Sudden floods drew attention earlier this month in the United States, with records being broken almost consecutively in various regions of the country, such as Texas, North Carolina, Illinois and New Mexico.
The 4th of July caused more rain than usual throughout the summer, causing rivers to overflow and more than 130 people die.
Over the same weekend, the Chantal Tropical Storm poured almost 30 centimeters of rain in part of the center of North Carolina.
In addition, the level of the Eno River rose about 8 meters, breaking a record previously established by Hurricane Fran in 1996. The flood killed at least six people.
Already on Tuesday (15), recorded amount of rain equivalent to an event that occurs once every thousand years, while in the mountainous city of noisy, in the storms caused unprecedented floods that destroyed houses and left three dead.
All these events were extreme and occurred successively. See why they are happening now and why floods are intensifying.
Summer and the sudden flood season in the USA
Sudden floods are more common in summer in the United States, when intense heat during the day contributes to storm formation.
Hot air can also retain more moisture, giving the storms greater potential to produce heavy rainfall compared to lower temperatures.
In Texas, the storms were fed by record levels of remaining atmospheric moisture of the Barry Tropical Storm.
In North Carolina, the tropical moisture of the Chantal Storm played a similar role, contributing to the heavy rains that caused fatal floods.
When storms decrease or stop, rain can accumulate in the same area for hours and fall faster than soil can absorb it or the infrastructure can drain it by preparing the scenery for a sudden flood.
This happened in the Texas mountainous region, where a strong storm poured over 18 centimeters of rain, and in Chicago, where it was dumped up to 1.2 centimeter of rain in just 90 minutes, quickly flooding some streets and houses.
In urban areas, pavement and asphalt can cause even more problems, preventing water from penetrating the soil and sending it to manholes, which can quickly overflow or be obstructed with debris.
Forest fires also increases the risk of sudden floods, as happened in noisy with the devastating South Fork and Salt fires.
When vegetation burns, landscapes lose their natural ability to absorb rainwater. In addition, the extreme heat of a fire can change the soil itself, creating a repellent layer to the water just below the surface.
Rain in these “fire -marked” lands tends to flow quickly – especially in steep land – increasing the risk of sudden floods, even if the amount of rain is not extreme.
The village of Ruidos, in the state of New Mexico, and nearby areas have received at least 12 sudden flood emergency alerts since the 2024 fires.
Droughts have a similar effect: when the soil dries for long periods, it can compress or form crusts, reducing its ability to absorb water.
Severe dry or pre -existing droughts helped intensify floods in Texas and New Mexico last week.
Climate change worsens situation
Climate change caused by fossil fuel pollution is intensifying conditions that make the floods suddenly more likely and severe.
For each heating Celsius degree, the atmosphere can retain about 7% more water vapor, providing more “fuel” for storms that produce intense rainfall.
And as global temperatures increase, air -laden air – previously limited to tropics – can reach more distant areas of the equator, bringing intense rainfall to more regions of the world.
At the same time, forest and dried fires are becoming more frequent and serious with global warming, leaving more land marked by fire and vulnerable to flooding areas.
Precipitation rates have become more intense in almost 90% of large US cities since 1970, according to a recent study by the non-profit climate Central research group.
In Chicago, for example, the average intensity increased by 8%, and Tuesday rains exceeded the records established in the 1970s for extreme short-term rain events in the city.
Many US roads, sewers and drainage systems are not designed to support the types of rainfall that are becoming more common.
Sudden floods have always been a threat during the summer, but the risks are changing.
As the atmosphere warms and precipitation patterns continue to transform, more communities may face extreme rainfall events in the coming years.
