By A. Sezin Tokar, Ph.D., Senior Hydrometeorological Hazard Advisor, USAID’s Office of U.S. Foreign Disaster Assistance
Flash floods are the number one weather-related killer and the most fatal side effect of hurricanes. They kill thousands of people every year and cause millions of dollars in damage by destroying buildings and bridges, uprooting trees and overflowing rivers within mere minutes.
Flash floods occur when excess water caused by heavy and rapid rainfall from tropical storms or hurricanes cannot be quickly absorbed into the earth. This fast-moving water can be extremely powerful, reaching heights of more than 30 feet. But it takes only six inches of water to knock a person to the ground or 18 inches to float a moving car.
USAID’s Office of U.S. Foreign Disaster Assistance recognizes that while flash floods are deadly in even the most developed countries, they can really wreak havoc in densely populated regions around the world that lack strong infrastructure. Hurricane-prone regions throughout Latin America and the Caribbean are especially vulnerable, which is why USAID works with host countries year-round to help them prepare.
Even though the onset of flash floods is almost immediate, it is possible to give up to a six hour window of advanced notice—just enough time to save lives.
The advanced warning is given through the Flash Flood Guidance System, a scientific method of accumulating rainfall data and analyzing the rate at which the ground absorbs it. USAID works closely with meteorological experts in hurricane-prone countries, training them on how this system works so that they can be on the lookout for potential flash floods. Using the system gives disaster-prone countries the opportunity to use those crucial six hours before a flash flood hits to implement emergency plans and move as many people out of harm’s way.
Six hours may seem like a lot of lead time, but it’s actually not when you’re rushing to alert remote and heavily populated villages—with limited communication—about an approaching disaster. Flash floods can’t be prevented, but USAID is committed to helping people better prepare for and recover from them. Because when it comes to saving lives and alleviating suffering, every minute counts.