Gis based flood risk mapping a case study of flood risk assessment using analytic hierarchy process in tram tau district, yen bai province, vietnam

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY HANNA JOY TILPO ORDANZA GIS-BASED FLOOD RISK MAPPING: A CASE STUDY OF FLOOD RISK ASSESSMENT USING ANALYTIC HIERARCHY PROCESS IN TRAM TAU DISTRICT, YEN BAI PROVINCE, VIETNAM BACHELOR THESIS Study Mode: Full-time Major: Environmental Science and Management Faculty: Advance Education Program Office Batch: K49 - AEP Thai Nguyen, 05/11/2021 DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student Name Hanna Joy Tilpo Ordanza Student ID DTN1754190025 Thesis Title GIS-Based Flood Risk Mapping: A Case Study of Flood Risk Assessment Using Analytic Hierarchy Process in Tram Tau District, Yen Bai Province, Vietnam Supervisor (s) Dr Nguyen Van Hieu Supervisor’s Signature Abstract: Flooding is one of the most common hazards that occurs either naturally or induced by human The optimal way to gain solid understanding about the occurrence of flood risk is through mapping spatial assessment Hence, this study aims to locate the areas prone of flooding using GIS and to give relative importance in different triggering factors through multi-criteria analysis The area of study is Tram Tau which is a micro-community in Yen Bai province There are no studies in Tram Tau regarding flood risk mapping The triggering factors included in this assessment are: distance to river, distance to road, drainage density, elevation, land cover, population density, rainfall, road density, slope, and TWI These indicators were ranked based on their importance and given their corresponding criteria weights using Analytic Hierarchy Process (AHP) There are three scenarios each for hazard index and vulnerability index These scenarios were then combined to present nine different combinations under unique conditions The results were the flood risk maps and alternatively validated by performing comparison analysis wherein two sets of scenarios were compared to prime combination which is considered as the most reliable case of flood risk assessment Ultimately, this assessment predicted that the communes namely Phinh Ho, Tram Tau, and Hat Luu are the areas with the highest possibility of being damaged by flooding in the whole district Given the limited local knowledge about GIS and RS, this study is carried out to introduce flood risk assessment using GIS to future environmental scientists and managers GIS, RS, AHP, MCDA, Flood risk assessment, flood risk Keywords: mapping Page number 90 Date of Submission 05/11/2021 i ACKNOWLEDGEMENT Praise and Glory belong to HIM, my Jesus and Savior He allowed me to walk in His will and display His goodness in my life He is my greatest privilege in this life I would like to thank all the people who stayed by my side all throughout this journey Three years have passed and they are still here with me cheering me up and giving me motivation as I continue thriving for my future My bachelor thesis is what I consider as the hardest part in my college life, but I am always reminded that the beginnings are always hard So this appreciation section is for the people who helped me a lot First, to my Mami and Dadi, for giving their full support to me financially, spiritually, and emotionally For all the prayers and pieces of advice they have imparted to me They never dictated my plans and they let me decide on my own while praying for me I can’t wait to spoil them with everything they want Second, to my siblings who had my parents’ back I know there are times that my parents could only provide enough but my brothers were there to shoulder the rest Third, to GIRC director, Prof Nguyen Van Hieu, for letting me work in this field with all of his support by sending Mr Mui Minh Tung He taught me a lot of things in GIS To Dr Quang Binh Bui because he is the first person who