Detention-Based Stormwater Drainage Management Using a Dynamic Programming Approach in a Selected Area in Dhaka
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DETENTION-BASED STORMWATER DRAINAGE MANAGEMENT USING A DYNAMIC PROGRAMMING APPROACH IN A SELECTED AREA IN DHAKA BY SOHELI NASRIN MASTER OF SCIENCE IN WATER RESOURCES DEVELOPMENT INSTITUTE OF WATER AND FLOOD MANAGEMENT BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY MARCH 2014 Detention-Based Stormwater Drainage Management Using a Dynamic Programming Approach in a Selected Area in Dhaka By Soheli Nasrin A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN WATER RESOURCES DEVELOPMENT Institute of Water and Flood Management BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY March 2014 BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY Institute of Water and Flood Management The thesis titled ‘Detention-Based Stormwater Drainage Management Using a Dynamic Programming Approach in a Selected Area in Dhaka’ submitted by Soheli Nasrin, Roll No. M10062810F, Session: October 2006, has been accepted as satisfactory in partial fulfillment of the requirements for the degree of Master of Science in Water Resources Development in March 31, 2014. BOARD OF EXAMINERS .................................................. Dr. M. Shah Alam Khan Chairman Professor (Supervisor) Institute of Water and Flood Management Bangladesh University of Engineering and Technology, Dhaka ................................................. Dr. G.M. Tarekul Islam Member Professor and Director (Ex - officio) Institute of Water and Flood Management Bangladesh University of Engineering and Technology, Dhaka ................................................ Dr. M. Shahjahan Mondal Member Professor Institute of Water and Flood Management Bangladesh University of Engineering and Technology, Dhaka ................................................. AFM Abdul Aziz Member Superintending Engineer & Project Director (External) Dhaka Water Supply and Sanitation Project Dhaka WASA, WASA Bhaban 98 Kazi Nazrul Islam Avenue, Karwan Bazar, Dhaka-1205 ii CANDIDATE’S DECLARATION It is hereby declared that this thesis or any part of it has not been submitted elsewhere for the award of any degree or diploma. ……………………….. Soheli Nasrin Roll No. M10062810F Session: October, 2006 iii DEDICATION Those who supported, support and continue to support my cause from my formation into my mother’s embryo to the last breathe iv ACKNOWLEDGEMENTS First of all, I would like to thank almighty Allah for giving me the ability to complete the work. It is a great pleasure to express my esteemed gratitude and sincere thanks to Dr. M. Shah Alam Khan, Professor, Institute of Water and Flood, Management (IWFM), Bangladesh University of Engineering and Technology, Dhaka, Bangladesh who provided careful supervision and guidance, continuous cooperation and timely advice, necessary suggestion and uninterrupted encouragement at every stage of my period of research. Besides I thank all of the faculties of IWFM who taught me several courses and inspired me to do this type of research. I owe deep gratitude to Dr. K. M. Nabiul Islam, Researcher, Bangladesh Institute of Development Studies (BIDS), for his utmost and sincere assistance to advance the study. Last but not the least, I appreciate the patience and all sorts of privations borne by my family members during my study. Soheli Nasrin v ABSTRACT Unplanned urbanization and encroachment of storm runoff detention areas pose serious challenges to stormwater drainage management in Dhaka City. The arbitrary- rule based stormwater management in the Hatirjheel detention system, the largest gravity-drainage detention basin in the city, is often inadequate to drain internal storm runoff in extreme flood years when the downstream regulator gates are closed due to high external river water level, and temporary pumping is required. A Dynamic Programming model is developed using a forward recursive algorithm and following an Incremental Dynamic Programming approach to optimize the weekly pumping requirements. System constraints are defined by the gate-closing water level, and the allowable maximum and minimum water levels in the system. Runoff from 12 sub- catchments of the system is calculated with runoff ratios estimated from satellite photo interpretation and field observation. Model application results indicate that pumping required at the optimum condition is significantly lower than that required by the current practice. In extreme flood year 1998, the pumping requirements under optimum condition and current practice would be 26.118 Mm3 and 35.925 Mm3, respectively. The feasibility of using the DP model for real-time stormwater management decision making is tested based on 14 optimal Runoff Scenarios. The pumping decision at the current stage can be taken by matching the observed runoff trend in the current year with one of these scenarios. Low-lying areas around the