Space Borne Hydrodynamic Model Development: The Case of Ganges and Brahmaputra River Basin Mehedi Maswood A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science University of Washington 2015 Committee: Faisal Hossain Rebecca B. Neumann Program Authorized to Offer Degree: Department of Civil and Environmental Engineering ©Copyright 2015 Mehedi Maswood University of Washington Abstract Space Borne Hydrodynamic Model Development: The Case of Ganges and Brahmaputra River Basin Mehedi Maswood Chair of the Supervisory Committee: Associate Professor Faisal Hossain Department of Civil and Environmental Engineering River modeling is an important component of flood forecasting system that can simulate the water flow dynamics of a stream network and forecast river levels in flood prone regions. Around the world, especially in the developing regions, many large river basins are mostly ungauged. For these basins river model setup is very challenging due to lack of necessary in-situ and routine measurement of river bathymetry, flood plain and river boundary data. Moreover, lack of data sharing among the countries occupying the trans-boundary rivers, also a hurdle to river model development. For such basins, proxy approaches depending on the satellite based remotely sensed data could be an alternative solution. In this study, one dimensional hydrodynamic model has been developed for the Ganges, Brahmaputra and Meghna basin region using the Hydrologic Engineering Center River Analysis System (HEC-RAS). Only 7% of the total basin area has good quality in-situ measurement of river hydraulics. For the remaining part, remotely sensed data have been utilized for river model development. This study utilized: a) LANDSAT/MODIS for identifying flow path of river network, b) Shuttle Radar Topographic Mission (SRTM) for extracting river profile c) Radar altimeter for establishing depth-width relationship and d) Precipitation data to generate sub basin wise flow data. Simulated model results have been tested at two downstream low lying locations. The outcome of the study showed significant improvement of root mean square error (RMSE) for river level simulation from 3.0m to 1.0m. A step by step ‘rule book’ has been documented to facilitate the setting up river models for similar type basins around the world for operational water agencies. Dedication This thesis dedicated to my wife and my children ACKNOWLEDGEMENTS First and foremost, I wish to express my gratitude and sincerest appreciation to my supervisor Dr. Faisal Hossain for inspiring me to conduct this thesis work and to provide me intellectual support in all respect. I am also thankful for the support of Dr. Rebecca B. Neumann and her help as a committee member. I express my profound thanks to Safat Sikder for his cooperation and also special thanks to A. H. M. Siddique-E-Akbor for providing hydrodynamic model setup of the major rivers of Bangladesh for this study. The Ivanhoe Foundation and NASA are gratefully acknowledged for supporting my study. At last I am grateful to my family members for their great inspiration and support all through the work. Table of Contents List of Figures ……………………………………………………………………………………...III List of Tables ……………………………………………………………………………………… V 1. CHAPTER 1 – INTRODUCTION ............................................................................................................... 1 1.1 Background ................................................................................................................................... 1 1.2 Motivation ..................................................................................................................................... 2 1.3 Literature Review .......................................................................................................................... 5 1.4 Objective of the Study .................................................................................................................. 9 1.5 Thesis Outline .............................................................................................................................. 10 2. CHAPTER 2 – MATERIALS & METHODS ............................................................................................... 11 2.1 Study Area ................................................................................................................................... 11 2.1.1 Overview ............................................................................................................................. 11 2.1.2 Climate ................................................................................................................................ 12 2.1.3 Topography ......................................................................................................................... 12 2.1.4 Major Rivers ........................................................................................................................ 14 2.2 Data ............................................................................................................................................. 14 2.3 Model .......................................................................................................................................... 20 2.4 Methodology for Hydrodynamic Model Development .............................................................. 21 2.4.1 Satellite Based River Network Delineation ......................................................................... 24 2.4.2 Non-SRTM River Bathymetry Data ...................................................................................... 30 2.4.3 SRTM River Bathymetry Data .............................................................................................. 32 2.4.4 Factorized Boundary Flow Data .......................................................................................... 34 2.4.5 VIC Model Output as Boundary Data .................................................................................. 35 2.4.6 Land Water Classification .................................................................................................... 38 3. CHAPTER 3 – RESULTS & DISCUSSION ................................................................................................ 42 3.1 Hydrodynamic Models Result ..................................................................................................... 42 3.1.1 Non-SRTM RAS Model with Factorized Boundary Flow Data ............................................. 43 3.1.2 SRTM RAS Model with Factorized Boundary Flow Data ..................................................... 44 3.1.3 SRTM RAS Model with Hydrologic Model Derived Boundary Flow Data ............................ 45 3.2 Comparisons at Ungauged River Locations with Satellite Observations .................................... 46 i 4. CHAPTER 4 – CONCLUSIONS ............................................................................................................... 51 4.1 Findings of the Study................................................................................................................... 51 REFERENCES…….………………………………………………………………..……………….54 APPENDICES……………………………………………………………………………………….59 ii List of Figures Figure 1.1: GBM basins and similarly ungauged river basin around the world showing the major river network, delta (flood prone region) and flow direction ................................................................................ 3 Figure 1.2: Schematic representation of flood forecasting problem in flood prone downstream nations in large and ungauged transboundary basins .................................................................................................... 4 Figure 2.1: Ganges, Brahmaputra and Meghna river basin area showing the gauging station at upstream points of the flood forecasting domain (Hardinge Bridge on Ganges and Bahadurabad Station on Jamuna). .................................................................................................................................................................... 13 Figure 2.2: The Base model developed on the basis of ground based measurement for the flood prone Bangladesh region (after Siddique-E-Akbor et al., 2011) ........................................................................... 15 Figure 2.3: HEC-RAS Geometric Data window for setting up river network and cross section. ............... 16 Figure 2.4: HEC-RAS cross section data setup window ............................................................................. 17 Figure 2.5: HEC-RAS unsteady flow boundary data setup window........................................................ 17 Figure 2.6: SRTM Digital Elevation Model for the entire GBM basin. ..................................................... 18 Figure 2.7 : The flow chart showing the GBM basin river model development work. .............................. 22 Figure 2.8 : Plan View of Non SRTM Bathymetry with Factorized Boundary Data Based HEC RAS Model .......................................................................................................................................................... 23 Figure 2.9 : Plan View of SRTM Bathymetry with VIC Generated Boundary Data Based HEC RAS Model .......................................................................................................................................................... 24 Figure 2.10 : Digitized river network for the entire GBM