FLOODPLAINS

The South River is a mixed alluvial-bedrock river composed of sand, gravel, and numerous outcrops of exposed bedrock (2). The floodplain of the watershed is continuously shaped by erosion or a buildup of sediment (1). Over time, there has been a significant increase in agricultural land use and other anthropogenic modifications (2). Urban development along the river and implementation of 13 mill dams have greatly impacted the rate of erosion and sedimentation. Although, by 1974, the dams had all been removed because of failure due to natural events. The landscape has also been altered by the removal of large trees and creation of bridges across the river. Unfortunately, the mercury that was released by DuPont contaminated the floodplain soils. Erosion of the South River’s riverbanks accounts for 96% of the annual mercury load that is transported downstream, as shown in the image above. This hazardous release of mercury into the river is predicted to continue for decades.

 

1. FEMA Flood Map Service Center: Hazus. FEMA Flood Map Service Center | Hazus. (n.d.). Retrieved from https://msc.fema.gov/portal/resources/hazus  

 

2. Kelly, A. (2021). Pools and riffles in the bedrock-alluvial south river, VA are systematically different than pool-riffle sequences in alluvial rivers. Retrieved from https://www.proquest.com/dissertations-theses/pools-riffles-bedrock-alluvial-south-river-va-are/docview/2591200697/se-2