BOARD01965

• Board Meeting Date: 3/22/2005
• Description: Flood Section - Presentation of the CWCB's Draft Rules and Regulations for Regulatory Floodplains in Colorado
• Board Meetings - Doc Type: Memo

Term
Floodplain Maps

Floodplains Studies

Floodway

Foreseeable
Development

Freeboard

Geographic
InforrDation Systems
(G.I.S.)

Hydrologic Analysis

Definition
Maps that show in a plan view the horizontal boundary of floods of
various magnitudes or frequencies. Such maps include, but are not limited
to, Flood Hazard Boundary Maps (FHBM), Flood Insurance Rate Maps
(FIRM), and Digital Flood Insurance Rate Maps (DFIRM) published by
FEMA, Flood prone Area Maps published by the U.S. Geological Survey
(USGS), Flooded Area Maps published by the U. S. Army Corps of
Engineers (COE), Flood Hazard Area Delineations (FHAD) published by
the Urban Drainage and Flood Control District (UD&FCD).

A formal presentation of the study process, results, and technical support
information developed for floodplain maps.

Highest hazard portion of the floodplain where floodwater is the deepest
and fastest. It is the area of the floodplain that shall be kept free of
obstructions to allow floodwaters to move downstream. It is further
defined as that portion of the floodplain required for the passage or
conveyance of the one-hundred year flood where the one-hundred year
flood will be raised by some pre-defined maximum amount (e.g., FEMA
criteria is one foot, but the CWCB recognizes and endorses more stringent
criteria adopted by individual communities), after considering a reasonable
expectation of blockage at bridges and other obstructions in the floodplain.

The potential future development of, or changes in, the land uses that are
likely to take place during the period of time covered by a comrnunity's
adopted master land use plan, or comprehensive community plan, over a
20-year period. If there is no adopted community plan, then potential
development patterns based on zoning, annexations, and other relevant
factors shall be evaluated.

The vertical distance in feet above a predicted water surface elevation
intended to provide a margin of safety to compensate for unknown factors
that could contribute to flood heights greater than the height calculated for
a selected size flood such as bridge openings and the hydrological effect of
urbanization of the watershed.

Cornputer software that utilizes databases and terrain mapping to store and
display special and tabular data, such as floodplains, as layers (e.g.,
political boundaries, roadways, structures, topographic information, etc.)
for natural resource management and other uses.

The determination of the peak rate of flow, or discharge in cubic feet per
second, for various selected probabilities for streams, channels, or basins
based on a scientific analysis of the physical process.

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