Heavy rainfall from Hurricane Matthew is expected to cause severe flooding on the Waccamaw River and Little Pee Dee River at Galivants Ferry this weekend, according to National Weather Service forecasters.
In addition, officials are closely monitoring the northeast Cape Fear, Black, Sampit and South Santee rivers, given that the bulk of the rainfall may end up in the river basins.
“We’re going with extreme impact on flooding, especially with the rainfall that we’ve had over the last several weeks,” said Reid Hawkins, science and operations officer for the National Weather Service.
Horry County is under a flash flood watch that is also focused on the coastal region, where the storm surge is predicted as high as six feet.
On Thursday evening, the Waccamaw River was more than one foot below action stage at 10 feet, minor flood stage is at 11 feet. During the historic rains one year ago, the Waccamaw rose higher than 16 feet — the third highest crest on record.
The risk for flash flooding will increase Saturday as very heavy rainfall moves across the area, and flooding is expected to continue into next week.
The chances of major flooding on the Waccamaw are 36 percent, 50 percent for moderate flooding and 70 percent for minor flooding this weekend.
For the Little Pee Dee, chances of major flooding are 19 percent, moderate flooding is 30 percent, and minor flooding is 79 percent, the National Weather Service said.
With average rainfalls along the coastal area now predicted at more than 10 inches, weather officials advise those who live near the rivers to check forecasts next week, after the hurricane passes.
“We’re not out of the woods, don’t let your guard down,” Steven Pfaff with the National Weather Service said. “It looks like a large swath of tropical moisture is coming into the area that is not associated with Matthew,” Pfaff said.
Weather authorities bumped flood impacts up to “extreme” for coastal areas Thursday afternoon.
The ground is already saturated from September storms, so the amount of rainfall occurring within a relatively short period of time will quickly lead to run-off and flooding.