2023 Top Project: Stream restoration mitigates flooding, improves water quality

The College Down Stream Restoration Project planned to mitigate flooding and bank erosion along a section of the stream located within the College Downs Subdivision of Rock Hill, South Carolina. The neighborhood was developed in the late 1960s and had experienced creek flooding and bank erosion ever since. Heavy rainfall would cause increased bank erosion as well as flooding of King Drive and surrounding homes.

The restoration project sought to reduce the frequency of flooding, and improve water quality by reducing streaming velocity and eliminating downstream bank erosion. The project work included removing excess soil in overbank areas to create flood benches and additional storage.

The project began in spring of 2021, where city crews buried existing aerial power lines in the project area. Next, they began excavation of flood benches along the creek to minimize flooding by lowering the water surface elevation.

A significant challenge over the course of the project was frequent rainfall. Each rain event would essentially halt construction for several days to prevent sediment transport. In the end, the project converted about 1,100 feet of overhead electrical lines underground, restored 1,200 feet of stream bank, removed about 2,200 cubic yards of material from the floodplain, and planted 1,100 live states and 40 trees along the creek.

The project was completed in the spring of 2022, but receives ongoing maintenance after each flood event. The work has greatly reduced water levels, allowing King Drive to remain passable during flood events. The city is discussing a second project phase with York County, which would involve roughly 4,000 feet of stream resto- ration immediately downstream to further mitigate flooding.