FLOOD10104

• County: Alamosa
• Community: Alamosa
• Stream Name: Rio Grande
• Basin: Rio Grande
• Title: Riverwood Estates Subdivision Rio Grande Floodway Evaluation
• Date: 4/3/1987
• Prepared For: Alamosa
• Prepared By: Muller Engineering Company, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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BACKGROUND INFORMATION

Previ ous study efforts
completing the study.
in this section.

and surveys have been utilized as a basis for
A summary of the information used is included

Flood Insurance Study (FIS) (1976)

A floodplain study of the Rio Grande through Alamosa was completed for
the Federal Insurance Administration (FIA) by the Albuquerque District
of the Corps of Engineers (COE). The report is dated December, 1976.

Topographic mapping prepared by the COE in 1973 for the FrS was also
used in thi s study to document the condi ti on of the ri ver pri or to
1976. The COE al so surveyed the cross sections to supplement the
topographi c mappi ng. Th is F I S cross secti on i nformati on was
documented in the HEC-2 model prepared by the COE, a copy of which was
provided for this study.

Hydrologic data used by the COE in the FrS was also used in this
eval uati on. The total ri ver flow rate for the lOa-year event i-s
10,900 cfs. Channel roughness values of .04 were used in the FrS.
Overbank roughness values of .08 were used in the FIS hydraulic
analysis.

The FIS identified the regulatory floodway to be along the river
levees existing at the time of the study. Along the right (west and
south) bank, the right overbank levee was assumed to be the floodway
1 imit from Section 29 downstream. Above Section 29, the right bank
floodway limit was assumed, in accordance with the City of Alamosa
development plans, according to the FrS. The left (east and north)
overbank levee was assumed to be the left floodway limit through the
study length.

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