Preparing for proactive dam removal decisions

Vahedifard, Farshid; Madani, Kaveh; AghaKouchak, Amir; Thota, Sannith Kumar

doi:10.1126/science.abc9953

Cited by 12 publications

(3 citation statements)

References 2 publications

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“…These findings can inform future efforts to restore rivers by removing dams, given the growing international interest in this approach (Birnie‐Gauvin et al, 2020; Habel et al, 2020; Ibisate et al, 2016; Maxwell et al, 2021; Ravot et al, 2020; Wang & Kuo, 2016). Environmental planning of rivers, not only through dam removal but also dam renovation and revised operations, will remain a major application of fluvial geomorphology in an era of changing hydroclimate and the need for non‐fossil‐fuel energy (Chartrand, 2022; Curry et al, 2020; Guetz et al, 2022; Kondolf & Yi, 2022; Zarfl et al, 2015), as will proactively removing dams that are safety hazards (Vahedifard et al, 2020). We encourage additional research into the effects of these actions on river channels, even when geomorphic responses are not dramatic, to expand the literature base on which environmental management decisions are made.…”

Section: Discussionmentioning

confidence: 99%

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

East

Harrison

Smith

et al. 2023

Earth Surf Processes Landf

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Measuring river response to dam removal affords a rare, important opportunity to study fluvial response to sediment pulses on a large field scale. We present a before-after/control-impact study of the Carmel River, California, measuring fluvial geomorphic and grain-size evolution over 8 years, six of which postdated removal of a 32 m-high dam (one of the largest dams removed worldwide) and included 11 flow events exceeding the 2-year flood magnitude. We find that the reservoir-sediment pulse following dam removal was relatively small (97 000 ± 24 000 t over 4 years), owing to deliberate reservoir-sediment stabilization. Scaled to the size of the Carmel River watershed and compared against long-term bedrock denudation rates, the post-dam-removal sediment release was slightly less than the annualized long-term sediment export from this basin. New sediment transited >30 km to the river mouth in less than 2 years, assisted by floods 2 and 4 years after dam removal. The sediment pulse fined the downstream riverbed while causing mostly low-magnitude bed-elevation changes: commonly 0.5 to 1 m or smaller, occurring as discontinuous sediment patches or interstitial deposits, aside from the filling and subsequent partial scour of deep pools. There was no major geomorphic reset downstream from the dam site. Geomorphic changes were driven almost entirely by flow rather than by the modest increase in sediment supply, in contrast to recent examples from other large dam removals. The relatively minor disturbance caused by dam removal on the Carmel River is likely analogous to many future dam removals: a relatively small sediment pulse after deliberate limitation of reservoir-sediment erosion, and with an upstream dam remaining in place. Thus, a large dam removal need not lead to major downstream impacts.

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Section: Discussionmentioning

confidence: 99%

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

East

Harrison

Smith

et al. 2023

Earth Surf Processes Landf

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“…Dams were designed for specific flows, and upward shifts in flood regimes (Huang et al., 2020; Lee et al., 2016) mean that the probable maximum floods may be exceeded at some dams. The failure of the main spillway and partial failure of the emergency spillway at California's Oroville Dam in 2017 (Henn et al., 2020) and the complete failures of Edenville and Sanford dams in Michigan during unusually large storm runoffs in 2020 were reminders of the growing need to address the safety of aging dams despite the associated high financial costs (France et al., 2022; Vahedifard et al., 2020). Globally, the September 2023 flood disaster in Libya, where extreme rainfall resulted in the collapse of two storage dams (Washington Post, 2023), underscores the growing risk of aging and inadequately sized infrastructure.…”

Section: Figurementioning

confidence: 99%

A Watershed Moment for Western U.S. Dams

East,

Grant

2023

Water Resources Research

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The summer of 2023 is a notable time for water‐resource management in the western United States: Glen Canyon Dam, on the Colorado River, turns 60 years old while the largest dam‐removal project in history is beginning on the Klamath River. This commentary discusses these events in the context of a changing paradigm for dam and reservoir management in this region. Since the era of large dam building began to wane six decades ago, new challenges have arisen for dam and reservoir management owing to climate change, population increase, reservoir sedimentation, declining safety of aging dams, and more environmentally focused management objectives. Today we also better understand dams' benefits, costs, and environmental impacts, including some that were unforeseen and took decades to become apparent. Where dams have become unsafe, obsolete (e.g., due to excessive reservoir sedimentation), and uneconomical beyond saving, dam removal has become common. The science and practice of dam removal are accelerating rapidly, and some long‐term physical and biological response studies are now available. Removal of four hydroelectric dams on the Klamath River will be a larger and more complex project than any previous dam removal. The imminency of this project reflects a very different situation for dam and reservoir management than 60 years ago. Looking forward, dam and reservoir management in the western United States and worldwide will require continued collaboration and innovative thinking to meet a wide range of objectives and to manage water resources sustainably for future generations.

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“…In this paper we refer to the suite of actions from retaining and restoring through to full removal of a weir, as remediation. While there are a growing number of examples in literature (Birnie‐Gauvin et al, 2018) and media (see https://www.theguardian.com/environment/2022/may/16/record-number-of-dams-removed-from-europe-rivers-in-2021-aoe) about full removal of weirs, there are gaps in understanding about how weir remediation projects proceed and factors that influence why planned weir removals go ahead or not (Doyle et al, 2008; Vahedifard et al, 2020). There remains a need to consider and evaluate cases where planned weir removals have taken alternative trajectories, such as when a removal was intended but weir retention and construction of a fish pass resulted instead.…”

Section: Introductionmentioning

confidence: 99%

When unlocking rivers results in building more infrastructure: A group mental model shares lessons from weir remediation in the United Kingdom

Januchowski‐Hartley,

Thomas,

Bristol

et al. 2024

Conservat Sci and Prac

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The last several decades have seen a rise in efforts to remove weirs, but there is little research investigating how projects are carried out, potential areas for improvement, or sharing of lessons to facilitate reconnection of more rivers. The aim of the study presented here was to explore how people involved in weir remediation perceive project processes, factors that facilitate or hinder action implementation, and possible ways processes could be improved to reconnect more rivers. We carried out semi‐structured interviews with people (n = 11) who had been actively involved in weir remediation processes in the Severn River Catchment, United Kingdom, and used their responses to create a group mental model. The group mental model was created to support learning and communication about weir remediation projects between individuals and groups. We found broad agreement from those involved in creating the group mental model about weir remediation project processes and potential areas for improvement. One of the only points of divergence within the group mental model was associated with the impact of different weir remediation actions, particularly weir removal. Based on the group mental model, we set out three calls to action to reconnect more rivers in the UK. First, move beyond opportunistic projects and establish national goals and catchment‐scale plans for weir remediation. Second, reform fish passage legislation and legislate weir ownership. Doing so would support more effective remediation solutions by recognizing the diversity of fish species that reside in UK rivers and help mitigate risks from hazardous weirs through owner accountability. Third, build cross‐sector and public partnerships to encourage removal or improved fish pass designs. We direct the three calls to action to policy makers and anyone already engaged in or envisioning weir remediation projects in the UK. The calls also have potential implications and relevance to people in other countries in Europe and beyond.

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Preparing for proactive dam removal decisions

Cited by 12 publications

References 2 publications

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

A Watershed Moment for Western U.S. Dams

When unlocking rivers results in building more infrastructure: A group mental model shares lessons from weir remediation in the United Kingdom

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