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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

8

DRAINAGE BASIN PARAMETERS (Cont.)
Projected
Basin Development
Creek Name Area Len'jlth Lea s~~fe Perv Ct ~
Subbasin ( iiii"2T (ml.) (mi) m-
Third Creek
TC-l 6.34 5.23 3.26 .40 50 .27 .47
TC-2 7.82 3.98 2.27 .38 70 .34 .51
TC-3 2.21 2.46 1. 44 1. 36 95 .43 .53
TC-4 7.57 3.07 1. 74 .45 95 .43 .53
TC-5 6.79 3.98 1. 70 .91 95 .43 .53
Total 30.73 18.72

Hydraulic Analysis

Typical flood hydrographs for each stream are provided in Figures
15 and 16. Discharge Probability Profiles for Second Creek and
Third Creek are provided in Figure 17. This chart relates the
peak discharge at any point within the basin for the 10-, 50-
and 100-year storm frequencies. Table 4 lists the flood fre-
quencies and discharges used for each of the streams at selected
reference points.

Hydraulic analyses of each stream were completed to determine the

water surface elevations for the 100-year storm event. The

elevations were compiled using the Corps of Engineers HEC-2

Water Surface Profiles computer program. Valley cross sections

were measured on the 1" = 100' scale, 2-foot contour topographic

mapping provided by the District. Estimates of channel and over-

bank roughness factors were made after field investigation of the

study area. Typical roughness or Manning's "n" values used in

this study are:

channel - .030 to .040
overbank - .035 to .050

TABLE 4
FLOOD FREQUENCY AND DISCHARGE

The computed flood profiles are plotted on the Flood Hazard Area
Delineation Map Drawings. Also, the computed flood elevations
for Second Creek and Third Creek are tabulated at each reference
point in Tables 5 and 6, respectively.

Location 10-Year 50-Year 100-Year
(cfs) (cfs) (cfs)
Second Creek
Mouth 3,080 5,350 1,265*
O'Brian Canal 2,800 5,060 6,000
Tower Road 2,240 4,410 4,700
Third Creek
Mouth 3,370 5,710 11,770*
0' Brian Canal 2,590 5,020 5,890
Irondale Road 1,090 2,220 2,700
*Di verted Flood Discharges
Detailed information on the hydrologic analysis is available at

Detailed information on the hydraulic calculations is available
from the Urban Drainage and Flood Control District.

- FUTURE FLOODS -

Flood Frequency and DiSCharge

the offices of the Urban Drainage & Flood Control District.

Floods of the same and greater magnitude as those that have
occurred in the past will occur in the future. With development
in the basins, flooding will occur more frequently. The discharges