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CONCEPTUAL DRAINAGE IMPROVEMENT PLANS FOR THE MAONG RIVER CATCHMENT AREA
Peter Bruwa Ak Minah
g 07 Bachelor of Engineering with Honours P478 (Civil Engineering) 2004 2004 Universiti Malaysia Sarawak Kota Samarahan
fk BORANG PENYERAHAN TESIS
Judul: CONCEPTUAL DRAINAGE IMPROVEMENT PLANS FOR THE MAONG RIVER CATCHMENT AREA
SESI PENGAJIAN: 2000 - 2004
Saya PETER BRUWA AK MINAH (HURUF BESAR)
mengaku membenarkan tesis ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut:
I. Hakmilik kertas projek adalah di bawah nama penulis melainkan penulisan sebagai projek bersama dan dibiayai oleh UNIMAS, hakmiliknya adalah kepunyaan UNIMAS. 2. Naskhah salinan di dalam bentuk kertas atau mikro hanya boleh dibuat dengan kebenaran bertulis daripada penulis. 3. Pusat Khidmat Maklumat Akademik, UNIMAS dibenarkan membuat salinan untuk pengajian mereka. 4. Kertas projek hanya boleh diterbitkan dengan kebenaran penulis. Bayaran royalti adalah mengikut kadar yang dipersetujui kelak. 5. * Saya membenarkan/tidak membenarkan Perpustakaan membuat salinan kertas projek ini sebagai bahan pertukaran di antara institusi pengajian tinggi. 6. ** Sila tandakan ()
I SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972). I TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/ badan di mana penyelidikan dijalankan). 0 TIDAK TERHAD
isahkan oleh --- A ýfi., / (TANDATANGAN PENULIS) (TANDrATANGAN PENYELIA)
Alamat tetap: 9F, JLN TUN AHMAD ZAIDI Assoc. Prof. Dr. F.J. Putuhena ADRUCE, 93150 KUCHING, SARAWAK. ( Nama Penyelia )
Tarikh: 30 Mac 2004 Tarikh: 30 Mac 2004
CATATAN * Potong yang tidak berkenaan. ** Jika Kerins Projek ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/ organisasi berkenaan dengan menyertakan sekali tempoh kertas projek. Ini perlu dikelaskan sebagai SU LIT stau TERHAD.
Pks 2000 The Following Final Year Project:
Title: CONCEPTUAL DRAINAGE IMPROVEMENT PLANS FOR THE MAONG
RIVER CATCHMENT AREA
Name of the author: PETER BRUWA AK MINAH
Matrix number: 5287
was read and certified by:
30" Aa-)y Assoc. Prof. Dr. F.J. Putuhena Date (Supervisor) P.KHIDMATMAKLUMATAKADEMIK UNIMAS immiiniiMUUNm1000125605 CONCEPTUAL DRAINAGE IMPROVEMENT PLANS FOR THE MAONG RIVER CATCHMENT AREA
PETER BRUWA AK MINAH
This project is submitted in partial fulfillment of the requirements for the degree of Bachelor of Engineering with Honours (Civil Engineering)
Faculty of Engineering UNNERSITI MALAYSIA SARAWAK 2004
1 To my beloved mother, Madam Jenifer Nyim.
ii ACKNOWLEDGEMENT
First and foremost, thank you Jesusfor the love and blessings that you have given me through the years.
To my supervisor, Associate Professor Dr. F.J. Putuhena, thank you for your guidance and endlesspatience that you have shown me throughout the duration of the project.
To all my lecturers, thank you.
To my family, especially mom; I love you all.
111 ABSTRACT
The study is particularly evolves around the strategic ideas to tackle flood problem in the Maong river catchment area vis-ä-vis the development cycles that of the study area. In other words, both of the variables are in `direct relation' towards each other. It is based on the February 2003 flood event; refer to Appendix B. The February 2003 flood event flood is associated with a 20-years return period of rainfall. It is computed by using the recorded rainfall data from the Kuching Airport rainfall station. Plenty of areas in the upstream of the barrage were inundated during the event as well as some parts of the area in the Maong river catchment area. For that reason, the conceptual drainage improvement plans are generated. Among the proposed structures in this study are levees or flood walls, storage, tidal control device and pumping facilities. Several data collection and calculation processes will follow through in this project. Whereby, the computed value of Qp k by using the modified rational method is 263.58m3/s and estimated storm water volume to be stored is 2,851,200m3. The computed data will be used in the discussion section. This study is still in the identification stage of the stages in project planning. In addition, according to Carpenter (2002), "the protection of areas of floodplain reduces out of bank storage and changes the shape of the flood wave... potentially increasing flood risk downstream". In short, there is no total solution for flood problem.
iv ABSTRAK
Kajian ini berkisar terhadap idea-idea strategik untuk mengatasi masalah banjir di kawasan tadahan Sungai Maong di mana is berkadar terus dengan kitaran pembangunan di kawasan kajian. Kajian adalah berdasarkan kepada kejadian banjir pada Februari 2003, rujuk Appendix B. Kejadian banjir pada Februari 2003 dikaitkan dengan `return period' 20 tahun. Keputusan yang diperolehi adalah berdasarkan data yang direkodkan di stesen hujan Kuching Airport. Beberapa kawasan yang berada di hulu `barrage' termasuk beberapa kawasan di kawasan tadahan Sungai Maong turnt dibanjiri. Di atas sebab itu, pelan-pelan pembaikan perparitan secara teori telah disediakan. Antara struktur-struktur yang dicadangkan dalam kajian ini ialah tetambak penghalang ombak atau tembok banjir, `storage', struktur penghalang ombak dan kemudahan mengepam. Proses pengumpulan maklumat dan pengiraan akan dilakukan sepanjang projek. Di mana, nilai Qpeakyang diperolehi melalui kaedah `modified rational method' ialah 263.58m3/s dan anggaran bagi isipadu air hujan yang perlu di takung ialah 2,851,200m3. Data-data yang telah dikira akan digunakan dalam bahagian diskusi. Kajian ini berada pada peringkat identifikasi untuk peringkat-peringkat dalam `project planning'. Tambahan pula, menurut Carpenter (2002), "the protection of areas of floodplain reduces out of bank storage and changes the shape of the flood wave... potentially increasing flood risk downstream". Secara ringkas, tiada penyelesaian yang menyeluruh untuk masalah banjir.
V Table of Contents
Content Page Number
Acknowledgement iii
Abstract iv
Abstrak V
List of Tables X
List of Figures R1
Chapter 1: Introduction
1.1 Background I
1.2 Statementof Problem 1
1.2.1 Floods in Maong River Catchment Area 2
1.2.2 The Current Drainage System 3
1.3 Objective 4
1.4 Scope of Work 4
Chapter 2: Literature Review
2.1 Planning 5
2.2 Floods 6
2.3 River Flood Control 7
2.3.1 Structural Alternatives 8
2.3.1.1 Flood-Control Reservoir 8
V1 2.3.1.2 Diversion 8
2.3.1.3 Levees or Floodwalls 8
2.3.1.4 Channel Modifications 10
2.3.2 Non-Structural Measures 11
2.3.2.1 Flood Proofing 11
2.3.2.2 Flood Warning Preparedness(FWP plan) 11
2.3.2.3 Land-Use control 11
2.4 Example of Flood Control Failures 12
2.5 Flap-gates or Flood-gates 13
2.6 Drainage System 13
2.6.1 External System 14
2.6.2 Internal System 14
2.6.3 Functions 14
2.6.4 Hydrological Cycle 15
2.6.4.1 Interception 15
2.6.4.2 The Rainfall-Runoff Relationship 17
2.6.4.2.1 Runoff 18
2.6.4.3 Intensity-Duration-Frequency (IDF) 18
2.6.5 Watershed 20
2.6.6 The Modified Rational Method 21
2.6.6.1 Runoff Coefficient, C 21
2.6.6.2 Time Parameters 22
2.6.6.3 Time of Concentration, tc 23
2.6.6.4 Storage Coefficient, CS 23
vii 2.6.6.5 Rainfall Intensity 23
2.6.6.6 Drainage Area 24
2.6.6.7 Assumptions 24
2.7 Brasby-Williams Formula 25
2.8 Frequency Analysis 25
2.8.1 Gumbel's Distribution 25
2.8.2 Standard Deviation 26
2.9 Reservoir Routing 26
Chapter 3: Methodology
3.1 General 28
3.1.1 Data Collection 28
3.1.2 Delineating the Catchment Area 29
3.1.3 Determination of the Return Period of Rainfall 29
3.1.4 Calculating the Design Discharge, Qp k 29
3.1.5 Estimating the storm water volume to be stored 30
3.2 Conceptual Drainage Improvement Plans 30
3.3 Improvement versus Degree of Developments 30
Chapter 4: Data and Analysis
4.1 Delineating the Catchment Area 31
4.2 Determination of the Return Period of Rainfall 33
4.3 Calculating the Design Discharge, Qpaik 35
viii 4.4 Estimating the Storm Water Volume to be Stored 44
4.5 Discussion 45
4.5.1 Limitations 45
4.5.2 Assumptions 46
4.5.3 Comments on Results 46
Chapter 5: Conceptual Drainage Improvement Plans
5.1 Conceptual Drainage Improvement Plans 48
5.1.1 Keep the Maong River as it is 48
5.1.2 Extensive Protection of the Study Area 49
5.2 Improvement versus Degreeof Developments 51
Chapter 6: Conclusion and Recommendations
6.1 Conclusion 52
6.2 Recommendations 53
