Registration No. 11-1750140-000189-01
Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam and Lao PDR (Ⅰ )
Dec, 2016
National Disaster Management Research Institute Research Project: Construction of Forecasting and Warning Systemfor Disaster Risk Reduction in Vietnam& Lao PDR(Ⅰ )
Research Period: 2016. 06. 14 ~ 2016. 12. 22
Service Supervisor
Supervisor: Lee, Chihun Research official, NDMI Vice-supervisor: Choi, Seung-yong Research official, NDMI
Research Staff
Research Manager: Yang, Dongmin NOAA SNC
Researcher: Park, Moonhyun Dongbu Engineering
Ha, Sangmin IoT Solution
Research Assistant: Choi, Yongbok NOAA SNC
Kwon, Hyukjong NOAA SNC
Kim, Cheolhan NOAA SNC
Oh, Seojin NOAA SNC
Chang, Kwonhee NOAA SNC
Chae, Yongju NOAA SNC
Kim, Dohan NOAA SNC
Lee, Byunghyun NOAA SNC
Kim, Boram NOAA SNC
Kang, Seoungbu NOAA SNC
Ahn, Sujeong NOAA SNC
Uh, Gyu NOAA SNC
Kim, Hunbeom NOAA SNC Research Staff
Jeong, Sunchan Dongbu Engineering
Kim, Jiho Dongbu Engineering
Park, Yongseup Dongbu Engineering
Seong, Yeongdu Dongbu Engineering
Kim, Juouk Dongbu Engineering
Kim, Byungseon Dongbu Engineering
Lee, Seonghee Dongbu Engineering
Kim, Byunghoon Dongbu Engineering
Kim, Taeshik Dongbu Engineering
Lee, Baeseong Dongbu Engineering
Hwang, Jonghun Dongbu Engineering
Jeon, Jaebok Dongbu Engineering
Oh, Jinsu Dongbu Engineering
Lee, Jeongyong Dongbu Engineering
Choi, Seungyoon Dongbu Engineering
Go, Seokhyun Dongbu Engineering
Lim, Ingyu Dongbu Engineering
Kwon, Yongchan Dongbu Engineering
Cho, Jinhyeng IoT Solution
Kim, Jonghun IoT Solution
Kim, Jonghun IoT Solution
Kim, Juouk IoT Solution
Assistant: Kim, Danbi NOAA SNC Report
To the National Disaster Management Research Institute
I submit this as the final report on the Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Lao PDR(Ⅰ ).
2016. 12.
NOAA SNC C E O Yang, Dongmin (sign) IoT Solution C E O Cho, Jinhyeng (sign) Dongbu Engineering C E O Nho, Jaehwa (sign)
SUMMARY
Ⅰ. Title
Construction of forecasting and warning system for disaster risk reduction in
Vietnam and Lao PDR(Ⅰ )
Ⅱ. Objectives
1. Floods in mountainous area due to flash flood which has short travel time and
fast velocity characteristic cause the facilities and human life, and need to
fundamental corresponding measures for damage reduction
2. Need to technology combination and diffusion of “ARWS(Automated Rainfall
Warning System)” and “FFAS(Flash Flood Alert System)” for damage reduction
in domestic mountains and valleys
3. Training and technological skills transfer for system application of recipient
country after project completion
Ⅲ. Contents
1. Pre-investigation for advancement of the FFAS (Flash Flood Alert System) and
installation of the additional ARWS (Automatic Rainfall Warning System)
A. Data collection and selection of the potential sites for system installation
2. Demonstration construction of the FFAS and ARWS
A. Demonstration construction of FFAS in Vietnam and Lao PDR
B. Demonstration construction of ARWS (two water gauges, two rain gauges and
warning stations for each country)
3. Calibration of the FFAS and the ARWS
4. River survey for target area and implementation of hydraulic and hydrological analysis
A. River survey for the major sites of the basin (including main river and points) through field survey for the existing rain and water level gauge sites
B. Establishment of the warning criteria using water level data of the basin
5. Analysis of the risk against a flash flood occurring in target area and construction of the risk map
A. Dividing watershed by applying the concept of flash flood
B. Construction of the flash flood map (1:5,000) through risk analysis 6. System training for public officers and experts related to disaster management of
Vietnam and Lao PDR
A. In-depth training of theory and practical exercise of hydraulic and hydrological analysis for experts
B. System operation training for local site personnel
C. Production of detailed manual related to the system maintenance and operation 7. Write the reports of the ODA project
A. Performance report and satisfaction survey report
8. Make the publicity material(English, Vietnamese and Lao language) in each country of “Construction of forecasting and warning system for disaster
mitigation in Vietnam and Lao PDR”
A. Make the pamphlet and promotional video of the ODA project
Ⅳ. Conclusions
1. Construction of the ARWS(two rain gauges, two water gauges and two warning
stations)
2. Construction of FFAS in Vietnam and Lao PDR 3. Writing a flooding map and a risk map of target area
4. Establishment of warning criteria through river survey Table of Contents
List of Figures ································································································· ⅹ
List of Tables ································································································· ⅹⅴ
Abbreviations ····································································································· ⅹⅹ
Chapter 1. Introduction ···················································································· 1
1.1 Necessity of Study ························································································3 1.2 Purpose of Study ························································································· 3 1.3 Content of Study ·························································································· 4
1.4 Expected Effects ····························································································5
Chapter 2. Local Survey and Preliminary Research ······································ 7
2.1 Basic Data Collection & Analysis ·························································· 9
2.2 Establishment of Automatic Rainfall Warning Facilities and Installation of the Flash Flood Forecasting/Warning System ·············24
Chapter 3. Establishment of Automatic Rainfall Warning Facilities and Installation of the Flash Flood Forecasting/Warning System ······················ 29
3.1 Establishment of Automatic Rainfall Warning Facilities ············· 31 3.2 Flash Flood Alert System (FFAS) Installation ·································· 68
Chapter 4. Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis ················································································································83
4.1 Survey on Target Basin Rivers ···························································· 85 4.2 Hydraulic/Hydrological Analysis ·························································· 107
- viii - Chapter 5. Flash Flood Hazard Analysis & Hazard Mapping ·················· 159
5.1 Concept & System of Hazard Estimation ······································ 161
5.2 Selection of Flash Flood Hazard Indexes ······································ 163 5.3 Methods of Flash Flood Hazard Estimation ····································167 5.4 Estimation Results ·················································································· 170
Chapter 6. Conclusion ···················································································· 173
Reference ········································································································· 177
- ix - Figure 2.1 Collected DEM Data ·································································· 11 Figure 2.2 Target Basin Land Cover Map ··············································· 12 Figure 2.3 Vang Vieng Region Landuse Map ········································· 14
Figure 2.4 Lao Cai Region Landuse Map ················································ 15 Figure 2.5 Major Meteorological Stations & Same Yearly Precipitation Map··· 16 Figure 2.6 Meteorological Stations in Vietnam ··································· 19
Figure 2.7 Damaged Districts of Typhoon Haima ······························· 23 Figure 2.8 Course of Typhoon Nida ························································· 24 Figure 3.1 Diagram of Laos ARWS Installation ····································· 32
Figure 3.2 Diagram of Vietnam ARWS Installation ····························· 32 Figure 3.3 Installation Process of Pha Tang Bridge Rainfall Observatory System ·························································································· 45
Figure 3.4 Installation Process of Vang Pho Rainfall Observatory System·· 47 Figure 3.5 Installation Process of the Water Level Observation System ·· 49 Figure 3.6 Installation Process of Vang Pho Bridge Water Level
Observation System ·························································································· 51 Figure 3.7 Installation Process of Muang Xong Temple Automatic Warning System ································································································· 52
Figure 3.8 Installation Process of Huay Nyae Primary School Automatic Warning System ··············································································54 Figure 3.9 Installation Process of Tả Phờ i School Rainfall Observatory System·· 56
Figure 3.10 Process of Installing a Rainfall Observatory System in a Vacant Lot, Tả Phờ i ························································································· 57 Figure 3.11 Installation Process of the Water Level Observation System ·· 59
- x - Figure 3.12 Installation Process of Dien Cao Bridge Water Level Observation System ·························································································· 61
Figure 3.13 Installation Process of Tả Phờ i Office Automatic Warning System·· 62 Figure 3.14 Installation Process of Dien Cao Vacant Lot Automatic Warning System ································································································· 63
Figure 3.15 Installation Location of Automatic Rainfall Warning Facilities ··············································································································· 65 Figure 3.16 Target Regions of FFAS Service ·········································· 68
Figure 3.17 FFAS Laos DMH Installation Photos ·································· 69 Figure 3.18 FFAS Basic Frame of the Function Definition System ·· 71 Figure 3.19 Main Page Menu Frame ························································· 77
Figure 3.20 FFAS Screen Definition ··························································· 77 Figure 3.21 Main Screen ················································································ 78 Figure 3.22 Hazard Map ················································································ 78
Figure 3.23 Flooding Map ············································································· 79 Figure 3.24 River Information ····································································· 79 Figure 4.1 Vietnam Measuring Areas ························································ 85
Figure 4.2 Laos Measuring Areas ································································ 86 Figure 4.3 Laos Vang Vieng River Shape ················································ 87 Figure 4.4 Laos Pateng River Shape ························································· 88
Figure 4.5 Vietnam Lao Cai River Shape ················································ 88 Figure 4.6 GPS Body and RTK RADIO MODEM ···································· 90 Figure 4.7 Drone Phantom 3 Pro ······························································ 91
Figure 4.8 Precise Sounder and Transducer ·········································· 91 Figure 4.9 Principle of RTK-GPS ······························································· 92 Figure 4.10 Drone-based Measurement ···················································· 92
- xi - Figure 4.11 Flow Chart of Drone Measurement ··································· 93 Figure 4.12 Flow Chart of Water Level Measurement ························ 94
Figure 4.13 Principle and Computation of Water Level Measurement ·· 94 Figure 4.14 Laos Vang Vieng Geomorphological Photo ···················· 96 Figure 4.15 Laos Pateng Geomorphological Photo ······························ 97
Figure 4.16 Enlarged Spots of Laos Pateng ··········································· 98 Figure 4.17 Vietnam Lao Cai Geomorphological Photo ···················· 99 Figure 4.18 Enlarged Spots of Vietnam Lao Cai ································ 100
Figure 4.19 Laos Water Level Measurement ········································· 101 Figure 4.20 Vietnam Water Level Measurement ·································· 101 Figure 4.21 Laos Vang Vieng Cross Sectional Data Extraction ···· 102
Figure 4.22 Longitudinal/Cross Sectional Drawing ······························102 Figure 4.23 Existing Water Level Observatory Station Leveling ···· 103 Figure 4.24 Local Laying Spot (Laos_Vang Vieng) ····························· 104
Figure 4.25 Local Laying Spot (Laos_Pateng) ······································ 105 Figure 4.26 Local Laying Spot (Laos_Pateng) ······································ 106 Figure 4.27 Warning Criteria Based on Hydraulic/Hydrological
Analysis ·············································································································· 108 Figure 4.28 Hydraulic/Hydrological Analysis Procedures in Vietnam ··· 109 Figure 4.29 Altitude Distribution ······························································ 111
Figure 4.30 Slope Distribution ·································································· 112 Figure 4.31 Strike Map ················································································ 113 Figure 4.32 Suoi Peng River Sub-basin Division ······························· 114
Figure 4.33 IDF Curves ················································································ 119 Figure 4.34 Topographical Data ······························································· 120 Figure 4.35 Graph of Flood Rate Estimation by Frequency ·········· 128
- xii - Figure 4.36 Flooding Map Design by Means of an HEC-GeoRAS Model ·················································································································· 131
Figure 4.37 DEM Interpolation Results ·················································· 133 Figure 4.38 HEC-RAS Topographical Foundation and Flood Level Estimation Process ························································································· 135
Figure 4.39 PostRAS Configuration ·························································· 136 Figure 4.40 Flooding Map (1yr) ································································ 136 Figure 4.41 Flooding Map (2 yr) ······························································ 137
Figure 4.42 Flooding Map (5 yr) ······························································ 137 Figure 4.43 Flooding Map (10 yr) ···························································· 137 Figure 4.44 Flooding Map (20 yr) ···························································· 138
Figure 4.45 Flooding Map (50 yr) ···························································· 138 Figure 4.46 Flooding Map (100 yr) ·························································· 138 Figure 4.47 Flood Level Planning on a Decade Basis ······················ 140
Figure 4.48 Hợ p Thà nh Levee Warning Criteria ································ 140 Figure 4.49 Dien Cao Bridge Warning Criteria ·································· 140 Figure 4.50 Laos Hydraulic/Hydrological Analysis Procedures ······ 141
Figure 4.51 Altitude Distribution ······························································ 143 Figure 4.52 Slope Distribution ·································································· 144 Figure 4.53 Strike Map ················································································ 145
Figure 4.54 Positions of Flood Rate Data Observation ················· 147 Figure 4.55 Maximum Likelihood Method PDF Graph ···················· 149 Figure 4.56 Maximum Likelihood Method CDF Graph ···················· 150
Figure 4.57 PreRAS Configuration ··························································· 152 Figure 4.58 DEM Interpolation Results ·················································· 153 Figure 4.59 HEC-RAS Topographical Foundation and Flood Level
- xiii - Estimation Process ························································································· 154 Figure 4.60 Flooding Map (2yr) ································································ 155
Figure 4.61 Flooding Map (5yr) ································································ 155 Figure 4.62 Flooding Map (10yr) ······························································ 155 Figure 4.63 Flooding Map (50yr) ······························································ 156
Figure 4.64 Flooding Map (100yr) ···························································· 156 Figure 4.65 Flooding Map (150yr) ···························································· 156 Figure 4.66 Pha Tang Bridge Warning Criteria ·································· 157
Figure 4.67 Vang Vienge Warning Criteria ·········································· 157 Figure 5.1 Disaster Hazard Assessment System ··································· 162 Figure 5.2 Laos, Vietnam Sub-basin ······················································· 163
Figure 5.3 Flash Flood Hazard Assessment by Indexes ··················· 170 Figure 5.4 Laos Flash Flood Hazard Map ············································· 171 Figure 5.5 Flash Flood Hazard Assessment by Indexes ··················· 172
Figure 5.6 Vietnam Flash Flood Hazard Map ······································ 172
- xiv - List of Tables
Table 2.1 Basic Data Collection Method ················································· 10 Table 2.2 Basic Data Collection Method ················································· 13
Table 2.3 Major Meteorological Stations in Laos ································· 16 Table 2.4 Yearly Min./Max. Runoff ··························································· 17 Table 2.5 Monthly Climate Information ··················································· 18
Table 2.6 Monthly Climate Information ··················································· 20 Table 2.7 Administrative Districts and Populations of the Target Basin in Laos ····································································································· 21
Table 2.8 Administrative Districts and Populations of the Target Basin in Vietnam ······························································································ 22 Table 2.9 Candidate Areas for Automatic Rainfall Alert Facility
Installation in Laos ·························································································· 25 Table 2.10 Candidate Areas for Alert Station Installation ················ 26 Table 2.11 Candidate Areas for Rainfall and Water Level
Observatory Installation ·················································································· 26 Table 2.12 Candidate Areas for Automatic Rainfall Alert Facility Installation ··········································································································· 27
Table 2.13 Candidate Areas for Basin Alert Stations in Lao Cai, Vietnam ················································································································ 27 Table 2.14 Candidate Areas for Basin Rainfall Observatory System
Installation in Lao Cai, Vietnam ································································· 28 Table 2.15 Candidate Areas for Basin Water Level Observatory System Installation in Lao Cai, Vietnam ················································· 28
Table 3.1 Configuration of the Rainfall Observatory System ·········· 33
- xv - Table 3.2 Specifications of the Rainfall and Water Level Observatory System ··················································································································· 35
Table 3.3 Configuration of the Rainfall Observatory System ·········· 37 Table 3.4 Specifications of the Rainfall and Water Level Observatory System ··················································································································· 38
Table 3.5 Specifications of the Automatic Rainfall Warning System ·· 41 Table 3.6 Specifications of the Automatic Warning System ············ 43 Table 3.7 Locations for Pha Tang Bridge Rainfall Observatory
System Installation ···························································································· 44 Table 3.8 Locations for Vang Pho Bridge Rainfall Observatory System ··· 46 Table 3.9 Pha Tang Bridge Water Level Observatory System
Locations ·············································································································· 48 Table 3.10 Vang Pho Bridge Water Level Observatory System Locations ·············································································································· 49
Table 3.11 Pha Tang Bridge Water Level Observatory System Locations ·············································································································· 51 Table 3.12 Huay Nyae Primary School Water Level Observatory
System Locations ······························································································· 53 Table 3.13 Tả Phờ i School Rainfall Observatory System Locations ··· 55 Table 3.14 Tả Phờ i Vacant Lot Rainfall Observatory System Locations ··· 57
Table 3.15 Hợ p Thà nh Levee Water Level Observatory System Locations ·············································································································· 58 Table 3.16 Dien Cao Bridge Water Level Observatory System
Locations ·············································································································· 60 Table 3.17 Pha Tang Bridge Water Level Observatory System Locations ·············································································································· 61
- xvi - Table 3.18 Dien Cao Vacant Lot Water Level Observatory System Locations ·············································································································· 63
Table 3.19 Current Conditions of Automatic Rainfall Warning Facilities Installed by National Disaster Management Research Institute ·············64 Table 3.20 Major Aspects of Automatic Rainfall Alert Facility
Operation ············································································································· 66 Table 3.21 Major Aspects of Automatic Rainfall Alert Facility Operation ············································································································· 67
Table 3.22 System Functions & Services ················································· 69 Table 3.23 Requirement Definitions ·························································· 70 Table 3.24 Function Definitions ································································· 72
Table 3.25 Table Definition (BASIN_INFO) ············································ 73 Table 3.26 Table Definition (BASIN_PRECIPITATION) ······················· 73 Table 3.27 Table Definition (AWS_INFO) ················································ 74
Table 3.28 Table Definition (AWS_PRECIPITATION) ························· 75 Table 3.29 Table Definition (AWS_PRECIPITATION_DP) ·················· 75 Table 3.30 FFAS Screen Layout ································································· 76
Table 3.31 System Development Environment ······································· 80 Table 3.32 HW Specifications ······································································ 81 Table 4.1 Scope of Measurement ······························································· 87
Table 4.2 Scope of Measurement ······························································· 95 Table 4.3 Characteristics of Suoi Peng River Basin ························· 110 Table 4.4 Cumulative Area and Component Ratio by Altitude ···· 112
Table 4.5 Cumulative Area and Component Ratio by Slope ········· 113 Table 4.6 Area Distribution by Direction ············································· 114 Table 4.7 Geometric Characteristics at Each Estimation Location ··· 115
- xvii - Table 4.8 Rainfall Quantile ········································································ 116 Table 4.9 Probable Rainfall Intensity for Each Rainfall Duration ·· 117
Table 4.10 Determination Coefficient Comparison ··························· 118 Table 4.11 Probable Rainfall Intensity Formula ································· 119 Table 4.12 Arrival Time Formula Applicable ······································· 122
Table 4.13 Result of Arrival Time Calculation ··································· 122 Table 4.14 Empirical Equation of the Storage Constant ················· 123 Table 4.15 Result of Storage Constant Calculation ··························· 123
Table 4.16 Classification of Existing Soil Water Content Conditions ·· 125 Table 4.17 Classification of Hydrological Soil Groups ···················· 125 Table 4.18 Runoff Curve Indexes for Each Estimation Point(CN) ·· 126
Table 4.19 Runoff Curve Indexes of Agricultural and Forestry Regions (AMC-Ⅱ Conditions) ····································································· 127 Table 4.20 Calculation of Flood Rates by Frequency ······················ 128
Table 4.21 PreRAS Components ······························································· 132 Table 4.22 Flood Level at Each Major Location by Frequency ···· 134 Table 4.23 PostPAS Components ······························································ 136
Table 4.24 Criteria for Flood Alert ························································· 141 Table 4.25 Characteristics of Nam Xong River Basin ······················ 142 Table 4.26 Cumulative Area and Component Ratio by Altitude ·· 143
Table 4.27 Cumulative Area and Component Ratio by Slope ······ 145 Table 4.28 Area Distribution by Direction ··········································· 146 Table 4.29 Locations of Flood Level Measurement ··························· 147
Table 4.30 Flood Level Data by Year ···················································· 148 Table 4.31 Result of Flood Level Calculation ····································· 149 Table 4.32 Suitability Test Results by Probable Distribution Type ·· 150
- xviii - Table 4.33 Flood Level at Each Major Location by Frequency ···· 153 Table 4.34 Criteria for Flood Alert ························································· 158
Table 5.1 Flood & Typhoon Hazard Assessment Indexes ··············· 164 Table 5.2 Flood & Typhoon Hazard Assessment Indexes ··············· 165 Table 5.3 Laos Hazard Assessment Indexes ········································· 166
Table 5.4 Vietnam Hazard Assessment Indexes ·································· 167 Table 5.5 Vietnam/Laos Hazard Assessment Indexes ······················· 168
- xix - Abbreviations
ARWS Automatic Rainfall Warning System AWS Automatic Weather Station
CN Curve Number DEM Digital Elevation Model DMH Department of Meteorology and Hydrology
FFAS Flash Flood Alert System GSM Global System for Mobile Communication IPCC Intergovernmental Panel on Climate Change
NDMI National Disaster Management Institute ODA Official Development Assistance OECD Organization for Economic Co-operation and Development
PDR People's Democratic Republic SIM Subscriber Identity Module SMS Short Message Service
UNESCO United Nations Educational, Scientific and Cultural Organization UNISDR United Nations International Strategy for Disaster Reduction VAWR Vietnam Academy for Water Resources
WLMS Water Level Monitoring Station WMO World Meteorological Organization
- xx -
Chapter 1. Introduction
1.1 Necessity of Study
1.2 Purpose of Study
1.3 Content of Study
1.4 Expected Effects
Chapter 1 Introduction | 3
Chapter 1 Introduction
1.1 Necessity of Study
Recently, typhoons and localized torrential downpours occur more frequently than before over Asia-pacific regions due to climate changes. Particularly, flash, localized torrential downpours that are concentrated within a short period of time have become a meteorological phenomena, causing serious and frequent damages. When such natural disasters occur in developing countries in relation to climate changes, lack of recognition of flood symptoms or measures for prevention and evacuation has caused substantial damages. Accordingly, it is necessary to develop ways of reducing and minimizing damages from such disasters.
