FLOOD05386

• County: Arapahoe
• Community: Sheridan
• Stream Name: Bear Creek
• Basin: South Platte
• Title: Flood Insurance Study - City of Sheridan
• Date: 12/4/1985
• Prepared For: Sheridan
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

remain separated from the main channel downstream to the yicinity
of cross section B (Reference 6). The extent and depth of this
shallow flooding were determined using normal-depth calculations.

The approximate 100-year flood elevations along the South Platte
River were developed by the COE, Omaha District (Reference 9).

Locations of selected cross sections used in the hydraulic analyses
are shown on the Flood Profiles, (Exhibit 1). For stream segments
for which a floodway was computed (Section 4.2), selected cross
section locations are also shown on the Flood Boundary and Floodway
Map (Exhibit 2).

The hydraulic analyses for this' study were based on unobstructed
flow. The flood elevations shown on the profiles are thus con-
sidered valid only if hydraulic structures remain unobstructed,
operate properly, and do not fail.

All elevations are referenced to the National Geodetic Vertical
Datum of 1929 (NGVD). Elevation reference marks used in this
study are shown on the maps. '

4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS

The National Flood Insurance Program (NFIP) encourages State and local
governments to adopt sound flood plain management programs. Therefore,
each Flood Insurance Study produces maps designed to assist communities
in developing flood plain management ~easures.

4.1 Flood 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 flood plain management purposes.
The 0.2 percent annual chance (500-year) flood is employed to
indicate additional areas of flpod risk in the community. For
each stream studied in detail, the 100- and SOO-year flood plain
boundaries have been delineated! using the flood elevations determined
at each cross section. Between! cross sections, the boundaries
were interpolated using topographic maps at a scale of 1:1,200,
with a contour interval of 2 feet (Reference 8).

Boundaries for the shallow flooding areas were delineated using
topographic maps at a scale of ~:1,200, with a contour interval
of 2 feet (Reference 8) in conj~nction with previously determined
elevations.

Approximate flood boundaries alpng the South Platte 'River were
taken from the Flood Insurance ,Rate Maps for the CitY of Sheridan
and Arapahoe County (References, 10 and 11).

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