believed in my skills in GIS He is one of the foundations of my confidence I also want to thank Ate Mary Joy Ongkiatco for not getting tired of answering my questions about thesis and GIS and for her sweet words of encouragement And to my former housemates for all the good times and bad times we have shared together Especially, to my roomie/bessy, Roxy, for always believing in me  and for being there every single time from eating and doing what we want up to the point that we stay up late until a.m to finish this thesis Luv u all!! ii TABLE OF CONTENTS DOCUMENTATION PAGE WITH ABSTRACT i ACKNOWLEDGEMENT ii TABLE OF CONTENTS iii LIST OF FIGURES v LIST OF TABLES viii LIST OF EQUATIONS xi LIST OF ABBREVIATIONS xii Chapter I INTRODUCTION 1.1 Research Rationale 1.2 Research Questions and Hypotheses 1.2.1 Collecting and processing data using Geographic Information System and Remote Sensing 1.2.2 Influence of mapping and modeling in disaster management 1.2.3 Effects of varying order of importance of map layers using AHP in creating final flood risk map 1.3 Research objectives 1.3.1 General objective of this study 1.3.2 Specific objective of this study 1.4 Significance of the Study 1.5 Scope and Limitations 1.6 Definition of Terms Chapter II 10 LITERATURE REVIEW 10 iii 2.1 Disaster Management 11 2.2 Flood Risk Assessment and its Frameworks 13 2.3 Multi-Criteria Decision Analysis in Flood Risk Assessment 16 2.4 GIS-based Approach in Flood Risk Assessment 19 2.5 Conclusion 21 Chapter III 23 METHODOLOGY 23 3.1 Study Area 24 3.2 Methodological Framework 25 3.3 Data Source and Description 26 3.3.1 Data Source 26 3.3.2 Data Description 27 3.4 Methods 30 3.4.1 Spatial Data Pre-processing and Maps Delineation 30 3.4.2 Multi-criteria Decision Analysis 43 Chapter IV 57 RESULTS AND ANALYSIS 57 4.1 Flood Hazard Maps 58 4.2 Flood Vulnerability Maps 62 4.3 Flood Risk Maps 66 4.4 Flood Risk Maps Comparison 80 Chapter V 82 DISCUSSION AND CONCLUSION 82 REFERENCES 85 APPENDICES iv LIST OF FIGURES Figure Study Area (a) Map of Vietnam; (b) Map of Yen Bai Province; (c) Elevation Map of Tram Tau District 24 Figure Methodological Framework Chart of Flood Risk Assessment in Tram Tau District 26 Figure Slope Map (a) default slope map, (b) reclassified slope map 31 Figure Elevation Map (a) default elevation map, (b) reclassified slope map 32 Figure Rainfall Map (a) default rainfall map, (b) reclassified rainfall map 33 Figure Drainage Density Map (a) default drainage density map, (b) reclassified drainage density map 34 Figure Distance to River Map (a) reclassified distance to river, (b) close-up look of the map 35 Figure Land Cover Statistics 37 Figure Land Cover Map (a) LandSat image of Tram Tau district, (b) classified LandSat image 37 Figure 10 TWI Map (a) default TWI map, (b) reclassified TWI map 40 Figure 11 Population Density Map (a) default population density, (b) reclassified population density 41 Figure 12 Road Density Map (a) default road density, (b) reclassified road density 42 Figure 13 Distance to Road Map (a) reclassified distance to road, (b) close-up look of the map 43 v Figure 14 Flood Hazard Index, Scenarios 1-3.(a) Dd: Drainage density, (b) Dr: Distance to river, (c) E: Elevation, (d) Lc: Land cover, (e) R: Rainfall, (f) Sl: Slope, (g) TWI: Topographic Wetness Index 49 Figure 15 Flood Vulnerability Index Scenarios 1-3 (a) Dro: Distance to road, (b) Pd: Population density, (c) Rd: Road density 53 Figure 16 Combination of Hazard and Vulnerability (a) 1H: Hazard S1, (b) 2H: Hazard S2, (c) 3H: Hazard S3, (d) V1: Vulnerability S1, (e) V2: Vulnerability S2, (f) V3: Vulnerability S3 57 Figure 17 1H Hazard Scenario (Left) default Flood Hazard Map (S1) (Right) reclassified Flood Hazard Map (S1) 59 Figure 18 2H Hazard Scenario (Left) default Flood Hazard Map (S2) (Right) reclassified Flood Hazard Map (S2) 60 Figure 19 3H Hazard Scenario (Left) default Flood Hazard Map (S3) (Right) reclassified Flood Hazard Map (S3) 61 Figure 20 V1 Vulnerability Scenario (Left) default Flood Vulnerability Map (S1) (Right) reclassified Flood Vulnerability Map (S1) 63 Figure 21 V2 Vulnerability Scenario (Left) default Flood Vulnerability Map (S2) (Right) reclassified Flood Vulnerability Map (S2) 64 Figure 22 V3 Vulnerability Scenario (Left) default Flood Vulnerability Map (S3) (Right) reclassified Flood Vulnerability Map (S3) 65 Figure 23 Combinations of Hazard S1 and Vulnerability S1-3 Statistics 68 Figure 24 Combinations of Hazard S2 and Vulnerability S1-3 Statistics 69 Figure 25 Combinations of Hazard S3 and Vulnerability S1-3 Statistics 69 Figure 26 (1H-V1) Combination of Hazard S1 and Vulnerability S1 70 vi Figure 27 (1H-V2) Combination of Hazard S1 and Vulnerability S2 71 Figure 28 (1H-V3) Combination of Hazard S1 and Vulnerability S3 72 Figure 29 (2H-V1) Combination of Hazard S2 and Vulnerability S1 73 Figure 30 (2H-V2) Combination of Hazard S2 and Vulnerability S2 74 Figure 31 (2H-V3) Combination of Hazard S2 and Vulnerability S3 75 Figure 32 (3H-V1) Combination of Hazard S3 and Vulnerability S1 76 Figure 33 (3H-V2) Combination of Hazard S3 and Vulnerability S2 77 Figure 34 (3H-V3) Combination of Hazard S3 and Vulnerability S3 78 Figure 35 Flood Risk Maps in all combinations 79 Figure 36 FR change (Percentage of Total Area) (a) FR change in Vulnerability S1, (b) FR change in Vulnerability S2, (c) FR change in Vulnerability S3 81 vii LIST OF TABLES Table Chosen FRA-related publications 23 Table Data Source 27 Table Slope map classification 31 Table Elevation map reclassification 32 Table Rainfall map classification 33 Table Drainage density map classification 34 Table Distance to river map classification 35 Table Land Cover Classification and Statistics 36 Table TWI map classification 39 Table 10 Population density map classification 40 Table 11 Road density map classification 41 Table 12 Distance to road map classification 43 Table 13 Saaty’s scale for pairwise comparison (Saaty, 1980) 45 Table 14 Saaty’s Random Index (Saaty, 1980) 48 Table 15 HI Standardized criteria weight of each indicator in three different scenarios of FHI (Note: This is arranged in alphabetical order.) 51 Table 16 HI Weighted Sum Vector and Consistency Vector 51 Table 17 VI Standardized criteria weight of each indicator of FVI (Note: This is arranged in alphabetical order.) 54 Table 18 VI Weighted Sum Vector and Consistency Vector 54 Table 19 1H Total percentage of area covered by each class of Flood Hazard Map (S1) 59 viii Table 20 2H Total percentage of area covered by each class of Flood Hazard Map (S2) 60 Table 21 3H Total percentage of area covered by each class of Flood Hazard Map (S3) 61 Table 22 V1 Total percentage of area covered by each class of Flood Vulnerability Map (S1) 63 Table 23 V2 Total percentage of area covered by each class of Flood Vulnerability Map (S2) 64 Table 24 V3 Total percentage of area covered by each class of Flood Vulnerability Map (S3) 65 Table 25 Combination Combinations of Hazard S1 and Vulnerability S1-3 Total percentage of area covered by each class of C1 Maps 68 Table 26 Combination Combinations of Hazard S2 and Vulnerability S1-3 Total percentage of area covered by each class of Combination Maps 68 Table 27 Combination Combinations of Hazard S3 and Vulnerability S1-3 Total percentage of area covered by each class of Combination Maps 69 Table 28 (1H-V1) Ranking of Communes in Total High and Very High Risk 70 Table 29 (1H-V1) Percentage of Total Area Covered by each Class in each Commune 70 Table 30 (1H-V2) Ranking of Communes in Total High and Very High Risk 71 Table 31 (1H-V2) Percentage of Total Area Covered by each Class in each Commune 71 Table 32 (1H-V3) Ranking of Communes in Total High and Very High Risk 72 ix Pairwise Comparison (Sub-criteria layer) Rainfall Sub-Criteria 3200 3100 2800 2500 2300 Sum Slope Sub-Criteria