multi sensor flood monitoring
DESCRIPTION
TRANSCRIPT
Flood monitoring from remote sensing multi-sensor data analysis
J-F. Crétaux, M. Leblanc, S. Tweed,S. Calmant, R. Abarca Del Rio,G. Ramillien, & A. Cazenave
Geneva, November 2007
Monash University
Objectives: Mapping water extent variation
On high temporal resolutionMedium spatial resolution
Estimating water volume variation
Targets:Floodplain and highly variable lakes
In arid zones
Instruments:Modis sensor
Radar altimetry
Framework of the methodology
3 case studies
Steppes of Central AsiaAltiplano lakes & salars
Physic of the optical remote sensing measurements
What do we measure ?
MODIS
Band 1 (620 – 670 nm)Band 2 (841 – 876 nm)Band 3 (459 – 479 nm)Band 4 (545 – 565 nm)
Band 5 (1230 – 1250 nm)Band 6 (1628 – 1652 nm)Band 7 (2107 – 2155 nm)
Surface classification from Combination of band
Usual simple classification 1/2
From modis: B2<1000 or NDVI=(B2-B1)/(B2+B1) < 0 open waterNDVI>0.3/0.4 vegetation0<NDVI<0.3/0.4 dry land
Not true for:shallow water bodiesflood event (with suspended sediments)presence of aquatic vegetation
Usual simple classification 2/2
From radar altimetry:σ0 > 20 db open water
Only valid along altimeter profile=> no water extentNot true on dry salt lake
Backscatter with Topex on Lake Eyre
30
32
34
36
38
40
42
44
46
2002,5 2003 2003,5 2004 2004,5 2005 2005,5 2006
Backscatter envisat for lake Eyre
25272931333537394143
2002,5 2003 2003,5 2004 2004,5 2005 2005,5 2006
Lake cover by salt crust Lake filled by water
Case of shallow waterand floodplain
0
500
1000
1500
2000
2500
3000
3500
4000
4500
-27 -26,9 -26,8 -26,7 -26,6 -26,5 -26,4
Latitude (deg)
norm
aliz
ed re
flect
ance
Modis: Band 5
Modis: Band 2
-500
0
500
1000
1500
2000
2500
3000
3500
4000
4500
44,4 44,6 44,8 45 45,2 45,4 45,6
latitude(deg)
norm
alis
ed re
flect
ance
Modis Band 5
Modis Band 2
Profile over Aral Sea Profile over Diamantina river
What happened if aquatic vegetation ?
NDVI & Band 5 surface reflectance are increasing
0
1000
2000
3000
4000
5000
6000
-26,95 -26,9 -26,85 -26,8 -26,75 -26,7 -26,65 -26,6 -26,55 -26,5 -26,45
Modis band 5
-0,3
-0,2
-0,1
0
0,1
0,2
0,3
0,4
-26,95 -26,9 -26,85 -26,8 -26,75 -26,7 -26,65 -26,6 -26,55 -26,5 -26,45
Modis NDVI
Open water Aquatic vegetation Vegetation Dry land
Classification of surface: threshold criterium
Open water if:Modis Band 5 < 1200
Aquatic vegetation if:1200<Modis Band 5 <2700 &NDVI < 0.4
Vegetation ifNDVI > 0.4
Dry land ifModis band 5 > 2700 &NDVI < 0.4
Lake Eyre and Diamantina river
March 9, 2003 March 16, 2003
Sequence of flood on Diamantina in 2003
March 30, 2003 April 30, 2003
Water: Black, Aquatic Veg: Red, Veg: Orange, Land: White
T/P crossover point on Goyder Lagoon
20
20,5
21
21,5
22
22,5
23
23,5
2003,2 2003,4 2003,6 2003,8 2004 2004,2 2004,4 2004,6 2004,8Date (year)
Hei
ght a
bove
geo
id (m
)
Surface and volume variation from Altimetry+Modis data
Goyder Lagoon, 2004's flood
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2003,9 2004 2004,1 2004,2 2004,3 2004,4 2004,5 2004,6 2004,7 2004,8 2004,9 2005
