BOARD00391

• Board Meeting Date: 5/23/2005
• Description: Flood Section - Floodplain Rules and Regulations Opportunity for Board and Public Comment
• Board Meetings - Doc Type: Memo

.

Term
Floodplain Maps

Floodplains Studies

Floodway

Foreseeable
Development

. Freeboard

Geographic
Information Systems
(G.I.S.)

_ __.Hydrologic Analysis

Hydraulic 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 likely to be
deepest and fastest. It is the area of the floodplain that must be kept free of
obstructions to allow floodwaters to move downstream.

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 community'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.

Computer 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, structnres, topographic information, etc.)
for natural resource management and other uses.

The determination of the peak rate of flow, or discharge_in_ cu~Lc_ feet per
second, for various selected probabilities for streams, channels, or basins
based on a scientific analysis of the physical process.

The determination of flood elevations and velocities for various
probabilities based on a scientific analysis of the movement and behavior
of floodwaters in channels or basins.

7

DRAFT