Assessing stream restoration potential of recreational enhancements on an urban stream, Springfield, Ohio

Abstract The stream restoration potential of recreational modifications made to lowhead dams on an urban reach of Buck Creek, in Springfield, Ohio, is dependent on constraints imposed by the urban infrastructure on stream grade. A privately led initiative to improve the recreational potential of a 9 km reach of Buck Creek and its tributary Beaver Creek includes the modification of four lowhead dams. The hydraulic heights of these dams will be replaced with a series of v-shaped drop structures engineered to create hydraulics conducive to kayak play. The drop structure is a constructed channel constriction composed of a hard step in the long stream profile immediately upstream of a scour pool, forming a morphologic sequence of constriction, step, and pool. In this study, we assess the potential benefits of these changes for urban stream restoration. Two of the dams have been modified to date. Stream quality, as measured by the qualitative habitat evaluation index (QHEI), dissolved oxygen of surface and substrate water, and the pollution tolerance index (PTI), increased at the Snyder Park site but decreased at the Art Museum site. Stream quality increased at the Snyder Park site, where stream grade could be lowered upstream of the lowhead dam, but decreased at the Art Museum site, where grade upstream of the lowhead dam had to be maintained because of water and wastewater utilities buried in the channel bed. Where stream grade is lowered in the former impoundment, sand and gravel deposits upstream of the constriction are not embedded with finer particles and organic matter. Increased QHEI values, particularly the substrate metric, and greater abundance and diversity of pollution-intolerant macroinvertebrates, supported by higher dissolved oxygen in the substrate water, characterize the Snyder Park site. At the Art Museum site, the v-shaped constriction increased the upstream impounded area. The substrate has become embedded with fine sands, silts, and organics, lowering QHEI values, dissolved oxygen is critically low in the substrate, and macroinvertebrate populations are more pollution-tolerant. The results highlight the significance of stream grade if stream restoration is to be incorporated into the engineering design of in-stream recreational features.