrigation, hydroelectric power generation, and navigation. Dam and appurtenant

structures also regulate rivers to reduce damages caused by floods. Public recreation,

water quality, erosion and sedimentation, and protection and enhancement of fauna and

other environmental resources are important considerations in management of reservoir

systems.

2

It is important to view the reservoir as a part of a river in order to appreciate the

influence of reservoir sedimentation on the environment. This is because before the

existence of a reservoir, the rivers use to attain stability condition. Construction of a

reservoir disturbs the normal flow pattern and sediment is deposited in the reservoir

basin, in an attempt to restore the original progress that has been made towards

stability.

In the construction of dam and reservoir, the stream equilibrium will always

interferes by modifying stream flow and consequently, the sediment transport capacity

of the stream. Sedimentation occurs in reservoirs when the eroded sediment is

transported down the river system into the reservoir. The efficiency of the transport

process is expressed by the sediment delivery ratio, which is the proportion of sediment

eroded from the land that is discharged into rivers (Morgan and Davidson, 1986). All

reservoir are subjected to some degree of sedimentation (sediment deposition), and

eventually all reservoirs will fill with sediments. Some will fill faster than other,

depending primarily on sediment yield of the tributary drainage basin, transport

capability of the stream, and the size of the reservoir.

Sediment is derived from the erosion (wearing away) of the land surface by

natural forces which are water, wind, ice and gravity. Sediment transported by streams is

derived from the scour and erosion of the streambed and banks as well as from erosion

of the land surface and rill of the drainage basin. Sediment yield varies with land slope,

3

land use, vegetative cover, soil type, amount and type of precipitation, climate factors

and nature of the catchment area. Natural erosion rates are accelerated by human

activities, including deforestation, urbanization, farming, grazing and channelization of

streams. Moreover, estimation of sediment yield has therefore become of great

importance, especially when sediment is capable of seriously reduce the capacity of

reservoirs (Amore et al., 2004).

Reservoir storage capacity is lost over time due to the sedimentation. Depending

on flow rate and sediments load in the river flowing the reservoir, the rate of

sedimentation deposition various tremendously between reservoir sites. Many reservoirs

are subject to some degree of sediment inflow and deposition. It is estimated that some

0.5% - 1% of the world reservoir volume is lost from sedimentation annually (Mahmood

et al., 1987). Moreover, reservoir sedimentation also varies greatly over time with the

random occurrence of floods since sediment transport increases greatly during flood

events.

The most critical problem associated with sediment is depletion of reservoir

storage due to deposition in the reservoir. Depletion of reservoir storage capacity that

occurred more rapidly than projected or is greater than projected is a very serious

consideration in estimating project benefits. For examples, if conservation storage is

4

significantly decreased over the first 20 years of project operation rather than as

projected near the end of the 100 years project life, average annual yield will be

decreased and future benefits will be less than projected with the full conservation

storage available.

Streams transport sediments as both suspended and bed load. Where a river flows

into a large body of water, such as a reservoir, the water depth and cross-sectional area

increase and stream velocity decrease rather rapidly, thus reducing the sediment

transport capacity of the stream and resulting in deposition of sediment in the

headwaters of the reservoir. With time, some of the fine deposits move down through

the reservoir and deposit against the dam, and some are flushed through the system.

Typical deposition pattern are shown in Figure 1.1.

5

Figure 1.1: Typical Reservoir

1.2 Problem of statement

This study is conducted to estimate the sediments yield by analyzing sediment

that accumulated in existing reservoir which is Batang Ai dam. One of the problems that

always occur at reservoir is accumulation of sediment which cause by soil erosion

processes.

Soil erosion is the detachment and transportation of the soil. Uncontrolled

deforestation, forest fires, grazing, improper method of tillage, and unwise agricultural

and land use practices accelerate soil erosion resulting in a large increase of sediment

inflow into streams. The deposition of sediment in channels or reservoir creates a variety

6

of problems, such as raising of stream beds, increasing flood heights, choking of

navigation channels and, of course, depletion of capacity in storage reservoirs. Other

than that, it may carry pollutants into water systems and cause significant water quality

problems. In addition, the total quantity of sediment transported annually to the sea by

rivers of the world is about 2 x 1010

tons or about 13.5 km3

in terms of volume (Alma et

al., 2001). Assuming that all this sediment enters into the reservoirs of the world, it

would take about 481 years to fill up the estimated 6500 km3

of the storage volume

available.

In addition, Malaysia faces the reservoir sedimentation problem, for example,

from Reservoir Sedimentation journal of Sultan Abu Bakar dam which is situated at

Cameron Highland, Pahang (Choy and Hamzah, 1997). Since the early 1970s, mitigation

measures for sedimentation have been carried out periodically at various locations in the

Cameron Highlands Scheme to minimize its impact on the operation and maintenance of

the five hydro stations (Goh and Hamzah, 1997). These measures include construction

of a silt retention weir, pumping of sediment, and de-silting of tunnels, and have

successfully reduced sediment inflow into the reservoir.

Other than that, according to journal of Bed Load Transport from a Regenerated

Forest Catchment in Sarawak by Geoffery James Gerusu and Zulkifli Yusop, they were

declared that because of the large scale forest and land clearing operation especially in

the seventies had accelerated erosion and sedimentation rate in Malaysia and led to

7

dramatic increases in sediment loads of major rivers. For example Klang River and Pari

River recorded sediment load exceeded 5000 t/km²/yr (Leong, 1989). Until now, river

sedimentation associated with agricultural and construction activities remain a major

challenge in river management. While considerable number of studies has measured

suspended sediment load (Douglas, 1968; Burgess, 1971) very few include the bedload

portion. As such the scale of sedimentation problem might be underestimated.

1.3 Objective

The main objectives of this study are as follow:-

i) To investigate the sediment yield accumulation in a Batang Ai reservoir site.

ii) To determine accumulation rate of sediment at Batang Ai dam.

iii) To apply the MUSLE equation for sediment yield accumulation at Batang Ai

dam.