FLOOD04440

• County: Statewide
• Community: All
• Stream Name: All
• Basin: Statewide
• Title: Colorado Flood Map Modernization Business Case Plan - March 2004
• Date: 3/1/2004
• Prepared For: FEMA
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SECTION THREE

Program Plan

and hydraulic data overlaid on that planimetric information are accurate. If such a maintenance
plan is not in place or it is not properly funded, there is a risk that Colorado's flood maps will
become outdated and unreliable. To address these concerns, the CWCB would like to conduct
comprehensive flood mapping on a countywide basis, to be complemented by detailed
engineering updates on a site- specific basis. The CWCB will work closely with community
officials to assess the site-specific H&H needs and to meet as many of those site-specific needs
as possible.

The CWCB will also work to ensure that mapping updates conform with FEMA's current
Guidelines and Specifications for Flood Hazard Mapping Partners. The CWCB supports
FEMA's efforts to make floodplain information available digitally, and is interested in pursuing
the initiative to give digital floodplain maps the same legal authority that the paper maps
currently have. To support this initiative, Colorado's flood mapping program is designed to be
flexible enough to incorporate the creation of solely digital floodplain maps in the future.
CWCB believes that occasional needs for paper maps can be met through "print-on-demand"
technology.

The CWCB strives to create countywide mapping in the NA VD 1988 vertical datum, NAD 83
horizontal datum, and Universe Transverse Mercator projection for the sake of statewide
consistency, however it is recognized that available local data or local desire may make the
conversion from one datum or projection to another infeasible. Those issues can, therefore be
addressed during the scoping process as they arise.

3.1.4.1 Topographic and Base Mapping

Topographic and base mapping are the foundation components of any flood map update. The
CWCB is committed to utilizing base map information from available sources that meet FEMA
specifications. The CWCB prefers to use local vector GIS as the source for DFIRM creation,
however In areas where a local GIS is not available the U.S.G.S. Digital Orthophoto Quarter
Quads (DOQQ's) can be used. For topographic mapping, the CWCB will use locally available
or locally developed topographic mapping. The required level of topographic mapping will be
study-specific; however the CWCB encourages the use of topographic data that meets the
CWCB's Statewide Drainage Criteria Manual. Topographic mapping that does not meet the
state's minimum standards will be evaluated on a study-by-study basis to determine if the use of
such data would be an improvement to the data that is currently represented on the effective
FIRM, and is accurate enough to be defensible. Topographic data that is developed by the
CWCB for a flood study will be generated by the Study Contractor according to the terms of
their contract, or will be developed by the local communities in coordination with the CWCB
and with possible financial assistance from FEMA. The CWCB feels that up-to-date and
accurate base and topographic mapping are extremely important in the flood mapping process
and FEMA is hereby requested to consider the funding or partial funding of such activities in the
future.

3.1.4.2 Countywide Mapping

As discussed in subsection 3.1.3, after studies are identified for countywide mapping in a
particular fiscal year, a Scoping Meeting will be held and a Site Specific Needs Assessment will
be performed in each selected county. Utilizing data gathered prior to and during Initial

Colorado Business Case Plan - March 2004

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