In Vietnam and Laos, for example, casualties and material loss are increasing as a result of flash floods that involve a tremendous amount of rain within a short period of time. In case of flash floods, therefore, it is required to develop damage-reducing plans that secure sufficient time for residents' evacuation and to establish a warning and real-time notification system that can minimize casualties and material loss.
Accordingly, the present study aims to adopt the current domestic forecasting/warning system and automatic rainfall warning facilities to Vietnam and Laos according to the local conditions and to minimize the disaster preventive effects based on objective data of high-risk regions and more accurate predictive information. .
1.2 Purpose of Study
○ The flash flood forecasting/warning system is a preemptive disaster 4 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
responsive system that strengthens the recipient country's capacity of reducing disaster hazards unlike other systems that provide relief materials and human resources after a disaster occurs.
○ For recipient countries vulnerable to natural disasters, the disaster control/safety management technologies and policies of the National Disaster Management Research Institute are transferred to share disaster-related information and expand the project of the Official Development Assistance (ODA) project for disaster hazard reduction.
1.3 Content of Study
○ Preliminary researches are conducted in the local areas in order to enhance the effectiveness of the pilot project that adopts the flash flood forecasting/warning system and automatic rainfall warning facilities.
- Basic data of the target basins in Laos, Vietnam, is collected and the installation locations are decided.
○ A pilot project that adopts the flash flood forecasting/warning system and automatic rainfall warning facilities
- A pilot project for the flash flood forecasting/warning system in Vietnam and Laos
- A pilot project for the automatic rainfall warning system (2 water gauges, 2 rain gauges, and 2 warning stations in each country)
○ Test and calibration of the flash flood forecasting/warning system and automatic rainfall warning facilities
○ Hydraulic/hydrological analysis based on a survey over the target river basins
- River survey on major target basins (including the mainstreams and specific locations) including field investigation on existing water Chapter 1 Introduction | 5
level ·rain gauge data
- Establishment of warning criteria based on basin water level data
○ Flash Flood Hazard Analysis & Hazard Mapping over target basins
- Basin divisional mapping in application of the flash flood concept
- Hazard analysis for flash flood risk mapping (1:5,000)
○ System education for public officials and experts in the area of disaster prevention in Vietnam and Laos
- Education for experts including hydraulic․ hydrological analysis theories and practice
- Education on system operation for local hands-on workers
- Detailed manual on system maintenance and operation
○ Preparation of ODA project performance report and satisfaction survey report
- Preparation of ODA project performance report and satisfaction survey report
○ Promotion data for each country regarding the results of “Establishment of the Forecasting/Warning System for Disaster Risk Reduction in Vietnam and Laos" (in English, Vietnamese, and Lao)
- Production of ODA project promotion materials and brochures
1.4 Expected Effects
○ As domestic disaster prevention technologies are supplied to developing countries, their independence and capabilities for continued maintenance and disaster preventive systems will be strengthened.
○ Expenses for restoration from damages after a disaster in the recipient country are reduced while the productivity in the industry of disaster prevention increases. 6 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
○ The experience of participating in the ODA project will make it possible to address problems of existing approaches and develop global leadership
○ The technical excellence of the existing flash flood forecasting/warning system in Korea has been proved, and its capability of disaster prevention will be strengthened on a global scale as it is developed further. Chapter 2. Local Survey and Preliminary Research
Basic Data Collection & 2.1 Analysis Establishment of Automatic Rainfall Warning Facilities 2.2 and Installation of the Flash Flood Forecasting/Warning System
Chapter 2 Local Survey and Preliminary Research | 9
Chapter 2 Local Survey and Preliminary Research
As unusual weather conditions cause serious damages one after another around the globe, one of the most influential causes of disasters in developing countries is flash floods. Flash floods are related to heavy rains that pass slowly through a topographically narrow and steep basin, localized torrential downpours or typhoons that move rapidly within the same local region, or drastic increase of the river water level within a short period of time due to typhoons. Such disasters result from unusual climate phenomena and occur repeatedly around the globe. The scale of damage increases gradually.
To minimize such damages, the National Disaster Management Research Institute installed successfully the Flash Flood Alert System (FFAS) and Automatic Rainfall Warning Facilities in the northern region of Mindanao Island, the Philippines, for 3 years from 2013 to 2015. In the annual meeting (May) and integrated workshop (November) of the Typhoons Committee Disaster Prevention Department held in 2014, it was decided that the establishment of the forecasting/warning system (I) would be initiated for Vietnam and Laos this year as the request of the delegates of Vietnam and Laos for the ODA project was accepted. In May 2015, the validity investigation was conducted in the local areas of Vietnam and Laos. For 3 years from 2016, the Flash Flood Alert System (FFAS) and Automatic Rainfall Warning Facilities will be installed in high-risk regions of Vietnam and Laos.
2.1. Basic Data Collection & Analysis 10 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2.1.1. Collection of Basic Data
A. Basic Data Collection Method
Basic data was collected from Suoi Peng River in Lao Cai, Vietnam Lao Cai, and Nam Xong River Basin in Vang Vieng, Laos for hydraulic/hydrological analysis. Although it may be possible to collect directly or process data, entrusting a related public agency with collection and management of data is more efficient in terms of data reliability, expense, and time. In the event that the quality of data secured by the agency is too low, however, a plan for direct collection of data should be established. For the current project, it will be most appropriate to utilize an online method of high efficiency, among various basic data collection methods, in consideration of the schedule and distance from the object region.
Table 2.1 Basic Data Collection Method
Expe Colle Suitabi Method Time Remark nse ction lity Interview Since data should be collected from more than one institution, the -based × △ ○ △ collecting process requires time and survey expense. Telephon Data collection through calls to e-based △ △ × × managers in charge may save time and survey cost, data collection is challenging. Mailing-based survey is appropriate Mailing △ × △ △ when the period of survey and data survey collection is sufficiently long.
In consideration of project characteristics including the expense, Online ○ ○ △ ○ data collection period, and collection (E-mail) rate, this method is more efficient than other data collecting methods. Source: The Forecasting/Warning System Establishment Project for Disaster Reduction in the Philippines - Ⅱ, 2014 Chapter 2 Local Survey and Preliminary Research | 11
B. Basic Data Collection
For hydraulic/hydrological analysis, the basic data needs to include topographical data such as DEM and numerical maps, rainfall observation data, water level-flow rate data for flood rate examination, geological maps, land cover maps, etc. In addition, flood occurrence history records, population density data, and disaster history records are also necessary to grasp actual damages to the target regions in the past.
(1) DEM (Digital Elevation Model, 90m)
DEM-based numerical altitude data is of a 3D data format that represents irregular topographical fluctuation. This type of data is utilized in various areas such as urban planning, civil engineering, environment, and so forth. The DEM data collected for this project is of 90m resolution, and an example of the collected DEM data is as below:
Figure 2.1 Collected DEM Data 12 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(2) Land Cover Map
A land cover map classifies physical formations on the surface such as vegetation based on environmental values, natural and ecological uses, etc. A land cover map is used for parameter determination when basin runoff should be calculated. The following is a land cover map based on target basin data collected for this project:
Laos Vietnam Figure 2.2 Target Basin Land Cover Map
C. Current Condition of Basic Data Collection
Data that has been collected for the present study includes DEM data, land cover map, and regional population density. Details are as follows: Chapter 2 Local Survey and Preliminary Research | 13
Table 2.2 Basic Data Collection Method
Collected Data Complem Item Data Future Plan Provided entation Available A middle-level DEM data ○ ○ - resolution DEM to be purchased Land cover map × ○ ○ Impermeable rate Unable to collect Flood damage × × × data Flood history × × - - Regional population ○ ○ - - density No. of warnings Unable to collect × × × issued data Damage by flash Unable to collect × × × floods (amount) data
2.1.2. Basin Information
A. Laos Nam Xong River Basin
Nam Xong River is a small river that runs through Vang Vieng. It is located in a region visited by a number of tourists. Its river course is originated from Phou Keo and extended all the day to Man Lik. The basin is as large as 864㎢ , and its channel is as long as 36km. The major tributaries of Nam Xong River are Nam Ssnen (35 km2) and Nam Pamom (24 km2). Its average rainfall is 2,481mm per year, and the average annual rainfall over Vang Vieng region is 3,330mm. The average annual runoff over Vang Vieng is 47.96 m³/s.
As for the land use of Nam Xong River Basin, 40% of it is forests, 14 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
25% rice fields, 20% hilly areas, 8% cities, 1% lakes, rivers, and wetland, and 6% others respectively. Nam Xong River Basin is a region where the population density is quite high due to the rapid growth and urbanization. Commercial facilities also have increased as tourism grows. Due to the drastic population increase, water shortage is serious during the dry season while a lot of deposits are accumulated during the rainy season.
Figure 2.3 Vang Vieng Region Landuse Map
B. Vietnam Ta Phoi Basin
Located around Ta Phoi Basin, Suoi Peng River is one of the narrow courses of Red River. This basin consists mainly of mountainous areas. As its topography is complicated, there are various climatic zones in this region. In more than 80% of this region, the slope is 25 degrees or higher. The flow rate over Lao Cai region during the rainy season accounts for 70 to 75% of the yearly quantity of flow which is about 1,400mm to 3,000mm. During the rainy season from April to October, many flash floods and landslides occur. Chapter 2 Local Survey and Preliminary Research | 15
Figure 2.4 Lao Cai Region Landuse Map
2.1.3. Meteorological Characteristics
A. Meteorological Conditions in Laos
1) Meteorological Observation
A meteorological station is located in Vang Vieng along with Nam Xong River, and its records trace back to 1969. Including Vang Vieng Meteorological Station installed near Nam Xong River, Major Meteorological Stations in Laos are as below: 16 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 2.3 Major Meteorological Stations in Laos
Location Average Observato Altitude Observation Annual No. ry Latitude Longitude (EL.m) Period Rainfall (mm)
1 Phatang 19° 08' 00" 102° 34' 00" 340 1995- 2,248.3
2 Vangvieng 18° 56' 00" 102° 27' 00" 296 1969- 3,330.1
3 Hineheup 18° 48' 00" 102° 20' 00" 200 1991- 1,665.3
Figure 2.5 Major Meteorological Stations & Same Yearly Precipitation Map Chapter 2 Local Survey and Preliminary Research | 17
2) Climates in Laos
The target basin is part of the monsoon tropical climate zone where the rainy season lasts from May to October and the dry season from November to April. The average annual temperature is 29°C, and it rains most in August. Table 2.4 Yearly Min./Max. Runoff
Max. Min. Max. Min.
Year Flow Year Flow Flow Flow Date Month Rate Date Rate Month Rate Rate [m³/s] [m³/s] [m³/s]
1987 Sep. 2 258.00 April 4.80 1995 Aug. 14 526.00 April 6.89
1988 Aug. 31 350.00 March 6.64 1996 - - - -
1989 June14 314.00 April 6.64 1997 Sep. 2 799.00 March 10.0
1990 Sep. 11 357.00 April 6.50 1998 Aug. 14 285.00 May 4.95
1991 July 15 312.00 March 8.00 1999 Aug. 13 238.428 Feb. 8.60
1992 July 26 370.00 May 2.67 2000 June27 184.167 April 11.1
1993 June30 364.00 March 5.86 2001 July 4 473.682 Feb. 9.1
1994 Aug. 30 366.00 May 3.09 2002 Aug. 6 470.203 Feb. 10.1 18 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
The following is meterological information collected at Vang Vieng Meteorological Station including monthly temperature, rainfall, evaporation rate, etc.
Table 2.5 Monthly Climate Information
Obser Year Class. Jan. Feb. Mar. April May June July Aug. Sep. Oct. Nov. Dec. vation ly Period
Tem 20. 22. 25. 27. 27. 27. 26. 26. 27. 26. 24. 21. 1972 p. 25.3 7 7 8 6 5 6 8 6 0 4 2 5 - 83 (°C)
Rainf 11. 21. 54. 15 32 62 87 65 42 12 53. 14. 3,33 1,969 all 1 0 5 0.0 1.0 1.9 5.2 9.5 2.5 5.3 4 6 0.1 - 98
Evap 60. 76. 12 15 16 15 15 14 14 13 92. 66. 1,47 1,972 orati 0 0 7 1 3 8 7 9 1 2 0 0 2.0 - 83 on Solar 14. 19. 22. 20. 19. 18. 17. 16. 16. 16. 14. 14. 15. 1,972 Radi 5 4 4 8 4 4 7 9 8 4 4 4 97 - 83 ation
B. Meteorological Conditions in Vietnam
1) Meteorological Observation
There are 176 meteorological stations and 764 rainfall observatories in Vietnam. Among 764 rainfall observatories, 371 are part of the network of hydraulic/hydrometric stations and the rest are not. Figure 2.5 shows the map of meteorological stations in Vietnam. Chapter 2 Local Survey and Preliminary Research | 19
Figure 2.6 Meteorological Stations in Vietnam
2) Climatal Characteristics in Vietnam
Topographically, Lao Cai consists mainly of mountainous regions. Its dry season is between October and March, and the rainy season is between April and September. The average annual temperature is 23°C, and the general range of temperature is between 18 and 28°C. Thunderstorms and flood tides occur in April, May, and June while floods and flash floods occur mainly in June, July, August, and September.
The following is information on monthly temperature and rainfall in Lao Cai. 20 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 2.6 Monthly Climate Information
Marc Class. Jan. Feb. April May June July Aug. Sep. Oct. 1Jan. Dec. h
Temp . 20.7 22.7 25.8 27.6 27.5 27.6 26.8 26.6 27.0 26.4 24.2 21.5 (°C)
Lowe st Temp 13.2 14.5 17.5 20.1 22.8 24.5 24.4 24.5 23.4 20 17.3 14.3 . (°C) Highe st Temp 20 22.1 24.9 28.3 31.7 32.6 32.9 32.8 32.2 29.7 25.8 22.7 . (°C)
Rainfa 18 48 48 140 207 251 308 270 265 117 47 21 ll Chapter 2 Local Survey and Preliminary Research | 21
2.1.4. Humanities and Social Phenomena
A. Administrative Districts and Populations in Laos
Nam Xong River Basin is part of Vang Vieng region, and Vang Vieng belongs to Vientiane City. The following table shows the administrative districts and populations in Vientiane.
Table 2.7 Administrative Districts and Populations of Target Basins in Laos
Administration Population City Administrative District Code (individuals)
Phonhong 1001 60,716
Thoulakhom 1002 52,169
Keo oudom 1003 18,629
Kasy 1004 27,534
Vangvieng 1005 47,046
Feuang 1006 54,535
Xanakharm 1007 38,732 Vientiane Mad 1008 17,715
Viengkham 1009 26,520
Hinherb 1010 18,295
Hom 1011 8,015
Xaysomboon 1012 28,428
Muen 1013 18,989
Total 417,323 22 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Administrative Districts and Populations in Vietnam
Lao Cai State is divided to 9 regions including Lao Cai City. 8 districts except Lao Cai City are classified as districts.
Table 2.8 Administrative Districts and Populations of Target Basins in Vietnam
Area Population State Administrative District (km²) (individuals)
Lao Cai District 221.5 94,192
Bắ c Hà District 680 48,988
Bả o Thắ ng District 674 107,174
Bả o Yê n District 821 73,924
Bá t Xá t District 1050 62,477 Lao Cai Mườ ng Khươ ng District 552 48,242
Sa Pa District 677 42,095
Si Ma Cai District 241 25,554
Vă n Bà n District 557.5 73,183
Total 5474 575,829 Chapter 2 Local Survey and Preliminary Research | 23
2.1.5. Damages from Floods
A. Laos typhoons
1) Typhoon “Haima"
Typhoon Haima occurred on June 24, 2011, and its influence lasted for 3 days, causing damage to Bolikhamxay, Xayaboury, Vientiane, and Xiengkhouang. This typhoon resulted in at least 18 deaths, more than 100 injuries, and direct harm to 87,403 individuals. In addition, residences, crops, schools, hospitals, roads, bridges, electric facilities, levees, and other structures were destroyed. The estimated loss amounted to 67 million dollars in total.
Figure 2.7 Damaged Districts of Typhoon Haima 24 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Typhoons in Vietnam
1) Typhoon “Nida"
Typhoon Nida occurred on August 2, 2016, causing flash floods and landslides in Lao Cai region. It rained continually until the 5th when Red River and surrounding regions were flooded. In addition to 5 death, it left 7 missing and 9 injured. More than 1,000 houses were demolished or damaged. Bridges, roads, and agricultural facilities were damaged as well. 10,150ha of rice fields, 1,054ha of dry fields, and 1,127ha of farming lands were destroyed with a lot of livestock and poultry damaged. For 24 hours, it rained as much as 71mm.
