Technical Assistance Consultant’s Report Project Number: 46496-001 December 2016 Republic of the Union of Myanmar: Transformation of Urban Management - Flood Management Component (Financed by the Japanese Fund for Poverty Reduction) FINAL REPORT PART 2 (Part 2 of 7) Prepared by International Centre for Water Hazard and Risk Management (ICHARM), Public Works Research Institute (PWRI) (Tsukuba, Japan) CTI Engineering International Co., Ltd. (Tokyo, Japan) CTI Engineering Co., Ltd. (Tokyo, Japan) PASCO CORPORATION (Tokyo, Japan) For: Ministry of Construction and Ministry of Transport and Communications, Department of Meteorology and Hydrology, under the Ministry of Transport and Communications. This consultant’s report does not necessarily reflect the views of ADB or the Government concerned, and ADB and the Government cannot be held liable for its contents. (For project preparatory technical assistance: All the views expressed herein may not be incorporated into the proposed project’s design). Chapter 4 TA -8456 MYA: Transformation of Urban Management – Part II Flood Management CHAPTER 4 HYDRO-METEOROLOGICAL ANALYSIS 4.1 Introduction The consultant team conducted hydro-meteorological analysis for the river basins where the three target cities are located. The Rainfall Runoff Inundation (RRI) Model was applied to flood inundation simulation. The RRI Model is a grid-based distributed runoff model which can simulate rainfall-runoff and flood inundation simultaneously to reproduce flood inundation in low-lying areas. A storm surge simulation model with Myers formula was developed for coastal flood hazards. In this chapter, the key activities of hydro-meteorological analysis, that is, the development of flood inundation and storm surge simulation models, are presented. The models were calibrated and adjusted for each basin. The results of hazard assessment were utilized to create flood hazard maps and to implement agricultural damage risk assessment in the following chapters. In this TA, flood inundation models for the three target cities, Yangon, Mandalay and Mawlamyine, were developed by using the RRI Model. For the continuous support and improvement of the models after this TA, personnel in charge of this task are assigned by DMH for each city (see Table 4.1.1). Though elevation data is essential in modeling, it is difficult to obtain ground survey data or aerial survey data in Myanmar at this moment; therefore, this TA used globally available satellite data for simulation. Such data can be used at the primary stage of simulation modeling. The developed model was calibrated and verified by comparing the result from the reproduction of an inundation area by the model and the satellite images of past flood events. Through this process, DMH staff learned a great deal about not only flood hazard simulation and mapping but also the importance of data quality that should be improved continuously. While the initial products were able to give the basic outline of the inundation condition, some parts of the target area required simulation with accuracy greater than that of globally available satellite data such as HydroSHEDS, which was applied to the initial modeling. Therefore, in March 2016, the consultant team procured more accurate DEM called AW3D with 2 m resolution for the central part of the three target cities, and improved the quality of elevation for the RRI Model. Rainfall obtained is only daily data; therefore the data was divided equally into 24 hours to obtain average hourly data for simulation. Hourly data is essential in simulating the condition of inland inundation in the city area, because inland inundation progresses on an hourly basis while a river flood in a large river basin on a daily or weekly basis. It should be noted, however, that such average hourly data do not show an actual rainfall pattern with distribution and a peak value in a day. Afterward, the consultant team was able to obtain a rainfall intensity formula for Yangon, and applied hourly rainfall data obtained from this formula. The results are presented in sections 4.2.4, 4.2.6 and 4.2.8. In addition to the original target cities, Bago city, which is located in the eastern side of Yangon, was also modeled by the trainees from the Irrigation Department (ID). Furthermore, in response to the request of the Myanmar side, two other areas, Nyaung Don and Kale, were included as additional targets in the model development to reproduce the 2015 flood caused by Cyclone Komen. The training on flood inundation simulation with the RRI and storm surge models is one of the featured outputs of TA-8456 Part II. Thus, this chapter explains the outline of a flood inundation simulation model using the RRI and storm surge models and future challenges in the simulation. Table 4.1.1 Assignment of DMH Staff Target Area Sta ff Assigned Period Remarks RRI Model January 2015 to October 2015 Ms. Myo Myat Thu *Ms. Thu studied abroad (ICHARM, Japan) from October 2015 to Yangon