Date (year)
Surface (km
2 ) - Free Water
Acquatic Vegetation
Vegetation on dry land
Goyder Lagoon, 2004's Flood
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
2003,9 2004 2004,1 2004,2 2004,3 2004,4 2004,5 2004,6 2004,7 2004,8 2004,9 2005
Date (year)
Volume (km
3 ) -
Flooding sequence onLake EyreTopex / poseidon
-14,4-14,35-14,3
-14,25-14,2
-14,15-14,1
-14,05-14
-13,95
2004 2004,2 2004,4 2004,6 2004,8 2005
Date (Year)
Hei
ght a
bove
geo
id (m
)
From Modis surface reflectance
Topex / Poseidon
-14,4-14,35-14,3
-14,25-14,2
-14,15-14,1
-14,05-14
-13,95
2004 2004,2 2004,4 2004,6 2004,8 2005
Date (Year)
Hei
ght a
bove
Geo
id (m
)
Topex / Poseidon
-14,3-14,25-14,2
-14,15-14,1
-14,05-14
-13,95-13,9
2004,3 2004,4 2004,5 2004,6 2004,7 2004,8 2004,9 2005
Date (year)
Hei
ght a
bove
Geo
id (m
)
Validation of the method with Aral Sea
From altimetry + bathymetry = > variation of surfaceNorth Aral
39,5
40
40,5
41
41,5
42
42,5
43
43,5
1993 1995 1997 1999 2001 2003 2005 2007
Date (year)
Leve
l (m
Dam Dam
Dam Release
58.00 58.50 59.00 59.50 60.00 60.50 61.00 61.50 62.0043.00
43.50
44.00
44.50
45.00
45.50
46.00
46.50
47.00
0
5
10
15
20
25
30
35
40
45
50
55
60
65
Surface deduced from Altimetry+bathymetry
2200
2400
2600
2800
3000
3200
3400
3600
3800
1992 1994 1996 1998 2000 2002 2004 2006 2008
date (year)
surf
ace(
km 2 )
-
Direct measurement from analysis of the Modis images
Sept 5, 2004
Oct 10, 2005 Sept 14, 2007Sept 5, 2004
Modis / altimetry Aral surface variations
0
5000
10000
15000
20000
0 5000 10000 15000 20000Modis surface (km2)
Alti
met
ry s
urfa
ce (k
m2)
Small Aral Big Aral
Correlation modis/altimetry = 0.996
White:New underwaterSurface : 400 km2
Poopo and Salars (Coipasa/ Uyuni), Bolivia
Jan 28 Mar 03
Apr 19 Aug 29
Jan 09
Jan 29
May 25
2006
2004
2004Jan 28
Apr 19
Mar 03
Coipasa
0
500
1000
1500
2000
2500
3000
3500
2001 2002 2003 2004 2005 2006 2007 2008
Surfac
e of w
ater
(km2)
Uyuni
0
2000
4000
6000
8000
10000
12000
14000
2001 2002 2003 2004 2005 2006 2007 2008
Date(year)
Surface of water (k
m2)
Lake Poopo
0
500
1000
1500
2000
2500
3000
3500
4000
2001 2002 2003 2004 2005 2006 2007 2008Date (year)
surface (km2)
ConclusionConclusion
♦♦♦♦♦♦Modis data provide good mean to measure extent of water Modis data provide good mean to measure extent of water with high temporal resolution well designed for specific cases:with high temporal resolution well designed for specific cases:
shallow lakes, temporary lakes, & floodplains mainly in shallow lakes, temporary lakes, & floodplains mainly in arid zonearid zone
♦♦♦♦♦♦It provides valuable information on vegetation and aquatic It provides valuable information on vegetation and aquatic vegetationvegetation’’s dynamics dynamic♦♦♦It is not suitable in region covered by clouds most of the It is not suitable in region covered by clouds most of the timetime
=>=>Monitoring of floodplain extent and volume variation of Monitoring of floodplain extent and volume variation of lakes in synergy with radar altimetry is possiblelakes in synergy with radar altimetry is possible