Figure 2.8 Course of Typhoon Nida Chapter 2 Local Survey and Preliminary Research | 25
2.2. Preliminary Research for the Pilot Project of Automatic Rainfall Warning Facilities
A pilot project was conducted over river basins in Laos Vang Vieng region and Vietnam Lao Cai region. In each country, 1 automatic rainfall warning facility (2 rainfall observatory systems, 2 water level observation systems, and 2 warning stations) were constructed. At its early stage, preliminary field investigation was also conducted.
2.2.1. Candidate Areas for Automatic Rainfall Alert Facility Installation in Laos
Candidate areas for automatic rainfall warning facilities were selected around Laos target basin as in the table below:
Table 2.9 Candidate Areas for Automatic Rainfall Alert Facility Installation in Laos
Target Quan Class. Location Note Basin tity Situation ∙ Viengkeo Temple propaganda system 2 ∙ Huay Nyae Primary School (warning station) Rainfall ∙ Pha Tang Bridge Laos observation 2 Vang system ∙ Nam Kai Bridge Vieng (Rain gauge) Water level ∙ Pha Tang Bridge observation 2 system ∙ Nam Kai Bridge (water gauge)
In Vang Vieng basin, the following facilities will be installed: 2 rainfall observation systems, 2 water level observation systems, and 2 situation propaganda systems. Candidate areas for installation are as follows: 26 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 2.10 Candidate Areas for Alert Station Installation
Class. Location Feature Photo
∙ A temple in Viengkeo region ∙ A warning station to Viengkeo be installed in the Temple empty land in front Situation of a tower in the propagand temple a ∙ The playground of System Huay Nyae Primary (warning School ∙ A warning station to station) Huay Nyae be installed at the Primary School right edge of the playground in direction of the village
Table 2.11 Candidate Areas for Rainfall and Water Level Observatory Installation
Class. Location Feature Photo
∙ A bridge in Pha Tang region ∙ Pha Tang A rainfall and water level observation Bridge system to be Rainfall/W installed outside the ater bridge downstream Level ∙ A bridge in Nam Observati Kai region on ∙ A rainfall and water System level observation Nam Kai Bridge system to be installed with a fixing panel on the main tower downstream Chapter 2 Local Survey and Preliminary Research | 27
2.2.2. Candidate Areas for Automatic Rainfall Alert Facility Installation in Vietnam
In Ta Phoi basin, the following facilities will be installed: 2 rainfall observation systems, 2 water level observation systems, and 2 situation propaganda systems. Candidate areas for installation are as follows:
Table 2.12 Candidate Areas for Automatic Rainfall Alert Facility Installation
Target Quan Class. Location Note Basin tity Situation ∙ Tả Phờ i Office propaganda 2 system ∙ Dien Cao Vacant lot (warning station) Rainfall ∙ Tả Phờ i School Vietnam observation 2 Lao Cai system ∙ Tả Phờ i Vacant lot (Rain gauge) Water level ∙ Hợ p Thà nh levee observation 2 system ∙ Dien Cao Bridge (water gauge)
Table 2.13 Candidate Areas for Basin Alert Stations in Lao Cai, Vietnam
Class. Location Feature Photo ∙ A governmental office in Tả Phờ i Office Building Tả Phờ i Office ∙ To be installed on Situation the empty land in propagan front of Tả Phiờ da Office Building ∙ Empty land at a system town in Dien Cao (warning region station) Dien Cao ∙ To be installed at Vacant lot empty land in front of a building at a town in Dien Cao region 28 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 2.14 Candidate Areas for Basin Rainfall Observatory System Installation in Lao Cai, Vietnam
Class. Location Feature Photo
∙ In front of Tả Phờ i School Tả Phờ i ∙ To be installed on School the concrete blocks in front of Tả Phờ i Rainfall School observati on ∙ Empty land in Tả system Phờ i region Tả Phờ i ∙ To be installed on Vacant lot the concrete blocks in empty land of Tả Phờ i region
Table 2.15 Candidate Areas for Basin Water Level Observatory System Installation in Lao Cai, Vietnam
Class. Location Feature Photo
∙ Hợ p Thà nh region ∙ To be installed in Hợ p Thà nh front of the dike at levee which rivers of Hợ p Water Thà nh region meet level observati on ∙ A bridge in Dien system Cao region Dien Cao ∙ To be installed under Bridge the upper panel of a bridge in Dien Cao region Chapter 3. Establishment of A utomatic Rainfall Warning Facil ities and Installation of the Fla sh Flood Forecasting/Warning System
Establishment of Automatic 3.1 Rainfall Warning Facilities
Flash Flood Forecasting 3.2 /Warning System Installation
Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 31
Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Alert System (FFAS)
According to the annual plans for this study project, a pilot project was conducted for Suoi Peng River in Lao Cai, Vietnam, and Nam Xong River in Vang Vieng, Laos, in the 1st year, with the flash flood forecasting/warning system and automatic rainfall warning facilities(2 rainfall meters, 2 water gauges, and 2 warning stations in each country) installed.
3.1. Establishment of Automatic Rainfall Warning Facilities
Automatic rainfall alert facilities installed in Laos and Vietnam issue forecast/warning notifications upon a flash flood in consideration of rainfall and water level changes. In general, such facilities are classified to the rainfall observation system, water level observation system, automatic warning system, etc. Specifically, 2 rainfall observatories, 2 water level observatories, and 2 automatic warning systems were established.
3.1.1. Installation Layout of Automatic Rainfall Warning Facilities in Laos
The layout of automatic rainfall warning facilities installed in Laos for this project is as below: 32 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 3.1 Diagram of Laos ARWS Installation
3.1.2. Installation Layout of Automatic Rainfall Warning Facilities in Vietnam
The layout of automatic rainfall warning facilities installed in Vietnam for this project is as below:
Figure 3.2 Diagram of ARWS Installed in Vietnam Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 33
3.1.3. Formation of Automatic Rainfall Warning Facilities
A. Rainfall and Water Level Observatory System (1 Rainfall Observation Station)
1) System Configuration
The rainfall and water level observatory system (1 rainfall observation station) is divided mainly to the rainfall gauge, power supply, data logger, etc. as shown in the figure below:
Table 3.1 Configuration of the Rainfall Observatory System
Class. Major Components
Rainfall and water level observation system
Rainfall gauge Power supply Data logger 34 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) System Operation
(1) Data Observation Station (Rainfall Gauge)
The rainfall gauge moves buckets as the tipping bucket sensor recognizes a rainfall event. The rainfall is measured by generating pulse signals as much as 0.5mm every time a bucket is moved.
(2) Power Supply
The power supply consists of solar batteries, batteries, and the charge/discharge regulator. Batteries are the basic power supply to the system, and they are recharged automatically by means of the charge/discharge regulator and solar batteries.
(3) Data Logger (Data Management)
Data collected by means of the rain gauge is saved and transmitted: Once data is collected, it is transmitted to the IDC in Korea through TCP/IP communication on a regular basis according to the schedule and then saved in the database. The servers in Vang Vieng and Vientiane then acquire the stored data so that administrators at the Flash Flood Alert System (FFAS) can check it out. Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 35
3) System Specifications
Specifications of the Rainfall and Water Level Observatory System are presented in the table below: Table 3.2 Specifications of the Rainfall and Water Level Observatory System
Class. specifications ∙ Resolution: 0.5mm Rain Gauge ∙ Measuring Mode: 1 pulse per 0.5mm of rainfall ∙ Output Signal: No-load voltage contact point at the Reed Switch ∙ Precision: ± 5% ∙ Type: Inverted-type magnetic rain gauge (rain receiving vessel) ∙ Size: Ø 20cm × 450mm (standard for atmospheric check) ∙ Solar Battery Power Supply - Max. Power: 30W - Max. Power Voltage: 19.6V - Max. Power Current: 1.64A - Open Circuit Voltage: 24V - Short Circuit Current: 1.77A - Size: 535 × 425 × 25mm - Weight: 2.7kg ∙ Battery (2 ea) - Voltage : 12V - Capacity : 40Ah(40000mAh) - Size : 197mm(L) 165mm(W) 170mm(H) - Weight : 14.0kg ∙ Charge/Discharge Regulator - System Voltage: 12V - Max. Input Voltage: 25V - Rated Input Current: 6A - Rated Output Current: 6A - PV Short Circuit Current: 9A - Battery Low-voltage Block: 11.5V - Battery Low-voltage Recovery: 12.5V - Size: 156 × 55 × 27 mm 36 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Class. Specifications ∙ Processor : CUBLOC ∙ A/D converter : 12 bit. 16 CH ∙ Operation Temp. : -25 - 55℃ ∙ Data Memory: 32kb EEPROM, 32kb RAM, 64kb Program EEPROM, Micro SD ∙ Sensor Interface: voltage / current / counter ∙ Instrument Interface: RS232C / RS485 ∙ Communication Method: CDMA, Zigbee, LTE, Ethernet ∙ Cellular Interface - Standards: GSM/GPRS - Band Options: Quad-band 850/900/1800/1900 MHz - GPRS Multi-slot Class: Class 10 - GPRS Terminal Device Class: Class B - GPRS Coding Schemes: CS1 to CS4 - CSD Data Transmission Rate: Up to 14,400 bps - Tx Power: 1 watt GSM 1800/1900, 2 watts EGSM 900/GSM 850 ∙ SIM Interface - Number of SIMs: 1 (NOTE: This product does not include a SIM card.) - SIM Control: 3 V ∙ Serial Interface - Number of Ports: 1 - Serial Standards: RS-232 (DB9 female connector) ∙ Serial Communication Parameters - Data Bits: 8 - Stop Bits: 1 - Parity: None - Flow Control: RTS/CTS Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 37
- Baudrate: 300 bps to 230.4 Kbps ∙ Environmental Limits - Operating Temperature OnCell: -20 to 55°C (-4 to 131°F) - Storage Temperature: -40 to 75°C (-40 to 167°F) ∙ Power Requirements - Input Voltage: 12 to 48 VDC - Power: 12 to 48 VDC, 100 mA (idle), 625 mA (max.)
B. Rainfall and Water Level Observatory System (1 Water Level Observation Station)
1) System Configuration
The rainfall and water level observatory system consists of the radar water gauge, power supply, data logger, etc. as illustrated in the figure below:
Table 3.3 Configuration of the Rainfall Observatory System
Class. Main Components
Rainfall and water level observation system
Water gauge Power supply Data logger 38 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) System Operation
(1) Data Observation (Radar Water Gauge)
The radar water gauge generates rada pulse signals on the water surface and receives the echoing signals to measure the distance from the water surface by calculating the turnaround time. The radar water gauge is advantageous in that it is not sensitive to temperature or surroundings.
(2) Power Supply
The power supply consists of solar batteries, batteries, and the charge/discharge regulator. The basic power supply is the batteries, which are charged automatically by means of the solar batteries and charge/discharge regulator.
(3) Data Logger (data management)
Data collected from the rain gauge is saved and transmitted. On a regular basis according to a preset schedule, data is transmitted to the IDC in Korea and saved in the database. The local servers in Vang Vieng and Vientiane then acquire the saved data so that administrators can check it out at the Flash Flood Alert System (FFAS). Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 39
3) System Specifications
Specifications of the Rainfall and Water Level Observatory System are presented in the table below:
Table 3.4 Specifications of the Rainfall and Water Level Observatory System
Class. Specifications water gauge ∙ Range : 35m ∙ Deviation : ± 2mm ∙ Output : 4 -20 mA ∙ Power : 12 - 24 VDC ∙ Protection : IP 67 ∙ Weight : 2.5 kg ∙ Solar Battery power supply - Max. Power: 30W - Max. Power Voltage: 19.6V - Max. Power Current: 1.64A - Open Circuit Voltage: 24V - Short Circuit Current: 1.77A - Size: 535 × 425 × 25mm - Weight: 2.7kg ∙ Battery(2 ea) - Voltage : 12V - Capacity : 40Ah(40000mAh) - Size : 197mm(L) 165mm(W) 170mm(H) - Weight : 14.0kg ∙ Charge/discharge regulator - System voltage: 12V - Max. input voltage: 25V - Rated input current: 6A - Rated output current: 6A - PV short circuit current: 9A - Battery low-voltage block: 11.5V - Battery low-voltage recovery: 12.5V - Size: 156 × 55 × 27 mm 40 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Class. Specifications ∙ Processor : CUBLOC Data logger(TCP@RT) ∙ A/D Converter : 12 bit. 16 CH ∙ Operation Temp. : -25 - 55℃ ∙ Data Memory: 32kb EEPROM, 32kb RAM, 64kb Program EEPROM, Micro SD ∙ Sensor Interface: voltage / current / counter ∙ Instrument Interface: RS232C / RS485 ∙ Communication Mode: CDMA, Zigbee, LTE, Ethernet ∙ Cellular Interface Modem (OnCell G2111) - Standards: GSM/GPRS - Band Options: Quad-band 850/900/1800/1900 MHz - GPRS Multi-slot Class: Class 10 - GPRS Terminal Device Class: Class B - GPRS Coding Schemes: CS1 to CS4 - CSD Data Transmission Rate: Up to 14,400 bps - Tx Power: 1 watt GSM 1800/1900, 2 watts EGSM 900/GSM 850 ∙ SIM Interface - Number of SIMs: 1 (NOTE: This product does not include a SIM card.) - SIM Control: 3 V ∙ Serial Interface - Number of Ports: 1 - Serial Standards: RS-232 (DB9 female connector) ∙ Serial Communication Parameters - Data Bits: 8 - Stop Bits: 1 - Parity: None - Flow Control: RTS/CTS Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 41
- Baudrate: 300 bps to 230.4 Kbps ∙ Environmental Limits - Operating Temperature OnCell: -20 to 55°C (-4 to 131°F) - Storage Temperature: -40 to 75°C (-40 to 167°F) ∙ Power Requirements - Input Voltage: 12 to 48 VDC - Power: 12 to 48 VDC, 100 mA (idle), 625 mA (max.)
C. Automatic Warning System
1) System Configuration
As shown in Table 3.5, the Automatic Warning System consists mainly of the speaker, auto-receiving terminal, manual warning devices, power supply, etc.
Table 3.5 Specifications of the Automatic Rainfall Warning System
System Photo
Warning Station Auto-receiving terminal/ Speaker Power supply manual warning device 42 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) Principle of Data Collection
(1) Data Receiving (data logger)
Information on warning events is received from the server in the format of SMS, and then the warning commands are delivered.
(2) Alert Delivery (auto-receiving terminal)
Alerts are delivered from the server or warning notifications are issued manually with siren.
(3) Siren (speaker)
Warning notifications are issued. Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 43
3) System Specifications
Specifications of the Automatic Warning System are presented in the table below:
Table 3.6 Specifications of the Automatic Warning System
Class. specifications Auto-receiving terminal ∙ Service line: national line ∙ (all-in-one) Input Impedance : 600Ω ± 10% ∙ Frequency: 300 - 3400㎐ ∙ Power: AC 220V/60㎐ /DC 24V ∙ CPU: Multiplex control by one chip micom ∙ Control mode: DTMF control ∙ Operation condition: Temp. 0℃ - 50℃ ∙ Outer box: 420(L) × 313(W) × 80(H) ± 10% standard rank Digital amp. ∙ Rated output :360W+360W(720W) ∙ Frequency: 50Hz-18KHz ∙ Output Impedance : 18Ω /70V, 27Ω /100V ∙ Type : Digital AMP ∙ Radiation: 45℃ + variable-speed fan ∙ Input level: 1V-5V(rms) ∙ Power: AC220V 50/60㎐ DC24V ∙ Size: 483(W) × 44(H) × 330(D) Speaker ∙ Rated output : 75W, 8 sets ∙ Structure: unit/matching trans/casting(hot galvanizing) ∙ Impedance : 8Ω ∙ Frequency Characteristics : 380Hz-5KHz Power supply ∙ Solar Battery - Max. Power: 200W - Max. Power Voltage: 19.1V - Max. Power Current: 4.45A - Open Circuit Voltage: 23.5V - Short Circuit Current: 4.81A - Size: 535 x 934 x 35mm - Weight: 6.18kg ∙ Battery(2ea) - Voltage : 12V - Capacity : 200Ah - Size : 443mm(L) 167mm(W) 204mm(H) - Weight : 32.0kg 44 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
3.1.4. Establishment of Automatic Rainfall Warning Facilities
In consideration of various aspects including local conditions, 2 rainfall and water level observatories were installed in the spots that could represent the basin's general rainfall and water level upstream, and 2 automatic warning systems were established in regions downstream where there were many residences and damage from flood could be minimized through warning upon a flood.
A. Vang Vieng Basin
1) Rainfall Observatory System
(1) Pha Tang Bridge
① Overview
A preliminary field investigation was conducted to plan the process of installing a rainfall observatory near Pha Tang Bridge. The main support panel was installed on the top panel of the bridge before the rainfall observatory system was constructed. The location of the rainfall observatory system is as in the table below:
Table 3.7 Location of Pha Tang Bridge Rainfall Observatory
Location Class. Quantity Map (Latitude/Longitude)
Rainfall Pha Tang Bridge observati 1 Set (19.07722N, on 102.42916E) system Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 45
② Installation Process
The process of installing a rainfall observatory system near Pha Tang Bridge is presented in Figure 3.3.
Preparation for installation Main panel installation
Rainfall gauge and solar battery Wiring installation
Rainfall observatory system Rainfall gauge installation completed installation completed Figure 3.3 Installation Process of Pha Tang Bridge Rainfall Observatory System 46 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(2) Vang Pho Bridge
① Overview
A preliminary field investigation was conducted to plan the process of installing a rainfall observatory system near Vang Pho Bridge. Since Vang Pho Bridge had no upper panel, the main support panel was installed on bridge column so that the rainfall observatory system could be established on top of the main support panel. The location is as in the table below:
Table 3.8 Locations for Vang Pho Bridge Rainfall Observatory System
Location Class. Quantity Map (Latitude/Longitude)
Rainfall Vang Pho Bridge observati 1 Set (19.07722N, on 102.42916E) system
② Installation Process
The process of installing a rainfall observatory system near Vang Pho Bridge is presented in Figure 3.4. Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 47
Main panel installation Solar battery installation
Rainfall gauge installation Main panel installation
Rainfall gauge and solar battery Rainfall observatory system setting installation completed Figure 3.4 Installation Process of Vang Pho Rainfall Observatory System 48 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) Water Level Observation System
(1) Pha Tang Bridge
① Overview
A preliminary field investigation was conducted to plan the process of installing a water level observation system near Pha Tang Bridge. This water level observation system was installed in the same area with Pha Tang Bridge rainfall observation.
Table 3.9 Location of Pha Tang Bridge Water Level Observatory System
Location Class. Quantity Map (Latitude/Longitude)
Water level Pha Tang Bridge observati 1 Set (19.07722N, on 102.42916E) system
② Installation Process
The process of installing a water level observation system near Pha Tang Bridge is presented in Figure 3.5. Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 49
Radar-based water gauge setting Radar-based water gauge installation
Water level observation system Measuring box installation installation completed Figure 3.5 Installation Process of the Water Level Observation System
(2) Vang Pho Bridge
① Overview
A preliminary field investigation was conducted to plan the process of installing a water level observation system near Vang Pho Bridge에 water level observation system. This water level observation system was installed in the same area with Vang Pho Bridge Rainfall Observatory. Table 3.10 Location of Vang Pho Bridge Water Level Observatory
Location Class. Quantity Map (Latitude/Longitude)
Rainfall Vang Pho Bridge observati 1 Set (19.07722N, on 102.42916E) system 50 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
② Installation Process
The process of installing a water level observation system near Pha Tang Bridge is presented in Figure 3.5.
