Hydrodynamic Analysis of the Proposed Flood Bypass Channel Upstream of Kuching City
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HYDRODYNAMIC ANALYSIS OF THE PROPOSED FLOOD BYPASS CHANNEL UPSTREAM OF KUCHING CITY Norliza Binti Aslan Joe @ Joshua Bachelor of Engineering with Honours (Civil Engineering) 2009 For my beloved family. ii ACKNOWLEDGEMENT In the Name of Allah, the Most Gracious, the Most Merciful. All the praises and thanks be to Allah, the Lord of the Universe, for His Kindness this final year project thesis is finally completed. First of all I would like to express my highest gratitude to my honoured project supervisor, Prof. Dr. F.J. Putuhena for his advice and guidance throughout my entire project writing period. Secondly I would like to thank Mr. Darrien Mah Yau Seng for helping me throughout doing the modeling and simulation. Without your professional help, it would be impossible for me to complete this project on time. Thank you once again. My gratitude also goes to Mr. Wong Wen Hong and Miss Inja Hellegers from the Department of Irrigation and Drainage (DID) Kuching for providing me with the required data and information needed for this project. To my father, sisters and other family members, thank you for always being there for me when I needed you most. Your love and support has given me the inner strength to go the extra mile to complete my studies . And lastly not forgetting all my friends and all those involved directly or indirectly in the completion of this thesis, thank you very much. May Allah Bless you all. iii ABSTRAK Sejak 50 tahun yang lepas, Sungai Sarawak telah mengalami beberapa bencana banjir bermula dengan yang berlaku pada tahun 1963, diikuti pada Februari 2003, seterusnya pada Januari 2004 dan yang terbaru pada bulan Januari tahun ini. Satu terusan banjir buatan sepanjang 8 km dengan kelebaran dasar 250 m bermula dari Kampong Paroh ke Batang Salak telah dicadangkan untuk menghala keluar sebahagian air dari Sungai Sarawak daripada mengalir ke kawasan Bandar Raya Kuching terutamanya semasa musim banjir. Tujuan utama kajian ini dijalankan ialah untuk mengkaji semula masalah di kawasan-kawasan kerap banjir di sekitar Sungai Sarawak dan untuk menjalankan analisis hidrodinamik terhadap Sungai Sarawak beserta dengan impak daripada terusan banjir buatan yang bakal dibina. Model Sungai Sarawak telah dihasilkan menggunakan permodelan hidrodinamik 1-Dimensi dengan mengaplikasikan dua perisian kejuruteraan iaitu InfoWorks River Simulation (RS) dan juga GIS menggunakan data daripada banjir yang berlaku pada Januari 2004 bagi mendapatkan profil banjir di sepanjang Sungai Sarawak. Hasil simulasi menunjukkan bahawa terusan banjir tersebut telah mengurangkan kadar banjir di Sungai Sarawak. Keputusan yang diambil dari kawasan Batu Kawa menunjukkan pengurangan paras air sebanyak 48.45% telah membuktikan keberkesanan terusan banjir tersebut. iv ABSTRACT Sarawak River had experienced several disastrous flood events over the past 50 years, with the worst being in 1963, followed by February 2003, January 2004 and January 2009 flood. A flood bypass channel had been suggested as a flood mitigation measure to reduce the flooding effects along the Sarawak River. The proposed flood bypass channel is 8 km long with 250 m base width man-made channel starting from Kampong Paroh to divert a significant portion of flood waters from Sarawak River away from Kuching city to Batang Salak. The main purpose of this project was to review the flooding problems in flood-prone areas of Sarawak River basin and to carry out hydrodynamic analysis on the Sarawak River together with the impacts of the upcoming flood bypass channel. Sarawak River and its floodplains were modeled using one-dimensional hydrodynamic modeling approach, by utilising the Wallingford Software model - InfoWorks River Simulation (RS), coupled with its embedded GIS applications, to obtain the flood hydrographs of the river and its floodplains in extreme flooding condition of January 2004 flood. The simulated results of January 2004 flood obtained showed that the flood bypass channel had been diverting significant portion of flood waters from Sarawak River. Results taken from Batu Kawa showed an average water level reduction of 48.45% which reflects the effectiveness of the flood bypass channel. v TABLE OF CONTENTS Content Page Number Acknowledgement iii Abstrak iv Abstract v List of Tables x List of Figures xi List of Nomenclature xiv List of Abbreviation xvi Chapter 1 INTRODUCTION 1.1 Background 1 1.2 The Sarawak River Basin 2 1.3 Flooding occurrence in Sarawak River 3 1.4 Flood mitigation 6 1.5 Objectives of study 9 Chapter 2 LITERATURE REVIEW 2.1 Flood 10 2.2 Major flood events and causes of flooding 10 2.3 Rainfall-runoff relationship 11 2.3.1 Modified Rational Method 11 vi 2.4 Roughness coefficient 12 2.5 Hydrodynamic routing 15 2.5.1 Saint-Venant Equations 15 2.6 Open channel 20 2.6.1 Open channel flow 20 2.7 Natural