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Alessandria and Asti (Italy), November 1994
During the first few days of November 1994 a big storm struck
the Eastern Alps with heavy rains in northern Italy that produced
the region's worst disaster since 1913. Seventy people lost their
lives and 450.000 hectares were flooded, with the cost of the
damage running to $5 Billion.
Highways, railways and roads were closed for several days,
some of them requiring months to repair or rebuild. The towns of
Alba, Asti and Alessandria, along the Tanaro river, were badly
hit. The extent of the flooding in these areas was clearly
evident from the ERS-1 satellite images acquired by ESA.
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Map of Area
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Click on the thumbnails to view the full size images
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670x573 pixels, 180 Kb JPEG
Image area coverage: 100 x 150 km
Acquired on 9 November 1994 |
This ERS-1 SAR image, acquired during the storm, comprising
two standard ERS-1 scenes, shows the Po and Tanaro rivers around
the Alessandria, Alba and Pavia areas.
Water is a relatively smooth surface and thus is black in this
image, clearly showing the flooded areas along the two rivers and
the unusual width of the Po river. |
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670x659 pixels, 197 Kb JPEG
Image
area coverage: 150 x 150 km
In Red:
9 Nov 95 - In Green:
4 Oct 95- In Blue:
4 Oct 95 |
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700x453 pixels, 288 Kb JPEG
Image area coverage: 30 x 25 km
4 October 1994 |
These ERS-1 images, show the situation before and during the
flooding around the city of Alessandria along the Tanaro river.
The first image is termed a "reference image", and
shows the normal situation, with the Tanaro flowing through the
almost circular town of Alessandria. In the second image the
extensive flooded areas along the river and in the town are
clearly visible. The railway station, located in the north east
part of the town, was submerged by water and mud, isolating the
area. |
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700x500 pixels, 317 Kb JPEG
Image area coverage: 30 x 25 km
9 November 1994 |
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501x358 pixels, 99 Kb JPEG
Image area coverage: 30 x 25 km
9 November 1994 |
These interpreted images were annotated immediately on arrival
of the images from the reception station, and before the
reference image had been retrieved from the archive. |
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501x358 pixels, 109 Kb JPEG
Image area coverage: 30 x 25 km
9 November 1994 |
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700x443 pixels, 310 Kb JPEG
Image area coverage: 30 x 25 km
In Red:
9 Nov 94 - In Green:
4 Oct 94- In Blue:
4 Oct 94 |
Two days later (11 November) the Earth Watching team received
the reference images and made these two multitemporal images of
Alessandria. The first one is created assigning the flooded scene
to the Red and Green channels and the "normal" or
reference image to the Blue channel.
To better identify detailed changes, a second image was
created adding an artificial channel created with the
"second principal component" of the original scenes.
The area where the most significant changes have taken place
are shown in cyan and are the flooded areas. They are located
mainly along the Tanaro river, representing a total surface
within the image of 15,7 sq km. |
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700x443 pixels, 288 Kb JPEG
Image area coverage: 30 x 25 km
In Red:
9 Nov 94 - In Green:
4 Oct 94- In Blue:
2nd Principal component |
Technical information about the images:
- Satellite / Sensor: ERS-1 SAR
- Acquisition dates: Octber 3rd 1994, November 9th 1994
- Orbits: 16823, 17354 Frame 2691,2709
- Acquired by: Fucino (Italy)
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