South Carolina should expect a minor chance of river flooding this spring, according to a forecast released Thursday by the National Oceanic and Atmospheric Administration.
The forecast, which predicts a slight impact for all of the Palmetto State and a higher risk in the Savannah River basin, comes after a wet winter drenched the Upstate and parts of the Pee Dee.
That water took weeks to filter down, swelling waterways like the Edisto River at Ghivans Ferry and the Santee River near Jamestown and the rural southern end of Georgetown County.
Soil saturated with water from those rains is still a concern, said Todd Hamill of NOAA’s Southeast River Forecast Center.
But plants have awoken earlier this year, and as growth continues, foliage will be in more competition for groundwater, helping to lower the flooding threat.
‘Green-up’ in South Carolina has come a little bit more quickly this year,” Hamill said.
Springtime tends to carry a lesser threat for rainfall-driven flooding in part because of that plant growth and traditionally drier weather patterns: Sudden cloudbursts erupt during times of unsettled atmosphere in the summer, and tropical weather is concentrated in months when ocean temperatures are highest, generally in the autumn.
Climate change, or the average raising of global air and water temperatures, promises to make those rain events more severe, if not necessarily more common. Simply: a warmer atmosphere can hold, and dump, more water.
But many different factors go into NOAA’s flooding forecast, and some of them have little to do with those climate impacts. Among the factors are soil saturation, predicted atmospheric phenomenon like “el niño” and “la niña,” geography of watersheds and past rain.
Nationally, the biggest threats for 2020 flooding will be in the upper Midwest, with areas of concern for minor to major flooding stretching from North Dakota down to Texas, and over to the southeast Atlantic Coast.
“We anticipate that one-third of the country will experience some type of flood risk this year,” Ed Clark, director of NOAA’s National Water Center, said on a call with reporters.
The Midwest likewise saw devastating flooding last year; at Cape Girardeau, Mo., river gauges measured 144 consecutive days of flooding, said Mary Erickson, deputy director of the National Weather Service.
Floodwaters are “a dangerous and underrated killer,” Erickson said, with many people perishing after they drive their cars into unexpectedly high or fast-moving water. Flooding is also the single most costly disaster in the United States, according to NOAA.
In South Carolina, the river predictions call for some level of flooding over the entire state. NOAA defines “minor flooding” as that which would potentially cover roadways but not damage homes; “moderate flooding” would involve some property damage to structures near a waterway. Moderate levels are only called for along the state’s southeastern edge.
The predictions do not, however, include chances of tidal inundation, a different threat driven by sea level rise, phases of the moon, the direction of coastal winds and ocean circulation.