Reclamation has developed a new, cost-effective solution to what has been a problematic maintenance issue for the agency and its customers. 

The new technology will help prevent the condition in which the downstream, recirculating flow of water can draw sand, gravel, rock and other abrasive materials against the concrete surface of a dam structure.  When the water becomes turbulent it can pound the dam surface with abrasive materials and cause damage rapidly.  The process is called “stilling basin abrasion.”

The top graphic is a representation of abrasion damage caused by a recirculating flow pattern in a stilling basin. The bottom graphic shows how a flow deflector improves the flow pattern, thus preventing the abrasion damage.

Reclamation’s new technology utilizes flow deflectors that alter downstream water flow patterns, minimizing the attraction of abrasive materials and minimizing the potential for costly damage.

The flow deflector, developed by Hydraulic Engineers Leslie Hanna and Brent Mefford in Reclamation’s Technical Service Center, improves the flow through the stilling basin and into the riverbed, preventing the abrasive materials from entering the stilling basin.

“Each dam will require a different design based upon the geometry and the flow characteristics of the basin,” said Hanna. “Right now, the flow deflectors are limited to basin widths of 30 feet, but we are in the process of studying the use in wider basins.”

The first flow deflector was installed in 2002 at Mason Dam in Ore., through a partnership of Reclamation’s Science and Technology Program and Snake River Area Office with the Baker Valley Irrigation District. Reclamation has calculated the District will save an estimated $375,000 in reduced maintenance needs and increased water reliability over the anticipated 50 year lifespan of the flow deflector.

“This is a great example of Reclamation and our irrigation districts working together to bring a water management solution from the laboratory to practical use,” said Chuck Hennig, Reclamation’s Research Coordinator. “Once success was demonstrated at Mason Dam, Reclamation was soon receiving other requests to design and install flow deflectors at other dams.”

One of those requests was to install two flow deflectors at Choke Canyon Dam, operated by the city of Corpus Christi, Texas. Reclamation calculated that they will save an estimated $1.2 million over the 50 years the flow deflectors are anticipated to be in operation.

Hanna’s research was funded by Reclamation’s Science and Technology Program. To learn more about this project or other Reclamation research activities, please visit:
http://www.usbr.gov/research.