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From an observation platform overlooking a test
dam, Greg Hanson records the test for use in computer modeling. Click the
image for more information about it.
Maintaining the Safety of Earthen Dams
By Luis Pons
August 4, 2005
Agricultural Research Service (ARS) scientists have gone the extra
mile--plus a few thousand actual ones--to assure the accuracy of computer
models that help them understand and predict the failure of earthen dams.
Hanson, a hydraulic engineer in the ARS Hydraulic Engineering Research Unit
in Stillwater, Okla., recently traveled to England and Norway to assist in
dam-breach tests and acquire real-time data useful in verifying
He assisted in seven of 23 small-scale tests conducted in Wallingford,
England, and in one of seven large-scale tests in Mo I Rana, Norway. These
tests were primarily funded by the European
Union and the Research
Council of Norway.
The trips were part of research by Stillwater scientists on the phenomenon
of overtopping, which causes about 35 percent of all U.S. dam failures.
Overtopping, which occurs when water overflows a dam, can lead to embankment
erosion and eventual failure of earthen dams. Causes include inadequate or
blocked spillways, extreme rainfall and large-scale snowmelt.
Hanson and fellow hydraulic engineer
Temple lead efforts at HERU to develop and use computer models and research
flumes to determine in advance how embankments will perform if they do overtop.
Their latest work involves the SIMplified Breach Analysis (SIMBA) model, and
WINDAM (WINdows Dam Analysis Modules).
SIMBA reproduces key features observed in embankment-dam failure tests,
dividing the breach process into four stages because more than one type of
erosion may be dominant during a given stage. The researchers hope to integrate
SIMBA into WINDAM.
Hanson is focused on smaller earthen embankments, many of which are within
communities and range in height from a few feet to a couple of hundred feet.
Although U.S. dams have an admirable safety record, about 57,000 of the 80,000
dams in the National
Dam Inventory have potential to overtop, according to Hanson.
more about the research in the August 2005 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.