ANNUAL FLOOD REPORT 2018 FLOOD FORECASTING & WARNING CENTRE PROCESSING & FLOOD FORECASTING CIRCLE BANGLADESH WATER DEVELOPMENT BOARD Annual Flood Report 2018 Flood Forecasting and Warning Centre (FFWC) Bangladesh Water Development Board (BWDB) WAPDA Building (8th Floor), Motijheel C/A, Dhaka-1000 Phone : 9550755; 9553118 Fax : 9557386 Email ; [email protected] ; [email protected] Web : www.ffwc.gov.bd Editing & Compilation: Md. Arifuzzaman Bhuyan, Executive Engineer, FFWC, BWDB Contribution: Sarder Udoy Raihan, Sub-Divisional Engineer, FFWC, BWDB Md. Alraji Leon, Assistant Engineer, FFWC, BWDB Partho Protim Barua, Assistant Engineer, FFWC, BWDB Preetom Kumar Sarker, Assistant Engineer, FFWC, BWDB Review: Md. Saiful Hossain, Superintending Engineer, PFFC, BWDB Published by the FFWC, BWDB, Ministry of Water Resources, Dhaka TABLE OF CONTENTS LIST OF TABLES .......................................................................................................................... 5 LIST OF FIGURES ........................................................................................................................ 7 PREFACE ..................................................................................................................................... 10 EXECUTIVE SUMMARY .......................................................................................................... 12 LIST OF ABBREVIATIONS ..................................................................................................... 13 CHAPTER 1 : INTRODUCTION ............................................................................................. 15 1.1. THE PHYSICAL SETTING .................................................................................................................. 15 1.2. THE RIVER SYSTEM ......................................................................................................................... 15 1.3. ACTIVITIES OF FFWC ...................................................................................................................... 17 1.4. OPERATIONAL STAGES BEFORE FORECAST MODEL RUN ................................................................ 19 1.5. NATURE AND CAUSES OF FLOODING ............................................................................................. 20 1.5.1. Causative Factors ............................................................................................................................ 20 1.5.2. Statistics of Flooding ...................................................................................................................... 21 CHAPTER 2 : RAINFALL SITUATION ................................................................................. 22 2.1 MARCH .......................................................................................................................................... 23 2.2 APRIL ............................................................................................................................................. 23 2.3 MAY ............................................................................................................................................... 24 2.4 JUNE .............................................................................................................................................. 25 2.5 JULY ............................................................................................................................................... 27 2.6 AUGUST ......................................................................................................................................... 28 2.7 SEPTEMBER .................................................................................................................................... 29 2.8 OCTOBER ....................................................................................................................................... 30 CHAPTER 3 : RIVER SITUATION ......................................................................................... 38 3.1 THE BRAHMAPUTRA BASIN ............................................................................................................. 38 3.2 THE GANGES BASIN ......................................................................................................................... 41 3.3 THE MEGHNA BASIN ........................................................................................................................ 44 3.4 THE SOUTH EASTERN HILL BASIN ..................................................................................................... 48 3.5 PEAK AND RECORDED HIGHEST WATER LEVELS ............................................................................... 50 CHAPTER 4 : FORECAST EVALUATION, 2018 ................................................................ 76 4.1 EVALUATION CRITERIA OF FORECAST PERFORMANCE ..................................................................... 77 4.1.1 Mean Absolute Error (MAE) ......................................................................................................... 77 4.1.2 Co-efficient of Determination, r2 ................................................................................................... 77 4.2 PRE-DEFINED SCALES TO EVALUATE FORECAST PERFORMANCE ...................................................... 78 4.3 DETERMINISTIC FORECAST STATISTICS AND PERFORMANCE, 2018 .................................................. 78 4.3.1 Deterministic Forecast Performance ................................................................................................ 78 4.3.2 Medium Range (upto 10-days) Probabilistic Forecast Performance ............................................... 89 CHAPTER 5 : INUNDATION STATUS .................................................................................. 90 5.1 BASINWISE INUNDATION STATUS ..................................................................................................... 90 5.2 COUNTRYWIDE INUNDATION 2018 ................................................................................................... 92 CHAPTER 6 : CHARACTERISTICS AND SPECIAL EVENTS OF 2018 FLOOD ........ 100 6.1 Characteristics of 2018 Flood .......................................................................................................... 100 6.2 Special Events of 2018 Flood ........................................................................................................... 101 6.2.1 The Manu River Flood in Moulvibazar ......................................................................................... 101 6.2.2 The Brahmaputra Flood in Tibet, China ........................................................................................ 104 Annual Flood Report 2018 Page- 3 CHAPTER 7 : RESEARCH AND DEVELOPMENT ........................................................... 106 7.1 Experimental Pre-monsoon Danger Level for the North-Eastern Region ......................................... 106 7.2 Expansion of Flash Flood Monitoring and Forecasting Stations ....................................................... 107 7.3 BWDB Flood App ............................................................................................................................. 107 CHAPTER 8 : CONCLUSION ................................................................................................ 109 ANNEX-1 .................................................................................................................................. 112 ANNEX-2 .................................................................................................................................. 113 ANNEX-3 .................................................................................................................................. 114 ANNEX-4 .................................................................................................................................. 115 ANNEX-5 .................................................................................................................................. 116 ANNEX-6 .................................................................................................................................. 117 ANNEX-7 .................................................................................................................................. 118 ANNEX-8 .................................................................................................................................. 119 ANNEX-9 .................................................................................................................................. 120 Annual Flood Report 2018 Page- 4 LIST OF TABLES TABLE 1.1 :YEAR-WISE FLOOD AFFECTED AREA IN BANGLADESH ...................... 21 TABLE 2.1: RAINFALL STATISTICS FOR THE MONSOON-2018 OVER THE FOUR BASINS ........................................................................................................................... 22 TABLE 2.2 : SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF MARCH-2018 ................................................................................................................. 23 TABLE 2.3 : SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF APRIL-2018 .................................................................................................................... 24 TABLE 2.4 : SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF MAY-2018 .....................................................................................................................