Geology topics

Roger J. Peters

Publications and source records attributed to Roger J. Peters.

3 recordsLinked to original sources

USGS2026

From sediment pulse to ecological recovery: A nine-year study of benthic macroinvertebrate response to Elwha River dam removal

Large dam removals are increasingly important river restoration actions, but long-term ecological responses remain poorly understood, especially for removals involving large sediment releases. We evaluated benthic macroinvertebrate (BMI) responses following removal of the Elwha and Glines Canyon dams on the Elwha River, Washington, USA. At the time of removal (2011–2014), these were the largest dams to be dismantled worldwide. Dam removal reconnected over 90% of the watershed to anadromous fish, released more than 20 megatonnes of reservoir sediment downstream, and restored natural sediment and wood transport processes. Using nine years of monitoring data spanning periods before, during, and after dam removal, we quantified changes in BMI density, taxa richness, and community composition across five river sections exposed to different combinations of sediment disturbance, reservoir succession, and fish reintroduction. Sediment release substantially altered downstream physical habitat and was accompanied by pronounced declines in BMI density and richness, particularly downstream of both dams. Density declined by up to 95% during active dam removal but rebounded to near baseline levels within three years after peak sediment transport subsided. In contrast, taxa richness and community composition remained significantly altered three years after dam removal, with persistent reductions particularly evident among Trichoptera and long-lived taxa. Fine sediment was the environmental variable most strongly associated with changes in BMI community structure. Our results demonstrate that large dam removal can cause severe but largely transient reductions in BMI abundance while producing longer-lasting changes in taxonomic diversity and community composition. These findings highlight the importance of distinguishing between numerical and ecological recovery and suggest that recovery trajectories following large dam removal extend well beyond the period of active sediment release.

Washington↗

USGS2024

Challenges of implementing a multi-agency monitoring and adaptive management strategy for federally threatened Chinook salmon and steelhead trout during and after dam removal in the Elwha River

Adaptive management, a process of planning, implementing, and evaluating management strategies, is often recommended for monitoring ecological systems. However, few examples of successful implementation and retrospective case studies exist. We provide a case study of adaptively managing hatchery-assisted protection and recovery for Chinook salmon ( Oncorhynchus tshawytscha ) and winter steelhead trout ( O. mykiss ) during and after the removal of two large mainstem dams in the Elwha River, WA. We summarize key aspects of the monitoring and adaptive management plan over the last decade and highlight successes, challenges, and complications during the plan’s implementation. The Elwha Monitoring and Adaptive Management Guidelines included a trigger-based system for moving through four phases of recovery that included preservation, recolonization, local adaptation, and viable natural population, each with differing levels of hatchery production as the management actions. The monitoring component of the plan has been very successful, providing critical data to guide management actions that otherwise may not have occurred and, opportunistically, provided data for other native species in the Elwha River. Implementing adaptive management provided mixed results and was at times hindered by divergent management goals among project partners, the inflexibility of the Endangered Species Act regulatory requirements as implemented for this project, and conflicting information among guidance documents. We learned that some metrics and triggers in the plan were ill-defined or too difficult to measure in the field. In some cases, the performance indicators and/or triggers were successfully modified to incorporate what was learned; however, in other cases, we were unable to revise the values due to differing opinions among partners. The ability to reach consensus on revised triggers appeared to be influenced by the recovery trajectory of the species involved. The implemented adaptive management strategy resulted in substantial collaboration and learning, which resulted in revised management strategies, but was imperfect. Sufficient long-term funding is necessary to implement a well-designed monitoring program and could benefit from including a defined leadership position to shepherd and facilitate a multi-stakeholder adaptive management program. Additionally, incorporating adaptive management into legally binding conditions under the Endangered Species Act is feasible, but requires substantial pre-planning in close coordination with regulatory agencies.

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USGS2021

Reconnecting the Elwha River: Spatial patterns of fish response to dam removal

The removal of two large dams on the Elwha River was completed in 2014 with a goal of restoring anadromous salmonid populations. Using observations from ongoing field studies, we compiled a timeline of migratory fish passage upstream of each dam. We also used spatially continuous snorkeling surveys in consecutive years before (2007, 2008) and after (2018, 2019) dam removal during summer baseflow to assess changes in fish distribution and density over 65 km of the mainstem Elwha River. Before dam removal, anadromous fishes were limited to the 7.9 km section of river downstream of Elwha Dam, potamodromous species could not migrate throughout the river system, and resident trout were the most abundant species. After dam removal, there was rapid passage into areas upstream of Elwha Dam, with 8 anadromous species (Chinook, Coho, Sockeye, Pink, Chum, Winter Steelhead, Summer Steelhead, Pacific Lamprey, and Bull Trout) observed within 2.5 years. All of these runs except Chum Salmon were also observed in upper Elwha upstream of Glines Canyon Dam within 5 years. The spatial extent of fish passage by adult Chinook Salmon and Summer Steelhead increased by 50 km and 60 km, respectively, after dam removal. Adult Chinook Salmon densities in some previously inaccessible reaches in the middle section of the river exceeded the highest densities observed in the lower section of the river prior to dam removal. The large number (>100) of adult Summer Steelhead in the upper river after dam removal was notable because it was among the rarest anadromous species in the Elwha River prior to dam removal. The spatial extent of trout and Bull Trout remained unchanged after dam removal, but their total abundance increased and their highest densities shifted from the lower 25 km of the river to the upper 40 km. Our results show that reconnecting the Elwha River through dam removal provided fish access to portions of the watershed that had been blocked for nearly a century.

Washington↗