Puget Sound Stream Benthos

Boeing Creek - Hidden Lake Dam Removal Biomonitoring, University of Washington

Small dam removals are increasing across the United States and globally to address issues of freshwater health and fish passage. The removal of a dam typically causes an immediate but often temporary pulse disturbance via processes of sediment exposure, erosion and redistribution, but in the longer term, dam removal is thought to lead to ecological improvement. Expectations of an ecological improvement are often integral to decisions of removal, yet scientific knowledge of actual organism responses and their controlling factors are surprisingly limited. Case studies of macroinvertebrate responses to dam removal indicate highly spatiotemporally dynamic patterns, with initial responses frequently negative including decreased densities and taxa richness, and different ensuing longer-term recovery trends. This study was interested in assessing the short- and long-term effects of the Hidden Lake dam removal (2022) on macroinvertebrate communities of Boeing Creek. A classic Before-After-Control-Impact study design was deployed where macroinvertebrate communities were monitoring both before and after dam removal at locations both downstream (lower Boeing Creek) and upstream (upper Boeing Creek) of Hidden Lake. Analyses were conducted to determine macroinvertebrate responses and recovery to dam removal using the Puget Lowlands Benthic Index of Biotic Integrity (B-IBI) and other measures of taxonomic and functional (trait) biodiversity.

Contact information
Julian D. Olden
School of Aquatic and Fishery Sciences
University of Washington