SEDIMENTATION IN SUNGAI SARAWAK : POSTBARRAGE In Sungai Sarawak ; Post...  akan meninggikan paras

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.' Chai Su Boon .

Master of Environmental Science

(Land Use and Water Resource Management)


Pusat Khidmat Maklumat Akademik



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A thesis submitted

In partial fulfilment of the requirements for the degree of

Masters ofEnvironmental Science (Sustainable Land use and Water

Resource Management)


-Faculty ofResource Science and Technology

Universiti Malaysia Sarawak



I am greatly indebted to my thesis supervisor, Associate Professor Dr. Lau

Seng for his kind advice and guidance throughout the course of thls study.

His comments have been of great help every time, guiding me through the

process of finishing this thesis. My gratitude also goes to all the lecturers

that have been involved in this programme leading up to this final module

for channelling their knowledge in a thoughtful and passionate manner. I

would also like to thank all the parties which have contributed to this

study whether information wise or through moral support. Thank you to

Kuching Barrage Management Sdn. Bhd., The Sarawak Marine

Department and The Sarawak Rivers Board just to name a few.

This dissertation is dedicated to my family, friends and course mates

whose example and aspirations in life will be with me always.

Chai SuBoon (2006)


Pusat Khidmat Maklumat Akademil< UNlVERSm MALAYSIA SARAWAK

Table of Contents


Acknowledgement 11

Table of Contents ill

List of Figures -Vll

Abstract lX

List of Tables vi

Abstrak x

Chapter 1 -Introduction 1

Hypothesis 10

Study Objective 10

-Chapter 2 - Literature Review 11

2.1 Sediment Transport and Deposition 11

2.2 Barrage 13

2.3 Turbidity 15

2.4 Total Suspended Solids 16

2.5 Impacts of Barrages and Dams from a Sedimentation

-Perspective 17


2;6 Summary - Sungai SarawakEnvironmental Control and River

Management Study: Sedimentation Study 20

Chapter 3 - Methodology 2-9

3.1 Study Area 29

3.2 Barrage Operation 29

3.3 -Riverbed Survey Data 31

3.4 Water Quality Data 32

3.5 Data Analysis 34

Chapter 4 - Results and Discussion 37

4.1 Sungai Sarawak Regulation Scheme 37

4.2 Barrage Operation 37

4.2.1 -Intended-Operation Approach 37

4.2.2 Present Operation Approach 39

4.2.3 Classification of Barrage Gate Operation 44

4.3 Riverbed Survey Data 47

4.3.1 Cross-section Profile Comparison 47

4.3.2 Longitudinal Profile Comparison 50,

4.4 Water Quality Data 54


544.4.1 Cross-section Profile Comparison

564.4.2 Water Quality Comparison


59Chapter 5 - Conclusion


Appendix 63


List of Tables

Table 2.1 - Simulated Trap Efficiency

Table 4.1 - Turbidity Measurements and Corresponding TSS Levels



List of Figures

Figure 1.1 - Locality Plan of the Sungai Sarawak Barrage

Figure 2.1 - Idealized Sediment Transport

Figure 2.2 - Sungai Sarawak Barrage, Malaysia

Figure 2.3 - Locality Plan of the Three Gorges Dam, China

Figure 3.1 - Location of the Study Area (Henderson Point to Sungai

Sarawak Barrage

Figure 3.2 - Location ofGenerated -Cross Sections (01 to -12)

Figure 3.3 - Location of Water Quality Sampling Sites

Figure 4.1 - Sungai Sarawak Barrage Operation Levels II

Figure 4.2 - Barrage Gate Operation (1-998 - 2005)

Figure 4.3 - Barrage Operation 2005


Figure 4.4 - Typical -Cross-section Profile -Comparison Template

Figure 4.5 - Cross Sectional Area Comparison

Figure 4;6 - Comparison ofMaximum Depth at Each Cross Section

Figure 4.7 - Longitudinal Profile Comparison (Scenario F & 2003)

Figure 4.8 - Longitudinal Profile -Comparison (Scenario A & 2003~

Figure 4.9 - -Differences in Bed Level (Compared to Baseline Simulation)

Figure 4.10 - Total Suspended Solids Trend(LKIM Jetty)

Figure 4.11 - Total Suspended Solids Trend (Satok Bridge)



The general objective of this ~tudy was to reVIew the findings of the

sedimentation study that was conducted as part of the Sungai Sarawak

Environmental Control and River Management Study, 1997. One of the

crucial problems related to the performance of reservoirs such as the

Sungai Sarawak Barrage impoundment is the progressive reduction in

storage capacity due to sedimentation. Reservoir sedimentation raises

flood plain levels reducing its effectiveness for flood mitigation purposes.

