FLOOD10655 ‎(2)‎

• County: Chaffee
• Community: Salida
• Title: FIS - Salida
• Date: 9/30/1982
• Prepared For: Salida
• Prepared By: FEMA
• Floodplain - Doc Type: Current FEMA Regulatory Floodplain Information

flow for the South Arkansas River was obtained from a set of corre-
lations that resulted in a relationship obtained frOOl the period
of common records between the South Arkansas River near Salida and
the Arkansas River at Salida.

The results of the regional analysis were compared to the results of
the Floodplain Information Report for the Lower South Arkansas River
{Reference 1). The IOO-year discharge agreed within 5 percent of
Reference 1, and therefore the hydrologic analysis as presented in
thi s previous study was adopted for use in estimating the f1 Dad
boundaries for the South Arkansas River. The peak discharges are
presented in Table 1.

Table 1 - Summary of Discharges

Flood Source and Location

Drainage Area
(sq. mi.) 10-year

Peak Discharge (cfs)
50-year IOO-year 50D-year

South Arkansas River
Confl uence wi th
Arkansas River

At County Road 107
3.2 Hydraulic Analyses

208
200

1,350
1,330

1 ,830
1,800

2,010
1,980

2,500
2,470

Analyses of the hydraulic characteristics of the flooding sources
studied in detail ;n the community were carried out to provide esti-
mates of the el evations of floads of the sel ected recurrence
intervals along each of these flood sources.

Water surface el evations for the 10-, 50- t 100- and SOD-year f1 oods
for the South Arkansas River were canputed usi ng the Corps of Engi-
neers HEC-2 Water Surface Profil es Program (Reference 5). Topo-
graphic mapping and cross sections for this analysis were compiled
from aerial photographs flown in May, 1978 (Reference 6), coupled
with appropriate field verification. All bridges and culverts were
measured in the field to obtain elevation data and structural
geometry.

locations of selected cross sections used in the hydraul ic analyses
are shown on the Flood Profiles. For stream segments for which a
floodway is computed (Section 4.2Jt selected cross section locations
are also shown on the Flood Boundary and Floodway Map.

Roughness factors (Mannings II nil valves) were determined by field
inspection. Ground level photography aided in the selection of
roughness factors and aerial photography was used to determine the
limits of each roughness zone. Roughness values for the main channel
of the South Arkansa-s River ranged from 0.038 to 0.040 wi th fl Dod
plain values ranging from 0.032 to 0.085 for all floods.

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