How hydrologists forecast flooding

How hydrologists forecast flooding

HATTIESBURG, MS (WDAM) - While meteorologists forecast weather systems like rain in the atmosphere, hydrologists forecast flooding.

"The job of a hydrologist is to basically take characteristics of the storm itself, combine those with what the conditions are on the ground's surface, and be able to forecast how rapidly water will get to streams and creeks and rivers," said Frank Heitmuller, associate professor of geology at The University of Southern Mississippi.

Marty Pope, a hydrologist with the National Weather Service in Jackson, said, "When the rainfall hits the ground, that's when the hydrologist takes the water, and we take all the information and put it into river forecasting models."

Pope said the National Weather Service gathers data from stream gauges via satellite to track river levels every hour.

He said the hardest part of forecasting flooding is determining where the heaviest rain will fall.

"Rainfall areas are very important because if you're just 50 miles off, and you're outside the Leaf River basin, and you don't get as much as you think you're going to get or if a heavier rain band than we're predicting falls over, say, the Leaf River basin itself, we could get more (flooding)," Pope said.

Heitmuller said another factor for forecasting flooding is how much moisture is currently in the soil.

"Right now, everything, all the little passageways in between the soil particles are just jam packed with water," he said. "There's not a lot of room. The water from the rain can't technically infiltrate and be stored there because the storage is all gone."

Heitmuller said slope of the land and urbanization also play a role in flooding.

Both said spring flooding is typical in the Pine Belt.

"Usually in this area, it's expected that rivers flood at least a little bit every one and a half to two years on average," Heitmuller said. "That's just based on data collected historically, so it's not abnormal that we're seeing this kind of flooding at all right now. Of course, El Nino is predicting these kind of wet early springs and winters."

Pope said, "This year is a transition from what we call El Nino to La Nina. That was the same thing that occurred back in 1983 when we had the big floods.That's why we're going to have to keep an eye on this. That year, flood season actually extended more into May, which recently if we reached April, we wouldn't have any threat."