Radar water gauge setting Radar-based water gauge installation
Measuring box installation Main panel installation
Figure 3.6 Installation Process of Vang Pho Bridge Water Level Observation System
3) Automatic Warning System
(1) Muang Xong Temple
① Overview Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 51
A preliminary field investigation was conducted to plan the process of installing an automatic warning system near Muang Xong Temple. The location of Muang Xong Temple is as in the table below:
Table 3.11 Location of Pha Tang Bridge Water Level Observatory
Location Class. Quantity Map (Latitude/Longitude)
Muang Xong Automati Temple c warning 1 Set (18.91805N, system 102.44666E)
② Installation Process
The process of installing an automatic warning system near Muang Xong Temple is as below: 52 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Speaker assembly Speaker installation
Lighting rod assembly Solar battery installation
Automatic warning system installation Measuring box installation completed Figure 3.7 Installation Process of Muang Xong Temple Automatic Warning System Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 53
(2) Huay Nyae Primary School
① Overview
A preliminary field investigation was conducted to plan the process of installing an automatic warning system at Huay Nyae Primary School. There was an advance consultation for the automatic warning system to be established at a side of the playground. The location of Huay Nyae Primary School is as in the table below:
Table 3.12 Location of Huay Nyae Primary School Water Level Observatory System
Location Class. Quantity Map (Latitude/Longitude)
Huay Nyae Primary Automati School c warning 1 Set (18.91916N, system 102.44138E)
② Installation Process
The process of installing an automatic warning system at Huay Nyae Primary School was as below: 54 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Speaker assembly Speaker installation
Lighting rod assembly Solar battery installation
Automatic warning system installation Measuring box installation completed Figure 3.8 Installation Process of Huay Nyae Primary School Automatic Warning System Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 55
B. Lao Cai Basin
1) Rainfall Observatory System
(1) Tả Phờ i School
① Overview
A preliminary field investigation was conducted to plan the process of installing a rainfall observatory system at Tả Phờ i School. The system was established in front of Education Hall. Its location is as in the table below:
Table 3.13 Tả Phời School Rainfall Observatory System Locations
Location Class. Quantity Map (Latitude/Longitude)
Rainfall Tả Phờ i School observati 1 Set (22.3666N, on 103.95416E) system 56 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
② Installation Process
The process of establishing a rainfall observatory system at Tả Phờ i School is presented in Figure 3.2.
Basic anchor bolting Measuring box installation
Rainfall observatory system Rainfall gauge installation installation completed Figure 3.9 Installation Process of Tả Phời School Rainfall Observatory System
(2) Installation in a Vacant Lot, Tả Phờ i
① Overview
A preliminary field investigation was conducted to plan the process of installing a rainfall observatory system in a vacant lot, Tả Phờ i. Since the there was no upper panel in the vacant lot, the main support panel was installed on a bridge column so that the rainfall observatory system could be installed on it. The location is as in the table below: Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 57
Table 3.14 Location of the Rainfall Observatory System in a Vacant Lot, Tả Phời
Location Class. Quantity Map (Latitude/Longitude)
rainfall Tả Phờ i Vacant lot observati 1 Set (22.39333N, on 103.97833E) system
② Installation Process The process of installing a rainfall observatory in a vacant lot, Tả Phờ i, is as in the figure below:
Rainfall gauge installation Solar battery installation
Battery installation Rainfall observatory system installation Figure 3.10 Process of Installing a Rainfall Observatory System in a Vacant Lot, Tả Phời 58 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) Water Level Observation System
(1) Hợ p Thà nh Levee
① Overview
A preliminary field investigation was conducted to plan the process of installing a water level observation system in Hợ p Thà nh Levee. Its location is as below:
Table 3.15 Location of the Water Level Observatory System near Hợp Thành Levee
Location Class. Quantity Map (Latitude/Longitude)
Wwater level Hợ p Thà nh levee observati 1 Set (22.39315N, on 103.99907E) system
② Installation Process
The process of installing a water level observation system near Hợ p Thà nh Levee is presented in Figure 3.11. Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 59
Main panel installation Radar-based water gauge installation
Water level observation system Battery installation installation completed Figure 3.11 Installation Process of the Water Level Observation System 60 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(2) Dien Cao Bridge
① Overview
A preliminary field investigation was conducted to plan the process of installing a water level observation system near Dien Cao Bridge. Its location is as below:
Table 3.16 Location of the Water Level Observatory System near Dien Cao Bridge
Location Class. Quantity Map (Latitude/Longitude)
Water level Dien Cao Bridge observati 1 Set (22.39500N, on 104.00681E) system
② Installation Process
The process of installing a water level observation system near Dien Cao Bridge is presented in Figure 3.12.
Main panel installation Radar-based water gauge installation Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 61
Water level observation system Battery installation installation completed Figure 3.12 Installation Process of Dien Cao Bridge Water Level Observation System
3) Automatic Warning System
(1) Tả Phờ i Office
① Overview
A preliminary field investigation was conducted to plan the process of installing an automatic warning system near Tả Phờ i Office, and its location is as below: Table 3.17 Location of the Water Level Observatory near Pha Tang Bridge
Location Class. Quantity Map (Latitude/Longitude)
Automati Tả Phờ i Office c warning 1 Set (22.40055N, system 103.97750E) 62 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
② Installation Process
The process of installing an automatic warning system near Tả Phờ i Office was as below:
Speaker installation Solar battery installation
Automatic warning system installation Box body installation completed Figure 3.13 Installation Process of Tả Phời Office Automatic Warning System
(2) Dien Cao Vacant lot
① Overview
A preliminary field investigation was conducted to plan the process of installing an automatic warning system in a vacant lot, Dien Cao. Its location is as in the table below: Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 63
Table 3.18 Location of the Water Level Observatory System in a Vacant Lot, Dien Cao
Location Class. Quantity Map (Latitude/Longitude)
Automati Dien Cao Vacant c warning 1 Set lot(22.39666N, system 104.00944E)
② Installation Process
The process of installing an automatic warning system in a vacant lot, Dien Cao, was as below:
Speaker installation Solar battery installation
Automatic warning system installation Box body installation completed Figure 3.14 Installation Process of the Automatic Warning System in a Vacant Lot, Dien Cao 64 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
3.1.5. Result of Automatic Rainfall Warning Facility Installation
A. Installation Result
For the present study, the National Disaster Management Research Institute installed Automatic Rainfall Warning Facilities in Vang Vieng regions as follows: 2 rainfall observation stations; 2 water level observation stations; and 2 automatic warning systems (warning stations).
Table 3.19 Current Conditions of Automatic Rainfall Warning Facilities Installed by the National Disaster Management Research Institute
Note Target Quan Class. Location (year of Basin tity installation)
rainfall ∙ Pha Tang Bridge 2016 observatory 2 system (Rain gauge) ∙ Vang Pho Bridge 2016
Water level ∙ Pha Tang Bridge 2016 observation Vang Vieng system 2 (radar water ∙ Vang Pho Bridge 2016 gauge)
Situation ∙ Muang Xong Temple 2016 propaganda system 2 (warning ∙ Huay Nyae Primary 2016 station) School Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 65
Figure 3.15 Installation Locations of Automatic Rainfall Warning Facilities 66 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Major Aspects of Operation and Management
1) Major Aspects of Operation and Management in Laos
As for maintenance of Automatic Rainfall Warning System (ARWS), the major aspects are summarized in Table 3.20. The DMH of Laos has concluded an agreement with Lao-Telecom (GSM mode) on the communication network for disaster response, which specifies that the SIM-card shall be used for Automatic Rainfall Warning Facilities installed by the National Disaster Management Research Institute. Accordingly, the SIM-card of Lao-Telecom was used except Vang Pho Bridge (BeeLine was used instead) where the status of Lao-Telecom communication network was not satisfactory. In addition, rechargeable solar batteries were installed in consideration of the battery capacity that had to last at least for 14 days after full recharge. Observation facilities were installed in areas that would represent general observation sites. The system had to be easy-to-maintain and involve no risk of inundation in case of a flood.
Table 3.20 Major Aspects of Automatic Rainfall Alert Facility Operation
Target Class. Location Sim-Card Power Supply Basin
Rainfall Solar Battery 30W ∙ Pha Tang Bridge Lao-Tel observatory battery 80Ah system Solar Battery 30W ∙ Vang Pho Bridge Bee Line (Rain gauge) battery 80Ah Water level Solar Battery 30W ∙ Pha Tang Bridge Lao-Tel Vang observation system battery 80Ah Vieng (radar water Solar Battery 30W ∙ Vang Pho Bridge gauge) Lao-Tel battery 80Ah Situation ∙ Muang Xong Solar Battery 200W Lao-Tel propaganda Temple battery 200Ah system ∙ Huay Nyae Primary Solar Battery 200W (warning station) School Lao-Tel battery 200Ah Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 67
2) Major Aspects of Operation in Vietnam
Major aspects of Automatic Rainfall Warning System (ARWS) maintenance are summarized in Table 3.21. The SIM card for onsite communication was provided by MOBIFONE (GSM mode) in cooperation with Vietnam VAWR (Vietnam Academy of Water Resources). Every system was installed with MOBIFONE (GSM mode) SIM cards, and rechargeable solar batteries were installed in consideration of the battery capacity that had to last at least for 14 days after full recharge. Observation facilities were installed in areas that would represent general observation sites. The system had to be easy-to-maintain and involve no risk of inundation in case of a flood.
Table 3.21 Major Aspects of Automatic Rainfall Alert Facility Operation
Target Class. Location Sim-Card Power Supply Basin Solar Battery Rainfall ∙ Tả Phờ i School MOBIFONE 30W observatory battery 80Ah system Solar Battery ∙ Tả Phờ i Vacant (Rain gauge) 30W lot MOBIFONE battery 80Ah Solar Battery Water level ∙ Hợ p Thà nh levee MOBIFONE 30W observation battery 80Ah Lao Cai system (radar water Solar Battery gauge) ∙ Dien Cao Bridge MOBIFONE 30W battery 80Ah Solar Battery Situation ∙ Tả Phờ i Office MOBIFONE 200W propaganda battery 200Ah system Solar Battery ∙ Dien Cao Vacant (warning station) 200W lot MOBIFONE battery 200Ah 68 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
3.2. Flash Flood Alert System (FFAS) Installation
3.2.1. Overview
The Flash Flood Alert System (FFAS) is a web-based system that is designed to monitor hydrological data (rainfall, water level) real-time collected from hydrometric stations (AWS/ARWS/WLMS)installed in Lao Cai, Vietnam, and Vang Vieng, Laos, in order to reduce the risk of flash floods. It also issues warning notifications for residents' evacuation. This system provides additional materials such as flooding map, hazard map, and river information in order to prepare possible risks of flash floods around the target basin.
This system was developed in reflection of opinions collected from the National Disaster Management Research Institute(NDMI) as well as responsible institutes in Vietnam and Laos. The VAWR in Vietnam and the DMH in Laos can monitor observation data by means of this system. In addition to that, institutions in charge of target basin disaster control can issue warning notifications automatically or manually. Target Regions of FFAS Service are presented in Figure 3.16, and the list of flash flood forecasting/warning systems installed in Laos DMH and Vietnam VAWR is presented in Figure 3.17.
Figure 3.16 Target Regions of FFAS Service Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 69
Figure 3.17 Photos of the DMH and FFAS Installed in Laos
3.2.2. System Design
A. System Functions & Services
Since the main objective of Flash Flood Alert System (FFAS) installation is to establish an integrated system for the target basin, one of the top priorities is to grasp the current condition of observation data necessary for basin data integration. In addition, additional services such as flooding map, hazard map, and river information need to be included with the established warning criteria applied. Major functions and services necessary for an integrated basin system are presented in the table below: Table 3.22 System Functions & Services
Class. Content Note Data Hydrological ∙ Local rainfall observation data Every 10 min. connection observation data ∙ Water level observation data Every 10 min. Warning criteria∙ Warning criteria for each water level range Warning ∙ Automatic/manual warning for each Warning warning station Flooding map∙ Flood mapping for each frequency range Service Hazard map∙ Risk grading for each sub-basin River info.∙ River survey results and river info. ∙ Inquiry and saving of observation data during a certain period Etc. Download ∙ Data of river sections ∙ Storage of major achievements (report, manual) 70 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Requirement Definitions
Requirement Definitions aim to develop a system that meets requirements in comprehensive review of accumulated feedbacks from users over general aspects of the system such as scope, function, etc. The level of satisfaction can be improved as users' requirements and needs are collected and reflected.
As basic aspects and warning functions of the integrated basin system required by the National Disaster Management Research Institute, hydrological information download functions required by the DMH and VAWR, and other opinions are reflected and summarized as in the table below:
Table 3.23 Requirement Definitions
Class. Content Note
∙ AWS observation data Hhydrological Data observation At every 10 connecti ∙ ARG observation data data min. on (AWS/ARG/WLMS) At every 10 ∙ WLMS observation data min. ∙ Warning Criteria applied for each Warning Criteria water level range Warning ∙ Automatic/manual warning for each Warning warning station Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 71
C. Function Definitions
Function Definitions seek to induce interested parties to express their demands for a project as many as possible in order to expect the final product precisely. With system functions classified, the system menu items are categorized under the high/middle/low classification levels to indicate the flow of information between processes specifically.
As shown in the figure below, major functions of the Flash Flood Alert System (FFAS) reflect above-mentioned Requirement Definitions and basically facilitate the presentation of hydrological observation data through the system. Additional services such as flooding map, hazard map, and river information are also provided. Specific details of each function are as below:
Figure 3.18 Basic Frame of the Function Definition System
As shown in the table below, Function Definitions are classified mainly to the Main Screen, weather information, warning system, Base Map, information table, and Log. The warning system displays observatory information and hydrological information. The map service provides 72 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
various types of information including AWS, hazard map, flooding map, river information, etc. Hydrological information is saved in an information table of the forecasting/warning system so that it can be referred to for warning. Data of a certain period also can be downloaded.
Table 3.24 Function Definitions
High- level Middle-level Low-level Applic Remark Class. Class. ability Class. System name ∙ Main page of the Main & project ○ forecasting/warning system name ∙ Cloud images over Mindanao Weathe r Web page × Island, Philippines
∙ Observation station name and Warning type system/ table ○ ∙ Information (rainfall/ water Forecas view level ) display ting/Wa ∙ Data link display rning System Info. at Info. table the bottom ○ opening of the main map
∙ Rainfall analysis for each duration range AWS ○ ∙ Color change for each level ∙ Explanatory notes Hazard map ○ ∙ Explanatory notes ∙ Base Flooding map ○ Explanatory notes Map ∙ Measuring point name ∙ Sectional image downloading River ∙ River info. downloading River info. survey ○ (Excel) output ∙ Information table display ∙ Measuring point symbol ∙ Explanatory notes ∙ Forecasting/ CODE ∙ NAME, observation timing Info. Warning ○ ∙ Rainfall and water level Table System info. table measurements ∙ Warning level display Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 73
D. Table List and Definitions
1) Table List
The list of tables in each area of service that will be accumulated in a physical database is presented based on Requirement Definitions and the logical data modeling of the system to be embodied.
2) Table Definitions
Specific details and physical attributes of each table are related in reference to the list of tables. Item specified in the list of tables are as in tables below. Table 3.25 Table definitions (BASIN_INFO)
Table Name: BASIN_INFO Table Des. BASIN_INFO Data Attribute Seq. Attribute NULL? Default PK_FK Type Definition Number NOT 1 BASIN_CODE PK (10) NULL Varchar2 NOT 2 BASIN_NAME (30) NULL Varchar2 3 GIS_CODE NULL (20) DATET NOT 4 REG_DATE IME NULL
Table 3.26 Table definitions (BASIN_PRECIPITATION)
Table Name: Basin QPE Table Des. BASIN_PRECIPITATION Information Data Attribute Seq. Attribute NULL? Default PK_FK Type Definition Number NOT 1 BASIN_INFO_ID PK (10) NULL Number 2 AVERAGE_RAIN NULL (5) OBSERVATION 3 Char(14) NULL _TIME DATET NOT 4 REG_DATE IME NULL 74 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 3.27 Table definitions (AWS_INFO)
AWS Branch Table Name: AWS_INFO Table Des. Information Data Attribute Seq. Attribute NULL? Default PK_FK Type Definition Number NOT 1 AWS_CODE PK (10) NULL Varchar2 NOT 2 AWS_NAME (30) NULL Varchar2 3 LATITUDE NULL (10) Varchar2 4 LONGITUDE NULL (10) Varchar2 5 GIS_CODE NULL (20) DATET NOT 6 REG_DATE IME NULL NOT 7 WARN_TYPE CHAR(1) NULL NOT 8 RAIN_ALERT NUMBER NULL NOT 9 RAIN_ALARM NUMBER NULL NOT 10 RAIN_CRITICAL NUMBER NULL NOT 11 WATER_ALERT NUMBER NULL NOT 12 WATER_ALARM NUMBER NULL NOT 12 WATER_CRITICAL NUMBER NULL
VARCHA NOT 13 AWS_TIME R2(20) NULL Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 75
Table 3.28 Table definitions (AWS_PRECIPITATION)
Table Name: AWS Precipitation Table Des. AWS_PRECIPITATION Information Data Attribute Seq. Attribute NULL? Default PK_FK Type Definition Number NOT 1 AWS_INFO_ID PK (10) NULL OBSERVATION Char 2 NULL PK _TIME (14) OBSERVATION Number 3 NULL _RAIN (5) DATET NOT 4 REG_DATE IME NULL VARCHA NOT 5 VOLT R2(10) NULL
Table 3.29 Table definitions (AWS_PRECIPITATION_DP)
Table Name: AWS Precipitation Table Des. AWS_PRECIPITATION Information Data Attribute Seq. Attribute NULL? Default PK_FK Type Definition Number NOT 1 AWS_INFO_ID PK (10) NULL OBSERVATION Char 2 NULL PK _TIME (14) OBSERVATION Number 3 NULL _RAIN (5) DATET NOT 4 REG_DATE IME NULL VARCHA NOT 5 VOLT R2(10) NULL 76 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
3.2.3. Screen Design
'Screen Design' means to make up a screen layout with various functions and menu components as a user interface by using documents that contain layout details and functional features. Various aspects such as user requirements, functions, menu items, page capacity, and arrangement need to be taken into consideration.
For the screen design of the Flash Flood Alert System (FFAS), items were classified to main screen information, mapping, trouble-shooting, etc., and the map is divided into four sections: observation station (AWS), hazard map, flooding map, and river information. Each item is displayed as a button for users' convenience. The screen layout is standardized as in the existing system. The basic layout of the Flash Flood Alert System (FFAS) is as in the following table:
Table 3.30 FFAS Screen Layout
High-level Middle-level Low-level Class. Content Class. Class. No. Observatory name Current status of the Observation data Related info. forecasting/warning (rainfall, water level) system Warning status Main Recent observation time screen Related info. opening Observation station AWS: observation (AWS) facility symbol Map layout Hazard map Flooding map River info. River survey result Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 77
Figure 3.19 Main Page Menu Frame
Figure 3.20 FFAS Screen Definition 78 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 3.21 Main Screen
Figure 3.22 Hazard Map Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 79
Figure 3.23 Flooding Map
Figure 3.24 River Information 80 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
A. System Development Environment
The Flash Flood Alert System (FFAS) is a Window-based operation system. Its map plays a role as a system control center, and the Google Map APIs describe regions specifically and reduce the cost and time for system redesign as they can adapt to future system upgrades flexibly.
