Transcript Slide 1

Flood Inundation Map of Bangladesh
using MODIS Surface Reflectance Data
AKM Saiful Islam
Sujit Kumar Bala
Anisul Haque
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineering and Technology (BUET)
2nd International Conference on Water and Flood Management ICWFM-2009
Introduction
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Flood is very common phenomenon in
Bangladesh due to its geographic location.
Every year one third of Bangladesh has gone
under floods.
Status of flood inundation in time and space is
important in evaluating the relationships between
variations in the water regime, local agricultural
activity, and ecosystem behaviour from a global
viewpoint.
2nd International Conference on Water and Flood Management ICWFM-2009
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Remote sensing images can be effective and
efficient tools to determine flood inundation
areas.
MODIS satellite with its moderate-resolution
optical sensor of 250–500 m becomes useful
tools for scientific studies and research.
Sakamoto et al. (2007) was developed a
methodology to detect the spatio-temporal flood
distribution in the Cambodia and Vietnam using
MODIS data.
In this study this algorithm was modified to
determine extent of flood inundation of
Bangladesh.
2nd International Conference on Water and Flood Management ICWFM-2009
Data Used
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MODIS satellite data
TERRA sensor
Surface Reflectance (band 1-8)
8-Day temporal resolution
Product of Level 3 (atmospherically corrected)
Version 5
Global coverage
500 meter spatial resolution
Two major floods during 2004 and 2007
2nd International Conference on Water and Flood Management ICWFM-2009
Study area
2nd International Conference on Water and Flood Management ICWFM-2009
Landuse/Land Cover Classes
1. Single-crop rainfed rice in the Haor area of the
north-eastern region
2. Single-crop irrigate rice in the south-western
region
3. Double-cropped irrigated rice in the northern
region
4. Triple-cropped irrigated rice in the Brand area of
the north-western region
5. Forest area in the Sundarbans
6. settlement area of Dhaka city
7. Kaptai lake
8. Bay of Bengal ocean
9. the Padma river.
2nd International Conference on Water and Flood Management ICWFM-2009
MODIS derived indices
NDVI
NDWI
EVI
LSWI
2nd International Conference on Water and Flood Management ICWFM-2009
MODIS derived indices
EVI
LSWI
DVEL
=EVI-LSWI
2nd International Conference on Water and Flood Management ICWFM-2009
EVI
0.7
Single-Shrimp
farm (Khulna)
0.6
Singe-Haor
(Shylhet)
0.5
double crop
0.4
Tripple
0.3
Mangrove
Forest
(Sundarbans)
Settelment
(Dhaka)
0.2
0.1
0
Lake (Kaptai)
-0.1
Sea (Bay of
Bengal)
-0.2
River (Padma)
-0.3
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LSWI
Single-Shrimp
farm (Khulna)
0.9
Singe-Haor
(Shylhet)
0.7
double crop
Tripple
0.5
Mangrove
Forest
(Sundarbans)
Settelment
(Dhaka)
0.3
0.1
Lake (Kaptai)
-0.1
Sea (Bay of
Bengal)
-0.3
River (Padma)
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Flood chart of Flood inundation map
MODIS 8 day reflectance images
MODIS derived indices: EVI, LSWI, DVEL
ρBLUE ≥ 0.2
Cloud free indices: EVI, LSWI, DVEL
DVEL ≤ 0.05
EVI ≤ 0.05
EVI ≤ 0.3
LSWI ≥ 0.0
NO
EVI > 0.3
Non-Flood
Water related pixel
0.1 < EVI
EVI ≤ 0.3
Mixture
EVI ≤ 0.1
Flood
total duration of
water pixel > 120 days
Water bodies
Flood Inundation Map
2nd International Conference on Water and Flood Management ICWFM-2009
Long Term Water Bodies
Inundation >120 days
Long term Water bodies in 2007
2nd International Conference on Water and Flood Management ICWFM-2009
Chronology of 2004 & 2007 floods
2nd International Conference on Water and Flood Management ICWFM-2009
Comparing MODIS with RADARSAT
Inundation map on 28th July, 2007
Using MODIS
RADARSAT Inundation
on 3rd August , 2007
2nd International Conference on Water and Flood Management ICWFM-2009
Comparison with RADARSAT
Image
RADARSAT Vs MODIS
Comparing Pixels
2nd International Conference on Water and Flood Management ICWFM-2009
Maximum Extend of 2004 & 2007
Floods
2004 Flood
2007 Flood
2nd International Conference on Water and Flood Management ICWFM-2009
Start & End date and Duration
Parameters
River
Date of crossing
Danger Level at
rising stage
Brahmaputra
Date of crossing
Danger Level at
falling stage
Duration of flood
in days above
Danger Level
Gauge Stn.
Bahadurabad
2007
2004
27.07.07 &
08.09.07
11.07.04
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Ganges
Hardinge Br.
Meghna
Bhairab Bazar
30.07.07 &
12.09.07
11.07.04
Bahadurabad
06.08.07&
17.09.07
26.07.04
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Brahmaputra
Ganges
Hardinge Br.
Meghna
Bhairab Bazar
21.08.07 &
25.09.07
18.08.04
Bahadurabad
21
15
Brahmaputra
Ganges
Hardinge Br.
0
0
Meghna
Bhairab Bazar
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2nd International Conference on Water and Flood Management ICWFM-2009
Conclusion
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This study modifies a methodology which was developed
by Sakamoto et al. in order to detect spatial extents and
temporal changes of flood inundation of Bangladesh
during monsoon season.
MODIS satellite images were used develop
inundation maps for floods in 2007 and 2004.
flood
This low resolution (500m) MODIS based maps area
compared with subsequent flood inundation maps based
on high resolution (50m) RADARSAT satellite images.
MODIS estimates show strong correlation with the
inundation areas derived from RADARSAT with R2 values
of 0.96.
MODIS images can be used successfully to determine start
& end date, duration and maximum extent of flood.
2nd International Conference on Water and Flood Management ICWFM-2009