FLOOD01611

• County: Boulder
• Community: Boulder County
• Stream Name: Upper Lefthand Creek-Foothills Hwy to Peak to Peak
• Title: Flood Information Report
• Date: 8/1/1983
• Prepared For: Boulder County
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Table 2

Location

Approximate
Drainage Area
(square miles)

Records

Table 4
Peak Flood Discharges
10- Year 50-year 100-Year 500-Year
Peak Peak Peak Peak
Di scharge Di sc ha rge Di scha rge Discharge
Location (cfs) (cfs) (cfs) (cfs)
Lefthand Creek 1,035 4,145 6,700 14,990
Downstream Study
limi t
Lefthand Creek 890 3,190 5,420 12,540
Upstream of Spruce
Gul ch
Lefthand Creek 830 2,850 4,940 11 ,630
Upstream of
Si x Mi 1 e Canyon
Lefthand Creek 430 2,100 3,690 10,430
Upstream of
J ames Creek
Lefthand Creek 400 1,800 3,180 9,060
Upstream of Lick
Skillet Gulch
Lefthand Creek 60 360 600 1,460
at Peak to Peak
Drive
J ames Creek 390 2,660 4,810 13,500
Mouth
James Creek at 300 1,800 3,230 8,920
Mainstreet
(Jamestown)
J ames Creek 200 1,190 2,140 6,010
Upstream of Little
James Creek
Little James Creek 130 650 1,160 3,220
Mouth

Rainfall Values in Inches

Rainfall James Creek Lefthand Creek 1 2 3
Lefthand Creek Lefthand Creek
Frequency (i-Hour Storm) (I-Hour Stonn) (3-Hour Stonn) (6-Hour Storm)
500 2.8 2.8 3.6 4.0
100 2.1 2.1 2.7 3.1
50 1.8 1.8 2.3 2.7
10 1.3 1.3 1.6 1.9

1 Ward to Spring Gulch
2 Spring Gulch to James Creek
3 Below James Creek

Stream gaging records used in this study are listed in Table 3.

Table 3

Lefthand Creek Basin Stream Gage Data

Lefthand Creek Near Boulder
(Parshall flume 1.6 miles
above the Foothills Highway)

52

May 1929-Sep 1931
Apr 1947-Dec 1953
Oct 1955-Sep 1957
Oct 1976-Present

James Creek Mouth*

18.7

7 May 1969

*Spot discharge measurement.

The peak flood discharges at several locations are given in Table 4.

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