ANNUAL FLOOD REPORT 2017 FLOOD FORECASTING & WARNING CENTER PROCESSING & FLOOD FORECASTING CIRCLE BANGLADESH WATER DEVELOPMENT BOARD TABLE OF CONTENTS TABLE OF CONTENTS................................................................................................................. 2 LIST OF TABLES ........................................................................................................................... 3 LIST OF FIGURE ............................................................................................................................ 5 PREFACE ......................................................................................................................................... 7 EXECUTIVE SUMMARY .............................................................................................................. 9 LIST OF ABBREVIATIONS ...................................................................................................... 10 CHAPTER 1: INTRODUCTION ............................................................................................... 12 1.1. THE PHYSICAL SETTING ................................................................................................................... 12 1.2. THE RIVER SYSTEM .......................................................................................................................... 12 1.3. ACTIVITIES OF FFWC ....................................................................................................................... 14 1.4. OPERATIONAL STAGES BEFORE FORECAST MODEL RUN ................................................................. 15 1.5. NATURE AND CAUSES OF FLOODING .............................................................................................. 16 1.5.1. Causative Factors ............................................................................................................................. 16 1.5.2. Statistics of Flooding ....................................................................................................................... 17 CHAPTER 2 : RAINFALL SITUATION .................................................................................. 19 2.1 MAY ................................................................................................................................................ 19 2.2 JUNE ............................................................................................................................................... 21 2.3 JULY ................................................................................................................................................ 22 2.4 AUGUST .......................................................................................................................................... 23 2.5 SEPTEMBER ..................................................................................................................................... 24 2.6 OCTOBER ........................................................................................................................................ 25 CHAPTER 3: RIVER SITUATION ..................................................................................... 33 3.1 THE BRAHMAPUTRA BASIN ................................................................................................................ 33 3.2 THE GANGES BASIN .......................................................................................................................... 37 3.3 THE MEGHNA BASIN ......................................................................................................................... 40 3.4 THE SOUTH EASTERN HILL BASIN ...................................................................................................... 44 3.5 PEAK AND RECORDED HIGHEST WATER LEVELS ................................................................................ 45 CHAPTER 4: FORECAST EVALUATION, 2017 ................................................................. 70 4.1 GENERAL .......................................................................................................................................... 70 4.2 EVALUATION CRITERIA OF FORECAST PERFORMANCE ...................................................................... 71 4.2.1. Mean Absolute Error (MAE) ......................................................................................................... 71 4.2.2. Co-efficient of Determination, r2 ................................................................................................... 71 4.3 PRE-DEFINED SCALES TO EVALUATE FORECAST PERFORMANCE ....................................................... 72 4.4 DETERMINISTIC FORECAST STATISTICS AND PERFORMANCE, 2017 ................................................... 72 CHAPTER 5 : INUNDATION STATUS ................................................................................... 83 CHAPTER 6: RESEARCH AND DEVELOPMENT ................................................................ 93 6.1 Flash Flood Forecast for North East Part............................................................................................. 93 CHAPTER 7: PATTERN AND MAGNITUDE OF 2017 FLOODS ................................... 94 7.1 Early Flood in North East Region ........................................................................................................ 94 7.2 Flood in North-West region ............................................................................................................... 98 7.3 Flood in Assam ................................................................................................................................. 101 CHAPTER 8: CONCLUSION ................................................................................................. 102 ANNEX-1 .................................................................................................................................... 104 ANNEX-2 .................................................................................................................................... 105 ANNEX-3 .................................................................................................................................... 106 ANNEX-4 .................................................................................................................................... 107 ANNEX-5 .................................................................................................................................... 108 Annual Flood Report 2017 Page- 2 LIST OF TABLES TABLE 1.1 :YEAR-WISE FLOOD AFFECTED AREA IN BANGLADESH ................ 18 TABLE 2.1: RAINFALL STATISTICS FOR THE MONSOON 2017 OVER THE FOUR BASINS ..................................................................................................................... 19 TABLE 2.2 : SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF MAY-2017 ........................................................................................................... 20 TABLE 2.3: SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF JUNE -2017 ......................................................................................................... 21 TABLE 2.4: SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF JULY-2017 .......................................................................................................... 22 TABLE 2.5: SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF AUGUST-2017 .................................................................................................... 24 TABLE 2.6: SUMMARY OF THE RAINFALL SITUATION DURING THE MONTH OF SEPTEMBER-2017 ............................................................................................. 25 TABLE 2.7: SUMMARY OF RAINFALL FOR THE MONTH OF OCTOBER-2017 ... 26 TABLE 3.1 : COMPARISON OF WATER LEVEL (IN MPWD) OF 2017 AND HISTORICAL EVENTS OF 1988 & 1998 OF SOME IMPORTANT STATIONS IN THE BRAHMAPUTRA BASIN. .............................................................................. 36 TABLE 3.2 : COMPARISON OF WATER LEVEL (IN MPWD) OF 2017 AND HISTORICAL EVENTS OF 1988 & 1998 OF SOME IMPORTANT STATIONS IN GANGES BASIN. ..................................................................................................... 39 TABLE 3.3: COMPARISON OF WATER LEVEL (IN MPWD) OF 2017 AND HISTORICAL EVENTS OF 1988 & 1998 OF SOME IMPORTANT STATIONS IN MEGHNA BASIN. .................................................................................................... 43 TABLE 3.4 : COMPARISON OF WATER LEVEL OF 2017 (IN MPWD) AND HISTORICAL EVENTS OF 1988 AND 1998 OF SOME IMPORTANT STATION IN SOUTH EASTERN HILL BASIN. ...................................................................... 45 TABLE 3.5: RECORDED PEAK WATER LEVEL (IN MPWD) WITH DATES DURING THE MONSOON-2017 ............................................................................. 45 TABLE 3.6: RECORDED HISTORICAL HIGHEST WATER LEVELS (IN MPWD) WITH DATES ........................................................................................................... 48 51 59 TABLE 4.1 : SCALES USED FOR PERFORMANCE EVALUATION ......................... 72 TABLE 4.2: STATISTICS FOR 24-HOURS FORECAST PERFORMANCE (YEAR, 2017) .......................................................................................................................... 73 TABLE 4.3: STATISTICS FOR 48-HOURS FORECAST PERFORMANCE (YEAR, 2017) 74 TABLE 4.4: STATISTICS FOR 72-HOURS FORECAST PERFORMANCE (YEAR, 2017) .........................................................................................................................