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Giriraj Amarnath International Water Management Institute (IWMI), Colombo, Sri Lanka
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Water for a food-secure world
BANGLADESH FLOOD RISK ATLAS
Giriraj Amarnath
International Water Management Institute (IWMI), Colombo, Sri Lanka
www.iwmi.org
Water for a food-secure world
THE PROBLEM
• Floods – primary natural disasters
• Precipitation intensity and variability is projected to increase – increasing risks of flooding globally 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
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Water for a food-secure world
FLOOD INUNDATION MAPS
• Inundation maps are needed for decision makers to better mitigate the impacts of flooding and build more resilient communities
• An easily accessible flood maps will provide users more awareness of the flood hazards in their local community.
• Currently, only a limited number of agencies have a flood risk mapping interface.
• Our research program address mapping the extent of South Asia and country level flood risk assessment for better flood management.
www.iwmi.org
Water for a food-secure world
FLOOD 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 to
discriminate between Water pixels and Non–water pixels. If the smoothed DVEL is less than 0.05 pixel is assumed to be a Water pixel;
• Several procedure further differentiate between permanent water bodies and temporary Flood pixels
• Applied in South Asia • Being applied in South East Asia
MODIS 8-day composites of surface reflectance (MOD09A1)
Interim Map of inundated areas
Cloud mask
NDSI NDVI EVI LSWI
Snow mask
Permanent Water mask
Vegetation + Crop area
DEM Global Wetland Database
Validation and Accuracy assessment
Final map of inundated areas (2000 – 2011)
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Water for a food-secure world
INDICES AND PRODUCTS
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Water for a food-secure world
ANNUAL FLOOD INUNDATION PATTERN (2000 – 2011)
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Water for a food-secure world
DURATION OF INUNDATION CYCLE
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Water for a food-secure world
SEASONAL INUNDATION PATTERN
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Water for a food-secure world
FLOOD RISK MAP
• Current flood mapping for the entire Bangladesh has mapped areas at risk of flooding.
• Provides a good foundation for efficient flood-risk management.
• Useful input in drawing up flood-risk management plans, for preventing flood damages, in land use planning, for providing information on floods, in rescue operations in order to avoid flood risk.
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Water for a food-secure world
Time-series of flood inundation pattern (2001 – 2011)
Yearly Flood Statistics
Monthly Flood Statistics
(2005 – 2011)
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Water for a food-secure world
BANGLADESH FLOOD RISK ATLAS
• EightDay_product• Flood_Duration• Flood_Monthly• Flood_Occurence• Flood_Seasonal• Maps• Statistics