Hatirjheel detention basin are vulnerable to local inundation due to high water levels in the basin that prevents gravity drainage from these areas. Inundation maps prepared from a DEM indicate that 1.15 km2 area is inundated for a water level of +7.0 m PWD. A household-survey based flood damage assessment indicates that the potential damage in an extreme condition is higher for the high income group. The potential damage for the industrial area could not be assessed due to the lack of adequate information on the variations with depths and durations. vi TABLE OF CONTENTS Page No. Acknowledgements v Abstract vi List of Tables x List of Figures xi Abbreviations xiii Chapter One: Introduction 1-6 1.1 Background of the Study 1 1.2 Rationale of the Study 4 1.3 Objectives of the Study 4 1.4 Scope and Limitation of the Study 5 1.5 Organization of the Thesis 5 Chapter Two: Literature Review 7-24 2.1 Introduction 7 2.2 Characteristics of Urban Catchments 7 2.2.1 Land Use 7 2.2.2 Stormwater Drainage 10 2.2.3 Drainage Network 10 2.2.4 Detention Areas 12 2.2.5 Urban Wastewater and Pollutant 12 2.3 Stormwater Management 13 2.4 Drainage Master Plan for Dhaka 15 2.5 Numerical Models for Urban Stormwater Management 16 2.5.1 SWMM 16 2.5.2 MIKE 17 2.5.3 MOUSE 17 2.6 Dynamic Programming Models for Urban Stormwater 17 Management 2.6.1 Incremental Dynamic Programming 18 vii 2.6.2 Stochastic Dynamic Programming 19 2.6.3 Dynamic Programming Model Applications 20 2.7 Flood Damage Estimation 21 Chapter Three: Study Area 25-37 3.1 Location 25 3.2 Demography 24 3.3 Landform and Land Use 28 3.4 Climate 29 3.5 Stormwater Management Practices 30 3.6 Hatirjheel Integrated Project 30 3.7 Permanent Pumping Station 34 Chapter Four: Study Methodology 38-47 4.1 Methodological Framework 38 4.2 Base Map Preparation and Catchment Delineation 38 4.3 Storm Runoff Estimation 40 4.4 Dynamic Programming Model Development 40 4.4.1 Conceptual Basis 40 4.4.2 Model Formulation 42 4.5 Flood Damage Assessment 44 4.5.1 Questionnaire Survey 45 4.5.2 Data Analysis 47 Chapter Five: Results and Discussion 48-75 5.1 Rainfall-Runoff Estimation 48 5.1.1 Catchment Characteristics 4 8 5.1.2 Runoff Ratio 50 5.1.3 Storm Runoff 54 5.2 Downstream Water Level 55 5.2.1 Water Level Hydrograph and Rainfall 55 viii 5.2.2 Present Gate Operation Rule and Practice 56 5.3 Stage-Wise Pumping Optimization 57 5.4 Real-time Decision Making 60 5.5 Flood Inundation Mapping 62 5.6 Flood Damage Assessment 63 5.6.1 Residential 69 5.6.2 Industrial 74 Chapter Six: Conclusion and Recommendations 76-78 Conclusion 76 Recommendations 78 References 79-82 Appendices 83-125 Appendix A: Sample Questionnaire for Surveys 83-102 Appendix B: Dynamic Programming Spread Sheet 103-106 Appendix C: Rainfall and Water Level Relationship 107-113 Appendix D: Stage-Wise Optimal Pumping and Water Level for 114-125 Different Scenarios Appendix E: Intangible Damage Matrix for Residential Area 126 ix LIST OF TABLES Page No. Table 2.1: Components of Dhaka Metropolitan Development Plan 9 (DMDP) 1995- 2015. Table 2.2: Storage related parameters of major depression storages in 12 Dhaka West. Table 3.1: Monthly variations in important climatic variables in Dhaka 29 City. Table 3.2: Discharge and velocities at different zones of intake channel 35 sump in ideal condition. Table 5.1: Calculated areas of the sub-catchments in the study area. 49 Table 5.2: Qualitative criteria and associated runoff ratio for different 52 land use classes. Table 5.3: Runoff ratio for different sub-catchments. 53 . Table 5.4: Selected runoff scenarios for real-time decision making. 61 Table 5.5: Inundated area at different inundation depths. 63 Table 5.6: Intangible damage based on respondents’ perception. 73 x LIST OF FIGURES Page No. Figure 2.1: Incremental dynamic programming approach with iterative 19 searching of optimal solution within a corridor. Figure 3.1: Map of Dhaka City showing location of the study area and 26 related drainage network. Figure 3.2: Important features of the study area. 27 Figure 3.3: Isometric view of Combined Sewer Overflow structure. 33 Figure 3.4: Intake channel layout of Rampura Pumping Station at the 36 new site. Figure 3.5: Layout plan of Rampura Pumping Station at the new site 37 Figure 4.1: Methodological framework of the study. 39 Figure 4.2:Water balance components in the detention basin, assuming 41 a wide rectangular basin. Figure 4.3: Incremental dynamic programming approach adopted for 42 the Hatirjheel system, showing discrete states at each stage. Figure 5.1: Composite satellite photo of the study area. 49 Figure 5.2: Sub-catchments of the Hatirjheel system. 50 Figure 5.3: Land use map of the catchment of the Hatirjheel system. 51 Figure 5.4: The land use pattern of G3 sub-catchment in the study 53 area. Figure 5.5: Variation in weekly rainfall and runoff in 1998. 54 Figure 5.6: Water level hydrograph and rainfall for 1998. 55 Figure 5.7: Mean water level hydrograph and 1:5 year rainfall.