The development environment of the Flash Flood Alert System (FFAS) is as in the table below. The operation system is Window 7 pro; the development languages are Visual C# and Java SE 1.7; development tools are Visual Studio 12 and Eclipse 3.5.1; the web server is IIS 8.0; and the database was established by means of Oracle 11g.
Table 3.31 System Development Environment
Class. Content Note
Operation system ∙ Windows 7 Professional
Development ∙ JavaSE-1.7 language ∙ Visual Studio 12 Development tool ∙ Eclipse 3.5.1
Webserver∙ IIS8.0
DataBase ∙ Oracle 11g
∙ Google MAP Map service ∙ Google MAP API
B. HW Specifications Info.
The hardware for FFAS installation was prorivded to Laos DMH and Vietnam VAWR. Its specifications are as in the table below: Chapter 3 Establishment of Automatic Rainfall Warning Facilities and Flash Flood Forecasting/Warning System| 81
Table 3.32 HW Specifications
Item Class. Requirements
Processor Intel Core i5-6600 3.3G
Chipset Intel® H81 Express
Standard memory 4GB
HDD 1TB
Graphics Geforce GT730 2GB Desktop PC ODD HP Slim ODD
SLOT (3) PCIe x1 slots, (1) PCIe x16 slot Front: 2 USB3.0 headphone and microphone Ports Rear: 4 USB2.0, 1 Serial, 2 PS2, RJ-45, VGA LAN Intel Lan Card(10/100/1,000Gbps)
Monitor Screen Size 27inch
Enclosure - Micro Tower
Power - 300 Watt
O/S Windows 8.1 Windows 8.1 64BIT
Chapter 4. Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis
Survey on Target Basin 4.1 Rivers H y d r a u l i c / H y d r o l o g i c a l 4.2 Analysis
Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 85
Chapter 4 Target Basin River Survey and Hydraulic/Hydrological Analysis
4.1. Survey on Target Basin Rivers
4.1.1. Overview
River surveys were planned to implement hydraulic‧ hydrological analysis of target basins in Vietnam and Laos and to develop Warning Criteria. River survey targets were decided in consideration of locations of warning stations and water level observatories, flood rate estimation points, etc.
As the target basin outlet was located downstream of the water level observatory near Suoi Peng River in Lao Cai, Vietnam, this outlet, which was the estimation point of the downstream flood rate, was selected as the beginning point of the river survey. The measuring area was 1km downstream and upstream from the water gauge point.
Figure 4.1 Vietnam Measuring Areas 86 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
The river survey area of Nam Xong River basin, Laos, was as long as about 4km. As in the case of Suoi Peng River basin, Vietnam, the measuring area was 1km upstream and downstream from the water gauge point at the basin outlet. The water gauge point located at the basin outlet was essential for forecast/warning precision test as the river-crossing bridge was installed in that area. The area where a tributary downstream of Vang Vieng City meets is one of the flood rate estimation points (warning station point), and it is a vital point for forecast/warning over Vang Vieng region. With these aspects considered, the location was decided and indicated in Figure 4.2 below:
Figure 4.2 Laos Measuring Areas Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 87
Table 4.1 Scope of Measurement
Measuring Extension Crossing Gap River Name Region ()㎞ (m)
Nam Xong Vang Vieng 2.0 100 Laos River Pateng 2.0 100 Suoi Peng Vietnam Lao Cai 2.6 200 River
4.1.2. Preliminary Research
Once the target basin was decided, a preliminary field survey was conducted in reference to available maps and satellite photos. In this step, the vertical and horizontal river shapes were analyzed by means of Google Map.
Figure 4.3 Laos Vang Vieng River Shape 88 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.4 Laos Pateng River Shape
Figure 4.5 Vietnam Lao Cai River Shape Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 89
National datum points around the target area were searched for device calibration prior to actual measurement. In addition, thorough examination was conducted on each measuring point in the basin with the focus on the accessibility from the measuring point to the river.
4.1.3. Work Plan
A. Datum Point Measurement
For datum point measurement, WGS 84 was used as the coordinate system. Both in Laos and Vietnam, 48 Q region UTM coordinate was referred to.
With GPS static measurement as the basis, framework measurement was basically conducted and GPS-RTK was also conducted for specific measurement. The river-crossing datum points and drone photos were referred to for installation.
The water level was measured in reference to the elipsoidal height. In In Laos, the Orthometric values were measured in reference to the national standard point available, and in Vietnam, the values were calculated in reference to the Geoid height conversion.
B. Inland Drone Photographing
For inland traversal measurement, drone-based photographing was implemented since it was difficult to cross and move around the river. Date of actual conditions was collected, and intersectional information was extracted.
C. Water Level Measurement 90 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
In areas where the water level was relatively deep, measurement was implemented by means of the echo sounding method. When the depth was under 1.5m, 'staff and lead measurement' was added for complementation.
4.1.4. River Survey Method
A. Applied Equipment
1) GPS-based Measurement
For GPS-based static and RTK measurement, LEICA Grade 1 equipment was applied. The radio modem type method was able to acquire accurate data even in adverse local conditions.
Figure 4.6 GPS Body and RTK RADIO MODEM
2) Drone-based Photographing Equipment
As for the mapping-drone unit for measurement, Phantom 3 PRO of DJI with the auto aviation function was adopted. Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 91
Figure 4.7 Drone Phantom 3 Pro
3) Water Level Measuring Device
For water level measurement, the precise sounder for offshore use (HYDROTRAC_HT97001) was utilized. Model BR200/9 200Khz 9。 (4.5。 , half beam angle) was adopted as the transducer.
The accuracy was 0.01m±0.1% (after sound speed calibration), and the range of sounding was 0.5 to 200m.
Figure 4.8 Precise Sounder and Transducer 92 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Measuring Method
1) Datum Point Measurement
Framework measurement was conducted by means of the GPS and in reference to the World Geodetic Coordinate System. For specific measurement, the RTK-GPS was adopted. Datum point performance at each position was as below:
Figure 4.9 Principle of RTK-GPS
2) Inland Drone-based Measurement
The measurement was implemented in the same way with the existing aerial photographing. The serial photographing method was used to take clear, high-resolution photos in low-altitude flight.
Figure 4.10 Drone-based Measurement Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 93
Figure 4.11 Flow Chart of Drone Measurement
3) Water Level Measurement
Water level measurement was implemented by means of an echo sounding method. Photos of the horizontal section at right angle from the river were saved in a laptop computer for precise water level measurement at each position by means of the DGPS. The following shows the flow chart of water level measurement, principles, and computing process. 94 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.12 Flowchart of Water Depth Measurement
Figure 4.13 Principle and Computation of Water Level Measurement Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 95
4.1.5. Measurement Result
A. Datum Point Performance
Drone local datum points were designated by means of the GPS static and RTK-GPS methods. For drone-based photographing, air-photo signal datum points (hereunder, GCP) were additionally designated. Table 4.2 below shows the datum point performance at each site.
Table 4.2 Scope of Measurement
Site Name Point Title Y(E) X(N) Z(Orthometric) B1 230837.460 2093829.939 230.620 B2 230895.845 2094306.773 228.523 B3 230819.514 2094093.368 227.635 C1 230783.384 2093841.634 230.511 Laos B4 230753.661 2093846.134 230.988 (Vang Vieng) B5 230654.690 2093576.872 230.749 B6 230619.609 2093078.812 227.757 B7 230701.360 2092985.792 229.265 B8 230826.252 2092704.365 228.305 B9 230930.340 2092560.259 227.916 P1 229556.048 2111342.272 276.227 P2 229495.263 2111392.296 278.028 P3 229462.564 2111111.687 270.480 P4 229347.614 2110715.640 269.527 Laos P5 229332.865 2110499.617 269.442 P6 229517.666 2110835.678 285.843 (Pateng) P7 229551.991 2111433.369 279.995 P8 229708.787 2111244.369 290.957 P9 229778.327 2111044.629 270.188 P10 229898.905 2111190.192 279.929 P11 229828.487 2111356.050 277.586 LC01 2476825.191 397795.6213 230.620 LC02 2476667.145 396957.0243 228.523 LC03 2476861.556 397731.1215 227.635 GCP1 2476823.331 397787.9245 230.511 GCP2 2476865.284 397758.0177 230.988 GCP3 2477048.852 397876.6164 230.749 GCP4 2477293.233 398049.4094 227.757 Vietnam GCP5 2477492.312 398201.3636 229.265 (Lao Cai) GCP6 2476581.239 397701.0917 228.305 GCP7 2476565.671 397536.6119 227.916 GCP7 2476565.671 397536.6103 276.227 GCP8 2476744.354 397276.9304 278.028 GCP9 2476861.695 397181.7518 270.480 GCP10 2476537.492 396851.0563 269.527 GCP11 2476671.307 396956.5483 269.442 GCP12 2476837.929 397038.9856 285.843 96 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Inland Drone-based Measurement
The DTM (Digital Terrain Model) and ortho photos were produced through inland drone-based photographing. Ortho photos of each site are as below:
Figure 4.14 Geomorphological Photo of Vang Vieng, Laos Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 97
Figure 4.15 Geomorphological Photo of Pateng, Laos 98 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.16 Enlarged Spot of Pateng, Laos Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 99
Figure 4.17 Geomorphological Photo of Lao Cai, Vietnam 100 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.18 Enlarged Spot of Lao Cai, Vietnam Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 101
C. Water Level Measurement
Horizontal sections deep in water were measured by means of the echo sounding method while low-depth regions were measured by the staff.
Figure 4.19 Water Level Measurement in Laos
Figure 4.20 Water Level Measurement in Vietnam 102 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
D. Vertical/Horizontal Sectional Measurement
Horizontal sectional measurements were extracted by means of the Global Mapper program and in reference to the inland regional DTM and ortho photos taken by using a drone, and underwater data was also applied to draw vertical/horizontal sectional views of each river.
Figure 4.21 Cross Sectional Data Extraction from Vang Vieng, Laos
Figure 4.22 Longitudinal/Cross Sectional Drawing Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 103
E. Water Level Observation Work
The water level indication at the top of the existing water level observatory installed in Pha Tang Bridge was recorded by means of the P.1 datum point in the bridge in a way of direct level measurement.
The level value at the top of the existing water level observatory in Pha Tang Bridge was EL=277.321m (Orthometric).
Figure 4.23 Water Leveling at the Existing Observatory Station 104 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
4.1.6. Survey Datum
Survey Datum Title Local Laying Spot No. B.1 Map No. Map Title Location Near Nam Xong River, Vang Vieng, Laos Date of Dec. 2016 Observed by Kim. Min-su Observation coordinate altitude N(X) E(Y) Original Point system (Orthometric) Result WGS84 2,093,829.939 230,837.460 230.620 48Q UTM At the top of the left-side revetment 250m downstream from Wooden Route Bridge in Vang Vieng Rough Map
Near View Distant View
Figure 4.24 Local Laying Spot (Laos_Vang Vieng) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 105
Survey Datum Title Local Laying Spot No. P.1 Map No. Map Title Location Pha Tang Bridge in Laos Date of Dec. 2016 Observed by Kim. Min-su Observation
coordinate altitude N(X) E(Y) Original Point system (Orthometric) Result WGS84 2,111,342.272 229,556.048 276.227 48Q UTM Route At the left top of Pha Tang Bridge Brief Map
Near View Distant View
Figure 4.25 Local Laying Spot (Laos_Pateng) 106 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Survey Datum Title Local Laying Spot No. P.1 Map No. Map Title Location Upstream of the bridge in Lao Cai, Vietnam Date of Feb. 2017 Observed by Kim. Min-su Observation
coordinate altitude N(X) E(Y) Original Point system (Orthometric) Result WGS84 2,476,825.191 397,795.621 230.620 48Q UTM Route On the concrete road at the right side of the bridge upstream Brief Map
Near View Distant View
Figure 4.26 Local Laying Spot (Laos_Pateng) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 107
4.2. Hydraulic/Hydrological Analysis
4.2.1. Overview
Upon a localized torrential downpour due to climate changes, the water level rises after the flash flood, even causing casualties around the river. To reduce damage from such floods, the need to introduce a flood prediction system has been emphasized, and major flood forecast/warning systems in Korea include one at Han River flood control center, the flood analysis system at Gyeongin Arabaetgil, and one near Onjeon River. The present study includes hydraulic․ hydrological analysis in order to establish warning criteria for casualty reduction and resident evacuation near Suoi Peng River in Vietnam and Nam Xong River in Laos. To this end, a flood frequency investigation was conducted in Laos in reference to yearly flood rate data and rainfall and topographical data in related databases. In Vietnam where there was no flood level data by year was available, the flood rate was calculated based on rainfall analysis and estimation of coefficients such as arrival time, runoff curve indexes, etc. Based on the flood rate estimation results and river survey data, the flooding map was drawn with warning criteria established in reflection of the flood level and flood rate. Figure 4.27 below shows the procedures of hydraulic/hydrological analysis for warning criteria. 108 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.27 Warning Criteria Based on Hydraulic/Hydrological Analysis Process
4.2.2. Hydraulic· Hydrological Analysis in Vietnam
A. Overview
According to the procedure of establishing Warning Criteria, a hydraulic‧ hydrological analysis was conducted on Suoi Peng River basin in Vietnam. Since no flood level data by year was available for Suoi Peng River basin, the flood rate was calculated by means of an HEC-1 model. The hydraulic/hydrological analysis procedures are presented in Figure 4.28, according to which the characteristics of Suoi Peng River basin such as altitude, slope, and basin orientation were analyzed and the flood rate estimation point map was drawn. For the rainfall analysis, the Rainfall Quantile of IHP Report「 Asian Pacific FRIEND, UNESCO (2008)」 was utilized. Additionally, the continued Kraven method was used as for arrival time, Sabol method for storage constant, and Clark basin tracking method for flood rate respectively. In reference to estimated Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 109
flood rate parameters, the flood rate was calculated according to the flood frequency over Suoi Peng River basin, Vietnam. The flood level was calculated in reference to the estimated flood rate by frequency and by means of Hec-RAS in order to draw a flooding map of Suoi Peng River basin flooding map and to establish Warning Criteria.
Figure 4.28 Hydraulic/Hydrological Analysis Procedures in Vietnam
B. Analysis of Target Basin Characteristics
Suoi Peng River basin in Vietnam is in the monsoon and subtropical zone. The average annual rainfall is 1,600㎜ to 1,800㎜ . The dry season lasts from March to October, and the rainy season from April to September. The area of forests is as large as 11,431ha, and the forest cover rate is about 45.6%. The average annual temperature is about 22.8℃ , and the lowest is about 16℃ . Lao Cai City that is adjacent has various soil structures, being advantageous in developing various species that belong to tropical and subtropical zones. 110 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Planar characteristics of a basin are important in grasping the river's flow characteristics such as flow scale. These factors include basin area, channel extension, basin width on average, and basin profile coefficients, which are all of great importance in understanding the river and analyzing the basin's hydrological aspects. Accordingly, the basin area, channel extension, average basin width, and basin profile coefficients of Suoi Peng River in Vietnam were estimated, and the values are presented in Table 4.1. Basin profile coefficients are dimensionless values that represent the shape of a basin. As the profile coefficient is close to 1.0, the shape of the basin is close to a square. As the profile coefficient is large, the flow concentration is significant, increasing the peak flood rate accordingly. As the profile coefficient is small, the flow concentration is weak, presumably decreasing the peak flood rate.
Table 4.3 Characteristics of Suoi Peng River Basin
Channel Average Basin Profile Basin Area River Name Extension Basin Width Coefficient A()㎢ L(㎞ ) A/L(㎞ ) (A/L²) Suoi Peng River 83.92 18.26 4.60 0.25
3-dimensional factors of determination of a basin include the river slope, basin slope, area distribution by altitude, etc. These are major factors that determine the flow characteristics such as flood arrival time. In this study, area distribution values by altitude and slope and the basin orientation of Suoi Peng River basin were calculated. Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 111
1) Area Distribution by Altitude
Area distribution by altitude is a factor that affects altitude-related elements such as rainfall, evaporation, vegetation, hydrological characteristics, etc. This is utilized as one of the analysis methods for 3-dimensional topography features. As for area distribution by altitude over Suoi Peng River basin, the area of 1,000m or lower altitude was as large as 41.86㎢ , and the area of 2,000m or lower was as large as 70.25 ㎢ (see Figure 4.29 and Table 4.4).
Figure 4.29 Altitude Distribution 112 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.4 Cumulative Area and Component Ratio by Altitude
Area Distribution by Altitude(EL.m) Class. 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,399 or or or or or or or or or or or lower lower lower lower lower lower lower lower lower lower lower Area 14.05 21.08 28.10 35.13 42.15 49.18 56.20 63.23 70.25 77.28 83.92 ()㎢ Percent 16.74 25.12 33.49 41.86 50.23 58.60 66.97 75.35 83.72 92.09 100.00 age (%)
2) Area Distribution by Slope
Area distribution by slope is a factor that affects river outflow, soil and earth erosion, hydrological characteristics, etc. this is utilized as one of the analysis methods for 3-dimensional topography features. As for area distribution by slope over Suoi Peng River basin, the area of 10° or higher area distribution rates was as large as 88.50㎢ (86.29%) (see Figure 4.30 and Table 4.5).
Figure 4.30 Slope Distribution Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 113
Table 4.5 Cumulative Area and Component Ratio by Slope
Area Distribution by Slope(°) Class. 5or 10or 15or 20or 25or 30or 35or 45or 55or 65or 75or lower lower lower lower lower lower lower lower lower lower lower Area(㎢ ) 5.75 11.50 17.26 23.01 28.76 34.51 40.26 51.77 63.27 74.78 83.92 Percent 6.85 13.71 20.56 27.42 34.27 41.13 47.98 61.69 75.40 89.10 100.00 age(%)
3) Basin Orientation
The relation between the water system slope's orientation and the direction of the wind in a rainy day may affect the general rainfall over the water system. The direction of the water system and the direction of the rainy front progress too can affect the hydrological curve of a flood. According to the record of area distribution by slope, the area facing north accounted for the largest portion (16.41%). The result of basin orientation analysis is presented in Table 4.6, and the strike map is in Figure 4.31.
Figure 4.31 Strike Map 114 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.6 Area Distribution by Direction
North South South North River Name Flat North East South West Total East East West West Suoi Area(㎢ ) 0.01 13.77 18.57 15.91 9.23 7.54 3.87 5.36 9.66 83.92 Peng Percenta 0.01 16.41 22.13 18.96 11 8.98 4.62 6.37 11.52 100 River ge(%)
C. Flood Rate Estimation Point Mapping
As for flood rate estimation, referring directly to the water level and flow rate data from the basin observatory will produce the most accurate result. In this target basin, however, there was neither precise rainfall data of years nor a water level observatory available, and thus the indirect method to estimate based on the basin topographical characteristics was adopted. The basin was divided into 5 sub-basins in reference to collected DEM data in order to decide flood rate estimation points. Each estimation point is illustrated in Figure 4.32 below, and their characteristics are presented in Table 4.7.
