Multidisciplinary Assessment Of The Removal Of A Small Run-Of-River Dam In The Southern Appalachian Mountains

Dam removals are a commonly employed tool of water resource managers for stream restoration projects. Most dam removals are performed without the accompaniment of a scientific study to evaluate their efficacy or biological consequences, and many of the ones which are studied are situated in low gradient, warmwater streams. The removal of the Ward Mill Dam on the Watauga River in the Appalachian Mountains of North Carolina provided an ideal case study for a dam removal in a moderate gradient, coolwater stream. Benthic macroinvertebrate samples were collected and sediments surveyed from 8 sites along the Watauga River for 6 months following the dam removal to identify the downstream extent and temporal persistence of changes to the benthic community. Sites further than 1 km downstream of the dam showed moderate to extreme long-lasting alterations to the median streambed particle size, but few changes to the benthic community. Sites within the former impoundment and immediately downstream of the dam experienced drastic changes to channel morphology and macroinvertebrate community structure. At 6 months post removal nearly all benthic community metrics had recovered to reference condition. This suggests that headwater streams may recover more slowly to geomorphic changes following dam removals, however benthic macroinvertebrate communities rebound quickly to refill the vacated ecological roles following the disturbance.