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What would you do if in just minutes the water completely surrounded you with no time to escape?
Important points
Flash floods are one of the most dangerous and underestimated extreme weather phenomena. In this episode of Atmospheric TurbulenceCaptain Martinez and his crew guide us through an informative journey on how they are formed, why they are so lethal, and what we can do to protect ourselves.
What is a flash flood?
Flash floods occur without warning, usually in a matter of minutes or hours, leaving very little time to react. They are usually caused by extremely heavy rainfall in a short period of time, although in many cases the water comes from elevated areas where it has rained upstream, without a single drop falling in the affected area.
This type of phenomenon is most common in dry canyons, ravines, small rivers, poorly drained urban areas, mountainous or saturated terrain, and areas near dams or levees. One particularly alarming fact: more than 60 % of flash flood deaths in the U.S. occur when people attempt to cross flooded roads in their vehicles.
When hurricanes bring more than just wind
Hurricanes are powerful generators of floods, and their danger is not limited to torrential rains. One of the most destructive phenomena associated with these systems is the storm surge (storm surge): a rapid and violent rise in sea level caused by the hurricane's strong winds that push enormous volumes of water towards the coast. This sea level rise can inundate coastal areas even before it starts rainingThe force is sufficient to devastate homes, roads and critical infrastructure.
History has shown how lethal this combination can be. During the Hurricane Katrina in 2005more than 1,800 people diedand most of those deaths were related not to the wind, but to the flooding caused by storm surge and the collapse of the protection levees in New Orleans. The water covered about 80 % of the city, reaching heights of up to 20 feet in some neighborhoods. Katrina thus became a tragic example of the devastating power of water in hurricanes, and a wake-up call for the need for more resilient coastal protection systems and better disaster preparedness.
History of major floods in the U.S.
Kamila, part of the crew, reviewed some of the worst water disasters:
- Galveston, Texas (1900): 8,000 killed by hurricane and 15-foot storm surge.
- Johnstown, Pennsylvania (1889): A dam collapse killed 2,209 people.
- Hurricane Harvey (2017): Record rainfall in Texas with damages of more than $125 billion.
Measuring rainfall: millimeters or inches?
Rainfall can be measured in:
- Millimeters (mm)1 mm is equivalent to 1 liter of water per square meter.
- Liters per square meter (l/m²)used in agricultural or technical contexts.
- Inches (in)common in the U.S.; 1 inch = 25.4 mm.
Fun fact: The first official rain gauge was invented in Korea in 1441, and in Europe, Christopher Wren developed a modern one in 1662.
Where does it rain the most?
- USA: Mount Waiʻaleʻale (Hawaii) with more than 9,000 l/m² per year.
- Latin America: Lloro (Chocó, Colombia) exceeds 12,000 l/m² per year.
- Europe: Scottish Highlands and western Norway.
- Asia: Mawsynram (India), the rainiest place on the planet.
Understanding alerts can save your life
The NWS (National Weather Service) classifies warnings as follows:
- Flood Watch: favorable conditions.
- Warning: imminent flooding or flooding already in progress.
- Urban or small stream warnings: areas affected.
- Flood emergency: is the highest level and precautions must be taken.
Turn Around, Don't Drown - Turn around, don't drown.
Only 15 cm of moving water can make you lose control of the car. With 30 cm, you can be swept away.
🧰 Are you ready?
- Have a emergency kitwater, radio, flashlight, medicines.
- Make sure you know the high areas close to your home.
- Check if your insurance covers floods.
- Inform your family on what to do in case of an emergency.