Figure 4.32 Sub-basinDivisionofSuoiPengRiver Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 115
Table 4.7 Geometric Characteristics at Each Estimation Spot
Channel Average Basin Profile Basin Area Estimation Point Extension Basin Width Coefficient A()㎢ L(㎞ ) A/L(㎞ ) (A/L²) End Point (5) 83.92 18,259 4.596 0.252 After Suoi 2 79.72 15,551 5.126 0.330 Conflux (4) Before Suoi 2 55.19 15,551 3.549 0.228 Conflux (3) After Suoi 4 48.22 11,200 4.305 0.384 Conflux (2) Before Suoi 4 37.75 11,200 3.370 0.301 Conflux (1)
D. Rainfall Analysis and Topographical Data Collection
1) Rainfall Analysis
To establish warning criteria based on hydraulic/hydrological analysis, past flood flow records need to be examined in reference to accumulated hydrological data with estimation of rainfall quantile by duration preceding. Particularly with regard to rainfall, basic requirements for the topographicalgeographical․ conditions, period of data accumulation, and data reliability need to be met. As for Suoi Peng River basin, however, rainfall analysis is impossible since there is no hydrological data applicable to a rainfall-outflow model. Thus, the present study utilizes the Rainfall Quantile of IHP Report「 Asian Pacific FRIEND, UNESCO(2008)」 for rainfall analysis. As IHP Report presents the Rainfall Quantil in Vietnam as in Table 4.8, a rainfall intensity expression was induced in reference to the data. 116 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.8 Rainfall Quantile
Duration Return period(mm) (min) 1 2 5 10 20 50 100 10 22.35 24.57 27.72 30.27 32.89 36.80 39.94 60 48.87 65.71 84.95 96.81 106.42 117.37 124.04 120 50.52 71.33 93.98 108.06 119.56 132.78 140.90 360 83.79 105.51 125.24 135.43 142.56 149.42 152.91 720 117.58 142.84 162.75 171.63 177.12 181.71 183.72 1440 151.39 172.05 186.01 191.29 194.14 196.19 196.95
Source: Asian Pacific FRIEND, UNESCO(2008)
As for rainfall intensity by frequency, binomial regression constants such as Talbot, Sherman, Japanese, and Semi-Log and 3-term regression constants such as General have been applied. Recently, polynomial expressions as that suggested in｢ A Study on Rainfall Quantile Improvement and Complementation (2011.11, Ministry of Land, Transport, and Maritime Affairs)｣ have also been introduced.
a Talbot Type : It t b a Sherman Type : It tn a Japanese Type : It t b S e m i - L o g : It a blogt Type a General Type : It tn b P o l y n o m i a l : lnI a blnth clnth dlnth elnth flnth Expression
Where, It indicates rainfall intensity (mm/hr) by rainfall duration, t Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 117
rainfall duration(min), th rainfall duration (hr), and a b c d e f g n regression constants respectively. In this study, General type whose determination coefficient value is relatively large is adopted as shown in Table 4.10 to induce the rainfall intensity expression presented in Table 4.9.
Table 4.9 Probable Rainfall Intensity for Each Rainfall Duration
Probable Rainfall Intensity by Frequency (mm/hr) Duration(min) 1 2 5 10 20 50 100 10 134.10 147.42 166.32 181.62 197.34 220.80 239.64 60 48.87 65.71 84.95 96.81 106.42 117.37 124.04 120 25.26 35.67 46.99 54.03 59.78 66.39 70.45 360 13.97 17.59 20.87 22.57 23.76 24.90 25.49 720 9.80 11.90 13.56 14.30 14.76 15.14 15.31 1440 6.31 7.17 7.75 7.97 8.09 8.17 8.21 118 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.10 Determination Coefficient Comparison
Talbot Sherman Japanese General Period Class. Adopted Type Type Type Type Short- 0.9994 0.9951 0.9935 1.0000 term 1 (year) General Long- 0.9909 0.9994 0.9991 0.9996 term Short- 0.9988 0.9887 0.9888 1.0000 term 2 General Long- 0.9937 0.9994 0.9988 0.9994 term Short- 0.9970 0.9784 0.9814 1.0000 term 5 General Long- 0.9960 0.9994 0.9987 0.9995 term Short- 0.9961 0.9739 0.9782 1.0000 term 10 General Long- 0.9969 0.9993 0.9987 0.9996 term Short- 0.9960 0.9729 0.9777 1.0000 term 20 General Long- 0.9975 0.9993 0.9987 0.9996 term Short- 0.9968 0.9757 0.9800 1.0000 term 50 General Long- 0.9980 0.9992 0.9988 0.9997 term Short- 0.9977 0.9794 0.9828 1.0000 term 100 General Long- 0.9983 0.9991 0.9989 0.9997 term Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 119
Table 4.11 Probable Rainfall Intensity Formula
Rainfall Intensity Expression Rainfall Intensity Expression Period (Short-term) (Long-term) 1 (year) 2 5 10 20 50 100
(a) Short-term (b) Long-term Figure 4.33 IDF Curves
2) Rainfall Scenario
As for distribution of design rainfall by time, a statistical analysis may be conducted on the distribution pattern of rainfall intensity depending on 120 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
the rainfall duration based on accumulated actual rainfall data. In this case, a rainfall scenario model specifically for the target region can be established with design conditions for hydraulic structures reflected. Methods to determine a design rainfall scenario include Mononobe method, Huff method, Keifer & Chu method, Pilgrim & Cordery method, Yen & Chow method, alternating block method, etc. In Korea, Huff's rainfall distribution method is most widely used, but it is inappropriate in Vietnam because its regional constants are not applicable. According to an forecasting/warning system establishment project for disaster reduction in the Philippines (National Disaster Management Research Institute, 2014), among various rainfall scenario setting methods, the alternative blocking method is applicable to a region where there is no rainfall data available. Thus, the alternative blocking method was applied to this study for its design rainfall scenario.
3) Topographical Data
As for topographical data, the grid size 30ｍ×30ｍ DEM (Digital Elevation Model) provided by NASA is utilized in this study. In addition, MODIS sallite image data is utilized for the landuse map and soil map.
DEM(30ｍ×30ｍ ) Landuse Map Soil Map
Figure 4.34 Topographical Data Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 121
E. Flood Rate Parameters
As mentioned earlier, sub-basins are divided for flood rate estimation by taking into consideration basin topography, branch conflux, and tributary comprehensively. For flood tracking at each sub-basin, sub-basin factors such as flood arrival time, storage constant, Rrunoff curve indexes(CN), etc. need to be calculated.
1) Arrival Time Estimation
Basin arrival time means the time that rainfall flows from the highest point to the bottom (basin outlet) of a basin. At the arrival time, there will be the peak runoff at the mouth of the basin, and this time point will be the standard for warning criteria. Hence, accurate estimation of arrival time is an important factor when it comes to designing a runoff model. There are various formulae for arrival time estimation: Kirpich formular, Rizha formular, Kraven formular, etc. (Table 4.12), and this study adopts continuous Kraven formular. 122 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.12 Arrival Time Formulae Applicable
Formula Arrival Time Formula (Tc, min) Name Kirpich L=basin's longest river length (㎞ ); S=basin's average slope (H/L, m/m) Rziha L=channel length(㎞ ), S=basin's average slope (H/L, m/m) Kraven-Ⅰ L=channel length(㎞ ), S=channel slope (H/L, m/m) Kraven-Ⅱ L=channel length(㎞ ), V= velocity at the slope(㎧ ), S=natural river slope V V Steep slope (S>3/400): S , max =4.5 m/s; gentle Continuous Kraven slope (S≤ 3/400): V S S ,Vmin =1.6 m/s
Table 4.13 Result of Arrival Time Calculation
Arrival Time (min) Continuo Adopt Estimation Point Kirpich Rziha Kraven-Ⅰ Kraven-Ⅱ us ed Kraven End Point (5) 115.55 88.92 36.87 86.95 69.70 69.70 After Suoi 2 80.13 51.91 22.70 74.05 57.96 57.96 conflux (4) Before Suoi 2 80.13 51.91 22.70 74.05 57.96 57.96 conflux (3) After Suoi 4 51.74 28.04 12.77 53.33 41.48 41.48 conflux (2) Before Suoi 4 51.74 28.04 12.77 53.33 41.48 41.48 conflux (1) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 123
2) Storage Constant Determination
This study examines storage constants of empirical equations commonly used in the field. To determine storage constants, Sabol formula was chosen among Clark, Linsley, Russel, and Sabol formulae in consideration of the basin's general shape. The results are presented in the tables below:
Table 4.14 Empirical Equation of the Storage Constant
Formula Name Storage Constant Formula (K, hr) Clark Linsley
Russel
Sabol
Table 4.15 Result of Storage Constant Calculation
Basin Sub-bas Clark Linsley Russel Sabol Applied Area in Name C K b K α Tc K K K ()㎢ End 83.92 1.00 79.45 0.02 14.56 2.15 1.45 3.12 1.04 1.04 Point(5) After Suoi 2 79.72 1.00 49.39 0.02 8.82 2.15 1.23 2.65 0.81 0.81 conflux (4) Before Suoi 2 55.19 1.00 49.39 0.02 7.34 2.15 1.23 2.65 0.89 0.89 conflux (3) After Suoi 4 48.22 1.00 27.99 0.02 3.89 2.15 0.89 1.91 0.56 0.56 conflux (2) Before Suoi 4 37.75 1.00 27.99 0.02 3.44 2.15 0.89 1.91 0.59 0.59 conflux (1) 124 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
3) Estimation of Runoff Curve Indexes (Curve Number)
The rainfall-runoff model for flood rate estimation is designed to calculate the relation between the effective rainfall and direct runoff. Estimation methods include the index method, W index method, NRCS (US Soil Conservation Service), etc. This study adopts the NRCS method, which is to estimate runoff curve indexes ( , Curve Number) in consideration of the target basin's soil, landuse, past rainfall records, etc. and then the effective rainfall in reference to the relation between Runoff Curve Indexes and the effective rainfall. The relation of the total rainfall-total effective rainfall, which is the basis for the effective rainfall estimation method, is as below:
Where, : The total accumulated rainfall during a rainfall period (or accumulated rainfall,㎜ )
: Target basin's max. potential rainfall capacity (㎜ )
: Direct runoff in relation to the total accumulated rainfall
In the expression above, represents hydrological soil/land cover characteristics such as soil and land use or treatment over the basin. Its relation with Runoff Curve Index (runoff curve number) that indicates a target basin's runoff capacity may be defined as in the following expression:
Hence, deciding the value of is of importance in estimating the effective rainfall by applying the NRCS method, and the value is Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 125
calculated by overlapping the soil map, landuse map and and sub-basin map. Hydrological soil groups are classified to Type A to Type D depending on the soil characteristics as shown in Table 4.15. Conditions of antecedent soil moisture are classified into three kinds - AMC-Ⅰ , AMC-Ⅱ , and AMC-Ⅲ - according to U.S. Soil Conservation Service (SCS) (Table 4.16).
Table 4.16 Classification of Existing Soil Water Content Conditions
5-day Rainfall in the past P(㎜ ) AMC Remark Non-peak Peak Season Season ㆍThe basin's runoff rate is quite low as I P < 13 P < 36 the soil is dry in general II 13≦ P≦ 28 36≦ P≦ 53 ㆍThe runoff rate is moderate ㆍThe runoff rate is quite high as the III P > 28 P > 53 basin's soil is almost saturated with water Table 4.17 Classification of Hydrological Soil Groups
Group Soil Nature ㆍPenetration rate is high even when it is completely wet Type ㆍWater permeation into soil is very fast; runoff possibility is low; soil layer is deep A ㆍContaining sand or gravel whose water permeation rate is high or quite high ㆍPenetration rate is moderate when it is completely wet Type ㆍSoil layer is somewhat deep or deep; drainage is somewhat good or good B ㆍSoil nature is fine or somewhat corase ㆍWater permeation rate is normal ㆍPenetration rate is low when it is completely wet Type ㆍContaining a layer that hinders water flows C ㆍSoil nature is somewhat fine or fine ㆍWater permeation rate is low ㆍPenetration rate is quite low when it is completely wet Type e.g.) expansion rate is high; underground water level is high D ㆍThere is a clay pan or a clay layer on the surface or in the shallow soil layer ㆍImpermeable medium in the shallow soil layer; penetration rate is quite low 126 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
The Ⅱ value that is calculated according to the AMC-Ⅱ condition and in reflection of the antecedent soil moisture condition needs to be adjusted (Table 4.17), and as for Ⅰ in the AMC-Ⅰ condition or Ⅲ in the AMC-Ⅲ , the following expression is applied:
,
In this study, the value was calculated according to the NRCS Runoff coefficient estimation in reference to the soil map and landuse map of Suoi Peng River basin. As for the antecedent soil moisture condition, the normal AMC-Ⅱ condition is applied. The estimated value of CN is presented in Table 4.18 below:
Table 4.18 Runoff Curve Indexes for Each Estimation Point(CN)
Basin Runoff Curve Indexes (CN) River Estimation Point Area Adopted Name Name AMC-Ⅰ AMC-Ⅱ AMC-Ⅲ ()㎢ End Point(5) 83.92 68.08 83.62 92.24 83.62 After Suoi 2 79.72 68.84 84.18 92.55 84.18 conflux(4) Suoi Before Suoi 2 55.19 68.55 83.96 92.42 83.96 Peng conflux(3) After Suoi 4 River 48.22 68.86 84.17 92.53 84.17 conflux(2) Before Suoi 4 37.75 68.54 83.94 92.40 83.94 conflux(1) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 127
Table 4.19 Runoff Curve Indexes of Agricultural and Forestry Regions (AMC-Ⅱ Condition)
Soil Type Soil's Vegetation Cover and Land Cover Hydrological Landuse Condition A B C D
Fallow Sslope tilth - 77 86 91 94
Slope tilth Drainage Bad 72 81 88 91
Slope tilth Drainage Good 67 78 85 89
Countour tilth Drainage Bad 70 79 84 88 Row Crops Countour tilth Drainage Good 65 75 82 86
Countour and terrace tilth Drainage Bad 66 74 80 82
Countour and terrace tilth Drainage Good 62 71 78 81
Slope tilth Drainage Bad 65 76 84 88
Slope tilth Drainage Good 63 75 83 87
Countour tilth Drainage Bad 63 74 82 85 Small Grains Countour tilth Drainage Good 61 73 81 84
Countour and terrace tilth Drainage Bad 61 72 79 82
Countour and terrace tilth Drainage Good 59 70 78 81
Slope tilth Drainage Bad 66 77 85 89
Slope tilth Drainage Good 58 72 81 85
Closed-seeded Legumes Countour tilth Drainage Bad 64 75 83 85 or Rotation Meadow Countour tilth Drainage Good 55 69 78 83
Countour and terrace tilth Drainage Bad 63 73 80 83
Countour and terrace tilth Drainage Good 51 67 76 80
Slope tilth Drainage Bad 68 79 86 89
Drainage Slope tilth 49 69 79 84 Normal
Pasture Slope tilth Drainage Good 39 61 74 80 or Range Countour tilth Drainage Bad 47 67 81 88 Drainage Countour tilth 25 59 75 83 Normal
Countour tilth Drainage Good 6 35 70 79
Drainage Good 30 58 71 78
초지 — Drainage Bad 45 66 77 83 (meadow) Drainage 36 60 73 79 Normal
삼림(woods) — Drainage Good 25 55 70 77
관목숲(forests) 매우 듬성듬성 - 56 75 86 91
농가(farm steads) — - 59 74 82 86 128 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
F. Flood Rate Calculation
The flood rate was calculated based on the rainfall time factors - frequency (1yr, 2yr, 5yr, 10yr, 20yr, 50yr, 100yr) and duration (10min, 60min, 120min, 360min, 720min, 1440min) - in utilization of an HEC-1 model. As mentioned earlier, the rainfall scenario applied here is the alternative blocking method. Based on the result of flood level calculation, the flood rate for the frequency of 10 years, 20 years, 50 years, and 100 years, corresponding to the duration of 1440min, was 1,257m3/s, 1,386m3/s, 1,524m3/s, and 1,604m3/s respectively. Flood volume estimations are summarized in Table 4.20, and Figure 4.35 shows the runoff curves by frequency.
Table 4.20 Calculation of Flood Rates by Frequency
Flood Rate by Frequency (m3/s) Duration(min) 1 2 5 10 20 50 100 10 42 55 77 92 119 154 183 60 262 443 667 799 932 1,075 1,164 120 276 492 749 904 1,050 1,210 1,310 360 466 682 936 1,060 1,185 1,317 1,396 720 578 795 1,051 1,169 1,295 1,428 1,506 1440 657 875 1,132 1,257 1,386 1,524 1,604
1 yr Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 129
2 yr
5 yr
10 yr 130 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
20 yr
50 yr
100 yr Figure 4.35 Graph of Flood Rate Estimation by Frequency Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 131
G. Flood Level Estimation & Flooding Mapping
In Suoi Peng River basin, Vietnam, the section over which a river survey was conducted was chosen for the flooding mapping (1km upstream and downstream from the water gauge point; about 2.4km from the river mouth). For flooding mapping, the pre-treatment process was conducted to collect topographical data by means of PreRAS which is one of the HEC-GeoRAS processing methods. The flood level was estimated based on the survey result and by means of HEC-RAS, and then the flood map was drawn with the flood level estimation and by means of PostRAS. The procedures are illustrated in Figure 4.36 below:
Figure 4.36 Flooding Map Design by Means of an HEC-GeoRAS Model
Source: HEC-GeoRAS GIS Tools Support of HEC-RAS Using ArcGIS User Manual, US Army Corps of Engineers(2009) 132 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
1) Topographical Data Collection by Means of PreRAS
For flooding mapping, A topographical database needs to be established by means of PreRAS. PreRAS components includes the DEM with altitude information, triangulated irregular network (TIN), river centerline, left/right river bank line, sideline extending to protected lowland, and flood range setting. These are summarized in Table 4.21 below. By means of PreRAS of Suoi Peng River, Vietnam, the topographical database was established by means of the target section's DEM and HEC-GeoRAS as shown in Figure 4.37.
