Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rivers recover natural conditions quickly following dam removal

09.10.2014

A study of the removal of two dams in Oregon suggests that rivers can return surprisingly fast to a condition close to their natural state, both physically and biologically, and that the biological recovery might outpace the physical recovery.

The analysis, published by researchers from Oregon State University in the journal PLOS One, examined portions of two rivers – the Calapooia River and Rogue River. It illustrated how rapidly rivers can recover, both from the long-term impact of the dam and from the short-term impact of releasing stored sediment when the dam is removed.


Removing Savage Rapids Dam

Most dams have decades of accumulated sediment behind them, and a primary concern has been whether the sudden release of all that sediment could cause significant damage to river ecology or infrastructure.

However, this study concluded that the continued presence of a dam on the river constituted more of a sustained and significant alteration of river status than did the sediment pulse caused by dam removal.

“The processes of ecological and physical recovery of river systems following dam removal are important, because thousands of dams are being removed all over the world,” said Desirée Tullos, an associate professor in the OSU Department of Biological and Ecological Engineering.

“Dams are a significant element in our nation’s aging infrastructure,” she said. “In many cases, the dams haven’t been adequately maintained and they are literally falling apart. Depending on the benefits provided by the dam, it’s often cheaper to remove them than to repair them.”

According to the American Society of Civil Engineers, the United States has 84,000 dams with an average age of 52 years. Almost 2,000 are now considered both deficient and “high hazard,” and it would take $21 billion to repair them. Rehabilitating all dams would cost $57 billion. Thus, the removal of older dams that generate only modest benefits is happening at an increasing rate.

In this study, the scientists examined the two rivers both before and after removal of the Brownsville Dam on the Calapooia River and the Savage Rapids Dam on the Rogue River. Within about one year after dam removal, the river ecology at both sites, as assessed by aquatic insect populations, was similar to the conditions upstream where there had been no dam impact.

Recovery of the physical structure of the river took a little longer. Following dam removal, some river pools downstream weren’t as deep as they used to be, some bars became thicker and larger, and the grain size of river beds changed. But those geomorphic changes diminished quickly as periodic floods flushed the river system, scientists said.

Within about two years, surveys indicated that the river was returning to the pre-removal structure, indicating that the impacts of the sediment released with dam removal were temporary and didn’t appear to do any long-term damage.

Instead, it was the presence of the dam that appeared to have the most persistent impact on the river biology and structure – what scientists call a “press” disturbance that will remain in place so long as the dam is there.

This press disturbance of dams can increase water temperatures, change sediment flow, and alter the types of fish, plants and insects that live in portions of rivers.  But the river also recovered rapidly from those impacts once the dam was gone.

It’s likely, the researchers said, that the rapid recovery found at these sites will mirror recovery on rivers with much larger dams, but more studies are needed.

For example, large scale and rapid changes are now taking place on the Elwha River in Washington state, following the largest dam removal project in the world. The ecological recovery there appears to be occurring rapidly as well. In 2014, Chinook salmon were observed in the area formerly occupied by one of the reservoirs, the first salmon to see that spot in 102 years.

“Disturbance is a natural river process,” Tullos said. “In the end, most of these large pulses of sediment aren’t that big of a deal, and there’s often no need to panic. The most surprising finding to us was that indicators of the biological recovery appeared to happen faster than our indicators of the physical recovery.”

The rates of recovery will vary across sites, though. Rivers with steeper gradients, more energetic flow patterns, and non-cohesive sediments will recover more quickly than flatter rivers with cohesive sediments, researchers said.

This research was supported by the Oregon Watershed Enhancement Board, the National Oceanic and Atmospheric Association and the National Marine Fisheries Service. It was a collaboration of researchers from the OSU College of Agricultural Sciences, College of Engineering, and College of Science.

The study this story is based on is available online: http://bit.ly/1rdQ4wL

About Oregon State University:

OSU is one of only two U.S. universities designated a land-, sea-, space- and sun-grant institution. OSU is also Oregon’s only university to hold both the Carnegie Foundation’s top designation for research institutions and its prestigious Community Engagement classification. Its more than 26,000 students come from all 50 states and more than 90 nations. OSU programs touch every county within Oregon, and its faculty teach and conduct research on issues of national and global importance.

 

Desirée Tullos | Eurek Alert!
Further information:
http://oregonstate.edu/ua/ncs/archives/2014/oct/rivers-recover-natural-conditions-quickly-following-dam-removal

More articles from Ecology, The Environment and Conservation:

nachricht How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>