This document discusses applications of remote sensing and modeling for flood risk analysis and irrigation water management. It identifies global flood hotspots, particularly in Asia, and quantifies associated economic and human losses. Products including 8-day flood inundation maps of South Asia at 500m resolution from 2000-2011 are presented. Successful operational flood mapping and forecasting systems developed for the Gash Delta region of Sudan using MODIS and Landsat imagery, biomass modeling, and HEC modeling tools like HMS and RAS are summarized. The systems provide weekly flood maps and crop/irrigation performance updates to help farmers manage land and water resources.

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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

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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
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. Mapping Flood Hotspots for Climatic Change

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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

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Water for a food-secure world
IDENTIFYING FLOOD HOTSPOTS
• 100 km grid over the globe;
• numbers of floods in each cell over 1900-2011

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Water for a food-secure world
CHARACTERISING FLOOD HOTSPOTS
AGRICULTURE;
PAGE (2005)
POPULATION
CIESIN - 2010
FLOOD EXPOSED
GDP
WB, 2010

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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. South Asia flood risk mapping and assessment
Flooding in Indus river, Pakistan

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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

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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. Photo:DavidBrazier/IWMIPhoto:TomvanCakenberghe/IWMIPhoto:TomvanCakenberghe/IWMI
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Water for a food-secure world
Sep 22, 2011
Estimated inundation extent
MODIS Satellite Image
FLOOD MAPPING RESULTS– GANGES EXAMPLE

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. Flood Data Now Online !!

15. Flood Mapping and Modeling in Spate Irrigation
System in Sudan
Canal Uptake and Sorghum flowering in Gash Delta, Sudan

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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

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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

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OPERATIONAL BIOMASS PRODUCT
Raw DMC satellite data for 21-11-2012 (L), and derived daily
evapotranspiration (M) and biomass production (R).

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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. 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

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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”

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Water for a food-secure world
From pixels….to information….to simple action messages

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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

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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: a.giriraj@cgiar.org