flow condition 21 2.8 Most economical section of a channel 22 2.9 Flood mitigation measures 22 2.10 Structural measures 23 2.10.1 Flood bypass channel or tunnel 24 2.10.1.1 Proposed flood bypass channel Kuching 26 2.10.1.2 Yolo Bypass Channel 28 2.10.2 Construction of barrage 31 2.10.2.1 Kuching Barrage 31 2.10.3 Flood control dams 33 2.10.4 Canalisation and related works 33 2.10.5 Bunding of rivers 33 2.10.6 Storage ponds of flood attenuation 34 2.10.7 Poldering (ring bund) 34 2.11 Non structural measures 35 2.11.1 Integrated River Basin Management (IRBM) 35 2.11.2 Preparation of guidelines and design standards 35 2.11.3 Resettlement of population 36 2.11.4 Flood proofing 37 2.11.5 Flood forecasting and warning system 37 vii Chapter 3 METHODOLOGY 3.1 Review of flooding problems in Sarawak River 39 3.2 Information and data collection 40 3.3 Sarawak River modeling 41 3.3.1 Application of ESRI ArcView 41 3.3.2 Application of InfoWorks RS 43 3.4 Model calibration and verification 44 3.4.1 Model calibration 44 3.4.2 Model verifications 45 3.4.2.1 Observed and modelled water level at 47 Siniawan 3.4.2.2 Observed and modelled water level at 48 Batu Kitang 3.4.2.3 Observed and modelled water level at 49 Batu Kawa 3.5 Scenarios of river simulation 50 Chapter 4 RESULTS, ANALYSIS AND DISCUSSION 4.1 General 52 4.1.1 Hydraulic model without flood bypass channel 52 4.1.2 Hydraulic model with flood bypass channel 54 4.2 Water level at river section 57 4.2.1 Water level without flood bypass channel 57 4.2.2 Water level with flood bypass channel 59 4.3 Water level data comparison 61 viii 4.4 Longitudinal section 63 4.5 Design flood simulation results 65 4.6 Discussion 66 Chapter 5 CONCLUSIONS AND RECOMMENDATIONS 5.2 Conclusion 67 5.2 Recommendations 68 REFERENCES 69 ix LIST OF TABLE Table Page 1.1 Some historical Flood Events Recorded involving 4 Sarawak River and Kuching City (DID) 1.2 Design Flood Level (Sungai Sarawak Flood Mitigation 6 Options Study 2003) 4.1 Maximum water level difference 62 x LIST OF FIGURES Figure Page 1.1 River Basins in Sarawak 2 1.2 Flood affected areas in Kuching 3 1.3 An aerial view of the proposed Flood Bypass Channel 7 1.4 Locations of the starting and ending points of the 8 proposed flood bypass channel 2.1 Layout of the Sungai Sarawak Flood Bypass Channel 27 2.2 Location of the projects 28 2.3 Yolo Bypass and its sources 29 2.4 Schematic of the Yolo Bypass in California 30 2.5 Sarawak River Regulation Scheme 32 3.1 Triangulated Irregular Network (TIN) surface model 42 with flood bypass channel 3.2 Digital Terrain Model (DTM) 42 3.3 Location of cross sections S46, S66 (Batu Kawa) SR6 46 (Siniawan) and S76 (Batu Kitang) at Sarawak River 3.4 (a) Observed and modeled water level at Siniawan 47 (b) Observed and modeled water level at Batu Kitang 48 (c) Observed and modeled water level at Batu Kawa 49 xi 3.5 Modeling approaches 50 4.1 Maximum flood extent without flood bypass channel 53 4.2 Enlarged view of maximum flood extent at Batu Kawa 54 and Batu Kitang areas 4.3 Maximum flood extent with flood bypass channel 55 4.4 Enlarged view of maximum flood extent at Batu Kawa 55 and Batu Kitang areas 4.5 Maximum flood extents with and without flood bypass 56 channel at Sarawak River 4.6 Location of cross sections S66 (Batu Kawa) and S76 57 (Batu Kitang) at Sarawak River 4.7 Modeled 100-years Flood without Flood Bypass Channel (a) Sarawak River (S66 – Batu Kawa) Cross Section 58 (b) Sarawak River (S76 – Batu Kitang) Cross Section 58 4.8 Modeled 100-years Flood with Flood Bypass Channel (a) Sarawak River (S66 – Batu Kawa) Cross Section 59 (b) Sarawak River (S76 – Batu Kitang) Cross Section 60 4.9 Water level comparison graph for Batu Kawa river 61 section 4.10 Water level comparison graph for Batu Kitang river 62 section 4.11 Flood Profile of Sarawak River without flood bypass 64 channel 4.12 Flood Profile of Sarawak River with flood bypass 64 xii channel 4.13 Maximum flood extents with flood bypass channel at 65 Sarawak River for design flood event xiii LIST OF NOMENCLATURE A - Cross section area A1 - Catchment area B - Water surface width C - Runoff coefficient representing a ratio of runoff to rainfall Cs - Channel Storage Coefficient g - Gravitational acceleration H - Water surface elevation above datum I - Average rainfall intensity for a duration equal to the time of concentration, for selected return period K - Channel conveyance km - kilometre mm - milimetre m - metre n - Manning's roughness coefficient P - Wetted perimeter Q - Flow Qp - Peak flow q - Lateral inflow per unit length of channel R - Hydraulic radius Sf - Friction slope So - Channel bed slope t - Time xiv V - Average velocity of water x - Longitudinal channel distance y - Depth of water ß - Momentum correction coefficient - Angle of inflow xv LIST OF ABBREVIATION ARI - Average Recurrence Interval DID - Department of Drainage and Irrigation DTM - Digital terrain Model ESRI - Envinronmental Systems Research Institute etc.