Table 4.21 PreRAS Components
Themes Remark TIN Required for altitude inputs in other files Upstream/downstream classification with the stream Stream centerline centerline Main channel banks Data on embankment positions on the cross section Providing channel length info. for cross section Flow path centerline investigation Cross section cut lines Providing information on the stream sections Land use-manning table A file of roughness info. that contains land use data Providing information on areas where the flow is Levee alignment hindered as it is higher than the embankment Providing information on the range where the river Infective flow areas does not run Providing information on the range where the river Storage areas flow remains
Source: Establishment of an Forecasting/Warning System for Disaster Reduction in the Philippines (Ⅲ ), National Disaster Management Research Institute(2015) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 133
Figure 4.37 DEM Interpolation Results
2) Flood Level Estimation
Topographical data over the 14 cross sectional points were collected from PreRAS and then imported into HEC-RAS. To estimate the flood level by means of an HEC-RAS model, it was required to determine the boundary conditions upstream and downstream of the target section. The roughness setting for each cross section was 0.03, and the normal depth condition was applied for the downstream boundary water level since there was no observation data available. For the upstream area, the flood level was estimated in reference to the flood rate calculated by means of an HEC-HMS model. The estimation result is presented in Table 4.22 below. 134 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.22 Flood Level at Each Major Location by Frequency
Measuri Distance (m) Flood Frequency Flood Rate ng Point Sectio Accumul Level Note (yr) (㎥ /s) No. n ation (EL.m) 1 262 97.42 2 443 98.26 River 5 667 99.07 Mouth 0 0 0 10 799 99.49 (measuring 20 932 99.86 point) 50 1,075 100.24 100 1,164 100.46 1 262 102.52 2 443 103.12 5 667 103.54 Dien Cao 1+000 1,000 1,000 10 799 103.83 Bridge 20 932 104.09 50 1,075 104.54 100 1,164 104.69 1 262 114.58 2 443 115.13 5 667 115.63 Hợ p Thà nh 2+400 1,400 2,400 10 799 115.86 Levee 20 932 116.03 50 1,075 116.22 100 1,164 116.30 Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 135
(a) Topographical Data Imported into (b) HEC-RAS Cross Section Check & HEC-RAS Correction
(c) Upstream/Downstream Boundary (d) Flood Level Estimation Conditions Established
Figure 4.38 HEC-RAS Topographical Foundation and Flood Level Estimation Process
3) Flooding Mapping
The result of HEC-RAS application was then imported into HEC-GeoRAS, and then the post-treatment process was also conducted for mapping. PostRAS components for flooding mapping included Water Surface TIN, Depth Grid, Velocity Tin and Grid, etc. (Table 4.23), and the flood level estimation was converted into an Arc-Gis file. The completed flooding map was corrected and then organized by frequency (1, 2, 5, 10, 20, 50, 100, etc. (years)) as shown in Figures 4.40-4.46. 136 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.23 PostPAS Components
Themes Remark Generated on the basis of the bounding polygon of the cross Water Surface TIN sectional line and each water surface curve ID Depth Grid A polyline theme to identify flood spots and depth grids Velocity TIN Water surface curves that represent changes in the Velocity Grid velocity
Figure 4.39 PostRAS Configuration
Figure 4.40 Flooding Map (1yr) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 137
Figure 4.41 Flooding Map (2 yr)
Figure 4.42 Flooding Map (5 yr)
Figure 4.43 Flooding Map (10 yr) 138 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.44 Flooding Map (20 yr)
Figure 4.45 Flooding Map (50 yr)
Figure 4.46 Flooding Map (100 yr) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 139
H. Establishment of Warning Criteria
This study examines and presents criteria for flood alert over Hợ p Thà nh Levee and Dien Cao Bridge where water gauges were installed nearby Suoi Peng River basin. Domestic criteria for flood alert (Article 23 of the Enforcement Regulations of the river Act) were investigated, and the details are as follows:
○ Alarming Water Level: The water level that needs attention as it increases over nearby banks, bridges, etc. This range is calculated in the following way:
- 60 percentage out of 100 from the average low water level for 5 years at the flood forecast point to the calculated flood level
○ Critical Water Level: The water level that exceeds the alarming water level and involves a risk of demolition of nearby banks and bridges. This range is calculated in the following way:
- 80 percentage out of 100 from the average low water level for 5 years at the flood forecast point to the calculated flood level
In reference to the domestic criteria for flood alert, the flood level at each measuring point over Hợ p Thà nh levee and Dien Cao Bridge where a water gauge was installed. According to the one-dimensional hydraulic analysis result, the levee height at the point of Dien Cao Bridge (No.1+000) was 103.75ｍ , but the flood level at the frequency of 10yr was 103.83ｍ , which indicates that overflow would occur even at the frequency of 10yr (Figure 4.47). 140 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.47 Flood Level Planning on a Decade Basis
Thus, this study classifies Criteria for Flood Alert into three levels - Alert(40%), Alarm(60%), and Critical(80%) - in consideration of regional characteristics (area of constant flowing), technical judgment after field investigation, basin characteristics, and full water levels at Hợ p Thà nh Levee and Dien Cao Bridge (Figures 4.48-4.49 and Table 4.24).
Figure 4.48 Hợp Thành Levee Warning Criteria
Figure 4.49 Dien Cao Bridge Warning Criteria Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 141
Table 4.24 Criteria for Flood Alert (Unit: EL. m) Water Level Warning Criteria Note No. Alert Alarm Critical Observatory (40%) (60%) (80%) (basin) 1 Hợ p Thà nh levee 112.89 113.31 113.73 Suoi Peng 2 DienCaoBridge 102.19 102.71 103.23 River
4.2.3. Hydraulic· Hydrological Analysis in Laos
A. Overview
Hydraulic/hydrological analysis was conducted over Nam Xong River basin in Laos according to the procedures of warning criteria establishment as shown in Figure 4.50. The flood rate was calculated based on the flood frequency and in reference to Nam Xong River basin flood level data by year in UNESCO Report「 Southeast Asia and The Pacific-VolumeⅤ , 2004」 . With flood rate estimation data and Hec-Ras utilized, warning criteria for Nam Xong River basin were established, with the flooding map drawn.
Figure 4.50 Laos Hydraulic/Hydrological Analysis Procedures 142 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
B. Analysis of Target Basin Characteristics
Laos Nam Xong River is originated from Phou Keo, passes through Vang Vieng City, and flows into Nam Lik River. The basin area is as large as about 1819.90㎢ , and the channel extension is as long as 102.09 ㎞. The basin profile coefficient is a non-dimensional value that represents the basin's shape. As the profile coefficient is close to 1.0, the basin's shape is close to a square. as the profile coefficient value is large, the runoff concentration level is high, presumably causing the high peak flood rate. Table 4.25 shows general characteristics of Nam Xong River Basin.
Table 4.25 Characteristics of Nam Xong River Basin
Average Channel Basin Profile Basin Area Width of the River Name Extension Coefficient A()㎢ Basin L(㎞ ) (A/L²) A/L(㎞ ) Nam Xong 1819.90 102.09 17.83 0.17 River
3-dimensional factors of determination of a basin include the river slope, basin slope, area distribution by altitude, etc. In this study, area distribution values by altitude and slope and the basin orientation of Nam Xong River basin were calculated.
1) Area Distribution by Altitude
Area distribution by altitude is a factor that affects altitude-related factors such as rainfall, evaporation, vegetation, and hydrological features. This is referred to in analyzing 3-dimensional topography characteristics. As for area distribution by altitude over Nam Xong River basin, the area Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 143
of 1,000m or lower altitude was as large as 752.96㎢ , and the area of 2,000m or lower altitude was as large as 1,505.92㎢ (Figure 4.51 and Table 4.26).
Table 4.26 Cumulative Area and Component Ratio by Altitude
Area Distribution by Altitude(EL.m) 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,417 Class. or or or or or or or or or or or lower lower lower lower lower lower lower lower lower lower lower Area 301.18 451.77 602.37 752.96 903.55 1054.14 1204.73 1355.32 1505.92 1656.51 1819.90 ()㎢ Percentage 16.55 24.82 33.10 41.37 49.64 57.92 66.20 74.47 82.75 91.02 100.00 (%)
Figure 4.51 Altitude Distribution 144 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
2) Area Distribution by Slope
Area distribution by slope affects runoff, soil/earth erosion, and hydrological characteristics. This element is referred to in analyzing 3-dimensional topography features. As for area distribution by slope over Nam Xong River basin, the area of 10°or lower slope was as large as 244.06㎢ , which accounts for about 13.41%, and the area of 30°or lower slope was as large as 732.08㎢ (40.23%) (Figure 4.52 and Table 4.27).
Figure 4.52 Slope Distribution Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 145
Table 4.27 Cumulative Area and Component Ratio by Slope
Area Distribution by Slope(°) Class. 5or 10or 15or 20or 25or 30or 35or 45or 55or 65or 75or lower lower lower lower lower lower lower lower lower lower lower Area (㎢ ) 122.01 244.03 366.04 488.05 610.07 732.08 854.10 1098.12 1342.15 1586.18 1819.90 Ratio (%) 6.70 13.41 20.11 26.82 33.52 40.23 46.93 60.34 73.75 87.16 100.00
3) Basin Orientation
The relation between the water system slope orientation and the wind direction on a rainy day may affect the rainfall over the water system. The main direction of the water system and the route of the호 rainy front may affect flood hydrological curves. According to the survey result of area distribution by slope, the area facing north accounted for 11.48%, and the area facing south 12.96%. Results of basin orientation analysis are presented in Table 4.28 and Figure 4.53.
Figure 4.53 Strike Map 146 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.28 Area Distribution by Direction
North South South North River Name Flat North East South West Total East East West West
Area(㎢ ) Percentage( %)
C. Flood Rate Estimation
Flood rate estimation methods are divided mainly to the design rainfall-runoff method and the flood rate data frequency analysis method. The design rainfall-runoff method is to utilize rainfall data that is relatively sufficient when there is little flood rate data. Since there is a little amount of actual flood rate measurement data in Korea, most irrigation plans such as basic plans for comprehensive irrigation and river management adopt the design rainfall-runoff method. The flood rate data frequency analysis method examines flood rate data directly to grasp the frequency and estimate the design flood rate. Theoretically, this is the most direct and best method (Practical Water Resources Design, 2007).
As for Nam Xong River basin in Laos, the flood rate was calculated by applying the flood rate data frequency analysis method in reference to annual flood rate data over Vang Vieng City where a warning station was located. The probability distribution types which were applied to flood rate frequency analysis of Nam Xong River basin included Gamma Distribution (bivariate, ternary), GEV(General Extreme Value) Distribution, Gumbel Distribution, log-Gumbel(bivariate, ternary) Distribution, log-normal(bivariate, ternary) Distribution, log-Pearson TypeⅢ Distribution, Weibull(bivariate, ternary) Distribution, etc. For parameter estimation of each probability distribution type, the Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 147
following methods were utilized: Method of Moments, Method of maximum Likelihood, and Method of Probability Weighted Moments. For the probability distribution type suitability test, the following four methods were utilized: χ Test, Kolmogorov-Smirnov Test, Cramer Von Mises Test, and Probability plot correlation coefficient(PPCC) Test.
1) Flood Rate Data by Year
Flood rate data by year that was collected from the area of Vang Vieng City in Nam Xong River basin, Laos, is presented in Table 4.30, and the locations are as in Table 4.29 and Figure 4.54.
Table 4.29 Locations of Flood Level Measurement
Station Location Observation Period N 18°54’24” Vangvieng 1987-2002 E 102°26’54” Source: Southeast Asia and The Pacific-VolumeⅤ , 2004
Figure 4.54 Positions of Flood Rate Data Observation 148 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.30 Flood Level Data by Year
Maximum Discharge Minimum Discharge Year (m3/s) (m3/s) 1987 258.00 4.80 1988 350.00 6.64 1989 314.00 6.64 1990 357.00 6.50 1991 312.00 8.00 1992 370.00 2.67 1993 364.00 5.86 1994 366.00 3.09 1995 526.00 6.89 1996 - - 1997 799.00 10.0 1998 285.00 4.95 1999 238.428 8.60 2000 184.167 11.1 2001 476.682 9.1 2002 470.203 10.1 Source: Southeast Asia and The Pacific-Volume Ⅴ, 2004
2) Result of Flood Rate Calculation
To calculate the flood rate by frequency in reference to collected annual max. flood rate data, FARD2006 program provided by the National Disaster Management Research Institute was utilized. Parameters were presumed by means of various probability distribution types of FARD2006 program, and the suitability of presumed probability distribution types was determined by means of probability paper and suitability test methods to find out which of them would be appropriate most in expressing collected observation data. As a result of the suitability test, it turned out that Gamma Distribution (bivariate), GEV Distribution, Gumbel Distribution, and log-Gumbel(bivariate) were appropriate for K-S and PPCC Tests (Table 4.32). In addition, the CDP and PDF files of each probability distribution type corresponding to actual measurement data were Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 149
converted into probability paper for comparison. As a result, it turned out that the Gamma Distribution (bivariate) of the Method of Maximum Likelihood was closest to the sample group (Figure 4.55 and Figure 4.56). Among probability distribution types, Gev Distribution (bivariate) of the Method of Maximum Likelihood was chosen in reference to the suitability test result and probability paper illustration. In this method's Calculation of Flood Rates by Frequency, the flood rate of the 10-year frequency was 556m3/s, 50-year frequency 770m3/s, 100-year frequency 870m3/s, and 150-year frequency 931m3/s respectively as shown in Table 4.31 below:
Table 4.31 Result of Flood Level Calculation
Frequency 2 5 10 50 100 150 (year) Flood Rate 349 469 556 770 870 931 (m3/s)
Figure 4.55 Maximum Likelihood Method PDF Graph 150 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.56 CDP of the Maximum Likelihood Method CDF in Graph
Table 4.32 Suitability Test Results by Probable Distribution Type
Maximum Likelihood Probability Weighted Suitability Probability Moment Method Method Moment Method Test Distribution Calculat Judgme Calculat Judgme Calculat Judgme Method Type Critical Critical Critical ion nt ion nt ion nt GAM2 1.20 3.84 O 1.20 3.84 O 1.20 3.84 O χ² GEV 1.63 3.84 O 1.63 3.84 O 1.63 3.84 O Test GUM 0.20 3.84 O 0.20 3.84 O 0.20 3.84 O LGU2 1.27 3.84 O 0.73 3.84 O 0.73 3.84 O GAM2 0.20 0.34 O 0.21 0.34 O 0.21 0.34 O K-S GEV 0.17 0.34 O 0.16 0.34 O 0.15 0.34 O Test GUM 0.19 0.34 O 0.18 0.34 O 0.19 0.34 O LGU2 0.12 0.34 O 0.14 0.34 O 0.11 0.34 O CRAME GAM2 0.08 0.46 O 0.07 0.46 O 0.07 0.46 O R VON GEV 0.05 0.46 O 0.04 0.46 O 0.05 0.46 O MISES GUM 0.06 0.46 O 0.05 0.46 O 0.06 0.46 O Test LGU2 0.05 0.46 O 0.06 0.46 O 0.06 0.46 O GAM2 0.95 0.94 O 0.95 0.94 O 0.95 0.94 O PPCC GEV 0.96 0.93 O 0.96 0.93 O 0.97 0.93 O Test GUM 0.97 0.93 O 0.97 0.93 O 0.97 0.93 O LGU2 0.98 0.92 O 0.99 0.92 O 0.99 0.92 O Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 151
D. Flood Level Estimation Flooding Mapping
For the river survey project over Nam Xong River basin, Laos, the position of upstream water gauge installation and the annual flood rate observation point (downstream warning station), which were essential points for flood forecast/warning, were selected. River survey was conducted 1km downstream and upstream from the selected positions. Over the areas of the upstream/downstream water level observation stations where a river survey was conducted for flooding mapping, DEM interpolation procedures were implemented. Over sections where no survey was conducted, topographical data was collected by means of PreRAS and cross-sectional data extracted from the DEM. The flooding mapping procedures were the same with those used in Vietnam. The flood level and flooding maps were drawn through the pre-treatment step for topographical data collection by means of PreRAS.
1) PreRAS-based Topographical Data Collection
PreRAS components included TIN, river centerline, dike lines at the left/right sides of the river, sideline extending toward the low-land, and flood range setting. Topographical data was collected in the same way that was applied to Vietnam. Figure 4.57 shows PreRAS configuration elements such as Tin, Stream centerline, main channel banks, flow path centerline, etc. Figure 4.58 shows DEM interpolation results in the section of survey. 152 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(a)Tin Generation (b) Stream Centerline Drawing
(c) Main Channel Bank Drawing (d) Flow Path Centerline Drawing
Figure 4.57 PreRAS Configuration Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 153
Figure 4.58 DEM Interpolation Results
2) Flood Level Estimation
Topographical data collected from PreRAS was imported to HEC-RAS, and then the data on the designated cross section was input. The righness of each cross section was set to 0.03 based on the field investigation result. As for the water level over the downstream boundary, the normal depth condition was applied (Figure 4.59). For the upstream area, the flood rate estimated in the flood rate data frequency analysis was referred to. The result of flood rate estimation is presented in Table 4.33. Table 4.33 Flood Level at Each Major Location by Frequency
Measuring Distance (m) Frequency Flood Rate Flood Level Note Point No. Section Accumulation (yr) (㎥ /s) (EL.m) 2 349 226.51 5 469 227.01 River 10 556 227.34 Mouth 0 0 0 50 770 228.14 (Measurin 100 870 228.45 g Point) 150 931 228.64 2 349 228.52 5 469 229.14 Warning 10 556 229.45 Station 1+500 1,500 1,500 50 770 230.13 (Vang 100 870 230.46 Vieng) 150 931 230.69 2 349 270.20 Water 5 469 270.54 Gauge 10 556 270.84 23+762.67 22,262.67 23,762.67 (Pha 50 770 270.98 Tang 100 870 271.13 Bridge) 150 931 271.46 154 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(a) Topographical Data Imported to (b) HEC-RAS Cross Section Checking HEC-RAS & Correcting
(c) Establishment of Upstream/Downstream Boundary (d) Flood Level Estimation Conditions Figure 4.59 HEC-RAS Topographical Base and Flood Level Estimation Process
3) Flooding Mapping
Flood data collected from HEC-RAS was imported to HEC-GeoRAS, and the post-treatment process was conducted for mapping. In the same analysis procedures with those in Vietnam, the data was converted to an Arc-Gis file, and as in the figure below, the flooding map was drawn for different frequencies: 2yr, 5yr, 10yr, 50yr, 100yr, 150yr, etc. (Figures 4.60-4.65). Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 155
Figure 4.60 Flooding Map (2yr)
Figure 4.61 Flooding Map (5yr)
Figure 4.62 Flooding Map (10yr) 156 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Figure 4.63 Flooding Map (50yr)
Figure 4.64 Flooding Map (100yr)
Figure 4.65 Flooding Map (150yr) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 157
E. Establishment of Forecast/Warning Criteria
Criteria for flood alert was established in 3 steps - Alert(40%), Alarm(60%), Critical(80%) - for the upstream water gauge point (Pha Tang Bridge) and the downstream warning station point (Vang Vienge) of Nam Xong River basin in consideration of the domestic criteria for flood alert (Article 23 of the Enforcement Regulations of the river Act), regional characteristics (extra surface region, etc.), basin characteristics, and full water level (Figures 4.66-4.67 and Table 4.34).
Figure 4.66 Pha Tang Bridge Warning Criteria
Figure 4.67 Vang Vienge Warning Criteria 158 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 4.34 Criteria for Flood Alert (Unit : EL. m)
Warning Criteria water level Note No. observatory Alert Alarm Critical (basin) (40%) (60%) (80%)
1 Pha Tang Bridge 269.86 270.66 271.47 Nam Xong River 2 Vang Vienge 227.78 228.68 229.49 Chapter 5. Flash Flood Hazard Analysis & Hazard Mapping
Concept & System of 5.1 Hazard Estimation Selection of Flash Flood 5.2 Hazard Indexes Methods of Flash Flood 5.3 Hazard Estimation
5.4 Estimation Results
Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 161
Chapter 5 Flash Flood Hazard Analysis & Hazard Mapping
A flash flood hazard map is designed to predict the risk of river flooding over inland regions after a heavy rainfall such as typhoon, storm, etc. A flash flood hazard map is connected with the Flash Flood Alert System (FFAS) which analyzes rainfall data real-time and issues warnings based on the currently available data and prediction data. It also indicates regions of high risk of flash floods based on hydrological analysis of quantitative flash flood factors over a certain region. This kind of map can be utilized for regional risk analysis when embankment and urban plans and response systems in a region with a risk of inundation need to be established, and its data can be useful for analysis of regions with little rainfall data and selection of regions where automatic rainfall warning facilities are to be installed.
There have been a number of researches on flash flood hazards in Korea, but the present study is significant in that it analyzes such hazards in application of the disaster hazard assessment method introduced in the "Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies(2014-2015)" conducted by the National Disaster Management Research Institute.
5.1. Concept & System of Hazard Estimation
For hazard estimation in the present study, the hazard assessment system of「 Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies (National Disaster 162 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Management Research Institute, 2014-2015)」 which adopts concepts suggested by international organizations such as UNISDR, IPCC, WMO (Hazard, Exposure, and Vulnerability) and their hazard assessment systems.