The primary study area was the river section beginning from Henderson

Point (near Ban Hock Wharf) to the Sungai Sarawak Barrage further

downstream. Channel cross-section and longitudinal profiles were

generated through manual profiling using navigation charts.

Subsequently, comparative analyses of the profiling results were done

using traditional methods. Comparisons between actual and simulated

levels were conducted. The effectiveness of barrage operation from a

sediment re-suspension aspect was roughly gauged by comparing turbidity

measurements taken prior to and during barrage gate operation. The

assessment of cross sectional profiles conducted in this study suggests that

most sections of the river reach in question were deeper and wider. This

indicates that the river reach from Henderson Point to Sungai Sarawak

Barrage has not been affected by impoundment sedimentation in any

detrimental manner. The increase in total suspended solids level during

gate operation as opposed to levels prior to operation was quite

appreciable. It is reasonable to assume that the turbulence created during

gate operations is sufficient to re-suspend some of the settled sediment .,'

particles and effectively transport the pa:rticles out of the impoundment.

Generally, the impoundment sedimentation upstream of the Sungai

Sarawak is not significant due to regmar gate operation.



Objective am tesis ini adalah untuk menelitikembali kesimpulan

kesimpulan kajian mendakan yang dijalankan sebagai sebahagian

daripada "Sungai Sarawak Environmental Control and River

Management Study, 1997". Salah satu masalah utama yang dihadapi

dalam pengendalian kawasan tadahan air seperti yang terdapat di Baraj

Sungai Sarawak adalah pengurangan progresif isipadu takungan air

yang disebabkan olehmendakan. Mendakan di kawasan takungan air ini

akan meninggikan paras dataran dan mengurangkan keberkesananya

dalam perihal perlindungan banjir. Kawasan utama kajian ini meliputi

bahagian sungai bermula dari Henderson Point di hulu sehingga Baraj

Sungai Sarawak di hilir. Profilsungai secara melintang and memanjang

telah dihasilkan secara kasar menggunakan carta navigasi. Profil sungai

yang dihasilkan akan dibandingkan dengan menggunakan cara-cara

tradisi. Perbandingan di antara paras sebenar dan paras simulasi telah

dilakukan. Keberkesanan operasi baraj dari segi menimbulkan semula

mendakan dapat dinilai secara kasar melalui perbandingan ukuran

turbiditi" sebelumdan semasa operasi pintu baraj. Perbandingan profil

sungai dalam kajian ini menunjukkan bahawa secara amnya bahagian

sungai yang dikaji telah menjadi lebih Lebar dan dalam. Ini menandakan

bahawa bahagian sungai dari Henderson Point menuju ke Baraj Sungai

Sarawak tidak mengalami masalah mendakan yang serius. Kenaikan

paras pepejal terampai semasa operasi pintu baraj jika dibandingkan

dengan paras sebelum operasiadalahagak ketara. Jadiadalah

munasabahjika menganggap bahawa arus air yang dihasilkan semasa .,'

operasi baraj adalah cukup untuk menimbulkan sebahagian mendakan

dan membawanya keluar daripada , kawasan tadahan ke laut. &cara

amnya, masalah mendakan dikawasan tadahanbaraj telah dapat

dikurangkan dengan operasi pintu baraj yang sentiasa.



Chapter 1 - Introduction

The progress of human civilization has been sustained by rivers for many

centuries. Various essential needs such as water supply, generation of

electricity, agricultural irrigation and ship navigation are fulfilled by river

systems such as Sungai Sarawak. The river is a vital water supply source for

Kuching City and various other communities along the river stretch. Sungai

Sarawak is also a key transportation route for goods and people via small

craft as well as larger container ships. This method of transport is still

crucial for some communities, especially in the upper basin areas that are not

linked by roads. All along Sungai Sarawak numerous agricultural activities

can be found such as aquaculture schemes, plantations and animal farms,

which rely on the river for irrigation