FLOOD01207

• Designation Number: 58
• County: Adams
• Community: Unincorporated Adams County
• Stream Name: Second Creek and Third Creek
• Title: Flood Hazard Area Delineation - Second Creek and Third Creek - Adams County
• Date: 2/1/1976
• Designation Date: 3/1/1976
• Floodplain - Doc Type: Floodplain Report/Masterplan

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9

reported on Figure l7 for the 10-, 50- and lOO-year flood
frequencies represent the relative extent and impact of each
flood event. The discharge information is usable not only
for flood plain regulation but also for planning, engineering
and flood plain improvement.

of failure or damage is economically feasible and the hazard to
life and property is lower or non-existent.

The lOO-year flood event, which can be expected to occur at any

time in a given area, based upon recorded historical precipita-

tion and other valid data, has a one percent chance of being

equalled or exceeded during anyone year. The lOO-year flood

event provides a lower risk of failure than the lO-year or

50-year flood event, when considering structural flood plain

improvements.

Flood magnitudes greater than the laO-year flood magnitude can
and will occur. Land improvement adjacent to the lOO-year flood
plain limit should consider the remote chance for possible flood
damage.

The lOO-year flood event is considered by the Urban Drainage &

Flood Control District, the Colorado Water Conservation Board,

and the Federal Insurance Administration as the flood magnitude

for which flood plains should be designated for regulatory and

improvement purposes. In Colorado, the lOO-year flood plain
represents an area of state interest as defined in H.B. l04l.

The lOa-year flood discharges on Second and Third Creeks are

greatly affected by the Fulton Ditch, the Union Pacific Railroad

and U.S. 85. At each of these locations, flood flows from Second

Creek are diverted into Third Creek because of insufficient

capacity and obstructions at these crossings. A summary of the

lOO-year flow diversion used in this flood plain analysis is

provided in Tables 4, 5, and 6.

The lO- and 50-year recurrence flood magnitudes have also been

calculated at various design points along each creek. These

flood magnitudes represent events which can cause severe damage

but would not inundate the area characteristic of a lOO-year

event. The peak flows for these events should be used in the

planning and engineering of improvements where the higher risk

Theoretically, it is conceivable that flood waters, once diverted

north along the Union Pacific Railroad and U.S. 85 embankments,

could continue flowing north into the southern limits of Brighton.

However, the flatness of the area, the many county road embank-

ments and irrigation ditches which cross the path of such an

extreme flood plain, and the agricultural use of the potential

flood plain land with a permeable surface would tend to dispute

the possibility of such a circumstance. Regardless, future county

and city planning should consider possible ground contouring

revisions north of Third Creek to eliminate any possibility of

such a flood occurrence.