September 2016. Ms. Aye Aye Naing October 2015 to October 2016 Mandalay Mr. Myo Tun Oo January 2015 to November 2015 International Centre for Water Hazard and Risk Management (ICHARM), 4-1 Public Works Research Institute (PWRI) CTI Engineering International CO., Ltd. CTI Engineering CO., Ltd. PASCO CORPORATION TA-8456 MYA: Transformation of Urban Management – Chapter 4 Part II Flood Management Target Area Staff Assigned Period Remarks July 2016 to October 2016 Ms. Khin Min Wun Soe January 2016 to June 2016 January 2015 to October 2016 Mawlamyine Mr. Zaw Myo Khaing *Mr. Khaing and Ms. Aye Aye Naing were in charge of preparation of coastal flood hazard maps in Yangon and Mawlamyine. Storm Surge Model Dr. Than Naing February 2015 to October 2016 Ms. Khine Soe Oo February 2015 to October 2016 Ms. Sanda Wai February 2015 to October 2016 - Ms. Witt Yi Soe February 2015 to May 2015 June 2015 to February 2016 Dr. War War Thein Dr. War War studies abroad in India 4.2 Development of Flood Inundation Simulation Model using RRI Model 4.2.1 Outline of RRI Model (1) Features of RRI Model The Rainfall-Runoff-Inundation (RRI) Model1, developed by ICHARM, was used for flood inundation analysis for the three cities (Mandalay, Yangon and Mawlamyine). The RRI Model is a grid-based distributed runoff model, which can simulate rainfall-runoff and flood inundation simultaneously to reproduce flood inundation in low-lying areas. This type of simulation is difficult if conventional flood prediction models are used. The model is available as free software, which can be easily handled and modified to adjust to actual field conditions. The RRI Model can simulate flood inundation depth and area during floods, as well as river water level and discharge volume during normal flows. The model requires such input data as topographical information, rainfall data and sea tide data. It is designed to calculate flood inundation based on lateral water movement in an inundated area. The RRI Model can be used to identify flood inundation areas and evaluate the effectiveness of structural measures by showing changes in flood inundation area before and after the completion of structural measures (e.g., dam, dike, etc.). Simulation by the RRI Model can be also utilized for non-structural measures (e.g. flood hazard maps to indicate the area and depth of inundation during a flood for the identification of evacuation routes and locations of evacuation shelters) in flood management. 1D Diffusion in River Subsurface + Surface Vertical Infiltration 2D Diffusion on Land Figure 4.2.1 Conceptual Diagram of RRI Model 1 RRI Model was awarded for its excellence in 2013 by the Japan Society of Civil Engineers and by Japan Institute of Country-ology and Engineering. 4-2 International Centre for Water Hazard and Risk Management (ICHARM), Public Works Research Institute (PWRI) CTI Engineering International CO., Ltd. CTI Engineering CO., Ltd. PASCO CORPORATION Chapter 4 TA-8456 MYA: Transformation of Urban Management – Part II Flood Management (2) Application examples of RRI Model The RRI Model has already been applied to flood management, providing assistance for governments in various countries and regions as follows: (a) Pampanga River basin, the Philippines To conduct flood disaster risk assessment for agricultural damage, the RRI Model was applied to estimate flood inundation depth, area and duration in the Pampanga River basin of the Philippines. With different scales in return period, inundation was simulated (Figure 4.2.2) to estimate agricultural flood damage (Figure 4.2.3). 25-Year Flood 50-Year Flood 100-Year Flood Inundated area (>0.5m depth)= Inundated area (>0.5m depth)= Inundated area (>0.5m depth)= 141,264 ha 89,849 ha 115,425 ha Figure 4.2.2 Maximum Inundation Depth (Pampanga River basin) 25-Year Flood 50-Year Flood 100-Year Flood Estimated damage: Estimated damage: Estimated damage: 2248.3 million Peso 1031.13 million Peso 1648.37 million Peso Figure 4.2.3 Distribution of Calculated Agricultural Flood Damage (Pampanga River basin) (b) Indus River basin, Pakistan Under the UNESCO-ICHARM project, “Strategic Strengthening of Flood Warning and Management Capacity of Pakistan”, which was completed in June 2014, the RRI Model was applied to flood forecasting and flood hazard analysis in the Indus River Basin of Pakistan. The aim of the project was to strengthen their flood forecasting and early warning systems and flood International Centre for Water Hazard and Risk Management (ICHARM), 4-3 Public Works Research Institute (PWRI) CTI Engineering International CO., Ltd. CTI Engineering CO., Ltd. PASCO CORPORATION TA-8456 MYA: Transformation of Urban Management – Chapter 4 Part II Flood Management hazard analysis capacity with the Integrated Flood Analysis System (IFAS) and the RRI model, both of which were developed by ICHARM. The Flood Forecasting Division (FFD) of Pakistan Meteorological Department (PMD) established a flood forecasting system based on IFAS and the RRI Model.