BOARD02398

• Board Meeting Date: 9/22/2003
• Description: Flood Section - Floodplain Designations and Approvals
• Board Meetings - Doc Type: Memo

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Community response: Eagle County has been supportive of this stndy since the time it started. The
county acquired funding to supplement the CWCB funding needed to complete the stndy. County staff
conducted the field surveys that were an integral part of the topographic analysis, along with funding the
GIS topographic mapping used in the hydraulic analysis. The stndy results were presented to county and
municipal staff for the affected towns at the draft and final stages of the analysis. No objections have
been raised during the stndy process, and local staff and elected officials have been supportive of the
stndy effort. Eagle County and the affected towns will be submitting the entire stndy to be included as
part of the DFlRMs for Eagle County and its incorporated municipalities.

Staff findings: CWCB staffhas determined that the subject 100-year detailed floodplain information for
the Eagle and Colorado Rivers is conformance with the CWCB's rules and regulations for floodplain
designation and approval. The subject information replaces non-published information, approximate Zone
A information, and a very small amount of outdated detailed information for said stndy reaches. The
CWCB endorses this stndy as contaiuing the most current floodplain mapping available and urges Eagle
County and its affected incorporated communities to adopt said stndy for land use regulation purposes
pursuant to statntory authority. CWCB staff recommends that the superseded approximate floodplain
information be rescinded.

Staff recommendation: Staff recommends that the Board: 1) designate and approve the 100-year
detailed floodplain information contained in said report for the Eagle and Colorado Rivers, and 2)
authorize staff to prepare a floodplain resolution to be signed by the Director and transmitted to FEMA,
Eagle County, and to the communities of Eagle Vail, Avon, Edwards, Wolcott, Eagle, Gypsum, and
Dotsero. This action is recommended in order to meet statntory requirements.

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2) Al!:enda Item 3.b
Floodplain Resolution Number: FPR 03-572
Mfected Community: Town of Otis
Name of study to be formally acted on: "Floodplain Update Report, Town of Otis, Colorado" dated
September 2003.
Studied Streams: Southwest Drainage
Technical Issues: The Town of Otis requested that the CWCB assist the community in addressing a
number of questions regarding the town's floodplains. The CWCB began a study and completed new
detailed hydrology information as one task in the process of generating new floodplain mapping for the
Southwest Darinage portion of the Town. The hydrology for the Southwest Drainage was accepted by the
Town and designated and approved by the Board at its January 2002 meeting. Subsequently, the CWCB
contracted with McLaughlin Water Engineers to provide hydraulic modeling and floodplain boundaries
for the Southwest Drainage and to complete the subject floodplain report. The floodplain updates are
based on revised hydrology, updated and very detailed (I-foot contour interval) topographic mapping,
recent physical changes to the main channel and floodplain, and detailed hydraulic modeling that analyzes
potential overflows. The revised floodplain information contained in said report for the Southwest
Drainage extends from the western corporate limit of the Town (Dade Street) east approximately 2,500
feet to the Burlington Northern Railroad culvert crossing. Because of the flat stream gradient and the
limited hydraulic capacity of the railroad crossing, the 100-year floodplain in the stndy reach affects a
large portion of the south side of Otis. For that reason, CWCB staff and McLaughlin Water Engineers
will follow up this effort with a stndy to identii)' mitigation alternatives for that floodprone portion of the

Flood Protection. Water Project Planning and Financing. Stream and Lake Protection
Water Supply Protection. Conservation Planning

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