References 55
Appendix A 56
Appendix B 57
Appendix C 58
Appendix D 59
ix List of Tables
Table Page Number
2.1 Runoff coefficient, C 21
4.1 Sub-catchmentsarea 31
4.2 Data to calculate return period of rainfall 34
4.3 Year 2000 land use in Kuching City (%) 36
4.4 Determining, t,, and td 37
4.5 Possible routes and calculating, tc 40
4.6 Summation of AC 42
4.7 Intensity, I 43
4.8 Storagecoefficient, CS 43
X List of Figures
Figure Page Number
2.1 Flood protection levee constructions 10
2.2 Hydrologic cycle of a natural environment 16
2.3 Hydrologic cycle of a developed environment 17
2.4 IDF curve for Kuching Airport 19
2.5 Delineation of watershed boundary 20
4.1 Schematic representations of the flow paths 35
4.2 Retarding storage volume 44
4.3 Maximum observed flood peaks 47
5.1 Structures for river control 50
R1 Chapter 1
Introduction
1.1 Background
The nature of this study is basically based on the February 2003 flood event that hit
Kuching town. Refer to Appendix B (flood indication map, dated 5th February 2003). The
study area for this study is the Maong river catchment area. It is the largest sub-catchment of
the Sarawak river catchment area, which covers an area of nearly "40 km2" (KTA, 1997). The
information pertain to the flood event will be obtain from the relevant authorities, for
example, from the Department of Irrigation and Drainage (DID), Sarawak.
1.2 Statement of Problem
During the February 2003 flood event, considerable amount of areas in the upstream of
the barrage was inundated.
The closure of the barrage gates due to king tide coincided with the heavy down pour
that last for several days has prevented the storm water from flowing out of the system and
was forced to accumulated in the upstreamof the barrage, thus transforming the large areasin
the upstream into a temporary retarding basin. Majority of those areas that acted as the temporary retarding basin further upstream are undeveloped land, so it is good in the sense
1 that it help to contained and attenuated the flood wave instead of inundating the large
developedareas in the downstream.
Moreover, the situation worsens when the barrage gates are open. This is due to the King
tide coming into the river systems that prevented the discharge of storm water into the sea,
thus allows for the accumulation of storm water in the river systems. Therefore, the water
level in the river rise and the overflowing of storm water into the adjacent areas of the river
happens.
Some part of the areasin Maong river catchment area which mainly areasadjacent to the
Maong river are flooded or in other words operating as the temporary retarding basin during
the February 2003 flood event due to the over-bank flow from the Maong river.
Maong river catchment area is more developed than the other flooded areas located in the
upstreamof the barrage, so there is a significant reason to protect and to improve the drainage
system that of the catchment area. Besides, the author believes that Maong river catchment areahave the potential to grow in the coming years.
1.2.1 Floods in Maong River Catchment Area
Maong river catchment area is situated in the upstream of the barrage system, by which the water level in the Sarawak river and its tributaries is controlled by the barrage operation with respect to the control of water level upstream of the barrage and the tidal affected
Sarawak river downstream. During the February 2003 flood event, the existing discharge carrying capacity of the Maong river channel has failed to safely regulate the storm water, which caused overflowing of storm water to the areas adjacent to the river and inflicted inconveniencesto the affected public. Data obtained from DID on Kuching City flood report
2 (2003) shows that few parts of the areasnamely Desa Wira, MJC Bridge and Jalan Batu Kawa
inundated level are practically with storm water ranges from 0.4m - 0.8m above road level.
