A timely boost in the science of dam removal and river recovery

Over a period of several months, two dozen papers on dam removal and river restoration are being published in a single edition of the online journal Frontiers in Ecology and Evolution. This tranche of papers represents a significant advance in the science behind dam removals.

The timing is superb, as publishing coincides with removal of four large dams on the Klamath River in northern California – the largest dam removal project in history. When the Klamath dams are out later this year, the river will flow freely for the first time in more than a century.

These papers were inspired by a gathering of federal, state, Tribal, and academic scientists, plus regulators and nonprofit staff, including Resources Legacy Fund staff who work on the Open Rivers Fund program. Held in the summer of 2022 and hosted by the Lower Elwha Klallam Tribe, sessions focused on assessing, sharing, and building on lessons learned in the ten years since the removal of two major dams from the Elwha River, on the Olympic Peninsula.

While reflecting on their Elwha work, conference organizers had the great wisdom to look ahead and include practitioners currently engaged in work to restore the Klamath River basin. Their presence shaped several of the conference breakout sessions, which included discussions about how best to coordinate field research efforts across different disciplines and how to streamline and focus monitoring.

The notion of synthesizing the scientific outcomes seen after a decade on the Elwha with other large dam removals in the U.S. and abroad led to this edition of Frontiers, co-edited by two Americans and two Europeans. More than 155 authors contributed to these articles, with U.S. affiliations that include five Tribes, ten government agencies, and many universities.

The spate of papers is no small blip on the radar, given the recent state of play. In 2017, not long after the Open Rivers Fund was established, a published review of the scientific literature showed that only 53 dam removals in the U.S. had peer-reviewed studies to examine their impacts. When other credible studies were considered, including academic theses and reports by state and federal agencies, that number only climbed to 103. To put these numbers in context, at the time, more than 1200 dams had been removed in the U.S. Furthermore, most of the studies were short in duration (less than four years) and had limited baseline data (1-2 years) to show conditions before removal. The authors of that 2017 literature review warned that the lack of academic support could hamper future dam removals.

In addition to the scientific and practical value of these new papers, the research collection is making for a hugely interesting trove, detailing how land, water, and biota have changed in the wake of dam removals and what factors are contributing to restoration. One paper offers a review of salmonid species in the Klamath River and the unique pathogen and disease challenges facing each, setting the stage for future monitoring and research efforts as salmon return to the Klamath Basin. Another offers a tool to predict the cost of potential dam removals in the U.S, using such factors as dam size and type, river flows, geographic region, and project complexity – this can help advocates, government agencies, and others planning level cost estimates of to prioritize their efforts.

Currently, 21 of the papers are available online with another three papers finishing the publication process. The journal guest editors are also planning a synthesis paper of findings and recommendations. The remaining papers will be available in the first half of this year.

The landing page for the Frontiers edition offers short synopses of the papers, with links and free access to each.

This leap of scientific understanding is meaningful beyond academe. For anyone with a stake in water management, fishery restoration, and healthy rivers, these new materials can be helpful in expediting planning, targeting resources, and optimizing the many benefits of dam removal and river restoration for people and wildlife.