Embankment Dam Failure Analysis (FEMA 541) - Association of ...

Dam name: Castlewood Dam
Location: near Franktown, Colorado (about 35 miles upstream from Denver.
Dam Characteristics:
Dam type: rockfill
Dam height: 70 feet
Dam crest length: 600 feet
Reservoir volume: 3430 acre-feet at spillway crest; 5000 acre-feet at elevation of failure.
Spillway: Central overflow, 100 feet long, 4 feet deep.
History of Dam:
Purpose: irrigation
Dam completed: 1890
Dam failed: about midnight August 3, 1933
Failure cause: overtopping
Details on Detection of Failure/Deciding to warn:
The dam begins failing due to overtopping about• midnight. Caretaker lives nearby but phone not
working. Drives 12 miles to use phone. At 2:30 a.m. caretaker uses phone to initiate warning
process.
Details on dissemination of warnings and technologies used:
Residents in upstream areas probably received no official warning. Flooding occurred in Denver
between about 5:30 a.m. and 8:00 a.m. Warnings by police and firemen preceded the arrival of
floodwaters.
Details on response to the warning:
Many people evacuated. A newspaper reported, “A stampede of 5,000, man clad in nightclothes,
fled from the lowlands.” People also drove to the banks of Cherry Creek to view the flood.
Description of flooding resulting from dam failure:
In the Denver area, flooding caused significant damage. The flood depth and velocity, however,
were not great enough to destroy (move or collapse) buildings.
The losses included:
2 fatalities occurred. A woman was thrown into Cherry Creek while viewing the flood on
horseback and a man stepped into a deep hole while wading toward high ground. $1.7 million in.
damage.
Prepared by Wayne Graham