Bangladesh Flood Risk Atlas

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Giriraj Amarnath

International Water Management Institute (IWMI),
Colombo, Sri Lanka

Published in: Technology, Economy & Finance
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  • GHF – Global Humanitarian Forum
  • Acronyms NDSI – Normalized Difference Snow Index; NDVI – Normalized Difference Vegetation Index; EVI – Enhanced Vegetation Index; LSWI – Land Surface Water IndexEvery 8 days for each 500 m pixel.The above algorithm has been used for SA (India, Pakistan, Nepal, Bhutan Bangladesh, SL). We are doing this now for SEA
  • Bangladesh Flood Risk Atlas

    1. 1. www.iwmi.orgWater for a food-secure worldBANGLADESH FLOOD RISK ATLASGiriraj AmarnathInternational Water Management Institute (IWMI),Colombo, Sri Lanka
    2. 2. www.iwmi.orgWater for a food-secure worldTHE PROBLEM• Floods – primary natural disasters• Precipitation intensity and variability is projectedto increase – increasing risks of floodingglobally and in Asia• Global economic losses from natural disasters -over $165 billion annually– More than current aid flow– Floods take the lion share of this• May rise to over $450 bill. by 2030
    3. 3. www.iwmi.orgWater for a food-secure worldFLOOD INUNDATION MAPS• Inundation maps are needed for decision makers to better mitigate theimpacts of flooding and build more resilient communities• An easily accessible flood maps will provide users more awareness ofthe flood hazards in their local community.• Currently, only a limited number of agencies have a flood risk mappinginterface.• Our research program address mapping the extent of South Asia andcountry level flood risk assessment for better flood management.
    4. 4. www.iwmi.orgWater for a food-secure worldFLOOD INUNDATION MAPPING ALGORITHM• MODIS surface reflectance• Global• Temporal resolution : 8 days• Spatial resolution – 500 m• Period : 2000 – 2011• Indices : EVI, NDWI, LSWI, NDSI• DVEL (EVI-LSWI) was used todiscriminate between Water pixelsand Non–water pixels. If thesmoothed DVEL is less than 0.05 pixelis assumed to be a Water pixel;• Several procedure furtherdifferentiate between permanentwater bodies and temporary Floodpixels• Applied in South Asia• Being applied in South East AsiaMODIS 8-day composites of surface reflectance (MOD09A1)Interim Map of inundated areasCloudmaskNDSI NDVI EVI LSWISnowmaskPermanent WatermaskVegetation + CropareaDEMGlobal WetlandDatabaseValidation and AccuracyassessmentFinal map of inundated areas (2000 – 2011)
    5. 5. www.iwmi.orgWater for a food-secure worldINDICES AND PRODUCTS
    6. 6. www.iwmi.orgWater for a food-secure worldANNUAL FLOOD INUNDATION PATTERN (2000 – 2011)
    7. 7. www.iwmi.orgWater for a food-secure worldDURATION OF INUNDATION CYCLE
    8. 8. www.iwmi.orgWater for a food-secure worldSEASONAL INUNDATION PATTERN
    9. 9. www.iwmi.orgWater for a food-secure worldFLOOD RISK MAP• Current flood mapping for the entireBangladesh has mapped areas at risk offlooding.• Provides a good foundation for efficientflood-risk management.• Useful input in drawing up flood-riskmanagement plans, for preventing flooddamages, in land use planning, forproviding information on floods, in rescueoperations in order to avoid flood risk.
    10. 10. www.iwmi.orgWater for a food-secure worldTime-series of flood inundationpattern (2001 – 2011)Yearly Flood StatisticsMonthly Flood Statistics(2005 – 2011)
    11. 11. www.iwmi.orgWater for a food-secure worldBANGLADESH FLOOD RISK ATLAS• EightDay_product• Flood_Duration• Flood_Monthly• Flood_Occurence• Flood_Seasonal• Maps• Statistics
    12. 12. www.iwmi.orgWater for a food-secure worldThank YouContact : a.giriraj@cgiar.org

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