Satellite before and after

Rio Grande do Sul floods 2024: Porto Alegre and the Patos Lagoon, Brazil

Storms and torrential rain from late April 2024 caused deadly flooding across the Brazilian state of Rio Grande do Sul that lasted through much of May, including in the state capital, Porto Alegre.

Porto Alegre, the Guaíba and the Patos Lagoon, Rio Grande do Sul, Brazil · Late April to May 2024 · Flood · Brazil

Compare the imagery

Drag the divider, or focus it and use the arrow keys. Left of the divider is 21 Apr 2024, right is 6 May 2024, 15 days apart.

The interactive comparison needs JavaScript. Both images are shown below.

In this false-colour view water is dark blue to black, vegetation is bright green, bare ground is tan, freshly burned land is red-brown and cloud is cyan.

The two images

Satellite image of Porto Alegre, the Guaíba and the Patos Lagoon, Rio Grande do Sul, Brazil on 21 Apr 2024, before the event, in false colour (MODIS bands 7-2-1).
Before: Terra, 21 Apr 2024 · Open in NASA Worldview · original from GIBS
Satellite image of Porto Alegre, the Guaíba and the Patos Lagoon, Rio Grande do Sul, Brazil on 6 May 2024, after the event, in false colour (MODIS bands 7-2-1).
After: Aqua, 6 May 2024 · Open in NASA Worldview · original from GIBS

What the images show

On 21 April the rivers feeding the Guaíba west of Porto Alegre are thin dark lines. On 6 May they have spread into wide dark bands of water, and pale, sediment-laden runoff pours into the Patos Lagoon.

About the event

  • NASA Earth Observatory reported that floodwater inundated Porto Alegre's historic district, closed its international airport and left several highways impassable.
  • It cited Rio Grande do Sul's civil defence agency: more than 160,000 people displaced.

Limits of this comparison

The before-image is from Terra and the after-image from Aqua: the instruments are identical, but the two pass at different times of day. Haze and thin cloud cover the south-west corner of the after-image.

Each image is one satellite pass at about 250 metres a pixel. It shows where water or burned land is visible from space on that day; it does not measure damage, and cloud or haze can hide what is underneath.

Dates were chosen by checking the imagery on both satellites for several days either side and keeping the clearest pass; the two images come from different satellites carrying the same instrument. Both use the same layer, MODIS Corrected Reflectance, bands 7-2-1.

Sources

We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Comparison slider: leaflet-side-by-side (MIT licence). Case last updated 12 Sep 2026.

Questions

What does the satellite image of Porto Alegre, the Guaíba and the Patos Lagoon, Rio Grande do Sul, Brazil show?

On 21 April the rivers feeding the Guaíba west of Porto Alegre are thin dark lines. On 6 May they have spread into wide dark bands of water, and pale, sediment-laden runoff pours into the Patos Lagoon.

When were the two satellite images taken?

The before-image was taken by Terra, 21 Apr 2024 and the after-image by Aqua, 6 May 2024, 15 days apart.

What can this before-and-after comparison not show?

The before-image is from Terra and the after-image from Aqua: the instruments are identical, but the two pass at different times of day. Haze and thin cloud cover the south-west corner of the after-image. Each image is one satellite pass at about 250 metres a pixel. It shows where water or burned land is visible from space on that day; it does not measure damage, and cloud or haze can hide what is underneath.

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