Assessing the Pre-Dam Removal Ecological Functions of Blackwater Creek, 90 Years after the Construction of College Lake Dam: A High Hazard Dam

Brandon Alderman, Senior Stream Restoration Designer, AECOM

Erin Hawkins, CFM, Water Quality Manager, City of Lynchburg Department of Water Resources

Aging infrastructure and impacts from climate change have recently accelerated the need for maintenance and demolition of dams across the country. The College Lake Dam in the City of Lynchburg, Virginia is a local example of the threat that aging, outdated dams can pose to public safety and river health. In the last 50 years, over 1,400 dam removals have occurred in the United States, and the number of dams removed per year is increasing. Dams are removed for many reasons including public safety, operating and maintenance costs, loss of function, and recovery of ecosystems. When the College Lake Dam was constructed in 1934 it was not anticipated, nor widely known, what the ecological impacts associated with installing a dam within a riverine ecosystem would be. The Blackwater Creek watershed evolved from a connected lotic (moving) to an isolated lentic (standing) ecosystem, resulting in disruptions to macroinvertebrate habitat, fish passage, sediment transport and negatively impacting the water’s turbidity, bacteria levels, temperature, and dissolved oxygen.

College Lake Dam is classified as high hazard-potential because the spillway size was inadequate, and a dam failure could result in loss of life, so in 2018 the City initiated the process of removing the dam. Goals of the dam removal project include alleviating catastrophic flood potential and restoring a thriving ecosystem within the Blackwater Creek watershed. One of the many desired outcomes of the project is devolution of the Blackwater Creek aquatic and riparian ecosystem back to a riverine environment.

During the last 3 years the City of Lynchburg and AECOM have performed various functional assessments on the stream and wetland habitat upstream and downstream of the existing dam to provide a baseline for ecosystem health prior to removal of the dam. The results will not only support the need for dam removal but will also encourage future dam research.  The nearby University of Lynchburg faculty and students can continue to study the effects of the College Lake Dam removal and the rate at which the Blackwater Creek watershed reaches a new dynamic equilibrium. The results of the functional assessments also allowed for the engineering design team to use nature-based techniques that will promote an increase in wetland habitat,  fish passage, floodplain re-connection, diverse vegetation, and riffle/pool habitat all of which will lead to an increase in aquatic functions and values.

Author Bio

Mr. Alderman has over 13 years of experience designing, assessing, monitoring, and implementing various stream and wetland establishment, restoration, and enhancement projects. He is the Senior Stream Restoration Designer for AECOM’s Southeast region and technical project lead for the design of the College Lake Dam removal project. Mr. Alderman has received extensive training in natural stream channel design and has completed all four levels of Dave Rosgen’s natural stream design courses.

Ms. Hawkins has a diverse background in environmental issues including urban stormwater management. Erin currently works for the City of Lynchburg as the Water Quality Manager and is project manager for the College Lake Dam removal project. Her primary duties include managing the City's MS4 Chesapeake Bay stormwater program and review of floodplain mapping.