Little-Understood Weather Pattern May Cause Floods, Says UF Scientist

June 21, 1996

GAINESVILLE —Ocean cooling in another part of the world may help explain sudden storms that flood Florida rivers and streams during summer, says a University of Florida researcher.

Matt Zorn, a UF researcher in geography, has found a link between water cooling in the Pacific Ocean off South America, a phenomenon called La Niña, and Florida’s inland waters flooding in summer.

“What we’re finding is a higher variability in river and stream flow in the summer season during La Niña years,” said Zorn, who is studying how the climate-shaping event affects inland water levels throughout the state. “In some areas, there is severe flooding, particularly in the Panhandle and South Florida.”

La Niña may slow upper level winds streaming over the Atlantic Ocean, allowing more tropical storms to form and bring their heavy rain to Florida, Zorn said.

“More hurricanes and tropical storms in the Atlantic bring more moisture to the state in the form of rain, causing rivers to flood,” he said. “Typically, the Panhandle and South Florida are the two hot spots smacked by these tropical storms. Other parts of the state that are less hard hit by these weather systems, such as north central Florida, are much less prone to flooding.”

Evidence suggests that another La Niña may be approaching, Zorn said. However, normal conditions now prevail, with neither La Niña nor the warm current called El Niño in force.

El Niño means “The Child,” referring to the Christ child, because it typically first appears around Christmas.

Zorn, who is recording water levels at 34 rivers in Florida for his dissertation, said he eventually hopes to develop a model for predicting stream flow in state rivers under El Niño and La Niña conditions. Such a tool could be of great use not only to farmers, but also to residents of South Florida, who are affected by water shortages, he said.

“Water resource allocation is a critical part of modern life,” Zorn said. “If we can more accurately predict how much flow we’re likely to have in our streams at different times of the year and under different sets of conditions, our ability to allocate water will improve tremendously.”

Scientists have been less aware of how El Niño and La Niña affect inland waters during summer than winter because these phenomena are generally weaker worldwide during the summer months, Zorn said.

In Florida rivers, for example, flooding has not been as heavy or as consistent in summer as in winter, he said. The most recent case of severe flooding occurred in the winter of 1993, an El Niño year, when several north Florida rivers overflowed their banks, he said.

“Learning more about what happens during the summer is still important, however, because that is our growing season and the season of greatest demand for water,” Zorn said. “If we succeed in developing a model for predicting river and stream levels, farmers and agricultural extension agents can make good use of this information.”