Trends in Dam Removal: Reversing Irreversible Decisions, by Don Orth

The precautionary principle warns us not to make irreversible decisions. Yet building a dam proves to be an irreversible decision.  Someone else must deal with dam removal much later.    While dams provide services to our communities and economies, the average age of the 90,580 dams in the USA is 56 years.  Many billions of dollars are needed to repair aging and often high-hazard structures (Source).   

When I first began studying rivers in the 1970s, the idea of removing dams for purposes aside from safety would be heresy. Yet, more than 1,200 dams have been removed, especially in the Northeast, Midwest, and Pacific Northwest USA (Bellmore et al. 2017).  More than half of these were demolished in the past decade!   Understanding the effects of dam removal is limited due to the rarity of before-and-after studies of biophysical responses.  Therefore, the responses to dam removal cannot be easily generalized.  Surprisingly, in a few cases, a new river channel stabilizes relatively quickly and may even approach pre-dam morphology (see e.g., East et al. 2015).  If you wish to examine dam removals in your region, review the American Rivers dam removal database. 

 

U.S. distribution of (a) existing dams listed in the National Anthropogenic Barrier Dataset (n = 50,772); (b) removed dams from the Dam Removal Inventory Project (n = 874); (c) removed dams with before-after studies (n = 63). (Foley et al. 2017).

Dam removal science relies on the study of basic river geomorphology and ecology.  However, fewer than 10% of dam removals have been scientifically evaluated (Bellmore et al. 2017; Foley et al. 2017) and few studies examine important linkages between the physical and ecological consequences. Gordon Grant, Research Hydrologist with the US Forest Service, says “You can take a dam out all at once, or you can take it out slowly, and the consequences for the way sediment is released are profoundly different depending on how you do it.”  (Oliver and Grant 2017).  Major uncertainties exist as to the (1) degree and rate of reservoir sediment erosion, (2) excessive channel incision upstream of reservoirs, (3) downstream sediment aggradation, (4) elevated downstream turbidity, (5) drawdown impacts on local water infrastructure, (6) colonization of reservoir sediments by nonnative plants, and (7) expansion of invasive fish. These uncertainties hinder the full application of dam removal as a stream restoration strategy (Tullos et al. 2016).  Removals of the 64-m-high Glines Canyon Dam and the 32-m-high Elwha Dam were well-studied.  Here, investigators revealed that mainstem riffles were restored to cobble dominance after sediment was released and transported through the system (Peters et al. 2017).  

What’s happening in our local region? Unions and Simpkins Dam on the Patapsco River were removed in 2010 and removal of Bloede Dam, which is a complete barrier to upstream fish migration, is now underway (Harbold et al. 2015; Maryland DNR 2017).  These dam removals will provide an additional 65 miles of spawning habitat for blueback herring, alewife, American shad, hickory shad, and more than 183 miles for American eel in the Patapsco River watershed.

In Virginia, three dams were recently demolished after decades of planning and permitting.

Harvell dam was removed in 2014 from the Appomattox River, Virginia, permitting many migratory American Eel, American Shad, Alewife, Blueback Herring, and Hickory Shad to access spawning habitats over 100 miles upstream of the historic dam.   Watch the dam removal video.  

Monumental Mills Dam, built in 1816 on the Hazel River, was the 17^th dam removed in the Chesapeake Bay watershed of Virginia since 2004.  It is the most recent dam removal by the Department of Game and Inland Fisheries.  

The Pigg River power dam removal was in the works for 13 years before its removal in 2016.  This dam removal is outside the Chesapeake Bay watershed and benefits the Endangered Roanoke Logperch Percina rex as well as local paddlers. 

Roanoke Logperch.  Photo by Chris Crippen. 

The Roanoke Logperch exists in five isolated tributaries and the Pigg River population may now be able to expand with the removal of the dam.  The Roanoke Logperch does not occupy the slow, silty habitats that existed upstream from the dam. These fish feed on benthic insects that exist in clean, well-scoured habitats.   To find their prey, they often use their pointed snout to dislodge and turn over pebbles, thereby exposing their prey.   To witness this unique feeding behavior, watch this underwater video taken by Derek Wheaton.  

  

Pigg River Power Dam before (photo by USFWS) and during demolition (photo by Roanoke Times) 

Jordan’s Point Dam, an historic cotton mill dam on the Maury River near Lexington, Virginia, may be next on the removal list. Jordan’s Point Dam poses  a drowning hazard and is a barrier for fish passage. Jordan’s Point Dam is owned by the City of Lexington ,which is liable for lawsuits and must pay for repairs.  Maintenance and repair costs are more expensive than dam removal.  In June, 2017, City Council voted to remove the dam. 

Because dams change the landscape and waterscape in ways that may attract development, the removal of dams is often met with significant opposition.  This week the Millburnie Dam on the Neuse River, North Carolina, was removed.  Not all were in full agreement with the dam’s removal.   Dams create novel landscapes and waterscapes that in some cases is preferred by those growing up with the dam.  One planned Massachusett dam removal was halted as opposition grew.  One protester reflected that “You kill the dam, you are killing a part of me" (Fox et al. 2016). 

