FLOOD04661

• County: Boulder
• Community: Boulder
• Stream Name: South Boulder Creek
• Basin: South Platte
• Title: Floodplain Analyses of South Boulder Creek at Flatiron Property
• Date: 8/12/1996
• Prepared For: University of Colorado at Boulder
• Prepared By: Love & Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 1

ALLOCATION OF MAIN CHANNEL AND OVERFLOW SPILL
DISCHARGES IN CFS AT US mGHW A Y 36 (Cross Section 20010)

Spill to Total Spill Total 100-yr
HEC.2 Mainl Interceptor Spill We.t North of Discharge
Mod h 1 h t 6 in
\16
'"'~ll' 4,500 cf. O'cfs 1,660 cf. 1,660' cf. 6,160 cf.
\l' , . U Regulatory
(;t \
h~1\1 Condition 1 2,480 cf. 3,190 cfs 490 cfs 3,680' cf. 6,160 cf.
,(
LI~ilt Condition 2 3,540 cf. O'cfs 2,620 cfs 2,620 cfs 6,160 cf.

, Main Channel flows are those flows which remain in the South Boulder Creek channel and pas.
through the bridge structure at US Highway 36.
, The l00-year flood discharge is contained within the main channel or between the Flood Protection
Levee and the main channel floodplain and does not enter the interceptor channel.
, The regulatory model incorrectly identifies more flows remaining in the South Boulder Creek main
channel floodplain than physical land features would allow.
. The 3,190 cfs and 490 cfs are combined for the total spill of 3,680 cfs north of US Highway 36.

PRESENTATION OF FINDINGS

Upon completion of the HEC-2 models, a meeting was held at the offices of Love &
Associates, Inc. on Thursday, July 11, 1996. The purpose of the meeting was to meet
with floodplain regulatory officials from FEMA, CWCB, UD&FCD, Boulder County
and the City of Boulder to present the preliminary findings of the Love & Associates
floodplain analyses and determine if these public officials had additional information
regarding the data presented. Approximately twenty (20) public sector representatives
were present at the meeting. David Love provided the attendees with detailed
information on the analyses, presented floodplain delineations and explained his position
regarding the numerous errors in the G&OIFIS regulatory floodplain models. He also
explained, in detail, the two hydraulic models that were analyzed for the Flatiron
Property. Information was provided to all representatives present concerning the split
flows that leave the main channel of South Boulder Creek and proceed westward and
northerly along the highway embankment of U.S. Highway 36 until they approach a low

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