The over-bank flow had inundated quite a long stretch of Jalan Batu Kawa, which
significantly disrupts the traffic flow along that flood-affected roadway.
The over-bank flow during the February 2003 flood event proved that the existing
discharge carrying capacity of Maong river channel is insufficient to accommodate any large
quantity of storm water from a heavy and consistent downpour event plus the influx of tidal
water from the tidal affected Sarawak river.
In addition, the frequent occurrence of flood event in the Maong river catchment area is
also due to the fact that it is located at low-lying areas.
1.2.2 The Current Drainage System
The current drainage system especially that of the observed system (Maong river
catchment area drainage system) is depending on the barrage operation which significantly
influences the water level at the confluence of Sarawak river and Maong river, through its
opening and closing operation. The entire drainage systems in the areas upstream of the
barrage link up very effectively with the barrage operation under the normal situation.
The problem arises when the gates are closed and the concurrent event of heavy downpour and King tide occurs, the water level in the Sarawak river channel particularly at the upstream of the barrage will rise due to the increased in the storm water volume and the backwater effect from the tidal affected Sarawak river when the gates are opened to allow free flow of water. Thus, the over-bank flow happens as the accumulated storm water in the river
3 system exceededthe maximum discharge carrying capacity that of the tributaries river system,
in this case, of the Maong river.
In addition, there are apparently no devices to control the back flooding at the confluence
of Sarawak river and Maong river.
Apart from that, the current drainage systems existing in the catchment area is seen as
inadequateto support the current pace of developmentsin the study area.
1.3 Objective
Based on the available data and information, several conceptual drainage improvement plans will be generatedfor the study area. In addition, the discussion regarding the phasing of the generated conceptual drainage improvement plans in relation to the degree of developments in the study areawill be carried out.
The purpose of the conceptual drainage improvement plans is to cater for the current and future developments in the Maong river catchment area and to reduce the flood risk if the flood like the one in February 2003 or designed flood happens. The Sarawak river and Sarawak river barragewill be the boundary condition for the conceptual drainage system.
1.4 Scope of Work
Considering the data availability, this study is within the identification stageof the project planning process.Whereby, areas affected by the February 2003 flood event are recorded. Consequently,the study area is being identified and several conceptual drainage improvement plans will be generated.
4 Chapter 2
Literature Review
2.1 Planning
Planning can be defined as the orderly consideration of a project from the original statement of purpose through the evaluation of alternatives to the final decision on a course of action. It includes all the work associated with the design of a project except the detailed engineering of the structures (Linsley, Franzini, Freyberg et Tchobanglous, 1992). Dept.
Pekerjaan Umum (1985), summarised the stages in planning as below:
Inventories by province or river basin of potential for development, discernable on
aerial photography at reconnaissancelevel, in terms of land and water availability and
access.
" Identification of projects by name, during or after the inventories, and notification of
interested parties.
" Reconnaissanceto clarify aspects not resolved during the inventory, and classification
to determine scopeof further studies, if any.
Pre-feasibility study and screening to compare outlines or types of schemewhich may
fulfil the objectives, to compare approximate costs and benefits, to select schemesfor
further study, and to determine the requirementsfor surveys and investigations.
" Feasibility study to establish the need, to define precisely the scheme to meet,
recommend a program for implementation, draw attention to possible problems,
5 calculate capital and running costs and benefits, and indicate whether the project is
technically and economically viable.
Design is preliminary designs and/or detailed final designs, contract documents, and
cost estimates.
Construction is the implementation of agricultural and administrative aspects,
including operation and maintenance.
Monitoring of progress in construction and expenditure of area brought under
irrigation and/or other objectives achieved and of benefits arising from the project.
2.2 Floods
Flooding is the inundation of normally dry land as a result of a rise in the level of surface
waters or the rapid accumulation of storm-water runoff. It will become flood hazard when it
has the potential to induce economic loss and threaten human life or health. Flooding is
strictly a natural process, in which the event is bound to occur no matter what. The author
believes that there is no drainage system that can prevent flood.
