This document reports on findings, conclusions and recommendations derived from scientific literature and knowledge regarding the effectiveness of tide gate removal or upgrade in improving conditions for Oregon’s native migratory fish species, particularly salmonids, and other plant and animal species that utilize estuarine ecosystems. The project was commissioned by the Oregon Watershed Enhancement Board (OWEB) to foster better understanding of the effectiveness of their past investments in estuary habitat restoration involving tide gates, and to aid in targeting future investments. This will be especially important because many less-complicated projects (e.g. those on public land, smaller, single-action projects, those with consensus on land use) have already been completed, and restoration efforts are becoming increasingly complex and resource intensive. Additionally, restoration actions and benefits can vary considerably according to local conditions. Thus, key questions going forward involve project prioritization and design to achieve maximum return on investments in an environment where demand for projects exceeds available resources. Users of this information may include applicants submitting tide gate and estuary restoration proposals to OWEB, reviewers of these proposals, other OWEB staff, and the OWEB Board of Directors.
The project is premised on the assumption that the ecological effects of existing tide gates are understood well enough to make estuary restoration involving removal or upgrades of aging tide gates generally worthwhile in terms of improved fish passage and estuarine habitat conditions. However, the data on tide gate restoration (removal or upgrade) was not cohesively synthesized. To address this information gap we focused our work around the following four tasks.
Task 1: A review of literature pertaining to tide gate removals and upgrades;
Task 2: Summary and review of completed, primarily OWEB-funded tide gate removal and/or upgrade projects and associated effectiveness monitoring;
Task 3: Summary and review of completed tide gate removal and/or upgrade projects and associated effectiveness monitoring not funded primarily by OWEB; and
Task 4: Summary and synthesis, including findings and recommendations.
Souder, J.A., L.M. Tomaro, G.R. Giannico and J.R. Behan. 2018. Ecological Effects of Tide Gate Upgrade or Removal: A Literature Review and Knowledge Synthesis. Report to Oregon Watershed Enhancement Board. Institute for Natural Resources, Oregon State University. Corvallis, OR. 136 pp. Submitted to Oregon Watershed Enhancement Board in fulfillment of grant #217-8500-14090.