FLOOD03947

• County: Weld
• Community: Milliken
• Stream Name: Local Drainage
• Basin: South Platte
• Title: Floodplain Information Report
• Date: 10/1/1982
• Prepared For: Milliken
• Prepared By: Simons Li & Associates Inc.
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Table~. One-Hour Rainfall Intensities (inches per hour).

Technical Addendwm. Table 4 lists the p4ra~eter9 used and the range of values
selected. Storage-discharge curves for pondinq behind railroad crossinge were

Recurrence Interval in years
Endcf Period
(minutes) , '" " ;0 '"' '"
, 0.48 0.60 0.73 0.86 0.92 1.19
'" 0.60 0.75 0.91 1.08 1.22 1.50 i
,
I
" 0.84 0.98 1.19 1.41 1.54 1.96 i
,
" 0.96 1.1) 1.3B 1.63 1.84 2.27 ,
i
,
" 1.44 1.73 2.11 2.48 2.76 ].47
" 2.76 3,30 4.02 4.75 5.22 6.63
" 3.96 4.80 5.85 6.90 7.68 9.63
" 1.80 2.09 2.55 3.01 3.38 4.20
.- 1.20 1.50 1.83 2.15 2.46 3.!lO
" 0.84 0.98 1.19 1.41 1.54 1.96
" 0.60 0.75 0.91 1.0e 1.22 1.50
" 0.48 0.60 0.73 0.86 0.92 1.19

defined from topographic ~pping and weir flow equations. Flow splite were
based on field observation. The ~tailed drainage basin parameters are pre-
8ent,,<iintheTechnicalAddendum.

Results of HYdrologic ~alysis
Rainfall-runoff data were not available for the Milliken watershed. For

this reason, the results of the Fossil Creek"nd Boxelder Creek studies w..re

used to evaluate and justify the results of this study. The peak dischsrges
per square mile from ~lliken and Cooper Slough are similar. The Fossil Creek
basin produces higher peak flows per square mile because of Bteeper slop.." and
lower infiltration rates than the Millik..n watershed. A oomparison of the
stUdy resulte with those of the previous studies i8 presented in the Technioal

Addendwo..

A summary of th.. peak flows in the Town of Milliken i8 given in Table 5.
A detailed description of the methodology used and hydrologic results are
given in the Technical Addendum.

HYdraulic Analysis
Back'lround
AnalyeIe of the hydraulic characteristics of the Town of Killiken was

oonducted to determine th.. water eurface elevation for peak flow" of the 5-,
10-,25.,50-, 100-,and500-yearfloode. Thewat",rsurfaceelevatianswere
co~uted using the U.S. Army Corps of Engine..rs' HEC-2 w"ter surfaoe profile
computer program (reference 9). Cross-seotional dat<> for the Lola Park

Tributary..ndth" Eaatern Flow P..th wer.. provided in HEC-2 for.....tby the town .
Minor o<>rrections w"re made to the eross aections based on field Investigation
~n~ fto~d ~un~ary delineation.
Culvert ~o~tri~a wer~ fie16 measured. Elevations for top of roa~
crossings and downstream and upstream ehannel inverts were surveyed.
RougMness coefficients were selected aft",r field investigation and an..lysis of
photographs taken Q\lr1n9 flein reconnaissance.