BOARD01485

• Board Meeting Date: 11/19/2001
• Description: Flood Section - Floodplain Designations and Approvals
• Board Meetings - Doc Type: Memo

statutorily authorized zoning powers. Approximate floodplain information means floodplain .
information prepared using a significantly reduced level $f detail to arrive at a hazard delineation
without water surface profiles. CWCB staff performs tecpmca1 reviews on the following types of
reports and maps for approval and designation by the Bo:\rd:

. "Flood Insurance Study" (FIS), which is produced by the Federal Emergency Management
Agency (FEMA) and used for floodplain management, regulation, and insurance purposes.
. "Flood Insurance Rate Map" (FIRM), which is proquced by FEMA and used for floodplain
management, regulation, and insurance purposes, A (FIRM may be published with or without
an associated hydrologic and hydraulic report. :
. "Flood Hazard Boundary Map" (FHBM), which )vas produced by the Federal Insurance
Administration and are' used for floodplain managetP,ent, regulation, and insurance purposes.
An FHBM usually depicts approximate floodplain boundaries only, and does not have an
accompanying report, Note: For all FHBM designations, the CWCB staff will perform (in-
house or by contract with a consultant) hydrologic ll11alyses.
. "Floodplain Information Reports", which are produced by local governments, state and
federal agencies, special districts, or the priva~e seCtor, and are used for floodplain
management purposes and usually adopted by FEryIA for use in Flood Insurance Rate Map
revisions.
. Various hydrology studies and related floodplain studies (conununity-wide or site specific)
that depict 100-year floodplain information that is useful for floodplain management
purposes. .
. "Floodplain Information" is a generic term used to describe any of the above types of reports
and/or maps in the CWCB's "rules and regulations,. ,"
. "Floodplain Resolution" is a formal document prepared by CWCB staff describing the
Floodplain Information that is to be designated and, approved by the Board.

1) Ae:enda Item 2.a
Floodplain resolution number: FPR 01-554
Affected communities: Town of Basalt, Eagle County,' Pitkin County
Name of study to be formally acted on: ''Floodplain Information Report, Roaring Fork River,
Town of Basalt, Eagle and Pitkin Counties, Colorado": dated October 2001 (revised) - prepared by
Matrix Design Group i
Studied streams: The report includes detailed 100-year floodplain information for the Roaring
Fork River in the vicinity of Basalt, Colorado. The Roaring Fork River is tributary to the.
Colorado River

Technical issues: The new floodplain information ryPort was prepared in response to significant
concerns-.aIL.:tluLpart of the affected local govemme~ts andCWCB s:taf'L. Preliminary work was:
prepared under contract to FEMA by J.F, Sato & Assbciates, The concerns related to modeling of
the levee constructed by CDOT immediately adjacetit to and upstream of the Highway 82 Upper
Bypass Bridge. Also, a complicated hydraulic condi;~ions exists where a flow split that begins at
that levee, flows downstream through the portion of Basalt known as South Side, and then returns .
flow from the South Side back to the main river channel. The new model provides for inclusion of

Flood Protection. Water Project Planning and Fin~ncing' Stream and Lake Protection
Water Supply Protection. C~nservation Planning

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