Predicting peak outflow from breached embankment dams

Construction of dams has been a long-established practice with the oldest known dam, the
Sadd el-Kafara near Cairo, Egypt, being built between 2950 and 2750 B.C. (Smith, 1971).
Historically, many of the early dams were small, in-channel structures built by locals with little or no
engineering background. Griffen (1974) suggests that dam safety for early dams was less of a concern
because the areas around early dams were less densely populated and, therefore, few people were
directly affected by the dams, these dams were generally small in relation to modern dams, and the
dams were generally built by cultures who took pride in their work.
Modern dam-safety analysis has been an evolving science since the 1970s. Between 1972 and
1977, four notable dam failures occurred in the United States: Buffalo Creek, West Virginia; Canyon
Lake, South Dakota; Teton, Idaho; and Kelly Barnes, Georgia. In April 1977, President Carter issued
a memorandum directing the review of federal dam-safety activities by a committee of recognized
experts. In June 1979, the Interagency Committee on Dam Safety (ICODS) issued its report
containing the first dam-safety guidelines for Federal agency dam owners.
Analysis of dam breaching and the resulting floods are essential to identifying and reducing
potential for loss of life and damage in the downstream floodplain. In recent years, computer
modeling has become available to simulate dam-break hydrographs and route these hydrographs
through the area downstream of the dam. Commonly used dam-break analysis programs require
estimates of certain geometric and temporal characteristics of the dam breach as inputs for the model.
Inundated areas, flow velocities, and flow depths can then be estimated to assess the potential damage
caused by the dam breach as portrayed in Figure 1.