Resetting Oregon’s floodplains to rehabilitate native fish habitats

Abstract

Human settlement has historically degraded floodplains and valley floors by introducing structures, such as dikes and dams, to control water flow and steer flooding away from areas where people live and work. In the past decade, land managers in the Pacific Northwest have devised projects to reconnect rivers with their floodplains. They’ve designed these projects to increase the abundance and diversity of freshwater organisms by increasing habitat complexity.

To further understand this new rehabilitation method, scientists from the USDA Forest Service Pacific Northwest Research Station investigated the short- and long-term effects of these floodplain projects, which varied in novelty, size, and intensity. They found that rehabilitation efforts increased wetted area during summer low-flows and resulted in a more complex environment that supported more aquatic life throughout the floodplain. They also found that in the first years after restoration, before shrubs and vegetation had recovered, stream temperatures could be higher and more varied than before restoration.

The State of Oregon, local watershed councils, and the National Forest System are using data from comprehensive monitoring of these floodplain rehabilitation efforts to support further projects designed to increase ecosystem resilience in floodplains.

Citation

Vizcarra, Natasha; Flitcroft, Rebecca. 2024. Resetting Oregon’s floodplains to rehabilitate native fish habitats. Science Findings 264. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p.