FLOOD01790

• County: Adams
• Community: Adams County
• Stream Name: Second Creek, Third Creek
• Title: Flood Hazard Area Delineation - Second and Third Creek
• Date: 2/1/1976
• Prepared For: Adams County
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

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3

miles south of Brighton. The regional location of the streams
is shown on Drawing I-I.

sand and gravel operations, farm buildings, and residential and
commercial development.

The study reach for each stream extends from the confluence with
the South Platte to the eastern boundary of the Urban Drainage &
Flood Control District, a distance of approximately 16.8 miles
on Second Creek and 17.1 miles on Third Creek.

Drainage Basin Characteristics

The streams are intermittent flowing streams meandering through
pasture and agricultural lands. The flood plain is confined to
definite channel limits in the upper reaches of the study and
spreads widely in the lower and flatter reaches.

The drainage basin boundary limits for the Second and Third
Creek basins are shown on Drawing 1-4. The streams are located
on the high plains approximately 20 miles east of the foothills.
The basins are presently undeveloped except for localized improve-
ments. The streams are primarily natural in location and size.
The flood plains are not heavily covered with vegetation but
remain open and clear and highly erodible.

The streams have natural, irregular channel sections. Minor

The Second Creek drainage area ranges in elevation from approx-
imately 4990 at the South Platte River to 5650 at the basin divide.
The average stream gradient through the basin is 36.3 feet per mile.
Similarly, the Third Creek basin rises from elevation 4960 at the
mouth to elevation 5485 at the basin divide, an average gradient
of 33.1 feet per mile through the basin.

channel improvements have been made on both streams near U.S. 85

and the Union Pacific Railroad. No major flood control structures

have been made nor are under consideration at the time of this

study.

There are 18 major facility crossings on Second Creek including
13 roads and highways, 2 railroads, and 3 irrigation canals.
On Third Creek there are 16 major crossings consisting of 11
roads and highways, 2 railroads and 3 irrigation canals. These
facilities represent obstructions to flood flow, causing back-
water conditions which increase flood heights and velocities.

Third Creek drains a larger area than Second Creek, 30.7 square

miles versus 27.4 square miles. The drainage areas to other

points along the study reach are shown in Table 1.

TABLE 1
DRAINAGE AREAS

Location

Drainage Area - Sq. Mi.
Second Creek Third Creek

Other unnatural obstructions to flood flow exist in the lower
reaches of both creeks below U.S. 85. These obstructions include

South Platte River
O'Brian Canal near 1-76
Irondale Road
UD&FCD Boundary

27.4
23.6
17.4
1.0

30.7
24.4
16.6
1.0