Because Sally has shifted east, river flooding in Hancock and Harrison Counties is less of a concern than initially forecast. But it remains an issue in Jackson County.
The Escatawpa River, north of Orange Grove, is projected to crest Wednesday afternoon at three-and-a-half feet above the flood stage, at 11.5 feet. That’s only a few inches shy of its record height, according to the National Weather Service projections. The Pascagoula River at Graham Ferry is forecast to crest Friday afternoon, 18 inches above flood level, at 17.5 feet.
Further north, in Greene County, the Leaf River near McLain could surge 6 feet above flood level by Thursday afternoon. And major flooding is predicted for the rivers around Mobile by late Wednesday.
“This will be the top concern,” said Jack Cullen, a meteorologist in the Mobile office of the National Weather Service. “Every storm is different but with this one, the river flooding is going to be first.”
Rivers tend to flood hours or even days after a major storm has passed because they’re collecting the rainfall dumped across their entire watershed. As a Category 1 storm, Hurricane Sally doesn’t have a great deal of strength, but has been projected to dump large amounts of rain as it moves over southeastern Mississippi, Alabama and Florida. That rain has to go somewhere: into the Gulf, or into a river.
“[The flood] continues on for a couple days after, even after it peaks, because all that water is still running off,” Cullen said. “So it’s kind of slow to go up, slow to come down.”
On Tuesday afternoon, the National Weather Service office in Slidell dramatically reduced its forecasts for flooding in Harrison County’s Biloxi, Tchoutacabouffa and Wolf Rivers. All had been expected to exceed their flood stage by at least seven feet. Now, they are each forecast to rise only about six inches above flood level.
Julie Lesko, senior service hydrologist at the NWS office in Slidell, said that they had lowered the flood estimates for Harrison County rivers because the county is now predicted to receive relatively little rain, likely between 1 and 4 inches. In Jackson County, Lesko said, there will be more rain, especially in the eastern part of the county.
While western Jackson County may receive about 5 inches, there could be as much as 15 inches near the border with Alabama, she said
River flooding is influenced by two factors: rainfall collected over time and storm surge pushing water from the Gulf up into rivers.
“The Escatawpa River in Orange Grove is definitely still in that bullseye of where they could see some pretty heavy rain,” Lesko said. “We’ll still see a little increase of the river as some of the surge comes up.”
Cullen said that people living along rivers should watch forecasts closely and be ready to evacuate. But Cullen, Lesko and local officials interviewed all said that people who live near rivers tend to know the drill when it comes to flooding.
On Tuesday, Gulfport city council member RLee Flowers drove to visit residents of Retreat Village and Biloxi River Estates along the Biloxi River in Harrison County. Retreat Village had some water over low-lying roads, he said. But people had already moved items that needed to be moved by Monday, and there was no real sense of alarm.
“They’ve been through more floods than Noah,” he said. “They know how to do it.”
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