Applications of remote sensing and modelling in flood risk analysis and irrigation water management


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Floods can be hugely destructive, but they also offer opportunities for farmers and fisherfolk. If their frequency and extent can be measured, then we will be better able to mitigate costs and maximise benefits. Digital geospatial flood inundation mapping is a powerful new approach for flood response that shows floodwater extent and depth on the land surface. IWMI research will evaluate this new technology and develop a prototype flood inundation map for South Asia. Also discussed is a project to flood map and model in a spate irrigation system in Sudan.

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Applications of remote sensing and modelling in flood risk analysis and irrigation water management

  1. 1. Water for a food-secure world APPLICATIONS OF REMOTE SENSING AND MODELING IN FLOOD RISK ANALYSIS AND IRRIGATION WATER MANAGEMENT Giriraj Amarnath International Water Management Institute (IWMI), Colombo, Sri Lanka Presented at the World Irrigation Forum, Mardin, Turkey
  2. 2. 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 $450 bill by 2030
  3. 3. Water for a food-secure world FLOODS: GOOD AND BAD Floods costs and benefits: • Costs = loss of life; disruption to livelihoods, disruption of transport, damage to infrastructure, loss of crops • Benefits = fisheries, soil fertilization, g/w recharge, soil moisture and ecology • Spatial distribution of costs and benefits is very uneven In the LMB: annual costs of flooding = US$ 60-70 million annual benefits of floods = US$ 8-10 billion
  4. 4. Mapping Flood Hotspots for Climatic Change
  5. 5. Water for a food-secure world CATASTROPHIC FLOODS IN ASIA: 1900-2011 • Collated from 6 global sources • >4000 floods globally • Around 35% - in Asia Annual Flood Occurrence < 10 days < 50 days > 50days Flood Duration Country Flood Occurrence India 237 China P Rep 209 United States 155 Indonesia 142 Philippines 116 Brazil 112 Bangladesh 83 Iran Islam Rep 72 Pakistan 72 Vietnam 67
  6. 6. Water for a food-secure world IDENTIFYING FLOOD HOTSPOTS • 100 km grid over the globe; • numbers of floods in each cell over 1900-2011
  8. 8. Water for a food-secure world CHARACHERIZING FLOOD HOTSPOTS • Globally - 90 grid cells with catastrophic flood occurrence ≥ 5; • 60% of these cells -in Asia • Estimated total over these hotspots: – annual economic loss due to floods - $20bn – 30 million affected people – 500,000 km2 of affected croplands
  9. 9. South Asia flood risk mapping and assessment Flooding in Indus river, Pakistan
  10. 10. Water for a food-secure world SUB-CONTINENTAL SCALE FLOOD MAPPING Examples from SA and SEA – MODIS images Indus Mekong August 18, 2009 August 17, 2010 August 26, 2010 August 24, 2011
  11. 11. 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)
  12. 12. Photo:DavidBrazier/IWMIPhoto:TomvanCakenberghe/IWMIPhoto:TomvanCakenberghe/IWMI Water for a food-secure world Sep 22, 2011 Estimated inundation extent MODIS Satellite Image FLOOD MAPPING RESULTS– GANGES EXAMPLE
  13. 13. EXAMPLE PRODUCTS • 8-days maps of inundation extent • Annual maps of maximum inundation • Inter-annual variation of regional flooding extent Flood Mixed (Crop) Water bodies Inter-annual variation (2000 – 2011) Normal River 2010 2010
  14. 14. Flood Data Now Online !!
  15. 15. Flood Mapping and Modeling in Spate Irrigation System in Sudan Canal Uptake and Sorghum flowering in Gash Delta, Sudan
  16. 16. Water for a food-secure world RESEARCH COMPONENTS Crop Biomass Flood Inundation Mapping Flood Services Flood Forecasting Model Fieldlook Portal + SMS Operational Services Daily / Weekly Flood Inundation Extent Weekly Crop growth and Irrigation Performance
  17. 17. Water for a food-secure world OPERATIONAL FLOOD INUNDATION MAPPING (MODIS + Landsat Images) • Weekly inundation mapping services • High. Res. Flood maps from Landsat • Fieldlook Dissemination
  18. 18. Water for a food-secure world OPERATIONAL BIOMASS PRODUCT Raw DMC satellite data for 21-11-2012 (L), and derived daily evapotranspiration (M) and biomass production (R).
  19. 19. Water for a food-secure world DEVELOPMENT OF FLOOD FORECASTING SYSTEM HEC HMS+RAS Basin Characteristics 25 sub-basin Watershed ~20,000km2 12 river segments HMS Parameters Loss (SCS Curve Number) Transform (SCS Unit Hydrograph) Baseflow (Constant Monthly) Routing (Muskingum) Model Inputs 5 raingauges (Ethiopia) El Gera flow data (GRTU) TRMM, RFE, CMORPH SRE Data DEM, LULC, FAO Soil Data
  20. 20. SRTM DEM HEC-GeoHMS Slope, watershed and flow direction developed Hydrological modeling HEC-HMSRainfall: • Meteo. Stations • Satellite estimates • GCM CCAFS Data Interaction between HEC- RAS and HEC-HMS to get outflow relationship Peak Flows Land Use Land Classification Data Hydraulic structures inputted into Drainage System Geometry HEC-RAS HEC-GeoRAS Drainage network characterized SRTM DEM TIN Finalized Geometry HEC-RAS Hydraulic Modeling HEC-GeoRAS Flood Inundation Extent, Flood Depth and Water level Stream Centerline Banks Flowpaths Cross sections Hydraulic Structure Data Current | Future DEVELOPMENT OF FLOOD FORECASTING SYSTEM USING HEC TOOLS
  21. 21. Water for a food-secure world DEVELOPMENT OF FLOOD FORECASTING SYSTEM USING HEC-HMS Observed vs. Simulated flow data “2011 flood season” Observed vs. Simulated flow data “2007 flood season”
  22. 22. Water for a food-secure world From pixels….to information….to simple action messages
  23. 23. Water for a food-secure world SUMMARY • Global flood hot spots identified and characterized in terms of economic and human losses • Several spatial products quantifying flood inundation pattern in South Asia with a resolution of 500 m and 8 days available • Demonstrated how remote sensing data and Smart-ICT can help farmers for effective management of land and water resources in Gash Delta • Potential uses - flood water harvesting and flood-based farming, insurance, estimation of GHGs emissions from temporary flooded areas
  24. 24. Water for a food-secure world “ Let not a single drop of water received from rains go waste into the sea without benefiting the man and the beast ” King Parakramabahu (1153-1186 AD) THANK YOU Email contact: