Evaluating large wood additions as a scalable method of urban stream restoration
Urban streams suffer from erosion and habitat loss, yet conventional restoration is costly and limited in scale. This study tested large‑wood additions in an urban headwater stream in Cincinnati, Ohio, using a before‑after‑control‑impact design. While stable wood jams rapidly increased pool habitat, most structures were frequently mobilized by high‑flow events. Large wood did not reduce bed‑mobilization probability but did shorten sediment‑transport distances. These results show that large‑wood additions can enhance habitat but require better understanding of stability and site conditions to guide effective, scalable urban‑stream restoration.
Subject Tags
- Rivers
- Habitat restoration
Abstract
Urbanization is associated with increased erosion and habitat homogenization in stream ecosystems. This habitat degradation often has biological consequences, such as decreased species richness. Conventional stream restoration practices are costly, and projects are limited to small areas with easy access. A scalable, low-cost method of stream restoration is needed to address the widespread degradation occurring in urban streams. Large wood (LW) is an important element in stream ecosystems that is typically abundant in forested watersheds but scarce in urban streams. LW can reduce water velocities, generate pool habitat, decrease erosion, and provide cover for aquatic organisms. In this study, we performed experimental LW installations to assess the capacity of LW restoration to improve habitat and reduce sediment transport in an urban headwater stream in Cincinnati, Ohio. We tracked the geomorphic effects of these installations using a before-after-control-impact study design in four 60-m reaches, two treatment and two control, over a 1.5-year period to investigate the following questions: (1) Will unanchored LW additions remain stable in a flashy urban stream? (2) Will LW additions increase the availability of pool habitat? (3) Will wood additions increase bed stability and modify sediment size distributions? We found that LW installations rapidly increased pool habitat availability (size) around stable jams, but a majority of the LW jams were frequently mobilized and reconfigured by high-flow events. LW additions had no significant impact on the probability of stream bed mobilization, likely due to the instability of LW; however, the distance particles traveled once mobilized significantly decreased. While LW additions can increase the availability of pool habitat in urban headwater streams, further investigation is needed to understand the stability of such structures and the environmental context where these additions will be most beneficial.
Citation
Grap, P., Matter, S. F., Lehmann, A., Ward, D., & Booth, M. T. (2025). Evaluating Large Wood Additions as a Scalable Method of Urban Stream Restoration. River Research and Applications, 41(9), 2032-2051. https://doi.org/10.1002/rra.70007
TNC Authors
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Adam Lehmann
Central Ohio Water Manager
The Nature Conservancy
Email: adam.lehmann@tnc.org