FLOOD00046

• County: Denver
• Community: Denver
• Stream Name: Coon Creek, First Creek, First Creek Tributary
• Title: Flood Insurance Study - City and County of Denver, Volume 1 of 2
• Date: 9/7/1998
• Prepared For: Denver
• Prepared By: FEMA
• 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 cOllllllunities in developing floodplain
management measures.

4.1 Floodplain Boundaries

To provide a national standard without regional discrimination, the
1 percent annual chance (lOa-year) flood has been adopted by "E~A
as the base flood for floodplain management purposes. The 0.2
percent annual chance (SOD-year) flood is employed to indicate
additional areas of flood risk in the community. For each st,ream
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 lOa-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 SOO-year flOOdplain boundaries are shown on the Flood
Insurance Rate Map. In cases where tbe 100- and SOO-year
floodplain boundaries are close together, only the 100-year
floodplain boundary bas been sbown. Small areas witbin tbe
floodplain boundaries may lie above tbe flood elevations but cannot
be sbown due to limitations of the map scale and/or lack of
detailed topographic data.

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

4.2 F100dways

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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