FLOOD00608

• Designation Number: 516
• County: Denver
• Community: Denver
• Title: Flood Insurance Study - Denver, CO, Volume I
• Date: 3/1/1996
• Designation Date: 5/1/2000
• Floodplain - Doc Type: Floodplain Report/Masterplan

4,0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound
floodplain management programs. Therefore, each Flood Insurance Study
produces maps designed to assist communities in developing floodplain
management measures.

4,1

Floodplain Boundaries

.

To provide a national standard without regional discrimination, the
1 percent annual chance (lOO-year) flood has been adopted by FEMA
as the base flood for floodplain management purposes. The 0.2
percent annual chance (500-year) flood is employed to indicate
additional areas of flood risk in the community. For each stream
studied by detailed methods, the 100- and 500-year floodplain
boundaries have been delineated using the flood elevations
determined at each cross section. Between cross sections, the
boundaries were interpolated using topographic maps at scales of
1:20, 1:1,200 and 1:24,000, with contour intervals of I, 2 and 10
feet (References 47, 50, 55-59, 61, 63, 70, 71, 72, and 73),

Boundaries for the shallow flooding areas were delineated using
topographic maps at scales of 1:1,200 and 1:24,000, with contour
intervals of 2 and 10 feet (References 55, 57, 58, 59, 61, and 63)
in conjunction with the previously determined elevations,

For the streams studied by approximate methods, the boundaries of
the 100-year flood were delineated on topographic maps at scales of
1:600 and 1:1,200, with contour intervals of 1 and 2 feet
(References 61, 62, and 74-80).

Approximate floodplain boundaries in some portions of the study
area were taken from the Flood Hazard Boundary Map (Reference 81),

The 100- and 500-year floodplain boundaries are shown on the Flood
Insurance Rate Map. In cases where the 100- and 500-year
floodplain boundaries are close together, only the 100-year
floodplain boundary has been shown. Small areas within the
floodplain boundaries may lie above the flood elevations but cannot
be shown due to limitations of the map scale and/or lack of
detailed topographic data,

For the streams studied by approximate methods, only the lOO-year
floodplain boundary is shown,

4.2 Floodways

Encroachment on floodplains, such as structures and fill, reduces
flood-carrying capacity, increases flood heights and velocities,
and increases flood hazards in areas beyond the encroachment
itself. One aspect of floodplain management involves balancing the
economic gain from floodplain development against the resulting
increase in flood hazard. For purposes of the National Flood
Insurance Program, a floodway is used as a tool to assist local

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