FLOOD09132

• County: Weld
• Community: Greeley
• Stream Name: Cache La Poudre River
• Basin: South Platte
• Title: Floodplain Study
• Date: 10/1/1999
• Prepared For: Greeley
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

4.0 HVDiROLOGIC DATA.

The peak flood discharges used in this study were developed by the Omaha District for

the 1988 :ep0l1, "Hydrologic Analysis of the Cache La Poudre River Basin", which is

reproduc(:d in Appendix 1. The 1988 dischargcs were approved by the Colorado V-iater

Conservation Board for use in future studies on the river in Larimer and Weld Counties. A

su:nmary of the computed peak flood flows along the Cae he La Poudre River at selected
locations in Weld County are given in Table 1.
To provide for gradual changes in discharge between locations where the peak flood
discharges were computed, a lin~ar now proration bas(:d on the stream channel distance between
locations was used to adjust the discharges in the hydrauli.~ model.

TABLE 1

(

Location and Drain
Station (squa
Mouth 1
(0.0)
At Eaton Draw I
(36060)
Down~.tream of
:oalba ~k Creek* I
(47860)
Upstream of
:oalba ~k Creek* I
(47860)
DownBtream of
Law Ditch 1
(11 0950)
Jpstream of Law 1
Ditch (11 0950)

age Area
re miles)

10-y,car
(cfs)

50-year
(cfs)

890

33]0

7550

--- ------
100-year 500-year
(ds) (ds)
---- -----
10600 22800
--- ------
10700 22700

875

3400

7660

810

3900 8540 11800 24400
-,----- _._----.- ------
3870 8470 11700 24200
--.-.--- ------- --- ------
4620 9720 13200 26300
---..--"--- -.----- ----
4590 9640 13100 26100

(

747

707

1

662

--- --,---- _._-- ------+
'Coalban< Creek in 1988 Hydrology Report is shown on local maps as Graham Seep.

2