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Impacts of stream daylighting on habitat fragmentation - Examining unitended consequences in an urban stream restoration in Cincinnati, OH
Citation:
Hintz, C., M. Booth, T. Newcomer-Johnson, K. Fritz, AND I. Buffam. Impacts of stream daylighting on habitat fragmentation - Examining unitended consequences in an urban stream restoration in Cincinnati, OH. 2021 Ohio River Basin Alliance Summit and Ohio River Basin Consortium for Research and Education Symposium, Crestview Hills, KY, October 06 - 08, 2021.
Impact/Purpose:
The burial of streams in culverts is a common practice in densely populated urban areas. In this study, we address the ecological impact of stream burial in two urban streams that include long (>100 m) culvert reaches in Cincinnati, OH. While our work focuses on urban streams, this work is of general interest because this work demonstrates how different stream ecosystem parameters transition in response to abrupt changes within the stream channel and adds to the body of work regarding how streams respond to changes in surrounding land use. This is the first study to longitudinally characterize the impacts of culverts, and the study has management implications which could inform current stream monitoring and future stream restoration work.
Description:
Urbanization, and specifically, stream burial negatively impacts lotic waters ranging from headwater streams to large rivers. Stream burial changes key drivers of stream ecosystems – eliminating light, altering physical habitat within the buried reach, and reducing basal resources and macroinvertebrates leading to increased habitat fragmentation. A goal of restoration projects is often to improve habitat within urban streams and culvert removal, aka, “daylighting” is a type of restoration that may lift habitat, improve water quality, and help control stormwater. We evaluated how daylighting (>100 m length) and subsequent channel restoration has influenced habitat fragmentation in an urban stream within Cincinnati, OH, by using a before-after-control-impact (BACI) study design. In particular, we are estimating near-term impacts on physical habitat characteristics, stream water physiochemistry, periphyton biomass, and macroinvertebrate density and diversity. Within the first 12 months of monitoring post-restoration, the newly daylighted reach experienced substantial seasonal drying increasing habitat fragmentation. Drying has reduced periphyton biomass in the newly daylighted channel when compared to the “before” period – both in comparison to the upstream reach and formerly culverted reach. Additionally, channel morphology has continued to evolve through the monitoring period altering substrate size. Although reduced flow connectivity was an unintended short-term consequence of this restoration, long-term project effectiveness remains unclear, as evolution of the stream channel and riparian regrowth is ongoing.
