BOARD02290

• Board Meeting Date: 11/23/1998
• Description: Flood Section - Floodplain Designation and Approvals
• Board Meetings - Doc Type: Memo

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ATTACBMENTl

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FPR 98-472
Flood Insurance Study, City of Westminster, Colorado, Adams and Jefferson
Counties, September 30, 1988

KEY ISSUES:
. The FIS contains detailed and approximate floodplain information for streams within the
community.

. There is a previously designated FHAD by the Urban Drainage and Flood Control District
(UD&FCD) for all of the streams studied by detailed methods.

. For those streams studied by detailed methods, the UD&FCD FHAD used "future conditions"
hydrology to better address long-term floodplain management needs; the FIS used "existing
conditions" hydrology to better address current flood insurance needs. The two sets of
floodplain delineations are different from one another. The City of Westminster uses the
FHAD information for floodplain management purposes and uses the FIS information for flood
msurance purposes.

. The approximate floodplain delineations were derived from other UD&FCD reports with
detailed floodplain information. The inforrna.tion for Ketner Creek has not been designated by .
the CWCB. The information for Shaw Heights Tributary and for Little Dry Creek was
designated by the CWCB in 1978.

COMMUNITY RESPONSE:
The City of Westminster sent a letter to the CWCB requesting designation ofthe 1988 FIS.
CWCB staff met with the city's floodplain administrator and discussed the proposed
designation and the city's floodplain management program. The city is supportive of the
Board's proposed designation and approval of the 1988 FIS, as long as it does not affect the
designation status of the previously designated "future conditions" detailed floodplain
information in the FHAD.

SUMMARY:
The staff recommends Board approval of the floodplain resolution for the City ofWestrninster designating
the September 30, 1988 FIS. The proposed designation action would leave in place the designation of the
FHAD detailed floodplain information for floodplain management purposes and would designate, in
addition, for flood insurance purposes, the FlS infonnation. There will be explicit acknowledgement that,
due to the different sets of hydrologic assumptions used, the two studies show different floodplain
boundaries for the same stream reaches. The detailed and approximate floodplain information contained in
the FlS meets the Board's "Floodplain Designation tmdApproval Rules". The designation, along with the
designations of revised FIS' from 1991 and 1993, Will assure that current floodplain information for the
City of Westminster complies with state statutory requirements.

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