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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obtained west of the G&O mapping limits at U.S. Highway 36. The low point in U,S,
Highway 36 was found to be west of the limits of the G&O mapping at this location,
Additionally, the G&O HEC-2 models assumed that the entire lOO-year discharge for
South Boulder Creek crossed U,S. Highway 36 within their mapping limits. Since
portions of the Flatiron Property outside of the G&O mapping limits could be inundated
during a lOO-year event, it was detennined a re-analysis the flood flows that split away
from the main channel flows at U.S. Highway 36 should be undertaken.

HYDRAULIC METHODS UTILIZED IN LOVE RE-ANAL YSIS

Upon completion of the technical review of the G&O model, Love & Associates
detennined that the G&O model did not accurately reflect the existing floodplain
conditions of the Flatiron Property. Following a site visit and a complete review of all
files pertaining to the G&O analysis, it was apparent that the berm constructed around
the Flatiron Property had not been certified by FEMA as a flood protection levee. It is
FEMA's policy that for the purpose of preparing floodplain maps any levee constructed
for flood protection purposes must meet or exceed all of FEMA's levee criteria as
defined in Sections 60.12, 60.3, 60.4 and 60,5 of the FEMA National Flood Insurance
Program: (Regulations for Floodplain Management and Flood Hazard Identification).
revised as of October 1, 1990 a copy of which is attached in the Technical Appendix at
the back of this report.

The Love & Associates' study examined the full extent of the 1oo-year floodplain in the
vicinity of the Flatiron Property utilizing the HEC-2 backwater analysis program
developed by the V,S, Army Corps of Engineers. The Love HEC-2 models were
developed using the regulatory (G&O) models supplemented with May, 1993
topographic mapping in the vicinity of the Property. The U.S, Highway 36 bridge and
cross sections downstream of U.S. 36 were modeled using information taken directly
from the regulatory model.

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