The Waccamaw River in Conway and the Little Pee Dee River in Galivants Ferry are expected to reach “major flood” levels, according to the National Weather Service in Wilmington, N.C.
The Waccamaw River reached its “moderate” flood level Sunday night and is projected to surpass its record flood stage. The Little Pee Dee was approaching its minor flood level Sunday and is projected to come within a foot of its record level set in the aftermath of Hurricane Matthew in 2016.
Tropical Depression Florence — which was downgraded from hurricane status on Friday — continues to slowly move through the Myrtle Beach area and was expected to drop up to 2.5 more inches of rain Sunday afternoon and evening in many parts of Horry County, further bloating the rivers.
The Waccamaw River was measured at 12.53 feet in Conway at 9 p.m. Sunday, while its flood stages begin at 11 feet. According to National Weather Service projections, it is expected to rise to its major flood stage of 14 feet by Tuesday night and could exceed its record level of 17.9 feet set after Hurricane Matthew by 3 feet around Sept. 26.
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If the river reaches 15.9 feet, the NWS predicts flooding will occur at the Conway Marina, railroad trestles in downtown Conway and in residential properties and roads off U.S. 501 Business, S.C. 905 and S.C. 90, including Riverfront South, Lees Landing, Savannah Bluff, Pitch Landing, Jackson Bluff and Bucksville.
The NWS also predicts the Waccamaw River will crest at 24 feet on Saturday in the Longs area, which would result in widespread flooding.
The Little Pee Dee River around Galivants Ferry is forecast to rise to its minor flood stage of 9 feet Monday and reach a major flood stage of 12 feet by Tuesday night. The NWS warns the river level could come within a foot of its record level of 17.1 feet around Sept. 23. The river level at 9 p.m. Sunday was 8.50 feet, which was an increase of more than 5 1/2 feet since noon Thursday.
Little Pee Dee flooding is expected to affect dozens of homes in the Fork Retch community near Nichols while also flowing into swampland and over boat landings.
Overall in southeastern North Carolina and northeastern South Carolina, six rivers — the Waccamaw, Little Pee Dee, Pee Dee, Cape Fear, Northeast Cape Fear and Lumber — are all expected to reach major flood stages at some locations. Black Creek is projected to reach a “moderate” flood stage, and the Lynches and Santee rivers are forecast to reach “minor” flood stages.
In addition to the Waccamaw, the Cape Fear, Northeast Cape Fear, Lumber and Pee Dee rivers may reach record water levels. Officials have called the potential flooding catastrophic and life-threatening.
According to NWS Doppler weather readings as of 3 p.m. Sunday, Myrtle Beach had received approximately 4 inches of rain from the storm and other parts of Horry County had received as much as 8 inches. The highest rainfall total registered in the state was 13.3 inches in neighboring Marion County, and parts of Pender County, N.C., had received 26 inches.
Richard Neuherz, a hydrologist with the federal National Oceanic and Atmospheric Administration who is based in Wilmington, said the river level forecasts are based on where the NOAA and NWS predict the rain will actually fall. If the predictions for areas of heaviest rainfall or the amounts are off at all, it will affect how the rivers respond.
S.C. Secretary of Transportation Christy Hall said during a press conference Saturday that the state plans to construct a 1.5-mile temporary flood control barrier to keep possible Waccamaw River flood water off U.S. 501 in Conway and a 1-mile barrier to keep flood water from the Lynches River off U.S. 378.
The state intends to have them in place by Monday night. Hall said it’s predicted the Waccamaw River could overtake the 501 roadway by 3 feet, and S.C. 378 could be overtaken by about a foot of flood water.
The barriers are meant to ensure there is a primary route into Horry County, and their construction began Saturday.
The state is looking at solutions to other potential problem areas on U.S. 701 at the convergence of the Little Pee Dee and Great Pee Dee rivers, U.S. 17 at the bridge in downtown Georgetown, and several locations on Interstate 95.