Major indicators of hazards are Hazard, Exposure, and Vulnerability, each of which has its sub-indicators. Hazard assessment results are classified into 5 different grades, and Grade 1 is the most hazardous. The concepts of Hazard, Exposure, and Vulnerability that are referred to in this study's hazard assessment are as follows:
∙ Hazard: Elements that cause direct impact on disaster occurrence (climate elements)
∙ Exposure: Elements that are located in a region of risk and may cause damage upon a disaster (properties, populations, etc. in the region of disaster risk
∙ Vulnerability: Elements that are closely related to disaster occurrence and are likely to be affected (topographical, social, and financial elements)
- Social Elements: Classes and facilities vulnerable to disasters
- Financial Elements: Elements that involve a high risk of damage
Figure 5.1 Disaster Risk Assessment System Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 163
5.2. Selection of Flash Flood Hazard Indexes
In this study, regions of high risk are selected and an analysis system is established in order to improve disaster-preventive effects of this flash flood warning system.
In Korea, areas of risk are classified in the unit of administrative districts, but for easy understanding of flash flood hazards in this study, regions of high risk - 9 sub-basins over Cagayan de Oro basin and 3 sub-basins over Iponan basin - were selected.
For risk assessment over such regions, elements that might affect floods were taken into consideration when the indexes - Hazard, Exposure, and Vulnerability - were selected. The appropriateness of related indexes and the easiness of data acquisition were also considered.
Laos Nam-xong River, Basin(13) Vietnam Coc River, Basin(5) Figure 5.2 Sub-basins in Laos and Vietnam 164 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
5.2.1. Selection of Hazard Indexes
Flash floods around the target basins result from typhoons and cause severe damage. To select hazard indexes of flash floods, this study refers to hazard indexes of floods and typhoons introduced by the 「Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies (National Disaster Management Research Institute, 2014-2015)」 . Flood & Typhoon Hazard Assessment Indexes are classified to Hazard, Exposure, and Vulnerability, which are explained specifically in Table 5.1 below:
Table 5.1 Flood & Typhoon Hazard Assessment Indexes
Related Class. Definition Indexes Elements ∙ Average rainfall for 6 hours during the year is at least 70㎜ (present) Rainfall Elements ∙ Average annual rainfall is at least 70㎜ that cause /day (future) Hazard direct impact ∙ Average annual instantaneous wind on disaster Wind occurrence velocity is at least 20m/s (present) velocity ∙ Average annual wind velocity is at least 20m/s (future) ∙ The population located in a region of Elements Populatio flood/typhoon risks (present) that are n ∙ The population located in a region of located in flood/typhoon risks (future) Exposur the region of ∙ Roads located in a region of disaster risk e flood/typhoon risks and may Propertie ∙ The area of buildings located in a cause s damage region of flood/typhoon risks (residence-related buildings) Elements ∙ Impermeable rate (present) Topograp that are ∙ Impermeable rate(future) Vulnerab closely hic ∙ Low land(slope) ility related to ∙ No. of individuals vulnerable to disaster Social occurrence disasters (present) Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 165
∙ No. of individuals vulnerable to disasters (future) ∙ No. of households living on a semi-basement floor ∙ No. of large-size buildings and are likely to be ∙ River density affected ∙ Area of harbor facilities ∙ Area of fishing port facilities ∙ Area of fish breeding ∙ No. of greenhouses Financial∙ Asset values (official land price) Source: 「Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies I (National Disaster Management Research Institute, 2014-2015)」
5.2.2. Selection of Assessment Indexes
To select flash flood hazard assessment indexes in Vietnam and Laos, related factors such as appropriateness, available databases, etc. were taken into consideration. First of all, future-predictive data was excluded since it was difficult to collect such data in the target countries, and the current data only was referred to in selecting assessment indexes.
Table 5.2 Flood & Typhoon Hazard Assessment Indexes
DB DB Appro Availa Availa Class. Indexes priate bility bility ness (Vietna (Laos) m) ∙ Average rainfall for 6 hours during the year is at ○ ○ ○ least 70㎜ (present) ∙ Average annual rainfall is at least 70㎜ × × × /day (future) Hazard ∙ Average annual instantaneous wind ○ × × velocity is at least 20m/s (present) ∙ Average annual wind velocity is at ○ × × least 20m/s (future) ∙ The population located in a region of Exposur ○ ○ ○ flood/typhoon risks (present) 166 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
∙ The population located in a region of ○ × × flood/typhoon risks (future) ∙ Roads located in a region of ○ ○ ○ e flood/typhoon risks ∙ The area of buildings located in a region of flood/typhoon risks ○ × × (residence-related buildings) ∙ Impermeable rate(present) ○ ○ × ∙ Impermeable rate(future) ○ × × ∙ Low land(slope) ○ ○ ○ ∙ No. of individuals vulnerable to × × × disasters (present) ∙ No. of individuals vulnerable to × × × disasters (future) ∙ No. of households living on a Vulnerab × × × semi-basement floor ility ∙ No. of large-size buildings × × × ∙ River density ○ × × ∙ Area of harbor facilities × × × ∙ Area of harbor facilities × × × ∙ Area of fishing port facilities × × × ∙ No. of greenhouses × × × ∙ Asset values (official land price) ○ × ×
Table 5.3 Laos Hazard Assessment Indexes
DB Class. Selection Indexes Selection Availability
∙ Average rainfall for 6 hours during the Hazard ○ ○ year is at least 70㎜ (present)
∙ The population located in a region of ○ ○ flood/typhoon risks Exposure ∙ Roads located in a region of flood/typhoon ○ ○ risks
∙ Impermeable rate ○ ○ Vulnerabi lity ∙ Low land (slope) ○ ○ Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 167
Table 5.4 Vietnam Hazard Assessment Indexes
DB Class. Selection Indexes Selection Availability
∙ Average rainfall for 6 hours during the Hazard ○ ○ year is at least 70㎜ (present)
∙ The population located in a region of ○ ○ flood/typhoon risks Exposure ∙ Roads located in a region of flood/typhoon ○ ○ risks
Vulnerabi ∙ Low land (slope) ○ ○ lity
5.3. Methods of Flash Flood Hazard Estimation
5.3.1. DB Establishment
As sub-indicators of typhoon hazard, exposure, and vulnerability, the following factors were selected in Laos: rainfall (Hazard); population and road in regions of risk (Exposure); and impermeable rate and low land (slope) (Vulnerability). In Vietnam, rainfall (Hazard); population and road in regions of risk (Exposure); and low land (slope) (Vulnerability) were selected. How to establish a DB is summarized in the table below: 168 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
Table 5.5 Vietnam, Laos Hazard Assessment Indexes
Year of Class. Selection Indexes Data Data Used Source Collection ∙ Average rainfall for 6 AWS data hours during the year Hazard 2015 (rainfall of 1 CHRS is at least 70㎜ hour) (present) ∙ The population located in a region of 2010 GIS data DIVA-GIS Exposur flood/typhoon risks e ∙ Roads located in a region of flood/typhoon - GIS data DIVA-GIS risks GIS data ∙ Impermeable rate 2010 DIVA-GIS Vulnerab (Landcover) ility ∙ Low land (slope) - DEM DIVA-GIS
5.3.2. Assessment Method
As for the index-developing method for hazard assessment that this study adopts, data of sub-indicators was collected and standardized with indexes finalized for hazard assessment. Since it might be problematic to regard every standardized index as of the same value, weights were applied depending on the importance among indexes, their effects on the result, etc. For weight calculation, the Entropy Method was adopted.
The Entropy Method is a comparatively objective method that calculates weights in a hydraulic manner only based on actual measurements. When the difference in score points among alternatives is significant, the entropy value decreases. When the different is small, the entropy value increases. The weight of each attribute can be determined by calculating Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 169
the entropy value this way. Since the score points of each alternative item are quantified with different units and criteria applied, it is recommended to standardize them first before the assessment score table is finalized. When the score of alternative K to attribute is defined
as , of each attribute is calculated to convert these score
points into a figure between 0 and 1. indicates the highest score of
. With the values of combined and defined as , their percentages are calculated. In reference to the values above, the entropy figure is calculated with the following equation:
Where, m is the number of alternatives, and K is a constant. log. The value of K is determined this way so that the max. value of becomes 1. With the entropy value applied, the weight is calculated with the following equation:
n: No. of attributes 170 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
5.4. Estimation Results
5.4.1. Laos Hazard Estimation Results
The results of hazard estimation over Nam Xong River basin, Vang Vieng, Laos, are as follows:
It turned out that hazard elements were more in the upstream region whee rainfall would be frequent. The level of exposure was highest in Nam Xong 9 Basin where the population and roads were concentrated, and it was high over the downstream region as well. The level of vulnerability was high over Nam Xong 9 Region where the impermeable rate was high and Nam Xong 13 Region which was a type of low land.
(a) Hazard (b) Exposure (c) Vulnerability Figure 5.3 Flash Flood Hazard Assessment by Indexes
The results of flash flood hazard estimation in reference to Hazard, Exposure, and Vulnerability indexes are as follows:
Among 13 basins, the hazard grade was high (grades 1 and 2) in 3 (23%), and the grade was low (grades 4 and 5) in 7 (53%). Chapter 4 Survey on Target Basin Rivers and Hydraulic/Hydrological Analysis | 171
Figure 5.4 Laos Flash Flood Hazard Map
5.4.2. Vietnam Hazard Estimation Results
The results of hazard assessment over Suoi Peng Basin, Lao Cai, Vietnam, are as follows:
The level of hazard was high over the downstream region where rainfall would be frequent. The level of exposure was high over the downstream region which was a downtown where the population and roads were concentrated. The level of both hazard and exposure was highest in Suoi 2 Region. The level of vulnerability was high in Suoi 1 Region which was a type of low land where the impermeable rate was high. 172 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
(a) Hazard (b) Exposure (c) Vulnerability Figure 5.5 Flash Flood Hazard Assessment by Indexes
The results of flash flood hazard estimation in reference to Hazard, Exposure, and Vulnerability indexes are as follows:
Among 5 basins, the grade of hazard was high (grades 1 and 2) in 2 (40%) while the grade was low (grades 4 and 4) in 2 (40%).
Figure 5.6 Vietnam Flash Flood Hazard Map Chapter 6. Conclusion
Chapter 6 Conclusion | 175
Chapter 6 Conclusion
At the 44th Typhoon Committee General Assembly (February 2012) for which Korea is serving as the chair country of its Disaster Prevention Department, Philippines Korean Meteorological Administration (PAGASA) requested a flash flood forecasting/warning system as a non-structural measure for the large-scale damage by typhoon “Washi” (December 2011) over Mindanao Island, the Philippines. In response, Korea has provided the recipient country, the Philippines, with its advanced technology for the Flash Flood Alert System (FFAS) which is a preemptive measure for flash floods and for the Automatic Rainfall Warning Facilities (ARWS) which reduce flood damage over mountainous regions from 2013 to 2015.
In the Annual Meeting of the Typhoon Committee Disaster Prevention Department (May) and its Integrated Workshop (January 1) held in 2014, the delegates of Vietnam and Laos requested the ODA Project, and accordingly, a series of steps were taken: the pre-validation survey was conducted with a field investigation in Vietnam and Laos in May 2015; and the forecasting/warning system establishment project (I) for disaster reduction in Vietnam and Laos was initiated in 2016. In this project, the flash flood forecasting/warning system and automatic rainfall warning facilities (2 rain gauges, 2 water gauges, and 2 warning stations in each country) were established over Ta Phoi basin in Lao Cai, Vietnam, and Nam Xong River basin in Vang Vieng, Laos.
The Flash Flood Alert System (FFAS) established in Vietnam VAWR 176 | Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR(Ⅰ )
and Laos DMH was designed to monitor observation data collected at the hydrometric stations in Ta Phoi and Nam Xong River basins real-time, and the Flash Flood Alert System (FFAS) had warning station control functions for automatic/manual warning upon a flash flood.
In addition, hydraulic/hydrological analysis was conducted based on river surveys in order for flooding mapping.
The hazard assessment method introduced in the「 Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies (National Disaster Management Research Institute, 2014-2015)」 was adopted to analyze hazard factors and draw a hazard map. For the automatic rainfall warning facilities installed for this study to be actively utilized by the local agencies in charge in the future, a system manual was prepared specifically for the public officials with workshops conducted for education.
It is expected that the non-structural flood measures for flash flood risk reduction proposed by this study will help reducing damage from flash floods in the target regions. As an OECD member country and the 15th economic power in the world, Korea will take preemptive measures to protect a number of humans and properties from disasters such as typhoon, flood, and tsunami over developing countries. To this end, there should be continued participation and expansion of the scope of support. References Reference
Brath, A., Castellarin, A., Franchini, M., and Galeati, G., Estimating the index flood using indirect methods, 2001
Carpenter, T. M., Sperfslage J. A., Georgakakos K. P., Sweeney T., and Fread D. L., National threshold runoff estimation utilizing GIS in support of operational flash flood warning systems, 1999
Chanthirath, K., Forest utilization by local people in Vang Vieng District, 1999
Dalrymple, T., Flood frequency analyses, 1960
Disaster Management Research Center of the National Disaster Management Institute, The Expansion of the Flash Flood Prediction System and the Development of a Process for the Decision-making Assistant System, 2009
Food and Agriculture Organization, Strengthening Capacities to Enhance Coordinated and Integrated Disaster Risk Reduction Actions and Adaptation to Climate Change in Agriculture in the Northern Mountain Regions of Viet Nam, 2011
Food and Agriculture Organization & Ministry of Agriculture and Rural Development, Guidelines for integrating disaster risk reduction and climate change adaptation into agriculture development planning plans in the Phu Tho, Yen Bai and Lao Cai Provinces, 2012
Georgakakos, K. P., Real time prediction for flood warning and management, U.S.-Italy Research Workshop on the Hydrometeorology, Impacts, and Management of Extreme Floods Perugia (Italy), November 1995
Georgakakos, K. P., Analytical results for operational flash flood guidance, 2006
Hansen, Final report: Vang Vieng town and environs master plan, 2010-2020, 2009
Hydrologic Engineering Center, Hydrologic modeling system (HEC-HMS), 2003
Institute for Social and Environmental Transition-International, Climate action plan for Lao Cai city, 2014
Japan International Cooperation Agency, Master plan study on integrated agricultural development in Lao People's Democratic Republic; Volume 3, 2001
Kirkb, M. J., Tests of the random network model and its application to basin hydrology, 1976
Kull, D. W. and Feldman A. D., Evolution of Clark’s unit graph method to spatially distributed runoff, 1998
Lao People's Democratic Republic Place Independence Democracy Unity Prosperity, Typhoon Haima joint damage, losses and needs assessment, 2011
Martina, M. L. V., Todini E., and Libralon, A., A Bayesian decision approach to rainfall thresholds based flood warning, 2006
Ministry of Land, Transport and Maritime Affairs, A Study for Probable Rainfall Intensity Improvement and Complementation, 2011
Nash, J. E. and Sutcliffe, J. V., River flow forecasting through conceptual models 1: A discussion of principles, 1970 National Disaster Management Research Institute, Establishment of the Fundamental Technology for Disaster Hazard Assessment and Response Technologies (Ⅰ ), 2014
National Disaster Management Research Institute, The Forecasting/Warning System Establishment Project for Disaster Reduction in the Philippines (III), 2015
National Hydro-Meteorological Service of Viet Nam, Current status and future plan of surface, climate and upper-air observations of National Hydro-Meteorological Service of Viet Nam, 2010
National Hydro-Meteorological Service of Viet Nam, Report of National Hydro-Meteorological Services of Viet Nam, 2015
Neary, D. G. and Swift, L. W., Rainfall thresholds for triggering a debris flow avalanching event in the southern Appalachian Mountains, 1987
Pilgrim, D. H. and Cordery I., Flood runoff: Handbook of hydrology, 1993
Rodriguez-Iturbe, I. and Valdes, J. B., The geomorphologic structure of hydrologic response, 1979
Socialist republic of Viet Nam. Country report: ESCAP/WMO Typhoon Committee 10th IWS, 2015
Soil Conservation Service, Urban hydrology for small watersheds. Technical Release 55, US Department of Agriculture, 1986
United Nations Educational, Scientific and Cultural Organization, Asian Pacific FRIEND Rainfall Intensity Duration Frequency(IDF) Analysis for Asia Pacific Region, 2008
United Nations Educational, Scientific and Cultural Organization, Catalogue of rivers for Southeast Asia and The Pacific - Volume V, 2004
United Nations International Strategy for Disaster Reduction, Country assessment report for Lao PDR: Strengthening of hydrometeorological service in Southeast Asia, 2013
United Nations International Strategy for Disaster Reduction, Country assessment report for Viet Nam: Strengthening of hydrometeorological service in Southeast Asia, 2013
US Army Corps of Engineers, HEC-GeoRAS GIS Tools Support of HEC-RAS using ArcGIS User’s Manual, 2009
Yu, P. S. and Yang T. C, Using synthetic flow duration curves for rainfall-runoff model calibration at ungauged sites, 2000 REPORT DOCUMENTATION PAGE
1. Report No. 2. Research development phase 3. Report Date Development research phase 2016. 12
4. Title and Subtitle 5. Period Covered Construction of forecasting and warning system for 2016. 6 ~ 2016. 12 disaster risk reduction in the Vietnam and Lao PDR(Ⅰ ) 6. Performing Organization Name and Address 7. Author(s) NOAA Solution Co., Ltd. Yang, Dongmin & other 13 12F, Sinhan Innoplex Bld, 151, Gasan digital 1-ro, (NOAA Solution Co., Ltd.) Geumcheon-gu, Seoul, Korea Park, Munhyeon & other 19 Tel. +82-2-6105-6600 (Dongbu Engineering Co., Ltd.) Fax. +82-2-6105-6625 Ha, Sangmin (IOT Solution) 8. Co-performing Organization Name and Address 9. Sponsoring Agency Name and Address Dongbu Engineering Co., Ltd. 14F, Gateway Tower, 12, Dongja-Dong, Yongsan-Gu, Seoul, Korea, 140-709 Tel. +82-2-2122-6890 Fax. +82-2-2122-6899 National Disaster IOT Solution Co., Ltd. Management Institute 304-ho, 1, Mandeok 3-ro 16beon-gil, Buk-gu, Busan, Republic of Korea Tel. +82-51-558-0918 Fax. +82-51-793-0918 10. Abstract In this study, Korea provided FFAS for making anticipative action of flash flood and ARWS for reducing flood damage in disaster vulnerable area which is advanced technology to aid recipient, Vietnam and Lao PDR The ARWS were installed for Taphoi basin in Lao cai, Vietnam and Nam Xong basin in Vang Vieng, Lao PDR. Two rain gauges, two water gauges and two warning stations were installed. FFAS was installed in VAWR(Vietnam) and DHM(Lao PDR) which is constructed as basin integrated system that can monitor hydrological situation in target area. Also, hydraulic and hydrological analysis through river survey and make the flooding map and risk map. 11. Keywords
Forecasting and warning system, ARWS, Flash flood, Vietnam, Lao PDR
12. Security Classification 13. No. of Pages 14. Distribution Statement 15. Price
Unclassified Page 181 Released Unlimited Construction of Forecasting and Warning System for Disaster Risk Reduction in Vietnam & Laos PDR ()Ⅰ Issued by Shim, Jae-hyeon Organization National Disaster Management Research Institute Jonggaro 365, Jung-gu, Ulsan City www.ndmi.go.kr Tel 052) 928-8000, Fax 052) 928-8009 Printed on Dec. 16, 2016 Issued on Dec. 16, 2016
Printed by D&P Dongin Twegyero 27gil-61 (Jeo-dong 2-ga), Jung-gu, Seoul Tel 02) 2275-1545