FLOOD10053

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: A Study to Identify Attitudes and Problems with Integrating Floodplain Management and Dam Safety
• Date: 8/1/1984
• Prepared For: University of Denver
• Prepared By: Stephen A. Spann
• Floodplain - Doc Type: Educational/Technical/Reference Information

7

that the failure was an Act-of-God.

Second,

the dam owner

should

not have any liability if all the property damage had

occured prior to the dam failure.

To gain a perspective of

the relationship

of

the

probable maximum flood

(flood caused

by probable maximum

precipitation)

and

the

100-year

flood

(flood caused

by

100-year

precipitation) ,

it would be prudent to compare the

probable

maximum

precipitation

(PMP)

and

the

100-year

precipitation.

Figure 1 shows a simi-Iogrithmi~ plot of

the

2, 10, 25, 50, 100-year,' and the PMp2 rainfall

depth

which

.

could be expected to fall over a six

hour

period

on

the

Cherry Creek drainage basin.

It can be seen that the

ry
~,

10,

rye
~-',

50

and

100-year

precipitation values lie on a straight line. This follows the

rules of

probability and

statistics used by hydrologists,

however, the reader will note that the 25-inch PMP does not

lie on the line and, in fact, by projection, the reoccurance

interval is significantly well beyond the 10000-year event.

While the reader may claim that the PMP event cannot really

occur, there have been three storm events in Colorado which

'U.S., Department of Commerce, National Oceanic and
Atmospheric Administration, Precipitation-Frequency Atlas of
the Western United States, vol. III-Colorado, (Silver Spring,
Maryland: Government Printing Office, 1973)

2U.S., Department of Commerece, National Oceanic and
Atmospheric Administration, U.S.,' Department of the Army,
Corps of Engfneers, U.S., Department of the Interior, Bureau
of Reclamation, Hydrometeoroloqical Report No. 55. Probable
Maximum Precipitation Estimates-United States Between the
Continental Divide and the 103rd Meridian, (Silver Springs,
Maryland: Government Printing Office, 1984)