New Designs for Making Old Dams Safer
By Don Comis
June 26, 2009
A group of Agricultural Research
Service (ARS) hydraulic engineers are helping to rehabilitate aging small
dams across the country.
Efforts are underway to upgrade existing auxiliary spillways or build
new spillways for these dams, especially in Oklahoma. These upgraded or new
spillways meet current dam safety standards and will increase the useful lives
of the dams.
The U.S. Department of
Agriculture's Natural Resources
Conservation Service (NRCS) has helped build more than 11,000 earthen dams
over the years as part of its
Watershed Protection and
Flood Prevention Operations Program. These dams serve many purposes, but
the primary purpose is flood control. Since the program began in 1944,
Hydraulic Engineering Research Unit (HERU) engineers in Stillwater, Okla.,
have partnered with NRCS in the development of design standards for the dams.
When ARS hydraulic engineer
L. Hunt and her colleagues were asked recently by NRCS to help evaluate and
design retrofitted Roller Compacted Concrete (RCC) stepped spillways for dams
in Georgia and North Dakota, they found the same technology also can help
increase flow capacity on many of these dams across the country. So they
developed generalized criteria for designs that could be used anywhere in the
Compacting concrete with a roller is a fast way to make a tough
With the many changes that have occurred over the yearsincluding
deterioration, changes in upstream and downstream land use and population, and
changes in dam safety lawsthe research by the HERU engineers with this
technology is once again helping NRCS, which has the lead for design and
construction of these earthen dams.
The ARS engineers conduct model studies both indoors at small scales
and also outdoors at large scales. This summer Hunt will begin using a
large-scale flume outdoors that is the actual size of the RCC spillways being
designed for these dams. ARS engineers will use the data from the water flow on
their experimental spillways to develop design and construction guidelines.
ARS is the principal intramural scientific research agency in