Most of Lexington and Richland counties received less than two inches of rain in the second week of November 2020, a relative pittance spread out over 48 hours. That sort of soaking seldom causes more than a minor blip on river levels.
But the West Columbia and Cayce riverwalks were closed because of flooding Nov. 14-15, providing a lesson in river basins. Upstream in the Broad River basin, which covers 2,252 square miles in South Carolina, the rainfall associated with Tropical Storm Eta drenched some areas with 8-10 inches.
The Saluda River basin, encompassing 2,523 square miles in the state, got about 3-4 inches of rain. The resulting slug of water worked its way down the basin and combined with the water coming down the Broad to push the Congaree River to flood stage. And that meant the Cayce and West Columbia riverwalks had to be closed on what turned out to be an ideal weekend to get out in nature in the Midlands.
According to the National Weather Service, water begins to lap at the greenway in several spots in Cayce and West Columbia when the river level reaches 10 feet at the official Congaree river gauge in Columbia. The municipalities closed the walkways early Friday as the river quickly rose from 10 to 14 feet. Overnight, the river made it to 19 feet, and it peaked just above 20 feet, according to the U.S. Geological Survey waterdata website.
For reference, river floods have topped 20 feet at the Congaree’s Columbia gauge only 23 times in the past three decades (five of those were during the historic final three months of 2015). The rain sure didn’t seem to 2015 levels last month.
The flooding not only affected the walkway along the river, but it backed up water into Congaree Creek in Cayce’s 12,000 Year History Park. Basically, the water running downstream in the creek couldn’t flow into the river, so it swamped the creek’s floodplain. Dozens of people that Saturday found the “Trail Closed” signs hard to believe and tried to walk or bike on the Timmerman Trail. They didn’t get far. Some might have waded through the spots where a few inches of water covered the trail, but they eventually came to spots where the water was knee deep (as the image above shows in flood and post-flood photos).
I was among those folks, and I gave up quickly. I saw cyclists on mountain bikes heading north on Old State Road, where they at least could ride through a little mud and then up the asphalt section of the highway for a few miles. I opted to turn around and head home.
West Columbia and, especially, Cayce deserve kudos for cleaning debris off the trail quickly. Some sections were re-opened by midweek, and the entire greenway on the west bank of the river was open by the weekend. Biking the six miles from Cayce Tennis and Fitness Center to the north end of the trail in West Columbia the Saturday after the flood made it clear how much work the cleanup had required. The silty film left after the flood debris was scraped off the trail seemed to cover nearly five of the six miles. The only noticeable damage was one small riverside tree that toppled and a section of bank erosion that prompted red tape around a picnic table.
The weekend lessons: River basins can cover vast areas, and if the Congaree river gauge is in the high teens, we should avoid Timmerman Trail and head to Columbia’s Riverfront Park, where we can walk, run or bike the high-and-dry Canal Embankment section.
Questions or comments: I’ll respond to anything left on the blog post or at [email protected]. Thanks for reading.