The Flood: What Happened and What Happens Next...
Earlier this month South Carolina experienced flooding that caused widespread devastation and destruction. Some areas of the Midlands received more then 20 inches of rain in just two days. Homes, businesses and infrastructure were destroyed, and many lives were lost. As we continue to recover and rebuild we should examine what happened and look at the next steps we can take.
First, it is important to describe the recent events in the appropriate scientific and historic context. We did not experience a 1,000 year flood. Still, some areas did receive a 1,000 year rain event (rainfall amounts that have a 0.1% chance of occurring any given year) and many new flood records were set. The Congaree River, which crested at 31.8 feet on October 4th, was only the 8th highest peak in the 100 plus years of record (equating to something between a 25 and 50 year flood). It is also important to note that the terms like 1,000 and 100 year flood are probability statements and do not indicate when we can expect a similar event to occur. To better understand this you can read this Q&A and this technical report from the USGS.
On October 6th we partnered with SouthWings to conduct aerial reconnaissance of flood impacts around the Midlands. We were able to document several issues including damaged wastewater plants, flooding in the former Green Diamond property, and the Columbia Canal breach. You can view the air photos here.
During the flood 36 dams across South Carolina failed, including at least 20 in the Midlands. You can view updates on the status of dams on DHEC's website here and a list of dam failures here. Our partners at the Gills Creek Watershed Association produced this graphic detailing the dam failures in that hard hit watershed. DHEC has issued emergency orders covering 75 dams over the past few weeks. There has also been significant discussion over how, or even if, private dams that failed will be rebuilt.
In addition to the multiple dam failures, the Columbia Canal also breached. The canal is the drinking water source for nearly 200,000 people in the Columbia area. Emergency repairs were conducted, a temporary dam has been built and work to stabilize the canal continues. The City is currently using mobile pumps in the canal and the Broad river to supply water to the treatment plant.
The flooding also caused significant sewer issues. Almost every sewer provider in the region experienced sewer overflows and multiple wastewater treatment plants (including several on the Lower Saluda) flooded and were bypassing raw sewage. There are still ongoing sewer spills in the Gills Creek/Lake Katherine area as well as near Millrace Rapid on the Saluda River.
In the wake of this disaster there are several things we can and should do to create stronger, safer and more resilient communities:
- Use FEMA's Flood Hazard Mitigation Program to implement floodplain buybacks to take people and property out of harms way.
- Strengthen local floodplain regulations.
- Improve South Carolina's dam safety program.
- Strengthen infrastructure, including roads, bridges, dams and water & sewer systems.
- Add USGS gages to improve data collection and flood warnings.