Rainfall and flooding in the Carolinas reveals highways that aren’t built for increasingly intense storms.
Hurricane Florence battered the Carolina coasts with heavy rain, strong winds, and a devastating storm surge over the weekend. But even after the rain has dissipated, it still presents a danger from disastrous flooding, which the North Carolina Department of Transportation warns will still get worse in the days to come. Already, Wilmington is completely cut off.
Trillions of gallons of water are flowing toward lower-lying parts of the state and biblical flooding is wreaking havoc on the Carolinas, making it nearly impossible to travel in many parts of the region. Homes, farms, and communities have been completely overrun by water, and 25 are reported dead so far—including a one-year-old swept away by floodwaters. The death toll is expected to rise.
Winding their way between trees, houses, and other structures, the region’s roadways offer a particularly harrowing view of the extent and damage of the flooding. With long, open lines of sight, the scope of the flooding is evident along the routes that might otherwise be used for evacuation. In south-eastern North Carolina, which faced the heaviest rainfall, huge swaths of Interstate 40 have transformed into a miles-long waterway, as the video below shows.
This isn't a river...this is Interstate 40. @NCAviation captured this drone footage today as part of damage assessment near mile marker 387 in Pender County. This illustrates our message that travel in this area is impassable and unsafe. #FlorenceNC pic.twitter.com/28Ok6Tjpcu— NCDOT (@NCDOT) September 17, 2018
Interstate 40 at Pender County pic.twitter.com/d8XYXCZRsE— MG(R) Jim Trogdon PE (@NCDOT_Trogdon) September 17, 2018
Interstate 95, too, is completely inaccessible in many portions, as nearby rivers have topped their banks and swallowed stretches of highway.
North Carolina’s design standards require that interstate highways in low-elevation parts of the state must be built to withstand and drain 50-year floods, or flood levels that, based on historical data, occur on average once every 50 years. In many parts of the state, Florence’s flooding represents a 1,000-year event.
On rural roads, the discrepancy is even larger. Local roads that receive NCDOT funding need only withstand 25-year flood events.
One way roads are designed to drain floodwaters is by elevating them over their surrounding landscapes. As a result, when flood waters cover large portions of highways, the water in the area is several inches or feet higher than it appears from the road.
Even when floodwaters aren’t flowing at dangerous speeds, they hide all sorts of dangers. In North Topsail Beach, North Carolina, a firefighter found venomous snakes in the floodwaters, and rising waters throughout the state could bring coal ash and hog waste floating through neighborhoods.
It could be days before flood waters on streets and highways recede enough in North Carolina for the roads to be passable. And even then, the debris they leave behind could pose problems for clean up crews for days and weeks to come.