Independent Science Team Completes Review of Restoration Projects Trinity River
May 29, 2014
For Release On: May 29, 2014
Independent Science Team Completes Review of Trinity River Restoration Projects
WEAVERVILLE, Calif. – The Bureau of Reclamation and the U.S. Fish and Wildlife Service announce that the Science Advisory Board of the Trinity River Restoration Program (Program or TRRP) completed its review of mainstem-river channel rehabilitation projects that have occurred on the Trinity River between 2005 and 2010.
Conclusions and recommendations for carrying out Phase 2 of the Program’s channel rehabilitation strategy are included in the report, which is available at www.trrp.net. The review and recommendations in the report represent the culmination of over two years of analysis and synthesis by SAB members and their support contractors.
The SAB relied on reports and data collected by technical experts within the TRRP over several years. In addition, the SAB issued a draft report in November 2013 and solicited comments from TRRP partners. These comments have been addressed by the SAB, and the final version of the report has been revised accordingly.
The report concluded that substantial progress has been made and that rehabilitation projects are creating habitat and a more complex river, but the effects on fish production are unclear given limited data sets available to date. The SAB has identified areas where the TRRP can improve, specifically by tightly integrating activities around the Program’s overarching goal of fishery restoration.
“I thank the Science Advisory Board for their work in reviewing the important restoration projects that have occurred in the mainstem Trinity River,” said Robin Schrock, Trinity River Restoration Program Executive Director. “The Science Advisory Board has identified areas where the program can improve, and we look forward to working with our partners to ensure we carry out these important recommendations, which we wholeheartedly agree will help advance the recovery of this important fishery.”
The TRRP consists of the following partner agencies: the Hoopa Valley Tribe, the Yurok Tribe, Trinity County, the California Resources Agency (Department of Water Resources and Department of Fish and Wildlife), the U.S. Forest Service, the National Marine Fisheries Service, the Bureau of Reclamation and the U.S. Fish and Wildlife Service.
Below is a Summary of Recommendations from the TRRP’s SAB:
In going forward with Phase 2 of channel rehabilitation projects, the SAB recommends the following:
• Develop a Decision Support System, which is a series of linked physical and biological models that will allow the Program to: predict site and system response to alternative management actions in relation to the Record of Decision and stakeholder objectives; make such predictions in a timely fashion (ahead of monitoring results); focus and refine monitoring efforts; and provide a necessary tool for adaptive management. Additionally, it will help to better structure and integrate Program activities and increase the defensibility and transparency of management actions. The proposed DSS will shift the Program from the current focus on means objectives (i.e., creating fish rearing habitat) toward a focus on the fundamental objective (restoring in-river fish production) through a better understanding of the roles and synergistic effects of Program actions (management of flow, temperature, sediment and channel morphology) on fish production over space and time.
• Use the DSS to critically assess channel rehabilitation actions needed to achieve fish population objectives. What habitats are needed and in which locations of the river to achieve objectives at local and system scales in concert with other Program activities (management of flow, temperature and sediment)?
• Use the DSS to formally test the foundational hypothesis that a dynamic, complex channel can be created and that, together with other Program activities, will restore fish populations.
• Use the DSS to critically evaluate the change in design strategy that has occurred (i.e., minimal vs. intensive mechanical intervention). A key factor to quantify in this regard is the response time for creating desired channel conditions and fish populations. The desired response time greatly influences the type of management actions (i.e., size, frequency and degree of manipulation). Similarly, consider the potential benefits of several large projects vs. many small ones. Are large channel rehabilitation projects more effective at meeting Program objectives than small ones, and which objectives are best met by each approach?
• Phase 2 projects should continue to use opportunistic design strategies to promote dynamic alluvial reaches where possible, while working with local constraints on channel morphology in this semi-alluvial river. However, because the river is less alluvial than originally envisioned, a dichotomy of project designs may be needed (i.e., those that specifically drive geomorphic processes over time, producing dynamic habitat response in alluvial sections of the river vs. building static habitat features intended to persist over time in less alluvial reaches).
• Continue to use a diversity of design elements in Phase 2 projects. Although the effectiveness of specific rehabilitation projects and design elements could not be evaluated in terms of fish production due to data limitations, the various design elements all contribute to increased juvenile fish habitat and reduce habitat bottlenecks observed at modest flows. Side channels offer a potential means for maximizing habitat availability but may be more prone to aggradation, so their potential benefits depend on the dynamic longevity of such features, and they should only be located in reaches that have potential for anabranching morphology. In addition, diversity of design elements and associated habitats is recommended as this may promote species resilience to changing environmental conditions.
• Design objectives for Phase 1 projects initially invoked the Program’s ROD and Integrated Assessment Plan objectives without demonstrating how they would be achieved. In contrast, recent efforts are more defensible—employing mechanistic, predictive models to evaluate as-built changes, design alternatives and site evolution. Phase 2 projects should continue these more rigorous efforts in combination with a DSS and fish production model.
• Incorporate into study plans metrics for quantifying juvenile fish numbers, growth and health as major components of fish population modeling for estimating annual in-river fish production, and examine the role of annual water temperature regimes with regard to fish growth and general health across years. As the river system evolves in response to post-ROD management actions, the Program’s foundational hypothesis of juvenile rearing habitat being the primary limiting factor may be expected to change. Use the DSS and fish population modeling as a surrogate for the actual fish population to periodically examine alternative population limiting hypotheses. For example, (1) juvenile fish production vs. adult escapement and (2) carrying capacity of physical habitat vs. water temperature and its effect on fish growth and health.
• Better articulate program and stakeholder objectives and explicitly identify the relations among objectives. The current management actions tend to address means objectives (e.g., create habitat), rather than fundamental objectives (e.g., increase fish populations). As a result, disagreement about science is often conflated with disagreement about objectives, significantly hindering scientific advancement. Similarly, scientific disagreement should be explicitly incorporated into the process using alternative models that represent the alternative scientific hypotheses about system dynamics.
• Adopt rigorous hypothesis testing for Program activities and scientific investigations, which is critical for improving the effectiveness of such actions. Treat rehabilitation projects as opportunities to formally test the hypotheses and goals articulated by the ROD and IAP.
• Integrate workgroup activities to better achieve Program objectives. The workgroups include interdisciplinary membership but need better coordination and exchange of information across workgroups (development of a DSS should facilitate this integration). In addition, the internal review process of Program reports should be streamlined to disseminate findings more rapidly. Publication in peer-review journals also is encouraged to both have peer input and to better disseminate Program findings.
• Develop a system-wide, one-dimensional sediment routing model in concert with existing sediment transport monitoring and additional tracer studies to more finely resolve the sediment budget and the fate of gravel augmentation.