RAPID HAZARD AND RISK ASSESSMENT POST -FLOOD RETURN ANALYSIS UNESCO on behalf of OCHA and UNCT, NEPAL Funded by UNDP Supported by ICON/ADAPT Nepal TABLE OF CONTENT TABLE OF CONTENT.......................................................................................................II LIST OF TABLES..............................................................................................................IV LIST OF FIGURES.............................................................................................................V 1 INTRODUCTION .................................................................................................. 1 1.1 BACKGROUND .......................................................................................................... 1 1.2 OBJECTIVES /SCOPE OF THE STUDY ................................................................................2 1.3 METHODOLOGY AND ORGANIZATION OF THE REPORT ..................................................... 3 1.4 LIMITATION .............................................................................................................. 6 1.5 ASSESSMENT TEAM ....................................................................................................6 2 RIVER KOSHI AND THE BREACH .......................................................................8 2.1 INTRODUCTION ......................................................................................................... 8 2.2 RIVER SYSTEM ........................................................................................................... 9 2.2.1 Sunkoshi Basin ..................................................................................................... 10 2.2.2 Arun River Basin .................................................................................................. 11 2.2.3 Tamur River Basin ................................................................................................ 12 2.3 KOSHI AREA TOPOGRAPHY ....................................................................................... 12 2.4 THE KOSHI PROJECT ................................................................................................ 14 2.5 CHARACTERISTICS OF THE RIVER KOSHI CHANNELS WITH RESPECT TO GEOMORPHIC CONTEXT GENERAL ......................................................................................................... 18 2.6 RIVER CHANNEL CHARACTERISTICS ........................................................................... 19 2.6.1 River Channel Geometry and Processes ..................................................................... 20 2.6.2 Response of Koshi River in Altered Conditions ........................................................... 23 2.6.3 Historical Records ................................................................................................. 26 2.6.4 Sediment Load ...................................................................................................... 26 2.6.5 Bed and Flood Profile Slopes .................................................................................... 27 2.7 SPUR FAILURE ......................................................................................................... 30 2.8 HYDROL OGICAL ASPECTS .......................................................................................... 36 2.9 ASSESSMENT OF THE EVENT OF THE EMBANKMENT BREACH FLOOD ON 18 TH AUGUST 2008. 40 3 OBSERVATIONS FROM THE FIELD VISIT......................................................... 44 3.1 AREA AND PEOPLE AFFECTED .................................................................................... 44 3.2 PROPERTIES LOST ..................................................................................................... 45 3.3 BREACH REPAIR ...................................................................................................... 52 3.4 CONDITIONS OF THE SPURS AND MAINTENANCE .......................................................... 52 3.5 REHABILITATION WORKS IN PROGRESS ....................................................................... 54 3.6 ASSESSMENT OF BREACH FLOOD RISK ......................................................................... 54 3.7 EXPOSURES T O POTENTIAL RISK ................................................................................. 57 3.8 LOCAL CAPACITY TO COPE WITH FLOOD RISK ............................................................... 63 3.9 FLOOD RISK MANAGEMENT ...................................................................................... 65 3.9.1 The August 2008 breach flood ................................................................................. 65 3.10 PREPAREDNESS ....................................................................................................... 74 3.11 FLOOD FIGHTING AND PREPAREDNESS ( FF&P)............................................................ 75 4 CONCLUSIONS AND KEY ISSUES..................................................................... 77 4.1 INTRODUCTION ....................................................................................................... 77 4.2 TECHNICAL ISSUES :.................................................................................................. 77 4.3 INSTITUTIONAL ISSUES :............................................................................................. 79 4.4 SOCIAL ISSUES ......................................................................................................... 79 4.5 PREPAREDNESS ISSUES :............................................................................................. 80 5 RECOMMENDATION FOR RISK REDUCTION.................................................. 82 5.1 IMPROVING PREPAREDNESS....................................................................................... 82 5.2 PREPARATION OF FLOOD STANDING ORDER ................................................................ 83 5.2.1 Nepal-India History of Flood Forecasting Cooperation ................................................. 84 5.2.2 Review of the existing hydrological and meteorological network ..................................... 88 5.2.3 Strategy to prepare a Flood Standing Order ............................................................... 90 5.3 ASSESSMENT OF EARLY WARNING SYSTEM (EWS) AND STRATEGY FOR CREATING EWS ..... 91 5.4 MAINTENANCE OF SPURS .......................................................................................... 95 5.5 COMPREHENSIVE STUDY TO REDESIGN THE SPURS ......................................................... 96 5.6 DAM BREAK ANALYSIS .............................................................................................. 97 5.7 GENERATING ‘WHAT -IF SCENARIOS ’ ........................................................................... 98 5.8 MONITORING MECHANISM ........................................................................................ 98 5.9 MANPOWER TRAINING :............................................................................................ 99 5.10 CONSTRUCTION OF RETIRED EMBANKMENT ................................................................. 99 5.11 LONG TERM ISSUES – CLIMATE CHANGE ......................................................................100 5.12 RECOMMENDED ACTIVITIES AND RESPONSIBILITIES ......................................................101 5.13 MEDIUM TERM PLAN ..............................................................................................102 6 REFERENCES......................................................................................................103 Rapid Hazard and Risk Assessment iii Final Report: 20 March 2009 Koshi River Embankment Breach LIST OF TABLES Table 2.1: Aggradation/Degradation of the River Koshi (GFCC & CBIP, 1986)..........26 Table 2.2: Hydraulic Parameters of the Koshi River (GFCC & CBIP, 1986).................29 Table 2.3: Flood frequency analysis at Chatara ............................................................38 Table 3.1: Number of households and population figures for the affected VDCs.......44 Table 3.2: Number of deaths and injuries.....................................................................45 Table 3.3: Loss of /damage to private properties.........................................................46 Table 3.4: Extent of damage to cultivated land............................................................46 Table 3.5: Number of livestock lost...............................................................................47 Table 3.6: Loss of crops in quintal.................................................................................48 Table 3.7: Loss of fruits in quintal.................................................................................48 Table 3.8: Losses of vegetables in quintal.....................................................................49 Table 3.9: Loss of household goods in number.............................................................50 Table 3.10: Estimated monetary loss...............................................................................50 Table 3.11: Loss/damage of roads and trails..................................................................51 Table 3.12: Damage toinfrastructure..............................................................................51 Table 3.13: Number of days when the flow of goods and services were closed............52 Table 3.14: Elements exposed to the potential risk of breach flood in Koshi.................59 Table