GEI has analyzed fl ood

inundation due to

dam overtopping and

dam breach on over

20 earthfi ll dams using

the National Weather

Service’s DAMBRK

model or a combination

of HEC-1, HEC-2, and

HEC-RAS hydrologic

models.

These analyses indicate the

downstream maximum water

surface and inundated area.

The dam breach models use

data on the initial and breach

conditions at the dam and the

geometry of the downstream

fl oodplain to produce maximum

fl ood-water fl ows and velocities,

fl ood-wave arrival times,

elevations, and inundated areas.

GEI has modeled Probable

Maximum Flood (PMF) and

sunny day dam breach conditions,

and breaches in both single and

multiple dams. In addition to

earthfi ll dams, GEI has performed

dam breach analyses for roller-

compacted concrete, concrete

gravity, and rockfi ll embankments

with heights ranging from 16 to

340 feet. The results are used to

determine effects of fl ooding on

urban centers and major roadways

and also in development of

Emergency Action Plans (EAP)

and Early Warning Systems (EWS).

Earthfi ll Dam Breach AnalysisVarious States

Dam Height (ft) Type Location

Black Lake No. 1 24.5 Earthfi ll ColoradoClear Lake 16 Earthfi ll/Rockfi ll ColoradoCrown Butte Mine 50 Earthfi ll WyomingDillon 300 Earthfi ll ColoradoGrama 54 Earthfi ll OklahomaLower Cabin Creek 95 Earthfi ll/Rockfi ll ColoradoMaple Grove 50 Earthfi ll Colorado Meadow Creek Lake 100 Earthfi ll ColoradoRay Lake 28 Earthfi ll WyomingTrapped Rock 30 Earthfi ll New MexicoWashakie 62 Earthfi ll Wyoming

Representative Projects Involving Earthfi ll Dam Breach Analysis