A combination of factors explains the impact of rain in Vale do Taquari (RS); understand | National Newspaper

A combination of factors explains the devastating impact of the rains in the Taquari Valley.

Another rain above normal and, once again, the cities of Vale do Taquari, in Rio Grande do Sul, are underwater. In September, a tropical cyclone left homes submerged and killed 54 people. Two months later, storms left five more dead.

Now, the rains started in early April. Until the 18th, it rained 230 millimeters in the central region of the valley, already above the average for the region, which is 151 millimeters. The river level rose and began to invade the cities.

And from April 28th until this Thursday (2nd) morning, there were another 501 millimeters, in four days. The already waterlogged soil helped water flow from the headwaters of smaller rivers to the Taquari River and flood cities. A satellite image shows the normal path of the Taquari River. The dark spot is the land that has been covered by water. This photo was taken this Thursday.

Meteorologist Gilvan Sampaio explains that three phenomena came together. From the Amazon come humid winds. The white patch over the southern region is a strong cold front. And, in the center of the country, an area of ​​high pressure does not let the clouds pass. They are parked and cause constant rain.

“This is another sign of the El Niño phenomenon. This allows the fronts to become blocked there in the south of Brazil. So, that’s what happened there at the end of last year, in the second half of 2023, and that’s what’s happening now. Although El Niño is now losing intensity, it still also contributes to this phenomenon that is occurring now”, says Gilvan.

This historic rain is already enough to cause major damage in Rio Grande do Sul. But the Taquari Valley has another characteristic that increases the destructive power of storms. And this doesn’t come from the sky, it has much more to do with the earth.

The cities of the valley were built on the banks of the river, in flat, low-lying areas, called floodplains by geologists because they are naturally flooded when the river level rises. The city of Muçum is an example of this. And the pattern is repeated in neighboring cities.

“The Taquari River basin is very, very wide, right? I think the length is more than 200 km. All the water that falls within this area will converge into the main river, which is the Taquari River. That’s why this volume it all converges and ends up overflowing”, explains Edilson Pizzato, professor at USP’s Institute of Geosciences.