Title Page
Abstract
Contents
CHAPTER 1. INTRODUCTION 11
1.1. BACKGROUND 11
1.2. OBJECTIVES OF THE RESEARCH 13
1.3. MOTIVATION 14
1.4. LITERATURE REVIEW 16
1.5. RESEARCH FLOWCHART 25
CHAPTER 2. METHODOLOGY 26
2.1. SOFTWARE AND MODEL DESCRIPTION 26
2.1.1. FARD 2006 26
2.1.2. HEC-HMS Model and HEC-Geo HMS Model 27
2.1.3. HEC-RAS Model 30
2.1.4. ArcGIS 32
2.2. PROBABILITY DISTRIBUTION 34
2.2.1. Gumbel Distribution 34
2.2.2. Weibull Distribution 34
2.2.3. Gamma-2 Distribution 35
2.3. PARAMETER ESTIMATION 36
2.3.1. Method of Moments 36
2.3.2. Maximum Likelihood Estimation 37
2.4. GOODNESS OF FIT TEST 38
2.4.1. Chi-square Test 38
2.4.2. Kolmogorov-Smirnov Test 40
2.5. FREQUENCY ANALYSIS 41
2.6. FLOOD RISK ASSESSMENT USING INDICATOR BASED APPROACH 43
CHAPTER 3. SIMULATIONS OF FREQUENCY BASED DISCHARGE AND WATER LEVELS 45
3.1. STUDY AREA AND DATA COLLECTION 45
3.1.1. Study Area 45
3.1.2. Soil Map and Land Cover Map 49
3.1.3. Rainfall and Discharge Data 50
3.2. SELECTION OF PROPER DISTRIBUTION OF RAINFALL DATA 56
3.2.1. Results of Chi-square Test 56
3.2.2. Results of Kolmogorov-Smirnov Test 58
3.3. RAINFALL FREQUENCY ANALYSIS 60
3.4. DISCHARGE HYDROGRPH SIMULATION BY HEC-HMS MODEL 65
3.4.1. Loss Method: SCS Curve Number 65
3.4.2. Transform Method: Clark Unit Hydrograph 66
3.4.3. Baseflow Method: Recession 71
3.4.4. Simulated Discharge Hydrograph and Peak Discharge 72
3.5. SIMULATION OF WATER SURFACE PROFILE BY HEC-RAS MODEL 78
(1) Water Level Elevation Map for the 2011 Flood event 86
(2) Water Level Elevation Map for the 2020 Flood event 88
CHAPTER 4. ESTIMATION OF FLOOD RISK INDEX 91
4.1. ESTIMATION OF HAZARD INDEX AND EXPOSURE INDEX 91
4.1.1. Indicator Determination for Hazard and Exposure 91
4.1.2. Hazard Index Estimation 92
4.1.3. Exposure Index Estimation 95
4.2. ESTIMATION OF FLOOD RISK INDEX 97
CHAPTER 5. SUMMARY AND CONCLUSION 103
REFERENCES 106
〈Table 3.1〉 Rainfall station code and name. 47
〈Table 3.2〉 Water level station code and name. 47
〈Table 3.3〉 Data resources and information about the Gapcheon Stream Basin. 48
〈Table 3.4〉 Soil type characteristics of the study area. 50
〈Table 3.5〉 Results of Chi-square Test in the Gapcheon Stream Basin. 56
〈Table 3.6〉 Results of Kolmogorov-Smirnov Test in the Gapcheon Stream Basin. 58
〈Table 3.7〉 The maximum amounts of rainfall in the Gapcheon Stream Basin. 60
〈Table 3.8〉 Precipitation depths (mm) as a function of different return periods. 61
〈Table 3.9〉 Summary of rainfall in the Gapcheon Stream Basin. 61
〈Table 3.10〉 Curve values (intensity, duration, frequency) for different return periods in the Gapcheon Stream Basin. 62
〈Table 3.11〉 Depth (mm) of rainfall for different return periods in the Gapcheon Stream Basin. 63
〈Table 3.12〉 Flood data for different return periods in the study area. 72
〈Table 3.13〉 Flood data for the 2011 flood event in HEC-HMS. 74
〈Table 3.14〉 Flood data for the 2020 flood event in HEC-HMS. 76
〈Table 4.1〉 Hazard index 1 in the Gapcheon Stream Basin. 92
〈Table 4.2〉 Hazard index 2 in the Gapcheon Stream Basin. 93
〈Table 4.3〉 Exposure Index in the Gapcheon Stream Basin. 95
〈Table 4.4〉 Flood Risk Index 1 in the Gapcheon Stream Basin. 100
〈Table 4.5〉 Flood Risk Index 2 in the Gapcheon Stream Basin. 101
〈Figure 1.1〉 The flowchart of this study. 25
〈Figure 2.1〉 Flowchart for HEC-HMS methodology. 28
〈Figure 2.2〉 Flowchart for HEC-RAS methodology. 32
〈Figure 2.3〉 Flowchart for Flood Risk Assessment. 44
〈Figure 3.1〉 Geographical location of the study area. 45
〈Figure 3.2〉 Subbasins and Thiessen Polygon. 46
〈Figure 3.3〉 Soil map of the Gapcheon Stream Basin. 49
〈Figure 3.4〉 Land cover map of the Gapcheon Stream Basin. 49
〈Figure 3.5〉 Rainfall data in the Gapcheon Stream Basin from 2002 to 2022. 53
〈Figure 3.6〉 Discharge data in the Gapcheon Stream Basin from 2002 to 2022. 56
〈Figure 3.7〉 Curve values (intensity, duration, and frequency) in the Gapcheon Stream Basin. 62
〈Figure 3.8〉 Curve values (depth, duration, and frequency) in the Gapcheon Stream Basin. 63
〈Figure 3.9〉 Hydrograph of the flood water of the Gapcheon Stream Basin for different return periods. 73
〈Figure 3.10〉 Flow data of the Gapcheon Stream Basin for different return periods. 73
〈Figure 3.11〉 Hydrograph of the 2011 flood event in HEC-HMS. 76
〈Figure 3.12〉 Hydrograph of the 2020 flood event in HEC-HMS. 77
〈Figure 3.13〉 The Water Level Elevation Map for different return periods. 84
〈Figure 3.14〉 The Upstream Water Level Elevation Map for the 2011 flood event. 86
〈Figure 3.15〉 The Downstream Water Level Elevation Map for the 2011 flood event. 87
〈Figure 3.16〉 The Upstream Water Level Elevation Map for the 2020 flood event. 88
〈Figure 3.17〉 The Downstream Water Level Elevation Map for the 2020 flood event. 89