On the other hand, rapid development has in turn increase the amount of impervious
surfaces and changethe natural hydrological balance, in which it cause considerableeffect on
the frequency and severity of floods. Flooding can take many forms - river floods, storm- related flash floods and coastal floods and they can be causedby many reasons.
The major contributors to the flood event in our country are normally heavy rains and poor drainage systems.
6 2.3 River Flood Control
It is a counter-floods measure aim at reduces the adverse effects of flooding. The constant threat of flood especially to those living in the flood-prone areas has prompted the design and implementation of flood control schemes by civil engineers and relevant authorities in order to lower the risk of flood to those subjected to flood. According to Smart et Herbertson (1992), "In many cases flood control schemes which are of local benefit will have an adverseeffect elsewhere, notably further downstream".
Flood control can be classified into two main categories. As Mays (2001) observes,
"Construction of flood-control facilities, referred to as structural measures, are usually designed to consider the flood characteristics including reservoirs, diversions, levees or dikes, and channel modifications. Flood-control measuresthat modify the damage susceptibility of floodplains are usually referred to as non-structural measures and may require minor engineering works. Non-structural measuresinclude flood proofing, flood warning, and land- use controls".
7 2.3.1 Structural Alternatives
According to Mays (2001);
2.3.1.1 Flood-Control Reservoir
Flood-control reservoirs are used to store flood waters for release after the flood event, reducing the magnitude of the peak discharges.Reservoirs modify the flood-flow frequency curve, which is lowered becauseof the decreaseof the peak dischargeof a specific event.
2.3.1.2 Diversion
Diversion structures are used to reroute or bypass flood flows from damage centers in order to reduce the peak flows at the damage centers. Diversion structures are designed to modify (lower) the frequency curve so that the flow magnitude for a specific event is lowered at the damagecenter.
2.3.1.3 Levees or Floodwalls
Levees or floodwalls are used to keep flood flows from floodplain areas where damage due to flood can occur. The effect of levee is to reduce the damage in protected areas from water surface stageswithin the stream or main channel by constricting the flow to flow within levee, thus reduces the amount of natural storage of a flood-wave, causing an increase in peak discharge downstream. Even though levee has the purpose of protecting property and lives,
8 they also bring the potential for major disasters when design discharges are exceeded and
areasare inundated that had been consideredsafe.
Besides, Petersen (1986) writes based on the U. S. Army, Corps of Engineers (1978)
listed the following general steps levee design:
" Conduct geological studies based on a thorough review of available data, including
aerial photographs, and initiate preliminary subsurfaceexplorations.
" Analyse preliminary explorations data and establish preliminary soil profiles, borrow
locations, and embankmentsections.
" Initiate final explorations to obtain additional soil profile data, undisturbed strengths of
foundation materials, and more detailed information on borrow areas and any other
excavation.
" Using final explorations data determine embankment and foundation soil parameters
and refine preliminary sections, compute rough quantities of suitable material, and
refine borrow area locations.
" Divide the entire levee into reaches of similar foundation conditions, embankment
height, and fill material, and design a typical trial section for each reach.
" Analyse each trial section for under seepageand through-embankment seepage,slope
stability, and settlement, as required.
" Design special treatment for any problem areasidentified.
" Establish final typical sectionsfor each reach.
" Compute final quantities needed;determine final borrow area locations.
" Design embankment slope protection, if required.
Where there are limited spacesfor levee construction thus flood wall is used instead.
9 1-\ /'Týý.... ý""'
FLOOD WALL SLUICE (for drainage i ,vhere there s ;mufhc; ant space release of internal for Levee construction) when river is not in flood)
DRAINAGE DITCH (tor internal drainage requires retention pond, diversion sluice ot Low flow L_ 'Set-backdislance pumping when no gravity release is season possible during floods) river L Design flood V. 0 Freeboard
Occasional need lur BORROW PIT * Potential wetlands r.rattress rcgin ma! enal for Ievei or n Op habitat for rovetrlent to train main construction) fl0td end fauna hannel course or protect floodplain activity
Figure 2.1 Flood protection levee constructions
(From Carpenter, T. G., 2001)
2.3.1.4 Channel Modifications
Channel Modifications (channel improvements) are performed to improve the conveyance the discharges for flood passed at characteristics of a stream.. . peak events are lower stages, decreasing the effect of natural valley storage during passage of a flood wave.
This effect result in higher peak discharges downstream.
10