  

Migratory fish benefit from dam removals.  The American Shad and Blueback Herring now use over 28 additional miles of the Rappahannock River after the Embrey Dam was removed in 2004. Furthermore, Hickory Shad, Alewife, and Striped Bass have been documented above the Embrey Dam site, and American Eel increased in the upper watershed.  Bosher Dam on the James River, built in 1840, may still be a bottleneck for American Shad passage even though a fish passage was constructed. 

Dams removed from 1999 through 2016. Source: Caffin and Gosnell (2017). 

Dam removal trends are likely to continue as dams age and no longer serve original purposes.  Experience indicates that permitting requires work by numerous partners over a decade-long timeframe. The majority of US dam removals were privately owned, non-hydropower dams, which includes many investor-owned dams. Many of these were small and removal had minimal impacts, thereby allowing easier permitting under federal laws.  Other dams were authorized by legislative or executive actions, will prove more difficult to remove and removal will be subject to NEPA, ESA, and state water quality certification under the CWA.   

FERC relicensing is an opportunity to analyze choices as the FPA (Energy Policy Act of 2005, Public Law 109-58 § 241) recognizes that dams have a finite, useful lifespan and should be operated under the public interest (Chaffin and Gosnell 2017). Hydroelectric project owners should request an alternative licensing process (ALP) when substantial opposition to dam relicensing indicates a lengthy, mediated conflict resolution that may lead to decommissioning.  As public opposition to existing dams builds, it is important that we systematically study the effects of dam removal.  Each dam removal is a different large-scale experiment. We need to learn from each one in order to fill the gaps in our science (see below).   Restoring free-flowing rivers provides many new opportunities for connecting our youth with freshwater habitats.  

Gaps in the Science of Dam Removal (Bellmore et al. 2017)

·       Only 9% of dam removals have been described in published scientific literature.

·       No dam removal studies exist in the central U.S., and many states have few studies relative to the number of removed dams.

·       There are few studies of the smallest dam removals (those less than 2 m in height) relative to the prevalence of their removal.

·       Monitoring is generally short-term (1–2 years) and often includes little or no data prior to dam removal.

·       Fewer studies report biological and water-quality responses to dam removal relative to physical responses (e.g., sediment and flow).

·       Few holistic ecosystem-level studies exist that attempt to measure linkages among physical, water-quality, and biological responses.

Kids snorkeling in a river.  Photo: Jason Meador, Citizen Science Program Manager for Mainstream Conservation Trust. 

References

Bellmore, J.R., J.J. Duda, L.S. Craig, S.L. Green, C.E. Torgersen, M.J. Collins, and K. Vittum. 2017. Status and trends of dam removal in the United States. Wiley Interdisciplinary Reviews: Water 4:e1164.  doi: 10.1002/wat2.1164

Chaffin, B.C., and H. Gosnell.  2017. Beyond mandatory fishways: Federal hydropower relicensing as a window of opportunity for dam removal and adaptive governance of riverine landscapes in the United States.   Water Alternatives 10:819-839.     

East AE, Pess GR, Bountry JA, Magirl CS, Ritchie AC, Logan JB, et al. 2015. Large-scale dam removal on the Elwha River, Washington, USA: River channel and floodplain geomorphic change. Geomorphology 228:765–86. https://doi.org/10.1016/j.geomorph.2014.08.028

Foley, M.M. and ten coauthors. 2017. Landscape context and the biophysical response of rivers to dam removal in the United States.  PLOS ONE https://doi.org/10.1371/journal.pone.0180107  

Fox, C.A., F.J. Magilligan, and C.S. Sneddon. 2016. “You kill the dam, you are killing a part of me”: Dam removal and the environmental politics of river restoration.  Geoforum 70:93-104.  

Harbold, W., J. Kilian, and P. Graves.  2015.  Patpsco River dam removal study: Assessing changes in American Eel distribution and aquatic communities, 2013-2014.  Maryland Department of Natural Resources, Annapolis.   

Magilligan F, Graber B, Nislow K, Chipman J, Sneddon C, Fox C. River restoration by dam removal: Enhancing connectivity at watershed scales. Elementa 2016:4.

Oliver, M., and G. Grant. 2017. Liberated rivers: lessons from 40 years of dam removal. Science Findings 193. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 5 p.

Peters, R.J., M. Liermann, M.L. McHenry, P. Bakke, and G.R. Pess. 2017.  Changes in streambed composition in salmonid spawning habitat of the Elwha River during dam removal. Journal of the American Water Resources Association 53:871-885. DOI: 10.1111/1752-1688.12536

Tullos, D.D., M.J. Collins, J.R. Bellmore, J.A. Bountry, P.J. Connolly, P.B. Shafroth, and A.C. Wilcox. 2016. Synthesis of common management concerns associated with dam removal. Journal of the American Water Resources Association 52:1179-1206. DOI: 10.1111/1752-1688.12450