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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7

- FLOOD RELATED STUDIES AND OTHER PERTINENT DATA -

Varying rainfall intensities were assumed to occur in each basin.

No other flood related studies have been completed on Second

Table 2 lists the maximum rainfall depths for each storm frequency

for a 2-hour duration storm. An infiltration rate of 0.5 inches

and Third Creeks excepting approximate flood boundary delineations
completed for the Federal Insurance Administration (FIA). The

per hour was utilized in all of the study basins. The runoff

FIA flood outlines are not intended to define the actual limits

computations included considerations of the percentage of water-

of flooding but rather indicate the existence of a flood plain

sheds developed and planned future development, as determined by

in the area.

field reconnaissance and planning studies by Adams County.

TABLE 2
RAINFALL DATA

As no other flood data is available for these streams and since

the flood profiles and outlines provided herein are representa-

tive of present-day flood plain conditions, this data is author-

Maximum, Total Rainfall Depth*
10-Yr. 50-Yr. 100-Yr.

itative for flood plain definition.

Second Creek
Third Creek

1. 7 in.
1.6

2.2 in.
1.9

2.4 in.
2.1

- HYDROLOGIC AND HYDRAULIC DETERMINATIONS -

*S~orm Duration, 2 hours

Hydrologic Analysis

Ref: Rainfall/Runoff Information, Project REUSE,
UDFCD, May 19 72 .

A hydrologic analysis was carried out to establish the peak

laO-year recurrence intervals for each stream in the study area.

TABLE 3
DRAINAGE BASIN PARAMETERS
Projected
Basin Development
Creek Name Area Length Lca Slope Perv .s:. 92-
Subbasin (mi~) (mi) (mi) (%) (%)""
Second Creek
SC-l 3.74 5.30 2.58 .85 50 .28 .47
SC-2 6.l8 4.47 2.3l .40 55 .29 .49
SC-3 7.42 4.51 2.12 .52 90 .40 .52
SC-4 3.02 4.24 1. 6l 1.23 60 .31 .49
SC-5 5.05 4.74 1. 89 1. 37 95 .43 .53
SC-6 1. 95 2.92 1. 33 1. 51 9'i .43 .53
Total 27.36 26.18

diSCharge-frequency relationships for floods of 10-, 50- and

The Colorado Urban Hydrograph Procedure, as outlined in the

Urban Storm Drainage Criteria Manual, was used to determine the

peak discharges for each storm frequency on each stream. The

calculations used rainfall data characteristic of the study area

and provided in the Urban Storm Drainage Criteria Manual. A

summary of the rainfall data used in the study and the drainage

basin characteristics is provided in Tables 2 and 3 respectively.