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
AECOM
Roanoke, VA
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 The College Lake Dam in the City of Lynchburg (City), Virginia, is an example of the threat that aging, outdated dams can pose to public safety and river health. 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. As development in the watershed continued, increases in stormwater runoff led to rapid accumulation of sediment and nutrients in the lake, reducing the lake’s storage and aquatic function.
College Lake Dam is classified by Virginia DCR as high hazard potential, and a dam failure could result in downstream loss of life. Goals of the dam removal project include alleviating catastrophic flood potential and restoring a thriving ecosystem within the Blackwater Creek watershed.
Very few dam removals have been studied for ecological functions, and even fewer include pre-dam removal baseline data to support future research. During the last 3 years, AECOM has 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 support the value of dam removal and also encourage future dam research. Nearby University faculty and students will continue the work completed by AECOM to study the effects of the dam removal and the rate at which the Blackwater Creek watershed approaches a new dynamic equilibrium. The results of the completed 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 and terrestrial wildlife functions and values.
About Brandon Alderman
Brandon Alderman has over 15 years of experience designing, assessing, monitoring, and implementing various stream and wetland restoration projects. As AECOM’s National Practice Leader for stream restoration, he leads stream and wetland design of ecosystem restoration, stream bank stabilization, dam removal, outfall restoration, and mitigation banking and permittee responsible mitigation projects. He also provides construction oversite and management of implementation of ecological restoration projects. Brandon has received extensive training in natural stream channel design and has completed all four levels of Dave Rosgen’s natural stream design courses. Brandon has been involved in the design and construction of over 350,000 linear feet of stream restoration activities and establishment of over 250 acres of wetlands in 11 different states throughout the Eastern United States and Midwest Regions.
